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000
FXUS63 KLOT 261612
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1012 AM CST MON JAN 26 2015

.SHORT TERM...
315 AM CST

THROUGH TONIGHT...

AN IMPRESSIVE WATER VAPOR LOOP THIS MORNING AS ROARING SUBTROPICAL
JET ACROSS THE SOUTHEAST IS DEEPENING A SIGNIFICANT SYSTEM THAT WILL
IMPACT THE NORTHEAST U.S. OVER THE NEXT 24 TO 36 HOURS. THE NORTHERN
STREAM JET WHICH IS ALSO HELPING TO CARVE OUT THE DEVELOPING TROUGH
IS DIVING SOUTHWARD OVER OUR REGION TODAY. ON THE CYCLONIC SIDE OF
THIS...FROM MANITOBA TO THE LOWER OHIO VALLEY...AN ELONGATED AREA OF
VORTICITY GENERATION WILL SUPPORT FORCING FOR ASCENT TODAY AND
TONIGHT...WITH THE MOST FOCUSED ZONE BEING A BETTER DEFINED WAVE
SEEN OVER CENTRAL MN EARLY THIS MORNING. THE RUN-TO-RUN TREND ON THE
RAP MODEL EARLY THIS MORNING IS FURTHER
WEST/SOUTHWEST...SUPPORTING UPSTREAM RADAR TRENDS AND FAVORING
NORTH CENTRAL IL TO GET IN A PERIOD OF SNOW BEGINNING LATER THIS
MORNING FOLLOWED BY A GRADUAL EXPANSION EAST. WHILE MOST OF THE
SNOW WILL BE LIGHT...THERE IS A WINDOW OF TIME LATE THIS MORNING
AND EARLY THIS AFTERNOON OVER NORTH CENTRAL ILLINOIS WHERE
850-700MB CONVERGENCE AND A F-GEN INDUCED CIRCULATION MAY ALLOW
FOR SPOTTY BURSTS OF MODERATE SNOW...WHICH HIGH-RESOLUTION
GUIDANCE TRIES TO INDICATE TOO. WITH ADJACENT OFFICES AND WPC
COLLABORATION...HAVE AROUND AN INCH FORECAST IN THE ROCKFORD
AREA...WITH AROUND A HALF INCH FURTHER EAST OF THERE. SOUTHWARD IN
THE FORECAST AREA THE DRY AIR SEEMS MORE PRONOUNCED...SO MAY END
UP JUST BEING FLURRIES AT TIMES.

THE FORCING ALOFT WEAKENS LATER THIS AFTERNOON AND EVENING SO
EXPECTING LIGHT SNOW TO BECOME MORE PATCHY IN COVERAGE. THE MOISTURE
IN THE ICE LAYER GRADUALLY DIMINISHES FROM WEST TO EAST THROUGH THE
EVENING...WITH STILL SOME LIGHT ADIABATIC ASCENT IN THE LOWEST
COUPLE THOUSAND FEET. IF THAT LOWEST LAYER IS SATURATED OR ABLE TO
THERE COULD BE A FREEZING DRIZZLE CONCERN...SO MAINTAIN THE GOING
CHANCE IN THE FORECAST.

FOR TEMPERATURES TODAY...DID BUMP DOWN SEVERAL DEGREES AS CLEARING
LAST NIGHT ALLOWED PLACES TO DROP QUICKLY AND NOW THE CLOUD CANOPY
WILL HINDER THEM FROM WARMING MUCH. FORECAST HIGHS ARE MAINLY IN THE
MID 20S WITH A FEW UPPER 20S POSSIBLE. WHILE THAT DOES NOT MAKE
HEADLINES IN JANUARY...IF THE FORECAST PANS OUT THIS WOULD BE THE
FIRST DAY WITH HIGHS BELOW 30 SINCE JANUARY 14TH.

MTF

&&

.LONG TERM...
315 AM CST

TUESDAY THROUGH SUNDAY...

HIGH PRESSURE WILL MOVE OVER THE AREA TUESDAY AFTERNOON AND NIGHT
BEFORE RETURN FLOW ON WEDNESDAY. THE CHALLENGE OF CLOUD COVER
PRESENTS ITSELF AGAIN ON TUESDAY AND WHILE HAVE SLOWED THE
CLEARING TREND TUESDAY MORNING...STILL THINK THE AFTERNOON SHOULD
SEE SOME BREAKS OF SUN AREAWIDE. SOUTHERLY FLOW ON WEDNESDAY IS
FORECAST TO BRING 925MB TEMPERATURES TO AROUND 0C WHICH USING
CLIMATOLOGY WITH LIMITED SNOW COVER SHOULD SUPPORT WIDESPREAD MID
TO UPPER 30S WITH A FEW LOWER 40S POSSIBLE IN THE SOUTHWEST CWA
OR CHICAGO METRO.

THE LARGE CLOSED LOW OFF THE BAJA OF CALIFORNIA THIS MORNING IS
FORECAST BY THE SUITE OF GUIDANCE TO DRIFT NORTHWARD AND GET CAUGHT
UP IN THE WESTERLIES BECOMING AN OPEN WAVE ACROSS THE MIDDLE OF THE
COUNTRY. WITH THE MASSIVE SYSTEM OFF THE NORTHEAST LIKELY TO SLOW
THINGS A BIT...CONTINUE TO LEAN WITH THE SLOWER EC AND GEM MODELS
WHICH WOULD FAVOR PRECIPITATION CHANCES MORE SO LATE WEDNESDAY NIGHT
AND THURSDAY...AROUND 12H SLOWER THAN THE GFS. FORECAST VERTICAL
PROFILES ON BOTH MODELS WOULD SUPPORT MORE OF RAIN AHEAD OF THIS
SYSTEM...ESPECIALLY CONSIDERING LOW-LEVEL TEMPERATURES SHOULD AT THE
VERY LEAST HOLD STEADY IF NOT MODERATE WEDNESDAY NIGHT...POTENTIALLY
TO 35 TO 38 DEGREES GIVEN EC AND GEM SOLUTIONS. ON THE BACKSIDE OF
THIS SYSTEM IT WOULD SEEM THERE WOULD BE AT LEAST A PERIOD OF SNOW
CHANCES. OBVIOUSLY A FEW DAYS OUT AND A CUTOFF LOW INVOLVED...A
LOT COULD CHANGE WITH SPECIFICS...BUT RIGHT NOW THIS IS NOT
LOOKING LIKE A HIGH IMPACT EVENT.

LATE THIS WEEK INTO THE WEEKEND THE NORTHERN STREAM FLOW PATTERN
IS FORECAST TO REMAIN QUITE PROGRESSIVE WHILE ANOTHER CUTOFF LOW
IS PROGGED TO DEVELOP OVER THE FAR SOUTHWEST US. THE 00Z EC HAS
FORECAST A STRONG SYSTEM IN THE NORTHWEST FLOW TO WIN OUT ABOUT A
WEEK FROM NOW AND DRAG DOWN -15C TO -20C 850MB TEMPERATURES.
SOMETHING TO MONITOR AS WE HEAD TOWARD THE FIRST DAYS OF FEBRUARY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* LIGHT SNOW DEVELOPING AROUND MID-DAY. MVFR CIGS/IFR VSBY
  POSSIBLE THIS AFTERNOON. MINOR ACCUMULATIONS.

* IFR CIGS AND MVFR FOG POSSIBLE TONIGHT WITH LINGERING FLURRIES.

* LIGHT SOUTH WINDS THROUGH THIS AFTERNOON AND SOUTHEAST THIS
  EVENING. GENERALLY LESS THAN 10 KT. WINDS THEN BECOME LIGHT
  EAST-NORTHEAST LATE TONIGHT.

RATZER/DEUBELBEISS

//DISCUSSION...UPDATED 12Z...

WEAK SURFACE HIGH PRESSURE OVER THE AREA WILL MOVE QUICKLY OFF TO
THE SOUTHEAST THIS MORNING...AS AN AREA OF LOW PRESSURE RAPIDLY
APPROACHES FROM THE UPPER MIDWEST. VFR CLOUDS EXPECTED TO LOWER
THROUGH THE MORNING...WITH DEVELOPMENT OF LIGHT SNOW AND MVFR CIGS
BY/AROUND MID-DAY. A PERIOD OF LIGHT ACCUMULATING SNOW IS LIKELY
THROUGH THE AFTERNOON...WITH OCCASIONAL IFR VSBYS. SNOW IS
EXPECTED TO TAPER OFF BY EVENING THOUGH WILL LINGER IN LIGHTER
FASHION AND MAY MIX OR CHANGE TO FREEZING DRIZZLE LATE BEFORE
ENDING. MOIST LOW LEVELS AND LIGHT WINDS SUPPORT A PERIOD OF IFR
CIGS AND MVFR VSBYS IN FOG OVERNIGHT AS THE SURFACE LOW FILLS TO
JUST A TROUGH. SNOW ACCUMULATIONS LOOK TO RANGE FROM PERHAPS AN
INCH AROUND RFD...TO LESS THAN AN INCH FARTHER EAST ACROSS CHI
METRO TERMINALS.

WINDS CURRENTLY LIGHT/VARIABLE AS THE SURFACE RIDGE AXIS PASSES
ACROSS THE FORECAST AREA EARLY THIS MORNING. WINDS TO SHIFT SOUTH
DURING THE MORNING...THEN SOUTHEAST BY EVENING. SPEEDS GENERALLY
LESS THAN 10 KTS...THOUGH IF APPROACHING LOW IS SLOWER TO WEAKEN
THAN EXPECTED SOUTHEAST WINDS AROUND 10 KT WOULD BE POSSIBLE LATER
THIS AFTERNOON. WINDS TO TURN LIGHT NORTHEAST LATER TONIGHT INTO
EARLY TUESDAY.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM CONFIDENCE IN SNOW TIMING/INTENSITY TODAY INTO THIS
  EVENING.

* MEDIUM-LOW CONFIDENCE IN VIS/CIG TRENDS OVERNIGHT.

RATZER/DEUBELBEISS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...MAINLY VFR.

WEDNESDAY...MAINLY VFR DURING THE DAY. CHANCE OF RAIN/SNOW AT
NIGHT WITH MVFR/IFR POSSIBLE.

THURSDAY...CHANCE OF LIGHT SNOW. MVFR LIKELY/IFR POSSIBLE.

FRIDAY...MAINLY VFR.

SATURDAY...CHANCE OF SNOW/MVFR CIGS.

SUNDAY...MVFR CIGS POSSIBLE.

RATZER

&&

.MARINE...
143 AM CST

ONLY MARINE FORECAST CONCERNS ARE A BRIEF PERIOD OF ENHANCED
SOUTH-SOUTHEAST WINDS THIS AFTERNOON AND EVENING ESPECIALLY ON THE
NORTHERN PORTION OF THE LAKE...AND AGAIN WEDNESDAY AFTERNOON. GUSTY
NORTH WINDS NEAR 30 KT ARE ALSO LIKELY THURSDAY AND THURSDAY
NIGHT.

WINDS CONTINUE TO DIMINISH QUICKLY ACROSS LAKE MICHIGAN EARLY THIS
MORNING...AS WEAK HIGH PRESSURE RIDING SLIDES SOUTHEAST ACROSS THE
LAKE. THIS RIDGE WILL ALSO PASS QUICKLY OFF TO THE SOUTHEAST THIS
AFTERNOON IN WHAT REMAINS A PROGRESSIVE WEATHER PATTERN...WITH
ANOTHER LOW PRESSURE SYSTEM CURRENTLY NEAR LAKE WINNIPEG MOVING
QUICKLY SOUTHEAST INTO ILLINOIS BY MIDNIGHT TONIGHT WHILE FILLING.
THIS WILL RESULT IN WINDS BECOMING SOUTH AND INCREASING TO AROUND 20
KTS ON THE LAKE THIS AFTERNOON...THEN DECREASING AND BACKING TO THE
NORTHEAST INTO TUESDAY MORNING AS THE LOW PASSES AND WEAKENS.
ANOTHER HIGH PRESSURE RIDGE WILL SETTLE ACROSS THE WESTERN LAKES BY
TUESDAY EVENING.

ANOTHER MORE DEVELOPED LOW WILL FORM ACROSS THE LAKES TUESDAY
NIGHT...AND WILL DEEPEN SLIGHTLY AS IT APPROACHES FROM THE WEST
WEDNESDAY AND PASSES JUST SOUTH OF LAKE MICHIGAN EARLY THURSDAY
MORNING. THIS WILL AGAIN RESULT IN WINDS INITIALLY BECOMING SOUTH
AND INCREASING TO 20-25 KT WEDNESDAY AFTERNOON AND EVENING...THEN
BACKING TO THE NORTH EARLY THURSDAY AND GUSTING NEAR 30 KT AS THE
LOW PULLS AWAY ACROSS THE EASTERN LAKES AND UPPER OHIO VALLEY
THROUGH THURSDAY AFTERNOON AND NIGHT. HIGH PRESSURE THEN SPREADS
ACROSS THE REGION BY FRIDAY AFTERNOON.

FOR THE ILLINOIS AND NORTHWEST INDIANA NEARSHORE WATERS...AS SMALL
CRAFT ADVISORY REMAINS IN EFFECT UNTIL MID-MORNING TODAY...AS WAVES
CONTINUE TO SUBSIDE FROM YESTERDAY/LAST EVENINGS STRONG NORTHEAST
WINDS.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 261612
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1012 AM CST MON JAN 26 2015

.SHORT TERM...
315 AM CST

THROUGH TONIGHT...

AN IMPRESSIVE WATER VAPOR LOOP THIS MORNING AS ROARING SUBTROPICAL
JET ACROSS THE SOUTHEAST IS DEEPENING A SIGNIFICANT SYSTEM THAT WILL
IMPACT THE NORTHEAST U.S. OVER THE NEXT 24 TO 36 HOURS. THE NORTHERN
STREAM JET WHICH IS ALSO HELPING TO CARVE OUT THE DEVELOPING TROUGH
IS DIVING SOUTHWARD OVER OUR REGION TODAY. ON THE CYCLONIC SIDE OF
THIS...FROM MANITOBA TO THE LOWER OHIO VALLEY...AN ELONGATED AREA OF
VORTICITY GENERATION WILL SUPPORT FORCING FOR ASCENT TODAY AND
TONIGHT...WITH THE MOST FOCUSED ZONE BEING A BETTER DEFINED WAVE
SEEN OVER CENTRAL MN EARLY THIS MORNING. THE RUN-TO-RUN TREND ON THE
RAP MODEL EARLY THIS MORNING IS FURTHER
WEST/SOUTHWEST...SUPPORTING UPSTREAM RADAR TRENDS AND FAVORING
NORTH CENTRAL IL TO GET IN A PERIOD OF SNOW BEGINNING LATER THIS
MORNING FOLLOWED BY A GRADUAL EXPANSION EAST. WHILE MOST OF THE
SNOW WILL BE LIGHT...THERE IS A WINDOW OF TIME LATE THIS MORNING
AND EARLY THIS AFTERNOON OVER NORTH CENTRAL ILLINOIS WHERE
850-700MB CONVERGENCE AND A F-GEN INDUCED CIRCULATION MAY ALLOW
FOR SPOTTY BURSTS OF MODERATE SNOW...WHICH HIGH-RESOLUTION
GUIDANCE TRIES TO INDICATE TOO. WITH ADJACENT OFFICES AND WPC
COLLABORATION...HAVE AROUND AN INCH FORECAST IN THE ROCKFORD
AREA...WITH AROUND A HALF INCH FURTHER EAST OF THERE. SOUTHWARD IN
THE FORECAST AREA THE DRY AIR SEEMS MORE PRONOUNCED...SO MAY END
UP JUST BEING FLURRIES AT TIMES.

THE FORCING ALOFT WEAKENS LATER THIS AFTERNOON AND EVENING SO
EXPECTING LIGHT SNOW TO BECOME MORE PATCHY IN COVERAGE. THE MOISTURE
IN THE ICE LAYER GRADUALLY DIMINISHES FROM WEST TO EAST THROUGH THE
EVENING...WITH STILL SOME LIGHT ADIABATIC ASCENT IN THE LOWEST
COUPLE THOUSAND FEET. IF THAT LOWEST LAYER IS SATURATED OR ABLE TO
THERE COULD BE A FREEZING DRIZZLE CONCERN...SO MAINTAIN THE GOING
CHANCE IN THE FORECAST.

FOR TEMPERATURES TODAY...DID BUMP DOWN SEVERAL DEGREES AS CLEARING
LAST NIGHT ALLOWED PLACES TO DROP QUICKLY AND NOW THE CLOUD CANOPY
WILL HINDER THEM FROM WARMING MUCH. FORECAST HIGHS ARE MAINLY IN THE
MID 20S WITH A FEW UPPER 20S POSSIBLE. WHILE THAT DOES NOT MAKE
HEADLINES IN JANUARY...IF THE FORECAST PANS OUT THIS WOULD BE THE
FIRST DAY WITH HIGHS BELOW 30 SINCE JANUARY 14TH.

MTF

&&

.LONG TERM...
315 AM CST

TUESDAY THROUGH SUNDAY...

HIGH PRESSURE WILL MOVE OVER THE AREA TUESDAY AFTERNOON AND NIGHT
BEFORE RETURN FLOW ON WEDNESDAY. THE CHALLENGE OF CLOUD COVER
PRESENTS ITSELF AGAIN ON TUESDAY AND WHILE HAVE SLOWED THE
CLEARING TREND TUESDAY MORNING...STILL THINK THE AFTERNOON SHOULD
SEE SOME BREAKS OF SUN AREAWIDE. SOUTHERLY FLOW ON WEDNESDAY IS
FORECAST TO BRING 925MB TEMPERATURES TO AROUND 0C WHICH USING
CLIMATOLOGY WITH LIMITED SNOW COVER SHOULD SUPPORT WIDESPREAD MID
TO UPPER 30S WITH A FEW LOWER 40S POSSIBLE IN THE SOUTHWEST CWA
OR CHICAGO METRO.

THE LARGE CLOSED LOW OFF THE BAJA OF CALIFORNIA THIS MORNING IS
FORECAST BY THE SUITE OF GUIDANCE TO DRIFT NORTHWARD AND GET CAUGHT
UP IN THE WESTERLIES BECOMING AN OPEN WAVE ACROSS THE MIDDLE OF THE
COUNTRY. WITH THE MASSIVE SYSTEM OFF THE NORTHEAST LIKELY TO SLOW
THINGS A BIT...CONTINUE TO LEAN WITH THE SLOWER EC AND GEM MODELS
WHICH WOULD FAVOR PRECIPITATION CHANCES MORE SO LATE WEDNESDAY NIGHT
AND THURSDAY...AROUND 12H SLOWER THAN THE GFS. FORECAST VERTICAL
PROFILES ON BOTH MODELS WOULD SUPPORT MORE OF RAIN AHEAD OF THIS
SYSTEM...ESPECIALLY CONSIDERING LOW-LEVEL TEMPERATURES SHOULD AT THE
VERY LEAST HOLD STEADY IF NOT MODERATE WEDNESDAY NIGHT...POTENTIALLY
TO 35 TO 38 DEGREES GIVEN EC AND GEM SOLUTIONS. ON THE BACKSIDE OF
THIS SYSTEM IT WOULD SEEM THERE WOULD BE AT LEAST A PERIOD OF SNOW
CHANCES. OBVIOUSLY A FEW DAYS OUT AND A CUTOFF LOW INVOLVED...A
LOT COULD CHANGE WITH SPECIFICS...BUT RIGHT NOW THIS IS NOT
LOOKING LIKE A HIGH IMPACT EVENT.

LATE THIS WEEK INTO THE WEEKEND THE NORTHERN STREAM FLOW PATTERN
IS FORECAST TO REMAIN QUITE PROGRESSIVE WHILE ANOTHER CUTOFF LOW
IS PROGGED TO DEVELOP OVER THE FAR SOUTHWEST US. THE 00Z EC HAS
FORECAST A STRONG SYSTEM IN THE NORTHWEST FLOW TO WIN OUT ABOUT A
WEEK FROM NOW AND DRAG DOWN -15C TO -20C 850MB TEMPERATURES.
SOMETHING TO MONITOR AS WE HEAD TOWARD THE FIRST DAYS OF FEBRUARY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* LIGHT SNOW DEVELOPING AROUND MID-DAY. MVFR CIGS/IFR VSBY
  POSSIBLE THIS AFTERNOON. MINOR ACCUMULATIONS.

* IFR CIGS AND MVFR FOG POSSIBLE TONIGHT WITH LINGERING FLURRIES.

* LIGHT SOUTH WINDS THROUGH THIS AFTERNOON AND SOUTHEAST THIS
  EVENING. GENERALLY LESS THAN 10 KT. WINDS THEN BECOME LIGHT
  EAST-NORTHEAST LATE TONIGHT.

RATZER/DEUBELBEISS

//DISCUSSION...UPDATED 12Z...

WEAK SURFACE HIGH PRESSURE OVER THE AREA WILL MOVE QUICKLY OFF TO
THE SOUTHEAST THIS MORNING...AS AN AREA OF LOW PRESSURE RAPIDLY
APPROACHES FROM THE UPPER MIDWEST. VFR CLOUDS EXPECTED TO LOWER
THROUGH THE MORNING...WITH DEVELOPMENT OF LIGHT SNOW AND MVFR CIGS
BY/AROUND MID-DAY. A PERIOD OF LIGHT ACCUMULATING SNOW IS LIKELY
THROUGH THE AFTERNOON...WITH OCCASIONAL IFR VSBYS. SNOW IS
EXPECTED TO TAPER OFF BY EVENING THOUGH WILL LINGER IN LIGHTER
FASHION AND MAY MIX OR CHANGE TO FREEZING DRIZZLE LATE BEFORE
ENDING. MOIST LOW LEVELS AND LIGHT WINDS SUPPORT A PERIOD OF IFR
CIGS AND MVFR VSBYS IN FOG OVERNIGHT AS THE SURFACE LOW FILLS TO
JUST A TROUGH. SNOW ACCUMULATIONS LOOK TO RANGE FROM PERHAPS AN
INCH AROUND RFD...TO LESS THAN AN INCH FARTHER EAST ACROSS CHI
METRO TERMINALS.

WINDS CURRENTLY LIGHT/VARIABLE AS THE SURFACE RIDGE AXIS PASSES
ACROSS THE FORECAST AREA EARLY THIS MORNING. WINDS TO SHIFT SOUTH
DURING THE MORNING...THEN SOUTHEAST BY EVENING. SPEEDS GENERALLY
LESS THAN 10 KTS...THOUGH IF APPROACHING LOW IS SLOWER TO WEAKEN
THAN EXPECTED SOUTHEAST WINDS AROUND 10 KT WOULD BE POSSIBLE LATER
THIS AFTERNOON. WINDS TO TURN LIGHT NORTHEAST LATER TONIGHT INTO
EARLY TUESDAY.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM CONFIDENCE IN SNOW TIMING/INTENSITY TODAY INTO THIS
  EVENING.

* MEDIUM-LOW CONFIDENCE IN VIS/CIG TRENDS OVERNIGHT.

RATZER/DEUBELBEISS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...MAINLY VFR.

WEDNESDAY...MAINLY VFR DURING THE DAY. CHANCE OF RAIN/SNOW AT
NIGHT WITH MVFR/IFR POSSIBLE.

THURSDAY...CHANCE OF LIGHT SNOW. MVFR LIKELY/IFR POSSIBLE.

FRIDAY...MAINLY VFR.

SATURDAY...CHANCE OF SNOW/MVFR CIGS.

SUNDAY...MVFR CIGS POSSIBLE.

RATZER

&&

.MARINE...
143 AM CST

ONLY MARINE FORECAST CONCERNS ARE A BRIEF PERIOD OF ENHANCED
SOUTH-SOUTHEAST WINDS THIS AFTERNOON AND EVENING ESPECIALLY ON THE
NORTHERN PORTION OF THE LAKE...AND AGAIN WEDNESDAY AFTERNOON. GUSTY
NORTH WINDS NEAR 30 KT ARE ALSO LIKELY THURSDAY AND THURSDAY
NIGHT.

WINDS CONTINUE TO DIMINISH QUICKLY ACROSS LAKE MICHIGAN EARLY THIS
MORNING...AS WEAK HIGH PRESSURE RIDING SLIDES SOUTHEAST ACROSS THE
LAKE. THIS RIDGE WILL ALSO PASS QUICKLY OFF TO THE SOUTHEAST THIS
AFTERNOON IN WHAT REMAINS A PROGRESSIVE WEATHER PATTERN...WITH
ANOTHER LOW PRESSURE SYSTEM CURRENTLY NEAR LAKE WINNIPEG MOVING
QUICKLY SOUTHEAST INTO ILLINOIS BY MIDNIGHT TONIGHT WHILE FILLING.
THIS WILL RESULT IN WINDS BECOMING SOUTH AND INCREASING TO AROUND 20
KTS ON THE LAKE THIS AFTERNOON...THEN DECREASING AND BACKING TO THE
NORTHEAST INTO TUESDAY MORNING AS THE LOW PASSES AND WEAKENS.
ANOTHER HIGH PRESSURE RIDGE WILL SETTLE ACROSS THE WESTERN LAKES BY
TUESDAY EVENING.

ANOTHER MORE DEVELOPED LOW WILL FORM ACROSS THE LAKES TUESDAY
NIGHT...AND WILL DEEPEN SLIGHTLY AS IT APPROACHES FROM THE WEST
WEDNESDAY AND PASSES JUST SOUTH OF LAKE MICHIGAN EARLY THURSDAY
MORNING. THIS WILL AGAIN RESULT IN WINDS INITIALLY BECOMING SOUTH
AND INCREASING TO 20-25 KT WEDNESDAY AFTERNOON AND EVENING...THEN
BACKING TO THE NORTH EARLY THURSDAY AND GUSTING NEAR 30 KT AS THE
LOW PULLS AWAY ACROSS THE EASTERN LAKES AND UPPER OHIO VALLEY
THROUGH THURSDAY AFTERNOON AND NIGHT. HIGH PRESSURE THEN SPREADS
ACROSS THE REGION BY FRIDAY AFTERNOON.

FOR THE ILLINOIS AND NORTHWEST INDIANA NEARSHORE WATERS...AS SMALL
CRAFT ADVISORY REMAINS IN EFFECT UNTIL MID-MORNING TODAY...AS WAVES
CONTINUE TO SUBSIDE FROM YESTERDAY/LAST EVENINGS STRONG NORTHEAST
WINDS.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 261406
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
806 AM CST MON JAN 26 2015

.SHORT TERM...
315 AM CST

THROUGH TONIGHT...

AN IMPRESSIVE WATER VAPOR LOOP THIS MORNING AS ROARING SUBTROPICAL
JET ACROSS THE SOUTHEAST IS DEEPENING A SIGNIFICANT SYSTEM THAT WILL
IMPACT THE NORTHEAST U.S. OVER THE NEXT 24 TO 36 HOURS. THE NORTHERN
STREAM JET WHICH IS ALSO HELPING TO CARVE OUT THE DEVELOPING TROUGH
IS DIVING SOUTHWARD OVER OUR REGION TODAY. ON THE CYCLONIC SIDE OF
THIS...FROM MANITOBA TO THE LOWER OHIO VALLEY...AN ELONGATED AREA OF
VORTICITY GENERATION WILL SUPPORT FORCING FOR ASCENT TODAY AND
TONIGHT...WITH THE MOST FOCUSED ZONE BEING A BETTER DEFINED WAVE
SEEN OVER CENTRAL MN EARLY THIS MORNING. THE RUN-TO-RUN TREND ON THE
RAP MODEL EARLY THIS MORNING IS FURTHER
WEST/SOUTHWEST...SUPPORTING UPSTREAM RADAR TRENDS AND FAVORING
NORTH CENTRAL IL TO GET IN A PERIOD OF SNOW BEGINNING LATER THIS
MORNING FOLLOWED BY A GRADUAL EXPANSION EAST. WHILE MOST OF THE
SNOW WILL BE LIGHT...THERE IS A WINDOW OF TIME LATE THIS MORNING
AND EARLY THIS AFTERNOON OVER NORTH CENTRAL ILLINOIS WHERE
850-700MB CONVERGENCE AND A F-GEN INDUCED CIRCULATION MAY ALLOW
FOR SPOTTY BURSTS OF MODERATE SNOW...WHICH HIGH-RESOLUTION
GUIDANCE TRIES TO INDICATE TOO. WITH ADJACENT OFFICES AND WPC
COLLABORATION...HAVE AROUND AN INCH FORECAST IN THE ROCKFORD
AREA...WITH AROUND A HALF INCH FURTHER EAST OF THERE. SOUTHWARD IN
THE FORECAST AREA THE DRY AIR SEEMS MORE PRONOUNCED...SO MAY END
UP JUST BEING FLURRIES AT TIMES.

THE FORCING ALOFT WEAKENS LATER THIS AFTERNOON AND EVENING SO
EXPECTING LIGHT SNOW TO BECOME MORE PATCHY IN COVERAGE. THE MOISTURE
IN THE ICE LAYER GRADUALLY DIMINISHES FROM WEST TO EAST THROUGH THE
EVENING...WITH STILL SOME LIGHT ADIABATIC ASCENT IN THE LOWEST
COUPLE THOUSAND FEET. IF THAT LOWEST LAYER IS SATURATED OR ABLE TO
THERE COULD BE A FREEZING DRIZZLE CONCERN...SO MAINTAIN THE GOING
CHANCE IN THE FORECAST.

FOR TEMPERATURES TODAY...DID BUMP DOWN SEVERAL DEGREES AS CLEARING
LAST NIGHT ALLOWED PLACES TO DROP QUICKLY AND NOW THE CLOUD CANOPY
WILL HINDER THEM FROM WARMING MUCH. FORECAST HIGHS ARE MAINLY IN THE
MID 20S WITH A FEW UPPER 20S POSSIBLE. WHILE THAT DOES NOT MAKE
HEADLINES IN JANUARY...IF THE FORECAST PANS OUT THIS WOULD BE THE
FIRST DAY WITH HIGHS BELOW 30 SINCE JANUARY 14TH.

MTF

&&

.LONG TERM...
315 AM CST

TUESDAY THROUGH SUNDAY...

HIGH PRESSURE WILL MOVE OVER THE AREA TUESDAY AFTERNOON AND NIGHT
BEFORE RETURN FLOW ON WEDNESDAY. THE CHALLENGE OF CLOUD COVER
PRESENTS ITSELF AGAIN ON TUESDAY AND WHILE HAVE SLOWED THE
CLEARING TREND TUESDAY MORNING...STILL THINK THE AFTERNOON SHOULD
SEE SOME BREAKS OF SUN AREAWIDE. SOUTHERLY FLOW ON WEDNESDAY IS
FORECAST TO BRING 925MB TEMPERATURES TO AROUND 0C WHICH USING
CLIMATOLOGY WITH LIMITED SNOW COVER SHOULD SUPPORT WIDESPREAD MID
TO UPPER 30S WITH A FEW LOWER 40S POSSIBLE IN THE SOUTHWEST CWA
OR CHICAGO METRO.

THE LARGE CLOSED LOW OFF THE BAJA OF CALIFORNIA THIS MORNING IS
FORECAST BY THE SUITE OF GUIDANCE TO DRIFT NORTHWARD AND GET CAUGHT
UP IN THE WESTERLIES BECOMING AN OPEN WAVE ACROSS THE MIDDLE OF THE
COUNTRY. WITH THE MASSIVE SYSTEM OFF THE NORTHEAST LIKELY TO SLOW
THINGS A BIT...CONTINUE TO LEAN WITH THE SLOWER EC AND GEM MODELS
WHICH WOULD FAVOR PRECIPITATION CHANCES MORE SO LATE WEDNESDAY NIGHT
AND THURSDAY...AROUND 12H SLOWER THAN THE GFS. FORECAST VERTICAL
PROFILES ON BOTH MODELS WOULD SUPPORT MORE OF RAIN AHEAD OF THIS
SYSTEM...ESPECIALLY CONSIDERING LOW-LEVEL TEMPERATURES SHOULD AT THE
VERY LEAST HOLD STEADY IF NOT MODERATE WEDNESDAY NIGHT...POTENTIALLY
TO 35 TO 38 DEGREES GIVEN EC AND GEM SOLUTIONS. ON THE BACKSIDE OF
THIS SYSTEM IT WOULD SEEM THERE WOULD BE AT LEAST A PERIOD OF SNOW
CHANCES. OBVIOUSLY A FEW DAYS OUT AND A CUTOFF LOW INVOLVED...A
LOT COULD CHANGE WITH SPECIFICS...BUT RIGHT NOW THIS IS NOT
LOOKING LIKE A HIGH IMPACT EVENT.

LATE THIS WEEK INTO THE WEEKEND THE NORTHERN STREAM FLOW PATTERN
IS FORECAST TO REMAIN QUITE PROGRESSIVE WHILE ANOTHER CUTOFF LOW
IS PROGGED TO DEVELOP OVER THE FAR SOUTHWEST US. THE 00Z EC HAS
FORECAST A STRONG SYSTEM IN THE NORTHWEST FLOW TO WIN OUT ABOUT A
WEEK FROM NOW AND DRAG DOWN -15C TO -20C 850MB TEMPERATURES.
SOMETHING TO MONITOR AS WE HEAD TOWARD THE FIRST DAYS OF FEBRUARY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* LIGHT SNOW DEVELOPING AROUND MID-DAY. MVFR CIGS/IFR VSBY
  POSSIBLE THIS AFTERNOON. MINOR ACCUMULATIONS.

* IFR CIGS AND MVFR FOG POSSIBLE TONIGHT WITH LINGERING FLURRIES.

* LIGHT/VARIABLE WINDS BECOME LIGHT SOUTH TODAY AND SOUTHEAST THIS
  EVENING. GENERALLY LESS THAN 10 KT. WINDS THEN BECOME LIGHT
  EAST-NORTHEAST LATE TONIGHT.

RATZER/DEUBELBEISS

//DISCUSSION...UPDATED 12Z...

WEAK SURFACE HIGH PRESSURE OVER THE AREA WILL MOVE QUICKLY OFF TO
THE SOUTHEAST THIS MORNING...AS AN AREA OF LOW PRESSURE RAPIDLY
APPROACHES FROM THE UPPER MIDWEST. VFR CLOUDS EXPECTED TO LOWER
THROUGH THE MORNING...WITH DEVELOPMENT OF LIGHT SNOW AND MVFR CIGS
BY/AROUND MID-DAY. A PERIOD OF LIGHT ACCUMULATING SNOW IS LIKELY
THROUGH THE AFTERNOON...WITH OCCASIONAL IFR VSBYS. SNOW IS
EXPECTED TO TAPER OFF BY EVENING THOUGH WILL LINGER IN LIGHTER
FASHION AND MAY MIX OR CHANGE TO FREEZING DRIZZLE LATE BEFORE
ENDING. MOIST LOW LEVELS AND LIGHT WINDS SUPPORT A PERIOD OF IFR
CIGS AND MVFR VSBYS IN FOG OVERNIGHT AS THE SURFACE LOW FILLS TO
JUST A TROUGH. SNOW ACCUMULATIONS LOOK TO RANGE FROM PERHAPS AN
INCH AROUND RFD...TO LESS THAN AN INCH FARTHER EAST ACROSS CHI
METRO TERMINALS.

WINDS CURRENTLY LIGHT/VARIABLE AS THE SURFACE RIDGE AXIS PASSES
ACROSS THE FORECAST AREA EARLY THIS MORNING. WINDS TO SHIFT SOUTH
DURING THE MORNING...THEN SOUTHEAST BY EVENING. SPEEDS GENERALLY
LESS THAN 10 KTS...THOUGH IF APPROACHING LOW IS SLOWER TO WEAKEN
THAN EXPECTED SOUTHEAST WINDS AROUND 10 KT WOULD BE POSSIBLE LATER
THIS AFTERNOON. WINDS TO TURN LIGHT NORTHEAST LATER TONIGHT INTO
EARLY TUESDAY.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM CONFIDENCE IN SNOW TIMING/INTENSITY TODAY INTO THIS
  EVENING.

* MEDIUM-LOW CONFIDENCE IN VIS/CIG TRENDS OVERNIGHT.

RATZER/DEUBELBEISS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...MAINLY VFR.

WEDNESDAY...MAINLY VFR DURING THE DAY. CHANCE OF RAIN/SNOW AT
NIGHT WITH MVFR/IFR POSSIBLE.

THURSDAY...CHANCE OF LIGHT SNOW. MVFR LIKELY/IFR POSSIBLE.

FRIDAY...MAINLY VFR.

SATURDAY...CHANCE OF SNOW/MVFR CIGS.

SUNDAY...MVFR CIGS POSSIBLE.

RATZER

&&

.MARINE...
143 AM CST

ONLY MARINE FORECAST CONCERNS ARE A BRIEF PERIOD OF ENHANCED
SOUTH-SOUTHEAST WINDS THIS AFTERNOON AND EVENING ESPECIALLY ON THE
NORTHERN PORTION OF THE LAKE...AND AGAIN WEDNESDAY AFTERNOON. GUSTY
NORTH WINDS NEAR 30 KT ARE ALSO LIKELY THURSDAY AND THURSDAY
NIGHT.

WINDS CONTINUE TO DIMINISH QUICKLY ACROSS LAKE MICHIGAN EARLY THIS
MORNING...AS WEAK HIGH PRESSURE RIDING SLIDES SOUTHEAST ACROSS THE
LAKE. THIS RIDGE WILL ALSO PASS QUICKLY OFF TO THE SOUTHEAST THIS
AFTERNOON IN WHAT REMAINS A PROGRESSIVE WEATHER PATTERN...WITH
ANOTHER LOW PRESSURE SYSTEM CURRENTLY NEAR LAKE WINNIPEG MOVING
QUICKLY SOUTHEAST INTO ILLINOIS BY MIDNIGHT TONIGHT WHILE FILLING.
THIS WILL RESULT IN WINDS BECOMING SOUTH AND INCREASING TO AROUND 20
KTS ON THE LAKE THIS AFTERNOON...THEN DECREASING AND BACKING TO THE
NORTHEAST INTO TUESDAY MORNING AS THE LOW PASSES AND WEAKENS.
ANOTHER HIGH PRESSURE RIDGE WILL SETTLE ACROSS THE WESTERN LAKES BY
TUESDAY EVENING.

ANOTHER MORE DEVELOPED LOW WILL FORM ACROSS THE LAKES TUESDAY
NIGHT...AND WILL DEEPEN SLIGHTLY AS IT APPROACHES FROM THE WEST
WEDNESDAY AND PASSES JUST SOUTH OF LAKE MICHIGAN EARLY THURSDAY
MORNING. THIS WILL AGAIN RESULT IN WINDS INITIALLY BECOMING SOUTH
AND INCREASING TO 20-25 KT WEDNESDAY AFTERNOON AND EVENING...THEN
BACKING TO THE NORTH EARLY THURSDAY AND GUSTING NEAR 30 KT AS THE
LOW PULLS AWAY ACROSS THE EASTERN LAKES AND UPPER OHIO VALLEY
THROUGH THURSDAY AFTERNOON AND NIGHT. HIGH PRESSURE THEN SPREADS
ACROSS THE REGION BY FRIDAY AFTERNOON.

FOR THE ILLINOIS AND NORTHWEST INDIANA NEARSHORE WATERS...AS SMALL
CRAFT ADVISORY REMAINS IN EFFECT UNTIL MID-MORNING TODAY...AS WAVES
CONTINUE TO SUBSIDE FROM YESTERDAY/LAST EVENINGS STRONG NORTHEAST
WINDS.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 261406
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
806 AM CST MON JAN 26 2015

.SHORT TERM...
315 AM CST

THROUGH TONIGHT...

AN IMPRESSIVE WATER VAPOR LOOP THIS MORNING AS ROARING SUBTROPICAL
JET ACROSS THE SOUTHEAST IS DEEPENING A SIGNIFICANT SYSTEM THAT WILL
IMPACT THE NORTHEAST U.S. OVER THE NEXT 24 TO 36 HOURS. THE NORTHERN
STREAM JET WHICH IS ALSO HELPING TO CARVE OUT THE DEVELOPING TROUGH
IS DIVING SOUTHWARD OVER OUR REGION TODAY. ON THE CYCLONIC SIDE OF
THIS...FROM MANITOBA TO THE LOWER OHIO VALLEY...AN ELONGATED AREA OF
VORTICITY GENERATION WILL SUPPORT FORCING FOR ASCENT TODAY AND
TONIGHT...WITH THE MOST FOCUSED ZONE BEING A BETTER DEFINED WAVE
SEEN OVER CENTRAL MN EARLY THIS MORNING. THE RUN-TO-RUN TREND ON THE
RAP MODEL EARLY THIS MORNING IS FURTHER
WEST/SOUTHWEST...SUPPORTING UPSTREAM RADAR TRENDS AND FAVORING
NORTH CENTRAL IL TO GET IN A PERIOD OF SNOW BEGINNING LATER THIS
MORNING FOLLOWED BY A GRADUAL EXPANSION EAST. WHILE MOST OF THE
SNOW WILL BE LIGHT...THERE IS A WINDOW OF TIME LATE THIS MORNING
AND EARLY THIS AFTERNOON OVER NORTH CENTRAL ILLINOIS WHERE
850-700MB CONVERGENCE AND A F-GEN INDUCED CIRCULATION MAY ALLOW
FOR SPOTTY BURSTS OF MODERATE SNOW...WHICH HIGH-RESOLUTION
GUIDANCE TRIES TO INDICATE TOO. WITH ADJACENT OFFICES AND WPC
COLLABORATION...HAVE AROUND AN INCH FORECAST IN THE ROCKFORD
AREA...WITH AROUND A HALF INCH FURTHER EAST OF THERE. SOUTHWARD IN
THE FORECAST AREA THE DRY AIR SEEMS MORE PRONOUNCED...SO MAY END
UP JUST BEING FLURRIES AT TIMES.

THE FORCING ALOFT WEAKENS LATER THIS AFTERNOON AND EVENING SO
EXPECTING LIGHT SNOW TO BECOME MORE PATCHY IN COVERAGE. THE MOISTURE
IN THE ICE LAYER GRADUALLY DIMINISHES FROM WEST TO EAST THROUGH THE
EVENING...WITH STILL SOME LIGHT ADIABATIC ASCENT IN THE LOWEST
COUPLE THOUSAND FEET. IF THAT LOWEST LAYER IS SATURATED OR ABLE TO
THERE COULD BE A FREEZING DRIZZLE CONCERN...SO MAINTAIN THE GOING
CHANCE IN THE FORECAST.

FOR TEMPERATURES TODAY...DID BUMP DOWN SEVERAL DEGREES AS CLEARING
LAST NIGHT ALLOWED PLACES TO DROP QUICKLY AND NOW THE CLOUD CANOPY
WILL HINDER THEM FROM WARMING MUCH. FORECAST HIGHS ARE MAINLY IN THE
MID 20S WITH A FEW UPPER 20S POSSIBLE. WHILE THAT DOES NOT MAKE
HEADLINES IN JANUARY...IF THE FORECAST PANS OUT THIS WOULD BE THE
FIRST DAY WITH HIGHS BELOW 30 SINCE JANUARY 14TH.

MTF

&&

.LONG TERM...
315 AM CST

TUESDAY THROUGH SUNDAY...

HIGH PRESSURE WILL MOVE OVER THE AREA TUESDAY AFTERNOON AND NIGHT
BEFORE RETURN FLOW ON WEDNESDAY. THE CHALLENGE OF CLOUD COVER
PRESENTS ITSELF AGAIN ON TUESDAY AND WHILE HAVE SLOWED THE
CLEARING TREND TUESDAY MORNING...STILL THINK THE AFTERNOON SHOULD
SEE SOME BREAKS OF SUN AREAWIDE. SOUTHERLY FLOW ON WEDNESDAY IS
FORECAST TO BRING 925MB TEMPERATURES TO AROUND 0C WHICH USING
CLIMATOLOGY WITH LIMITED SNOW COVER SHOULD SUPPORT WIDESPREAD MID
TO UPPER 30S WITH A FEW LOWER 40S POSSIBLE IN THE SOUTHWEST CWA
OR CHICAGO METRO.

THE LARGE CLOSED LOW OFF THE BAJA OF CALIFORNIA THIS MORNING IS
FORECAST BY THE SUITE OF GUIDANCE TO DRIFT NORTHWARD AND GET CAUGHT
UP IN THE WESTERLIES BECOMING AN OPEN WAVE ACROSS THE MIDDLE OF THE
COUNTRY. WITH THE MASSIVE SYSTEM OFF THE NORTHEAST LIKELY TO SLOW
THINGS A BIT...CONTINUE TO LEAN WITH THE SLOWER EC AND GEM MODELS
WHICH WOULD FAVOR PRECIPITATION CHANCES MORE SO LATE WEDNESDAY NIGHT
AND THURSDAY...AROUND 12H SLOWER THAN THE GFS. FORECAST VERTICAL
PROFILES ON BOTH MODELS WOULD SUPPORT MORE OF RAIN AHEAD OF THIS
SYSTEM...ESPECIALLY CONSIDERING LOW-LEVEL TEMPERATURES SHOULD AT THE
VERY LEAST HOLD STEADY IF NOT MODERATE WEDNESDAY NIGHT...POTENTIALLY
TO 35 TO 38 DEGREES GIVEN EC AND GEM SOLUTIONS. ON THE BACKSIDE OF
THIS SYSTEM IT WOULD SEEM THERE WOULD BE AT LEAST A PERIOD OF SNOW
CHANCES. OBVIOUSLY A FEW DAYS OUT AND A CUTOFF LOW INVOLVED...A
LOT COULD CHANGE WITH SPECIFICS...BUT RIGHT NOW THIS IS NOT
LOOKING LIKE A HIGH IMPACT EVENT.

LATE THIS WEEK INTO THE WEEKEND THE NORTHERN STREAM FLOW PATTERN
IS FORECAST TO REMAIN QUITE PROGRESSIVE WHILE ANOTHER CUTOFF LOW
IS PROGGED TO DEVELOP OVER THE FAR SOUTHWEST US. THE 00Z EC HAS
FORECAST A STRONG SYSTEM IN THE NORTHWEST FLOW TO WIN OUT ABOUT A
WEEK FROM NOW AND DRAG DOWN -15C TO -20C 850MB TEMPERATURES.
SOMETHING TO MONITOR AS WE HEAD TOWARD THE FIRST DAYS OF FEBRUARY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* LIGHT SNOW DEVELOPING AROUND MID-DAY. MVFR CIGS/IFR VSBY
  POSSIBLE THIS AFTERNOON. MINOR ACCUMULATIONS.

* IFR CIGS AND MVFR FOG POSSIBLE TONIGHT WITH LINGERING FLURRIES.

* LIGHT/VARIABLE WINDS BECOME LIGHT SOUTH TODAY AND SOUTHEAST THIS
  EVENING. GENERALLY LESS THAN 10 KT. WINDS THEN BECOME LIGHT
  EAST-NORTHEAST LATE TONIGHT.

RATZER/DEUBELBEISS

//DISCUSSION...UPDATED 12Z...

WEAK SURFACE HIGH PRESSURE OVER THE AREA WILL MOVE QUICKLY OFF TO
THE SOUTHEAST THIS MORNING...AS AN AREA OF LOW PRESSURE RAPIDLY
APPROACHES FROM THE UPPER MIDWEST. VFR CLOUDS EXPECTED TO LOWER
THROUGH THE MORNING...WITH DEVELOPMENT OF LIGHT SNOW AND MVFR CIGS
BY/AROUND MID-DAY. A PERIOD OF LIGHT ACCUMULATING SNOW IS LIKELY
THROUGH THE AFTERNOON...WITH OCCASIONAL IFR VSBYS. SNOW IS
EXPECTED TO TAPER OFF BY EVENING THOUGH WILL LINGER IN LIGHTER
FASHION AND MAY MIX OR CHANGE TO FREEZING DRIZZLE LATE BEFORE
ENDING. MOIST LOW LEVELS AND LIGHT WINDS SUPPORT A PERIOD OF IFR
CIGS AND MVFR VSBYS IN FOG OVERNIGHT AS THE SURFACE LOW FILLS TO
JUST A TROUGH. SNOW ACCUMULATIONS LOOK TO RANGE FROM PERHAPS AN
INCH AROUND RFD...TO LESS THAN AN INCH FARTHER EAST ACROSS CHI
METRO TERMINALS.

WINDS CURRENTLY LIGHT/VARIABLE AS THE SURFACE RIDGE AXIS PASSES
ACROSS THE FORECAST AREA EARLY THIS MORNING. WINDS TO SHIFT SOUTH
DURING THE MORNING...THEN SOUTHEAST BY EVENING. SPEEDS GENERALLY
LESS THAN 10 KTS...THOUGH IF APPROACHING LOW IS SLOWER TO WEAKEN
THAN EXPECTED SOUTHEAST WINDS AROUND 10 KT WOULD BE POSSIBLE LATER
THIS AFTERNOON. WINDS TO TURN LIGHT NORTHEAST LATER TONIGHT INTO
EARLY TUESDAY.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM CONFIDENCE IN SNOW TIMING/INTENSITY TODAY INTO THIS
  EVENING.

* MEDIUM-LOW CONFIDENCE IN VIS/CIG TRENDS OVERNIGHT.

RATZER/DEUBELBEISS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...MAINLY VFR.

WEDNESDAY...MAINLY VFR DURING THE DAY. CHANCE OF RAIN/SNOW AT
NIGHT WITH MVFR/IFR POSSIBLE.

THURSDAY...CHANCE OF LIGHT SNOW. MVFR LIKELY/IFR POSSIBLE.

FRIDAY...MAINLY VFR.

SATURDAY...CHANCE OF SNOW/MVFR CIGS.

SUNDAY...MVFR CIGS POSSIBLE.

RATZER

&&

.MARINE...
143 AM CST

ONLY MARINE FORECAST CONCERNS ARE A BRIEF PERIOD OF ENHANCED
SOUTH-SOUTHEAST WINDS THIS AFTERNOON AND EVENING ESPECIALLY ON THE
NORTHERN PORTION OF THE LAKE...AND AGAIN WEDNESDAY AFTERNOON. GUSTY
NORTH WINDS NEAR 30 KT ARE ALSO LIKELY THURSDAY AND THURSDAY
NIGHT.

WINDS CONTINUE TO DIMINISH QUICKLY ACROSS LAKE MICHIGAN EARLY THIS
MORNING...AS WEAK HIGH PRESSURE RIDING SLIDES SOUTHEAST ACROSS THE
LAKE. THIS RIDGE WILL ALSO PASS QUICKLY OFF TO THE SOUTHEAST THIS
AFTERNOON IN WHAT REMAINS A PROGRESSIVE WEATHER PATTERN...WITH
ANOTHER LOW PRESSURE SYSTEM CURRENTLY NEAR LAKE WINNIPEG MOVING
QUICKLY SOUTHEAST INTO ILLINOIS BY MIDNIGHT TONIGHT WHILE FILLING.
THIS WILL RESULT IN WINDS BECOMING SOUTH AND INCREASING TO AROUND 20
KTS ON THE LAKE THIS AFTERNOON...THEN DECREASING AND BACKING TO THE
NORTHEAST INTO TUESDAY MORNING AS THE LOW PASSES AND WEAKENS.
ANOTHER HIGH PRESSURE RIDGE WILL SETTLE ACROSS THE WESTERN LAKES BY
TUESDAY EVENING.

ANOTHER MORE DEVELOPED LOW WILL FORM ACROSS THE LAKES TUESDAY
NIGHT...AND WILL DEEPEN SLIGHTLY AS IT APPROACHES FROM THE WEST
WEDNESDAY AND PASSES JUST SOUTH OF LAKE MICHIGAN EARLY THURSDAY
MORNING. THIS WILL AGAIN RESULT IN WINDS INITIALLY BECOMING SOUTH
AND INCREASING TO 20-25 KT WEDNESDAY AFTERNOON AND EVENING...THEN
BACKING TO THE NORTH EARLY THURSDAY AND GUSTING NEAR 30 KT AS THE
LOW PULLS AWAY ACROSS THE EASTERN LAKES AND UPPER OHIO VALLEY
THROUGH THURSDAY AFTERNOON AND NIGHT. HIGH PRESSURE THEN SPREADS
ACROSS THE REGION BY FRIDAY AFTERNOON.

FOR THE ILLINOIS AND NORTHWEST INDIANA NEARSHORE WATERS...AS SMALL
CRAFT ADVISORY REMAINS IN EFFECT UNTIL MID-MORNING TODAY...AS WAVES
CONTINUE TO SUBSIDE FROM YESTERDAY/LAST EVENINGS STRONG NORTHEAST
WINDS.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 261149
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
549 AM CST MON JAN 26 2015

.SHORT TERM...
315 AM CST

THROUGH TONIGHT...

AN IMPRESSIVE WATER VAPOR LOOP THIS MORNING AS ROARING SUBTROPICAL
JET ACROSS THE SOUTHEAST IS DEEPENING A SIGNIFICANT SYSTEM THAT WILL
IMPACT THE NORTHEAST U.S. OVER THE NEXT 24 TO 36 HOURS. THE NORTHERN
STREAM JET WHICH IS ALSO HELPING TO CARVE OUT THE DEVELOPING TROUGH
IS DIVING SOUTHWARD OVER OUR REGION TODAY. ON THE CYCLONIC SIDE OF
THIS...FROM MANITOBA TO THE LOWER OHIO VALLEY...AN ELONGATED AREA OF
VORTICITY GENERATION WILL SUPPORT FORCING FOR ASCENT TODAY AND
TONIGHT...WITH THE MOST FOCUSED ZONE BEING A BETTER DEFINED WAVE
SEEN OVER CENTRAL MN EARLY THIS MORNING. THE RUN-TO-RUN TREND ON THE
RAP MODEL EARLY THIS MORNING IS FURTHER
WEST/SOUTHWEST...SUPPORTING UPSTREAM RADAR TRENDS AND FAVORING
NORTH CENTRAL IL TO GET IN A PERIOD OF SNOW BEGINNING LATER THIS
MORNING FOLLOWED BY A GRADUAL EXPANSION EAST. WHILE MOST OF THE
SNOW WILL BE LIGHT...THERE IS A WINDOW OF TIME LATE THIS MORNING
AND EARLY THIS AFTERNOON OVER NORTH CENTRAL ILLINOIS WHERE
850-700MB CONVERGENCE AND A F-GEN INDUCED CIRCULATION MAY ALLOW
FOR SPOTTY BURSTS OF MODERATE SNOW...WHICH HIGH-RESOLUTION
GUIDANCE TRIES TO INDICATE TOO. WITH ADJACENT OFFICES AND WPC
COLLABORATION...HAVE AROUND AN INCH FORECAST IN THE ROCKFORD
AREA...WITH AROUND A HALF INCH FURTHER EAST OF THERE. SOUTHWARD IN
THE FORECAST AREA THE DRY AIR SEEMS MORE PRONOUNCED...SO MAY END
UP JUST BEING FLURRIES AT TIMES.

THE FORCING ALOFT WEAKENS LATER THIS AFTERNOON AND EVENING SO
EXPECTING LIGHT SNOW TO BECOME MORE PATCHY IN COVERAGE. THE MOISTURE
IN THE ICE LAYER GRADUALLY DIMINISHES FROM WEST TO EAST THROUGH THE
EVENING...WITH STILL SOME LIGHT ADIABATIC ASCENT IN THE LOWEST
COUPLE THOUSAND FEET. IF THAT LOWEST LAYER IS SATURATED OR ABLE TO
THERE COULD BE A FREEZING DRIZZLE CONCERN...SO MAINTAIN THE GOING
CHANCE IN THE FORECAST.

FOR TEMPERATURES TODAY...DID BUMP DOWN SEVERAL DEGREES AS CLEARING
LAST NIGHT ALLOWED PLACES TO DROP QUICKLY AND NOW THE CLOUD CANOPY
WILL HINDER THEM FROM WARMING MUCH. FORECAST HIGHS ARE MAINLY IN THE
MID 20S WITH A FEW UPPER 20S POSSIBLE. WHILE THAT DOES NOT MAKE
HEADLINES IN JANUARY...IF THE FORECAST PANS OUT THIS WOULD BE THE
FIRST DAY WITH HIGHS BELOW 30 SINCE JANUARY 14TH.

MTF

&&

.LONG TERM...
315 AM CST

TUESDAY THROUGH SUNDAY...

HIGH PRESSURE WILL MOVE OVER THE AREA TUESDAY AFTERNOON AND NIGHT
BEFORE RETURN FLOW ON WEDNESDAY. THE CHALLENGE OF CLOUD COVER
PRESENTS ITSELF AGAIN ON TUESDAY AND WHILE HAVE SLOWED THE
CLEARING TREND TUESDAY MORNING...STILL THINK THE AFTERNOON SHOULD
SEE SOME BREAKS OF SUN AREAWIDE. SOUTHERLY FLOW ON WEDNESDAY IS
FORECAST TO BRING 925MB TEMPERATURES TO AROUND 0C WHICH USING
CLIMATOLOGY WITH LIMITED SNOW COVER SHOULD SUPPORT WIDESPREAD MID
TO UPPER 30S WITH A FEW LOWER 40S POSSIBLE IN THE SOUTHWEST CWA
OR CHICAGO METRO.

THE LARGE CLOSED LOW OFF THE BAJA OF CALIFORNIA THIS MORNING IS
FORECAST BY THE SUITE OF GUIDANCE TO DRIFT NORTHWARD AND GET CAUGHT
UP IN THE WESTERLIES BECOMING AN OPEN WAVE ACROSS THE MIDDLE OF THE
COUNTRY. WITH THE MASSIVE SYSTEM OFF THE NORTHEAST LIKELY TO SLOW
THINGS A BIT...CONTINUE TO LEAN WITH THE SLOWER EC AND GEM MODELS
WHICH WOULD FAVOR PRECIPITATION CHANCES MORE SO LATE WEDNESDAY NIGHT
AND THURSDAY...AROUND 12H SLOWER THAN THE GFS. FORECAST VERTICAL
PROFILES ON BOTH MODELS WOULD SUPPORT MORE OF RAIN AHEAD OF THIS
SYSTEM...ESPECIALLY CONSIDERING LOW-LEVEL TEMPERATURES SHOULD AT THE
VERY LEAST HOLD STEADY IF NOT MODERATE WEDNESDAY NIGHT...POTENTIALLY
TO 35 TO 38 DEGREES GIVEN EC AND GEM SOLUTIONS. ON THE BACKSIDE OF
THIS SYSTEM IT WOULD SEEM THERE WOULD BE AT LEAST A PERIOD OF SNOW
CHANCES. OBVIOUSLY A FEW DAYS OUT AND A CUTOFF LOW INVOLVED...A
LOT COULD CHANGE WITH SPECIFICS...BUT RIGHT NOW THIS IS NOT
LOOKING LIKE A HIGH IMPACT EVENT.

LATE THIS WEEK INTO THE WEEKEND THE NORTHERN STREAM FLOW PATTERN
IS FORECAST TO REMAIN QUITE PROGRESSIVE WHILE ANOTHER CUTOFF LOW
IS PROGGED TO DEVELOP OVER THE FAR SOUTHWEST US. THE 00Z EC HAS
FORECAST A STRONG SYSTEM IN THE NORTHWEST FLOW TO WIN OUT ABOUT A
WEEK FROM NOW AND DRAG DOWN -15C TO -20C 850MB TEMPERATURES.
SOMETHING TO MONITOR AS WE HEAD TOWARD THE FIRST DAYS OF FEBRUARY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* LIGHT SNOW DEVELOPING AROUND MID-DAY. MVFR CIGS/IFR VSBY
  POSSIBLE THIS AFTERNOON. MINOR ACCUMULATIONS.

* IFR CIGS AND MVFR FOG POSSIBLE TONIGHT WITH LINGERING FLURRIES.

* LIGHT/VARIABLE WINDS BECOME LIGHT SOUTH TODAY AND SOUTHEAST THIS
  EVENING. GENERALLY LESS THAN 10 KT. WINDS THEN BECOME LIGHT
  EAST-NORTHEAST LATE TONIGHT.

RATZER

//DISCUSSION...UPDATED 12Z...

WEAK SURFACE HIGH PRESSURE OVER THE AREA WILL MOVE QUICKLY OFF TO
THE SOUTHEAST THIS MORNING...AS AN AREA OF LOW PRESSURE RAPIDLY
APPROACHES FROM THE UPPER MIDWEST. VFR CLOUDS EXPECTED TO LOWER
THROUGH THE MORNING...WITH DEVELOPMENT OF LIGHT SNOW AND MVFR CIGS
BY/AROUND MID-DAY. A PERIOD OF LIGHT ACCUMULATING SNOW IS LIKELY
THROUGH THE AFTERNOON...WITH OCCASIONAL IFR VSBYS. SNOW IS
EXPECTED TO TAPER OFF BY EVENING THOUGH WILL LINGER IN LIGHTER
FASHION AND MAY MIX OR CHANGE TO FREEZING DRIZZLE LATE BEFORE
ENDING. MOIST LOW LEVELS AND LIGHT WINDS SUPPORT A PERIOD OF IFR
CIGS AND MVFR VSBYS IN FOG OVERNIGHT AS THE SURFACE LOW FILLS TO
JUST A TROUGH. SNOW ACCUMULATIONS LOOK TO RANGE FROM PERHAPS AN
INCH AROUND RFD...TO LESS THAN AN INCH FARTHER EAST ACROSS CHI
METRO TERMINALS.

WINDS CURRENTLY LIGHT/VARIABLE AS THE SURFACE RIDGE AXIS PASSES
ACROSS THE FORECAST AREA EARLY THIS MORNING. WINDS TO SHIFT SOUTH
DURING THE MORNING...THEN SOUTHEAST BY EVENING. SPEEDS GENERALLY
LESS THAN 10 KTS...THOUGH IF APPROACHING LOW IS SLOWER TO WEAKEN
THAN EXPECTED SOUTHEAST WINDS AROUND 10 KT WOULD BE POSSIBLE LATER
THIS AFTERNOON. WINDS TO TURN LIGHT NORTHEAST LATER TONIGHT INTO
EARLY TUESDAY.

RATZER


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM CONFIDENCE IN SNOW TIMING/INTENSITY TODAY INTO THIS
  EVENING.

* MEDIUM-LOW CONFIDENCE IN VIS/CIG TRENDS OVERNIGHT.

RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...MAINLY VFR.

WEDNESDAY...MAINLY VFR DURING THE DAY. CHANCE OF RAIN/SNOW AT
NIGHT WITH MVFR/IFR POSSIBLE.

THURSDAY...CHANCE OF LIGHT SNOW. MVFR LIKELY/IFR POSSIBLE.

FRIDAY...MAINLY VFR.

SATURDAY...CHANCE OF SNOW/MVFR CIGS.

SUNDAY...MVFR CIGS POSSIBLE.

RATZER

&&

.MARINE...
143 AM CST

ONLY MARINE FORECAST CONCERNS ARE A BRIEF PERIOD OF ENHANCED
SOUTH-SOUTHEAST WINDS THIS AFTERNOON AND EVENING ESPECIALLY ON THE
NORTHERN PORTION OF THE LAKE...AND AGAIN WEDNESDAY AFTERNOON. GUSTY
NORTH WINDS NEAR 30 KT ARE ALSO LIKELY THURSDAY AND THURSDAY
NIGHT.

WINDS CONTINUE TO DIMINISH QUICKLY ACROSS LAKE MICHIGAN EARLY THIS
MORNING...AS WEAK HIGH PRESSURE RIDING SLIDES SOUTHEAST ACROSS THE
LAKE. THIS RIDGE WILL ALSO PASS QUICKLY OFF TO THE SOUTHEAST THIS
AFTERNOON IN WHAT REMAINS A PROGRESSIVE WEATHER PATTERN...WITH
ANOTHER LOW PRESSURE SYSTEM CURRENTLY NEAR LAKE WINNIPEG MOVING
QUICKLY SOUTHEAST INTO ILLINOIS BY MIDNIGHT TONIGHT WHILE FILLING.
THIS WILL RESULT IN WINDS BECOMING SOUTH AND INCREASING TO AROUND 20
KTS ON THE LAKE THIS AFTERNOON...THEN DECREASING AND BACKING TO THE
NORTHEAST INTO TUESDAY MORNING AS THE LOW PASSES AND WEAKENS.
ANOTHER HIGH PRESSURE RIDGE WILL SETTLE ACROSS THE WESTERN LAKES BY
TUESDAY EVENING.

ANOTHER MORE DEVELOPED LOW WILL FORM ACROSS THE LAKES TUESDAY
NIGHT...AND WILL DEEPEN SLIGHTLY AS IT APPROACHES FROM THE WEST
WEDNESDAY AND PASSES JUST SOUTH OF LAKE MICHIGAN EARLY THURSDAY
MORNING. THIS WILL AGAIN RESULT IN WINDS INITIALLY BECOMING SOUTH
AND INCREASING TO 20-25 KT WEDNESDAY AFTERNOON AND EVENING...THEN
BACKING TO THE NORTH EARLY THURSDAY AND GUSTING NEAR 30 KT AS THE
LOW PULLS AWAY ACROSS THE EASTERN LAKES AND UPPER OHIO VALLEY
THROUGH THURSDAY AFTERNOON AND NIGHT. HIGH PRESSURE THEN SPREADS
ACROSS THE REGION BY FRIDAY AFTERNOON.

FOR THE ILLINOIS AND NORTHWEST INDIANA NEARSHORE WATERS...AS SMALL
CRAFT ADVISORY REMAINS IN EFFECT UNTIL MID-MORNING TODAY...AS WAVES
CONTINUE TO SUBSIDE FROM YESTERDAY/LAST EVENINGS STRONG NORTHEAST
WINDS.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 260919
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
319 AM CST MON JAN 26 2015

.SHORT TERM...
315 AM CST

THROUGH TONIGHT...

AN IMPRESSIVE WATER VAPOR LOOP THIS MORNING AS ROARING SUBTROPICAL
JET ACROSS THE SOUTHEAST IS DEEPENING A SIGNIFICANT SYSTEM THAT WILL
IMPACT THE NORTHEAST U.S. OVER THE NEXT 24 TO 36 HOURS. THE NORTHERN
STREAM JET WHICH IS ALSO HELPING TO CARVE OUT THE DEVELOPING TROUGH
IS DIVING SOUTHWARD OVER OUR REGION TODAY. ON THE CYCLONIC SIDE OF
THIS...FROM MANITOBA TO THE LOWER OHIO VALLEY...AN ELONGATED AREA OF
VORTICITY GENERATION WILL SUPPORT FORCING FOR ASCENT TODAY AND
TONIGHT...WITH THE MOST FOCUSED ZONE BEING A BETTER DEFINED WAVE
SEEN OVER CENTRAL MN EARLY THIS MORNING. THE RUN-TO-RUN TREND ON THE
RAP MODEL EARLY THIS MORNING IS FURTHER
WEST/SOUTHWEST...SUPPORTING UPSTREAM RADAR TRENDS AND FAVORING
NORTH CENTRAL IL TO GET IN A PERIOD OF SNOW BEGINNING LATER THIS
MORNING FOLLOWED BY A GRADUAL EXPANSION EAST. WHILE MOST OF THE
SNOW WILL BE LIGHT...THERE IS A WINDOW OF TIME LATE THIS MORNING
AND EARLY THIS AFTERNOON OVER NORTH CENTRAL ILLINOIS WHERE
850-700MB CONVERGENCE AND A F-GEN INDUCED CIRCULATION MAY ALLOW
FOR SPOTTY BURSTS OF MODERATE SNOW...WHICH HIGH-RESOLUTION
GUIDANCE TRIES TO INDICATE TOO. WITH ADJACENT OFFICES AND WPC
COLLABORATION...HAVE AROUND AN INCH FORECAST IN THE ROCKFORD
AREA...WITH AROUND A HALF INCH FURTHER EAST OF THERE. SOUTHWARD IN
THE FORECAST AREA THE DRY AIR SEEMS MORE PRONOUNCED...SO MAY END
UP JUST BEING FLURRIES AT TIMES.

THE FORCING ALOFT WEAKENS LATER THIS AFTERNOON AND EVENING SO
EXPECTING LIGHT SNOW TO BECOME MORE PATCHY IN COVERAGE. THE MOISTURE
IN THE ICE LAYER GRADUALLY DIMINISHES FROM WEST TO EAST THROUGH THE
EVENING...WITH STILL SOME LIGHT ADIABATIC ASCENT IN THE LOWEST
COUPLE THOUSAND FEET. IF THAT LOWEST LAYER IS SATURATED OR ABLE TO
THERE COULD BE A FREEZING DRIZZLE CONCERN...SO MAINTAIN THE GOING
CHANCE IN THE FORECAST.

FOR TEMPERATURES TODAY...DID BUMP DOWN SEVERAL DEGREES AS CLEARING
LAST NIGHT ALLOWED PLACES TO DROP QUICKLY AND NOW THE CLOUD CANOPY
WILL HINDER THEM FROM WARMING MUCH. FORECAST HIGHS ARE MAINLY IN THE
MID 20S WITH A FEW UPPER 20S POSSIBLE. WHILE THAT DOES NOT MAKE
HEADLINES IN JANUARY...IF THE FORECAST PANS OUT THIS WOULD BE THE
FIRST DAY WITH HIGHS BELOW 30 SINCE JANUARY 14TH.

MTF

&&

.LONG TERM...
315 AM CST

TUESDAY THROUGH SUNDAY...

HIGH PRESSURE WILL MOVE OVER THE AREA TUESDAY AFTERNOON AND NIGHT
BEFORE RETURN FLOW ON WEDNESDAY. THE CHALLENGE OF CLOUD COVER
PRESENTS ITSELF AGAIN ON TUESDAY AND WHILE HAVE SLOWED THE
CLEARING TREND TUESDAY MORNING...STILL THINK THE AFTERNOON SHOULD
SEE SOME BREAKS OF SUN AREAWIDE. SOUTHERLY FLOW ON WEDNESDAY IS
FORECAST TO BRING 925MB TEMPERATURES TO AROUND 0C WHICH USING
CLIMATOLOGY WITH LIMITED SNOW COVER SHOULD SUPPORT WIDESPREAD MID
TO UPPER 30S WITH A FEW LOWER 40S POSSIBLE IN THE SOUTHWEST CWA
OR CHICAGO METRO.

THE LARGE CLOSED LOW OFF THE BAJA OF CALIFORNIA THIS MORNING IS
FORECAST BY THE SUITE OF GUIDANCE TO DRIFT NORTHWARD AND GET CAUGHT
UP IN THE WESTERLIES BECOMING AN OPEN WAVE ACROSS THE MIDDLE OF THE
COUNTRY. WITH THE MASSIVE SYSTEM OFF THE NORTHEAST LIKELY TO SLOW
THINGS A BIT...CONTINUE TO LEAN WITH THE SLOWER EC AND GEM MODELS
WHICH WOULD FAVOR PRECIPITATION CHANCES MORE SO LATE WEDNESDAY NIGHT
AND THURSDAY...AROUND 12H SLOWER THAN THE GFS. FORECAST VERTICAL
PROFILES ON BOTH MODELS WOULD SUPPORT MORE OF RAIN AHEAD OF THIS
SYSTEM...ESPECIALLY CONSIDERING LOW-LEVEL TEMPERATURES SHOULD AT THE
VERY LEAST HOLD STEADY IF NOT MODERATE WEDNESDAY NIGHT...POTENTIALLY
TO 35 TO 38 DEGREES GIVEN EC AND GEM SOLUTIONS. ON THE BACKSIDE OF
THIS SYSTEM IT WOULD SEEM THERE WOULD BE AT LEAST A PERIOD OF SNOW
CHANCES. OBVIOUSLY A FEW DAYS OUT AND A CUTOFF LOW INVOLVED...A
LOT COULD CHANGE WITH SPECIFICS...BUT RIGHT NOW THIS IS NOT
LOOKING LIKE A HIGH IMPACT EVENT.

LATE THIS WEEK INTO THE WEEKEND THE NORTHERN STREAM FLOW PATTERN
IS FORECAST TO REMAIN QUITE PROGRESSIVE WHILE ANOTHER CUTOFF LOW
IS PROGGED TO DEVELOP OVER THE FAR SOUTHWEST US. THE 00Z EC HAS
FORECAST A STRONG SYSTEM IN THE NORTHWEST FLOW TO WIN OUT ABOUT A
WEEK FROM NOW AND DRAG DOWN -15C TO -20C 850MB TEMPERATURES.
SOMETHING TO MONITOR AS WE HEAD TOWARD THE FIRST DAYS OF FEBRUARY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* BRIEF HIGH-END MVFR CIGS OFF LAKE MICHIGAN SHOULD SCATTER BY
  SUNRISE.

* PERIOD OF LIGHT SNOW POSSIBLE THIS AFTERNOON/EVENING WITH
  REDEVELOPMENT OF MVFR CIGS WHICH LINGER TONIGHT.

RATZER

//DISCUSSION...UPDATED 06Z...

WEAK HIGH PRESSURE RIDGE QUICKLY MOVING INTO FORECAST AREA FROM
THE NORTHWEST OVERNIGHT...THOUGH NORTHEAST WINDS HAVE RESULTED IN
A LAKE-INDUCED PLUME OF MVFR STRATOCU FROM ABOUT ORD EAST...WITH
BASES AROUND 2500 FT. THESE CIGS WILL LIKELY AFFECT ORD/MDW/GYY
UNTIL ABOUT SUNRISE...WHEN MODELS DEPICT NORTHEAST FLOW QUICKLY
BECOMING DISORGANIZED WITH APPROACH OF SFC RIDGE. SFC WINDS TO
BECOME LIGHT/VARIABLE FOR A TIME THIS MORNING AS THE SURFACE HIGH
PRESSURE RIDGE MOVES ACROSS THE TERMINALS...GENERALLY FLOPPING
FROM LIGHT NORTHERLY TO LIGHT SOUTHERLY BY MID-DAY.

IR SATELLITE PICS ALREADY SHOWING HIGH CLOUDS SPILLING INTO THE
REGION FROM THE NORTHWEST AHEAD OF THE NEXT WEAK CLIPPER SYSTEM
WHICH WILL AFFECT THE AREA MONDAY AFTERNOON/EVENING. LOW LEVELS
ARE INITIALLY DRY AND WILL TAKE SOME WORK TO SATURATE FROM ABOVE
AS MID-LEVEL FORCING INCREASES MID-DAY INTO EARLY AFTERNOON. MOST
GUIDANCE DOES INDICATE SOME LIGHT SNOW DEVELOPING DURING THE
PERIOD...THOUGH A COMBINATION OF WEAKENING FORCING AND FORCING
FOCUSED BELOW TEMP LAYER CONDUCIVE TO LARGER SNOWFLAKE GROWTH
SUGGESTS THIS WILL BE RATHER LIGHT. WHILE A FEW INCONSEQUENTIAL
FLURRIES COULD BEGIN SOONER...THE TIMING OF THE PERIOD MOST
LIKELY TO SEE SOME LIGHT SNOW AND MVFR CIG/POSSIBLE IFR VSBY LOOKS
TO BE DURING THE AFTERNOON AT RFD...AND DURING THE LATE AFTN/EARLY
EVENING FOR CHICAGO TERMINALS. SNOW SHOULD TAPER OFF DURING THE
EVENING AT RFD AND BY LATE EVENING FOR CHICAGO TERMINALS...WITH
LOSS OF STRONGER LIFT AND DRYING IN MID-LEVELS. SOME INDICATION
THAT THERE COULD BE A BRIEF PERIOD OF FREEZING DRIZZLE AS THE SNOW
ENDS ESPECIALLY AT RFD WHERE MID-LEVELS DRY A LITTLE MORE
QUICKLY...THOUGH MODELS MAY BE OVERDOING THE DEGREE OF SATURATION
IN THE BOUNDARY LAYER AND CONFIDENCE IS LOW THAT FZDZ WOULD OCCUR.
IT DOES HOWEVER APPEAR THAT SOME SORT OF HIGH-IFR OR LOW-MVFR CIG
MAY LINGER DURING THE NIGHT.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH IN WIND TRENDS.

* MEDIUM-LOW IN SNOW TIMING/INTENSITY THIS AFTERNOON AND EVENING.

RATZER

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...VFR DURING THE DAY THEN CHANCE OF -RASN AND MVFR/IFR
AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR LIKELY/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS...ESPECIALLY EARLY.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR CIGS.

IZZI

&&

.MARINE...
143 AM CST

ONLY MARINE FORECAST CONCERNS ARE A BRIEF PERIOD OF ENHANCED
SOUTH-SOUTHEAST WINDS THIS AFTERNOON AND EVENING ESPECIALLY ON THE
NORTHERN PORTION OF THE LAKE...AND AGAIN WEDNESDAY AFTERNOON. GUSTY
NORTH WINDS NEAR 30 KT ARE ALSO LIKELY THURSDAY AND THURSDAY
NIGHT.

WINDS CONTINUE TO DIMINISH QUICKLY ACROSS LAKE MICHIGAN EARLY THIS
MORNING...AS WEAK HIGH PRESSURE RIDING SLIDES SOUTHEAST ACROSS THE
LAKE. THIS RIDGE WILL ALSO PASS QUICKLY OFF TO THE SOUTHEAST THIS
AFTERNOON IN WHAT REMAINS A PROGRESSIVE WEATHER PATTERN...WITH
ANOTHER LOW PRESSURE SYSTEM CURRENTLY NEAR LAKE WINNIPEG MOVING
QUICKLY SOUTHEAST INTO ILLINOIS BY MIDNIGHT TONIGHT WHILE FILLING.
THIS WILL RESULT IN WINDS BECOMING SOUTH AND INCREASING TO AROUND 20
KTS ON THE LAKE THIS AFTERNOON...THEN DECREASING AND BACKING TO THE
NORTHEAST INTO TUESDAY MORNING AS THE LOW PASSES AND WEAKENS.
ANOTHER HIGH PRESSURE RIDGE WILL SETTLE ACROSS THE WESTERN LAKES BY
TUESDAY EVENING.

ANOTHER MORE DEVELOPED LOW WILL FORM ACROSS THE LAKES TUESDAY
NIGHT...AND WILL DEEPEN SLIGHTLY AS IT APPROACHES FROM THE WEST
WEDNESDAY AND PASSES JUST SOUTH OF LAKE MICHIGAN EARLY THURSDAY
MORNING. THIS WILL AGAIN RESULT IN WINDS INITIALLY BECOMING SOUTH
AND INCREASING TO 20-25 KT WEDNESDAY AFTERNOON AND EVENING...THEN
BACKING TO THE NORTH EARLY THURSDAY AND GUSTING NEAR 30 KT AS THE
LOW PULLS AWAY ACROSS THE EASTERN LAKES AND UPPER OHIO VALLEY
THROUGH THURSDAY AFTERNOON AND NIGHT. HIGH PRESSURE THEN SPREADS
ACROSS THE REGION BY FRIDAY AFTERNOON.

FOR THE ILLINOIS AND NORTHWEST INDIANA NEARSHORE WATERS...AS SMALL
CRAFT ADVISORY REMAINS IN EFFECT UNTIL MID-MORNING TODAY...AS WAVES
CONTINUE TO SUBSIDE FROM YESTERDAY/LAST EVENINGS STRONG NORTHEAST
WINDS.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 260919
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
319 AM CST MON JAN 26 2015

.SHORT TERM...
315 AM CST

THROUGH TONIGHT...

AN IMPRESSIVE WATER VAPOR LOOP THIS MORNING AS ROARING SUBTROPICAL
JET ACROSS THE SOUTHEAST IS DEEPENING A SIGNIFICANT SYSTEM THAT WILL
IMPACT THE NORTHEAST U.S. OVER THE NEXT 24 TO 36 HOURS. THE NORTHERN
STREAM JET WHICH IS ALSO HELPING TO CARVE OUT THE DEVELOPING TROUGH
IS DIVING SOUTHWARD OVER OUR REGION TODAY. ON THE CYCLONIC SIDE OF
THIS...FROM MANITOBA TO THE LOWER OHIO VALLEY...AN ELONGATED AREA OF
VORTICITY GENERATION WILL SUPPORT FORCING FOR ASCENT TODAY AND
TONIGHT...WITH THE MOST FOCUSED ZONE BEING A BETTER DEFINED WAVE
SEEN OVER CENTRAL MN EARLY THIS MORNING. THE RUN-TO-RUN TREND ON THE
RAP MODEL EARLY THIS MORNING IS FURTHER
WEST/SOUTHWEST...SUPPORTING UPSTREAM RADAR TRENDS AND FAVORING
NORTH CENTRAL IL TO GET IN A PERIOD OF SNOW BEGINNING LATER THIS
MORNING FOLLOWED BY A GRADUAL EXPANSION EAST. WHILE MOST OF THE
SNOW WILL BE LIGHT...THERE IS A WINDOW OF TIME LATE THIS MORNING
AND EARLY THIS AFTERNOON OVER NORTH CENTRAL ILLINOIS WHERE
850-700MB CONVERGENCE AND A F-GEN INDUCED CIRCULATION MAY ALLOW
FOR SPOTTY BURSTS OF MODERATE SNOW...WHICH HIGH-RESOLUTION
GUIDANCE TRIES TO INDICATE TOO. WITH ADJACENT OFFICES AND WPC
COLLABORATION...HAVE AROUND AN INCH FORECAST IN THE ROCKFORD
AREA...WITH AROUND A HALF INCH FURTHER EAST OF THERE. SOUTHWARD IN
THE FORECAST AREA THE DRY AIR SEEMS MORE PRONOUNCED...SO MAY END
UP JUST BEING FLURRIES AT TIMES.

THE FORCING ALOFT WEAKENS LATER THIS AFTERNOON AND EVENING SO
EXPECTING LIGHT SNOW TO BECOME MORE PATCHY IN COVERAGE. THE MOISTURE
IN THE ICE LAYER GRADUALLY DIMINISHES FROM WEST TO EAST THROUGH THE
EVENING...WITH STILL SOME LIGHT ADIABATIC ASCENT IN THE LOWEST
COUPLE THOUSAND FEET. IF THAT LOWEST LAYER IS SATURATED OR ABLE TO
THERE COULD BE A FREEZING DRIZZLE CONCERN...SO MAINTAIN THE GOING
CHANCE IN THE FORECAST.

FOR TEMPERATURES TODAY...DID BUMP DOWN SEVERAL DEGREES AS CLEARING
LAST NIGHT ALLOWED PLACES TO DROP QUICKLY AND NOW THE CLOUD CANOPY
WILL HINDER THEM FROM WARMING MUCH. FORECAST HIGHS ARE MAINLY IN THE
MID 20S WITH A FEW UPPER 20S POSSIBLE. WHILE THAT DOES NOT MAKE
HEADLINES IN JANUARY...IF THE FORECAST PANS OUT THIS WOULD BE THE
FIRST DAY WITH HIGHS BELOW 30 SINCE JANUARY 14TH.

MTF

&&

.LONG TERM...
315 AM CST

TUESDAY THROUGH SUNDAY...

HIGH PRESSURE WILL MOVE OVER THE AREA TUESDAY AFTERNOON AND NIGHT
BEFORE RETURN FLOW ON WEDNESDAY. THE CHALLENGE OF CLOUD COVER
PRESENTS ITSELF AGAIN ON TUESDAY AND WHILE HAVE SLOWED THE
CLEARING TREND TUESDAY MORNING...STILL THINK THE AFTERNOON SHOULD
SEE SOME BREAKS OF SUN AREAWIDE. SOUTHERLY FLOW ON WEDNESDAY IS
FORECAST TO BRING 925MB TEMPERATURES TO AROUND 0C WHICH USING
CLIMATOLOGY WITH LIMITED SNOW COVER SHOULD SUPPORT WIDESPREAD MID
TO UPPER 30S WITH A FEW LOWER 40S POSSIBLE IN THE SOUTHWEST CWA
OR CHICAGO METRO.

THE LARGE CLOSED LOW OFF THE BAJA OF CALIFORNIA THIS MORNING IS
FORECAST BY THE SUITE OF GUIDANCE TO DRIFT NORTHWARD AND GET CAUGHT
UP IN THE WESTERLIES BECOMING AN OPEN WAVE ACROSS THE MIDDLE OF THE
COUNTRY. WITH THE MASSIVE SYSTEM OFF THE NORTHEAST LIKELY TO SLOW
THINGS A BIT...CONTINUE TO LEAN WITH THE SLOWER EC AND GEM MODELS
WHICH WOULD FAVOR PRECIPITATION CHANCES MORE SO LATE WEDNESDAY NIGHT
AND THURSDAY...AROUND 12H SLOWER THAN THE GFS. FORECAST VERTICAL
PROFILES ON BOTH MODELS WOULD SUPPORT MORE OF RAIN AHEAD OF THIS
SYSTEM...ESPECIALLY CONSIDERING LOW-LEVEL TEMPERATURES SHOULD AT THE
VERY LEAST HOLD STEADY IF NOT MODERATE WEDNESDAY NIGHT...POTENTIALLY
TO 35 TO 38 DEGREES GIVEN EC AND GEM SOLUTIONS. ON THE BACKSIDE OF
THIS SYSTEM IT WOULD SEEM THERE WOULD BE AT LEAST A PERIOD OF SNOW
CHANCES. OBVIOUSLY A FEW DAYS OUT AND A CUTOFF LOW INVOLVED...A
LOT COULD CHANGE WITH SPECIFICS...BUT RIGHT NOW THIS IS NOT
LOOKING LIKE A HIGH IMPACT EVENT.

LATE THIS WEEK INTO THE WEEKEND THE NORTHERN STREAM FLOW PATTERN
IS FORECAST TO REMAIN QUITE PROGRESSIVE WHILE ANOTHER CUTOFF LOW
IS PROGGED TO DEVELOP OVER THE FAR SOUTHWEST US. THE 00Z EC HAS
FORECAST A STRONG SYSTEM IN THE NORTHWEST FLOW TO WIN OUT ABOUT A
WEEK FROM NOW AND DRAG DOWN -15C TO -20C 850MB TEMPERATURES.
SOMETHING TO MONITOR AS WE HEAD TOWARD THE FIRST DAYS OF FEBRUARY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* BRIEF HIGH-END MVFR CIGS OFF LAKE MICHIGAN SHOULD SCATTER BY
  SUNRISE.

* PERIOD OF LIGHT SNOW POSSIBLE THIS AFTERNOON/EVENING WITH
  REDEVELOPMENT OF MVFR CIGS WHICH LINGER TONIGHT.

RATZER

//DISCUSSION...UPDATED 06Z...

WEAK HIGH PRESSURE RIDGE QUICKLY MOVING INTO FORECAST AREA FROM
THE NORTHWEST OVERNIGHT...THOUGH NORTHEAST WINDS HAVE RESULTED IN
A LAKE-INDUCED PLUME OF MVFR STRATOCU FROM ABOUT ORD EAST...WITH
BASES AROUND 2500 FT. THESE CIGS WILL LIKELY AFFECT ORD/MDW/GYY
UNTIL ABOUT SUNRISE...WHEN MODELS DEPICT NORTHEAST FLOW QUICKLY
BECOMING DISORGANIZED WITH APPROACH OF SFC RIDGE. SFC WINDS TO
BECOME LIGHT/VARIABLE FOR A TIME THIS MORNING AS THE SURFACE HIGH
PRESSURE RIDGE MOVES ACROSS THE TERMINALS...GENERALLY FLOPPING
FROM LIGHT NORTHERLY TO LIGHT SOUTHERLY BY MID-DAY.

IR SATELLITE PICS ALREADY SHOWING HIGH CLOUDS SPILLING INTO THE
REGION FROM THE NORTHWEST AHEAD OF THE NEXT WEAK CLIPPER SYSTEM
WHICH WILL AFFECT THE AREA MONDAY AFTERNOON/EVENING. LOW LEVELS
ARE INITIALLY DRY AND WILL TAKE SOME WORK TO SATURATE FROM ABOVE
AS MID-LEVEL FORCING INCREASES MID-DAY INTO EARLY AFTERNOON. MOST
GUIDANCE DOES INDICATE SOME LIGHT SNOW DEVELOPING DURING THE
PERIOD...THOUGH A COMBINATION OF WEAKENING FORCING AND FORCING
FOCUSED BELOW TEMP LAYER CONDUCIVE TO LARGER SNOWFLAKE GROWTH
SUGGESTS THIS WILL BE RATHER LIGHT. WHILE A FEW INCONSEQUENTIAL
FLURRIES COULD BEGIN SOONER...THE TIMING OF THE PERIOD MOST
LIKELY TO SEE SOME LIGHT SNOW AND MVFR CIG/POSSIBLE IFR VSBY LOOKS
TO BE DURING THE AFTERNOON AT RFD...AND DURING THE LATE AFTN/EARLY
EVENING FOR CHICAGO TERMINALS. SNOW SHOULD TAPER OFF DURING THE
EVENING AT RFD AND BY LATE EVENING FOR CHICAGO TERMINALS...WITH
LOSS OF STRONGER LIFT AND DRYING IN MID-LEVELS. SOME INDICATION
THAT THERE COULD BE A BRIEF PERIOD OF FREEZING DRIZZLE AS THE SNOW
ENDS ESPECIALLY AT RFD WHERE MID-LEVELS DRY A LITTLE MORE
QUICKLY...THOUGH MODELS MAY BE OVERDOING THE DEGREE OF SATURATION
IN THE BOUNDARY LAYER AND CONFIDENCE IS LOW THAT FZDZ WOULD OCCUR.
IT DOES HOWEVER APPEAR THAT SOME SORT OF HIGH-IFR OR LOW-MVFR CIG
MAY LINGER DURING THE NIGHT.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH IN WIND TRENDS.

* MEDIUM-LOW IN SNOW TIMING/INTENSITY THIS AFTERNOON AND EVENING.

RATZER

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...VFR DURING THE DAY THEN CHANCE OF -RASN AND MVFR/IFR
AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR LIKELY/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS...ESPECIALLY EARLY.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR CIGS.

IZZI

&&

.MARINE...
143 AM CST

ONLY MARINE FORECAST CONCERNS ARE A BRIEF PERIOD OF ENHANCED
SOUTH-SOUTHEAST WINDS THIS AFTERNOON AND EVENING ESPECIALLY ON THE
NORTHERN PORTION OF THE LAKE...AND AGAIN WEDNESDAY AFTERNOON. GUSTY
NORTH WINDS NEAR 30 KT ARE ALSO LIKELY THURSDAY AND THURSDAY
NIGHT.

WINDS CONTINUE TO DIMINISH QUICKLY ACROSS LAKE MICHIGAN EARLY THIS
MORNING...AS WEAK HIGH PRESSURE RIDING SLIDES SOUTHEAST ACROSS THE
LAKE. THIS RIDGE WILL ALSO PASS QUICKLY OFF TO THE SOUTHEAST THIS
AFTERNOON IN WHAT REMAINS A PROGRESSIVE WEATHER PATTERN...WITH
ANOTHER LOW PRESSURE SYSTEM CURRENTLY NEAR LAKE WINNIPEG MOVING
QUICKLY SOUTHEAST INTO ILLINOIS BY MIDNIGHT TONIGHT WHILE FILLING.
THIS WILL RESULT IN WINDS BECOMING SOUTH AND INCREASING TO AROUND 20
KTS ON THE LAKE THIS AFTERNOON...THEN DECREASING AND BACKING TO THE
NORTHEAST INTO TUESDAY MORNING AS THE LOW PASSES AND WEAKENS.
ANOTHER HIGH PRESSURE RIDGE WILL SETTLE ACROSS THE WESTERN LAKES BY
TUESDAY EVENING.

ANOTHER MORE DEVELOPED LOW WILL FORM ACROSS THE LAKES TUESDAY
NIGHT...AND WILL DEEPEN SLIGHTLY AS IT APPROACHES FROM THE WEST
WEDNESDAY AND PASSES JUST SOUTH OF LAKE MICHIGAN EARLY THURSDAY
MORNING. THIS WILL AGAIN RESULT IN WINDS INITIALLY BECOMING SOUTH
AND INCREASING TO 20-25 KT WEDNESDAY AFTERNOON AND EVENING...THEN
BACKING TO THE NORTH EARLY THURSDAY AND GUSTING NEAR 30 KT AS THE
LOW PULLS AWAY ACROSS THE EASTERN LAKES AND UPPER OHIO VALLEY
THROUGH THURSDAY AFTERNOON AND NIGHT. HIGH PRESSURE THEN SPREADS
ACROSS THE REGION BY FRIDAY AFTERNOON.

FOR THE ILLINOIS AND NORTHWEST INDIANA NEARSHORE WATERS...AS SMALL
CRAFT ADVISORY REMAINS IN EFFECT UNTIL MID-MORNING TODAY...AS WAVES
CONTINUE TO SUBSIDE FROM YESTERDAY/LAST EVENINGS STRONG NORTHEAST
WINDS.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 260743
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
143 AM CST MON JAN 26 2015

.UPDATE...
820 PM CST

PCPN IS WINDING DOWN ACROSS THE AREA WITH ONLY SOME LINGERING
LIGHT SNOW SOUTH OF THE KANKAKEE RIVER. WHILE WINDS ARE CURRENTLY
STILL RATHER BREEZY ACROSS THE AREA...THE GENERAL TREND OF THE
REMAINDER OF THE EVENING AND OVERNIGHT SHOULD BE FOR WINDS TO
DIMINISH AND ANY LINGERING SNOW SHOULD PUSH OUT OF THE AREA.
TEMPERATURES SHOULD ALSO DROP OFF WITH PARTIALLY CLEARING SKIES
AND SOME COOLER AIR FILTERING IN AS THE LOW PRESSURE CENTER
ASSOCIATED WITH THE SYSTEM THAT BROUGHT TODAY`S PRECIPITATION
MOVES OFF TO THE SOUTHEAST.

HAVE MADE SOME CHANGES TO THE GOING FORECAST FOR TOMORROW. THE
LATEST 00Z MODEL RUNS ARE TRENDING TOWARD THE NEXT CLIPPER
DROPPING A LITTLE FARTHER SOUTH...WITH SOME MODEST LIFT IN THE
ZONE AHEAD OF A WEAK WARM FRONT ASSOCIATED WITH THE NEXT CLIPPER.
SO HAVE INCREASED POPS...WITH LIKELY POPS FOR THE AFTERNOON HOURS
ACROSS MUCH OF THE AREA...WITH THE EXCEPTION OF THE FAR SOUTHERN
PORTIONS OF THE CWA. ALSO...THE THERMAL PROFILES IN THE LATEST
MODEL SOUNDINGS SUGGEST THAT THE PCPN SHOULD BE ALL SNOW...WITH A
DEEP ENOUGH SATURATED LAYER TO SUPPORT ALL SNOW...AND LESSER
CHANCES FOR FREEZING DRIZZLE. SO...HAVE REMOVED THE FREEZING
DRIZZLE MENTION FOR THE DAYTIME HOURS. STILL FEEL THAT THERE IS A
BETTER CHANCE FOR FREEZING DRIZZLE TOMORROW NIGHT AS DRIER AIR
ALOFT LOWERS THE DEPTH OF THE SATURATED LAYER ENOUGH TO MINIMIZE
THE CHANCE FOR ICE PRODUCTION IN THE SATURATED LAYER. WHILE POPS
HAVE BEEN RAISED...THERE IS LITTLE AVAILABLE DEEP LAYER
MOISTURE...SO ACTUAL SNOWFALL AMOUNTS SHOULD BE LIGHT...ONLY
PERHAPS A COUPLE TENTHS OF AN INCH OF ACCUMULATION.

KREIN

&&

.SHORT TERM...
206 PM CST

TONIGHT THROUGH MONDAY NIGHT...

COOL AIR HAS STRUGGLED TO SLIDE SOUTH THIS AFTERNOON...HOWEVER TEMPS
ARE BEGINNING TO FALL INTO THE UPR 20S ACROSS FAR NORTHEAST IL.
ACROSS THE CENTRAL/SOUTHERN CWFA TEMPS REMAIN IN THE LOW 30S WITH
DEW POINT DEPRESSIONS NOT MUCH MORE THAN 1 TO 2 DEGREES. NORTH OF
I-80 PRECIP IS MAINLY FLURRIES...WITH A RAIN/SNOW MIX SLOWLY
CHANGING TO ALL SNOW LATER THIS AFTERNOON ACROSS THE SOUTHERN CWFA.
THE SHORTWAVE THAT BROUGHT THE LIGHT SNOW CONTINUES TO SLIDE EAST
ACROSS SOUTHERN IL...AND WILL STEADILY BRING AN END TO THE PRECIP
ACROSS THE FORECAST AREA THIS EVENING FROM NORTHWEST TO SOUTHEAST.
WINDS WILL GRADUALLY DIMINISH AS WELL AS THE PRESSURE GRADIENT
RELAXES.

SFC RIDGE CENTERED TO THE NORTH THIS AFTERNOON...WILL SAG SOUTH AND
EXPAND TO COVER A PORTION OF THE WESTERN GREAT LAKES/MISSOURI VALLEY
OVERNIGHT. WHILE SOME EROSION TO THE CLOUDS IS PROBABLE NORTH OF THE
FORECAST AREA...EXPECT SOME DECREASE IN CLOUDS CLOSER TO DAYBREAK
MON. CURRENTLY EXPECT OVERNIGHT LOWS TO DIP INTO THE MID/UPR
TEENS...HOWEVER THIS WILL LIKELY NOT OCCUR UNTIL CLOSER TO DAYBREAK
MON.

THE BRIEF BREAK IN CLOUDS MON MORNING WILL QUICKLY GIVE WAY TO THE
NEXT CLIPPER SYSTEM ARRIVING MON AFTN/EVE. GUIDANCE HAS MAINTAINED A
PROGRESSIVE LOOK TO THIS NEXT WAVE...HOWEVER OPERATIONAL SOLUTIONS
ARE EQUALLY BULLISH ON EROSION OF MOISTURE WITHIN THE LOWEST FEW
LAYERS OF THE ATMOS LATE MON NGT. HAVE SOME CONCERN ABOUT P-TYPE MON
AFTN/EVE. AT THE ONSET MOISTURE WILL QUICKLY SATURATE THRU THE -10
DEG C LAYER AND TOUCH THE FAVORED DGZ...HOWEVER THE DEPTH OF THE
MOISTURE BECOMES MORE SHALLOW MON EVE. ALONG WITH THE LACK OF GOOD
LIFT AND SHALLOW MOISTURE...IT IS LOOKING MORE LIKELY THAT PRECIP
MAY BE A MIX OF FREEZING DRIZZLE/LGT-SNOW.

A WEAK THERMAL RIDGE TRIES TO PUSH OVERHEAD MON AFTN...AS LLVL FLOW
TURNS SOUTHWESTERLY. TEMPS SHUD HOVER ARND FREEZING...HOWEVER THIS
WILL HINGE ON CLOUD COVER ARRIVAL AND DEVELOPMENT OF PRECIP. IF THIS
IS DELAYED...TEMPS COULD PUSH A FEW DEGREES WARMER MON EARLY AFTN.

HEIGHTS SLOWLY INCREASE MON NGT...WITH THE MOISTURE PEELING EAST
ALONG WITH THE WEAKENING SHORTWAVE. AT THIS TIME HAVE MAINTAINED A
MENTION OF LGT SNOW OR PATCHY FREEZING DRIZZLE MON NGT...BUT COULD
END UP WITH A DRY PERIOD.

BEACHLER

&&

.LONG TERM...
206 PM CST

TUESDAY THROUGH SUNDAY...
TOWARDS THE MIDDLE OF THE WEEK ENSEMBLES MAINTAIN A HIGH CONFIDENCE
IN THE TROUGH ALONG THE SOUTHEAST CONUS WEAKENING WITH RIDGING
EXPANDING EAST ACROSS THE CENTRAL PLAINS. THIS SHUD PLACE THE BULK
OF THE REGION INTO A WEAK SFC RIDGE TUE/WED. WED AFTN THE SFC RIDGE
QUICKLY SLIDES SOUTHEAST...WHICH COULD ALLOW SOME WARM AIR TO ADVECT
NORTHEAST INTO THE CWFA AND PUSH SFC TEMPS CLOSE TO 40 DEG.

WITH A QUASI-ZONAL SETUP WED NGT/THUR...GUIDANCE SUGGESTS A ROBUST
MID-LVL VORT WILL QUICKLY SLIDE EAST FROM THE ROCKIES TOWARDS THE
PLAINS WED EVE. GUIDANCE THEN FURTHER STRENGTHENS THIS WAVE AND
LIFTS NORTHEAST ACROSS THE FORECAST AREA THUR. SOUNDINGS SUGGESTS
THAT PRECIP COULD START AS MAINLY RAIN WITH THIS SYSTEM...THEN
DYNAMICALLY COOL OVERNIGHT INTO THUR AND TRANSITION PRECIP OVER TO
LGT SNOW.

A RELATIVELY ACTIVE PATTERN CONTINUES TOWARDS THE END OF THE WEEK
INTO EARLY NEXT WEEKEND...WITH TEMPS GENERALLY IN THE UPR 20S/LOW
30S.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* BRIEF HIGH-END MVFR CIGS OFF LAKE MICHIGAN SHOULD SCATTER BY
  SUNRISE.

* PERIOD OF LIGHT SNOW POSSIBLE THIS AFTERNOON/EVENING WITH
  REDEVELOPMENT OF MVFR CIGS WHICH LINGER TONIGHT.

RATZER

//DISCUSSION...UPDATED 06Z...

WEAK HIGH PRESSURE RIDGE QUICKLY MOVING INTO FORECAST AREA FROM
THE NORTHWEST OVERNIGHT...THOUGH NORTHEAST WINDS HAVE RESULTED IN
A LAKE-INDUCED PLUME OF MVFR STRATOCU FROM ABOUT ORD EAST...WITH
BASES AROUND 2500 FT. THESE CIGS WILL LIKELY AFFECT ORD/MDW/GYY
UNTIL ABOUT SUNRISE...WHEN MODELS DEPICT NORTHEAST FLOW QUICKLY
BECOMING DISORGANIZED WITH APPROACH OF SFC RIDGE. SFC WINDS TO
BECOME LIGHT/VARIABLE FOR A TIME THIS MORNING AS THE SURFACE HIGH
PRESSURE RIDGE MOVES ACROSS THE TERMINALS...GENERALLY FLOPPING
FROM LIGHT NORTHERLY TO LIGHT SOUTHERLY BY MID-DAY.

IR SATELLITE PICS ALREADY SHOWING HIGH CLOUDS SPILLING INTO THE
REGION FROM THE NORTHWEST AHEAD OF THE NEXT WEAK CLIPPER SYSTEM
WHICH WILL AFFECT THE AREA MONDAY AFTERNOON/EVENING. LOW LEVELS
ARE INITIALLY DRY AND WILL TAKE SOME WORK TO SATURATE FROM ABOVE
AS MID-LEVEL FORCING INCREASES MID-DAY INTO EARLY AFTERNOON. MOST
GUIDANCE DOES INDICATE SOME LIGHT SNOW DEVELOPING DURING THE
PERIOD...THOUGH A COMBINATION OF WEAKENING FORCING AND FORCING
FOCUSED BELOW TEMP LAYER CONDUCIVE TO LARGER SNOWFLAKE GROWTH
SUGGESTS THIS WILL BE RATHER LIGHT. WHILE A FEW INCONSEQUENTIAL
FLURRIES COULD BEGIN SOONER...THE TIMING OF THE PERIOD MOST
LIKELY TO SEE SOME LIGHT SNOW AND MVFR CIG/POSSIBLE IFR VSBY LOOKS
TO BE DURING THE AFTERNOON AT RFD...AND DURING THE LATE AFTN/EARLY
EVENING FOR CHICAGO TERMINALS. SNOW SHOULD TAPER OFF DURING THE
EVENING AT RFD AND BY LATE EVENING FOR CHICAGO TERMINALS...WITH
LOSS OF STRONGER LIFT AND DRYING IN MID-LEVELS. SOME INDICATION
THAT THERE COULD BE A BRIEF PERIOD OF FREEZING DRIZZLE AS THE SNOW
ENDS ESPECIALLY AT RFD WHERE MID-LEVELS DRY A LITTLE MORE
QUICKLY...THOUGH MODELS MAY BE OVERDOING THE DEGREE OF SATURATION
IN THE BOUNDARY LAYER AND CONFIDENCE IS LOW THAT FZDZ WOULD OCCUR.
IT DOES HOWEVER APPEAR THAT SOME SORT OF HIGH-IFR OR LOW-MVFR CIG
MAY LINGER DURING THE NIGHT.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND TRENDS.

* MEDIUM-LOW IN SNOW TIMING/INTENSITY THIS AFTERNOON AND EVENING.

RATZER

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...VFR DURING THE DAY THEN CHANCE OF -RASN AND MVFR/IFR
AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR LIKELY/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS...ESPECIALLY EARLY.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR CIGS.

IZZI

&&

.MARINE...
143 AM CST

ONLY MARINE FORECAST CONCERNS ARE A BRIEF PERIOD OF ENHANCED
SOUTH-SOUTHEAST WINDS THIS AFTERNOON AND EVENING ESPECIALLY ON THE
NORTHERN PORTION OF THE LAKE...AND AGAIN WEDNESDAY AFTERNOON. GUSTY
NORTH WINDS NEAR 30 KT ARE ALSO LIKELY THURSDAY AND THURSDAY
NIGHT.

WINDS CONTINUE TO DIMINISH QUICKLY ACROSS LAKE MICHIGAN EARLY THIS
MORNING...AS WEAK HIGH PRESSURE RIDING SLIDES SOUTHEAST ACROSS THE
LAKE. THIS RIDGE WILL ALSO PASS QUICKLY OFF TO THE SOUTHEAST THIS
AFTERNOON IN WHAT REMAINS A PROGRESSIVE WEATHER PATTERN...WITH
ANOTHER LOW PRESSURE SYSTEM CURRENTLY NEAR LAKE WINNIPEG MOVING
QUICKLY SOUTHEAST INTO ILLINOIS BY MIDNIGHT TONIGHT WHILE FILLING.
THIS WILL RESULT IN WINDS BECOMING SOUTH AND INCREASING TO AROUND 20
KTS ON THE LAKE THIS AFTERNOON...THEN DECREASING AND BACKING TO THE
NORTHEAST INTO TUESDAY MORNING AS THE LOW PASSES AND WEAKENS.
ANOTHER HIGH PRESSURE RIDGE WILL SETTLE ACROSS THE WESTERN LAKES BY
TUESDAY EVENING.

ANOTHER MORE DEVELOPED LOW WILL FORM ACROSS THE LAKES TUESDAY
NIGHT...AND WILL DEEPEN SLIGHTLY AS IT APPROACHES FROM THE WEST
WEDNESDAY AND PASSES JUST SOUTH OF LAKE MICHIGAN EARLY THURSDAY
MORNING. THIS WILL AGAIN RESULT IN WINDS INITIALLY BECOMING SOUTH
AND INCREASING TO 20-25 KT WEDNESDAY AFTERNOON AND EVENING...THEN
BACKING TO THE NORTH EARLY THURSDAY AND GUSTING NEAR 30 KT AS THE
LOW PULLS AWAY ACROSS THE EASTERN LAKES AND UPPER OHIO VALLEY
THROUGH THURSDAY AFTERNOON AND NIGHT. HIGH PRESSURE THEN SPREADS
ACROSS THE REGION BY FRIDAY AFTERNOON.

FOR THE ILLINOIS AND NORTHWEST INDIANA NEARSHORE WATERS...AS SMALL
CRAFT ADVISORY REMAINS IN EFFECT UNTIL MID-MORNING TODAY...AS WAVES
CONTINUE TO SUBSIDE FROM YESTERDAY/LAST EVENINGS STRONG NORTHEAST
WINDS.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO








000
FXUS63 KLOT 260554
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1154 PM CST SUN JAN 25 2015

.UPDATE...
820 PM CST

PCPN IS WINDING DOWN ACROSS THE AREA WITH ONLY SOME LINGERING
LIGHT SNOW SOUTH OF THE KANKAKEE RIVER. WHILE WINDS ARE CURRENTLY
STILL RATHER BREEZY ACROSS THE AREA...THE GENERAL TREND OF THE
REMAINDER OF THE EVENING AND OVERNIGHT SHOULD BE FOR WINDS TO
DIMINISH AND ANY LINGERING SNOW SHOULD PUSH OUT OF THE AREA.
TEMPERATURES SHOULD ALSO DROP OFF WITH PARTIALLY CLEARING SKIES
AND SOME COOLER AIR FILTERING IN AS THE LOW PRESSURE CENTER
ASSOCIATED WITH THE SYSTEM THAT BROUGHT TODAY`S PRECIPITATION
MOVES OFF TO THE SOUTHEAST.

HAVE MADE SOME CHANGES TO THE GOING FORECAST FOR TOMORROW. THE
LATEST 00Z MODEL RUNS ARE TRENDING TOWARD THE NEXT CLIPPER
DROPPING A LITTLE FARTHER SOUTH...WITH SOME MODEST LIFT IN THE
ZONE AHEAD OF A WEAK WARM FRONT ASSOCIATED WITH THE NEXT CLIPPER.
SO HAVE INCREASED POPS...WITH LIKELY POPS FOR THE AFTERNOON HOURS
ACROSS MUCH OF THE AREA...WITH THE EXCEPTION OF THE FAR SOUTHERN
PORTIONS OF THE CWA. ALSO...THE THERMAL PROFILES IN THE LATEST
MODEL SOUNDINGS SUGGEST THAT THE PCPN SHOULD BE ALL SNOW...WITH A
DEEP ENOUGH SATURATED LAYER TO SUPPORT ALL SNOW...AND LESSER
CHANCES FOR FREEZING DRIZZLE. SO...HAVE REMOVED THE FREEZING
DRIZZLE MENTION FOR THE DAYTIME HOURS. STILL FEEL THAT THERE IS A
BETTER CHANCE FOR FREEZING DRIZZLE TOMORROW NIGHT AS DRIER AIR
ALOFT LOWERS THE DEPTH OF THE SATURATED LAYER ENOUGH TO MINIMIZE
THE CHANCE FOR ICE PRODUCTION IN THE SATURATED LAYER. WHILE POPS
HAVE BEEN RAISED...THERE IS LITTLE AVAILABLE DEEP LAYER
MOISTURE...SO ACTUAL SNOWFALL AMOUNTS SHOULD BE LIGHT...ONLY
PERHAPS A COUPLE TENTHS OF AN INCH OF ACCUMULATION.

KREIN

&&

.SHORT TERM...
206 PM CST

TONIGHT THROUGH MONDAY NIGHT...

COOL AIR HAS STRUGGLED TO SLIDE SOUTH THIS AFTERNOON...HOWEVER TEMPS
ARE BEGINNING TO FALL INTO THE UPR 20S ACROSS FAR NORTHEAST IL.
ACROSS THE CENTRAL/SOUTHERN CWFA TEMPS REMAIN IN THE LOW 30S WITH
DEW POINT DEPRESSIONS NOT MUCH MORE THAN 1 TO 2 DEGREES. NORTH OF
I-80 PRECIP IS MAINLY FLURRIES...WITH A RAIN/SNOW MIX SLOWLY
CHANGING TO ALL SNOW LATER THIS AFTERNOON ACROSS THE SOUTHERN CWFA.
THE SHORTWAVE THAT BROUGHT THE LIGHT SNOW CONTINUES TO SLIDE EAST
ACROSS SOUTHERN IL...AND WILL STEADILY BRING AN END TO THE PRECIP
ACROSS THE FORECAST AREA THIS EVENING FROM NORTHWEST TO SOUTHEAST.
WINDS WILL GRADUALLY DIMINISH AS WELL AS THE PRESSURE GRADIENT
RELAXES.

SFC RIDGE CENTERED TO THE NORTH THIS AFTERNOON...WILL SAG SOUTH AND
EXPAND TO COVER A PORTION OF THE WESTERN GREAT LAKES/MISSOURI VALLEY
OVERNIGHT. WHILE SOME EROSION TO THE CLOUDS IS PROBABLE NORTH OF THE
FORECAST AREA...EXPECT SOME DECREASE IN CLOUDS CLOSER TO DAYBREAK
MON. CURRENTLY EXPECT OVERNIGHT LOWS TO DIP INTO THE MID/UPR
TEENS...HOWEVER THIS WILL LIKELY NOT OCCUR UNTIL CLOSER TO DAYBREAK
MON.

THE BRIEF BREAK IN CLOUDS MON MORNING WILL QUICKLY GIVE WAY TO THE
NEXT CLIPPER SYSTEM ARRIVING MON AFTN/EVE. GUIDANCE HAS MAINTAINED A
PROGRESSIVE LOOK TO THIS NEXT WAVE...HOWEVER OPERATIONAL SOLUTIONS
ARE EQUALLY BULLISH ON EROSION OF MOISTURE WITHIN THE LOWEST FEW
LAYERS OF THE ATMOS LATE MON NGT. HAVE SOME CONCERN ABOUT P-TYPE MON
AFTN/EVE. AT THE ONSET MOISTURE WILL QUICKLY SATURATE THRU THE -10
DEG C LAYER AND TOUCH THE FAVORED DGZ...HOWEVER THE DEPTH OF THE
MOISTURE BECOMES MORE SHALLOW MON EVE. ALONG WITH THE LACK OF GOOD
LIFT AND SHALLOW MOISTURE...IT IS LOOKING MORE LIKELY THAT PRECIP
MAY BE A MIX OF FREEZING DRIZZLE/LGT-SNOW.

A WEAK THERMAL RIDGE TRIES TO PUSH OVERHEAD MON AFTN...AS LLVL FLOW
TURNS SOUTHWESTERLY. TEMPS SHUD HOVER ARND FREEZING...HOWEVER THIS
WILL HINGE ON CLOUD COVER ARRIVAL AND DEVELOPMENT OF PRECIP. IF THIS
IS DELAYED...TEMPS COULD PUSH A FEW DEGREES WARMER MON EARLY AFTN.

HEIGHTS SLOWLY INCREASE MON NGT...WITH THE MOISTURE PEELING EAST
ALONG WITH THE WEAKENING SHORTWAVE. AT THIS TIME HAVE MAINTAINED A
MENTION OF LGT SNOW OR PATCHY FREEZING DRIZZLE MON NGT...BUT COULD
END UP WITH A DRY PERIOD.

BEACHLER

&&

.LONG TERM...
206 PM CST

TUESDAY THROUGH SUNDAY...
TOWARDS THE MIDDLE OF THE WEEK ENSEMBLES MAINTAIN A HIGH CONFIDENCE
IN THE TROUGH ALONG THE SOUTHEAST CONUS WEAKENING WITH RIDGING
EXPANDING EAST ACROSS THE CENTRAL PLAINS. THIS SHUD PLACE THE BULK
OF THE REGION INTO A WEAK SFC RIDGE TUE/WED. WED AFTN THE SFC RIDGE
QUICKLY SLIDES SOUTHEAST...WHICH COULD ALLOW SOME WARM AIR TO ADVECT
NORTHEAST INTO THE CWFA AND PUSH SFC TEMPS CLOSE TO 40 DEG.

WITH A QUASI-ZONAL SETUP WED NGT/THUR...GUIDANCE SUGGESTS A ROBUST
MID-LVL VORT WILL QUICKLY SLIDE EAST FROM THE ROCKIES TOWARDS THE
PLAINS WED EVE. GUIDANCE THEN FURTHER STRENGTHENS THIS WAVE AND
LIFTS NORTHEAST ACROSS THE FORECAST AREA THUR. SOUNDINGS SUGGESTS
THAT PRECIP COULD START AS MAINLY RAIN WITH THIS SYSTEM...THEN
DYNAMICALLY COOL OVERNIGHT INTO THUR AND TRANSITION PRECIP OVER TO
LGT SNOW.

A RELATIVELY ACTIVE PATTERN CONTINUES TOWARDS THE END OF THE WEEK
INTO EARLY NEXT WEEKEND...WITH TEMPS GENERALLY IN THE UPR 20S/LOW
30S.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* BRIEF HIGH-END MVFR CIGS OFF LAKE MICHIGAN SHOULD SCATTER BY
  SUNRISE.

* PERIOD OF LIGHT SNOW POSSIBLE THIS AFTERNOON/EVENING WITH
  REDEVELOPMENT OF MVFR CIGS WHICH LINGER TONIGHT.

RATZER

//DISCUSSION...UPDATED 06Z...

WEAK HIGH PRESSURE RIDGE QUICKLY MOVING INTO FORECAST AREA FROM
THE NORTHWEST OVERNIGHT...THOUGH NORTHEAST WINDS HAVE RESULTED IN
A LAKE-INDUCED PLUME OF MVFR STRATOCU FROM ABOUT ORD EAST...WITH
BASES AROUND 2500 FT. THESE CIGS WILL LIKELY AFFECT ORD/MDW/GYY
UNTIL ABOUT SUNRISE...WHEN MODELS DEPICT NORTHEAST FLOW QUICKLY
BECOMING DISORGANIZED WITH APPROACH OF SFC RIDGE. SFC WINDS TO
BECOME LIGHT/VARIABLE FOR A TIME THIS MORNING AS THE SURFACE HIGH
PRESSURE RIDGE MOVES ACROSS THE TERMINALS...GENERALLY FLOPPING
FROM LIGHT NORTHERLY TO LIGHT SOUTHERLY BY MID-DAY.

IR SATELLITE PICS ALREADY SHOWING HIGH CLOUDS SPILLING INTO THE
REGION FROM THE NORTHWEST AHEAD OF THE NEXT WEAK CLIPPER SYSTEM
WHICH WILL AFFECT THE AREA MONDAY AFTERNOON/EVENING. LOW LEVELS
ARE INITIALLY DRY AND WILL TAKE SOME WORK TO SATURATE FROM ABOVE
AS MID-LEVEL FORCING INCREASES MID-DAY INTO EARLY AFTERNOON. MOST
GUIDANCE DOES INDICATE SOME LIGHT SNOW DEVELOPING DURING THE
PERIOD...THOUGH A COMBINATION OF WEAKENING FORCING AND FORCING
FOCUSED BELOW TEMP LAYER CONDUCIVE TO LARGER SNOWFLAKE GROWTH
SUGGESTS THIS WILL BE RATHER LIGHT. WHILE A FEW INCONSEQUENTIAL
FLURRIES COULD BEGIN SOONER...THE TIMING OF THE PERIOD MOST
LIKELY TO SEE SOME LIGHT SNOW AND MVFR CIG/POSSIBLE IFR VSBY LOOKS
TO BE DURING THE AFTERNOON AT RFD...AND DURING THE LATE AFTN/EARLY
EVENING FOR CHICAGO TERMINALS. SNOW SHOULD TAPER OFF DURING THE
EVENING AT RFD AND BY LATE EVENING FOR CHICAGO TERMINALS...WITH
LOSS OF STRONGER LIFT AND DRYING IN MID-LEVELS. SOME INDICATION
THAT THERE COULD BE A BRIEF PERIOD OF FREEZING DRIZZLE AS THE SNOW
ENDS ESPECIALLY AT RFD WHERE MID-LEVELS DRY A LITTLE MORE
QUICKLY...THOUGH MODELS MAY BE OVERDOING THE DEGREE OF SATURATION
IN THE BOUNDARY LAYER AND CONFIDENCE IS LOW THAT FZDZ WOULD OCCUR.
IT DOES HOWEVER APPEAR THAT SOME SORT OF HIGH-IFR OR LOW-MVFR CIG
MAY LINGER DURING THE NIGHT.

RATZER


//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND TRENDS.

* MEDIUM-LOW IN SNOW TIMING/INTENSITY THIS AFTERNOON AND EVENING.

RATZER

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...VFR DURING THE DAY THEN CHANCE OF -RASN AND MVFR/IFR
AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR LIKELY/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS...ESPECIALLY EARLY.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR CIGS.

IZZI

&&

.MARINE...
131 PM CST

A QUICK MOVING CLIPPER SYSTEM...CURRENTLY CENTERED ACROSS SOUTHERN
ILLINOIS...WILL RAPIDLY SHIFT EASTWARD TOWARDS THE ATLANTIC COAST
BY MONDAY MORNING. NORTHEASTERLY WINDS OF 30-35 KT CONTINUE ACROSS
THE SOUTHERN 1/3RD OF LAKE MICHIGAN...AND THESE WINDS LOOK TO
CONTINUE FOR THE NEXT FEW HOURS...BEFORE A DIMINISHING TREND BEGINS
EARLY THIS EVENING. ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD JUST
WEST OF THE LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A
PERIOD OF SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN
THE WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION.
THIS SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A
PERIOD OF STRONG NORTHERLY WINDS THURSDAY INTO EARLY FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 260554
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1154 PM CST SUN JAN 25 2015

.UPDATE...
820 PM CST

PCPN IS WINDING DOWN ACROSS THE AREA WITH ONLY SOME LINGERING
LIGHT SNOW SOUTH OF THE KANKAKEE RIVER. WHILE WINDS ARE CURRENTLY
STILL RATHER BREEZY ACROSS THE AREA...THE GENERAL TREND OF THE
REMAINDER OF THE EVENING AND OVERNIGHT SHOULD BE FOR WINDS TO
DIMINISH AND ANY LINGERING SNOW SHOULD PUSH OUT OF THE AREA.
TEMPERATURES SHOULD ALSO DROP OFF WITH PARTIALLY CLEARING SKIES
AND SOME COOLER AIR FILTERING IN AS THE LOW PRESSURE CENTER
ASSOCIATED WITH THE SYSTEM THAT BROUGHT TODAY`S PRECIPITATION
MOVES OFF TO THE SOUTHEAST.

HAVE MADE SOME CHANGES TO THE GOING FORECAST FOR TOMORROW. THE
LATEST 00Z MODEL RUNS ARE TRENDING TOWARD THE NEXT CLIPPER
DROPPING A LITTLE FARTHER SOUTH...WITH SOME MODEST LIFT IN THE
ZONE AHEAD OF A WEAK WARM FRONT ASSOCIATED WITH THE NEXT CLIPPER.
SO HAVE INCREASED POPS...WITH LIKELY POPS FOR THE AFTERNOON HOURS
ACROSS MUCH OF THE AREA...WITH THE EXCEPTION OF THE FAR SOUTHERN
PORTIONS OF THE CWA. ALSO...THE THERMAL PROFILES IN THE LATEST
MODEL SOUNDINGS SUGGEST THAT THE PCPN SHOULD BE ALL SNOW...WITH A
DEEP ENOUGH SATURATED LAYER TO SUPPORT ALL SNOW...AND LESSER
CHANCES FOR FREEZING DRIZZLE. SO...HAVE REMOVED THE FREEZING
DRIZZLE MENTION FOR THE DAYTIME HOURS. STILL FEEL THAT THERE IS A
BETTER CHANCE FOR FREEZING DRIZZLE TOMORROW NIGHT AS DRIER AIR
ALOFT LOWERS THE DEPTH OF THE SATURATED LAYER ENOUGH TO MINIMIZE
THE CHANCE FOR ICE PRODUCTION IN THE SATURATED LAYER. WHILE POPS
HAVE BEEN RAISED...THERE IS LITTLE AVAILABLE DEEP LAYER
MOISTURE...SO ACTUAL SNOWFALL AMOUNTS SHOULD BE LIGHT...ONLY
PERHAPS A COUPLE TENTHS OF AN INCH OF ACCUMULATION.

KREIN

&&

.SHORT TERM...
206 PM CST

TONIGHT THROUGH MONDAY NIGHT...

COOL AIR HAS STRUGGLED TO SLIDE SOUTH THIS AFTERNOON...HOWEVER TEMPS
ARE BEGINNING TO FALL INTO THE UPR 20S ACROSS FAR NORTHEAST IL.
ACROSS THE CENTRAL/SOUTHERN CWFA TEMPS REMAIN IN THE LOW 30S WITH
DEW POINT DEPRESSIONS NOT MUCH MORE THAN 1 TO 2 DEGREES. NORTH OF
I-80 PRECIP IS MAINLY FLURRIES...WITH A RAIN/SNOW MIX SLOWLY
CHANGING TO ALL SNOW LATER THIS AFTERNOON ACROSS THE SOUTHERN CWFA.
THE SHORTWAVE THAT BROUGHT THE LIGHT SNOW CONTINUES TO SLIDE EAST
ACROSS SOUTHERN IL...AND WILL STEADILY BRING AN END TO THE PRECIP
ACROSS THE FORECAST AREA THIS EVENING FROM NORTHWEST TO SOUTHEAST.
WINDS WILL GRADUALLY DIMINISH AS WELL AS THE PRESSURE GRADIENT
RELAXES.

SFC RIDGE CENTERED TO THE NORTH THIS AFTERNOON...WILL SAG SOUTH AND
EXPAND TO COVER A PORTION OF THE WESTERN GREAT LAKES/MISSOURI VALLEY
OVERNIGHT. WHILE SOME EROSION TO THE CLOUDS IS PROBABLE NORTH OF THE
FORECAST AREA...EXPECT SOME DECREASE IN CLOUDS CLOSER TO DAYBREAK
MON. CURRENTLY EXPECT OVERNIGHT LOWS TO DIP INTO THE MID/UPR
TEENS...HOWEVER THIS WILL LIKELY NOT OCCUR UNTIL CLOSER TO DAYBREAK
MON.

THE BRIEF BREAK IN CLOUDS MON MORNING WILL QUICKLY GIVE WAY TO THE
NEXT CLIPPER SYSTEM ARRIVING MON AFTN/EVE. GUIDANCE HAS MAINTAINED A
PROGRESSIVE LOOK TO THIS NEXT WAVE...HOWEVER OPERATIONAL SOLUTIONS
ARE EQUALLY BULLISH ON EROSION OF MOISTURE WITHIN THE LOWEST FEW
LAYERS OF THE ATMOS LATE MON NGT. HAVE SOME CONCERN ABOUT P-TYPE MON
AFTN/EVE. AT THE ONSET MOISTURE WILL QUICKLY SATURATE THRU THE -10
DEG C LAYER AND TOUCH THE FAVORED DGZ...HOWEVER THE DEPTH OF THE
MOISTURE BECOMES MORE SHALLOW MON EVE. ALONG WITH THE LACK OF GOOD
LIFT AND SHALLOW MOISTURE...IT IS LOOKING MORE LIKELY THAT PRECIP
MAY BE A MIX OF FREEZING DRIZZLE/LGT-SNOW.

A WEAK THERMAL RIDGE TRIES TO PUSH OVERHEAD MON AFTN...AS LLVL FLOW
TURNS SOUTHWESTERLY. TEMPS SHUD HOVER ARND FREEZING...HOWEVER THIS
WILL HINGE ON CLOUD COVER ARRIVAL AND DEVELOPMENT OF PRECIP. IF THIS
IS DELAYED...TEMPS COULD PUSH A FEW DEGREES WARMER MON EARLY AFTN.

HEIGHTS SLOWLY INCREASE MON NGT...WITH THE MOISTURE PEELING EAST
ALONG WITH THE WEAKENING SHORTWAVE. AT THIS TIME HAVE MAINTAINED A
MENTION OF LGT SNOW OR PATCHY FREEZING DRIZZLE MON NGT...BUT COULD
END UP WITH A DRY PERIOD.

BEACHLER

&&

.LONG TERM...
206 PM CST

TUESDAY THROUGH SUNDAY...
TOWARDS THE MIDDLE OF THE WEEK ENSEMBLES MAINTAIN A HIGH CONFIDENCE
IN THE TROUGH ALONG THE SOUTHEAST CONUS WEAKENING WITH RIDGING
EXPANDING EAST ACROSS THE CENTRAL PLAINS. THIS SHUD PLACE THE BULK
OF THE REGION INTO A WEAK SFC RIDGE TUE/WED. WED AFTN THE SFC RIDGE
QUICKLY SLIDES SOUTHEAST...WHICH COULD ALLOW SOME WARM AIR TO ADVECT
NORTHEAST INTO THE CWFA AND PUSH SFC TEMPS CLOSE TO 40 DEG.

WITH A QUASI-ZONAL SETUP WED NGT/THUR...GUIDANCE SUGGESTS A ROBUST
MID-LVL VORT WILL QUICKLY SLIDE EAST FROM THE ROCKIES TOWARDS THE
PLAINS WED EVE. GUIDANCE THEN FURTHER STRENGTHENS THIS WAVE AND
LIFTS NORTHEAST ACROSS THE FORECAST AREA THUR. SOUNDINGS SUGGESTS
THAT PRECIP COULD START AS MAINLY RAIN WITH THIS SYSTEM...THEN
DYNAMICALLY COOL OVERNIGHT INTO THUR AND TRANSITION PRECIP OVER TO
LGT SNOW.

A RELATIVELY ACTIVE PATTERN CONTINUES TOWARDS THE END OF THE WEEK
INTO EARLY NEXT WEEKEND...WITH TEMPS GENERALLY IN THE UPR 20S/LOW
30S.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* BRIEF HIGH-END MVFR CIGS OFF LAKE MICHIGAN SHOULD SCATTER BY
  SUNRISE.

* PERIOD OF LIGHT SNOW POSSIBLE THIS AFTERNOON/EVENING WITH
  REDEVELOPMENT OF MVFR CIGS WHICH LINGER TONIGHT.

RATZER

//DISCUSSION...UPDATED 06Z...

WEAK HIGH PRESSURE RIDGE QUICKLY MOVING INTO FORECAST AREA FROM
THE NORTHWEST OVERNIGHT...THOUGH NORTHEAST WINDS HAVE RESULTED IN
A LAKE-INDUCED PLUME OF MVFR STRATOCU FROM ABOUT ORD EAST...WITH
BASES AROUND 2500 FT. THESE CIGS WILL LIKELY AFFECT ORD/MDW/GYY
UNTIL ABOUT SUNRISE...WHEN MODELS DEPICT NORTHEAST FLOW QUICKLY
BECOMING DISORGANIZED WITH APPROACH OF SFC RIDGE. SFC WINDS TO
BECOME LIGHT/VARIABLE FOR A TIME THIS MORNING AS THE SURFACE HIGH
PRESSURE RIDGE MOVES ACROSS THE TERMINALS...GENERALLY FLOPPING
FROM LIGHT NORTHERLY TO LIGHT SOUTHERLY BY MID-DAY.

IR SATELLITE PICS ALREADY SHOWING HIGH CLOUDS SPILLING INTO THE
REGION FROM THE NORTHWEST AHEAD OF THE NEXT WEAK CLIPPER SYSTEM
WHICH WILL AFFECT THE AREA MONDAY AFTERNOON/EVENING. LOW LEVELS
ARE INITIALLY DRY AND WILL TAKE SOME WORK TO SATURATE FROM ABOVE
AS MID-LEVEL FORCING INCREASES MID-DAY INTO EARLY AFTERNOON. MOST
GUIDANCE DOES INDICATE SOME LIGHT SNOW DEVELOPING DURING THE
PERIOD...THOUGH A COMBINATION OF WEAKENING FORCING AND FORCING
FOCUSED BELOW TEMP LAYER CONDUCIVE TO LARGER SNOWFLAKE GROWTH
SUGGESTS THIS WILL BE RATHER LIGHT. WHILE A FEW INCONSEQUENTIAL
FLURRIES COULD BEGIN SOONER...THE TIMING OF THE PERIOD MOST
LIKELY TO SEE SOME LIGHT SNOW AND MVFR CIG/POSSIBLE IFR VSBY LOOKS
TO BE DURING THE AFTERNOON AT RFD...AND DURING THE LATE AFTN/EARLY
EVENING FOR CHICAGO TERMINALS. SNOW SHOULD TAPER OFF DURING THE
EVENING AT RFD AND BY LATE EVENING FOR CHICAGO TERMINALS...WITH
LOSS OF STRONGER LIFT AND DRYING IN MID-LEVELS. SOME INDICATION
THAT THERE COULD BE A BRIEF PERIOD OF FREEZING DRIZZLE AS THE SNOW
ENDS ESPECIALLY AT RFD WHERE MID-LEVELS DRY A LITTLE MORE
QUICKLY...THOUGH MODELS MAY BE OVERDOING THE DEGREE OF SATURATION
IN THE BOUNDARY LAYER AND CONFIDENCE IS LOW THAT FZDZ WOULD OCCUR.
IT DOES HOWEVER APPEAR THAT SOME SORT OF HIGH-IFR OR LOW-MVFR CIG
MAY LINGER DURING THE NIGHT.

RATZER


//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND TRENDS.

* MEDIUM-LOW IN SNOW TIMING/INTENSITY THIS AFTERNOON AND EVENING.

RATZER

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...VFR DURING THE DAY THEN CHANCE OF -RASN AND MVFR/IFR
AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR LIKELY/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS...ESPECIALLY EARLY.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR CIGS.

IZZI

&&

.MARINE...
131 PM CST

A QUICK MOVING CLIPPER SYSTEM...CURRENTLY CENTERED ACROSS SOUTHERN
ILLINOIS...WILL RAPIDLY SHIFT EASTWARD TOWARDS THE ATLANTIC COAST
BY MONDAY MORNING. NORTHEASTERLY WINDS OF 30-35 KT CONTINUE ACROSS
THE SOUTHERN 1/3RD OF LAKE MICHIGAN...AND THESE WINDS LOOK TO
CONTINUE FOR THE NEXT FEW HOURS...BEFORE A DIMINISHING TREND BEGINS
EARLY THIS EVENING. ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD JUST
WEST OF THE LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A
PERIOD OF SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN
THE WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION.
THIS SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A
PERIOD OF STRONG NORTHERLY WINDS THURSDAY INTO EARLY FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 260310
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
910 PM CST SUN JAN 25 2015

.UPDATE...
820 PM CST

PCPN IS WINDING DOWN ACROSS THE AREA WITH ONLY SOME LINGERING
LIGHT SNOW SOUTH OF THE KANKAKEE RIVER. WHILE WINDS ARE CURRENTLY
STILL RATHER BREEZY ACROSS THE AREA...THE GENERAL TREND OF THE
REMAINDER OF THE EVENING AND OVERNIGHT SHOULD BE FOR WINDS TO
DIMINISH AND ANY LINGERING SNOW SHOULD PUSH OUT OF THE AREA.
TEMPERATURES SHOULD ALSO DROP OFF WITH PARTIALLY CLEARING SKIES
AND SOME COOLER AIR FILTERING IN AS THE LOW PRESSURE CENTER
ASSOCIATED WITH THE SYSTEM THAT BROUGHT TODAY`S PRECIPITATION
MOVES OFF TO THE SOUTHEAST.

HAVE MADE SOME CHANGES TO THE GOING FORECAST FOR TOMORROW. THE
LATEST 00Z MODEL RUNS ARE TRENDING TOWARD THE NEXT CLIPPER
DROPPING A LITTLE FARTHER SOUTH...WITH SOME MODEST LIFT IN THE
ZONE AHEAD OF A WEAK WARM FRONT ASSOCIATED WITH THE NEXT CLIPPER.
SO HAVE INCREASED POPS...WITH LIKELY POPS FOR THE AFTERNOON HOURS
ACROSS MUCH OF THE AREA...WITH THE EXCEPTION OF THE FAR SOUTHERN
PORTIONS OF THE CWA. ALSO...THE THERMAL PROFILES IN THE LATEST
MODEL SOUNDINGS SUGGEST THAT THE PCPN SHOULD BE ALL SNOW...WITH A
DEEP ENOUGH SATURATED LAYER TO SUPPORT ALL SNOW...AND LESSER
CHANCES FOR FREEZING DRIZZLE. SO...HAVE REMOVED THE FREEZING
DRIZZLE MENTION FOR THE DAYTIME HOURS. STILL FEEL THAT THERE IS A
BETTER CHANCE FOR FREEZING DRIZZLE TOMORROW NIGHT AS DRIER AIR
ALOFT LOWERS THE DEPTH OF THE SATURATED LAYER ENOUGH TO MINIMIZE
THE CHANCE FOR ICE PRODUCTION IN THE SATURATED LAYER. WHILE POPS
HAVE BEEN RAISED...THERE IS LITTLE AVAILABLE DEEP LAYER
MOISTURE...SO ACTUAL SNOWFALL AMOUNTS SHOULD BE LIGHT...ONLY
PERHAPS A COUPLE TENTHS OF AN INCH OF ACCUMULATION.

KREIN

&&

.SHORT TERM...
206 PM CST

TONIGHT THROUGH MONDAY NIGHT...

COOL AIR HAS STRUGGLED TO SLIDE SOUTH THIS AFTERNOON...HOWEVER TEMPS
ARE BEGINNING TO FALL INTO THE UPR 20S ACROSS FAR NORTHEAST IL.
ACROSS THE CENTRAL/SOUTHERN CWFA TEMPS REMAIN IN THE LOW 30S WITH
DEW POINT DEPRESSIONS NOT MUCH MORE THAN 1 TO 2 DEGREES. NORTH OF
I-80 PRECIP IS MAINLY FLURRIES...WITH A RAIN/SNOW MIX SLOWLY
CHANGING TO ALL SNOW LATER THIS AFTERNOON ACROSS THE SOUTHERN CWFA.
THE SHORTWAVE THAT BROUGHT THE LIGHT SNOW CONTINUES TO SLIDE EAST
ACROSS SOUTHERN IL...AND WILL STEADILY BRING AN END TO THE PRECIP
ACROSS THE FORECAST AREA THIS EVENING FROM NORTHWEST TO SOUTHEAST.
WINDS WILL GRADUALLY DIMINISH AS WELL AS THE PRESSURE GRADIENT
RELAXES.

SFC RIDGE CENTERED TO THE NORTH THIS AFTERNOON...WILL SAG SOUTH AND
EXPAND TO COVER A PORTION OF THE WESTERN GREAT LAKES/MISSOURI VALLEY
OVERNIGHT. WHILE SOME EROSION TO THE CLOUDS IS PROBABLE NORTH OF THE
FORECAST AREA...EXPECT SOME DECREASE IN CLOUDS CLOSER TO DAYBREAK
MON. CURRENTLY EXPECT OVERNIGHT LOWS TO DIP INTO THE MID/UPR
TEENS...HOWEVER THIS WILL LIKELY NOT OCCUR UNTIL CLOSER TO DAYBREAK
MON.

THE BRIEF BREAK IN CLOUDS MON MORNING WILL QUICKLY GIVE WAY TO THE
NEXT CLIPPER SYSTEM ARRIVING MON AFTN/EVE. GUIDANCE HAS MAINTAINED A
PROGRESSIVE LOOK TO THIS NEXT WAVE...HOWEVER OPERATIONAL SOLUTIONS
ARE EQUALLY BULLISH ON EROSION OF MOISTURE WITHIN THE LOWEST FEW
LAYERS OF THE ATMOS LATE MON NGT. HAVE SOME CONCERN ABOUT P-TYPE MON
AFTN/EVE. AT THE ONSET MOISTURE WILL QUICKLY SATURATE THRU THE -10
DEG C LAYER AND TOUCH THE FAVORED DGZ...HOWEVER THE DEPTH OF THE
MOISTURE BECOMES MORE SHALLOW MON EVE. ALONG WITH THE LACK OF GOOD
LIFT AND SHALLOW MOISTURE...IT IS LOOKING MORE LIKELY THAT PRECIP
MAY BE A MIX OF FREEZING DRIZZLE/LGT-SNOW.

A WEAK THERMAL RIDGE TRIES TO PUSH OVERHEAD MON AFTN...AS LLVL FLOW
TURNS SOUTHWESTERLY. TEMPS SHUD HOVER ARND FREEZING...HOWEVER THIS
WILL HINGE ON CLOUD COVER ARRIVAL AND DEVELOPMENT OF PRECIP. IF THIS
IS DELAYED...TEMPS COULD PUSH A FEW DEGREES WARMER MON EARLY AFTN.

HEIGHTS SLOWLY INCREASE MON NGT...WITH THE MOISTURE PEELING EAST
ALONG WITH THE WEAKENING SHORTWAVE. AT THIS TIME HAVE MAINTAINED A
MENTION OF LGT SNOW OR PATCHY FREEZING DRIZZLE MON NGT...BUT COULD
END UP WITH A DRY PERIOD.

BEACHLER

&&

.LONG TERM...
206 PM CST

TUESDAY THROUGH SUNDAY...
TOWARDS THE MIDDLE OF THE WEEK ENSEMBLES MAINTAIN A HIGH CONFIDENCE
IN THE TROUGH ALONG THE SOUTHEAST CONUS WEAKENING WITH RIDGING
EXPANDING EAST ACROSS THE CENTRAL PLAINS. THIS SHUD PLACE THE BULK
OF THE REGION INTO A WEAK SFC RIDGE TUE/WED. WED AFTN THE SFC RIDGE
QUICKLY SLIDES SOUTHEAST...WHICH COULD ALLOW SOME WARM AIR TO ADVECT
NORTHEAST INTO THE CWFA AND PUSH SFC TEMPS CLOSE TO 40 DEG.

WITH A QUASI-ZONAL SETUP WED NGT/THUR...GUIDANCE SUGGESTS A ROBUST
MID-LVL VORT WILL QUICKLY SLIDE EAST FROM THE ROCKIES TOWARDS THE
PLAINS WED EVE. GUIDANCE THEN FURTHER STRENGTHENS THIS WAVE AND
LIFTS NORTHEAST ACROSS THE FORECAST AREA THUR. SOUNDINGS SUGGESTS
THAT PRECIP COULD START AS MAINLY RAIN WITH THIS SYSTEM...THEN
DYNAMICALLY COOL OVERNIGHT INTO THUR AND TRANSITION PRECIP OVER TO
LGT SNOW.

A RELATIVELY ACTIVE PATTERN CONTINUES TOWARDS THE END OF THE WEEK
INTO EARLY NEXT WEEKEND...WITH TEMPS GENERALLY IN THE UPR 20S/LOW
30S.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* LIGHT SNOW POSSIBLE MONDAY AFTERNOON/EVENING

IZZI

//DISCUSSION...UPDATED 00Z...

SYSTEM RESPONSIBLE FOR TODAY`S WEATHER IS QUICKLY MOVING AWAY AND
ANTICIPATE WINDS TO QUICKLY SUBSIDE THIS EVENING AND SKIES TO
CLEAR OUT. MID-HIGH LEVEL CLOUDINESS WILL ARRIVE LATER TONIGHT IN
ADVANCE OF THE NEXT FAST MOVING WEAK SYSTEM SLATED TO AFFECT THE
AREA MONDAY AFTERNOON AND EVENING. STILL LOOKS LIKE A SEVERAL HOUR
PERIOD OF LIGHT SNOW COULD OCCUR MONDAY AFTERNOON AND
EVENING...BUT AMOUNTS WOULD BE LIGHT AND CONFIDENCE NOT TERRIBLY
HIGH SO HAVE JUST MAINTAINED PROB30 FOR NOW. GUIDANCE CONTINUES TO
APPEAR OVERLY PESSIMISTIC WITH RESPECT TO LOW CLOUD DEVELOPMENT
MONDAY AND HAVE LEANED TOWARD THE RECENTLY MORE SUPERIORLY
PERFORMING MAV GUIDANCE WITH JUST SOME MVFR CIGS IN THE AFTERNOON.
LIGHT WINDS OVERNIGHT INTO MONDAY MORNING WILL TREND MORE LIGHT
SOUTH TO SOUTHEAST MONDAY AFTERNOON AND EVENING.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM CONFIDENCE IN TIMING AND LOW CONFIDENCE IN OCCURRENCE OF
  LIGHT SNOW MONDAY
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...VFR DURING THE DAY THEN CHANCE OF -RASN AND MVFR/IFR
AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR LIKELY/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS...ESPECIALLY EARLY.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR CIGS.

IZZI

&&

.MARINE...
131 PM CST

A QUICK MOVING CLIPPER SYSTEM...CURRENTLY CENTERED ACROSS SOUTHERN
ILLINOIS...WILL RAPIDLY SHIFT EASTWARD TOWARDS THE ATLANTIC COAST
BY MONDAY MORNING. NORTHEASTERLY WINDS OF 30-35 KT CONTINUE ACROSS
THE SOUTHERN 1/3RD OF LAKE MICHIGAN...AND THESE WINDS LOOK TO
CONTINUE FOR THE NEXT FEW HOURS...BEFORE A DIMINISHING TREND BEGINS
EARLY THIS EVENING. ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD JUST
WEST OF THE LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A
PERIOD OF SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN
THE WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION.
THIS SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A
PERIOD OF STRONG NORTHERLY WINDS THURSDAY INTO EARLY FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 260233
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
833 PM CST SUN JAN 25 2015

.UPDATE...
820 PM CST

PCPN IS WINDING DOWN ACROSS THE AREA WITH ONLY SOME LINGERING
LIGHT SNOW SOUTH OF THE KANKAKEE RIVER. WHILE WINDS ARE CURRENTLY
STILL RATHER BREEZY ACROSS THE AREA...THE GENERAL TREND OF THE
REMAINDER OF THE EVENING AND OVERNIGHT SHOULD BE FOR WINDS TO
DIMINISH AND ANY LINGERING SNOW SHOULD PUSH OUT OF THE AREA.
TEMPERATURES SHOULD ALSO DROP OFF WITH PARTIALLY CLEARING SKIES
AND SOME COOLER AIR FILTERING IN AS THE LOW PRESSURE CENTER
ASSOCIATED WITH THE SYSTEM THAT BROUGHT TODAY`S PRECIPITATION
MOVES OFF TO THE SOUTHEAST.

HAVE MADE SOME CHANGES TO THE GOING FORECAST FOR TOMORROW. THE
LATEST 00Z MODEL RUNS ARE TRENDING TOWARD THE NEXT CLIPPER
DROPPING A LITTLE FARTHER SOUTH...WITH SOME MODEST LIFT IN THE
ZONE AHEAD OF A WEAK WARM FRONT ASSOCIATED WITH THE NEXT CLIPPER.
SO HAVE INCREASED POPS...WITH LIKELY POPS FOR THE AFTERNOON HOURS
ACROSS MUCH OF THE AREA...WITH THE EXCEPTION OF THE FAR SOUTHERN
PORTIONS OF THE CWA. ALSO...THE THERMAL PROFILES IN THE LATEST
MODEL SOUNDINGS SUGGEST THAT THE PCPN SHOULD BE ALL SNOW...WITH A
DEEP ENOUGH SATURATED LAYER TO SUPPORT ALL SNOW...AND LESSER
CHANCES FOR FREEZING DRIZZLE. SO...HAVE REMOVED THE FREEZING
DRIZZLE MENTION FOR THE DAYTIME HOURS. STILL FEEL THAT THERE IS A
BETTER CHANCE FOR FREEZING DRIZZLE TOMORROW NIGHT AS DRIER AIR
ALOFT LOWERS THE DEPTH OF THE SATURATED LAYER ENOUGH TO MINIMIZE
THE CHANCE FOR ICE PRODUCTION IN THE SATURATED LAYER. WHILE POPS
HAVE BEEN RAISED...THERE IS LITTLE AVAILABLE DEEP LAYER
MOISTURE...SO ACTUAL SNOWFALL AMOUNTS SHOULD BE LIGHT...ONLY
PERHAPS A COUPLE TENTHS OF AN INCH OF ACCUMULATION.

KREIN

&&

.SHORT TERM...
206 PM CST

TONIGHT THROUGH MONDAY NIGHT...

COOL AIR HAS STRUGGLED TO SLIDE SOUTH THIS AFTERNOON...HOWEVER TEMPS
ARE BEGINNING TO FALL INTO THE UPR 20S ACROSS FAR NORTHEAST IL.
ACROSS THE CENTRAL/SOUTHERN CWFA TEMPS REMAIN IN THE LOW 30S WITH
DEW POINT DEPRESSIONS NOT MUCH MORE THAN 1 TO 2 DEGREES. NORTH OF
I-80 PRECIP IS MAINLY FLURRIES...WITH A RAIN/SNOW MIX SLOWLY
CHANGING TO ALL SNOW LATER THIS AFTERNOON ACROSS THE SOUTHERN CWFA.
THE SHORTWAVE THAT BROUGHT THE LIGHT SNOW CONTINUES TO SLIDE EAST
ACROSS SOUTHERN IL...AND WILL STEADILY BRING AN END TO THE PRECIP
ACROSS THE FORECAST AREA THIS EVENING FROM NORTHWEST TO SOUTHEAST.
WINDS WILL GRADUALLY DIMINISH AS WELL AS THE PRESSURE GRADIENT
RELAXES.

SFC RIDGE CENTERED TO THE NORTH THIS AFTERNOON...WILL SAG SOUTH AND
EXPAND TO COVER A PORTION OF THE WESTERN GREAT LAKES/MISSOURI VALLEY
OVERNIGHT. WHILE SOME EROSION TO THE CLOUDS IS PROBABLE NORTH OF THE
FORECAST AREA...EXPECT SOME DECREASE IN CLOUDS CLOSER TO DAYBREAK
MON. CURRENTLY EXPECT OVERNIGHT LOWS TO DIP INTO THE MID/UPR
TEENS...HOWEVER THIS WILL LIKELY NOT OCCUR UNTIL CLOSER TO DAYBREAK
MON.

THE BRIEF BREAK IN CLOUDS MON MORNING WILL QUICKLY GIVE WAY TO THE
NEXT CLIPPER SYSTEM ARRIVING MON AFTN/EVE. GUIDANCE HAS MAINTAINED A
PROGRESSIVE LOOK TO THIS NEXT WAVE...HOWEVER OPERATIONAL SOLUTIONS
ARE EQUALLY BULLISH ON EROSION OF MOISTURE WITHIN THE LOWEST FEW
LAYERS OF THE ATMOS LATE MON NGT. HAVE SOME CONCERN ABOUT P-TYPE MON
AFTN/EVE. AT THE ONSET MOISTURE WILL QUICKLY SATURATE THRU THE -10
DEG C LAYER AND TOUCH THE FAVORED DGZ...HOWEVER THE DEPTH OF THE
MOISTURE BECOMES MORE SHALLOW MON EVE. ALONG WITH THE LACK OF GOOD
LIFT AND SHALLOW MOISTURE...IT IS LOOKING MORE LIKELY THAT PRECIP
MAY BE A MIX OF FREEZING DRIZZLE/LGT-SNOW.

A WEAK THERMAL RIDGE TRIES TO PUSH OVERHEAD MON AFTN...AS LLVL FLOW
TURNS SOUTHWESTERLY. TEMPS SHUD HOVER ARND FREEZING...HOWEVER THIS
WILL HINGE ON CLOUD COVER ARRIVAL AND DEVELOPMENT OF PRECIP. IF THIS
IS DELAYED...TEMPS COULD PUSH A FEW DEGREES WARMER MON EARLY AFTN.

HEIGHTS SLOWLY INCREASE MON NGT...WITH THE MOISTURE PEELING EAST
ALONG WITH THE WEAKENING SHORTWAVE. AT THIS TIME HAVE MAINTAINED A
MENTION OF LGT SNOW OR PATCHY FREEZING DRIZZLE MON NGT...BUT COULD
END UP WITH A DRY PERIOD.

BEACHLER

&&

.LONG TERM...
206 PM CST

TUESDAY THROUGH SUNDAY...
TOWARDS THE MIDDLE OF THE WEEK ENSEMBLES MAINTAIN A HIGH CONFIDENCE
IN THE TROUGH ALONG THE SOUTHEAST CONUS WEAKENING WITH RIDGING
EXPANDING EAST ACROSS THE CENTRAL PLAINS. THIS SHUD PLACE THE BULK
OF THE REGION INTO A WEAK SFC RIDGE TUE/WED. WED AFTN THE SFC RIDGE
QUICKLY SLIDES SOUTHEAST...WHICH COULD ALLOW SOME WARM AIR TO ADVECT
NORTHEAST INTO THE CWFA AND PUSH SFC TEMPS CLOSE TO 40 DEG.

WITH A QUASI-ZONAL SETUP WED NGT/THUR...GUIDANCE SUGGESTS A ROBUST
MID-LVL VORT WILL QUICKLY SLIDE EAST FROM THE ROCKIES TOWARDS THE
PLAINS WED EVE. GUIDANCE THEN FURTHER STRENGTHENS THIS WAVE AND
LIFTS NORTHEAST ACROSS THE FORECAST AREA THUR. SOUNDINGS SUGGESTS
THAT PRECIP COULD START AS MAINLY RAIN WITH THIS SYSTEM...THEN
DYNAMICALLY COOL OVERNIGHT INTO THUR AND TRANSITION PRECIP OVER TO
LGT SNOW.

A RELATIVELY ACTIVE PATTERN CONTINUES TOWARDS THE END OF THE WEEK
INTO EARLY NEXT WEEKEND...WITH TEMPS GENERALLY IN THE UPR 20S/LOW
30S.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* LIGHT SNOW POSSIBLE MONDAY AFTERNOON/EARLY EVENING

IZZI

//DISCUSSION...UPDATED 00Z...

SYSTEM RESPONSIBLE FOR TODAY`S WEATHER IS QUICKLY MOVING AWAY AND
ANTICIPATE WINDS TO QUICKLY SUBSIDE THIS EVENING AND SKIES TO
CLEAR OUT. MID-HIGH LEVEL CLOUDINESS WILL ARRIVE LATER TONIGHT IN
ADVANCE OF THE NEXT FAST MOVING WEAK SYSTEM SLATED TO AFFECT THE
AREA MONDAY AFTERNOON AND EVENING. STILL LOOKS LIKE A SEVERAL HOUR
PERIOD OF LIGHT SNOW COULD OCCUR MONDAY AFTERNOON AND
EVENING...BUT AMOUNTS WOULD BE LIGHT AND CONFIDENCE NOT TERRIBLY
HIGH SO HAVE JUST MAINTAINED PROB30 FOR NOW. GUIDANCE CONTINUES TO
APPEAR OVERLY PESSIMISTIC WITH RESPECT TO LOW CLOUD DEVELOPMENT
MONDAY AND HAVE LEANED TOWARD THE RECENTLY MORE SUPERIORLY
PERFORMING MAV GUIDANCE WITH JUST SOME MVFR CIGS IN THE AFTERNOON.
LIGHT WINDS OVERNIGHT INTO MONDAY MORNING WILL TREND MORE LIGHT
SOUTH TO SOUTHEAST MONDAY AFTERNOON AND EVENING.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM CONFIDENCE IN TIMING AND LOW CONFIDENCE IN OCCURRENCE OF
  LIGHT SNOW MONDAY
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...VFR DURING THE DAY THEN CHANCE OF -RASN AND MVFR/IFR
AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR LIKELY/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS...ESPECIALLY EARLY.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR CIGS.

IZZI

&&

.MARINE...
131 PM CST

A QUICK MOVING CLIPPER SYSTEM...CURRENTLY CENTERED ACROSS SOUTHERN
ILLINOIS...WILL RAPIDLY SHIFT EASTWARD TOWARDS THE ATLANTIC COAST
BY MONDAY MORNING. NORTHEASTERLY WINDS OF 30-35 KT CONTINUE ACROSS
THE SOUTHERN 1/3RD OF LAKE MICHIGAN...AND THESE WINDS LOOK TO
CONTINUE FOR THE NEXT FEW HOURS...BEFORE A DIMINISHING TREND BEGINS
EARLY THIS EVENING. ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD JUST
WEST OF THE LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A
PERIOD OF SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN
THE WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION.
THIS SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A
PERIOD OF STRONG NORTHERLY WINDS THURSDAY INTO EARLY FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 260233
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
833 PM CST SUN JAN 25 2015

.UPDATE...
820 PM CST

PCPN IS WINDING DOWN ACROSS THE AREA WITH ONLY SOME LINGERING
LIGHT SNOW SOUTH OF THE KANKAKEE RIVER. WHILE WINDS ARE CURRENTLY
STILL RATHER BREEZY ACROSS THE AREA...THE GENERAL TREND OF THE
REMAINDER OF THE EVENING AND OVERNIGHT SHOULD BE FOR WINDS TO
DIMINISH AND ANY LINGERING SNOW SHOULD PUSH OUT OF THE AREA.
TEMPERATURES SHOULD ALSO DROP OFF WITH PARTIALLY CLEARING SKIES
AND SOME COOLER AIR FILTERING IN AS THE LOW PRESSURE CENTER
ASSOCIATED WITH THE SYSTEM THAT BROUGHT TODAY`S PRECIPITATION
MOVES OFF TO THE SOUTHEAST.

HAVE MADE SOME CHANGES TO THE GOING FORECAST FOR TOMORROW. THE
LATEST 00Z MODEL RUNS ARE TRENDING TOWARD THE NEXT CLIPPER
DROPPING A LITTLE FARTHER SOUTH...WITH SOME MODEST LIFT IN THE
ZONE AHEAD OF A WEAK WARM FRONT ASSOCIATED WITH THE NEXT CLIPPER.
SO HAVE INCREASED POPS...WITH LIKELY POPS FOR THE AFTERNOON HOURS
ACROSS MUCH OF THE AREA...WITH THE EXCEPTION OF THE FAR SOUTHERN
PORTIONS OF THE CWA. ALSO...THE THERMAL PROFILES IN THE LATEST
MODEL SOUNDINGS SUGGEST THAT THE PCPN SHOULD BE ALL SNOW...WITH A
DEEP ENOUGH SATURATED LAYER TO SUPPORT ALL SNOW...AND LESSER
CHANCES FOR FREEZING DRIZZLE. SO...HAVE REMOVED THE FREEZING
DRIZZLE MENTION FOR THE DAYTIME HOURS. STILL FEEL THAT THERE IS A
BETTER CHANCE FOR FREEZING DRIZZLE TOMORROW NIGHT AS DRIER AIR
ALOFT LOWERS THE DEPTH OF THE SATURATED LAYER ENOUGH TO MINIMIZE
THE CHANCE FOR ICE PRODUCTION IN THE SATURATED LAYER. WHILE POPS
HAVE BEEN RAISED...THERE IS LITTLE AVAILABLE DEEP LAYER
MOISTURE...SO ACTUAL SNOWFALL AMOUNTS SHOULD BE LIGHT...ONLY
PERHAPS A COUPLE TENTHS OF AN INCH OF ACCUMULATION.

KREIN

&&

.SHORT TERM...
206 PM CST

TONIGHT THROUGH MONDAY NIGHT...

COOL AIR HAS STRUGGLED TO SLIDE SOUTH THIS AFTERNOON...HOWEVER TEMPS
ARE BEGINNING TO FALL INTO THE UPR 20S ACROSS FAR NORTHEAST IL.
ACROSS THE CENTRAL/SOUTHERN CWFA TEMPS REMAIN IN THE LOW 30S WITH
DEW POINT DEPRESSIONS NOT MUCH MORE THAN 1 TO 2 DEGREES. NORTH OF
I-80 PRECIP IS MAINLY FLURRIES...WITH A RAIN/SNOW MIX SLOWLY
CHANGING TO ALL SNOW LATER THIS AFTERNOON ACROSS THE SOUTHERN CWFA.
THE SHORTWAVE THAT BROUGHT THE LIGHT SNOW CONTINUES TO SLIDE EAST
ACROSS SOUTHERN IL...AND WILL STEADILY BRING AN END TO THE PRECIP
ACROSS THE FORECAST AREA THIS EVENING FROM NORTHWEST TO SOUTHEAST.
WINDS WILL GRADUALLY DIMINISH AS WELL AS THE PRESSURE GRADIENT
RELAXES.

SFC RIDGE CENTERED TO THE NORTH THIS AFTERNOON...WILL SAG SOUTH AND
EXPAND TO COVER A PORTION OF THE WESTERN GREAT LAKES/MISSOURI VALLEY
OVERNIGHT. WHILE SOME EROSION TO THE CLOUDS IS PROBABLE NORTH OF THE
FORECAST AREA...EXPECT SOME DECREASE IN CLOUDS CLOSER TO DAYBREAK
MON. CURRENTLY EXPECT OVERNIGHT LOWS TO DIP INTO THE MID/UPR
TEENS...HOWEVER THIS WILL LIKELY NOT OCCUR UNTIL CLOSER TO DAYBREAK
MON.

THE BRIEF BREAK IN CLOUDS MON MORNING WILL QUICKLY GIVE WAY TO THE
NEXT CLIPPER SYSTEM ARRIVING MON AFTN/EVE. GUIDANCE HAS MAINTAINED A
PROGRESSIVE LOOK TO THIS NEXT WAVE...HOWEVER OPERATIONAL SOLUTIONS
ARE EQUALLY BULLISH ON EROSION OF MOISTURE WITHIN THE LOWEST FEW
LAYERS OF THE ATMOS LATE MON NGT. HAVE SOME CONCERN ABOUT P-TYPE MON
AFTN/EVE. AT THE ONSET MOISTURE WILL QUICKLY SATURATE THRU THE -10
DEG C LAYER AND TOUCH THE FAVORED DGZ...HOWEVER THE DEPTH OF THE
MOISTURE BECOMES MORE SHALLOW MON EVE. ALONG WITH THE LACK OF GOOD
LIFT AND SHALLOW MOISTURE...IT IS LOOKING MORE LIKELY THAT PRECIP
MAY BE A MIX OF FREEZING DRIZZLE/LGT-SNOW.

A WEAK THERMAL RIDGE TRIES TO PUSH OVERHEAD MON AFTN...AS LLVL FLOW
TURNS SOUTHWESTERLY. TEMPS SHUD HOVER ARND FREEZING...HOWEVER THIS
WILL HINGE ON CLOUD COVER ARRIVAL AND DEVELOPMENT OF PRECIP. IF THIS
IS DELAYED...TEMPS COULD PUSH A FEW DEGREES WARMER MON EARLY AFTN.

HEIGHTS SLOWLY INCREASE MON NGT...WITH THE MOISTURE PEELING EAST
ALONG WITH THE WEAKENING SHORTWAVE. AT THIS TIME HAVE MAINTAINED A
MENTION OF LGT SNOW OR PATCHY FREEZING DRIZZLE MON NGT...BUT COULD
END UP WITH A DRY PERIOD.

BEACHLER

&&

.LONG TERM...
206 PM CST

TUESDAY THROUGH SUNDAY...
TOWARDS THE MIDDLE OF THE WEEK ENSEMBLES MAINTAIN A HIGH CONFIDENCE
IN THE TROUGH ALONG THE SOUTHEAST CONUS WEAKENING WITH RIDGING
EXPANDING EAST ACROSS THE CENTRAL PLAINS. THIS SHUD PLACE THE BULK
OF THE REGION INTO A WEAK SFC RIDGE TUE/WED. WED AFTN THE SFC RIDGE
QUICKLY SLIDES SOUTHEAST...WHICH COULD ALLOW SOME WARM AIR TO ADVECT
NORTHEAST INTO THE CWFA AND PUSH SFC TEMPS CLOSE TO 40 DEG.

WITH A QUASI-ZONAL SETUP WED NGT/THUR...GUIDANCE SUGGESTS A ROBUST
MID-LVL VORT WILL QUICKLY SLIDE EAST FROM THE ROCKIES TOWARDS THE
PLAINS WED EVE. GUIDANCE THEN FURTHER STRENGTHENS THIS WAVE AND
LIFTS NORTHEAST ACROSS THE FORECAST AREA THUR. SOUNDINGS SUGGESTS
THAT PRECIP COULD START AS MAINLY RAIN WITH THIS SYSTEM...THEN
DYNAMICALLY COOL OVERNIGHT INTO THUR AND TRANSITION PRECIP OVER TO
LGT SNOW.

A RELATIVELY ACTIVE PATTERN CONTINUES TOWARDS THE END OF THE WEEK
INTO EARLY NEXT WEEKEND...WITH TEMPS GENERALLY IN THE UPR 20S/LOW
30S.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* LIGHT SNOW POSSIBLE MONDAY AFTERNOON/EARLY EVENING

IZZI

//DISCUSSION...UPDATED 00Z...

SYSTEM RESPONSIBLE FOR TODAY`S WEATHER IS QUICKLY MOVING AWAY AND
ANTICIPATE WINDS TO QUICKLY SUBSIDE THIS EVENING AND SKIES TO
CLEAR OUT. MID-HIGH LEVEL CLOUDINESS WILL ARRIVE LATER TONIGHT IN
ADVANCE OF THE NEXT FAST MOVING WEAK SYSTEM SLATED TO AFFECT THE
AREA MONDAY AFTERNOON AND EVENING. STILL LOOKS LIKE A SEVERAL HOUR
PERIOD OF LIGHT SNOW COULD OCCUR MONDAY AFTERNOON AND
EVENING...BUT AMOUNTS WOULD BE LIGHT AND CONFIDENCE NOT TERRIBLY
HIGH SO HAVE JUST MAINTAINED PROB30 FOR NOW. GUIDANCE CONTINUES TO
APPEAR OVERLY PESSIMISTIC WITH RESPECT TO LOW CLOUD DEVELOPMENT
MONDAY AND HAVE LEANED TOWARD THE RECENTLY MORE SUPERIORLY
PERFORMING MAV GUIDANCE WITH JUST SOME MVFR CIGS IN THE AFTERNOON.
LIGHT WINDS OVERNIGHT INTO MONDAY MORNING WILL TREND MORE LIGHT
SOUTH TO SOUTHEAST MONDAY AFTERNOON AND EVENING.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM CONFIDENCE IN TIMING AND LOW CONFIDENCE IN OCCURRENCE OF
  LIGHT SNOW MONDAY
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...VFR DURING THE DAY THEN CHANCE OF -RASN AND MVFR/IFR
AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR LIKELY/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS...ESPECIALLY EARLY.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR CIGS.

IZZI

&&

.MARINE...
131 PM CST

A QUICK MOVING CLIPPER SYSTEM...CURRENTLY CENTERED ACROSS SOUTHERN
ILLINOIS...WILL RAPIDLY SHIFT EASTWARD TOWARDS THE ATLANTIC COAST
BY MONDAY MORNING. NORTHEASTERLY WINDS OF 30-35 KT CONTINUE ACROSS
THE SOUTHERN 1/3RD OF LAKE MICHIGAN...AND THESE WINDS LOOK TO
CONTINUE FOR THE NEXT FEW HOURS...BEFORE A DIMINISHING TREND BEGINS
EARLY THIS EVENING. ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD JUST
WEST OF THE LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A
PERIOD OF SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN
THE WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION.
THIS SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A
PERIOD OF STRONG NORTHERLY WINDS THURSDAY INTO EARLY FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 252342
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
542 PM CST SUN JAN 25 2015

.SHORT TERM...
206 PM CST

TONIGHT THROUGH MONDAY NIGHT...

COOL AIR HAS STRUGGLED TO SLIDE SOUTH THIS AFTERNOON...HOWEVER TEMPS
ARE BEGINNING TO FALL INTO THE UPR 20S ACROSS FAR NORTHEAST IL.
ACROSS THE CENTRAL/SOUTHERN CWFA TEMPS REMAIN IN THE LOW 30S WITH
DEW POINT DEPRESSIONS NOT MUCH MORE THAN 1 TO 2 DEGREES. NORTH OF
I-80 PRECIP IS MAINLY FLURRIES...WITH A RAIN/SNOW MIX SLOWLY
CHANGING TO ALL SNOW LATER THIS AFTERNOON ACROSS THE SOUTHERN CWFA.
THE SHORTWAVE THAT BROUGHT THE LIGHT SNOW CONTINUES TO SLIDE EAST
ACROSS SOUTHERN IL...AND WILL STEADILY BRING AN END TO THE PRECIP
ACROSS THE FORECAST AREA THIS EVENING FROM NORTHWEST TO SOUTHEAST.
WINDS WILL GRADUALLY DIMINISH AS WELL AS THE PRESSURE GRADIENT
RELAXES.

SFC RIDGE CENTERED TO THE NORTH THIS AFTERNOON...WILL SAG SOUTH AND
EXPAND TO COVER A PORTION OF THE WESTERN GREAT LAKES/MISSOURI VALLEY
OVERNIGHT. WHILE SOME EROSION TO THE CLOUDS IS PROBABLE NORTH OF THE
FORECAST AREA...EXPECT SOME DECREASE IN CLOUDS CLOSER TO DAYBREAK
MON. CURRENTLY EXPECT OVERNIGHT LOWS TO DIP INTO THE MID/UPR
TEENS...HOWEVER THIS WILL LIKELY NOT OCCUR UNTIL CLOSER TO DAYBREAK
MON.

THE BRIEF BREAK IN CLOUDS MON MORNING WILL QUICKLY GIVE WAY TO THE
NEXT CLIPPER SYSTEM ARRIVING MON AFTN/EVE. GUIDANCE HAS MAINTAINED A
PROGRESSIVE LOOK TO THIS NEXT WAVE...HOWEVER OPERATIONAL SOLUTIONS
ARE EQUALLY BULLISH ON EROSION OF MOISTURE WITHIN THE LOWEST FEW
LAYERS OF THE ATMOS LATE MON NGT. HAVE SOME CONCERN ABOUT P-TYPE MON
AFTN/EVE. AT THE ONSET MOISTURE WILL QUICKLY SATURATE THRU THE -10
DEG C LAYER AND TOUCH THE FAVORED DGZ...HOWEVER THE DEPTH OF THE
MOISTURE BECOMES MORE SHALLOW MON EVE. ALONG WITH THE LACK OF GOOD
LIFT AND SHALLOW MOISTURE...IT IS LOOKING MORE LIKELY THAT PRECIP
MAY BE A MIX OF FREEZING DRIZZLE/LGT-SNOW.

A WEAK THERMAL RIDGE TRIES TO PUSH OVERHEAD MON AFTN...AS LLVL FLOW
TURNS SOUTHWESTERLY. TEMPS SHUD HOVER ARND FREEZING...HOWEVER THIS
WILL HINGE ON CLOUD COVER ARRIVAL AND DEVELOPMENT OF PRECIP. IF THIS
IS DELAYED...TEMPS COULD PUSH A FEW DEGREES WARMER MON EARLY AFTN.

HEIGHTS SLOWLY INCREASE MON NGT...WITH THE MOISTURE PEELING EAST
ALONG WITH THE WEAKENING SHORTWAVE. AT THIS TIME HAVE MAINTAINED A
MENTION OF LGT SNOW OR PATCHY FREEZING DRIZZLE MON NGT...BUT COULD
END UP WITH A DRY PERIOD.

BEACHLER

&&

.LONG TERM...
206 PM CST

TUESDAY THROUGH SUNDAY...
TOWARDS THE MIDDLE OF THE WEEK ENSEMBLES MAINTAIN A HIGH CONFIDENCE
IN THE TROUGH ALONG THE SOUTHEAST CONUS WEAKENING WITH RIDGING
EXPANDING EAST ACROSS THE CENTRAL PLAINS. THIS SHUD PLACE THE BULK
OF THE REGION INTO A WEAK SFC RIDGE TUE/WED. WED AFTN THE SFC RIDGE
QUICKLY SLIDES SOUTHEAST...WHICH COULD ALLOW SOME WARM AIR TO ADVECT
NORTHEAST INTO THE CWFA AND PUSH SFC TEMPS CLOSE TO 40 DEG.

WITH A QUASI-ZONAL SETUP WED NGT/THUR...GUIDANCE SUGGESTS A ROBUST
MID-LVL VORT WILL QUICKLY SLIDE EAST FROM THE ROCKIES TOWARDS THE
PLAINS WED EVE. GUIDANCE THEN FURTHER STRENGTHENS THIS WAVE AND
LIFTS NORTHEAST ACROSS THE FORECAST AREA THUR. SOUNDINGS SUGGESTS
THAT PRECIP COULD START AS MAINLY RAIN WITH THIS SYSTEM...THEN
DYNAMICALLY COOL OVERNIGHT INTO THUR AND TRANSITION PRECIP OVER TO
LGT SNOW.

A RELATIVELY ACTIVE PATTERN CONTINUES TOWARDS THE END OF THE WEEK
INTO EARLY NEXT WEEKEND...WITH TEMPS GENERALLY IN THE UPR 20S/LOW
30S.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* LIGHT SNOW POSSIBLE MONDAY AFTERNOON/EARLY EVENING

IZZI

//DISCUSSION...UPDATED 00Z...

SYSTEM RESPONSIBLE FOR TODAY`S WEATHER IS QUICKLY MOVING AWAY AND
ANTICIPATE WINDS TO QUICKLY SUBSIDE THIS EVENING AND SKIES TO
CLEAR OUT. MID-HIGH LEVEL CLOUDINESS WILL ARRIVE LATER TONIGHT IN
ADVANCE OF THE NEXT FAST MOVING WEAK SYSTEM SLATED TO AFFECT THE
AREA MONDAY AFTERNOON AND EVENING. STILL LOOKS LIKE A SEVERAL HOUR
PERIOD OF LIGHT SNOW COULD OCCUR MONDAY AFTERNOON AND
EVENING...BUT AMOUNTS WOULD BE LIGHT AND CONFIDENCE NOT TERRIBLY
HIGH SO HAVE JUST MAINTAINED PROB30 FOR NOW. GUIDANCE CONTINUES TO
APPEAR OVERLY PESSIMISTIC WITH RESPECT TO LOW CLOUD DEVELOPMENT
MONDAY AND HAVE LEANED TOWARD THE RECENTLY MORE SUPERIORLY
PERFORMING MAV GUIDANCE WITH JUST SOME MVFR CIGS IN THE AFTERNOON.
LIGHT WINDS OVERNIGHT INTO MONDAY MORNING WILL TREND MORE LIGHT
SOUTH TO SOUTHEAST MONDAY AFTERNOON AND EVENING.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM CONFIDENCE IN TIMING AND LOW CONFIDENCE IN OCCURRENCE OF
  LIGHT SNOW MONDAY
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...VFR DURING THE DAY THEN CHANCE OF -RASN AND MVFR/IFR
AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR LIKELY/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS...ESPECIALLY EARLY.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR CIGS.

IZZI

&&

.MARINE...
131 PM CST

A QUICK MOVING CLIPPER SYSTEM...CURRENTLY CENTERED ACROSS SOUTHERN
ILLINOIS...WILL RAPIDLY SHIFT EASTWARD TOWARDS THE ATLANTIC COAST
BY MONDAY MORNING. NORTHEASTERLY WINDS OF 30-35 KT CONTINUE ACROSS
THE SOUTHERN 1/3RD OF LAKE MICHIGAN...AND THESE WINDS LOOK TO
CONTINUE FOR THE NEXT FEW HOURS...BEFORE A DIMINISHING TREND BEGINS
EARLY THIS EVENING. ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD JUST
WEST OF THE LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A
PERIOD OF SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN
THE WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION.
THIS SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A
PERIOD OF STRONG NORTHERLY WINDS THURSDAY INTO EARLY FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-LMZ743-
     LMZ744-LMZ745-LMZ777-LMZ779-LMZ874-LMZ876-LMZ878 UNTIL 6 PM
     SUNDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 252342
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
542 PM CST SUN JAN 25 2015

.SHORT TERM...
206 PM CST

TONIGHT THROUGH MONDAY NIGHT...

COOL AIR HAS STRUGGLED TO SLIDE SOUTH THIS AFTERNOON...HOWEVER TEMPS
ARE BEGINNING TO FALL INTO THE UPR 20S ACROSS FAR NORTHEAST IL.
ACROSS THE CENTRAL/SOUTHERN CWFA TEMPS REMAIN IN THE LOW 30S WITH
DEW POINT DEPRESSIONS NOT MUCH MORE THAN 1 TO 2 DEGREES. NORTH OF
I-80 PRECIP IS MAINLY FLURRIES...WITH A RAIN/SNOW MIX SLOWLY
CHANGING TO ALL SNOW LATER THIS AFTERNOON ACROSS THE SOUTHERN CWFA.
THE SHORTWAVE THAT BROUGHT THE LIGHT SNOW CONTINUES TO SLIDE EAST
ACROSS SOUTHERN IL...AND WILL STEADILY BRING AN END TO THE PRECIP
ACROSS THE FORECAST AREA THIS EVENING FROM NORTHWEST TO SOUTHEAST.
WINDS WILL GRADUALLY DIMINISH AS WELL AS THE PRESSURE GRADIENT
RELAXES.

SFC RIDGE CENTERED TO THE NORTH THIS AFTERNOON...WILL SAG SOUTH AND
EXPAND TO COVER A PORTION OF THE WESTERN GREAT LAKES/MISSOURI VALLEY
OVERNIGHT. WHILE SOME EROSION TO THE CLOUDS IS PROBABLE NORTH OF THE
FORECAST AREA...EXPECT SOME DECREASE IN CLOUDS CLOSER TO DAYBREAK
MON. CURRENTLY EXPECT OVERNIGHT LOWS TO DIP INTO THE MID/UPR
TEENS...HOWEVER THIS WILL LIKELY NOT OCCUR UNTIL CLOSER TO DAYBREAK
MON.

THE BRIEF BREAK IN CLOUDS MON MORNING WILL QUICKLY GIVE WAY TO THE
NEXT CLIPPER SYSTEM ARRIVING MON AFTN/EVE. GUIDANCE HAS MAINTAINED A
PROGRESSIVE LOOK TO THIS NEXT WAVE...HOWEVER OPERATIONAL SOLUTIONS
ARE EQUALLY BULLISH ON EROSION OF MOISTURE WITHIN THE LOWEST FEW
LAYERS OF THE ATMOS LATE MON NGT. HAVE SOME CONCERN ABOUT P-TYPE MON
AFTN/EVE. AT THE ONSET MOISTURE WILL QUICKLY SATURATE THRU THE -10
DEG C LAYER AND TOUCH THE FAVORED DGZ...HOWEVER THE DEPTH OF THE
MOISTURE BECOMES MORE SHALLOW MON EVE. ALONG WITH THE LACK OF GOOD
LIFT AND SHALLOW MOISTURE...IT IS LOOKING MORE LIKELY THAT PRECIP
MAY BE A MIX OF FREEZING DRIZZLE/LGT-SNOW.

A WEAK THERMAL RIDGE TRIES TO PUSH OVERHEAD MON AFTN...AS LLVL FLOW
TURNS SOUTHWESTERLY. TEMPS SHUD HOVER ARND FREEZING...HOWEVER THIS
WILL HINGE ON CLOUD COVER ARRIVAL AND DEVELOPMENT OF PRECIP. IF THIS
IS DELAYED...TEMPS COULD PUSH A FEW DEGREES WARMER MON EARLY AFTN.

HEIGHTS SLOWLY INCREASE MON NGT...WITH THE MOISTURE PEELING EAST
ALONG WITH THE WEAKENING SHORTWAVE. AT THIS TIME HAVE MAINTAINED A
MENTION OF LGT SNOW OR PATCHY FREEZING DRIZZLE MON NGT...BUT COULD
END UP WITH A DRY PERIOD.

BEACHLER

&&

.LONG TERM...
206 PM CST

TUESDAY THROUGH SUNDAY...
TOWARDS THE MIDDLE OF THE WEEK ENSEMBLES MAINTAIN A HIGH CONFIDENCE
IN THE TROUGH ALONG THE SOUTHEAST CONUS WEAKENING WITH RIDGING
EXPANDING EAST ACROSS THE CENTRAL PLAINS. THIS SHUD PLACE THE BULK
OF THE REGION INTO A WEAK SFC RIDGE TUE/WED. WED AFTN THE SFC RIDGE
QUICKLY SLIDES SOUTHEAST...WHICH COULD ALLOW SOME WARM AIR TO ADVECT
NORTHEAST INTO THE CWFA AND PUSH SFC TEMPS CLOSE TO 40 DEG.

WITH A QUASI-ZONAL SETUP WED NGT/THUR...GUIDANCE SUGGESTS A ROBUST
MID-LVL VORT WILL QUICKLY SLIDE EAST FROM THE ROCKIES TOWARDS THE
PLAINS WED EVE. GUIDANCE THEN FURTHER STRENGTHENS THIS WAVE AND
LIFTS NORTHEAST ACROSS THE FORECAST AREA THUR. SOUNDINGS SUGGESTS
THAT PRECIP COULD START AS MAINLY RAIN WITH THIS SYSTEM...THEN
DYNAMICALLY COOL OVERNIGHT INTO THUR AND TRANSITION PRECIP OVER TO
LGT SNOW.

A RELATIVELY ACTIVE PATTERN CONTINUES TOWARDS THE END OF THE WEEK
INTO EARLY NEXT WEEKEND...WITH TEMPS GENERALLY IN THE UPR 20S/LOW
30S.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* LIGHT SNOW POSSIBLE MONDAY AFTERNOON/EARLY EVENING

IZZI

//DISCUSSION...UPDATED 00Z...

SYSTEM RESPONSIBLE FOR TODAY`S WEATHER IS QUICKLY MOVING AWAY AND
ANTICIPATE WINDS TO QUICKLY SUBSIDE THIS EVENING AND SKIES TO
CLEAR OUT. MID-HIGH LEVEL CLOUDINESS WILL ARRIVE LATER TONIGHT IN
ADVANCE OF THE NEXT FAST MOVING WEAK SYSTEM SLATED TO AFFECT THE
AREA MONDAY AFTERNOON AND EVENING. STILL LOOKS LIKE A SEVERAL HOUR
PERIOD OF LIGHT SNOW COULD OCCUR MONDAY AFTERNOON AND
EVENING...BUT AMOUNTS WOULD BE LIGHT AND CONFIDENCE NOT TERRIBLY
HIGH SO HAVE JUST MAINTAINED PROB30 FOR NOW. GUIDANCE CONTINUES TO
APPEAR OVERLY PESSIMISTIC WITH RESPECT TO LOW CLOUD DEVELOPMENT
MONDAY AND HAVE LEANED TOWARD THE RECENTLY MORE SUPERIORLY
PERFORMING MAV GUIDANCE WITH JUST SOME MVFR CIGS IN THE AFTERNOON.
LIGHT WINDS OVERNIGHT INTO MONDAY MORNING WILL TREND MORE LIGHT
SOUTH TO SOUTHEAST MONDAY AFTERNOON AND EVENING.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM CONFIDENCE IN TIMING AND LOW CONFIDENCE IN OCCURRENCE OF
  LIGHT SNOW MONDAY
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...VFR DURING THE DAY THEN CHANCE OF -RASN AND MVFR/IFR
AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR LIKELY/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS...ESPECIALLY EARLY.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR CIGS.

IZZI

&&

.MARINE...
131 PM CST

A QUICK MOVING CLIPPER SYSTEM...CURRENTLY CENTERED ACROSS SOUTHERN
ILLINOIS...WILL RAPIDLY SHIFT EASTWARD TOWARDS THE ATLANTIC COAST
BY MONDAY MORNING. NORTHEASTERLY WINDS OF 30-35 KT CONTINUE ACROSS
THE SOUTHERN 1/3RD OF LAKE MICHIGAN...AND THESE WINDS LOOK TO
CONTINUE FOR THE NEXT FEW HOURS...BEFORE A DIMINISHING TREND BEGINS
EARLY THIS EVENING. ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD JUST
WEST OF THE LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A
PERIOD OF SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN
THE WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION.
THIS SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A
PERIOD OF STRONG NORTHERLY WINDS THURSDAY INTO EARLY FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-LMZ743-
     LMZ744-LMZ745-LMZ777-LMZ779-LMZ874-LMZ876-LMZ878 UNTIL 6 PM
     SUNDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 252209
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
409 PM CST SUN JAN 25 2015

.SHORT TERM...
206 PM CST

TONIGHT THROUGH MONDAY NIGHT...

COOL AIR HAS STRUGGLED TO SLIDE SOUTH THIS AFTERNOON...HOWEVER TEMPS
ARE BEGINNING TO FALL INTO THE UPR 20S ACROSS FAR NORTHEAST IL.
ACROSS THE CENTRAL/SOUTHERN CWFA TEMPS REMAIN IN THE LOW 30S WITH
DEW POINT DEPRESSIONS NOT MUCH MORE THAN 1 TO 2 DEGREES. NORTH OF
I-80 PRECIP IS MAINLY FLURRIES...WITH A RAIN/SNOW MIX SLOWLY
CHANGING TO ALL SNOW LATER THIS AFTERNOON ACROSS THE SOUTHERN CWFA.
THE SHORTWAVE THAT BROUGHT THE LIGHT SNOW CONTINUES TO SLIDE EAST
ACROSS SOUTHERN IL...AND WILL STEADILY BRING AN END TO THE PRECIP
ACROSS THE FORECAST AREA THIS EVENING FROM NORTHWEST TO SOUTHEAST.
WINDS WILL GRADUALLY DIMINISH AS WELL AS THE PRESSURE GRADIENT
RELAXES.

SFC RIDGE CENTERED TO THE NORTH THIS AFTERNOON...WILL SAG SOUTH AND
EXPAND TO COVER A PORTION OF THE WESTERN GREAT LAKES/MISSOURI VALLEY
OVERNIGHT. WHILE SOME EROSION TO THE CLOUDS IS PROBABLE NORTH OF THE
FORECAST AREA...EXPECT SOME DECREASE IN CLOUDS CLOSER TO DAYBREAK
MON. CURRENTLY EXPECT OVERNIGHT LOWS TO DIP INTO THE MID/UPR
TEENS...HOWEVER THIS WILL LIKELY NOT OCCUR UNTIL CLOSER TO DAYBREAK
MON.

THE BRIEF BREAK IN CLOUDS MON MORNING WILL QUICKLY GIVE WAY TO THE
NEXT CLIPPER SYSTEM ARRIVING MON AFTN/EVE. GUIDANCE HAS MAINTAINED A
PROGRESSIVE LOOK TO THIS NEXT WAVE...HOWEVER OPERATIONAL SOLUTIONS
ARE EQUALLY BULLISH ON EROSION OF MOISTURE WITHIN THE LOWEST FEW
LAYERS OF THE ATMOS LATE MON NGT. HAVE SOME CONCERN ABOUT P-TYPE MON
AFTN/EVE. AT THE ONSET MOISTURE WILL QUICKLY SATURATE THRU THE -10
DEG C LAYER AND TOUCH THE FAVORED DGZ...HOWEVER THE DEPTH OF THE
MOISTURE BECOMES MORE SHALLOW MON EVE. ALONG WITH THE LACK OF GOOD
LIFT AND SHALLOW MOISTURE...IT IS LOOKING MORE LIKELY THAT PRECIP
MAY BE A MIX OF FREEZING DRIZZLE/LGT-SNOW.

A WEAK THERMAL RIDGE TRIES TO PUSH OVERHEAD MON AFTN...AS LLVL FLOW
TURNS SOUTHWESTERLY. TEMPS SHUD HOVER ARND FREEZING...HOWEVER THIS
WILL HINGE ON CLOUD COVER ARRIVAL AND DEVELOPMENT OF PRECIP. IF THIS
IS DELAYED...TEMPS COULD PUSH A FEW DEGREES WARMER MON EARLY AFTN.

HEIGHTS SLOWLY INCREASE MON NGT...WITH THE MOISTURE PEELING EAST
ALONG WITH THE WEAKENING SHORTWAVE. AT THIS TIME HAVE MAINTAINED A
MENTION OF LGT SNOW OR PATCHY FREEZING DRIZZLE MON NGT...BUT COULD
END UP WITH A DRY PERIOD.

BEACHLER

&&

.LONG TERM...
206 PM CST

TUESDAY THROUGH SUNDAY...
TOWARDS THE MIDDLE OF THE WEEK ENSEMBLES MAINTAIN A HIGH CONFIDENCE
IN THE TROUGH ALONG THE SOUTHEAST CONUS WEAKENING WITH RIDGING
EXPANDING EAST ACROSS THE CENTRAL PLAINS. THIS SHUD PLACE THE BULK
OF THE REGION INTO A WEAK SFC RIDGE TUE/WED. WED AFTN THE SFC RIDGE
QUICKLY SLIDES SOUTHEAST...WHICH COULD ALLOW SOME WARM AIR TO ADVECT
NORTHEAST INTO THE CWFA AND PUSH SFC TEMPS CLOSE TO 40 DEG.

WITH A QUASI-ZONAL SETUP WED NGT/THUR...GUIDANCE SUGGESTS A ROBUST
MID-LVL VORT WILL QUICKLY SLIDE EAST FROM THE ROCKIES TOWARDS THE
PLAINS WED EVE. GUIDANCE THEN FURTHER STRENGTHENS THIS WAVE AND
LIFTS NORTHEAST ACROSS THE FORECAST AREA THUR. SOUNDINGS SUGGESTS
THAT PRECIP COULD START AS MAINLY RAIN WITH THIS SYSTEM...THEN
DYNAMICALLY COOL OVERNIGHT INTO THUR AND TRANSITION PRECIP OVER TO
LGT SNOW.

A RELATIVELY ACTIVE PATTERN CONTINUES TOWARDS THE END OF THE WEEK
INTO EARLY NEXT WEEKEND...WITH TEMPS GENERALLY IN THE UPR 20S/LOW
30S.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* MVFR CIGS UNTIL EARLY EVENING
* STRONG/GUSTY NORTHEAST WINDS UNTIL EARLY EVENING
* LIGHT SNOW LATE MONDAY AFTERNOON

IZZI

//DISCUSSION...UPDATED 18Z...

LOW PRESSURE NEAR STL WILL SLOWLY TRACK EAST ACROSS THE OHIO
VALLEY THIS AFTERNOON INTO TONIGHT. AS IT DOES...LIGHT SNOW WILL
SLOWLY TAPER OFF TO FLURRIES. NORTHEAST WINDS OFF THE LAKE MAY
ALLOW SOME LIGHT SNOW SHOWERS TO CONTINUE NEAR THE LAKE BUT NOT
EXPECTING ANYTHING SIGNIFICANT. HAVE MAINTAINED MENTION OF VFR
LIGHT SNOW THROUGH EARLY EVENING THOUGH CONFIDENCE REGARDING END
TIME IS FAIRLY LOW. VISIBILITIES AND CIGS ARE SLOWLY TRENDING UP
AND THIS WILL CONTINUE THRU THE AFTERNOON WITH PREVAILING MVFR
EXPECTED. NORTHEAST WINDS WILL REMAIN STRONG AND GUSTY WITH GUSTS
INTO THE MID/UPPER 20 KT RANGE THROUGH LATE AFTERNOON WITH A SLOW
RELAXING OF THE SPEEDS/GUSTS THRU THE EVENING. A RIDGE AXIS WILL
MOVE ACROSS THE AREA TOWARD DAYBREAK WITH WINDS BECOMING LIGHT AND
VARIABLE AND THEN SWITCHING TO SOUTHERLY MID/LATE MONDAY MORNING.

A WEAK CLIPPER SYSTEM WILL MOVE SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT AND WHILE THIS FEATURE HAS BEEN
CONSISTENT FOR A FEW DAYS...IT HAS LIMITED MOISTURE. HOWEVER...
THERE COULD BE A PERIOD OF LIGHT SNOW BY MID/LATE AFTERNOON ACROSS
NORTHERN IL THAT CONTINUES INTO MONDAY EVENING. THE CLOUD LAYERS
APPEAR DEEP ENOUGH FOR LIGHT SNOW BUT AS THE MID LEVELS DRY OUT IN
THE EVENING...PRECIP COULD TRANSITION TO LIGHT FREEZING DRIZZLE.
STILL SOME UNCERTAINTY HOW THIS PLAYS OUT...BUT OPTED TO INCLUDE A
PROB30 IN THE 30HR ORD TAF. CMS

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM FOR LIGHT SNOW MONDAY AFTERNOON...LOW FOR ASSOCIATED
  CIGS/VIS.
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE LIGHT SNOW/MVFR.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR.

RATZER

&&

.MARINE...
131 PM CST

A QUICK MOVING CLIPPER SYSTEM...CURRENTLY CENTERED ACROSS SOUTHERN
ILLINOIS...WILL RAPIDLY SHIFT EASTWARD TOWARDS THE ATLANTIC COAST
BY MONDAY MORNING. NORTHEASTERLY WINDS OF 30-35 KT CONTINUE ACROSS
THE SOUTHERN 1/3RD OF LAKE MICHIGAN...AND THESE WINDS LOOK TO
CONTINUE FOR THE NEXT FEW HOURS...BEFORE A DIMINISHING TREND BEGINS
EARLY THIS EVENING. ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD JUST
WEST OF THE LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A
PERIOD OF SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN
THE WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION.
THIS SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A
PERIOD OF STRONG NORTHERLY WINDS THURSDAY INTO EARLY FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-LMZ743-
     LMZ744-LMZ745-LMZ777-LMZ779-LMZ874-LMZ876-LMZ878 UNTIL 6 PM
     SUNDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 252209
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
409 PM CST SUN JAN 25 2015

.SHORT TERM...
206 PM CST

TONIGHT THROUGH MONDAY NIGHT...

COOL AIR HAS STRUGGLED TO SLIDE SOUTH THIS AFTERNOON...HOWEVER TEMPS
ARE BEGINNING TO FALL INTO THE UPR 20S ACROSS FAR NORTHEAST IL.
ACROSS THE CENTRAL/SOUTHERN CWFA TEMPS REMAIN IN THE LOW 30S WITH
DEW POINT DEPRESSIONS NOT MUCH MORE THAN 1 TO 2 DEGREES. NORTH OF
I-80 PRECIP IS MAINLY FLURRIES...WITH A RAIN/SNOW MIX SLOWLY
CHANGING TO ALL SNOW LATER THIS AFTERNOON ACROSS THE SOUTHERN CWFA.
THE SHORTWAVE THAT BROUGHT THE LIGHT SNOW CONTINUES TO SLIDE EAST
ACROSS SOUTHERN IL...AND WILL STEADILY BRING AN END TO THE PRECIP
ACROSS THE FORECAST AREA THIS EVENING FROM NORTHWEST TO SOUTHEAST.
WINDS WILL GRADUALLY DIMINISH AS WELL AS THE PRESSURE GRADIENT
RELAXES.

SFC RIDGE CENTERED TO THE NORTH THIS AFTERNOON...WILL SAG SOUTH AND
EXPAND TO COVER A PORTION OF THE WESTERN GREAT LAKES/MISSOURI VALLEY
OVERNIGHT. WHILE SOME EROSION TO THE CLOUDS IS PROBABLE NORTH OF THE
FORECAST AREA...EXPECT SOME DECREASE IN CLOUDS CLOSER TO DAYBREAK
MON. CURRENTLY EXPECT OVERNIGHT LOWS TO DIP INTO THE MID/UPR
TEENS...HOWEVER THIS WILL LIKELY NOT OCCUR UNTIL CLOSER TO DAYBREAK
MON.

THE BRIEF BREAK IN CLOUDS MON MORNING WILL QUICKLY GIVE WAY TO THE
NEXT CLIPPER SYSTEM ARRIVING MON AFTN/EVE. GUIDANCE HAS MAINTAINED A
PROGRESSIVE LOOK TO THIS NEXT WAVE...HOWEVER OPERATIONAL SOLUTIONS
ARE EQUALLY BULLISH ON EROSION OF MOISTURE WITHIN THE LOWEST FEW
LAYERS OF THE ATMOS LATE MON NGT. HAVE SOME CONCERN ABOUT P-TYPE MON
AFTN/EVE. AT THE ONSET MOISTURE WILL QUICKLY SATURATE THRU THE -10
DEG C LAYER AND TOUCH THE FAVORED DGZ...HOWEVER THE DEPTH OF THE
MOISTURE BECOMES MORE SHALLOW MON EVE. ALONG WITH THE LACK OF GOOD
LIFT AND SHALLOW MOISTURE...IT IS LOOKING MORE LIKELY THAT PRECIP
MAY BE A MIX OF FREEZING DRIZZLE/LGT-SNOW.

A WEAK THERMAL RIDGE TRIES TO PUSH OVERHEAD MON AFTN...AS LLVL FLOW
TURNS SOUTHWESTERLY. TEMPS SHUD HOVER ARND FREEZING...HOWEVER THIS
WILL HINGE ON CLOUD COVER ARRIVAL AND DEVELOPMENT OF PRECIP. IF THIS
IS DELAYED...TEMPS COULD PUSH A FEW DEGREES WARMER MON EARLY AFTN.

HEIGHTS SLOWLY INCREASE MON NGT...WITH THE MOISTURE PEELING EAST
ALONG WITH THE WEAKENING SHORTWAVE. AT THIS TIME HAVE MAINTAINED A
MENTION OF LGT SNOW OR PATCHY FREEZING DRIZZLE MON NGT...BUT COULD
END UP WITH A DRY PERIOD.

BEACHLER

&&

.LONG TERM...
206 PM CST

TUESDAY THROUGH SUNDAY...
TOWARDS THE MIDDLE OF THE WEEK ENSEMBLES MAINTAIN A HIGH CONFIDENCE
IN THE TROUGH ALONG THE SOUTHEAST CONUS WEAKENING WITH RIDGING
EXPANDING EAST ACROSS THE CENTRAL PLAINS. THIS SHUD PLACE THE BULK
OF THE REGION INTO A WEAK SFC RIDGE TUE/WED. WED AFTN THE SFC RIDGE
QUICKLY SLIDES SOUTHEAST...WHICH COULD ALLOW SOME WARM AIR TO ADVECT
NORTHEAST INTO THE CWFA AND PUSH SFC TEMPS CLOSE TO 40 DEG.

WITH A QUASI-ZONAL SETUP WED NGT/THUR...GUIDANCE SUGGESTS A ROBUST
MID-LVL VORT WILL QUICKLY SLIDE EAST FROM THE ROCKIES TOWARDS THE
PLAINS WED EVE. GUIDANCE THEN FURTHER STRENGTHENS THIS WAVE AND
LIFTS NORTHEAST ACROSS THE FORECAST AREA THUR. SOUNDINGS SUGGESTS
THAT PRECIP COULD START AS MAINLY RAIN WITH THIS SYSTEM...THEN
DYNAMICALLY COOL OVERNIGHT INTO THUR AND TRANSITION PRECIP OVER TO
LGT SNOW.

A RELATIVELY ACTIVE PATTERN CONTINUES TOWARDS THE END OF THE WEEK
INTO EARLY NEXT WEEKEND...WITH TEMPS GENERALLY IN THE UPR 20S/LOW
30S.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* MVFR CIGS UNTIL EARLY EVENING
* STRONG/GUSTY NORTHEAST WINDS UNTIL EARLY EVENING
* LIGHT SNOW LATE MONDAY AFTERNOON

IZZI

//DISCUSSION...UPDATED 18Z...

LOW PRESSURE NEAR STL WILL SLOWLY TRACK EAST ACROSS THE OHIO
VALLEY THIS AFTERNOON INTO TONIGHT. AS IT DOES...LIGHT SNOW WILL
SLOWLY TAPER OFF TO FLURRIES. NORTHEAST WINDS OFF THE LAKE MAY
ALLOW SOME LIGHT SNOW SHOWERS TO CONTINUE NEAR THE LAKE BUT NOT
EXPECTING ANYTHING SIGNIFICANT. HAVE MAINTAINED MENTION OF VFR
LIGHT SNOW THROUGH EARLY EVENING THOUGH CONFIDENCE REGARDING END
TIME IS FAIRLY LOW. VISIBILITIES AND CIGS ARE SLOWLY TRENDING UP
AND THIS WILL CONTINUE THRU THE AFTERNOON WITH PREVAILING MVFR
EXPECTED. NORTHEAST WINDS WILL REMAIN STRONG AND GUSTY WITH GUSTS
INTO THE MID/UPPER 20 KT RANGE THROUGH LATE AFTERNOON WITH A SLOW
RELAXING OF THE SPEEDS/GUSTS THRU THE EVENING. A RIDGE AXIS WILL
MOVE ACROSS THE AREA TOWARD DAYBREAK WITH WINDS BECOMING LIGHT AND
VARIABLE AND THEN SWITCHING TO SOUTHERLY MID/LATE MONDAY MORNING.

A WEAK CLIPPER SYSTEM WILL MOVE SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT AND WHILE THIS FEATURE HAS BEEN
CONSISTENT FOR A FEW DAYS...IT HAS LIMITED MOISTURE. HOWEVER...
THERE COULD BE A PERIOD OF LIGHT SNOW BY MID/LATE AFTERNOON ACROSS
NORTHERN IL THAT CONTINUES INTO MONDAY EVENING. THE CLOUD LAYERS
APPEAR DEEP ENOUGH FOR LIGHT SNOW BUT AS THE MID LEVELS DRY OUT IN
THE EVENING...PRECIP COULD TRANSITION TO LIGHT FREEZING DRIZZLE.
STILL SOME UNCERTAINTY HOW THIS PLAYS OUT...BUT OPTED TO INCLUDE A
PROB30 IN THE 30HR ORD TAF. CMS

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM FOR LIGHT SNOW MONDAY AFTERNOON...LOW FOR ASSOCIATED
  CIGS/VIS.
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE LIGHT SNOW/MVFR.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR.

RATZER

&&

.MARINE...
131 PM CST

A QUICK MOVING CLIPPER SYSTEM...CURRENTLY CENTERED ACROSS SOUTHERN
ILLINOIS...WILL RAPIDLY SHIFT EASTWARD TOWARDS THE ATLANTIC COAST
BY MONDAY MORNING. NORTHEASTERLY WINDS OF 30-35 KT CONTINUE ACROSS
THE SOUTHERN 1/3RD OF LAKE MICHIGAN...AND THESE WINDS LOOK TO
CONTINUE FOR THE NEXT FEW HOURS...BEFORE A DIMINISHING TREND BEGINS
EARLY THIS EVENING. ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD JUST
WEST OF THE LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A
PERIOD OF SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN
THE WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION.
THIS SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A
PERIOD OF STRONG NORTHERLY WINDS THURSDAY INTO EARLY FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-LMZ743-
     LMZ744-LMZ745-LMZ777-LMZ779-LMZ874-LMZ876-LMZ878 UNTIL 6 PM
     SUNDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 252008
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
208 PM CST SUN JAN 25 2015

.SHORT TERM...
206 PM CST

TONIGHT THROUGH MONDAY NIGHT...

COOL AIR HAS STRUGGLED TO SLIDE SOUTH THIS AFTERNOON...HOWEVER TEMPS
ARE BEGINNING TO FALL INTO THE UPR 20S ACROSS FAR NORTHEAST IL.
ACROSS THE CENTRAL/SOUTHERN CWFA TEMPS REMAIN IN THE LOW 30S WITH
DEW POINT DEPRESSIONS NOT MUCH MORE THAN 1 TO 2 DEGREES. NORTH OF
I-80 PRECIP IS MAINLY FLURRIES...WITH A RAIN/SNOW MIX SLOWLY
CHANGING TO ALL SNOW LATER THIS AFTERNOON ACROSS THE SOUTHERN CWFA.
THE SHORTWAVE THAT BROUGHT THE LIGHT SNOW CONTINUES TO SLIDE EAST
ACROSS SOUTHERN IL...AND WILL STEADILY BRING AN END TO THE PRECIP
ACROSS THE FORECAST AREA THIS EVENING FROM NORTHWEST TO SOUTHEAST.
WINDS WILL GRADUALLY DIMINISH AS WELL AS THE PRESSURE GRADIENT
RELAXES.

SFC RIDGE CENTERED TO THE NORTH THIS AFTERNOON...WILL SAG SOUTH AND
EXPAND TO COVER A PORTION OF THE WESTERN GREAT LAKES/MISSOURI VALLEY
OVERNIGHT. WHILE SOME EROSION TO THE CLOUDS IS PROBABLE NORTH OF THE
FORECAST AREA...EXPECT SOME DECREASE IN CLOUDS CLOSER TO DAYBREAK
MON. CURRENTLY EXPECT OVERNIGHT LOWS TO DIP INTO THE MID/UPR
TEENS...HOWEVER THIS WILL LIKELY NOT OCCUR UNTIL CLOSER TO DAYBREAK
MON.

THE BRIEF BREAK IN CLOUDS MON MORNING WILL QUICKLY GIVE WAY TO THE
NEXT CLIPPER SYSTEM ARRIVING MON AFTN/EVE. GUIDANCE HAS MAINTAINED A
PROGRESSIVE LOOK TO THIS NEXT WAVE...HOWEVER OPERATIONAL SOLUTIONS
ARE EQUALLY BULLISH ON EROSION OF MOISTURE WITHIN THE LOWEST FEW
LAYERS OF THE ATMOS LATE MON NGT. HAVE SOME CONCERN ABOUT P-TYPE MON
AFTN/EVE. AT THE ONSET MOISTURE WILL QUICKLY SATURATE THRU THE -10
DEG C LAYER AND TOUCH THE FAVORED DGZ...HOWEVER THE DEPTH OF THE
MOISTURE BECOMES MORE SHALLOW MON EVE. ALONG WITH THE LACK OF GOOD
LIFT AND SHALLOW MOISTURE...IT IS LOOKING MORE LIKELY THAT PRECIP
MAY BE A MIX OF FREEZING DRIZZLE/LGT-SNOW.

A WEAK THERMAL RIDGE TRIES TO PUSH OVERHEAD MON AFTN...AS LLVL FLOW
TURNS SOUTHWESTERLY. TEMPS SHUD HOVER ARND FREEZING...HOWEVER THIS
WILL HINGE ON CLOUD COVER ARRIVAL AND DEVELOPMENT OF PRECIP. IF THIS
IS DELAYED...TEMPS COULD PUSH A FEW DEGREES WARMER MON EARLY AFTN.

HEIGHTS SLOWLY INCREASE MON NGT...WITH THE MOISTURE PEELING EAST
ALONG WITH THE WEAKENING SHORTWAVE. AT THIS TIME HAVE MAINTAINED A
MENTION OF LGT SNOW OR PATCHY FREEZING DRIZZLE MON NGT...BUT COULD
END UP WITH A DRY PERIOD.

BEACHLER

&&

.LONG TERM...
206 PM CST

TUESDAY THROUGH SUNDAY...
TOWARDS THE MIDDLE OF THE WEEK ENSEMBLES MAINTAIN A HIGH CONFIDENCE
IN THE TROUGH ALONG THE SOUTHEAST CONUS WEAKENING WITH RIDGING
EXPANDING EAST ACROSS THE CENTRAL PLAINS. THIS SHUD PLACE THE BULK
OF THE REGION INTO A WEAK SFC RIDGE TUE/WED. WED AFTN THE SFC RIDGE
QUICKLY SLIDES SOUTHEAST...WHICH COULD ALLOW SOME WARM AIR TO ADVECT
NORTHEAST INTO THE CWFA AND PUSH SFC TEMPS CLOSE TO 40 DEG.

WITH A QUASI-ZONAL SETUP WED NGT/THUR...GUIDANCE SUGGESTS A ROBUST
MID-LVL VORT WILL QUICKLY SLIDE EAST FROM THE ROCKIES TOWARDS THE
PLAINS WED EVE. GUIDANCE THEN FURTHER STRENGTHENS THIS WAVE AND
LIFTS NORTHEAST ACROSS THE FORECAST AREA THUR. SOUNDINGS SUGGESTS
THAT PRECIP COULD START AS MAINLY RAIN WITH THIS SYSTEM...THEN
DYNAMICALLY COOL OVERNIGHT INTO THUR AND TRANSITION PRECIP OVER TO
LGT SNOW.

A RELATIVELY ACTIVE PATTERN CONTINUES TOWARDS THE END OF THE WEEK
INTO EARLY NEXT WEEKEND...WITH TEMPS GENERALLY IN THE UPR 20S/LOW
30S.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* LIGHT SNOW TAPERING TO FLURRIES THIS AFTERNOON.
* MVFR CIGS LIFTING THIS AFTERNOON THEN SCATTERING OUT TONIGHT.
* STRONG/GUSTY NORTHEAST WINDS THRU MID EVENING.
* LIGHT SNOW LATE MONDAY AFTERNOON. CMS

//DISCUSSION...UPDATED 18Z...

LOW PRESSURE NEAR STL WILL SLOWLY TRACK EAST ACROSS THE OHIO
VALLEY THIS AFTERNOON INTO TONIGHT. AS IT DOES...LIGHT SNOW WILL
SLOWLY TAPER OFF TO FLURRIES. NORTHEAST WINDS OFF THE LAKE MAY
ALLOW SOME LIGHT SNOW SHOWERS TO CONTINUE NEAR THE LAKE BUT NOT
EXPECTING ANYTHING SIGNIFICANT. HAVE MAINTAINED MENTION OF VFR
LIGHT SNOW THROUGH EARLY EVENING THOUGH CONFIDENCE REGARDING END
TIME IS FAIRLY LOW. VISIBILITIES AND CIGS ARE SLOWLY TRENDING UP
AND THIS WILL CONTINUE THRU THE AFTERNOON WITH PREVAILING MVFR
EXPECTED. NORTHEAST WINDS WILL REMAIN STRONG AND GUSTY WITH GUSTS
INTO THE MID/UPPER 20 KT RANGE THROUGH LATE AFTERNOON WITH A SLOW
RELAXING OF THE SPEEDS/GUSTS THRU THE EVENING. A RIDGE AXIS WILL
MOVE ACROSS THE AREA TOWARD DAYBREAK WITH WINDS BECOMING LIGHT AND
VARIABLE AND THEN SWITCHING TO SOUTHERLY MID/LATE MONDAY MORNING.

A WEAK CLIPPER SYSTEM WILL MOVE SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT AND WHILE THIS FEATURE HAS BEEN
CONSISTENT FOR A FEW DAYS...IT HAS LIMITED MOISTURE. HOWEVER...
THERE COULD BE A PERIOD OF LIGHT SNOW BY MID/LATE AFTERNOON ACROSS
NORTHERN IL THAT CONTINUES INTO MONDAY EVENING. THE CLOUD LAYERS
APPEAR DEEP ENOUGH FOR LIGHT SNOW BUT AS THE MID LEVELS DRY OUT IN
THE EVENING...PRECIP COULD TRANSITION TO LIGHT FREEZING DRIZZLE.
STILL SOME UNCERTAINTY HOW THIS PLAYS OUT...BUT OPTED TO INCLUDE A
PROB30 IN THE 30HR ORD TAF. CMS

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH FOR LIGHT SNOW TAPERING TO FLURRIES THIS AFTERNOON...LOW
  FOR SPECIFIC TIMING AND ASSOCIATED CIGS/VIS.
* MEDIUM FOR CIGS THRU THE PERIOD.
* HIGH FOR WINDS THRU THE PERIOD.
* MEDIUM FOR LIGHT SNOW MONDAY AFTERNOON...LOW FOR ASSOCIATED
  CIGS/VIS. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE LIGHT SNOW/MVFR.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR.

RATZER

&&

.MARINE...
131 PM CST

A QUICK MOVING CLIPPER SYSTEM...CURRENTLY CENTERED ACROSS SOUTHERN
ILLINOIS...WILL RAPIDLY SHIFT EASTWARD TOWARDS THE ATLANTIC COAST
BY MONDAY MORNING. NORTHEASTERLY WINDS OF 30-35 KT CONTINUE ACROSS
THE SOUTHERN 1/3RD OF LAKE MICHIGAN...AND THESE WINDS LOOK TO
CONTINUE FOR THE NEXT FEW HOURS...BEFORE A DIMINISHING TREND BEGINS
EARLY THIS EVENING. ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD JUST
WEST OF THE LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A
PERIOD OF SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN
THE WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION.
THIS SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A
PERIOD OF STRONG NORTHERLY WINDS THURSDAY INTO EARLY FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-LMZ743-
     LMZ744-LMZ745-LMZ777-LMZ779-LMZ874-LMZ876-LMZ878 UNTIL 6 PM
     SUNDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 PM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 251950
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
150 PM CST SUN JAN 25 2015

.SHORT TERM...
329 AM CST

THROUGH TONIGHT...

HAVE FURTHERED THE DIMINISHING SNOWFALL TREND IN THE FORECAST FOR
TODAY...MAINLY NORTH OF INTERSTATE 80. ACROSS THE ENTIRE AREA THIS
LOOKS TO BE A MAINLY LOW IMPACT...NUISANCE TYPE SNOW...WITH SOME
COMMUNITIES IN THE NORTH QUITE POSSIBLY NOT SEEING ANY
ACCUMULATION. HAVE CONTINUED A SPECIAL WEATHER STATEMENT FOR AREAS
ALONG AND SOUTH OF I-80.

SATELLITE IMAGERY THIS MORNING DEPICTS THE CLOSED UPPER CIRCULATION
ACROSS WESTERN IA WITH AN AREA OF COOLING CLOUD TOPS IN ADVANCE OF
THIS MOVING INTO NORTHWEST IL. THIS IS CORRELATING WITH MAINLY LIGHT
RAIN OR RAIN/SNOW MIX IN THE SMALL WINDOW OF DEEPER MOIST
ADVECTION AHEAD OF THE LOW. SIMPLE EXTRAPOLATION OF THE CURRENT
AREA OF PRECIP IN IOWA AND THE DEVELOPING DEFORMATION ON THE
BACKSIDE CLEARLY INDICATE THE SOUTHERN CWA IS MORE SUPPORTED FOR
PRECIPITATION THAN THE NORTH. AT THE SURFACE...TEMPERATURES ARE
AROUND OR JUST ABOVE FREEZING ACROSS MUCH OF THE FORECAST AREA. A
DEVELOPING COLD FRONT IS ADVANCING SOUTHWARD INTO NORTHERN IL WITH
DEW POINTS IN THE MID TO UPPER 20S NORTH OF THIS FEATURE...ANOTHER
HINDRANCE OF APPRECIABLE PRECIPITATION IN NORTHERN AREAS OF THE
FORECAST AREA.

SHORT RANGE GUIDANCE LIKE ITS LONG RANGE COUNTERPARTS THE PAST
SEVERAL DAYS SHOW A FAIR AMOUNT OF DISCREPANCY...NAMELY ON COVERAGE
OF PRECIP TODAY AND PRECIP TYPE IN THE SOUTHERN CWA THIS
MORNING...BUT THEY LEND SUPPORT TO THE OBSERVATIONAL TRENDS. AS
THE AREA OF RAIN ASSOCIATED WITH ELEVATED ISENTROPIC ASCENT MOVES
INTO THE SOUTHERN FORECAST AREA...PROFILES SUPPORT A PERIOD OF
RAIN OR MIX INITIALLY...AND SOME LOCATIONS MIGHT HAVE AIR
TEMPERATURES RIGHT AT FREEZING. WOULD EXPECT ANY FREEZING RAIN
THREAT TO BE SHORT LIVED AS PROFILES TREND TOWARD SNOW. MESOSCALE
CONVERGENCE AND BAROCLINIC FORCING FOR INDUCED LIFT WOULD BECOME
MORE FAVORED JUST TO THE NORTHEAST OF THE CLOSED 850MB
CIRCULATION AS IT PIVOTS MORE EASTWARD. THAT IS FAVORED ACROSS
THE SOUTHERN TIER OR TWO OF COUNTIES LATER THIS MORNING INTO
EARLY AFTERNOON. PROFILES ARE MILD FOR IDEAL SNOW GROWTH...AND
MAYBE EVEN FOR SNOW AT ALL DOWN TOWARD GIBSON CITY FOR MUCH OF THE
MORNING. HAVE SNOW TOTALS AROUND ONE TO TWO INCHES FROM PERU TO
RENSSELAER AND SOUTHWARD FOR TODAY...WITH SNOW DEPARTING NEAR OR
SOON AFTER SUNDOWN.

AS FOR AREAS NORTH OF INTERSTATE 80...SHOULD SEE A GRADUAL INCREASE
IN LIGHT SNOW AREAWIDE BY MID-MORNING. DRY CORRIDOR NEAR 850MB
SEEN ON EARLY MORNING AMDAR SOUNDINGS OVER CHICAGO SHOULD LIMIT
INTENSITY OF ANY SNOW IN THE NORTHERN FORECAST AREA...AS WILL JUST
LESS FORCING. AREAS OF NORTHEAST ILLINOIS STILL LOOK TO HAVE
ONSHORE FLOW BEHIND THE COLD FRONT...BUT FORECAST INVERSION
HEIGHTS AS WELL AS ADAPTED ONES FROM THE 00Z GRB RAOB LAST
EVE...INDICATE VERY MARGINAL DEPTH OF CONVECTIVE CLOUDS. THUS NOT
EXPECTING MUCH IF ANY ENHANCEMENT TO ALREADY MINIMAL SYNOPTIC
FORCING OVER NORTHEAST IL. COULD SEE SOME DISORGANIZED LIGHT SNOW
OR FLURRIES LATE THIS AFTERNOON INTO THIS EVENING AS PROFILES OF
THE LAKE INDUCED STRATOCU COOL INTO THE ICE INITIATION LAYER...BUT
THIS SHOULD NOT BE A BIG DEAL.

AREAWIDE THE NORTHEAST WINDS WILL INCREASE TO 30 MPH AND MAYBE EVEN
A LITTLE HIGHER JUST OF THE LAKE. WITH MINIMAL SNOW NORTH NOT
EXPECTING ANY BLOWING SNOW ISSUES...AND SOUTH THE LOW SNOW-TO-
LIQUID RATIOS SHOULD SUPPRESS MUCH FOR BLOWING ISSUES...THOUGH
COULD LEAD TO MORE REDUCED VISIBILITY DURING THE TIME OF FALLING
SNOW THIS AFTERNOON.

MTF

&&

.LONG TERM...
329 AM CST

MONDAY THROUGH SATURDAY...

THE DISTURBED FLOW PATTERN WILL TURN MORE NORTHWESTERLY MONDAY AND
TUESDAY AS A MAJOR SYSTEM IS EXPECTED TO DEVELOP OFF THE NORTHEAST
COAST. GIVEN THIS POSSIBLY LEADING TO A SLOWER PATTERN...AS WELL
AS THE TREND OF TODAYS SYSTEM...IT IS QUITE CONCEIVABLE THAT THE
NEXT DISTURBANCE FOR MONDAY AFTERNOON AND NIGHT TRENDS WEST AS
WELL...WHICH THE EC HAS HAD IN ITS SOLUTION FOR THREE CONSECUTIVE
RUNS. THIS SYSTEM THOUGH IS NOT AS STRONG AS TODAYS AS IT IS MORE
OF A SHEARED AREA OF VORTICITY ALONG THE LINGERING BAROCLINIC
ZONE. FORCING FOR PRECIP LOOKS PRETTY LIGHT ONCE AGAIN MONDAY
AFTERNOON AND NIGHT BUT ENOUGH TO GO A LITTLE HIGHER ON POPS FOR
NORTHERN PARTS OF THE FORECAST AREA. RIGHT NOW GUIDANCE IS IN
DECENT AGREEMENT WITH SATURATING DEEP ENOUGH FOR PRECIP TYPE TO BE
LIGHT SNOW IF IT CAN OCCUR...BUT NEED TO KEEP AN EYE OUT FOR SOME
FREEZING DRIZZLE POTENTIAL IN THESE LIGHT ASCENT SITUATIONS.

A SLOW MODERATION LOOKS TO OCCUR TUESDAY INTO WEDNESDAY AND THIS
COULD BE VERY MINIMAL DEPENDING ON CLOUD COVER WHICH REMAINS A BIG
QUESTION MARK. HAVE LEANED MORE CLOUDY TUESDAY BUT STILL THINK
WITH A WESTERLY PUSH WEDNESDAY WOULD HAVE SUN POTENTIAL. LONG
RANGE GUIDANCE INDICATES A PACIFIC SYSTEM TO BE THE NEXT ONE TO
POSSIBLY BRING PRECIPITATION TO THE AREA WEDNESDAY NIGHT INTO
THURSDAY. CONTINUE POPS DURING THIS TIME FRAME AND AT THIS POINT
PROFILES ARE NEAR THE BORDER FOR RAIN OR SNOW...SO DID NOT GET TOO
FANCY WITH THE FORECAST PRECIPITATION TYPE. BEHIND THIS SYSTEM IT
SEEMS FAVORED FOR TEMPERATURES TO COOL SOME DURING THE LATTER
HALF OF THE WEEK...TO SLIGHTLY BELOW NORMAL VALUES. OBVIOUSLY ANY
FRESH SNOW COVER WOULD HELP LEAN THAT MORE TOWARD BELOW NORMAL.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* LIGHT SNOW TAPERING TO FLURRIES THIS AFTERNOON.
* MVFR CIGS LIFTING THIS AFTERNOON THEN SCATTERING OUT TONIGHT.
* STRONG/GUSTY NORTHEAST WINDS THRU MID EVENING.
* LIGHT SNOW LATE MONDAY AFTERNOON. CMS

//DISCUSSION...UPDATED 18Z...

LOW PRESSURE NEAR STL WILL SLOWLY TRACK EAST ACROSS THE OHIO
VALLEY THIS AFTERNOON INTO TONIGHT. AS IT DOES...LIGHT SNOW WILL
SLOWLY TAPER OFF TO FLURRIES. NORTHEAST WINDS OFF THE LAKE MAY
ALLOW SOME LIGHT SNOW SHOWERS TO CONTINUE NEAR THE LAKE BUT NOT
EXPECTING ANYTHING SIGNIFICANT. HAVE MAINTAINED MENTION OF VFR
LIGHT SNOW THROUGH EARLY EVENING THOUGH CONFIDENCE REGARDING END
TIME IS FAIRLY LOW. VISIBILITIES AND CIGS ARE SLOWLY TRENDING UP
AND THIS WILL CONTINUE THRU THE AFTERNOON WITH PREVAILING MVFR
EXPECTED. NORTHEAST WINDS WILL REMAIN STRONG AND GUSTY WITH GUSTS
INTO THE MID/UPPER 20 KT RANGE THROUGH LATE AFTERNOON WITH A SLOW
RELAXING OF THE SPEEDS/GUSTS THRU THE EVENING. A RIDGE AXIS WILL
MOVE ACROSS THE AREA TOWARD DAYBREAK WITH WINDS BECOMING LIGHT AND
VARIABLE AND THEN SWITCHING TO SOUTHERLY MID/LATE MONDAY MORNING.

A WEAK CLIPPER SYSTEM WILL MOVE SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT AND WHILE THIS FEATURE HAS BEEN
CONSISTENT FOR A FEW DAYS...IT HAS LIMITED MOISTURE. HOWEVER...
THERE COULD BE A PERIOD OF LIGHT SNOW BY MID/LATE AFTERNOON ACROSS
NORTHERN IL THAT CONTINUES INTO MONDAY EVENING. THE CLOUD LAYERS
APPEAR DEEP ENOUGH FOR LIGHT SNOW BUT AS THE MID LEVELS DRY OUT IN
THE EVENING...PRECIP COULD TRANSITION TO LIGHT FREEZING DRIZZLE.
STILL SOME UNCERTAINTY HOW THIS PLAYS OUT...BUT OPTED TO INCLUDE A
PROB30 IN THE 30HR ORD TAF. CMS

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH FOR LIGHT SNOW TAPERING TO FLURRIES THIS AFTERNOON...LOW
  FOR SPECIFIC TIMING AND ASSOCIATED CIGS/VIS.
* MEDIUM FOR CIGS THRU THE PERIOD.
* HIGH FOR WINDS THRU THE PERIOD.
* MEDIUM FOR LIGHT SNOW MONDAY AFTERNOON...LOW FOR ASSOCIATED
  CIGS/VIS. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE LIGHT SNOW/MVFR.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR.

RATZER

&&

.MARINE...
131 PM CST

A QUICK MOVING CLIPPER SYSTEM...CURRENTLY CENTERED ACROSS SOUTHERN
ILLINOIS...WILL RAPIDLY SHIFT EASTWARD TOWARDS THE ATLANTIC COAST
BY MONDAY MORNING. NORTHEASTERLY WINDS OF 30-35 KT CONTINUE ACROSS
THE SOUTHERN 1/3RD OF LAKE MICHIGAN...AND THESE WINDS LOOK TO
CONTINUE FOR THE NEXT FEW HOURS...BEFORE A DIMINISHING TREND BEGINS
EARLY THIS EVENING. ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD JUST
WEST OF THE LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A
PERIOD OF SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN
THE WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION.
THIS SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A
PERIOD OF STRONG NORTHERLY WINDS THURSDAY INTO EARLY FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 6 PM SUNDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 PM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 251950
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
150 PM CST SUN JAN 25 2015

.SHORT TERM...
329 AM CST

THROUGH TONIGHT...

HAVE FURTHERED THE DIMINISHING SNOWFALL TREND IN THE FORECAST FOR
TODAY...MAINLY NORTH OF INTERSTATE 80. ACROSS THE ENTIRE AREA THIS
LOOKS TO BE A MAINLY LOW IMPACT...NUISANCE TYPE SNOW...WITH SOME
COMMUNITIES IN THE NORTH QUITE POSSIBLY NOT SEEING ANY
ACCUMULATION. HAVE CONTINUED A SPECIAL WEATHER STATEMENT FOR AREAS
ALONG AND SOUTH OF I-80.

SATELLITE IMAGERY THIS MORNING DEPICTS THE CLOSED UPPER CIRCULATION
ACROSS WESTERN IA WITH AN AREA OF COOLING CLOUD TOPS IN ADVANCE OF
THIS MOVING INTO NORTHWEST IL. THIS IS CORRELATING WITH MAINLY LIGHT
RAIN OR RAIN/SNOW MIX IN THE SMALL WINDOW OF DEEPER MOIST
ADVECTION AHEAD OF THE LOW. SIMPLE EXTRAPOLATION OF THE CURRENT
AREA OF PRECIP IN IOWA AND THE DEVELOPING DEFORMATION ON THE
BACKSIDE CLEARLY INDICATE THE SOUTHERN CWA IS MORE SUPPORTED FOR
PRECIPITATION THAN THE NORTH. AT THE SURFACE...TEMPERATURES ARE
AROUND OR JUST ABOVE FREEZING ACROSS MUCH OF THE FORECAST AREA. A
DEVELOPING COLD FRONT IS ADVANCING SOUTHWARD INTO NORTHERN IL WITH
DEW POINTS IN THE MID TO UPPER 20S NORTH OF THIS FEATURE...ANOTHER
HINDRANCE OF APPRECIABLE PRECIPITATION IN NORTHERN AREAS OF THE
FORECAST AREA.

SHORT RANGE GUIDANCE LIKE ITS LONG RANGE COUNTERPARTS THE PAST
SEVERAL DAYS SHOW A FAIR AMOUNT OF DISCREPANCY...NAMELY ON COVERAGE
OF PRECIP TODAY AND PRECIP TYPE IN THE SOUTHERN CWA THIS
MORNING...BUT THEY LEND SUPPORT TO THE OBSERVATIONAL TRENDS. AS
THE AREA OF RAIN ASSOCIATED WITH ELEVATED ISENTROPIC ASCENT MOVES
INTO THE SOUTHERN FORECAST AREA...PROFILES SUPPORT A PERIOD OF
RAIN OR MIX INITIALLY...AND SOME LOCATIONS MIGHT HAVE AIR
TEMPERATURES RIGHT AT FREEZING. WOULD EXPECT ANY FREEZING RAIN
THREAT TO BE SHORT LIVED AS PROFILES TREND TOWARD SNOW. MESOSCALE
CONVERGENCE AND BAROCLINIC FORCING FOR INDUCED LIFT WOULD BECOME
MORE FAVORED JUST TO THE NORTHEAST OF THE CLOSED 850MB
CIRCULATION AS IT PIVOTS MORE EASTWARD. THAT IS FAVORED ACROSS
THE SOUTHERN TIER OR TWO OF COUNTIES LATER THIS MORNING INTO
EARLY AFTERNOON. PROFILES ARE MILD FOR IDEAL SNOW GROWTH...AND
MAYBE EVEN FOR SNOW AT ALL DOWN TOWARD GIBSON CITY FOR MUCH OF THE
MORNING. HAVE SNOW TOTALS AROUND ONE TO TWO INCHES FROM PERU TO
RENSSELAER AND SOUTHWARD FOR TODAY...WITH SNOW DEPARTING NEAR OR
SOON AFTER SUNDOWN.

AS FOR AREAS NORTH OF INTERSTATE 80...SHOULD SEE A GRADUAL INCREASE
IN LIGHT SNOW AREAWIDE BY MID-MORNING. DRY CORRIDOR NEAR 850MB
SEEN ON EARLY MORNING AMDAR SOUNDINGS OVER CHICAGO SHOULD LIMIT
INTENSITY OF ANY SNOW IN THE NORTHERN FORECAST AREA...AS WILL JUST
LESS FORCING. AREAS OF NORTHEAST ILLINOIS STILL LOOK TO HAVE
ONSHORE FLOW BEHIND THE COLD FRONT...BUT FORECAST INVERSION
HEIGHTS AS WELL AS ADAPTED ONES FROM THE 00Z GRB RAOB LAST
EVE...INDICATE VERY MARGINAL DEPTH OF CONVECTIVE CLOUDS. THUS NOT
EXPECTING MUCH IF ANY ENHANCEMENT TO ALREADY MINIMAL SYNOPTIC
FORCING OVER NORTHEAST IL. COULD SEE SOME DISORGANIZED LIGHT SNOW
OR FLURRIES LATE THIS AFTERNOON INTO THIS EVENING AS PROFILES OF
THE LAKE INDUCED STRATOCU COOL INTO THE ICE INITIATION LAYER...BUT
THIS SHOULD NOT BE A BIG DEAL.

AREAWIDE THE NORTHEAST WINDS WILL INCREASE TO 30 MPH AND MAYBE EVEN
A LITTLE HIGHER JUST OF THE LAKE. WITH MINIMAL SNOW NORTH NOT
EXPECTING ANY BLOWING SNOW ISSUES...AND SOUTH THE LOW SNOW-TO-
LIQUID RATIOS SHOULD SUPPRESS MUCH FOR BLOWING ISSUES...THOUGH
COULD LEAD TO MORE REDUCED VISIBILITY DURING THE TIME OF FALLING
SNOW THIS AFTERNOON.

MTF

&&

.LONG TERM...
329 AM CST

MONDAY THROUGH SATURDAY...

THE DISTURBED FLOW PATTERN WILL TURN MORE NORTHWESTERLY MONDAY AND
TUESDAY AS A MAJOR SYSTEM IS EXPECTED TO DEVELOP OFF THE NORTHEAST
COAST. GIVEN THIS POSSIBLY LEADING TO A SLOWER PATTERN...AS WELL
AS THE TREND OF TODAYS SYSTEM...IT IS QUITE CONCEIVABLE THAT THE
NEXT DISTURBANCE FOR MONDAY AFTERNOON AND NIGHT TRENDS WEST AS
WELL...WHICH THE EC HAS HAD IN ITS SOLUTION FOR THREE CONSECUTIVE
RUNS. THIS SYSTEM THOUGH IS NOT AS STRONG AS TODAYS AS IT IS MORE
OF A SHEARED AREA OF VORTICITY ALONG THE LINGERING BAROCLINIC
ZONE. FORCING FOR PRECIP LOOKS PRETTY LIGHT ONCE AGAIN MONDAY
AFTERNOON AND NIGHT BUT ENOUGH TO GO A LITTLE HIGHER ON POPS FOR
NORTHERN PARTS OF THE FORECAST AREA. RIGHT NOW GUIDANCE IS IN
DECENT AGREEMENT WITH SATURATING DEEP ENOUGH FOR PRECIP TYPE TO BE
LIGHT SNOW IF IT CAN OCCUR...BUT NEED TO KEEP AN EYE OUT FOR SOME
FREEZING DRIZZLE POTENTIAL IN THESE LIGHT ASCENT SITUATIONS.

A SLOW MODERATION LOOKS TO OCCUR TUESDAY INTO WEDNESDAY AND THIS
COULD BE VERY MINIMAL DEPENDING ON CLOUD COVER WHICH REMAINS A BIG
QUESTION MARK. HAVE LEANED MORE CLOUDY TUESDAY BUT STILL THINK
WITH A WESTERLY PUSH WEDNESDAY WOULD HAVE SUN POTENTIAL. LONG
RANGE GUIDANCE INDICATES A PACIFIC SYSTEM TO BE THE NEXT ONE TO
POSSIBLY BRING PRECIPITATION TO THE AREA WEDNESDAY NIGHT INTO
THURSDAY. CONTINUE POPS DURING THIS TIME FRAME AND AT THIS POINT
PROFILES ARE NEAR THE BORDER FOR RAIN OR SNOW...SO DID NOT GET TOO
FANCY WITH THE FORECAST PRECIPITATION TYPE. BEHIND THIS SYSTEM IT
SEEMS FAVORED FOR TEMPERATURES TO COOL SOME DURING THE LATTER
HALF OF THE WEEK...TO SLIGHTLY BELOW NORMAL VALUES. OBVIOUSLY ANY
FRESH SNOW COVER WOULD HELP LEAN THAT MORE TOWARD BELOW NORMAL.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* LIGHT SNOW TAPERING TO FLURRIES THIS AFTERNOON.
* MVFR CIGS LIFTING THIS AFTERNOON THEN SCATTERING OUT TONIGHT.
* STRONG/GUSTY NORTHEAST WINDS THRU MID EVENING.
* LIGHT SNOW LATE MONDAY AFTERNOON. CMS

//DISCUSSION...UPDATED 18Z...

LOW PRESSURE NEAR STL WILL SLOWLY TRACK EAST ACROSS THE OHIO
VALLEY THIS AFTERNOON INTO TONIGHT. AS IT DOES...LIGHT SNOW WILL
SLOWLY TAPER OFF TO FLURRIES. NORTHEAST WINDS OFF THE LAKE MAY
ALLOW SOME LIGHT SNOW SHOWERS TO CONTINUE NEAR THE LAKE BUT NOT
EXPECTING ANYTHING SIGNIFICANT. HAVE MAINTAINED MENTION OF VFR
LIGHT SNOW THROUGH EARLY EVENING THOUGH CONFIDENCE REGARDING END
TIME IS FAIRLY LOW. VISIBILITIES AND CIGS ARE SLOWLY TRENDING UP
AND THIS WILL CONTINUE THRU THE AFTERNOON WITH PREVAILING MVFR
EXPECTED. NORTHEAST WINDS WILL REMAIN STRONG AND GUSTY WITH GUSTS
INTO THE MID/UPPER 20 KT RANGE THROUGH LATE AFTERNOON WITH A SLOW
RELAXING OF THE SPEEDS/GUSTS THRU THE EVENING. A RIDGE AXIS WILL
MOVE ACROSS THE AREA TOWARD DAYBREAK WITH WINDS BECOMING LIGHT AND
VARIABLE AND THEN SWITCHING TO SOUTHERLY MID/LATE MONDAY MORNING.

A WEAK CLIPPER SYSTEM WILL MOVE SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT AND WHILE THIS FEATURE HAS BEEN
CONSISTENT FOR A FEW DAYS...IT HAS LIMITED MOISTURE. HOWEVER...
THERE COULD BE A PERIOD OF LIGHT SNOW BY MID/LATE AFTERNOON ACROSS
NORTHERN IL THAT CONTINUES INTO MONDAY EVENING. THE CLOUD LAYERS
APPEAR DEEP ENOUGH FOR LIGHT SNOW BUT AS THE MID LEVELS DRY OUT IN
THE EVENING...PRECIP COULD TRANSITION TO LIGHT FREEZING DRIZZLE.
STILL SOME UNCERTAINTY HOW THIS PLAYS OUT...BUT OPTED TO INCLUDE A
PROB30 IN THE 30HR ORD TAF. CMS

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH FOR LIGHT SNOW TAPERING TO FLURRIES THIS AFTERNOON...LOW
  FOR SPECIFIC TIMING AND ASSOCIATED CIGS/VIS.
* MEDIUM FOR CIGS THRU THE PERIOD.
* HIGH FOR WINDS THRU THE PERIOD.
* MEDIUM FOR LIGHT SNOW MONDAY AFTERNOON...LOW FOR ASSOCIATED
  CIGS/VIS. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE LIGHT SNOW/MVFR.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR.

RATZER

&&

.MARINE...
131 PM CST

A QUICK MOVING CLIPPER SYSTEM...CURRENTLY CENTERED ACROSS SOUTHERN
ILLINOIS...WILL RAPIDLY SHIFT EASTWARD TOWARDS THE ATLANTIC COAST
BY MONDAY MORNING. NORTHEASTERLY WINDS OF 30-35 KT CONTINUE ACROSS
THE SOUTHERN 1/3RD OF LAKE MICHIGAN...AND THESE WINDS LOOK TO
CONTINUE FOR THE NEXT FEW HOURS...BEFORE A DIMINISHING TREND BEGINS
EARLY THIS EVENING. ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD JUST
WEST OF THE LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A
PERIOD OF SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN
THE WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION.
THIS SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A
PERIOD OF STRONG NORTHERLY WINDS THURSDAY INTO EARLY FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 6 PM SUNDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 PM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 251931
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
131 PM CST SUN JAN 25 2015

.SHORT TERM...
329 AM CST

THROUGH TONIGHT...

HAVE FURTHERED THE DIMINISHING SNOWFALL TREND IN THE FORECAST FOR
TODAY...MAINLY NORTH OF INTERSTATE 80. ACROSS THE ENTIRE AREA THIS
LOOKS TO BE A MAINLY LOW IMPACT...NUISANCE TYPE SNOW...WITH SOME
COMMUNITIES IN THE NORTH QUITE POSSIBLY NOT SEEING ANY
ACCUMULATION. HAVE CONTINUED A SPECIAL WEATHER STATEMENT FOR AREAS
ALONG AND SOUTH OF I-80.

SATELLITE IMAGERY THIS MORNING DEPICTS THE CLOSED UPPER CIRCULATION
ACROSS WESTERN IA WITH AN AREA OF COOLING CLOUD TOPS IN ADVANCE OF
THIS MOVING INTO NORTHWEST IL. THIS IS CORRELATING WITH MAINLY LIGHT
RAIN OR RAIN/SNOW MIX IN THE SMALL WINDOW OF DEEPER MOIST
ADVECTION AHEAD OF THE LOW. SIMPLE EXTRAPOLATION OF THE CURRENT
AREA OF PRECIP IN IOWA AND THE DEVELOPING DEFORMATION ON THE
BACKSIDE CLEARLY INDICATE THE SOUTHERN CWA IS MORE SUPPORTED FOR
PRECIPITATION THAN THE NORTH. AT THE SURFACE...TEMPERATURES ARE
AROUND OR JUST ABOVE FREEZING ACROSS MUCH OF THE FORECAST AREA. A
DEVELOPING COLD FRONT IS ADVANCING SOUTHWARD INTO NORTHERN IL WITH
DEW POINTS IN THE MID TO UPPER 20S NORTH OF THIS FEATURE...ANOTHER
HINDRANCE OF APPRECIABLE PRECIPITATION IN NORTHERN AREAS OF THE
FORECAST AREA.

SHORT RANGE GUIDANCE LIKE ITS LONG RANGE COUNTERPARTS THE PAST
SEVERAL DAYS SHOW A FAIR AMOUNT OF DISCREPANCY...NAMELY ON COVERAGE
OF PRECIP TODAY AND PRECIP TYPE IN THE SOUTHERN CWA THIS
MORNING...BUT THEY LEND SUPPORT TO THE OBSERVATIONAL TRENDS. AS
THE AREA OF RAIN ASSOCIATED WITH ELEVATED ISENTROPIC ASCENT MOVES
INTO THE SOUTHERN FORECAST AREA...PROFILES SUPPORT A PERIOD OF
RAIN OR MIX INITIALLY...AND SOME LOCATIONS MIGHT HAVE AIR
TEMPERATURES RIGHT AT FREEZING. WOULD EXPECT ANY FREEZING RAIN
THREAT TO BE SHORT LIVED AS PROFILES TREND TOWARD SNOW. MESOSCALE
CONVERGENCE AND BAROCLINIC FORCING FOR INDUCED LIFT WOULD BECOME
MORE FAVORED JUST TO THE NORTHEAST OF THE CLOSED 850MB
CIRCULATION AS IT PIVOTS MORE EASTWARD. THAT IS FAVORED ACROSS
THE SOUTHERN TIER OR TWO OF COUNTIES LATER THIS MORNING INTO
EARLY AFTERNOON. PROFILES ARE MILD FOR IDEAL SNOW GROWTH...AND
MAYBE EVEN FOR SNOW AT ALL DOWN TOWARD GIBSON CITY FOR MUCH OF THE
MORNING. HAVE SNOW TOTALS AROUND ONE TO TWO INCHES FROM PERU TO
RENSSELAER AND SOUTHWARD FOR TODAY...WITH SNOW DEPARTING NEAR OR
SOON AFTER SUNDOWN.

AS FOR AREAS NORTH OF INTERSTATE 80...SHOULD SEE A GRADUAL INCREASE
IN LIGHT SNOW AREAWIDE BY MID-MORNING. DRY CORRIDOR NEAR 850MB
SEEN ON EARLY MORNING AMDAR SOUNDINGS OVER CHICAGO SHOULD LIMIT
INTENSITY OF ANY SNOW IN THE NORTHERN FORECAST AREA...AS WILL JUST
LESS FORCING. AREAS OF NORTHEAST ILLINOIS STILL LOOK TO HAVE
ONSHORE FLOW BEHIND THE COLD FRONT...BUT FORECAST INVERSION
HEIGHTS AS WELL AS ADAPTED ONES FROM THE 00Z GRB RAOB LAST
EVE...INDICATE VERY MARGINAL DEPTH OF CONVECTIVE CLOUDS. THUS NOT
EXPECTING MUCH IF ANY ENHANCEMENT TO ALREADY MINIMAL SYNOPTIC
FORCING OVER NORTHEAST IL. COULD SEE SOME DISORGANIZED LIGHT SNOW
OR FLURRIES LATE THIS AFTERNOON INTO THIS EVENING AS PROFILES OF
THE LAKE INDUCED STRATOCU COOL INTO THE ICE INITIATION LAYER...BUT
THIS SHOULD NOT BE A BIG DEAL.

AREAWIDE THE NORTHEAST WINDS WILL INCREASE TO 30 MPH AND MAYBE EVEN
A LITTLE HIGHER JUST OF THE LAKE. WITH MINIMAL SNOW NORTH NOT
EXPECTING ANY BLOWING SNOW ISSUES...AND SOUTH THE LOW SNOW-TO-
LIQUID RATIOS SHOULD SUPPRESS MUCH FOR BLOWING ISSUES...THOUGH
COULD LEAD TO MORE REDUCED VISIBILITY DURING THE TIME OF FALLING
SNOW THIS AFTERNOON.

MTF

&&

.LONG TERM...
329 AM CST

MONDAY THROUGH SATURDAY...

THE DISTURBED FLOW PATTERN WILL TURN MORE NORTHWESTERLY MONDAY AND
TUESDAY AS A MAJOR SYSTEM IS EXPECTED TO DEVELOP OFF THE NORTHEAST
COAST. GIVEN THIS POSSIBLY LEADING TO A SLOWER PATTERN...AS WELL
AS THE TREND OF TODAYS SYSTEM...IT IS QUITE CONCEIVABLE THAT THE
NEXT DISTURBANCE FOR MONDAY AFTERNOON AND NIGHT TRENDS WEST AS
WELL...WHICH THE EC HAS HAD IN ITS SOLUTION FOR THREE CONSECUTIVE
RUNS. THIS SYSTEM THOUGH IS NOT AS STRONG AS TODAYS AS IT IS MORE
OF A SHEARED AREA OF VORTICITY ALONG THE LINGERING BAROCLINIC
ZONE. FORCING FOR PRECIP LOOKS PRETTY LIGHT ONCE AGAIN MONDAY
AFTERNOON AND NIGHT BUT ENOUGH TO GO A LITTLE HIGHER ON POPS FOR
NORTHERN PARTS OF THE FORECAST AREA. RIGHT NOW GUIDANCE IS IN
DECENT AGREEMENT WITH SATURATING DEEP ENOUGH FOR PRECIP TYPE TO BE
LIGHT SNOW IF IT CAN OCCUR...BUT NEED TO KEEP AN EYE OUT FOR SOME
FREEZING DRIZZLE POTENTIAL IN THESE LIGHT ASCENT SITUATIONS.

A SLOW MODERATION LOOKS TO OCCUR TUESDAY INTO WEDNESDAY AND THIS
COULD BE VERY MINIMAL DEPENDING ON CLOUD COVER WHICH REMAINS A BIG
QUESTION MARK. HAVE LEANED MORE CLOUDY TUESDAY BUT STILL THINK
WITH A WESTERLY PUSH WEDNESDAY WOULD HAVE SUN POTENTIAL. LONG
RANGE GUIDANCE INDICATES A PACIFIC SYSTEM TO BE THE NEXT ONE TO
POSSIBLY BRING PRECIPITATION TO THE AREA WEDNESDAY NIGHT INTO
THURSDAY. CONTINUE POPS DURING THIS TIME FRAME AND AT THIS POINT
PROFILES ARE NEAR THE BORDER FOR RAIN OR SNOW...SO DID NOT GET TOO
FANCY WITH THE FORECAST PRECIPITATION TYPE. BEHIND THIS SYSTEM IT
SEEMS FAVORED FOR TEMPERATURES TO COOL SOME DURING THE LATTER
HALF OF THE WEEK...TO SLIGHTLY BELOW NORMAL VALUES. OBVIOUSLY ANY
FRESH SNOW COVER WOULD HELP LEAN THAT MORE TOWARD BELOW NORMAL.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* LIGHT SNOW TAPERING TO FLURRIES THIS AFTERNOON.
* MVFR CIGS LIFTING THIS AFTERNOON THEN SCATTERING OUT TONIGHT.
* STRONG/GUSTY NORTHEAST WINDS THRU MID EVENING.
* LIGHT SNOW LATE MONDAY AFTERNOON. CMS

//DISCUSSION...UPDATED 18Z...

LOW PRESSURE NEAR STL WILL SLOWLY TRACK EAST ACROSS THE OHIO
VALLEY THIS AFTERNOON INTO TONIGHT. AS IT DOES...LIGHT SNOW WILL
SLOWLY TAPER OFF TO FLURRIES. NORTHEAST WINDS OFF THE LAKE MAY
ALLOW SOME LIGHT SNOW SHOWERS TO CONTINUE NEAR THE LAKE BUT NOT
EXPECTING ANYTHING SIGNIFICANT. HAVE MAINTAINED MENTION OF VFR
LIGHT SNOW THROUGH EARLY EVENING THOUGH CONFIDENCE REGARDING END
TIME IS FAIRLY LOW. VISIBILITIES AND CIGS ARE SLOWLY TRENDING UP
AND THIS WILL CONTINUE THRU THE AFTERNOON WITH PREVAILING MVFR
EXPECTED. NORTHEAST WINDS WILL REMAIN STRONG AND GUSTY WITH GUSTS
INTO THE MID/UPPER 20 KT RANGE THROUGH LATE AFTERNOON WITH A SLOW
RELAXING OF THE SPEEDS/GUSTS THRU THE EVENING. A RIDGE AXIS WILL
MOVE ACROSS THE AREA TOWARD DAYBREAK WITH WINDS BECOMING LIGHT AND
VARIABLE AND THEN SWITCHING TO SOUTHERLY MID/LATE MONDAY MORNING.

A WEAK CLIPPER SYSTEM WILL MOVE SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT AND WHILE THIS FEATURE HAS BEEN
CONSISTENT FOR A FEW DAYS...IT HAS LIMITED MOISTURE. HOWEVER...
THERE COULD BE A PERIOD OF LIGHT SNOW BY MID/LATE AFTERNOON ACROSS
NORTHERN IL THAT CONTINUES INTO MONDAY EVENING. THE CLOUD LAYERS
APPEAR DEEP ENOUGH FOR LIGHT SNOW BUT AS THE MID LEVELS DRY OUT IN
THE EVENING...PRECIP COULD TRANSITION TO LIGHT FREEZING DRIZZLE.
STILL SOME UNCERTAINTY HOW THIS PLAYS OUT...BUT OPTED TO INCLUDE A
PROB30 IN THE 30HR ORD TAF. CMS

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH FOR LIGHT SNOW TAPERING TO FLURRIES THIS AFTERNOON...LOW
  FOR SPECIFIC TIMING AND ASSOCIATED CIGS/VIS.
* MEDIUM FOR CIGS THRU THE PERIOD.
* HIGH FOR WINDS THRU THE PERIOD.
* MEDIUM FOR LIGHT SNOW MONDAY AFTERNOON...LOW FOR ASSOCIATED
  CIGS/VIS. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE LIGHT SNOW/MVFR.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR.

RATZER

&&

.MARINE...
131 PM CST

A QUICK MOVING CLIPPER SYSTEM...CURRENTLY CENTERED ACROSS SOUTHERN
ILLINOIS...WILL RAPIDLY SHIFT EASTWARD TOWARDS THE ATLANTIC COAST
BY MONDAY MORNING. NORTHEASTERLY WINDS OF 30-35 KT CONTINUE ACROSS
THE SOUTHERN 1/3RD OF LAKE MICHIGAN...AND THESE WINDS LOOK TO
CONTINUE FOR THE NEXT FEW HOURS...BEFORE A DIMINISHING TREND BEGINS
EARLY THIS EVENING. ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD JUST
WEST OF THE LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A
PERIOD OF SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN
THE WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION.
THIS SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A
PERIOD OF STRONG NORTHERLY WINDS THURSDAY INTO EARLY FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 6 PM SUNDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 PM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 251931
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
131 PM CST SUN JAN 25 2015

.SHORT TERM...
329 AM CST

THROUGH TONIGHT...

HAVE FURTHERED THE DIMINISHING SNOWFALL TREND IN THE FORECAST FOR
TODAY...MAINLY NORTH OF INTERSTATE 80. ACROSS THE ENTIRE AREA THIS
LOOKS TO BE A MAINLY LOW IMPACT...NUISANCE TYPE SNOW...WITH SOME
COMMUNITIES IN THE NORTH QUITE POSSIBLY NOT SEEING ANY
ACCUMULATION. HAVE CONTINUED A SPECIAL WEATHER STATEMENT FOR AREAS
ALONG AND SOUTH OF I-80.

SATELLITE IMAGERY THIS MORNING DEPICTS THE CLOSED UPPER CIRCULATION
ACROSS WESTERN IA WITH AN AREA OF COOLING CLOUD TOPS IN ADVANCE OF
THIS MOVING INTO NORTHWEST IL. THIS IS CORRELATING WITH MAINLY LIGHT
RAIN OR RAIN/SNOW MIX IN THE SMALL WINDOW OF DEEPER MOIST
ADVECTION AHEAD OF THE LOW. SIMPLE EXTRAPOLATION OF THE CURRENT
AREA OF PRECIP IN IOWA AND THE DEVELOPING DEFORMATION ON THE
BACKSIDE CLEARLY INDICATE THE SOUTHERN CWA IS MORE SUPPORTED FOR
PRECIPITATION THAN THE NORTH. AT THE SURFACE...TEMPERATURES ARE
AROUND OR JUST ABOVE FREEZING ACROSS MUCH OF THE FORECAST AREA. A
DEVELOPING COLD FRONT IS ADVANCING SOUTHWARD INTO NORTHERN IL WITH
DEW POINTS IN THE MID TO UPPER 20S NORTH OF THIS FEATURE...ANOTHER
HINDRANCE OF APPRECIABLE PRECIPITATION IN NORTHERN AREAS OF THE
FORECAST AREA.

SHORT RANGE GUIDANCE LIKE ITS LONG RANGE COUNTERPARTS THE PAST
SEVERAL DAYS SHOW A FAIR AMOUNT OF DISCREPANCY...NAMELY ON COVERAGE
OF PRECIP TODAY AND PRECIP TYPE IN THE SOUTHERN CWA THIS
MORNING...BUT THEY LEND SUPPORT TO THE OBSERVATIONAL TRENDS. AS
THE AREA OF RAIN ASSOCIATED WITH ELEVATED ISENTROPIC ASCENT MOVES
INTO THE SOUTHERN FORECAST AREA...PROFILES SUPPORT A PERIOD OF
RAIN OR MIX INITIALLY...AND SOME LOCATIONS MIGHT HAVE AIR
TEMPERATURES RIGHT AT FREEZING. WOULD EXPECT ANY FREEZING RAIN
THREAT TO BE SHORT LIVED AS PROFILES TREND TOWARD SNOW. MESOSCALE
CONVERGENCE AND BAROCLINIC FORCING FOR INDUCED LIFT WOULD BECOME
MORE FAVORED JUST TO THE NORTHEAST OF THE CLOSED 850MB
CIRCULATION AS IT PIVOTS MORE EASTWARD. THAT IS FAVORED ACROSS
THE SOUTHERN TIER OR TWO OF COUNTIES LATER THIS MORNING INTO
EARLY AFTERNOON. PROFILES ARE MILD FOR IDEAL SNOW GROWTH...AND
MAYBE EVEN FOR SNOW AT ALL DOWN TOWARD GIBSON CITY FOR MUCH OF THE
MORNING. HAVE SNOW TOTALS AROUND ONE TO TWO INCHES FROM PERU TO
RENSSELAER AND SOUTHWARD FOR TODAY...WITH SNOW DEPARTING NEAR OR
SOON AFTER SUNDOWN.

AS FOR AREAS NORTH OF INTERSTATE 80...SHOULD SEE A GRADUAL INCREASE
IN LIGHT SNOW AREAWIDE BY MID-MORNING. DRY CORRIDOR NEAR 850MB
SEEN ON EARLY MORNING AMDAR SOUNDINGS OVER CHICAGO SHOULD LIMIT
INTENSITY OF ANY SNOW IN THE NORTHERN FORECAST AREA...AS WILL JUST
LESS FORCING. AREAS OF NORTHEAST ILLINOIS STILL LOOK TO HAVE
ONSHORE FLOW BEHIND THE COLD FRONT...BUT FORECAST INVERSION
HEIGHTS AS WELL AS ADAPTED ONES FROM THE 00Z GRB RAOB LAST
EVE...INDICATE VERY MARGINAL DEPTH OF CONVECTIVE CLOUDS. THUS NOT
EXPECTING MUCH IF ANY ENHANCEMENT TO ALREADY MINIMAL SYNOPTIC
FORCING OVER NORTHEAST IL. COULD SEE SOME DISORGANIZED LIGHT SNOW
OR FLURRIES LATE THIS AFTERNOON INTO THIS EVENING AS PROFILES OF
THE LAKE INDUCED STRATOCU COOL INTO THE ICE INITIATION LAYER...BUT
THIS SHOULD NOT BE A BIG DEAL.

AREAWIDE THE NORTHEAST WINDS WILL INCREASE TO 30 MPH AND MAYBE EVEN
A LITTLE HIGHER JUST OF THE LAKE. WITH MINIMAL SNOW NORTH NOT
EXPECTING ANY BLOWING SNOW ISSUES...AND SOUTH THE LOW SNOW-TO-
LIQUID RATIOS SHOULD SUPPRESS MUCH FOR BLOWING ISSUES...THOUGH
COULD LEAD TO MORE REDUCED VISIBILITY DURING THE TIME OF FALLING
SNOW THIS AFTERNOON.

MTF

&&

.LONG TERM...
329 AM CST

MONDAY THROUGH SATURDAY...

THE DISTURBED FLOW PATTERN WILL TURN MORE NORTHWESTERLY MONDAY AND
TUESDAY AS A MAJOR SYSTEM IS EXPECTED TO DEVELOP OFF THE NORTHEAST
COAST. GIVEN THIS POSSIBLY LEADING TO A SLOWER PATTERN...AS WELL
AS THE TREND OF TODAYS SYSTEM...IT IS QUITE CONCEIVABLE THAT THE
NEXT DISTURBANCE FOR MONDAY AFTERNOON AND NIGHT TRENDS WEST AS
WELL...WHICH THE EC HAS HAD IN ITS SOLUTION FOR THREE CONSECUTIVE
RUNS. THIS SYSTEM THOUGH IS NOT AS STRONG AS TODAYS AS IT IS MORE
OF A SHEARED AREA OF VORTICITY ALONG THE LINGERING BAROCLINIC
ZONE. FORCING FOR PRECIP LOOKS PRETTY LIGHT ONCE AGAIN MONDAY
AFTERNOON AND NIGHT BUT ENOUGH TO GO A LITTLE HIGHER ON POPS FOR
NORTHERN PARTS OF THE FORECAST AREA. RIGHT NOW GUIDANCE IS IN
DECENT AGREEMENT WITH SATURATING DEEP ENOUGH FOR PRECIP TYPE TO BE
LIGHT SNOW IF IT CAN OCCUR...BUT NEED TO KEEP AN EYE OUT FOR SOME
FREEZING DRIZZLE POTENTIAL IN THESE LIGHT ASCENT SITUATIONS.

A SLOW MODERATION LOOKS TO OCCUR TUESDAY INTO WEDNESDAY AND THIS
COULD BE VERY MINIMAL DEPENDING ON CLOUD COVER WHICH REMAINS A BIG
QUESTION MARK. HAVE LEANED MORE CLOUDY TUESDAY BUT STILL THINK
WITH A WESTERLY PUSH WEDNESDAY WOULD HAVE SUN POTENTIAL. LONG
RANGE GUIDANCE INDICATES A PACIFIC SYSTEM TO BE THE NEXT ONE TO
POSSIBLY BRING PRECIPITATION TO THE AREA WEDNESDAY NIGHT INTO
THURSDAY. CONTINUE POPS DURING THIS TIME FRAME AND AT THIS POINT
PROFILES ARE NEAR THE BORDER FOR RAIN OR SNOW...SO DID NOT GET TOO
FANCY WITH THE FORECAST PRECIPITATION TYPE. BEHIND THIS SYSTEM IT
SEEMS FAVORED FOR TEMPERATURES TO COOL SOME DURING THE LATTER
HALF OF THE WEEK...TO SLIGHTLY BELOW NORMAL VALUES. OBVIOUSLY ANY
FRESH SNOW COVER WOULD HELP LEAN THAT MORE TOWARD BELOW NORMAL.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* LIGHT SNOW TAPERING TO FLURRIES THIS AFTERNOON.
* MVFR CIGS LIFTING THIS AFTERNOON THEN SCATTERING OUT TONIGHT.
* STRONG/GUSTY NORTHEAST WINDS THRU MID EVENING.
* LIGHT SNOW LATE MONDAY AFTERNOON. CMS

//DISCUSSION...UPDATED 18Z...

LOW PRESSURE NEAR STL WILL SLOWLY TRACK EAST ACROSS THE OHIO
VALLEY THIS AFTERNOON INTO TONIGHT. AS IT DOES...LIGHT SNOW WILL
SLOWLY TAPER OFF TO FLURRIES. NORTHEAST WINDS OFF THE LAKE MAY
ALLOW SOME LIGHT SNOW SHOWERS TO CONTINUE NEAR THE LAKE BUT NOT
EXPECTING ANYTHING SIGNIFICANT. HAVE MAINTAINED MENTION OF VFR
LIGHT SNOW THROUGH EARLY EVENING THOUGH CONFIDENCE REGARDING END
TIME IS FAIRLY LOW. VISIBILITIES AND CIGS ARE SLOWLY TRENDING UP
AND THIS WILL CONTINUE THRU THE AFTERNOON WITH PREVAILING MVFR
EXPECTED. NORTHEAST WINDS WILL REMAIN STRONG AND GUSTY WITH GUSTS
INTO THE MID/UPPER 20 KT RANGE THROUGH LATE AFTERNOON WITH A SLOW
RELAXING OF THE SPEEDS/GUSTS THRU THE EVENING. A RIDGE AXIS WILL
MOVE ACROSS THE AREA TOWARD DAYBREAK WITH WINDS BECOMING LIGHT AND
VARIABLE AND THEN SWITCHING TO SOUTHERLY MID/LATE MONDAY MORNING.

A WEAK CLIPPER SYSTEM WILL MOVE SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT AND WHILE THIS FEATURE HAS BEEN
CONSISTENT FOR A FEW DAYS...IT HAS LIMITED MOISTURE. HOWEVER...
THERE COULD BE A PERIOD OF LIGHT SNOW BY MID/LATE AFTERNOON ACROSS
NORTHERN IL THAT CONTINUES INTO MONDAY EVENING. THE CLOUD LAYERS
APPEAR DEEP ENOUGH FOR LIGHT SNOW BUT AS THE MID LEVELS DRY OUT IN
THE EVENING...PRECIP COULD TRANSITION TO LIGHT FREEZING DRIZZLE.
STILL SOME UNCERTAINTY HOW THIS PLAYS OUT...BUT OPTED TO INCLUDE A
PROB30 IN THE 30HR ORD TAF. CMS

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH FOR LIGHT SNOW TAPERING TO FLURRIES THIS AFTERNOON...LOW
  FOR SPECIFIC TIMING AND ASSOCIATED CIGS/VIS.
* MEDIUM FOR CIGS THRU THE PERIOD.
* HIGH FOR WINDS THRU THE PERIOD.
* MEDIUM FOR LIGHT SNOW MONDAY AFTERNOON...LOW FOR ASSOCIATED
  CIGS/VIS. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE LIGHT SNOW/MVFR.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR.

RATZER

&&

.MARINE...
131 PM CST

A QUICK MOVING CLIPPER SYSTEM...CURRENTLY CENTERED ACROSS SOUTHERN
ILLINOIS...WILL RAPIDLY SHIFT EASTWARD TOWARDS THE ATLANTIC COAST
BY MONDAY MORNING. NORTHEASTERLY WINDS OF 30-35 KT CONTINUE ACROSS
THE SOUTHERN 1/3RD OF LAKE MICHIGAN...AND THESE WINDS LOOK TO
CONTINUE FOR THE NEXT FEW HOURS...BEFORE A DIMINISHING TREND BEGINS
EARLY THIS EVENING. ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD JUST
WEST OF THE LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A
PERIOD OF SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN
THE WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION.
THIS SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A
PERIOD OF STRONG NORTHERLY WINDS THURSDAY INTO EARLY FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 6 PM SUNDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 PM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 251758
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1158 AM CST SUN JAN 25 2015

.SHORT TERM...
329 AM CST

THROUGH TONIGHT...

HAVE FURTHERED THE DIMINISHING SNOWFALL TREND IN THE FORECAST FOR
TODAY...MAINLY NORTH OF INTERSTATE 80. ACROSS THE ENTIRE AREA THIS
LOOKS TO BE A MAINLY LOW IMPACT...NUISANCE TYPE SNOW...WITH SOME
COMMUNITIES IN THE NORTH QUITE POSSIBLY NOT SEEING ANY
ACCUMULATION. HAVE CONTINUED A SPECIAL WEATHER STATEMENT FOR AREAS
ALONG AND SOUTH OF I-80.

SATELLITE IMAGERY THIS MORNING DEPICTS THE CLOSED UPPER CIRCULATION
ACROSS WESTERN IA WITH AN AREA OF COOLING CLOUD TOPS IN ADVANCE OF
THIS MOVING INTO NORTHWEST IL. THIS IS CORRELATING WITH MAINLY LIGHT
RAIN OR RAIN/SNOW MIX IN THE SMALL WINDOW OF DEEPER MOIST
ADVECTION AHEAD OF THE LOW. SIMPLE EXTRAPOLATION OF THE CURRENT
AREA OF PRECIP IN IOWA AND THE DEVELOPING DEFORMATION ON THE
BACKSIDE CLEARLY INDICATE THE SOUTHERN CWA IS MORE SUPPORTED FOR
PRECIPITATION THAN THE NORTH. AT THE SURFACE...TEMPERATURES ARE
AROUND OR JUST ABOVE FREEZING ACROSS MUCH OF THE FORECAST AREA. A
DEVELOPING COLD FRONT IS ADVANCING SOUTHWARD INTO NORTHERN IL WITH
DEW POINTS IN THE MID TO UPPER 20S NORTH OF THIS FEATURE...ANOTHER
HINDRANCE OF APPRECIABLE PRECIPITATION IN NORTHERN AREAS OF THE
FORECAST AREA.

SHORT RANGE GUIDANCE LIKE ITS LONG RANGE COUNTERPARTS THE PAST
SEVERAL DAYS SHOW A FAIR AMOUNT OF DISCREPANCY...NAMELY ON COVERAGE
OF PRECIP TODAY AND PRECIP TYPE IN THE SOUTHERN CWA THIS
MORNING...BUT THEY LEND SUPPORT TO THE OBSERVATIONAL TRENDS. AS
THE AREA OF RAIN ASSOCIATED WITH ELEVATED ISENTROPIC ASCENT MOVES
INTO THE SOUTHERN FORECAST AREA...PROFILES SUPPORT A PERIOD OF
RAIN OR MIX INITIALLY...AND SOME LOCATIONS MIGHT HAVE AIR
TEMPERATURES RIGHT AT FREEZING. WOULD EXPECT ANY FREEZING RAIN
THREAT TO BE SHORT LIVED AS PROFILES TREND TOWARD SNOW. MESOSCALE
CONVERGENCE AND BAROCLINIC FORCING FOR INDUCED LIFT WOULD BECOME
MORE FAVORED JUST TO THE NORTHEAST OF THE CLOSED 850MB
CIRCULATION AS IT PIVOTS MORE EASTWARD. THAT IS FAVORED ACROSS
THE SOUTHERN TIER OR TWO OF COUNTIES LATER THIS MORNING INTO
EARLY AFTERNOON. PROFILES ARE MILD FOR IDEAL SNOW GROWTH...AND
MAYBE EVEN FOR SNOW AT ALL DOWN TOWARD GIBSON CITY FOR MUCH OF THE
MORNING. HAVE SNOW TOTALS AROUND ONE TO TWO INCHES FROM PERU TO
RENSSELAER AND SOUTHWARD FOR TODAY...WITH SNOW DEPARTING NEAR OR
SOON AFTER SUNDOWN.

AS FOR AREAS NORTH OF INTERSTATE 80...SHOULD SEE A GRADUAL INCREASE
IN LIGHT SNOW AREAWIDE BY MID-MORNING. DRY CORRIDOR NEAR 850MB
SEEN ON EARLY MORNING AMDAR SOUNDINGS OVER CHICAGO SHOULD LIMIT
INTENSITY OF ANY SNOW IN THE NORTHERN FORECAST AREA...AS WILL JUST
LESS FORCING. AREAS OF NORTHEAST ILLINOIS STILL LOOK TO HAVE
ONSHORE FLOW BEHIND THE COLD FRONT...BUT FORECAST INVERSION
HEIGHTS AS WELL AS ADAPTED ONES FROM THE 00Z GRB RAOB LAST
EVE...INDICATE VERY MARGINAL DEPTH OF CONVECTIVE CLOUDS. THUS NOT
EXPECTING MUCH IF ANY ENHANCEMENT TO ALREADY MINIMAL SYNOPTIC
FORCING OVER NORTHEAST IL. COULD SEE SOME DISORGANIZED LIGHT SNOW
OR FLURRIES LATE THIS AFTERNOON INTO THIS EVENING AS PROFILES OF
THE LAKE INDUCED STRATOCU COOL INTO THE ICE INITIATION LAYER...BUT
THIS SHOULD NOT BE A BIG DEAL.

AREAWIDE THE NORTHEAST WINDS WILL INCREASE TO 30 MPH AND MAYBE EVEN
A LITTLE HIGHER JUST OF THE LAKE. WITH MINIMAL SNOW NORTH NOT
EXPECTING ANY BLOWING SNOW ISSUES...AND SOUTH THE LOW SNOW-TO-
LIQUID RATIOS SHOULD SUPPRESS MUCH FOR BLOWING ISSUES...THOUGH
COULD LEAD TO MORE REDUCED VISIBILITY DURING THE TIME OF FALLING
SNOW THIS AFTERNOON.

MTF

&&

.LONG TERM...
329 AM CST

MONDAY THROUGH SATURDAY...

THE DISTURBED FLOW PATTERN WILL TURN MORE NORTHWESTERLY MONDAY AND
TUESDAY AS A MAJOR SYSTEM IS EXPECTED TO DEVELOP OFF THE NORTHEAST
COAST. GIVEN THIS POSSIBLY LEADING TO A SLOWER PATTERN...AS WELL
AS THE TREND OF TODAYS SYSTEM...IT IS QUITE CONCEIVABLE THAT THE
NEXT DISTURBANCE FOR MONDAY AFTERNOON AND NIGHT TRENDS WEST AS
WELL...WHICH THE EC HAS HAD IN ITS SOLUTION FOR THREE CONSECUTIVE
RUNS. THIS SYSTEM THOUGH IS NOT AS STRONG AS TODAYS AS IT IS MORE
OF A SHEARED AREA OF VORTICITY ALONG THE LINGERING BAROCLINIC
ZONE. FORCING FOR PRECIP LOOKS PRETTY LIGHT ONCE AGAIN MONDAY
AFTERNOON AND NIGHT BUT ENOUGH TO GO A LITTLE HIGHER ON POPS FOR
NORTHERN PARTS OF THE FORECAST AREA. RIGHT NOW GUIDANCE IS IN
DECENT AGREEMENT WITH SATURATING DEEP ENOUGH FOR PRECIP TYPE TO BE
LIGHT SNOW IF IT CAN OCCUR...BUT NEED TO KEEP AN EYE OUT FOR SOME
FREEZING DRIZZLE POTENTIAL IN THESE LIGHT ASCENT SITUATIONS.

A SLOW MODERATION LOOKS TO OCCUR TUESDAY INTO WEDNESDAY AND THIS
COULD BE VERY MINIMAL DEPENDING ON CLOUD COVER WHICH REMAINS A BIG
QUESTION MARK. HAVE LEANED MORE CLOUDY TUESDAY BUT STILL THINK
WITH A WESTERLY PUSH WEDNESDAY WOULD HAVE SUN POTENTIAL. LONG
RANGE GUIDANCE INDICATES A PACIFIC SYSTEM TO BE THE NEXT ONE TO
POSSIBLY BRING PRECIPITATION TO THE AREA WEDNESDAY NIGHT INTO
THURSDAY. CONTINUE POPS DURING THIS TIME FRAME AND AT THIS POINT
PROFILES ARE NEAR THE BORDER FOR RAIN OR SNOW...SO DID NOT GET TOO
FANCY WITH THE FORECAST PRECIPITATION TYPE. BEHIND THIS SYSTEM IT
SEEMS FAVORED FOR TEMPERATURES TO COOL SOME DURING THE LATTER
HALF OF THE WEEK...TO SLIGHTLY BELOW NORMAL VALUES. OBVIOUSLY ANY
FRESH SNOW COVER WOULD HELP LEAN THAT MORE TOWARD BELOW NORMAL.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* LIGHT SNOW TAPERING TO FLURRIES THIS AFTERNOON.
* MVFR CIGS LIFTING THIS AFTERNOON THEN SCATTERING OUT TONIGHT.
* STRONG/GUSTY NORTHEAST WINDS THRU MID EVENING.
* LIGHT SNOW LATE MONDAY AFTERNOON. CMS

//DISCUSSION...UPDATED 18Z...

LOW PRESSURE NEAR STL WILL SLOWLY TRACK EAST ACROSS THE OHIO
VALLEY THIS AFTERNOON INTO TONIGHT. AS IT DOES...LIGHT SNOW WILL
SLOWLY TAPER OFF TO FLURRIES. NORTHEAST WINDS OFF THE LAKE MAY
ALLOW SOME LIGHT SNOW SHOWERS TO CONTINUE NEAR THE LAKE BUT NOT
EXPECTING ANYTHING SIGNIFICANT. HAVE MAINTAINED MENTION OF VFR
LIGHT SNOW THROUGH EARLY EVENING THOUGH CONFIDENCE REGARDING END
TIME IS FAIRLY LOW. VISIBILITIES AND CIGS ARE SLOWLY TRENDING UP
AND THIS WILL CONTINUE THRU THE AFTERNOON WITH PREVAILING MVFR
EXPECTED. NORTHEAST WINDS WILL REMAIN STRONG AND GUSTY WITH GUSTS
INTO THE MID/UPPER 20 KT RANGE THROUGH LATE AFTERNOON WITH A SLOW
RELAXING OF THE SPEEDS/GUSTS THRU THE EVENING. A RIDGE AXIS WILL
MOVE ACROSS THE AREA TOWARD DAYBREAK WITH WINDS BECOMING LIGHT AND
VARIABLE AND THEN SWITCHING TO SOUTHERLY MID/LATE MONDAY MORNING.

A WEAK CLIPPER SYSTEM WILL MOVE SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT AND WHILE THIS FEATURE HAS BEEN
CONSISTENT FOR A FEW DAYS...IT HAS LIMITED MOISTURE. HOWEVER...
THERE COULD BE A PERIOD OF LIGHT SNOW BY MID/LATE AFTERNOON ACROSS
NORTHERN IL THAT CONTINUES INTO MONDAY EVENING. THE CLOUD LAYERS
APPEAR DEEP ENOUGH FOR LIGHT SNOW BUT AS THE MID LEVELS DRY OUT IN
THE EVENING...PRECIP COULD TRANSITION TO LIGHT FREEZING DRIZZLE.
STILL SOME UNCERTAINTY HOW THIS PLAYS OUT...BUT OPTED TO INCLUDE A
PROB30 IN THE 30HR ORD TAF. CMS

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH FOR LIGHT SNOW TAPERING TO FLURRIES THIS AFTERNOON...LOW
  FOR SPECIFIC TIMING AND ASSOCIATED CIGS/VIS.
* MEDIUM FOR CIGS THRU THE PERIOD.
* HIGH FOR WINDS THRU THE PERIOD.
* MEDIUM FOR LIGHT SNOW MONDAY AFTERNOON...LOW FOR ASSOCIATED
  CIGS/VIS. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE LIGHT SNOW/MVFR.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR.

RATZER

&&

.MARINE...
137 AM CST

MAIN MARINE FORECAST FOCUS CONTINUES TO BE A PERIOD OF STRONG
NORTHEAST WINDS ACROSS THE SOUTHERN 2/3 OR SO OF LAKE MICHIGAN
THROUGH THIS EVENING.

A COLD FRONT HAS PUSHED SOUTH ACROSS MUCH OF LAKE MICHIGAN SINCE
SATURDAY MORNING...WITH COLD HIGH PRESSURE SPREADING ACROSS
MANITOBA...WESTERN ONTARIO AND THE NORTHERN LAKES. EARLY THIS
MORNING AN AREA OF LOW PRESSURE WAS OVER IOWA...AND THIS LOW WILL
MOVE QUICKLY SOUTHEAST TO THE LOWER OHIO VALLEY BY THIS EVENING.
THIS LOW AND THE HIGH PRESSURE TO THE NORTH OF THE LAKES WILL
COMBINE TO RAPIDLY TIGHTEN THE SURFACE PRESSURE GRADIENT ACROSS THE
LAKE THIS MORNING...WITH NORTH-NORTHEAST WINDS INCREASING TO 25-30
KT. RECENT OBSERVATION PLATFORMS ALONG THE WEST SHORE OF THE LAKE
HAVE BEEN GUSTING 26-27 KTS BEHIND THE COLD FRONT AS FAR SOUTH AS
MILWAUKEE. THESE STRONGER WINDS WILL CONTINUE TO DEVELOP SOUTHWARD
DOWN THE REMAINDER OF THE LAKE THIS MORNING. FORECAST SOUNDINGS
INDICATE WINDS TO 30 KT WILL BE PREVALENT THROUGH THE DAY...WITH A
FEW GALE FORCE GUSTS TO 35 KT POSSIBLE. WINDS WILL REMAIN GUSTY INTO
THE EVENING HOURS ACROSS THE FAR SOUTHERN PORTION OF THE LAKE...BUT
WILL DIMINISH RAPIDLY FROM THE NORTH AS A WEAK RIDGE OF HIGH
PRESSURE SPREADS IN BEHIND THE QUICK MOVING LOW WHICH MOVE TO THE
CAROLINA COAST BY MONDAY MORNING.

THE WEAK RIDGE WILL MOVE QUICKLY SOUTHEAST OF THE LAKE MONDAY...
WITH WINDS BRIEFLY BECOMING SOUTHERLY AND INCREASING BACK AROUND 20
KT OR SO AHEAD OF ANOTHER LOW PRESSURE SYSTEM WHICH WILL DROP
SOUTHEAST ACROSS THE LAKE MONDAY NIGHT...WHILE FILLING. WEAK
GRADIENT CONDITIONS WILL THEN LINGER ACROSS THE LAKE TUESDAY AND
TUESDAY NIGHT AS THE TROUGH FILLS AND A WEAK RIDGE MOVES ACROSS THE
REGION. INDICATIONS ARE THAT ANOTHER LOW WILL DEVELOP ACROSS THE
PLAINS MID-WEEK...AND WILL APPROACH THE LAKE FROM THE WEST LATE
WEDNESDAY. THIS MAY RESULT IN A BRIEF PERIOD OF ENHANCED
EAST-SOUTHEAST WINDS LATE WEDNESDAY OR WEDNESDAY NIGHT...WITH A
PERIOD OF GUSTY NORTHERLY WINDS POSSIBLE THURSDAY AS THE LOW MOVES
EAST OF THE LAKE.

FOR THE IL/NORTHWEST INDIANA NEARSHORE AREA...SMALL CRAFT ADVISORY
IS IN EFFECT FROM 6 AM CST THIS MORNING AS WINDS/WAVES QUICKLY
INCREASE AND BUILD. ADVISORY HEADLINE WILL REMAIN IN EFFECT THROUGH
MID-MORNING MONDAY...AS WAVES SLOWLY SUBSIDE BELOW 4 FT.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 6 PM SUNDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 PM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 251758
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1158 AM CST SUN JAN 25 2015

.SHORT TERM...
329 AM CST

THROUGH TONIGHT...

HAVE FURTHERED THE DIMINISHING SNOWFALL TREND IN THE FORECAST FOR
TODAY...MAINLY NORTH OF INTERSTATE 80. ACROSS THE ENTIRE AREA THIS
LOOKS TO BE A MAINLY LOW IMPACT...NUISANCE TYPE SNOW...WITH SOME
COMMUNITIES IN THE NORTH QUITE POSSIBLY NOT SEEING ANY
ACCUMULATION. HAVE CONTINUED A SPECIAL WEATHER STATEMENT FOR AREAS
ALONG AND SOUTH OF I-80.

SATELLITE IMAGERY THIS MORNING DEPICTS THE CLOSED UPPER CIRCULATION
ACROSS WESTERN IA WITH AN AREA OF COOLING CLOUD TOPS IN ADVANCE OF
THIS MOVING INTO NORTHWEST IL. THIS IS CORRELATING WITH MAINLY LIGHT
RAIN OR RAIN/SNOW MIX IN THE SMALL WINDOW OF DEEPER MOIST
ADVECTION AHEAD OF THE LOW. SIMPLE EXTRAPOLATION OF THE CURRENT
AREA OF PRECIP IN IOWA AND THE DEVELOPING DEFORMATION ON THE
BACKSIDE CLEARLY INDICATE THE SOUTHERN CWA IS MORE SUPPORTED FOR
PRECIPITATION THAN THE NORTH. AT THE SURFACE...TEMPERATURES ARE
AROUND OR JUST ABOVE FREEZING ACROSS MUCH OF THE FORECAST AREA. A
DEVELOPING COLD FRONT IS ADVANCING SOUTHWARD INTO NORTHERN IL WITH
DEW POINTS IN THE MID TO UPPER 20S NORTH OF THIS FEATURE...ANOTHER
HINDRANCE OF APPRECIABLE PRECIPITATION IN NORTHERN AREAS OF THE
FORECAST AREA.

SHORT RANGE GUIDANCE LIKE ITS LONG RANGE COUNTERPARTS THE PAST
SEVERAL DAYS SHOW A FAIR AMOUNT OF DISCREPANCY...NAMELY ON COVERAGE
OF PRECIP TODAY AND PRECIP TYPE IN THE SOUTHERN CWA THIS
MORNING...BUT THEY LEND SUPPORT TO THE OBSERVATIONAL TRENDS. AS
THE AREA OF RAIN ASSOCIATED WITH ELEVATED ISENTROPIC ASCENT MOVES
INTO THE SOUTHERN FORECAST AREA...PROFILES SUPPORT A PERIOD OF
RAIN OR MIX INITIALLY...AND SOME LOCATIONS MIGHT HAVE AIR
TEMPERATURES RIGHT AT FREEZING. WOULD EXPECT ANY FREEZING RAIN
THREAT TO BE SHORT LIVED AS PROFILES TREND TOWARD SNOW. MESOSCALE
CONVERGENCE AND BAROCLINIC FORCING FOR INDUCED LIFT WOULD BECOME
MORE FAVORED JUST TO THE NORTHEAST OF THE CLOSED 850MB
CIRCULATION AS IT PIVOTS MORE EASTWARD. THAT IS FAVORED ACROSS
THE SOUTHERN TIER OR TWO OF COUNTIES LATER THIS MORNING INTO
EARLY AFTERNOON. PROFILES ARE MILD FOR IDEAL SNOW GROWTH...AND
MAYBE EVEN FOR SNOW AT ALL DOWN TOWARD GIBSON CITY FOR MUCH OF THE
MORNING. HAVE SNOW TOTALS AROUND ONE TO TWO INCHES FROM PERU TO
RENSSELAER AND SOUTHWARD FOR TODAY...WITH SNOW DEPARTING NEAR OR
SOON AFTER SUNDOWN.

AS FOR AREAS NORTH OF INTERSTATE 80...SHOULD SEE A GRADUAL INCREASE
IN LIGHT SNOW AREAWIDE BY MID-MORNING. DRY CORRIDOR NEAR 850MB
SEEN ON EARLY MORNING AMDAR SOUNDINGS OVER CHICAGO SHOULD LIMIT
INTENSITY OF ANY SNOW IN THE NORTHERN FORECAST AREA...AS WILL JUST
LESS FORCING. AREAS OF NORTHEAST ILLINOIS STILL LOOK TO HAVE
ONSHORE FLOW BEHIND THE COLD FRONT...BUT FORECAST INVERSION
HEIGHTS AS WELL AS ADAPTED ONES FROM THE 00Z GRB RAOB LAST
EVE...INDICATE VERY MARGINAL DEPTH OF CONVECTIVE CLOUDS. THUS NOT
EXPECTING MUCH IF ANY ENHANCEMENT TO ALREADY MINIMAL SYNOPTIC
FORCING OVER NORTHEAST IL. COULD SEE SOME DISORGANIZED LIGHT SNOW
OR FLURRIES LATE THIS AFTERNOON INTO THIS EVENING AS PROFILES OF
THE LAKE INDUCED STRATOCU COOL INTO THE ICE INITIATION LAYER...BUT
THIS SHOULD NOT BE A BIG DEAL.

AREAWIDE THE NORTHEAST WINDS WILL INCREASE TO 30 MPH AND MAYBE EVEN
A LITTLE HIGHER JUST OF THE LAKE. WITH MINIMAL SNOW NORTH NOT
EXPECTING ANY BLOWING SNOW ISSUES...AND SOUTH THE LOW SNOW-TO-
LIQUID RATIOS SHOULD SUPPRESS MUCH FOR BLOWING ISSUES...THOUGH
COULD LEAD TO MORE REDUCED VISIBILITY DURING THE TIME OF FALLING
SNOW THIS AFTERNOON.

MTF

&&

.LONG TERM...
329 AM CST

MONDAY THROUGH SATURDAY...

THE DISTURBED FLOW PATTERN WILL TURN MORE NORTHWESTERLY MONDAY AND
TUESDAY AS A MAJOR SYSTEM IS EXPECTED TO DEVELOP OFF THE NORTHEAST
COAST. GIVEN THIS POSSIBLY LEADING TO A SLOWER PATTERN...AS WELL
AS THE TREND OF TODAYS SYSTEM...IT IS QUITE CONCEIVABLE THAT THE
NEXT DISTURBANCE FOR MONDAY AFTERNOON AND NIGHT TRENDS WEST AS
WELL...WHICH THE EC HAS HAD IN ITS SOLUTION FOR THREE CONSECUTIVE
RUNS. THIS SYSTEM THOUGH IS NOT AS STRONG AS TODAYS AS IT IS MORE
OF A SHEARED AREA OF VORTICITY ALONG THE LINGERING BAROCLINIC
ZONE. FORCING FOR PRECIP LOOKS PRETTY LIGHT ONCE AGAIN MONDAY
AFTERNOON AND NIGHT BUT ENOUGH TO GO A LITTLE HIGHER ON POPS FOR
NORTHERN PARTS OF THE FORECAST AREA. RIGHT NOW GUIDANCE IS IN
DECENT AGREEMENT WITH SATURATING DEEP ENOUGH FOR PRECIP TYPE TO BE
LIGHT SNOW IF IT CAN OCCUR...BUT NEED TO KEEP AN EYE OUT FOR SOME
FREEZING DRIZZLE POTENTIAL IN THESE LIGHT ASCENT SITUATIONS.

A SLOW MODERATION LOOKS TO OCCUR TUESDAY INTO WEDNESDAY AND THIS
COULD BE VERY MINIMAL DEPENDING ON CLOUD COVER WHICH REMAINS A BIG
QUESTION MARK. HAVE LEANED MORE CLOUDY TUESDAY BUT STILL THINK
WITH A WESTERLY PUSH WEDNESDAY WOULD HAVE SUN POTENTIAL. LONG
RANGE GUIDANCE INDICATES A PACIFIC SYSTEM TO BE THE NEXT ONE TO
POSSIBLY BRING PRECIPITATION TO THE AREA WEDNESDAY NIGHT INTO
THURSDAY. CONTINUE POPS DURING THIS TIME FRAME AND AT THIS POINT
PROFILES ARE NEAR THE BORDER FOR RAIN OR SNOW...SO DID NOT GET TOO
FANCY WITH THE FORECAST PRECIPITATION TYPE. BEHIND THIS SYSTEM IT
SEEMS FAVORED FOR TEMPERATURES TO COOL SOME DURING THE LATTER
HALF OF THE WEEK...TO SLIGHTLY BELOW NORMAL VALUES. OBVIOUSLY ANY
FRESH SNOW COVER WOULD HELP LEAN THAT MORE TOWARD BELOW NORMAL.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* LIGHT SNOW TAPERING TO FLURRIES THIS AFTERNOON.
* MVFR CIGS LIFTING THIS AFTERNOON THEN SCATTERING OUT TONIGHT.
* STRONG/GUSTY NORTHEAST WINDS THRU MID EVENING.
* LIGHT SNOW LATE MONDAY AFTERNOON. CMS

//DISCUSSION...UPDATED 18Z...

LOW PRESSURE NEAR STL WILL SLOWLY TRACK EAST ACROSS THE OHIO
VALLEY THIS AFTERNOON INTO TONIGHT. AS IT DOES...LIGHT SNOW WILL
SLOWLY TAPER OFF TO FLURRIES. NORTHEAST WINDS OFF THE LAKE MAY
ALLOW SOME LIGHT SNOW SHOWERS TO CONTINUE NEAR THE LAKE BUT NOT
EXPECTING ANYTHING SIGNIFICANT. HAVE MAINTAINED MENTION OF VFR
LIGHT SNOW THROUGH EARLY EVENING THOUGH CONFIDENCE REGARDING END
TIME IS FAIRLY LOW. VISIBILITIES AND CIGS ARE SLOWLY TRENDING UP
AND THIS WILL CONTINUE THRU THE AFTERNOON WITH PREVAILING MVFR
EXPECTED. NORTHEAST WINDS WILL REMAIN STRONG AND GUSTY WITH GUSTS
INTO THE MID/UPPER 20 KT RANGE THROUGH LATE AFTERNOON WITH A SLOW
RELAXING OF THE SPEEDS/GUSTS THRU THE EVENING. A RIDGE AXIS WILL
MOVE ACROSS THE AREA TOWARD DAYBREAK WITH WINDS BECOMING LIGHT AND
VARIABLE AND THEN SWITCHING TO SOUTHERLY MID/LATE MONDAY MORNING.

A WEAK CLIPPER SYSTEM WILL MOVE SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT AND WHILE THIS FEATURE HAS BEEN
CONSISTENT FOR A FEW DAYS...IT HAS LIMITED MOISTURE. HOWEVER...
THERE COULD BE A PERIOD OF LIGHT SNOW BY MID/LATE AFTERNOON ACROSS
NORTHERN IL THAT CONTINUES INTO MONDAY EVENING. THE CLOUD LAYERS
APPEAR DEEP ENOUGH FOR LIGHT SNOW BUT AS THE MID LEVELS DRY OUT IN
THE EVENING...PRECIP COULD TRANSITION TO LIGHT FREEZING DRIZZLE.
STILL SOME UNCERTAINTY HOW THIS PLAYS OUT...BUT OPTED TO INCLUDE A
PROB30 IN THE 30HR ORD TAF. CMS

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH FOR LIGHT SNOW TAPERING TO FLURRIES THIS AFTERNOON...LOW
  FOR SPECIFIC TIMING AND ASSOCIATED CIGS/VIS.
* MEDIUM FOR CIGS THRU THE PERIOD.
* HIGH FOR WINDS THRU THE PERIOD.
* MEDIUM FOR LIGHT SNOW MONDAY AFTERNOON...LOW FOR ASSOCIATED
  CIGS/VIS. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE LIGHT SNOW/MVFR.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR.

RATZER

&&

.MARINE...
137 AM CST

MAIN MARINE FORECAST FOCUS CONTINUES TO BE A PERIOD OF STRONG
NORTHEAST WINDS ACROSS THE SOUTHERN 2/3 OR SO OF LAKE MICHIGAN
THROUGH THIS EVENING.

A COLD FRONT HAS PUSHED SOUTH ACROSS MUCH OF LAKE MICHIGAN SINCE
SATURDAY MORNING...WITH COLD HIGH PRESSURE SPREADING ACROSS
MANITOBA...WESTERN ONTARIO AND THE NORTHERN LAKES. EARLY THIS
MORNING AN AREA OF LOW PRESSURE WAS OVER IOWA...AND THIS LOW WILL
MOVE QUICKLY SOUTHEAST TO THE LOWER OHIO VALLEY BY THIS EVENING.
THIS LOW AND THE HIGH PRESSURE TO THE NORTH OF THE LAKES WILL
COMBINE TO RAPIDLY TIGHTEN THE SURFACE PRESSURE GRADIENT ACROSS THE
LAKE THIS MORNING...WITH NORTH-NORTHEAST WINDS INCREASING TO 25-30
KT. RECENT OBSERVATION PLATFORMS ALONG THE WEST SHORE OF THE LAKE
HAVE BEEN GUSTING 26-27 KTS BEHIND THE COLD FRONT AS FAR SOUTH AS
MILWAUKEE. THESE STRONGER WINDS WILL CONTINUE TO DEVELOP SOUTHWARD
DOWN THE REMAINDER OF THE LAKE THIS MORNING. FORECAST SOUNDINGS
INDICATE WINDS TO 30 KT WILL BE PREVALENT THROUGH THE DAY...WITH A
FEW GALE FORCE GUSTS TO 35 KT POSSIBLE. WINDS WILL REMAIN GUSTY INTO
THE EVENING HOURS ACROSS THE FAR SOUTHERN PORTION OF THE LAKE...BUT
WILL DIMINISH RAPIDLY FROM THE NORTH AS A WEAK RIDGE OF HIGH
PRESSURE SPREADS IN BEHIND THE QUICK MOVING LOW WHICH MOVE TO THE
CAROLINA COAST BY MONDAY MORNING.

THE WEAK RIDGE WILL MOVE QUICKLY SOUTHEAST OF THE LAKE MONDAY...
WITH WINDS BRIEFLY BECOMING SOUTHERLY AND INCREASING BACK AROUND 20
KT OR SO AHEAD OF ANOTHER LOW PRESSURE SYSTEM WHICH WILL DROP
SOUTHEAST ACROSS THE LAKE MONDAY NIGHT...WHILE FILLING. WEAK
GRADIENT CONDITIONS WILL THEN LINGER ACROSS THE LAKE TUESDAY AND
TUESDAY NIGHT AS THE TROUGH FILLS AND A WEAK RIDGE MOVES ACROSS THE
REGION. INDICATIONS ARE THAT ANOTHER LOW WILL DEVELOP ACROSS THE
PLAINS MID-WEEK...AND WILL APPROACH THE LAKE FROM THE WEST LATE
WEDNESDAY. THIS MAY RESULT IN A BRIEF PERIOD OF ENHANCED
EAST-SOUTHEAST WINDS LATE WEDNESDAY OR WEDNESDAY NIGHT...WITH A
PERIOD OF GUSTY NORTHERLY WINDS POSSIBLE THURSDAY AS THE LOW MOVES
EAST OF THE LAKE.

FOR THE IL/NORTHWEST INDIANA NEARSHORE AREA...SMALL CRAFT ADVISORY
IS IN EFFECT FROM 6 AM CST THIS MORNING AS WINDS/WAVES QUICKLY
INCREASE AND BUILD. ADVISORY HEADLINE WILL REMAIN IN EFFECT THROUGH
MID-MORNING MONDAY...AS WAVES SLOWLY SUBSIDE BELOW 4 FT.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 6 PM SUNDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 PM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 251605
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1005 AM CST SUN JAN 25 2015

.SHORT TERM...
329 AM CST

THROUGH TONIGHT...

HAVE FURTHERED THE DIMINISHING SNOWFALL TREND IN THE FORECAST FOR
TODAY...MAINLY NORTH OF INTERSTATE 80. ACROSS THE ENTIRE AREA THIS
LOOKS TO BE A MAINLY LOW IMPACT...NUISANCE TYPE SNOW...WITH SOME
COMMUNITIES IN THE NORTH QUITE POSSIBLY NOT SEEING ANY
ACCUMULATION. HAVE CONTINUED A SPECIAL WEATHER STATEMENT FOR AREAS
ALONG AND SOUTH OF I-80.

SATELLITE IMAGERY THIS MORNING DEPICTS THE CLOSED UPPER CIRCULATION
ACROSS WESTERN IA WITH AN AREA OF COOLING CLOUD TOPS IN ADVANCE OF
THIS MOVING INTO NORTHWEST IL. THIS IS CORRELATING WITH MAINLY LIGHT
RAIN OR RAIN/SNOW MIX IN THE SMALL WINDOW OF DEEPER MOIST
ADVECTION AHEAD OF THE LOW. SIMPLE EXTRAPOLATION OF THE CURRENT
AREA OF PRECIP IN IOWA AND THE DEVELOPING DEFORMATION ON THE
BACKSIDE CLEARLY INDICATE THE SOUTHERN CWA IS MORE SUPPORTED FOR
PRECIPITATION THAN THE NORTH. AT THE SURFACE...TEMPERATURES ARE
AROUND OR JUST ABOVE FREEZING ACROSS MUCH OF THE FORECAST AREA. A
DEVELOPING COLD FRONT IS ADVANCING SOUTHWARD INTO NORTHERN IL WITH
DEW POINTS IN THE MID TO UPPER 20S NORTH OF THIS FEATURE...ANOTHER
HINDRANCE OF APPRECIABLE PRECIPITATION IN NORTHERN AREAS OF THE
FORECAST AREA.

SHORT RANGE GUIDANCE LIKE ITS LONG RANGE COUNTERPARTS THE PAST
SEVERAL DAYS SHOW A FAIR AMOUNT OF DISCREPANCY...NAMELY ON COVERAGE
OF PRECIP TODAY AND PRECIP TYPE IN THE SOUTHERN CWA THIS
MORNING...BUT THEY LEND SUPPORT TO THE OBSERVATIONAL TRENDS. AS
THE AREA OF RAIN ASSOCIATED WITH ELEVATED ISENTROPIC ASCENT MOVES
INTO THE SOUTHERN FORECAST AREA...PROFILES SUPPORT A PERIOD OF
RAIN OR MIX INITIALLY...AND SOME LOCATIONS MIGHT HAVE AIR
TEMPERATURES RIGHT AT FREEZING. WOULD EXPECT ANY FREEZING RAIN
THREAT TO BE SHORT LIVED AS PROFILES TREND TOWARD SNOW. MESOSCALE
CONVERGENCE AND BAROCLINIC FORCING FOR INDUCED LIFT WOULD BECOME
MORE FAVORED JUST TO THE NORTHEAST OF THE CLOSED 850MB
CIRCULATION AS IT PIVOTS MORE EASTWARD. THAT IS FAVORED ACROSS
THE SOUTHERN TIER OR TWO OF COUNTIES LATER THIS MORNING INTO
EARLY AFTERNOON. PROFILES ARE MILD FOR IDEAL SNOW GROWTH...AND
MAYBE EVEN FOR SNOW AT ALL DOWN TOWARD GIBSON CITY FOR MUCH OF THE
MORNING. HAVE SNOW TOTALS AROUND ONE TO TWO INCHES FROM PERU TO
RENSSELAER AND SOUTHWARD FOR TODAY...WITH SNOW DEPARTING NEAR OR
SOON AFTER SUNDOWN.

AS FOR AREAS NORTH OF INTERSTATE 80...SHOULD SEE A GRADUAL INCREASE
IN LIGHT SNOW AREAWIDE BY MID-MORNING. DRY CORRIDOR NEAR 850MB
SEEN ON EARLY MORNING AMDAR SOUNDINGS OVER CHICAGO SHOULD LIMIT
INTENSITY OF ANY SNOW IN THE NORTHERN FORECAST AREA...AS WILL JUST
LESS FORCING. AREAS OF NORTHEAST ILLINOIS STILL LOOK TO HAVE
ONSHORE FLOW BEHIND THE COLD FRONT...BUT FORECAST INVERSION
HEIGHTS AS WELL AS ADAPTED ONES FROM THE 00Z GRB RAOB LAST
EVE...INDICATE VERY MARGINAL DEPTH OF CONVECTIVE CLOUDS. THUS NOT
EXPECTING MUCH IF ANY ENHANCEMENT TO ALREADY MINIMAL SYNOPTIC
FORCING OVER NORTHEAST IL. COULD SEE SOME DISORGANIZED LIGHT SNOW
OR FLURRIES LATE THIS AFTERNOON INTO THIS EVENING AS PROFILES OF
THE LAKE INDUCED STRATOCU COOL INTO THE ICE INITIATION LAYER...BUT
THIS SHOULD NOT BE A BIG DEAL.

AREAWIDE THE NORTHEAST WINDS WILL INCREASE TO 30 MPH AND MAYBE EVEN
A LITTLE HIGHER JUST OF THE LAKE. WITH MINIMAL SNOW NORTH NOT
EXPECTING ANY BLOWING SNOW ISSUES...AND SOUTH THE LOW SNOW-TO-
LIQUID RATIOS SHOULD SUPPRESS MUCH FOR BLOWING ISSUES...THOUGH
COULD LEAD TO MORE REDUCED VISIBILITY DURING THE TIME OF FALLING
SNOW THIS AFTERNOON.

MTF

&&

.LONG TERM...
329 AM CST

MONDAY THROUGH SATURDAY...

THE DISTURBED FLOW PATTERN WILL TURN MORE NORTHWESTERLY MONDAY AND
TUESDAY AS A MAJOR SYSTEM IS EXPECTED TO DEVELOP OFF THE NORTHEAST
COAST. GIVEN THIS POSSIBLY LEADING TO A SLOWER PATTERN...AS WELL
AS THE TREND OF TODAYS SYSTEM...IT IS QUITE CONCEIVABLE THAT THE
NEXT DISTURBANCE FOR MONDAY AFTERNOON AND NIGHT TRENDS WEST AS
WELL...WHICH THE EC HAS HAD IN ITS SOLUTION FOR THREE CONSECUTIVE
RUNS. THIS SYSTEM THOUGH IS NOT AS STRONG AS TODAYS AS IT IS MORE
OF A SHEARED AREA OF VORTICITY ALONG THE LINGERING BAROCLINIC
ZONE. FORCING FOR PRECIP LOOKS PRETTY LIGHT ONCE AGAIN MONDAY
AFTERNOON AND NIGHT BUT ENOUGH TO GO A LITTLE HIGHER ON POPS FOR
NORTHERN PARTS OF THE FORECAST AREA. RIGHT NOW GUIDANCE IS IN
DECENT AGREEMENT WITH SATURATING DEEP ENOUGH FOR PRECIP TYPE TO BE
LIGHT SNOW IF IT CAN OCCUR...BUT NEED TO KEEP AN EYE OUT FOR SOME
FREEZING DRIZZLE POTENTIAL IN THESE LIGHT ASCENT SITUATIONS.

A SLOW MODERATION LOOKS TO OCCUR TUESDAY INTO WEDNESDAY AND THIS
COULD BE VERY MINIMAL DEPENDING ON CLOUD COVER WHICH REMAINS A BIG
QUESTION MARK. HAVE LEANED MORE CLOUDY TUESDAY BUT STILL THINK
WITH A WESTERLY PUSH WEDNESDAY WOULD HAVE SUN POTENTIAL. LONG
RANGE GUIDANCE INDICATES A PACIFIC SYSTEM TO BE THE NEXT ONE TO
POSSIBLY BRING PRECIPITATION TO THE AREA WEDNESDAY NIGHT INTO
THURSDAY. CONTINUE POPS DURING THIS TIME FRAME AND AT THIS POINT
PROFILES ARE NEAR THE BORDER FOR RAIN OR SNOW...SO DID NOT GET TOO
FANCY WITH THE FORECAST PRECIPITATION TYPE. BEHIND THIS SYSTEM IT
SEEMS FAVORED FOR TEMPERATURES TO COOL SOME DURING THE LATTER
HALF OF THE WEEK...TO SLIGHTLY BELOW NORMAL VALUES. OBVIOUSLY ANY
FRESH SNOW COVER WOULD HELP LEAN THAT MORE TOWARD BELOW NORMAL.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* LIGHT SNOW THROUGH THIS AFTERNOON.
* IFR CIGS LIFTING TO MVFR BY THIS AFTERNOON...THEN SCATTERING OUT
  TONIGHT.
* STRONG/GUSTY NORTHEAST WINDS THRU MID EVENING. CMS

//DISCUSSION...UPDATED 14Z...

LOW PRESSURE OVER NORTHEAST MISSOURI WILL MOVE ACROSS THE OHIO
VALLEY TONIGHT. NORTHEAST WINDS WILL REMAIN STRONG AND GUSTY THRU
THIS EVENING WITH GUSTS IN THE MID/UPPER 20KT RANGE. HEAVIEST
PRECIP SHOULD REMAIN ALONG AND SOUTH OF I-80 WITH LIGHTER AMOUNTS
NORTH. MANY AREAS REPORTING LIGHT SNOW BUT STILL SOME MIXED RAIN
AT MDW AND GYY...WHICH SHOULD TRANSITION TO SNOW BY LATE MORNING.
CMS

PREVIOUS 12Z DISCUSSION...

WEAK COLD FRONTAL BOUNDARY HAS SAGGED INTO NORTHEAST ILLINOIS
EARLY THIS MORNING...WITH IFR/LIFR CIGS NOTED IN THE VICINITY OF
THE FRONTAL BOUNDARY. EXPECT THE LIFR CIGS TO BE SOMEWHAT SHORT-
LIVED HOWEVER...AS WINDS RAMP UP FROM THE NORTHEAST.

RADAR CLEARLY SHOWS CIRCULATION WITH ALBERTA CLIPPER DROPPING
SOUTHEAST ACROSS IA...WITH EXPANSION OF WEAK RETURNS OVER NORTHERN
ILLINOIS AND A FEW REPORTS OF LIGHT SNOW BEGINNING TO REACH THE
GROUND. HIGH-RES HRRR HAS BEEN FAIRLY CONSISTENT IN BRINING NORTH
EDGE OF MORE ORGANIZED SNOW BAND ACROSS THE TERMINALS THIS MORNING
INTO MIDDAY/EARLY AFTERNOON...AND IS EXPECTED TO PRODUCE A PERIOD
OF LIGHT ACCUMULATING SNOW WITH OCCASIONAL IFR VSBYS. SNOW SHOULD
TAPER OFF TO LIGHT SNOW SHOWERS/FLURRIES THIS AFTERNOON WITH CIGS
RISING TO MVFR.

AS INDICATED ABOVE...STRONG/GUSTY NORTHEAST WINDS ARE ALREADY
RAMPING UP EARLY THIS MORNING WITH GUSTS 20-30 KT ALREAD ACROSS
FAR NORTHERN IL. 040-060 DEG WINDS NEAR 20 KT WITH GUSTS NEAR 30
KT ARE EXPECTED TO CONTIUNE INTO THE AFTERNOON BEFORE SLOW DECLINE
IN WIND SPEEDS AND A GRADUAL BACKING TO THE NORTH OCCURS. WINDS
WILL DIMINISH MORE QUICKLY TONIGHT...AS A WEAK HIGH PRESSURE RIDGE
BUILDS IN FROM THE NORTHWEST. THIS SHOULD ALLOW LOWER CLOUDS TO
SCATTER OUT OVERNIGHT.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* HIGH FOR LIGHT SNOW...MEDIUM FOR DURATION/END TIME THIS
  AFTERNOON OR EARLY THIS EVENING.
* HIGH FOR CIGS THRU THIS AFTERNOON...THEN MEDIUM FOR THE REST OF
  THE PERIOD.
* HIGH FOR WIND SPEEDS/GUSTS/DIRECTIONS THRU THE PERIOD. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE LIGHT SNOW/MVFR.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR.

RATZER

&&

.MARINE...
137 AM CST

MAIN MARINE FORECAST FOCUS CONTINUES TO BE A PERIOD OF STRONG
NORTHEAST WINDS ACROSS THE SOUTHERN 2/3 OR SO OF LAKE MICHIGAN
THROUGH THIS EVENING.

A COLD FRONT HAS PUSHED SOUTH ACROSS MUCH OF LAKE MICHIGAN SINCE
SATURDAY MORNING...WITH COLD HIGH PRESSURE SPREADING ACROSS
MANITOBA...WESTERN ONTARIO AND THE NORTHERN LAKES. EARLY THIS
MORNING AN AREA OF LOW PRESSURE WAS OVER IOWA...AND THIS LOW WILL
MOVE QUICKLY SOUTHEAST TO THE LOWER OHIO VALLEY BY THIS EVENING.
THIS LOW AND THE HIGH PRESSURE TO THE NORTH OF THE LAKES WILL
COMBINE TO RAPIDLY TIGHTEN THE SURFACE PRESSURE GRADIENT ACROSS THE
LAKE THIS MORNING...WITH NORTH-NORTHEAST WINDS INCREASING TO 25-30
KT. RECENT OBSERVATION PLATFORMS ALONG THE WEST SHORE OF THE LAKE
HAVE BEEN GUSTING 26-27 KTS BEHIND THE COLD FRONT AS FAR SOUTH AS
MILWAUKEE. THESE STRONGER WINDS WILL CONTINUE TO DEVELOP SOUTHWARD
DOWN THE REMAINDER OF THE LAKE THIS MORNING. FORECAST SOUNDINGS
INDICATE WINDS TO 30 KT WILL BE PREVALENT THROUGH THE DAY...WITH A
FEW GALE FORCE GUSTS TO 35 KT POSSIBLE. WINDS WILL REMAIN GUSTY INTO
THE EVENING HOURS ACROSS THE FAR SOUTHERN PORTION OF THE LAKE...BUT
WILL DIMINISH RAPIDLY FROM THE NORTH AS A WEAK RIDGE OF HIGH
PRESSURE SPREADS IN BEHIND THE QUICK MOVING LOW WHICH MOVE TO THE
CAROLINA COAST BY MONDAY MORNING.

THE WEAK RIDGE WILL MOVE QUICKLY SOUTHEAST OF THE LAKE MONDAY...
WITH WINDS BRIEFLY BECOMING SOUTHERLY AND INCREASING BACK AROUND 20
KT OR SO AHEAD OF ANOTHER LOW PRESSURE SYSTEM WHICH WILL DROP
SOUTHEAST ACROSS THE LAKE MONDAY NIGHT...WHILE FILLING. WEAK
GRADIENT CONDITIONS WILL THEN LINGER ACROSS THE LAKE TUESDAY AND
TUESDAY NIGHT AS THE TROUGH FILLS AND A WEAK RIDGE MOVES ACROSS THE
REGION. INDICATIONS ARE THAT ANOTHER LOW WILL DEVELOP ACROSS THE
PLAINS MID-WEEK...AND WILL APPROACH THE LAKE FROM THE WEST LATE
WEDNESDAY. THIS MAY RESULT IN A BRIEF PERIOD OF ENHANCED
EAST-SOUTHEAST WINDS LATE WEDNESDAY OR WEDNESDAY NIGHT...WITH A
PERIOD OF GUSTY NORTHERLY WINDS POSSIBLE THURSDAY AS THE LOW MOVES
EAST OF THE LAKE.

FOR THE IL/NORTHWEST INDIANA NEARSHORE AREA...SMALL CRAFT ADVISORY
IS IN EFFECT FROM 6 AM CST THIS MORNING AS WINDS/WAVES QUICKLY
INCREASE AND BUILD. ADVISORY HEADLINE WILL REMAIN IN EFFECT THROUGH
MID-MORNING MONDAY...AS WAVES SLOWLY SUBSIDE BELOW 4 FT.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 6 PM SUNDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 PM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 251413
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
813 AM CST SUN JAN 25 2015

.SHORT TERM...
329 AM CST

THROUGH TONIGHT...

HAVE FURTHERED THE DIMINISHING SNOWFALL TREND IN THE FORECAST FOR
TODAY...MAINLY NORTH OF INTERSTATE 80. ACROSS THE ENTIRE AREA THIS
LOOKS TO BE A MAINLY LOW IMPACT...NUISANCE TYPE SNOW...WITH SOME
COMMUNITIES IN THE NORTH QUITE POSSIBLY NOT SEEING ANY
ACCUMULATION. HAVE CONTINUED A SPECIAL WEATHER STATEMENT FOR AREAS
ALONG AND SOUTH OF I-80.

SATELLITE IMAGERY THIS MORNING DEPICTS THE CLOSED UPPER CIRCULATION
ACROSS WESTERN IA WITH AN AREA OF COOLING CLOUD TOPS IN ADVANCE OF
THIS MOVING INTO NORTHWEST IL. THIS IS CORRELATING WITH MAINLY LIGHT
RAIN OR RAIN/SNOW MIX IN THE SMALL WINDOW OF DEEPER MOIST
ADVECTION AHEAD OF THE LOW. SIMPLE EXTRAPOLATION OF THE CURRENT
AREA OF PRECIP IN IOWA AND THE DEVELOPING DEFORMATION ON THE
BACKSIDE CLEARLY INDICATE THE SOUTHERN CWA IS MORE SUPPORTED FOR
PRECIPITATION THAN THE NORTH. AT THE SURFACE...TEMPERATURES ARE
AROUND OR JUST ABOVE FREEZING ACROSS MUCH OF THE FORECAST AREA. A
DEVELOPING COLD FRONT IS ADVANCING SOUTHWARD INTO NORTHERN IL WITH
DEW POINTS IN THE MID TO UPPER 20S NORTH OF THIS FEATURE...ANOTHER
HINDRANCE OF APPRECIABLE PRECIPITATION IN NORTHERN AREAS OF THE
FORECAST AREA.

SHORT RANGE GUIDANCE LIKE ITS LONG RANGE COUNTERPARTS THE PAST
SEVERAL DAYS SHOW A FAIR AMOUNT OF DISCREPANCY...NAMELY ON COVERAGE
OF PRECIP TODAY AND PRECIP TYPE IN THE SOUTHERN CWA THIS
MORNING...BUT THEY LEND SUPPORT TO THE OBSERVATIONAL TRENDS. AS
THE AREA OF RAIN ASSOCIATED WITH ELEVATED ISENTROPIC ASCENT MOVES
INTO THE SOUTHERN FORECAST AREA...PROFILES SUPPORT A PERIOD OF
RAIN OR MIX INITIALLY...AND SOME LOCATIONS MIGHT HAVE AIR
TEMPERATURES RIGHT AT FREEZING. WOULD EXPECT ANY FREEZING RAIN
THREAT TO BE SHORT LIVED AS PROFILES TREND TOWARD SNOW. MESOSCALE
CONVERGENCE AND BAROCLINIC FORCING FOR INDUCED LIFT WOULD BECOME
MORE FAVORED JUST TO THE NORTHEAST OF THE CLOSED 850MB
CIRCULATION AS IT PIVOTS MORE EASTWARD. THAT IS FAVORED ACROSS
THE SOUTHERN TIER OR TWO OF COUNTIES LATER THIS MORNING INTO
EARLY AFTERNOON. PROFILES ARE MILD FOR IDEAL SNOW GROWTH...AND
MAYBE EVEN FOR SNOW AT ALL DOWN TOWARD GIBSON CITY FOR MUCH OF THE
MORNING. HAVE SNOW TOTALS AROUND ONE TO TWO INCHES FROM PERU TO
RENSSELAER AND SOUTHWARD FOR TODAY...WITH SNOW DEPARTING NEAR OR
SOON AFTER SUNDOWN.

AS FOR AREAS NORTH OF INTERSTATE 80...SHOULD SEE A GRADUAL INCREASE
IN LIGHT SNOW AREAWIDE BY MID-MORNING. DRY CORRIDOR NEAR 850MB
SEEN ON EARLY MORNING AMDAR SOUNDINGS OVER CHICAGO SHOULD LIMIT
INTENSITY OF ANY SNOW IN THE NORTHERN FORECAST AREA...AS WILL JUST
LESS FORCING. AREAS OF NORTHEAST ILLINOIS STILL LOOK TO HAVE
ONSHORE FLOW BEHIND THE COLD FRONT...BUT FORECAST INVERSION
HEIGHTS AS WELL AS ADAPTED ONES FROM THE 00Z GRB RAOB LAST
EVE...INDICATE VERY MARGINAL DEPTH OF CONVECTIVE CLOUDS. THUS NOT
EXPECTING MUCH IF ANY ENHANCEMENT TO ALREADY MINIMAL SYNOPTIC
FORCING OVER NORTHEAST IL. COULD SEE SOME DISORGANIZED LIGHT SNOW
OR FLURRIES LATE THIS AFTERNOON INTO THIS EVENING AS PROFILES OF
THE LAKE INDUCED STRATOCU COOL INTO THE ICE INITIATION LAYER...BUT
THIS SHOULD NOT BE A BIG DEAL.

AREAWIDE THE NORTHEAST WINDS WILL INCREASE TO 30 MPH AND MAYBE EVEN
A LITTLE HIGHER JUST OF THE LAKE. WITH MINIMAL SNOW NORTH NOT
EXPECTING ANY BLOWING SNOW ISSUES...AND SOUTH THE LOW SNOW-TO-
LIQUID RATIOS SHOULD SUPPRESS MUCH FOR BLOWING ISSUES...THOUGH
COULD LEAD TO MORE REDUCED VISIBILITY DURING THE TIME OF FALLING
SNOW THIS AFTERNOON.

MTF

&&

.LONG TERM...
329 AM CST

MONDAY THROUGH SATURDAY...

THE DISTURBED FLOW PATTERN WILL TURN MORE NORTHWESTERLY MONDAY AND
TUESDAY AS A MAJOR SYSTEM IS EXPECTED TO DEVELOP OFF THE NORTHEAST
COAST. GIVEN THIS POSSIBLY LEADING TO A SLOWER PATTERN...AS WELL
AS THE TREND OF TODAYS SYSTEM...IT IS QUITE CONCEIVABLE THAT THE
NEXT DISTURBANCE FOR MONDAY AFTERNOON AND NIGHT TRENDS WEST AS
WELL...WHICH THE EC HAS HAD IN ITS SOLUTION FOR THREE CONSECUTIVE
RUNS. THIS SYSTEM THOUGH IS NOT AS STRONG AS TODAYS AS IT IS MORE
OF A SHEARED AREA OF VORTICITY ALONG THE LINGERING BAROCLINIC
ZONE. FORCING FOR PRECIP LOOKS PRETTY LIGHT ONCE AGAIN MONDAY
AFTERNOON AND NIGHT BUT ENOUGH TO GO A LITTLE HIGHER ON POPS FOR
NORTHERN PARTS OF THE FORECAST AREA. RIGHT NOW GUIDANCE IS IN
DECENT AGREEMENT WITH SATURATING DEEP ENOUGH FOR PRECIP TYPE TO BE
LIGHT SNOW IF IT CAN OCCUR...BUT NEED TO KEEP AN EYE OUT FOR SOME
FREEZING DRIZZLE POTENTIAL IN THESE LIGHT ASCENT SITUATIONS.

A SLOW MODERATION LOOKS TO OCCUR TUESDAY INTO WEDNESDAY AND THIS
COULD BE VERY MINIMAL DEPENDING ON CLOUD COVER WHICH REMAINS A BIG
QUESTION MARK. HAVE LEANED MORE CLOUDY TUESDAY BUT STILL THINK
WITH A WESTERLY PUSH WEDNESDAY WOULD HAVE SUN POTENTIAL. LONG
RANGE GUIDANCE INDICATES A PACIFIC SYSTEM TO BE THE NEXT ONE TO
POSSIBLY BRING PRECIPITATION TO THE AREA WEDNESDAY NIGHT INTO
THURSDAY. CONTINUE POPS DURING THIS TIME FRAME AND AT THIS POINT
PROFILES ARE NEAR THE BORDER FOR RAIN OR SNOW...SO DID NOT GET TOO
FANCY WITH THE FORECAST PRECIPITATION TYPE. BEHIND THIS SYSTEM IT
SEEMS FAVORED FOR TEMPERATURES TO COOL SOME DURING THE LATTER
HALF OF THE WEEK...TO SLIGHTLY BELOW NORMAL VALUES. OBVIOUSLY ANY
FRESH SNOW COVER WOULD HELP LEAN THAT MORE TOWARD BELOW NORMAL.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* LIGHT SNOW THROUGH THIS AFTERNOON...MIXING WITH LIGHT RAIN/SLEET
  THIS MORNING WITH IFR VIS POSSIBLE.
* IFR CIGS LIFTING TO MVFR THIS AFTERNOON...THEN SCATTERING OUT
  TONIGHT.
* STRONG/GUSTY NORTHEAST WINDS THRU MID EVENING. CMS

//DISCUSSION...UPDATED 14Z...

LOW PRESSURE OVER NORTHEAST MISSOURI WILL MOVE ACROSS THE OHIO
VALLEY TONIGHT. NORTHEAST WINDS WILL REMAIN STRONG AND GUSTY THRU
THIS EVENING WITH GUSTS IN THE MID/UPPER 20KT RANGE. HEAVIEST
PRECIP SHOULD REMAIN ALONG AND SOUTH OF I-80 WITH LIGHTER AMOUNTS
NORTH. MANY AREAS REPORTING LIGHT SNOW BUT STILL SOME MIXED RAIN
AT MDW AND GYY...WHICH SHOULD TRANSITION TO SNOW BY LATE MORNING.
CMS

PREVIOUS 12Z DISCUSSION...

WEAK COLD FRONTAL BOUNDARY HAS SAGGED INTO NORTHEAST ILLINOIS
EARLY THIS MORNING...WITH IFR/LIFR CIGS NOTED IN THE VICINITY OF
THE FRONTAL BOUNDARY. EXPECT THE LIFR CIGS TO BE SOMEWHAT SHORT-
LIVED HOWEVER...AS WINDS RAMP UP FROM THE NORTHEAST.

RADAR CLEARLY SHOWS CIRCULATION WITH ALBERTA CLIPPER DROPPING
SOUTHEAST ACROSS IA...WITH EXPANSION OF WEAK RETURNS OVER NORTHERN
ILLINOIS AND A FEW REPORTS OF LIGHT SNOW BEGINNING TO REACH THE
GROUND. HIGH-RES HRRR HAS BEEN FAIRLY CONSISTENT IN BRINING NORTH
EDGE OF MORE ORGANIZED SNOW BAND ACROSS THE TERMINALS THIS MORNING
INTO MIDDAY/EARLY AFTERNOON...AND IS EXPECTED TO PRODUCE A PERIOD
OF LIGHT ACCUMULATING SNOW WITH OCCASIONAL IFR VSBYS. SNOW SHOULD
TAPER OFF TO LIGHT SNOW SHOWERS/FLURRIES THIS AFTERNOON WITH CIGS
RISING TO MVFR.

AS INDICATED ABOVE...STRONG/GUSTY NORTHEAST WINDS ARE ALREADY
RAMPING UP EARLY THIS MORNING WITH GUSTS 20-30 KT ALREAD ACROSS
FAR NORTHERN IL. 040-060 DEG WINDS NEAR 20 KT WITH GUSTS NEAR 30
KT ARE EXPECTED TO CONTIUNE INTO THE AFTERNOON BEFORE SLOW DECLINE
IN WIND SPEEDS AND A GRADUAL BACKING TO THE NORTH OCCURS. WINDS
WILL DIMINISH MORE QUICKLY TONIGHT...AS A WEAK HIGH PRESSURE RIDGE
BUILDS IN FROM THE NORTHWEST. THIS SHOULD ALLOW LOWER CLOUDS TO
SCATTER OUT OVERNIGHT.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH FOR LIGHT SNOW...MEDIUM FOR INTENSITY AND MIXED PRECIP.
* HIGH FOR CIGS THRU THIS AFTERNOON...THEN MEDIUM FOR THE REST OF
  THE PERIOD.
* HIGH FOR WIND SPEEDS/GUSTS/DIRECTIONS THRU THE PERIOD. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE LIGHT SNOW/MVFR.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR.

RATZER

&&

.MARINE...
137 AM CST

MAIN MARINE FORECAST FOCUS CONTINUES TO BE A PERIOD OF STRONG
NORTHEAST WINDS ACROSS THE SOUTHERN 2/3 OR SO OF LAKE MICHIGAN
THROUGH THIS EVENING.

A COLD FRONT HAS PUSHED SOUTH ACROSS MUCH OF LAKE MICHIGAN SINCE
SATURDAY MORNING...WITH COLD HIGH PRESSURE SPREADING ACROSS
MANITOBA...WESTERN ONTARIO AND THE NORTHERN LAKES. EARLY THIS
MORNING AN AREA OF LOW PRESSURE WAS OVER IOWA...AND THIS LOW WILL
MOVE QUICKLY SOUTHEAST TO THE LOWER OHIO VALLEY BY THIS EVENING.
THIS LOW AND THE HIGH PRESSURE TO THE NORTH OF THE LAKES WILL
COMBINE TO RAPIDLY TIGHTEN THE SURFACE PRESSURE GRADIENT ACROSS THE
LAKE THIS MORNING...WITH NORTH-NORTHEAST WINDS INCREASING TO 25-30
KT. RECENT OBSERVATION PLATFORMS ALONG THE WEST SHORE OF THE LAKE
HAVE BEEN GUSTING 26-27 KTS BEHIND THE COLD FRONT AS FAR SOUTH AS
MILWAUKEE. THESE STRONGER WINDS WILL CONTINUE TO DEVELOP SOUTHWARD
DOWN THE REMAINDER OF THE LAKE THIS MORNING. FORECAST SOUNDINGS
INDICATE WINDS TO 30 KT WILL BE PREVALENT THROUGH THE DAY...WITH A
FEW GALE FORCE GUSTS TO 35 KT POSSIBLE. WINDS WILL REMAIN GUSTY INTO
THE EVENING HOURS ACROSS THE FAR SOUTHERN PORTION OF THE LAKE...BUT
WILL DIMINISH RAPIDLY FROM THE NORTH AS A WEAK RIDGE OF HIGH
PRESSURE SPREADS IN BEHIND THE QUICK MOVING LOW WHICH MOVE TO THE
CAROLINA COAST BY MONDAY MORNING.

THE WEAK RIDGE WILL MOVE QUICKLY SOUTHEAST OF THE LAKE MONDAY...
WITH WINDS BRIEFLY BECOMING SOUTHERLY AND INCREASING BACK AROUND 20
KT OR SO AHEAD OF ANOTHER LOW PRESSURE SYSTEM WHICH WILL DROP
SOUTHEAST ACROSS THE LAKE MONDAY NIGHT...WHILE FILLING. WEAK
GRADIENT CONDITIONS WILL THEN LINGER ACROSS THE LAKE TUESDAY AND
TUESDAY NIGHT AS THE TROUGH FILLS AND A WEAK RIDGE MOVES ACROSS THE
REGION. INDICATIONS ARE THAT ANOTHER LOW WILL DEVELOP ACROSS THE
PLAINS MID-WEEK...AND WILL APPROACH THE LAKE FROM THE WEST LATE
WEDNESDAY. THIS MAY RESULT IN A BRIEF PERIOD OF ENHANCED
EAST-SOUTHEAST WINDS LATE WEDNESDAY OR WEDNESDAY NIGHT...WITH A
PERIOD OF GUSTY NORTHERLY WINDS POSSIBLE THURSDAY AS THE LOW MOVES
EAST OF THE LAKE.

FOR THE IL/NORTHWEST INDIANA NEARSHORE AREA...SMALL CRAFT ADVISORY
IS IN EFFECT FROM 6 AM CST THIS MORNING AS WINDS/WAVES QUICKLY
INCREASE AND BUILD. ADVISORY HEADLINE WILL REMAIN IN EFFECT THROUGH
MID-MORNING MONDAY...AS WAVES SLOWLY SUBSIDE BELOW 4 FT.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 251413
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
813 AM CST SUN JAN 25 2015

.SHORT TERM...
329 AM CST

THROUGH TONIGHT...

HAVE FURTHERED THE DIMINISHING SNOWFALL TREND IN THE FORECAST FOR
TODAY...MAINLY NORTH OF INTERSTATE 80. ACROSS THE ENTIRE AREA THIS
LOOKS TO BE A MAINLY LOW IMPACT...NUISANCE TYPE SNOW...WITH SOME
COMMUNITIES IN THE NORTH QUITE POSSIBLY NOT SEEING ANY
ACCUMULATION. HAVE CONTINUED A SPECIAL WEATHER STATEMENT FOR AREAS
ALONG AND SOUTH OF I-80.

SATELLITE IMAGERY THIS MORNING DEPICTS THE CLOSED UPPER CIRCULATION
ACROSS WESTERN IA WITH AN AREA OF COOLING CLOUD TOPS IN ADVANCE OF
THIS MOVING INTO NORTHWEST IL. THIS IS CORRELATING WITH MAINLY LIGHT
RAIN OR RAIN/SNOW MIX IN THE SMALL WINDOW OF DEEPER MOIST
ADVECTION AHEAD OF THE LOW. SIMPLE EXTRAPOLATION OF THE CURRENT
AREA OF PRECIP IN IOWA AND THE DEVELOPING DEFORMATION ON THE
BACKSIDE CLEARLY INDICATE THE SOUTHERN CWA IS MORE SUPPORTED FOR
PRECIPITATION THAN THE NORTH. AT THE SURFACE...TEMPERATURES ARE
AROUND OR JUST ABOVE FREEZING ACROSS MUCH OF THE FORECAST AREA. A
DEVELOPING COLD FRONT IS ADVANCING SOUTHWARD INTO NORTHERN IL WITH
DEW POINTS IN THE MID TO UPPER 20S NORTH OF THIS FEATURE...ANOTHER
HINDRANCE OF APPRECIABLE PRECIPITATION IN NORTHERN AREAS OF THE
FORECAST AREA.

SHORT RANGE GUIDANCE LIKE ITS LONG RANGE COUNTERPARTS THE PAST
SEVERAL DAYS SHOW A FAIR AMOUNT OF DISCREPANCY...NAMELY ON COVERAGE
OF PRECIP TODAY AND PRECIP TYPE IN THE SOUTHERN CWA THIS
MORNING...BUT THEY LEND SUPPORT TO THE OBSERVATIONAL TRENDS. AS
THE AREA OF RAIN ASSOCIATED WITH ELEVATED ISENTROPIC ASCENT MOVES
INTO THE SOUTHERN FORECAST AREA...PROFILES SUPPORT A PERIOD OF
RAIN OR MIX INITIALLY...AND SOME LOCATIONS MIGHT HAVE AIR
TEMPERATURES RIGHT AT FREEZING. WOULD EXPECT ANY FREEZING RAIN
THREAT TO BE SHORT LIVED AS PROFILES TREND TOWARD SNOW. MESOSCALE
CONVERGENCE AND BAROCLINIC FORCING FOR INDUCED LIFT WOULD BECOME
MORE FAVORED JUST TO THE NORTHEAST OF THE CLOSED 850MB
CIRCULATION AS IT PIVOTS MORE EASTWARD. THAT IS FAVORED ACROSS
THE SOUTHERN TIER OR TWO OF COUNTIES LATER THIS MORNING INTO
EARLY AFTERNOON. PROFILES ARE MILD FOR IDEAL SNOW GROWTH...AND
MAYBE EVEN FOR SNOW AT ALL DOWN TOWARD GIBSON CITY FOR MUCH OF THE
MORNING. HAVE SNOW TOTALS AROUND ONE TO TWO INCHES FROM PERU TO
RENSSELAER AND SOUTHWARD FOR TODAY...WITH SNOW DEPARTING NEAR OR
SOON AFTER SUNDOWN.

AS FOR AREAS NORTH OF INTERSTATE 80...SHOULD SEE A GRADUAL INCREASE
IN LIGHT SNOW AREAWIDE BY MID-MORNING. DRY CORRIDOR NEAR 850MB
SEEN ON EARLY MORNING AMDAR SOUNDINGS OVER CHICAGO SHOULD LIMIT
INTENSITY OF ANY SNOW IN THE NORTHERN FORECAST AREA...AS WILL JUST
LESS FORCING. AREAS OF NORTHEAST ILLINOIS STILL LOOK TO HAVE
ONSHORE FLOW BEHIND THE COLD FRONT...BUT FORECAST INVERSION
HEIGHTS AS WELL AS ADAPTED ONES FROM THE 00Z GRB RAOB LAST
EVE...INDICATE VERY MARGINAL DEPTH OF CONVECTIVE CLOUDS. THUS NOT
EXPECTING MUCH IF ANY ENHANCEMENT TO ALREADY MINIMAL SYNOPTIC
FORCING OVER NORTHEAST IL. COULD SEE SOME DISORGANIZED LIGHT SNOW
OR FLURRIES LATE THIS AFTERNOON INTO THIS EVENING AS PROFILES OF
THE LAKE INDUCED STRATOCU COOL INTO THE ICE INITIATION LAYER...BUT
THIS SHOULD NOT BE A BIG DEAL.

AREAWIDE THE NORTHEAST WINDS WILL INCREASE TO 30 MPH AND MAYBE EVEN
A LITTLE HIGHER JUST OF THE LAKE. WITH MINIMAL SNOW NORTH NOT
EXPECTING ANY BLOWING SNOW ISSUES...AND SOUTH THE LOW SNOW-TO-
LIQUID RATIOS SHOULD SUPPRESS MUCH FOR BLOWING ISSUES...THOUGH
COULD LEAD TO MORE REDUCED VISIBILITY DURING THE TIME OF FALLING
SNOW THIS AFTERNOON.

MTF

&&

.LONG TERM...
329 AM CST

MONDAY THROUGH SATURDAY...

THE DISTURBED FLOW PATTERN WILL TURN MORE NORTHWESTERLY MONDAY AND
TUESDAY AS A MAJOR SYSTEM IS EXPECTED TO DEVELOP OFF THE NORTHEAST
COAST. GIVEN THIS POSSIBLY LEADING TO A SLOWER PATTERN...AS WELL
AS THE TREND OF TODAYS SYSTEM...IT IS QUITE CONCEIVABLE THAT THE
NEXT DISTURBANCE FOR MONDAY AFTERNOON AND NIGHT TRENDS WEST AS
WELL...WHICH THE EC HAS HAD IN ITS SOLUTION FOR THREE CONSECUTIVE
RUNS. THIS SYSTEM THOUGH IS NOT AS STRONG AS TODAYS AS IT IS MORE
OF A SHEARED AREA OF VORTICITY ALONG THE LINGERING BAROCLINIC
ZONE. FORCING FOR PRECIP LOOKS PRETTY LIGHT ONCE AGAIN MONDAY
AFTERNOON AND NIGHT BUT ENOUGH TO GO A LITTLE HIGHER ON POPS FOR
NORTHERN PARTS OF THE FORECAST AREA. RIGHT NOW GUIDANCE IS IN
DECENT AGREEMENT WITH SATURATING DEEP ENOUGH FOR PRECIP TYPE TO BE
LIGHT SNOW IF IT CAN OCCUR...BUT NEED TO KEEP AN EYE OUT FOR SOME
FREEZING DRIZZLE POTENTIAL IN THESE LIGHT ASCENT SITUATIONS.

A SLOW MODERATION LOOKS TO OCCUR TUESDAY INTO WEDNESDAY AND THIS
COULD BE VERY MINIMAL DEPENDING ON CLOUD COVER WHICH REMAINS A BIG
QUESTION MARK. HAVE LEANED MORE CLOUDY TUESDAY BUT STILL THINK
WITH A WESTERLY PUSH WEDNESDAY WOULD HAVE SUN POTENTIAL. LONG
RANGE GUIDANCE INDICATES A PACIFIC SYSTEM TO BE THE NEXT ONE TO
POSSIBLY BRING PRECIPITATION TO THE AREA WEDNESDAY NIGHT INTO
THURSDAY. CONTINUE POPS DURING THIS TIME FRAME AND AT THIS POINT
PROFILES ARE NEAR THE BORDER FOR RAIN OR SNOW...SO DID NOT GET TOO
FANCY WITH THE FORECAST PRECIPITATION TYPE. BEHIND THIS SYSTEM IT
SEEMS FAVORED FOR TEMPERATURES TO COOL SOME DURING THE LATTER
HALF OF THE WEEK...TO SLIGHTLY BELOW NORMAL VALUES. OBVIOUSLY ANY
FRESH SNOW COVER WOULD HELP LEAN THAT MORE TOWARD BELOW NORMAL.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* LIGHT SNOW THROUGH THIS AFTERNOON...MIXING WITH LIGHT RAIN/SLEET
  THIS MORNING WITH IFR VIS POSSIBLE.
* IFR CIGS LIFTING TO MVFR THIS AFTERNOON...THEN SCATTERING OUT
  TONIGHT.
* STRONG/GUSTY NORTHEAST WINDS THRU MID EVENING. CMS

//DISCUSSION...UPDATED 14Z...

LOW PRESSURE OVER NORTHEAST MISSOURI WILL MOVE ACROSS THE OHIO
VALLEY TONIGHT. NORTHEAST WINDS WILL REMAIN STRONG AND GUSTY THRU
THIS EVENING WITH GUSTS IN THE MID/UPPER 20KT RANGE. HEAVIEST
PRECIP SHOULD REMAIN ALONG AND SOUTH OF I-80 WITH LIGHTER AMOUNTS
NORTH. MANY AREAS REPORTING LIGHT SNOW BUT STILL SOME MIXED RAIN
AT MDW AND GYY...WHICH SHOULD TRANSITION TO SNOW BY LATE MORNING.
CMS

PREVIOUS 12Z DISCUSSION...

WEAK COLD FRONTAL BOUNDARY HAS SAGGED INTO NORTHEAST ILLINOIS
EARLY THIS MORNING...WITH IFR/LIFR CIGS NOTED IN THE VICINITY OF
THE FRONTAL BOUNDARY. EXPECT THE LIFR CIGS TO BE SOMEWHAT SHORT-
LIVED HOWEVER...AS WINDS RAMP UP FROM THE NORTHEAST.

RADAR CLEARLY SHOWS CIRCULATION WITH ALBERTA CLIPPER DROPPING
SOUTHEAST ACROSS IA...WITH EXPANSION OF WEAK RETURNS OVER NORTHERN
ILLINOIS AND A FEW REPORTS OF LIGHT SNOW BEGINNING TO REACH THE
GROUND. HIGH-RES HRRR HAS BEEN FAIRLY CONSISTENT IN BRINING NORTH
EDGE OF MORE ORGANIZED SNOW BAND ACROSS THE TERMINALS THIS MORNING
INTO MIDDAY/EARLY AFTERNOON...AND IS EXPECTED TO PRODUCE A PERIOD
OF LIGHT ACCUMULATING SNOW WITH OCCASIONAL IFR VSBYS. SNOW SHOULD
TAPER OFF TO LIGHT SNOW SHOWERS/FLURRIES THIS AFTERNOON WITH CIGS
RISING TO MVFR.

AS INDICATED ABOVE...STRONG/GUSTY NORTHEAST WINDS ARE ALREADY
RAMPING UP EARLY THIS MORNING WITH GUSTS 20-30 KT ALREAD ACROSS
FAR NORTHERN IL. 040-060 DEG WINDS NEAR 20 KT WITH GUSTS NEAR 30
KT ARE EXPECTED TO CONTIUNE INTO THE AFTERNOON BEFORE SLOW DECLINE
IN WIND SPEEDS AND A GRADUAL BACKING TO THE NORTH OCCURS. WINDS
WILL DIMINISH MORE QUICKLY TONIGHT...AS A WEAK HIGH PRESSURE RIDGE
BUILDS IN FROM THE NORTHWEST. THIS SHOULD ALLOW LOWER CLOUDS TO
SCATTER OUT OVERNIGHT.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH FOR LIGHT SNOW...MEDIUM FOR INTENSITY AND MIXED PRECIP.
* HIGH FOR CIGS THRU THIS AFTERNOON...THEN MEDIUM FOR THE REST OF
  THE PERIOD.
* HIGH FOR WIND SPEEDS/GUSTS/DIRECTIONS THRU THE PERIOD. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE LIGHT SNOW/MVFR.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR.

RATZER

&&

.MARINE...
137 AM CST

MAIN MARINE FORECAST FOCUS CONTINUES TO BE A PERIOD OF STRONG
NORTHEAST WINDS ACROSS THE SOUTHERN 2/3 OR SO OF LAKE MICHIGAN
THROUGH THIS EVENING.

A COLD FRONT HAS PUSHED SOUTH ACROSS MUCH OF LAKE MICHIGAN SINCE
SATURDAY MORNING...WITH COLD HIGH PRESSURE SPREADING ACROSS
MANITOBA...WESTERN ONTARIO AND THE NORTHERN LAKES. EARLY THIS
MORNING AN AREA OF LOW PRESSURE WAS OVER IOWA...AND THIS LOW WILL
MOVE QUICKLY SOUTHEAST TO THE LOWER OHIO VALLEY BY THIS EVENING.
THIS LOW AND THE HIGH PRESSURE TO THE NORTH OF THE LAKES WILL
COMBINE TO RAPIDLY TIGHTEN THE SURFACE PRESSURE GRADIENT ACROSS THE
LAKE THIS MORNING...WITH NORTH-NORTHEAST WINDS INCREASING TO 25-30
KT. RECENT OBSERVATION PLATFORMS ALONG THE WEST SHORE OF THE LAKE
HAVE BEEN GUSTING 26-27 KTS BEHIND THE COLD FRONT AS FAR SOUTH AS
MILWAUKEE. THESE STRONGER WINDS WILL CONTINUE TO DEVELOP SOUTHWARD
DOWN THE REMAINDER OF THE LAKE THIS MORNING. FORECAST SOUNDINGS
INDICATE WINDS TO 30 KT WILL BE PREVALENT THROUGH THE DAY...WITH A
FEW GALE FORCE GUSTS TO 35 KT POSSIBLE. WINDS WILL REMAIN GUSTY INTO
THE EVENING HOURS ACROSS THE FAR SOUTHERN PORTION OF THE LAKE...BUT
WILL DIMINISH RAPIDLY FROM THE NORTH AS A WEAK RIDGE OF HIGH
PRESSURE SPREADS IN BEHIND THE QUICK MOVING LOW WHICH MOVE TO THE
CAROLINA COAST BY MONDAY MORNING.

THE WEAK RIDGE WILL MOVE QUICKLY SOUTHEAST OF THE LAKE MONDAY...
WITH WINDS BRIEFLY BECOMING SOUTHERLY AND INCREASING BACK AROUND 20
KT OR SO AHEAD OF ANOTHER LOW PRESSURE SYSTEM WHICH WILL DROP
SOUTHEAST ACROSS THE LAKE MONDAY NIGHT...WHILE FILLING. WEAK
GRADIENT CONDITIONS WILL THEN LINGER ACROSS THE LAKE TUESDAY AND
TUESDAY NIGHT AS THE TROUGH FILLS AND A WEAK RIDGE MOVES ACROSS THE
REGION. INDICATIONS ARE THAT ANOTHER LOW WILL DEVELOP ACROSS THE
PLAINS MID-WEEK...AND WILL APPROACH THE LAKE FROM THE WEST LATE
WEDNESDAY. THIS MAY RESULT IN A BRIEF PERIOD OF ENHANCED
EAST-SOUTHEAST WINDS LATE WEDNESDAY OR WEDNESDAY NIGHT...WITH A
PERIOD OF GUSTY NORTHERLY WINDS POSSIBLE THURSDAY AS THE LOW MOVES
EAST OF THE LAKE.

FOR THE IL/NORTHWEST INDIANA NEARSHORE AREA...SMALL CRAFT ADVISORY
IS IN EFFECT FROM 6 AM CST THIS MORNING AS WINDS/WAVES QUICKLY
INCREASE AND BUILD. ADVISORY HEADLINE WILL REMAIN IN EFFECT THROUGH
MID-MORNING MONDAY...AS WAVES SLOWLY SUBSIDE BELOW 4 FT.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 251149
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
549 AM CST SUN JAN 25 2015

.SHORT TERM...
329 AM CST

THROUGH TONIGHT...

HAVE FURTHERED THE DIMINISHING SNOWFALL TREND IN THE FORECAST FOR
TODAY...MAINLY NORTH OF INTERSTATE 80. ACROSS THE ENTIRE AREA THIS
LOOKS TO BE A MAINLY LOW IMPACT...NUISANCE TYPE SNOW...WITH SOME
COMMUNITIES IN THE NORTH QUITE POSSIBLY NOT SEEING ANY
ACCUMULATION. HAVE CONTINUED A SPECIAL WEATHER STATEMENT FOR AREAS
ALONG AND SOUTH OF I-80.

SATELLITE IMAGERY THIS MORNING DEPICTS THE CLOSED UPPER CIRCULATION
ACROSS WESTERN IA WITH AN AREA OF COOLING CLOUD TOPS IN ADVANCE OF
THIS MOVING INTO NORTHWEST IL. THIS IS CORRELATING WITH MAINLY LIGHT
RAIN OR RAIN/SNOW MIX IN THE SMALL WINDOW OF DEEPER MOIST
ADVECTION AHEAD OF THE LOW. SIMPLE EXTRAPOLATION OF THE CURRENT
AREA OF PRECIP IN IOWA AND THE DEVELOPING DEFORMATION ON THE
BACKSIDE CLEARLY INDICATE THE SOUTHERN CWA IS MORE SUPPORTED FOR
PRECIPITATION THAN THE NORTH. AT THE SURFACE...TEMPERATURES ARE
AROUND OR JUST ABOVE FREEZING ACROSS MUCH OF THE FORECAST AREA. A
DEVELOPING COLD FRONT IS ADVANCING SOUTHWARD INTO NORTHERN IL WITH
DEW POINTS IN THE MID TO UPPER 20S NORTH OF THIS FEATURE...ANOTHER
HINDRANCE OF APPRECIABLE PRECIPITATION IN NORTHERN AREAS OF THE
FORECAST AREA.

SHORT RANGE GUIDANCE LIKE ITS LONG RANGE COUNTERPARTS THE PAST
SEVERAL DAYS SHOW A FAIR AMOUNT OF DISCREPANCY...NAMELY ON COVERAGE
OF PRECIP TODAY AND PRECIP TYPE IN THE SOUTHERN CWA THIS
MORNING...BUT THEY LEND SUPPORT TO THE OBSERVATIONAL TRENDS. AS
THE AREA OF RAIN ASSOCIATED WITH ELEVATED ISENTROPIC ASCENT MOVES
INTO THE SOUTHERN FORECAST AREA...PROFILES SUPPORT A PERIOD OF
RAIN OR MIX INITIALLY...AND SOME LOCATIONS MIGHT HAVE AIR
TEMPERATURES RIGHT AT FREEZING. WOULD EXPECT ANY FREEZING RAIN
THREAT TO BE SHORT LIVED AS PROFILES TREND TOWARD SNOW. MESOSCALE
CONVERGENCE AND BAROCLINIC FORCING FOR INDUCED LIFT WOULD BECOME
MORE FAVORED JUST TO THE NORTHEAST OF THE CLOSED 850MB
CIRCULATION AS IT PIVOTS MORE EASTWARD. THAT IS FAVORED ACROSS
THE SOUTHERN TIER OR TWO OF COUNTIES LATER THIS MORNING INTO
EARLY AFTERNOON. PROFILES ARE MILD FOR IDEAL SNOW GROWTH...AND
MAYBE EVEN FOR SNOW AT ALL DOWN TOWARD GIBSON CITY FOR MUCH OF THE
MORNING. HAVE SNOW TOTALS AROUND ONE TO TWO INCHES FROM PERU TO
RENSSELAER AND SOUTHWARD FOR TODAY...WITH SNOW DEPARTING NEAR OR
SOON AFTER SUNDOWN.

AS FOR AREAS NORTH OF INTERSTATE 80...SHOULD SEE A GRADUAL INCREASE
IN LIGHT SNOW AREAWIDE BY MID-MORNING. DRY CORRIDOR NEAR 850MB
SEEN ON EARLY MORNING AMDAR SOUNDINGS OVER CHICAGO SHOULD LIMIT
INTENSITY OF ANY SNOW IN THE NORTHERN FORECAST AREA...AS WILL JUST
LESS FORCING. AREAS OF NORTHEAST ILLINOIS STILL LOOK TO HAVE
ONSHORE FLOW BEHIND THE COLD FRONT...BUT FORECAST INVERSION
HEIGHTS AS WELL AS ADAPTED ONES FROM THE 00Z GRB RAOB LAST
EVE...INDICATE VERY MARGINAL DEPTH OF CONVECTIVE CLOUDS. THUS NOT
EXPECTING MUCH IF ANY ENHANCEMENT TO ALREADY MINIMAL SYNOPTIC
FORCING OVER NORTHEAST IL. COULD SEE SOME DISORGANIZED LIGHT SNOW
OR FLURRIES LATE THIS AFTERNOON INTO THIS EVENING AS PROFILES OF
THE LAKE INDUCED STRATOCU COOL INTO THE ICE INITIATION LAYER...BUT
THIS SHOULD NOT BE A BIG DEAL.

AREAWIDE THE NORTHEAST WINDS WILL INCREASE TO 30 MPH AND MAYBE EVEN
A LITTLE HIGHER JUST OF THE LAKE. WITH MINIMAL SNOW NORTH NOT
EXPECTING ANY BLOWING SNOW ISSUES...AND SOUTH THE LOW SNOW-TO-
LIQUID RATIOS SHOULD SUPPRESS MUCH FOR BLOWING ISSUES...THOUGH
COULD LEAD TO MORE REDUCED VISIBILITY DURING THE TIME OF FALLING
SNOW THIS AFTERNOON.

MTF

&&

.LONG TERM...
329 AM CST

MONDAY THROUGH SATURDAY...

THE DISTURBED FLOW PATTERN WILL TURN MORE NORTHWESTERLY MONDAY AND
TUESDAY AS A MAJOR SYSTEM IS EXPECTED TO DEVELOP OFF THE NORTHEAST
COAST. GIVEN THIS POSSIBLY LEADING TO A SLOWER PATTERN...AS WELL
AS THE TREND OF TODAYS SYSTEM...IT IS QUITE CONCEIVABLE THAT THE
NEXT DISTURBANCE FOR MONDAY AFTERNOON AND NIGHT TRENDS WEST AS
WELL...WHICH THE EC HAS HAD IN ITS SOLUTION FOR THREE CONSECUTIVE
RUNS. THIS SYSTEM THOUGH IS NOT AS STRONG AS TODAYS AS IT IS MORE
OF A SHEARED AREA OF VORTICITY ALONG THE LINGERING BAROCLINIC
ZONE. FORCING FOR PRECIP LOOKS PRETTY LIGHT ONCE AGAIN MONDAY
AFTERNOON AND NIGHT BUT ENOUGH TO GO A LITTLE HIGHER ON POPS FOR
NORTHERN PARTS OF THE FORECAST AREA. RIGHT NOW GUIDANCE IS IN
DECENT AGREEMENT WITH SATURATING DEEP ENOUGH FOR PRECIP TYPE TO BE
LIGHT SNOW IF IT CAN OCCUR...BUT NEED TO KEEP AN EYE OUT FOR SOME
FREEZING DRIZZLE POTENTIAL IN THESE LIGHT ASCENT SITUATIONS.

A SLOW MODERATION LOOKS TO OCCUR TUESDAY INTO WEDNESDAY AND THIS
COULD BE VERY MINIMAL DEPENDING ON CLOUD COVER WHICH REMAINS A BIG
QUESTION MARK. HAVE LEANED MORE CLOUDY TUESDAY BUT STILL THINK
WITH A WESTERLY PUSH WEDNESDAY WOULD HAVE SUN POTENTIAL. LONG
RANGE GUIDANCE INDICATES A PACIFIC SYSTEM TO BE THE NEXT ONE TO
POSSIBLY BRING PRECIPITATION TO THE AREA WEDNESDAY NIGHT INTO
THURSDAY. CONTINUE POPS DURING THIS TIME FRAME AND AT THIS POINT
PROFILES ARE NEAR THE BORDER FOR RAIN OR SNOW...SO DID NOT GET TOO
FANCY WITH THE FORECAST PRECIPITATION TYPE. BEHIND THIS SYSTEM IT
SEEMS FAVORED FOR TEMPERATURES TO COOL SOME DURING THE LATTER
HALF OF THE WEEK...TO SLIGHTLY BELOW NORMAL VALUES. OBVIOUSLY ANY
FRESH SNOW COVER WOULD HELP LEAN THAT MORE TOWARD BELOW NORMAL.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* IFR CIGS EARLY WITH LIGHT SNOW DEVELOPING THIS MORNING. CIGS MAY
  ACTUALLY COME UP A BIT WITH THE SNOW...THOUGH VSBYS MVFR/OCNL
  IFR ARE PROBABLE WITH SOME LIGHT ACCUMULATION. SNOW EXPECTED TO
  TAPER OFF TO LIGHT SHSN/FLURRIES BY EARLY AFTERNOON.

* MVFR CIGS EXPECTED THIS AFTERNOON AND THIS EVENING.

* STRONG GUSTY NORTHEAST WINDS AROUND 30 KT AT TIMES. WINDS SLOWLY
  DIMINISH THROUGH THIS EVENING.

RATZER

//DISCUSSION...UPDATED 12Z...

WEAK COLD FRONTAL BOUNDARY HAS SAGGED INTO NORTHEAST ILLINOIS
EARLY THIS MORNING...WITH IFR/LIFR CIGS NOTED IN THE VICINITY OF
THE FRONTAL BOUNDARY. EXPECT THE LIFR CIGS TO BE SOMEWHAT SHORT-
LIVED HOWEVER...AS WINDS RAMP UP FROM THE NORTHEAST.

RADAR CLEARLY SHOWS CIRCULATION WITH ALBERTA CLIPPER DROPPING
SOUTHEAST ACROSS IA...WITH EXPANSION OF WEAK RETURNS OVER NORTHERN
ILLINOIS AND A FEW REPORTS OF LIGHT SNOW BEGINNING TO REACH THE
GROUND. HIGH-RES HRRR HAS BEEN FAIRLY CONSISTENT IN BRINING NORTH
EDGE OF MORE ORGANIZED SNOW BAND ACROSS THE TERMINALS THIS MORNING
INTO MIDDAY/EARLY AFTERNOON...AND IS EXPECTED TO PRODUCE A PERIOD
OF LIGHT ACCUMULATING SNOW WITH OCCASIONAL IFR VSBYS. SNOW SHOULD
TAPER OFF TO LIGHT SNOW SHOWERS/FLURRIES THIS AFTERNOON WITH CIGS
RISING TO MVFR.

AS INDICATED ABOVE...STRONG/GUSTY NORTHEAST WINDS ARE ALREADY
RAMPING UP EARLY THIS MORNING WITH GUSTS 20-30 KT ALREAD ACROSS
FAR NORTHERN IL. 040-060 DEG WINDS NEAR 20 KT WITH GUSTS NEAR 30
KT ARE EXPECTED TO CONTIUNE INTO THE AFTERNOON BEFORE SLOW DECLINE
IN WIND SPEEDS AND A GRADUAL BACKING TO THE NORTH OCCURS. WINDS
WILL DIMINISH MORE QUICKLY TONIGHT...AS A WEAK HIGH PRESSURE RIDGE
BUILDS IN FROM THE NORTHWEST. THIS SHOULD ALLOW LOWER CLOUDS TO
SCATTER OUT OVERNIGHT.

RATZER


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH IN WIND TRENDS.

* MEDIUM-HIGH IN SNOW TIMING...MEDIUM IN DETAILS OF CIG/VSBY
  THROUGH MID-DAY.

* MEDIUM-LOW IN TIMING OF SCATTERING MVFR CIGS TONIGHT.

RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE LIGHT SNOW/MVFR.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR.

RATZER

&&

.MARINE...
137 AM CST

MAIN MARINE FORECAST FOCUS CONTINUES TO BE A PERIOD OF STRONG
NORTHEAST WINDS ACROSS THE SOUTHERN 2/3 OR SO OF LAKE MICHIGAN
THROUGH THIS EVENING.

A COLD FRONT HAS PUSHED SOUTH ACROSS MUCH OF LAKE MICHIGAN SINCE
SATURDAY MORNING...WITH COLD HIGH PRESSURE SPREADING ACROSS
MANITOBA...WESTERN ONTARIO AND THE NORTHERN LAKES. EARLY THIS
MORNING AN AREA OF LOW PRESSURE WAS OVER IOWA...AND THIS LOW WILL
MOVE QUICKLY SOUTHEAST TO THE LOWER OHIO VALLEY BY THIS EVENING.
THIS LOW AND THE HIGH PRESSURE TO THE NORTH OF THE LAKES WILL
COMBINE TO RAPIDLY TIGHTEN THE SURFACE PRESSURE GRADIENT ACROSS THE
LAKE THIS MORNING...WITH NORTH-NORTHEAST WINDS INCREASING TO 25-30
KT. RECENT OBSERVATION PLATFORMS ALONG THE WEST SHORE OF THE LAKE
HAVE BEEN GUSTING 26-27 KTS BEHIND THE COLD FRONT AS FAR SOUTH AS
MILWAUKEE. THESE STRONGER WINDS WILL CONTINUE TO DEVELOP SOUTHWARD
DOWN THE REMAINDER OF THE LAKE THIS MORNING. FORECAST SOUNDINGS
INDICATE WINDS TO 30 KT WILL BE PREVALENT THROUGH THE DAY...WITH A
FEW GALE FORCE GUSTS TO 35 KT POSSIBLE. WINDS WILL REMAIN GUSTY INTO
THE EVENING HOURS ACROSS THE FAR SOUTHERN PORTION OF THE LAKE...BUT
WILL DIMINISH RAPIDLY FROM THE NORTH AS A WEAK RIDGE OF HIGH
PRESSURE SPREADS IN BEHIND THE QUICK MOVING LOW WHICH MOVE TO THE
CAROLINA COAST BY MONDAY MORNING.

THE WEAK RIDGE WILL MOVE QUICKLY SOUTHEAST OF THE LAKE MONDAY...
WITH WINDS BRIEFLY BECOMING SOUTHERLY AND INCREASING BACK AROUND 20
KT OR SO AHEAD OF ANOTHER LOW PRESSURE SYSTEM WHICH WILL DROP
SOUTHEAST ACROSS THE LAKE MONDAY NIGHT...WHILE FILLING. WEAK
GRADIENT CONDITIONS WILL THEN LINGER ACROSS THE LAKE TUESDAY AND
TUESDAY NIGHT AS THE TROUGH FILLS AND A WEAK RIDGE MOVES ACROSS THE
REGION. INDICATIONS ARE THAT ANOTHER LOW WILL DEVELOP ACROSS THE
PLAINS MID-WEEK...AND WILL APPROACH THE LAKE FROM THE WEST LATE
WEDNESDAY. THIS MAY RESULT IN A BRIEF PERIOD OF ENHANCED
EAST-SOUTHEAST WINDS LATE WEDNESDAY OR WEDNESDAY NIGHT...WITH A
PERIOD OF GUSTY NORTHERLY WINDS POSSIBLE THURSDAY AS THE LOW MOVES
EAST OF THE LAKE.

FOR THE IL/NORTHWEST INDIANA NEARSHORE AREA...SMALL CRAFT ADVISORY
IS IN EFFECT FROM 6 AM CST THIS MORNING AS WINDS/WAVES QUICKLY
INCREASE AND BUILD. ADVISORY HEADLINE WILL REMAIN IN EFFECT THROUGH
MID-MORNING MONDAY...AS WAVES SLOWLY SUBSIDE BELOW 4 FT.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 9 AM MONDAY.

     SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 251149
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
549 AM CST SUN JAN 25 2015

.SHORT TERM...
329 AM CST

THROUGH TONIGHT...

HAVE FURTHERED THE DIMINISHING SNOWFALL TREND IN THE FORECAST FOR
TODAY...MAINLY NORTH OF INTERSTATE 80. ACROSS THE ENTIRE AREA THIS
LOOKS TO BE A MAINLY LOW IMPACT...NUISANCE TYPE SNOW...WITH SOME
COMMUNITIES IN THE NORTH QUITE POSSIBLY NOT SEEING ANY
ACCUMULATION. HAVE CONTINUED A SPECIAL WEATHER STATEMENT FOR AREAS
ALONG AND SOUTH OF I-80.

SATELLITE IMAGERY THIS MORNING DEPICTS THE CLOSED UPPER CIRCULATION
ACROSS WESTERN IA WITH AN AREA OF COOLING CLOUD TOPS IN ADVANCE OF
THIS MOVING INTO NORTHWEST IL. THIS IS CORRELATING WITH MAINLY LIGHT
RAIN OR RAIN/SNOW MIX IN THE SMALL WINDOW OF DEEPER MOIST
ADVECTION AHEAD OF THE LOW. SIMPLE EXTRAPOLATION OF THE CURRENT
AREA OF PRECIP IN IOWA AND THE DEVELOPING DEFORMATION ON THE
BACKSIDE CLEARLY INDICATE THE SOUTHERN CWA IS MORE SUPPORTED FOR
PRECIPITATION THAN THE NORTH. AT THE SURFACE...TEMPERATURES ARE
AROUND OR JUST ABOVE FREEZING ACROSS MUCH OF THE FORECAST AREA. A
DEVELOPING COLD FRONT IS ADVANCING SOUTHWARD INTO NORTHERN IL WITH
DEW POINTS IN THE MID TO UPPER 20S NORTH OF THIS FEATURE...ANOTHER
HINDRANCE OF APPRECIABLE PRECIPITATION IN NORTHERN AREAS OF THE
FORECAST AREA.

SHORT RANGE GUIDANCE LIKE ITS LONG RANGE COUNTERPARTS THE PAST
SEVERAL DAYS SHOW A FAIR AMOUNT OF DISCREPANCY...NAMELY ON COVERAGE
OF PRECIP TODAY AND PRECIP TYPE IN THE SOUTHERN CWA THIS
MORNING...BUT THEY LEND SUPPORT TO THE OBSERVATIONAL TRENDS. AS
THE AREA OF RAIN ASSOCIATED WITH ELEVATED ISENTROPIC ASCENT MOVES
INTO THE SOUTHERN FORECAST AREA...PROFILES SUPPORT A PERIOD OF
RAIN OR MIX INITIALLY...AND SOME LOCATIONS MIGHT HAVE AIR
TEMPERATURES RIGHT AT FREEZING. WOULD EXPECT ANY FREEZING RAIN
THREAT TO BE SHORT LIVED AS PROFILES TREND TOWARD SNOW. MESOSCALE
CONVERGENCE AND BAROCLINIC FORCING FOR INDUCED LIFT WOULD BECOME
MORE FAVORED JUST TO THE NORTHEAST OF THE CLOSED 850MB
CIRCULATION AS IT PIVOTS MORE EASTWARD. THAT IS FAVORED ACROSS
THE SOUTHERN TIER OR TWO OF COUNTIES LATER THIS MORNING INTO
EARLY AFTERNOON. PROFILES ARE MILD FOR IDEAL SNOW GROWTH...AND
MAYBE EVEN FOR SNOW AT ALL DOWN TOWARD GIBSON CITY FOR MUCH OF THE
MORNING. HAVE SNOW TOTALS AROUND ONE TO TWO INCHES FROM PERU TO
RENSSELAER AND SOUTHWARD FOR TODAY...WITH SNOW DEPARTING NEAR OR
SOON AFTER SUNDOWN.

AS FOR AREAS NORTH OF INTERSTATE 80...SHOULD SEE A GRADUAL INCREASE
IN LIGHT SNOW AREAWIDE BY MID-MORNING. DRY CORRIDOR NEAR 850MB
SEEN ON EARLY MORNING AMDAR SOUNDINGS OVER CHICAGO SHOULD LIMIT
INTENSITY OF ANY SNOW IN THE NORTHERN FORECAST AREA...AS WILL JUST
LESS FORCING. AREAS OF NORTHEAST ILLINOIS STILL LOOK TO HAVE
ONSHORE FLOW BEHIND THE COLD FRONT...BUT FORECAST INVERSION
HEIGHTS AS WELL AS ADAPTED ONES FROM THE 00Z GRB RAOB LAST
EVE...INDICATE VERY MARGINAL DEPTH OF CONVECTIVE CLOUDS. THUS NOT
EXPECTING MUCH IF ANY ENHANCEMENT TO ALREADY MINIMAL SYNOPTIC
FORCING OVER NORTHEAST IL. COULD SEE SOME DISORGANIZED LIGHT SNOW
OR FLURRIES LATE THIS AFTERNOON INTO THIS EVENING AS PROFILES OF
THE LAKE INDUCED STRATOCU COOL INTO THE ICE INITIATION LAYER...BUT
THIS SHOULD NOT BE A BIG DEAL.

AREAWIDE THE NORTHEAST WINDS WILL INCREASE TO 30 MPH AND MAYBE EVEN
A LITTLE HIGHER JUST OF THE LAKE. WITH MINIMAL SNOW NORTH NOT
EXPECTING ANY BLOWING SNOW ISSUES...AND SOUTH THE LOW SNOW-TO-
LIQUID RATIOS SHOULD SUPPRESS MUCH FOR BLOWING ISSUES...THOUGH
COULD LEAD TO MORE REDUCED VISIBILITY DURING THE TIME OF FALLING
SNOW THIS AFTERNOON.

MTF

&&

.LONG TERM...
329 AM CST

MONDAY THROUGH SATURDAY...

THE DISTURBED FLOW PATTERN WILL TURN MORE NORTHWESTERLY MONDAY AND
TUESDAY AS A MAJOR SYSTEM IS EXPECTED TO DEVELOP OFF THE NORTHEAST
COAST. GIVEN THIS POSSIBLY LEADING TO A SLOWER PATTERN...AS WELL
AS THE TREND OF TODAYS SYSTEM...IT IS QUITE CONCEIVABLE THAT THE
NEXT DISTURBANCE FOR MONDAY AFTERNOON AND NIGHT TRENDS WEST AS
WELL...WHICH THE EC HAS HAD IN ITS SOLUTION FOR THREE CONSECUTIVE
RUNS. THIS SYSTEM THOUGH IS NOT AS STRONG AS TODAYS AS IT IS MORE
OF A SHEARED AREA OF VORTICITY ALONG THE LINGERING BAROCLINIC
ZONE. FORCING FOR PRECIP LOOKS PRETTY LIGHT ONCE AGAIN MONDAY
AFTERNOON AND NIGHT BUT ENOUGH TO GO A LITTLE HIGHER ON POPS FOR
NORTHERN PARTS OF THE FORECAST AREA. RIGHT NOW GUIDANCE IS IN
DECENT AGREEMENT WITH SATURATING DEEP ENOUGH FOR PRECIP TYPE TO BE
LIGHT SNOW IF IT CAN OCCUR...BUT NEED TO KEEP AN EYE OUT FOR SOME
FREEZING DRIZZLE POTENTIAL IN THESE LIGHT ASCENT SITUATIONS.

A SLOW MODERATION LOOKS TO OCCUR TUESDAY INTO WEDNESDAY AND THIS
COULD BE VERY MINIMAL DEPENDING ON CLOUD COVER WHICH REMAINS A BIG
QUESTION MARK. HAVE LEANED MORE CLOUDY TUESDAY BUT STILL THINK
WITH A WESTERLY PUSH WEDNESDAY WOULD HAVE SUN POTENTIAL. LONG
RANGE GUIDANCE INDICATES A PACIFIC SYSTEM TO BE THE NEXT ONE TO
POSSIBLY BRING PRECIPITATION TO THE AREA WEDNESDAY NIGHT INTO
THURSDAY. CONTINUE POPS DURING THIS TIME FRAME AND AT THIS POINT
PROFILES ARE NEAR THE BORDER FOR RAIN OR SNOW...SO DID NOT GET TOO
FANCY WITH THE FORECAST PRECIPITATION TYPE. BEHIND THIS SYSTEM IT
SEEMS FAVORED FOR TEMPERATURES TO COOL SOME DURING THE LATTER
HALF OF THE WEEK...TO SLIGHTLY BELOW NORMAL VALUES. OBVIOUSLY ANY
FRESH SNOW COVER WOULD HELP LEAN THAT MORE TOWARD BELOW NORMAL.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* IFR CIGS EARLY WITH LIGHT SNOW DEVELOPING THIS MORNING. CIGS MAY
  ACTUALLY COME UP A BIT WITH THE SNOW...THOUGH VSBYS MVFR/OCNL
  IFR ARE PROBABLE WITH SOME LIGHT ACCUMULATION. SNOW EXPECTED TO
  TAPER OFF TO LIGHT SHSN/FLURRIES BY EARLY AFTERNOON.

* MVFR CIGS EXPECTED THIS AFTERNOON AND THIS EVENING.

* STRONG GUSTY NORTHEAST WINDS AROUND 30 KT AT TIMES. WINDS SLOWLY
  DIMINISH THROUGH THIS EVENING.

RATZER

//DISCUSSION...UPDATED 12Z...

WEAK COLD FRONTAL BOUNDARY HAS SAGGED INTO NORTHEAST ILLINOIS
EARLY THIS MORNING...WITH IFR/LIFR CIGS NOTED IN THE VICINITY OF
THE FRONTAL BOUNDARY. EXPECT THE LIFR CIGS TO BE SOMEWHAT SHORT-
LIVED HOWEVER...AS WINDS RAMP UP FROM THE NORTHEAST.

RADAR CLEARLY SHOWS CIRCULATION WITH ALBERTA CLIPPER DROPPING
SOUTHEAST ACROSS IA...WITH EXPANSION OF WEAK RETURNS OVER NORTHERN
ILLINOIS AND A FEW REPORTS OF LIGHT SNOW BEGINNING TO REACH THE
GROUND. HIGH-RES HRRR HAS BEEN FAIRLY CONSISTENT IN BRINING NORTH
EDGE OF MORE ORGANIZED SNOW BAND ACROSS THE TERMINALS THIS MORNING
INTO MIDDAY/EARLY AFTERNOON...AND IS EXPECTED TO PRODUCE A PERIOD
OF LIGHT ACCUMULATING SNOW WITH OCCASIONAL IFR VSBYS. SNOW SHOULD
TAPER OFF TO LIGHT SNOW SHOWERS/FLURRIES THIS AFTERNOON WITH CIGS
RISING TO MVFR.

AS INDICATED ABOVE...STRONG/GUSTY NORTHEAST WINDS ARE ALREADY
RAMPING UP EARLY THIS MORNING WITH GUSTS 20-30 KT ALREAD ACROSS
FAR NORTHERN IL. 040-060 DEG WINDS NEAR 20 KT WITH GUSTS NEAR 30
KT ARE EXPECTED TO CONTIUNE INTO THE AFTERNOON BEFORE SLOW DECLINE
IN WIND SPEEDS AND A GRADUAL BACKING TO THE NORTH OCCURS. WINDS
WILL DIMINISH MORE QUICKLY TONIGHT...AS A WEAK HIGH PRESSURE RIDGE
BUILDS IN FROM THE NORTHWEST. THIS SHOULD ALLOW LOWER CLOUDS TO
SCATTER OUT OVERNIGHT.

RATZER


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH IN WIND TRENDS.

* MEDIUM-HIGH IN SNOW TIMING...MEDIUM IN DETAILS OF CIG/VSBY
  THROUGH MID-DAY.

* MEDIUM-LOW IN TIMING OF SCATTERING MVFR CIGS TONIGHT.

RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...CHANCE LIGHT SNOW/MVFR.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

SATURDAY...CHANCE OF LIGHT SNOW/MVFR.

RATZER

&&

.MARINE...
137 AM CST

MAIN MARINE FORECAST FOCUS CONTINUES TO BE A PERIOD OF STRONG
NORTHEAST WINDS ACROSS THE SOUTHERN 2/3 OR SO OF LAKE MICHIGAN
THROUGH THIS EVENING.

A COLD FRONT HAS PUSHED SOUTH ACROSS MUCH OF LAKE MICHIGAN SINCE
SATURDAY MORNING...WITH COLD HIGH PRESSURE SPREADING ACROSS
MANITOBA...WESTERN ONTARIO AND THE NORTHERN LAKES. EARLY THIS
MORNING AN AREA OF LOW PRESSURE WAS OVER IOWA...AND THIS LOW WILL
MOVE QUICKLY SOUTHEAST TO THE LOWER OHIO VALLEY BY THIS EVENING.
THIS LOW AND THE HIGH PRESSURE TO THE NORTH OF THE LAKES WILL
COMBINE TO RAPIDLY TIGHTEN THE SURFACE PRESSURE GRADIENT ACROSS THE
LAKE THIS MORNING...WITH NORTH-NORTHEAST WINDS INCREASING TO 25-30
KT. RECENT OBSERVATION PLATFORMS ALONG THE WEST SHORE OF THE LAKE
HAVE BEEN GUSTING 26-27 KTS BEHIND THE COLD FRONT AS FAR SOUTH AS
MILWAUKEE. THESE STRONGER WINDS WILL CONTINUE TO DEVELOP SOUTHWARD
DOWN THE REMAINDER OF THE LAKE THIS MORNING. FORECAST SOUNDINGS
INDICATE WINDS TO 30 KT WILL BE PREVALENT THROUGH THE DAY...WITH A
FEW GALE FORCE GUSTS TO 35 KT POSSIBLE. WINDS WILL REMAIN GUSTY INTO
THE EVENING HOURS ACROSS THE FAR SOUTHERN PORTION OF THE LAKE...BUT
WILL DIMINISH RAPIDLY FROM THE NORTH AS A WEAK RIDGE OF HIGH
PRESSURE SPREADS IN BEHIND THE QUICK MOVING LOW WHICH MOVE TO THE
CAROLINA COAST BY MONDAY MORNING.

THE WEAK RIDGE WILL MOVE QUICKLY SOUTHEAST OF THE LAKE MONDAY...
WITH WINDS BRIEFLY BECOMING SOUTHERLY AND INCREASING BACK AROUND 20
KT OR SO AHEAD OF ANOTHER LOW PRESSURE SYSTEM WHICH WILL DROP
SOUTHEAST ACROSS THE LAKE MONDAY NIGHT...WHILE FILLING. WEAK
GRADIENT CONDITIONS WILL THEN LINGER ACROSS THE LAKE TUESDAY AND
TUESDAY NIGHT AS THE TROUGH FILLS AND A WEAK RIDGE MOVES ACROSS THE
REGION. INDICATIONS ARE THAT ANOTHER LOW WILL DEVELOP ACROSS THE
PLAINS MID-WEEK...AND WILL APPROACH THE LAKE FROM THE WEST LATE
WEDNESDAY. THIS MAY RESULT IN A BRIEF PERIOD OF ENHANCED
EAST-SOUTHEAST WINDS LATE WEDNESDAY OR WEDNESDAY NIGHT...WITH A
PERIOD OF GUSTY NORTHERLY WINDS POSSIBLE THURSDAY AS THE LOW MOVES
EAST OF THE LAKE.

FOR THE IL/NORTHWEST INDIANA NEARSHORE AREA...SMALL CRAFT ADVISORY
IS IN EFFECT FROM 6 AM CST THIS MORNING AS WINDS/WAVES QUICKLY
INCREASE AND BUILD. ADVISORY HEADLINE WILL REMAIN IN EFFECT THROUGH
MID-MORNING MONDAY...AS WAVES SLOWLY SUBSIDE BELOW 4 FT.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 9 AM MONDAY.

     SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO








000
FXUS63 KLOT 250932
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
332 AM CST SUN JAN 25 2015

.SHORT TERM...
329 AM CST

THROUGH TONIGHT...

HAVE FURTHERED THE DIMINISHING SNOWFALL TREND IN THE FORECAST FOR
TODAY...MAINLY NORTH OF INTERSTATE 80. ACROSS THE ENTIRE AREA THIS
LOOKS TO BE A MAINLY LOW IMPACT...NUISANCE TYPE SNOW...WITH SOME
COMMUNITIES IN THE NORTH QUITE POSSIBLY NOT SEEING ANY
ACCUMULATION. HAVE CONTINUED A SPECIAL WEATHER STATEMENT FOR AREAS
ALONG AND SOUTH OF I-80.

SATELLITE IMAGERY THIS MORNING DEPICTS THE CLOSED UPPER CIRCULATION
ACROSS WESTERN IA WITH AN AREA OF COOLING CLOUD TOPS IN ADVANCE OF
THIS MOVING INTO NORTHWEST IL. THIS IS CORRELATING WITH MAINLY LIGHT
RAIN OR RAIN/SNOW MIX IN THE SMALL WINDOW OF DEEPER MOIST
ADVECTION AHEAD OF THE LOW. SIMPLE EXTRAPOLATION OF THE CURRENT
AREA OF PRECIP IN IOWA AND THE DEVELOPING DEFORMATION ON THE
BACKSIDE CLEARLY INDICATE THE SOUTHERN CWA IS MORE SUPPORTED FOR
PRECIPITATION THAN THE NORTH. AT THE SURFACE...TEMPERATURES ARE
AROUND OR JUST ABOVE FREEZING ACROSS MUCH OF THE FORECAST AREA. A
DEVELOPING COLD FRONT IS ADVANCING SOUTHWARD INTO NORTHERN IL WITH
DEW POINTS IN THE MID TO UPPER 20S NORTH OF THIS FEATURE...ANOTHER
HINDRANCE OF APPRECIABLE PRECIPITATION IN NORTHERN AREAS OF THE
FORECAST AREA.

SHORT RANGE GUIDANCE LIKE ITS LONG RANGE COUNTERPARTS THE PAST
SEVERAL DAYS SHOW A FAIR AMOUNT OF DISCREPANCY...NAMELY ON COVERAGE
OF PRECIP TODAY AND PRECIP TYPE IN THE SOUTHERN CWA THIS
MORNING...BUT THEY LEND SUPPORT TO THE OBSERVATIONAL TRENDS. AS
THE AREA OF RAIN ASSOCIATED WITH ELEVATED ISENTROPIC ASCENT MOVES
INTO THE SOUTHERN FORECAST AREA...PROFILES SUPPORT A PERIOD OF
RAIN OR MIX INITIALLY...AND SOME LOCATIONS MIGHT HAVE AIR
TEMPERATURES RIGHT AT FREEZING. WOULD EXPECT ANY FREEZING RAIN
THREAT TO BE SHORT LIVED AS PROFILES TREND TOWARD SNOW. MESOSCALE
CONVERGENCE AND BAROCLINIC FORCING FOR INDUCED LIFT WOULD BECOME
MORE FAVORED JUST TO THE NORTHEAST OF THE CLOSED 850MB
CIRCULATION AS IT PIVOTS MORE EASTWARD. THAT IS FAVORED ACROSS
THE SOUTHERN TIER OR TWO OF COUNTIES LATER THIS MORNING INTO
EARLY AFTERNOON. PROFILES ARE MILD FOR IDEAL SNOW GROWTH...AND
MAYBE EVEN FOR SNOW AT ALL DOWN TOWARD GIBSON CITY FOR MUCH OF THE
MORNING. HAVE SNOW TOTALS AROUND ONE TO TWO INCHES FROM PERU TO
RENSSELAER AND SOUTHWARD FOR TODAY...WITH SNOW DEPARTING NEAR OR
SOON AFTER SUNDOWN.

AS FOR AREAS NORTH OF INTERSTATE 80...SHOULD SEE A GRADUAL INCREASE
IN LIGHT SNOW AREAWIDE BY MID-MORNING. DRY CORRIDOR NEAR 850MB
SEEN ON EARLY MORNING AMDAR SOUNDINGS OVER CHICAGO SHOULD LIMIT
INTENSITY OF ANY SNOW IN THE NORTHERN FORECAST AREA...AS WILL JUST
LESS FORCING. AREAS OF NORTHEAST ILLINOIS STILL LOOK TO HAVE
ONSHORE FLOW BEHIND THE COLD FRONT...BUT FORECAST INVERSION
HEIGHTS AS WELL AS ADAPTED ONES FROM THE 00Z GRB RAOB LAST
EVE...INDICATE VERY MARGINAL DEPTH OF CONVECTIVE CLOUDS. THUS NOT
EXPECTING MUCH IF ANY ENHANCEMENT TO ALREADY MINIMAL SYNOPTIC
FORCING OVER NORTHEAST IL. COULD SEE SOME DISORGANIZED LIGHT SNOW
OR FLURRIES LATE THIS AFTERNOON INTO THIS EVENING AS PROFILES OF
THE LAKE INDUCED STRATOCU COOL INTO THE ICE INITIATION LAYER...BUT
THIS SHOULD NOT BE A BIG DEAL.

AREAWIDE THE NORTHEAST WINDS WILL INCREASE TO 30 MPH AND MAYBE EVEN
A LITTLE HIGHER JUST OF THE LAKE. WITH MINIMAL SNOW NORTH NOT
EXPECTING ANY BLOWING SNOW ISSUES...AND SOUTH THE LOW SNOW-TO-
LIQUID RATIOS SHOULD SUPPRESS MUCH FOR BLOWING ISSUES...THOUGH
COULD LEAD TO MORE REDUCED VISIBILITY DURING THE TIME OF FALLING
SNOW THIS AFTERNOON.

MTF

&&

.LONG TERM...
329 AM CST

MONDAY THROUGH SATURDAY...

THE DISTURBED FLOW PATTERN WILL TURN MORE NORTHWESTERLY MONDAY AND
TUESDAY AS A MAJOR SYSTEM IS EXPECTED TO DEVELOP OFF THE NORTHEAST
COAST. GIVEN THIS POSSIBLY LEADING TO A SLOWER PATTERN...AS WELL
AS THE TREND OF TODAYS SYSTEM...IT IS QUITE CONCEIVABLE THAT THE
NEXT DISTURBANCE FOR MONDAY AFTERNOON AND NIGHT TRENDS WEST AS
WELL...WHICH THE EC HAS HAD IN ITS SOLUTION FOR THREE CONSECUTIVE
RUNS. THIS SYSTEM THOUGH IS NOT AS STRONG AS TODAYS AS IT IS MORE
OF A SHEARED AREA OF VORTICITY ALONG THE LINGERING BAROCLINIC
ZONE. FORCING FOR PRECIP LOOKS PRETTY LIGHT ONCE AGAIN MONDAY
AFTERNOON AND NIGHT BUT ENOUGH TO GO A LITTLE HIGHER ON POPS FOR
NORTHERN PARTS OF THE FORECAST AREA. RIGHT NOW GUIDANCE IS IN
DECENT AGREEMENT WITH SATURATING DEEP ENOUGH FOR PRECIP TYPE TO BE
LIGHT SNOW IF IT CAN OCCUR...BUT NEED TO KEEP AN EYE OUT FOR SOME
FREEZING DRIZZLE POTENTIAL IN THESE LIGHT ASCENT SITUATIONS.

A SLOW MODERATION LOOKS TO OCCUR TUESDAY INTO WEDNESDAY AND THIS
COULD BE VERY MINIMAL DEPENDING ON CLOUD COVER WHICH REMAINS A BIG
QUESTION MARK. HAVE LEANED MORE CLOUDY TUESDAY BUT STILL THINK
WITH A WESTERLY PUSH WEDNESDAY WOULD HAVE SUN POTENTIAL. LONG
RANGE GUIDANCE INDICATES A PACIFIC SYSTEM TO BE THE NEXT ONE TO
POSSIBLY BRING PRECIPITATION TO THE AREA WEDNESDAY NIGHT INTO
THURSDAY. CONTINUE POPS DURING THIS TIME FRAME AND AT THIS POINT
PROFILES ARE NEAR THE BORDER FOR RAIN OR SNOW...SO DID NOT GET TOO
FANCY WITH THE FORECAST PRECIPITATION TYPE. BEHIND THIS SYSTEM IT
SEEMS FAVORED FOR TEMPERATURES TO COOL SOME DURING THE LATTER
HALF OF THE WEEK...TO SLIGHTLY BELOW NORMAL VALUES. OBVIOUSLY ANY
FRESH SNOW COVER WOULD HELP LEAN THAT MORE TOWARD BELOW NORMAL.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* MVFR/PATCHY IFR CIGS DEVELOPING PRE-DAWN.

* NORTHEAST WINDS INCREASING QUICKLY TOWARD SUNRISE...AND GUST
  NEAR 30 KT AT TIMES LATE MORNING AND AFTERNOON.

* SNOW DEVELOPING EARLY-MID MORNING...WITH MVFR VSBY LIKELY AND
  IFR AND SOME ACCUMULATION PROBABLE THROUGH MIDDAY BEFORE
  TAPERING TO LIGHT SNOW SHOWERS OR FLURRIES EARLY THIS AFTERNOON.

* MVFR CIGS THIS AFTERNOON INTO THIS EVENING.

RATZER

//DISCUSSION...UPDATED 09Z...

LOW PRESSURE OVER CENTRAL IOWA WILL MOVE SOUTHEAST ACROSS
NORTHEAST MISSOURI AND INTO SOUTHERN ILLINOIS TODAY. NORTHEAST
WINDS WILL INCREASE QUICKLY TOWARD MORNING AS THE SURFACE PRESSURE
GRADIENT TIGHTENS IN RESPONSE TO THE RAPIDLY MOVING LOW PRESSURE
SYSTEM...MAKING FOR WINDY CONDITIONS WITH SUSTAINED SPEEDS 15-20
KT AND GUSTS 25-30 KT DURING THE LATE MORNING AND AFTERNOON HOURS.
WINDS WILL GRADUALLY DIMINISH TONIGHT AS WEAK HIGH PRESSURE
APPROACHES BY MONDAY MORNING.

AN EXTENSIVE AREA OF MVFR AND PATCHY IFR STRATUS OVER
MICHIGAN/WISCONSIN AND LAKE MICHIGAN IS EXPECTED TO SPREAD BACK
ACROSS THE TERMINALS EARLY THIS MORNING AS NORTHEAST WINDS
INCREASE. SNOW CURRENTLY DEPICTED BY RADAR RETURNS OVER SOUTHERN
MINNESOTA AND NORTHERN IOWA WILL SPREAD SOUTHEAST INTO THE REGION
THIS MORNING...WITH THE BULK OF THE HEAVIER SNOW EXPECTED OFF TO
THE SOUTHWEST OF THE TERMINALS. STILL...THE MID-MORNING THROUGH
NOON HOURS SHOULD SEE THE GREATEST PROBABILITY OF MINOR
ACCUMULATIONS AND MVFR/IFR VISIBILITY IN LIGHT SNOW. SNOW SHOULD
TAPER TO LIGHT SNOW SHOWERS AND FLURRIES THIS AFTERNOON.

MVFR STRATOCU LOOKS TO LINGER INTO TONIGHT...THOUGH SHOULD BECOME
THINNER WITH TIME AS DRIER AIR IS DRAWN IN FROM THE NORTHEAST.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* MEDIUM IN CIG TRENDS EARLY THIS MORNING AND IN SNOW
  TIMING/IMPACT.

* HIGH IN WIND TRENDS.

* MEDIUM IN CIGS BEYOND THIS EVENING.

RATZER

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...SLIGHT CHANCE -SN IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

IZZI

&&

.MARINE...
137 AM CST

MAIN MARINE FORECAST FOCUS CONTINUES TO BE A PERIOD OF STRONG
NORTHEAST WINDS ACROSS THE SOUTHERN 2/3 OR SO OF LAKE MICHIGAN
THROUGH THIS EVENING.

A COLD FRONT HAS PUSHED SOUTH ACROSS MUCH OF LAKE MICHIGAN SINCE
SATURDAY MORNING...WITH COLD HIGH PRESSURE SPREADING ACROSS
MANITOBA...WESTERN ONTARIO AND THE NORTHERN LAKES. EARLY THIS
MORNING AN AREA OF LOW PRESSURE WAS OVER IOWA...AND THIS LOW WILL
MOVE QUICKLY SOUTHEAST TO THE LOWER OHIO VALLEY BY THIS EVENING.
THIS LOW AND THE HIGH PRESSURE TO THE NORTH OF THE LAKES WILL
COMBINE TO RAPIDLY TIGHTEN THE SURFACE PRESSURE GRADIENT ACROSS THE
LAKE THIS MORNING...WITH NORTH-NORTHEAST WINDS INCREASING TO 25-30
KT. RECENT OBSERVATION PLATFORMS ALONG THE WEST SHORE OF THE LAKE
HAVE BEEN GUSTING 26-27 KTS BEHIND THE COLD FRONT AS FAR SOUTH AS
MILWAUKEE. THESE STRONGER WINDS WILL CONTINUE TO DEVELOP SOUTHWARD
DOWN THE REMAINDER OF THE LAKE THIS MORNING. FORECAST SOUNDINGS
INDICATE WINDS TO 30 KT WILL BE PREVALENT THROUGH THE DAY...WITH A
FEW GALE FORCE GUSTS TO 35 KT POSSIBLE. WINDS WILL REMAIN GUSTY INTO
THE EVENING HOURS ACROSS THE FAR SOUTHERN PORTION OF THE LAKE...BUT
WILL DIMINISH RAPIDLY FROM THE NORTH AS A WEAK RIDGE OF HIGH
PRESSURE SPREADS IN BEHIND THE QUICK MOVING LOW WHICH MOVE TO THE
CAROLINA COAST BY MONDAY MORNING.

THE WEAK RIDGE WILL MOVE QUICKLY SOUTHEAST OF THE LAKE MONDAY...
WITH WINDS BRIEFLY BECOMING SOUTHERLY AND INCREASING BACK AROUND 20
KT OR SO AHEAD OF ANOTHER LOW PRESSURE SYSTEM WHICH WILL DROP
SOUTHEAST ACROSS THE LAKE MONDAY NIGHT...WHILE FILLING. WEAK
GRADIENT CONDITIONS WILL THEN LINGER ACROSS THE LAKE TUESDAY AND
TUESDAY NIGHT AS THE TROUGH FILLS AND A WEAK RIDGE MOVES ACROSS THE
REGION. INDICATIONS ARE THAT ANOTHER LOW WILL DEVELOP ACROSS THE
PLAINS MID-WEEK...AND WILL APPROACH THE LAKE FROM THE WEST LATE
WEDNESDAY. THIS MAY RESULT IN A BRIEF PERIOD OF ENHANCED
EAST-SOUTHEAST WINDS LATE WEDNESDAY OR WEDNESDAY NIGHT...WITH A
PERIOD OF GUSTY NORTHERLY WINDS POSSIBLE THURSDAY AS THE LOW MOVES
EAST OF THE LAKE.

FOR THE IL/NORTHWEST INDIANA NEARSHORE AREA...SMALL CRAFT ADVISORY
IS IN EFFECT FROM 6 AM CST THIS MORNING AS WINDS/WAVES QUICKLY
INCREASE AND BUILD. ADVISORY HEADLINE WILL REMAIN IN EFFECT THROUGH
MID-MORNING MONDAY...AS WAVES SLOWLY SUBSIDE BELOW 4 FT.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 9 AM MONDAY.

     SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 250932
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
332 AM CST SUN JAN 25 2015

.SHORT TERM...
329 AM CST

THROUGH TONIGHT...

HAVE FURTHERED THE DIMINISHING SNOWFALL TREND IN THE FORECAST FOR
TODAY...MAINLY NORTH OF INTERSTATE 80. ACROSS THE ENTIRE AREA THIS
LOOKS TO BE A MAINLY LOW IMPACT...NUISANCE TYPE SNOW...WITH SOME
COMMUNITIES IN THE NORTH QUITE POSSIBLY NOT SEEING ANY
ACCUMULATION. HAVE CONTINUED A SPECIAL WEATHER STATEMENT FOR AREAS
ALONG AND SOUTH OF I-80.

SATELLITE IMAGERY THIS MORNING DEPICTS THE CLOSED UPPER CIRCULATION
ACROSS WESTERN IA WITH AN AREA OF COOLING CLOUD TOPS IN ADVANCE OF
THIS MOVING INTO NORTHWEST IL. THIS IS CORRELATING WITH MAINLY LIGHT
RAIN OR RAIN/SNOW MIX IN THE SMALL WINDOW OF DEEPER MOIST
ADVECTION AHEAD OF THE LOW. SIMPLE EXTRAPOLATION OF THE CURRENT
AREA OF PRECIP IN IOWA AND THE DEVELOPING DEFORMATION ON THE
BACKSIDE CLEARLY INDICATE THE SOUTHERN CWA IS MORE SUPPORTED FOR
PRECIPITATION THAN THE NORTH. AT THE SURFACE...TEMPERATURES ARE
AROUND OR JUST ABOVE FREEZING ACROSS MUCH OF THE FORECAST AREA. A
DEVELOPING COLD FRONT IS ADVANCING SOUTHWARD INTO NORTHERN IL WITH
DEW POINTS IN THE MID TO UPPER 20S NORTH OF THIS FEATURE...ANOTHER
HINDRANCE OF APPRECIABLE PRECIPITATION IN NORTHERN AREAS OF THE
FORECAST AREA.

SHORT RANGE GUIDANCE LIKE ITS LONG RANGE COUNTERPARTS THE PAST
SEVERAL DAYS SHOW A FAIR AMOUNT OF DISCREPANCY...NAMELY ON COVERAGE
OF PRECIP TODAY AND PRECIP TYPE IN THE SOUTHERN CWA THIS
MORNING...BUT THEY LEND SUPPORT TO THE OBSERVATIONAL TRENDS. AS
THE AREA OF RAIN ASSOCIATED WITH ELEVATED ISENTROPIC ASCENT MOVES
INTO THE SOUTHERN FORECAST AREA...PROFILES SUPPORT A PERIOD OF
RAIN OR MIX INITIALLY...AND SOME LOCATIONS MIGHT HAVE AIR
TEMPERATURES RIGHT AT FREEZING. WOULD EXPECT ANY FREEZING RAIN
THREAT TO BE SHORT LIVED AS PROFILES TREND TOWARD SNOW. MESOSCALE
CONVERGENCE AND BAROCLINIC FORCING FOR INDUCED LIFT WOULD BECOME
MORE FAVORED JUST TO THE NORTHEAST OF THE CLOSED 850MB
CIRCULATION AS IT PIVOTS MORE EASTWARD. THAT IS FAVORED ACROSS
THE SOUTHERN TIER OR TWO OF COUNTIES LATER THIS MORNING INTO
EARLY AFTERNOON. PROFILES ARE MILD FOR IDEAL SNOW GROWTH...AND
MAYBE EVEN FOR SNOW AT ALL DOWN TOWARD GIBSON CITY FOR MUCH OF THE
MORNING. HAVE SNOW TOTALS AROUND ONE TO TWO INCHES FROM PERU TO
RENSSELAER AND SOUTHWARD FOR TODAY...WITH SNOW DEPARTING NEAR OR
SOON AFTER SUNDOWN.

AS FOR AREAS NORTH OF INTERSTATE 80...SHOULD SEE A GRADUAL INCREASE
IN LIGHT SNOW AREAWIDE BY MID-MORNING. DRY CORRIDOR NEAR 850MB
SEEN ON EARLY MORNING AMDAR SOUNDINGS OVER CHICAGO SHOULD LIMIT
INTENSITY OF ANY SNOW IN THE NORTHERN FORECAST AREA...AS WILL JUST
LESS FORCING. AREAS OF NORTHEAST ILLINOIS STILL LOOK TO HAVE
ONSHORE FLOW BEHIND THE COLD FRONT...BUT FORECAST INVERSION
HEIGHTS AS WELL AS ADAPTED ONES FROM THE 00Z GRB RAOB LAST
EVE...INDICATE VERY MARGINAL DEPTH OF CONVECTIVE CLOUDS. THUS NOT
EXPECTING MUCH IF ANY ENHANCEMENT TO ALREADY MINIMAL SYNOPTIC
FORCING OVER NORTHEAST IL. COULD SEE SOME DISORGANIZED LIGHT SNOW
OR FLURRIES LATE THIS AFTERNOON INTO THIS EVENING AS PROFILES OF
THE LAKE INDUCED STRATOCU COOL INTO THE ICE INITIATION LAYER...BUT
THIS SHOULD NOT BE A BIG DEAL.

AREAWIDE THE NORTHEAST WINDS WILL INCREASE TO 30 MPH AND MAYBE EVEN
A LITTLE HIGHER JUST OF THE LAKE. WITH MINIMAL SNOW NORTH NOT
EXPECTING ANY BLOWING SNOW ISSUES...AND SOUTH THE LOW SNOW-TO-
LIQUID RATIOS SHOULD SUPPRESS MUCH FOR BLOWING ISSUES...THOUGH
COULD LEAD TO MORE REDUCED VISIBILITY DURING THE TIME OF FALLING
SNOW THIS AFTERNOON.

MTF

&&

.LONG TERM...
329 AM CST

MONDAY THROUGH SATURDAY...

THE DISTURBED FLOW PATTERN WILL TURN MORE NORTHWESTERLY MONDAY AND
TUESDAY AS A MAJOR SYSTEM IS EXPECTED TO DEVELOP OFF THE NORTHEAST
COAST. GIVEN THIS POSSIBLY LEADING TO A SLOWER PATTERN...AS WELL
AS THE TREND OF TODAYS SYSTEM...IT IS QUITE CONCEIVABLE THAT THE
NEXT DISTURBANCE FOR MONDAY AFTERNOON AND NIGHT TRENDS WEST AS
WELL...WHICH THE EC HAS HAD IN ITS SOLUTION FOR THREE CONSECUTIVE
RUNS. THIS SYSTEM THOUGH IS NOT AS STRONG AS TODAYS AS IT IS MORE
OF A SHEARED AREA OF VORTICITY ALONG THE LINGERING BAROCLINIC
ZONE. FORCING FOR PRECIP LOOKS PRETTY LIGHT ONCE AGAIN MONDAY
AFTERNOON AND NIGHT BUT ENOUGH TO GO A LITTLE HIGHER ON POPS FOR
NORTHERN PARTS OF THE FORECAST AREA. RIGHT NOW GUIDANCE IS IN
DECENT AGREEMENT WITH SATURATING DEEP ENOUGH FOR PRECIP TYPE TO BE
LIGHT SNOW IF IT CAN OCCUR...BUT NEED TO KEEP AN EYE OUT FOR SOME
FREEZING DRIZZLE POTENTIAL IN THESE LIGHT ASCENT SITUATIONS.

A SLOW MODERATION LOOKS TO OCCUR TUESDAY INTO WEDNESDAY AND THIS
COULD BE VERY MINIMAL DEPENDING ON CLOUD COVER WHICH REMAINS A BIG
QUESTION MARK. HAVE LEANED MORE CLOUDY TUESDAY BUT STILL THINK
WITH A WESTERLY PUSH WEDNESDAY WOULD HAVE SUN POTENTIAL. LONG
RANGE GUIDANCE INDICATES A PACIFIC SYSTEM TO BE THE NEXT ONE TO
POSSIBLY BRING PRECIPITATION TO THE AREA WEDNESDAY NIGHT INTO
THURSDAY. CONTINUE POPS DURING THIS TIME FRAME AND AT THIS POINT
PROFILES ARE NEAR THE BORDER FOR RAIN OR SNOW...SO DID NOT GET TOO
FANCY WITH THE FORECAST PRECIPITATION TYPE. BEHIND THIS SYSTEM IT
SEEMS FAVORED FOR TEMPERATURES TO COOL SOME DURING THE LATTER
HALF OF THE WEEK...TO SLIGHTLY BELOW NORMAL VALUES. OBVIOUSLY ANY
FRESH SNOW COVER WOULD HELP LEAN THAT MORE TOWARD BELOW NORMAL.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* MVFR/PATCHY IFR CIGS DEVELOPING PRE-DAWN.

* NORTHEAST WINDS INCREASING QUICKLY TOWARD SUNRISE...AND GUST
  NEAR 30 KT AT TIMES LATE MORNING AND AFTERNOON.

* SNOW DEVELOPING EARLY-MID MORNING...WITH MVFR VSBY LIKELY AND
  IFR AND SOME ACCUMULATION PROBABLE THROUGH MIDDAY BEFORE
  TAPERING TO LIGHT SNOW SHOWERS OR FLURRIES EARLY THIS AFTERNOON.

* MVFR CIGS THIS AFTERNOON INTO THIS EVENING.

RATZER

//DISCUSSION...UPDATED 09Z...

LOW PRESSURE OVER CENTRAL IOWA WILL MOVE SOUTHEAST ACROSS
NORTHEAST MISSOURI AND INTO SOUTHERN ILLINOIS TODAY. NORTHEAST
WINDS WILL INCREASE QUICKLY TOWARD MORNING AS THE SURFACE PRESSURE
GRADIENT TIGHTENS IN RESPONSE TO THE RAPIDLY MOVING LOW PRESSURE
SYSTEM...MAKING FOR WINDY CONDITIONS WITH SUSTAINED SPEEDS 15-20
KT AND GUSTS 25-30 KT DURING THE LATE MORNING AND AFTERNOON HOURS.
WINDS WILL GRADUALLY DIMINISH TONIGHT AS WEAK HIGH PRESSURE
APPROACHES BY MONDAY MORNING.

AN EXTENSIVE AREA OF MVFR AND PATCHY IFR STRATUS OVER
MICHIGAN/WISCONSIN AND LAKE MICHIGAN IS EXPECTED TO SPREAD BACK
ACROSS THE TERMINALS EARLY THIS MORNING AS NORTHEAST WINDS
INCREASE. SNOW CURRENTLY DEPICTED BY RADAR RETURNS OVER SOUTHERN
MINNESOTA AND NORTHERN IOWA WILL SPREAD SOUTHEAST INTO THE REGION
THIS MORNING...WITH THE BULK OF THE HEAVIER SNOW EXPECTED OFF TO
THE SOUTHWEST OF THE TERMINALS. STILL...THE MID-MORNING THROUGH
NOON HOURS SHOULD SEE THE GREATEST PROBABILITY OF MINOR
ACCUMULATIONS AND MVFR/IFR VISIBILITY IN LIGHT SNOW. SNOW SHOULD
TAPER TO LIGHT SNOW SHOWERS AND FLURRIES THIS AFTERNOON.

MVFR STRATOCU LOOKS TO LINGER INTO TONIGHT...THOUGH SHOULD BECOME
THINNER WITH TIME AS DRIER AIR IS DRAWN IN FROM THE NORTHEAST.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* MEDIUM IN CIG TRENDS EARLY THIS MORNING AND IN SNOW
  TIMING/IMPACT.

* HIGH IN WIND TRENDS.

* MEDIUM IN CIGS BEYOND THIS EVENING.

RATZER

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...SLIGHT CHANCE -SN IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

IZZI

&&

.MARINE...
137 AM CST

MAIN MARINE FORECAST FOCUS CONTINUES TO BE A PERIOD OF STRONG
NORTHEAST WINDS ACROSS THE SOUTHERN 2/3 OR SO OF LAKE MICHIGAN
THROUGH THIS EVENING.

A COLD FRONT HAS PUSHED SOUTH ACROSS MUCH OF LAKE MICHIGAN SINCE
SATURDAY MORNING...WITH COLD HIGH PRESSURE SPREADING ACROSS
MANITOBA...WESTERN ONTARIO AND THE NORTHERN LAKES. EARLY THIS
MORNING AN AREA OF LOW PRESSURE WAS OVER IOWA...AND THIS LOW WILL
MOVE QUICKLY SOUTHEAST TO THE LOWER OHIO VALLEY BY THIS EVENING.
THIS LOW AND THE HIGH PRESSURE TO THE NORTH OF THE LAKES WILL
COMBINE TO RAPIDLY TIGHTEN THE SURFACE PRESSURE GRADIENT ACROSS THE
LAKE THIS MORNING...WITH NORTH-NORTHEAST WINDS INCREASING TO 25-30
KT. RECENT OBSERVATION PLATFORMS ALONG THE WEST SHORE OF THE LAKE
HAVE BEEN GUSTING 26-27 KTS BEHIND THE COLD FRONT AS FAR SOUTH AS
MILWAUKEE. THESE STRONGER WINDS WILL CONTINUE TO DEVELOP SOUTHWARD
DOWN THE REMAINDER OF THE LAKE THIS MORNING. FORECAST SOUNDINGS
INDICATE WINDS TO 30 KT WILL BE PREVALENT THROUGH THE DAY...WITH A
FEW GALE FORCE GUSTS TO 35 KT POSSIBLE. WINDS WILL REMAIN GUSTY INTO
THE EVENING HOURS ACROSS THE FAR SOUTHERN PORTION OF THE LAKE...BUT
WILL DIMINISH RAPIDLY FROM THE NORTH AS A WEAK RIDGE OF HIGH
PRESSURE SPREADS IN BEHIND THE QUICK MOVING LOW WHICH MOVE TO THE
CAROLINA COAST BY MONDAY MORNING.

THE WEAK RIDGE WILL MOVE QUICKLY SOUTHEAST OF THE LAKE MONDAY...
WITH WINDS BRIEFLY BECOMING SOUTHERLY AND INCREASING BACK AROUND 20
KT OR SO AHEAD OF ANOTHER LOW PRESSURE SYSTEM WHICH WILL DROP
SOUTHEAST ACROSS THE LAKE MONDAY NIGHT...WHILE FILLING. WEAK
GRADIENT CONDITIONS WILL THEN LINGER ACROSS THE LAKE TUESDAY AND
TUESDAY NIGHT AS THE TROUGH FILLS AND A WEAK RIDGE MOVES ACROSS THE
REGION. INDICATIONS ARE THAT ANOTHER LOW WILL DEVELOP ACROSS THE
PLAINS MID-WEEK...AND WILL APPROACH THE LAKE FROM THE WEST LATE
WEDNESDAY. THIS MAY RESULT IN A BRIEF PERIOD OF ENHANCED
EAST-SOUTHEAST WINDS LATE WEDNESDAY OR WEDNESDAY NIGHT...WITH A
PERIOD OF GUSTY NORTHERLY WINDS POSSIBLE THURSDAY AS THE LOW MOVES
EAST OF THE LAKE.

FOR THE IL/NORTHWEST INDIANA NEARSHORE AREA...SMALL CRAFT ADVISORY
IS IN EFFECT FROM 6 AM CST THIS MORNING AS WINDS/WAVES QUICKLY
INCREASE AND BUILD. ADVISORY HEADLINE WILL REMAIN IN EFFECT THROUGH
MID-MORNING MONDAY...AS WAVES SLOWLY SUBSIDE BELOW 4 FT.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 9 AM MONDAY.

     SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 250739
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
139 AM CST SUN JAN 25 2015

.UPDATE...
900 PM CST

EVENING UPDATE...

HAVE UPDATED GRIDS TO REFLECT MUCH LOWER SNOWFALL AMOUNTS ON SUNDAY
TO THE NORTH OF INTERSTATE 80 AND ALSO SLOWED ARRIVAL OF
PRECIPITATION MAINLY TO EARLY TO MID SUNDAY MORNING. RADAR...SURFACE
ANALYSIS AND SATELLITE TRENDS SUPPORT THE NEW 00Z GUIDANCE AND
LATEST HIGHER RESOLUTION GUIDANCE ROLLING IN DIGGING THE 500 MB WAVE
FARTHER SOUTHWEST AND ASSOCIATED SURFACE LOW FARTHER SOUTHWEST AND
THEN SOUTH OF THE CWA.  NOW LOOKING AT GENERALLY AROUND A FEW TENTHS
TO UP TO AN INCH NORTH OF INTERSTATE 88...ONE TO TWO INCHES BETWEEN
I-88 AND I-80 AND ONE TO THREE INCHES SOUTH OF INTERSTATE 80. IF THE
FARTHER SOUTH TREND BECOMES MORE AGGRESSIVE AS THE SYSTEM APPROACHES
SUNDAY...THEN EVEN THESE AMOUNTS COULD END UP BEING TOO HIGH.
NAM/WRF AND OTHER HIGHER-RES GUIDANCE CONTINUES TO HINT AT LAKE
ENHANCEMENT DURING THE DAY SUNDAY INTO THE AFTERNOON INTO PARTS OF
NORTHEAST IL AND NW IN...BUT UNLESS FRICTIONAL CONVERGENCE CAN
ENHANCE RATES A BIT...THE THERMODYNAMICS AND INVERSION HEIGHTS ARE
VERY MARGINAL TO ACTUALLY ADD MUCH TO SNOW TOTALS.

REGARDING THE MIXED PRECIPITATION IN THE SOUTHERN CWA...THE
SOUTHWARD TREND AND DELAYED TIMING OF THE SYSTEM SHOULD ALLOW FOR
COLDER AIR TO BLEED SOUTHWARD AND SUPPRESS THE MIXING ZONE SOUTHWARD
FROM THE PREVIOUS FORECAST. ANY WINTRY MIX/RAIN SNOW MIX IN THE FAR
SOUTHERN CWA WILL LIKELY TRANSITION TO SNOW BY MID DAY/EARLY
AFTERNOON.

UPDATED ZONES WILL BE SENT SHORTLY.

RC/KREIN

&&

.SHORT TERM...
250 PM CST

THROUGH SUNDAY...

MAIN FORECAST CONCERN WILL BE PASSAGE OF A CLIPPER SYSTEM ACROSS THE
MIDWEST BRINGING ACCUMULATING SNOWFALL AND FOR SOME AREAS A WINTRY
MIX OF PRECIPITATION. CLOUD COVER WILL CONTINUE TO INCREASE THE
REMAINDER OF THE TODAY AS THE LOW DIVES ACROSS THE DAKOTAS INTO
MINNESOTA. MODELS ARE IN DECENT AGREEMENT TRACKING THE SURFACE LOW
ACROSS FAR NE MO LATE TONIGHT INTO DOWNSTATE IL BY SUNDAY AFTERNOON.
1000MB-700MB LAYER MAX WETBULBS ARE UP TO 2C SOUTH OF THE I-80
CORRIDOR THROUGH LATE MORNING/EARLY AFTERNOON SUNDAY...THEN START TO
FALL QUICKLY FROM THE NORTH THROUGH THE AFTERNOON HOURS. WITH THAT
IN MIND...THINK THAT PRECIP WILL BEGIN AS PRIMARILY SNOW NORTH OF
THE I-80 CORRIDOR WITH RAIN/SLEET TO THE SOUTH...EVENTUALLY CHANGING
OVER TO ALL SNOW. MODELS IN GENERAL HAVE THE AXIS OF HIGHEST QPF
SOUTH OF I-80...BUT WITH WARMER TEMPERATURES...IT APPEARS THE
HIGHEST SNOWFALL MAY OCCUR A LITTLE FARTHER NORTH. DID BUMP UP SNOW
TOTALS ACROSS PORTIONS OF THE CHICAGO METRO WHERE MODELS CONTINUE TO
ADVERTISE AN INCREASE IN THE LOW LEVEL LAPSE RATES AS WINDS TURN NE
OFF LAKE MICHIGAN WITH LAKE ENHANCEMENT APPEARING AT LEAST POSSIBLE.
NAM AND REGIONAL GEM GUIDANCE BOTH SHOW A SLIGHT MAX IN THE QPF
VALUES OVER THE AREA AND HAVE BEEN CONSISTENTLY ADVERTISING A BUMP IN
THE LOW LEVEL OMEGA STARTING LATE MORNING INTO THE AFTERNOON.
FORECAST SNOW TOTALS FOR THIS EVENT WILL BE 1-3 INCHES WEST OF A
WAUKEGAN TO STREATOR LINE...AND 2-4 INCHES EAST. WILL HAVE TO
MONITOR THE MESOSCALE BANDING THREAT FOR SOME LOCALLY HIGHER
AMOUNTS. NAM GUIDANCE IN PARTICULAR WAS HINTING AT AN AREA OF LOW
LEVEL FGEN DEVELOPING FOR EAST CENTRAL IL AND NORTHWEST
INDIANA...BUT LAPSE RATES UPSTAIRS ARENT OVERLY IMPRESSIVE IN THE
LATEST MODELS RUNS. ALSO SURFACE LOW SLOWLY FILLING AS IT MOVES
TOWARDS THE OHIO VALLEY WILL ALSO BE A LIMITING FACTOR. WILL ISSUE
AN UPDATED SPS THIS AFTERNOON FOR THE SNOWFALL. AS MENTIONED...STILL
CANNOT RULE OUT SOME LOCALLY HIGHER AMOUNTS THAT MIGHT REQUIRE AN
ADVISORY HOWEVER DONT HAVE MUCH CONFIDENCE WHERE OR EVEN IF THIS
WOULD OCCUR.

WINDS WILL START TO RAMP UP FROM EARLY MORNING ON OUT OF THE
NORTHEAST AS A TIGHT GRADIENT SWEEPS ACROSS THE REGION ON THE BACK
SIDE OF THE LOW. NORTHEAST WINDS ARE EXPECTED TO GUST 30-35 MPH AT
TIMES ACROSS THE AREA. THESE MODERATELY STRONG NORTHEAST WINDS OVER
LAKE MICHIGAN WILL DRIVE 8-11 FOOT WAVES INTO THE NEARSHORE WATERS
AND SOME OF THESE WAVES MAY RESULT IN SOME MINOR LAKE SHORE FLOODING
TO EXPOSED AREAS. IN ADDITION...BLOWING SNOW MAY BECOME A PROBLEM
ESPECIALLY IN OPEN AREAS. WETTER THAN AVERAGE SNOW...PARTICULARLY
SOUTH OF I-80 MAY HELP LIMIT THE BLOWING SNOW SOME.

DEUBELBEISS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE A CHANCE OF LIGHT SNOW MONDAY
AFTERNOON INTO MONDAY NIGHT AND THEN THE POTENTIAL FOR A WINTRY
MIX WEDNESDAY NIGHT.

LIGHT SNOW WILL BE ENDING ACROSS THE SOUTHEAST CWA SUNDAY EVENING
AS NORTHEAST WINDS STEADILY DIMINISH SUNDAY EVENING. LAKE EFFECT
CLOUDS AND PERHAPS A FEW FLURRIES ARE POSSIBLE SUNDAY EVENING. LOWS
BY MONDAY MORNING WILL DIP INTO THE TEENS MOST LOCATIONS BUT AS A
WEAK RIDGE PASSES ACROSS THE AREA AND WINDS BECOME LIGHT OR CALM...
LOWS COULD BE SEVERAL DEGREES COLDER DEPENDING ON CLOUD COVER.

ANOTHER WEAK CLIPPER SYSTEM MOVES SOUTHEAST ACROSS THE WESTERN
LAKES MONDAY AFTERNOON INTO MONDAY NIGHT AS IT SLOWLY BEGINS TO
WEAKEN. MODELS VARY SOME ON TIMING AND PRECIP ARRIVAL. A CONSENSUS
WOULD HAVE THE ARRIVAL DURING MONDAY AFTERNOON. INITIALLY THE
SATURATION IS DEEP ENOUGH THAT PRECIP SHOULD BEGIN AS LIGHT SNOW.
BUT INTO THE EVENING...MID LEVELS BEGIN TO DRY OUT SOME AND PRECIP
COULD TRANSITION MORE TO A LIGHT SNOW MIXED WITH OR JUST FREEZING
DRIZZLE. FAIRLY LOW CONFIDENCE AT THIS POINT...SO MAINTAINED JUST
LIGHT SNOW FOR THE ENTIRE DURATION FOR NOW.

PROGRESSIVE PATTERN BRINGS ANOTHER RIDGE OF HIGH PRESSURE ACROSS
THE REGION TUESDAY NIGHT INTO WEDNESDAY AND THEN ANOTHER STORM
SYSTEM WEDNESDAY NIGHT INTO THURSDAY MORNING. MODELS CURRENTLY IN
DECENT AGREEMENT WITH THE TRACK OF THIS LOW GENERALLY RIGHT ACROSS
THE CWA EARLY THURSDAY MORNING. WITH THIS TRACK...TEMPS LIKELY TO
REMAIN FAIRLY STEADY IN THE LOWER/MID 30S WEDNESDAY NIGHT AND
THERMAL PROFILES WOULD SUGGEST PRECIP WOULD BE MAINLY RAIN OR
PERHAPS FREEZING RAIN...IF SURFACE TEMPS REMAINED BELOW FREEZING.
AND ALSO COULD BE SOME SNOW IF THE LOW WERE TO SPEED UP AND/OR
TRACK FURTHER SOUTH. THUS DID NOT GET TOO SPECIFIC WITH PRECIP
TYPE WEDNESDAY NIGHT INTO THURSDAY BUT A WINTRY MIX IS POSSIBLE.
CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* MVFR/PATCHY IFR CIGS DEVELOPING PRE-DAWN.

* NORTHEAST WINDS INCREASING QUICKLY TOWARD SUNRISE...AND GUST
  NEAR 30 KT AT TIMES LATE MORNING AND AFTERNOON.

* SNOW DEVELOPING EARLY-MID MORNING...WITH MVFR VSBY LIKELY AND
  IFR AND SOME ACCUMULATION PROBABLE THROUGH MIDDAY BEFORE
  TAPERING TO LIGHT SNOW SHOWERS OR FLURRIES EARLY THIS AFTERNOON.

* MVFR CIGS THIS AFTERNOON INTO THIS EVENING.

RATZER

//DISCUSSION...UPDATED 06Z...

LOW PRESSURE OVER CENTRAL IOWA WILL MOVE SOUTHEAST ACROSS
NORTHEAST MISSOURI AND INTO SOUTHERN ILLINOIS TODAY. NORTHEAST
WINDS WILL INCREASE QUICKLY TOWARD MORNING AS THE SURFACE PRESSURE
GRADIENT TIGHTENS IN RESPONSE TO THE RAPIDLY MOVING LOW PRESSURE
SYSTEM...MAKING FOR WINDY CONDITIONS WITH SUSTAINED SPEEDS 15-20
KT AND GUSTS 25-30 KT DURING THE LATE MORNING AND AFTERNOON HOURS.
WINDS WILL GRADUALLY DIMINISH TONIGHT AS WEAK HIGH PRESSURE
APPROACHES BY MONDAY MORNING.

AN EXTENSIVE AREA OF MVFR AND PATCHY IFR STRATUS OVER
MICHIGAN/WISCONSIN AND LAKE MICHIGAN IS EXPECTED TO SPREAD BACK
ACROSS THE TERMINALS EARLY THIS MORNING AS NORTHEAST WINDS
INCREASE. SNOW CURRENTLY DEPICTED BY RADAR RETURNS OVER SOUTHERN
MINNESOTA AND NORTHERN IOWA WILL SPREAD SOUTHEAST INTO THE REGION
THIS MORNING...WITH THE BULK OF THE HEAVIER SNOW EXPECTED OFF TO
THE SOUTHWEST OF THE TERMINALS. STILL...THE MID-MORNING THROUGH
NOON HOURS SHOULD SEE THE GREATEST PROBABILITY OF MINOR
ACCUMULATIONS AND MVFR/IFR VISIBILITY IN LIGHT SNOW. SNOW SHOULD
TAPER TO LIGHT SNOW SHOWERS AND FLURRIES THIS AFTERNOON.

MVFR STRATOCU LOOKS TO LINGER INTO TONIGHT...THOUGH SHOULD BECOME
THINNER WITH TIME AS DRIER AIR IS DRAWN IN FROM THE NORTHEAST.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM IN CIG TRENDS EARLY THIS MORNING AND IN SNOW
  TIMING/IMPACT.

* HIGH IN WIND TRENDS.

* MEDIUM IN CIGS BEYOND THIS EVENING.

RATZER

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...SLIGHT CHANCE -SN IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

IZZI

&&

.MARINE...
137 AM CST

MAIN MARINE FORECAST FOCUS CONTINUES TO BE A PERIOD OF STRONG
NORTHEAST WINDS ACROSS THE SOUTHERN 2/3 OR SO OF LAKE MICHIGAN
THROUGH THIS EVENING.

A COLD FRONT HAS PUSHED SOUTH ACROSS MUCH OF LAKE MICHIGAN SINCE
SATURDAY MORNING...WITH COLD HIGH PRESSURE SPREADING ACROSS
MANITOBA...WESTERN ONTARIO AND THE NORTHERN LAKES. EARLY THIS
MORNING AN AREA OF LOW PRESSURE WAS OVER IOWA...AND THIS LOW WILL
MOVE QUICKLY SOUTHEAST TO THE LOWER OHIO VALLEY BY THIS EVENING.
THIS LOW AND THE HIGH PRESSURE TO THE NORTH OF THE LAKES WILL
COMBINE TO RAPIDLY TIGHTEN THE SURFACE PRESSURE GRADIENT ACROSS THE
LAKE THIS MORNING...WITH NORTH-NORTHEAST WINDS INCREASING TO 25-30
KT. RECENT OBSERVATION PLATFORMS ALONG THE WEST SHORE OF THE LAKE
HAVE BEEN GUSTING 26-27 KTS BEHIND THE COLD FRONT AS FAR SOUTH AS
MILWAUKEE. THESE STRONGER WINDS WILL CONTINUE TO DEVELOP SOUTHWARD
DOWN THE REMAINDER OF THE LAKE THIS MORNING. FORECAST SOUNDINGS
INDICATE WINDS TO 30 KT WILL BE PREVALENT THROUGH THE DAY...WITH A
FEW GALE FORCE GUSTS TO 35 KT POSSIBLE. WINDS WILL REMAIN GUSTY INTO
THE EVENING HOURS ACROSS THE FAR SOUTHERN PORTION OF THE LAKE...BUT
WILL DIMINISH RAPIDLY FROM THE NORTH AS A WEAK RIDGE OF HIGH
PRESSURE SPREADS IN BEHIND THE QUICK MOVING LOW WHICH MOVE TO THE
CAROLINA COAST BY MONDAY MORNING.

THE WEAK RIDGE WILL MOVE QUICKLY SOUTHEAST OF THE LAKE MONDAY...
WITH WINDS BRIEFLY BECOMING SOUTHERLY AND INCREASING BACK AROUND 20
KT OR SO AHEAD OF ANOTHER LOW PRESSURE SYSTEM WHICH WILL DROP
SOUTHEAST ACROSS THE LAKE MONDAY NIGHT...WHILE FILLING. WEAK
GRADIENT CONDITIONS WILL THEN LINGER ACROSS THE LAKE TUESDAY AND
TUESDAY NIGHT AS THE TROUGH FILLS AND A WEAK RIDGE MOVES ACROSS THE
REGION. INDICATIONS ARE THAT ANOTHER LOW WILL DEVELOP ACROSS THE
PLAINS MID-WEEK...AND WILL APPROACH THE LAKE FROM THE WEST LATE
WEDNESDAY. THIS MAY RESULT IN A BRIEF PERIOD OF ENHANCED
EAST-SOUTHEAST WINDS LATE WEDNESDAY OR WEDNESDAY NIGHT...WITH A
PERIOD OF GUSTY NORTHERLY WINDS POSSIBLE THURSDAY AS THE LOW MOVES
EAST OF THE LAKE.

FOR THE IL/NORTHWEST INDIANA NEARSHORE AREA...SMALL CRAFT ADVISORY
IS IN EFFECT FROM 6 AM CST THIS MORNING AS WINDS/WAVES QUICKLY
INCREASE AND BUILD. ADVISORY HEADLINE WILL REMAIN IN EFFECT THROUGH
MID-MORNING MONDAY...AS WAVES SLOWLY SUBSIDE BELOW 4 FT.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO








000
FXUS63 KLOT 250739
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
139 AM CST SUN JAN 25 2015

.UPDATE...
900 PM CST

EVENING UPDATE...

HAVE UPDATED GRIDS TO REFLECT MUCH LOWER SNOWFALL AMOUNTS ON SUNDAY
TO THE NORTH OF INTERSTATE 80 AND ALSO SLOWED ARRIVAL OF
PRECIPITATION MAINLY TO EARLY TO MID SUNDAY MORNING. RADAR...SURFACE
ANALYSIS AND SATELLITE TRENDS SUPPORT THE NEW 00Z GUIDANCE AND
LATEST HIGHER RESOLUTION GUIDANCE ROLLING IN DIGGING THE 500 MB WAVE
FARTHER SOUTHWEST AND ASSOCIATED SURFACE LOW FARTHER SOUTHWEST AND
THEN SOUTH OF THE CWA.  NOW LOOKING AT GENERALLY AROUND A FEW TENTHS
TO UP TO AN INCH NORTH OF INTERSTATE 88...ONE TO TWO INCHES BETWEEN
I-88 AND I-80 AND ONE TO THREE INCHES SOUTH OF INTERSTATE 80. IF THE
FARTHER SOUTH TREND BECOMES MORE AGGRESSIVE AS THE SYSTEM APPROACHES
SUNDAY...THEN EVEN THESE AMOUNTS COULD END UP BEING TOO HIGH.
NAM/WRF AND OTHER HIGHER-RES GUIDANCE CONTINUES TO HINT AT LAKE
ENHANCEMENT DURING THE DAY SUNDAY INTO THE AFTERNOON INTO PARTS OF
NORTHEAST IL AND NW IN...BUT UNLESS FRICTIONAL CONVERGENCE CAN
ENHANCE RATES A BIT...THE THERMODYNAMICS AND INVERSION HEIGHTS ARE
VERY MARGINAL TO ACTUALLY ADD MUCH TO SNOW TOTALS.

REGARDING THE MIXED PRECIPITATION IN THE SOUTHERN CWA...THE
SOUTHWARD TREND AND DELAYED TIMING OF THE SYSTEM SHOULD ALLOW FOR
COLDER AIR TO BLEED SOUTHWARD AND SUPPRESS THE MIXING ZONE SOUTHWARD
FROM THE PREVIOUS FORECAST. ANY WINTRY MIX/RAIN SNOW MIX IN THE FAR
SOUTHERN CWA WILL LIKELY TRANSITION TO SNOW BY MID DAY/EARLY
AFTERNOON.

UPDATED ZONES WILL BE SENT SHORTLY.

RC/KREIN

&&

.SHORT TERM...
250 PM CST

THROUGH SUNDAY...

MAIN FORECAST CONCERN WILL BE PASSAGE OF A CLIPPER SYSTEM ACROSS THE
MIDWEST BRINGING ACCUMULATING SNOWFALL AND FOR SOME AREAS A WINTRY
MIX OF PRECIPITATION. CLOUD COVER WILL CONTINUE TO INCREASE THE
REMAINDER OF THE TODAY AS THE LOW DIVES ACROSS THE DAKOTAS INTO
MINNESOTA. MODELS ARE IN DECENT AGREEMENT TRACKING THE SURFACE LOW
ACROSS FAR NE MO LATE TONIGHT INTO DOWNSTATE IL BY SUNDAY AFTERNOON.
1000MB-700MB LAYER MAX WETBULBS ARE UP TO 2C SOUTH OF THE I-80
CORRIDOR THROUGH LATE MORNING/EARLY AFTERNOON SUNDAY...THEN START TO
FALL QUICKLY FROM THE NORTH THROUGH THE AFTERNOON HOURS. WITH THAT
IN MIND...THINK THAT PRECIP WILL BEGIN AS PRIMARILY SNOW NORTH OF
THE I-80 CORRIDOR WITH RAIN/SLEET TO THE SOUTH...EVENTUALLY CHANGING
OVER TO ALL SNOW. MODELS IN GENERAL HAVE THE AXIS OF HIGHEST QPF
SOUTH OF I-80...BUT WITH WARMER TEMPERATURES...IT APPEARS THE
HIGHEST SNOWFALL MAY OCCUR A LITTLE FARTHER NORTH. DID BUMP UP SNOW
TOTALS ACROSS PORTIONS OF THE CHICAGO METRO WHERE MODELS CONTINUE TO
ADVERTISE AN INCREASE IN THE LOW LEVEL LAPSE RATES AS WINDS TURN NE
OFF LAKE MICHIGAN WITH LAKE ENHANCEMENT APPEARING AT LEAST POSSIBLE.
NAM AND REGIONAL GEM GUIDANCE BOTH SHOW A SLIGHT MAX IN THE QPF
VALUES OVER THE AREA AND HAVE BEEN CONSISTENTLY ADVERTISING A BUMP IN
THE LOW LEVEL OMEGA STARTING LATE MORNING INTO THE AFTERNOON.
FORECAST SNOW TOTALS FOR THIS EVENT WILL BE 1-3 INCHES WEST OF A
WAUKEGAN TO STREATOR LINE...AND 2-4 INCHES EAST. WILL HAVE TO
MONITOR THE MESOSCALE BANDING THREAT FOR SOME LOCALLY HIGHER
AMOUNTS. NAM GUIDANCE IN PARTICULAR WAS HINTING AT AN AREA OF LOW
LEVEL FGEN DEVELOPING FOR EAST CENTRAL IL AND NORTHWEST
INDIANA...BUT LAPSE RATES UPSTAIRS ARENT OVERLY IMPRESSIVE IN THE
LATEST MODELS RUNS. ALSO SURFACE LOW SLOWLY FILLING AS IT MOVES
TOWARDS THE OHIO VALLEY WILL ALSO BE A LIMITING FACTOR. WILL ISSUE
AN UPDATED SPS THIS AFTERNOON FOR THE SNOWFALL. AS MENTIONED...STILL
CANNOT RULE OUT SOME LOCALLY HIGHER AMOUNTS THAT MIGHT REQUIRE AN
ADVISORY HOWEVER DONT HAVE MUCH CONFIDENCE WHERE OR EVEN IF THIS
WOULD OCCUR.

WINDS WILL START TO RAMP UP FROM EARLY MORNING ON OUT OF THE
NORTHEAST AS A TIGHT GRADIENT SWEEPS ACROSS THE REGION ON THE BACK
SIDE OF THE LOW. NORTHEAST WINDS ARE EXPECTED TO GUST 30-35 MPH AT
TIMES ACROSS THE AREA. THESE MODERATELY STRONG NORTHEAST WINDS OVER
LAKE MICHIGAN WILL DRIVE 8-11 FOOT WAVES INTO THE NEARSHORE WATERS
AND SOME OF THESE WAVES MAY RESULT IN SOME MINOR LAKE SHORE FLOODING
TO EXPOSED AREAS. IN ADDITION...BLOWING SNOW MAY BECOME A PROBLEM
ESPECIALLY IN OPEN AREAS. WETTER THAN AVERAGE SNOW...PARTICULARLY
SOUTH OF I-80 MAY HELP LIMIT THE BLOWING SNOW SOME.

DEUBELBEISS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE A CHANCE OF LIGHT SNOW MONDAY
AFTERNOON INTO MONDAY NIGHT AND THEN THE POTENTIAL FOR A WINTRY
MIX WEDNESDAY NIGHT.

LIGHT SNOW WILL BE ENDING ACROSS THE SOUTHEAST CWA SUNDAY EVENING
AS NORTHEAST WINDS STEADILY DIMINISH SUNDAY EVENING. LAKE EFFECT
CLOUDS AND PERHAPS A FEW FLURRIES ARE POSSIBLE SUNDAY EVENING. LOWS
BY MONDAY MORNING WILL DIP INTO THE TEENS MOST LOCATIONS BUT AS A
WEAK RIDGE PASSES ACROSS THE AREA AND WINDS BECOME LIGHT OR CALM...
LOWS COULD BE SEVERAL DEGREES COLDER DEPENDING ON CLOUD COVER.

ANOTHER WEAK CLIPPER SYSTEM MOVES SOUTHEAST ACROSS THE WESTERN
LAKES MONDAY AFTERNOON INTO MONDAY NIGHT AS IT SLOWLY BEGINS TO
WEAKEN. MODELS VARY SOME ON TIMING AND PRECIP ARRIVAL. A CONSENSUS
WOULD HAVE THE ARRIVAL DURING MONDAY AFTERNOON. INITIALLY THE
SATURATION IS DEEP ENOUGH THAT PRECIP SHOULD BEGIN AS LIGHT SNOW.
BUT INTO THE EVENING...MID LEVELS BEGIN TO DRY OUT SOME AND PRECIP
COULD TRANSITION MORE TO A LIGHT SNOW MIXED WITH OR JUST FREEZING
DRIZZLE. FAIRLY LOW CONFIDENCE AT THIS POINT...SO MAINTAINED JUST
LIGHT SNOW FOR THE ENTIRE DURATION FOR NOW.

PROGRESSIVE PATTERN BRINGS ANOTHER RIDGE OF HIGH PRESSURE ACROSS
THE REGION TUESDAY NIGHT INTO WEDNESDAY AND THEN ANOTHER STORM
SYSTEM WEDNESDAY NIGHT INTO THURSDAY MORNING. MODELS CURRENTLY IN
DECENT AGREEMENT WITH THE TRACK OF THIS LOW GENERALLY RIGHT ACROSS
THE CWA EARLY THURSDAY MORNING. WITH THIS TRACK...TEMPS LIKELY TO
REMAIN FAIRLY STEADY IN THE LOWER/MID 30S WEDNESDAY NIGHT AND
THERMAL PROFILES WOULD SUGGEST PRECIP WOULD BE MAINLY RAIN OR
PERHAPS FREEZING RAIN...IF SURFACE TEMPS REMAINED BELOW FREEZING.
AND ALSO COULD BE SOME SNOW IF THE LOW WERE TO SPEED UP AND/OR
TRACK FURTHER SOUTH. THUS DID NOT GET TOO SPECIFIC WITH PRECIP
TYPE WEDNESDAY NIGHT INTO THURSDAY BUT A WINTRY MIX IS POSSIBLE.
CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* MVFR/PATCHY IFR CIGS DEVELOPING PRE-DAWN.

* NORTHEAST WINDS INCREASING QUICKLY TOWARD SUNRISE...AND GUST
  NEAR 30 KT AT TIMES LATE MORNING AND AFTERNOON.

* SNOW DEVELOPING EARLY-MID MORNING...WITH MVFR VSBY LIKELY AND
  IFR AND SOME ACCUMULATION PROBABLE THROUGH MIDDAY BEFORE
  TAPERING TO LIGHT SNOW SHOWERS OR FLURRIES EARLY THIS AFTERNOON.

* MVFR CIGS THIS AFTERNOON INTO THIS EVENING.

RATZER

//DISCUSSION...UPDATED 06Z...

LOW PRESSURE OVER CENTRAL IOWA WILL MOVE SOUTHEAST ACROSS
NORTHEAST MISSOURI AND INTO SOUTHERN ILLINOIS TODAY. NORTHEAST
WINDS WILL INCREASE QUICKLY TOWARD MORNING AS THE SURFACE PRESSURE
GRADIENT TIGHTENS IN RESPONSE TO THE RAPIDLY MOVING LOW PRESSURE
SYSTEM...MAKING FOR WINDY CONDITIONS WITH SUSTAINED SPEEDS 15-20
KT AND GUSTS 25-30 KT DURING THE LATE MORNING AND AFTERNOON HOURS.
WINDS WILL GRADUALLY DIMINISH TONIGHT AS WEAK HIGH PRESSURE
APPROACHES BY MONDAY MORNING.

AN EXTENSIVE AREA OF MVFR AND PATCHY IFR STRATUS OVER
MICHIGAN/WISCONSIN AND LAKE MICHIGAN IS EXPECTED TO SPREAD BACK
ACROSS THE TERMINALS EARLY THIS MORNING AS NORTHEAST WINDS
INCREASE. SNOW CURRENTLY DEPICTED BY RADAR RETURNS OVER SOUTHERN
MINNESOTA AND NORTHERN IOWA WILL SPREAD SOUTHEAST INTO THE REGION
THIS MORNING...WITH THE BULK OF THE HEAVIER SNOW EXPECTED OFF TO
THE SOUTHWEST OF THE TERMINALS. STILL...THE MID-MORNING THROUGH
NOON HOURS SHOULD SEE THE GREATEST PROBABILITY OF MINOR
ACCUMULATIONS AND MVFR/IFR VISIBILITY IN LIGHT SNOW. SNOW SHOULD
TAPER TO LIGHT SNOW SHOWERS AND FLURRIES THIS AFTERNOON.

MVFR STRATOCU LOOKS TO LINGER INTO TONIGHT...THOUGH SHOULD BECOME
THINNER WITH TIME AS DRIER AIR IS DRAWN IN FROM THE NORTHEAST.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM IN CIG TRENDS EARLY THIS MORNING AND IN SNOW
  TIMING/IMPACT.

* HIGH IN WIND TRENDS.

* MEDIUM IN CIGS BEYOND THIS EVENING.

RATZER

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...SLIGHT CHANCE -SN IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

IZZI

&&

.MARINE...
137 AM CST

MAIN MARINE FORECAST FOCUS CONTINUES TO BE A PERIOD OF STRONG
NORTHEAST WINDS ACROSS THE SOUTHERN 2/3 OR SO OF LAKE MICHIGAN
THROUGH THIS EVENING.

A COLD FRONT HAS PUSHED SOUTH ACROSS MUCH OF LAKE MICHIGAN SINCE
SATURDAY MORNING...WITH COLD HIGH PRESSURE SPREADING ACROSS
MANITOBA...WESTERN ONTARIO AND THE NORTHERN LAKES. EARLY THIS
MORNING AN AREA OF LOW PRESSURE WAS OVER IOWA...AND THIS LOW WILL
MOVE QUICKLY SOUTHEAST TO THE LOWER OHIO VALLEY BY THIS EVENING.
THIS LOW AND THE HIGH PRESSURE TO THE NORTH OF THE LAKES WILL
COMBINE TO RAPIDLY TIGHTEN THE SURFACE PRESSURE GRADIENT ACROSS THE
LAKE THIS MORNING...WITH NORTH-NORTHEAST WINDS INCREASING TO 25-30
KT. RECENT OBSERVATION PLATFORMS ALONG THE WEST SHORE OF THE LAKE
HAVE BEEN GUSTING 26-27 KTS BEHIND THE COLD FRONT AS FAR SOUTH AS
MILWAUKEE. THESE STRONGER WINDS WILL CONTINUE TO DEVELOP SOUTHWARD
DOWN THE REMAINDER OF THE LAKE THIS MORNING. FORECAST SOUNDINGS
INDICATE WINDS TO 30 KT WILL BE PREVALENT THROUGH THE DAY...WITH A
FEW GALE FORCE GUSTS TO 35 KT POSSIBLE. WINDS WILL REMAIN GUSTY INTO
THE EVENING HOURS ACROSS THE FAR SOUTHERN PORTION OF THE LAKE...BUT
WILL DIMINISH RAPIDLY FROM THE NORTH AS A WEAK RIDGE OF HIGH
PRESSURE SPREADS IN BEHIND THE QUICK MOVING LOW WHICH MOVE TO THE
CAROLINA COAST BY MONDAY MORNING.

THE WEAK RIDGE WILL MOVE QUICKLY SOUTHEAST OF THE LAKE MONDAY...
WITH WINDS BRIEFLY BECOMING SOUTHERLY AND INCREASING BACK AROUND 20
KT OR SO AHEAD OF ANOTHER LOW PRESSURE SYSTEM WHICH WILL DROP
SOUTHEAST ACROSS THE LAKE MONDAY NIGHT...WHILE FILLING. WEAK
GRADIENT CONDITIONS WILL THEN LINGER ACROSS THE LAKE TUESDAY AND
TUESDAY NIGHT AS THE TROUGH FILLS AND A WEAK RIDGE MOVES ACROSS THE
REGION. INDICATIONS ARE THAT ANOTHER LOW WILL DEVELOP ACROSS THE
PLAINS MID-WEEK...AND WILL APPROACH THE LAKE FROM THE WEST LATE
WEDNESDAY. THIS MAY RESULT IN A BRIEF PERIOD OF ENHANCED
EAST-SOUTHEAST WINDS LATE WEDNESDAY OR WEDNESDAY NIGHT...WITH A
PERIOD OF GUSTY NORTHERLY WINDS POSSIBLE THURSDAY AS THE LOW MOVES
EAST OF THE LAKE.

FOR THE IL/NORTHWEST INDIANA NEARSHORE AREA...SMALL CRAFT ADVISORY
IS IN EFFECT FROM 6 AM CST THIS MORNING AS WINDS/WAVES QUICKLY
INCREASE AND BUILD. ADVISORY HEADLINE WILL REMAIN IN EFFECT THROUGH
MID-MORNING MONDAY...AS WAVES SLOWLY SUBSIDE BELOW 4 FT.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 250542
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1142 PM CST SAT JAN 24 2015

.UPDATE...
900 PM CST

EVENING UPDATE...

HAVE UPDATED GRIDS TO REFLECT MUCH LOWER SNOWFALL AMOUNTS ON SUNDAY
TO THE NORTH OF INTERSTATE 80 AND ALSO SLOWED ARRIVAL OF
PRECIPITATION MAINLY TO EARLY TO MID SUNDAY MORNING. RADAR...SURFACE
ANALYSIS AND SATELLITE TRENDS SUPPORT THE NEW 00Z GUIDANCE AND
LATEST HIGHER RESOLUTION GUIDANCE ROLLING IN DIGGING THE 500 MB WAVE
FARTHER SOUTHWEST AND ASSOCIATED SURFACE LOW FARTHER SOUTHWEST AND
THEN SOUTH OF THE CWA.  NOW LOOKING AT GENERALLY AROUND A FEW TENTHS
TO UP TO AN INCH NORTH OF INTERSTATE 88...ONE TO TWO INCHES BETWEEN
I-88 AND I-80 AND ONE TO THREE INCHES SOUTH OF INTERSTATE 80. IF THE
FARTHER SOUTH TREND BECOMES MORE AGGRESSIVE AS THE SYSTEM APPROACHES
SUNDAY...THEN EVEN THESE AMOUNTS COULD END UP BEING TOO HIGH.
NAM/WRF AND OTHER HIGHER-RES GUIDANCE CONTINUES TO HINT AT LAKE
ENHANCEMENT DURING THE DAY SUNDAY INTO THE AFTERNOON INTO PARTS OF
NORTHEAST IL AND NW IN...BUT UNLESS FRICTIONAL CONVERGENCE CAN
ENHANCE RATES A BIT...THE THERMODYNAMICS AND INVERSION HEIGHTS ARE
VERY MARGINAL TO ACTUALLY ADD MUCH TO SNOW TOTALS.

REGARDING THE MIXED PRECIPITATION IN THE SOUTHERN CWA...THE
SOUTHWARD TREND AND DELAYED TIMING OF THE SYSTEM SHOULD ALLOW FOR
COLDER AIR TO BLEED SOUTHWARD AND SUPPRESS THE MIXING ZONE SOUTHWARD
FROM THE PREVIOUS FORECAST. ANY WINTRY MIX/RAIN SNOW MIX IN THE FAR
SOUTHERN CWA WILL LIKELY TRANSITION TO SNOW BY MID DAY/EARLY
AFTERNOON.

UPDATED ZONES WILL BE SENT SHORTLY.

RC/KREIN

&&

.SHORT TERM...
250 PM CST

THROUGH SUNDAY...

MAIN FORECAST CONCERN WILL BE PASSAGE OF A CLIPPER SYSTEM ACROSS THE
MIDWEST BRINGING ACCUMULATING SNOWFALL AND FOR SOME AREAS A WINTRY
MIX OF PRECIPITATION. CLOUD COVER WILL CONTINUE TO INCREASE THE
REMAINDER OF THE TODAY AS THE LOW DIVES ACROSS THE DAKOTAS INTO
MINNESOTA. MODELS ARE IN DECENT AGREEMENT TRACKING THE SURFACE LOW
ACROSS FAR NE MO LATE TONIGHT INTO DOWNSTATE IL BY SUNDAY AFTERNOON.
1000MB-700MB LAYER MAX WETBULBS ARE UP TO 2C SOUTH OF THE I-80
CORRIDOR THROUGH LATE MORNING/EARLY AFTERNOON SUNDAY...THEN START TO
FALL QUICKLY FROM THE NORTH THROUGH THE AFTERNOON HOURS. WITH THAT
IN MIND...THINK THAT PRECIP WILL BEGIN AS PRIMARILY SNOW NORTH OF
THE I-80 CORRIDOR WITH RAIN/SLEET TO THE SOUTH...EVENTUALLY CHANGING
OVER TO ALL SNOW. MODELS IN GENERAL HAVE THE AXIS OF HIGHEST QPF
SOUTH OF I-80...BUT WITH WARMER TEMPERATURES...IT APPEARS THE
HIGHEST SNOWFALL MAY OCCUR A LITTLE FARTHER NORTH. DID BUMP UP SNOW
TOTALS ACROSS PORTIONS OF THE CHICAGO METRO WHERE MODELS CONTINUE TO
ADVERTISE AN INCREASE IN THE LOW LEVEL LAPSE RATES AS WINDS TURN NE
OFF LAKE MICHIGAN WITH LAKE ENHANCEMENT APPEARING AT LEAST POSSIBLE.
NAM AND REGIONAL GEM GUIDANCE BOTH SHOW A SLIGHT MAX IN THE QPF
VALUES OVER THE AREA AND HAVE BEEN CONSISTENTLY ADVERTISING A BUMP IN
THE LOW LEVEL OMEGA STARTING LATE MORNING INTO THE AFTERNOON.
FORECAST SNOW TOTALS FOR THIS EVENT WILL BE 1-3 INCHES WEST OF A
WAUKEGAN TO STREATOR LINE...AND 2-4 INCHES EAST. WILL HAVE TO
MONITOR THE MESOSCALE BANDING THREAT FOR SOME LOCALLY HIGHER
AMOUNTS. NAM GUIDANCE IN PARTICULAR WAS HINTING AT AN AREA OF LOW
LEVEL FGEN DEVELOPING FOR EAST CENTRAL IL AND NORTHWEST
INDIANA...BUT LAPSE RATES UPSTAIRS ARENT OVERLY IMPRESSIVE IN THE
LATEST MODELS RUNS. ALSO SURFACE LOW SLOWLY FILLING AS IT MOVES
TOWARDS THE OHIO VALLEY WILL ALSO BE A LIMITING FACTOR. WILL ISSUE
AN UPDATED SPS THIS AFTERNOON FOR THE SNOWFALL. AS MENTIONED...STILL
CANNOT RULE OUT SOME LOCALLY HIGHER AMOUNTS THAT MIGHT REQUIRE AN
ADVISORY HOWEVER DONT HAVE MUCH CONFIDENCE WHERE OR EVEN IF THIS
WOULD OCCUR.

WINDS WILL START TO RAMP UP FROM EARLY MORNING ON OUT OF THE
NORTHEAST AS A TIGHT GRADIENT SWEEPS ACROSS THE REGION ON THE BACK
SIDE OF THE LOW. NORTHEAST WINDS ARE EXPECTED TO GUST 30-35 MPH AT
TIMES ACROSS THE AREA. THESE MODERATELY STRONG NORTHEAST WINDS OVER
LAKE MICHIGAN WILL DRIVE 8-11 FOOT WAVES INTO THE NEARSHORE WATERS
AND SOME OF THESE WAVES MAY RESULT IN SOME MINOR LAKE SHORE FLOODING
TO EXPOSED AREAS. IN ADDITION...BLOWING SNOW MAY BECOME A PROBLEM
ESPECIALLY IN OPEN AREAS. WETTER THAN AVERAGE SNOW...PARTICULARLY
SOUTH OF I-80 MAY HELP LIMIT THE BLOWING SNOW SOME.

DEUBELBEISS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE A CHANCE OF LIGHT SNOW MONDAY
AFTERNOON INTO MONDAY NIGHT AND THEN THE POTENTIAL FOR A WINTRY
MIX WEDNESDAY NIGHT.

LIGHT SNOW WILL BE ENDING ACROSS THE SOUTHEAST CWA SUNDAY EVENING
AS NORTHEAST WINDS STEADILY DIMINISH SUNDAY EVENING. LAKE EFFECT
CLOUDS AND PERHAPS A FEW FLURRIES ARE POSSIBLE SUNDAY EVENING. LOWS
BY MONDAY MORNING WILL DIP INTO THE TEENS MOST LOCATIONS BUT AS A
WEAK RIDGE PASSES ACROSS THE AREA AND WINDS BECOME LIGHT OR CALM...
LOWS COULD BE SEVERAL DEGREES COLDER DEPENDING ON CLOUD COVER.

ANOTHER WEAK CLIPPER SYSTEM MOVES SOUTHEAST ACROSS THE WESTERN
LAKES MONDAY AFTERNOON INTO MONDAY NIGHT AS IT SLOWLY BEGINS TO
WEAKEN. MODELS VARY SOME ON TIMING AND PRECIP ARRIVAL. A CONSENSUS
WOULD HAVE THE ARRIVAL DURING MONDAY AFTERNOON. INITIALLY THE
SATURATION IS DEEP ENOUGH THAT PRECIP SHOULD BEGIN AS LIGHT SNOW.
BUT INTO THE EVENING...MID LEVELS BEGIN TO DRY OUT SOME AND PRECIP
COULD TRANSITION MORE TO A LIGHT SNOW MIXED WITH OR JUST FREEZING
DRIZZLE. FAIRLY LOW CONFIDENCE AT THIS POINT...SO MAINTAINED JUST
LIGHT SNOW FOR THE ENTIRE DURATION FOR NOW.

PROGRESSIVE PATTERN BRINGS ANOTHER RIDGE OF HIGH PRESSURE ACROSS
THE REGION TUESDAY NIGHT INTO WEDNESDAY AND THEN ANOTHER STORM
SYSTEM WEDNESDAY NIGHT INTO THURSDAY MORNING. MODELS CURRENTLY IN
DECENT AGREEMENT WITH THE TRACK OF THIS LOW GENERALLY RIGHT ACROSS
THE CWA EARLY THURSDAY MORNING. WITH THIS TRACK...TEMPS LIKELY TO
REMAIN FAIRLY STEADY IN THE LOWER/MID 30S WEDNESDAY NIGHT AND
THERMAL PROFILES WOULD SUGGEST PRECIP WOULD BE MAINLY RAIN OR
PERHAPS FREEZING RAIN...IF SURFACE TEMPS REMAINED BELOW FREEZING.
AND ALSO COULD BE SOME SNOW IF THE LOW WERE TO SPEED UP AND/OR
TRACK FURTHER SOUTH. THUS DID NOT GET TOO SPECIFIC WITH PRECIP
TYPE WEDNESDAY NIGHT INTO THURSDAY BUT A WINTRY MIX IS POSSIBLE.
CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* MVFR/PATCHY IFR CIGS DEVELOPING PRE-DAWN.

* NORTHEAST WINDS INCREASING QUICKLY TOWARD SUNRISE...AND GUST
  NEAR 30 KT AT TIMES LATE MORNING AND AFTERNOON.

* SNOW DEVELOPING EARLY-MID MORNING...WITH MVFR VSBY LIKELY AND
  IFR AND SOME ACCUMULATION PROBABLE THROUGH MIDDAY BEFORE
  TAPERING TO LIGHT SNOW SHOWERS OR FLURRIES EARLY THIS AFTERNOON.

* MVFR CIGS THIS AFTERNOON INTO THIS EVENING.

RATZER

//DISCUSSION...UPDATED 06Z...

LOW PRESSURE OVER CENTRAL IOWA WILL MOVE SOUTHEAST ACROSS
NORTHEAST MISSOURI AND INTO SOUTHERN ILLINOIS TODAY. NORTHEAST
WINDS WILL INCREASE QUICKLY TOWARD MORNING AS THE SURFACE PRESSURE
GRADIENT TIGHTENS IN RESPONSE TO THE RAPIDLY MOVING LOW PRESSURE
SYSTEM...MAKING FOR WINDY CONDITIONS WITH SUSTAINED SPEEDS 15-20
KT AND GUSTS 25-30 KT DURING THE LATE MORNING AND AFTERNOON HOURS.
WINDS WILL GRADUALLY DIMINISH TONIGHT AS WEAK HIGH PRESSURE
APPROACHES BY MONDAY MORNING.

AN EXTENSIVE AREA OF MVFR AND PATCHY IFR STRATUS OVER
MICHIGAN/WISCONSIN AND LAKE MICHIGAN IS EXPECTED TO SPREAD BACK
ACROSS THE TERMINALS EARLY THIS MORNING AS NORTHEAST WINDS
INCREASE. SNOW CURRENTLY DEPICTED BY RADAR RETURNS OVER SOUTHERN
MINNESOTA AND NORTHERN IOWA WILL SPREAD SOUTHEAST INTO THE REGION
THIS MORNING...WITH THE BULK OF THE HEAVIER SNOW EXPECTED OFF TO
THE SOUTHWEST OF THE TERMINALS. STILL...THE MID-MORNING THROUGH
NOON HOURS SHOULD SEE THE GREATEST PROBABILITY OF MINOR
ACCUMULATIONS AND MVFR/IFR VISIBILITY IN LIGHT SNOW. SNOW SHOULD
TAPER TO LIGHT SNOW SHOWERS AND FLURRIES THIS AFTERNOON.

MVFR STRATOCU LOOKS TO LINGER INTO TONIGHT...THOUGH SHOULD BECOME
THINNER WITH TIME AS DRIER AIR IS DRAWN IN FROM THE NORTHEAST.

RATZER


//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM IN CIG TRENDS EARLY THIS MORNING AND IN SNOW
  TIMING/IMPACT.

* HIGH IN WIND TRENDS.

* MEDIUM IN CIGS BEYOND THIS EVENING.

RATZER

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...SLIGHT CHANCE -SN IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

IZZI

&&

.MARINE...
127 PM CST

A COLD FRONT WILL BEGIN TO SHIFT SOUTHWARD DOWN LAKE MICHIGAN LATE
THIS AFTERNOON...WITH WINDS EXPECTED TO PICK UP OUT OF THE NORTH
INTO TONIGHT. WINDS OVER THE LAKE WILL THEN CONTINUE TO INCREASE
INTO SUNDAY AS A QUICK MOVING CLIPPER SYSTEM TRACKS SOUTHEASTWARD
ACROSS SOUTHERN ILLINOIS. THIS WILL RESULT IN NORTHEASTERLY WINDS UP
TO 30 KT BY EARLY SUNDAY MORNING ACROSS MOST OF THE LAKE...WITH THE
STRONGEST WINDS EXPECTED ACROSS THE SOUTHERN END OF THE LAKE...WHERE
A FEW GALE FORCE GUSTS TO 35 KT ARE POSSIBLE ON SUNDAY. THIS WILL
RESULT IN WAVES UP TO 10 FEET INTO THE NORTHEAST ILLINOIS SHORES
THROUGH SUNDAY EVENING. THE WINDS WILL QUICKLY ABATE ACROSS THE LAKE
SUNDAY NIGHT AS THE LOW SHIFTS TOWARDS THE EASTERN SEABOARD.

ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD OVER OR JUST WEST OF THE
LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A PERIOD OF
LIGHT SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN THE
WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION. THIS
SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS WEDNESDAY NIGHT...FOLLOWED BY STRONG NORTHERLY WINDS
THURSDAY INTO FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 250542
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1142 PM CST SAT JAN 24 2015

.UPDATE...
900 PM CST

EVENING UPDATE...

HAVE UPDATED GRIDS TO REFLECT MUCH LOWER SNOWFALL AMOUNTS ON SUNDAY
TO THE NORTH OF INTERSTATE 80 AND ALSO SLOWED ARRIVAL OF
PRECIPITATION MAINLY TO EARLY TO MID SUNDAY MORNING. RADAR...SURFACE
ANALYSIS AND SATELLITE TRENDS SUPPORT THE NEW 00Z GUIDANCE AND
LATEST HIGHER RESOLUTION GUIDANCE ROLLING IN DIGGING THE 500 MB WAVE
FARTHER SOUTHWEST AND ASSOCIATED SURFACE LOW FARTHER SOUTHWEST AND
THEN SOUTH OF THE CWA.  NOW LOOKING AT GENERALLY AROUND A FEW TENTHS
TO UP TO AN INCH NORTH OF INTERSTATE 88...ONE TO TWO INCHES BETWEEN
I-88 AND I-80 AND ONE TO THREE INCHES SOUTH OF INTERSTATE 80. IF THE
FARTHER SOUTH TREND BECOMES MORE AGGRESSIVE AS THE SYSTEM APPROACHES
SUNDAY...THEN EVEN THESE AMOUNTS COULD END UP BEING TOO HIGH.
NAM/WRF AND OTHER HIGHER-RES GUIDANCE CONTINUES TO HINT AT LAKE
ENHANCEMENT DURING THE DAY SUNDAY INTO THE AFTERNOON INTO PARTS OF
NORTHEAST IL AND NW IN...BUT UNLESS FRICTIONAL CONVERGENCE CAN
ENHANCE RATES A BIT...THE THERMODYNAMICS AND INVERSION HEIGHTS ARE
VERY MARGINAL TO ACTUALLY ADD MUCH TO SNOW TOTALS.

REGARDING THE MIXED PRECIPITATION IN THE SOUTHERN CWA...THE
SOUTHWARD TREND AND DELAYED TIMING OF THE SYSTEM SHOULD ALLOW FOR
COLDER AIR TO BLEED SOUTHWARD AND SUPPRESS THE MIXING ZONE SOUTHWARD
FROM THE PREVIOUS FORECAST. ANY WINTRY MIX/RAIN SNOW MIX IN THE FAR
SOUTHERN CWA WILL LIKELY TRANSITION TO SNOW BY MID DAY/EARLY
AFTERNOON.

UPDATED ZONES WILL BE SENT SHORTLY.

RC/KREIN

&&

.SHORT TERM...
250 PM CST

THROUGH SUNDAY...

MAIN FORECAST CONCERN WILL BE PASSAGE OF A CLIPPER SYSTEM ACROSS THE
MIDWEST BRINGING ACCUMULATING SNOWFALL AND FOR SOME AREAS A WINTRY
MIX OF PRECIPITATION. CLOUD COVER WILL CONTINUE TO INCREASE THE
REMAINDER OF THE TODAY AS THE LOW DIVES ACROSS THE DAKOTAS INTO
MINNESOTA. MODELS ARE IN DECENT AGREEMENT TRACKING THE SURFACE LOW
ACROSS FAR NE MO LATE TONIGHT INTO DOWNSTATE IL BY SUNDAY AFTERNOON.
1000MB-700MB LAYER MAX WETBULBS ARE UP TO 2C SOUTH OF THE I-80
CORRIDOR THROUGH LATE MORNING/EARLY AFTERNOON SUNDAY...THEN START TO
FALL QUICKLY FROM THE NORTH THROUGH THE AFTERNOON HOURS. WITH THAT
IN MIND...THINK THAT PRECIP WILL BEGIN AS PRIMARILY SNOW NORTH OF
THE I-80 CORRIDOR WITH RAIN/SLEET TO THE SOUTH...EVENTUALLY CHANGING
OVER TO ALL SNOW. MODELS IN GENERAL HAVE THE AXIS OF HIGHEST QPF
SOUTH OF I-80...BUT WITH WARMER TEMPERATURES...IT APPEARS THE
HIGHEST SNOWFALL MAY OCCUR A LITTLE FARTHER NORTH. DID BUMP UP SNOW
TOTALS ACROSS PORTIONS OF THE CHICAGO METRO WHERE MODELS CONTINUE TO
ADVERTISE AN INCREASE IN THE LOW LEVEL LAPSE RATES AS WINDS TURN NE
OFF LAKE MICHIGAN WITH LAKE ENHANCEMENT APPEARING AT LEAST POSSIBLE.
NAM AND REGIONAL GEM GUIDANCE BOTH SHOW A SLIGHT MAX IN THE QPF
VALUES OVER THE AREA AND HAVE BEEN CONSISTENTLY ADVERTISING A BUMP IN
THE LOW LEVEL OMEGA STARTING LATE MORNING INTO THE AFTERNOON.
FORECAST SNOW TOTALS FOR THIS EVENT WILL BE 1-3 INCHES WEST OF A
WAUKEGAN TO STREATOR LINE...AND 2-4 INCHES EAST. WILL HAVE TO
MONITOR THE MESOSCALE BANDING THREAT FOR SOME LOCALLY HIGHER
AMOUNTS. NAM GUIDANCE IN PARTICULAR WAS HINTING AT AN AREA OF LOW
LEVEL FGEN DEVELOPING FOR EAST CENTRAL IL AND NORTHWEST
INDIANA...BUT LAPSE RATES UPSTAIRS ARENT OVERLY IMPRESSIVE IN THE
LATEST MODELS RUNS. ALSO SURFACE LOW SLOWLY FILLING AS IT MOVES
TOWARDS THE OHIO VALLEY WILL ALSO BE A LIMITING FACTOR. WILL ISSUE
AN UPDATED SPS THIS AFTERNOON FOR THE SNOWFALL. AS MENTIONED...STILL
CANNOT RULE OUT SOME LOCALLY HIGHER AMOUNTS THAT MIGHT REQUIRE AN
ADVISORY HOWEVER DONT HAVE MUCH CONFIDENCE WHERE OR EVEN IF THIS
WOULD OCCUR.

WINDS WILL START TO RAMP UP FROM EARLY MORNING ON OUT OF THE
NORTHEAST AS A TIGHT GRADIENT SWEEPS ACROSS THE REGION ON THE BACK
SIDE OF THE LOW. NORTHEAST WINDS ARE EXPECTED TO GUST 30-35 MPH AT
TIMES ACROSS THE AREA. THESE MODERATELY STRONG NORTHEAST WINDS OVER
LAKE MICHIGAN WILL DRIVE 8-11 FOOT WAVES INTO THE NEARSHORE WATERS
AND SOME OF THESE WAVES MAY RESULT IN SOME MINOR LAKE SHORE FLOODING
TO EXPOSED AREAS. IN ADDITION...BLOWING SNOW MAY BECOME A PROBLEM
ESPECIALLY IN OPEN AREAS. WETTER THAN AVERAGE SNOW...PARTICULARLY
SOUTH OF I-80 MAY HELP LIMIT THE BLOWING SNOW SOME.

DEUBELBEISS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE A CHANCE OF LIGHT SNOW MONDAY
AFTERNOON INTO MONDAY NIGHT AND THEN THE POTENTIAL FOR A WINTRY
MIX WEDNESDAY NIGHT.

LIGHT SNOW WILL BE ENDING ACROSS THE SOUTHEAST CWA SUNDAY EVENING
AS NORTHEAST WINDS STEADILY DIMINISH SUNDAY EVENING. LAKE EFFECT
CLOUDS AND PERHAPS A FEW FLURRIES ARE POSSIBLE SUNDAY EVENING. LOWS
BY MONDAY MORNING WILL DIP INTO THE TEENS MOST LOCATIONS BUT AS A
WEAK RIDGE PASSES ACROSS THE AREA AND WINDS BECOME LIGHT OR CALM...
LOWS COULD BE SEVERAL DEGREES COLDER DEPENDING ON CLOUD COVER.

ANOTHER WEAK CLIPPER SYSTEM MOVES SOUTHEAST ACROSS THE WESTERN
LAKES MONDAY AFTERNOON INTO MONDAY NIGHT AS IT SLOWLY BEGINS TO
WEAKEN. MODELS VARY SOME ON TIMING AND PRECIP ARRIVAL. A CONSENSUS
WOULD HAVE THE ARRIVAL DURING MONDAY AFTERNOON. INITIALLY THE
SATURATION IS DEEP ENOUGH THAT PRECIP SHOULD BEGIN AS LIGHT SNOW.
BUT INTO THE EVENING...MID LEVELS BEGIN TO DRY OUT SOME AND PRECIP
COULD TRANSITION MORE TO A LIGHT SNOW MIXED WITH OR JUST FREEZING
DRIZZLE. FAIRLY LOW CONFIDENCE AT THIS POINT...SO MAINTAINED JUST
LIGHT SNOW FOR THE ENTIRE DURATION FOR NOW.

PROGRESSIVE PATTERN BRINGS ANOTHER RIDGE OF HIGH PRESSURE ACROSS
THE REGION TUESDAY NIGHT INTO WEDNESDAY AND THEN ANOTHER STORM
SYSTEM WEDNESDAY NIGHT INTO THURSDAY MORNING. MODELS CURRENTLY IN
DECENT AGREEMENT WITH THE TRACK OF THIS LOW GENERALLY RIGHT ACROSS
THE CWA EARLY THURSDAY MORNING. WITH THIS TRACK...TEMPS LIKELY TO
REMAIN FAIRLY STEADY IN THE LOWER/MID 30S WEDNESDAY NIGHT AND
THERMAL PROFILES WOULD SUGGEST PRECIP WOULD BE MAINLY RAIN OR
PERHAPS FREEZING RAIN...IF SURFACE TEMPS REMAINED BELOW FREEZING.
AND ALSO COULD BE SOME SNOW IF THE LOW WERE TO SPEED UP AND/OR
TRACK FURTHER SOUTH. THUS DID NOT GET TOO SPECIFIC WITH PRECIP
TYPE WEDNESDAY NIGHT INTO THURSDAY BUT A WINTRY MIX IS POSSIBLE.
CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* MVFR/PATCHY IFR CIGS DEVELOPING PRE-DAWN.

* NORTHEAST WINDS INCREASING QUICKLY TOWARD SUNRISE...AND GUST
  NEAR 30 KT AT TIMES LATE MORNING AND AFTERNOON.

* SNOW DEVELOPING EARLY-MID MORNING...WITH MVFR VSBY LIKELY AND
  IFR AND SOME ACCUMULATION PROBABLE THROUGH MIDDAY BEFORE
  TAPERING TO LIGHT SNOW SHOWERS OR FLURRIES EARLY THIS AFTERNOON.

* MVFR CIGS THIS AFTERNOON INTO THIS EVENING.

RATZER

//DISCUSSION...UPDATED 06Z...

LOW PRESSURE OVER CENTRAL IOWA WILL MOVE SOUTHEAST ACROSS
NORTHEAST MISSOURI AND INTO SOUTHERN ILLINOIS TODAY. NORTHEAST
WINDS WILL INCREASE QUICKLY TOWARD MORNING AS THE SURFACE PRESSURE
GRADIENT TIGHTENS IN RESPONSE TO THE RAPIDLY MOVING LOW PRESSURE
SYSTEM...MAKING FOR WINDY CONDITIONS WITH SUSTAINED SPEEDS 15-20
KT AND GUSTS 25-30 KT DURING THE LATE MORNING AND AFTERNOON HOURS.
WINDS WILL GRADUALLY DIMINISH TONIGHT AS WEAK HIGH PRESSURE
APPROACHES BY MONDAY MORNING.

AN EXTENSIVE AREA OF MVFR AND PATCHY IFR STRATUS OVER
MICHIGAN/WISCONSIN AND LAKE MICHIGAN IS EXPECTED TO SPREAD BACK
ACROSS THE TERMINALS EARLY THIS MORNING AS NORTHEAST WINDS
INCREASE. SNOW CURRENTLY DEPICTED BY RADAR RETURNS OVER SOUTHERN
MINNESOTA AND NORTHERN IOWA WILL SPREAD SOUTHEAST INTO THE REGION
THIS MORNING...WITH THE BULK OF THE HEAVIER SNOW EXPECTED OFF TO
THE SOUTHWEST OF THE TERMINALS. STILL...THE MID-MORNING THROUGH
NOON HOURS SHOULD SEE THE GREATEST PROBABILITY OF MINOR
ACCUMULATIONS AND MVFR/IFR VISIBILITY IN LIGHT SNOW. SNOW SHOULD
TAPER TO LIGHT SNOW SHOWERS AND FLURRIES THIS AFTERNOON.

MVFR STRATOCU LOOKS TO LINGER INTO TONIGHT...THOUGH SHOULD BECOME
THINNER WITH TIME AS DRIER AIR IS DRAWN IN FROM THE NORTHEAST.

RATZER


//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM IN CIG TRENDS EARLY THIS MORNING AND IN SNOW
  TIMING/IMPACT.

* HIGH IN WIND TRENDS.

* MEDIUM IN CIGS BEYOND THIS EVENING.

RATZER

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...SLIGHT CHANCE -SN IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

IZZI

&&

.MARINE...
127 PM CST

A COLD FRONT WILL BEGIN TO SHIFT SOUTHWARD DOWN LAKE MICHIGAN LATE
THIS AFTERNOON...WITH WINDS EXPECTED TO PICK UP OUT OF THE NORTH
INTO TONIGHT. WINDS OVER THE LAKE WILL THEN CONTINUE TO INCREASE
INTO SUNDAY AS A QUICK MOVING CLIPPER SYSTEM TRACKS SOUTHEASTWARD
ACROSS SOUTHERN ILLINOIS. THIS WILL RESULT IN NORTHEASTERLY WINDS UP
TO 30 KT BY EARLY SUNDAY MORNING ACROSS MOST OF THE LAKE...WITH THE
STRONGEST WINDS EXPECTED ACROSS THE SOUTHERN END OF THE LAKE...WHERE
A FEW GALE FORCE GUSTS TO 35 KT ARE POSSIBLE ON SUNDAY. THIS WILL
RESULT IN WAVES UP TO 10 FEET INTO THE NORTHEAST ILLINOIS SHORES
THROUGH SUNDAY EVENING. THE WINDS WILL QUICKLY ABATE ACROSS THE LAKE
SUNDAY NIGHT AS THE LOW SHIFTS TOWARDS THE EASTERN SEABOARD.

ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD OVER OR JUST WEST OF THE
LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A PERIOD OF
LIGHT SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN THE
WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION. THIS
SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS WEDNESDAY NIGHT...FOLLOWED BY STRONG NORTHERLY WINDS
THURSDAY INTO FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 250307
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
907 PM CST SAT JAN 24 2015

.UPDATE...
900 PM CST

EVENING UPDATE...

HAVE UPDATED GRIDS TO REFLECT MUCH LOWER SNOWFALL AMOUNTS ON SUNDAY
TO THE NORTH OF INTERSTATE 80 AND ALSO SLOWED ARRIVAL OF
PRECIPITATION MAINLY TO EARLY TO MID SUNDAY MORNING. RADAR...SURFACE
ANALYSIS AND SATELLITE TRENDS SUPPORT THE NEW 00Z GUIDANCE AND
LATEST HIGHER RESOLUTION GUIDANCE ROLLING IN DIGGING THE 500 MB WAVE
FARTHER SOUTHWEST AND ASSOCIATED SURFACE LOW FARTHER SOUTHWEST AND
THEN SOUTH OF THE CWA.  NOW LOOKING AT GENERALLY AROUND A FEW TENTHS
TO UP TO AN INCH NORTH OF INTERSTATE 88...ONE TO TWO INCHES BETWEEN
I-88 AND I-80 AND ONE TO THREE INCHES SOUTH OF INTERSTATE 80. IF THE
FARTHER SOUTH TREND BECOMES MORE AGGRESSIVE AS THE SYSTEM APPROACHES
SUNDAY...THEN EVEN THESE AMOUNTS COULD END UP BEING TOO HIGH.
NAM/WRF AND OTHER HIGHER-RES GUIDANCE CONTINUES TO HINT AT LAKE
ENHANCEMENT DURING THE DAY SUNDAY INTO THE AFTERNOON INTO PARTS OF
NORTHEAST IL AND NW IN...BUT UNLESS FRICTIONAL CONVERGENCE CAN
ENHANCE RATES A BIT...THE THERMODYNAMICS AND INVERSION HEIGHTS ARE
VERY MARGINAL TO ACTUALLY ADD MUCH TO SNOW TOTALS.

REGARDING THE MIXED PRECIPITATION IN THE SOUTHERN CWA...THE
SOUTHWARD TREND AND DELAYED TIMING OF THE SYSTEM SHOULD ALLOW FOR
COLDER AIR TO BLEED SOUTHWARD AND SUPPRESS THE MIXING ZONE SOUTHWARD
FROM THE PREVIOUS FORECAST. ANY WINTRY MIX/RAIN SNOW MIX IN THE FAR
SOUTHERN CWA WILL LIKELY TRANSITION TO SNOW BY MID DAY/EARLY
AFTERNOON.

UPDATED ZONES WILL BE SENT SHORTLY.

RC/KREIN

&&

.SHORT TERM...
250 PM CST

THROUGH SUNDAY...

MAIN FORECAST CONCERN WILL BE PASSAGE OF A CLIPPER SYSTEM ACROSS THE
MIDWEST BRINGING ACCUMULATING SNOWFALL AND FOR SOME AREAS A WINTRY
MIX OF PRECIPITATION. CLOUD COVER WILL CONTINUE TO INCREASE THE
REMAINDER OF THE TODAY AS THE LOW DIVES ACROSS THE DAKOTAS INTO
MINNESOTA. MODELS ARE IN DECENT AGREEMENT TRACKING THE SURFACE LOW
ACROSS FAR NE MO LATE TONIGHT INTO DOWNSTATE IL BY SUNDAY AFTERNOON.
1000MB-700MB LAYER MAX WETBULBS ARE UP TO 2C SOUTH OF THE I-80
CORRIDOR THROUGH LATE MORNING/EARLY AFTERNOON SUNDAY...THEN START TO
FALL QUICKLY FROM THE NORTH THROUGH THE AFTERNOON HOURS. WITH THAT
IN MIND...THINK THAT PRECIP WILL BEGIN AS PRIMARILY SNOW NORTH OF
THE I-80 CORRIDOR WITH RAIN/SLEET TO THE SOUTH...EVENTUALLY CHANGING
OVER TO ALL SNOW. MODELS IN GENERAL HAVE THE AXIS OF HIGHEST QPF
SOUTH OF I-80...BUT WITH WARMER TEMPERATURES...IT APPEARS THE
HIGHEST SNOWFALL MAY OCCUR A LITTLE FARTHER NORTH. DID BUMP UP SNOW
TOTALS ACROSS PORTIONS OF THE CHICAGO METRO WHERE MODELS CONTINUE TO
ADVERTISE AN INCREASE IN THE LOW LEVEL LAPSE RATES AS WINDS TURN NE
OFF LAKE MICHIGAN WITH LAKE ENHANCEMENT APPEARING AT LEAST POSSIBLE.
NAM AND REGIONAL GEM GUIDANCE BOTH SHOW A SLIGHT MAX IN THE QPF
VALUES OVER THE AREA AND HAVE BEEN CONSISTENTLY ADVERTISING A BUMP IN
THE LOW LEVEL OMEGA STARTING LATE MORNING INTO THE AFTERNOON.
FORECAST SNOW TOTALS FOR THIS EVENT WILL BE 1-3 INCHES WEST OF A
WAUKEGAN TO STREATOR LINE...AND 2-4 INCHES EAST. WILL HAVE TO
MONITOR THE MESOSCALE BANDING THREAT FOR SOME LOCALLY HIGHER
AMOUNTS. NAM GUIDANCE IN PARTICULAR WAS HINTING AT AN AREA OF LOW
LEVEL FGEN DEVELOPING FOR EAST CENTRAL IL AND NORTHWEST
INDIANA...BUT LAPSE RATES UPSTAIRS ARENT OVERLY IMPRESSIVE IN THE
LATEST MODELS RUNS. ALSO SURFACE LOW SLOWLY FILLING AS IT MOVES
TOWARDS THE OHIO VALLEY WILL ALSO BE A LIMITING FACTOR. WILL ISSUE
AN UPDATED SPS THIS AFTERNOON FOR THE SNOWFALL. AS MENTIONED...STILL
CANNOT RULE OUT SOME LOCALLY HIGHER AMOUNTS THAT MIGHT REQUIRE AN
ADVISORY HOWEVER DONT HAVE MUCH CONFIDENCE WHERE OR EVEN IF THIS
WOULD OCCUR.

WINDS WILL START TO RAMP UP FROM EARLY MORNING ON OUT OF THE
NORTHEAST AS A TIGHT GRADIENT SWEEPS ACROSS THE REGION ON THE BACK
SIDE OF THE LOW. NORTHEAST WINDS ARE EXPECTED TO GUST 30-35 MPH AT
TIMES ACROSS THE AREA. THESE MODERATELY STRONG NORTHEAST WINDS OVER
LAKE MICHIGAN WILL DRIVE 8-11 FOOT WAVES INTO THE NEARSHORE WATERS
AND SOME OF THESE WAVES MAY RESULT IN SOME MINOR LAKE SHORE FLOODING
TO EXPOSED AREAS. IN ADDITION...BLOWING SNOW MAY BECOME A PROBLEM
ESPECIALLY IN OPEN AREAS. WETTER THAN AVERAGE SNOW...PARTICULARLY
SOUTH OF I-80 MAY HELP LIMIT THE BLOWING SNOW SOME.

DEUBELBEISS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE A CHANCE OF LIGHT SNOW MONDAY
AFTERNOON INTO MONDAY NIGHT AND THEN THE POTENTIAL FOR A WINTRY
MIX WEDNESDAY NIGHT.

LIGHT SNOW WILL BE ENDING ACROSS THE SOUTHEAST CWA SUNDAY EVENING
AS NORTHEAST WINDS STEADILY DIMINISH SUNDAY EVENING. LAKE EFFECT
CLOUDS AND PERHAPS A FEW FLURRIES ARE POSSIBLE SUNDAY EVENING. LOWS
BY MONDAY MORNING WILL DIP INTO THE TEENS MOST LOCATIONS BUT AS A
WEAK RIDGE PASSES ACROSS THE AREA AND WINDS BECOME LIGHT OR CALM...
LOWS COULD BE SEVERAL DEGREES COLDER DEPENDING ON CLOUD COVER.

ANOTHER WEAK CLIPPER SYSTEM MOVES SOUTHEAST ACROSS THE WESTERN
LAKES MONDAY AFTERNOON INTO MONDAY NIGHT AS IT SLOWLY BEGINS TO
WEAKEN. MODELS VARY SOME ON TIMING AND PRECIP ARRIVAL. A CONSENSUS
WOULD HAVE THE ARRIVAL DURING MONDAY AFTERNOON. INITIALLY THE
SATURATION IS DEEP ENOUGH THAT PRECIP SHOULD BEGIN AS LIGHT SNOW.
BUT INTO THE EVENING...MID LEVELS BEGIN TO DRY OUT SOME AND PRECIP
COULD TRANSITION MORE TO A LIGHT SNOW MIXED WITH OR JUST FREEZING
DRIZZLE. FAIRLY LOW CONFIDENCE AT THIS POINT...SO MAINTAINED JUST
LIGHT SNOW FOR THE ENTIRE DURATION FOR NOW.

PROGRESSIVE PATTERN BRINGS ANOTHER RIDGE OF HIGH PRESSURE ACROSS
THE REGION TUESDAY NIGHT INTO WEDNESDAY AND THEN ANOTHER STORM
SYSTEM WEDNESDAY NIGHT INTO THURSDAY MORNING. MODELS CURRENTLY IN
DECENT AGREEMENT WITH THE TRACK OF THIS LOW GENERALLY RIGHT ACROSS
THE CWA EARLY THURSDAY MORNING. WITH THIS TRACK...TEMPS LIKELY TO
REMAIN FAIRLY STEADY IN THE LOWER/MID 30S WEDNESDAY NIGHT AND
THERMAL PROFILES WOULD SUGGEST PRECIP WOULD BE MAINLY RAIN OR
PERHAPS FREEZING RAIN...IF SURFACE TEMPS REMAINED BELOW FREEZING.
AND ALSO COULD BE SOME SNOW IF THE LOW WERE TO SPEED UP AND/OR
TRACK FURTHER SOUTH. THUS DID NOT GET TOO SPECIFIC WITH PRECIP
TYPE WEDNESDAY NIGHT INTO THURSDAY BUT A WINTRY MIX IS POSSIBLE.
CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* MVFR OR IFR CIGS LIKELY MOVE BACK TONIGHT AND CONTINUE THROUGH
  SUNDAY EVENING
* SNOW DEVELOPS SUNDAY MORNING THE TAPERS OFF SUNDAY
  AFTERNOON...MVFR VSBY LIKELY WITH PERIODIC IFR PROBABLE
* STRONG NE WINDS DEVELOP SUNDAY MORNING CONTINUE INTO EARLY
  SUNDAY EVENING...GUSTS TO 30KT AT TIMES SUNDAY LATE MORNING AND
  AFTERNOON

IZZI

//DISCUSSION...UPDATED 03Z...

HAVE MADE SOME ADJUSTMENTS TO THE TERMINAL FORECASTS TO SLOW THE
ARRIVAL OF THE SNOW SUNDAY MORNING AND ALSO CUT BACK ON THE
INTENSITY AND DURATION. AS REFERENCED IN THE UPDATE SECTION OF THE
DISCUSSION ABOVE...IT APPEARS THE SYSTEM IS TRACKING FARTHER SOUTH
OF THE AREA AND TERMINALS NOW LOOK TO GET MORE OF A GLANCING BLOW
OF SNOW FOCUSING ON LATE SUNDAY MORNING FOR ANY LIGHT
ACCUMULATIONS.

IZZI

UPDATED 00Z...

LOW END MVFR/SPOTTY IFR CIGS SHOULD CLEAR EASTERN TERMINALS SOON
WITH IT LOOKING MORE LIKELY THAT VFR CONDITIONS WILL BE THE RULE
THIS EVENING. OVERNIGHT WINDS WILL TURN NORTHEAST AND SHOULD ALLOW
LOW END MVFR/HIGH END IFR CIGS TO SLOSH BACK SOUTH INTO THE AREA
OVERNIGHT WITH THE WIND SHIFT. SNOW IS STILL EXPECTED TO DEVELOP
AROUND OR JUST PRIOR TO SUNRISE AND CONTINUE THROUGH SUNDAY
MORNING BEFORE TAPERING OFF TO LIGHT NON-ACCUMULATING SNOW OR
FLURRIES DURING THE EARLY/MID AFTERNOON. AS SNOW ENDS CIGS SHOULD
LIFT AND COULD EVEN SCATTER OUT SUNDAY EVENING AS THE SYSTEM PULLS
QUICKLY AWAY FROM THE REGION. OTHER ISSUE IS EXPECTED TO BE THE
STRONG NORTHEAST WINDS THAT WILL DEVELOP SUNDAY MORNING AND
CONTINUE INTO THE AFTERNOON WITH GUSTS OF 25-30KT LOOKING QUITE
LIKELY FROM MID MORNING THROUGH LATE AFTERNOON SUNDAY.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* HIGH CONFIDENCE IN GENERAL CIG TRENDS THROUGH THE PERIOD BUT
  LOWER CONFIDENCE ON PRECISE TIMING OF CATEGORY CHANGES
* MEDIUM-HIGH CONFIDENCE IN WINDS
* MEDIUM CONFIDENCE IN SNOW AND RELATED VSBY TRENDS IN TAFS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...SLIGHT CHANCE -SN IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

IZZI

&&

.MARINE...
127 PM CST

A COLD FRONT WILL BEGIN TO SHIFT SOUTHWARD DOWN LAKE MICHIGAN LATE
THIS AFTERNOON...WITH WINDS EXPECTED TO PICK UP OUT OF THE NORTH
INTO TONIGHT. WINDS OVER THE LAKE WILL THEN CONTINUE TO INCREASE
INTO SUNDAY AS A QUICK MOVING CLIPPER SYSTEM TRACKS SOUTHEASTWARD
ACROSS SOUTHERN ILLINOIS. THIS WILL RESULT IN NORTHEASTERLY WINDS UP
TO 30 KT BY EARLY SUNDAY MORNING ACROSS MOST OF THE LAKE...WITH THE
STRONGEST WINDS EXPECTED ACROSS THE SOUTHERN END OF THE LAKE...WHERE
A FEW GALE FORCE GUSTS TO 35 KT ARE POSSIBLE ON SUNDAY. THIS WILL
RESULT IN WAVES UP TO 10 FEET INTO THE NORTHEAST ILLINOIS SHORES
THROUGH SUNDAY EVENING. THE WINDS WILL QUICKLY ABATE ACROSS THE LAKE
SUNDAY NIGHT AS THE LOW SHIFTS TOWARDS THE EASTERN SEABOARD.

ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD OVER OR JUST WEST OF THE
LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A PERIOD OF
LIGHT SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN THE
WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION. THIS
SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS WEDNESDAY NIGHT...FOLLOWED BY STRONG NORTHERLY WINDS
THURSDAY INTO FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 250301
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
901 PM CST SAT JAN 24 2015

.UPDATE...
900 PM CST

EVENING UPDATE...

HAVE UPDATED GRIDS TO REFLECT MUCH LOWER SNOWFALL AMOUNTS ON SUNDAY
TO THE NORTH OF INTERSTATE 80 AND ALSO SLOWED ARRIVAL OF
PRECIPITATION MAINLY TO EARLY TO MID SUNDAY MORNING. RADAR...SURFACE
ANALYSIS AND SATELLITE TRENDS SUPPORT THE NEW 00Z GUIDANCE AND
LATEST HIGHER RESOLUTION GUIDANCE ROLLING IN DIGGING THE 500 MB WAVE
FARTHER SOUTHWEST AND ASSOCIATED SURFACE LOW FARTHER SOUTHWEST AND
THEN SOUTH OF THE CWA.  NOW LOOKING AT GENERALLY AROUND A FEW TENTHS
TO UP TO AN INCH NORTH OF INTERSTATE 88...ONE TO TWO INCHES BETWEEN
I-88 AND I-80 AND ONE TO THREE INCHES SOUTH OF INTERSTATE 80. IF THE
FARTHER SOUTH TREND BECOMES MORE AGGRESSIVE AS THE SYSTEM APPROACHES
SUNDAY...THEN EVEN THESE AMOUNTS COULD END UP BEING TOO HIGH.
NAM/WRF AND OTHER HIGHER-RES GUIDANCE CONTINUES TO HINT AT LAKE
ENHANCEMENT DURING THE DAY SUNDAY INTO THE AFTERNOON INTO PARTS OF
NORTHEAST IL AND NW IN...BUT UNLESS FRICTIONAL CONVERGENCE CAN
ENHANCE RATES A BIT...THE THERMODYNAMICS AND INVERSION HEIGHTS ARE
VERY MARGINAL TO ACTUALLY ADD MUCH TO SNOW TOTALS.

REGARDING THE MIXED PRECIPITATION IN THE SOUTHERN CWA...THE
SOUTHWARD TREND AND DELAYED TIMING OF THE SYSTEM SHOULD ALLOW FOR
COLDER AIR TO BLEED SOUTHWARD AND SUPPRESS THE MIXING ZONE SOUTHWARD
FROM THE PREVIOUS FORECAST. ANY WINTRY MIX/RAIN SNOW MIX IN THE FAR
SOUTHERN CWA WILL LIKELY TRANSITION TO SNOW BY MID DAY/EARLY
AFTERNOON.

UPDATED ZONES WILL BE SENT SHORTLY.

RC/KREIN

&&

.SHORT TERM...
250 PM CST

THROUGH SUNDAY...

MAIN FORECAST CONCERN WILL BE PASSAGE OF A CLIPPER SYSTEM ACROSS THE
MIDWEST BRINGING ACCUMULATING SNOWFALL AND FOR SOME AREAS A WINTRY
MIX OF PRECIPITATION. CLOUD COVER WILL CONTINUE TO INCREASE THE
REMAINDER OF THE TODAY AS THE LOW DIVES ACROSS THE DAKOTAS INTO
MINNESOTA. MODELS ARE IN DECENT AGREEMENT TRACKING THE SURFACE LOW
ACROSS FAR NE MO LATE TONIGHT INTO DOWNSTATE IL BY SUNDAY AFTERNOON.
1000MB-700MB LAYER MAX WETBULBS ARE UP TO 2C SOUTH OF THE I-80
CORRIDOR THROUGH LATE MORNING/EARLY AFTERNOON SUNDAY...THEN START TO
FALL QUICKLY FROM THE NORTH THROUGH THE AFTERNOON HOURS. WITH THAT
IN MIND...THINK THAT PRECIP WILL BEGIN AS PRIMARILY SNOW NORTH OF
THE I-80 CORRIDOR WITH RAIN/SLEET TO THE SOUTH...EVENTUALLY CHANGING
OVER TO ALL SNOW. MODELS IN GENERAL HAVE THE AXIS OF HIGHEST QPF
SOUTH OF I-80...BUT WITH WARMER TEMPERATURES...IT APPEARS THE
HIGHEST SNOWFALL MAY OCCUR A LITTLE FARTHER NORTH. DID BUMP UP SNOW
TOTALS ACROSS PORTIONS OF THE CHICAGO METRO WHERE MODELS CONTINUE TO
ADVERTISE AN INCREASE IN THE LOW LEVEL LAPSE RATES AS WINDS TURN NE
OFF LAKE MICHIGAN WITH LAKE ENHANCEMENT APPEARING AT LEAST POSSIBLE.
NAM AND REGIONAL GEM GUIDANCE BOTH SHOW A SLIGHT MAX IN THE QPF
VALUES OVER THE AREA AND HAVE BEEN CONSISTENTLY ADVERTISING A BUMP IN
THE LOW LEVEL OMEGA STARTING LATE MORNING INTO THE AFTERNOON.
FORECAST SNOW TOTALS FOR THIS EVENT WILL BE 1-3 INCHES WEST OF A
WAUKEGAN TO STREATOR LINE...AND 2-4 INCHES EAST. WILL HAVE TO
MONITOR THE MESOSCALE BANDING THREAT FOR SOME LOCALLY HIGHER
AMOUNTS. NAM GUIDANCE IN PARTICULAR WAS HINTING AT AN AREA OF LOW
LEVEL FGEN DEVELOPING FOR EAST CENTRAL IL AND NORTHWEST
INDIANA...BUT LAPSE RATES UPSTAIRS ARENT OVERLY IMPRESSIVE IN THE
LATEST MODELS RUNS. ALSO SURFACE LOW SLOWLY FILLING AS IT MOVES
TOWARDS THE OHIO VALLEY WILL ALSO BE A LIMITING FACTOR. WILL ISSUE
AN UPDATED SPS THIS AFTERNOON FOR THE SNOWFALL. AS MENTIONED...STILL
CANNOT RULE OUT SOME LOCALLY HIGHER AMOUNTS THAT MIGHT REQUIRE AN
ADVISORY HOWEVER DONT HAVE MUCH CONFIDENCE WHERE OR EVEN IF THIS
WOULD OCCUR.

WINDS WILL START TO RAMP UP FROM EARLY MORNING ON OUT OF THE
NORTHEAST AS A TIGHT GRADIENT SWEEPS ACROSS THE REGION ON THE BACK
SIDE OF THE LOW. NORTHEAST WINDS ARE EXPECTED TO GUST 30-35 MPH AT
TIMES ACROSS THE AREA. THESE MODERATELY STRONG NORTHEAST WINDS OVER
LAKE MICHIGAN WILL DRIVE 8-11 FOOT WAVES INTO THE NEARSHORE WATERS
AND SOME OF THESE WAVES MAY RESULT IN SOME MINOR LAKE SHORE FLOODING
TO EXPOSED AREAS. IN ADDITION...BLOWING SNOW MAY BECOME A PROBLEM
ESPECIALLY IN OPEN AREAS. WETTER THAN AVERAGE SNOW...PARTICULARLY
SOUTH OF I-80 MAY HELP LIMIT THE BLOWING SNOW SOME.

DEUBELBEISS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE A CHANCE OF LIGHT SNOW MONDAY
AFTERNOON INTO MONDAY NIGHT AND THEN THE POTENTIAL FOR A WINTRY
MIX WEDNESDAY NIGHT.

LIGHT SNOW WILL BE ENDING ACROSS THE SOUTHEAST CWA SUNDAY EVENING
AS NORTHEAST WINDS STEADILY DIMINISH SUNDAY EVENING. LAKE EFFECT
CLOUDS AND PERHAPS A FEW FLURRIES ARE POSSIBLE SUNDAY EVENING. LOWS
BY MONDAY MORNING WILL DIP INTO THE TEENS MOST LOCATIONS BUT AS A
WEAK RIDGE PASSES ACROSS THE AREA AND WINDS BECOME LIGHT OR CALM...
LOWS COULD BE SEVERAL DEGREES COLDER DEPENDING ON CLOUD COVER.

ANOTHER WEAK CLIPPER SYSTEM MOVES SOUTHEAST ACROSS THE WESTERN
LAKES MONDAY AFTERNOON INTO MONDAY NIGHT AS IT SLOWLY BEGINS TO
WEAKEN. MODELS VARY SOME ON TIMING AND PRECIP ARRIVAL. A CONSENSUS
WOULD HAVE THE ARRIVAL DURING MONDAY AFTERNOON. INITIALLY THE
SATURATION IS DEEP ENOUGH THAT PRECIP SHOULD BEGIN AS LIGHT SNOW.
BUT INTO THE EVENING...MID LEVELS BEGIN TO DRY OUT SOME AND PRECIP
COULD TRANSITION MORE TO A LIGHT SNOW MIXED WITH OR JUST FREEZING
DRIZZLE. FAIRLY LOW CONFIDENCE AT THIS POINT...SO MAINTAINED JUST
LIGHT SNOW FOR THE ENTIRE DURATION FOR NOW.

PROGRESSIVE PATTERN BRINGS ANOTHER RIDGE OF HIGH PRESSURE ACROSS
THE REGION TUESDAY NIGHT INTO WEDNESDAY AND THEN ANOTHER STORM
SYSTEM WEDNESDAY NIGHT INTO THURSDAY MORNING. MODELS CURRENTLY IN
DECENT AGREEMENT WITH THE TRACK OF THIS LOW GENERALLY RIGHT ACROSS
THE CWA EARLY THURSDAY MORNING. WITH THIS TRACK...TEMPS LIKELY TO
REMAIN FAIRLY STEADY IN THE LOWER/MID 30S WEDNESDAY NIGHT AND
THERMAL PROFILES WOULD SUGGEST PRECIP WOULD BE MAINLY RAIN OR
PERHAPS FREEZING RAIN...IF SURFACE TEMPS REMAINED BELOW FREEZING.
AND ALSO COULD BE SOME SNOW IF THE LOW WERE TO SPEED UP AND/OR
TRACK FURTHER SOUTH. THUS DID NOT GET TOO SPECIFIC WITH PRECIP
TYPE WEDNESDAY NIGHT INTO THURSDAY BUT A WINTRY MIX IS POSSIBLE.
CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* MVFR OR IFR CIGS LIKELY MOVE BACK IN LATER TONIGHT CONTINUE
  THROUGH SUNDAY EVENING
* SNOW DEVELOPS EARLY SUNDAY MORNING THE TAPERS OFF SUNDAY
  AFTERNOON...IFR VSBY LIKELY WITH PERIODIC LIFR POSSIBLE
* STRONG NE WINDS DEVELOP SUNDAY MORNING CONTINUE INTO EARLY
  SUNDAY EVENING...GUSTS TO 30KT AT TIMES SUNDAY LATE MORNING AND
  AFTERNOON

IZZI

//DISCUSSION...UPDATED 00Z...

LOW END MVFR/SPOTTY IFR CIGS SHOULD CLEAR EASTERN TERMINALS SOON
WITH IT LOOKING MORE LIKELY THAT VFR CONDITIONS WILL BE THE RULE
THIS EVENING. OVERNIGHT WINDS WILL TURN NORTHEAST AND SHOULD ALLOW
LOW END MVFR/HIGH END IFR CIGS TO SLOSH BACK SOUTH INTO THE AREA
OVERNIGHT WITH THE WIND SHIFT. SNOW IS STILL EXPECTED TO DEVELOP
AROUND OR JUST PRIOR TO SUNRISE AND CONTINUE THROUGH SUNDAY
MORNING BEFORE TAPERING OFF TO LIGHT NON-ACCUMULATING SNOW OR
FLURRIES DURING THE EARLY/MID AFTERNOON. AS SNOW ENDS CIGS SHOULD
LIFT AND COULD EVEN SCATTER OUT SUNDAY EVENING AS THE SYSTEM PULLS
QUICKLY AWAY FROM THE REGION. OTHER ISSUE IS EXPECTED TO BE THE
STRONG NORTHEAST WINDS THAT WILL DEVELOP SUNDAY MORNING AND
CONTINUE INTO THE AFTERNOON WITH GUSTS OF 25-30KT LOOKING QUITE
LIKELY FROM MID MORNING THROUGH LATE AFTERNOON SUNDAY.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* HIGH CONFIDENCE IN GENERAL CIG TRENDS THROUGH THE PERIOD BUT
  LOWER CONFIDENCE ON PRECISE TIMING OF CATEGORY CHANGES
* MEDIUM-HIGH CONFIDENCE IN WINDS
* MEDIUM CONFIDENCE IN SNOW AND RELATED VSBY TRENDS IN TAFS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...SLIGHT CHANCE -SN IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

IZZI

&&

.MARINE...
127 PM CST

A COLD FRONT WILL BEGIN TO SHIFT SOUTHWARD DOWN LAKE MICHIGAN LATE
THIS AFTERNOON...WITH WINDS EXPECTED TO PICK UP OUT OF THE NORTH
INTO TONIGHT. WINDS OVER THE LAKE WILL THEN CONTINUE TO INCREASE
INTO SUNDAY AS A QUICK MOVING CLIPPER SYSTEM TRACKS SOUTHEASTWARD
ACROSS SOUTHERN ILLINOIS. THIS WILL RESULT IN NORTHEASTERLY WINDS UP
TO 30 KT BY EARLY SUNDAY MORNING ACROSS MOST OF THE LAKE...WITH THE
STRONGEST WINDS EXPECTED ACROSS THE SOUTHERN END OF THE LAKE...WHERE
A FEW GALE FORCE GUSTS TO 35 KT ARE POSSIBLE ON SUNDAY. THIS WILL
RESULT IN WAVES UP TO 10 FEET INTO THE NORTHEAST ILLINOIS SHORES
THROUGH SUNDAY EVENING. THE WINDS WILL QUICKLY ABATE ACROSS THE LAKE
SUNDAY NIGHT AS THE LOW SHIFTS TOWARDS THE EASTERN SEABOARD.

ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD OVER OR JUST WEST OF THE
LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A PERIOD OF
LIGHT SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN THE
WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION. THIS
SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS WEDNESDAY NIGHT...FOLLOWED BY STRONG NORTHERLY WINDS
THURSDAY INTO FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 250301
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
901 PM CST SAT JAN 24 2015

.UPDATE...
900 PM CST

EVENING UPDATE...

HAVE UPDATED GRIDS TO REFLECT MUCH LOWER SNOWFALL AMOUNTS ON SUNDAY
TO THE NORTH OF INTERSTATE 80 AND ALSO SLOWED ARRIVAL OF
PRECIPITATION MAINLY TO EARLY TO MID SUNDAY MORNING. RADAR...SURFACE
ANALYSIS AND SATELLITE TRENDS SUPPORT THE NEW 00Z GUIDANCE AND
LATEST HIGHER RESOLUTION GUIDANCE ROLLING IN DIGGING THE 500 MB WAVE
FARTHER SOUTHWEST AND ASSOCIATED SURFACE LOW FARTHER SOUTHWEST AND
THEN SOUTH OF THE CWA.  NOW LOOKING AT GENERALLY AROUND A FEW TENTHS
TO UP TO AN INCH NORTH OF INTERSTATE 88...ONE TO TWO INCHES BETWEEN
I-88 AND I-80 AND ONE TO THREE INCHES SOUTH OF INTERSTATE 80. IF THE
FARTHER SOUTH TREND BECOMES MORE AGGRESSIVE AS THE SYSTEM APPROACHES
SUNDAY...THEN EVEN THESE AMOUNTS COULD END UP BEING TOO HIGH.
NAM/WRF AND OTHER HIGHER-RES GUIDANCE CONTINUES TO HINT AT LAKE
ENHANCEMENT DURING THE DAY SUNDAY INTO THE AFTERNOON INTO PARTS OF
NORTHEAST IL AND NW IN...BUT UNLESS FRICTIONAL CONVERGENCE CAN
ENHANCE RATES A BIT...THE THERMODYNAMICS AND INVERSION HEIGHTS ARE
VERY MARGINAL TO ACTUALLY ADD MUCH TO SNOW TOTALS.

REGARDING THE MIXED PRECIPITATION IN THE SOUTHERN CWA...THE
SOUTHWARD TREND AND DELAYED TIMING OF THE SYSTEM SHOULD ALLOW FOR
COLDER AIR TO BLEED SOUTHWARD AND SUPPRESS THE MIXING ZONE SOUTHWARD
FROM THE PREVIOUS FORECAST. ANY WINTRY MIX/RAIN SNOW MIX IN THE FAR
SOUTHERN CWA WILL LIKELY TRANSITION TO SNOW BY MID DAY/EARLY
AFTERNOON.

UPDATED ZONES WILL BE SENT SHORTLY.

RC/KREIN

&&

.SHORT TERM...
250 PM CST

THROUGH SUNDAY...

MAIN FORECAST CONCERN WILL BE PASSAGE OF A CLIPPER SYSTEM ACROSS THE
MIDWEST BRINGING ACCUMULATING SNOWFALL AND FOR SOME AREAS A WINTRY
MIX OF PRECIPITATION. CLOUD COVER WILL CONTINUE TO INCREASE THE
REMAINDER OF THE TODAY AS THE LOW DIVES ACROSS THE DAKOTAS INTO
MINNESOTA. MODELS ARE IN DECENT AGREEMENT TRACKING THE SURFACE LOW
ACROSS FAR NE MO LATE TONIGHT INTO DOWNSTATE IL BY SUNDAY AFTERNOON.
1000MB-700MB LAYER MAX WETBULBS ARE UP TO 2C SOUTH OF THE I-80
CORRIDOR THROUGH LATE MORNING/EARLY AFTERNOON SUNDAY...THEN START TO
FALL QUICKLY FROM THE NORTH THROUGH THE AFTERNOON HOURS. WITH THAT
IN MIND...THINK THAT PRECIP WILL BEGIN AS PRIMARILY SNOW NORTH OF
THE I-80 CORRIDOR WITH RAIN/SLEET TO THE SOUTH...EVENTUALLY CHANGING
OVER TO ALL SNOW. MODELS IN GENERAL HAVE THE AXIS OF HIGHEST QPF
SOUTH OF I-80...BUT WITH WARMER TEMPERATURES...IT APPEARS THE
HIGHEST SNOWFALL MAY OCCUR A LITTLE FARTHER NORTH. DID BUMP UP SNOW
TOTALS ACROSS PORTIONS OF THE CHICAGO METRO WHERE MODELS CONTINUE TO
ADVERTISE AN INCREASE IN THE LOW LEVEL LAPSE RATES AS WINDS TURN NE
OFF LAKE MICHIGAN WITH LAKE ENHANCEMENT APPEARING AT LEAST POSSIBLE.
NAM AND REGIONAL GEM GUIDANCE BOTH SHOW A SLIGHT MAX IN THE QPF
VALUES OVER THE AREA AND HAVE BEEN CONSISTENTLY ADVERTISING A BUMP IN
THE LOW LEVEL OMEGA STARTING LATE MORNING INTO THE AFTERNOON.
FORECAST SNOW TOTALS FOR THIS EVENT WILL BE 1-3 INCHES WEST OF A
WAUKEGAN TO STREATOR LINE...AND 2-4 INCHES EAST. WILL HAVE TO
MONITOR THE MESOSCALE BANDING THREAT FOR SOME LOCALLY HIGHER
AMOUNTS. NAM GUIDANCE IN PARTICULAR WAS HINTING AT AN AREA OF LOW
LEVEL FGEN DEVELOPING FOR EAST CENTRAL IL AND NORTHWEST
INDIANA...BUT LAPSE RATES UPSTAIRS ARENT OVERLY IMPRESSIVE IN THE
LATEST MODELS RUNS. ALSO SURFACE LOW SLOWLY FILLING AS IT MOVES
TOWARDS THE OHIO VALLEY WILL ALSO BE A LIMITING FACTOR. WILL ISSUE
AN UPDATED SPS THIS AFTERNOON FOR THE SNOWFALL. AS MENTIONED...STILL
CANNOT RULE OUT SOME LOCALLY HIGHER AMOUNTS THAT MIGHT REQUIRE AN
ADVISORY HOWEVER DONT HAVE MUCH CONFIDENCE WHERE OR EVEN IF THIS
WOULD OCCUR.

WINDS WILL START TO RAMP UP FROM EARLY MORNING ON OUT OF THE
NORTHEAST AS A TIGHT GRADIENT SWEEPS ACROSS THE REGION ON THE BACK
SIDE OF THE LOW. NORTHEAST WINDS ARE EXPECTED TO GUST 30-35 MPH AT
TIMES ACROSS THE AREA. THESE MODERATELY STRONG NORTHEAST WINDS OVER
LAKE MICHIGAN WILL DRIVE 8-11 FOOT WAVES INTO THE NEARSHORE WATERS
AND SOME OF THESE WAVES MAY RESULT IN SOME MINOR LAKE SHORE FLOODING
TO EXPOSED AREAS. IN ADDITION...BLOWING SNOW MAY BECOME A PROBLEM
ESPECIALLY IN OPEN AREAS. WETTER THAN AVERAGE SNOW...PARTICULARLY
SOUTH OF I-80 MAY HELP LIMIT THE BLOWING SNOW SOME.

DEUBELBEISS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE A CHANCE OF LIGHT SNOW MONDAY
AFTERNOON INTO MONDAY NIGHT AND THEN THE POTENTIAL FOR A WINTRY
MIX WEDNESDAY NIGHT.

LIGHT SNOW WILL BE ENDING ACROSS THE SOUTHEAST CWA SUNDAY EVENING
AS NORTHEAST WINDS STEADILY DIMINISH SUNDAY EVENING. LAKE EFFECT
CLOUDS AND PERHAPS A FEW FLURRIES ARE POSSIBLE SUNDAY EVENING. LOWS
BY MONDAY MORNING WILL DIP INTO THE TEENS MOST LOCATIONS BUT AS A
WEAK RIDGE PASSES ACROSS THE AREA AND WINDS BECOME LIGHT OR CALM...
LOWS COULD BE SEVERAL DEGREES COLDER DEPENDING ON CLOUD COVER.

ANOTHER WEAK CLIPPER SYSTEM MOVES SOUTHEAST ACROSS THE WESTERN
LAKES MONDAY AFTERNOON INTO MONDAY NIGHT AS IT SLOWLY BEGINS TO
WEAKEN. MODELS VARY SOME ON TIMING AND PRECIP ARRIVAL. A CONSENSUS
WOULD HAVE THE ARRIVAL DURING MONDAY AFTERNOON. INITIALLY THE
SATURATION IS DEEP ENOUGH THAT PRECIP SHOULD BEGIN AS LIGHT SNOW.
BUT INTO THE EVENING...MID LEVELS BEGIN TO DRY OUT SOME AND PRECIP
COULD TRANSITION MORE TO A LIGHT SNOW MIXED WITH OR JUST FREEZING
DRIZZLE. FAIRLY LOW CONFIDENCE AT THIS POINT...SO MAINTAINED JUST
LIGHT SNOW FOR THE ENTIRE DURATION FOR NOW.

PROGRESSIVE PATTERN BRINGS ANOTHER RIDGE OF HIGH PRESSURE ACROSS
THE REGION TUESDAY NIGHT INTO WEDNESDAY AND THEN ANOTHER STORM
SYSTEM WEDNESDAY NIGHT INTO THURSDAY MORNING. MODELS CURRENTLY IN
DECENT AGREEMENT WITH THE TRACK OF THIS LOW GENERALLY RIGHT ACROSS
THE CWA EARLY THURSDAY MORNING. WITH THIS TRACK...TEMPS LIKELY TO
REMAIN FAIRLY STEADY IN THE LOWER/MID 30S WEDNESDAY NIGHT AND
THERMAL PROFILES WOULD SUGGEST PRECIP WOULD BE MAINLY RAIN OR
PERHAPS FREEZING RAIN...IF SURFACE TEMPS REMAINED BELOW FREEZING.
AND ALSO COULD BE SOME SNOW IF THE LOW WERE TO SPEED UP AND/OR
TRACK FURTHER SOUTH. THUS DID NOT GET TOO SPECIFIC WITH PRECIP
TYPE WEDNESDAY NIGHT INTO THURSDAY BUT A WINTRY MIX IS POSSIBLE.
CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* MVFR OR IFR CIGS LIKELY MOVE BACK IN LATER TONIGHT CONTINUE
  THROUGH SUNDAY EVENING
* SNOW DEVELOPS EARLY SUNDAY MORNING THE TAPERS OFF SUNDAY
  AFTERNOON...IFR VSBY LIKELY WITH PERIODIC LIFR POSSIBLE
* STRONG NE WINDS DEVELOP SUNDAY MORNING CONTINUE INTO EARLY
  SUNDAY EVENING...GUSTS TO 30KT AT TIMES SUNDAY LATE MORNING AND
  AFTERNOON

IZZI

//DISCUSSION...UPDATED 00Z...

LOW END MVFR/SPOTTY IFR CIGS SHOULD CLEAR EASTERN TERMINALS SOON
WITH IT LOOKING MORE LIKELY THAT VFR CONDITIONS WILL BE THE RULE
THIS EVENING. OVERNIGHT WINDS WILL TURN NORTHEAST AND SHOULD ALLOW
LOW END MVFR/HIGH END IFR CIGS TO SLOSH BACK SOUTH INTO THE AREA
OVERNIGHT WITH THE WIND SHIFT. SNOW IS STILL EXPECTED TO DEVELOP
AROUND OR JUST PRIOR TO SUNRISE AND CONTINUE THROUGH SUNDAY
MORNING BEFORE TAPERING OFF TO LIGHT NON-ACCUMULATING SNOW OR
FLURRIES DURING THE EARLY/MID AFTERNOON. AS SNOW ENDS CIGS SHOULD
LIFT AND COULD EVEN SCATTER OUT SUNDAY EVENING AS THE SYSTEM PULLS
QUICKLY AWAY FROM THE REGION. OTHER ISSUE IS EXPECTED TO BE THE
STRONG NORTHEAST WINDS THAT WILL DEVELOP SUNDAY MORNING AND
CONTINUE INTO THE AFTERNOON WITH GUSTS OF 25-30KT LOOKING QUITE
LIKELY FROM MID MORNING THROUGH LATE AFTERNOON SUNDAY.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* HIGH CONFIDENCE IN GENERAL CIG TRENDS THROUGH THE PERIOD BUT
  LOWER CONFIDENCE ON PRECISE TIMING OF CATEGORY CHANGES
* MEDIUM-HIGH CONFIDENCE IN WINDS
* MEDIUM CONFIDENCE IN SNOW AND RELATED VSBY TRENDS IN TAFS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...SLIGHT CHANCE -SN IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

IZZI

&&

.MARINE...
127 PM CST

A COLD FRONT WILL BEGIN TO SHIFT SOUTHWARD DOWN LAKE MICHIGAN LATE
THIS AFTERNOON...WITH WINDS EXPECTED TO PICK UP OUT OF THE NORTH
INTO TONIGHT. WINDS OVER THE LAKE WILL THEN CONTINUE TO INCREASE
INTO SUNDAY AS A QUICK MOVING CLIPPER SYSTEM TRACKS SOUTHEASTWARD
ACROSS SOUTHERN ILLINOIS. THIS WILL RESULT IN NORTHEASTERLY WINDS UP
TO 30 KT BY EARLY SUNDAY MORNING ACROSS MOST OF THE LAKE...WITH THE
STRONGEST WINDS EXPECTED ACROSS THE SOUTHERN END OF THE LAKE...WHERE
A FEW GALE FORCE GUSTS TO 35 KT ARE POSSIBLE ON SUNDAY. THIS WILL
RESULT IN WAVES UP TO 10 FEET INTO THE NORTHEAST ILLINOIS SHORES
THROUGH SUNDAY EVENING. THE WINDS WILL QUICKLY ABATE ACROSS THE LAKE
SUNDAY NIGHT AS THE LOW SHIFTS TOWARDS THE EASTERN SEABOARD.

ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD OVER OR JUST WEST OF THE
LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A PERIOD OF
LIGHT SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN THE
WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION. THIS
SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS WEDNESDAY NIGHT...FOLLOWED BY STRONG NORTHERLY WINDS
THURSDAY INTO FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO








000
FXUS63 KLOT 250019
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
619 PM CST SAT JAN 24 2015

.SHORT TERM...
250 PM CST

THROUGH SUNDAY...

MAIN FORECAST CONCERN WILL BE PASSAGE OF A CLIPPER SYSTEM ACROSS THE
MIDWEST BRINGING ACCUMULATING SNOWFALL AND FOR SOME AREAS A WINTRY
MIX OF PRECIPITATION. CLOUD COVER WILL CONTINUE TO INCREASE THE
REMAINDER OF THE TODAY AS THE LOW DIVES ACROSS THE DAKOTAS INTO
MINNESOTA. MODELS ARE IN DECENT AGREEMENT TRACKING THE SURFACE LOW
ACROSS FAR NE MO LATE TONIGHT INTO DOWNSTATE IL BY SUNDAY AFTERNOON.
1000MB-700MB LAYER MAX WETBULBS ARE UP TO 2C SOUTH OF THE I-80
CORRIDOR THROUGH LATE MORNING/EARLY AFTERNOON SUNDAY...THEN START TO
FALL QUICKLY FROM THE NORTH THROUGH THE AFTERNOON HOURS. WITH THAT
IN MIND...THINK THAT PRECIP WILL BEGIN AS PRIMARILY SNOW NORTH OF
THE I-80 CORRIDOR WITH RAIN/SLEET TO THE SOUTH...EVENTUALLY CHANGING
OVER TO ALL SNOW. MODELS IN GENERAL HAVE THE AXIS OF HIGHEST QPF
SOUTH OF I-80...BUT WITH WARMER TEMPERATURES...IT APPEARS THE
HIGHEST SNOWFALL MAY OCCUR A LITTLE FARTHER NORTH. DID BUMP UP SNOW
TOTALS ACROSS PORTIONS OF THE CHICAGO METRO WHERE MODELS CONTINUE TO
ADVERTISE AN INCREASE IN THE LOW LEVEL LAPSE RATES AS WINDS TURN NE
OFF LAKE MICHIGAN WITH LAKE ENHANCEMENT APPEARING AT LEAST POSSIBLE.
NAM AND REGIONAL GEM GUIDANCE BOTH SHOW A SLIGHT MAX IN THE QPF
VALUES OVER THE AREA AND HAVE BEEN CONSISTENTLY ADVERTISING A BUMP IN
THE LOW LEVEL OMEGA STARTING LATE MORNING INTO THE AFTERNOON.
FORECAST SNOW TOTALS FOR THIS EVENT WILL BE 1-3 INCHES WEST OF A
WAUKEGAN TO STREATOR LINE...AND 2-4 INCHES EAST. WILL HAVE TO
MONITOR THE MESOSCALE BANDING THREAT FOR SOME LOCALLY HIGHER
AMOUNTS. NAM GUIDANCE IN PARTICULAR WAS HINTING AT AN AREA OF LOW
LEVEL FGEN DEVELOPING FOR EAST CENTRAL IL AND NORTHWEST
INDIANA...BUT LAPSE RATES UPSTAIRS ARENT OVERLY IMPRESSIVE IN THE
LATEST MODELS RUNS. ALSO SURFACE LOW SLOWLY FILLING AS IT MOVES
TOWARDS THE OHIO VALLEY WILL ALSO BE A LIMITING FACTOR. WILL ISSUE
AN UPDATED SPS THIS AFTERNOON FOR THE SNOWFALL. AS MENTIONED...STILL
CANNOT RULE OUT SOME LOCALLY HIGHER AMOUNTS THAT MIGHT REQUIRE AN
ADVISORY HOWEVER DONT HAVE MUCH CONFIDENCE WHERE OR EVEN IF THIS
WOULD OCCUR.

WINDS WILL START TO RAMP UP FROM EARLY MORNING ON OUT OF THE
NORTHEAST AS A TIGHT GRADIENT SWEEPS ACROSS THE REGION ON THE BACK
SIDE OF THE LOW. NORTHEAST WINDS ARE EXPECTED TO GUST 30-35 MPH AT
TIMES ACROSS THE AREA. THESE MODERATELY STRONG NORTHEAST WINDS OVER
LAKE MICHIGAN WILL DRIVE 8-11 FOOT WAVES INTO THE NEARSHORE WATERS
AND SOME OF THESE WAVES MAY RESULT IN SOME MINOR LAKE SHORE FLOODING
TO EXPOSED AREAS. IN ADDITION...BLOWING SNOW MAY BECOME A PROBLEM
ESPECIALLY IN OPEN AREAS. WETTER THAN AVERAGE SNOW...PARTICULARLY
SOUTH OF I-80 MAY HELP LIMIT THE BLOWING SNOW SOME.

DEUBELBEISS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE A CHANCE OF LIGHT SNOW MONDAY
AFTERNOON INTO MONDAY NIGHT AND THEN THE POTENTIAL FOR A WINTRY
MIX WEDNESDAY NIGHT.

LIGHT SNOW WILL BE ENDING ACROSS THE SOUTHEAST CWA SUNDAY EVENING
AS NORTHEAST WINDS STEADILY DIMINISH SUNDAY EVENING. LAKE EFFECT
CLOUDS AND PERHAPS A FEW FLURRIES ARE POSSIBLE SUNDAY EVENING. LOWS
BY MONDAY MORNING WILL DIP INTO THE TEENS MOST LOCATIONS BUT AS A
WEAK RIDGE PASSES ACROSS THE AREA AND WINDS BECOME LIGHT OR CALM...
LOWS COULD BE SEVERAL DEGREES COLDER DEPENDING ON CLOUD COVER.

ANOTHER WEAK CLIPPER SYSTEM MOVES SOUTHEAST ACROSS THE WESTERN
LAKES MONDAY AFTERNOON INTO MONDAY NIGHT AS IT SLOWLY BEGINS TO
WEAKEN. MODELS VARY SOME ON TIMING AND PRECIP ARRIVAL. A CONSENSUS
WOULD HAVE THE ARRIVAL DURING MONDAY AFTERNOON. INITIALLY THE
SATURATION IS DEEP ENOUGH THAT PRECIP SHOULD BEGIN AS LIGHT SNOW.
BUT INTO THE EVENING...MID LEVELS BEGIN TO DRY OUT SOME AND PRECIP
COULD TRANSITION MORE TO A LIGHT SNOW MIXED WITH OR JUST FREEZING
DRIZZLE. FAIRLY LOW CONFIDENCE AT THIS POINT...SO MAINTAINED JUST
LIGHT SNOW FOR THE ENTIRE DURATION FOR NOW.

PROGRESSIVE PATTERN BRINGS ANOTHER RIDGE OF HIGH PRESSURE ACROSS
THE REGION TUESDAY NIGHT INTO WEDNESDAY AND THEN ANOTHER STORM
SYSTEM WEDNESDAY NIGHT INTO THURSDAY MORNING. MODELS CURRENTLY IN
DECENT AGREEMENT WITH THE TRACK OF THIS LOW GENERALLY RIGHT ACROSS
THE CWA EARLY THURSDAY MORNING. WITH THIS TRACK...TEMPS LIKELY TO
REMAIN FAIRLY STEADY IN THE LOWER/MID 30S WEDNESDAY NIGHT AND
THERMAL PROFILES WOULD SUGGEST PRECIP WOULD BE MAINLY RAIN OR
PERHAPS FREEZING RAIN...IF SURFACE TEMPS REMAINED BELOW FREEZING.
AND ALSO COULD BE SOME SNOW IF THE LOW WERE TO SPEED UP AND/OR
TRACK FURTHER SOUTH. THUS DID NOT GET TOO SPECIFIC WITH PRECIP
TYPE WEDNESDAY NIGHT INTO THURSDAY BUT A WINTRY MIX IS POSSIBLE.
CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* MVFR OR IFR CIGS LIKELY MOVE BACK IN LATER TONIGHT CONTINUE
  THROUGH SUNDAY EVENING
* SNOW DEVELOPS EARLY SUNDAY MORNING THE TAPERS OFF SUNDAY
  AFTERNOON...IFR VSBY LIKELY WITH PERIODIC LIFR POSSIBLE
* STRONG NE WINDS DEVELOP SUNDAY MORNING CONTINUE INTO EARLY
  SUNDAY EVENING...GUSTS TO 30KT AT TIMES SUNDAY LATE MORNING AND
  AFTERNOON

IZZI

//DISCUSSION...UPDATED 00Z...

LOW END MVFR/SPOTTY IFR CIGS SHOULD CLEAR EASTERN TERMINALS SOON
WITH IT LOOKING MORE LIKELY THAT VFR CONDITIONS WILL BE THE RULE
THIS EVENING. OVERNIGHT WINDS WILL TURN NORTHEAST AND SHOULD ALLOW
LOW END MVFR/HIGH END IFR CIGS TO SLOSH BACK SOUTH INTO THE AREA
OVERNIGHT WITH THE WIND SHIFT. SNOW IS STILL EXPECTED TO DEVELOP
AROUND OR JUST PRIOR TO SUNRISE AND CONTINUE THROUGH SUNDAY
MORNING BEFORE TAPERING OFF TO LIGHT NON-ACCUMULATING SNOW OR
FLURRIES DURING THE EARLY/MID AFTERNOON. AS SNOW ENDS CIGS SHOULD
LIFT AND COULD EVEN SCATTER OUT SUNDAY EVENING AS THE SYSTEM PULLS
QUICKLY AWAY FROM THE REGION. OTHER ISSUE IS EXPECTED TO BE THE
STRONG NORTHEAST WINDS THAT WILL DEVELOP SUNDAY MORNING AND
CONTINUE INTO THE AFTERNOON WITH GUSTS OF 25-30KT LOOKING QUITE
LIKELY FROM MID MORNING THROUGH LATE AFTERNOON SUNDAY.

IZZI


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* HIGH CONFIDENCE IN GENERAL CIG TRENDS THROUGH THE PERIOD BUT
  LOWER CONFIDENCE ON PRECISE TIMING OF CATEGORY CHANGES
* MEDIUM-HIGH CONFIDENCE IN WINDS
* MEDIUM CONFIDENCE IN SNOW AND RELATED VSBY TRENDS IN TAFS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...SLIGHT CHANCE -SN IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

IZZI

&&

.MARINE...
127 PM CST

A COLD FRONT WILL BEGIN TO SHIFT SOUTHWARD DOWN LAKE MICHIGAN LATE
THIS AFTERNOON...WITH WINDS EXPECTED TO PICK UP OUT OF THE NORTH
INTO TONIGHT. WINDS OVER THE LAKE WILL THEN CONTINUE TO INCREASE
INTO SUNDAY AS A QUICK MOVING CLIPPER SYSTEM TRACKS SOUTHEASTWARD
ACROSS SOUTHERN ILLINOIS. THIS WILL RESULT IN NORTHEASTERLY WINDS UP
TO 30 KT BY EARLY SUNDAY MORNING ACROSS MOST OF THE LAKE...WITH THE
STRONGEST WINDS EXPECTED ACROSS THE SOUTHERN END OF THE LAKE...WHERE
A FEW GALE FORCE GUSTS TO 35 KT ARE POSSIBLE ON SUNDAY. THIS WILL
RESULT IN WAVES UP TO 10 FEET INTO THE NORTHEAST ILLINOIS SHORES
THROUGH SUNDAY EVENING. THE WINDS WILL QUICKLY ABATE ACROSS THE LAKE
SUNDAY NIGHT AS THE LOW SHIFTS TOWARDS THE EASTERN SEABOARD.

ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD OVER OR JUST WEST OF THE
LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A PERIOD OF
LIGHT SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN THE
WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION. THIS
SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS WEDNESDAY NIGHT...FOLLOWED BY STRONG NORTHERLY WINDS
THURSDAY INTO FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 250019
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
619 PM CST SAT JAN 24 2015

.SHORT TERM...
250 PM CST

THROUGH SUNDAY...

MAIN FORECAST CONCERN WILL BE PASSAGE OF A CLIPPER SYSTEM ACROSS THE
MIDWEST BRINGING ACCUMULATING SNOWFALL AND FOR SOME AREAS A WINTRY
MIX OF PRECIPITATION. CLOUD COVER WILL CONTINUE TO INCREASE THE
REMAINDER OF THE TODAY AS THE LOW DIVES ACROSS THE DAKOTAS INTO
MINNESOTA. MODELS ARE IN DECENT AGREEMENT TRACKING THE SURFACE LOW
ACROSS FAR NE MO LATE TONIGHT INTO DOWNSTATE IL BY SUNDAY AFTERNOON.
1000MB-700MB LAYER MAX WETBULBS ARE UP TO 2C SOUTH OF THE I-80
CORRIDOR THROUGH LATE MORNING/EARLY AFTERNOON SUNDAY...THEN START TO
FALL QUICKLY FROM THE NORTH THROUGH THE AFTERNOON HOURS. WITH THAT
IN MIND...THINK THAT PRECIP WILL BEGIN AS PRIMARILY SNOW NORTH OF
THE I-80 CORRIDOR WITH RAIN/SLEET TO THE SOUTH...EVENTUALLY CHANGING
OVER TO ALL SNOW. MODELS IN GENERAL HAVE THE AXIS OF HIGHEST QPF
SOUTH OF I-80...BUT WITH WARMER TEMPERATURES...IT APPEARS THE
HIGHEST SNOWFALL MAY OCCUR A LITTLE FARTHER NORTH. DID BUMP UP SNOW
TOTALS ACROSS PORTIONS OF THE CHICAGO METRO WHERE MODELS CONTINUE TO
ADVERTISE AN INCREASE IN THE LOW LEVEL LAPSE RATES AS WINDS TURN NE
OFF LAKE MICHIGAN WITH LAKE ENHANCEMENT APPEARING AT LEAST POSSIBLE.
NAM AND REGIONAL GEM GUIDANCE BOTH SHOW A SLIGHT MAX IN THE QPF
VALUES OVER THE AREA AND HAVE BEEN CONSISTENTLY ADVERTISING A BUMP IN
THE LOW LEVEL OMEGA STARTING LATE MORNING INTO THE AFTERNOON.
FORECAST SNOW TOTALS FOR THIS EVENT WILL BE 1-3 INCHES WEST OF A
WAUKEGAN TO STREATOR LINE...AND 2-4 INCHES EAST. WILL HAVE TO
MONITOR THE MESOSCALE BANDING THREAT FOR SOME LOCALLY HIGHER
AMOUNTS. NAM GUIDANCE IN PARTICULAR WAS HINTING AT AN AREA OF LOW
LEVEL FGEN DEVELOPING FOR EAST CENTRAL IL AND NORTHWEST
INDIANA...BUT LAPSE RATES UPSTAIRS ARENT OVERLY IMPRESSIVE IN THE
LATEST MODELS RUNS. ALSO SURFACE LOW SLOWLY FILLING AS IT MOVES
TOWARDS THE OHIO VALLEY WILL ALSO BE A LIMITING FACTOR. WILL ISSUE
AN UPDATED SPS THIS AFTERNOON FOR THE SNOWFALL. AS MENTIONED...STILL
CANNOT RULE OUT SOME LOCALLY HIGHER AMOUNTS THAT MIGHT REQUIRE AN
ADVISORY HOWEVER DONT HAVE MUCH CONFIDENCE WHERE OR EVEN IF THIS
WOULD OCCUR.

WINDS WILL START TO RAMP UP FROM EARLY MORNING ON OUT OF THE
NORTHEAST AS A TIGHT GRADIENT SWEEPS ACROSS THE REGION ON THE BACK
SIDE OF THE LOW. NORTHEAST WINDS ARE EXPECTED TO GUST 30-35 MPH AT
TIMES ACROSS THE AREA. THESE MODERATELY STRONG NORTHEAST WINDS OVER
LAKE MICHIGAN WILL DRIVE 8-11 FOOT WAVES INTO THE NEARSHORE WATERS
AND SOME OF THESE WAVES MAY RESULT IN SOME MINOR LAKE SHORE FLOODING
TO EXPOSED AREAS. IN ADDITION...BLOWING SNOW MAY BECOME A PROBLEM
ESPECIALLY IN OPEN AREAS. WETTER THAN AVERAGE SNOW...PARTICULARLY
SOUTH OF I-80 MAY HELP LIMIT THE BLOWING SNOW SOME.

DEUBELBEISS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE A CHANCE OF LIGHT SNOW MONDAY
AFTERNOON INTO MONDAY NIGHT AND THEN THE POTENTIAL FOR A WINTRY
MIX WEDNESDAY NIGHT.

LIGHT SNOW WILL BE ENDING ACROSS THE SOUTHEAST CWA SUNDAY EVENING
AS NORTHEAST WINDS STEADILY DIMINISH SUNDAY EVENING. LAKE EFFECT
CLOUDS AND PERHAPS A FEW FLURRIES ARE POSSIBLE SUNDAY EVENING. LOWS
BY MONDAY MORNING WILL DIP INTO THE TEENS MOST LOCATIONS BUT AS A
WEAK RIDGE PASSES ACROSS THE AREA AND WINDS BECOME LIGHT OR CALM...
LOWS COULD BE SEVERAL DEGREES COLDER DEPENDING ON CLOUD COVER.

ANOTHER WEAK CLIPPER SYSTEM MOVES SOUTHEAST ACROSS THE WESTERN
LAKES MONDAY AFTERNOON INTO MONDAY NIGHT AS IT SLOWLY BEGINS TO
WEAKEN. MODELS VARY SOME ON TIMING AND PRECIP ARRIVAL. A CONSENSUS
WOULD HAVE THE ARRIVAL DURING MONDAY AFTERNOON. INITIALLY THE
SATURATION IS DEEP ENOUGH THAT PRECIP SHOULD BEGIN AS LIGHT SNOW.
BUT INTO THE EVENING...MID LEVELS BEGIN TO DRY OUT SOME AND PRECIP
COULD TRANSITION MORE TO A LIGHT SNOW MIXED WITH OR JUST FREEZING
DRIZZLE. FAIRLY LOW CONFIDENCE AT THIS POINT...SO MAINTAINED JUST
LIGHT SNOW FOR THE ENTIRE DURATION FOR NOW.

PROGRESSIVE PATTERN BRINGS ANOTHER RIDGE OF HIGH PRESSURE ACROSS
THE REGION TUESDAY NIGHT INTO WEDNESDAY AND THEN ANOTHER STORM
SYSTEM WEDNESDAY NIGHT INTO THURSDAY MORNING. MODELS CURRENTLY IN
DECENT AGREEMENT WITH THE TRACK OF THIS LOW GENERALLY RIGHT ACROSS
THE CWA EARLY THURSDAY MORNING. WITH THIS TRACK...TEMPS LIKELY TO
REMAIN FAIRLY STEADY IN THE LOWER/MID 30S WEDNESDAY NIGHT AND
THERMAL PROFILES WOULD SUGGEST PRECIP WOULD BE MAINLY RAIN OR
PERHAPS FREEZING RAIN...IF SURFACE TEMPS REMAINED BELOW FREEZING.
AND ALSO COULD BE SOME SNOW IF THE LOW WERE TO SPEED UP AND/OR
TRACK FURTHER SOUTH. THUS DID NOT GET TOO SPECIFIC WITH PRECIP
TYPE WEDNESDAY NIGHT INTO THURSDAY BUT A WINTRY MIX IS POSSIBLE.
CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* MVFR OR IFR CIGS LIKELY MOVE BACK IN LATER TONIGHT CONTINUE
  THROUGH SUNDAY EVENING
* SNOW DEVELOPS EARLY SUNDAY MORNING THE TAPERS OFF SUNDAY
  AFTERNOON...IFR VSBY LIKELY WITH PERIODIC LIFR POSSIBLE
* STRONG NE WINDS DEVELOP SUNDAY MORNING CONTINUE INTO EARLY
  SUNDAY EVENING...GUSTS TO 30KT AT TIMES SUNDAY LATE MORNING AND
  AFTERNOON

IZZI

//DISCUSSION...UPDATED 00Z...

LOW END MVFR/SPOTTY IFR CIGS SHOULD CLEAR EASTERN TERMINALS SOON
WITH IT LOOKING MORE LIKELY THAT VFR CONDITIONS WILL BE THE RULE
THIS EVENING. OVERNIGHT WINDS WILL TURN NORTHEAST AND SHOULD ALLOW
LOW END MVFR/HIGH END IFR CIGS TO SLOSH BACK SOUTH INTO THE AREA
OVERNIGHT WITH THE WIND SHIFT. SNOW IS STILL EXPECTED TO DEVELOP
AROUND OR JUST PRIOR TO SUNRISE AND CONTINUE THROUGH SUNDAY
MORNING BEFORE TAPERING OFF TO LIGHT NON-ACCUMULATING SNOW OR
FLURRIES DURING THE EARLY/MID AFTERNOON. AS SNOW ENDS CIGS SHOULD
LIFT AND COULD EVEN SCATTER OUT SUNDAY EVENING AS THE SYSTEM PULLS
QUICKLY AWAY FROM THE REGION. OTHER ISSUE IS EXPECTED TO BE THE
STRONG NORTHEAST WINDS THAT WILL DEVELOP SUNDAY MORNING AND
CONTINUE INTO THE AFTERNOON WITH GUSTS OF 25-30KT LOOKING QUITE
LIKELY FROM MID MORNING THROUGH LATE AFTERNOON SUNDAY.

IZZI


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* HIGH CONFIDENCE IN GENERAL CIG TRENDS THROUGH THE PERIOD BUT
  LOWER CONFIDENCE ON PRECISE TIMING OF CATEGORY CHANGES
* MEDIUM-HIGH CONFIDENCE IN WINDS
* MEDIUM CONFIDENCE IN SNOW AND RELATED VSBY TRENDS IN TAFS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...SLIGHT CHANCE -SN IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR DURING THE DAY THEN CHANCE OF -RASN AND
MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS.

IZZI

&&

.MARINE...
127 PM CST

A COLD FRONT WILL BEGIN TO SHIFT SOUTHWARD DOWN LAKE MICHIGAN LATE
THIS AFTERNOON...WITH WINDS EXPECTED TO PICK UP OUT OF THE NORTH
INTO TONIGHT. WINDS OVER THE LAKE WILL THEN CONTINUE TO INCREASE
INTO SUNDAY AS A QUICK MOVING CLIPPER SYSTEM TRACKS SOUTHEASTWARD
ACROSS SOUTHERN ILLINOIS. THIS WILL RESULT IN NORTHEASTERLY WINDS UP
TO 30 KT BY EARLY SUNDAY MORNING ACROSS MOST OF THE LAKE...WITH THE
STRONGEST WINDS EXPECTED ACROSS THE SOUTHERN END OF THE LAKE...WHERE
A FEW GALE FORCE GUSTS TO 35 KT ARE POSSIBLE ON SUNDAY. THIS WILL
RESULT IN WAVES UP TO 10 FEET INTO THE NORTHEAST ILLINOIS SHORES
THROUGH SUNDAY EVENING. THE WINDS WILL QUICKLY ABATE ACROSS THE LAKE
SUNDAY NIGHT AS THE LOW SHIFTS TOWARDS THE EASTERN SEABOARD.

ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD OVER OR JUST WEST OF THE
LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A PERIOD OF
LIGHT SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN THE
WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION. THIS
SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS WEDNESDAY NIGHT...FOLLOWED BY STRONG NORTHERLY WINDS
THURSDAY INTO FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 242052
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
252 PM CST SAT JAN 24 2015

.SHORT TERM...
250 PM CST

THROUGH SUNDAY...

MAIN FORECAST CONCERN WILL BE PASSAGE OF A CLIPPER SYSTEM ACROSS THE
MIDWEST BRINGING ACCUMULATING SNOWFALL AND FOR SOME AREAS A WINTRY
MIX OF PRECIPITATION. CLOUD COVER WILL CONTINUE TO INCREASE THE
REMAINDER OF THE TODAY AS THE LOW DIVES ACROSS THE DAKOTAS INTO
MINNESOTA. MODELS ARE IN DECENT AGREEMENT TRACKING THE SURFACE LOW
ACROSS FAR NE MO LATE TONIGHT INTO DOWNSTATE IL BY SUNDAY AFTERNOON.
1000MB-700MB LAYER MAX WETBULBS ARE UP TO 2C SOUTH OF THE I-80
CORRIDOR THROUGH LATE MORNING/EARLY AFTERNOON SUNDAY...THEN START TO
FALL QUICKLY FROM THE NORTH THROUGH THE AFTERNOON HOURS. WITH THAT
IN MIND...THINK THAT PRECIP WILL BEGIN AS PRIMARILY SNOW NORTH OF
THE I-80 CORRIDOR WITH RAIN/SLEET TO THE SOUTH...EVENTUALLY CHANGING
OVER TO ALL SNOW. MODELS IN GENERAL HAVE THE AXIS OF HIGHEST QPF
SOUTH OF I-80...BUT WITH WARMER TEMPERATURES...IT APPEARS THE
HIGHEST SNOWFALL MAY OCCUR A LITTLE FARTHER NORTH. DID BUMP UP SNOW
TOTALS ACROSS PORTIONS OF THE CHICAGO METRO WHERE MODELS CONTINUE TO
ADVERTISE AN INCREASE IN THE LOW LEVEL LAPSE RATES AS WINDS TURN NE
OFF LAKE MICHIGAN WITH LAKE ENHANCEMENT APPEARING AT LEAST POSSIBLE.
NAM AND REGIONAL GEM GUIDANCE BOTH SHOW A SLIGHT MAX IN THE QPF
VALUES OVER THE AREA AND HAVE BEEN CONSISTENTLY ADVERTISING A BUMP IN
THE LOW LEVEL OMEGA STARTING LATE MORNING INTO THE AFTERNOON.
FORECAST SNOW TOTALS FOR THIS EVENT WILL BE 1-3 INCHES WEST OF A
WAUKEGAN TO STREATOR LINE...AND 2-4 INCHES EAST. WILL HAVE TO
MONITOR THE MESOSCALE BANDING THREAT FOR SOME LOCALLY HIGHER
AMOUNTS. NAM GUIDANCE IN PARTICULAR WAS HINTING AT AN AREA OF LOW
LEVEL FGEN DEVELOPING FOR EAST CENTRAL IL AND NORTHWEST
INDIANA...BUT LAPSE RATES UPSTAIRS ARENT OVERLY IMPRESSIVE IN THE
LATEST MODELS RUNS. ALSO SURFACE LOW SLOWLY FILLING AS IT MOVES
TOWARDS THE OHIO VALLEY WILL ALSO BE A LIMITING FACTOR. WILL ISSUE
AN UPDATED SPS THIS AFTERNOON FOR THE SNOWFALL. AS MENTIONED...STILL
CANNOT RULE OUT SOME LOCALLY HIGHER AMOUNTS THAT MIGHT REQUIRE AN
ADVISORY HOWEVER DONT HAVE MUCH CONFIDENCE WHERE OR EVEN IF THIS
WOULD OCCUR.

WINDS WILL START TO RAMP UP FROM EARLY MORNING ON OUT OF THE
NORTHEAST AS A TIGHT GRADIENT SWEEPS ACROSS THE REGION ON THE BACK
SIDE OF THE LOW. NORTHEAST WINDS ARE EXPECTED TO GUST 30-35 MPH AT
TIMES ACROSS THE AREA. THESE MODERATELY STRONG NORTHEAST WINDS OVER
LAKE MICHIGAN WILL DRIVE 8-11 FOOT WAVES INTO THE NEARSHORE WATERS
AND SOME OF THESE WAVES MAY RESULT IN SOME MINOR LAKESHORE FLOODING
TO EXPOSED AREAS. IN ADDITION...BLOWING SNOW MAY BECOME A PROBLEM
ESPECIALLY IN OPEN AREAS. WETTER THAN AVERAGE SNOW...PARTICULARLY
SOUTH OF I-80 MAY HELP LIMIT THE BLOWING SNOW SOME.

DEUBELBEISS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE A CHANCE OF LIGHT SNOW MONDAY
AFTERNOON INTO MONDAY NIGHT AND THEN THE POTENTIAL FOR A WINTRY
MIX WEDNESDAY NIGHT.

LIGHT SNOW WILL BE ENDING ACROSS THE SOUTHEAST CWA SUNDAY EVENING
AS NORTHEAST WINDS STEADILY DIMINISH SUNDAY EVENING. LAKE EFFECT
CLOUDS AND PERHAPS A FEW FLURRIES ARE POSSIBLE SUNDAY EVENING. LOWS
BY MONDAY MORNING WILL DIP INTO THE TEENS MOST LOCATIONS BUT AS A
WEAK RIDGE PASSES ACROSS THE AREA AND WINDS BECOME LIGHT OR CALM...
LOWS COULD BE SEVERAL DEGREES COLDER DEPENDING ON CLOUD COVER.

ANOTHER WEAK CLIPPER SYSTEM MOVES SOUTHEAST ACROSS THE WESTERN
LAKES MONDAY AFTERNOON INTO MONDAY NIGHT AS IT SLOWLY BEGINS TO
WEAKEN. MODELS VARY SOME ON TIMING AND PRECIP ARRIVAL. A CONSENSUS
WOULD HAVE THE ARRIVAL DURING MONDAY AFTERNOON. INITIALLY THE
SATURATION IS DEEP ENOUGH THAT PRECIP SHOULD BEGIN AS LIGHT SNOW.
BUT INTO THE EVENING...MID LEVELS BEGIN TO DRY OUT SOME AND PRECIP
COULD TRANSITION MORE TO A LIGHT SNOW MIXED WITH OR JUST FREEZING
DRIZZLE. FAIRLY LOW CONFIDENCE AT THIS POINT...SO MAINTAINED JUST
LIGHT SNOW FOR THE ENTIRE DURATION FOR NOW.

PROGRESSIVE PATTERN BRINGS ANOTHER RIDGE OF HIGH PRESSURE ACROSS
THE REGION TUESDAY NIGHT INTO WEDNESDAY AND THEN ANOTHER STORM
SYSTEM WEDNESDAY NIGHT INTO THURSDAY MORNING. MODELS CURRENTLY IN
DECENT AGREEMENT WITH THE TRACK OF THIS LOW GENERALLY RIGHT ACROSS
THE CWA EARLY THURSDAY MORNING. WITH THIS TRACK...TEMPS LIKELY TO
REMAIN FAIRLY STEADY IN THE LOWER/MID 30S WEDNESDAY NIGHT AND
THERMAL PROFILES WOULD SUGGEST PRECIP WOULD BE MAINLY RAIN OR
PERHAPS FREEZING RAIN...IF SURFACE TEMPS REMAINED BELOW FREEZING.
AND ALSO COULD BE SOME SNOW IF THE LOW WERE TO SPEED UP AND/OR
TRACK FURTHER SOUTH. THUS DID NOT GET TOO SPECIFIC WITH PRECIP
TYPE WEDNESDAY NIGHT INTO THURSDAY BUT A WINTRY MIX IS POSSIBLE.
CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* MVFR CIGS WILL LOWER TOWARDS 700-1000FT AGL ARND 21Z THEN
  POSSIBLY DIP FURTHER TO NEAR 400-600FT AFT 6Z.

* WEST WINDS ARND 5-10KT...QUICKLY SHIFTING EAST AFTER MIDNIGHT
  AND INCREASING TO 10-18KT GUSTS TO 25KT BY DAYBREAK SUN. GUSTS
  INCREASE TOWARDS 30KT SUN MORNING.

* SNOW DEVELOPS JUST BEFORE DAYBREAK SUN...WITH PEAK TIMING
  BETWEEN 14-17Z FROM PERIODS OF STEADIER SNOW. CIGS WILL LOWER
  TOWARDS IFR CONDS WITH POSSIBLE IFR VSBYS FROM STEADY SNOW.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY INDICATES SOME CLEARING HAS TAKEN PLACE LATE THIS
MORNING ACROSS NORTHEAST IL/NORTHWEST IN...HOWEVER THERE IS A
WEDGE OF MVFR CIGS STARTING TO CREEP SOUTHEAST ACROSS NORTHWEST
IL. GUIDANCE AND TIMING WOULD INDICATE THE MVFR CIGS RETURNING TO
ORD/MDW ARND 19Z. THEN THE FOCUS WILL TURN TOWARDS THE APPROACHING
WINTER STORM SYSTEM. GUIDANCE CONTINUES TO SHIFT THE TRACK OF THE
SYSTEM FURTHER SOUTH/SOUTHWEST OF CHICAGO. THIS WILL LIKELY
DICTATE WHERE THE STEADIER/TIMING OF SNOW WILL OCCUR SUN MORNING.
AT THIS TIME HAVE ONLY MADE MINOR ADJUSTMENTS TO THE GOING
FORECAST...WITH SNOW DEVELOPING AFTER MIDNIGHT. POSSIBLY SEEING
REDUCED VSBYS FROM STEADIER SNOW BETWEEN 13-17Z. AS THE LOW PASSES
TO THE SOUTH...THE PRESSURE GRADIENT WILL RAPIDLY INCREASE ALONG
THE NORTHERN TIER OR NEAR THE TAF SITES. THIS WILL RESULT IN A
QUICK SHIFT TO EAST WINDS AND GUSTS APPROACHING 20KT ARND
DAYBREAK...THEN INCREASING TO NEAR 30KT BY MID TO LATE MORNING.

IFR CIGS WILL REMAIN ACROSS THE TAF SITES INTO SUN MIDDAY...THEN
SOME DRIER AIR WILL BEGIN TO FILTER INTO THE REGION AND BRING CIGS
BACK TO MVFR LATE SUN AFTN.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN CIGS RETURNING TO MVFR CONDS...MEDIUM
  CONFIDENCE IN PRECISE TIMING OF MVFR CIGS.

* MEDIUM CONFIDENCE IN IFR CIGS DEVELOPING THIS AFTN...ALONG WITH
  DURATION OF IFR CIGS.

* MEDIUM CONFIDENCE IN TIMING OF CIGS LOWERING FURTHER TO IFR
  CONDS LATER TONIGHT.

* HIGH CONFIDENCE IN SNOW DEVELOPING AFTER MIDNIGHT...MEDIUM
  CONFIDENCE IN PRECISE TIMING OF STEADIER SNOW BETWEEN 13-17Z.

* HIGH CONFIDENCE IN WINDS QUICKLY TURNING EAST AND GUSTS
  DEVELOPING.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...MVFR CIGS POSSIBLE.

MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR...CHANCE OF SNOW AND MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR/IFR POSSIBLE.

FRIDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
127 PM CST

A COLD FRONT WILL BEGIN TO SHIFT SOUTHWARD DOWN LAKE MICHIGAN LATE
THIS AFTERNOON...WITH WINDS EXPECTED TO PICK UP OUT OF THE NORTH
INTO TONIGHT. WINDS OVER THE LAKE WILL THEN CONTINUE TO INCREASE
INTO SUNDAY AS A QUICK MOVING CLIPPER SYSTEM TRACKS SOUTHEASTWARD
ACROSS SOUTHERN ILLINOIS. THIS WILL RESULT IN NORTHEASTERLY WINDS UP
TO 30 KT BY EARLY SUNDAY MORNING ACROSS MOST OF THE LAKE...WITH THE
STRONGEST WINDS EXPECTED ACROSS THE SOUTHERN END OF THE LAKE...WHERE
A FEW GALE FORCE GUSTS TO 35 KT ARE POSSIBLE ON SUNDAY. THIS WILL
RESULT IN WAVES UP TO 10 FEET INTO THE NORTHEAST ILLINOIS SHORES
THROUGH SUNDAY EVENING. THE WINDS WILL QUICKLY ABATE ACROSS THE LAKE
SUNDAY NIGHT AS THE LOW SHIFTS TOWARDS THE EASTERN SEABOARD.

ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD OVER OR JUST WEST OF THE
LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A PERIOD OF
LIGHT SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN THE
WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION. THIS
SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS WEDNESDAY NIGHT...FOLLOWED BY STRONG NORTHERLY WINDS
THURSDAY INTO FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 242052
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
252 PM CST SAT JAN 24 2015

.SHORT TERM...
250 PM CST

THROUGH SUNDAY...

MAIN FORECAST CONCERN WILL BE PASSAGE OF A CLIPPER SYSTEM ACROSS THE
MIDWEST BRINGING ACCUMULATING SNOWFALL AND FOR SOME AREAS A WINTRY
MIX OF PRECIPITATION. CLOUD COVER WILL CONTINUE TO INCREASE THE
REMAINDER OF THE TODAY AS THE LOW DIVES ACROSS THE DAKOTAS INTO
MINNESOTA. MODELS ARE IN DECENT AGREEMENT TRACKING THE SURFACE LOW
ACROSS FAR NE MO LATE TONIGHT INTO DOWNSTATE IL BY SUNDAY AFTERNOON.
1000MB-700MB LAYER MAX WETBULBS ARE UP TO 2C SOUTH OF THE I-80
CORRIDOR THROUGH LATE MORNING/EARLY AFTERNOON SUNDAY...THEN START TO
FALL QUICKLY FROM THE NORTH THROUGH THE AFTERNOON HOURS. WITH THAT
IN MIND...THINK THAT PRECIP WILL BEGIN AS PRIMARILY SNOW NORTH OF
THE I-80 CORRIDOR WITH RAIN/SLEET TO THE SOUTH...EVENTUALLY CHANGING
OVER TO ALL SNOW. MODELS IN GENERAL HAVE THE AXIS OF HIGHEST QPF
SOUTH OF I-80...BUT WITH WARMER TEMPERATURES...IT APPEARS THE
HIGHEST SNOWFALL MAY OCCUR A LITTLE FARTHER NORTH. DID BUMP UP SNOW
TOTALS ACROSS PORTIONS OF THE CHICAGO METRO WHERE MODELS CONTINUE TO
ADVERTISE AN INCREASE IN THE LOW LEVEL LAPSE RATES AS WINDS TURN NE
OFF LAKE MICHIGAN WITH LAKE ENHANCEMENT APPEARING AT LEAST POSSIBLE.
NAM AND REGIONAL GEM GUIDANCE BOTH SHOW A SLIGHT MAX IN THE QPF
VALUES OVER THE AREA AND HAVE BEEN CONSISTENTLY ADVERTISING A BUMP IN
THE LOW LEVEL OMEGA STARTING LATE MORNING INTO THE AFTERNOON.
FORECAST SNOW TOTALS FOR THIS EVENT WILL BE 1-3 INCHES WEST OF A
WAUKEGAN TO STREATOR LINE...AND 2-4 INCHES EAST. WILL HAVE TO
MONITOR THE MESOSCALE BANDING THREAT FOR SOME LOCALLY HIGHER
AMOUNTS. NAM GUIDANCE IN PARTICULAR WAS HINTING AT AN AREA OF LOW
LEVEL FGEN DEVELOPING FOR EAST CENTRAL IL AND NORTHWEST
INDIANA...BUT LAPSE RATES UPSTAIRS ARENT OVERLY IMPRESSIVE IN THE
LATEST MODELS RUNS. ALSO SURFACE LOW SLOWLY FILLING AS IT MOVES
TOWARDS THE OHIO VALLEY WILL ALSO BE A LIMITING FACTOR. WILL ISSUE
AN UPDATED SPS THIS AFTERNOON FOR THE SNOWFALL. AS MENTIONED...STILL
CANNOT RULE OUT SOME LOCALLY HIGHER AMOUNTS THAT MIGHT REQUIRE AN
ADVISORY HOWEVER DONT HAVE MUCH CONFIDENCE WHERE OR EVEN IF THIS
WOULD OCCUR.

WINDS WILL START TO RAMP UP FROM EARLY MORNING ON OUT OF THE
NORTHEAST AS A TIGHT GRADIENT SWEEPS ACROSS THE REGION ON THE BACK
SIDE OF THE LOW. NORTHEAST WINDS ARE EXPECTED TO GUST 30-35 MPH AT
TIMES ACROSS THE AREA. THESE MODERATELY STRONG NORTHEAST WINDS OVER
LAKE MICHIGAN WILL DRIVE 8-11 FOOT WAVES INTO THE NEARSHORE WATERS
AND SOME OF THESE WAVES MAY RESULT IN SOME MINOR LAKESHORE FLOODING
TO EXPOSED AREAS. IN ADDITION...BLOWING SNOW MAY BECOME A PROBLEM
ESPECIALLY IN OPEN AREAS. WETTER THAN AVERAGE SNOW...PARTICULARLY
SOUTH OF I-80 MAY HELP LIMIT THE BLOWING SNOW SOME.

DEUBELBEISS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE A CHANCE OF LIGHT SNOW MONDAY
AFTERNOON INTO MONDAY NIGHT AND THEN THE POTENTIAL FOR A WINTRY
MIX WEDNESDAY NIGHT.

LIGHT SNOW WILL BE ENDING ACROSS THE SOUTHEAST CWA SUNDAY EVENING
AS NORTHEAST WINDS STEADILY DIMINISH SUNDAY EVENING. LAKE EFFECT
CLOUDS AND PERHAPS A FEW FLURRIES ARE POSSIBLE SUNDAY EVENING. LOWS
BY MONDAY MORNING WILL DIP INTO THE TEENS MOST LOCATIONS BUT AS A
WEAK RIDGE PASSES ACROSS THE AREA AND WINDS BECOME LIGHT OR CALM...
LOWS COULD BE SEVERAL DEGREES COLDER DEPENDING ON CLOUD COVER.

ANOTHER WEAK CLIPPER SYSTEM MOVES SOUTHEAST ACROSS THE WESTERN
LAKES MONDAY AFTERNOON INTO MONDAY NIGHT AS IT SLOWLY BEGINS TO
WEAKEN. MODELS VARY SOME ON TIMING AND PRECIP ARRIVAL. A CONSENSUS
WOULD HAVE THE ARRIVAL DURING MONDAY AFTERNOON. INITIALLY THE
SATURATION IS DEEP ENOUGH THAT PRECIP SHOULD BEGIN AS LIGHT SNOW.
BUT INTO THE EVENING...MID LEVELS BEGIN TO DRY OUT SOME AND PRECIP
COULD TRANSITION MORE TO A LIGHT SNOW MIXED WITH OR JUST FREEZING
DRIZZLE. FAIRLY LOW CONFIDENCE AT THIS POINT...SO MAINTAINED JUST
LIGHT SNOW FOR THE ENTIRE DURATION FOR NOW.

PROGRESSIVE PATTERN BRINGS ANOTHER RIDGE OF HIGH PRESSURE ACROSS
THE REGION TUESDAY NIGHT INTO WEDNESDAY AND THEN ANOTHER STORM
SYSTEM WEDNESDAY NIGHT INTO THURSDAY MORNING. MODELS CURRENTLY IN
DECENT AGREEMENT WITH THE TRACK OF THIS LOW GENERALLY RIGHT ACROSS
THE CWA EARLY THURSDAY MORNING. WITH THIS TRACK...TEMPS LIKELY TO
REMAIN FAIRLY STEADY IN THE LOWER/MID 30S WEDNESDAY NIGHT AND
THERMAL PROFILES WOULD SUGGEST PRECIP WOULD BE MAINLY RAIN OR
PERHAPS FREEZING RAIN...IF SURFACE TEMPS REMAINED BELOW FREEZING.
AND ALSO COULD BE SOME SNOW IF THE LOW WERE TO SPEED UP AND/OR
TRACK FURTHER SOUTH. THUS DID NOT GET TOO SPECIFIC WITH PRECIP
TYPE WEDNESDAY NIGHT INTO THURSDAY BUT A WINTRY MIX IS POSSIBLE.
CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* MVFR CIGS WILL LOWER TOWARDS 700-1000FT AGL ARND 21Z THEN
  POSSIBLY DIP FURTHER TO NEAR 400-600FT AFT 6Z.

* WEST WINDS ARND 5-10KT...QUICKLY SHIFTING EAST AFTER MIDNIGHT
  AND INCREASING TO 10-18KT GUSTS TO 25KT BY DAYBREAK SUN. GUSTS
  INCREASE TOWARDS 30KT SUN MORNING.

* SNOW DEVELOPS JUST BEFORE DAYBREAK SUN...WITH PEAK TIMING
  BETWEEN 14-17Z FROM PERIODS OF STEADIER SNOW. CIGS WILL LOWER
  TOWARDS IFR CONDS WITH POSSIBLE IFR VSBYS FROM STEADY SNOW.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY INDICATES SOME CLEARING HAS TAKEN PLACE LATE THIS
MORNING ACROSS NORTHEAST IL/NORTHWEST IN...HOWEVER THERE IS A
WEDGE OF MVFR CIGS STARTING TO CREEP SOUTHEAST ACROSS NORTHWEST
IL. GUIDANCE AND TIMING WOULD INDICATE THE MVFR CIGS RETURNING TO
ORD/MDW ARND 19Z. THEN THE FOCUS WILL TURN TOWARDS THE APPROACHING
WINTER STORM SYSTEM. GUIDANCE CONTINUES TO SHIFT THE TRACK OF THE
SYSTEM FURTHER SOUTH/SOUTHWEST OF CHICAGO. THIS WILL LIKELY
DICTATE WHERE THE STEADIER/TIMING OF SNOW WILL OCCUR SUN MORNING.
AT THIS TIME HAVE ONLY MADE MINOR ADJUSTMENTS TO THE GOING
FORECAST...WITH SNOW DEVELOPING AFTER MIDNIGHT. POSSIBLY SEEING
REDUCED VSBYS FROM STEADIER SNOW BETWEEN 13-17Z. AS THE LOW PASSES
TO THE SOUTH...THE PRESSURE GRADIENT WILL RAPIDLY INCREASE ALONG
THE NORTHERN TIER OR NEAR THE TAF SITES. THIS WILL RESULT IN A
QUICK SHIFT TO EAST WINDS AND GUSTS APPROACHING 20KT ARND
DAYBREAK...THEN INCREASING TO NEAR 30KT BY MID TO LATE MORNING.

IFR CIGS WILL REMAIN ACROSS THE TAF SITES INTO SUN MIDDAY...THEN
SOME DRIER AIR WILL BEGIN TO FILTER INTO THE REGION AND BRING CIGS
BACK TO MVFR LATE SUN AFTN.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN CIGS RETURNING TO MVFR CONDS...MEDIUM
  CONFIDENCE IN PRECISE TIMING OF MVFR CIGS.

* MEDIUM CONFIDENCE IN IFR CIGS DEVELOPING THIS AFTN...ALONG WITH
  DURATION OF IFR CIGS.

* MEDIUM CONFIDENCE IN TIMING OF CIGS LOWERING FURTHER TO IFR
  CONDS LATER TONIGHT.

* HIGH CONFIDENCE IN SNOW DEVELOPING AFTER MIDNIGHT...MEDIUM
  CONFIDENCE IN PRECISE TIMING OF STEADIER SNOW BETWEEN 13-17Z.

* HIGH CONFIDENCE IN WINDS QUICKLY TURNING EAST AND GUSTS
  DEVELOPING.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...MVFR CIGS POSSIBLE.

MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR...CHANCE OF SNOW AND MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR/IFR POSSIBLE.

FRIDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
127 PM CST

A COLD FRONT WILL BEGIN TO SHIFT SOUTHWARD DOWN LAKE MICHIGAN LATE
THIS AFTERNOON...WITH WINDS EXPECTED TO PICK UP OUT OF THE NORTH
INTO TONIGHT. WINDS OVER THE LAKE WILL THEN CONTINUE TO INCREASE
INTO SUNDAY AS A QUICK MOVING CLIPPER SYSTEM TRACKS SOUTHEASTWARD
ACROSS SOUTHERN ILLINOIS. THIS WILL RESULT IN NORTHEASTERLY WINDS UP
TO 30 KT BY EARLY SUNDAY MORNING ACROSS MOST OF THE LAKE...WITH THE
STRONGEST WINDS EXPECTED ACROSS THE SOUTHERN END OF THE LAKE...WHERE
A FEW GALE FORCE GUSTS TO 35 KT ARE POSSIBLE ON SUNDAY. THIS WILL
RESULT IN WAVES UP TO 10 FEET INTO THE NORTHEAST ILLINOIS SHORES
THROUGH SUNDAY EVENING. THE WINDS WILL QUICKLY ABATE ACROSS THE LAKE
SUNDAY NIGHT AS THE LOW SHIFTS TOWARDS THE EASTERN SEABOARD.

ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD OVER OR JUST WEST OF THE
LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A PERIOD OF
LIGHT SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN THE
WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION. THIS
SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS WEDNESDAY NIGHT...FOLLOWED BY STRONG NORTHERLY WINDS
THURSDAY INTO FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 242004
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
204 PM CST SAT JAN 24 2015

.SHORT TERM...
308 AM CST

TODAY THROUGH SUNDAY NIGHT...

THE MAIN FORECAST ISSUE WILL BE ACCUMULATING SNOW AND GUSTY WINDS
STARTING LATER TONIGHT CONTINUING THROUGH MUCH OF SUNDAY. WATER
VAPOR IMAGERY SHOWS A LONGWAVE TROUGH STRETCHING FROM HUDSON BAY
SOUTH TO THE GULF COAST WITH BROAD RIDGING OVER THE EASTERN
PACIFIC AND MUCH OF WESTERN CANADA AND THE NORTHWEST U.S. A WEAK
COOL FRONT IS CROSSING THE AREA BEHIND THE PASSAGE OF THE LONGWAVE
TROUGH AXIS. COOL ADVECTION THIS MORNING WILL GIVE WAY TO MODEST
WARM ADVECTION LATE THIS AFTERNOON. CLOUD COVER WILL BE THE WILD
CARD WITH TEMPS. STRATUS IS SPREADING SOUTHEAST ACROSS THE AREA
THIS MORNING BUT SATELLITE SHOWS GAPS IN COVERAGE UPSTREAM.
GUIDANCE IS MIXED WITH THE EXTENT OF CLOUD COVER BUT SUSPECT THERE
WILL BE BREAKS IN THE CLOUDS...ESPECIALLY THIS AFTERNOON...WITH
ANY MEANINGFUL SUNSHINE DURING THE EARLY/MID AFTERNOON HELPING
TEMPS SOMEWHAT. THIS IS MOST FAVORED SOUTH AND WEST SO WILL NUDGE
TEMPS UP SLIGHTLY THERE WHILE CARRYING UPPER 30S ACROSS THE REST
OF THE AREA.

THE MAIN FEATURE OF CONCERN IS A WAVE MOVING EAST-SOUTHEAST ACROSS
SOUTHERN ALBERTA. EVENING UPPER AIR ANALYSIS SHOWS A STRONG JET
PUSHING INTO THE PACIFIC NORTHWEST AND PIVOTING SOUTHEASTWARD AS
ADDITIONAL ENERGY PUSHES EASTWARD AMPLIFYING THE RIDGE. THE WAVE OF
CONCERN WILL DIG SOUTHEASTWARD ACROSS THE NORTHERN PLAINS TOWARD THE
MID MISSISSIPPI RIVER VALLEY AS A RESULT AND AMPLIFY AS IT DOES SO
INTO TONIGHT. THE SOUTH/WEST TREND OF THE TRACK OF THE SURFACE LOW
HAS CONTINUED AND DIFFERENCES REMAIN...ESPECIALLY WITH SOME OF THE
HIGH RES GUIDANCE WHICH TAKES THE LOW MUCH FURTHER SOUTH AND WEST
THAN SOME OF THE LOWER RES OPTIONS. IT APPEARS THAT THE LOW WILL NOT
TRACK NORTH OF ROUGHLY A BURLINGTON IOWA TO TERRE HAUTE INDIANA LINE
AT THIS POINT. WITH THE WAVE STILL TAKING SHAPE AND THE UPPER JET
STILL COMING ASHORE OVER THE PAC NORTHWEST FEEL THAT CONFIDENCE HAS
ROOM FOR IMPROVEMENT WITH THE MORNING UPPER AIR ANALYSIS AND
SUBSEQUENT 12Z GUIDANCE. THE MAIN QUESTION WILL BE PLACEMENT BUT
HAVE BETTER CONFIDENCE IN THE TREND OF WHAT OCCURS. PRECIP IS ON
TRACK TO QUICKLY SPREAD SOUTHEAST ACROSS THE AREA OVERNIGHT/AFTER
06Z/ AND SOUTHWEST AREAS STILL LOOK TO SEE A MIX OF RAIN OR SNOW AND
EVEN SOME SLEET THROUGH MID MORNING WHEN COLD AIR WILL TAKE OVER
CHANGING THINGS TO SNOW. PEAK PRECIP INTENSITY WILL BE AFTER
DAYBREAK INTO THE EARLY AFTERNOON. WINDS WILL TURN NORTHEAST AND
INCREASE DURING THE MORNING SETTING UP A DECENT FETCH DOWN LAKE
MICHIGAN. LAKE EFFECT PARAMETERS ARE SUB PAR BUT WHEN COMBINED WITH
SYNOPTIC SCALE ASCENT ARE PROBABLY SUFFICIENT TO PROVIDE SOME
MINIMAL ENHANCEMENT...MAINLY DUE TO INCREASED MOISTURE FLUX.
GUIDANCE VARIES WITH LIQUID OUTPUT WITH SOME RATHER HIGH AMOUNTS
NOTED PROBABLY SUGGESTIVE OF STRONG BANDING WHICH IS CERTAINLY
POSSIBLE. GIVEN PRECIPITABLE WATER VALUES OF AROUND 0.5 INCHES AND
FORCING OF 6 TO MAYBE 9 HOURS PEAK LIQUID AMOUNTS OF 0.3 TO 0.4
INCHES STILL SEEMS REASONABLE. LOCATION OF THESE AMOUNTS IS EXPECTED
ACROSS THE SOUTHERN CWA WITH AMOUNTS OF ONLY AROUND 0.1 INCHES
ACROSS THE NORTH. WITH SOUTHERN AREAS ALSO SEEING A MIX NOT ALL OF
THE LIQUID WILL GO TOWARD SNOW ACCUMULATION. THUS HIGHEST SNOW
AMOUNTS WILL OCCUR JUST TO THE NORTH...THOUGH WITH SOMEWHAT LOW
LIQUID EQUIVALENT. WILL DEPICT THE PEAK SNOWFALL FROM ROUGHLY
LASALLE COUNTY EAST-SOUTHEAST ALONG AND JUST SOUTH OF INTERSTATE 80
TO ROUGHLY KANKAKEE TO RENSSELAER. WILL CARRY 2-4 INCHES FOR THIS
AREA WITH AMOUNTS TAPERING TO ABOUT AN INCH ALONG THE WI
BORDER...WITH 1-2 INCHES ACROSS THE FAR NORTHERN CHICAGO METRO TO
AROUND 3 POSSIBLY 4 INCHES ACROSS THE FAR SOUTHERN CHICAGO METRO.
THERE IS STILL A CHANCE THIS COULD SHIFT FURTHER SOUTH.
PRECIPITATION QUICKLY ENDS MID TO LATE SUNDAY AFTERNOON WITH LITTLE
IF ANY LAKE EFFECT LINGERING GIVEN POOR INVERSION HEIGHTS.

HEADLINE POTENTIAL...WILL HOLD OFF ON ANY HEADLINES FOR NOW GIVEN
THAT A FURTHER SOUTH SHIFT IS STILL PLAUSIBLE. ANOTHER CONCERN IS
WIND SPEEDS WHICH WILL INCREASE TO 20 TO 25 MPH WITH GUSTS OF 30-35
MPH POSSIBLE SUNDAY MORNING THROUGH THE AFTERNOON. HOWEVER...WITH
FAIRLY WET SNOW RATIOS BLOWING WILL BE MINIMIZED BUT PROBABLY STILL
OCCUR. THERE IS ALSO A WINDOW FROM LATE MORNING THROUGH EARLY
AFTERNOON WHERE THE FALLING SNOW AND WIND MAY PUSH VISIBILITIES DOWN
UNDER A HALF OR QUARTER MILE...BUT THIS MAY OCCUR OVER A RATHER
SMALL AREA. EXPECT TO NEED A WINTER WEATHER ADVISORY ACROSS THE PEAK
SNOW AREA BUT AGAIN THE LOCATION MAY SHIFT AND IF BANDING DEVELOPS
THE SWATH OF SNOW COULD REALLY NARROW SO WOULD LIKE TO SEE THE
SYSTEM EVOLVE A LITTLE BIT MORE BEFORE DECIDING WHICH AREAS WILL SEE
THE BIGGEST IMPACT. WILL ISSUE A SPECIAL WEATHER STATEMENT
HIGHLIGHTING THE POTENTIAL IMPACTS FOR NOW.

MDB

&&

.LONG TERM...
308 AM CST

MONDAY THROUGH FRIDAY...

A MUCH BETTER DEFINED RIDGE WILL BE OVER WESTERN NORTH AMERICA
WITH A DEEP TROUGH OVER THE EAST COAST BY MONDAY. ANOTHER WAVE
WILL BE TRAVERSING THE RIDGE THEN DROP SOUTHEAST ACROSS THE GREAT
LAKES MONDAY BRINGING LOW CHANCES FOR SOME LIGHT SNOW. HIGH
PRESSURE WILL BUILD IN FROM THE WEST MONDAY NIGHT TURNING WINDS
MORE NORTHERLY. LAKE PARAMETERS WILL LIKELY BE MARGINAL BUT COULD
SEE SOME FLURRY OR LIGHT SNOW ACTIVITY DEVELOP FOR TUESDAY. THE
UPPER RIDGE BEGINS TO SHIFT EASTWARD WEDNESDAY WITH THE SURFACE
HIGH SHIFTING EAST AS WELL. THIS WILL LEAD TO A SHIFT TO SOUTHERLY
WINDS AND WARMING TEMPS LATE IN THE WEEK. GUIDANCE IS IN AGREEMENT
ON A LOW CROSSING THE AREA FIRST THING THURSDAY BRINGING MIXED
PRECIP POTENTIAL OR EVEN JUST RAIN. COLDER AIR BUILDS IN BEHIND
THE SYSTEM FRIDAY AS HIGH PRESSURE BUILDS INTO THE PLAINS. OVERALL
EXPECT TEMPS TO BE AT OR ABOVE NORMAL FROM TUESDAY ONWARD.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* MVFR CIGS WILL LOWER TOWARDS 700-1000FT AGL ARND 21Z THEN
  POSSIBLY DIP FURTHER TO NEAR 400-600FT AFT 6Z.

* WEST WINDS ARND 5-10KT...QUICKLY SHIFTING EAST AFTER MIDNIGHT
  AND INCREASING TO 10-18KT GUSTS TO 25KT BY DAYBREAK SUN. GUSTS
  INCREASE TOWARDS 30KT SUN MORNING.

* SNOW DEVELOPS JUST BEFORE DAYBREAK SUN...WITH PEAK TIMING
  BETWEEN 14-17Z FROM PERIODS OF STEADIER SNOW. CIGS WILL LOWER
  TOWARDS IFR CONDS WITH POSSIBLE IFR VSBYS FROM STEADY SNOW.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY INDICATES SOME CLEARING HAS TAKEN PLACE LATE THIS
MORNING ACROSS NORTHEAST IL/NORTHWEST IN...HOWEVER THERE IS A
WEDGE OF MVFR CIGS STARTING TO CREEP SOUTHEAST ACROSS NORTHWEST
IL. GUIDANCE AND TIMING WOULD INDICATE THE MVFR CIGS RETURNING TO
ORD/MDW ARND 19Z. THEN THE FOCUS WILL TURN TOWARDS THE APPROACHING
WINTER STORM SYSTEM. GUIDANCE CONTINUES TO SHIFT THE TRACK OF THE
SYSTEM FURTHER SOUTH/SOUTHWEST OF CHICAGO. THIS WILL LIKELY
DICTATE WHERE THE STEADIER/TIMING OF SNOW WILL OCCUR SUN MORNING.
AT THIS TIME HAVE ONLY MADE MINOR ADJUSTMENTS TO THE GOING
FORECAST...WITH SNOW DEVELOPING AFTER MIDNIGHT. POSSIBLY SEEING
REDUCED VSBYS FROM STEADIER SNOW BETWEEN 13-17Z. AS THE LOW PASSES
TO THE SOUTH...THE PRESSURE GRADIENT WILL RAPIDLY INCREASE ALONG
THE NORTHERN TIER OR NEAR THE TAF SITES. THIS WILL RESULT IN A
QUICK SHIFT TO EAST WINDS AND GUSTS APPROACHING 20KT ARND
DAYBREAK...THEN INCREASING TO NEAR 30KT BY MID TO LATE MORNING.

IFR CIGS WILL REMAIN ACROSS THE TAF SITES INTO SUN MIDDAY...THEN
SOME DRIER AIR WILL BEGIN TO FILTER INTO THE REGION AND BRING CIGS
BACK TO MVFR LATE SUN AFTN.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN CIGS RETURNING TO MVFR CONDS...MEDIUM
  CONFIDENCE IN PRECISE TIMING OF MVFR CIGS.

* MEDIUM CONFIDENCE IN IFR CIGS DEVELOPING THIS AFTN...ALONG WITH
  DURATION OF IFR CIGS.

* MEDIUM CONFIDENCE IN TIMING OF CIGS LOWERING FURTHER TO IFR
  CONDS LATER TONIGHT.

* HIGH CONFIDENCE IN SNOW DEVELOPING AFTER MIDNIGHT...MEDIUM
  CONFIDENCE IN PRECISE TIMING OF STEADIER SNOW BETWEEN 13-17Z.

* HIGH CONFIDENCE IN WINDS QUICKLY TURNING EAST AND GUSTS
  DEVELOPING.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...MVFR CIGS POSSIBLE.

MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR...CHANCE OF SNOW AND MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR/IFR POSSIBLE.

FRIDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
127 PM CST

A COLD FRONT WILL BEGIN TO SHIFT SOUTHWARD DOWN LAKE MICHIGAN LATE
THIS AFTERNOON...WITH WINDS EXPECTED TO PICK UP OUT OF THE NORTH
INTO TONIGHT. WINDS OVER THE LAKE WILL THEN CONTINUE TO INCREASE
INTO SUNDAY AS A QUICK MOVING CLIPPER SYSTEM TRACKS SOUTHEASTWARD
ACROSS SOUTHERN ILLINOIS. THIS WILL RESULT IN NORTHEASTERLY WINDS UP
TO 30 KT BY EARLY SUNDAY MORNING ACROSS MOST OF THE LAKE...WITH THE
STRONGEST WINDS EXPECTED ACROSS THE SOUTHERN END OF THE LAKE...WHERE
A FEW GALE FORCE GUSTS TO 35 KT ARE POSSIBLE ON SUNDAY. THIS WILL
RESULT IN WAVES UP TO 10 FEET INTO THE NORTHEAST ILLINOIS SHORES
THROUGH SUNDAY EVENING. THE WINDS WILL QUICKLY ABATE ACROSS THE LAKE
SUNDAY NIGHT AS THE LOW SHIFTS TOWARDS THE EASTERN SEABOARD.

ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD OVER OR JUST WEST OF THE
LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A PERIOD OF
LIGHT SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN THE
WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION. THIS
SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS WEDNESDAY NIGHT...FOLLOWED BY STRONG NORTHERLY WINDS
THURSDAY INTO FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 241928
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
128 PM CST SAT JAN 24 2015

.SHORT TERM...
308 AM CST

TODAY THROUGH SUNDAY NIGHT...

THE MAIN FORECAST ISSUE WILL BE ACCUMULATING SNOW AND GUSTY WINDS
STARTING LATER TONIGHT CONTINUING THROUGH MUCH OF SUNDAY. WATER
VAPOR IMAGERY SHOWS A LONGWAVE TROUGH STRETCHING FROM HUDSON BAY
SOUTH TO THE GULF COAST WITH BROAD RIDGING OVER THE EASTERN
PACIFIC AND MUCH OF WESTERN CANADA AND THE NORTHWEST U.S. A WEAK
COOL FRONT IS CROSSING THE AREA BEHIND THE PASSAGE OF THE LONGWAVE
TROUGH AXIS. COOL ADVECTION THIS MORNING WILL GIVE WAY TO MODEST
WARM ADVECTION LATE THIS AFTERNOON. CLOUD COVER WILL BE THE WILD
CARD WITH TEMPS. STRATUS IS SPREADING SOUTHEAST ACROSS THE AREA
THIS MORNING BUT SATELLITE SHOWS GAPS IN COVERAGE UPSTREAM.
GUIDANCE IS MIXED WITH THE EXTENT OF CLOUD COVER BUT SUSPECT THERE
WILL BE BREAKS IN THE CLOUDS...ESPECIALLY THIS AFTERNOON...WITH
ANY MEANINGFUL SUNSHINE DURING THE EARLY/MID AFTERNOON HELPING
TEMPS SOMEWHAT. THIS IS MOST FAVORED SOUTH AND WEST SO WILL NUDGE
TEMPS UP SLIGHTLY THERE WHILE CARRYING UPPER 30S ACROSS THE REST
OF THE AREA.

THE MAIN FEATURE OF CONCERN IS A WAVE MOVING EAST-SOUTHEAST ACROSS
SOUTHERN ALBERTA. EVENING UPPER AIR ANALYSIS SHOWS A STRONG JET
PUSHING INTO THE PACIFIC NORTHWEST AND PIVOTING SOUTHEASTWARD AS
ADDITIONAL ENERGY PUSHES EASTWARD AMPLIFYING THE RIDGE. THE WAVE OF
CONCERN WILL DIG SOUTHEASTWARD ACROSS THE NORTHERN PLAINS TOWARD THE
MID MISSISSIPPI RIVER VALLEY AS A RESULT AND AMPLIFY AS IT DOES SO
INTO TONIGHT. THE SOUTH/WEST TREND OF THE TRACK OF THE SURFACE LOW
HAS CONTINUED AND DIFFERENCES REMAIN...ESPECIALLY WITH SOME OF THE
HIGH RES GUIDANCE WHICH TAKES THE LOW MUCH FURTHER SOUTH AND WEST
THAN SOME OF THE LOWER RES OPTIONS. IT APPEARS THAT THE LOW WILL NOT
TRACK NORTH OF ROUGHLY A BURLINGTON IOWA TO TERRE HAUTE INDIANA LINE
AT THIS POINT. WITH THE WAVE STILL TAKING SHAPE AND THE UPPER JET
STILL COMING ASHORE OVER THE PAC NORTHWEST FEEL THAT CONFIDENCE HAS
ROOM FOR IMPROVEMENT WITH THE MORNING UPPER AIR ANALYSIS AND
SUBSEQUENT 12Z GUIDANCE. THE MAIN QUESTION WILL BE PLACEMENT BUT
HAVE BETTER CONFIDENCE IN THE TREND OF WHAT OCCURS. PRECIP IS ON
TRACK TO QUICKLY SPREAD SOUTHEAST ACROSS THE AREA OVERNIGHT/AFTER
06Z/ AND SOUTHWEST AREAS STILL LOOK TO SEE A MIX OF RAIN OR SNOW AND
EVEN SOME SLEET THROUGH MID MORNING WHEN COLD AIR WILL TAKE OVER
CHANGING THINGS TO SNOW. PEAK PRECIP INTENSITY WILL BE AFTER
DAYBREAK INTO THE EARLY AFTERNOON. WINDS WILL TURN NORTHEAST AND
INCREASE DURING THE MORNING SETTING UP A DECENT FETCH DOWN LAKE
MICHIGAN. LAKE EFFECT PARAMETERS ARE SUB PAR BUT WHEN COMBINED WITH
SYNOPTIC SCALE ASCENT ARE PROBABLY SUFFICIENT TO PROVIDE SOME
MINIMAL ENHANCEMENT...MAINLY DUE TO INCREASED MOISTURE FLUX.
GUIDANCE VARIES WITH LIQUID OUTPUT WITH SOME RATHER HIGH AMOUNTS
NOTED PROBABLY SUGGESTIVE OF STRONG BANDING WHICH IS CERTAINLY
POSSIBLE. GIVEN PRECIPITABLE WATER VALUES OF AROUND 0.5 INCHES AND
FORCING OF 6 TO MAYBE 9 HOURS PEAK LIQUID AMOUNTS OF 0.3 TO 0.4
INCHES STILL SEEMS REASONABLE. LOCATION OF THESE AMOUNTS IS EXPECTED
ACROSS THE SOUTHERN CWA WITH AMOUNTS OF ONLY AROUND 0.1 INCHES
ACROSS THE NORTH. WITH SOUTHERN AREAS ALSO SEEING A MIX NOT ALL OF
THE LIQUID WILL GO TOWARD SNOW ACCUMULATION. THUS HIGHEST SNOW
AMOUNTS WILL OCCUR JUST TO THE NORTH...THOUGH WITH SOMEWHAT LOW
LIQUID EQUIVALENT. WILL DEPICT THE PEAK SNOWFALL FROM ROUGHLY
LASALLE COUNTY EAST-SOUTHEAST ALONG AND JUST SOUTH OF INTERSTATE 80
TO ROUGHLY KANKAKEE TO RENSSELAER. WILL CARRY 2-4 INCHES FOR THIS
AREA WITH AMOUNTS TAPERING TO ABOUT AN INCH ALONG THE WI
BORDER...WITH 1-2 INCHES ACROSS THE FAR NORTHERN CHICAGO METRO TO
AROUND 3 POSSIBLY 4 INCHES ACROSS THE FAR SOUTHERN CHICAGO METRO.
THERE IS STILL A CHANCE THIS COULD SHIFT FURTHER SOUTH.
PRECIPITATION QUICKLY ENDS MID TO LATE SUNDAY AFTERNOON WITH LITTLE
IF ANY LAKE EFFECT LINGERING GIVEN POOR INVERSION HEIGHTS.

HEADLINE POTENTIAL...WILL HOLD OFF ON ANY HEADLINES FOR NOW GIVEN
THAT A FURTHER SOUTH SHIFT IS STILL PLAUSIBLE. ANOTHER CONCERN IS
WIND SPEEDS WHICH WILL INCREASE TO 20 TO 25 MPH WITH GUSTS OF 30-35
MPH POSSIBLE SUNDAY MORNING THROUGH THE AFTERNOON. HOWEVER...WITH
FAIRLY WET SNOW RATIOS BLOWING WILL BE MINIMIZED BUT PROBABLY STILL
OCCUR. THERE IS ALSO A WINDOW FROM LATE MORNING THROUGH EARLY
AFTERNOON WHERE THE FALLING SNOW AND WIND MAY PUSH VISIBILITIES DOWN
UNDER A HALF OR QUARTER MILE...BUT THIS MAY OCCUR OVER A RATHER
SMALL AREA. EXPECT TO NEED A WINTER WEATHER ADVISORY ACROSS THE PEAK
SNOW AREA BUT AGAIN THE LOCATION MAY SHIFT AND IF BANDING DEVELOPS
THE SWATH OF SNOW COULD REALLY NARROW SO WOULD LIKE TO SEE THE
SYSTEM EVOLVE A LITTLE BIT MORE BEFORE DECIDING WHICH AREAS WILL SEE
THE BIGGEST IMPACT. WILL ISSUE A SPECIAL WEATHER STATEMENT
HIGHLIGHTING THE POTENTIAL IMPACTS FOR NOW.

MDB

&&

.LONG TERM...
308 AM CST

MONDAY THROUGH FRIDAY...

A MUCH BETTER DEFINED RIDGE WILL BE OVER WESTERN NORTH AMERICA
WITH A DEEP TROUGH OVER THE EAST COAST BY MONDAY. ANOTHER WAVE
WILL BE TRAVERSING THE RIDGE THEN DROP SOUTHEAST ACROSS THE GREAT
LAKES MONDAY BRINGING LOW CHANCES FOR SOME LIGHT SNOW. HIGH
PRESSURE WILL BUILD IN FROM THE WEST MONDAY NIGHT TURNING WINDS
MORE NORTHERLY. LAKE PARAMETERS WILL LIKELY BE MARGINAL BUT COULD
SEE SOME FLURRY OR LIGHT SNOW ACTIVITY DEVELOP FOR TUESDAY. THE
UPPER RIDGE BEGINS TO SHIFT EASTWARD WEDNESDAY WITH THE SURFACE
HIGH SHIFTING EAST AS WELL. THIS WILL LEAD TO A SHIFT TO SOUTHERLY
WINDS AND WARMING TEMPS LATE IN THE WEEK. GUIDANCE IS IN AGREEMENT
ON A LOW CROSSING THE AREA FIRST THING THURSDAY BRINGING MIXED
PRECIP POTENTIAL OR EVEN JUST RAIN. COLDER AIR BUILDS IN BEHIND
THE SYSTEM FRIDAY AS HIGH PRESSURE BUILDS INTO THE PLAINS. OVERALL
EXPECT TEMPS TO BE AT OR ABOVE NORMAL FROM TUESDAY ONWARD.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* MVFR CIGS WILL RETURN WITH BASES ARND 3KFT AGL...THEN LOWER
  TOWARDS 1000-1200FT AGL AFTER MIDNIGHT.

* WEST WINDS ARND 5-10KT...QUICKLY SHIFTING EAST AFTER MIDNIGHT
  AND INCREASING TO 10-18KT GUSTS TO 25KT BY DAYBREAK SUN. GUSTS
  INCREASE TOWARDS 30KT SUN MORNING.

* SNOW DEVELOPS JUST BEFORE DAYBREAK SUN...WITH PEAK TIMING
  BETWEEN 14-17Z FROM PERIODS OF STEADIER SNOW. CIGS WILL LOWER
  TOWARDS IFR CONDS WITH POSSIBLE IFR VSBYS FROM STEADY SNOW.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY INDICATES SOME CLEARING HAS TAKEN PLACE LATE THIS
MORNING ACROSS NORTHEAST IL/NORTHWEST IN...HOWEVER THERE IS A
WEDGE OF MVFR CIGS STARTING TO CREEP SOUTHEAST ACROSS NORTHWEST
IL. GUIDANCE AND TIMING WOULD INDICATE THE MVFR CIGS RETURNING TO
ORD/MDW ARND 19Z. THEN THE FOCUS WILL TURN TOWARDS THE APPROACHING
WINTER STORM SYSTEM. GUIDANCE CONTINUES TO SHIFT THE TRACK OF THE
SYSTEM FURTHER SOUTH/SOUTHWEST OF CHICAGO. THIS WILL LIKELY
DICTATE WHERE THE STEADIER/TIMING OF SNOW WILL OCCUR SUN MORNING.
AT THIS TIME HAVE ONLY MADE MINOR ADJUSTMENTS TO THE GOING
FORECAST...WITH SNOW DEVELOPING AFTER MIDNIGHT. POSSIBLY SEEING
REDUCED VSBYS FROM STEADIER SNOW BETWEEN 13-17Z. AS THE LOW PASSES
TO THE SOUTH...THE PRESSURE GRADIENT WILL RAPIDLY INCREASE ALONG
THE NORTHERN TIER OR NEAR THE TAF SITES. THIS WILL RESULT IN A
QUICK SHIFT TO EAST WINDS AND GUSTS APPROACHING 20KT ARND
DAYBREAK...THEN INCREASING TO NEAR 30KT BY MID TO LATE MORNING.

IFR CIGS WILL REMAIN ACROSS THE TAF SITES INTO SUN MIDDAY...THEN
SOME DRIER AIR WILL BEGIN TO FILTER INTO THE REGION AND BRING CIGS
BACK TO MVFR LATE SUN AFTN.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN CIGS RETURNING TO MVFR CONDS...MEDIUM
  CONFIDENCE IN PRECISE TIMING OF MVFR CIGS.

* MEDIUM CONFIDENCE IN TIMING OF CIGS LOWERING FURTHER TO IFR
  CONDS LATER TONIGHT.

* HIGH CONFIDENCE IN SNOW DEVELOPING AFTER MIDNIGHT...MEDIUM
  CONFIDENCE IN PRECISE TIMING OF STEADIER SNOW BETWEEN 13-17Z.

* HIGH CONFIDENCE IN WINDS QUICKLY TURNING EAST AND GUSTS
  DEVELOPING.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...MVFR CIGS POSSIBLE.

MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR...CHANCE OF SNOW AND MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR/IFR POSSIBLE.

FRIDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
127 PM CST

A COLD FRONT WILL BEGIN TO SHIFT SOUTHWARD DOWN LAKE MICHIGAN LATE
THIS AFTERNOON...WITH WINDS EXPECTED TO PICK UP OUT OF THE NORTH
INTO TONIGHT. WINDS OVER THE LAKE WILL THEN CONTINUE TO INCREASE
INTO SUNDAY AS A QUICK MOVING CLIPPER SYSTEM TRACKS SOUTHEASTWARD
ACROSS SOUTHERN ILLINOIS. THIS WILL RESULT IN NORTHEASTERLY WINDS UP
TO 30 KT BY EARLY SUNDAY MORNING ACROSS MOST OF THE LAKE...WITH THE
STRONGEST WINDS EXPECTED ACROSS THE SOUTHERN END OF THE LAKE...WHERE
A FEW GALE FORCE GUSTS TO 35 KT ARE POSSIBLE ON SUNDAY. THIS WILL
RESULT IN WAVES UP TO 10 FEET INTO THE NORTHEAST ILLINOIS SHORES
THROUGH SUNDAY EVENING. THE WINDS WILL QUICKLY ABATE ACROSS THE LAKE
SUNDAY NIGHT AS THE LOW SHIFTS TOWARDS THE EASTERN SEABOARD.

ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD OVER OR JUST WEST OF THE
LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A PERIOD OF
LIGHT SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN THE
WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION. THIS
SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS WEDNESDAY NIGHT...FOLLOWED BY STRONG NORTHERLY WINDS
THURSDAY INTO FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 241928
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
128 PM CST SAT JAN 24 2015

.SHORT TERM...
308 AM CST

TODAY THROUGH SUNDAY NIGHT...

THE MAIN FORECAST ISSUE WILL BE ACCUMULATING SNOW AND GUSTY WINDS
STARTING LATER TONIGHT CONTINUING THROUGH MUCH OF SUNDAY. WATER
VAPOR IMAGERY SHOWS A LONGWAVE TROUGH STRETCHING FROM HUDSON BAY
SOUTH TO THE GULF COAST WITH BROAD RIDGING OVER THE EASTERN
PACIFIC AND MUCH OF WESTERN CANADA AND THE NORTHWEST U.S. A WEAK
COOL FRONT IS CROSSING THE AREA BEHIND THE PASSAGE OF THE LONGWAVE
TROUGH AXIS. COOL ADVECTION THIS MORNING WILL GIVE WAY TO MODEST
WARM ADVECTION LATE THIS AFTERNOON. CLOUD COVER WILL BE THE WILD
CARD WITH TEMPS. STRATUS IS SPREADING SOUTHEAST ACROSS THE AREA
THIS MORNING BUT SATELLITE SHOWS GAPS IN COVERAGE UPSTREAM.
GUIDANCE IS MIXED WITH THE EXTENT OF CLOUD COVER BUT SUSPECT THERE
WILL BE BREAKS IN THE CLOUDS...ESPECIALLY THIS AFTERNOON...WITH
ANY MEANINGFUL SUNSHINE DURING THE EARLY/MID AFTERNOON HELPING
TEMPS SOMEWHAT. THIS IS MOST FAVORED SOUTH AND WEST SO WILL NUDGE
TEMPS UP SLIGHTLY THERE WHILE CARRYING UPPER 30S ACROSS THE REST
OF THE AREA.

THE MAIN FEATURE OF CONCERN IS A WAVE MOVING EAST-SOUTHEAST ACROSS
SOUTHERN ALBERTA. EVENING UPPER AIR ANALYSIS SHOWS A STRONG JET
PUSHING INTO THE PACIFIC NORTHWEST AND PIVOTING SOUTHEASTWARD AS
ADDITIONAL ENERGY PUSHES EASTWARD AMPLIFYING THE RIDGE. THE WAVE OF
CONCERN WILL DIG SOUTHEASTWARD ACROSS THE NORTHERN PLAINS TOWARD THE
MID MISSISSIPPI RIVER VALLEY AS A RESULT AND AMPLIFY AS IT DOES SO
INTO TONIGHT. THE SOUTH/WEST TREND OF THE TRACK OF THE SURFACE LOW
HAS CONTINUED AND DIFFERENCES REMAIN...ESPECIALLY WITH SOME OF THE
HIGH RES GUIDANCE WHICH TAKES THE LOW MUCH FURTHER SOUTH AND WEST
THAN SOME OF THE LOWER RES OPTIONS. IT APPEARS THAT THE LOW WILL NOT
TRACK NORTH OF ROUGHLY A BURLINGTON IOWA TO TERRE HAUTE INDIANA LINE
AT THIS POINT. WITH THE WAVE STILL TAKING SHAPE AND THE UPPER JET
STILL COMING ASHORE OVER THE PAC NORTHWEST FEEL THAT CONFIDENCE HAS
ROOM FOR IMPROVEMENT WITH THE MORNING UPPER AIR ANALYSIS AND
SUBSEQUENT 12Z GUIDANCE. THE MAIN QUESTION WILL BE PLACEMENT BUT
HAVE BETTER CONFIDENCE IN THE TREND OF WHAT OCCURS. PRECIP IS ON
TRACK TO QUICKLY SPREAD SOUTHEAST ACROSS THE AREA OVERNIGHT/AFTER
06Z/ AND SOUTHWEST AREAS STILL LOOK TO SEE A MIX OF RAIN OR SNOW AND
EVEN SOME SLEET THROUGH MID MORNING WHEN COLD AIR WILL TAKE OVER
CHANGING THINGS TO SNOW. PEAK PRECIP INTENSITY WILL BE AFTER
DAYBREAK INTO THE EARLY AFTERNOON. WINDS WILL TURN NORTHEAST AND
INCREASE DURING THE MORNING SETTING UP A DECENT FETCH DOWN LAKE
MICHIGAN. LAKE EFFECT PARAMETERS ARE SUB PAR BUT WHEN COMBINED WITH
SYNOPTIC SCALE ASCENT ARE PROBABLY SUFFICIENT TO PROVIDE SOME
MINIMAL ENHANCEMENT...MAINLY DUE TO INCREASED MOISTURE FLUX.
GUIDANCE VARIES WITH LIQUID OUTPUT WITH SOME RATHER HIGH AMOUNTS
NOTED PROBABLY SUGGESTIVE OF STRONG BANDING WHICH IS CERTAINLY
POSSIBLE. GIVEN PRECIPITABLE WATER VALUES OF AROUND 0.5 INCHES AND
FORCING OF 6 TO MAYBE 9 HOURS PEAK LIQUID AMOUNTS OF 0.3 TO 0.4
INCHES STILL SEEMS REASONABLE. LOCATION OF THESE AMOUNTS IS EXPECTED
ACROSS THE SOUTHERN CWA WITH AMOUNTS OF ONLY AROUND 0.1 INCHES
ACROSS THE NORTH. WITH SOUTHERN AREAS ALSO SEEING A MIX NOT ALL OF
THE LIQUID WILL GO TOWARD SNOW ACCUMULATION. THUS HIGHEST SNOW
AMOUNTS WILL OCCUR JUST TO THE NORTH...THOUGH WITH SOMEWHAT LOW
LIQUID EQUIVALENT. WILL DEPICT THE PEAK SNOWFALL FROM ROUGHLY
LASALLE COUNTY EAST-SOUTHEAST ALONG AND JUST SOUTH OF INTERSTATE 80
TO ROUGHLY KANKAKEE TO RENSSELAER. WILL CARRY 2-4 INCHES FOR THIS
AREA WITH AMOUNTS TAPERING TO ABOUT AN INCH ALONG THE WI
BORDER...WITH 1-2 INCHES ACROSS THE FAR NORTHERN CHICAGO METRO TO
AROUND 3 POSSIBLY 4 INCHES ACROSS THE FAR SOUTHERN CHICAGO METRO.
THERE IS STILL A CHANCE THIS COULD SHIFT FURTHER SOUTH.
PRECIPITATION QUICKLY ENDS MID TO LATE SUNDAY AFTERNOON WITH LITTLE
IF ANY LAKE EFFECT LINGERING GIVEN POOR INVERSION HEIGHTS.

HEADLINE POTENTIAL...WILL HOLD OFF ON ANY HEADLINES FOR NOW GIVEN
THAT A FURTHER SOUTH SHIFT IS STILL PLAUSIBLE. ANOTHER CONCERN IS
WIND SPEEDS WHICH WILL INCREASE TO 20 TO 25 MPH WITH GUSTS OF 30-35
MPH POSSIBLE SUNDAY MORNING THROUGH THE AFTERNOON. HOWEVER...WITH
FAIRLY WET SNOW RATIOS BLOWING WILL BE MINIMIZED BUT PROBABLY STILL
OCCUR. THERE IS ALSO A WINDOW FROM LATE MORNING THROUGH EARLY
AFTERNOON WHERE THE FALLING SNOW AND WIND MAY PUSH VISIBILITIES DOWN
UNDER A HALF OR QUARTER MILE...BUT THIS MAY OCCUR OVER A RATHER
SMALL AREA. EXPECT TO NEED A WINTER WEATHER ADVISORY ACROSS THE PEAK
SNOW AREA BUT AGAIN THE LOCATION MAY SHIFT AND IF BANDING DEVELOPS
THE SWATH OF SNOW COULD REALLY NARROW SO WOULD LIKE TO SEE THE
SYSTEM EVOLVE A LITTLE BIT MORE BEFORE DECIDING WHICH AREAS WILL SEE
THE BIGGEST IMPACT. WILL ISSUE A SPECIAL WEATHER STATEMENT
HIGHLIGHTING THE POTENTIAL IMPACTS FOR NOW.

MDB

&&

.LONG TERM...
308 AM CST

MONDAY THROUGH FRIDAY...

A MUCH BETTER DEFINED RIDGE WILL BE OVER WESTERN NORTH AMERICA
WITH A DEEP TROUGH OVER THE EAST COAST BY MONDAY. ANOTHER WAVE
WILL BE TRAVERSING THE RIDGE THEN DROP SOUTHEAST ACROSS THE GREAT
LAKES MONDAY BRINGING LOW CHANCES FOR SOME LIGHT SNOW. HIGH
PRESSURE WILL BUILD IN FROM THE WEST MONDAY NIGHT TURNING WINDS
MORE NORTHERLY. LAKE PARAMETERS WILL LIKELY BE MARGINAL BUT COULD
SEE SOME FLURRY OR LIGHT SNOW ACTIVITY DEVELOP FOR TUESDAY. THE
UPPER RIDGE BEGINS TO SHIFT EASTWARD WEDNESDAY WITH THE SURFACE
HIGH SHIFTING EAST AS WELL. THIS WILL LEAD TO A SHIFT TO SOUTHERLY
WINDS AND WARMING TEMPS LATE IN THE WEEK. GUIDANCE IS IN AGREEMENT
ON A LOW CROSSING THE AREA FIRST THING THURSDAY BRINGING MIXED
PRECIP POTENTIAL OR EVEN JUST RAIN. COLDER AIR BUILDS IN BEHIND
THE SYSTEM FRIDAY AS HIGH PRESSURE BUILDS INTO THE PLAINS. OVERALL
EXPECT TEMPS TO BE AT OR ABOVE NORMAL FROM TUESDAY ONWARD.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* MVFR CIGS WILL RETURN WITH BASES ARND 3KFT AGL...THEN LOWER
  TOWARDS 1000-1200FT AGL AFTER MIDNIGHT.

* WEST WINDS ARND 5-10KT...QUICKLY SHIFTING EAST AFTER MIDNIGHT
  AND INCREASING TO 10-18KT GUSTS TO 25KT BY DAYBREAK SUN. GUSTS
  INCREASE TOWARDS 30KT SUN MORNING.

* SNOW DEVELOPS JUST BEFORE DAYBREAK SUN...WITH PEAK TIMING
  BETWEEN 14-17Z FROM PERIODS OF STEADIER SNOW. CIGS WILL LOWER
  TOWARDS IFR CONDS WITH POSSIBLE IFR VSBYS FROM STEADY SNOW.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY INDICATES SOME CLEARING HAS TAKEN PLACE LATE THIS
MORNING ACROSS NORTHEAST IL/NORTHWEST IN...HOWEVER THERE IS A
WEDGE OF MVFR CIGS STARTING TO CREEP SOUTHEAST ACROSS NORTHWEST
IL. GUIDANCE AND TIMING WOULD INDICATE THE MVFR CIGS RETURNING TO
ORD/MDW ARND 19Z. THEN THE FOCUS WILL TURN TOWARDS THE APPROACHING
WINTER STORM SYSTEM. GUIDANCE CONTINUES TO SHIFT THE TRACK OF THE
SYSTEM FURTHER SOUTH/SOUTHWEST OF CHICAGO. THIS WILL LIKELY
DICTATE WHERE THE STEADIER/TIMING OF SNOW WILL OCCUR SUN MORNING.
AT THIS TIME HAVE ONLY MADE MINOR ADJUSTMENTS TO THE GOING
FORECAST...WITH SNOW DEVELOPING AFTER MIDNIGHT. POSSIBLY SEEING
REDUCED VSBYS FROM STEADIER SNOW BETWEEN 13-17Z. AS THE LOW PASSES
TO THE SOUTH...THE PRESSURE GRADIENT WILL RAPIDLY INCREASE ALONG
THE NORTHERN TIER OR NEAR THE TAF SITES. THIS WILL RESULT IN A
QUICK SHIFT TO EAST WINDS AND GUSTS APPROACHING 20KT ARND
DAYBREAK...THEN INCREASING TO NEAR 30KT BY MID TO LATE MORNING.

IFR CIGS WILL REMAIN ACROSS THE TAF SITES INTO SUN MIDDAY...THEN
SOME DRIER AIR WILL BEGIN TO FILTER INTO THE REGION AND BRING CIGS
BACK TO MVFR LATE SUN AFTN.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN CIGS RETURNING TO MVFR CONDS...MEDIUM
  CONFIDENCE IN PRECISE TIMING OF MVFR CIGS.

* MEDIUM CONFIDENCE IN TIMING OF CIGS LOWERING FURTHER TO IFR
  CONDS LATER TONIGHT.

* HIGH CONFIDENCE IN SNOW DEVELOPING AFTER MIDNIGHT...MEDIUM
  CONFIDENCE IN PRECISE TIMING OF STEADIER SNOW BETWEEN 13-17Z.

* HIGH CONFIDENCE IN WINDS QUICKLY TURNING EAST AND GUSTS
  DEVELOPING.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...MVFR CIGS POSSIBLE.

MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR...CHANCE OF SNOW AND MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR/IFR POSSIBLE.

FRIDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
127 PM CST

A COLD FRONT WILL BEGIN TO SHIFT SOUTHWARD DOWN LAKE MICHIGAN LATE
THIS AFTERNOON...WITH WINDS EXPECTED TO PICK UP OUT OF THE NORTH
INTO TONIGHT. WINDS OVER THE LAKE WILL THEN CONTINUE TO INCREASE
INTO SUNDAY AS A QUICK MOVING CLIPPER SYSTEM TRACKS SOUTHEASTWARD
ACROSS SOUTHERN ILLINOIS. THIS WILL RESULT IN NORTHEASTERLY WINDS UP
TO 30 KT BY EARLY SUNDAY MORNING ACROSS MOST OF THE LAKE...WITH THE
STRONGEST WINDS EXPECTED ACROSS THE SOUTHERN END OF THE LAKE...WHERE
A FEW GALE FORCE GUSTS TO 35 KT ARE POSSIBLE ON SUNDAY. THIS WILL
RESULT IN WAVES UP TO 10 FEET INTO THE NORTHEAST ILLINOIS SHORES
THROUGH SUNDAY EVENING. THE WINDS WILL QUICKLY ABATE ACROSS THE LAKE
SUNDAY NIGHT AS THE LOW SHIFTS TOWARDS THE EASTERN SEABOARD.

ANOTHER WEAKENING LOW WILL SHIFT SOUTHWARD OVER OR JUST WEST OF THE
LAKE LATE MONDAY AND MONDAY NIGHT. THIS WILL RESULT IN A PERIOD OF
LIGHT SOUTHERLY WINDS OVER THE LAKE DURING THIS PERIOD. LATER IN THE
WEEK ANOTHER LOW IS EXPECTED TO IMPACT THE GREAT LAKES REGION. THIS
SYSTEM STILL HAS THE POTENTIAL TO PRODUCE A PERIOD OF STRONG
SOUTHERLY WINDS WEDNESDAY NIGHT...FOLLOWED BY STRONG NORTHERLY WINDS
THURSDAY INTO FRIDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 241802
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1202 PM CST SAT JAN 24 2015

.SHORT TERM...
308 AM CST

TODAY THROUGH SUNDAY NIGHT...

THE MAIN FORECAST ISSUE WILL BE ACCUMULATING SNOW AND GUSTY WINDS
STARTING LATER TONIGHT CONTINUING THROUGH MUCH OF SUNDAY. WATER
VAPOR IMAGERY SHOWS A LONGWAVE TROUGH STRETCHING FROM HUDSON BAY
SOUTH TO THE GULF COAST WITH BROAD RIDGING OVER THE EASTERN
PACIFIC AND MUCH OF WESTERN CANADA AND THE NORTHWEST U.S. A WEAK
COOL FRONT IS CROSSING THE AREA BEHIND THE PASSAGE OF THE LONGWAVE
TROUGH AXIS. COOL ADVECTION THIS MORNING WILL GIVE WAY TO MODEST
WARM ADVECTION LATE THIS AFTERNOON. CLOUD COVER WILL BE THE WILD
CARD WITH TEMPS. STRATUS IS SPREADING SOUTHEAST ACROSS THE AREA
THIS MORNING BUT SATELLITE SHOWS GAPS IN COVERAGE UPSTREAM.
GUIDANCE IS MIXED WITH THE EXTENT OF CLOUD COVER BUT SUSPECT THERE
WILL BE BREAKS IN THE CLOUDS...ESPECIALLY THIS AFTERNOON...WITH
ANY MEANINGFUL SUNSHINE DURING THE EARLY/MID AFTERNOON HELPING
TEMPS SOMEWHAT. THIS IS MOST FAVORED SOUTH AND WEST SO WILL NUDGE
TEMPS UP SLIGHTLY THERE WHILE CARRYING UPPER 30S ACROSS THE REST
OF THE AREA.

THE MAIN FEATURE OF CONCERN IS A WAVE MOVING EAST-SOUTHEAST ACROSS
SOUTHERN ALBERTA. EVENING UPPER AIR ANALYSIS SHOWS A STRONG JET
PUSHING INTO THE PACIFIC NORTHWEST AND PIVOTING SOUTHEASTWARD AS
ADDITIONAL ENERGY PUSHES EASTWARD AMPLIFYING THE RIDGE. THE WAVE OF
CONCERN WILL DIG SOUTHEASTWARD ACROSS THE NORTHERN PLAINS TOWARD THE
MID MISSISSIPPI RIVER VALLEY AS A RESULT AND AMPLIFY AS IT DOES SO
INTO TONIGHT. THE SOUTH/WEST TREND OF THE TRACK OF THE SURFACE LOW
HAS CONTINUED AND DIFFERENCES REMAIN...ESPECIALLY WITH SOME OF THE
HIGH RES GUIDANCE WHICH TAKES THE LOW MUCH FURTHER SOUTH AND WEST
THAN SOME OF THE LOWER RES OPTIONS. IT APPEARS THAT THE LOW WILL NOT
TRACK NORTH OF ROUGHLY A BURLINGTON IOWA TO TERRE HAUTE INDIANA LINE
AT THIS POINT. WITH THE WAVE STILL TAKING SHAPE AND THE UPPER JET
STILL COMING ASHORE OVER THE PAC NORTHWEST FEEL THAT CONFIDENCE HAS
ROOM FOR IMPROVEMENT WITH THE MORNING UPPER AIR ANALYSIS AND
SUBSEQUENT 12Z GUIDANCE. THE MAIN QUESTION WILL BE PLACEMENT BUT
HAVE BETTER CONFIDENCE IN THE TREND OF WHAT OCCURS. PRECIP IS ON
TRACK TO QUICKLY SPREAD SOUTHEAST ACROSS THE AREA OVERNIGHT/AFTER
06Z/ AND SOUTHWEST AREAS STILL LOOK TO SEE A MIX OF RAIN OR SNOW AND
EVEN SOME SLEET THROUGH MID MORNING WHEN COLD AIR WILL TAKE OVER
CHANGING THINGS TO SNOW. PEAK PRECIP INTENSITY WILL BE AFTER
DAYBREAK INTO THE EARLY AFTERNOON. WINDS WILL TURN NORTHEAST AND
INCREASE DURING THE MORNING SETTING UP A DECENT FETCH DOWN LAKE
MICHIGAN. LAKE EFFECT PARAMETERS ARE SUB PAR BUT WHEN COMBINED WITH
SYNOPTIC SCALE ASCENT ARE PROBABLY SUFFICIENT TO PROVIDE SOME
MINIMAL ENHANCEMENT...MAINLY DUE TO INCREASED MOISTURE FLUX.
GUIDANCE VARIES WITH LIQUID OUTPUT WITH SOME RATHER HIGH AMOUNTS
NOTED PROBABLY SUGGESTIVE OF STRONG BANDING WHICH IS CERTAINLY
POSSIBLE. GIVEN PRECIPITABLE WATER VALUES OF AROUND 0.5 INCHES AND
FORCING OF 6 TO MAYBE 9 HOURS PEAK LIQUID AMOUNTS OF 0.3 TO 0.4
INCHES STILL SEEMS REASONABLE. LOCATION OF THESE AMOUNTS IS EXPECTED
ACROSS THE SOUTHERN CWA WITH AMOUNTS OF ONLY AROUND 0.1 INCHES
ACROSS THE NORTH. WITH SOUTHERN AREAS ALSO SEEING A MIX NOT ALL OF
THE LIQUID WILL GO TOWARD SNOW ACCUMULATION. THUS HIGHEST SNOW
AMOUNTS WILL OCCUR JUST TO THE NORTH...THOUGH WITH SOMEWHAT LOW
LIQUID EQUIVALENT. WILL DEPICT THE PEAK SNOWFALL FROM ROUGHLY
LASALLE COUNTY EAST-SOUTHEAST ALONG AND JUST SOUTH OF INTERSTATE 80
TO ROUGHLY KANKAKEE TO RENSSELAER. WILL CARRY 2-4 INCHES FOR THIS
AREA WITH AMOUNTS TAPERING TO ABOUT AN INCH ALONG THE WI
BORDER...WITH 1-2 INCHES ACROSS THE FAR NORTHERN CHICAGO METRO TO
AROUND 3 POSSIBLY 4 INCHES ACROSS THE FAR SOUTHERN CHICAGO METRO.
THERE IS STILL A CHANCE THIS COULD SHIFT FURTHER SOUTH.
PRECIPITATION QUICKLY ENDS MID TO LATE SUNDAY AFTERNOON WITH LITTLE
IF ANY LAKE EFFECT LINGERING GIVEN POOR INVERSION HEIGHTS.

HEADLINE POTENTIAL...WILL HOLD OFF ON ANY HEADLINES FOR NOW GIVEN
THAT A FURTHER SOUTH SHIFT IS STILL PLAUSIBLE. ANOTHER CONCERN IS
WIND SPEEDS WHICH WILL INCREASE TO 20 TO 25 MPH WITH GUSTS OF 30-35
MPH POSSIBLE SUNDAY MORNING THROUGH THE AFTERNOON. HOWEVER...WITH
FAIRLY WET SNOW RATIOS BLOWING WILL BE MINIMIZED BUT PROBABLY STILL
OCCUR. THERE IS ALSO A WINDOW FROM LATE MORNING THROUGH EARLY
AFTERNOON WHERE THE FALLING SNOW AND WIND MAY PUSH VISIBILITIES DOWN
UNDER A HALF OR QUARTER MILE...BUT THIS MAY OCCUR OVER A RATHER
SMALL AREA. EXPECT TO NEED A WINTER WEATHER ADVISORY ACROSS THE PEAK
SNOW AREA BUT AGAIN THE LOCATION MAY SHIFT AND IF BANDING DEVELOPS
THE SWATH OF SNOW COULD REALLY NARROW SO WOULD LIKE TO SEE THE
SYSTEM EVOLVE A LITTLE BIT MORE BEFORE DECIDING WHICH AREAS WILL SEE
THE BIGGEST IMPACT. WILL ISSUE A SPECIAL WEATHER STATEMENT
HIGHLIGHTING THE POTENTIAL IMPACTS FOR NOW.

MDB

&&

.LONG TERM...
308 AM CST

MONDAY THROUGH FRIDAY...

A MUCH BETTER DEFINED RIDGE WILL BE OVER WESTERN NORTH AMERICA
WITH A DEEP TROUGH OVER THE EAST COAST BY MONDAY. ANOTHER WAVE
WILL BE TRAVERSING THE RIDGE THEN DROP SOUTHEAST ACROSS THE GREAT
LAKES MONDAY BRINGING LOW CHANCES FOR SOME LIGHT SNOW. HIGH
PRESSURE WILL BUILD IN FROM THE WEST MONDAY NIGHT TURNING WINDS
MORE NORTHERLY. LAKE PARAMETERS WILL LIKELY BE MARGINAL BUT COULD
SEE SOME FLURRY OR LIGHT SNOW ACTIVITY DEVELOP FOR TUESDAY. THE
UPPER RIDGE BEGINS TO SHIFT EASTWARD WEDNESDAY WITH THE SURFACE
HIGH SHIFTING EAST AS WELL. THIS WILL LEAD TO A SHIFT TO SOUTHERLY
WINDS AND WARMING TEMPS LATE IN THE WEEK. GUIDANCE IS IN AGREEMENT
ON A LOW CROSSING THE AREA FIRST THING THURSDAY BRINGING MIXED
PRECIP POTENTIAL OR EVEN JUST RAIN. COLDER AIR BUILDS IN BEHIND
THE SYSTEM FRIDAY AS HIGH PRESSURE BUILDS INTO THE PLAINS. OVERALL
EXPECT TEMPS TO BE AT OR ABOVE NORMAL FROM TUESDAY ONWARD.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* MVFR CIGS WILL RETURN WITH BASES ARND 3KFT AGL...THEN LOWER
  TOWARDS 1000-1200FT AGL AFTER MIDNIGHT.

* WEST WINDS ARND 5-10KT...QUICKLY SHIFTING EAST AFTER MIDNIGHT
  AND INCREASING TO 10-18KT GUSTS TO 25KT BY DAYBREAK SUN. GUSTS
  INCREASE TOWARDS 30KT SUN MORNING.

* SNOW DEVELOPS JUST BEFORE DAYBREAK SUN...WITH PEAK TIMING
  BETWEEN 14-17Z FROM PERIODS OF STEADIER SNOW. CIGS WILL LOWER
  TOWARDS IFR CONDS WITH POSSIBLE IFR VSBYS FROM STEADY SNOW.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY INDICATES SOME CLEARING HAS TAKEN PLACE LATE THIS
MORNING ACROSS NORTHEAST IL/NORTHWEST IN...HOWEVER THERE IS A
WEDGE OF MVFR CIGS STARTING TO CREEP SOUTHEAST ACROSS NORTHWEST
IL. GUIDANCE AND TIMING WOULD INDICATE THE MVFR CIGS RETURNING TO
ORD/MDW ARND 19Z. THEN THE FOCUS WILL TURN TOWARDS THE APPROACHING
WINTER STORM SYSTEM. GUIDANCE CONTINUES TO SHIFT THE TRACK OF THE
SYSTEM FURTHER SOUTH/SOUTHWEST OF CHICAGO. THIS WILL LIKELY
DICTATE WHERE THE STEADIER/TIMING OF SNOW WILL OCCUR SUN MORNING.
AT THIS TIME HAVE ONLY MADE MINOR ADJUSTMENTS TO THE GOING
FORECAST...WITH SNOW DEVELOPING AFTER MIDNIGHT. POSSIBLY SEEING
REDUCED VSBYS FROM STEADIER SNOW BETWEEN 13-17Z. AS THE LOW PASSES
TO THE SOUTH...THE PRESSURE GRADIENT WILL RAPIDLY INCREASE ALONG
THE NORTHERN TIER OR NEAR THE TAF SITES. THIS WILL RESULT IN A
QUICK SHIFT TO EAST WINDS AND GUSTS APPROACHING 20KT ARND
DAYBREAK...THEN INCREASING TO NEAR 30KT BY MID TO LATE MORNING.

IFR CIGS WILL REMAIN ACROSS THE TAF SITES INTO SUN MIDDAY...THEN
SOME DRIER AIR WILL BEGIN TO FILTER INTO THE REGION AND BRING CIGS
BACK TO MVFR LATE SUN AFTN.

BEACHLER


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN CIGS RETURNING TO MVFR CONDS...MEDIUM
  CONFIDENCE IN PRECISE TIMING OF MVFR CIGS.

* MEDIUM CONFIDENCE IN TIMING OF CIGS LOWERING FURTHER TO IFR
  CONDS LATER TONIGHT.

* HIGH CONFIDENCE IN SNOW DEVELOPING AFTER MIDNIGHT...MEDIUM
  CONFIDENCE IN PRECISE TIMING OF STEADIER SNOW BETWEEN 13-17Z.

* HIGH CONFIDENCE IN WINDS QUICKLY TURNING EAST AND GUSTS
  DEVELOPING.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...MVFR CIGS POSSIBLE.

MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR...CHANCE OF SNOW AND MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR/IFR POSSIBLE.

FRIDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
238 AM CST

MAIN MARINE CONCERNS FOCUS ON THE PERIOD FROM EARLY SUNDAY MORNING
THROUGH SUNDAY EVENING...AS NORTH-NORTHEASTERLY WINDS QUICKLY
INCREASE IN RESPONSE TO A FAST-MOVING DEEPENING ALBERTA-CLIPPER LOW
WHICH WILL DIG SOUTHEAST FROM IOWA INTO CENTRAL ILLINOIS AND
SOUTHERN INDIANA DURING THE DAY.

IN THE VERY NEAR TERM THIS MORNING...LOW PRESSURE WAS MOVING EAST OF
JAMES BAY ACROSS QUEBEC...WITH A COLD FRONT TRAILING FROM THE LOW
ACROSS LAKE SUPERIOR AND WEST ALONG THE INTERNATIONAL BORDER. THIS
FRONT WILL SAG SOUTH ACROSS NORTHERN LAKE MICHIGAN LATER TODAY WITH
WINDS SHIFTING NORTH AND INCREASING BEHIND IT AS HIGH PRESSURE
SPREADS SOUTHEAST ACROSS MANITOBA AND NORTHWEST QUEBEC. BY
TONIGHT...THE FAST-MOVING CLIPPER WILL ALSO ALREADY BE ENTERING
IOWA  AND MOVING INTO WEST-CENTRAL ILLINOIS BY SUNDAY MORNING WHILE
DEEPENING A BIT. THE TIGHTENING GRADIENT AROUND THE LOW WILL ALSO
HELP TO TURN WINDS NORTHEAST AND STRENGTHEN THEM ALL THE WAY TO THE
SOUTH END OF THE LAKE AS THE LOW EVENTUALLY TRACKS INTO THE OHIO
VALLEY IN THE AFTERNOON. MODEL FORECAST SOUNDINGS DEPICT A PERIOD OF
SOLID 30 KT NORTHEAST WINDS ACROSS THE SOUTH 2/3 OR 3/4 OF THE LAKE
SUNDAY...WITH A FEW GUSTS OVER 30 KTS (MARGINAL GALE FORCE) DURING
THE DAY. WITH THE LOW MOVING QUICKLY OFF TO THE SOUTHEAST SUNDAY
NIGHT...WINDS WILL DIMINISH AS QUICKLY AS THEY INCREASED EARLY IN
THE DAY...AS WEAK HIGH PRESSURE RIDGING MOVES ACROSS THE LAKE SUNDAY
NIGHT. WILL NEED A SMALL CRAFT ADVISORY FOR THE IL/NW IND NEARSHORE
WATERS FROM ABOUT 6 AM CST SUNDAY THROUGH ABOUT 6 AM CST MONDAY FOR
THE STRONG WINDS AND RESULTING WAVES.

EARLY NEXT WEEK THE PATTERN CONTINUES TO APPEAR RATHER
PROGRESSIVE...WITH THE WEEK HIGH PRESSURE RIDGE OVER THE LAKE SUNDAY
NIGHT QUICKLY BEING DISPLACED MONDAY BY ANOTHER LOW PRESSURE SYSTEM
WHICH MOVES INTO THE NORTHERN LAKES MONDAY AFTERNOON. THIS BRINGS
WINDS AROUND TO THE SOUTH AND INCREASING INTO THE 25 KT RANGE FOR A
TIME MONDAY AS THE LOW APPROACHES. THE LOW THEN WEAKENS AS IT MOVES
SOUTHEAST ACROSS THE LAKES MONDAY NIGHT...FILLING AS A DEEP LOW
DEVELOPS ALONG THE ATLANTIC COAST. WEAK HIGH PRESSURE SPREADS ACROSS
THE LAKE TUESDAY...BEFORE ANOTHER LOW DEVELOPS ACROSS THE CENTRAL
PLAINS AND MOVES INTO THE MID-MISSISSIPPI VALLEY REGION THROUGH LATE
WEDNESDAY.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 241802
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1202 PM CST SAT JAN 24 2015

.SHORT TERM...
308 AM CST

TODAY THROUGH SUNDAY NIGHT...

THE MAIN FORECAST ISSUE WILL BE ACCUMULATING SNOW AND GUSTY WINDS
STARTING LATER TONIGHT CONTINUING THROUGH MUCH OF SUNDAY. WATER
VAPOR IMAGERY SHOWS A LONGWAVE TROUGH STRETCHING FROM HUDSON BAY
SOUTH TO THE GULF COAST WITH BROAD RIDGING OVER THE EASTERN
PACIFIC AND MUCH OF WESTERN CANADA AND THE NORTHWEST U.S. A WEAK
COOL FRONT IS CROSSING THE AREA BEHIND THE PASSAGE OF THE LONGWAVE
TROUGH AXIS. COOL ADVECTION THIS MORNING WILL GIVE WAY TO MODEST
WARM ADVECTION LATE THIS AFTERNOON. CLOUD COVER WILL BE THE WILD
CARD WITH TEMPS. STRATUS IS SPREADING SOUTHEAST ACROSS THE AREA
THIS MORNING BUT SATELLITE SHOWS GAPS IN COVERAGE UPSTREAM.
GUIDANCE IS MIXED WITH THE EXTENT OF CLOUD COVER BUT SUSPECT THERE
WILL BE BREAKS IN THE CLOUDS...ESPECIALLY THIS AFTERNOON...WITH
ANY MEANINGFUL SUNSHINE DURING THE EARLY/MID AFTERNOON HELPING
TEMPS SOMEWHAT. THIS IS MOST FAVORED SOUTH AND WEST SO WILL NUDGE
TEMPS UP SLIGHTLY THERE WHILE CARRYING UPPER 30S ACROSS THE REST
OF THE AREA.

THE MAIN FEATURE OF CONCERN IS A WAVE MOVING EAST-SOUTHEAST ACROSS
SOUTHERN ALBERTA. EVENING UPPER AIR ANALYSIS SHOWS A STRONG JET
PUSHING INTO THE PACIFIC NORTHWEST AND PIVOTING SOUTHEASTWARD AS
ADDITIONAL ENERGY PUSHES EASTWARD AMPLIFYING THE RIDGE. THE WAVE OF
CONCERN WILL DIG SOUTHEASTWARD ACROSS THE NORTHERN PLAINS TOWARD THE
MID MISSISSIPPI RIVER VALLEY AS A RESULT AND AMPLIFY AS IT DOES SO
INTO TONIGHT. THE SOUTH/WEST TREND OF THE TRACK OF THE SURFACE LOW
HAS CONTINUED AND DIFFERENCES REMAIN...ESPECIALLY WITH SOME OF THE
HIGH RES GUIDANCE WHICH TAKES THE LOW MUCH FURTHER SOUTH AND WEST
THAN SOME OF THE LOWER RES OPTIONS. IT APPEARS THAT THE LOW WILL NOT
TRACK NORTH OF ROUGHLY A BURLINGTON IOWA TO TERRE HAUTE INDIANA LINE
AT THIS POINT. WITH THE WAVE STILL TAKING SHAPE AND THE UPPER JET
STILL COMING ASHORE OVER THE PAC NORTHWEST FEEL THAT CONFIDENCE HAS
ROOM FOR IMPROVEMENT WITH THE MORNING UPPER AIR ANALYSIS AND
SUBSEQUENT 12Z GUIDANCE. THE MAIN QUESTION WILL BE PLACEMENT BUT
HAVE BETTER CONFIDENCE IN THE TREND OF WHAT OCCURS. PRECIP IS ON
TRACK TO QUICKLY SPREAD SOUTHEAST ACROSS THE AREA OVERNIGHT/AFTER
06Z/ AND SOUTHWEST AREAS STILL LOOK TO SEE A MIX OF RAIN OR SNOW AND
EVEN SOME SLEET THROUGH MID MORNING WHEN COLD AIR WILL TAKE OVER
CHANGING THINGS TO SNOW. PEAK PRECIP INTENSITY WILL BE AFTER
DAYBREAK INTO THE EARLY AFTERNOON. WINDS WILL TURN NORTHEAST AND
INCREASE DURING THE MORNING SETTING UP A DECENT FETCH DOWN LAKE
MICHIGAN. LAKE EFFECT PARAMETERS ARE SUB PAR BUT WHEN COMBINED WITH
SYNOPTIC SCALE ASCENT ARE PROBABLY SUFFICIENT TO PROVIDE SOME
MINIMAL ENHANCEMENT...MAINLY DUE TO INCREASED MOISTURE FLUX.
GUIDANCE VARIES WITH LIQUID OUTPUT WITH SOME RATHER HIGH AMOUNTS
NOTED PROBABLY SUGGESTIVE OF STRONG BANDING WHICH IS CERTAINLY
POSSIBLE. GIVEN PRECIPITABLE WATER VALUES OF AROUND 0.5 INCHES AND
FORCING OF 6 TO MAYBE 9 HOURS PEAK LIQUID AMOUNTS OF 0.3 TO 0.4
INCHES STILL SEEMS REASONABLE. LOCATION OF THESE AMOUNTS IS EXPECTED
ACROSS THE SOUTHERN CWA WITH AMOUNTS OF ONLY AROUND 0.1 INCHES
ACROSS THE NORTH. WITH SOUTHERN AREAS ALSO SEEING A MIX NOT ALL OF
THE LIQUID WILL GO TOWARD SNOW ACCUMULATION. THUS HIGHEST SNOW
AMOUNTS WILL OCCUR JUST TO THE NORTH...THOUGH WITH SOMEWHAT LOW
LIQUID EQUIVALENT. WILL DEPICT THE PEAK SNOWFALL FROM ROUGHLY
LASALLE COUNTY EAST-SOUTHEAST ALONG AND JUST SOUTH OF INTERSTATE 80
TO ROUGHLY KANKAKEE TO RENSSELAER. WILL CARRY 2-4 INCHES FOR THIS
AREA WITH AMOUNTS TAPERING TO ABOUT AN INCH ALONG THE WI
BORDER...WITH 1-2 INCHES ACROSS THE FAR NORTHERN CHICAGO METRO TO
AROUND 3 POSSIBLY 4 INCHES ACROSS THE FAR SOUTHERN CHICAGO METRO.
THERE IS STILL A CHANCE THIS COULD SHIFT FURTHER SOUTH.
PRECIPITATION QUICKLY ENDS MID TO LATE SUNDAY AFTERNOON WITH LITTLE
IF ANY LAKE EFFECT LINGERING GIVEN POOR INVERSION HEIGHTS.

HEADLINE POTENTIAL...WILL HOLD OFF ON ANY HEADLINES FOR NOW GIVEN
THAT A FURTHER SOUTH SHIFT IS STILL PLAUSIBLE. ANOTHER CONCERN IS
WIND SPEEDS WHICH WILL INCREASE TO 20 TO 25 MPH WITH GUSTS OF 30-35
MPH POSSIBLE SUNDAY MORNING THROUGH THE AFTERNOON. HOWEVER...WITH
FAIRLY WET SNOW RATIOS BLOWING WILL BE MINIMIZED BUT PROBABLY STILL
OCCUR. THERE IS ALSO A WINDOW FROM LATE MORNING THROUGH EARLY
AFTERNOON WHERE THE FALLING SNOW AND WIND MAY PUSH VISIBILITIES DOWN
UNDER A HALF OR QUARTER MILE...BUT THIS MAY OCCUR OVER A RATHER
SMALL AREA. EXPECT TO NEED A WINTER WEATHER ADVISORY ACROSS THE PEAK
SNOW AREA BUT AGAIN THE LOCATION MAY SHIFT AND IF BANDING DEVELOPS
THE SWATH OF SNOW COULD REALLY NARROW SO WOULD LIKE TO SEE THE
SYSTEM EVOLVE A LITTLE BIT MORE BEFORE DECIDING WHICH AREAS WILL SEE
THE BIGGEST IMPACT. WILL ISSUE A SPECIAL WEATHER STATEMENT
HIGHLIGHTING THE POTENTIAL IMPACTS FOR NOW.

MDB

&&

.LONG TERM...
308 AM CST

MONDAY THROUGH FRIDAY...

A MUCH BETTER DEFINED RIDGE WILL BE OVER WESTERN NORTH AMERICA
WITH A DEEP TROUGH OVER THE EAST COAST BY MONDAY. ANOTHER WAVE
WILL BE TRAVERSING THE RIDGE THEN DROP SOUTHEAST ACROSS THE GREAT
LAKES MONDAY BRINGING LOW CHANCES FOR SOME LIGHT SNOW. HIGH
PRESSURE WILL BUILD IN FROM THE WEST MONDAY NIGHT TURNING WINDS
MORE NORTHERLY. LAKE PARAMETERS WILL LIKELY BE MARGINAL BUT COULD
SEE SOME FLURRY OR LIGHT SNOW ACTIVITY DEVELOP FOR TUESDAY. THE
UPPER RIDGE BEGINS TO SHIFT EASTWARD WEDNESDAY WITH THE SURFACE
HIGH SHIFTING EAST AS WELL. THIS WILL LEAD TO A SHIFT TO SOUTHERLY
WINDS AND WARMING TEMPS LATE IN THE WEEK. GUIDANCE IS IN AGREEMENT
ON A LOW CROSSING THE AREA FIRST THING THURSDAY BRINGING MIXED
PRECIP POTENTIAL OR EVEN JUST RAIN. COLDER AIR BUILDS IN BEHIND
THE SYSTEM FRIDAY AS HIGH PRESSURE BUILDS INTO THE PLAINS. OVERALL
EXPECT TEMPS TO BE AT OR ABOVE NORMAL FROM TUESDAY ONWARD.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* MVFR CIGS WILL RETURN WITH BASES ARND 3KFT AGL...THEN LOWER
  TOWARDS 1000-1200FT AGL AFTER MIDNIGHT.

* WEST WINDS ARND 5-10KT...QUICKLY SHIFTING EAST AFTER MIDNIGHT
  AND INCREASING TO 10-18KT GUSTS TO 25KT BY DAYBREAK SUN. GUSTS
  INCREASE TOWARDS 30KT SUN MORNING.

* SNOW DEVELOPS JUST BEFORE DAYBREAK SUN...WITH PEAK TIMING
  BETWEEN 14-17Z FROM PERIODS OF STEADIER SNOW. CIGS WILL LOWER
  TOWARDS IFR CONDS WITH POSSIBLE IFR VSBYS FROM STEADY SNOW.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY INDICATES SOME CLEARING HAS TAKEN PLACE LATE THIS
MORNING ACROSS NORTHEAST IL/NORTHWEST IN...HOWEVER THERE IS A
WEDGE OF MVFR CIGS STARTING TO CREEP SOUTHEAST ACROSS NORTHWEST
IL. GUIDANCE AND TIMING WOULD INDICATE THE MVFR CIGS RETURNING TO
ORD/MDW ARND 19Z. THEN THE FOCUS WILL TURN TOWARDS THE APPROACHING
WINTER STORM SYSTEM. GUIDANCE CONTINUES TO SHIFT THE TRACK OF THE
SYSTEM FURTHER SOUTH/SOUTHWEST OF CHICAGO. THIS WILL LIKELY
DICTATE WHERE THE STEADIER/TIMING OF SNOW WILL OCCUR SUN MORNING.
AT THIS TIME HAVE ONLY MADE MINOR ADJUSTMENTS TO THE GOING
FORECAST...WITH SNOW DEVELOPING AFTER MIDNIGHT. POSSIBLY SEEING
REDUCED VSBYS FROM STEADIER SNOW BETWEEN 13-17Z. AS THE LOW PASSES
TO THE SOUTH...THE PRESSURE GRADIENT WILL RAPIDLY INCREASE ALONG
THE NORTHERN TIER OR NEAR THE TAF SITES. THIS WILL RESULT IN A
QUICK SHIFT TO EAST WINDS AND GUSTS APPROACHING 20KT ARND
DAYBREAK...THEN INCREASING TO NEAR 30KT BY MID TO LATE MORNING.

IFR CIGS WILL REMAIN ACROSS THE TAF SITES INTO SUN MIDDAY...THEN
SOME DRIER AIR WILL BEGIN TO FILTER INTO THE REGION AND BRING CIGS
BACK TO MVFR LATE SUN AFTN.

BEACHLER


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN CIGS RETURNING TO MVFR CONDS...MEDIUM
  CONFIDENCE IN PRECISE TIMING OF MVFR CIGS.

* MEDIUM CONFIDENCE IN TIMING OF CIGS LOWERING FURTHER TO IFR
  CONDS LATER TONIGHT.

* HIGH CONFIDENCE IN SNOW DEVELOPING AFTER MIDNIGHT...MEDIUM
  CONFIDENCE IN PRECISE TIMING OF STEADIER SNOW BETWEEN 13-17Z.

* HIGH CONFIDENCE IN WINDS QUICKLY TURNING EAST AND GUSTS
  DEVELOPING.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...MVFR CIGS POSSIBLE.

MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR...CHANCE OF SNOW AND MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR/IFR POSSIBLE.

FRIDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
238 AM CST

MAIN MARINE CONCERNS FOCUS ON THE PERIOD FROM EARLY SUNDAY MORNING
THROUGH SUNDAY EVENING...AS NORTH-NORTHEASTERLY WINDS QUICKLY
INCREASE IN RESPONSE TO A FAST-MOVING DEEPENING ALBERTA-CLIPPER LOW
WHICH WILL DIG SOUTHEAST FROM IOWA INTO CENTRAL ILLINOIS AND
SOUTHERN INDIANA DURING THE DAY.

IN THE VERY NEAR TERM THIS MORNING...LOW PRESSURE WAS MOVING EAST OF
JAMES BAY ACROSS QUEBEC...WITH A COLD FRONT TRAILING FROM THE LOW
ACROSS LAKE SUPERIOR AND WEST ALONG THE INTERNATIONAL BORDER. THIS
FRONT WILL SAG SOUTH ACROSS NORTHERN LAKE MICHIGAN LATER TODAY WITH
WINDS SHIFTING NORTH AND INCREASING BEHIND IT AS HIGH PRESSURE
SPREADS SOUTHEAST ACROSS MANITOBA AND NORTHWEST QUEBEC. BY
TONIGHT...THE FAST-MOVING CLIPPER WILL ALSO ALREADY BE ENTERING
IOWA  AND MOVING INTO WEST-CENTRAL ILLINOIS BY SUNDAY MORNING WHILE
DEEPENING A BIT. THE TIGHTENING GRADIENT AROUND THE LOW WILL ALSO
HELP TO TURN WINDS NORTHEAST AND STRENGTHEN THEM ALL THE WAY TO THE
SOUTH END OF THE LAKE AS THE LOW EVENTUALLY TRACKS INTO THE OHIO
VALLEY IN THE AFTERNOON. MODEL FORECAST SOUNDINGS DEPICT A PERIOD OF
SOLID 30 KT NORTHEAST WINDS ACROSS THE SOUTH 2/3 OR 3/4 OF THE LAKE
SUNDAY...WITH A FEW GUSTS OVER 30 KTS (MARGINAL GALE FORCE) DURING
THE DAY. WITH THE LOW MOVING QUICKLY OFF TO THE SOUTHEAST SUNDAY
NIGHT...WINDS WILL DIMINISH AS QUICKLY AS THEY INCREASED EARLY IN
THE DAY...AS WEAK HIGH PRESSURE RIDGING MOVES ACROSS THE LAKE SUNDAY
NIGHT. WILL NEED A SMALL CRAFT ADVISORY FOR THE IL/NW IND NEARSHORE
WATERS FROM ABOUT 6 AM CST SUNDAY THROUGH ABOUT 6 AM CST MONDAY FOR
THE STRONG WINDS AND RESULTING WAVES.

EARLY NEXT WEEK THE PATTERN CONTINUES TO APPEAR RATHER
PROGRESSIVE...WITH THE WEEK HIGH PRESSURE RIDGE OVER THE LAKE SUNDAY
NIGHT QUICKLY BEING DISPLACED MONDAY BY ANOTHER LOW PRESSURE SYSTEM
WHICH MOVES INTO THE NORTHERN LAKES MONDAY AFTERNOON. THIS BRINGS
WINDS AROUND TO THE SOUTH AND INCREASING INTO THE 25 KT RANGE FOR A
TIME MONDAY AS THE LOW APPROACHES. THE LOW THEN WEAKENS AS IT MOVES
SOUTHEAST ACROSS THE LAKES MONDAY NIGHT...FILLING AS A DEEP LOW
DEVELOPS ALONG THE ATLANTIC COAST. WEAK HIGH PRESSURE SPREADS ACROSS
THE LAKE TUESDAY...BEFORE ANOTHER LOW DEVELOPS ACROSS THE CENTRAL
PLAINS AND MOVES INTO THE MID-MISSISSIPPI VALLEY REGION THROUGH LATE
WEDNESDAY.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 241612
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1012 AM CST SAT JAN 24 2015

.SHORT TERM...
308 AM CST

TODAY THROUGH SUNDAY NIGHT...

THE MAIN FORECAST ISSUE WILL BE ACCUMULATING SNOW AND GUSTY WINDS
STARTING LATER TONIGHT CONTINUING THROUGH MUCH OF SUNDAY. WATER
VAPOR IMAGERY SHOWS A LONGWAVE TROUGH STRETCHING FROM HUDSON BAY
SOUTH TO THE GULF COAST WITH BROAD RIDGING OVER THE EASTERN
PACIFIC AND MUCH OF WESTERN CANADA AND THE NORTHWEST U.S. A WEAK
COOL FRONT IS CROSSING THE AREA BEHIND THE PASSAGE OF THE LONGWAVE
TROUGH AXIS. COOL ADVECTION THIS MORNING WILL GIVE WAY TO MODEST
WARM ADVECTION LATE THIS AFTERNOON. CLOUD COVER WILL BE THE WILD
CARD WITH TEMPS. STRATUS IS SPREADING SOUTHEAST ACROSS THE AREA
THIS MORNING BUT SATELLITE SHOWS GAPS IN COVERAGE UPSTREAM.
GUIDANCE IS MIXED WITH THE EXTENT OF CLOUD COVER BUT SUSPECT THERE
WILL BE BREAKS IN THE CLOUDS...ESPECIALLY THIS AFTERNOON...WITH
ANY MEANINGFUL SUNSHINE DURING THE EARLY/MID AFTERNOON HELPING
TEMPS SOMEWHAT. THIS IS MOST FAVORED SOUTH AND WEST SO WILL NUDGE
TEMPS UP SLIGHTLY THERE WHILE CARRYING UPPER 30S ACROSS THE REST
OF THE AREA.

THE MAIN FEATURE OF CONCERN IS A WAVE MOVING EAST-SOUTHEAST ACROSS
SOUTHERN ALBERTA. EVENING UPPER AIR ANALYSIS SHOWS A STRONG JET
PUSHING INTO THE PACIFIC NORTHWEST AND PIVOTING SOUTHEASTWARD AS
ADDITIONAL ENERGY PUSHES EASTWARD AMPLIFYING THE RIDGE. THE WAVE OF
CONCERN WILL DIG SOUTHEASTWARD ACROSS THE NORTHERN PLAINS TOWARD THE
MID MISSISSIPPI RIVER VALLEY AS A RESULT AND AMPLIFY AS IT DOES SO
INTO TONIGHT. THE SOUTH/WEST TREND OF THE TRACK OF THE SURFACE LOW
HAS CONTINUED AND DIFFERENCES REMAIN...ESPECIALLY WITH SOME OF THE
HIGH RES GUIDANCE WHICH TAKES THE LOW MUCH FURTHER SOUTH AND WEST
THAN SOME OF THE LOWER RES OPTIONS. IT APPEARS THAT THE LOW WILL NOT
TRACK NORTH OF ROUGHLY A BURLINGTON IOWA TO TERRE HAUTE INDIANA LINE
AT THIS POINT. WITH THE WAVE STILL TAKING SHAPE AND THE UPPER JET
STILL COMING ASHORE OVER THE PAC NORTHWEST FEEL THAT CONFIDENCE HAS
ROOM FOR IMPROVEMENT WITH THE MORNING UPPER AIR ANALYSIS AND
SUBSEQUENT 12Z GUIDANCE. THE MAIN QUESTION WILL BE PLACEMENT BUT
HAVE BETTER CONFIDENCE IN THE TREND OF WHAT OCCURS. PRECIP IS ON
TRACK TO QUICKLY SPREAD SOUTHEAST ACROSS THE AREA OVERNIGHT/AFTER
06Z/ AND SOUTHWEST AREAS STILL LOOK TO SEE A MIX OF RAIN OR SNOW AND
EVEN SOME SLEET THROUGH MID MORNING WHEN COLD AIR WILL TAKE OVER
CHANGING THINGS TO SNOW. PEAK PRECIP INTENSITY WILL BE AFTER
DAYBREAK INTO THE EARLY AFTERNOON. WINDS WILL TURN NORTHEAST AND
INCREASE DURING THE MORNING SETTING UP A DECENT FETCH DOWN LAKE
MICHIGAN. LAKE EFFECT PARAMETERS ARE SUB PAR BUT WHEN COMBINED WITH
SYNOPTIC SCALE ASCENT ARE PROBABLY SUFFICIENT TO PROVIDE SOME
MINIMAL ENHANCEMENT...MAINLY DUE TO INCREASED MOISTURE FLUX.
GUIDANCE VARIES WITH LIQUID OUTPUT WITH SOME RATHER HIGH AMOUNTS
NOTED PROBABLY SUGGESTIVE OF STRONG BANDING WHICH IS CERTAINLY
POSSIBLE. GIVEN PRECIPITABLE WATER VALUES OF AROUND 0.5 INCHES AND
FORCING OF 6 TO MAYBE 9 HOURS PEAK LIQUID AMOUNTS OF 0.3 TO 0.4
INCHES STILL SEEMS REASONABLE. LOCATION OF THESE AMOUNTS IS EXPECTED
ACROSS THE SOUTHERN CWA WITH AMOUNTS OF ONLY AROUND 0.1 INCHES
ACROSS THE NORTH. WITH SOUTHERN AREAS ALSO SEEING A MIX NOT ALL OF
THE LIQUID WILL GO TOWARD SNOW ACCUMULATION. THUS HIGHEST SNOW
AMOUNTS WILL OCCUR JUST TO THE NORTH...THOUGH WITH SOMEWHAT LOW
LIQUID EQUIVALENT. WILL DEPICT THE PEAK SNOWFALL FROM ROUGHLY
LASALLE COUNTY EAST-SOUTHEAST ALONG AND JUST SOUTH OF INTERSTATE 80
TO ROUGHLY KANKAKEE TO RENSSELAER. WILL CARRY 2-4 INCHES FOR THIS
AREA WITH AMOUNTS TAPERING TO ABOUT AN INCH ALONG THE WI
BORDER...WITH 1-2 INCHES ACROSS THE FAR NORTHERN CHICAGO METRO TO
AROUND 3 POSSIBLY 4 INCHES ACROSS THE FAR SOUTHERN CHICAGO METRO.
THERE IS STILL A CHANCE THIS COULD SHIFT FURTHER SOUTH.
PRECIPITATION QUICKLY ENDS MID TO LATE SUNDAY AFTERNOON WITH LITTLE
IF ANY LAKE EFFECT LINGERING GIVEN POOR INVERSION HEIGHTS.

HEADLINE POTENTIAL...WILL HOLD OFF ON ANY HEADLINES FOR NOW GIVEN
THAT A FURTHER SOUTH SHIFT IS STILL PLAUSIBLE. ANOTHER CONCERN IS
WIND SPEEDS WHICH WILL INCREASE TO 20 TO 25 MPH WITH GUSTS OF 30-35
MPH POSSIBLE SUNDAY MORNING THROUGH THE AFTERNOON. HOWEVER...WITH
FAIRLY WET SNOW RATIOS BLOWING WILL BE MINIMIZED BUT PROBABLY STILL
OCCUR. THERE IS ALSO A WINDOW FROM LATE MORNING THROUGH EARLY
AFTERNOON WHERE THE FALLING SNOW AND WIND MAY PUSH VISIBILITIES DOWN
UNDER A HALF OR QUARTER MILE...BUT THIS MAY OCCUR OVER A RATHER
SMALL AREA. EXPECT TO NEED A WINTER WEATHER ADVISORY ACROSS THE PEAK
SNOW AREA BUT AGAIN THE LOCATION MAY SHIFT AND IF BANDING DEVELOPS
THE SWATH OF SNOW COULD REALLY NARROW SO WOULD LIKE TO SEE THE
SYSTEM EVOLVE A LITTLE BIT MORE BEFORE DECIDING WHICH AREAS WILL SEE
THE BIGGEST IMPACT. WILL ISSUE A SPECIAL WEATHER STATEMENT
HIGHLIGHTING THE POTENTIAL IMPACTS FOR NOW.

MDB

&&

.LONG TERM...
308 AM CST

MONDAY THROUGH FRIDAY...

A MUCH BETTER DEFINED RIDGE WILL BE OVER WESTERN NORTH AMERICA
WITH A DEEP TROUGH OVER THE EAST COAST BY MONDAY. ANOTHER WAVE
WILL BE TRAVERSING THE RIDGE THEN DROP SOUTHEAST ACROSS THE GREAT
LAKES MONDAY BRINGING LOW CHANCES FOR SOME LIGHT SNOW. HIGH
PRESSURE WILL BUILD IN FROM THE WEST MONDAY NIGHT TURNING WINDS
MORE NORTHERLY. LAKE PARAMETERS WILL LIKELY BE MARGINAL BUT COULD
SEE SOME FLURRY OR LIGHT SNOW ACTIVITY DEVELOP FOR TUESDAY. THE
UPPER RIDGE BEGINS TO SHIFT EASTWARD WEDNESDAY WITH THE SURFACE
HIGH SHIFTING EAST AS WELL. THIS WILL LEAD TO A SHIFT TO SOUTHERLY
WINDS AND WARMING TEMPS LATE IN THE WEEK. GUIDANCE IS IN AGREEMENT
ON A LOW CROSSING THE AREA FIRST THING THURSDAY BRINGING MIXED
PRECIP POTENTIAL OR EVEN JUST RAIN. COLDER AIR BUILDS IN BEHIND
THE SYSTEM FRIDAY AS HIGH PRESSURE BUILDS INTO THE PLAINS. OVERALL
EXPECT TEMPS TO BE AT OR ABOVE NORMAL FROM TUESDAY ONWARD.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* POTENTIAL FOR MVFR CIGS AGAIN THIS EVENING.

* SNOW DEVELOPING LATE TONIGHT WITH IFR/LIFR CONDITIONS EXPECTED
  SUNDAY MORNING WITH ACCUMULATING SNOW OF 1-3 INCHES.

* WESTERLY WINDS NEAR 10 KT TODAY/THIS EVENING...BECOMING
  NORTHEAST AFTER MIDNIGHT AND THEN STRONG/GUSTY NEAR 30 KTS BY
  SUNDAY MORNING AND CONTINUING DURING THE DAY.

RATZER/BEACHLER

//DISCUSSION...UPDATED 12Z...

PATCHY MVFR CIGS 2500-3000 FT ACROSS THE REGION THIS
MORNING...IN LIGHT WEST/NORTHWEST FLOW AHEAD OF COLD FRONT OVER
THE UPPER MIDWEST. EXPECTATION IS THAT MVFR CIGS WILL SCATTER OUT
BY MIDDAY. WESTERLY WINDS 260-290 DEGREES NEAR 10 KT WILL DIMINISH
THIS EVENING.

ATTENTION THEN TURNS TO QUICK MOVING ALBERTA-CLIPPER WHICH RAPIDLY
MOVES INTO THE AREA LATE TONIGHT AND BRINGS A PERIOD OF SNOW...AND
GUSTY NORTHEAST WINDS...TO THE TERMINALS. PERHAPS AM LEAST
CONFIDENT ABOUT CLOUDS DURING THE EVENING AND EARLY OVERNIGHT
HOURS AS GUIDANCE SATURATES THE BOUNDARY LAYER PRIOR TO MOISTURE
MOVING IN ALOFT. HAVE MAINTAINED PREVIOUS FORECAST TREND OF MVFR
CIGS REDEVELOPING AND EVENTUALLY LOWERING A BIT ALONG WITH SOME
MINOR VIS REDUCTION IN HAZE. MUCH GREATER CONFIDENCE IN SNOW
DEVELOPING PRIOR TO 12Z...WITH CIG/VIS CONDITIONS DETERIORATING TO
IFR/LIFR SHORTLY AFTER 12Z WITH STRONGEST/DEEPEST LIFT AND
SATURATION. IN ADDITION TO THE SNOW...THE SURFACE LOW WILL BE
DEEPENING AS IT PASSES SOUTHWEST OF THE AREA...RESULTING IN WINDS
SLACKING THIS EVENING AND THEN TURNING NORTHEAST AFTER MIDNIGHT.
WINDS THEN EXPECTED TO INCREASE RAPIDLY TOWARD MORNING...WITH
GUSTS NEAR 30 KT SUNDAY. SNOW EXPECTED TO ACCUMULATE 1-3 INCHES
ACROSS TERMINALS...WITH BLOWING SNOW/DRIFTING GIVEN THE STRONG
WINDS. SNOW SHOULD TAPER OFF BY EARLY AFTERNOON.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM CONFIDENCE IN MVFR CIGS TIMING THIS LATE AFTERNOON/EVENING.

* HIGH IN WIND TRENDS.

* MEDIUM-HIGH IN SNOW TIMING LATE TONIGHT/SUNDAY AND WITH CIG/VIS
  TRENDS.

RATZER/BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...MVFR CIGS POSSIBLE.

MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR...CHANCE OF SNOW AND MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR/IFR POSSIBLE.

FRIDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
238 AM CST

MAIN MARINE CONCERNS FOCUS ON THE PERIOD FROM EARLY SUNDAY MORNING
THROUGH SUNDAY EVENING...AS NORTH-NORTHEASTERLY WINDS QUICKLY
INCREASE IN RESPONSE TO A FAST-MOVING DEEPENING ALBERTA-CLIPPER LOW
WHICH WILL DIG SOUTHEAST FROM IOWA INTO CENTRAL ILLINOIS AND
SOUTHERN INDIANA DURING THE DAY.

IN THE VERY NEAR TERM THIS MORNING...LOW PRESSURE WAS MOVING EAST OF
JAMES BAY ACROSS QUEBEC...WITH A COLD FRONT TRAILING FROM THE LOW
ACROSS LAKE SUPERIOR AND WEST ALONG THE INTERNATIONAL BORDER. THIS
FRONT WILL SAG SOUTH ACROSS NORTHERN LAKE MICHIGAN LATER TODAY WITH
WINDS SHIFTING NORTH AND INCREASING BEHIND IT AS HIGH PRESSURE
SPREADS SOUTHEAST ACROSS MANITOBA AND NORTHWEST QUEBEC. BY
TONIGHT...THE FAST-MOVING CLIPPER WILL ALSO ALREADY BE ENTERING
IOWA  AND MOVING INTO WEST-CENTRAL ILLINOIS BY SUNDAY MORNING WHILE
DEEPENING A BIT. THE TIGHTENING GRADIENT AROUND THE LOW WILL ALSO
HELP TO TURN WINDS NORTHEAST AND STRENGTHEN THEM ALL THE WAY TO THE
SOUTH END OF THE LAKE AS THE LOW EVENTUALLY TRACKS INTO THE OHIO
VALLEY IN THE AFTERNOON. MODEL FORECAST SOUNDINGS DEPICT A PERIOD OF
SOLID 30 KT NORTHEAST WINDS ACROSS THE SOUTH 2/3 OR 3/4 OF THE LAKE
SUNDAY...WITH A FEW GUSTS OVER 30 KTS (MARGINAL GALE FORCE) DURING
THE DAY. WITH THE LOW MOVING QUICKLY OFF TO THE SOUTHEAST SUNDAY
NIGHT...WINDS WILL DIMINISH AS QUICKLY AS THEY INCREASED EARLY IN
THE DAY...AS WEAK HIGH PRESSURE RIDGING MOVES ACROSS THE LAKE SUNDAY
NIGHT. WILL NEED A SMALL CRAFT ADVISORY FOR THE IL/NW IND NEARSHORE
WATERS FROM ABOUT 6 AM CST SUNDAY THROUGH ABOUT 6 AM CST MONDAY FOR
THE STRONG WINDS AND RESULTING WAVES.

EARLY NEXT WEEK THE PATTERN CONTINUES TO APPEAR RATHER
PROGRESSIVE...WITH THE WEEK HIGH PRESSURE RIDGE OVER THE LAKE SUNDAY
NIGHT QUICKLY BEING DISPLACED MONDAY BY ANOTHER LOW PRESSURE SYSTEM
WHICH MOVES INTO THE NORTHERN LAKES MONDAY AFTERNOON. THIS BRINGS
WINDS AROUND TO THE SOUTH AND INCREASING INTO THE 25 KT RANGE FOR A
TIME MONDAY AS THE LOW APPROACHES. THE LOW THEN WEAKENS AS IT MOVES
SOUTHEAST ACROSS THE LAKES MONDAY NIGHT...FILLING AS A DEEP LOW
DEVELOPS ALONG THE ATLANTIC COAST. WEAK HIGH PRESSURE SPREADS ACROSS
THE LAKE TUESDAY...BEFORE ANOTHER LOW DEVELOPS ACROSS THE CENTRAL
PLAINS AND MOVES INTO THE MID-MISSISSIPPI VALLEY REGION THROUGH LATE
WEDNESDAY.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 241612
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1012 AM CST SAT JAN 24 2015

.SHORT TERM...
308 AM CST

TODAY THROUGH SUNDAY NIGHT...

THE MAIN FORECAST ISSUE WILL BE ACCUMULATING SNOW AND GUSTY WINDS
STARTING LATER TONIGHT CONTINUING THROUGH MUCH OF SUNDAY. WATER
VAPOR IMAGERY SHOWS A LONGWAVE TROUGH STRETCHING FROM HUDSON BAY
SOUTH TO THE GULF COAST WITH BROAD RIDGING OVER THE EASTERN
PACIFIC AND MUCH OF WESTERN CANADA AND THE NORTHWEST U.S. A WEAK
COOL FRONT IS CROSSING THE AREA BEHIND THE PASSAGE OF THE LONGWAVE
TROUGH AXIS. COOL ADVECTION THIS MORNING WILL GIVE WAY TO MODEST
WARM ADVECTION LATE THIS AFTERNOON. CLOUD COVER WILL BE THE WILD
CARD WITH TEMPS. STRATUS IS SPREADING SOUTHEAST ACROSS THE AREA
THIS MORNING BUT SATELLITE SHOWS GAPS IN COVERAGE UPSTREAM.
GUIDANCE IS MIXED WITH THE EXTENT OF CLOUD COVER BUT SUSPECT THERE
WILL BE BREAKS IN THE CLOUDS...ESPECIALLY THIS AFTERNOON...WITH
ANY MEANINGFUL SUNSHINE DURING THE EARLY/MID AFTERNOON HELPING
TEMPS SOMEWHAT. THIS IS MOST FAVORED SOUTH AND WEST SO WILL NUDGE
TEMPS UP SLIGHTLY THERE WHILE CARRYING UPPER 30S ACROSS THE REST
OF THE AREA.

THE MAIN FEATURE OF CONCERN IS A WAVE MOVING EAST-SOUTHEAST ACROSS
SOUTHERN ALBERTA. EVENING UPPER AIR ANALYSIS SHOWS A STRONG JET
PUSHING INTO THE PACIFIC NORTHWEST AND PIVOTING SOUTHEASTWARD AS
ADDITIONAL ENERGY PUSHES EASTWARD AMPLIFYING THE RIDGE. THE WAVE OF
CONCERN WILL DIG SOUTHEASTWARD ACROSS THE NORTHERN PLAINS TOWARD THE
MID MISSISSIPPI RIVER VALLEY AS A RESULT AND AMPLIFY AS IT DOES SO
INTO TONIGHT. THE SOUTH/WEST TREND OF THE TRACK OF THE SURFACE LOW
HAS CONTINUED AND DIFFERENCES REMAIN...ESPECIALLY WITH SOME OF THE
HIGH RES GUIDANCE WHICH TAKES THE LOW MUCH FURTHER SOUTH AND WEST
THAN SOME OF THE LOWER RES OPTIONS. IT APPEARS THAT THE LOW WILL NOT
TRACK NORTH OF ROUGHLY A BURLINGTON IOWA TO TERRE HAUTE INDIANA LINE
AT THIS POINT. WITH THE WAVE STILL TAKING SHAPE AND THE UPPER JET
STILL COMING ASHORE OVER THE PAC NORTHWEST FEEL THAT CONFIDENCE HAS
ROOM FOR IMPROVEMENT WITH THE MORNING UPPER AIR ANALYSIS AND
SUBSEQUENT 12Z GUIDANCE. THE MAIN QUESTION WILL BE PLACEMENT BUT
HAVE BETTER CONFIDENCE IN THE TREND OF WHAT OCCURS. PRECIP IS ON
TRACK TO QUICKLY SPREAD SOUTHEAST ACROSS THE AREA OVERNIGHT/AFTER
06Z/ AND SOUTHWEST AREAS STILL LOOK TO SEE A MIX OF RAIN OR SNOW AND
EVEN SOME SLEET THROUGH MID MORNING WHEN COLD AIR WILL TAKE OVER
CHANGING THINGS TO SNOW. PEAK PRECIP INTENSITY WILL BE AFTER
DAYBREAK INTO THE EARLY AFTERNOON. WINDS WILL TURN NORTHEAST AND
INCREASE DURING THE MORNING SETTING UP A DECENT FETCH DOWN LAKE
MICHIGAN. LAKE EFFECT PARAMETERS ARE SUB PAR BUT WHEN COMBINED WITH
SYNOPTIC SCALE ASCENT ARE PROBABLY SUFFICIENT TO PROVIDE SOME
MINIMAL ENHANCEMENT...MAINLY DUE TO INCREASED MOISTURE FLUX.
GUIDANCE VARIES WITH LIQUID OUTPUT WITH SOME RATHER HIGH AMOUNTS
NOTED PROBABLY SUGGESTIVE OF STRONG BANDING WHICH IS CERTAINLY
POSSIBLE. GIVEN PRECIPITABLE WATER VALUES OF AROUND 0.5 INCHES AND
FORCING OF 6 TO MAYBE 9 HOURS PEAK LIQUID AMOUNTS OF 0.3 TO 0.4
INCHES STILL SEEMS REASONABLE. LOCATION OF THESE AMOUNTS IS EXPECTED
ACROSS THE SOUTHERN CWA WITH AMOUNTS OF ONLY AROUND 0.1 INCHES
ACROSS THE NORTH. WITH SOUTHERN AREAS ALSO SEEING A MIX NOT ALL OF
THE LIQUID WILL GO TOWARD SNOW ACCUMULATION. THUS HIGHEST SNOW
AMOUNTS WILL OCCUR JUST TO THE NORTH...THOUGH WITH SOMEWHAT LOW
LIQUID EQUIVALENT. WILL DEPICT THE PEAK SNOWFALL FROM ROUGHLY
LASALLE COUNTY EAST-SOUTHEAST ALONG AND JUST SOUTH OF INTERSTATE 80
TO ROUGHLY KANKAKEE TO RENSSELAER. WILL CARRY 2-4 INCHES FOR THIS
AREA WITH AMOUNTS TAPERING TO ABOUT AN INCH ALONG THE WI
BORDER...WITH 1-2 INCHES ACROSS THE FAR NORTHERN CHICAGO METRO TO
AROUND 3 POSSIBLY 4 INCHES ACROSS THE FAR SOUTHERN CHICAGO METRO.
THERE IS STILL A CHANCE THIS COULD SHIFT FURTHER SOUTH.
PRECIPITATION QUICKLY ENDS MID TO LATE SUNDAY AFTERNOON WITH LITTLE
IF ANY LAKE EFFECT LINGERING GIVEN POOR INVERSION HEIGHTS.

HEADLINE POTENTIAL...WILL HOLD OFF ON ANY HEADLINES FOR NOW GIVEN
THAT A FURTHER SOUTH SHIFT IS STILL PLAUSIBLE. ANOTHER CONCERN IS
WIND SPEEDS WHICH WILL INCREASE TO 20 TO 25 MPH WITH GUSTS OF 30-35
MPH POSSIBLE SUNDAY MORNING THROUGH THE AFTERNOON. HOWEVER...WITH
FAIRLY WET SNOW RATIOS BLOWING WILL BE MINIMIZED BUT PROBABLY STILL
OCCUR. THERE IS ALSO A WINDOW FROM LATE MORNING THROUGH EARLY
AFTERNOON WHERE THE FALLING SNOW AND WIND MAY PUSH VISIBILITIES DOWN
UNDER A HALF OR QUARTER MILE...BUT THIS MAY OCCUR OVER A RATHER
SMALL AREA. EXPECT TO NEED A WINTER WEATHER ADVISORY ACROSS THE PEAK
SNOW AREA BUT AGAIN THE LOCATION MAY SHIFT AND IF BANDING DEVELOPS
THE SWATH OF SNOW COULD REALLY NARROW SO WOULD LIKE TO SEE THE
SYSTEM EVOLVE A LITTLE BIT MORE BEFORE DECIDING WHICH AREAS WILL SEE
THE BIGGEST IMPACT. WILL ISSUE A SPECIAL WEATHER STATEMENT
HIGHLIGHTING THE POTENTIAL IMPACTS FOR NOW.

MDB

&&

.LONG TERM...
308 AM CST

MONDAY THROUGH FRIDAY...

A MUCH BETTER DEFINED RIDGE WILL BE OVER WESTERN NORTH AMERICA
WITH A DEEP TROUGH OVER THE EAST COAST BY MONDAY. ANOTHER WAVE
WILL BE TRAVERSING THE RIDGE THEN DROP SOUTHEAST ACROSS THE GREAT
LAKES MONDAY BRINGING LOW CHANCES FOR SOME LIGHT SNOW. HIGH
PRESSURE WILL BUILD IN FROM THE WEST MONDAY NIGHT TURNING WINDS
MORE NORTHERLY. LAKE PARAMETERS WILL LIKELY BE MARGINAL BUT COULD
SEE SOME FLURRY OR LIGHT SNOW ACTIVITY DEVELOP FOR TUESDAY. THE
UPPER RIDGE BEGINS TO SHIFT EASTWARD WEDNESDAY WITH THE SURFACE
HIGH SHIFTING EAST AS WELL. THIS WILL LEAD TO A SHIFT TO SOUTHERLY
WINDS AND WARMING TEMPS LATE IN THE WEEK. GUIDANCE IS IN AGREEMENT
ON A LOW CROSSING THE AREA FIRST THING THURSDAY BRINGING MIXED
PRECIP POTENTIAL OR EVEN JUST RAIN. COLDER AIR BUILDS IN BEHIND
THE SYSTEM FRIDAY AS HIGH PRESSURE BUILDS INTO THE PLAINS. OVERALL
EXPECT TEMPS TO BE AT OR ABOVE NORMAL FROM TUESDAY ONWARD.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* POTENTIAL FOR MVFR CIGS AGAIN THIS EVENING.

* SNOW DEVELOPING LATE TONIGHT WITH IFR/LIFR CONDITIONS EXPECTED
  SUNDAY MORNING WITH ACCUMULATING SNOW OF 1-3 INCHES.

* WESTERLY WINDS NEAR 10 KT TODAY/THIS EVENING...BECOMING
  NORTHEAST AFTER MIDNIGHT AND THEN STRONG/GUSTY NEAR 30 KTS BY
  SUNDAY MORNING AND CONTINUING DURING THE DAY.

RATZER/BEACHLER

//DISCUSSION...UPDATED 12Z...

PATCHY MVFR CIGS 2500-3000 FT ACROSS THE REGION THIS
MORNING...IN LIGHT WEST/NORTHWEST FLOW AHEAD OF COLD FRONT OVER
THE UPPER MIDWEST. EXPECTATION IS THAT MVFR CIGS WILL SCATTER OUT
BY MIDDAY. WESTERLY WINDS 260-290 DEGREES NEAR 10 KT WILL DIMINISH
THIS EVENING.

ATTENTION THEN TURNS TO QUICK MOVING ALBERTA-CLIPPER WHICH RAPIDLY
MOVES INTO THE AREA LATE TONIGHT AND BRINGS A PERIOD OF SNOW...AND
GUSTY NORTHEAST WINDS...TO THE TERMINALS. PERHAPS AM LEAST
CONFIDENT ABOUT CLOUDS DURING THE EVENING AND EARLY OVERNIGHT
HOURS AS GUIDANCE SATURATES THE BOUNDARY LAYER PRIOR TO MOISTURE
MOVING IN ALOFT. HAVE MAINTAINED PREVIOUS FORECAST TREND OF MVFR
CIGS REDEVELOPING AND EVENTUALLY LOWERING A BIT ALONG WITH SOME
MINOR VIS REDUCTION IN HAZE. MUCH GREATER CONFIDENCE IN SNOW
DEVELOPING PRIOR TO 12Z...WITH CIG/VIS CONDITIONS DETERIORATING TO
IFR/LIFR SHORTLY AFTER 12Z WITH STRONGEST/DEEPEST LIFT AND
SATURATION. IN ADDITION TO THE SNOW...THE SURFACE LOW WILL BE
DEEPENING AS IT PASSES SOUTHWEST OF THE AREA...RESULTING IN WINDS
SLACKING THIS EVENING AND THEN TURNING NORTHEAST AFTER MIDNIGHT.
WINDS THEN EXPECTED TO INCREASE RAPIDLY TOWARD MORNING...WITH
GUSTS NEAR 30 KT SUNDAY. SNOW EXPECTED TO ACCUMULATE 1-3 INCHES
ACROSS TERMINALS...WITH BLOWING SNOW/DRIFTING GIVEN THE STRONG
WINDS. SNOW SHOULD TAPER OFF BY EARLY AFTERNOON.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM CONFIDENCE IN MVFR CIGS TIMING THIS LATE AFTERNOON/EVENING.

* HIGH IN WIND TRENDS.

* MEDIUM-HIGH IN SNOW TIMING LATE TONIGHT/SUNDAY AND WITH CIG/VIS
  TRENDS.

RATZER/BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...MVFR CIGS POSSIBLE.

MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR...CHANCE OF SNOW AND MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR/IFR POSSIBLE.

FRIDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
238 AM CST

MAIN MARINE CONCERNS FOCUS ON THE PERIOD FROM EARLY SUNDAY MORNING
THROUGH SUNDAY EVENING...AS NORTH-NORTHEASTERLY WINDS QUICKLY
INCREASE IN RESPONSE TO A FAST-MOVING DEEPENING ALBERTA-CLIPPER LOW
WHICH WILL DIG SOUTHEAST FROM IOWA INTO CENTRAL ILLINOIS AND
SOUTHERN INDIANA DURING THE DAY.

IN THE VERY NEAR TERM THIS MORNING...LOW PRESSURE WAS MOVING EAST OF
JAMES BAY ACROSS QUEBEC...WITH A COLD FRONT TRAILING FROM THE LOW
ACROSS LAKE SUPERIOR AND WEST ALONG THE INTERNATIONAL BORDER. THIS
FRONT WILL SAG SOUTH ACROSS NORTHERN LAKE MICHIGAN LATER TODAY WITH
WINDS SHIFTING NORTH AND INCREASING BEHIND IT AS HIGH PRESSURE
SPREADS SOUTHEAST ACROSS MANITOBA AND NORTHWEST QUEBEC. BY
TONIGHT...THE FAST-MOVING CLIPPER WILL ALSO ALREADY BE ENTERING
IOWA  AND MOVING INTO WEST-CENTRAL ILLINOIS BY SUNDAY MORNING WHILE
DEEPENING A BIT. THE TIGHTENING GRADIENT AROUND THE LOW WILL ALSO
HELP TO TURN WINDS NORTHEAST AND STRENGTHEN THEM ALL THE WAY TO THE
SOUTH END OF THE LAKE AS THE LOW EVENTUALLY TRACKS INTO THE OHIO
VALLEY IN THE AFTERNOON. MODEL FORECAST SOUNDINGS DEPICT A PERIOD OF
SOLID 30 KT NORTHEAST WINDS ACROSS THE SOUTH 2/3 OR 3/4 OF THE LAKE
SUNDAY...WITH A FEW GUSTS OVER 30 KTS (MARGINAL GALE FORCE) DURING
THE DAY. WITH THE LOW MOVING QUICKLY OFF TO THE SOUTHEAST SUNDAY
NIGHT...WINDS WILL DIMINISH AS QUICKLY AS THEY INCREASED EARLY IN
THE DAY...AS WEAK HIGH PRESSURE RIDGING MOVES ACROSS THE LAKE SUNDAY
NIGHT. WILL NEED A SMALL CRAFT ADVISORY FOR THE IL/NW IND NEARSHORE
WATERS FROM ABOUT 6 AM CST SUNDAY THROUGH ABOUT 6 AM CST MONDAY FOR
THE STRONG WINDS AND RESULTING WAVES.

EARLY NEXT WEEK THE PATTERN CONTINUES TO APPEAR RATHER
PROGRESSIVE...WITH THE WEEK HIGH PRESSURE RIDGE OVER THE LAKE SUNDAY
NIGHT QUICKLY BEING DISPLACED MONDAY BY ANOTHER LOW PRESSURE SYSTEM
WHICH MOVES INTO THE NORTHERN LAKES MONDAY AFTERNOON. THIS BRINGS
WINDS AROUND TO THE SOUTH AND INCREASING INTO THE 25 KT RANGE FOR A
TIME MONDAY AS THE LOW APPROACHES. THE LOW THEN WEAKENS AS IT MOVES
SOUTHEAST ACROSS THE LAKES MONDAY NIGHT...FILLING AS A DEEP LOW
DEVELOPS ALONG THE ATLANTIC COAST. WEAK HIGH PRESSURE SPREADS ACROSS
THE LAKE TUESDAY...BEFORE ANOTHER LOW DEVELOPS ACROSS THE CENTRAL
PLAINS AND MOVES INTO THE MID-MISSISSIPPI VALLEY REGION THROUGH LATE
WEDNESDAY.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 241410
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
810 AM CST SAT JAN 24 2015

.SHORT TERM...
308 AM CST

TODAY THROUGH SUNDAY NIGHT...

THE MAIN FORECAST ISSUE WILL BE ACCUMULATING SNOW AND GUSTY WINDS
STARTING LATER TONIGHT CONTINUING THROUGH MUCH OF SUNDAY. WATER
VAPOR IMAGERY SHOWS A LONGWAVE TROUGH STRETCHING FROM HUDSON BAY
SOUTH TO THE GULF COAST WITH BROAD RIDGING OVER THE EASTERN
PACIFIC AND MUCH OF WESTERN CANADA AND THE NORTHWEST U.S. A WEAK
COOL FRONT IS CROSSING THE AREA BEHIND THE PASSAGE OF THE LONGWAVE
TROUGH AXIS. COOL ADVECTION THIS MORNING WILL GIVE WAY TO MODEST
WARM ADVECTION LATE THIS AFTERNOON. CLOUD COVER WILL BE THE WILD
CARD WITH TEMPS. STRATUS IS SPREADING SOUTHEAST ACROSS THE AREA
THIS MORNING BUT SATELLITE SHOWS GAPS IN COVERAGE UPSTREAM.
GUIDANCE IS MIXED WITH THE EXTENT OF CLOUD COVER BUT SUSPECT THERE
WILL BE BREAKS IN THE CLOUDS...ESPECIALLY THIS AFTERNOON...WITH
ANY MEANINGFUL SUNSHINE DURING THE EARLY/MID AFTERNOON HELPING
TEMPS SOMEWHAT. THIS IS MOST FAVORED SOUTH AND WEST SO WILL NUDGE
TEMPS UP SLIGHTLY THERE WHILE CARRYING UPPER 30S ACROSS THE REST
OF THE AREA.

THE MAIN FEATURE OF CONCERN IS A WAVE MOVING EAST-SOUTHEAST ACROSS
SOUTHERN ALBERTA. EVENING UPPER AIR ANALYSIS SHOWS A STRONG JET
PUSHING INTO THE PACIFIC NORTHWEST AND PIVOTING SOUTHEASTWARD AS
ADDITIONAL ENERGY PUSHES EASTWARD AMPLIFYING THE RIDGE. THE WAVE OF
CONCERN WILL DIG SOUTHEASTWARD ACROSS THE NORTHERN PLAINS TOWARD THE
MID MISSISSIPPI RIVER VALLEY AS A RESULT AND AMPLIFY AS IT DOES SO
INTO TONIGHT. THE SOUTH/WEST TREND OF THE TRACK OF THE SURFACE LOW
HAS CONTINUED AND DIFFERENCES REMAIN...ESPECIALLY WITH SOME OF THE
HIGH RES GUIDANCE WHICH TAKES THE LOW MUCH FURTHER SOUTH AND WEST
THAN SOME OF THE LOWER RES OPTIONS. IT APPEARS THAT THE LOW WILL NOT
TRACK NORTH OF ROUGHLY A BURLINGTON IOWA TO TERRE HAUTE INDIANA LINE
AT THIS POINT. WITH THE WAVE STILL TAKING SHAPE AND THE UPPER JET
STILL COMING ASHORE OVER THE PAC NORTHWEST FEEL THAT CONFIDENCE HAS
ROOM FOR IMPROVEMENT WITH THE MORNING UPPER AIR ANALYSIS AND
SUBSEQUENT 12Z GUIDANCE. THE MAIN QUESTION WILL BE PLACEMENT BUT
HAVE BETTER CONFIDENCE IN THE TREND OF WHAT OCCURS. PRECIP IS ON
TRACK TO QUICKLY SPREAD SOUTHEAST ACROSS THE AREA OVERNIGHT/AFTER
06Z/ AND SOUTHWEST AREAS STILL LOOK TO SEE A MIX OF RAIN OR SNOW AND
EVEN SOME SLEET THROUGH MID MORNING WHEN COLD AIR WILL TAKE OVER
CHANGING THINGS TO SNOW. PEAK PRECIP INTENSITY WILL BE AFTER
DAYBREAK INTO THE EARLY AFTERNOON. WINDS WILL TURN NORTHEAST AND
INCREASE DURING THE MORNING SETTING UP A DECENT FETCH DOWN LAKE
MICHIGAN. LAKE EFFECT PARAMETERS ARE SUB PAR BUT WHEN COMBINED WITH
SYNOPTIC SCALE ASCENT ARE PROBABLY SUFFICIENT TO PROVIDE SOME
MINIMAL ENHANCEMENT...MAINLY DUE TO INCREASED MOISTURE FLUX.
GUIDANCE VARIES WITH LIQUID OUTPUT WITH SOME RATHER HIGH AMOUNTS
NOTED PROBABLY SUGGESTIVE OF STRONG BANDING WHICH IS CERTAINLY
POSSIBLE. GIVEN PRECIPITABLE WATER VALUES OF AROUND 0.5 INCHES AND
FORCING OF 6 TO MAYBE 9 HOURS PEAK LIQUID AMOUNTS OF 0.3 TO 0.4
INCHES STILL SEEMS REASONABLE. LOCATION OF THESE AMOUNTS IS EXPECTED
ACROSS THE SOUTHERN CWA WITH AMOUNTS OF ONLY AROUND 0.1 INCHES
ACROSS THE NORTH. WITH SOUTHERN AREAS ALSO SEEING A MIX NOT ALL OF
THE LIQUID WILL GO TOWARD SNOW ACCUMULATION. THUS HIGHEST SNOW
AMOUNTS WILL OCCUR JUST TO THE NORTH...THOUGH WITH SOMEWHAT LOW
LIQUID EQUIVALENT. WILL DEPICT THE PEAK SNOWFALL FROM ROUGHLY
LASALLE COUNTY EAST-SOUTHEAST ALONG AND JUST SOUTH OF INTERSTATE 80
TO ROUGHLY KANKAKEE TO RENSSELAER. WILL CARRY 2-4 INCHES FOR THIS
AREA WITH AMOUNTS TAPERING TO ABOUT AN INCH ALONG THE WI
BORDER...WITH 1-2 INCHES ACROSS THE FAR NORTHERN CHICAGO METRO TO
AROUND 3 POSSIBLY 4 INCHES ACROSS THE FAR SOUTHERN CHICAGO METRO.
THERE IS STILL A CHANCE THIS COULD SHIFT FURTHER SOUTH.
PRECIPITATION QUICKLY ENDS MID TO LATE SUNDAY AFTERNOON WITH LITTLE
IF ANY LAKE EFFECT LINGERING GIVEN POOR INVERSION HEIGHTS.

HEADLINE POTENTIAL...WILL HOLD OFF ON ANY HEADLINES FOR NOW GIVEN
THAT A FURTHER SOUTH SHIFT IS STILL PLAUSIBLE. ANOTHER CONCERN IS
WIND SPEEDS WHICH WILL INCREASE TO 20 TO 25 MPH WITH GUSTS OF 30-35
MPH POSSIBLE SUNDAY MORNING THROUGH THE AFTERNOON. HOWEVER...WITH
FAIRLY WET SNOW RATIOS BLOWING WILL BE MINIMIZED BUT PROBABLY STILL
OCCUR. THERE IS ALSO A WINDOW FROM LATE MORNING THROUGH EARLY
AFTERNOON WHERE THE FALLING SNOW AND WIND MAY PUSH VISIBILITIES DOWN
UNDER A HALF OR QUARTER MILE...BUT THIS MAY OCCUR OVER A RATHER
SMALL AREA. EXPECT TO NEED A WINTER WEATHER ADVISORY ACROSS THE PEAK
SNOW AREA BUT AGAIN THE LOCATION MAY SHIFT AND IF BANDING DEVELOPS
THE SWATH OF SNOW COULD REALLY NARROW SO WOULD LIKE TO SEE THE
SYSTEM EVOLVE A LITTLE BIT MORE BEFORE DECIDING WHICH AREAS WILL SEE
THE BIGGEST IMPACT. WILL ISSUE A SPECIAL WEATHER STATEMENT
HIGHLIGHTING THE POTENTIAL IMPACTS FOR NOW.

MDB

&&

.LONG TERM...
308 AM CST

MONDAY THROUGH FRIDAY...

A MUCH BETTER DEFINED RIDGE WILL BE OVER WESTERN NORTH AMERICA
WITH A DEEP TROUGH OVER THE EAST COAST BY MONDAY. ANOTHER WAVE
WILL BE TRAVERSING THE RIDGE THEN DROP SOUTHEAST ACROSS THE GREAT
LAKES MONDAY BRINGING LOW CHANCES FOR SOME LIGHT SNOW. HIGH
PRESSURE WILL BUILD IN FROM THE WEST MONDAY NIGHT TURNING WINDS
MORE NORTHERLY. LAKE PARAMETERS WILL LIKELY BE MARGINAL BUT COULD
SEE SOME FLURRY OR LIGHT SNOW ACTIVITY DEVELOP FOR TUESDAY. THE
UPPER RIDGE BEGINS TO SHIFT EASTWARD WEDNESDAY WITH THE SURFACE
HIGH SHIFTING EAST AS WELL. THIS WILL LEAD TO A SHIFT TO SOUTHERLY
WINDS AND WARMING TEMPS LATE IN THE WEEK. GUIDANCE IS IN AGREEMENT
ON A LOW CROSSING THE AREA FIRST THING THURSDAY BRINGING MIXED
PRECIP POTENTIAL OR EVEN JUST RAIN. COLDER AIR BUILDS IN BEHIND
THE SYSTEM FRIDAY AS HIGH PRESSURE BUILDS INTO THE PLAINS. OVERALL
EXPECT TEMPS TO BE AT OR ABOVE NORMAL FROM TUESDAY ONWARD.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* POTENTIAL FOR MVFR CIGS AGAIN THIS EVENING.

* SNOW DEVELOPING LATE TONIGHT WITH IFR/LIFR CONDITIONS EXPECTED
  SUNDAY MORNING WITH ACCUMULATING SNOW OF 1-3 INCHES.

* WESTERLY WINDS NEAR 10 KT TODAY/THIS EVENING...BECOMING
  NORTHEAST AFTER MIDNIGHT AND THEN STRONG/GUSTY NEAR 30 KTS BY
  SUNDAY MORNING AND CONTINUING DURING THE DAY.

RATZER/BEACHLER

//DISCUSSION...UPDATED 12Z...

PATCHY MVFR CIGS 2500-3000 FT ACROSS THE REGION THIS
MORNING...IN LIGHT WEST/NORTHWEST FLOW AHEAD OF COLD FRONT OVER
THE UPPER MIDWEST. EXPECTATION IS THAT MVFR CIGS WILL SCATTER OUT
BY MIDDAY. WESTERLY WINDS 260-290 DEGREES NEAR 10 KT WILL DIMINISH
THIS EVENING.

ATTENTION THEN TURNS TO QUICK MOVING ALBERTA-CLIPPER WHICH RAPIDLY
MOVES INTO THE AREA LATE TONIGHT AND BRINGS A PERIOD OF SNOW...AND
GUSTY NORTHEAST WINDS...TO THE TERMINALS. PERHAPS AM LEAST
CONFIDENT ABOUT CLOUDS DURING THE EVENING AND EARLY OVERNIGHT
HOURS AS GUIDANCE SATURATES THE BOUNDARY LAYER PRIOR TO MOISTURE
MOVING IN ALOFT. HAVE MAINTAINED PREVIOUS FORECAST TREND OF MVFR
CIGS REDEVELOPING AND EVENTUALLY LOWERING A BIT ALONG WITH SOME
MINOR VIS REDUCTION IN HAZE. MUCH GREATER CONFIDENCE IN SNOW
DEVELOPING PRIOR TO 12Z...WITH CIG/VIS CONDITIONS DETERIORATING TO
IFR/LIFR SHORTLY AFTER 12Z WITH STRONGEST/DEEPEST LIFT AND
SATURATION. IN ADDITION TO THE SNOW...THE SURFACE LOW WILL BE
DEEPENING AS IT PASSES SOUTHWEST OF THE AREA...RESULTING IN WINDS
SLACKING THIS EVENING AND THEN TURNING NORTHEAST AFTER MIDNIGHT.
WINDS THEN EXPECTED TO INCREASE RAPIDLY TOWARD MORNING...WITH
GUSTS NEAR 30 KT SUNDAY. SNOW EXPECTED TO ACCUMULATE 1-3 INCHES
ACROSS TERMINALS...WITH BLOWING SNOW/DRIFTING GIVEN THE STRONG
WINDS. SNOW SHOULD TAPER OFF BY EARLY AFTERNOON.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* MEDIUM CONFIDENCE IN MVFR CIGS TIMING THIS LATE AFTERNOON/EVENING.

* HIGH IN WIND TRENDS.

* MEDIUM-HIGH IN SNOW TIMING LATE TONIGHT/SUNDAY AND WITH CIG/VIS
  TRENDS.

RATZER/BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...MVFR CIGS POSSIBLE.

MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR...CHANCE OF SNOW AND MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR/IFR POSSIBLE.

FRIDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
238 AM CST

MAIN MARINE CONCERNS FOCUS ON THE PERIOD FROM EARLY SUNDAY MORNING
THROUGH SUNDAY EVENING...AS NORTH-NORTHEASTERLY WINDS QUICKLY
INCREASE IN RESPONSE TO A FAST-MOVING DEEPENING ALBERTA-CLIPPER LOW
WHICH WILL DIG SOUTHEAST FROM IOWA INTO CENTRAL ILLINOIS AND
SOUTHERN INDIANA DURING THE DAY.

IN THE VERY NEAR TERM THIS MORNING...LOW PRESSURE WAS MOVING EAST OF
JAMES BAY ACROSS QUEBEC...WITH A COLD FRONT TRAILING FROM THE LOW
ACROSS LAKE SUPERIOR AND WEST ALONG THE INTERNATIONAL BORDER. THIS
FRONT WILL SAG SOUTH ACROSS NORTHERN LAKE MICHIGAN LATER TODAY WITH
WINDS SHIFTING NORTH AND INCREASING BEHIND IT AS HIGH PRESSURE
SPREADS SOUTHEAST ACROSS MANITOBA AND NORTHWEST QUEBEC. BY
TONIGHT...THE FAST-MOVING CLIPPER WILL ALSO ALREADY BE ENTERING
IOWA  AND MOVING INTO WEST-CENTRAL ILLINOIS BY SUNDAY MORNING WHILE
DEEPENING A BIT. THE TIGHTENING GRADIENT AROUND THE LOW WILL ALSO
HELP TO TURN WINDS NORTHEAST AND STRENGTHEN THEM ALL THE WAY TO THE
SOUTH END OF THE LAKE AS THE LOW EVENTUALLY TRACKS INTO THE OHIO
VALLEY IN THE AFTERNOON. MODEL FORECAST SOUNDINGS DEPICT A PERIOD OF
SOLID 30 KT NORTHEAST WINDS ACROSS THE SOUTH 2/3 OR 3/4 OF THE LAKE
SUNDAY...WITH A FEW GUSTS OVER 30 KTS (MARGINAL GALE FORCE) DURING
THE DAY. WITH THE LOW MOVING QUICKLY OFF TO THE SOUTHEAST SUNDAY
NIGHT...WINDS WILL DIMINISH AS QUICKLY AS THEY INCREASED EARLY IN
THE DAY...AS WEAK HIGH PRESSURE RIDGING MOVES ACROSS THE LAKE SUNDAY
NIGHT. WILL NEED A SMALL CRAFT ADVISORY FOR THE IL/NW IND NEARSHORE
WATERS FROM ABOUT 6 AM CST SUNDAY THROUGH ABOUT 6 AM CST MONDAY FOR
THE STRONG WINDS AND RESULTING WAVES.

EARLY NEXT WEEK THE PATTERN CONTINUES TO APPEAR RATHER
PROGRESSIVE...WITH THE WEEK HIGH PRESSURE RIDGE OVER THE LAKE SUNDAY
NIGHT QUICKLY BEING DISPLACED MONDAY BY ANOTHER LOW PRESSURE SYSTEM
WHICH MOVES INTO THE NORTHERN LAKES MONDAY AFTERNOON. THIS BRINGS
WINDS AROUND TO THE SOUTH AND INCREASING INTO THE 25 KT RANGE FOR A
TIME MONDAY AS THE LOW APPROACHES. THE LOW THEN WEAKENS AS IT MOVES
SOUTHEAST ACROSS THE LAKES MONDAY NIGHT...FILLING AS A DEEP LOW
DEVELOPS ALONG THE ATLANTIC COAST. WEAK HIGH PRESSURE SPREADS ACROSS
THE LAKE TUESDAY...BEFORE ANOTHER LOW DEVELOPS ACROSS THE CENTRAL
PLAINS AND MOVES INTO THE MID-MISSISSIPPI VALLEY REGION THROUGH LATE
WEDNESDAY.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 241410
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
810 AM CST SAT JAN 24 2015

.SHORT TERM...
308 AM CST

TODAY THROUGH SUNDAY NIGHT...

THE MAIN FORECAST ISSUE WILL BE ACCUMULATING SNOW AND GUSTY WINDS
STARTING LATER TONIGHT CONTINUING THROUGH MUCH OF SUNDAY. WATER
VAPOR IMAGERY SHOWS A LONGWAVE TROUGH STRETCHING FROM HUDSON BAY
SOUTH TO THE GULF COAST WITH BROAD RIDGING OVER THE EASTERN
PACIFIC AND MUCH OF WESTERN CANADA AND THE NORTHWEST U.S. A WEAK
COOL FRONT IS CROSSING THE AREA BEHIND THE PASSAGE OF THE LONGWAVE
TROUGH AXIS. COOL ADVECTION THIS MORNING WILL GIVE WAY TO MODEST
WARM ADVECTION LATE THIS AFTERNOON. CLOUD COVER WILL BE THE WILD
CARD WITH TEMPS. STRATUS IS SPREADING SOUTHEAST ACROSS THE AREA
THIS MORNING BUT SATELLITE SHOWS GAPS IN COVERAGE UPSTREAM.
GUIDANCE IS MIXED WITH THE EXTENT OF CLOUD COVER BUT SUSPECT THERE
WILL BE BREAKS IN THE CLOUDS...ESPECIALLY THIS AFTERNOON...WITH
ANY MEANINGFUL SUNSHINE DURING THE EARLY/MID AFTERNOON HELPING
TEMPS SOMEWHAT. THIS IS MOST FAVORED SOUTH AND WEST SO WILL NUDGE
TEMPS UP SLIGHTLY THERE WHILE CARRYING UPPER 30S ACROSS THE REST
OF THE AREA.

THE MAIN FEATURE OF CONCERN IS A WAVE MOVING EAST-SOUTHEAST ACROSS
SOUTHERN ALBERTA. EVENING UPPER AIR ANALYSIS SHOWS A STRONG JET
PUSHING INTO THE PACIFIC NORTHWEST AND PIVOTING SOUTHEASTWARD AS
ADDITIONAL ENERGY PUSHES EASTWARD AMPLIFYING THE RIDGE. THE WAVE OF
CONCERN WILL DIG SOUTHEASTWARD ACROSS THE NORTHERN PLAINS TOWARD THE
MID MISSISSIPPI RIVER VALLEY AS A RESULT AND AMPLIFY AS IT DOES SO
INTO TONIGHT. THE SOUTH/WEST TREND OF THE TRACK OF THE SURFACE LOW
HAS CONTINUED AND DIFFERENCES REMAIN...ESPECIALLY WITH SOME OF THE
HIGH RES GUIDANCE WHICH TAKES THE LOW MUCH FURTHER SOUTH AND WEST
THAN SOME OF THE LOWER RES OPTIONS. IT APPEARS THAT THE LOW WILL NOT
TRACK NORTH OF ROUGHLY A BURLINGTON IOWA TO TERRE HAUTE INDIANA LINE
AT THIS POINT. WITH THE WAVE STILL TAKING SHAPE AND THE UPPER JET
STILL COMING ASHORE OVER THE PAC NORTHWEST FEEL THAT CONFIDENCE HAS
ROOM FOR IMPROVEMENT WITH THE MORNING UPPER AIR ANALYSIS AND
SUBSEQUENT 12Z GUIDANCE. THE MAIN QUESTION WILL BE PLACEMENT BUT
HAVE BETTER CONFIDENCE IN THE TREND OF WHAT OCCURS. PRECIP IS ON
TRACK TO QUICKLY SPREAD SOUTHEAST ACROSS THE AREA OVERNIGHT/AFTER
06Z/ AND SOUTHWEST AREAS STILL LOOK TO SEE A MIX OF RAIN OR SNOW AND
EVEN SOME SLEET THROUGH MID MORNING WHEN COLD AIR WILL TAKE OVER
CHANGING THINGS TO SNOW. PEAK PRECIP INTENSITY WILL BE AFTER
DAYBREAK INTO THE EARLY AFTERNOON. WINDS WILL TURN NORTHEAST AND
INCREASE DURING THE MORNING SETTING UP A DECENT FETCH DOWN LAKE
MICHIGAN. LAKE EFFECT PARAMETERS ARE SUB PAR BUT WHEN COMBINED WITH
SYNOPTIC SCALE ASCENT ARE PROBABLY SUFFICIENT TO PROVIDE SOME
MINIMAL ENHANCEMENT...MAINLY DUE TO INCREASED MOISTURE FLUX.
GUIDANCE VARIES WITH LIQUID OUTPUT WITH SOME RATHER HIGH AMOUNTS
NOTED PROBABLY SUGGESTIVE OF STRONG BANDING WHICH IS CERTAINLY
POSSIBLE. GIVEN PRECIPITABLE WATER VALUES OF AROUND 0.5 INCHES AND
FORCING OF 6 TO MAYBE 9 HOURS PEAK LIQUID AMOUNTS OF 0.3 TO 0.4
INCHES STILL SEEMS REASONABLE. LOCATION OF THESE AMOUNTS IS EXPECTED
ACROSS THE SOUTHERN CWA WITH AMOUNTS OF ONLY AROUND 0.1 INCHES
ACROSS THE NORTH. WITH SOUTHERN AREAS ALSO SEEING A MIX NOT ALL OF
THE LIQUID WILL GO TOWARD SNOW ACCUMULATION. THUS HIGHEST SNOW
AMOUNTS WILL OCCUR JUST TO THE NORTH...THOUGH WITH SOMEWHAT LOW
LIQUID EQUIVALENT. WILL DEPICT THE PEAK SNOWFALL FROM ROUGHLY
LASALLE COUNTY EAST-SOUTHEAST ALONG AND JUST SOUTH OF INTERSTATE 80
TO ROUGHLY KANKAKEE TO RENSSELAER. WILL CARRY 2-4 INCHES FOR THIS
AREA WITH AMOUNTS TAPERING TO ABOUT AN INCH ALONG THE WI
BORDER...WITH 1-2 INCHES ACROSS THE FAR NORTHERN CHICAGO METRO TO
AROUND 3 POSSIBLY 4 INCHES ACROSS THE FAR SOUTHERN CHICAGO METRO.
THERE IS STILL A CHANCE THIS COULD SHIFT FURTHER SOUTH.
PRECIPITATION QUICKLY ENDS MID TO LATE SUNDAY AFTERNOON WITH LITTLE
IF ANY LAKE EFFECT LINGERING GIVEN POOR INVERSION HEIGHTS.

HEADLINE POTENTIAL...WILL HOLD OFF ON ANY HEADLINES FOR NOW GIVEN
THAT A FURTHER SOUTH SHIFT IS STILL PLAUSIBLE. ANOTHER CONCERN IS
WIND SPEEDS WHICH WILL INCREASE TO 20 TO 25 MPH WITH GUSTS OF 30-35
MPH POSSIBLE SUNDAY MORNING THROUGH THE AFTERNOON. HOWEVER...WITH
FAIRLY WET SNOW RATIOS BLOWING WILL BE MINIMIZED BUT PROBABLY STILL
OCCUR. THERE IS ALSO A WINDOW FROM LATE MORNING THROUGH EARLY
AFTERNOON WHERE THE FALLING SNOW AND WIND MAY PUSH VISIBILITIES DOWN
UNDER A HALF OR QUARTER MILE...BUT THIS MAY OCCUR OVER A RATHER
SMALL AREA. EXPECT TO NEED A WINTER WEATHER ADVISORY ACROSS THE PEAK
SNOW AREA BUT AGAIN THE LOCATION MAY SHIFT AND IF BANDING DEVELOPS
THE SWATH OF SNOW COULD REALLY NARROW SO WOULD LIKE TO SEE THE
SYSTEM EVOLVE A LITTLE BIT MORE BEFORE DECIDING WHICH AREAS WILL SEE
THE BIGGEST IMPACT. WILL ISSUE A SPECIAL WEATHER STATEMENT
HIGHLIGHTING THE POTENTIAL IMPACTS FOR NOW.

MDB

&&

.LONG TERM...
308 AM CST

MONDAY THROUGH FRIDAY...

A MUCH BETTER DEFINED RIDGE WILL BE OVER WESTERN NORTH AMERICA
WITH A DEEP TROUGH OVER THE EAST COAST BY MONDAY. ANOTHER WAVE
WILL BE TRAVERSING THE RIDGE THEN DROP SOUTHEAST ACROSS THE GREAT
LAKES MONDAY BRINGING LOW CHANCES FOR SOME LIGHT SNOW. HIGH
PRESSURE WILL BUILD IN FROM THE WEST MONDAY NIGHT TURNING WINDS
MORE NORTHERLY. LAKE PARAMETERS WILL LIKELY BE MARGINAL BUT COULD
SEE SOME FLURRY OR LIGHT SNOW ACTIVITY DEVELOP FOR TUESDAY. THE
UPPER RIDGE BEGINS TO SHIFT EASTWARD WEDNESDAY WITH THE SURFACE
HIGH SHIFTING EAST AS WELL. THIS WILL LEAD TO A SHIFT TO SOUTHERLY
WINDS AND WARMING TEMPS LATE IN THE WEEK. GUIDANCE IS IN AGREEMENT
ON A LOW CROSSING THE AREA FIRST THING THURSDAY BRINGING MIXED
PRECIP POTENTIAL OR EVEN JUST RAIN. COLDER AIR BUILDS IN BEHIND
THE SYSTEM FRIDAY AS HIGH PRESSURE BUILDS INTO THE PLAINS. OVERALL
EXPECT TEMPS TO BE AT OR ABOVE NORMAL FROM TUESDAY ONWARD.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* POTENTIAL FOR MVFR CIGS AGAIN THIS EVENING.

* SNOW DEVELOPING LATE TONIGHT WITH IFR/LIFR CONDITIONS EXPECTED
  SUNDAY MORNING WITH ACCUMULATING SNOW OF 1-3 INCHES.

* WESTERLY WINDS NEAR 10 KT TODAY/THIS EVENING...BECOMING
  NORTHEAST AFTER MIDNIGHT AND THEN STRONG/GUSTY NEAR 30 KTS BY
  SUNDAY MORNING AND CONTINUING DURING THE DAY.

RATZER/BEACHLER

//DISCUSSION...UPDATED 12Z...

PATCHY MVFR CIGS 2500-3000 FT ACROSS THE REGION THIS
MORNING...IN LIGHT WEST/NORTHWEST FLOW AHEAD OF COLD FRONT OVER
THE UPPER MIDWEST. EXPECTATION IS THAT MVFR CIGS WILL SCATTER OUT
BY MIDDAY. WESTERLY WINDS 260-290 DEGREES NEAR 10 KT WILL DIMINISH
THIS EVENING.

ATTENTION THEN TURNS TO QUICK MOVING ALBERTA-CLIPPER WHICH RAPIDLY
MOVES INTO THE AREA LATE TONIGHT AND BRINGS A PERIOD OF SNOW...AND
GUSTY NORTHEAST WINDS...TO THE TERMINALS. PERHAPS AM LEAST
CONFIDENT ABOUT CLOUDS DURING THE EVENING AND EARLY OVERNIGHT
HOURS AS GUIDANCE SATURATES THE BOUNDARY LAYER PRIOR TO MOISTURE
MOVING IN ALOFT. HAVE MAINTAINED PREVIOUS FORECAST TREND OF MVFR
CIGS REDEVELOPING AND EVENTUALLY LOWERING A BIT ALONG WITH SOME
MINOR VIS REDUCTION IN HAZE. MUCH GREATER CONFIDENCE IN SNOW
DEVELOPING PRIOR TO 12Z...WITH CIG/VIS CONDITIONS DETERIORATING TO
IFR/LIFR SHORTLY AFTER 12Z WITH STRONGEST/DEEPEST LIFT AND
SATURATION. IN ADDITION TO THE SNOW...THE SURFACE LOW WILL BE
DEEPENING AS IT PASSES SOUTHWEST OF THE AREA...RESULTING IN WINDS
SLACKING THIS EVENING AND THEN TURNING NORTHEAST AFTER MIDNIGHT.
WINDS THEN EXPECTED TO INCREASE RAPIDLY TOWARD MORNING...WITH
GUSTS NEAR 30 KT SUNDAY. SNOW EXPECTED TO ACCUMULATE 1-3 INCHES
ACROSS TERMINALS...WITH BLOWING SNOW/DRIFTING GIVEN THE STRONG
WINDS. SNOW SHOULD TAPER OFF BY EARLY AFTERNOON.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* MEDIUM CONFIDENCE IN MVFR CIGS TIMING THIS LATE AFTERNOON/EVENING.

* HIGH IN WIND TRENDS.

* MEDIUM-HIGH IN SNOW TIMING LATE TONIGHT/SUNDAY AND WITH CIG/VIS
  TRENDS.

RATZER/BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...MVFR CIGS POSSIBLE.

MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR...CHANCE OF SNOW AND MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR/IFR POSSIBLE.

FRIDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
238 AM CST

MAIN MARINE CONCERNS FOCUS ON THE PERIOD FROM EARLY SUNDAY MORNING
THROUGH SUNDAY EVENING...AS NORTH-NORTHEASTERLY WINDS QUICKLY
INCREASE IN RESPONSE TO A FAST-MOVING DEEPENING ALBERTA-CLIPPER LOW
WHICH WILL DIG SOUTHEAST FROM IOWA INTO CENTRAL ILLINOIS AND
SOUTHERN INDIANA DURING THE DAY.

IN THE VERY NEAR TERM THIS MORNING...LOW PRESSURE WAS MOVING EAST OF
JAMES BAY ACROSS QUEBEC...WITH A COLD FRONT TRAILING FROM THE LOW
ACROSS LAKE SUPERIOR AND WEST ALONG THE INTERNATIONAL BORDER. THIS
FRONT WILL SAG SOUTH ACROSS NORTHERN LAKE MICHIGAN LATER TODAY WITH
WINDS SHIFTING NORTH AND INCREASING BEHIND IT AS HIGH PRESSURE
SPREADS SOUTHEAST ACROSS MANITOBA AND NORTHWEST QUEBEC. BY
TONIGHT...THE FAST-MOVING CLIPPER WILL ALSO ALREADY BE ENTERING
IOWA  AND MOVING INTO WEST-CENTRAL ILLINOIS BY SUNDAY MORNING WHILE
DEEPENING A BIT. THE TIGHTENING GRADIENT AROUND THE LOW WILL ALSO
HELP TO TURN WINDS NORTHEAST AND STRENGTHEN THEM ALL THE WAY TO THE
SOUTH END OF THE LAKE AS THE LOW EVENTUALLY TRACKS INTO THE OHIO
VALLEY IN THE AFTERNOON. MODEL FORECAST SOUNDINGS DEPICT A PERIOD OF
SOLID 30 KT NORTHEAST WINDS ACROSS THE SOUTH 2/3 OR 3/4 OF THE LAKE
SUNDAY...WITH A FEW GUSTS OVER 30 KTS (MARGINAL GALE FORCE) DURING
THE DAY. WITH THE LOW MOVING QUICKLY OFF TO THE SOUTHEAST SUNDAY
NIGHT...WINDS WILL DIMINISH AS QUICKLY AS THEY INCREASED EARLY IN
THE DAY...AS WEAK HIGH PRESSURE RIDGING MOVES ACROSS THE LAKE SUNDAY
NIGHT. WILL NEED A SMALL CRAFT ADVISORY FOR THE IL/NW IND NEARSHORE
WATERS FROM ABOUT 6 AM CST SUNDAY THROUGH ABOUT 6 AM CST MONDAY FOR
THE STRONG WINDS AND RESULTING WAVES.

EARLY NEXT WEEK THE PATTERN CONTINUES TO APPEAR RATHER
PROGRESSIVE...WITH THE WEEK HIGH PRESSURE RIDGE OVER THE LAKE SUNDAY
NIGHT QUICKLY BEING DISPLACED MONDAY BY ANOTHER LOW PRESSURE SYSTEM
WHICH MOVES INTO THE NORTHERN LAKES MONDAY AFTERNOON. THIS BRINGS
WINDS AROUND TO THE SOUTH AND INCREASING INTO THE 25 KT RANGE FOR A
TIME MONDAY AS THE LOW APPROACHES. THE LOW THEN WEAKENS AS IT MOVES
SOUTHEAST ACROSS THE LAKES MONDAY NIGHT...FILLING AS A DEEP LOW
DEVELOPS ALONG THE ATLANTIC COAST. WEAK HIGH PRESSURE SPREADS ACROSS
THE LAKE TUESDAY...BEFORE ANOTHER LOW DEVELOPS ACROSS THE CENTRAL
PLAINS AND MOVES INTO THE MID-MISSISSIPPI VALLEY REGION THROUGH LATE
WEDNESDAY.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 241153
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
553 AM CST SAT JAN 24 2015

.SHORT TERM...
308 AM CST

TODAY THROUGH SUNDAY NIGHT...

THE MAIN FORECAST ISSUE WILL BE ACCUMULATING SNOW AND GUSTY WINDS
STARTING LATER TONIGHT CONTINUING THROUGH MUCH OF SUNDAY. WATER
VAPOR IMAGERY SHOWS A LONGWAVE TROUGH STRETCHING FROM HUDSON BAY
SOUTH TO THE GULF COAST WITH BROAD RIDGING OVER THE EASTERN
PACIFIC AND MUCH OF WESTERN CANADA AND THE NORTHWEST U.S. A WEAK
COOL FRONT IS CROSSING THE AREA BEHIND THE PASSAGE OF THE LONGWAVE
TROUGH AXIS. COOL ADVECTION THIS MORNING WILL GIVE WAY TO MODEST
WARM ADVECTION LATE THIS AFTERNOON. CLOUD COVER WILL BE THE WILD
CARD WITH TEMPS. STRATUS IS SPREADING SOUTHEAST ACROSS THE AREA
THIS MORNING BUT SATELLITE SHOWS GAPS IN COVERAGE UPSTREAM.
GUIDANCE IS MIXED WITH THE EXTENT OF CLOUD COVER BUT SUSPECT THERE
WILL BE BREAKS IN THE CLOUDS...ESPECIALLY THIS AFTERNOON...WITH
ANY MEANINGFUL SUNSHINE DURING THE EARLY/MID AFTERNOON HELPING
TEMPS SOMEWHAT. THIS IS MOST FAVORED SOUTH AND WEST SO WILL NUDGE
TEMPS UP SLIGHTLY THERE WHILE CARRYING UPPER 30S ACROSS THE REST
OF THE AREA.

THE MAIN FEATURE OF CONCERN IS A WAVE MOVING EAST-SOUTHEAST ACROSS
SOUTHERN ALBERTA. EVENING UPPER AIR ANALYSIS SHOWS A STRONG JET
PUSHING INTO THE PACIFIC NORTHWEST AND PIVOTING SOUTHEASTWARD AS
ADDITIONAL ENERGY PUSHES EASTWARD AMPLIFYING THE RIDGE. THE WAVE OF
CONCERN WILL DIG SOUTHEASTWARD ACROSS THE NORTHERN PLAINS TOWARD THE
MID MISSISSIPPI RIVER VALLEY AS A RESULT AND AMPLIFY AS IT DOES SO
INTO TONIGHT. THE SOUTH/WEST TREND OF THE TRACK OF THE SURFACE LOW
HAS CONTINUED AND DIFFERENCES REMAIN...ESPECIALLY WITH SOME OF THE
HIGH RES GUIDANCE WHICH TAKES THE LOW MUCH FURTHER SOUTH AND WEST
THAN SOME OF THE LOWER RES OPTIONS. IT APPEARS THAT THE LOW WILL NOT
TRACK NORTH OF ROUGHLY A BURLINGTON IOWA TO TERRE HAUTE INDIANA LINE
AT THIS POINT. WITH THE WAVE STILL TAKING SHAPE AND THE UPPER JET
STILL COMING ASHORE OVER THE PAC NORTHWEST FEEL THAT CONFIDENCE HAS
ROOM FOR IMPROVEMENT WITH THE MORNING UPPER AIR ANALYSIS AND
SUBSEQUENT 12Z GUIDANCE. THE MAIN QUESTION WILL BE PLACEMENT BUT
HAVE BETTER CONFIDENCE IN THE TREND OF WHAT OCCURS. PRECIP IS ON
TRACK TO QUICKLY SPREAD SOUTHEAST ACROSS THE AREA OVERNIGHT/AFTER
06Z/ AND SOUTHWEST AREAS STILL LOOK TO SEE A MIX OF RAIN OR SNOW AND
EVEN SOME SLEET THROUGH MID MORNING WHEN COLD AIR WILL TAKE OVER
CHANGING THINGS TO SNOW. PEAK PRECIP INTENSITY WILL BE AFTER
DAYBREAK INTO THE EARLY AFTERNOON. WINDS WILL TURN NORTHEAST AND
INCREASE DURING THE MORNING SETTING UP A DECENT FETCH DOWN LAKE
MICHIGAN. LAKE EFFECT PARAMETERS ARE SUB PAR BUT WHEN COMBINED WITH
SYNOPTIC SCALE ASCENT ARE PROBABLY SUFFICIENT TO PROVIDE SOME
MINIMAL ENHANCEMENT...MAINLY DUE TO INCREASED MOISTURE FLUX.
GUIDANCE VARIES WITH LIQUID OUTPUT WITH SOME RATHER HIGH AMOUNTS
NOTED PROBABLY SUGGESTIVE OF STRONG BANDING WHICH IS CERTAINLY
POSSIBLE. GIVEN PRECIPITABLE WATER VALUES OF AROUND 0.5 INCHES AND
FORCING OF 6 TO MAYBE 9 HOURS PEAK LIQUID AMOUNTS OF 0.3 TO 0.4
INCHES STILL SEEMS REASONABLE. LOCATION OF THESE AMOUNTS IS EXPECTED
ACROSS THE SOUTHERN CWA WITH AMOUNTS OF ONLY AROUND 0.1 INCHES
ACROSS THE NORTH. WITH SOUTHERN AREAS ALSO SEEING A MIX NOT ALL OF
THE LIQUID WILL GO TOWARD SNOW ACCUMULATION. THUS HIGHEST SNOW
AMOUNTS WILL OCCUR JUST TO THE NORTH...THOUGH WITH SOMEWHAT LOW
LIQUID EQUIVALENT. WILL DEPICT THE PEAK SNOWFALL FROM ROUGHLY
LASALLE COUNTY EAST-SOUTHEAST ALONG AND JUST SOUTH OF INTERSTATE 80
TO ROUGHLY KANKAKEE TO RENSSELAER. WILL CARRY 2-4 INCHES FOR THIS
AREA WITH AMOUNTS TAPERING TO ABOUT AN INCH ALONG THE WI
BORDER...WITH 1-2 INCHES ACROSS THE FAR NORTHERN CHICAGO METRO TO
AROUND 3 POSSIBLY 4 INCHES ACROSS THE FAR SOUTHERN CHICAGO METRO.
THERE IS STILL A CHANCE THIS COULD SHIFT FURTHER SOUTH.
PRECIPITATION QUICKLY ENDS MID TO LATE SUNDAY AFTERNOON WITH LITTLE
IF ANY LAKE EFFECT LINGERING GIVEN POOR INVERSION HEIGHTS.

HEADLINE POTENTIAL...WILL HOLD OFF ON ANY HEADLINES FOR NOW GIVEN
THAT A FURTHER SOUTH SHIFT IS STILL PLAUSIBLE. ANOTHER CONCERN IS
WIND SPEEDS WHICH WILL INCREASE TO 20 TO 25 MPH WITH GUSTS OF 30-35
MPH POSSIBLE SUNDAY MORNING THROUGH THE AFTERNOON. HOWEVER...WITH
FAIRLY WET SNOW RATIOS BLOWING WILL BE MINIMIZED BUT PROBABLY STILL
OCCUR. THERE IS ALSO A WINDOW FROM LATE MORNING THROUGH EARLY
AFTERNOON WHERE THE FALLING SNOW AND WIND MAY PUSH VISIBILITIES DOWN
UNDER A HALF OR QUARTER MILE...BUT THIS MAY OCCUR OVER A RATHER
SMALL AREA. EXPECT TO NEED A WINTER WEATHER ADVISORY ACROSS THE PEAK
SNOW AREA BUT AGAIN THE LOCATION MAY SHIFT AND IF BANDING DEVELOPS
THE SWATH OF SNOW COULD REALLY NARROW SO WOULD LIKE TO SEE THE
SYSTEM EVOLVE A LITTLE BIT MORE BEFORE DECIDING WHICH AREAS WILL SEE
THE BIGGEST IMPACT. WILL ISSUE A SPECIAL WEATHER STATEMENT
HIGHLIGHTING THE POTENTIAL IMPACTS FOR NOW.

MDB

&&

.LONG TERM...
308 AM CST

MONDAY THROUGH FRIDAY...

A MUCH BETTER DEFINED RIDGE WILL BE OVER WESTERN NORTH AMERICA
WITH A DEEP TROUGH OVER THE EAST COAST BY MONDAY. ANOTHER WAVE
WILL BE TRAVERSING THE RIDGE THEN DROP SOUTHEAST ACROSS THE GREAT
LAKES MONDAY BRINGING LOW CHANCES FOR SOME LIGHT SNOW. HIGH
PRESSURE WILL BUILD IN FROM THE WEST MONDAY NIGHT TURNING WINDS
MORE NORTHERLY. LAKE PARAMETERS WILL LIKELY BE MARGINAL BUT COULD
SEE SOME FLURRY OR LIGHT SNOW ACTIVITY DEVELOP FOR TUESDAY. THE
UPPER RIDGE BEGINS TO SHIFT EASTWARD WEDNESDAY WITH THE SURFACE
HIGH SHIFTING EAST AS WELL. THIS WILL LEAD TO A SHIFT TO SOUTHERLY
WINDS AND WARMING TEMPS LATE IN THE WEEK. GUIDANCE IS IN AGREEMENT
ON A LOW CROSSING THE AREA FIRST THING THURSDAY BRINGING MIXED
PRECIP POTENTIAL OR EVEN JUST RAIN. COLDER AIR BUILDS IN BEHIND
THE SYSTEM FRIDAY AS HIGH PRESSURE BUILDS INTO THE PLAINS. OVERALL
EXPECT TEMPS TO BE AT OR ABOVE NORMAL FROM TUESDAY ONWARD.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* PATCHY MVFR CIGS 2500-3000 FT THIS MORNING.

* POTENTIAL FOR MVFR CIGS AGAIN THIS EVENING.

* SNOW DEVELOPING LATE TONIGHT WITH IFR/LIFR CONDITIONS EXPECTED
  SUNDAY MORNING WITH ACCUMULATING SNOW OF 1-3 INCHES.

* WESTERLY WINDS NEAR 10 KT TODAY/THIS EVENING...BECOMING
  NORTHEAST AFTER MIDNIGHT AND THEN STRONG/GUSTY NEAR 30 KTS BY
  SUNDAY MORNING AND CONTINUING DURING THE DAY.

RATZER

//DISCUSSION...UPDATED 12Z...

PATCHY MVFR CIGS 2500-3000 FT ACROSS THE REGION THIS
MORNING...IN LIGHT WEST/NORTHWEST FLOW AHEAD OF COLD FRONT OVER
THE UPPER MIDWEST. EXPECTATION IS THAT MVFR CIGS WILL SCATTER OUT
BY MIDDAY. WESTERLY WINDS 260-290 DEGREES NEAR 10 KT WILL DIMINISH
THIS EVENING.

ATTENTION THEN TURNS TO QUICK MOVING ALBERTA-CLIPPER WHICH RAPIDLY
MOVES INTO THE AREA LATE TONIGHT AND BRINGS A PERIOD OF SNOW...AND
GUSTY NORTHEAST WINDS...TO THE TERMINALS. PERHAPS AM LEAST
CONFIDENT ABOUT CLOUDS DURING THE EVENING AND EARLY OVERNIGHT
HOURS AS GUIDANCE SATURATES THE BOUNDARY LAYER PRIOR TO MOISTURE
MOVING IN ALOFT. HAVE MAINTAINED PREVIOUS FORECAST TREND OF MVFR
CIGS REDEVELOPING AND EVENTUALLY LOWERING A BIT ALONG WITH SOME
MINOR VIS REDUCTION IN HAZE. MUCH GREATER CONFIDENCE IN SNOW
DEVELOPING PRIOR TO 12Z...WITH CIG/VIS CONDITIONS DETERIORATING TO
IFR/LIFR SHORTLY AFTER 12Z WITH STRONGEST/DEEPEST LIFT AND
SATURATION. IN ADDITION TO THE SNOW...THE SURFACE LOW WILL BE
DEEPENING AS IT PASSES SOUTHWEST OF THE AREA...RESULTING IN WINDS
SLACKING THIS EVENING AND THEN TURNING NORTHEAST AFTER MIDNIGHT.
WINDS THEN EXPECTED TO INCREASE RAPIDLY TOWARD MORNING...WITH
GUSTS NEAR 30 KT SUNDAY. SNOW EXPECTED TO ACCUMULATE 1-3 INCHES
ACROSS TERMINALS...WITH BLOWING SNOW/DRIFTING GIVEN THE STRONG
WINDS. SNOW SHOULD TAPER OFF BY EARLY AFTERNOON.

RATZER


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM IN MVFR CIG HEIGHT AND TRENDS THIS MORNING. MEDIUM-LOW
  WITH REDEVELOPMENT THIS EVENING.

* HIGH IN WIND TRENDS.

* MEDIUM-HIGH IN SNOW TIMING LATE TONIGHT/SUNDAY AND WITH CIG/VIS
  TRENDS.

RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...MVFR CIGS POSSIBLE.

MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR...CHANCE OF SNOW AND MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR/IFR POSSIBLE.

FRIDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
238 AM CST

MAIN MARINE CONCERNS FOCUS ON THE PERIOD FROM EARLY SUNDAY MORNING
THROUGH SUNDAY EVENING...AS NORTH-NORTHEASTERLY WINDS QUICKLY
INCREASE IN RESPONSE TO A FAST-MOVING DEEPENING ALBERTA-CLIPPER LOW
WHICH WILL DIG SOUTHEAST FROM IOWA INTO CENTRAL ILLINOIS AND
SOUTHERN INDIANA DURING THE DAY.

IN THE VERY NEAR TERM THIS MORNING...LOW PRESSURE WAS MOVING EAST OF
JAMES BAY ACROSS QUEBEC...WITH A COLD FRONT TRAILING FROM THE LOW
ACROSS LAKE SUPERIOR AND WEST ALONG THE INTERNATIONAL BORDER. THIS
FRONT WILL SAG SOUTH ACROSS NORTHERN LAKE MICHIGAN LATER TODAY WITH
WINDS SHIFTING NORTH AND INCREASING BEHIND IT AS HIGH PRESSURE
SPREADS SOUTHEAST ACROSS MANITOBA AND NORTHWEST QUEBEC. BY
TONIGHT...THE FAST-MOVING CLIPPER WILL ALSO ALREADY BE ENTERING
IOWA  AND MOVING INTO WEST-CENTRAL ILLINOIS BY SUNDAY MORNING WHILE
DEEPENING A BIT. THE TIGHTENING GRADIENT AROUND THE LOW WILL ALSO
HELP TO TURN WINDS NORTHEAST AND STRENGTHEN THEM ALL THE WAY TO THE
SOUTH END OF THE LAKE AS THE LOW EVENTUALLY TRACKS INTO THE OHIO
VALLEY IN THE AFTERNOON. MODEL FORECAST SOUNDINGS DEPICT A PERIOD OF
SOLID 30 KT NORTHEAST WINDS ACROSS THE SOUTH 2/3 OR 3/4 OF THE LAKE
SUNDAY...WITH A FEW GUSTS OVER 30 KTS (MARGINAL GALE FORCE) DURING
THE DAY. WITH THE LOW MOVING QUICKLY OFF TO THE SOUTHEAST SUNDAY
NIGHT...WINDS WILL DIMINISH AS QUICKLY AS THEY INCREASED EARLY IN
THE DAY...AS WEAK HIGH PRESSURE RIDGING MOVES ACROSS THE LAKE SUNDAY
NIGHT. WILL NEED A SMALL CRAFT ADVISORY FOR THE IL/NW IND NEARSHORE
WATERS FROM ABOUT 6 AM CST SUNDAY THROUGH ABOUT 6 AM CST MONDAY FOR
THE STRONG WINDS AND RESULTING WAVES.

EARLY NEXT WEEK THE PATTERN CONTINUES TO APPEAR RATHER
PROGRESSIVE...WITH THE WEEK HIGH PRESSURE RIDGE OVER THE LAKE SUNDAY
NIGHT QUICKLY BEING DISPLACED MONDAY BY ANOTHER LOW PRESSURE SYSTEM
WHICH MOVES INTO THE NORTHERN LAKES MONDAY AFTERNOON. THIS BRINGS
WINDS AROUND TO THE SOUTH AND INCREASING INTO THE 25 KT RANGE FOR A
TIME MONDAY AS THE LOW APPROACHES. THE LOW THEN WEAKENS AS IT MOVES
SOUTHEAST ACROSS THE LAKES MONDAY NIGHT...FILLING AS A DEEP LOW
DEVELOPS ALONG THE ATLANTIC COAST. WEAK HIGH PRESSURE SPREADS ACROSS
THE LAKE TUESDAY...BEFORE ANOTHER LOW DEVELOPS ACROSS THE CENTRAL
PLAINS AND MOVES INTO THE MID-MISSISSIPPI VALLEY REGION THROUGH LATE
WEDNESDAY.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 241153
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
553 AM CST SAT JAN 24 2015

.SHORT TERM...
308 AM CST

TODAY THROUGH SUNDAY NIGHT...

THE MAIN FORECAST ISSUE WILL BE ACCUMULATING SNOW AND GUSTY WINDS
STARTING LATER TONIGHT CONTINUING THROUGH MUCH OF SUNDAY. WATER
VAPOR IMAGERY SHOWS A LONGWAVE TROUGH STRETCHING FROM HUDSON BAY
SOUTH TO THE GULF COAST WITH BROAD RIDGING OVER THE EASTERN
PACIFIC AND MUCH OF WESTERN CANADA AND THE NORTHWEST U.S. A WEAK
COOL FRONT IS CROSSING THE AREA BEHIND THE PASSAGE OF THE LONGWAVE
TROUGH AXIS. COOL ADVECTION THIS MORNING WILL GIVE WAY TO MODEST
WARM ADVECTION LATE THIS AFTERNOON. CLOUD COVER WILL BE THE WILD
CARD WITH TEMPS. STRATUS IS SPREADING SOUTHEAST ACROSS THE AREA
THIS MORNING BUT SATELLITE SHOWS GAPS IN COVERAGE UPSTREAM.
GUIDANCE IS MIXED WITH THE EXTENT OF CLOUD COVER BUT SUSPECT THERE
WILL BE BREAKS IN THE CLOUDS...ESPECIALLY THIS AFTERNOON...WITH
ANY MEANINGFUL SUNSHINE DURING THE EARLY/MID AFTERNOON HELPING
TEMPS SOMEWHAT. THIS IS MOST FAVORED SOUTH AND WEST SO WILL NUDGE
TEMPS UP SLIGHTLY THERE WHILE CARRYING UPPER 30S ACROSS THE REST
OF THE AREA.

THE MAIN FEATURE OF CONCERN IS A WAVE MOVING EAST-SOUTHEAST ACROSS
SOUTHERN ALBERTA. EVENING UPPER AIR ANALYSIS SHOWS A STRONG JET
PUSHING INTO THE PACIFIC NORTHWEST AND PIVOTING SOUTHEASTWARD AS
ADDITIONAL ENERGY PUSHES EASTWARD AMPLIFYING THE RIDGE. THE WAVE OF
CONCERN WILL DIG SOUTHEASTWARD ACROSS THE NORTHERN PLAINS TOWARD THE
MID MISSISSIPPI RIVER VALLEY AS A RESULT AND AMPLIFY AS IT DOES SO
INTO TONIGHT. THE SOUTH/WEST TREND OF THE TRACK OF THE SURFACE LOW
HAS CONTINUED AND DIFFERENCES REMAIN...ESPECIALLY WITH SOME OF THE
HIGH RES GUIDANCE WHICH TAKES THE LOW MUCH FURTHER SOUTH AND WEST
THAN SOME OF THE LOWER RES OPTIONS. IT APPEARS THAT THE LOW WILL NOT
TRACK NORTH OF ROUGHLY A BURLINGTON IOWA TO TERRE HAUTE INDIANA LINE
AT THIS POINT. WITH THE WAVE STILL TAKING SHAPE AND THE UPPER JET
STILL COMING ASHORE OVER THE PAC NORTHWEST FEEL THAT CONFIDENCE HAS
ROOM FOR IMPROVEMENT WITH THE MORNING UPPER AIR ANALYSIS AND
SUBSEQUENT 12Z GUIDANCE. THE MAIN QUESTION WILL BE PLACEMENT BUT
HAVE BETTER CONFIDENCE IN THE TREND OF WHAT OCCURS. PRECIP IS ON
TRACK TO QUICKLY SPREAD SOUTHEAST ACROSS THE AREA OVERNIGHT/AFTER
06Z/ AND SOUTHWEST AREAS STILL LOOK TO SEE A MIX OF RAIN OR SNOW AND
EVEN SOME SLEET THROUGH MID MORNING WHEN COLD AIR WILL TAKE OVER
CHANGING THINGS TO SNOW. PEAK PRECIP INTENSITY WILL BE AFTER
DAYBREAK INTO THE EARLY AFTERNOON. WINDS WILL TURN NORTHEAST AND
INCREASE DURING THE MORNING SETTING UP A DECENT FETCH DOWN LAKE
MICHIGAN. LAKE EFFECT PARAMETERS ARE SUB PAR BUT WHEN COMBINED WITH
SYNOPTIC SCALE ASCENT ARE PROBABLY SUFFICIENT TO PROVIDE SOME
MINIMAL ENHANCEMENT...MAINLY DUE TO INCREASED MOISTURE FLUX.
GUIDANCE VARIES WITH LIQUID OUTPUT WITH SOME RATHER HIGH AMOUNTS
NOTED PROBABLY SUGGESTIVE OF STRONG BANDING WHICH IS CERTAINLY
POSSIBLE. GIVEN PRECIPITABLE WATER VALUES OF AROUND 0.5 INCHES AND
FORCING OF 6 TO MAYBE 9 HOURS PEAK LIQUID AMOUNTS OF 0.3 TO 0.4
INCHES STILL SEEMS REASONABLE. LOCATION OF THESE AMOUNTS IS EXPECTED
ACROSS THE SOUTHERN CWA WITH AMOUNTS OF ONLY AROUND 0.1 INCHES
ACROSS THE NORTH. WITH SOUTHERN AREAS ALSO SEEING A MIX NOT ALL OF
THE LIQUID WILL GO TOWARD SNOW ACCUMULATION. THUS HIGHEST SNOW
AMOUNTS WILL OCCUR JUST TO THE NORTH...THOUGH WITH SOMEWHAT LOW
LIQUID EQUIVALENT. WILL DEPICT THE PEAK SNOWFALL FROM ROUGHLY
LASALLE COUNTY EAST-SOUTHEAST ALONG AND JUST SOUTH OF INTERSTATE 80
TO ROUGHLY KANKAKEE TO RENSSELAER. WILL CARRY 2-4 INCHES FOR THIS
AREA WITH AMOUNTS TAPERING TO ABOUT AN INCH ALONG THE WI
BORDER...WITH 1-2 INCHES ACROSS THE FAR NORTHERN CHICAGO METRO TO
AROUND 3 POSSIBLY 4 INCHES ACROSS THE FAR SOUTHERN CHICAGO METRO.
THERE IS STILL A CHANCE THIS COULD SHIFT FURTHER SOUTH.
PRECIPITATION QUICKLY ENDS MID TO LATE SUNDAY AFTERNOON WITH LITTLE
IF ANY LAKE EFFECT LINGERING GIVEN POOR INVERSION HEIGHTS.

HEADLINE POTENTIAL...WILL HOLD OFF ON ANY HEADLINES FOR NOW GIVEN
THAT A FURTHER SOUTH SHIFT IS STILL PLAUSIBLE. ANOTHER CONCERN IS
WIND SPEEDS WHICH WILL INCREASE TO 20 TO 25 MPH WITH GUSTS OF 30-35
MPH POSSIBLE SUNDAY MORNING THROUGH THE AFTERNOON. HOWEVER...WITH
FAIRLY WET SNOW RATIOS BLOWING WILL BE MINIMIZED BUT PROBABLY STILL
OCCUR. THERE IS ALSO A WINDOW FROM LATE MORNING THROUGH EARLY
AFTERNOON WHERE THE FALLING SNOW AND WIND MAY PUSH VISIBILITIES DOWN
UNDER A HALF OR QUARTER MILE...BUT THIS MAY OCCUR OVER A RATHER
SMALL AREA. EXPECT TO NEED A WINTER WEATHER ADVISORY ACROSS THE PEAK
SNOW AREA BUT AGAIN THE LOCATION MAY SHIFT AND IF BANDING DEVELOPS
THE SWATH OF SNOW COULD REALLY NARROW SO WOULD LIKE TO SEE THE
SYSTEM EVOLVE A LITTLE BIT MORE BEFORE DECIDING WHICH AREAS WILL SEE
THE BIGGEST IMPACT. WILL ISSUE A SPECIAL WEATHER STATEMENT
HIGHLIGHTING THE POTENTIAL IMPACTS FOR NOW.

MDB

&&

.LONG TERM...
308 AM CST

MONDAY THROUGH FRIDAY...

A MUCH BETTER DEFINED RIDGE WILL BE OVER WESTERN NORTH AMERICA
WITH A DEEP TROUGH OVER THE EAST COAST BY MONDAY. ANOTHER WAVE
WILL BE TRAVERSING THE RIDGE THEN DROP SOUTHEAST ACROSS THE GREAT
LAKES MONDAY BRINGING LOW CHANCES FOR SOME LIGHT SNOW. HIGH
PRESSURE WILL BUILD IN FROM THE WEST MONDAY NIGHT TURNING WINDS
MORE NORTHERLY. LAKE PARAMETERS WILL LIKELY BE MARGINAL BUT COULD
SEE SOME FLURRY OR LIGHT SNOW ACTIVITY DEVELOP FOR TUESDAY. THE
UPPER RIDGE BEGINS TO SHIFT EASTWARD WEDNESDAY WITH THE SURFACE
HIGH SHIFTING EAST AS WELL. THIS WILL LEAD TO A SHIFT TO SOUTHERLY
WINDS AND WARMING TEMPS LATE IN THE WEEK. GUIDANCE IS IN AGREEMENT
ON A LOW CROSSING THE AREA FIRST THING THURSDAY BRINGING MIXED
PRECIP POTENTIAL OR EVEN JUST RAIN. COLDER AIR BUILDS IN BEHIND
THE SYSTEM FRIDAY AS HIGH PRESSURE BUILDS INTO THE PLAINS. OVERALL
EXPECT TEMPS TO BE AT OR ABOVE NORMAL FROM TUESDAY ONWARD.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* PATCHY MVFR CIGS 2500-3000 FT THIS MORNING.

* POTENTIAL FOR MVFR CIGS AGAIN THIS EVENING.

* SNOW DEVELOPING LATE TONIGHT WITH IFR/LIFR CONDITIONS EXPECTED
  SUNDAY MORNING WITH ACCUMULATING SNOW OF 1-3 INCHES.

* WESTERLY WINDS NEAR 10 KT TODAY/THIS EVENING...BECOMING
  NORTHEAST AFTER MIDNIGHT AND THEN STRONG/GUSTY NEAR 30 KTS BY
  SUNDAY MORNING AND CONTINUING DURING THE DAY.

RATZER

//DISCUSSION...UPDATED 12Z...

PATCHY MVFR CIGS 2500-3000 FT ACROSS THE REGION THIS
MORNING...IN LIGHT WEST/NORTHWEST FLOW AHEAD OF COLD FRONT OVER
THE UPPER MIDWEST. EXPECTATION IS THAT MVFR CIGS WILL SCATTER OUT
BY MIDDAY. WESTERLY WINDS 260-290 DEGREES NEAR 10 KT WILL DIMINISH
THIS EVENING.

ATTENTION THEN TURNS TO QUICK MOVING ALBERTA-CLIPPER WHICH RAPIDLY
MOVES INTO THE AREA LATE TONIGHT AND BRINGS A PERIOD OF SNOW...AND
GUSTY NORTHEAST WINDS...TO THE TERMINALS. PERHAPS AM LEAST
CONFIDENT ABOUT CLOUDS DURING THE EVENING AND EARLY OVERNIGHT
HOURS AS GUIDANCE SATURATES THE BOUNDARY LAYER PRIOR TO MOISTURE
MOVING IN ALOFT. HAVE MAINTAINED PREVIOUS FORECAST TREND OF MVFR
CIGS REDEVELOPING AND EVENTUALLY LOWERING A BIT ALONG WITH SOME
MINOR VIS REDUCTION IN HAZE. MUCH GREATER CONFIDENCE IN SNOW
DEVELOPING PRIOR TO 12Z...WITH CIG/VIS CONDITIONS DETERIORATING TO
IFR/LIFR SHORTLY AFTER 12Z WITH STRONGEST/DEEPEST LIFT AND
SATURATION. IN ADDITION TO THE SNOW...THE SURFACE LOW WILL BE
DEEPENING AS IT PASSES SOUTHWEST OF THE AREA...RESULTING IN WINDS
SLACKING THIS EVENING AND THEN TURNING NORTHEAST AFTER MIDNIGHT.
WINDS THEN EXPECTED TO INCREASE RAPIDLY TOWARD MORNING...WITH
GUSTS NEAR 30 KT SUNDAY. SNOW EXPECTED TO ACCUMULATE 1-3 INCHES
ACROSS TERMINALS...WITH BLOWING SNOW/DRIFTING GIVEN THE STRONG
WINDS. SNOW SHOULD TAPER OFF BY EARLY AFTERNOON.

RATZER


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM IN MVFR CIG HEIGHT AND TRENDS THIS MORNING. MEDIUM-LOW
  WITH REDEVELOPMENT THIS EVENING.

* HIGH IN WIND TRENDS.

* MEDIUM-HIGH IN SNOW TIMING LATE TONIGHT/SUNDAY AND WITH CIG/VIS
  TRENDS.

RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...MVFR CIGS POSSIBLE.

MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE.

TUESDAY...MVFR CIGS POSSIBLE.

WEDNESDAY...MAINLY VFR...CHANCE OF SNOW AND MVFR/IFR AT NIGHT.

THURSDAY...CHANCE OF RAIN/SNOW. MVFR/IFR POSSIBLE.

FRIDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
238 AM CST

MAIN MARINE CONCERNS FOCUS ON THE PERIOD FROM EARLY SUNDAY MORNING
THROUGH SUNDAY EVENING...AS NORTH-NORTHEASTERLY WINDS QUICKLY
INCREASE IN RESPONSE TO A FAST-MOVING DEEPENING ALBERTA-CLIPPER LOW
WHICH WILL DIG SOUTHEAST FROM IOWA INTO CENTRAL ILLINOIS AND
SOUTHERN INDIANA DURING THE DAY.

IN THE VERY NEAR TERM THIS MORNING...LOW PRESSURE WAS MOVING EAST OF
JAMES BAY ACROSS QUEBEC...WITH A COLD FRONT TRAILING FROM THE LOW
ACROSS LAKE SUPERIOR AND WEST ALONG THE INTERNATIONAL BORDER. THIS
FRONT WILL SAG SOUTH ACROSS NORTHERN LAKE MICHIGAN LATER TODAY WITH
WINDS SHIFTING NORTH AND INCREASING BEHIND IT AS HIGH PRESSURE
SPREADS SOUTHEAST ACROSS MANITOBA AND NORTHWEST QUEBEC. BY
TONIGHT...THE FAST-MOVING CLIPPER WILL ALSO ALREADY BE ENTERING
IOWA  AND MOVING INTO WEST-CENTRAL ILLINOIS BY SUNDAY MORNING WHILE
DEEPENING A BIT. THE TIGHTENING GRADIENT AROUND THE LOW WILL ALSO
HELP TO TURN WINDS NORTHEAST AND STRENGTHEN THEM ALL THE WAY TO THE
SOUTH END OF THE LAKE AS THE LOW EVENTUALLY TRACKS INTO THE OHIO
VALLEY IN THE AFTERNOON. MODEL FORECAST SOUNDINGS DEPICT A PERIOD OF
SOLID 30 KT NORTHEAST WINDS ACROSS THE SOUTH 2/3 OR 3/4 OF THE LAKE
SUNDAY...WITH A FEW GUSTS OVER 30 KTS (MARGINAL GALE FORCE) DURING
THE DAY. WITH THE LOW MOVING QUICKLY OFF TO THE SOUTHEAST SUNDAY
NIGHT...WINDS WILL DIMINISH AS QUICKLY AS THEY INCREASED EARLY IN
THE DAY...AS WEAK HIGH PRESSURE RIDGING MOVES ACROSS THE LAKE SUNDAY
NIGHT. WILL NEED A SMALL CRAFT ADVISORY FOR THE IL/NW IND NEARSHORE
WATERS FROM ABOUT 6 AM CST SUNDAY THROUGH ABOUT 6 AM CST MONDAY FOR
THE STRONG WINDS AND RESULTING WAVES.

EARLY NEXT WEEK THE PATTERN CONTINUES TO APPEAR RATHER
PROGRESSIVE...WITH THE WEEK HIGH PRESSURE RIDGE OVER THE LAKE SUNDAY
NIGHT QUICKLY BEING DISPLACED MONDAY BY ANOTHER LOW PRESSURE SYSTEM
WHICH MOVES INTO THE NORTHERN LAKES MONDAY AFTERNOON. THIS BRINGS
WINDS AROUND TO THE SOUTH AND INCREASING INTO THE 25 KT RANGE FOR A
TIME MONDAY AS THE LOW APPROACHES. THE LOW THEN WEAKENS AS IT MOVES
SOUTHEAST ACROSS THE LAKES MONDAY NIGHT...FILLING AS A DEEP LOW
DEVELOPS ALONG THE ATLANTIC COAST. WEAK HIGH PRESSURE SPREADS ACROSS
THE LAKE TUESDAY...BEFORE ANOTHER LOW DEVELOPS ACROSS THE CENTRAL
PLAINS AND MOVES INTO THE MID-MISSISSIPPI VALLEY REGION THROUGH LATE
WEDNESDAY.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 240911
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
311 AM CST SAT JAN 24 2015

.SHORT TERM...
308 AM CST

TODAY THROUGH SUNDAY NIGHT...

THE MAIN FORECAST ISSUE WILL BE ACCUMULATING SNOW AND GUSTY WINDS
STARTING LATER TONIGHT CONTINUING THROUGH MUCH OF SUNDAY. WATER
VAPOR IMAGERY SHOWS A LONGWAVE TROUGH STRETCHING FROM HUDSON BAY
SOUTH TO THE GULF COAST WITH BROAD RIDGING OVER THE EASTERN
PACIFIC AND MUCH OF WESTERN CANADA AND THE NORTHWEST U.S. A WEAK
COOL FRONT IS CROSSING THE AREA BEHIND THE PASSAGE OF THE LONGWAVE
TROUGH AXIS. COOL ADVECTION THIS MORNING WILL GIVE WAY TO MODEST
WARM ADVECTION LATE THIS AFTERNOON. CLOUD COVER WILL BE THE WILD
CARD WITH TEMPS. STRATUS IS SPREADING SOUTHEAST ACROSS THE AREA
THIS MORNING BUT SATELLITE SHOWS GAPS IN COVERAGE UPSTREAM.
GUIDANCE IS MIXED WITH THE EXTENT OF CLOUD COVER BUT SUSPECT THERE
WILL BE BREAKS IN THE CLOUDS...ESPECIALLY THIS AFTERNOON...WITH
ANY MEANINGFUL SUNSHINE DURING THE EARLY/MID AFTERNOON HELPING
TEMPS SOMEWHAT. THIS IS MOST FAVORED SOUTH AND WEST SO WILL NUDGE
TEMPS UP SLIGHTLY THERE WHILE CARRYING UPPER 30S ACROSS THE REST
OF THE AREA.

THE MAIN FEATURE OF CONCERN IS A WAVE MOVING EAST-SOUTHEAST ACROSS
SOUTHERN ALBERTA. EVENING UPPER AIR ANALYSIS SHOWS A STRONG JET
PUSHING INTO THE PACIFIC NORTHWEST AND PIVOTING SOUTHEASTWARD AS
ADDITIONAL ENERGY PUSHES EASTWARD AMPLIFYING THE RIDGE. THE WAVE OF
CONCERN WILL DIG SOUTHEASTWARD ACROSS THE NORTHERN PLAINS TOWARD THE
MID MISSISSIPPI RIVER VALLEY AS A RESULT AND AMPLIFY AS IT DOES SO
INTO TONIGHT. THE SOUTH/WEST TREND OF THE TRACK OF THE SURFACE LOW
HAS CONTINUED AND DIFFERENCES REMAIN...ESPECIALLY WITH SOME OF THE
HIGH RES GUIDANCE WHICH TAKES THE LOW MUCH FURTHER SOUTH AND WEST
THAN SOME OF THE LOWER RES OPTIONS. IT APPEARS THAT THE LOW WILL NOT
TRACK NORTH OF ROUGHLY A BURLINGTON IOWA TO TERRE HAUTE INDIANA LINE
AT THIS POINT. WITH THE WAVE STILL TAKING SHAPE AND THE UPPER JET
STILL COMING ASHORE OVER THE PAC NORTHWEST FEEL THAT CONFIDENCE HAS
ROOM FOR IMPROVEMENT WITH THE MORNING UPPER AIR ANALYSIS AND
SUBSEQUENT 12Z GUIDANCE. THE MAIN QUESTION WILL BE PLACEMENT BUT
HAVE BETTER CONFIDENCE IN THE TREND OF WHAT OCCURS. PRECIP IS ON
TRACK TO QUICKLY SPREAD SOUTHEAST ACROSS THE AREA OVERNIGHT/AFTER
06Z/ AND SOUTHWEST AREAS STILL LOOK TO SEE A MIX OF RAIN OR SNOW AND
EVEN SOME SLEET THROUGH MID MORNING WHEN COLD AIR WILL TAKE OVER
CHANGING THINGS TO SNOW. PEAK PRECIP INTENSITY WILL BE AFTER
DAYBREAK INTO THE EARLY AFTERNOON. WINDS WILL TURN NORTHEAST AND
INCREASE DURING THE MORNING SETTING UP A DECENT FETCH DOWN LAKE
MICHIGAN. LAKE EFFECT PARAMETERS ARE SUB PAR BUT WHEN COMBINED WITH
SYNOPTIC SCALE ASCENT ARE PROBABLY SUFFICIENT TO PROVIDE SOME
MINIMAL ENHANCEMENT...MAINLY DUE TO INCREASED MOISTURE FLUX.
GUIDANCE VARIES WITH LIQUID OUTPUT WITH SOME RATHER HIGH AMOUNTS
NOTED PROBABLY SUGGESTIVE OF STRONG BANDING WHICH IS CERTAINLY
POSSIBLE. GIVEN PRECIPITABLE WATER VALUES OF AROUND 0.5 INCHES AND
FORCING OF 6 TO MAYBE 9 HOURS PEAK LIQUID AMOUNTS OF 0.3 TO 0.4
INCHES STILL SEEMS REASONABLE. LOCATION OF THESE AMOUNTS IS EXPECTED
ACROSS THE SOUTHERN CWA WITH AMOUNTS OF ONLY AROUND 0.1 INCHES
ACROSS THE NORTH. WITH SOUTHERN AREAS ALSO SEEING A MIX NOT ALL OF
THE LIQUID WILL GO TOWARD SNOW ACCUMULATION. THUS HIGHEST SNOW
AMOUNTS WILL OCCUR JUST TO THE NORTH...THOUGH WITH SOMEWHAT LOW
LIQUID EQUIVALENT. WILL DEPICT THE PEAK SNOWFALL FROM ROUGHLY
LASALLE COUNTY EAST-SOUTHEAST ALONG AND JUST SOUTH OF INTERSTATE 80
TO ROUGHLY KANKAKEE TO RENSSELAER. WILL CARRY 2-4 INCHES FOR THIS
AREA WITH AMOUNTS TAPERING TO ABOUT AN INCH ALONG THE WI
BORDER...WITH 1-2 INCHES ACROSS THE FAR NORTHERN CHICAGO METRO TO
AROUND 3 POSSIBLY 4 INCHES ACROSS THE FAR SOUTHERN CHICAGO METRO.
THERE IS STILL A CHANCE THIS COULD SHIFT FURTHER SOUTH.
PRECIPITATION QUICKLY ENDS MID TO LATE SUNDAY AFTERNOON WITH LITTLE
IF ANY LAKE EFFECT LINGERING GIVEN POOR INVERSION HEIGHTS.

HEADLINE POTENTIAL...WILL HOLD OFF ON ANY HEADLINES FOR NOW GIVEN
THAT A FURTHER SOUTH SHIFT IS STILL PLAUSIBLE. ANOTHER CONCERN IS
WIND SPEEDS WHICH WILL INCREASE TO 20 TO 25 MPH WITH GUSTS OF 30-35
MPH POSSIBLE SUNDAY MORNING THROUGH THE AFTERNOON. HOWEVER...WITH
FAIRLY WET SNOW RATIOS BLOWING WILL BE MINIMIZED BUT PROBABLY STILL
OCCUR. THERE IS ALSO A WINDOW FROM LATE MORNING THROUGH EARLY
AFTERNOON WHERE THE FALLING SNOW AND WIND MAY PUSH VISIBILITIES DOWN
UNDER A HALF OR QUARTER MILE...BUT THIS MAY OCCUR OVER A RATHER
SMALL AREA. EXPECT TO NEED A WINTER WEATHER ADVISORY ACROSS THE PEAK
SNOW AREA BUT AGAIN THE LOCATION MAY SHIFT AND IF BANDING DEVELOPS
THE SWATH OF SNOW COULD REALLY NARROW SO WOULD LIKE TO SEE THE
SYSTEM EVOLVE A LITTLE BIT MORE BEFORE DECIDING WHICH AREAS WILL SEE
THE BIGGEST IMPACT. WILL ISSUE A SPECIAL WEATHER STATEMENT
HIGHLIGHTING THE POTENTIAL IMPACTS FOR NOW.

MDB

&&

.LONG TERM...
308 AM CST

MONDAY THROUGH FRIDAY...

A MUCH BETTER DEFINED RIDGE WILL BE OVER WESTERN NORTH AMERICA
WITH A DEEP TROUGH OVER THE EAST COAST BY MONDAY. ANOTHER WAVE
WILL BE TRAVERSING THE RIDGE THEN DROP SOUTHEAST ACROSS THE GREAT
LAKES MONDAY BRINGING LOW CHANCES FOR SOME LIGHT SNOW. HIGH
PRESSURE WILL BUILD IN FROM THE WEST MONDAY NIGHT TURNING WINDS
MORE NORTHERLY. LAKE PARAMETERS WILL LIKELY BE MARGINAL BUT COULD
SEE SOME FLURRY OR LIGHT SNOW ACTIVITY DEVELOP FOR TUESDAY. THE
UPPER RIDGE BEGINS TO SHIFT EASTWARD WEDNESDAY WITH THE SURFACE
HIGH SHIFTING EAST AS WELL. THIS WILL LEAD TO A SHIFT TO SOUTHERLY
WINDS AND WARMING TEMPS LATE IN THE WEEK. GUIDANCE IS IN AGREEMENT
ON A LOW CROSSING THE AREA FIRST THING THURSDAY BRINGING MIXED
PRECIP POTENTIAL OR EVEN JUST RAIN. COLDER AIR BUILDS IN BEHIND
THE SYSTEM FRIDAY AS HIGH PRESSURE BUILDS INTO THE PLAINS. OVERALL
EXPECT TEMPS TO BE AT OR ABOVE NORMAL FROM TUESDAY ONWARD.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* MVFR CEILINGS HAVE MOVED IN FROM THE NORTHWEST AND WILL LINGER
  THROUGH THE MORNING.

* WESTERLY WINDS NEAR 10 KTS TODAY...DIMINISHING AND EVENTUALLY
  BECOMING EAST-NORTHEAST AFTER MIDNIGHT SATURDAY AND BECOMING
  GUSTY TOWARD MORNING.

* SNOW DEVELOPING TOWARD 12Z SUNDAY. IFR/LIFR CONDITIONS LIKELY
  IN SNOW JUST BEYOND END OF ORD 30 OUR TAF PERIOD.

RATZER

//DISCUSSION...UPDATED 06Z...

SURFACE LOW PRESSURE WAS MOVING EAST INTO EASTERN CANADA LATE THIS
EVENING...WITH A WEAKER TROUGH OF LOW PRESSURE TRAILING SOUTHWEST
INTO THE WESTERN GREAT LAKES REGION. THIS TROUGH WILL MOVE
SOUTHEAST ACROSS THE TERMINAL SITES EARLY THIS MORNING WITH A
SUBTLE WIND SHIFT FROM WEST-SOUTHWEST TO WEST-NORTHWEST...AS WELL
AS AN AREA OF MVFR STRATUS WHICH WILL SPREAD ACROSS THE AREA IN
THE 07-09Z TIME FRAME PER EXTRAPOLATION OF SATELLITE IMAGERY. SOME
LARGE BREAKS IN THE STRATUS BACK ACROSS WESTERN/NORTHWEST WISCONSIN
SUGGEST IT MAY TEND TO ALLOW SOME BREAKS TO VFR CONDITIONS BY
MIDDAY...THOUGH MODEL SOUNDINGS REMAIN FAIRLY MOIST IN THE LOWEST
FEW THOUSAND FEET NEAR THE GROUND.

OF GREATER CONFIDENCE IS THE APPROACH OF A DIGGING MID-LEVEL
DISTURBANCE TONIGHT...WITH ASSOCIATED DEEPENING SURFACE LOW
PRESSURE EXPECTED TO PASS SOUTHWEST OF TERMINALS EARLY SUNDAY
MORNING. MODELS HAVE BEEN FAIRLY CONSISTENT IN SATURATING THE
COLUMN DURING THE PRE-DAWN HOURS OF SUNDAY MORNING WITH SNOW
EXPECTED TO DEVELOP BY 12Z. IFR/LIFR CONDITIONS EXPECTED IN
SNOW SHORTLY THEREAFTER...JUST BEYOND END OF CURRENT TAF PERIODS.
IN ADDITION...DEEPENING OF THE SURFACE LOW TO THE SOUTHWEST OF THE
TERMINALS WILL RESULT IN WINDS SHIFTING TO THE EAST-NORTHEAST AND
INCREASING EARLY SUNDAY MORNING...LIKELY GUSTING 25-30 KT BY MID-
MORNING SUNDAY.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH IN WIND TRENDS...THOUGH MEDIUM-LOW IN DIRECTION SATURDAY
  EVENING AS SHIFT TO EAST-NORTHEAST OCCURS.

* LOW IN DISSIPATION OF MVFR TIMING LATER TODAY.

* MEDIUM-HIGH IN TIMING SNOW TO DEVELOP BEFORE SUNRISE SUNDAY.

RATZER

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...

SUNDAY...SNOW. IFR LIKELY PERIODIC LIFR POSSIBLE.

MONDAY...SLIGHT CHANCE OF -SN. MVFR PROBABLE W/CHANCE OF IFR.

TUESDAY THROUGH THURSDAY...PRIMARILY VFR. MAINLY DRY.

IZZI

&&

.MARINE...
238 AM CST

MAIN MARINE CONCERNS FOCUS ON THE PERIOD FROM EARLY SUNDAY MORNING
THROUGH SUNDAY EVENING...AS NORTH-NORTHEASTERLY WINDS QUICKLY
INCREASE IN RESPONSE TO A FAST-MOVING DEEPENING ALBERTA-CLIPPER LOW
WHICH WILL DIG SOUTHEAST FROM IOWA INTO CENTRAL ILLINOIS AND
SOUTHERN INDIANA DURING THE DAY.

IN THE VERY NEAR TERM THIS MORNING...LOW PRESSURE WAS MOVING EAST OF
JAMES BAY ACROSS QUEBEC...WITH A COLD FRONT TRAILING FROM THE LOW
ACROSS LAKE SUPERIOR AND WEST ALONG THE INTERNATIONAL BORDER. THIS
FRONT WILL SAG SOUTH ACROSS NORTHERN LAKE MICHIGAN LATER TODAY WITH
WINDS SHIFTING NORTH AND INCREASING BEHIND IT AS HIGH PRESSURE
SPREADS SOUTHEAST ACROSS MANITOBA AND NORTHWEST QUEBEC. BY
TONIGHT...THE FAST-MOVING CLIPPER WILL ALSO ALREADY BE ENTERING
IOWA  AND MOVING INTO WEST-CENTRAL ILLINOIS BY SUNDAY MORNING WHILE
DEEPENING A BIT. THE TIGHTENING GRADIENT AROUND THE LOW WILL ALSO
HELP TO TURN WINDS NORTHEAST AND STRENGTHEN THEM ALL THE WAY TO THE
SOUTH END OF THE LAKE AS THE LOW EVENTUALLY TRACKS INTO THE OHIO
VALLEY IN THE AFTERNOON. MODEL FORECAST SOUNDINGS DEPICT A PERIOD OF
SOLID 30 KT NORTHEAST WINDS ACROSS THE SOUTH 2/3 OR 3/4 OF THE LAKE
SUNDAY...WITH A FEW GUSTS OVER 30 KTS (MARGINAL GALE FORCE) DURING
THE DAY. WITH THE LOW MOVING QUICKLY OFF TO THE SOUTHEAST SUNDAY
NIGHT...WINDS WILL DIMINISH AS QUICKLY AS THEY INCREASED EARLY IN
THE DAY...AS WEAK HIGH PRESSURE RIDGING MOVES ACROSS THE LAKE SUNDAY
NIGHT. WILL NEED A SMALL CRAFT ADVISORY FOR THE IL/NW IND NEARSHORE
WATERS FROM ABOUT 6 AM CST SUNDAY THROUGH ABOUT 6 AM CST MONDAY FOR
THE STRONG WINDS AND RESULTING WAVES.

EARLY NEXT WEEK THE PATTERN CONTINUES TO APPEAR RATHER
PROGRESSIVE...WITH THE WEEK HIGH PRESSURE RIDGE OVER THE LAKE SUNDAY
NIGHT QUICKLY BEING DISPLACED MONDAY BY ANOTHER LOW PRESSURE SYSTEM
WHICH MOVES INTO THE NORTHERN LAKES MONDAY AFTERNOON. THIS BRINGS
WINDS AROUND TO THE SOUTH AND INCREASING INTO THE 25 KT RANGE FOR A
TIME MONDAY AS THE LOW APPROACHES. THE LOW THEN WEAKENS AS IT MOVES
SOUTHEAST ACROSS THE LAKES MONDAY NIGHT...FILLING AS A DEEP LOW
DEVELOPS ALONG THE ATLANTIC COAST. WEAK HIGH PRESSURE SPREADS ACROSS
THE LAKE TUESDAY...BEFORE ANOTHER LOW DEVELOPS ACROSS THE CENTRAL
PLAINS AND MOVES INTO THE MID-MISSISSIPPI VALLEY REGION THROUGH LATE
WEDNESDAY.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 240911
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
311 AM CST SAT JAN 24 2015

.SHORT TERM...
308 AM CST

TODAY THROUGH SUNDAY NIGHT...

THE MAIN FORECAST ISSUE WILL BE ACCUMULATING SNOW AND GUSTY WINDS
STARTING LATER TONIGHT CONTINUING THROUGH MUCH OF SUNDAY. WATER
VAPOR IMAGERY SHOWS A LONGWAVE TROUGH STRETCHING FROM HUDSON BAY
SOUTH TO THE GULF COAST WITH BROAD RIDGING OVER THE EASTERN
PACIFIC AND MUCH OF WESTERN CANADA AND THE NORTHWEST U.S. A WEAK
COOL FRONT IS CROSSING THE AREA BEHIND THE PASSAGE OF THE LONGWAVE
TROUGH AXIS. COOL ADVECTION THIS MORNING WILL GIVE WAY TO MODEST
WARM ADVECTION LATE THIS AFTERNOON. CLOUD COVER WILL BE THE WILD
CARD WITH TEMPS. STRATUS IS SPREADING SOUTHEAST ACROSS THE AREA
THIS MORNING BUT SATELLITE SHOWS GAPS IN COVERAGE UPSTREAM.
GUIDANCE IS MIXED WITH THE EXTENT OF CLOUD COVER BUT SUSPECT THERE
WILL BE BREAKS IN THE CLOUDS...ESPECIALLY THIS AFTERNOON...WITH
ANY MEANINGFUL SUNSHINE DURING THE EARLY/MID AFTERNOON HELPING
TEMPS SOMEWHAT. THIS IS MOST FAVORED SOUTH AND WEST SO WILL NUDGE
TEMPS UP SLIGHTLY THERE WHILE CARRYING UPPER 30S ACROSS THE REST
OF THE AREA.

THE MAIN FEATURE OF CONCERN IS A WAVE MOVING EAST-SOUTHEAST ACROSS
SOUTHERN ALBERTA. EVENING UPPER AIR ANALYSIS SHOWS A STRONG JET
PUSHING INTO THE PACIFIC NORTHWEST AND PIVOTING SOUTHEASTWARD AS
ADDITIONAL ENERGY PUSHES EASTWARD AMPLIFYING THE RIDGE. THE WAVE OF
CONCERN WILL DIG SOUTHEASTWARD ACROSS THE NORTHERN PLAINS TOWARD THE
MID MISSISSIPPI RIVER VALLEY AS A RESULT AND AMPLIFY AS IT DOES SO
INTO TONIGHT. THE SOUTH/WEST TREND OF THE TRACK OF THE SURFACE LOW
HAS CONTINUED AND DIFFERENCES REMAIN...ESPECIALLY WITH SOME OF THE
HIGH RES GUIDANCE WHICH TAKES THE LOW MUCH FURTHER SOUTH AND WEST
THAN SOME OF THE LOWER RES OPTIONS. IT APPEARS THAT THE LOW WILL NOT
TRACK NORTH OF ROUGHLY A BURLINGTON IOWA TO TERRE HAUTE INDIANA LINE
AT THIS POINT. WITH THE WAVE STILL TAKING SHAPE AND THE UPPER JET
STILL COMING ASHORE OVER THE PAC NORTHWEST FEEL THAT CONFIDENCE HAS
ROOM FOR IMPROVEMENT WITH THE MORNING UPPER AIR ANALYSIS AND
SUBSEQUENT 12Z GUIDANCE. THE MAIN QUESTION WILL BE PLACEMENT BUT
HAVE BETTER CONFIDENCE IN THE TREND OF WHAT OCCURS. PRECIP IS ON
TRACK TO QUICKLY SPREAD SOUTHEAST ACROSS THE AREA OVERNIGHT/AFTER
06Z/ AND SOUTHWEST AREAS STILL LOOK TO SEE A MIX OF RAIN OR SNOW AND
EVEN SOME SLEET THROUGH MID MORNING WHEN COLD AIR WILL TAKE OVER
CHANGING THINGS TO SNOW. PEAK PRECIP INTENSITY WILL BE AFTER
DAYBREAK INTO THE EARLY AFTERNOON. WINDS WILL TURN NORTHEAST AND
INCREASE DURING THE MORNING SETTING UP A DECENT FETCH DOWN LAKE
MICHIGAN. LAKE EFFECT PARAMETERS ARE SUB PAR BUT WHEN COMBINED WITH
SYNOPTIC SCALE ASCENT ARE PROBABLY SUFFICIENT TO PROVIDE SOME
MINIMAL ENHANCEMENT...MAINLY DUE TO INCREASED MOISTURE FLUX.
GUIDANCE VARIES WITH LIQUID OUTPUT WITH SOME RATHER HIGH AMOUNTS
NOTED PROBABLY SUGGESTIVE OF STRONG BANDING WHICH IS CERTAINLY
POSSIBLE. GIVEN PRECIPITABLE WATER VALUES OF AROUND 0.5 INCHES AND
FORCING OF 6 TO MAYBE 9 HOURS PEAK LIQUID AMOUNTS OF 0.3 TO 0.4
INCHES STILL SEEMS REASONABLE. LOCATION OF THESE AMOUNTS IS EXPECTED
ACROSS THE SOUTHERN CWA WITH AMOUNTS OF ONLY AROUND 0.1 INCHES
ACROSS THE NORTH. WITH SOUTHERN AREAS ALSO SEEING A MIX NOT ALL OF
THE LIQUID WILL GO TOWARD SNOW ACCUMULATION. THUS HIGHEST SNOW
AMOUNTS WILL OCCUR JUST TO THE NORTH...THOUGH WITH SOMEWHAT LOW
LIQUID EQUIVALENT. WILL DEPICT THE PEAK SNOWFALL FROM ROUGHLY
LASALLE COUNTY EAST-SOUTHEAST ALONG AND JUST SOUTH OF INTERSTATE 80
TO ROUGHLY KANKAKEE TO RENSSELAER. WILL CARRY 2-4 INCHES FOR THIS
AREA WITH AMOUNTS TAPERING TO ABOUT AN INCH ALONG THE WI
BORDER...WITH 1-2 INCHES ACROSS THE FAR NORTHERN CHICAGO METRO TO
AROUND 3 POSSIBLY 4 INCHES ACROSS THE FAR SOUTHERN CHICAGO METRO.
THERE IS STILL A CHANCE THIS COULD SHIFT FURTHER SOUTH.
PRECIPITATION QUICKLY ENDS MID TO LATE SUNDAY AFTERNOON WITH LITTLE
IF ANY LAKE EFFECT LINGERING GIVEN POOR INVERSION HEIGHTS.

HEADLINE POTENTIAL...WILL HOLD OFF ON ANY HEADLINES FOR NOW GIVEN
THAT A FURTHER SOUTH SHIFT IS STILL PLAUSIBLE. ANOTHER CONCERN IS
WIND SPEEDS WHICH WILL INCREASE TO 20 TO 25 MPH WITH GUSTS OF 30-35
MPH POSSIBLE SUNDAY MORNING THROUGH THE AFTERNOON. HOWEVER...WITH
FAIRLY WET SNOW RATIOS BLOWING WILL BE MINIMIZED BUT PROBABLY STILL
OCCUR. THERE IS ALSO A WINDOW FROM LATE MORNING THROUGH EARLY
AFTERNOON WHERE THE FALLING SNOW AND WIND MAY PUSH VISIBILITIES DOWN
UNDER A HALF OR QUARTER MILE...BUT THIS MAY OCCUR OVER A RATHER
SMALL AREA. EXPECT TO NEED A WINTER WEATHER ADVISORY ACROSS THE PEAK
SNOW AREA BUT AGAIN THE LOCATION MAY SHIFT AND IF BANDING DEVELOPS
THE SWATH OF SNOW COULD REALLY NARROW SO WOULD LIKE TO SEE THE
SYSTEM EVOLVE A LITTLE BIT MORE BEFORE DECIDING WHICH AREAS WILL SEE
THE BIGGEST IMPACT. WILL ISSUE A SPECIAL WEATHER STATEMENT
HIGHLIGHTING THE POTENTIAL IMPACTS FOR NOW.

MDB

&&

.LONG TERM...
308 AM CST

MONDAY THROUGH FRIDAY...

A MUCH BETTER DEFINED RIDGE WILL BE OVER WESTERN NORTH AMERICA
WITH A DEEP TROUGH OVER THE EAST COAST BY MONDAY. ANOTHER WAVE
WILL BE TRAVERSING THE RIDGE THEN DROP SOUTHEAST ACROSS THE GREAT
LAKES MONDAY BRINGING LOW CHANCES FOR SOME LIGHT SNOW. HIGH
PRESSURE WILL BUILD IN FROM THE WEST MONDAY NIGHT TURNING WINDS
MORE NORTHERLY. LAKE PARAMETERS WILL LIKELY BE MARGINAL BUT COULD
SEE SOME FLURRY OR LIGHT SNOW ACTIVITY DEVELOP FOR TUESDAY. THE
UPPER RIDGE BEGINS TO SHIFT EASTWARD WEDNESDAY WITH THE SURFACE
HIGH SHIFTING EAST AS WELL. THIS WILL LEAD TO A SHIFT TO SOUTHERLY
WINDS AND WARMING TEMPS LATE IN THE WEEK. GUIDANCE IS IN AGREEMENT
ON A LOW CROSSING THE AREA FIRST THING THURSDAY BRINGING MIXED
PRECIP POTENTIAL OR EVEN JUST RAIN. COLDER AIR BUILDS IN BEHIND
THE SYSTEM FRIDAY AS HIGH PRESSURE BUILDS INTO THE PLAINS. OVERALL
EXPECT TEMPS TO BE AT OR ABOVE NORMAL FROM TUESDAY ONWARD.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* MVFR CEILINGS HAVE MOVED IN FROM THE NORTHWEST AND WILL LINGER
  THROUGH THE MORNING.

* WESTERLY WINDS NEAR 10 KTS TODAY...DIMINISHING AND EVENTUALLY
  BECOMING EAST-NORTHEAST AFTER MIDNIGHT SATURDAY AND BECOMING
  GUSTY TOWARD MORNING.

* SNOW DEVELOPING TOWARD 12Z SUNDAY. IFR/LIFR CONDITIONS LIKELY
  IN SNOW JUST BEYOND END OF ORD 30 OUR TAF PERIOD.

RATZER

//DISCUSSION...UPDATED 06Z...

SURFACE LOW PRESSURE WAS MOVING EAST INTO EASTERN CANADA LATE THIS
EVENING...WITH A WEAKER TROUGH OF LOW PRESSURE TRAILING SOUTHWEST
INTO THE WESTERN GREAT LAKES REGION. THIS TROUGH WILL MOVE
SOUTHEAST ACROSS THE TERMINAL SITES EARLY THIS MORNING WITH A
SUBTLE WIND SHIFT FROM WEST-SOUTHWEST TO WEST-NORTHWEST...AS WELL
AS AN AREA OF MVFR STRATUS WHICH WILL SPREAD ACROSS THE AREA IN
THE 07-09Z TIME FRAME PER EXTRAPOLATION OF SATELLITE IMAGERY. SOME
LARGE BREAKS IN THE STRATUS BACK ACROSS WESTERN/NORTHWEST WISCONSIN
SUGGEST IT MAY TEND TO ALLOW SOME BREAKS TO VFR CONDITIONS BY
MIDDAY...THOUGH MODEL SOUNDINGS REMAIN FAIRLY MOIST IN THE LOWEST
FEW THOUSAND FEET NEAR THE GROUND.

OF GREATER CONFIDENCE IS THE APPROACH OF A DIGGING MID-LEVEL
DISTURBANCE TONIGHT...WITH ASSOCIATED DEEPENING SURFACE LOW
PRESSURE EXPECTED TO PASS SOUTHWEST OF TERMINALS EARLY SUNDAY
MORNING. MODELS HAVE BEEN FAIRLY CONSISTENT IN SATURATING THE
COLUMN DURING THE PRE-DAWN HOURS OF SUNDAY MORNING WITH SNOW
EXPECTED TO DEVELOP BY 12Z. IFR/LIFR CONDITIONS EXPECTED IN
SNOW SHORTLY THEREAFTER...JUST BEYOND END OF CURRENT TAF PERIODS.
IN ADDITION...DEEPENING OF THE SURFACE LOW TO THE SOUTHWEST OF THE
TERMINALS WILL RESULT IN WINDS SHIFTING TO THE EAST-NORTHEAST AND
INCREASING EARLY SUNDAY MORNING...LIKELY GUSTING 25-30 KT BY MID-
MORNING SUNDAY.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH IN WIND TRENDS...THOUGH MEDIUM-LOW IN DIRECTION SATURDAY
  EVENING AS SHIFT TO EAST-NORTHEAST OCCURS.

* LOW IN DISSIPATION OF MVFR TIMING LATER TODAY.

* MEDIUM-HIGH IN TIMING SNOW TO DEVELOP BEFORE SUNRISE SUNDAY.

RATZER

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...

SUNDAY...SNOW. IFR LIKELY PERIODIC LIFR POSSIBLE.

MONDAY...SLIGHT CHANCE OF -SN. MVFR PROBABLE W/CHANCE OF IFR.

TUESDAY THROUGH THURSDAY...PRIMARILY VFR. MAINLY DRY.

IZZI

&&

.MARINE...
238 AM CST

MAIN MARINE CONCERNS FOCUS ON THE PERIOD FROM EARLY SUNDAY MORNING
THROUGH SUNDAY EVENING...AS NORTH-NORTHEASTERLY WINDS QUICKLY
INCREASE IN RESPONSE TO A FAST-MOVING DEEPENING ALBERTA-CLIPPER LOW
WHICH WILL DIG SOUTHEAST FROM IOWA INTO CENTRAL ILLINOIS AND
SOUTHERN INDIANA DURING THE DAY.

IN THE VERY NEAR TERM THIS MORNING...LOW PRESSURE WAS MOVING EAST OF
JAMES BAY ACROSS QUEBEC...WITH A COLD FRONT TRAILING FROM THE LOW
ACROSS LAKE SUPERIOR AND WEST ALONG THE INTERNATIONAL BORDER. THIS
FRONT WILL SAG SOUTH ACROSS NORTHERN LAKE MICHIGAN LATER TODAY WITH
WINDS SHIFTING NORTH AND INCREASING BEHIND IT AS HIGH PRESSURE
SPREADS SOUTHEAST ACROSS MANITOBA AND NORTHWEST QUEBEC. BY
TONIGHT...THE FAST-MOVING CLIPPER WILL ALSO ALREADY BE ENTERING
IOWA  AND MOVING INTO WEST-CENTRAL ILLINOIS BY SUNDAY MORNING WHILE
DEEPENING A BIT. THE TIGHTENING GRADIENT AROUND THE LOW WILL ALSO
HELP TO TURN WINDS NORTHEAST AND STRENGTHEN THEM ALL THE WAY TO THE
SOUTH END OF THE LAKE AS THE LOW EVENTUALLY TRACKS INTO THE OHIO
VALLEY IN THE AFTERNOON. MODEL FORECAST SOUNDINGS DEPICT A PERIOD OF
SOLID 30 KT NORTHEAST WINDS ACROSS THE SOUTH 2/3 OR 3/4 OF THE LAKE
SUNDAY...WITH A FEW GUSTS OVER 30 KTS (MARGINAL GALE FORCE) DURING
THE DAY. WITH THE LOW MOVING QUICKLY OFF TO THE SOUTHEAST SUNDAY
NIGHT...WINDS WILL DIMINISH AS QUICKLY AS THEY INCREASED EARLY IN
THE DAY...AS WEAK HIGH PRESSURE RIDGING MOVES ACROSS THE LAKE SUNDAY
NIGHT. WILL NEED A SMALL CRAFT ADVISORY FOR THE IL/NW IND NEARSHORE
WATERS FROM ABOUT 6 AM CST SUNDAY THROUGH ABOUT 6 AM CST MONDAY FOR
THE STRONG WINDS AND RESULTING WAVES.

EARLY NEXT WEEK THE PATTERN CONTINUES TO APPEAR RATHER
PROGRESSIVE...WITH THE WEEK HIGH PRESSURE RIDGE OVER THE LAKE SUNDAY
NIGHT QUICKLY BEING DISPLACED MONDAY BY ANOTHER LOW PRESSURE SYSTEM
WHICH MOVES INTO THE NORTHERN LAKES MONDAY AFTERNOON. THIS BRINGS
WINDS AROUND TO THE SOUTH AND INCREASING INTO THE 25 KT RANGE FOR A
TIME MONDAY AS THE LOW APPROACHES. THE LOW THEN WEAKENS AS IT MOVES
SOUTHEAST ACROSS THE LAKES MONDAY NIGHT...FILLING AS A DEEP LOW
DEVELOPS ALONG THE ATLANTIC COAST. WEAK HIGH PRESSURE SPREADS ACROSS
THE LAKE TUESDAY...BEFORE ANOTHER LOW DEVELOPS ACROSS THE CENTRAL
PLAINS AND MOVES INTO THE MID-MISSISSIPPI VALLEY REGION THROUGH LATE
WEDNESDAY.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 240838
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
238 AM CST SAT JAN 24 2015

.SHORT TERM...

TONIGHT AND SATURDAY...

305 PM...NO CONCERNS THROUGH SATURDAY EVENING. LOW CLOUDS CONTINUE
TO ERODE FROM THE NORTH AND THE SOUTHWEST THIS AFTERNOON. THIS
TREND WILL CONTINUE THIS EVENING AS THE BACK EDGE PUSHES EAST.
HOWEVER...AN EXTENSIVE BAND OF MID CLOUDS WILL SPREAD BACK ACROSS
THE AREA THIS EVENING AHEAD OF AN APPROACHING COLD FRONT. VERY
LIMITED MOISTURE WITH THIS FRONT AND NOT EXPECTING ANY PRECIP
THOUGH A SPRINKLE OR FLURRY CAN/T BE COMPLETED RULED OUT...BUT NO
MENTION IN THE FORECAST. CLOUD COVER HELPED HOLD HIGHS TODAY IN
THE LOWER/MID 30S AND WITH SOME PARTIAL CLEARING AT TIMES...EXPECT
LOWS TONIGHT TO DIP INTO THE MID/UPPER 20S...THOUGH SOME
UNCERTAINTY WITH APPROACHING MID CLOUDS AND THEN ANOTHER AREA OF
LOW CLOUDS OVER THE UPPER MIDWEST WHICH WILL BE SPREADING SOUTH
ACROSS THE AREA SATURDAY MORNING. IF THIS CLOUD COVER DOES BECOME
OVERCAST...HIGHS ON SATURDAY WILL LIKELY BE TEMPERED SOME AS
WELL...PERHAPS ONLY IN THE MID 30S. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH FRIDAY...

305 PM...MAIN FORECAST CONCERN IS ACCUMULATING SNOW LATE SATURDAY
NIGHT THROUGH SUNDAY AFTERNOON...WITH POSSIBLE LAKE EFFECT SNOW
SHOWERS SUNDAY NIGHT AND ANOTHER WEAKER CLIPPER SYSTEM MONDAY
NIGHT...FOLLOWED BY MODERATE/MILD TEMPS MIDDLE OF NEXT WEEK.

DECENT AGREEMENT WITH THE TRACK OF THE SURFACE LOW OF THE NEXT
CLIPPER SYSTEM SATURDAY NIGHT INTO SUNDAY WITH THE 12Z GFS A BIT
FURTHER SOUTHWEST OF THE REST OF THE MODELS...WHICH TRACK THE LOW
FROM ROUGHLY MLI TO IND SUNDAY MORNING. THERMAL PROFILES SUGGEST
PRECIP TYPE WILL BE ALL SNOW...BUT INITIALLY COULD BE SOME RAIN
MIXED IN ACROSS THE SOUTHERN CWA. IN ADDITION...SNOW/WATER RATIOS
COULD BE RATHER LOW TO START...YIELDING A WETTER SNOW. BUT AS THE
LOW TRACKS TO THE SOUTHEAST...COLDER AIR WILL SLOWLY SPREAD ACROSS
THE AREA WITH THE SNOW LIKELY BECOMING DRIER BY LATE MORNING AND
INTO THE AFTERNOON. THIS MAKES SNOWFALL AMOUNTS A BIT TRICKY...
ESPECIALLY IF THE TRACK OF THE LOW ENDS UP A LITTLE FURTHER SOUTH
AS THE GFS SUGGESTS...COLDER AIR WOULD ARRIVE SOONER. POSSIBLE
LAKE ENHANCEMENT WITH NORTHEAST FLOW ALSO ADDS TO THE UNCERTAINTY
REGARDING AMOUNTS. THEREFORE...DIDN/T MAKE ANY SIGNIFICANT
CHANGES TO THE GOING FORECAST WITH 2-4 INCHES NORTH OF A SQI/IKK
LINE...1-2 INCHES SOUTH OF THAT LINE. BUT AS IS ALWAYS THE
CASE...MINOR CHANGES IN THE TRACK COULD CAUSE LARGE CHANGES TO THE
FORECAST AS TRENDS EMERGE.

TEMPERATURES BEGIN TO FALL BY MID/LATE SUNDAY AFTERNOON ACROSS THE
NORTH. NORTHEASTERLY WINDS INCREASE WITH GUSTS TO 30 MPH AND
DEPENDING ON HOW DRY THE SNOW BECOMES...THERE COULD BE SOME
BLOWING SNOW BUT AGAIN...ITS TOO EARLY FOR SPECIFICS OR HOW MUCH
OF A PROBLEM THIS COULD BECOME.

THE NORTHEAST AND THEN NORTHERLY WINDS MAY ALLOW SOME LAKE EFFECT
SNOW SHOWERS TO DEVELOP SUNDAY EVENING ACROSS NORTHEAST IL AND
THEN INTO NORTHWEST INDIANA. BUT INVERSION HEIGHTS ARE RATHER
LOW...PERHAPS NO HIGHER THAN 4KFT AND WINDS BEGIN TO TURN BACK
EASTERLY BY MONDAY MORNING. THUS ANY LAKE EFFECT POTENTIAL LOOKS
MINIMAL.

ANOTHER CLIPPER QUICKLY DROPS SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT...AS IT BEGINS TO WEAKEN. A
BAND OF LIGHT SNOW IS POSSIBLE WITH THIS FEATURE ESPECIALLY MONDAY
EVENING AND SOME AREAS MAY SEE AN INCH OR TWO DEPENDING ON WHERE
IT TRACKS. HAVE INCLUDED JUST LIGHT QPF AMOUNTS FOR NOW.

HIGH PRESSURE MOVES ACROSS THE AREA TUESDAY AND TUESDAY NIGHT AS
FLOW TURNS BACK SOUTH WEDNESDAY AND TEMPS MODIFY BACK INTO THE 30S
THOUGH WITH AN EXPECTED SNOW PACK BY THEN...LOW CONFIDENCE ON HOW
WARM TEMPS WILL BECOME. ANOTHER CLIPPER SYSTEM MOVES ACROSS THE
LAKES REGION WEDNESDAY NIGHT AND THURSDAY...WITH A CHANCE OF LIGHT
RAIN OR LIGHT SNOW WEDNESDAY NIGHT INTO THURSDAY MORNING. CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* MVFR CEILINGS MOVING IN FROM THE NORTHWEST AROUND 08Z AND
  LINGERING THROUGH SATURDAY MORNING.

* WESTERLY WINDS NEAR 10 KTS TODAY...DIMINISHING AND EVENTUALLY
  BECOMING EAST-NORTHEAST AFTER MIDNIGHT SATURDAY AND BECOMING
  GUSTY TOWARD MORNING.

* SNOW DEVELOPING TOWARD 12Z SUNDAY. IFR/LIFR CONDITIONS LIKELY
  IN SNOW JUST BEYOND END OF ORD 30 OUR TAF PERIOD.

RATZER

//DISCUSSION...UPDATED 06Z...

SURFACE LOW PRESSURE WAS MOVING EAST INTO EASTERN CANADA LATE THIS
EVENING...WITH A WEAKER TROUGH OF LOW PRESSURE TRAILING SOUTHWEST
INTO THE WESTERN GREAT LAKES REGION. THIS TROUGH WILL MOVE
SOUTHEAST ACROSS THE TERMINAL SITES EARLY THIS MORNING WITH A
SUBTLE WIND SHIFT FROM WEST-SOUTHWEST TO WEST-NORTHWEST...AS WELL
AS AN AREA OF MVFR STRATUS WHICH WILL SPREAD ACROSS THE AREA IN
THE 07-09Z TIME FRAME PER EXTRAPOLATION OF SATELLITE IMAGERY. SOME
LARGE BREAKS IN THE STRATUS BACK ACROSS WESTERN/NORTHWEST WISCONSIN
SUGGEST IT MAY TEND TO ALLOW SOME BREAKS TO VFR CONDITIONS BY
MIDDAY...THOUGH MODEL SOUNDINGS REMAIN FAIRLY MOIST IN THE LOWEST
FEW THOUSAND FEET NEAR THE GROUND.

OF GREATER CONFIDENCE IS THE APPROACH OF A DIGGING MID-LEVEL
DISTURBANCE TONIGHT...WITH ASSOCIATED DEEPENING SURFACE LOW
PRESSURE EXPECTED TO PASS SOUTHWEST OF TERMINALS EARLY SUNDAY
MORNING. MODELS HAVE BEEN FAIRLY CONSISTENT IN SATURATING THE
COLUMN DURING THE PRE-DAWN HOURS OF SUNDAY MORNING WITH SNOW
EXPECTED TO DEVELOP BY 12Z. IFR/LIFR CONDITIONS EXPECTED IN
SNOW SHORTLY THEREAFTER...JUST BEYOND END OF CURRENT TAF PERIODS.
IN ADDITION...DEEPENING OF THE SURFACE LOW TO THE SOUTHWEST OF THE
TERMINALS WILL RESULT IN WINDS SHIFTING TO THE EAST-NORTHEAST AND
INCREASING EARLY SUNDAY MORNING...LIKELY GUSTING 25-30 KT BY MID-
MORNING SUNDAY.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND TRENDS...THOUGH MEDIUM-LOW IN DIRECTION SATURDAY
  EVENING AS SHIFT TO EAST-NORTHEAST OCCURS.

* MEDIUM-HIGH IN TIMING OF MVFR DECK EARLY THIS MORNING. LOW IN
  DISSIPATION TIMING LATER TODAY.

* MEDIUM-HIGH IN TIMING SNOW TO DEVELOP BEFORE SUNRISE SUNDAY.

RATZER

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...

SUNDAY...SNOW. IFR LIKELY PERIODIC LIFR POSSIBLE.

MONDAY...SLIGHT CHANCE OF -SN. MVFR PROBABLE W/CHANCE OF IFR.

TUESDAY THROUGH THURSDAY...PRIMARILY VFR. MAINLY DRY.

IZZI

&&

.MARINE...
238 AM CST

MAIN MARINE CONCERNS FOCUS ON THE PERIOD FROM EARLY SUNDAY MORNING
THROUGH SUNDAY EVENING...AS NORTH-NORTHEASTERLY WINDS QUICKLY
INCREASE IN RESPONSE TO A FAST-MOVING DEEPENING ALBERTA-CLIPPER LOW
WHICH WILL DIG SOUTHEAST FROM IOWA INTO CENTRAL ILLINOIS AND
SOUTHERN INDIANA DURING THE DAY.

IN THE VERY NEAR TERM THIS MORNING...LOW PRESSURE WAS MOVING EAST OF
JAMES BAY ACROSS QUEBEC...WITH A COLD FRONT TRAILING FROM THE LOW
ACROSS LAKE SUPERIOR AND WEST ALONG THE INTERNATIONAL BORDER. THIS
FRONT WILL SAG SOUTH ACROSS NORTHERN LAKE MICHIGAN LATER TODAY WITH
WINDS SHIFTING NORTH AND INCREASING BEHIND IT AS HIGH PRESSURE
SPREADS SOUTHEAST ACROSS MANITOBA AND NORTHWEST QUEBEC. BY
TONIGHT...THE FAST-MOVING CLIPPER WILL ALSO ALREADY BE ENTERING
IOWA  AND MOVING INTO WEST-CENTRAL ILLINOIS BY SUNDAY MORNING WHILE
DEEPENING A BIT. THE TIGHTENING GRADIENT AROUND THE LOW WILL ALSO
HELP TO TURN WINDS NORTHEAST AND STRENGTHEN THEM ALL THE WAY TO THE
SOUTH END OF THE LAKE AS THE LOW EVENTUALLY TRACKS INTO THE OHIO
VALLEY IN THE AFTERNOON. MODEL FORECAST SOUNDINGS DEPICT A PERIOD OF
SOLID 30 KT NORTHEAST WINDS ACROSS THE SOUTH 2/3 OR 3/4 OF THE LAKE
SUNDAY...WITH A FEW GUSTS OVER 30 KTS (MARGINAL GALE FORCE) DURING
THE DAY. WITH THE LOW MOVING QUICKLY OFF TO THE SOUTHEAST SUNDAY
NIGHT...WINDS WILL DIMINISH AS QUICKLY AS THEY INCREASED EARLY IN
THE DAY...AS WEAK HIGH PRESSURE RIDGING MOVES ACROSS THE LAKE SUNDAY
NIGHT. WILL NEED A SMALL CRAFT ADVISORY FOR THE IL/NW IND NEARSHORE
WATERS FROM ABOUT 6 AM CST SUNDAY THROUGH ABOUT 6 AM CST MONDAY FOR
THE STRONG WINDS AND RESULTING WAVES.

EARLY NEXT WEEK THE PATTERN CONTINUES TO APPEAR RATHER
PROGRESSIVE...WITH THE WEEK HIGH PRESSURE RIDGE OVER THE LAKE SUNDAY
NIGHT QUICKLY BEING DISPLACED MONDAY BY ANOTHER LOW PRESSURE SYSTEM
WHICH MOVES INTO THE NORTHERN LAKES MONDAY AFTERNOON. THIS BRINGS
WINDS AROUND TO THE SOUTH AND INCREASING INTO THE 25 KT RANGE FOR A
TIME MONDAY AS THE LOW APPROACHES. THE LOW THEN WEAKENS AS IT MOVES
SOUTHEAST ACROSS THE LAKES MONDAY NIGHT...FILLING AS A DEEP LOW
DEVELOPS ALONG THE ATLANTIC COAST. WEAK HIGH PRESSURE SPREADS ACROSS
THE LAKE TUESDAY...BEFORE ANOTHER LOW DEVELOPS ACROSS THE CENTRAL
PLAINS AND MOVES INTO THE MID-MISSISSIPPI VALLEY REGION THROUGH LATE
WEDNESDAY.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 240838
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
238 AM CST SAT JAN 24 2015

.SHORT TERM...

TONIGHT AND SATURDAY...

305 PM...NO CONCERNS THROUGH SATURDAY EVENING. LOW CLOUDS CONTINUE
TO ERODE FROM THE NORTH AND THE SOUTHWEST THIS AFTERNOON. THIS
TREND WILL CONTINUE THIS EVENING AS THE BACK EDGE PUSHES EAST.
HOWEVER...AN EXTENSIVE BAND OF MID CLOUDS WILL SPREAD BACK ACROSS
THE AREA THIS EVENING AHEAD OF AN APPROACHING COLD FRONT. VERY
LIMITED MOISTURE WITH THIS FRONT AND NOT EXPECTING ANY PRECIP
THOUGH A SPRINKLE OR FLURRY CAN/T BE COMPLETED RULED OUT...BUT NO
MENTION IN THE FORECAST. CLOUD COVER HELPED HOLD HIGHS TODAY IN
THE LOWER/MID 30S AND WITH SOME PARTIAL CLEARING AT TIMES...EXPECT
LOWS TONIGHT TO DIP INTO THE MID/UPPER 20S...THOUGH SOME
UNCERTAINTY WITH APPROACHING MID CLOUDS AND THEN ANOTHER AREA OF
LOW CLOUDS OVER THE UPPER MIDWEST WHICH WILL BE SPREADING SOUTH
ACROSS THE AREA SATURDAY MORNING. IF THIS CLOUD COVER DOES BECOME
OVERCAST...HIGHS ON SATURDAY WILL LIKELY BE TEMPERED SOME AS
WELL...PERHAPS ONLY IN THE MID 30S. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH FRIDAY...

305 PM...MAIN FORECAST CONCERN IS ACCUMULATING SNOW LATE SATURDAY
NIGHT THROUGH SUNDAY AFTERNOON...WITH POSSIBLE LAKE EFFECT SNOW
SHOWERS SUNDAY NIGHT AND ANOTHER WEAKER CLIPPER SYSTEM MONDAY
NIGHT...FOLLOWED BY MODERATE/MILD TEMPS MIDDLE OF NEXT WEEK.

DECENT AGREEMENT WITH THE TRACK OF THE SURFACE LOW OF THE NEXT
CLIPPER SYSTEM SATURDAY NIGHT INTO SUNDAY WITH THE 12Z GFS A BIT
FURTHER SOUTHWEST OF THE REST OF THE MODELS...WHICH TRACK THE LOW
FROM ROUGHLY MLI TO IND SUNDAY MORNING. THERMAL PROFILES SUGGEST
PRECIP TYPE WILL BE ALL SNOW...BUT INITIALLY COULD BE SOME RAIN
MIXED IN ACROSS THE SOUTHERN CWA. IN ADDITION...SNOW/WATER RATIOS
COULD BE RATHER LOW TO START...YIELDING A WETTER SNOW. BUT AS THE
LOW TRACKS TO THE SOUTHEAST...COLDER AIR WILL SLOWLY SPREAD ACROSS
THE AREA WITH THE SNOW LIKELY BECOMING DRIER BY LATE MORNING AND
INTO THE AFTERNOON. THIS MAKES SNOWFALL AMOUNTS A BIT TRICKY...
ESPECIALLY IF THE TRACK OF THE LOW ENDS UP A LITTLE FURTHER SOUTH
AS THE GFS SUGGESTS...COLDER AIR WOULD ARRIVE SOONER. POSSIBLE
LAKE ENHANCEMENT WITH NORTHEAST FLOW ALSO ADDS TO THE UNCERTAINTY
REGARDING AMOUNTS. THEREFORE...DIDN/T MAKE ANY SIGNIFICANT
CHANGES TO THE GOING FORECAST WITH 2-4 INCHES NORTH OF A SQI/IKK
LINE...1-2 INCHES SOUTH OF THAT LINE. BUT AS IS ALWAYS THE
CASE...MINOR CHANGES IN THE TRACK COULD CAUSE LARGE CHANGES TO THE
FORECAST AS TRENDS EMERGE.

TEMPERATURES BEGIN TO FALL BY MID/LATE SUNDAY AFTERNOON ACROSS THE
NORTH. NORTHEASTERLY WINDS INCREASE WITH GUSTS TO 30 MPH AND
DEPENDING ON HOW DRY THE SNOW BECOMES...THERE COULD BE SOME
BLOWING SNOW BUT AGAIN...ITS TOO EARLY FOR SPECIFICS OR HOW MUCH
OF A PROBLEM THIS COULD BECOME.

THE NORTHEAST AND THEN NORTHERLY WINDS MAY ALLOW SOME LAKE EFFECT
SNOW SHOWERS TO DEVELOP SUNDAY EVENING ACROSS NORTHEAST IL AND
THEN INTO NORTHWEST INDIANA. BUT INVERSION HEIGHTS ARE RATHER
LOW...PERHAPS NO HIGHER THAN 4KFT AND WINDS BEGIN TO TURN BACK
EASTERLY BY MONDAY MORNING. THUS ANY LAKE EFFECT POTENTIAL LOOKS
MINIMAL.

ANOTHER CLIPPER QUICKLY DROPS SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT...AS IT BEGINS TO WEAKEN. A
BAND OF LIGHT SNOW IS POSSIBLE WITH THIS FEATURE ESPECIALLY MONDAY
EVENING AND SOME AREAS MAY SEE AN INCH OR TWO DEPENDING ON WHERE
IT TRACKS. HAVE INCLUDED JUST LIGHT QPF AMOUNTS FOR NOW.

HIGH PRESSURE MOVES ACROSS THE AREA TUESDAY AND TUESDAY NIGHT AS
FLOW TURNS BACK SOUTH WEDNESDAY AND TEMPS MODIFY BACK INTO THE 30S
THOUGH WITH AN EXPECTED SNOW PACK BY THEN...LOW CONFIDENCE ON HOW
WARM TEMPS WILL BECOME. ANOTHER CLIPPER SYSTEM MOVES ACROSS THE
LAKES REGION WEDNESDAY NIGHT AND THURSDAY...WITH A CHANCE OF LIGHT
RAIN OR LIGHT SNOW WEDNESDAY NIGHT INTO THURSDAY MORNING. CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* MVFR CEILINGS MOVING IN FROM THE NORTHWEST AROUND 08Z AND
  LINGERING THROUGH SATURDAY MORNING.

* WESTERLY WINDS NEAR 10 KTS TODAY...DIMINISHING AND EVENTUALLY
  BECOMING EAST-NORTHEAST AFTER MIDNIGHT SATURDAY AND BECOMING
  GUSTY TOWARD MORNING.

* SNOW DEVELOPING TOWARD 12Z SUNDAY. IFR/LIFR CONDITIONS LIKELY
  IN SNOW JUST BEYOND END OF ORD 30 OUR TAF PERIOD.

RATZER

//DISCUSSION...UPDATED 06Z...

SURFACE LOW PRESSURE WAS MOVING EAST INTO EASTERN CANADA LATE THIS
EVENING...WITH A WEAKER TROUGH OF LOW PRESSURE TRAILING SOUTHWEST
INTO THE WESTERN GREAT LAKES REGION. THIS TROUGH WILL MOVE
SOUTHEAST ACROSS THE TERMINAL SITES EARLY THIS MORNING WITH A
SUBTLE WIND SHIFT FROM WEST-SOUTHWEST TO WEST-NORTHWEST...AS WELL
AS AN AREA OF MVFR STRATUS WHICH WILL SPREAD ACROSS THE AREA IN
THE 07-09Z TIME FRAME PER EXTRAPOLATION OF SATELLITE IMAGERY. SOME
LARGE BREAKS IN THE STRATUS BACK ACROSS WESTERN/NORTHWEST WISCONSIN
SUGGEST IT MAY TEND TO ALLOW SOME BREAKS TO VFR CONDITIONS BY
MIDDAY...THOUGH MODEL SOUNDINGS REMAIN FAIRLY MOIST IN THE LOWEST
FEW THOUSAND FEET NEAR THE GROUND.

OF GREATER CONFIDENCE IS THE APPROACH OF A DIGGING MID-LEVEL
DISTURBANCE TONIGHT...WITH ASSOCIATED DEEPENING SURFACE LOW
PRESSURE EXPECTED TO PASS SOUTHWEST OF TERMINALS EARLY SUNDAY
MORNING. MODELS HAVE BEEN FAIRLY CONSISTENT IN SATURATING THE
COLUMN DURING THE PRE-DAWN HOURS OF SUNDAY MORNING WITH SNOW
EXPECTED TO DEVELOP BY 12Z. IFR/LIFR CONDITIONS EXPECTED IN
SNOW SHORTLY THEREAFTER...JUST BEYOND END OF CURRENT TAF PERIODS.
IN ADDITION...DEEPENING OF THE SURFACE LOW TO THE SOUTHWEST OF THE
TERMINALS WILL RESULT IN WINDS SHIFTING TO THE EAST-NORTHEAST AND
INCREASING EARLY SUNDAY MORNING...LIKELY GUSTING 25-30 KT BY MID-
MORNING SUNDAY.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND TRENDS...THOUGH MEDIUM-LOW IN DIRECTION SATURDAY
  EVENING AS SHIFT TO EAST-NORTHEAST OCCURS.

* MEDIUM-HIGH IN TIMING OF MVFR DECK EARLY THIS MORNING. LOW IN
  DISSIPATION TIMING LATER TODAY.

* MEDIUM-HIGH IN TIMING SNOW TO DEVELOP BEFORE SUNRISE SUNDAY.

RATZER

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...

SUNDAY...SNOW. IFR LIKELY PERIODIC LIFR POSSIBLE.

MONDAY...SLIGHT CHANCE OF -SN. MVFR PROBABLE W/CHANCE OF IFR.

TUESDAY THROUGH THURSDAY...PRIMARILY VFR. MAINLY DRY.

IZZI

&&

.MARINE...
238 AM CST

MAIN MARINE CONCERNS FOCUS ON THE PERIOD FROM EARLY SUNDAY MORNING
THROUGH SUNDAY EVENING...AS NORTH-NORTHEASTERLY WINDS QUICKLY
INCREASE IN RESPONSE TO A FAST-MOVING DEEPENING ALBERTA-CLIPPER LOW
WHICH WILL DIG SOUTHEAST FROM IOWA INTO CENTRAL ILLINOIS AND
SOUTHERN INDIANA DURING THE DAY.

IN THE VERY NEAR TERM THIS MORNING...LOW PRESSURE WAS MOVING EAST OF
JAMES BAY ACROSS QUEBEC...WITH A COLD FRONT TRAILING FROM THE LOW
ACROSS LAKE SUPERIOR AND WEST ALONG THE INTERNATIONAL BORDER. THIS
FRONT WILL SAG SOUTH ACROSS NORTHERN LAKE MICHIGAN LATER TODAY WITH
WINDS SHIFTING NORTH AND INCREASING BEHIND IT AS HIGH PRESSURE
SPREADS SOUTHEAST ACROSS MANITOBA AND NORTHWEST QUEBEC. BY
TONIGHT...THE FAST-MOVING CLIPPER WILL ALSO ALREADY BE ENTERING
IOWA  AND MOVING INTO WEST-CENTRAL ILLINOIS BY SUNDAY MORNING WHILE
DEEPENING A BIT. THE TIGHTENING GRADIENT AROUND THE LOW WILL ALSO
HELP TO TURN WINDS NORTHEAST AND STRENGTHEN THEM ALL THE WAY TO THE
SOUTH END OF THE LAKE AS THE LOW EVENTUALLY TRACKS INTO THE OHIO
VALLEY IN THE AFTERNOON. MODEL FORECAST SOUNDINGS DEPICT A PERIOD OF
SOLID 30 KT NORTHEAST WINDS ACROSS THE SOUTH 2/3 OR 3/4 OF THE LAKE
SUNDAY...WITH A FEW GUSTS OVER 30 KTS (MARGINAL GALE FORCE) DURING
THE DAY. WITH THE LOW MOVING QUICKLY OFF TO THE SOUTHEAST SUNDAY
NIGHT...WINDS WILL DIMINISH AS QUICKLY AS THEY INCREASED EARLY IN
THE DAY...AS WEAK HIGH PRESSURE RIDGING MOVES ACROSS THE LAKE SUNDAY
NIGHT. WILL NEED A SMALL CRAFT ADVISORY FOR THE IL/NW IND NEARSHORE
WATERS FROM ABOUT 6 AM CST SUNDAY THROUGH ABOUT 6 AM CST MONDAY FOR
THE STRONG WINDS AND RESULTING WAVES.

EARLY NEXT WEEK THE PATTERN CONTINUES TO APPEAR RATHER
PROGRESSIVE...WITH THE WEEK HIGH PRESSURE RIDGE OVER THE LAKE SUNDAY
NIGHT QUICKLY BEING DISPLACED MONDAY BY ANOTHER LOW PRESSURE SYSTEM
WHICH MOVES INTO THE NORTHERN LAKES MONDAY AFTERNOON. THIS BRINGS
WINDS AROUND TO THE SOUTH AND INCREASING INTO THE 25 KT RANGE FOR A
TIME MONDAY AS THE LOW APPROACHES. THE LOW THEN WEAKENS AS IT MOVES
SOUTHEAST ACROSS THE LAKES MONDAY NIGHT...FILLING AS A DEEP LOW
DEVELOPS ALONG THE ATLANTIC COAST. WEAK HIGH PRESSURE SPREADS ACROSS
THE LAKE TUESDAY...BEFORE ANOTHER LOW DEVELOPS ACROSS THE CENTRAL
PLAINS AND MOVES INTO THE MID-MISSISSIPPI VALLEY REGION THROUGH LATE
WEDNESDAY.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...6 AM SUNDAY TO 9 AM MONDAY.

&&

$$

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000
FXUS63 KLOT 240549
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1149 PM CST FRI JAN 23 2015

.SHORT TERM...

TONIGHT AND SATURDAY...

305 PM...NO CONCERNS THROUGH SATURDAY EVENING. LOW CLOUDS CONTINUE
TO ERODE FROM THE NORTH AND THE SOUTHWEST THIS AFTERNOON. THIS
TREND WILL CONTINUE THIS EVENING AS THE BACK EDGE PUSHES EAST.
HOWEVER...AN EXTENSIVE BAND OF MID CLOUDS WILL SPREAD BACK ACROSS
THE AREA THIS EVENING AHEAD OF AN APPROACHING COLD FRONT. VERY
LIMITED MOISTURE WITH THIS FRONT AND NOT EXPECTING ANY PRECIP
THOUGH A SPRINKLE OR FLURRY CAN/T BE COMPLETED RULED OUT...BUT NO
MENTION IN THE FORECAST. CLOUD COVER HELPED HOLD HIGHS TODAY IN
THE LOWER/MID 30S AND WITH SOME PARTIAL CLEARING AT TIMES...EXPECT
LOWS TONIGHT TO DIP INTO THE MID/UPPER 20S...THOUGH SOME
UNCERTAINTY WITH APPROACHING MID CLOUDS AND THEN ANOTHER AREA OF
LOW CLOUDS OVER THE UPPER MIDWEST WHICH WILL BE SPREADING SOUTH
ACROSS THE AREA SATURDAY MORNING. IF THIS CLOUD COVER DOES BECOME
OVERCAST...HIGHS ON SATURDAY WILL LIKELY BE TEMPERED SOME AS
WELL...PERHAPS ONLY IN THE MID 30S. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH FRIDAY...

305 PM...MAIN FORECAST CONCERN IS ACCUMULATING SNOW LATE SATURDAY
NIGHT THROUGH SUNDAY AFTERNOON...WITH POSSIBLE LAKE EFFECT SNOW
SHOWERS SUNDAY NIGHT AND ANOTHER WEAKER CLIPPER SYSTEM MONDAY
NIGHT...FOLLOWED BY MODERATE/MILD TEMPS MIDDLE OF NEXT WEEK.

DECENT AGREEMENT WITH THE TRACK OF THE SURFACE LOW OF THE NEXT
CLIPPER SYSTEM SATURDAY NIGHT INTO SUNDAY WITH THE 12Z GFS A BIT
FURTHER SOUTHWEST OF THE REST OF THE MODELS...WHICH TRACK THE LOW
FROM ROUGHLY MLI TO IND SUNDAY MORNING. THERMAL PROFILES SUGGEST
PRECIP TYPE WILL BE ALL SNOW...BUT INITIALLY COULD BE SOME RAIN
MIXED IN ACROSS THE SOUTHERN CWA. IN ADDITION...SNOW/WATER RATIOS
COULD BE RATHER LOW TO START...YIELDING A WETTER SNOW. BUT AS THE
LOW TRACKS TO THE SOUTHEAST...COLDER AIR WILL SLOWLY SPREAD ACROSS
THE AREA WITH THE SNOW LIKELY BECOMING DRIER BY LATE MORNING AND
INTO THE AFTERNOON. THIS MAKES SNOWFALL AMOUNTS A BIT TRICKY...
ESPECIALLY IF THE TRACK OF THE LOW ENDS UP A LITTLE FURTHER SOUTH
AS THE GFS SUGGESTS...COLDER AIR WOULD ARRIVE SOONER. POSSIBLE
LAKE ENHANCEMENT WITH NORTHEAST FLOW ALSO ADDS TO THE UNCERTAINTY
REGARDING AMOUNTS. THEREFORE...DIDN/T MAKE ANY SIGNIFICANT
CHANGES TO THE GOING FORECAST WITH 2-4 INCHES NORTH OF A SQI/IKK
LINE...1-2 INCHES SOUTH OF THAT LINE. BUT AS IS ALWAYS THE
CASE...MINOR CHANGES IN THE TRACK COULD CAUSE LARGE CHANGES TO THE
FORECAST AS TRENDS EMERGE.

TEMPERATURES BEGIN TO FALL BY MID/LATE SUNDAY AFTERNOON ACROSS THE
NORTH. NORTHEASTERLY WINDS INCREASE WITH GUSTS TO 30 MPH AND
DEPENDING ON HOW DRY THE SNOW BECOMES...THERE COULD BE SOME
BLOWING SNOW BUT AGAIN...ITS TOO EARLY FOR SPECIFICS OR HOW MUCH
OF A PROBLEM THIS COULD BECOME.

THE NORTHEAST AND THEN NORTHERLY WINDS MAY ALLOW SOME LAKE EFFECT
SNOW SHOWERS TO DEVELOP SUNDAY EVENING ACROSS NORTHEAST IL AND
THEN INTO NORTHWEST INDIANA. BUT INVERSION HEIGHTS ARE RATHER
LOW...PERHAPS NO HIGHER THAN 4KFT AND WINDS BEGIN TO TURN BACK
EASTERLY BY MONDAY MORNING. THUS ANY LAKE EFFECT POTENTIAL LOOKS
MINIMAL.

ANOTHER CLIPPER QUICKLY DROPS SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT...AS IT BEGINS TO WEAKEN. A
BAND OF LIGHT SNOW IS POSSIBLE WITH THIS FEATURE ESPECIALLY MONDAY
EVENING AND SOME AREAS MAY SEE AN INCH OR TWO DEPENDING ON WHERE
IT TRACKS. HAVE INCLUDED JUST LIGHT QPF AMOUNTS FOR NOW.

HIGH PRESSURE MOVES ACROSS THE AREA TUESDAY AND TUESDAY NIGHT AS
FLOW TURNS BACK SOUTH WEDNESDAY AND TEMPS MODIFY BACK INTO THE 30S
THOUGH WITH AN EXPECTED SNOW PACK BY THEN...LOW CONFIDENCE ON HOW
WARM TEMPS WILL BECOME. ANOTHER CLIPPER SYSTEM MOVES ACROSS THE
LAKES REGION WEDNESDAY NIGHT AND THURSDAY...WITH A CHANCE OF LIGHT
RAIN OR LIGHT SNOW WEDNESDAY NIGHT INTO THURSDAY MORNING. CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* MVFR CEILINGS MOVING IN FROM THE NORTHWEST AROUND 08Z AND
  LINGERING THROUGH SATURDAY MORNING.

* WESTERLY WINDS NEAR 10 KTS TODAY...DIMINISHING AND EVENTUALLY
  BECOMING EAST-NORTHEAST AFTER MIDNIGHT SATURDAY AND BECOMING
  GUSTY TOWARD MORNING.

* SNOW DEVELOPING TOWARD 12Z SUNDAY. IFR/LIFR CONDITIONS LIKELY
  IN SNOW JUST BEYOND END OF ORD 30 OUR TAF PERIOD.

RATZER

//DISCUSSION...UPDATED 06Z...

SURFACE LOW PRESSURE WAS MOVING EAST INTO EASTERN CANADA LATE THIS
EVENING...WITH A WEAKER TROUGH OF LOW PRESSURE TRAILING SOUTHWEST
INTO THE WESTERN GREAT LAKES REGION. THIS TROUGH WILL MOVE
SOUTHEAST ACROSS THE TERMINAL SITES EARLY THIS MORNING WITH A
SUBTLE WIND SHIFT FROM WEST-SOUTHWEST TO WEST-NORTHWEST...AS WELL
AS AN AREA OF MVFR STRATUS WHICH WILL SPREAD ACROSS THE AREA IN
THE 07-09Z TIME FRAME PER EXTRAPOLATION OF SATELLITE IMAGERY. SOME
LARGE BREAKS IN THE STRATUS BACK ACROSS WESTERN/NORTHWEST WISCONSIN
SUGGEST IT MAY TEND TO ALLOW SOME BREAKS TO VFR CONDITIONS BY
MIDDAY...THOUGH MODEL SOUNDINGS REMAIN FAIRLY MOIST IN THE LOWEST
FEW THOUSAND FEET NEAR THE GROUND.

OF GREATER CONFIDENCE IS THE APPROACH OF A DIGGING MID-LEVEL
DISTURBANCE TONIGHT...WITH ASSOCIATED DEEPENING SURFACE LOW
PRESSURE EXPECTED TO PASS SOUTHWEST OF TERMINALS EARLY SUNDAY
MORNING. MODELS HAVE BEEN FAIRLY CONSISTENT IN SATURATING THE
COLUMN DURING THE PRE-DAWN HOURS OF SUNDAY MORNING WITH SNOW
EXPECTED TO DEVELOP BY 12Z. IFR/LIFR CONDITIONS EXPECTED IN
SNOW SHORTLY THEREAFTER...JUST BEYOND END OF CURRENT TAF PERIODS.
IN ADDITION...DEEPENING OF THE SURFACE LOW TO THE SOUTHWEST OF THE
TERMINALS WILL RESULT IN WINDS SHIFTING TO THE EAST-NORTHEAST AND
INCREASING EARLY SUNDAY MORNING...LIKELY GUSTING 25-30 KT BY MID-
MORNING SUNDAY.

RATZER


//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND TRENDS...THOUGH MEDIUM-LOW IN DIRECTION SATURDAY
  EVENING AS SHIFT TO EAST-NORTHEAST OCCURS.

* MEDIUM-HIGH IN TIMING OF MVFR DECK EARLY THIS MORNING. LOW IN
  DISSIPATION TIMING LATER TODAY.

* MEDIUM-HIGH IN TIMING SNOW TO DEVELOP BEFORE SUNRISE SUNDAY.

RATZER

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...

SUNDAY...SNOW. IFR LIKELY PERIODIC LIFR POSSIBLE.

MONDAY...SLIGHT CHANCE OF -SN. MVFR PROBABLE W/CHANCE OF IFR.

TUESDAY THROUGH THURSDAY...PRIMARILY VFR. MAINLY DRY.

IZZI

&&

.MARINE...
122 PM CST

SOUTHWESTERLY WINDS WILL GRADUALLY WEAKEN TONIGHT...THEN A COLD
FRONT WILL SHIFT OVER THE LAKE ON SATURDAY AS THE PARENT SURFACE LOW
TRACKS ACROSS NORTHERN QUEBEC. THIS WILL SET UP A NORTHERLY FLOW
DOWN THE LAKE LATER SATURDAY. A FAST MOVING STOUT CLIPPER SYSTEM
WILL MOVE SOUTH OF THE LAKE ON SUNDAY MORNING...AND THIS LOOKS TO
SET THE STAGE FOR A PERIOD OF STRONG NORTHEASTERLY WINDS UP AROUND
30 KT OVER THE LAKE. THIS WILL LIKELY PRODUCE HIGH WAVES OVER 5 FEET
ACROSS MUCH OF SOUTHERN END OF LAKE MICHIGAN SUNDAY AND SUNDAY NIGHT.
FOLLOWING THIS SYSTEM...ANOTHER STORM SYSTEM IS EXPECTED TO IMPACT
THE GREAT LAKES REGION FOR THE MIDDLE TO END OF NEXT WEEK. IT
APPEARS THIS COULD PRODUCE SOUTHERLY GALE FORCE WINDS OVER MUCH OF
THE LAKE LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A PERIOD
OF POTENTIALLY GALE FORCE NORTHERLY WINDS THURSDAY AS THE SYSTEM
PASSES OVER THE EASTERN LAKES.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO








000
FXUS63 KLOT 240325
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
925 PM CST FRI JAN 23 2015

.SHORT TERM...

TONIGHT AND SATURDAY...

305 PM...NO CONCERNS THROUGH SATURDAY EVENING. LOW CLOUDS CONTINUE
TO ERODE FROM THE NORTH AND THE SOUTHWEST THIS AFTERNOON. THIS
TREND WILL CONTINUE THIS EVENING AS THE BACK EDGE PUSHES EAST.
HOWEVER...AN EXTENSIVE BAND OF MID CLOUDS WILL SPREAD BACK ACROSS
THE AREA THIS EVENING AHEAD OF AN APPROACHING COLD FRONT. VERY
LIMITED MOISTURE WITH THIS FRONT AND NOT EXPECTING ANY PRECIP
THOUGH A SPRINKLE OR FLURRY CAN/T BE COMPLETED RULED OUT...BUT NO
MENTION IN THE FORECAST. CLOUD COVER HELPED HOLD HIGHS TODAY IN
THE LOWER/MID 30S AND WITH SOME PARTIAL CLEARING AT TIMES...EXPECT
LOWS TONIGHT TO DIP INTO THE MID/UPPER 20S...THOUGH SOME
UNCERTAINTY WITH APPROACHING MID CLOUDS AND THEN ANOTHER AREA OF
LOW CLOUDS OVER THE UPPER MIDWEST WHICH WILL BE SPREADING SOUTH
ACROSS THE AREA SATURDAY MORNING. IF THIS CLOUD COVER DOES BECOME
OVERCAST...HIGHS ON SATURDAY WILL LIKELY BE TEMPERED SOME AS
WELL...PERHAPS ONLY IN THE MID 30S. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH FRIDAY...

305 PM...MAIN FORECAST CONCERN IS ACCUMULATING SNOW LATE SATURDAY
NIGHT THROUGH SUNDAY AFTERNOON...WITH POSSIBLE LAKE EFFECT SNOW
SHOWERS SUNDAY NIGHT AND ANOTHER WEAKER CLIPPER SYSTEM MONDAY
NIGHT...FOLLOWED BY MODERATE/MILD TEMPS MIDDLE OF NEXT WEEK.

DECENT AGREEMENT WITH THE TRACK OF THE SURFACE LOW OF THE NEXT
CLIPPER SYSTEM SATURDAY NIGHT INTO SUNDAY WITH THE 12Z GFS A BIT
FURTHER SOUTHWEST OF THE REST OF THE MODELS...WHICH TRACK THE LOW
FROM ROUGHLY MLI TO IND SUNDAY MORNING. THERMAL PROFILES SUGGEST
PRECIP TYPE WILL BE ALL SNOW...BUT INITIALLY COULD BE SOME RAIN
MIXED IN ACROSS THE SOUTHERN CWA. IN ADDITION...SNOW/WATER RATIOS
COULD BE RATHER LOW TO START...YIELDING A WETTER SNOW. BUT AS THE
LOW TRACKS TO THE SOUTHEAST...COLDER AIR WILL SLOWLY SPREAD ACROSS
THE AREA WITH THE SNOW LIKELY BECOMING DRIER BY LATE MORNING AND
INTO THE AFTERNOON. THIS MAKES SNOWFALL AMOUNTS A BIT TRICKY...
ESPECIALLY IF THE TRACK OF THE LOW ENDS UP A LITTLE FURTHER SOUTH
AS THE GFS SUGGESTS...COLDER AIR WOULD ARRIVE SOONER. POSSIBLE
LAKE ENHANCEMENT WITH NORTHEAST FLOW ALSO ADDS TO THE UNCERTAINTY
REGARDING AMOUNTS. THEREFORE...DIDN/T MAKE ANY SIGNIFICANT
CHANGES TO THE GOING FORECAST WITH 2-4 INCHES NORTH OF A SQI/IKK
LINE...1-2 INCHES SOUTH OF THAT LINE. BUT AS IS ALWAYS THE
CASE...MINOR CHANGES IN THE TRACK COULD CAUSE LARGE CHANGES TO THE
FORECAST AS TRENDS EMERGE.

TEMPERATURES BEGIN TO FALL BY MID/LATE SUNDAY AFTERNOON ACROSS THE
NORTH. NORTHEASTERLY WINDS INCREASE WITH GUSTS TO 30 MPH AND
DEPENDING ON HOW DRY THE SNOW BECOMES...THERE COULD BE SOME
BLOWING SNOW BUT AGAIN...ITS TOO EARLY FOR SPECIFICS OR HOW MUCH
OF A PROBLEM THIS COULD BECOME.

THE NORTHEAST AND THEN NORTHERLY WINDS MAY ALLOW SOME LAKE EFFECT
SNOW SHOWERS TO DEVELOP SUNDAY EVENING ACROSS NORTHEAST IL AND
THEN INTO NORTHWEST INDIANA. BUT INVERSION HEIGHTS ARE RATHER
LOW...PERHAPS NO HIGHER THAN 4KFT AND WINDS BEGIN TO TURN BACK
EASTERLY BY MONDAY MORNING. THUS ANY LAKE EFFECT POTENTIAL LOOKS
MINIMAL.

ANOTHER CLIPPER QUICKLY DROPS SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT...AS IT BEGINS TO WEAKEN. A
BAND OF LIGHT SNOW IS POSSIBLE WITH THIS FEATURE ESPECIALLY MONDAY
EVENING AND SOME AREAS MAY SEE AN INCH OR TWO DEPENDING ON WHERE
IT TRACKS. HAVE INCLUDED JUST LIGHT QPF AMOUNTS FOR NOW.

HIGH PRESSURE MOVES ACROSS THE AREA TUESDAY AND TUESDAY NIGHT AS
FLOW TURNS BACK SOUTH WEDNESDAY AND TEMPS MODIFY BACK INTO THE 30S
THOUGH WITH AN EXPECTED SNOW PACK BY THEN...LOW CONFIDENCE ON HOW
WARM TEMPS WILL BECOME. ANOTHER CLIPPER SYSTEM MOVES ACROSS THE
LAKES REGION WEDNESDAY NIGHT AND THURSDAY...WITH A CHANCE OF LIGHT
RAIN OR LIGHT SNOW WEDNESDAY NIGHT INTO THURSDAY MORNING. CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* MVFR CIGS LIKELY LATE TONIGHT AND SATURDAY

IZZI

//DISCUSSION...UPDATED 00Z...

ONLY MINOR AVIATION CONCERN THROUGH THIS TAF CYCLE IS WITH BANK OF
STRATUS AND MVFR CIGS OVER NORTHERN WISCONSIN AND NORTHEAST
MINNESOTA WHICH IS FORECAST TO MOVE SOUTHEAST INTO THE REGION LATE
TONIGHT AND INTO SATURDAY. SOME GUIDANCE WOULD SUGGEST MVFR CIGS
PERSIST ALL DAY SATURDAY...AND WHILE THIS IS CERTAINLY POSSIBLE
HAVE OPTED TO ERR A BIT ON THE OPTIMISTIC SIDE INDICATING SOME
SCATTERING OUT OF MVFR CIGS SATURDAY AFTERNOON IN LINE WITH MAV
GUIDANCE. CONFIDENCE IS LOW IN HOW CIGS PAN OUT TONIGHT AND
SATURDAY BUT CERTAINLY APPEARS LIKELY THAT CONDITIONS WILL BE MVFR
OR BETTER AND HAVE VERY LITTLE IMPACT ON AVIATION OPERATIONS.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM-HIGH CONFIDENCE IN MVFR CIGS LATE TONIGHT/SAT
  MORNING...LOW CONFIDENCE IN MVFR CIGS SCATTERING OUT SAT
  AFTERNOON
* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...

SUNDAY...SNOW. IFR LIKELY PERIODIC LIFR POSSIBLE.

MONDAY...SLIGHT CHANCE OF -SN. MVFR PROBABLE W/CHANCE OF IFR.

TUESDAY THROUGH THURSDAY...PRIMARILY VFR. MAINLY DRY.

IZZI

&&

.MARINE...
122 PM CST

SOUTHWESTERLY WINDS WILL GRADUALLY WEAKEN TONIGHT...THEN A COLD
FRONT WILL SHIFT OVER THE LAKE ON SATURDAY AS THE PARENT SURFACE LOW
TRACKS ACROSS NORTHERN QUEBEC. THIS WILL SET UP A NORTHERLY FLOW
DOWN THE LAKE LATER SATURDAY. A FAST MOVING STOUT CLIPPER SYSTEM
WILL MOVE SOUTH OF THE LAKE ON SUNDAY MORNING...AND THIS LOOKS TO
SET THE STAGE FOR A PERIOD OF STRONG NORTHEASTERLY WINDS UP AROUND
30 KT OVER THE LAKE. THIS WILL LIKELY PRODUCE HIGH WAVES OVER 5 FEET
ACROSS MUCH OF SOUTHERN END OF LAKE MICHIGAN SUNDAY AND SUNDAY NIGHT.
FOLLOWING THIS SYSTEM...ANOTHER STORM SYSTEM IS EXPECTED TO IMPACT
THE GREAT LAKES REGION FOR THE MIDDLE TO END OF NEXT WEEK. IT
APPEARS THIS COULD PRODUCE SOUTHERLY GALE FORCE WINDS OVER MUCH OF
THE LAKE LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A PERIOD
OF POTENTIALLY GALE FORCE NORTHERLY WINDS THURSDAY AS THE SYSTEM
PASSES OVER THE EASTERN LAKES.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 240325
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
925 PM CST FRI JAN 23 2015

.SHORT TERM...

TONIGHT AND SATURDAY...

305 PM...NO CONCERNS THROUGH SATURDAY EVENING. LOW CLOUDS CONTINUE
TO ERODE FROM THE NORTH AND THE SOUTHWEST THIS AFTERNOON. THIS
TREND WILL CONTINUE THIS EVENING AS THE BACK EDGE PUSHES EAST.
HOWEVER...AN EXTENSIVE BAND OF MID CLOUDS WILL SPREAD BACK ACROSS
THE AREA THIS EVENING AHEAD OF AN APPROACHING COLD FRONT. VERY
LIMITED MOISTURE WITH THIS FRONT AND NOT EXPECTING ANY PRECIP
THOUGH A SPRINKLE OR FLURRY CAN/T BE COMPLETED RULED OUT...BUT NO
MENTION IN THE FORECAST. CLOUD COVER HELPED HOLD HIGHS TODAY IN
THE LOWER/MID 30S AND WITH SOME PARTIAL CLEARING AT TIMES...EXPECT
LOWS TONIGHT TO DIP INTO THE MID/UPPER 20S...THOUGH SOME
UNCERTAINTY WITH APPROACHING MID CLOUDS AND THEN ANOTHER AREA OF
LOW CLOUDS OVER THE UPPER MIDWEST WHICH WILL BE SPREADING SOUTH
ACROSS THE AREA SATURDAY MORNING. IF THIS CLOUD COVER DOES BECOME
OVERCAST...HIGHS ON SATURDAY WILL LIKELY BE TEMPERED SOME AS
WELL...PERHAPS ONLY IN THE MID 30S. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH FRIDAY...

305 PM...MAIN FORECAST CONCERN IS ACCUMULATING SNOW LATE SATURDAY
NIGHT THROUGH SUNDAY AFTERNOON...WITH POSSIBLE LAKE EFFECT SNOW
SHOWERS SUNDAY NIGHT AND ANOTHER WEAKER CLIPPER SYSTEM MONDAY
NIGHT...FOLLOWED BY MODERATE/MILD TEMPS MIDDLE OF NEXT WEEK.

DECENT AGREEMENT WITH THE TRACK OF THE SURFACE LOW OF THE NEXT
CLIPPER SYSTEM SATURDAY NIGHT INTO SUNDAY WITH THE 12Z GFS A BIT
FURTHER SOUTHWEST OF THE REST OF THE MODELS...WHICH TRACK THE LOW
FROM ROUGHLY MLI TO IND SUNDAY MORNING. THERMAL PROFILES SUGGEST
PRECIP TYPE WILL BE ALL SNOW...BUT INITIALLY COULD BE SOME RAIN
MIXED IN ACROSS THE SOUTHERN CWA. IN ADDITION...SNOW/WATER RATIOS
COULD BE RATHER LOW TO START...YIELDING A WETTER SNOW. BUT AS THE
LOW TRACKS TO THE SOUTHEAST...COLDER AIR WILL SLOWLY SPREAD ACROSS
THE AREA WITH THE SNOW LIKELY BECOMING DRIER BY LATE MORNING AND
INTO THE AFTERNOON. THIS MAKES SNOWFALL AMOUNTS A BIT TRICKY...
ESPECIALLY IF THE TRACK OF THE LOW ENDS UP A LITTLE FURTHER SOUTH
AS THE GFS SUGGESTS...COLDER AIR WOULD ARRIVE SOONER. POSSIBLE
LAKE ENHANCEMENT WITH NORTHEAST FLOW ALSO ADDS TO THE UNCERTAINTY
REGARDING AMOUNTS. THEREFORE...DIDN/T MAKE ANY SIGNIFICANT
CHANGES TO THE GOING FORECAST WITH 2-4 INCHES NORTH OF A SQI/IKK
LINE...1-2 INCHES SOUTH OF THAT LINE. BUT AS IS ALWAYS THE
CASE...MINOR CHANGES IN THE TRACK COULD CAUSE LARGE CHANGES TO THE
FORECAST AS TRENDS EMERGE.

TEMPERATURES BEGIN TO FALL BY MID/LATE SUNDAY AFTERNOON ACROSS THE
NORTH. NORTHEASTERLY WINDS INCREASE WITH GUSTS TO 30 MPH AND
DEPENDING ON HOW DRY THE SNOW BECOMES...THERE COULD BE SOME
BLOWING SNOW BUT AGAIN...ITS TOO EARLY FOR SPECIFICS OR HOW MUCH
OF A PROBLEM THIS COULD BECOME.

THE NORTHEAST AND THEN NORTHERLY WINDS MAY ALLOW SOME LAKE EFFECT
SNOW SHOWERS TO DEVELOP SUNDAY EVENING ACROSS NORTHEAST IL AND
THEN INTO NORTHWEST INDIANA. BUT INVERSION HEIGHTS ARE RATHER
LOW...PERHAPS NO HIGHER THAN 4KFT AND WINDS BEGIN TO TURN BACK
EASTERLY BY MONDAY MORNING. THUS ANY LAKE EFFECT POTENTIAL LOOKS
MINIMAL.

ANOTHER CLIPPER QUICKLY DROPS SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT...AS IT BEGINS TO WEAKEN. A
BAND OF LIGHT SNOW IS POSSIBLE WITH THIS FEATURE ESPECIALLY MONDAY
EVENING AND SOME AREAS MAY SEE AN INCH OR TWO DEPENDING ON WHERE
IT TRACKS. HAVE INCLUDED JUST LIGHT QPF AMOUNTS FOR NOW.

HIGH PRESSURE MOVES ACROSS THE AREA TUESDAY AND TUESDAY NIGHT AS
FLOW TURNS BACK SOUTH WEDNESDAY AND TEMPS MODIFY BACK INTO THE 30S
THOUGH WITH AN EXPECTED SNOW PACK BY THEN...LOW CONFIDENCE ON HOW
WARM TEMPS WILL BECOME. ANOTHER CLIPPER SYSTEM MOVES ACROSS THE
LAKES REGION WEDNESDAY NIGHT AND THURSDAY...WITH A CHANCE OF LIGHT
RAIN OR LIGHT SNOW WEDNESDAY NIGHT INTO THURSDAY MORNING. CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* MVFR CIGS LIKELY LATE TONIGHT AND SATURDAY

IZZI

//DISCUSSION...UPDATED 00Z...

ONLY MINOR AVIATION CONCERN THROUGH THIS TAF CYCLE IS WITH BANK OF
STRATUS AND MVFR CIGS OVER NORTHERN WISCONSIN AND NORTHEAST
MINNESOTA WHICH IS FORECAST TO MOVE SOUTHEAST INTO THE REGION LATE
TONIGHT AND INTO SATURDAY. SOME GUIDANCE WOULD SUGGEST MVFR CIGS
PERSIST ALL DAY SATURDAY...AND WHILE THIS IS CERTAINLY POSSIBLE
HAVE OPTED TO ERR A BIT ON THE OPTIMISTIC SIDE INDICATING SOME
SCATTERING OUT OF MVFR CIGS SATURDAY AFTERNOON IN LINE WITH MAV
GUIDANCE. CONFIDENCE IS LOW IN HOW CIGS PAN OUT TONIGHT AND
SATURDAY BUT CERTAINLY APPEARS LIKELY THAT CONDITIONS WILL BE MVFR
OR BETTER AND HAVE VERY LITTLE IMPACT ON AVIATION OPERATIONS.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM-HIGH CONFIDENCE IN MVFR CIGS LATE TONIGHT/SAT
  MORNING...LOW CONFIDENCE IN MVFR CIGS SCATTERING OUT SAT
  AFTERNOON
* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...

SUNDAY...SNOW. IFR LIKELY PERIODIC LIFR POSSIBLE.

MONDAY...SLIGHT CHANCE OF -SN. MVFR PROBABLE W/CHANCE OF IFR.

TUESDAY THROUGH THURSDAY...PRIMARILY VFR. MAINLY DRY.

IZZI

&&

.MARINE...
122 PM CST

SOUTHWESTERLY WINDS WILL GRADUALLY WEAKEN TONIGHT...THEN A COLD
FRONT WILL SHIFT OVER THE LAKE ON SATURDAY AS THE PARENT SURFACE LOW
TRACKS ACROSS NORTHERN QUEBEC. THIS WILL SET UP A NORTHERLY FLOW
DOWN THE LAKE LATER SATURDAY. A FAST MOVING STOUT CLIPPER SYSTEM
WILL MOVE SOUTH OF THE LAKE ON SUNDAY MORNING...AND THIS LOOKS TO
SET THE STAGE FOR A PERIOD OF STRONG NORTHEASTERLY WINDS UP AROUND
30 KT OVER THE LAKE. THIS WILL LIKELY PRODUCE HIGH WAVES OVER 5 FEET
ACROSS MUCH OF SOUTHERN END OF LAKE MICHIGAN SUNDAY AND SUNDAY NIGHT.
FOLLOWING THIS SYSTEM...ANOTHER STORM SYSTEM IS EXPECTED TO IMPACT
THE GREAT LAKES REGION FOR THE MIDDLE TO END OF NEXT WEEK. IT
APPEARS THIS COULD PRODUCE SOUTHERLY GALE FORCE WINDS OVER MUCH OF
THE LAKE LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A PERIOD
OF POTENTIALLY GALE FORCE NORTHERLY WINDS THURSDAY AS THE SYSTEM
PASSES OVER THE EASTERN LAKES.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 232330
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
530 PM CST FRI JAN 23 2015

.SHORT TERM...

TONIGHT AND SATURDAY...

305 PM...NO CONCERNS THROUGH SATURDAY EVENING. LOW CLOUDS CONTINUE
TO ERODE FROM THE NORTH AND THE SOUTHWEST THIS AFTERNOON. THIS
TREND WILL CONTINUE THIS EVENING AS THE BACK EDGE PUSHES EAST.
HOWEVER...AN EXTENSIVE BAND OF MID CLOUDS WILL SPREAD BACK ACROSS
THE AREA THIS EVENING AHEAD OF AN APPROACHING COLD FRONT. VERY
LIMITED MOISTURE WITH THIS FRONT AND NOT EXPECTING ANY PRECIP
THOUGH A SPRINKLE OR FLURRY CAN/T BE COMPLETED RULED OUT...BUT NO
MENTION IN THE FORECAST. CLOUD COVER HELPED HOLD HIGHS TODAY IN
THE LOWER/MID 30S AND WITH SOME PARTIAL CLEARING AT TIMES...EXPECT
LOWS TONIGHT TO DIP INTO THE MID/UPPER 20S...THOUGH SOME
UNCERTAINTY WITH APPROACHING MID CLOUDS AND THEN ANOTHER AREA OF
LOW CLOUDS OVER THE UPPER MIDWEST WHICH WILL BE SPREADING SOUTH
ACROSS THE AREA SATURDAY MORNING. IF THIS CLOUD COVER DOES BECOME
OVERCAST...HIGHS ON SATURDAY WILL LIKELY BE TEMPERED SOME AS
WELL...PERHAPS ONLY IN THE MID 30S. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH FRIDAY...

305 PM...MAIN FORECAST CONCERN IS ACCUMULATING SNOW LATE SATURDAY
NIGHT THROUGH SUNDAY AFTERNOON...WITH POSSIBLE LAKE EFFECT SNOW
SHOWERS SUNDAY NIGHT AND ANOTHER WEAKER CLIPPER SYSTEM MONDAY
NIGHT...FOLLOWED BY MODERATE/MILD TEMPS MIDDLE OF NEXT WEEK.

DECENT AGREEMENT WITH THE TRACK OF THE SURFACE LOW OF THE NEXT
CLIPPER SYSTEM SATURDAY NIGHT INTO SUNDAY WITH THE 12Z GFS A BIT
FURTHER SOUTHWEST OF THE REST OF THE MODELS...WHICH TRACK THE LOW
FROM ROUGHLY MLI TO IND SUNDAY MORNING. THERMAL PROFILES SUGGEST
PRECIP TYPE WILL BE ALL SNOW...BUT INITIALLY COULD BE SOME RAIN
MIXED IN ACROSS THE SOUTHERN CWA. IN ADDITION...SNOW/WATER RATIOS
COULD BE RATHER LOW TO START...YIELDING A WETTER SNOW. BUT AS THE
LOW TRACKS TO THE SOUTHEAST...COLDER AIR WILL SLOWLY SPREAD ACROSS
THE AREA WITH THE SNOW LIKELY BECOMING DRIER BY LATE MORNING AND
INTO THE AFTERNOON. THIS MAKES SNOWFALL AMOUNTS A BIT TRICKY...
ESPECIALLY IF THE TRACK OF THE LOW ENDS UP A LITTLE FURTHER SOUTH
AS THE GFS SUGGESTS...COLDER AIR WOULD ARRIVE SOONER. POSSIBLE
LAKE ENHANCEMENT WITH NORTHEAST FLOW ALSO ADDS TO THE UNCERTAINTY
REGARDING AMOUNTS. THEREFORE...DIDN/T MAKE ANY SIGNIFICANT
CHANGES TO THE GOING FORECAST WITH 2-4 INCHES NORTH OF A SQI/IKK
LINE...1-2 INCHES SOUTH OF THAT LINE. BUT AS IS ALWAYS THE
CASE...MINOR CHANGES IN THE TRACK COULD CAUSE LARGE CHANGES TO THE
FORECAST AS TRENDS EMERGE.

TEMPERATURES BEGIN TO FALL BY MID/LATE SUNDAY AFTERNOON ACROSS THE
NORTH. NORTHEASTERLY WINDS INCREASE WITH GUSTS TO 30 MPH AND
DEPENDING ON HOW DRY THE SNOW BECOMES...THERE COULD BE SOME
BLOWING SNOW BUT AGAIN...ITS TOO EARLY FOR SPECIFICS OR HOW MUCH
OF A PROBLEM THIS COULD BECOME.

THE NORTHEAST AND THEN NORTHERLY WINDS MAY ALLOW SOME LAKE EFFECT
SNOW SHOWERS TO DEVELOP SUNDAY EVENING ACROSS NORTHEAST IL AND
THEN INTO NORTHWEST INDIANA. BUT INVERSION HEIGHTS ARE RATHER
LOW...PERHAPS NO HIGHER THAN 4KFT AND WINDS BEGIN TO TURN BACK
EASTERLY BY MONDAY MORNING. THUS ANY LAKE EFFECT POTENTIAL LOOKS
MINIMAL.

ANOTHER CLIPPER QUICKLY DROPS SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT...AS IT BEGINS TO WEAKEN. A
BAND OF LIGHT SNOW IS POSSIBLE WITH THIS FEATURE ESPECIALLY MONDAY
EVENING AND SOME AREAS MAY SEE AN INCH OR TWO DEPENDING ON WHERE
IT TRACKS. HAVE INCLUDED JUST LIGHT QPF AMOUNTS FOR NOW.

HIGH PRESSURE MOVES ACROSS THE AREA TUESDAY AND TUESDAY NIGHT AS
FLOW TURNS BACK SOUTH WEDNESDAY AND TEMPS MODIFY BACK INTO THE 30S
THOUGH WITH AN EXPECTED SNOW PACK BY THEN...LOW CONFIDENCE ON HOW
WARM TEMPS WILL BECOME. ANOTHER CLIPPER SYSTEM MOVES ACROSS THE
LAKES REGION WEDNESDAY NIGHT AND THURSDAY...WITH A CHANCE OF LIGHT
RAIN OR LIGHT SNOW WEDNESDAY NIGHT INTO THURSDAY MORNING. CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* MVFR CIGS POSSIBLE LATE TONIGHT AND SATURDAY

IZZI

//DISCUSSION...UPDATED 00Z...

ONLY MINOR AVIATION CONCERN THROUGH THIS TAF CYCLE IS WITH BANK OF
STRATUS AND MVFR CIGS OVER NORTHERN WISCONSIN AND NORTHEAST
MINNESOTA WHICH IS FORECAST TO MOVE SOUTHEAST INTO THE REGION LATE
TONIGHT AND INTO SATURDAY. SOME GUIDANCE WOULD SUGGEST MVFR CIGS
PERSIST ALL DAY SATURDAY...AND WHILE THIS IS CERTAINLY POSSIBLE
HAVE OPTED TO ERR A BIT ON THE OPTIMISTIC SIDE INDICATING SOME
SCATTERING OUT OF MVFR CIGS SATURDAY AFTERNOON IN LINE WITH MAV
GUIDANCE. CONFIDENCE IS LOW IN HOW CIGS PAN OUT TONIGHT AND
SATURDAY BUT CERTAINLY APPEARS LIKELY THAT CONDITIONS WILL BE MVFR
OR BETTER AND HAVE VERY LITTLE IMPACT ON AVIATION OPERATIONS.

IZZI


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* LOW CONFIDENCE IN CEILING FORECAST LATE TONIGHT AND SATURDAY
* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...

SUNDAY...SNOW. IFR LIKELY PERIODIC LIFR POSSIBLE.

MONDAY...SLIGHT CHANCE OF -SN. MVFR PROBABLE W/CHANCE OF IFR.

TUESDAY THROUGH THURSDAY...PRIMARILY VFR. MAINLY DRY.

IZZI

&&

.MARINE...
122 PM CST

SOUTHWESTERLY WINDS WILL GRADUALLY WEAKEN TONIGHT...THEN A COLD
FRONT WILL SHIFT OVER THE LAKE ON SATURDAY AS THE PARENT SURFACE LOW
TRACKS ACROSS NORTHERN QUEBEC. THIS WILL SET UP A NORTHERLY FLOW
DOWN THE LAKE LATER SATURDAY. A FAST MOVING STOUT CLIPPER SYSTEM
WILL MOVE SOUTH OF THE LAKE ON SUNDAY MORNING...AND THIS LOOKS TO
SET THE STAGE FOR A PERIOD OF STRONG NORTHEASTERLY WINDS UP AROUND
30 KT OVER THE LAKE. THIS WILL LIKELY PRODUCE HIGH WAVES OVER 5 FEET
ACROSS MUCH OF SOUTHERN END OF LAKE MICHIGAN SUNDAY AND SUNDAY NIGHT.
FOLLOWING THIS SYSTEM...ANOTHER STORM SYSTEM IS EXPECTED TO IMPACT
THE GREAT LAKES REGION FOR THE MIDDLE TO END OF NEXT WEEK. IT
APPEARS THIS COULD PRODUCE SOUTHERLY GALE FORCE WINDS OVER MUCH OF
THE LAKE LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A PERIOD
OF POTENTIALLY GALE FORCE NORTHERLY WINDS THURSDAY AS THE SYSTEM
PASSES OVER THE EASTERN LAKES.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 232209
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
409 PM CST FRI JAN 23 2015

.SHORT TERM...

TONIGHT AND SATURDAY...

305 PM...NO CONCERNS THROUGH SATURDAY EVENING. LOW CLOUDS CONTINUE
TO ERODE FROM THE NORTH AND THE SOUTHWEST THIS AFTERNOON. THIS
TREND WILL CONTINUE THIS EVENING AS THE BACK EDGE PUSHES EAST.
HOWEVER...AN EXTENSIVE BAND OF MID CLOUDS WILL SPREAD BACK ACROSS
THE AREA THIS EVENING AHEAD OF AN APPROACHING COLD FRONT. VERY
LIMITED MOISTURE WITH THIS FRONT AND NOT EXPECTING ANY PRECIP
THOUGH A SPRINKLE OR FLURRY CAN/T BE COMPLETED RULED OUT...BUT NO
MENTION IN THE FORECAST. CLOUD COVER HELPED HOLD HIGHS TODAY IN
THE LOWER/MID 30S AND WITH SOME PARTIAL CLEARING AT TIMES...EXPECT
LOWS TONIGHT TO DIP INTO THE MID/UPPER 20S...THOUGH SOME
UNCERTAINTY WITH APPROACHING MID CLOUDS AND THEN ANOTHER AREA OF
LOW CLOUDS OVER THE UPPER MIDWEST WHICH WILL BE SPREADING SOUTH
ACROSS THE AREA SATURDAY MORNING. IF THIS CLOUD COVER DOES BECOME
OVERCAST...HIGHS ON SATURDAY WILL LIKELY BE TEMPERED SOME AS
WELL...PERHAPS ONLY IN THE MID 30S. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH FRIDAY...

305 PM...MAIN FORECAST CONCERN IS ACCUMULATING SNOW LATE SATURDAY
NIGHT THROUGH SUNDAY AFTERNOON...WITH POSSIBLE LAKE EFFECT SNOW
SHOWERS SUNDAY NIGHT AND ANOTHER WEAKER CLIPPER SYSTEM MONDAY
NIGHT...FOLLOWED BY MODERATE/MILD TEMPS MIDDLE OF NEXT WEEK.

DECENT AGREEMENT WITH THE TRACK OF THE SURFACE LOW OF THE NEXT
CLIPPER SYSTEM SATURDAY NIGHT INTO SUNDAY WITH THE 12Z GFS A BIT
FURTHER SOUTHWEST OF THE REST OF THE MODELS...WHICH TRACK THE LOW
FROM ROUGHLY MLI TO IND SUNDAY MORNING. THERMAL PROFILES SUGGEST
PRECIP TYPE WILL BE ALL SNOW...BUT INITIALLY COULD BE SOME RAIN
MIXED IN ACROSS THE SOUTHERN CWA. IN ADDITION...SNOW/WATER RATIOS
COULD BE RATHER LOW TO START...YIELDING A WETTER SNOW. BUT AS THE
LOW TRACKS TO THE SOUTHEAST...COLDER AIR WILL SLOWLY SPREAD ACROSS
THE AREA WITH THE SNOW LIKELY BECOMING DRIER BY LATE MORNING AND
INTO THE AFTERNOON. THIS MAKES SNOWFALL AMOUNTS A BIT TRICKY...
ESPECIALLY IF THE TRACK OF THE LOW ENDS UP A LITTLE FURTHER SOUTH
AS THE GFS SUGGESTS...COLDER AIR WOULD ARRIVE SOONER. POSSIBLE
LAKE ENHANCEMENT WITH NORTHEAST FLOW ALSO ADDS TO THE UNCERTAINTY
REGARDING AMOUNTS. THEREFORE...DIDN/T MAKE ANY SIGNIFICANT
CHANGES TO THE GOING FORECAST WITH 2-4 INCHES NORTH OF A SQI/IKK
LINE...1-2 INCHES SOUTH OF THAT LINE. BUT AS IS ALWAYS THE
CASE...MINOR CHANGES IN THE TRACK COULD CAUSE LARGE CHANGES TO THE
FORECAST AS TRENDS EMERGE.

TEMPERATURES BEGIN TO FALL BY MID/LATE SUNDAY AFTERNOON ACROSS THE
NORTH. NORTHEASTERLY WINDS INCREASE WITH GUSTS TO 30 MPH AND
DEPENDING ON HOW DRY THE SNOW BECOMES...THERE COULD BE SOME
BLOWING SNOW BUT AGAIN...ITS TOO EARLY FOR SPECIFICS OR HOW MUCH
OF A PROBLEM THIS COULD BECOME.

THE NORTHEAST AND THEN NORTHERLY WINDS MAY ALLOW SOME LAKE EFFECT
SNOW SHOWERS TO DEVELOP SUNDAY EVENING ACROSS NORTHEAST IL AND
THEN INTO NORTHWEST INDIANA. BUT INVERSION HEIGHTS ARE RATHER
LOW...PERHAPS NO HIGHER THAN 4KFT AND WINDS BEGIN TO TURN BACK
EASTERLY BY MONDAY MORNING. THUS ANY LAKE EFFECT POTENTIAL LOOKS
MINIMAL.

ANOTHER CLIPPER QUICKLY DROPS SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT...AS IT BEGINS TO WEAKEN. A
BAND OF LIGHT SNOW IS POSSIBLE WITH THIS FEATURE ESPECIALLY MONDAY
EVENING AND SOME AREAS MAY SEE AN INCH OR TWO DEPENDING ON WHERE
IT TRACKS. HAVE INCLUDED JUST LIGHT QPF AMOUNTS FOR NOW.

HIGH PRESSURE MOVES ACROSS THE AREA TUESDAY AND TUESDAY NIGHT AS
FLOW TURNS BACK SOUTH WEDNESDAY AND TEMPS MODIFY BACK INTO THE 30S
THOUGH WITH AN EXPECTED SNOWPACK BY THEN...LOW CONFIDENCE ON HOW
WARM TEMPS WILL BECOME. ANOTHER CLIPPER SYSTEM MOVES ACROSS THE
LAKES REGION WEDNESDAY NIGHT AND THURSDAY...WITH A CHANCE OF LIGHT
RAIN OR LIGHT SNOW WEDNESDAY NIGHT INTO THURSDAY MORNING. CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* MVFR CIGS POSSIBLE AGAIN LATE TONIGHT INTO SATURDAY

IZZI

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS MORNING CONTINUED TO SHOW CONSIDERABLE CLOUD
COVER ACROSS THE REGION...WITH SOME CLEARING NOTED ACROSS EASTERN
IOWA. AS THE DAY HAS PROGRESSED SOME THINNING HAS BEGUN TO TAKE
PLACE ACROSS FAR NORTH/NORTHEAST ILLINOIS...AND MAY EVENTUALLY
MAKE IT INTO THE TAF SITES. AT THIS TIME THOUGH HAVE HELD ONTO THE
LOW CLOUDS THRU 00Z...WITH A SLOW IMPROVEMENT TOWARDS 2000-2500FT
AGL AFT 02Z. WINDS WILL CONTINUE TO BE SOUTHWESTERLY WITH SPEEDS
GENERALLY FROM 10-13KT. THRU THE AFTN ON OCCASION GUSTS MAY
OCCUR...AND NOT EXPECTED TO BE VERY FREQUENT WITH SPEEDS UP TO
17KT.

WITH A FRONTAL BOUNDARY SLIDING SOUTHEAST THIS EVENING...THERE IS
THE POTENTIAL FOR A FEW FLURRIES ACROSS ORD/MDW/DPA. ELSEWHERE
SHOULD BE TOO FAR REMOVED FROM THE BETTER MOISTURE TO SEE ANY
FLURRIES. THOUGH HAVE HELD ONTO A DRY FORECAST AS THIS TOO IS A
LOW CONFIDENCE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* LOW-MEDIUM CONFIDENCE IN CIGS SATURDAY
* HIGH CONFIDENCE IN ALL OTHER ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

SATURDAY NIGHT...SNOW LIKELY AFTER MIDNIGHT. ACCUMULATION LIKELY.
MVFR CIGS AND IFR VIS POSSIBLE.

SUNDAY...SNOW LIKELY. MVFR/IFR LIKELY.

MONDAY...CHANCE OF SNOW SHOWERS. MVFR POSSIBLE.

TUESDAY THROUGH THURSDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
122 PM CST

SOUTHWESTERLY WINDS WILL GRADUALLY WEAKEN TONIGHT...THEN A COLD
FRONT WILL SHIFT OVER THE LAKE ON SATURDAY AS THE PARENT SURFACE LOW
TRACKS ACROSS NORTHERN QUEBEC. THIS WILL SET UP A NORTHERLY FLOW
DOWN THE LAKE LATER SATURDAY. A FAST MOVING STOUT CLIPPER SYSTEM
WILL MOVE SOUTH OF THE LAKE ON SUNDAY MORNING...AND THIS LOOKS TO
SET THE STAGE FOR A PERIOD OF STRONG NORTHEASTERLY WINDS UP AROUND
30 KT OVER THE LAKE. THIS WILL LIKELY PRODUCE HIGH WAVES OVER 5 FEET
ACROSS MUCH OF SOUTHERN END OF LAKE MICHIGAN SUNDAY AND SUNDAY NIGHT.
FOLLOWING THIS SYSTEM...ANOTHER STORM SYSTEM IS EXPECTED TO IMPACT
THE GREAT LAKES REGION FOR THE MIDDLE TO END OF NEXT WEEK. IT
APPEARS THIS COULD PRODUCE SOUTHERLY GALE FORCE WINDS OVER MUCH OF
THE LAKE LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A PERIOD
OF POTENTIALLY GALE FORCE NORTHERLY WINDS THURSDAY AS THE SYSTEM
PASSES OVER THE EASTERN LAKES.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 232209
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
409 PM CST FRI JAN 23 2015

.SHORT TERM...

TONIGHT AND SATURDAY...

305 PM...NO CONCERNS THROUGH SATURDAY EVENING. LOW CLOUDS CONTINUE
TO ERODE FROM THE NORTH AND THE SOUTHWEST THIS AFTERNOON. THIS
TREND WILL CONTINUE THIS EVENING AS THE BACK EDGE PUSHES EAST.
HOWEVER...AN EXTENSIVE BAND OF MID CLOUDS WILL SPREAD BACK ACROSS
THE AREA THIS EVENING AHEAD OF AN APPROACHING COLD FRONT. VERY
LIMITED MOISTURE WITH THIS FRONT AND NOT EXPECTING ANY PRECIP
THOUGH A SPRINKLE OR FLURRY CAN/T BE COMPLETED RULED OUT...BUT NO
MENTION IN THE FORECAST. CLOUD COVER HELPED HOLD HIGHS TODAY IN
THE LOWER/MID 30S AND WITH SOME PARTIAL CLEARING AT TIMES...EXPECT
LOWS TONIGHT TO DIP INTO THE MID/UPPER 20S...THOUGH SOME
UNCERTAINTY WITH APPROACHING MID CLOUDS AND THEN ANOTHER AREA OF
LOW CLOUDS OVER THE UPPER MIDWEST WHICH WILL BE SPREADING SOUTH
ACROSS THE AREA SATURDAY MORNING. IF THIS CLOUD COVER DOES BECOME
OVERCAST...HIGHS ON SATURDAY WILL LIKELY BE TEMPERED SOME AS
WELL...PERHAPS ONLY IN THE MID 30S. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH FRIDAY...

305 PM...MAIN FORECAST CONCERN IS ACCUMULATING SNOW LATE SATURDAY
NIGHT THROUGH SUNDAY AFTERNOON...WITH POSSIBLE LAKE EFFECT SNOW
SHOWERS SUNDAY NIGHT AND ANOTHER WEAKER CLIPPER SYSTEM MONDAY
NIGHT...FOLLOWED BY MODERATE/MILD TEMPS MIDDLE OF NEXT WEEK.

DECENT AGREEMENT WITH THE TRACK OF THE SURFACE LOW OF THE NEXT
CLIPPER SYSTEM SATURDAY NIGHT INTO SUNDAY WITH THE 12Z GFS A BIT
FURTHER SOUTHWEST OF THE REST OF THE MODELS...WHICH TRACK THE LOW
FROM ROUGHLY MLI TO IND SUNDAY MORNING. THERMAL PROFILES SUGGEST
PRECIP TYPE WILL BE ALL SNOW...BUT INITIALLY COULD BE SOME RAIN
MIXED IN ACROSS THE SOUTHERN CWA. IN ADDITION...SNOW/WATER RATIOS
COULD BE RATHER LOW TO START...YIELDING A WETTER SNOW. BUT AS THE
LOW TRACKS TO THE SOUTHEAST...COLDER AIR WILL SLOWLY SPREAD ACROSS
THE AREA WITH THE SNOW LIKELY BECOMING DRIER BY LATE MORNING AND
INTO THE AFTERNOON. THIS MAKES SNOWFALL AMOUNTS A BIT TRICKY...
ESPECIALLY IF THE TRACK OF THE LOW ENDS UP A LITTLE FURTHER SOUTH
AS THE GFS SUGGESTS...COLDER AIR WOULD ARRIVE SOONER. POSSIBLE
LAKE ENHANCEMENT WITH NORTHEAST FLOW ALSO ADDS TO THE UNCERTAINTY
REGARDING AMOUNTS. THEREFORE...DIDN/T MAKE ANY SIGNIFICANT
CHANGES TO THE GOING FORECAST WITH 2-4 INCHES NORTH OF A SQI/IKK
LINE...1-2 INCHES SOUTH OF THAT LINE. BUT AS IS ALWAYS THE
CASE...MINOR CHANGES IN THE TRACK COULD CAUSE LARGE CHANGES TO THE
FORECAST AS TRENDS EMERGE.

TEMPERATURES BEGIN TO FALL BY MID/LATE SUNDAY AFTERNOON ACROSS THE
NORTH. NORTHEASTERLY WINDS INCREASE WITH GUSTS TO 30 MPH AND
DEPENDING ON HOW DRY THE SNOW BECOMES...THERE COULD BE SOME
BLOWING SNOW BUT AGAIN...ITS TOO EARLY FOR SPECIFICS OR HOW MUCH
OF A PROBLEM THIS COULD BECOME.

THE NORTHEAST AND THEN NORTHERLY WINDS MAY ALLOW SOME LAKE EFFECT
SNOW SHOWERS TO DEVELOP SUNDAY EVENING ACROSS NORTHEAST IL AND
THEN INTO NORTHWEST INDIANA. BUT INVERSION HEIGHTS ARE RATHER
LOW...PERHAPS NO HIGHER THAN 4KFT AND WINDS BEGIN TO TURN BACK
EASTERLY BY MONDAY MORNING. THUS ANY LAKE EFFECT POTENTIAL LOOKS
MINIMAL.

ANOTHER CLIPPER QUICKLY DROPS SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT...AS IT BEGINS TO WEAKEN. A
BAND OF LIGHT SNOW IS POSSIBLE WITH THIS FEATURE ESPECIALLY MONDAY
EVENING AND SOME AREAS MAY SEE AN INCH OR TWO DEPENDING ON WHERE
IT TRACKS. HAVE INCLUDED JUST LIGHT QPF AMOUNTS FOR NOW.

HIGH PRESSURE MOVES ACROSS THE AREA TUESDAY AND TUESDAY NIGHT AS
FLOW TURNS BACK SOUTH WEDNESDAY AND TEMPS MODIFY BACK INTO THE 30S
THOUGH WITH AN EXPECTED SNOWPACK BY THEN...LOW CONFIDENCE ON HOW
WARM TEMPS WILL BECOME. ANOTHER CLIPPER SYSTEM MOVES ACROSS THE
LAKES REGION WEDNESDAY NIGHT AND THURSDAY...WITH A CHANCE OF LIGHT
RAIN OR LIGHT SNOW WEDNESDAY NIGHT INTO THURSDAY MORNING. CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* MVFR CIGS POSSIBLE AGAIN LATE TONIGHT INTO SATURDAY

IZZI

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS MORNING CONTINUED TO SHOW CONSIDERABLE CLOUD
COVER ACROSS THE REGION...WITH SOME CLEARING NOTED ACROSS EASTERN
IOWA. AS THE DAY HAS PROGRESSED SOME THINNING HAS BEGUN TO TAKE
PLACE ACROSS FAR NORTH/NORTHEAST ILLINOIS...AND MAY EVENTUALLY
MAKE IT INTO THE TAF SITES. AT THIS TIME THOUGH HAVE HELD ONTO THE
LOW CLOUDS THRU 00Z...WITH A SLOW IMPROVEMENT TOWARDS 2000-2500FT
AGL AFT 02Z. WINDS WILL CONTINUE TO BE SOUTHWESTERLY WITH SPEEDS
GENERALLY FROM 10-13KT. THRU THE AFTN ON OCCASION GUSTS MAY
OCCUR...AND NOT EXPECTED TO BE VERY FREQUENT WITH SPEEDS UP TO
17KT.

WITH A FRONTAL BOUNDARY SLIDING SOUTHEAST THIS EVENING...THERE IS
THE POTENTIAL FOR A FEW FLURRIES ACROSS ORD/MDW/DPA. ELSEWHERE
SHOULD BE TOO FAR REMOVED FROM THE BETTER MOISTURE TO SEE ANY
FLURRIES. THOUGH HAVE HELD ONTO A DRY FORECAST AS THIS TOO IS A
LOW CONFIDENCE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* LOW-MEDIUM CONFIDENCE IN CIGS SATURDAY
* HIGH CONFIDENCE IN ALL OTHER ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

SATURDAY NIGHT...SNOW LIKELY AFTER MIDNIGHT. ACCUMULATION LIKELY.
MVFR CIGS AND IFR VIS POSSIBLE.

SUNDAY...SNOW LIKELY. MVFR/IFR LIKELY.

MONDAY...CHANCE OF SNOW SHOWERS. MVFR POSSIBLE.

TUESDAY THROUGH THURSDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
122 PM CST

SOUTHWESTERLY WINDS WILL GRADUALLY WEAKEN TONIGHT...THEN A COLD
FRONT WILL SHIFT OVER THE LAKE ON SATURDAY AS THE PARENT SURFACE LOW
TRACKS ACROSS NORTHERN QUEBEC. THIS WILL SET UP A NORTHERLY FLOW
DOWN THE LAKE LATER SATURDAY. A FAST MOVING STOUT CLIPPER SYSTEM
WILL MOVE SOUTH OF THE LAKE ON SUNDAY MORNING...AND THIS LOOKS TO
SET THE STAGE FOR A PERIOD OF STRONG NORTHEASTERLY WINDS UP AROUND
30 KT OVER THE LAKE. THIS WILL LIKELY PRODUCE HIGH WAVES OVER 5 FEET
ACROSS MUCH OF SOUTHERN END OF LAKE MICHIGAN SUNDAY AND SUNDAY NIGHT.
FOLLOWING THIS SYSTEM...ANOTHER STORM SYSTEM IS EXPECTED TO IMPACT
THE GREAT LAKES REGION FOR THE MIDDLE TO END OF NEXT WEEK. IT
APPEARS THIS COULD PRODUCE SOUTHERLY GALE FORCE WINDS OVER MUCH OF
THE LAKE LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A PERIOD
OF POTENTIALLY GALE FORCE NORTHERLY WINDS THURSDAY AS THE SYSTEM
PASSES OVER THE EASTERN LAKES.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 232105
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
305 PM CST FRI JAN 23 2015

.SHORT TERM...

TONIGHT AND SATURDAY...

305 PM...NO CONCERNS THROUGH SATURDAY EVENING. LOW CLOUDS CONTINUE
TO ERODE FROM THE NORTH AND THE SOUTHWEST THIS AFTERNOON. THIS
TREND WILL CONTINUE THIS EVENING AS THE BACK EDGE PUSHES EAST.
HOWEVER...AN EXTENSIVE BAND OF MID CLOUDS WILL SPREAD BACK ACROSS
THE AREA THIS EVENING AHEAD OF AN APPROACHING COLD FRONT. VERY
LIMITED MOISTURE WITH THIS FRONT AND NOT EXPECTING ANY PRECIP
THOUGH A SPRINKLE OR FLURRY CAN/T BE COMPLETED RULED OUT...BUT NO
MENTION IN THE FORECAST. CLOUD COVER HELPED HOLD HIGHS TODAY IN
THE LOWER/MID 30S AND WITH SOME PARTIAL CLEARING AT TIMES...EXPECT
LOWS TONIGHT TO DIP INTO THE MID/UPPER 20S...THOUGH SOME
UNCERTAINTY WITH APPROACHING MID CLOUDS AND THEN ANOTHER AREA OF
LOW CLOUDS OVER THE UPPER MIDWEST WHICH WILL BE SPREADING SOUTH
ACROSS THE AREA SATURDAY MORNING. IF THIS CLOUD COVER DOES BECOME
OVERCAST...HIGHS ON SATURDAY WILL LIKELY BE TEMPERED SOME AS
WELL...PERHAPS ONLY IN THE MID 30S. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH FRIDAY...

305 PM...MAIN FORECAST CONCERN IS ACCUMULATING SNOW LATE SATURDAY
NIGHT THROUGH SUNDAY AFTERNOON...WITH POSSIBLE LAKE EFFECT SNOW
SHOWERS SUNDAY NIGHT AND ANOTHER WEAKER CLIPPER SYSTEM MONDAY
NIGHT...FOLLOWED BY MODERATE/MILD TEMPS MIDDLE OF NEXT WEEK.

DECENT AGREEMENT WITH THE TRACK OF THE SURFACE LOW OF THE NEXT
CLIPPER SYSTEM SATURDAY NIGHT INTO SUNDAY WITH THE 12Z GFS A BIT
FURTHER SOUTHWEST OF THE REST OF THE MODELS...WHICH TRACK THE LOW
FROM ROUGHLY MLI TO IND SUNDAY MORNING. THERMAL PROFILES SUGGEST
PRECIP TYPE WILL BE ALL SNOW...BUT INITIALLY COULD BE SOME RAIN
MIXED IN ACROSS THE SOUTHERN CWA. IN ADDITION...SNOW/WATER RATIOS
COULD BE RATHER LOW TO START...YIELDING A WETTER SNOW. BUT AS THE
LOW TRACKS TO THE SOUTHEAST...COLDER AIR WILL SLOWLY SPREAD ACROSS
THE AREA WITH THE SNOW LIKELY BECOMING DRIER BY LATE MORNING AND
INTO THE AFTERNOON. THIS MAKES SNOWFALL AMOUNTS A BIT TRICKY...
ESPECIALLY IF THE TRACK OF THE LOW ENDS UP A LITTLE FURTHER SOUTH
AS THE GFS SUGGESTS...COLDER AIR WOULD ARRIVE SOONER. POSSIBLE
LAKE ENHANCEMENT WITH NORTHEAST FLOW ALSO ADDS TO THE UNCERTAINTY
REGARDING AMOUNTS. THEREFORE...DIDN/T MAKE ANY SIGNIFICANT
CHANGES TO THE GOING FORECAST WITH 2-4 INCHES NORTH OF A SQI/IKK
LINE...1-2 INCHES SOUTH OF THAT LINE. BUT AS IS ALWAYS THE
CASE...MINOR CHANGES IN THE TRACK COULD CAUSE LARGE CHANGES TO THE
FORECAST AS TRENDS EMERGE.

TEMPERATURES BEGIN TO FALL BY MID/LATE SUNDAY AFTERNOON ACROSS THE
NORTH. NORTHEASTERLY WINDS INCREASE WITH GUSTS TO 30 MPH AND
DEPENDING ON HOW DRY THE SNOW BECOMES...THERE COULD BE SOME
BLOWING SNOW BUT AGAIN...ITS TOO EARLY FOR SPECIFICS OR HOW MUCH
OF A PROBLEM THIS COULD BECOME.

THE NORTHEAST AND THEN NORTHERLY WINDS MAY ALLOW SOME LAKE EFFECT
SNOW SHOWERS TO DEVELOP SUNDAY EVENING ACROSS NORTHEAST IL AND
THEN INTO NORTHWEST INDIANA. BUT INVERSION HEIGHTS ARE RATHER
LOW...PERHAPS NO HIGHER THAN 4KFT AND WINDS BEGIN TO TURN BACK
EASTERLY BY MONDAY MORNING. THUS ANY LAKE EFFECT POTENTIAL LOOKS
MINIMAL.

ANOTHER CLIPPER QUICKLY DROPS SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT...AS IT BEGINS TO WEAKEN. A
BAND OF LIGHT SNOW IS POSSIBLE WITH THIS FEATURE ESPECIALLY MONDAY
EVENING AND SOME AREAS MAY SEE AN INCH OR TWO DEPENDING ON WHERE
IT TRACKS. HAVE INCLUDED JUST LIGHT QPF AMOUNTS FOR NOW.

HIGH PRESSURE MOVES ACROSS THE AREA TUESDAY AND TUESDAY NIGHT AS
FLOW TURNS BACK SOUTH WEDNESDAY AND TEMPS MODIFY BACK INTO THE 30S
THOUGH WITH AN EXPECTED SNOWPACK BY THEN...LOW CONFIDENCE ON HOW
WARM TEMPS WILL BECOME. ANOTHER CLIPPER SYSTEM MOVES ACROSS THE
LAKES REGION WEDNESDAY NIGHT AND THURSDAY...WITH A CHANCE OF LIGHT
RAIN OR LIGHT SNOW WEDNESDAY NIGHT INTO THURSDAY MORNING. CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* MVFR CIGS ARND 1500-1800FT AGL...SLOWLY LIFTING TO ARND 2KFT AGL
  AFT 00Z.

* SOUTHWEST WINDS ARND 10-14KT WITH OCCASIONAL GUSTS TO 15-17KT
  THRU 00Z.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS MORNING CONTINUED TO SHOW CONSIDERABLE CLOUD
COVER ACROSS THE REGION...WITH SOME CLEARING NOTED ACROSS EASTERN
IOWA. AS THE DAY HAS PROGRESSED SOME THINNING HAS BEGUN TO TAKE
PLACE ACROSS FAR NORTH/NORTHEAST ILLINOIS...AND MAY EVENTUALLY
MAKE IT INTO THE TAF SITES. AT THIS TIME THOUGH HAVE HELD ONTO THE
LOW CLOUDS THRU 00Z...WITH A SLOW IMPROVEMENT TOWARDS 2000-2500FT
AGL AFT 02Z. WINDS WILL CONTINUE TO BE SOUTHWESTERLY WITH SPEEDS
GENERALLY FROM 10-13KT. THRU THE AFTN ON OCCASION GUSTS MAY
OCCUR...AND NOT EXPECTED TO BE VERY FREQUENT WITH SPEEDS UP TO
17KT.

WITH A FRONTAL BOUNDARY SLIDING SOUTHEAST THIS EVENING...THERE IS
THE POTENTIAL FOR A FEW FLURRIES ACROSS ORD/MDW/DPA. ELSEWHERE
SHOULD BE TOO FAR REMOVED FROM THE BETTER MOISTURE TO SEE ANY
FLURRIES. THOUGH HAVE HELD ONTO A DRY FORECAST AS THIS TOO IS A
LOW CONFIDENCE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN CIGS REMAINING OVC THRU 23Z...MEDIUM
  CONFIDENCE IN TIMING OF CIGS LIFTING HIGHER.

* HIGH CONFIDENCE IN WIND DIR/SPEED.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

SATURDAY NIGHT...SNOW LIKELY AFTER MIDNIGHT. ACCUMULATION LIKELY.
MVFR CIGS AND IFR VIS POSSIBLE.

SUNDAY...SNOW LIKELY. MVFR/IFR LIKELY.

MONDAY...CHANCE OF SNOW SHOWERS. MVFR POSSIBLE.

TUESDAY THROUGH THURSDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
122 PM CST

SOUTHWESTERLY WINDS WILL GRADUALLY WEAKEN TONIGHT...THEN A COLD
FRONT WILL SHIFT OVER THE LAKE ON SATURDAY AS THE PARENT SURFACE LOW
TRACKS ACROSS NORTHERN QUEBEC. THIS WILL SET UP A NORTHERLY FLOW
DOWN THE LAKE LATER SATURDAY. A FAST MOVING STOUT CLIPPER SYSTEM
WILL MOVE SOUTH OF THE LAKE ON SUNDAY MORNING...AND THIS LOOKS TO
SET THE STAGE FOR A PERIOD OF STRONG NORTHEASTERLY WINDS UP AROUND
30 KT OVER THE LAKE. THIS WILL LIKELY PRODUCE HIGH WAVES OVER 5 FEET
ACROSS MUCH OF SOUTHERN END OF LAKE MICHIGAN SUNDAY AND SUNDAY NIGHT.
FOLLOWING THIS SYSTEM...ANOTHER STORM SYSTEM IS EXPECTED TO IMPACT
THE GREAT LAKES REGION FOR THE MIDDLE TO END OF NEXT WEEK. IT
APPEARS THIS COULD PRODUCE SOUTHERLY GALE FORCE WINDS OVER MUCH OF
THE LAKE LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A PERIOD
OF POTENTIALLY GALE FORCE NORTHERLY WINDS THURSDAY AS THE SYSTEM
PASSES OVER THE EASTERN LAKES.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565 UNTIL 3
     PM FRIDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 232105
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
305 PM CST FRI JAN 23 2015

.SHORT TERM...

TONIGHT AND SATURDAY...

305 PM...NO CONCERNS THROUGH SATURDAY EVENING. LOW CLOUDS CONTINUE
TO ERODE FROM THE NORTH AND THE SOUTHWEST THIS AFTERNOON. THIS
TREND WILL CONTINUE THIS EVENING AS THE BACK EDGE PUSHES EAST.
HOWEVER...AN EXTENSIVE BAND OF MID CLOUDS WILL SPREAD BACK ACROSS
THE AREA THIS EVENING AHEAD OF AN APPROACHING COLD FRONT. VERY
LIMITED MOISTURE WITH THIS FRONT AND NOT EXPECTING ANY PRECIP
THOUGH A SPRINKLE OR FLURRY CAN/T BE COMPLETED RULED OUT...BUT NO
MENTION IN THE FORECAST. CLOUD COVER HELPED HOLD HIGHS TODAY IN
THE LOWER/MID 30S AND WITH SOME PARTIAL CLEARING AT TIMES...EXPECT
LOWS TONIGHT TO DIP INTO THE MID/UPPER 20S...THOUGH SOME
UNCERTAINTY WITH APPROACHING MID CLOUDS AND THEN ANOTHER AREA OF
LOW CLOUDS OVER THE UPPER MIDWEST WHICH WILL BE SPREADING SOUTH
ACROSS THE AREA SATURDAY MORNING. IF THIS CLOUD COVER DOES BECOME
OVERCAST...HIGHS ON SATURDAY WILL LIKELY BE TEMPERED SOME AS
WELL...PERHAPS ONLY IN THE MID 30S. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH FRIDAY...

305 PM...MAIN FORECAST CONCERN IS ACCUMULATING SNOW LATE SATURDAY
NIGHT THROUGH SUNDAY AFTERNOON...WITH POSSIBLE LAKE EFFECT SNOW
SHOWERS SUNDAY NIGHT AND ANOTHER WEAKER CLIPPER SYSTEM MONDAY
NIGHT...FOLLOWED BY MODERATE/MILD TEMPS MIDDLE OF NEXT WEEK.

DECENT AGREEMENT WITH THE TRACK OF THE SURFACE LOW OF THE NEXT
CLIPPER SYSTEM SATURDAY NIGHT INTO SUNDAY WITH THE 12Z GFS A BIT
FURTHER SOUTHWEST OF THE REST OF THE MODELS...WHICH TRACK THE LOW
FROM ROUGHLY MLI TO IND SUNDAY MORNING. THERMAL PROFILES SUGGEST
PRECIP TYPE WILL BE ALL SNOW...BUT INITIALLY COULD BE SOME RAIN
MIXED IN ACROSS THE SOUTHERN CWA. IN ADDITION...SNOW/WATER RATIOS
COULD BE RATHER LOW TO START...YIELDING A WETTER SNOW. BUT AS THE
LOW TRACKS TO THE SOUTHEAST...COLDER AIR WILL SLOWLY SPREAD ACROSS
THE AREA WITH THE SNOW LIKELY BECOMING DRIER BY LATE MORNING AND
INTO THE AFTERNOON. THIS MAKES SNOWFALL AMOUNTS A BIT TRICKY...
ESPECIALLY IF THE TRACK OF THE LOW ENDS UP A LITTLE FURTHER SOUTH
AS THE GFS SUGGESTS...COLDER AIR WOULD ARRIVE SOONER. POSSIBLE
LAKE ENHANCEMENT WITH NORTHEAST FLOW ALSO ADDS TO THE UNCERTAINTY
REGARDING AMOUNTS. THEREFORE...DIDN/T MAKE ANY SIGNIFICANT
CHANGES TO THE GOING FORECAST WITH 2-4 INCHES NORTH OF A SQI/IKK
LINE...1-2 INCHES SOUTH OF THAT LINE. BUT AS IS ALWAYS THE
CASE...MINOR CHANGES IN THE TRACK COULD CAUSE LARGE CHANGES TO THE
FORECAST AS TRENDS EMERGE.

TEMPERATURES BEGIN TO FALL BY MID/LATE SUNDAY AFTERNOON ACROSS THE
NORTH. NORTHEASTERLY WINDS INCREASE WITH GUSTS TO 30 MPH AND
DEPENDING ON HOW DRY THE SNOW BECOMES...THERE COULD BE SOME
BLOWING SNOW BUT AGAIN...ITS TOO EARLY FOR SPECIFICS OR HOW MUCH
OF A PROBLEM THIS COULD BECOME.

THE NORTHEAST AND THEN NORTHERLY WINDS MAY ALLOW SOME LAKE EFFECT
SNOW SHOWERS TO DEVELOP SUNDAY EVENING ACROSS NORTHEAST IL AND
THEN INTO NORTHWEST INDIANA. BUT INVERSION HEIGHTS ARE RATHER
LOW...PERHAPS NO HIGHER THAN 4KFT AND WINDS BEGIN TO TURN BACK
EASTERLY BY MONDAY MORNING. THUS ANY LAKE EFFECT POTENTIAL LOOKS
MINIMAL.

ANOTHER CLIPPER QUICKLY DROPS SOUTHEAST ACROSS THE WESTERN LAKES
MONDAY AFTERNOON INTO MONDAY NIGHT...AS IT BEGINS TO WEAKEN. A
BAND OF LIGHT SNOW IS POSSIBLE WITH THIS FEATURE ESPECIALLY MONDAY
EVENING AND SOME AREAS MAY SEE AN INCH OR TWO DEPENDING ON WHERE
IT TRACKS. HAVE INCLUDED JUST LIGHT QPF AMOUNTS FOR NOW.

HIGH PRESSURE MOVES ACROSS THE AREA TUESDAY AND TUESDAY NIGHT AS
FLOW TURNS BACK SOUTH WEDNESDAY AND TEMPS MODIFY BACK INTO THE 30S
THOUGH WITH AN EXPECTED SNOWPACK BY THEN...LOW CONFIDENCE ON HOW
WARM TEMPS WILL BECOME. ANOTHER CLIPPER SYSTEM MOVES ACROSS THE
LAKES REGION WEDNESDAY NIGHT AND THURSDAY...WITH A CHANCE OF LIGHT
RAIN OR LIGHT SNOW WEDNESDAY NIGHT INTO THURSDAY MORNING. CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* MVFR CIGS ARND 1500-1800FT AGL...SLOWLY LIFTING TO ARND 2KFT AGL
  AFT 00Z.

* SOUTHWEST WINDS ARND 10-14KT WITH OCCASIONAL GUSTS TO 15-17KT
  THRU 00Z.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS MORNING CONTINUED TO SHOW CONSIDERABLE CLOUD
COVER ACROSS THE REGION...WITH SOME CLEARING NOTED ACROSS EASTERN
IOWA. AS THE DAY HAS PROGRESSED SOME THINNING HAS BEGUN TO TAKE
PLACE ACROSS FAR NORTH/NORTHEAST ILLINOIS...AND MAY EVENTUALLY
MAKE IT INTO THE TAF SITES. AT THIS TIME THOUGH HAVE HELD ONTO THE
LOW CLOUDS THRU 00Z...WITH A SLOW IMPROVEMENT TOWARDS 2000-2500FT
AGL AFT 02Z. WINDS WILL CONTINUE TO BE SOUTHWESTERLY WITH SPEEDS
GENERALLY FROM 10-13KT. THRU THE AFTN ON OCCASION GUSTS MAY
OCCUR...AND NOT EXPECTED TO BE VERY FREQUENT WITH SPEEDS UP TO
17KT.

WITH A FRONTAL BOUNDARY SLIDING SOUTHEAST THIS EVENING...THERE IS
THE POTENTIAL FOR A FEW FLURRIES ACROSS ORD/MDW/DPA. ELSEWHERE
SHOULD BE TOO FAR REMOVED FROM THE BETTER MOISTURE TO SEE ANY
FLURRIES. THOUGH HAVE HELD ONTO A DRY FORECAST AS THIS TOO IS A
LOW CONFIDENCE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN CIGS REMAINING OVC THRU 23Z...MEDIUM
  CONFIDENCE IN TIMING OF CIGS LIFTING HIGHER.

* HIGH CONFIDENCE IN WIND DIR/SPEED.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

SATURDAY NIGHT...SNOW LIKELY AFTER MIDNIGHT. ACCUMULATION LIKELY.
MVFR CIGS AND IFR VIS POSSIBLE.

SUNDAY...SNOW LIKELY. MVFR/IFR LIKELY.

MONDAY...CHANCE OF SNOW SHOWERS. MVFR POSSIBLE.

TUESDAY THROUGH THURSDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
122 PM CST

SOUTHWESTERLY WINDS WILL GRADUALLY WEAKEN TONIGHT...THEN A COLD
FRONT WILL SHIFT OVER THE LAKE ON SATURDAY AS THE PARENT SURFACE LOW
TRACKS ACROSS NORTHERN QUEBEC. THIS WILL SET UP A NORTHERLY FLOW
DOWN THE LAKE LATER SATURDAY. A FAST MOVING STOUT CLIPPER SYSTEM
WILL MOVE SOUTH OF THE LAKE ON SUNDAY MORNING...AND THIS LOOKS TO
SET THE STAGE FOR A PERIOD OF STRONG NORTHEASTERLY WINDS UP AROUND
30 KT OVER THE LAKE. THIS WILL LIKELY PRODUCE HIGH WAVES OVER 5 FEET
ACROSS MUCH OF SOUTHERN END OF LAKE MICHIGAN SUNDAY AND SUNDAY NIGHT.
FOLLOWING THIS SYSTEM...ANOTHER STORM SYSTEM IS EXPECTED TO IMPACT
THE GREAT LAKES REGION FOR THE MIDDLE TO END OF NEXT WEEK. IT
APPEARS THIS COULD PRODUCE SOUTHERLY GALE FORCE WINDS OVER MUCH OF
THE LAKE LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A PERIOD
OF POTENTIALLY GALE FORCE NORTHERLY WINDS THURSDAY AS THE SYSTEM
PASSES OVER THE EASTERN LAKES.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565 UNTIL 3
     PM FRIDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 231935
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
135 PM CST FRI JAN 23 2015

.SHORT TERM...
302 AM CST

THROUGH SATURDAY...

EARLY MORNING WATER VAPOR IMAGERY SHOWS A CLOSED UPPER LOW
SPINNING OVER TEXAS AS PART OF A LARGER SCALE TROUGH THAT IS CUT
OFF FROM THE MAIN STREAM OF FLOW TO THE NORTH. THIS MAIN STREAM IS
POSITIONED ACROSS SOUTHERN CANADA WITH WITH SEVERAL EMBEDDED WAVES
TRACKING ACROSS MANITOBA AND SASKATCHEWAN TOWARD THE UPPER MIDWEST
AND UPPER GREAT LAKES. FURTHER WEST...LOW AMPLITUDE RIDGING IS
POSITIONED OVER THE WEST COAST WITH A WELL- DEFINED TROUGH MOVING
EASTWARD TOWARDS BRITISH COLUMBIA. AT THE SURFACE...HIGH PRESSURE
IS STRETCHED FROM THE SOUTHERN PLAINS TO NEW ENGLAND WITH A
SURFACE LOW OFF THE LOUISIANA COAST IN CONJUNCTION WITH THE TEXAS
UPPER LOW. ANOTHER SURFACE LOW IS OVER NORTHERN ONTARIO IN
CONJUNCTION WITH ONE OF THE WAVES OVER CENTRAL CANADA WITH A
TROUGH AXIS EXTENDING SOUTHWARD ACROSS THE NORTHERN PLAINS.
ABUNDANT BUT THIN CLOUD COVER REMAINS ACROSS THE REGION WITH
SATELLITE SHOWING VERY SLOW EASTWARD MOVEMENT...WITH THE BACK EDGE
STILL ACROSS EASTERN IOWA.

THE CLOUD COVER WILL BE THE MAIN CHALLENGE TODAY. FORECAST SOUNDINGS
SHOW A MIX OF THOUGHTS ON HOW LONG CLOUD COVER WILL HANG ON AND DO
NOT SEE MUCH IMPROVEMENT THROUGH LATE MORNING...THOUGH WESTERN AREAS
HAVE THE BEST CHANCE FOR SCATTERING BY MIDDAY. THE PRESSURE GRADIENT
WILL BEGIN TO TIGHTEN UP AS THE ONTARIO SURFACE LOW MOVES EAST AND
THE ASSOCIATED TROUGH APPROACHES. THIS WILL ALLOW FOR STEADIER
SOUTHWEST WINDS TO DEVELOP. WITH THE IDEA THAT CLOUDS WILL HANG ON
THROUGH THE MORNING THEN SCATTER THIS AFTERNOON...HIGH TEMPS WILL
PROBABLY STRUGGLE DESPITE THE SOUTHWEST WINDS AND MODEST WARM
ADVECTION ALOFT. WILL CONTINUE WITH MID AND UPPER 30S FOR NOW BUT IF
SUN CAN MAKE AN APPEARANCE FOR SEVERAL HOURS THIS AFTERNOON THEN
HIGHS AROUND 40/LOW 40S WOULD BE PLAUSIBLE. A BAND OF MID CLOUDS
WILL ACCOMPANY THE TROUGH PASSAGE EARLY THIS EVENING WITH A FEW
FLURRIES NOT OUT OF THE QUESTION. WINDS TURN NORTHWEST TONIGHT AND
SATURDAY MORNING WITH COOL ADVECTION OCCURRING. CLOUD COVER LOOKS
ABUNDANT SO HIGHS WILL LIKELY BE HELD IN THE MID/UPPER 30S.

MDB

&&

.LONG TERM...
302 AM CST

SATURDAY NIGHT THROUGH MONDAY...ATTENTION TURNS TO THE UPPER TROUGH
OFF THE BRITISH COLUMBIA COAST THIS MORNING. A SHORTWAVE EJECTS FROM
THIS TROUGH AND TRACKS EAST THEN SOUTHEAST AND ACROSS THE LOCAL AREA
EARLY SUNDAY. SURFACE LOW PRESSURE DEVELOPS AND PASSES WITH THE
UPPER TROUGH DURING THE DAY SUNDAY. GUIDANCE CONTINUES TO DISAGREE
ON THE STRENGTH AND TRACK OF THE SYSTEM WITH RECENT RUNS SHOWING
QUITE A BIT OF VARIATION. THESE NORTHWEST SYSTEMS HAVE HAD A
TENDENCY TO TRACK FURTHER SOUTH OR SOUTH AND WEST THAN DEPICTED
AHEAD OF TIME SO WILL NEED TO KEEP A CLOSE EYE ON THE WAVE AS IT
MOVES ONSHORE OVER BRITISH COLUMBIA LATER TONIGHT. AT THIS POINT...A
LOW TRACK ACROSS NORTHWEST OR WEST-CENTRAL ILLINOIS...SIMILAR TO THE
00Z GFS/ECMWF...LOOKS TO BE FAVORED WHEN CONSIDERING THE CURRENT AND
EXPECTED UPPER FLOW PATTERN. WITH WESTERN RIDGING EXPECTED TO
SHARPEN AS MORE PACIFIC ENERGY PUSHES INTO IT FROM THE WEST...THE
FLOW OVER THE ROCKIES/PLAINS WILL TURN MORE NORTHWESTERLY. ONE COULD
MAKE THE CASE THAT IF THE WAVE WERE TO TRACK THROUGH THE CURRENT
UPPER FLOW PATTERN IT WOULD TAKE A TRACK ACROSS THE AREA SO A MORE
NORTHWESTERLY FLOW WOULD SUPPORT A MORE WESTERN TRACK. A TRACK
FURTHER NORTH/EAST SEEMS UNLIKELY BUT WOULD NOT BE SURPRISED TO SEE
IT TRACK WEST OF THE TRACK OF THE 00Z GFS/ECMWF BASED ON THE
ABOVE. GIVEN THE PACIFIC ORIGINS OF THE SYSTEM THERE WILL BE
MOISTURE TO WORK WITH SO PRECIPITATION IS LIKELY WITH IT AND SHOULD
AFFECT MOST OF THE AREA UNLESS A WILD SWING IN THE TRACK OCCURS.
PRECIP TYPE MAY BE MIXED FOR A TIME AT ONSET...MAINLY SOUTH AND WEST
WITH A MORE SOUTH/WEST TRACK LEADING TO MAINLY SNOW FOR MUCH OF THE
AREA. THE 00Z RUN OF THE GFS/ECMWF SUGGEST A MIX EARLY SOUTH AS A
NOSE OF WARM AIR BRIEFLY BUILDS IN BEFORE COLD AIR FILLS IN AGAIN.
BASED ON PRECIPITABLE WATER VALUES AND DURATION OF FORCING THE HEART
OF THE SYSTEM LOOKS TO BE ABLE TO PRODUCE 0.3 TO PERHAPS 0.4 INCHES
OF LIQUID EQUIVALENT PRECIP WITH IT BECOMING A MATTER OF WHERE THE
HEART OF THE SYSTEM  TRACKS.

ANOTHER ISSUE WILL BE THE POTENTIAL FOR LAKE ENHANCEMENT AS THE LOW
PASSES SUNDAY AFTERNOON/EVENING. A LOW TRACK TO THE SOUTH AND WEST
OF THE AREA WOULD BE SUPPORTIVE OF LAKE ENHANCEMENT OF SYNOPTIC
PRECIP ON THE BACK SIDE WITH THE COLUMN COLD ENOUGH TO SUPPORT SNOW
IN THIS SCENARIO. HIGH PRESSURE MOVES SOUTHWARD ACROSS ONTARIO INTO
MONDAY WITH ANOTHER SURFACE LOW/ELONGATED TROUGH STRETCHING FROM
MANITOBA TO THE CENTRAL PLAINS WHICH WILL TURN WINDS MORE EASTERLY
THEN SOUTHERLY INTO MONDAY EVENING. WITH FORECAST SOUNDINGS SHOWING
MARGINAL INVERSION HEIGHTS BUT SUFFICIENT DELTA T`S...MAY SEE A
SITUATION SIMILAR TO LAST WEEK WHERE LAKE EFFECT SNOW SHOWERS
PERSISTED IN THE EASTERLY LOW LEVEL FLOW BEFORE ENDING. THIS COULD
BE THE CASE FOR MUCH OF MONDAY. AS FAR AS TEMPS...HIGHS SUNDAY WILL
BE DICTATED BY THE LOW TRACK AND MONDAY LOOKS TO ONLY SEE HIGHS IN
THE 20S THANKS TO COLD ADVECTION.

TUESDAY THROUGH THURSDAY...BROAD RIDGING WEST AND TROUGHING EAST
WILL LEAVE THE LOCAL AREA UNDER A SHARP NORTHERLY UPPER FLOW
TUESDAY WITH HIGH PRESSURE AT THE SURFACE. THE RIDGING WILL
QUICKLY SHIFT EAST AND DE-AMPLIFY WEDNESDAY ALLOWING MILDER AIR TO
RETURN. THE FLOW MAY BE SOMEWHAT ACTIVE BUT PRECIP DETAILS ARE NOT
CLEAR AT THIS RANGE...THOUGH HAVE DECENT CONFIDENCE IN FAIRLY MILD
TEMPERATURES.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* MVFR CIGS ARND 1500-1800FT AGL...SLOWLY LIFTING TO ARND 2KFT AGL
  AFT 00Z.

* SOUTHWEST WINDS ARND 10-14KT WITH OCCASIONAL GUSTS TO 15-17KT
  THRU 00Z.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS MORNING CONTINUED TO SHOW CONSIDERABLE CLOUD
COVER ACROSS THE REGION...WITH SOME CLEARING NOTED ACROSS EASTERN
IOWA. AS THE DAY HAS PROGRESSED SOME THINNING HAS BEGUN TO TAKE
PLACE ACROSS FAR NORTH/NORTHEAST ILLINOIS...AND MAY EVENTUALLY
MAKE IT INTO THE TAF SITES. AT THIS TIME THOUGH HAVE HELD ONTO THE
LOW CLOUDS THRU 00Z...WITH A SLOW IMPROVEMENT TOWARDS 2000-2500FT
AGL AFT 02Z. WINDS WILL CONTINUE TO BE SOUTHWESTERLY WITH SPEEDS
GENERALLY FROM 10-13KT. THRU THE AFTN ON OCCASION GUSTS MAY
OCCUR...AND NOT EXPECTED TO BE VERY FREQUENT WITH SPEEDS UP TO
17KT.

WITH A FRONTAL BOUNDARY SLIDING SOUTHEAST THIS EVENING...THERE IS
THE POTENTIAL FOR A FEW FLURRIES ACROSS ORD/MDW/DPA. ELSEWHERE
SHOULD BE TOO FAR REMOVED FROM THE BETTER MOISTURE TO SEE ANY
FLURRIES. THOUGH HAVE HELD ONTO A DRY FORECAST AS THIS TOO IS A
LOW CONFIDENCE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN CIGS REMAINING OVC THRU 23Z...MEDIUM
  CONFIDENCE IN TIMING OF CIGS LIFTING HIGHER.

* HIGH CONFIDENCE IN WIND DIR/SPEED.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

SATURDAY NIGHT...SNOW LIKELY AFTER MIDNIGHT. ACCUMULATION LIKELY.
MVFR CIGS AND IFR VIS POSSIBLE.

SUNDAY...SNOW LIKELY. MVFR/IFR LIKELY.

MONDAY...CHANCE OF SNOW SHOWERS. MVFR POSSIBLE.

TUESDAY THROUGH THURSDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
122 PM CST

SOUTHWESTERLY WINDS WILL GRADUALLY WEAKEN TONIGHT...THEN A COLD
FRONT WILL SHIFT OVER THE LAKE ON SATURDAY AS THE PARENT SURFACE LOW
TRACKS ACROSS NORTHERN QUEBEC. THIS WILL SET UP A NORTHERLY FLOW
DOWN THE LAKE LATER SATURDAY. A FAST MOVING STOUT CLIPPER SYSTEM
WILL MOVE SOUTH OF THE LAKE ON SUNDAY MORNING...AND THIS LOOKS TO
SET THE STAGE FOR A PERIOD OF STRONG NORTHEASTERLY WINDS UP AROUND
30 KT OVER THE LAKE. THIS WILL LIKELY PRODUCE HIGH WAVES OVER 5 FEET
ACROSS MUCH OF SOUTHERN END OF LAKE MICHIGAN SUNDAY AND SUNDAY NIGHT.
FOLLOWING THIS SYSTEM...ANOTHER STORM SYSTEM IS EXPECTED TO IMPACT
THE GREAT LAKES REGION FOR THE MIDDLE TO END OF NEXT WEEK. IT
APPEARS THIS COULD PRODUCE SOUTHERLY GALE FORCE WINDS OVER MUCH OF
THE LAKE LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A PERIOD
OF POTENTIALLY GALE FORCE NORTHERLY WINDS THURSDAY AS THE SYSTEM
PASSES OVER THE EASTERN LAKES.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565 UNTIL 3
     PM FRIDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 231935
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
135 PM CST FRI JAN 23 2015

.SHORT TERM...
302 AM CST

THROUGH SATURDAY...

EARLY MORNING WATER VAPOR IMAGERY SHOWS A CLOSED UPPER LOW
SPINNING OVER TEXAS AS PART OF A LARGER SCALE TROUGH THAT IS CUT
OFF FROM THE MAIN STREAM OF FLOW TO THE NORTH. THIS MAIN STREAM IS
POSITIONED ACROSS SOUTHERN CANADA WITH WITH SEVERAL EMBEDDED WAVES
TRACKING ACROSS MANITOBA AND SASKATCHEWAN TOWARD THE UPPER MIDWEST
AND UPPER GREAT LAKES. FURTHER WEST...LOW AMPLITUDE RIDGING IS
POSITIONED OVER THE WEST COAST WITH A WELL- DEFINED TROUGH MOVING
EASTWARD TOWARDS BRITISH COLUMBIA. AT THE SURFACE...HIGH PRESSURE
IS STRETCHED FROM THE SOUTHERN PLAINS TO NEW ENGLAND WITH A
SURFACE LOW OFF THE LOUISIANA COAST IN CONJUNCTION WITH THE TEXAS
UPPER LOW. ANOTHER SURFACE LOW IS OVER NORTHERN ONTARIO IN
CONJUNCTION WITH ONE OF THE WAVES OVER CENTRAL CANADA WITH A
TROUGH AXIS EXTENDING SOUTHWARD ACROSS THE NORTHERN PLAINS.
ABUNDANT BUT THIN CLOUD COVER REMAINS ACROSS THE REGION WITH
SATELLITE SHOWING VERY SLOW EASTWARD MOVEMENT...WITH THE BACK EDGE
STILL ACROSS EASTERN IOWA.

THE CLOUD COVER WILL BE THE MAIN CHALLENGE TODAY. FORECAST SOUNDINGS
SHOW A MIX OF THOUGHTS ON HOW LONG CLOUD COVER WILL HANG ON AND DO
NOT SEE MUCH IMPROVEMENT THROUGH LATE MORNING...THOUGH WESTERN AREAS
HAVE THE BEST CHANCE FOR SCATTERING BY MIDDAY. THE PRESSURE GRADIENT
WILL BEGIN TO TIGHTEN UP AS THE ONTARIO SURFACE LOW MOVES EAST AND
THE ASSOCIATED TROUGH APPROACHES. THIS WILL ALLOW FOR STEADIER
SOUTHWEST WINDS TO DEVELOP. WITH THE IDEA THAT CLOUDS WILL HANG ON
THROUGH THE MORNING THEN SCATTER THIS AFTERNOON...HIGH TEMPS WILL
PROBABLY STRUGGLE DESPITE THE SOUTHWEST WINDS AND MODEST WARM
ADVECTION ALOFT. WILL CONTINUE WITH MID AND UPPER 30S FOR NOW BUT IF
SUN CAN MAKE AN APPEARANCE FOR SEVERAL HOURS THIS AFTERNOON THEN
HIGHS AROUND 40/LOW 40S WOULD BE PLAUSIBLE. A BAND OF MID CLOUDS
WILL ACCOMPANY THE TROUGH PASSAGE EARLY THIS EVENING WITH A FEW
FLURRIES NOT OUT OF THE QUESTION. WINDS TURN NORTHWEST TONIGHT AND
SATURDAY MORNING WITH COOL ADVECTION OCCURRING. CLOUD COVER LOOKS
ABUNDANT SO HIGHS WILL LIKELY BE HELD IN THE MID/UPPER 30S.

MDB

&&

.LONG TERM...
302 AM CST

SATURDAY NIGHT THROUGH MONDAY...ATTENTION TURNS TO THE UPPER TROUGH
OFF THE BRITISH COLUMBIA COAST THIS MORNING. A SHORTWAVE EJECTS FROM
THIS TROUGH AND TRACKS EAST THEN SOUTHEAST AND ACROSS THE LOCAL AREA
EARLY SUNDAY. SURFACE LOW PRESSURE DEVELOPS AND PASSES WITH THE
UPPER TROUGH DURING THE DAY SUNDAY. GUIDANCE CONTINUES TO DISAGREE
ON THE STRENGTH AND TRACK OF THE SYSTEM WITH RECENT RUNS SHOWING
QUITE A BIT OF VARIATION. THESE NORTHWEST SYSTEMS HAVE HAD A
TENDENCY TO TRACK FURTHER SOUTH OR SOUTH AND WEST THAN DEPICTED
AHEAD OF TIME SO WILL NEED TO KEEP A CLOSE EYE ON THE WAVE AS IT
MOVES ONSHORE OVER BRITISH COLUMBIA LATER TONIGHT. AT THIS POINT...A
LOW TRACK ACROSS NORTHWEST OR WEST-CENTRAL ILLINOIS...SIMILAR TO THE
00Z GFS/ECMWF...LOOKS TO BE FAVORED WHEN CONSIDERING THE CURRENT AND
EXPECTED UPPER FLOW PATTERN. WITH WESTERN RIDGING EXPECTED TO
SHARPEN AS MORE PACIFIC ENERGY PUSHES INTO IT FROM THE WEST...THE
FLOW OVER THE ROCKIES/PLAINS WILL TURN MORE NORTHWESTERLY. ONE COULD
MAKE THE CASE THAT IF THE WAVE WERE TO TRACK THROUGH THE CURRENT
UPPER FLOW PATTERN IT WOULD TAKE A TRACK ACROSS THE AREA SO A MORE
NORTHWESTERLY FLOW WOULD SUPPORT A MORE WESTERN TRACK. A TRACK
FURTHER NORTH/EAST SEEMS UNLIKELY BUT WOULD NOT BE SURPRISED TO SEE
IT TRACK WEST OF THE TRACK OF THE 00Z GFS/ECMWF BASED ON THE
ABOVE. GIVEN THE PACIFIC ORIGINS OF THE SYSTEM THERE WILL BE
MOISTURE TO WORK WITH SO PRECIPITATION IS LIKELY WITH IT AND SHOULD
AFFECT MOST OF THE AREA UNLESS A WILD SWING IN THE TRACK OCCURS.
PRECIP TYPE MAY BE MIXED FOR A TIME AT ONSET...MAINLY SOUTH AND WEST
WITH A MORE SOUTH/WEST TRACK LEADING TO MAINLY SNOW FOR MUCH OF THE
AREA. THE 00Z RUN OF THE GFS/ECMWF SUGGEST A MIX EARLY SOUTH AS A
NOSE OF WARM AIR BRIEFLY BUILDS IN BEFORE COLD AIR FILLS IN AGAIN.
BASED ON PRECIPITABLE WATER VALUES AND DURATION OF FORCING THE HEART
OF THE SYSTEM LOOKS TO BE ABLE TO PRODUCE 0.3 TO PERHAPS 0.4 INCHES
OF LIQUID EQUIVALENT PRECIP WITH IT BECOMING A MATTER OF WHERE THE
HEART OF THE SYSTEM  TRACKS.

ANOTHER ISSUE WILL BE THE POTENTIAL FOR LAKE ENHANCEMENT AS THE LOW
PASSES SUNDAY AFTERNOON/EVENING. A LOW TRACK TO THE SOUTH AND WEST
OF THE AREA WOULD BE SUPPORTIVE OF LAKE ENHANCEMENT OF SYNOPTIC
PRECIP ON THE BACK SIDE WITH THE COLUMN COLD ENOUGH TO SUPPORT SNOW
IN THIS SCENARIO. HIGH PRESSURE MOVES SOUTHWARD ACROSS ONTARIO INTO
MONDAY WITH ANOTHER SURFACE LOW/ELONGATED TROUGH STRETCHING FROM
MANITOBA TO THE CENTRAL PLAINS WHICH WILL TURN WINDS MORE EASTERLY
THEN SOUTHERLY INTO MONDAY EVENING. WITH FORECAST SOUNDINGS SHOWING
MARGINAL INVERSION HEIGHTS BUT SUFFICIENT DELTA T`S...MAY SEE A
SITUATION SIMILAR TO LAST WEEK WHERE LAKE EFFECT SNOW SHOWERS
PERSISTED IN THE EASTERLY LOW LEVEL FLOW BEFORE ENDING. THIS COULD
BE THE CASE FOR MUCH OF MONDAY. AS FAR AS TEMPS...HIGHS SUNDAY WILL
BE DICTATED BY THE LOW TRACK AND MONDAY LOOKS TO ONLY SEE HIGHS IN
THE 20S THANKS TO COLD ADVECTION.

TUESDAY THROUGH THURSDAY...BROAD RIDGING WEST AND TROUGHING EAST
WILL LEAVE THE LOCAL AREA UNDER A SHARP NORTHERLY UPPER FLOW
TUESDAY WITH HIGH PRESSURE AT THE SURFACE. THE RIDGING WILL
QUICKLY SHIFT EAST AND DE-AMPLIFY WEDNESDAY ALLOWING MILDER AIR TO
RETURN. THE FLOW MAY BE SOMEWHAT ACTIVE BUT PRECIP DETAILS ARE NOT
CLEAR AT THIS RANGE...THOUGH HAVE DECENT CONFIDENCE IN FAIRLY MILD
TEMPERATURES.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* MVFR CIGS ARND 1500-1800FT AGL...SLOWLY LIFTING TO ARND 2KFT AGL
  AFT 00Z.

* SOUTHWEST WINDS ARND 10-14KT WITH OCCASIONAL GUSTS TO 15-17KT
  THRU 00Z.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS MORNING CONTINUED TO SHOW CONSIDERABLE CLOUD
COVER ACROSS THE REGION...WITH SOME CLEARING NOTED ACROSS EASTERN
IOWA. AS THE DAY HAS PROGRESSED SOME THINNING HAS BEGUN TO TAKE
PLACE ACROSS FAR NORTH/NORTHEAST ILLINOIS...AND MAY EVENTUALLY
MAKE IT INTO THE TAF SITES. AT THIS TIME THOUGH HAVE HELD ONTO THE
LOW CLOUDS THRU 00Z...WITH A SLOW IMPROVEMENT TOWARDS 2000-2500FT
AGL AFT 02Z. WINDS WILL CONTINUE TO BE SOUTHWESTERLY WITH SPEEDS
GENERALLY FROM 10-13KT. THRU THE AFTN ON OCCASION GUSTS MAY
OCCUR...AND NOT EXPECTED TO BE VERY FREQUENT WITH SPEEDS UP TO
17KT.

WITH A FRONTAL BOUNDARY SLIDING SOUTHEAST THIS EVENING...THERE IS
THE POTENTIAL FOR A FEW FLURRIES ACROSS ORD/MDW/DPA. ELSEWHERE
SHOULD BE TOO FAR REMOVED FROM THE BETTER MOISTURE TO SEE ANY
FLURRIES. THOUGH HAVE HELD ONTO A DRY FORECAST AS THIS TOO IS A
LOW CONFIDENCE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN CIGS REMAINING OVC THRU 23Z...MEDIUM
  CONFIDENCE IN TIMING OF CIGS LIFTING HIGHER.

* HIGH CONFIDENCE IN WIND DIR/SPEED.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

SATURDAY NIGHT...SNOW LIKELY AFTER MIDNIGHT. ACCUMULATION LIKELY.
MVFR CIGS AND IFR VIS POSSIBLE.

SUNDAY...SNOW LIKELY. MVFR/IFR LIKELY.

MONDAY...CHANCE OF SNOW SHOWERS. MVFR POSSIBLE.

TUESDAY THROUGH THURSDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
122 PM CST

SOUTHWESTERLY WINDS WILL GRADUALLY WEAKEN TONIGHT...THEN A COLD
FRONT WILL SHIFT OVER THE LAKE ON SATURDAY AS THE PARENT SURFACE LOW
TRACKS ACROSS NORTHERN QUEBEC. THIS WILL SET UP A NORTHERLY FLOW
DOWN THE LAKE LATER SATURDAY. A FAST MOVING STOUT CLIPPER SYSTEM
WILL MOVE SOUTH OF THE LAKE ON SUNDAY MORNING...AND THIS LOOKS TO
SET THE STAGE FOR A PERIOD OF STRONG NORTHEASTERLY WINDS UP AROUND
30 KT OVER THE LAKE. THIS WILL LIKELY PRODUCE HIGH WAVES OVER 5 FEET
ACROSS MUCH OF SOUTHERN END OF LAKE MICHIGAN SUNDAY AND SUNDAY NIGHT.
FOLLOWING THIS SYSTEM...ANOTHER STORM SYSTEM IS EXPECTED TO IMPACT
THE GREAT LAKES REGION FOR THE MIDDLE TO END OF NEXT WEEK. IT
APPEARS THIS COULD PRODUCE SOUTHERLY GALE FORCE WINDS OVER MUCH OF
THE LAKE LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A PERIOD
OF POTENTIALLY GALE FORCE NORTHERLY WINDS THURSDAY AS THE SYSTEM
PASSES OVER THE EASTERN LAKES.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565 UNTIL 3
     PM FRIDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 231922
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
122 PM CST FRI JAN 23 2015

.SHORT TERM...
302 AM CST

THROUGH SATURDAY...

EARLY MORNING WATER VAPOR IMAGERY SHOWS A CLOSED UPPER LOW
SPINNING OVER TEXAS AS PART OF A LARGER SCALE TROUGH THAT IS CUT
OFF FROM THE MAIN STREAM OF FLOW TO THE NORTH. THIS MAIN STREAM IS
POSITIONED ACROSS SOUTHERN CANADA WITH WITH SEVERAL EMBEDDED WAVES
TRACKING ACROSS MANITOBA AND SASKATCHEWAN TOWARD THE UPPER MIDWEST
AND UPPER GREAT LAKES. FURTHER WEST...LOW AMPLITUDE RIDGING IS
POSITIONED OVER THE WEST COAST WITH A WELL- DEFINED TROUGH MOVING
EASTWARD TOWARDS BRITISH COLUMBIA. AT THE SURFACE...HIGH PRESSURE
IS STRETCHED FROM THE SOUTHERN PLAINS TO NEW ENGLAND WITH A
SURFACE LOW OFF THE LOUISIANA COAST IN CONJUNCTION WITH THE TEXAS
UPPER LOW. ANOTHER SURFACE LOW IS OVER NORTHERN ONTARIO IN
CONJUNCTION WITH ONE OF THE WAVES OVER CENTRAL CANADA WITH A
TROUGH AXIS EXTENDING SOUTHWARD ACROSS THE NORTHERN PLAINS.
ABUNDANT BUT THIN CLOUD COVER REMAINS ACROSS THE REGION WITH
SATELLITE SHOWING VERY SLOW EASTWARD MOVEMENT...WITH THE BACK EDGE
STILL ACROSS EASTERN IOWA.

THE CLOUD COVER WILL BE THE MAIN CHALLENGE TODAY. FORECAST SOUNDINGS
SHOW A MIX OF THOUGHTS ON HOW LONG CLOUD COVER WILL HANG ON AND DO
NOT SEE MUCH IMPROVEMENT THROUGH LATE MORNING...THOUGH WESTERN AREAS
HAVE THE BEST CHANCE FOR SCATTERING BY MIDDAY. THE PRESSURE GRADIENT
WILL BEGIN TO TIGHTEN UP AS THE ONTARIO SURFACE LOW MOVES EAST AND
THE ASSOCIATED TROUGH APPROACHES. THIS WILL ALLOW FOR STEADIER
SOUTHWEST WINDS TO DEVELOP. WITH THE IDEA THAT CLOUDS WILL HANG ON
THROUGH THE MORNING THEN SCATTER THIS AFTERNOON...HIGH TEMPS WILL
PROBABLY STRUGGLE DESPITE THE SOUTHWEST WINDS AND MODEST WARM
ADVECTION ALOFT. WILL CONTINUE WITH MID AND UPPER 30S FOR NOW BUT IF
SUN CAN MAKE AN APPEARANCE FOR SEVERAL HOURS THIS AFTERNOON THEN
HIGHS AROUND 40/LOW 40S WOULD BE PLAUSIBLE. A BAND OF MID CLOUDS
WILL ACCOMPANY THE TROUGH PASSAGE EARLY THIS EVENING WITH A FEW
FLURRIES NOT OUT OF THE QUESTION. WINDS TURN NORTHWEST TONIGHT AND
SATURDAY MORNING WITH COOL ADVECTION OCCURRING. CLOUD COVER LOOKS
ABUNDANT SO HIGHS WILL LIKELY BE HELD IN THE MID/UPPER 30S.

MDB

&&

.LONG TERM...
302 AM CST

SATURDAY NIGHT THROUGH MONDAY...ATTENTION TURNS TO THE UPPER TROUGH
OFF THE BRITISH COLUMBIA COAST THIS MORNING. A SHORTWAVE EJECTS FROM
THIS TROUGH AND TRACKS EAST THEN SOUTHEAST AND ACROSS THE LOCAL AREA
EARLY SUNDAY. SURFACE LOW PRESSURE DEVELOPS AND PASSES WITH THE
UPPER TROUGH DURING THE DAY SUNDAY. GUIDANCE CONTINUES TO DISAGREE
ON THE STRENGTH AND TRACK OF THE SYSTEM WITH RECENT RUNS SHOWING
QUITE A BIT OF VARIATION. THESE NORTHWEST SYSTEMS HAVE HAD A
TENDENCY TO TRACK FURTHER SOUTH OR SOUTH AND WEST THAN DEPICTED
AHEAD OF TIME SO WILL NEED TO KEEP A CLOSE EYE ON THE WAVE AS IT
MOVES ONSHORE OVER BRITISH COLUMBIA LATER TONIGHT. AT THIS POINT...A
LOW TRACK ACROSS NORTHWEST OR WEST-CENTRAL ILLINOIS...SIMILAR TO THE
00Z GFS/ECMWF...LOOKS TO BE FAVORED WHEN CONSIDERING THE CURRENT AND
EXPECTED UPPER FLOW PATTERN. WITH WESTERN RIDGING EXPECTED TO
SHARPEN AS MORE PACIFIC ENERGY PUSHES INTO IT FROM THE WEST...THE
FLOW OVER THE ROCKIES/PLAINS WILL TURN MORE NORTHWESTERLY. ONE COULD
MAKE THE CASE THAT IF THE WAVE WERE TO TRACK THROUGH THE CURRENT
UPPER FLOW PATTERN IT WOULD TAKE A TRACK ACROSS THE AREA SO A MORE
NORTHWESTERLY FLOW WOULD SUPPORT A MORE WESTERN TRACK. A TRACK
FURTHER NORTH/EAST SEEMS UNLIKELY BUT WOULD NOT BE SURPRISED TO SEE
IT TRACK WEST OF THE TRACK OF THE 00Z GFS/ECMWF BASED ON THE
ABOVE. GIVEN THE PACIFIC ORIGINS OF THE SYSTEM THERE WILL BE
MOISTURE TO WORK WITH SO PRECIPITATION IS LIKELY WITH IT AND SHOULD
AFFECT MOST OF THE AREA UNLESS A WILD SWING IN THE TRACK OCCURS.
PRECIP TYPE MAY BE MIXED FOR A TIME AT ONSET...MAINLY SOUTH AND WEST
WITH A MORE SOUTH/WEST TRACK LEADING TO MAINLY SNOW FOR MUCH OF THE
AREA. THE 00Z RUN OF THE GFS/ECMWF SUGGEST A MIX EARLY SOUTH AS A
NOSE OF WARM AIR BRIEFLY BUILDS IN BEFORE COLD AIR FILLS IN AGAIN.
BASED ON PRECIPITABLE WATER VALUES AND DURATION OF FORCING THE HEART
OF THE SYSTEM LOOKS TO BE ABLE TO PRODUCE 0.3 TO PERHAPS 0.4 INCHES
OF LIQUID EQUIVALENT PRECIP WITH IT BECOMING A MATTER OF WHERE THE
HEART OF THE SYSTEM  TRACKS.

ANOTHER ISSUE WILL BE THE POTENTIAL FOR LAKE ENHANCEMENT AS THE LOW
PASSES SUNDAY AFTERNOON/EVENING. A LOW TRACK TO THE SOUTH AND WEST
OF THE AREA WOULD BE SUPPORTIVE OF LAKE ENHANCEMENT OF SYNOPTIC
PRECIP ON THE BACK SIDE WITH THE COLUMN COLD ENOUGH TO SUPPORT SNOW
IN THIS SCENARIO. HIGH PRESSURE MOVES SOUTHWARD ACROSS ONTARIO INTO
MONDAY WITH ANOTHER SURFACE LOW/ELONGATED TROUGH STRETCHING FROM
MANITOBA TO THE CENTRAL PLAINS WHICH WILL TURN WINDS MORE EASTERLY
THEN SOUTHERLY INTO MONDAY EVENING. WITH FORECAST SOUNDINGS SHOWING
MARGINAL INVERSION HEIGHTS BUT SUFFICIENT DELTA T`S...MAY SEE A
SITUATION SIMILAR TO LAST WEEK WHERE LAKE EFFECT SNOW SHOWERS
PERSISTED IN THE EASTERLY LOW LEVEL FLOW BEFORE ENDING. THIS COULD
BE THE CASE FOR MUCH OF MONDAY. AS FAR AS TEMPS...HIGHS SUNDAY WILL
BE DICTATED BY THE LOW TRACK AND MONDAY LOOKS TO ONLY SEE HIGHS IN
THE 20S THANKS TO COLD ADVECTION.

TUESDAY THROUGH THURSDAY...BROAD RIDGING WEST AND TROUGHING EAST
WILL LEAVE THE LOCAL AREA UNDER A SHARP NORTHERLY UPPER FLOW
TUESDAY WITH HIGH PRESSURE AT THE SURFACE. THE RIDGING WILL
QUICKLY SHIFT EAST AND DE-AMPLIFY WEDNESDAY ALLOWING MILDER AIR TO
RETURN. THE FLOW MAY BE SOMEWHAT ACTIVE BUT PRECIP DETAILS ARE NOT
CLEAR AT THIS RANGE...THOUGH HAVE DECENT CONFIDENCE IN FAIRLY MILD
TEMPERATURES.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* MVFR CIGS ARND 1500-1800FT AGL THRU 00Z...SLOWLY LIFTING TO ARND
  2KFT AGL AFT 2Z.

* SOUTHWEST WINDS ARND 10-14KT WITH OCCASIONAL GUSTS TO 15-17KT
  THRU 00Z.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS MORNING CONTINUED TO SHOW CONSIDERABLE CLOUD
COVER ACROSS THE REGION...WITH SOME CLEARING NOTED ACROSS EASTERN
IOWA. AS THE DAY HAS PROGRESSED SOME THINNING HAS BEGUN TO TAKE
PLACE ACROSS FAR NORTH/NORTHEAST ILLINOIS...AND MAY EVENTUALLY
MAKE IT INTO THE TAF SITES. AT THIS TIME THOUGH HAVE HELD ONTO THE
LOW CLOUDS THRU 00Z...WITH A SLOW IMPROVEMENT TOWARDS 2000-2500FT
AGL AFT 02Z. WINDS WILL CONTINUE TO BE SOUTHWESTERLY WITH SPEEDS
GENERALLY FROM 10-13KT. THRU THE AFTN ON OCCASION GUSTS MAY
OCCUR...AND NOT EXPECTED TO BE VERY FREQUENT WITH SPEEDS UP TO
17KT.

WITH A FRONTAL BOUNDARY SLIDING SOUTHEAST THIS EVENING...THERE IS
THE POTENTIAL FOR A FEW FLURRIES ACROSS ORD/MDW/DPA. ELSEWHERE
SHOULD BE TOO FAR REMOVED FROM THE BETTER MOISTURE TO SEE ANY
FLURRIES. THOUGH HAVE HELD ONTO A DRY FORECAST AS THIS TOO IS A
LOW CONFIDENCE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN CIGS REMAINING OVC THRU 23Z...MEDIUM
  CONFIDENCE IN TIMING OF CIGS LIFTING HIGHER THAN 1600FT AGL.

* HIGH CONFIDENCE IN WIND DIR/SPEED.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

SATURDAY NIGHT...SNOW LIKELY AFTER MIDNIGHT. ACCUMULATION LIKELY.
MVFR CIGS AND IFR VIS POSSIBLE.

SUNDAY...SNOW LIKELY. MVFR/IFR LIKELY.

MONDAY...CHANCE OF SNOW SHOWERS. MVFR POSSIBLE.

TUESDAY THROUGH THURSDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
122 PM CST

SOUTHWESTERLY WINDS WILL GRADUALLY WEAKEN TONIGHT...THEN A COLD
FRONT WILL SHIFT OVER THE LAKE ON SATURDAY AS THE PARENT SURFACE LOW
TRACKS ACROSS NORTHERN QUEBEC. THIS WILL SET UP A NORTHERLY FLOW
DOWN THE LAKE LATER SATURDAY. A FAST MOVING STOUT CLIPPER SYSTEM
WILL MOVE SOUTH OF THE LAKE ON SUNDAY MORNING...AND THIS LOOKS TO
SET THE STAGE FOR A PERIOD OF STRONG NORTHEASTERLY WINDS UP AROUND
30 KT OVER THE LAKE. THIS WILL LIKELY PRODUCE HIGH WAVES OVER 5 FEET
ACROSS MUCH OF SOUTHERN END OF LAKE MICHIGAN SUNDAY AND SUNDAY NIGHT.
FOLLOWING THIS SYSTEM...ANOTHER STORM SYSTEM IS EXPECTED TO IMPACT
THE GREAT LAKES REGION FOR THE MIDDLE TO END OF NEXT WEEK. IT
APPEARS THIS COULD PRODUCE SOUTHERLY GALE FORCE WINDS OVER MUCH OF
THE LAKE LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A PERIOD
OF POTENTIALLY GALE FORCE NORTHERLY WINDS THURSDAY AS THE SYSTEM
PASSES OVER THE EASTERN LAKES.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565 UNTIL 3
     PM FRIDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 231922
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
122 PM CST FRI JAN 23 2015

.SHORT TERM...
302 AM CST

THROUGH SATURDAY...

EARLY MORNING WATER VAPOR IMAGERY SHOWS A CLOSED UPPER LOW
SPINNING OVER TEXAS AS PART OF A LARGER SCALE TROUGH THAT IS CUT
OFF FROM THE MAIN STREAM OF FLOW TO THE NORTH. THIS MAIN STREAM IS
POSITIONED ACROSS SOUTHERN CANADA WITH WITH SEVERAL EMBEDDED WAVES
TRACKING ACROSS MANITOBA AND SASKATCHEWAN TOWARD THE UPPER MIDWEST
AND UPPER GREAT LAKES. FURTHER WEST...LOW AMPLITUDE RIDGING IS
POSITIONED OVER THE WEST COAST WITH A WELL- DEFINED TROUGH MOVING
EASTWARD TOWARDS BRITISH COLUMBIA. AT THE SURFACE...HIGH PRESSURE
IS STRETCHED FROM THE SOUTHERN PLAINS TO NEW ENGLAND WITH A
SURFACE LOW OFF THE LOUISIANA COAST IN CONJUNCTION WITH THE TEXAS
UPPER LOW. ANOTHER SURFACE LOW IS OVER NORTHERN ONTARIO IN
CONJUNCTION WITH ONE OF THE WAVES OVER CENTRAL CANADA WITH A
TROUGH AXIS EXTENDING SOUTHWARD ACROSS THE NORTHERN PLAINS.
ABUNDANT BUT THIN CLOUD COVER REMAINS ACROSS THE REGION WITH
SATELLITE SHOWING VERY SLOW EASTWARD MOVEMENT...WITH THE BACK EDGE
STILL ACROSS EASTERN IOWA.

THE CLOUD COVER WILL BE THE MAIN CHALLENGE TODAY. FORECAST SOUNDINGS
SHOW A MIX OF THOUGHTS ON HOW LONG CLOUD COVER WILL HANG ON AND DO
NOT SEE MUCH IMPROVEMENT THROUGH LATE MORNING...THOUGH WESTERN AREAS
HAVE THE BEST CHANCE FOR SCATTERING BY MIDDAY. THE PRESSURE GRADIENT
WILL BEGIN TO TIGHTEN UP AS THE ONTARIO SURFACE LOW MOVES EAST AND
THE ASSOCIATED TROUGH APPROACHES. THIS WILL ALLOW FOR STEADIER
SOUTHWEST WINDS TO DEVELOP. WITH THE IDEA THAT CLOUDS WILL HANG ON
THROUGH THE MORNING THEN SCATTER THIS AFTERNOON...HIGH TEMPS WILL
PROBABLY STRUGGLE DESPITE THE SOUTHWEST WINDS AND MODEST WARM
ADVECTION ALOFT. WILL CONTINUE WITH MID AND UPPER 30S FOR NOW BUT IF
SUN CAN MAKE AN APPEARANCE FOR SEVERAL HOURS THIS AFTERNOON THEN
HIGHS AROUND 40/LOW 40S WOULD BE PLAUSIBLE. A BAND OF MID CLOUDS
WILL ACCOMPANY THE TROUGH PASSAGE EARLY THIS EVENING WITH A FEW
FLURRIES NOT OUT OF THE QUESTION. WINDS TURN NORTHWEST TONIGHT AND
SATURDAY MORNING WITH COOL ADVECTION OCCURRING. CLOUD COVER LOOKS
ABUNDANT SO HIGHS WILL LIKELY BE HELD IN THE MID/UPPER 30S.

MDB

&&

.LONG TERM...
302 AM CST

SATURDAY NIGHT THROUGH MONDAY...ATTENTION TURNS TO THE UPPER TROUGH
OFF THE BRITISH COLUMBIA COAST THIS MORNING. A SHORTWAVE EJECTS FROM
THIS TROUGH AND TRACKS EAST THEN SOUTHEAST AND ACROSS THE LOCAL AREA
EARLY SUNDAY. SURFACE LOW PRESSURE DEVELOPS AND PASSES WITH THE
UPPER TROUGH DURING THE DAY SUNDAY. GUIDANCE CONTINUES TO DISAGREE
ON THE STRENGTH AND TRACK OF THE SYSTEM WITH RECENT RUNS SHOWING
QUITE A BIT OF VARIATION. THESE NORTHWEST SYSTEMS HAVE HAD A
TENDENCY TO TRACK FURTHER SOUTH OR SOUTH AND WEST THAN DEPICTED
AHEAD OF TIME SO WILL NEED TO KEEP A CLOSE EYE ON THE WAVE AS IT
MOVES ONSHORE OVER BRITISH COLUMBIA LATER TONIGHT. AT THIS POINT...A
LOW TRACK ACROSS NORTHWEST OR WEST-CENTRAL ILLINOIS...SIMILAR TO THE
00Z GFS/ECMWF...LOOKS TO BE FAVORED WHEN CONSIDERING THE CURRENT AND
EXPECTED UPPER FLOW PATTERN. WITH WESTERN RIDGING EXPECTED TO
SHARPEN AS MORE PACIFIC ENERGY PUSHES INTO IT FROM THE WEST...THE
FLOW OVER THE ROCKIES/PLAINS WILL TURN MORE NORTHWESTERLY. ONE COULD
MAKE THE CASE THAT IF THE WAVE WERE TO TRACK THROUGH THE CURRENT
UPPER FLOW PATTERN IT WOULD TAKE A TRACK ACROSS THE AREA SO A MORE
NORTHWESTERLY FLOW WOULD SUPPORT A MORE WESTERN TRACK. A TRACK
FURTHER NORTH/EAST SEEMS UNLIKELY BUT WOULD NOT BE SURPRISED TO SEE
IT TRACK WEST OF THE TRACK OF THE 00Z GFS/ECMWF BASED ON THE
ABOVE. GIVEN THE PACIFIC ORIGINS OF THE SYSTEM THERE WILL BE
MOISTURE TO WORK WITH SO PRECIPITATION IS LIKELY WITH IT AND SHOULD
AFFECT MOST OF THE AREA UNLESS A WILD SWING IN THE TRACK OCCURS.
PRECIP TYPE MAY BE MIXED FOR A TIME AT ONSET...MAINLY SOUTH AND WEST
WITH A MORE SOUTH/WEST TRACK LEADING TO MAINLY SNOW FOR MUCH OF THE
AREA. THE 00Z RUN OF THE GFS/ECMWF SUGGEST A MIX EARLY SOUTH AS A
NOSE OF WARM AIR BRIEFLY BUILDS IN BEFORE COLD AIR FILLS IN AGAIN.
BASED ON PRECIPITABLE WATER VALUES AND DURATION OF FORCING THE HEART
OF THE SYSTEM LOOKS TO BE ABLE TO PRODUCE 0.3 TO PERHAPS 0.4 INCHES
OF LIQUID EQUIVALENT PRECIP WITH IT BECOMING A MATTER OF WHERE THE
HEART OF THE SYSTEM  TRACKS.

ANOTHER ISSUE WILL BE THE POTENTIAL FOR LAKE ENHANCEMENT AS THE LOW
PASSES SUNDAY AFTERNOON/EVENING. A LOW TRACK TO THE SOUTH AND WEST
OF THE AREA WOULD BE SUPPORTIVE OF LAKE ENHANCEMENT OF SYNOPTIC
PRECIP ON THE BACK SIDE WITH THE COLUMN COLD ENOUGH TO SUPPORT SNOW
IN THIS SCENARIO. HIGH PRESSURE MOVES SOUTHWARD ACROSS ONTARIO INTO
MONDAY WITH ANOTHER SURFACE LOW/ELONGATED TROUGH STRETCHING FROM
MANITOBA TO THE CENTRAL PLAINS WHICH WILL TURN WINDS MORE EASTERLY
THEN SOUTHERLY INTO MONDAY EVENING. WITH FORECAST SOUNDINGS SHOWING
MARGINAL INVERSION HEIGHTS BUT SUFFICIENT DELTA T`S...MAY SEE A
SITUATION SIMILAR TO LAST WEEK WHERE LAKE EFFECT SNOW SHOWERS
PERSISTED IN THE EASTERLY LOW LEVEL FLOW BEFORE ENDING. THIS COULD
BE THE CASE FOR MUCH OF MONDAY. AS FAR AS TEMPS...HIGHS SUNDAY WILL
BE DICTATED BY THE LOW TRACK AND MONDAY LOOKS TO ONLY SEE HIGHS IN
THE 20S THANKS TO COLD ADVECTION.

TUESDAY THROUGH THURSDAY...BROAD RIDGING WEST AND TROUGHING EAST
WILL LEAVE THE LOCAL AREA UNDER A SHARP NORTHERLY UPPER FLOW
TUESDAY WITH HIGH PRESSURE AT THE SURFACE. THE RIDGING WILL
QUICKLY SHIFT EAST AND DE-AMPLIFY WEDNESDAY ALLOWING MILDER AIR TO
RETURN. THE FLOW MAY BE SOMEWHAT ACTIVE BUT PRECIP DETAILS ARE NOT
CLEAR AT THIS RANGE...THOUGH HAVE DECENT CONFIDENCE IN FAIRLY MILD
TEMPERATURES.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* MVFR CIGS ARND 1500-1800FT AGL THRU 00Z...SLOWLY LIFTING TO ARND
  2KFT AGL AFT 2Z.

* SOUTHWEST WINDS ARND 10-14KT WITH OCCASIONAL GUSTS TO 15-17KT
  THRU 00Z.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS MORNING CONTINUED TO SHOW CONSIDERABLE CLOUD
COVER ACROSS THE REGION...WITH SOME CLEARING NOTED ACROSS EASTERN
IOWA. AS THE DAY HAS PROGRESSED SOME THINNING HAS BEGUN TO TAKE
PLACE ACROSS FAR NORTH/NORTHEAST ILLINOIS...AND MAY EVENTUALLY
MAKE IT INTO THE TAF SITES. AT THIS TIME THOUGH HAVE HELD ONTO THE
LOW CLOUDS THRU 00Z...WITH A SLOW IMPROVEMENT TOWARDS 2000-2500FT
AGL AFT 02Z. WINDS WILL CONTINUE TO BE SOUTHWESTERLY WITH SPEEDS
GENERALLY FROM 10-13KT. THRU THE AFTN ON OCCASION GUSTS MAY
OCCUR...AND NOT EXPECTED TO BE VERY FREQUENT WITH SPEEDS UP TO
17KT.

WITH A FRONTAL BOUNDARY SLIDING SOUTHEAST THIS EVENING...THERE IS
THE POTENTIAL FOR A FEW FLURRIES ACROSS ORD/MDW/DPA. ELSEWHERE
SHOULD BE TOO FAR REMOVED FROM THE BETTER MOISTURE TO SEE ANY
FLURRIES. THOUGH HAVE HELD ONTO A DRY FORECAST AS THIS TOO IS A
LOW CONFIDENCE.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN CIGS REMAINING OVC THRU 23Z...MEDIUM
  CONFIDENCE IN TIMING OF CIGS LIFTING HIGHER THAN 1600FT AGL.

* HIGH CONFIDENCE IN WIND DIR/SPEED.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

SATURDAY NIGHT...SNOW LIKELY AFTER MIDNIGHT. ACCUMULATION LIKELY.
MVFR CIGS AND IFR VIS POSSIBLE.

SUNDAY...SNOW LIKELY. MVFR/IFR LIKELY.

MONDAY...CHANCE OF SNOW SHOWERS. MVFR POSSIBLE.

TUESDAY THROUGH THURSDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
122 PM CST

SOUTHWESTERLY WINDS WILL GRADUALLY WEAKEN TONIGHT...THEN A COLD
FRONT WILL SHIFT OVER THE LAKE ON SATURDAY AS THE PARENT SURFACE LOW
TRACKS ACROSS NORTHERN QUEBEC. THIS WILL SET UP A NORTHERLY FLOW
DOWN THE LAKE LATER SATURDAY. A FAST MOVING STOUT CLIPPER SYSTEM
WILL MOVE SOUTH OF THE LAKE ON SUNDAY MORNING...AND THIS LOOKS TO
SET THE STAGE FOR A PERIOD OF STRONG NORTHEASTERLY WINDS UP AROUND
30 KT OVER THE LAKE. THIS WILL LIKELY PRODUCE HIGH WAVES OVER 5 FEET
ACROSS MUCH OF SOUTHERN END OF LAKE MICHIGAN SUNDAY AND SUNDAY NIGHT.
FOLLOWING THIS SYSTEM...ANOTHER STORM SYSTEM IS EXPECTED TO IMPACT
THE GREAT LAKES REGION FOR THE MIDDLE TO END OF NEXT WEEK. IT
APPEARS THIS COULD PRODUCE SOUTHERLY GALE FORCE WINDS OVER MUCH OF
THE LAKE LATE WEDNESDAY AND WEDNESDAY NIGHT...FOLLOWED BY A PERIOD
OF POTENTIALLY GALE FORCE NORTHERLY WINDS THURSDAY AS THE SYSTEM
PASSES OVER THE EASTERN LAKES.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565 UNTIL 3
     PM FRIDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 231802
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1202 PM CST FRI JAN 23 2015

.SHORT TERM...
302 AM CST

THROUGH SATURDAY...

EARLY MORNING WATER VAPOR IMAGERY SHOWS A CLOSED UPPER LOW
SPINNING OVER TEXAS AS PART OF A LARGER SCALE TROUGH THAT IS CUT
OFF FROM THE MAIN STREAM OF FLOW TO THE NORTH. THIS MAIN STREAM IS
POSITIONED ACROSS SOUTHERN CANADA WITH WITH SEVERAL EMBEDDED WAVES
TRACKING ACROSS MANITOBA AND SASKATCHEWAN TOWARD THE UPPER MIDWEST
AND UPPER GREAT LAKES. FURTHER WEST...LOW AMPLITUDE RIDGING IS
POSITIONED OVER THE WEST COAST WITH A WELL- DEFINED TROUGH MOVING
EASTWARD TOWARDS BRITISH COLUMBIA. AT THE SURFACE...HIGH PRESSURE
IS STRETCHED FROM THE SOUTHERN PLAINS TO NEW ENGLAND WITH A
SURFACE LOW OFF THE LOUISIANA COAST IN CONJUNCTION WITH THE TEXAS
UPPER LOW. ANOTHER SURFACE LOW IS OVER NORTHERN ONTARIO IN
CONJUNCTION WITH ONE OF THE WAVES OVER CENTRAL CANADA WITH A
TROUGH AXIS EXTENDING SOUTHWARD ACROSS THE NORTHERN PLAINS.
ABUNDANT BUT THIN CLOUD COVER REMAINS ACROSS THE REGION WITH
SATELLITE SHOWING VERY SLOW EASTWARD MOVEMENT...WITH THE BACK EDGE
STILL ACROSS EASTERN IOWA.

THE CLOUD COVER WILL BE THE MAIN CHALLENGE TODAY. FORECAST SOUNDINGS
SHOW A MIX OF THOUGHTS ON HOW LONG CLOUD COVER WILL HANG ON AND DO
NOT SEE MUCH IMPROVEMENT THROUGH LATE MORNING...THOUGH WESTERN AREAS
HAVE THE BEST CHANCE FOR SCATTERING BY MIDDAY. THE PRESSURE GRADIENT
WILL BEGIN TO TIGHTEN UP AS THE ONTARIO SURFACE LOW MOVES EAST AND
THE ASSOCIATED TROUGH APPROACHES. THIS WILL ALLOW FOR STEADIER
SOUTHWEST WINDS TO DEVELOP. WITH THE IDEA THAT CLOUDS WILL HANG ON
THROUGH THE MORNING THEN SCATTER THIS AFTERNOON...HIGH TEMPS WILL
PROBABLY STRUGGLE DESPITE THE SOUTHWEST WINDS AND MODEST WARM
ADVECTION ALOFT. WILL CONTINUE WITH MID AND UPPER 30S FOR NOW BUT IF
SUN CAN MAKE AN APPEARANCE FOR SEVERAL HOURS THIS AFTERNOON THEN
HIGHS AROUND 40/LOW 40S WOULD BE PLAUSIBLE. A BAND OF MID CLOUDS
WILL ACCOMPANY THE TROUGH PASSAGE EARLY THIS EVENING WITH A FEW
FLURRIES NOT OUT OF THE QUESTION. WINDS TURN NORTHWEST TONIGHT AND
SATURDAY MORNING WITH COOL ADVECTION OCCURRING. CLOUD COVER LOOKS
ABUNDANT SO HIGHS WILL LIKELY BE HELD IN THE MID/UPPER 30S.

MDB

&&

.LONG TERM...
302 AM CST

SATURDAY NIGHT THROUGH MONDAY...ATTENTION TURNS TO THE UPPER TROUGH
OFF THE BRITISH COLUMBIA COAST THIS MORNING. A SHORTWAVE EJECTS FROM
THIS TROUGH AND TRACKS EAST THEN SOUTHEAST AND ACROSS THE LOCAL AREA
EARLY SUNDAY. SURFACE LOW PRESSURE DEVELOPS AND PASSES WITH THE
UPPER TROUGH DURING THE DAY SUNDAY. GUIDANCE CONTINUES TO DISAGREE
ON THE STRENGTH AND TRACK OF THE SYSTEM WITH RECENT RUNS SHOWING
QUITE A BIT OF VARIATION. THESE NORTHWEST SYSTEMS HAVE HAD A
TENDENCY TO TRACK FURTHER SOUTH OR SOUTH AND WEST THAN DEPICTED
AHEAD OF TIME SO WILL NEED TO KEEP A CLOSE EYE ON THE WAVE AS IT
MOVES ONSHORE OVER BRITISH COLUMBIA LATER TONIGHT. AT THIS POINT...A
LOW TRACK ACROSS NORTHWEST OR WEST-CENTRAL ILLINOIS...SIMILAR TO THE
00Z GFS/ECMWF...LOOKS TO BE FAVORED WHEN CONSIDERING THE CURRENT AND
EXPECTED UPPER FLOW PATTERN. WITH WESTERN RIDGING EXPECTED TO
SHARPEN AS MORE PACIFIC ENERGY PUSHES INTO IT FROM THE WEST...THE
FLOW OVER THE ROCKIES/PLAINS WILL TURN MORE NORTHWESTERLY. ONE COULD
MAKE THE CASE THAT IF THE WAVE WERE TO TRACK THROUGH THE CURRENT
UPPER FLOW PATTERN IT WOULD TAKE A TRACK ACROSS THE AREA SO A MORE
NORTHWESTERLY FLOW WOULD SUPPORT A MORE WESTERN TRACK. A TRACK
FURTHER NORTH/EAST SEEMS UNLIKELY BUT WOULD NOT BE SURPRISED TO SEE
IT TRACK WEST OF THE TRACK OF THE 00Z GFS/ECMWF BASED ON THE
ABOVE. GIVEN THE PACIFIC ORIGINS OF THE SYSTEM THERE WILL BE
MOISTURE TO WORK WITH SO PRECIPITATION IS LIKELY WITH IT AND SHOULD
AFFECT MOST OF THE AREA UNLESS A WILD SWING IN THE TRACK OCCURS.
PRECIP TYPE MAY BE MIXED FOR A TIME AT ONSET...MAINLY SOUTH AND WEST
WITH A MORE SOUTH/WEST TRACK LEADING TO MAINLY SNOW FOR MUCH OF THE
AREA. THE 00Z RUN OF THE GFS/ECMWF SUGGEST A MIX EARLY SOUTH AS A
NOSE OF WARM AIR BRIEFLY BUILDS IN BEFORE COLD AIR FILLS IN AGAIN.
BASED ON PRECIPITABLE WATER VALUES AND DURATION OF FORCING THE HEART
OF THE SYSTEM LOOKS TO BE ABLE TO PRODUCE 0.3 TO PERHAPS 0.4 INCHES
OF LIQUID EQUIVALENT PRECIP WITH IT BECOMING A MATTER OF WHERE THE
HEART OF THE SYSTEM  TRACKS.

ANOTHER ISSUE WILL BE THE POTENTIAL FOR LAKE ENHANCEMENT AS THE LOW
PASSES SUNDAY AFTERNOON/EVENING. A LOW TRACK TO THE SOUTH AND WEST
OF THE AREA WOULD BE SUPPORTIVE OF LAKE ENHANCEMENT OF SYNOPTIC
PRECIP ON THE BACK SIDE WITH THE COLUMN COLD ENOUGH TO SUPPORT SNOW
IN THIS SCENARIO. HIGH PRESSURE MOVES SOUTHWARD ACROSS ONTARIO INTO
MONDAY WITH ANOTHER SURFACE LOW/ELONGATED TROUGH STRETCHING FROM
MANITOBA TO THE CENTRAL PLAINS WHICH WILL TURN WINDS MORE EASTERLY
THEN SOUTHERLY INTO MONDAY EVENING. WITH FORECAST SOUNDINGS SHOWING
MARGINAL INVERSION HEIGHTS BUT SUFFICIENT DELTA T`S...MAY SEE A
SITUATION SIMILAR TO LAST WEEK WHERE LAKE EFFECT SNOW SHOWERS
PERSISTED IN THE EASTERLY LOW LEVEL FLOW BEFORE ENDING. THIS COULD
BE THE CASE FOR MUCH OF MONDAY. AS FAR AS TEMPS...HIGHS SUNDAY WILL
BE DICTATED BY THE LOW TRACK AND MONDAY LOOKS TO ONLY SEE HIGHS IN
THE 20S THANKS TO COLD ADVECTION.

TUESDAY THROUGH THURSDAY...BROAD RIDGING WEST AND TROUGHING EAST
WILL LEAVE THE LOCAL AREA UNDER A SHARP NORTHERLY UPPER FLOW
TUESDAY WITH HIGH PRESSURE AT THE SURFACE. THE RIDGING WILL
QUICKLY SHIFT EAST AND DE-AMPLIFY WEDNESDAY ALLOWING MILDER AIR TO
RETURN. THE FLOW MAY BE SOMEWHAT ACTIVE BUT PRECIP DETAILS ARE NOT
CLEAR AT THIS RANGE...THOUGH HAVE DECENT CONFIDENCE IN FAIRLY MILD
TEMPERATURES.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* MVFR CIGS ARND 1500-1800FT AGL THRU 00Z...SLOWLY LIFTING TO ARND
  2KFT AGL AFT 2Z.

* SOUTHWEST WINDS ARND 10-14KT WITH OCCASIONAL GUSTS TO 15-17KT
  THRU 00Z.

BEACHLER

//DISCUSSION...UPDATED 18Z...

VISIBLE IMAGERY THIS MORNING CONTINUED TO SHOW CONSIDERABLE CLOUD
COVER ACROSS THE REGION...WITH SOME CLEARING NOTED ACROSS EASTERN
IOWA. AS THE DAY HAS PROGRESSED SOME THINNING HAS BEGUN TO TAKE
PLACE ACROSS FAR NORTH/NORTHEAST ILLINOIS...AND MAY EVENTUALLY
MAKE IT INTO THE TAF SITES. AT THIS TIME THOUGH HAVE HELD ONTO THE
LOW CLOUDS THRU 00Z...WITH A SLOW IMPROVEMENT TOWARDS 2000-2500FT
AGL AFT 02Z. WINDS WILL CONTINUE TO BE SOUTHWESTERLY WITH SPEEDS
GENERALLY FROM 10-13KT. THRU THE AFTN ON OCCASION GUSTS MAY
OCCUR...AND NOT EXPECTED TO BE VERY FREQUENT WITH SPEEDS UP TO
17KT.

WITH A FRONTAL BOUNDARY SLIDING SOUTHEAST THIS EVENING...THERE IS
THE POTENTIAL FOR A FEW FLURRIES ACROSS ORD/MDW/DPA. ELSEWHERE
SHOULD BE TOO FAR REMOVED FROM THE BETTER MOISTURE TO SEE ANY
FLURRIES. THOUGH HAVE HELD ONTO A DRY FORECAST AS THIS TOO IS A
LOW CONFIDENCE.

BEACHLER


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN CIGS REMAINING OVC THRU 23Z...MEDIUM
  CONFIDENCE IN TIMING OF CIGS LIFTING HIGHER THAN 1600FT AGL.

* HIGH CONFIDENCE IN WIND DIR/SPEED.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

SATURDAY NIGHT...SNOW LIKELY AFTER MIDNIGHT. ACCUMULATION LIKELY.
MVFR CIGS AND IFR VIS POSSIBLE.

SUNDAY...SNOW LIKELY. MVFR/IFR LIKELY.

MONDAY...CHANCE OF SNOW SHOWERS. MVFR POSSIBLE.

TUESDAY THROUGH THURSDAY...PRIMARILY VFR.

RATZER

&&

.MARINE...
217 AM CST

MARINE WEATHER CONCERNS INCLUDE SOUTHWESTERLY GALES ACROSS NORTHERN
LAKE MICHIGAN TODAY...THEN A BRIEF PERIOD OF STRONG NORTHEAST-NORTH
WINDS 25-30 KTS OVER CENTRAL/SOUTHERN LAKE MICHIGAN SUNDAY.

A STRONG AREA OF LOW PRESSURE WAS MOVING SLOWLY EAST ACROSS FAR
NORTHERN ONTARIO EARLY THIS MORNING...WHILE A WEST-EAST ORIENTED
RIDGE OF HIGH PRESSURE WAS ACROSS THE MIDWEST REGION SOUTH OF THE
GREAT LAKES. SURFACE PRESSURE FALLS ACROSS ONTARIO AND WESTERN
QUEBEC HAVE TIGHTENED THE GRADIENT ACROSS THE NORTHERN LAKES...AND
WILL REMAIN SO INTO THIS AFTERNOON BEFORE WEAKENING AS THE LOW
REACHES JAMES BAY AND A TRAILING SURFACE TROUGH APPROACHES FROM THE
WEST. SOUTHWEST WINDS HAVE INCREASED WITH A 34 KT GUST NOTED AT PORT
INLAND MI WITHIN THE PAST HOUR...AND A GALE WARNING IS IN EFFECT FOR
THE NORTHERN HALF OR SO OF THE LAKE THROUGH MID-AFTERNOON. WINDS
WILL EASE BELOW GALE FORCE BY LATE AFTERNOON AS THE GRADIENT BEGINS
TO WEAKEN...AND WILL FURTHER DIMINISH TONIGHT.

ANOTHER AREA OF LOW PRESSURE IS EXPECTED TO DEVELOP IN ASSOCIATION
WITH AN ALBERTA-CLIPPER OVER THE WEEKEND...WITH THE LOW DEEPENING
AND MOVING QUICKLY TO NORTHWEST ILLINOIS BY SUNDAY MORNING. WINDS
WILL BECOME NORTHEASTERLY SATURDAY NIGHT AS THE LOW APPROACHES...
AND ARE EXPECTED TO QUICKLY INCREASE TO NEAR 30 KT EARLY IN THE DAY
SUNDAY AS THE LOW MOVES INTO CENTRAL INDIANA. THE PERIOD OF STRONGER
WINDS APPEARS TO BE BRIEF...AS THE LOW BEGINS TO FILL AND RAPIDLY
EXITS THE REGION TO THE SOUTHEAST SUNDAY EVENING AND WEAK HIGH
PRESSURE RIDGING MOVES IN FROM THE NORTHWEST. WEAK HIGH PRESSURE
THEN LOOKS TO LINGER ACROSS THE WESTERN GREAT LAKES INTO EARLY NEXT
WEEK.

FOR THE ILLINOIS AND NORTHWEST INDIANA NEARSHORE WATERS...BREEZY
OFFSHORE WINDS EXPECTED TODAY AND SATURDAY. SMALL CRAFT ADVISORY
CONDITIONS ARE EXPECTED TO DEVELOP QUICKLY SUNDAY MORNING DUE TO THE
STRONG WINDS FROM THE CLIPPER...WITH THE DIMINISHING NORTH FETCH
KEEPING HIGHER WAVES LINGERING INTO EARLY MONDAY.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565 UNTIL 3
     PM FRIDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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