[top]
000
FXUS63 KDMX 161129
AFDDMX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
629 AM CDT WED MAY 16 2012
...UPDATED AVIATION DISCUSSION...
.SHORT TERM /TODAY/...
MUCH QUIETER AND COOLER WEATHER FORECAST FOR TODAY AS A HIGH
PRESSURE AREA SLIDES FROM MINNESOTA ACROSS WISCONSIN AND LAKE
MICHIGAN. THIS WILL CAUSE OUR WINDS TO SHIFT FROM NORTH THIS MORNING
TO SOUTH SOUTHEAST BY SUNSET...HOWEVER SPEEDS WILL REMAIN LIGHT FOR
MOST OF THE DAY ESPECIALLY IN OUR NORTHEASTERN AND EASTERN COUNTIES.
THIS SCENARIO WILL ALSO RESULT IN LITTLE IN THE WAY OF SENSIBLE
WEATHER ACROSS THE CWA WITH VIRTUALLY CLEAR SKIES. THE ONLY REAL
FORECAST QUESTION IS TEMPERATURES. THE COOLER AIRMASS MOVING IN WILL
BE AIDED BY LIGHT WINDS FOR THE MOST PART...HOWEVER THE NEAR-SURFACE
LAYER WILL BE VERY DRY AND IF ANY MIXING CAN OCCUR THEN TEMPERATURES
COULD WARM SOMEWHAT IN THE AFTERNOON. THIS SEEMS MOST FEASIBLE IN
OUR WEST AS THE HIGH MOVES OFF TO THE EAST LATE TODAY AND WE GET
SOME RETURN FLOW OVER THERE. HAVE FORECAST HIGH TEMPERATURES
SLIGHTLY ABOVE MOS ACROSS MOST OF ABOUT OUR WESTERN HALF AND NEAR
MOS IN THE EAST. AT ANY RATE IT WILL BE A GORGEOUS LATE SPRING DAY
FOR MOST OUTDOOR INTERESTS.
.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
HIGH PRESSURE WILL MOVE OFF TO THE EAST. TEMPERATURES WILL FALL
OFF QUICKLY THIS EVENING AND ARE EXPECTED TO LEVEL OFF AFTER
MIDNIGHT WITH SLOW FALLS IN THE SOUTHEAST AND STEADY OR EVEN RISING
A FEW DEGREES OVERNIGHT IN THE NORTHWEST AS WINDS INCREASE. AIRMASS
REMAINS QUITE DRY FOR THU AND FRI AND CONTINUED WITH THE DRY
FORECAST. GIVEN THE DRY ANTECEDENT CONDITIONS WOULD EXPECT TO SEE
MAX TEMPS RISE AOA MOS FORECASTS AND BUMPED THEM UP A LITTLE BOTH
DAYS. MODELS ARE CONSISTENT WITH THE MOVEMENT OF THE NEXT COLD
FRONT AND WENT WITH THE THINKING OF YESTERDAY WITH INTRODUCTION OF
TSRA OVER THE NORTHWEST LATE SAT AFTERNOON AS FRONT APPROACHES.
TEMPS WILL BE TRICKIER FOR SAT AS MOISTURE IS FINALLY WORKING INTO
THE ARE WITH PWAT GETTING UP TO NEAR 1.5 INCHES BY EVENING. WENT
WITH STRONG POPS FOR SATURDAY NIGHT THROUGH SUNDAY WHEN THE BEST
CHANCE FOR WIDESPREAD RAINFALL EXISTS. AS THE FRONT PASSES TO THE
EAST...TEMPS WILL FALL BACK TO NEAR NORMAL FOR A COUPLE DAYS. DON`T
EXPECT TO SEE THAT LAST LONG BEFORE WARMING RETURNS. A QUICK
COMMENT ABOUT THE SIGNIFICANT DIFFERENCES BETWEEN THE GFS AND ECMWF
IN THE POST DAY 7 TIMEFRAME...FEEL THE ECMWF IS THE BETTER SOLUTION
AS THE GFS DOES NOT APPEAR TO BE HANDLING MJO VERY WELL AT
ALL...LEADING TO THE RESPONSE OF STRONGLY RISING HEIGHTS OVER THE
EASTERN CONUS.
&&
.AVIATION 16/12Z...
VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD WITH VERY FEW IF ANY
CLOUDS AND NO PRECIP OR OBSCURATIONS. SHIFTING WIND DIRECTION
PROVIDES THE ONLY JUSTIFICATION FOR MULTI-LINE TAFS...BUT WIND
SPEEDS SHOULD REMAIN AOB 10 KT.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
.SHORT...LEE
.LONG...MS MAY 12
.AVIATION...LEE
[top]
000
FXUS63 KDVN 161126
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
626 AM CDT WED MAY 16 2012
.AVIATION...
VFR CONDITIONS ARE EXPECTED TO PERSIST THROUGH WED NGT. HIGH
PRESSURE WILL SLIDE FROM THE UPPER MIDWEST INTO THE GREAT
LAKES BY 12Z THU. N/NE WINDS GENERALLY AOB 10 KTS TO VEER TO
E THEN SE BY TNGT AS THE HIGH PRESSURE RIDGE MOVES EAST OF THE
REGION. 05
&&
.PREV DISCUSSION... /ISSUED 332 AM CDT WED MAY 16 2012/
SYNOPSIS...
COLD FRONT EXTENDS FROM NORTHERN IN THROUGH CENTRAL IL TO
CENTRAL KS AT 07Z. MEANWHILE... LAKE ENHANCED BOUNDARY
SAGGING SWWD THROUGH NORTHERN IL DENOTED BY NE WINDS AND
COOLER AIR WITH TEMPS LOWERING THROUGH THE 50S WITH 40S IN
SOUTHERN WI. SKIES WERE MAINLY CLEAR ACROSS THE REGION
WITH JUST SOME HIGH THIN CIRRUS SPILLING DOWN IN NORTHWEST
FLOW ALOFT ON LEE SIDE OF CANADIAN ROCKIES UPPER LEVEL RIDGE.
SHORT TERM...TODAY AND TONIGHT...
TRANQUIL AND VERY PLEASANT WEATHER ON TAP AS DOMINANT FEATURE
WILL BE SFC HIGH AS IT SLIDES S/E FROM THE UPPER MIDWEST
INTO GREAT LAKES. RESULTING N/NE WIND TDY TO USHER IN
COOLER AND DRIER AIR WITH TEMPS CLOSE TO NORMAL FOR MID MAY.
PROGGED LOW LEVEL THICKNESS (1000-800 MB) AND VERIFICATION
OF HIGHS YSTDY SUPPORTS MAXES TDY MAINLY IN U60S TO L70S WITH
GENERAL RANGE FROM 68-74F WITH COOLEST READINGS N/E AND WARMEST
S/W. LIGHT AND VARIABLE TO CALM WINDS THIS EVE WILL BECOME E/SE
AT 5-10 MPH OVRNGT AS HIGH PRESSURE SLIDES E. LOW LEVEL JET AND
ATTENDANT WARM ADVECTION ON BACKSIDE OF DEPARTING HIGH
MAY GENERATE SOME PCPN OVRNGT TO OUR N/W FROM EASTERN DAKOTAS
INTO MN. OUR SKIES EXPECTED TO BE MAINLY CLEAR WITH JUST SOME
HIGH CIRRUS. COMBINATION OF MAINLY CLEAR SKIES... DRY AIR AND
LIGHT WIND SUPPORTS SIDING NEAR COOL SIDE OF GUIDANCE ON LOWS WITH
WIDESPREAD 40S TO AROUND 50F. 05
LONG TERM...THURSDAY THROUGH NEXT TUESDAY...
THURSDAY AND FRIDAY...MASS FIELD PLACEMENT AND FORCING STRUCTURES
ADVERTISED BY MOST OF THE LATEST 00Z RUN MODELS SUGGEST A DRY AND
THERMALLY MODERATING END OF THE WEEK FOR THE DVN CWA. THE MAIN MCS
SPAWNING GROUNDS STILL APPEAR WILL SET UP IN MORE OF A MID SUMMER
PATTERN ALONG AND UNDER PERIPHERY OF UPPER RIDGE AXIS FROM THE
NORTHWESTERN HIGH PLAINS...EASTWARD INTO THE NORTHWEST HALF OF THE
GRT LKS. A LOW CHANCE FOR SOME OF THE CONVECTIVE DEBRIS OFF THESE
SYSTEMS MAKING IT/S WAY DOWN INTO THE NORTHERN CWA THU OR THU NIGHT.
SOUTHEAST RETURN FLOW TO TRANSLATE INTO HIGHS FROM THE MID 70S TO
AROUND 80 ON THU...WITH INCREASING SOUTHERLY FLOW AND WARM AIR
ADVECTION UNDER AMPLIFYING UPPER RIDGE LEADING TO HIGHS IN THE LOW
TO MID 80S ON FRI.
SATURDAY AND SUNDAY...TRENDS ON 00Z RUN MEDIUM RANGE
SOLUTIONS GENERALLY CONTINUE TO SUGGEST EASTERN PACIFIC UPPER JET
ENERGY AND INLAND PROPAGATING WAVES WILL COMBINE TO PUMMEL OUT
A L/W TROF COMPLEX ACRS THE WESTERN ROCKIES BY THE WEEKEND. UPPER
RIDGE AXIS AND THERMAL POOL CONTINUING TO GET PUMPED UP TO THE LEE
OF THESE PROCESSES SHOULD MEAN A MAINLY SUNNY AND WARM SATURDAY
WITH WIDESPREAD HIGHS IN THE MID TO UPPER 80S ALMOST SIMILAR TO WHAT
HAPPENED TEMP-WISE JUST THIS PAST TUE. A LARGE PIECE OF THE WESTERN
UPPER TROF WILL HAVE TO EVENTUALLY PUSH ACRS THE UPPER MIDWEST AND
STILL PREFER THE SLOWER ECMWF SOLUTION OF SHUNTING AN ASSOCIATED SFC
FRONT TOWARD THE AREA SOMETIME LATER SUNDAY NIGHT OR EVEN EARLY
MONDAY MORNING. WITH SOME MOISTURE CONVEYOR UP OFF THE WESTERN
GULF TO INTERACT WITH FORCING FIELDS FROM THIS INCOMING LLVL FRONT
AND APPROACHING UPPER TROF...THERE WILL BE AN INCREASING CHANCE OF
SHOWERS AND STORMS FROM THE WEST WITH THE HIGHER POP WINDOW APPEARING
TO BE LATE SUNDAY...SUNDAY NIGHT AND LINGERING INTO MONDAY MORNING
WITH SUNDAY NIGHT BEING THE PRIME WINDOW OF ACTIVITY. THREAT OF ANY
POTENTIALLY SEVERE STORMS OR LOCALLY HEAVY RAIN DURING THIS TIME
PERIOD STILL SOMEWHAT MUDDLED AT THIS POINT...BUT SOME RUN TO RUN
CONSISTENCY BY THE ECMWF OF AN ORGANIZED CONVECTIVE EVENT TO END THE
WEEKEND. INTERESTING THAT THE GFS HAS STAYED CONSISTENT AS WELL WITH
A MORE PROGRESSIVE SOLUTION WITH THE MAIN FROPA AND SHOWER/STORM
WINDOW DURING THE DAY ON SUNDAY WITH EVEN SOME INITIAL ACTIVITY
MAKING IT INTO THE AREA LAT SAT NIGHT. WITH PROJECTED STRENGTH OF THE
PRE-TROF UPPER RIDGE COMPLEX TO OVERCOME...FOR NOW WILL LEAN TOWARD
THE SLOWER HANDLING OF THE ECMWF.
MONDAY AND TUESDAY...SOME DISCREPANCIES IN THE LONGER RANGE BETWEEN
SOME MODELS SUCH AS THE 00Z GFS SUGGESTING POST L/W TROF REGIME OF
SFC RIDGING ACRS THE WESTERN GRT LKS AND UPPER MS RVR VALLEY FOR A
DRY COOLER PATTERN FOR MON INTO TUE. THIS IN CONTRAST TO THE NEW
ECMWF WHICH HAS REVERTED BACK TO A TEMPORARY REX BLOCK TYPE PATTERN
ACRS MUCH OF THE MS RVR VALLEY REGION...WHICH THE DVN CWA LIES ON
THE NORTHERN FLANK OF THE MAIN DEVELOPING CUT-OFF UPPER LOW AND
SUBJECT TO SOME SHOWER DEVELOPMENT ROTATING INTO THE AREA BY LATE
MON NIGHT OR TUESDAY. WILL ADVERTISE SLIGHT CHC POPS IN THE EAST ON
TUE AS A COMPROMISE BETWEEN THE TWO CAMPS OF THINKING...BUT
DEFINITELY A PERIOD THAT IS UNCERTAIN AND ONE TO WATCH FOR UPCOMING
TRENDS ON SUBSEQUENT MEDIUM RANGE MODEL RUNS. 12
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
000
FXUS63 KDVN 160832
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
332 AM CDT WED MAY 16 2012
.SYNOPSIS...
COLD FRONT EXTENDS FROM NORTHERN IN THROUGH CENTRAL IL TO
CENTRAL KS AT 07Z. MEANWHILE... LAKE ENHANCED BOUNDARY
SAGGING SWWD THROUGH NORTHERN IL DENOTED BY NE WINDS AND
COOLER AIR WITH TEMPS LOWERING THROUGH THE 50S WITH 40S IN
SOUTHERN WI. SKIES WERE MAINLY CLEAR ACROSS THE REGION
WITH JUST SOME HIGH THIN CIRRUS SPILLING DOWN IN NORTHWEST
FLOW ALOFT ON LEE SIDE OF CANADIAN ROCKIES UPPER LEVEL RIDGE.
&&
.SHORT TERM...TODAY AND TONIGHT...
TRANQUIL AND VERY PLEASANT WEATHER ON TAP AS DOMINANT FEATURE
WILL BE SFC HIGH AS IT SLIDES S/E FROM THE UPPER MIDWEST
INTO GREAT LAKES. RESULTING N/NE WIND TDY TO USHER IN
COOLER AND DRIER AIR WITH TEMPS CLOSE TO NORMAL FOR MID MAY.
PROGGED LOW LEVEL THICKNESS (1000-800 MB) AND VERIFICATION
OF HIGHS YSTDY SUPPORTS MAXES TDY MAINLY IN U60S TO L70S WITH
GENERAL RANGE FROM 68-74F WITH COOLEST READINGS N/E AND WARMEST
S/W. LIGHT AND VARIABLE TO CALM WINDS THIS EVE WILL BECOME E/SE
AT 5-10 MPH OVRNGT AS HIGH PRESSURE SLIDES E. LOW LEVEL JET AND
ATTENDANT WARM ADVECTION ON BACKSIDE OF DEPARTING HIGH
MAY GENERATE SOME PCPN OVRNGT TO OUR N/W FROM EASTERN DAKOTAS
INTO MN. OUR SKIES EXPECTED TO BE MAINLY CLEAR WITH JUST SOME
HIGH CIRRUS. COMBINATION OF MAINLY CLEAR SKIES... DRY AIR AND
LIGHT WIND SUPPORTS SIDING NEAR COOL SIDE OF GUIDANCE ON LOWS WITH
WIDESPREAD 40S TO AROUND 50F. ..05..
.LONG TERM...THURSDAY THROUGH NEXT TUESDAY...
THURSDAY AND FRIDAY...MASS FIELD PLACEMENT AND FORCING STRUCTURES
ADVERTISED BY MOST OF THE LATEST 00Z RUN MODELS SUGGEST A DRY AND
THERMALLY MODERATING END OF THE WEEK FOR THE DVN CWA. THE MAIN MCS
SPAWNING GROUNDS STILL APPEAR WILL SET UP IN MORE OF A MID SUMMER
PATTERN ALONG AND UNDER PERIPHERY OF UPPER RIDGE AXIS FROM THE
NORTHWESTERN HIGH PLAINS...EASTWARD INTO THE NORTHWEST HALF OF THE
GRT LKS. A LOW CHANCE FOR SOME OF THE CONVECTIVE DEBRIS OFF THESE
SYSTEMS MAKING IT/S WAY DOWN INTO THE NORTHERN CWA THU OR THU NIGHT.
SOUTHEAST RETURN FLOW TO TRANSLATE INTO HIGHS FROM THE MID 70S TO
AROUND 80 ON THU...WITH INCREASING SOUTHERLY FLOW AND WARM AIR
ADVECTION UNDER AMPLIFYING UPPER RIDGE LEADING TO HIGHS IN THE LOW
TO MID 80S ON FRI.
SATURDAY AND SUNDAY...TRENDS ON 00Z RUN MEDIUM RANGE
SOLUTIONS GENERALLY CONTINUE TO SUGGEST EASTERN PACIFIC UPPER JET
ENERGY AND INLAND PROPAGATING WAVES WILL COMBINE TO PUMMEL OUT
A L/W TROF COMPLEX ACRS THE WESTERN ROCKIES BY THE WEEKEND. UPPER
RIDGE AXIS AND THERMAL POOL CONTINUING TO GET PUMPED UP TO THE LEE
OF THESE PROCESSES SHOULD MEAN A MAINLY SUNNY AND WARM SATURDAY
WITH WIDESPREAD HIGHS IN THE MID TO UPPER 80S ALMOST SIMILAR TO WHAT
HAPPENED TEMP-WISE JUST THIS PAST TUE. A LARGE PIECE OF THE WESTERN
UPPER TROF WILL HAVE TO EVENTUALLY PUSH ACRS THE UPPER MIDWEST AND
STILL PREFER THE SLOWER ECMWF SOLUTION OF SHUNTING AN ASSOCIATED SFC
FRONT TOWARD THE AREA SOMETIME LATER SUNDAY NIGHT OR EVEN EARLY
MONDAY MORNING. WITH SOME MOISTURE CONVEYOR UP OFF THE WESTERN
GULF TO INTERACT WITH FORCING FIELDS FROM THIS INCOMING LLVL FRONT
AND APPROACHING UPPER TROF...THERE WILL BE AN INCREASING CHANCE OF
SHOWERS AND STORMS FROM THE WEST WITH THE HIGHER POP WINDOW APPEARING
TO BE LATE SUNDAY...SUNDAY NIGHT AND LINGERING INTO MONDAY MORNING
WITH SUNDAY NIGHT BEING THE PRIME WINDOW OF ACTIVITY. THREAT OF ANY
POTENTIALLY SEVERE STORMS OR LOCALLY HEAVY RAIN DURING THIS TIME
PERIOD STILL SOMEWHAT MUDDLED AT THIS POINT...BUT SOME RUN TO RUN
CONSISTENCY BY THE ECMWF OF AN ORGANIZED CONVECTIVE EVENT TO END THE
WEEKEND. INTERESTING THAT THE GFS HAS STAYED CONSISTENT AS WELL WITH
A MORE PROGRESSIVE SOLUTION WITH THE MAIN FROPA AND SHOWER/STORM
WINDOW DURING THE DAY ON SUNDAY WITH EVEN SOME INITIAL ACTIVITY
MAKING IT INTO THE AREA LAT SAT NIGHT. WITH PROJECTED STRENGTH OF THE
PRE-TROF UPPER RIDGE COMPLEX TO OVERCOME...FOR NOW WILL LEAN TOWARD
THE SLOWER HANDLING OF THE ECMWF.
MONDAY AND TUESDAY...SOME DISCREPANCIES IN THE LONGER RANGE BETWEEN
SOME MODELS SUCH AS THE 00Z GFS SUGGESTING POST L/W TROF REGIME OF
SFC RIDGING ACRS THE WESTERN GRT LKS AND UPPER MS RVR VALLEY FOR A
DRY COOLER PATTERN FOR MON INTO TUE. THIS IN CONTRAST TO THE NEW
ECMWF WHICH HAS REVERTED BACK TO A TEMPORARY REX BLOCK TYPE PATTERN
ACRS MUCH OF THE MS RVR VALLEY REGION...WHICH THE DVN CWA LIES ON
THE NORTHERN FLANK OF THE MAIN DEVELOPING CUT-OFF UPPER LOW AND
SUBJECT TO SOME SHOWER DEVELOPMENT ROTATING INTO THE AREA BY LATE
MON NIGHT OR TUESDAY. WILL ADVERTISE SLIGHT CHC POPS IN THE EAST ON
TUE AS A COMPROMISE BETWEEN THE TWO CAMPS OF THINKING...BUT
DEFINITELY A PERIOD THAT IS UNCERTAIN AND ONE TO WATCH FOR UPCOMING
TRENDS ON SUBSEQUENT MEDIUM RANGE MODEL RUNS. ..12..
&&
.AVIATION... /ISSUED 1144 PM CDT TUE MAY 15 2012/
VFR CONDITIONS ARE EXPECTED THROUGH WEDNESDAY EVENING. HIGH
PRESSURE OVER THE NORTHERN PLAINS WILL MOVE SOUTHEAST INTO THE
REGION BY WEDNESDAY MORNING. LIGHT NORTHERLY WINDS TONIGHT WILL
VEER TO THE EAST BY WEDNESDAY MORNING THEN TO THE SOUTHEAST
DURING THE AFTERNOON AND EVENING AS THE HIGH MOVES EAST OF THE
REGION. ..DLF..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
05/12
000
FXUS63 KDMX 160827 AAB
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
327 AM CDT WED MAY 16 2012
.SHORT TERM /TODAY/...
MUCH QUIETER AND COOLER WEATHER FORECAST FOR TODAY AS A HIGH
PRESSURE AREA SLIDES FROM MINNESOTA ACROSS WISCONSIN AND LAKE
MICHIGAN. THIS WILL CAUSE OUR WINDS TO SHIFT FROM NORTH THIS MORNING
TO SOUTH SOUTHEAST BY SUNSET...HOWEVER SPEEDS WILL REMAIN LIGHT FOR
MOST OF THE DAY ESPECIALLY IN OUR NORTHEASTERN AND EASTERN COUNTIES.
THIS SCENARIO WILL ALSO RESULT IN LITTLE IN THE WAY OF SENSIBLE
WEATHER ACROSS THE CWA WITH VIRTUALLY CLEAR SKIES. THE ONLY REAL
FORECAST QUESTION IS TEMPERATURES. THE COOLER AIRMASS MOVING IN WILL
BE AIDED BY LIGHT WINDS FOR THE MOST PART...HOWEVER THE NEAR-SURFACE
LAYER WILL BE VERY DRY AND IF ANY MIXING CAN OCCUR THEN TEMPERATURES
COULD WARM SOMEWHAT IN THE AFTERNOON. THIS SEEMS MOST FEASIBLE IN
OUR WEST AS THE HIGH MOVES OFF TO THE EAST LATE TODAY AND WE GET
SOME RETURN FLOW OVER THERE. HAVE FORECAST HIGH TEMPERATURES
SLIGHTLY ABOVE MOS ACROSS MOST OF ABOUT OUR WESTERN HALF AND NEAR
MOS IN THE EAST. AT ANY RATE IT WILL BE A GORGEOUS LATE SPRING DAY
FOR MOST OUTDOOR INTERESTS.
.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
HIGH PRESSURE WILL MOVE OFF TO THE EAST. TEMPERATURES WILL FALL
OFF QUICKLY THIS EVENING AND ARE EXPECTED TO LEVEL OFF AFTER
MIDNIGHT WITH SLOW FALLS IN THE SOUTHEAST AND STEADY OR EVEN RISING
A FEW DEGREES OVERNIGHT IN THE NORTHWEST AS WINDS INCREASE. AIRMASS
REMAINS QUITE DRY FOR THU AND FRI AND CONTINUED WITH THE DRY
FORECAST. GIVEN THE DRY ANTECEDENT CONDITIONS WOULD EXPECT TO SEE
MAX TEMPS RISE AOA MOS FORECASTS AND BUMPED THEM UP A LITTLE BOTH
DAYS. MODELS ARE CONSISTENT WITH THE MOVEMENT OF THE NEXT COLD
FRONT AND WENT WITH THE THINKING OF YESTERDAY WITH INTRODUCTION OF
TSRA OVER THE NORTHWEST LATE SAT AFTERNOON AS FRONT APPROACHES.
TEMPS WILL BE TRICKIER FOR SAT AS MOISTURE IS FINALLY WORKING INTO
THE ARE WITH PWAT GETTING UP TO NEAR 1.5 INCHES BY EVENING. WENT
WITH STRONG POPS FOR SATURDAY NIGHT THROUGH SUNDAY WHEN THE BEST
CHANCE FOR WIDESPREAD RAINFALL EXISTS. AS THE FRONT PASSES TO THE
EAST...TEMPS WILL FALL BACK TO NEAR NORMAL FOR A COUPLE DAYS. DON`T
EXPECT TO SEE THAT LAST LONG BEFORE WARMING RETURNS. A QUICK
COMMENT ABOUT THE SIGNIFICANT DIFFERENCES BETWEEN THE GFS AND ECMWF
IN THE POST DAY 7 TIMEFRAME...FEEL THE ECMWF IS THE BETTER SOLUTION
AS THE GFS DOES NOT APPEAR TO BE HANDLING MJO VERY WELL AT
ALL...LEADING TO THE RESPONSE OF STRONGLY RISING HEIGHTS OVER THE
EASTERN CONUS.
&&
.AVIATION 16/06Z...
HIGH PRESSURE BUILDS INTO THE TAF LOCATIONS THROUGH THE FORECAST
PD. VFR CONDITIONS EXPECTED ALONG WITH A NORTH WIND AROUND 10 KTS.
SOME MID/HIGH CLOUDS POSSIBLE WITH THE WIND SHIFT TO THE SOUTH LATER
IN THE DAY AS THE RIDGE AXIS SHIFTS TO THE EAST.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
.SHORT...LEE
.LONG...MS MAY 12
.AVIATION...FAB
000
FXUS63 KDVN 160444
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1144 PM CDT TUE MAY 15 2012
.AVIATION...
VFR CONDITIONS ARE EXPECTED THROUGH WEDNESDAY EVENING. HIGH
PRESSURE OVER THE NORTHERN PLAINS WILL MOVE SOUTHEAST INTO THE
REGION BY WEDNESDAY MORNING. LIGHT NORTHERLY WINDS TONIGHT WILL
VEER TO THE EAST BY WEDNESDAY MORNING THEN TO THE SOUTHEAST
DURING THE AFTERNOON AND EVENING AS THE HIGH MOVES EAST OF THE
REGION.
DLF
&&
.PREV DISCUSSION... /ISSUED 245 PM CDT TUE MAY 15 2012/
SYNOPSIS...
THE CWA IS BEGINNING TO EXPERIENCE A COLD FROPA FROM NORTHWEST TO
SOUTHEAST AS OF EARLY AFTERNOON...AND THUS FAR IT IS DRY. WHILE VERY
HIGH BASED CUMULUS HAVE FORMED...SURFACE DEWPOINTS HAVE MIXED DOWN
TO THE MID 30S TO LOWER 40S ALONG THE FRONT. IN
ADDITION...TEMPERATURES NEAR THE FRONT ARE IN THE UPPER 80S TO
90...RESULTING IN VERY LOW RH VALUES AROUND 20 TO 25 PERCENT.
OTHERWISE...TEMPERATURES AS OF 2 PM ARE IN THE LOWER TO MID 80S WITH
DEWPOINTS IN THE MID 40S TO LOWER 50S. AS THE FRONT
APPROACHES...FURTHER DROPS IN DEWPOINTS ARE EXPECTED.
SHORT TERM...TONIGHT AND WEDNESDAY...
THUNDERSTORM POTENTIAL TONIGHT WILL LIKELY BE MUCH LESS THAN ANY
MODEL SUGGESTS GIVEN THE MUCH LOWER FRONTAL SURFACE DEWPOINTS.
THUS...WILL KEEP MENTION OF AN ISOLATED STORM THROUGH 9 PM...BUT IN
REALITY IF NO STORMS FIRE BY 5 PM...THIS THREAT CAN BE REMOVED.
COVERAGE TO MENTION STORMS NEEDS TO BE 15 PERCENT OR HIGHER...THUS
THAT IS MY PERCENT CHANCE FORECAST. IN REALITY...THERE IS MORE LIKE
A 5 TO 10 PERCENT CHANCE OF STORMS IN ANY LOCATION. IT CERTAINLY IS
RARE TO SEE THE AFTERNOON DEWPOINT DEPRESSIONS OF 40 TO 50 DEGREES
THIS FAR EAST...AS THIS TYPE OF SPREAD IS MORE TYPICAL OF WESTERN
PLAINS...WEST OF A WARM SEASON DRYLINE.
LATE TONIGHT AND WEDNESDAY...NORTH TO NORTHEAST WINDS AND COLD
ADVECTION WILL COMMENCE...WITH LOWS FALLING THE MID 40S NORTHEAST TO
LOWER 50S SOUTH. WITH PLENTY OF SUN AGAIN...LOW DEWPOINTS...AND
DRYING GROUND..EXPECT ANOTHER DEEP MIXING DAY WEDNESDAY...WITH HIGHS
IN THE LOWER 70S EAST...TO MID 70S CENTRAL AND SOUTHWEST. ERVIN
LONG TERM...WEDNESDAY NIGHT THROUGH NEXT TUESDAY...
GENERALLY DRY UNTIL MONDAY...THEN CHANCES FOR THUNDERSTORMS.
OVERVIEW...INITIALIZATION GOOD ON KINEMATICS WITH BL TOO MOIST BIASES
CONTINUE. VERIFICATION AT 18Z SUGGESTS A 50/50 MIX OF THE 80KM NAM-
WRF AND HI-RES ECMWF WITH ADJUSTMENTS TOWARD DRIER BL CONDITIONS AND
IMPACTS ON DIURNAL TEMPERATURES. BEYOND DAY 3...A WEIGHTING OF A
60/40 TOWARD HI-RES ECMWF TO GFS DUE TO MOISTURE AND RUN TO RUN
CONTINUITY ISSUES.
WEDNESDAY NIGHT...SEASONABLY COOL AND MOSTLY CLEAR WITH LOWS MOSTLY
COOLER THAN GUIDANCE. LOCAL TOOLS SUGGEST AREAS THAT DECOUPLE MAY
NEED FURTHER LOWERING ON MINS BY UP TO 3 DEGREES FOR LATER SHIFTS.
LIGHT EAST WINDS AND SUBSIDENCE DO SUGGEST CALM TO NEARLY CALM
WINDS FOR SEVERAL HOURS.
THURSDAY INTO SATURDAY...UPPER RIDGING AND DECENT SOUTHERLY WINDS
FOR WARMER AIR ARRIVING TO RESULT IN FAIR SKIES WITH TEMPERATURES
ABOVE NORMAL. LARGE DIURNAL TEMPERATURES LIKELY MORE THAN GUIDANCE
WITH UPPER 70S TO 80+F THURSDAY AND LOWER TO MIDDLE 80S FRIDAY AND
SATURDAY AT A MINIMUM THAT MAY NEED RAISING A FEW DEGREES EACH DAY
MANY LOCATIONS FOR LATER SHIFTS. MINS IN THE 50S THURSDAY MORNING AND
MOSTLY IN THE LOWER TO MIDDLE 60S FRIDAY MORNING. SUBSIDENCE AND NO
FORCING AND MOISTURE FOR PRECIPITATION IS INDICATED AS DRY SPELL
CONTINUES.
SATURDAY NIGHT THROUGH MONDAY...SLOWLY INCREASING CHANCE OF
THUNDERSTORMS BY MONDAY AS SLOW MOVING AND WEAKENING COOL FRONT
ARRIVES. CHANCE POPS ARE SUGGESTED DUE TO POOR TIMING ISSUES FOR
LATER SHIFTS. SOME RISK OF SEVERE SUGGESTED WITH PM SBCAPES OF 1500-
2500+ J/KG SUGGESTED ATTM. LOCAL PAST EVENTS SUGGEST AN EPISODE OR
TWO OF MCS SYSTEMS WITH MOSTLY LIGHT TO MODERATE AMOUNTS FOR THE
AREA. HIGHS TO FALL INTO THE 70S BY MONDAY DUE TO CONSIDERABLE
CLOUDINESS FROM WEAK UPPER AND SFC LOW CONVERGENT FLOW. DEWPOINTS
SHOULD ALSO RISE AOA 60F FOR SOME HUMIDITY DURING THIS TIME PERIOD.
TUESDAY...KEPT SLIGHT CHANCE POPS ATTM BUT DRY AND NEAR SEASONABLE
TEMPERATURES SUGGESTED FOR LATTER PORTIONS OF MAY WITH MODERATING
HUMIDITY. NICHOLS
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
000
FXUS63 KDMX 160417 AAB
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1120 PM CDT TUE MAY 15 2012
.UPDATE FOR 16/06Z AVIATION DISCUSSION...
.SYNOPSIS...
COLD FRONT EXTENDED FROM CENTRAL WI TO CENTRAL IA TO SOUTHEAST
NEB AT MID AFTERNOON...WITH A LINE OF SHOWERS THAT JUST DEVELOPED
FROM ABOUT MARSHALLTOWN ON TO THE NORTHEAST INTO WI. WHILE VERY HIGH
BASED CUMULUS HAVE FORMED...SURFACE DEWPOINTS HAVE MIXED DOWN TO
THE MID 30S TO LOWER 40S ALONG THE FRONT. IN ADDITION...TEMPERATURES
NEAR THE FRONT ARE WELL INTO THE 80S TO NEAR 90...RESULTING IN
VERY LOW RH VALUES AROUND 20 TO 25 PERCENT. NORTH WINDS WERE
GUSTING TO OVER 30 MPH BEHIND THE FRONT WITH TEMPERATURES ONLY IN
THE 60S IN PORTIONS OF THE DAKOTAS AND MN.
&&
.SHORT TERM...TONIGHT AND WEDNESDAY...
FORECAST FOCUS ON DRY AND COOLER TEMPERATURES.
TONIGHT...WILL CARRY ONLY A SLIGHT CHANCE FOR A THUNDERSTORM IN
THE SOUTHEAST CWA LATE THIS AFTERNOON INTO EARLY THIS EVENING AS
COLD FRONT MAKES PROGRESS TO THE SOUTH. FOR THE REMAINDER OF THE
NIGHT EXPECT CLEAR SKIES ALONG WITH DIMINISHING WINDS AND COOLER
TEMPERATURES...AS HIGH PRESSURE RIDGE MOVES IN FROM THE WEST.
MINIMUM TEMPERATURES WILL DROP INTO THE MID 40S NORTH OF HIGHWAY
20 TO AROUND 50 IN THE SOUTHERN CWA.
WEDNESDAY...DELIGHTFUL DAY WITH HIGH PRESSURE OVER THE REGION
BRINGING PLENTY OF SUNSHINE AND RATHER LIGHT WINDS. MAX TEMPS WILL
BE IN THE 70S.
.LONG TERM...WEDNESDAY NIGHT THROUGH NEXT TUESDAY...
DRY AND WARMER THROUGH SATURDAY THEN CHANCES OF THUNDERSTORMS
RETURN.
WEDNESDAY NIGHT THROUGH SATURDAY...WITH RIDGING ALOFT BUILDING
INTO THE REGION ALONG WITH SOUTHERLY FLOW TEMPERATURES WILL BE
WARMING WELL INTO THE 80S. MIN TEMPS IN THE 50S WEDNESDAY NIGHT
WILL BE IN THE 60S THE REMAINDER OF THIS PERIOD.
SATURDAY NIGHT THROUGH TUESDAY...
UPPER TROUGH AND ASSOCIATED COLD FRONT WILL BE MOVING SLOWLY
ACROSS THE REGION. WILL BRING IN CHANCE POPS SATURDAY NIGHT WITH
LIKELY POPS SUNDAY INTO SUNDAY NIGHT. THUNDERSTORM CHANCES WILL
END ON MONDAY IN THE EASTERN CWA. WITH THE FRONT MOVING THROUGH
AND MORE CLOUD COVER...MAX TEMPS WILL ONCE AGAIN BE IN THE 70S.
&&
.AVIATION 16/06Z...
HIGH PRESSURE BUILDS INTO THE TAF LOCATIONS THROUGH THE FORECAST
PD. VFR CONDITIONS EXPECTED ALONG WITH A NORTH WIND AROUND 10 KTS.
SOME MID/HIGH CLOUDS POSSIBLE WITH THE WIND SHIFT TO THE SOUTH LATER
IN THE DAY AS THE RIDGE AXIS SHIFTS TO THE EAST.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
.SHORT AND LONG TERM...HAASE/DVN
.AVIATION...FAB
000
FXUS63 KDVN 160046
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
746 PM CDT TUE MAY 15 2012
.AVIATION...
A COLD FRONT WILL CONTINUE TO DROP SOUTHEAST THROUGH THE FORECAST
AREA THIS EVENING. THE FRONT IS ALREADY THROUGH KCID AND KDBQ AND
SHOULD MOVE PAST KMLI AND KBRL BY 03Z. ISOLATED SHRA/TSRA AHEAD OF
THE FRONT ARE PAST KMLI. THE SHRA/TSRA ARE EXPECTED TO DIMINISH IN
COVERAGE AND POSSIBLY DISSIPATE WITH THE LOSS OF HEATING AND WILL
PROBABLY NOT REACH KBRL. GUSTY POST FRONTAL NORTHWEST WINDS WILL
DIMINISH RAPIDLY EARLY THIS EVENING WITH WINDS GRADUALLY VEERING
TO THE NORTHEAST THEN EAST OVERNIGHT. HIGH PRESSURE BUILDING IN BY
WEDNESDAY AFTERNOON WILL BRING LIGHT AND VARIABLE WINDS TO THE
REGION. FLIGHT CONDITIONS WILL BE VFR THROUGH WEDNESDAY AFTERNOON.
&&
.PREV DISCUSSION... /ISSUED 245 PM CDT TUE MAY 15 2012/
SYNOPSIS...
THE CWA IS BEGINNING TO EXPERIENCE A COLD FROPA FROM NORTHWEST TO
SOUTHEAST AS OF EARLY AFTERNOON...AND THUS FAR IT IS DRY. WHILE VERY
HIGH BASED CUMULUS HAVE FORMED...SURFACE DEWPOINTS HAVE MIXED DOWN
TO THE MID 30S TO LOWER 40S ALONG THE FRONT. IN
ADDITION...TEMPERATURES NEAR THE FRONT ARE IN THE UPPER 80S TO
90...RESULTING IN VERY LOW RH VALUES AROUND 20 TO 25 PERCENT.
OTHERWISE...TEMPERATURES AS OF 2 PM ARE IN THE LOWER TO MID 80S WITH
DEWPOINTS IN THE MID 40S TO LOWER 50S. AS THE FRONT
APPROACHES...FURTHER DROPS IN DEWPOINTS ARE EXPECTED.
SHORT TERM...TONIGHT AND WEDNESDAY...
THUNDERSTORM POTENTIAL TONIGHT WILL LIKELY BE MUCH LESS THAN ANY
MODEL SUGGESTS GIVEN THE MUCH LOWER FRONTAL SURFACE DEWPOINTS.
THUS...WILL KEEP MENTION OF AN ISOLATED STORM THROUGH 9 PM...BUT IN
REALITY IF NO STORMS FIRE BY 5 PM...THIS THREAT CAN BE REMOVED.
COVERAGE TO MENTION STORMS NEEDS TO BE 15 PERCENT OR HIGHER...THUS
THAT IS MY PERCENT CHANCE FORECAST. IN REALITY...THERE IS MORE LIKE
A 5 TO 10 PERCENT CHANCE OF STORMS IN ANY LOCATION. IT CERTAINLY IS
RARE TO SEE THE AFTERNOON DEWPOINT DEPRESSIONS OF 40 TO 50 DEGREES
THIS FAR EAST...AS THIS TYPE OF SPREAD IS MORE TYPICAL OF WESTERN
PLAINS...WEST OF A WARM SEASON DRYLINE.
LATE TONIGHT AND WEDNESDAY...NORTH TO NORTHEAST WINDS AND COLD
ADVECTION WILL COMMENCE...WITH LOWS FALLING THE MID 40S NORTHEAST TO
LOWER 50S SOUTH. WITH PLENTY OF SUN AGAIN...LOW DEWPOINTS...AND
DRYING GROUND..EXPECT ANOTHER DEEP MIXING DAY WEDNESDAY...WITH HIGHS
IN THE LOWER 70S EAST...TO MID 70S CENTRAL AND SOUTHWEST. ERVIN
LONG TERM...WEDNESDAY NIGHT THROUGH NEXT TUESDAY...
GENERALLY DRY UNTIL MONDAY...THEN CHANCES FOR THUNDERSTORMS.
OVERVIEW...INITIALIZATION GOOD ON KINEMATICS WITH BL TOO MOIST BIASES
CONTINUE. VERIFICATION AT 18Z SUGGESTS A 50/50 MIX OF THE 80KM NAM-
WRF AND HI-RES ECMWF WITH ADJUSTMENTS TOWARD DRIER BL CONDITIONS AND
IMPACTS ON DIURNAL TEMPERATURES. BEYOND DAY 3...A WEIGHTING OF A
60/40 TOWARD HI-RES ECMWF TO GFS DUE TO MOISTURE AND RUN TO RUN
CONTINUITY ISSUES.
WEDNESDAY NIGHT...SEASONABLY COOL AND MOSTLY CLEAR WITH LOWS MOSTLY
COOLER THAN GUIDANCE. LOCAL TOOLS SUGGEST AREAS THAT DECOUPLE MAY
NEED FURTHER LOWERING ON MINS BY UP TO 3 DEGREES FOR LATER SHIFTS.
LIGHT EAST WINDS AND SUBSIDENCE DO SUGGEST CALM TO NEARLY CALM
WINDS FOR SEVERAL HOURS.
THURSDAY INTO SATURDAY...UPPER RIDGING AND DECENT SOUTHERLY WINDS
FOR WARMER AIR ARRIVING TO RESULT IN FAIR SKIES WITH TEMPERATURES
ABOVE NORMAL. LARGE DIURNAL TEMPERATURES LIKELY MORE THAN GUIDANCE
WITH UPPER 70S TO 80+F THURSDAY AND LOWER TO MIDDLE 80S FRIDAY AND
SATURDAY AT A MINIMUM THAT MAY NEED RAISING A FEW DEGREES EACH DAY
MANY LOCATIONS FOR LATER SHIFTS. MINS IN THE 50S THURSDAY MORNING AND
MOSTLY IN THE LOWER TO MIDDLE 60S FRIDAY MORNING. SUBSIDENCE AND NO
FORCING AND MOISTURE FOR PRECIPITATION IS INDICATED AS DRY SPELL
CONTINUES.
SATURDAY NIGHT THROUGH MONDAY...SLOWLY INCREASING CHANCE OF
THUNDERSTORMS BY MONDAY AS SLOW MOVING AND WEAKENING COOL FRONT
ARRIVES. CHANCE POPS ARE SUGGESTED DUE TO POOR TIMING ISSUES FOR
LATER SHIFTS. SOME RISK OF SEVERE SUGGESTED WITH PM SBCAPES OF 1500-
2500+ J/KG SUGGESTED ATTM. LOCAL PAST EVENTS SUGGEST AN EPISODE OR
TWO OF MCS SYSTEMS WITH MOSTLY LIGHT TO MODERATE AMOUNTS FOR THE
AREA. HIGHS TO FALL INTO THE 70S BY MONDAY DUE TO CONSIDERABLE
CLOUDINESS FROM WEAK UPPER AND SFC LOW CONVERGENT FLOW. DEWPOINTS
SHOULD ALSO RISE AOA 60F FOR SOME HUMIDITY DURING THIS TIME PERIOD.
TUESDAY...KEPT SLIGHT CHANCE POPS ATTM BUT DRY AND NEAR SEASONABLE
TEMPERATURES SUGGESTED FOR LATTER PORTIONS OF MAY WITH MODERATING
HUMIDITY. NICHOLS
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
000
FXUS63 KDMX 152305
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
605 PM CDT TUE MAY 15 2012
.UPDATE FOR 16/00Z AVIATION DISCUSSION...
.SYNOPSIS...
COLD FRONT EXTENDED FROM CENTRAL WI TO CENTRAL IA TO SOUTHEAST
NEB AT MID AFTERNOON...WITH A LINE OF SHOWERS THAT JUST DEVELOPED
FROM ABOUT MARSHALLTOWN ON TO THE NORTHEAST INTO WI. WHILE VERY HIGH
BASED CUMULUS HAVE FORMED...SURFACE DEWPOINTS HAVE MIXED DOWN TO
THE MID 30S TO LOWER 40S ALONG THE FRONT. IN ADDITION...TEMPERATURES
NEAR THE FRONT ARE WELL INTO THE 80S TO NEAR 90...RESULTING IN
VERY LOW RH VALUES AROUND 20 TO 25 PERCENT. NORTH WINDS WERE
GUSTING TO OVER 30 MPH BEHIND THE FRONT WITH TEMPERATURES ONLY IN
THE 60S IN PORTIONS OF THE DAKOTAS AND MN.
&&
.SHORT TERM...TONIGHT AND WEDNESDAY...
FORECAST FOCUS ON DRY AND COOLER TEMPERATURES.
TONIGHT...WILL CARRY ONLY A SLIGHT CHANCE FOR A THUNDERSTORM IN
THE SOUTHEAST CWA LATE THIS AFTERNOON INTO EARLY THIS EVENING AS
COLD FRONT MAKES PROGRESS TO THE SOUTH. FOR THE REMAINDER OF THE
NIGHT EXPECT CLEAR SKIES ALONG WITH DIMINISHING WINDS AND COOLER
TEMPERATURES...AS HIGH PRESSURE RIDGE MOVES IN FROM THE WEST.
MINIMUM TEMPERATURES WILL DROP INTO THE MID 40S NORTH OF HIGHWAY
20 TO AROUND 50 IN THE SOUTHERN CWA.
WEDNESDAY...DELIGHTFUL DAY WITH HIGH PRESSURE OVER THE REGION
BRINGING PLENTY OF SUNSHINE AND RATHER LIGHT WINDS. MAX TEMPS WILL
BE IN THE 70S.
.LONG TERM...WEDNESDAY NIGHT THROUGH NEXT TUESDAY...
DRY AND WARMER THROUGH SATURDAY THEN CHANCES OF THUNDERSTORMS
RETURN.
WEDNESDAY NIGHT THROUGH SATURDAY...WITH RIDGING ALOFT BUILDING
INTO THE REGION ALONG WITH SOUTHERLY FLOW TEMPERATURES WILL BE
WARMING WELL INTO THE 80S. MIN TEMPS IN THE 50S WEDNESDAY NIGHT
WILL BE IN THE 60S THE REMAINDER OF THIS PERIOD.
SATURDAY NIGHT THROUGH TUESDAY...
UPPER TROUGH AND ASSOCIATED COLD FRONT WILL BE MOVING SLOWLY
ACROSS THE REGION. WILL BRING IN CHANCE POPS SATURDAY NIGHT WITH
LIKELY POPS SUNDAY INTO SUNDAY NIGHT. THUNDERSTORM CHANCES WILL
END ON MONDAY IN THE EASTERN CWA. WITH THE FRONT MOVING THROUGH
AND MORE CLOUD COVER...MAX TEMPS WILL ONCE AGAIN BE IN THE 70S.
&&
.AVIATION 16/00Z...
FEW CONCERNS THIS PERIOD AS COLD FRONT PASSES SOUTHEAST OF REGION
THIS EVENING AND DRY AIRMASS DISPLACES THINNING LINE OF CU AND
MOISTURE ADVECTION SOUTH OF THE REGION. WINDS WILL REMAIN GUSTY THIS
EVENING BUT BOUNDARY LAYER SHOULD DECOUPLE BY 01-03Z TIME FRAME AS
WEAK HIGH BUILDS SOUTHEAST INTO THE AREA OVERNIGHT. HIGH TO SLIDE
EAST OF IOWA BY WEDNESDAY AFTERNOON AND WINDS SHOULD FIRST REMAIN
LIGHT FROM THE NORTHEAST/EAST THROUGH 18Z WEST...20Z EAST AND THE
BECOME MORE SOUTHEAST/SOUTH WITH TIME AFT 18Z WEST AND AFT 20Z EAST.
THIS WILL KEEP LIGHT WINDS AND VFR CIGS IN THE FORECAST WITH ONLY
SCT/BKN250 POSSIBLE OVER THE REGION AS SOME CLOUDS RETURN OVER TOP
OF RIDGE AXIS. /REV
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
.SHORT AND LONG TERM...HAASE/DVN
.AVIATION...REV/DMX
000
FXUS63 KDMX 152021
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
ISSUED BY NATIONAL WEATHER SERVICE QUAD CITIES IA IL
321 PM CDT TUE MAY 15 2012
.SYNOPSIS...
COLD FRONT EXTENDED FROM CENTRAL WI TO CENTRAL IA TO SOUTHEAST
NEB AT MID AFTERNOON...WITH A LINE OF SHOWERS THAT JUST DEVELOPED
FROM ABOUT MARSHALLTOWN ON TO THE NORTHEAST INTO WI. WHILE VERY HIGH
BASED CUMULUS HAVE FORMED...SURFACE DEWPOINTS HAVE MIXED DOWN TO
THE MID 30S TO LOWER 40S ALONG THE FRONT. IN ADDITION...TEMPERATURES
NEAR THE FRONT ARE WELL INTO THE 80S TO NEAR 90...RESULTING IN
VERY LOW RH VALUES AROUND 20 TO 25 PERCENT. NORTH WINDS WERE
GUSTING TO OVER 30 MPH BEHIND THE FRONT WITH TEMPERATURES ONLY IN
THE 60S IN PORTIONS OF THE DAKOTAS AND MN.
&&
.SHORT TERM...TONIGHT AND WEDNESDAY...
FORECAST FOCUS ON DRY AND COOLER TEMPERATURES.
TONIGHT...WILL CARRY ONLY A SLIGHT CHANCE FOR A THUNDERSTORM IN
THE SOUTHEAST CWA LATE THIS AFTERNOON INTO EARLY THIS EVENING AS
COLD FRONT MAKES PROGRESS TO THE SOUTH. FOR THE REMAINDER OF THE
NIGHT EXPECT CLEAR SKIES ALONG WITH DIMINISHING WINDS AND COOLER
TEMPERATURES...AS HIGH PRESSURE RIDGE MOVES IN FROM THE WEST.
MINIMUM TEMPERATURES WILL DROP INTO THE MID 40S NORTH OF HIGHWAY
20 TO AROUND 50 IN THE SOUTHERN CWA.
WEDNESDAY...DELIGHTFUL DAY WITH HIGH PRESSURE OVER THE REGION
BRINGING PLENTY OF SUNSHINE AND RATHER LIGHT WINDS. MAX TEMPS WILL
BE IN THE 70S.
.LONG TERM...WEDNESDAY NIGHT THROUGH NEXT TUESDAY...
DRY AND WARMER THROUGH SATURDAY THEN CHANCES OF THUNDERSTORMS
RETURN.
WEDNESDAY NIGHT THROUGH SATURDAY...WITH RIDGING ALOFT BUILDING
INTO THE REGION ALONG WITH SOUTHERLY FLOW TEMPERATURES WILL BE
WARMING WELL INTO THE 80S. MIN TEMPS IN THE 50S WEDNESDAY NIGHT
WILL BE IN THE 60S THE REMAINDER OF THIS PERIOD.
SATURDAY NIGHT THROUGH TUESDAY...
UPPER TROUGH AND ASSOCIATED COLD FRONT WILL BE MOVING SLOWLY
ACROSS THE REGION. WILL BRING IN CHANCE POPS SATURDAY NIGHT WITH
LIKELY POPS SUNDAY INTO SUNDAY NIGHT. THUNDERSTORM CHANCES WILL
END ON MONDAY IN THE EASTERN CWA. WITH THE FRONT MOVING THROUGH
AND MORE CLOUD COVER...MAX TEMPS WILL ONCE AGAIN BE IN THE 70S.
&&
.AVIATION...
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. WINDS WILL
CONTINUE TO SHIFT AND INCREASE FROM THE NORTH BEHIND ADVANCING COLD
FRONT. CLEAR SKIES WILL DOMINATE THE ENTIRE FORECAST PERIOD.
ISOLD TSRA POSSIBLE LATE THIS AFTN ALONG THE FRONT IN FAR SE
IA...AND HAVE NOT INCLUDED THIS IN TAF FORECAST DUE TO VERY LOW
COVERAGE AND CONFIDENCE IN IT OCCURRING.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
HAASE
000
FXUS63 KDVN 151945
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
245 PM CDT TUE MAY 15 2012
.SYNOPSIS...
THE CWA IS BEGINNING TO EXPERIENCE A COLD FROPA FROM NORTHWEST TO
SOUTHEAST AS OF EARLY AFTERNOON...AND THUS FAR IT IS DRY. WHILE VERY
HIGH BASED CUMULUS HAVE FORMED...SURFACE DEWPOINTS HAVE MIXED DOWN
TO THE MID 30S TO LOWER 40S ALONG THE FRONT. IN
ADDITION...TEMPERATURES NEAR THE FRONT ARE IN THE UPPER 80S TO
90...RESULTING IN VERY LOW RH VALUES AROUND 20 TO 25 PERCENT.
OTHERWISE...TEMPERATURES AS OF 2 PM ARE IN THE LOWER TO MID 80S WITH
DEWPOINTS IN THE MID 40S TO LOWER 50S. AS THE FRONT
APPROACHES...FURTHER DROPS IN DEWPOINTS ARE EXPECTED.
&&
.SHORT TERM...TONIGHT AND WEDNESDAY...
THUNDERSTORM POTENTIAL TONIGHT WILL LIKELY BE MUCH LESS THAN ANY
MODEL SUGGESTS GIVEN THE MUCH LOWER FRONTAL SURFACE DEWPOINTS.
THUS...WILL KEEP MENTION OF AN ISOLATED STORM THROUGH 9 PM...BUT IN
REALITY IF NO STORMS FIRE BY 5 PM...THIS THREAT CAN BE REMOVED.
COVERAGE TO MENTION STORMS NEEDS TO BE 15 PERCENT OR HIGHER...THUS
THAT IS MY PERCENT CHANCE FORECAST. IN REALITY...THERE IS MORE LIKE
A 5 TO 10 PERCENT CHANCE OF STORMS IN ANY LOCATION. IT CERTAINLY IS
RARE TO SEE THE AFTERNOON DEWPOINT DEPRESSIONS OF 40 TO 50 DEGREES
THIS FAR EAST...AS THIS TYPE OF SPREAD IS MORE TYPICAL OF WESTERN
PLAINS...WEST OF A WARM SEASON DRYLINE.
LATE TONIGHT AND WEDNESDAY...NORTH TO NORTHEAST WINDS AND COLD
ADVECTION WILL COMMENCE...WITH LOWS FALLING THE MID 40S NORTHEAST TO
LOWER 50S SOUTH. WITH PLENTY OF SUN AGAIN...LOW DEWPOINTS...AND
DRYING GROUND..EXPECT ANOTHER DEEP MIXING DAY WEDNESDAY...WITH HIGHS
IN THE LOWER 70S EAST...TO MID 70S CENTRAL AND SOUTHWEST. ERVIN
.LONG TERM...WEDNESDAY NIGHT THROUGH NEXT TUESDAY...
GENERALLY DRY UNTIL MONDAY...THEN CHANCES FOR THUNDERSTORMS.
OVERVIEW...INITIALIZATION GOOD ON KINEMATICS WITH BL TOO MOIST BIASES
CONTINUE. VERIFICATION AT 18Z SUGGESTS A 50/50 MIX OF THE 80KM NAM-
WRF AND HI-RES ECMWF WITH ADJUSTMENTS TOWARD DRIER BL CONDITIONS AND
IMPACTS ON DIURNAL TEMPERATURES. BEYOND DAY 3...A WEIGHTING OF A
60/40 TOWARD HI-RES ECMWF TO GFS DUE TO MOISTURE AND RUN TO RUN
CONTINUITY ISSUES.
WEDNESDAY NIGHT...SEASONABLY COOL AND MOSTLY CLEAR WITH LOWS MOSTLY
COOLER THAN GUIDANCE. LOCAL TOOLS SUGGEST AREAS THAT DECOUPLE MAY
NEED FURTHER LOWERING ON MINS BY UP TO 3 DEGREES FOR LATER SHIFTS.
LIGHT EAST WINDS AND SUBSIDENCE DO SUGGEST CALM TO NEARLY CALM
WINDS FOR SEVERAL HOURS.
THURSDAY INTO SATURDAY...UPPER RIDGING AND DECENT SOUTHERLY WINDS
FOR WARMER AIR ARRIVING TO RESULT IN FAIR SKIES WITH TEMPERATURES
ABOVE NORMAL. LARGE DIURNAL TEMPERATURES LIKELY MORE THAN GUIDANCE
WITH UPPER 70S TO 80+F THURSDAY AND LOWER TO MIDDLE 80S FRIDAY AND
SATURDAY AT A MINIMUM THAT MAY NEED RAISING A FEW DEGREES EACH DAY
MANY LOCATIONS FOR LATER SHIFTS. MINS IN THE 50S THURSDAY MORNING AND
MOSTLY IN THE LOWER TO MIDDLE 60S FRIDAY MORNING. SUBSIDENCE AND NO
FORCING AND MOISTURE FOR PRECIPITATION IS INDICATED AS DRY SPELL
CONTINUES.
SATURDAY NIGHT THROUGH MONDAY...SLOWLY INCREASING CHANCE OF
THUNDERSTORMS BY MONDAY AS SLOW MOVING AND WEAKENING COOL FRONT
ARRIVES. CHANCE POPS ARE SUGGESTED DUE TO POOR TIMING ISSUES FOR
LATER SHIFTS. SOME RISK OF SEVERE SUGGESTED WITH PM SBCAPES OF 1500-
2500+ J/KG SUGGESTED ATTM. LOCAL PAST EVENTS SUGGEST AN EPISODE OR
TWO OF MCS SYSTEMS WITH MOSTLY LIGHT TO MODERATE AMOUNTS FOR THE
AREA. HIGHS TO FALL INTO THE 70S BY MONDAY DUE TO CONSIDERABLE
CLOUDINESS FROM WEAK UPPER AND SFC LOW CONVERGENT FLOW. DEWPOINTS
SHOULD ALSO RISE AOA 60F FOR SOME HUMIDITY DURING THIS TIME PERIOD.
TUESDAY...KEPT SLIGHT CHANCE POPS ATTM BUT DRY AND NEAR SEASONABLE
TEMPERATURES SUGGESTED FOR LATTER PORTIONS OF MAY WITH MODERATING
HUMIDITY. NICHOLS
&&
.AVIATION...
WIDESPREAD VFR WEATHER WILL CONTINUE THROUGH THE NEXT 24 HOURS...AS
A FRONT PASSES THROUGH EASTERN IOWA AND ILLINOIS LATE THIS AFTERNOON
AND EVENING...FOLLOWED BY HIGH PRESSURE. A VERY LOW CHANCE FOR AN
ISOLATED THUNDERSTORMS EXISTS AT ALL SITES BETWEEN 21Z TODAY AND
02Z/16. THIS THREAT IS TOO LOW TO PLACE INTO A TAF FORECAST AT THIS
TIME...BUT WILL BE WATCHED FOR FUTURE UPDATES. WINDS WILL BE 10 TO
20 KTS FROM THE WEST SOUTHWEST TODAY...AND TOWARDS 00Z...WILL BECOME
NORTH. AFTER 02Z...NORTH WINDS WILL DECREASE TO 5 TO 10 KTS AND
REMAIN NORTH TO NORTHEAST THROUGH 18Z/16. ERVIN
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
ERVIN/NICHOLS
000
FXUS63 KDMX 151718 AAA
AFDDMX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
ISSUED BY NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1217 PM CDT TUE MAY 15 2012
...UPDATED AVIATION DISCUSSION...
.SHORT TERM /TODAY/...
BIG WEATHER MAKER FOR TODAY WILL BE THE COLD FRONT APPROACHING FROM
SD/MN LATER THIS MORNING. THE FRONT IS CURRENTLY IN NE SD AND
BARRELING SOUTHEASTWARD AT A PRETTY GOOD CLIP WITH A DECENT PUSH
BEHIND IT...SUSTAINED WINDS ARE AROUND 25 MPH CURRENTLY IN PARTS OF
EASTERN ND. AS THE PARENT LOW MOVES QUICKLY EASTWARD OVER THE GREAT
LAKES TODAY EXPECT THE FRONT WILL SLOW SLIGHTLY...BUT STILL CROSS
OUR AREA BY AROUND OR SHORTLY AFTER 00Z THIS EVENING. AHEAD OF THE
FRONT...MODEST SOUTHWEST BREEZES HAVE KEPT TEMPERATURES UP FOR THE
MOST PART EARLY THIS MORNING AND SHOULD PROVIDE FOR RAPID WARMING
AFTER SUNRISE TODAY DESPITE INCREASING HIGH CLOUDS. TEMPERATURES ARE
TRICKY FOR TODAY AS THE FRONTAL BOUNDARY SHOULD ENTER OUR NW CORNER
AROUND 14 OR 15Z...BUT THERE WILL BE A DELAY AFTER THAT IN THE
ARRIVAL OF THE REAL SURGE OF COLD AIR. HAVE TAKEN A BEST
GUESS...NEAR MOS IN THE FAR NORTH BUT ABOVE MOS EVERYWHERE ELSE
GIVEN WARM START TEMPERATURES...AND GONE WITH A NON-DIURNAL CURVE TO
TRY TO ACCOUNT FOR FROPA AS DISCUSSED ABOVE.
THE OTHER CONCERN WITH THE FRONT TODAY IS POTENTIAL FOR THUNDERSTORM
DEVELOPMENT THIS AFTERNOON. DEWPOINTS ARE CURRENTLY IN THE MID 30S
TO MID 40S ACROSS THE AREA...AND SHOULD PEAK ONLY IN THE LOWER 50S
OR SO IN OUR SOUTHEAST THIS AFTERNOON...SO MOISTURE IS RELATIVELY
LACKING. HOWEVER...WE SHOULD SEE DECENT LOW-LEVEL CONVERGENCE ALONG
THE BOUNDARY AND STRONG ENOUGH HEATING AHEAD OF IT TO PRODUCE SOME
INSTABILITY AND TRIGGER A FEW STORMS LATE IN THE AFTERNOON. HAVE
CONCENTRATED POPS MAINLY IN OUR SOUTHEASTERN HALF AFTER 21Z...BUT
EVEN THEN WENT WITH ONLY ISOLATED TO SCATTERED. BULK SHEAR IS
EXPECTED TO INCREASE ALONG THE BOUNDARY LATE IN THE DAY AND THERE IS
SOME LOW POTENTIAL FOR ISOLATED HAIL OR WIND GUSTS WITH SOME OF THE
STORMS...WHICH IS WELL ADVERTISED IN SPC DISCUSSIONS AND OTHER
PRODUCTS.
.LONG TERM /TONIGHT THROUGH MONDAY/...
COLD FRONT WILL EXIT THE CWA EARLY IN THE FORECAST PERIOD AND
CARRIED A SLIVER OF TSRA FOR THE FIRST FEW HOURS THIS EVENING.
COOLER AIR IF POURING SOUTH ACROSS ND AND NORTHERN MN AND WILL GO
BELOW MOS TEMPS FOR TONIGHT. WOULD NOT BE SURPRISED TO SEE IT GET A
FEW DEGREES BELOW WHAT IS IN THE GRID. QUITE WEATHER AFTER THAT FOR
A WHILE. WARMER AIR WILL PUSH NORTH FOR THU AND FRI...BUT IT WILL
REMAIN QUITE DRY. THOUGH THERE IS A DECENT PUSH OF WAA AND SOME
LIFT WITH THE RETURN OF THE WRMFNT...FEEL THERE WON`T BE ENOUGH FOR
IT TO GO. GFS KICKS OUT SOME TSRA ON FRI AND HAVE REAL DOUBTS ABOUT
THAT AND DID NOT INCLUDE. SOUNDINGS INDICATE A SIGNIFICANT CAP IN
PLACE IN SPITE OF 3000-4000 J/KG BY AFTERNOON. IT WOULD TAKE MORE
DYNAMICS THAN THERE ARE AVAILABLE TO KICK IT OFF. WITH THE WEATHER
FEATURE FOR THE WEEKEND HELD OFF RAIN UNTIL LATE SAT OVER THE
NORTHWEST PART OF THE CWA. SOUTHEAST SHOULD REMAIN DRY. NO REAL
CHANGES IN THE FORECAST FARTHER OUT. GFS WAS QUITE A BIT FASTER
THAN THE EC ON THE 12Z RUN...BUT THE TWO ARE FAIRLY CLOSE TONIGHT
AND THERE IS NO REAL REASON TO MAKE ADJUSTMENTS.
&&
.AVIATION...15/18Z
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. WINDS WILL SHIFT
AND INCREASE BEHIND ADVANCING COLD FRONT TODAY...HAVE TAKEN BEST
GUESS AT TIMING OF FROPA IN THE TAFS. DRY CONDITIONS WILL PRECLUDE
LOW CIGS WITH THE FRONT HOWEVER...ONLY HIGH CLOUDS OR CLEAR SKIES
FOR THE MOST PART THEN SKC BEHIND THE FRONT TONIGHT. ISOLD TSRA
POSSIBLE LATE THIS AFTN AND EVE ESPECIALLY IN FAR SE IA...AND HAVE
NO INCLUDED THIS IN TAF FORECAST DUE TO VERY LOW COVERAGE AND
CONFIDENCE IN IT OCCURRING.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...LEE
LONG TERM...MS MAY 12
AVIATION...ERVIN
000
FXUS63 KDVN 151713
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1213 PM CDT TUE MAY 15 2012
.AVIATION...
WIDESPREAD VFR WEATHER WILL CONTINUE THROUGH THE NEXT 24
HOURS...AS A FRONT PASSES THROUGH EASTERN IOWA AND ILLINOIS LATE
THIS AFTERNOON AND EVENING...FOLLOWED BY HIGH PRESSURE. A VERY LOW
CHANCE FOR AN ISOLATED THUNDERSTORMS EXISTS AT ALL SITES BETWEEN
21Z TODAY AND 02Z/16. THIS THREAT IS TOO LOW TO PLACE INTO A TAF
FORECAST AT THIS TIME...BUT WILL BE WATCHED FOR FUTURE UPDATES.
WINDS WILL BE 10 TO 20 KTS FROM THE WEST SOUTHWEST TODAY...AND
TOWARDS 00Z...WILL BECOME NORTH. AFTER 02Z...NORTH WINDS WILL
DECREASE TO 5 TO 10 KTS AND REMAIN NORTH TO NORTHEAST THROUGH
18Z/16. ERVIN
&&
.PREV DISCUSSION... /ISSUED 353 AM CDT TUE MAY 15 2012/
SYNOPSIS...
RATHER VIGOROUS COMPACT SHORTWAVE DIVING E/SE INTO WRN ONTARIO
PROVINCE AND NRN MN EARLY THIS AM. ATTENDANT WEAK SFC LOW WAS
LOCATED OVER THE ARROWHEAD OF MN WITH COLD FRONT TRAILING SWWD
THROUGH SD. LIMITED MOISTURE WITH FRONT WITH SFC DEWPTS IN THE
30S AND 40S... AND PRECIPITABLE WATER VALUES AROUND 0.5 INCH
OR LESS OVER THE UPPER MIDWEST.
SHORT TERM...TODAY AND TONIGHT...
MAIN FCST CONCERN IS PCPN CHCS AND SEVERE POTENTIAL WITH FRONT
THIS AFTN/EVE.
SHORTWAVE OVER NRN MN AND WESTERN ONTARIO AND ATTENDANT 100 KT
H3 JET WILL SLIDE S/E THROUGH GREAT LAKES TDY... WITH
CWA GENERALLY S/W OF MAIN FORCING IN FORM OF LEFT EXIT REGION
OF JET AND POSITIVE VORTICITY ADVECTION. COLD FRONT IS
EXPECTED TO MOVE INTO NORTHERN CWA BY MID AFTN AND CONTINUE
SLIDING S/E EXITING THE SOUTHERN CWA BY LATE EVE. MODELS INSIST
ON INCREASING SFC DEWPTS INTO THE MID/UPPER 50S AHEAD OF THE
FRONT WITH LAYER PRECIPITABLE WATER VALUES CLIMBING TO AROUND
1 INCH. BELIEVE THIS IS AGGRESSIVE GIVEN RECENT DRY STRETCH
COUPLED WITH GUSTY SW WINDS AND DEEP MIXING... AND VEERING H85
WINDS TO WESTERLY. ADJUSTING SFC DEWPTS INTO THE 40S TO
POSSIBLY LOWER 50S YIELDS MLCAPE GENERALLY ON THE ORDER OF 750-
1100 J/KG OR SO. WEAK SFC CONVERGENCE AND CONVECTIVE TEMPS
(83-86F) BREACHED SHOULD BE SUFFICIENT TO GENERATE AT LEAST
WIDELY SCT CONVECTION BY MID AFTN AHEAD OF THE FRONT SLIDING E/SE
INTO EVE. 0-6 KM BULK SHEAR OF 30-35 KTS AND STEEP MID LEVEL
LAPSE RATES COUPLED WITH DRY AIR WILL SUPPORT HAIL RISK WITH
LOCAL CALCULATIONS FOR KCID AT 21Z BASED ON T/TD OF 85/46F
SUGGESTS HAIL POTENTIAL AROUND 1.25 INCH IN DIAMETER. LARGE DEWPT
DEPRESSIONS SFC TO CLOUD BASE WITH INVERTED V TYPE SOUNDINGS
WOULD ALSO SUPPORT STRONG GUSTY WINDS. SO... BOTTOM LINE ANTICIPATE
ISOLD-SCT BKN LINE OF CONVECTION FIRING AHEAD OF FRONT AND
SLIDING S/E BETWEEN ROUGHLY 20Z-03Z... WITH ISOLD SEVERE THREAT IN
FORM OF OF LARGE HAIL AND DAMAGING WINDS. SEVERE RISK SUBJECT TO
CHANGE DEPENDING ON LOW LEVEL MOISTURE WITH SIGNFICANT IMPACT ON
THERMODYNAMICS. DEEP MIXING AOA 700 MB WITH GUSTY PRE-FRONTAL
COMPRESSIONAL HEATING SHOULD RESULT IN WIDESPREAD HIGHS IN MID 80S
WITH SOME UPPER 80S ESPECIALLY IN CORRIDOR FROM NEAR KDBQ AND KCID
TO KBRL WITHIN LOW LEVEL THERMAL RIDGE. FRONT TO BE SOUTH OF THE
CWA BY 03Z-06Z WITH CLEARING AND NORTH WINDS USHERING IN COOLER AND
DRIER AIR... WITH COOLEST LOWS NORTH (46-49F) AND WARMEST FAR SOUTH
(52-55F). ..05..
LONG TERM...WEDNESDAY THROUGH NEXT MONDAY...
WEDNESDAY...LATEST 00Z MODEL RUNS CONTINUE TO ADVERTISE THE IDEA OF
A BACKDOOR TYPE HIGH PRESSURE SYSTEM BUILDING DOWN THE WESTERN GRT
LKS EFFECTIVELY SHUNTING SFC BOUNDARY DOWN THROUGH THE MID/LOWER MS
RVR VALLEY...AS UPPER RIDGING AMPLIFIES ACRS THE NORTHERN PLAINS. THE
LATEST RUNS NOT AS ROBUST WITH STRENGTH AND DEPTH OF INCOMING POST-
FRONTAL NORTHEASTERN FETCH BUT STILL ENOUGH COOL AIR ADVECTION TO
HOLD DOWN TEMPS WELL IN THE 70S FOR WED HIGHS. SOME UPPER 60S EVEN
POSSIBLE IN NORTHWESTERN IL. WED NIGHT...LATEST INDICATIONS STILL
SUGGEST NOCTURNAL MCS GENERATION PARAMETERS INCLUDING A SOUTHERLY 50+
KT LLJ COME TOGETHER ACRS THE NORTHERN PLAINS AND THEN FEED ANY
RESULTANT CONVECTIVE SYSTEM EASTWARD ACRS THE EASTERN DAKOTAS...MN
AND WI INTO THU MORNING. THUS IT APPEARS LOW CHANCE OF ANY CONVECTION
MAKING IT INTO THE NORTHERN CWA BY THU MORNING AND WILL REMOVE
MENTIONABLE POPS. WED NIGHT RELATIVELY COOL IN THE LOWER 50S TO MID
40S BEFORE RETURN FLOW INCREASES TOWARD THU MORNING.
THURSDAY AND FRIDAY...00Z RUN MEDIUM RANGE SOLUTIONS INCLUDING THE
NEW GFS AND ECMWF GENERALLY AGREE THAT WARM FRONTAL RETREAT PROCESS
WILL COMBINE WITH RIDGE-RIDING VORT MAX/S FOR MCS GENERATION OR
REGENERATION THIS PERIOD MAINLY UP ACRS THE NORTHWESTERN HIGH
PLAINS...EASTWARD ACRS MN...WI AND INTO THE GRT LKS. THE DVN CWA
STILL LOOKS TO BE MAINLY SOUTH OF THESE CONVECTIVELY ACTION ZONES AND
INCREASINGLY IN THE WARM SECTOR WITH FRI HIGHS WELL UP IN THE 80S.
WILL IGNORE THE 00Z GFS SPURIOUS CONVECTIVE DEVELOPMENT RIGHT ACRS
THE DVN CWA FRI AFTERNOON AS CAPPING INVERSION WILL BE ON THE
INCREASE.
SATURDAY THROUGH MONDAY...LONGER RANGE TRENDS CONTINUING TO SUGGEST
EASTERN PACIFIC UPPER JET ENERGY AND INLAND PROPAGATING UPPER WAVES
WILL COMBINE TO PUMMEL OUT A L/W COMPLEX ACRS THE WESTERN ROCKIES BY
THE WEEKEND. IF THIS PROCESS UNFOLDS AS CURRENTLY INDICATED BY THE
FAVORED ECMWF AND UKMET SOLUTIONS...RESULTANT AMPLIFIED LEE SIDE
UPPER RIDGE WOULD MEAN A VERY WARM AND DRY SAT AND SAT NIGHT FOR THE
LOCAL FCST AREA WITH SAT HIGHS IN THE UPPER 80S. LOOKING AT UPPER
JET PROJECTILE PATHS...A LARGE PIECE OF THE WESTERN UPPER TROF WILL
HAVE TO EVENTUALLY PUSH ACRS THE UPPER MIDWEST AND PREFER THE SLOWER
ECMWF SOLUTION OF SHUNTING AN ASSOCIATED SFC FRONT TOWARD THE AREA
SOMETIME LATE SUNDAY NIGHT OR MONDAY MORNING. WITH ANY KIND OF
MOISTURE RETURN OFF THE WESTERN GULF/ALTHOUGH LATEST SOLUTIONS ARE
NOW MARGINAL WITH THIS PROCESS/...THERE WILL BE AN INCREASING
CHANCE OF SHOWERS AND STORMS FROM THE WEST WITH THE HIGHER POP WINDOW
APPEARING TO BE LATE SUNDAY...SUNDAY NIGHT AND LINGERING INTO MONDAY
MORNING IN POST-FRONTAL FORM BY THEN. TIMING AN HANDLING OF THIS
FEATURE AS WELL AS PHASING WITH THE BROAD SCALE FORCING STILL
SOMEWHAT UNCERTAIN AND DIFFICULT TO BETTER TO DEFINE AT THIS POINT.
ANY SLOW DOWN OF THESE PROCESSES WOULD MEAN A ANOTHER UNSEASONABLY
WARM AND MAINLY DRY DAY ON SUNDAY AND A STORMY MONDAY. THIS IS WHAT
THE 00Z ECMWF IS ADVERTISING WHILE THE MORE PROGRESSIVE GFS TARGETS
THE MAIN CONVECTIVE EVENT ON SUNDAY. LATEST AO/NAO PROGS SUGGEST A
DECENT COOL DOWN ACRS THE UPPER MIDWEST/WESTERN GRT LKS EARLY NEXT
WEEK BEHIND THE PASSING UPPER TROF. ..12..
AVIATION... /ISSUED 1158 PM CDT MON MAY 14 2012/
HIGH PRESSURE SOUTHEAST OF THE REGION WILL CONTINUE THE VFR
CONDITIONS WITH CLEAR SKIES AND LIGHT WEST WINDS THROUGH TUESDAY
AFTERNOON. TUESDAY MORNING WINDS WILL INCREASE OUT OF THE
SOUTHWEST AT 10 TO 20KTS WITH GUSTS. THERE IS A CHANCE OF
THUNDERSTORMS AFTER 21Z AS A COLD FRONT SLOWLY DROPS INTO THE
REGION. COVERAGE AND PROBABILITY IS STILL SOMEWHAT LOW...AS THERE
MAY BE MORE DRY AIR WHICH WOULD ACT TO SUPPRESS STORMS. FOR
NOW...HAVE PUT IN SOME VCSH TO KCID...KDBQ AND KMLI AS THESE WILL
BE CLOSEST TO THE FRONT AT THE TIMES WHEN IT IS MOST LIKELY TO
PRODUCE ANYTHING CONVECTIVE. THE REDUCED LOW LEVEL MOISTURE MAY DO
NO MORE THAN REDUCE STORM COVERAGE AND KEEP STORMS THAT DO FORM
RELATIVELY WEAK...SO HAVE GONE WITH JUST THE SHOWERS FOR NOW.
LATER FORECASTS WILL HAVE TO REFINE FURTHER. FOR NOW HAVE JUST VFR
CONDITIONS THOUGH ANY STORMS MAY HAVE MVFR CIGS AND VSBYS. LE
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
ERVIN
000
FXUS63 KDMX 151139 AAA
AFDDMX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
639 AM CDT TUE MAY 15 2012
...UPDATED AVIATION DISCUSSION...
.SHORT TERM /TODAY/...
BIG WEATHER MAKER FOR TODAY WILL BE THE COLD FRONT APPROACHING FROM
SD/MN LATER THIS MORNING. THE FRONT IS CURRENTLY IN NE SD AND
BARRELING SOUTHEASTWARD AT A PRETTY GOOD CLIP WITH A DECENT PUSH
BEHIND IT...SUSTAINED WINDS ARE AROUND 25 MPH CURRENTLY IN PARTS OF
EASTERN ND. AS THE PARENT LOW MOVES QUICKLY EASTWARD OVER THE GREAT
LAKES TODAY EXPECT THE FRONT WILL SLOW SLIGHTLY...BUT STILL CROSS
OUR AREA BY AROUND OR SHORTLY AFTER 00Z THIS EVENING. AHEAD OF THE
FRONT...MODEST SOUTHWEST BREEZES HAVE KEPT TEMPERATURES UP FOR THE
MOST PART EARLY THIS MORNING AND SHOULD PROVIDE FOR RAPID WARMING
AFTER SUNRISE TODAY DESPITE INCREASING HIGH CLOUDS. TEMPERATURES ARE
TRICKY FOR TODAY AS THE FRONTAL BOUNDARY SHOULD ENTER OUR NW CORNER
AROUND 14 OR 15Z...BUT THERE WILL BE A DELAY AFTER THAT IN THE
ARRIVAL OF THE REAL SURGE OF COLD AIR. HAVE TAKEN A BEST
GUESS...NEAR MOS IN THE FAR NORTH BUT ABOVE MOS EVERYWHERE ELSE
GIVEN WARM START TEMPERATURES...AND GONE WITH A NON-DIURNAL CURVE TO
TRY TO ACCOUNT FOR FROPA AS DISCUSSED ABOVE.
THE OTHER CONCERN WITH THE FRONT TODAY IS POTENTIAL FOR THUNDERSTORM
DEVELOPMENT THIS AFTERNOON. DEWPOINTS ARE CURRENTLY IN THE MID 30S
TO MID 40S ACROSS THE AREA...AND SHOULD PEAK ONLY IN THE LOWER 50S
OR SO IN OUR SOUTHEAST THIS AFTERNOON...SO MOISTURE IS RELATIVELY
LACKING. HOWEVER...WE SHOULD SEE DECENT LOW-LEVEL CONVERGENCE ALONG
THE BOUNDARY AND STRONG ENOUGH HEATING AHEAD OF IT TO PRODUCE SOME
INSTABILITY AND TRIGGER A FEW STORMS LATE IN THE AFTERNOON. HAVE
CONCENTRATED POPS MAINLY IN OUR SOUTHEASTERN HALF AFTER 21Z...BUT
EVEN THEN WENT WITH ONLY ISOLATED TO SCATTERED. BULK SHEAR IS
EXPECTED TO INCREASE ALONG THE BOUNDARY LATE IN THE DAY AND THERE IS
SOME LOW POTENTIAL FOR ISOLATED HAIL OR WIND GUSTS WITH SOME OF THE
STORMS...WHICH IS WELL ADVERTISED IN SPC DISCUSSIONS AND OTHER
PRODUCTS.
.LONG TERM /TONIGHT THROUGH MONDAY/...
COLD FRONT WILL EXIT THE CWA EARLY IN THE FORECAST PERIOD AND
CARRIED A SLIVER OF TSRA FOR THE FIRST FEW HOURS THIS EVENING.
COOLER AIR IF POURING SOUTH ACROSS ND AND NORTHERN MN AND WILL GO
BELOW MOS TEMPS FOR TONIGHT. WOULD NOT BE SURPRISED TO SEE IT GET A
FEW DEGREES BELOW WHAT IS IN THE GRID. QUITE WEATHER AFTER THAT FOR
A WHILE. WARMER AIR WILL PUSH NORTH FOR THU AND FRI...BUT IT WILL
REMAIN QUITE DRY. THOUGH THERE IS A DECENT PUSH OF WAA AND SOME
LIFT WITH THE RETURN OF THE WRMFNT...FEEL THERE WON`T BE ENOUGH FOR
IT TO GO. GFS KICKS OUT SOME TSRA ON FRI AND HAVE REAL DOUBTS ABOUT
THAT AND DID NOT INCLUDE. SOUNDINGS INDICATE A SIGNIFICANT CAP IN
PLACE IN SPITE OF 3000-4000 J/KG BY AFTERNOON. IT WOULD TAKE MORE
DYNAMICS THAN THERE ARE AVAILABLE TO KICK IT OFF. WITH THE WEATHER
FEATURE FOR THE WEEKEND HELD OFF RAIN UNTIL LATE SAT OVER THE
NORTHWEST PART OF THE CWA. SOUTHEAST SHOULD REMAIN DRY. NO REAL
CHANGES IN THE FORECAST FARTHER OUT. GFS WAS QUITE A BIT FASTER
THAN THE EC ON THE 12Z RUN...BUT THE TWO ARE FAIRLY CLOSE TONIGHT
AND THERE IS NO REAL REASON TO MAKE ADJUSTMENTS.
&&
.AVIATION...15/12Z
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. WINDS WILL SHIFT
AND INCREASE BEHIND ADVANCING COLD FRONT TODAY...HAVE TAKEN BEST
GUESS AT TIMING OF FROPA IN THE TAFS. DRY CONDITIONS WILL PRECLUDE
LOW CIGS WITH THE FRONT HOWEVER...ONLY HIGH CLOUDS FOR THE MOST PART
THEN SKC BEHIND THE FRONT TONIGHT. ISOLD TSRA POSSIBLE LATE THIS
AFTN AND EVE ESPECIALLY IN SE IA...AND HAVE INCLUDED VCTS AT KOTM
FOR A SHORT PERIOD ALTHOUGH COVERAGE IS EXPECTED TO BE LOW AND BRIEF.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...LEE
LONG TERM...MS MAY 12
AVIATION...LEE
000
FXUS63 KDVN 151132
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
632 AM CDT TUE MAY 15 2012
.AVIATION...
VFR CONDITIONS EXPECTED NEXT 24 HRS. COLD FRONT TO PASS THROUGH
THE TERMINALS BETWEEN 21Z AND 03Z BRINGING SHIFT IN WINDS FROM
W/SW TO N/NW. THERE IS A SMALL CHANCE OF A SHOWER OR THUNDERSTORM
AHEAD OF FRONT... BUT CONSIDERABLE UNCERTAINTY WITH DEVELOPMENT
AS MODELS VERIFYING TOO MOIST WITH SFC DEWPTS. THUS...FAVORING
A DRY FRONTAL PASSAGE AS DEPICTED BY RECENT RAP AND HRRR MODEL
RUNS GIVEN DEEP MIXING AND GUSTY SOUTHWEST WINDS 10-20+ KTS PRE-
FRONTAL DRYING OUT THE LOW LEVELS.
&&
.PREV DISCUSSION... /ISSUED 353 AM CDT TUE MAY 15 2012/
SYNOPSIS...
RATHER VIGOROUS COMPACT SHORTWAVE DIVING E/SE INTO WRN ONTARIO
PROVINCE AND NRN MN EARLY THIS AM. ATTENDANT WEAK SFC LOW WAS
LOCATED OVER THE ARROWHEAD OF MN WITH COLD FRONT TRAILING SWWD
THROUGH SD. LIMITED MOISTURE WITH FRONT WITH SFC DEWPTS IN THE
30S AND 40S... AND PRECIPITABLE WATER VALUES AROUND 0.5 INCH
OR LESS OVER THE UPPER MIDWEST.
SHORT TERM...TODAY AND TONIGHT...
MAIN FCST CONCERN IS PCPN CHCS AND SEVERE POTENTIAL WITH FRONT
THIS AFTN/EVE.
SHORTWAVE OVER NRN MN AND WESTERN ONTARIO AND ATTENDANT 100 KT
H3 JET WILL SLIDE S/E THROUGH GREAT LAKES TDY... WITH
CWA GENERALLY S/W OF MAIN FORCING IN FORM OF LEFT EXIT REGION
OF JET AND POSITIVE VORTICITY ADVECTION. COLD FRONT IS
EXPECTED TO MOVE INTO NORTHERN CWA BY MID AFTN AND CONTINUE
SLIDING S/E EXITING THE SOUTHERN CWA BY LATE EVE. MODELS INSIST
ON INCREASING SFC DEWPTS INTO THE MID/UPPER 50S AHEAD OF THE
FRONT WITH LAYER PRECIPITABLE WATER VALUES CLIMBING TO AROUND
1 INCH. BELIEVE THIS IS AGGRESSIVE GIVEN RECENT DRY STRETCH
COUPLED WITH GUSTY SW WINDS AND DEEP MIXING... AND VEERING H85
WINDS TO WESTERLY. ADJUSTING SFC DEWPTS INTO THE 40S TO
POSSIBLY LOWER 50S YIELDS MLCAPE GENERALLY ON THE ORDER OF 750-
1100 J/KG OR SO. WEAK SFC CONVERGENCE AND CONVECTIVE TEMPS
(83-86F) BREACHED SHOULD BE SUFFICIENT TO GENERATE AT LEAST
WIDELY SCT CONVECTION BY MID AFTN AHEAD OF THE FRONT SLIDING E/SE
INTO EVE. 0-6 KM BULK SHEAR OF 30-35 KTS AND STEEP MID LEVEL
LAPSE RATES COUPLED WITH DRY AIR WILL SUPPORT HAIL RISK WITH
LOCAL CALCULATIONS FOR KCID AT 21Z BASED ON T/TD OF 85/46F
SUGGESTS HAIL POTENTIAL AROUND 1.25 INCH IN DIAMETER. LARGE DEWPT
DEPRESSIONS SFC TO CLOUD BASE WITH INVERTED V TYPE SOUNDINGS
WOULD ALSO SUPPORT STRONG GUSTY WINDS. SO... BOTTOM LINE ANTICIPATE
ISOLD-SCT BKN LINE OF CONVECTION FIRING AHEAD OF FRONT AND
SLIDING S/E BETWEEN ROUGHLY 20Z-03Z... WITH ISOLD SEVERE THREAT IN
FORM OF OF LARGE HAIL AND DAMAGING WINDS. SEVERE RISK SUBJECT TO
CHANGE DEPENDING ON LOW LEVEL MOISTURE WITH SIGNFICANT IMPACT ON
THERMODYNAMICS. DEEP MIXING AOA 700 MB WITH GUSTY PRE-FRONTAL
COMPRESSIONAL HEATING SHOULD RESULT IN WIDESPREAD HIGHS IN MID 80S
WITH SOME UPPER 80S ESPECIALLY IN CORRIDOR FROM NEAR KDBQ AND KCID
TO KBRL WITHIN LOW LEVEL THERMAL RIDGE. FRONT TO BE SOUTH OF THE
CWA BY 03Z-06Z WITH CLEARING AND NORTH WINDS USHERING IN COOLER AND
DRIER AIR... WITH COOLEST LOWS NORTH (46-49F) AND WARMEST FAR SOUTH
(52-55F). ..05..
LONG TERM...WEDNESDAY THROUGH NEXT MONDAY...
WEDNESDAY...LATEST 00Z MODEL RUNS CONTINUE TO ADVERTISE THE IDEA OF
A BACKDOOR TYPE HIGH PRESSURE SYSTEM BUILDING DOWN THE WESTERN GRT
LKS EFFECTIVELY SHUNTING SFC BOUNDARY DOWN THROUGH THE MID/LOWER MS
RVR VALLEY...AS UPPER RIDGING AMPLIFIES ACRS THE NORTHERN PLAINS. THE
LATEST RUNS NOT AS ROBUST WITH STRENGTH AND DEPTH OF INCOMING POST-
FRONTAL NORTHEASTERN FETCH BUT STILL ENOUGH COOL AIR ADVECTION TO
HOLD DOWN TEMPS WELL IN THE 70S FOR WED HIGHS. SOME UPPER 60S EVEN
POSSIBLE IN NORTHWESTERN IL. WED NIGHT...LATEST INDICATIONS STILL
SUGGEST NOCTURNAL MCS GENERATION PARAMETERS INCLUDING A SOUTHERLY 50+
KT LLJ COME TOGETHER ACRS THE NORTHERN PLAINS AND THEN FEED ANY
RESULTANT CONVECTIVE SYSTEM EASTWARD ACRS THE EASTERN DAKOTAS...MN
AND WI INTO THU MORNING. THUS IT APPEARS LOW CHANCE OF ANY CONVECTION
MAKING IT INTO THE NORTHERN CWA BY THU MORNING AND WILL REMOVE
MENTIONABLE POPS. WED NIGHT RELATIVELY COOL IN THE LOWER 50S TO MID
40S BEFORE RETURN FLOW INCREASES TOWARD THU MORNING.
THURSDAY AND FRIDAY...00Z RUN MEDIUM RANGE SOLUTIONS INCLUDING THE
NEW GFS AND ECMWF GENERALLY AGREE THAT WARM FRONTAL RETREAT PROCESS
WILL COMBINE WITH RIDGE-RIDING VORT MAX/S FOR MCS GENERATION OR
REGENERATION THIS PERIOD MAINLY UP ACRS THE NORTHWESTERN HIGH
PLAINS...EASTWARD ACRS MN...WI AND INTO THE GRT LKS. THE DVN CWA
STILL LOOKS TO BE MAINLY SOUTH OF THESE CONVECTIVELY ACTION ZONES AND
INCREASINGLY IN THE WARM SECTOR WITH FRI HIGHS WELL UP IN THE 80S.
WILL IGNORE THE 00Z GFS SPURIOUS CONVECTIVE DEVELOPMENT RIGHT ACRS
THE DVN CWA FRI AFTERNOON AS CAPPING INVERSION WILL BE ON THE
INCREASE.
SATURDAY THROUGH MONDAY...LONGER RANGE TRENDS CONTINUING TO SUGGEST
EASTERN PACIFIC UPPER JET ENERGY AND INLAND PROPAGATING UPPER WAVES
WILL COMBINE TO PUMMEL OUT A L/W COMPLEX ACRS THE WESTERN ROCKIES BY
THE WEEKEND. IF THIS PROCESS UNFOLDS AS CURRENTLY INDICATED BY THE
FAVORED ECMWF AND UKMET SOLUTIONS...RESULTANT AMPLIFIED LEE SIDE
UPPER RIDGE WOULD MEAN A VERY WARM AND DRY SAT AND SAT NIGHT FOR THE
LOCAL FCST AREA WITH SAT HIGHS IN THE UPPER 80S. LOOKING AT UPPER
JET PROJECTILE PATHS...A LARGE PIECE OF THE WESTERN UPPER TROF WILL
HAVE TO EVENTUALLY PUSH ACRS THE UPPER MIDWEST AND PREFER THE SLOWER
ECMWF SOLUTION OF SHUNTING AN ASSOCIATED SFC FRONT TOWARD THE AREA
SOMETIME LATE SUNDAY NIGHT OR MONDAY MORNING. WITH ANY KIND OF
MOISTURE RETURN OFF THE WESTERN GULF/ALTHOUGH LATEST SOLUTIONS ARE
NOW MARGINAL WITH THIS PROCESS/...THERE WILL BE AN INCREASING
CHANCE OF SHOWERS AND STORMS FROM THE WEST WITH THE HIGHER POP WINDOW
APPEARING TO BE LATE SUNDAY...SUNDAY NIGHT AND LINGERING INTO MONDAY
MORNING IN POST-FRONTAL FORM BY THEN. TIMING AN HANDLING OF THIS
FEATURE AS WELL AS PHASING WITH THE BROAD SCALE FORCING STILL
SOMEWHAT UNCERTAIN AND DIFFICULT TO BETTER TO DEFINE AT THIS POINT.
ANY SLOW DOWN OF THESE PROCESSES WOULD MEAN A ANOTHER UNSEASONABLY
WARM AND MAINLY DRY DAY ON SUNDAY AND A STORMY MONDAY. THIS IS WHAT
THE 00Z ECMWF IS ADVERTISING WHILE THE MORE PROGRESSIVE GFS TARGETS
THE MAIN CONVECTIVE EVENT ON SUNDAY. LATEST AO/NAO PROGS SUGGEST A
DECENT COOL DOWN ACRS THE UPPER MIDWEST/WESTERN GRT LKS EARLY NEXT
WEEK BEHIND THE PASSING UPPER TROF. ..12..
AVIATION... /ISSUED 1158 PM CDT MON MAY 14 2012/
HIGH PRESSURE SOUTHEAST OF THE REGION WILL CONTINUE THE VFR
CONDITIONS WITH CLEAR SKIES AND LIGHT WEST WINDS THROUGH TUESDAY
AFTERNOON. TUESDAY MORNING WINDS WILL INCREASE OUT OF THE
SOUTHWEST AT 10 TO 20KTS WITH GUSTS. THERE IS A CHANCE OF
THUNDERSTORMS AFTER 21Z AS A COLD FRONT SLOWLY DROPS INTO THE
REGION. COVERAGE AND PROBABILITY IS STILL SOMEWHAT LOW...AS THERE
MAY BE MORE DRY AIR WHICH WOULD ACT TO SUPPRESS STORMS. FOR
NOW...HAVE PUT IN SOME VCSH TO KCID...KDBQ AND KMLI AS THESE WILL
BE CLOSEST TO THE FRONT AT THE TIMES WHEN IT IS MOST LIKELY TO
PRODUCE ANYTHING CONVECTIVE. THE REDUCED LOW LEVEL MOISTURE MAY DO
NO MORE THAN REDUCE STORM COVERAGE AND KEEP STORMS THAT DO FORM
RELATIVELY WEAK...SO HAVE GONE WITH JUST THE SHOWERS FOR NOW.
LATER FORECASTS WILL HAVE TO REFINE FURTHER. FOR NOW HAVE JUST VFR
CONDITIONS THOUGH ANY STORMS MAY HAVE MVFR CIGS AND VSBYS. LE
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
000
FXUS63 KDVN 150853
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
353 AM CDT TUE MAY 15 2012
.SYNOPSIS...
RATHER VIGOROUS COMPACT SHORTWAVE DIVING E/SE INTO WRN ONTARIO
PROVINCE AND NRN MN EARLY THIS AM. ATTENDANT WEAK SFC LOW WAS
LOCATED OVER THE ARROWHEAD OF MN WITH COLD FRONT TRAILING SWWD
THROUGH SD. LIMITED MOISTURE WITH FRONT WITH SFC DEWPTS IN THE
30S AND 40S... AND PRECIPITABLE WATER VALUES AROUND 0.5 INCH
OR LESS OVER THE UPPER MIDWEST.
&&
.SHORT TERM...TODAY AND TONIGHT...
MAIN FCST CONCERN IS PCPN CHCS AND SEVERE POTENTIAL WITH FRONT
THIS AFTN/EVE.
SHORTWAVE OVER NRN MN AND WESTERN ONTARIO AND ATTENDANT 100 KT
H3 JET WILL SLIDE S/E THROUGH GREAT LAKES TDY... WITH
CWA GENERALLY S/W OF MAIN FORCING IN FORM OF LEFT EXIT REGION
OF JET AND POSITIVE VORTICITY ADVECTION. COLD FRONT IS
EXPECTED TO MOVE INTO NORTHERN CWA BY MID AFTN AND CONTINUE
SLIDING S/E EXITING THE SOUTHERN CWA BY LATE EVE. MODELS INSIST
ON INCREASING SFC DEWPTS INTO THE MID/UPPER 50S AHEAD OF THE
FRONT WITH LAYER PRECIPITABLE WATER VALUES CLIMBING TO AROUND
1 INCH. BELIEVE THIS IS AGGRESSIVE GIVEN RECENT DRY STRETCH
COUPLED WITH GUSTY SW WINDS AND DEEP MIXING... AND VEERING H85
WINDS TO WESTERLY. ADJUSTING SFC DEWPTS INTO THE 40S TO
POSSIBLY LOWER 50S YIELDS MLCAPE GENERALLY ON THE ORDER OF 750-
1100 J/KG OR SO. WEAK SFC CONVERGENCE AND CONVECTIVE TEMPS
(83-86F) BREACHED SHOULD BE SUFFICIENT TO GENERATE AT LEAST
WIDELY SCT CONVECTION BY MID AFTN AHEAD OF THE FRONT SLIDING E/SE
INTO EVE. 0-6 KM BULK SHEAR OF 30-35 KTS AND STEEP MID LEVEL
LAPSE RATES COUPLED WITH DRY AIR WILL SUPPORT HAIL RISK WITH
LOCAL CALCULATIONS FOR KCID AT 21Z BASED ON T/TD OF 85/46F
SUGGESTS HAIL POTENTIAL AROUND 1.25 INCH IN DIAMETER. LARGE DEWPT
DEPRESSIONS SFC TO CLOUD BASE WITH INVERTED V TYPE SOUNDINGS
WOULD ALSO SUPPORT STRONG GUSTY WINDS. SO... BOTTOM LINE ANTICIPATE
ISOLD-SCT BKN LINE OF CONVECTION FIRING AHEAD OF FRONT AND
SLIDING S/E BETWEEN ROUGHLY 20Z-03Z... WITH ISOLD SEVERE THREAT IN
FORM OF OF LARGE HAIL AND DAMAGING WINDS. SEVERE RISK SUBJECT TO
CHANGE DEPENDING ON LOW LEVEL MOISTURE WITH SIGNFICANT IMPACT ON
THERMODYNAMICS. DEEP MIXING AOA 700 MB WITH GUSTY PRE-FRONTAL
COMPRESSIONAL HEATING SHOULD RESULT IN WIDESPREAD HIGHS IN MID 80S
WITH SOME UPPER 80S ESPECIALLY IN CORRIDOR FROM NEAR KDBQ AND KCID
TO KBRL WITHIN LOW LEVEL THERMAL RIDGE. FRONT TO BE SOUTH OF THE
CWA BY 03Z-06Z WITH CLEARING AND NORTH WINDS USHERING IN COOLER AND
DRIER AIR... WITH COOLEST LOWS NORTH (46-49F) AND WARMEST FAR SOUTH
(52-55F). ..05..
.LONG TERM...WEDNESDAY THROUGH NEXT MONDAY...
WEDNESDAY...LATEST 00Z MODEL RUNS CONTINUE TO ADVERTISE THE IDEA OF
A BACKDOOR TYPE HIGH PRESSURE SYSTEM BUILDING DOWN THE WESTERN GRT
LKS EFFECTIVELY SHUNTING SFC BOUNDARY DOWN THROUGH THE MID/LOWER MS
RVR VALLEY...AS UPPER RIDGING AMPLIFIES ACRS THE NORTHERN PLAINS. THE
LATEST RUNS NOT AS ROBUST WITH STRENGTH AND DEPTH OF INCOMING POST-
FRONTAL NORTHEASTERN FETCH BUT STILL ENOUGH COOL AIR ADVECTION TO
HOLD DOWN TEMPS WELL IN THE 70S FOR WED HIGHS. SOME UPPER 60S EVEN
POSSIBLE IN NORTHWESTERN IL. WED NIGHT...LATEST INDICATIONS STILL
SUGGEST NOCTURNAL MCS GENERATION PARAMETERS INCLUDING A SOUTHERLY 50+
KT LLJ COME TOGETHER ACRS THE NORTHERN PLAINS AND THEN FEED ANY
RESULTANT CONVECTIVE SYSTEM EASTWARD ACRS THE EASTERN DAKOTAS...MN
AND WI INTO THU MORNING. THUS IT APPEARS LOW CHANCE OF ANY CONVECTION
MAKING IT INTO THE NORTHERN CWA BY THU MORNING AND WILL REMOVE
MENTIONABLE POPS. WED NIGHT RELATIVELY COOL IN THE LOWER 50S TO MID
40S BEFORE RETURN FLOW INCREASES TOWARD THU MORNING.
THURSDAY AND FRIDAY...00Z RUN MEDIUM RANGE SOLUTIONS INCLUDING THE
NEW GFS AND ECMWF GENERALLY AGREE THAT WARM FRONTAL RETREAT PROCESS
WILL COMBINE WITH RIDGE-RIDING VORT MAX/S FOR MCS GENERATION OR
REGENERATION THIS PERIOD MAINLY UP ACRS THE NORTHWESTERN HIGH
PLAINS...EASTWARD ACRS MN...WI AND INTO THE GRT LKS. THE DVN CWA
STILL LOOKS TO BE MAINLY SOUTH OF THESE CONVECTIVELY ACTION ZONES AND
INCREASINGLY IN THE WARM SECTOR WITH FRI HIGHS WELL UP IN THE 80S.
WILL IGNORE THE 00Z GFS SPURIOUS CONVECTIVE DEVELOPMENT RIGHT ACRS
THE DVN CWA FRI AFTERNOON AS CAPPING INVERSION WILL BE ON THE
INCREASE.
SATURDAY THROUGH MONDAY...LONGER RANGE TRENDS CONTINUING TO SUGGEST
EASTERN PACIFIC UPPER JET ENERGY AND INLAND PROPAGATING UPPER WAVES
WILL COMBINE TO PUMMEL OUT A L/W COMPLEX ACRS THE WESTERN ROCKIES BY
THE WEEKEND. IF THIS PROCESS UNFOLDS AS CURRENTLY INDICATED BY THE
FAVORED ECMWF AND UKMET SOLUTIONS...RESULTANT AMPLIFIED LEE SIDE
UPPER RIDGE WOULD MEAN A VERY WARM AND DRY SAT AND SAT NIGHT FOR THE
LOCAL FCST AREA WITH SAT HIGHS IN THE UPPER 80S. LOOKING AT UPPER
JET PROJECTILE PATHS...A LARGE PIECE OF THE WESTERN UPPER TROF WILL
HAVE TO EVENTUALLY PUSH ACRS THE UPPER MIDWEST AND PREFER THE SLOWER
ECMWF SOLUTION OF SHUNTING AN ASSOCIATED SFC FRONT TOWARD THE AREA
SOMETIME LATE SUNDAY NIGHT OR MONDAY MORNING. WITH ANY KIND OF
MOISTURE RETURN OFF THE WESTERN GULF/ALTHOUGH LATEST SOLUTIONS ARE
NOW MARGINAL WITH THIS PROCESS/...THERE WILL BE AN INCREASING
CHANCE OF SHOWERS AND STORMS FROM THE WEST WITH THE HIGHER POP WINDOW
APPEARING TO BE LATE SUNDAY...SUNDAY NIGHT AND LINGERING INTO MONDAY
MORNING IN POST-FRONTAL FORM BY THEN. TIMING AN HANDLING OF THIS
FEATURE AS WELL AS PHASING WITH THE BROAD SCALE FORCING STILL
SOMEWHAT UNCERTAIN AND DIFFICULT TO BETTER TO DEFINE AT THIS POINT.
ANY SLOW DOWN OF THESE PROCESSES WOULD MEAN A ANOTHER UNSEASONABLY
WARM AND MAINLY DRY DAY ON SUNDAY AND A STORMY MONDAY. THIS IS WHAT
THE 00Z ECMWF IS ADVERTISING WHILE THE MORE PROGRESSIVE GFS TARGETS
THE MAIN CONVECTIVE EVENT ON SUNDAY. LATEST AO/NAO PROGS SUGGEST A
DECENT COOL DOWN ACRS THE UPPER MIDWEST/WESTERN GRT LKS EARLY NEXT
WEEK BEHIND THE PASSING UPPER TROF. ..12..
&&
.AVIATION... /ISSUED 1158 PM CDT MON MAY 14 2012/
HIGH PRESSURE SOUTHEAST OF THE REGION WILL CONTINUE THE VFR
CONDITIONS WITH CLEAR SKIES AND LIGHT WEST WINDS THROUGH TUESDAY
AFTERNOON. TUESDAY MORNING WINDS WILL INCREASE OUT OF THE
SOUTHWEST AT 10 TO 20KTS WITH GUSTS. THERE IS A CHANCE OF
THUNDERSTORMS AFTER 21Z AS A COLD FRONT SLOWLY DROPS INTO THE
REGION. COVERAGE AND PROBABILITY IS STILL SOMEWHAT LOW...AS THERE
MAY BE MORE DRY AIR WHICH WOULD ACT TO SUPPRESS STORMS. FOR
NOW...HAVE PUT IN SOME VCSH TO KCID...KDBQ AND KMLI AS THESE WILL
BE CLOSEST TO THE FRONT AT THE TIMES WHEN IT IS MOST LIKELY TO
PRODUCE ANYTHING CONVECTIVE. THE REDUCED LOW LEVEL MOISTURE MAY DO
NO MORE THAN REDUCE STORM COVERAGE AND KEEP STORMS THAT DO FORM
RELATIVELY WEAK...SO HAVE GONE WITH JUST THE SHOWERS FOR NOW.
LATER FORECASTS WILL HAVE TO REFINE FURTHER. FOR NOW HAVE JUST VFR
CONDITIONS THOUGH ANY STORMS MAY HAVE MVFR CIGS AND VSBYS. LE
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
05/12
000
FXUS63 KDMX 150833 AAB
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
333 AM CDT TUE MAY 15 2012
.SHORT TERM /TODAY/...
BIG WEATHER MAKER FOR TODAY WILL BE THE COLD FRONT APPROACHING FROM
SD/MN LATER THIS MORNING. THE FRONT IS CURRENTLY IN NE SD AND
BARRELING SOUTHEASTWARD AT A PRETTY GOOD CLIP WITH A DECENT PUSH
BEHIND IT...SUSTAINED WINDS ARE AROUND 25 MPH CURRENTLY IN PARTS OF
EASTERN ND. AS THE PARENT LOW MOVES QUICKLY EASTWARD OVER THE GREAT
LAKES TODAY EXPECT THE FRONT WILL SLOW SLIGHTLY...BUT STILL CROSS
OUR AREA BY AROUND OR SHORTLY AFTER 00Z THIS EVENING. AHEAD OF THE
FRONT...MODEST SOUTHWEST BREEZES HAVE KEPT TEMPERATURES UP FOR THE
MOST PART EARLY THIS MORNING AND SHOULD PROVIDE FOR RAPID WARMING
AFTER SUNRISE TODAY DESPITE INCREASING HIGH CLOUDS. TEMPERATURES ARE
TRICKY FOR TODAY AS THE FRONTAL BOUNDARY SHOULD ENTER OUR NW CORNER
AROUND 14 OR 15Z...BUT THERE WILL BE A DELAY AFTER THAT IN THE
ARRIVAL OF THE REAL SURGE OF COLD AIR. HAVE TAKEN A BEST
GUESS...NEAR MOS IN THE FAR NORTH BUT ABOVE MOS EVERYWHERE ELSE
GIVEN WARM START TEMPERATURES...AND GONE WITH A NON-DIURNAL CURVE TO
TRY TO ACCOUNT FOR FROPA AS DISCUSSED ABOVE.
THE OTHER CONCERN WITH THE FRONT TODAY IS POTENTIAL FOR THUNDERSTORM
DEVELOPMENT THIS AFTERNOON. DEWPOINTS ARE CURRENTLY IN THE MID 30S
TO MID 40S ACROSS THE AREA...AND SHOULD PEAK ONLY IN THE LOWER 50S
OR SO IN OUR SOUTHEAST THIS AFTERNOON...SO MOISTURE IS RELATIVELY
LACKING. HOWEVER...WE SHOULD SEE DECENT LOW-LEVEL CONVERGENCE ALONG
THE BOUNDARY AND STRONG ENOUGH HEATING AHEAD OF IT TO PRODUCE SOME
INSTABILITY AND TRIGGER A FEW STORMS LATE IN THE AFTERNOON. HAVE
CONCENTRATED POPS MAINLY IN OUR SOUTHEASTERN HALF AFTER 21Z...BUT
EVEN THEN WENT WITH ONLY ISOLATED TO SCATTERED. BULK SHEAR IS
EXPECTED TO INCREASE ALONG THE BOUNDARY LATE IN THE DAY AND THERE IS
SOME LOW POTENTIAL FOR ISOLATED HAIL OR WIND GUSTS WITH SOME OF THE
STORMS...WHICH IS WELL ADVERTISED IN SPC DISCUSSIONS AND OTHER
PRODUCTS.
.LONG TERM /TONIGHT THROUGH MONDAY/...
COLD FRONT WILL EXIT THE CWA EARLY IN THE FORECAST PERIOD AND
CARRIED A SLIVER OF TSRA FOR THE FIRST FEW HOURS THIS EVENING.
COOLER AIR IF POURING SOUTH ACROSS ND AND NORTHERN MN AND WILL GO
BELOW MOS TEMPS FOR TONIGHT. WOULD NOT BE SURPRISED TO SEE IT GET A
FEW DEGREES BELOW WHAT IS IN THE GRID. QUITE WEATHER AFTER THAT FOR
A WHILE. WARMER AIR WILL PUSH NORTH FOR THU AND FRI...BUT IT WILL
REMAIN QUITE DRY. THOUGH THERE IS A DECENT PUSH OF WAA AND SOME
LIFT WITH THE RETURN OF THE WRMFNT...FEEL THERE WON`T BE ENOUGH FOR
IT TO GO. GFS KICKS OUT SOME TSRA ON FRI AND HAVE REAL DOUBTS ABOUT
THAT AND DID NOT INCLUDE. SOUNDINGS INDICATE A SIGNIFICANT CAP IN
PLACE IN SPITE OF 3000-4000 J/KG BY AFTERNOON. IT WOULD TAKE MORE
DYNAMICS THAN THERE ARE AVAILABLE TO KICK IT OFF. WITH THE WEATHER
FEATURE FOR THE WEEKEND HELD OFF RAIN UNTIL LATE SAT OVER THE
NORTHWEST PART OF THE CWA. SOUTHEAST SHOULD REMAIN DRY. NO REAL
CHANGES IN THE FORECAST FARTHER OUT. GFS WAS QUITE A BIT FASTER
THAN THE EC ON THE 12Z RUN...BUT THE TWO ARE FAIRLY CLOSE TONIGHT
AND THERE IS NO REAL REASON TO MAKE ADJUSTMENTS.
&&
.AVIATION...15/06Z
CEILINGS WILL REMAIN VFR WITH HIGH PRESSURE PULLING SOUTH OF THE
REGION. WINDS WILL REMAIN PRIMARILY FROM THE SOUTHWEST. A COLD FRONT
WILL PUSH ACROSS THE REGION LATE IN THE PERIOD WITH WINDS SHIFTING
TO THE NORTH TO NORTHWEST. COULD SEE SOME PRECIPITATION ASSOCIATED
WITH THE FRONT ESPECIALLY ACROSS KMCW/KALO AND KOTM...BUT NOT
ENOUGH CONFIDENCE TO INCLUDE MENTION ATTM...AND CEILINGS WILL REMAIN
VFR.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...LEE
LONG TERM...MS MAY 12
AVIATION...AWB
000
FXUS63 KDVN 150458
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1158 PM CDT MON MAY 14 2012
.AVIATION...
HIGH PRESSURE SOUTHEAST OF THE REGION WILL CONTINUE THE VFR
CONDITIONS WITH CLEAR SKIES AND LIGHT WEST WINDS THROUGH TUESDAY
AFTERNOON. TUESDAY MORNING WINDS WILL INCREASE OUT OF THE
SOUTHWEST AT 10 TO 20KTS WITH GUSTS. THERE IS A CHANCE OF
THUNDERSTORMS AFTER 21Z AS A COLD FRONT SLOWLY DROPS INTO THE
REGION. COVERAGE AND PROBABILITY IS STILL SOMEWHAT LOW...AS THERE
MAY BE MORE DRY AIR WHICH WOULD ACT TO SUPPRESS STORMS. FOR
NOW...HAVE PUT IN SOME VCSH TO KCID...KDBQ AND KMLI AS THESE WILL
BE CLOSEST TO THE FRONT AT THE TIMES WHEN IT IS MOST LIKELY TO
PRODUCE ANYTHING CONVECTIVE. THE REDUCED LOW LEVEL MOISTURE MAY DO
NO MORE THAN REDUCE STORM COVERAGE AND KEEP STORMS THAT DO FORM
RELATIVELY WEAK...SO HAVE GONE WITH JUST THE SHOWERS FOR NOW.
LATER FORECASTS WILL HAVE TO REFINE FURTHER. FOR NOW HAVE JUST VFR
CONDITIONS THOUGH ANY STORMS MAY HAVE MVFR CIGS AND VSBYS. LE
&&
.PREV DISCUSSION... /ISSUED 308 PM CDT MON MAY 14 2012/
SYNOPSIS...
RIDGE OF HIGH PRESSURE EXTENDING FROM EASTERN KS TO LOWER MI
CONTINUED TO PROVIDE SUNNY SKIES...LIGHT WINDS AND WARM TEMPERATURES
OVER THE FORECAST AREA THIS AFTERNOON. THE DVN FORECAST SOUNDING
FROM THIS MORNING INDICATED A VERY DRY ATMOSPHERE...WITH A PW
VALUE OF ONLY .29...OR 40 PERCENT OF NORMAL. GULF MOISTURE
CONTINUES TO BE CUT OFF BY A SPLIT FLOW PATTERN THAT FEATURES
UPPER LEVEL SYSTEMS MOVING ALONG A WEAK SOUTHERN JET STREAM FROM
TX EAST ALONG THE GULF COAST...WHILE THE STRONGER NORTHERN JET
STREAM EXTENDED IN A SLIGHTLY CYCLONIC CONFIGURATION ACROSS SOUTH
CENTRAL INTO SOUTHEAST CANADA. THIS IS KEEPING A WEAK AND
SOMEWHAT SUBSIDENT FLOW IN BETWEEN INFLUENCING THE LOCAL AREA.
SHORT TERM...TONIGHT AND TUESDAY...
PRIMARY FOCUS IS ON CHANCES FOR THUNDERSTORMS TUESDAY AFTERNOON AS A
SHORTWAVE IN THE NORTHERN STREAM BEGINS TO CARVE OUT A LONGWAVE
UPPER LEVEL TROUGH TO OUR EAST...SENDING A CANADIAN COLD FRONT SOUTH
THROUGH THE FORECAST AREA DURING PEAK HEATING. 12Z MODELS HAVE
MAINTAINED SIMILAR TIMING WITH THE FRONT BISECTING THE FORECAST AREA
FROM SW TO NE BY 00Z. OVERALL...THE AMERICAN AND EUROPEAN MODELS
APPEAR OVERDONE WITH DEWPOINTS...SUGGESTED IN THE UPPER 50S TO
AROUND 60 ALONG AND AHEAD OF THE FRONT BY LATE AFTERNOON. 12Z
MOS...INCLUDING THE GFS/MAV AND NAM/MET APPEAR TO HAVE MORE
REALISTIC VALUES...IN THE 40S TO LOWER 50S...SIMILAR TO THE PAST
COUPLE DAYS. THESE LOWER VALUES LOOK MORE REALISTIC GIVEN THE
DEPTH OF MIXING EXPECTED IN THE SOUTHWEST PREFRONTAL FLOW. USING
THE MORE CONSERVATIVE SURFACE DEWPOINTS AND LIMITED MOISTURE
THROUGH 850 MB...CAPES WILL LIKELY BE IN THE UPPER HUNDREDS TO
JUST OVER 1000 J/KG...WITH INSTABILITY PARAMETERS AVERAGING IN A
MODERATE RANGE BASED ON SEVERAL PARAMETERS. SHEAR IS MODERATE AS
WELL...AND APPEARS TO BE HIGHEST OVER NW IL. SPC HAS ROUGHLY THE
NORTHEAST HALF OF THE FORECAST AREA IN DAY 2 SLIGHT RISK. LOCAL
SEVERE WEATHER ASSESSMENT SUGGESTS A POTENTIAL FOR SMALL HAIL AND
WIND GUSTS BELOW 50 KTS WITH POSSIBLE BOWING SEGMENTS ALONG THIS
FRONT DURING PEAK HEATING. HAVE INCREASED POPS TO AN AXIS OF 30
PERCENT ACROSS EASTERN IA INTO NW IL FOR LATE AFTERNOON...WITH
SLIGHT CHANCES ELSEWHERE.
TONIGHT...THERE SHOULD BE ENOUGH OF A SURFACE PRESSURE GRADIENT AS
THE SURFACE HIGH SHIFTS SOUTH AND THE FRONT IN SOUTHERN CANADA DROPS
SOUTH INTO MN AND WI. THIS SHOULD LIMIT THE LOCAL DRAINAGE EFFECTS
THAT RESULTED IN THE COOL TEMPERATURES THIS MORNING. HOWEVER...WITH
THE VERY DRY AIR IN PLACE AND ENHANCED DIURNAL EFFECTS...WILL STAY AT
THE LOW END OF GUIDANCE...THAT WAS TOO WARM FOR THIS
MORNING...AND FORECAST MINS FROM AROUND 50 TO THE MID 50S IN THE
FAR SOUTH. WOULD NOT BE SURPRISED TO STILL SEE A SITE OR TWO DIP
INTO THE UPPER 40S. TUESDAY...DEEP MIXING TO AT LEAST 850 MB AHEAD
OF THE LATE DAY FROPA SHOULD DRIVE TEMPERATURES IN THE LOWER 80S.
SHEETS
LONG TERM...TUESDAY NIGHT THROUGH NEXT MONDAY...
THE SCENARIO THAT APPEARS TO BE SETTING UP FOR LATE THURSDAY
AFTERNOON AND EVENING IS ONE OF TYPICAL DIURNAL CONVECTION. THE MAIN
QUESTION IS MOISTURE AVAILABILITY. IF THERE IS NOT ENOUGH MOISTURE
THEN THE WEAK CONVERGENCE ALONG THE FRONT WILL ONLY RESULT IN
CONVECTIVE CLOUDS THAT WILL DISSIPATE SHORTLY AFTER SUNSET. ASSUMING
THERE WILL BE JUST ENOUGH MOISTURE AVAILABLE...WILL CONTINUE THE
SCHC POPS FOR TUESDAY EVENING BUT SHIFT THEM FURTHER SOUTH BASED ON
THE EXPECTED FRONTAL POSITION AT 00Z.
QUIET AND DRY CONDITIONS ARE EXPECTED LATE TUES NIGHT THROUGH WED
EVENING AS HIGH PRESSURE MOVES THROUGH THE WESTERN GREAT LAKES.
THERE COULD BE QUITE A GRADIENT IN TEMPERATURES FROM NORTHEAST TO
SOUTHWEST ACROSS THE CWFA ON WEDNESDAY WITH THE DRY LOW LEVEL
EASTERLY FLOW.
LATE WED NIGHT INTO THURSDAY BECOMES MORE INTERESTING. A RESPECTABLE
LLJ WITH MOISTURE TRANSPORT SETS UP WELL WEST OF THE CWFA WED
EVENING. MCS TOOL IN COMBINATION WITH LIFT AND HEAVY RAIN TOOLS ARE
SUGGESTING A NOCTURNAL MCS WILL DEVELOP POSSIBLY ALONG THE IA/MN
BORDER. IF THIS IS THE LOCATION OF DEVELOPMENT...CORFIDI VECTORS
WOULD TAKE THE MCS GENERALLY EAST WITH POSSIBLY A SLOW DRIFT TO THE
SOUTH THAT MAY AFFECT THE EXTREME NORTHERN CWFA AROUND SUNRISE
THURSDAY. YESTERDAY...THE SAME INTERNAL SIGNALS SUGGESTED AN MCS
DEVELOPING FURTHER SOUTH. SO...THE THEME OF AN MCS DEVELOPING WEST
OF THE CWFA WED NIGHT WILL BE FOLLOWED. HOWEVER...GIVEN CURRENT
MODEL TRENDS WILL GO WITH THE IDEA OF IT DEVELOPING IN SOUTHWEST
MINNESOTA AND MOVING EAST OVERNIGHT. A POSSIBLE WAA WING OF PRECIP
MAY COME CLOSE TO THE HWY 20 CORRIDOR AROUND DAWN BUT FOR NOW WILL
CONTINUE TO KEEP THE CWFA DRY WED NIGHT.
IF THE MCS DEVELOPS IN SOUTHWEST MN...OUTFLOW AND A GRADUAL
PROPAGATION SOUTH OF THE DEVELOPING WAA WING OF PRECIP MAY CATCH THE
HWY 20 CORRIDOR FROM DUBUQUE EAST AFTER SUNRISE THURSDAY. THIS
SCENARIO IS ALL PREDICATED ON THE WARM FRONT MOVING INTO THE
NORTHERN CWFA SHORTLY AFTER SUNRISE. ALL MODELS PROG THE FRONT
THROUGH THE AREA BY MID DAY SO THE AFTERNOON HOURS SHOULD BE DRY.
THURSDAY NIGHT ON...
MODEL CONSENSUS HAS SCHC POPS FROM THURS NIGHT THROUGH SATURDAY. ANY
FORCING PRESENT IS WEAK WITH THE 500MB RIDGE BUILDING OVER THE
EASTERN CONUS. ALTHOUGH CONVECTION WILL BE POSSIBLE...THERE WILL BE
MANY HOURS OF DRY WX ACROSS THE AREA. THE OVERALL SIGNALS FROM THE
MODELS INDICATE DIURNAL CONVECTION DEVELOPING DURING THE AFTERNOON
HOURS AND DISSIPATING AFTER SUNSET.
STARTING SATURDAY NIGHT AND CONTINUING THROUGH MONDAY THINGS BECOME
MORE INTERESTING. A FRONT APPROACHES FROM THE WEST AND SLOWLY MOVES
ACROSS THE AREA SUNDAY THROUGH MONDAY. ALTHOUGH THE FRONT WILL NOT
BE PARALLEL TO THE FLOW ALOFT IT WILL NOT BE FAR FROM IT SO THE
FORWARD MOVEMENT WILL BE SLOW. THE MODEL CONSENSUS HAS SCHC POPS
SATURDAY NIGHT THAT EVOLVES INTO PROGRESSIVELY HIGHER CHC POPS
SUNDAY THROUGH MONDAY. IF THE SLOW MOVING FRONT SCENARIO PLAYS OUT
THEN THESE POPS WILL SLOWLY INCREASE AS THE WEEKEND GETS CLOSER.
PRIOR TO THE ARRIVAL OF THE FRONT TEMPERATURES SHOULD AVERAGE ABOVE
NORMAL. ..08..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
000
FXUS63 KDMX 150451 AAB
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1152 PM CDT MON MAY 14 2012
...UPDATED AVIATION DISCUSSION...
.SHORT TERM /TONIGHT/...
BROAD NORTHWEST FLOW WILL STEEPEN A BIT OVERNIGHT ACROSS THE CENTRAL
AND NORTHERN PLAINS. SASKATCHEWAN SHORT WAVE AND ASSOCIATED
ANOMALIES WILL DROP SOUTHEAST AND BE OVER WESTERN LAKE SUPERIOR BY
12Z TUESDAY AND WILL DRAG A COLD FRONT INTO SOUTHERN MN...POSSIBLY
INTO FAR NW IA BY THIS TIME. A DEEP DRY COLUMN WILL PRECLUDE ANY
POPS OVERNIGHT THOUGH A FEW MID LEVEL CLOUDS MAY REACH THE IA/MN
BORDER LATE. WARM ADVECTION IN ADVANCE OF THE APPROACHING BOUNDARY
AND SOUTHWEST WINDS OVERNIGHT WILL HELP KEEP TEMPERATURES MILD AND
WILL BE GENERALLY IN THE LOW TO MID 50S BY 6 AM.
.LONG TERM /TUESDAY THROUGH MONDAY/...
THE MODELS ARE STILL IN FAIRLY GOOD AGREEMENT ON THE PASSAGE OF A
COLD FRONT LATE IN THE DAY TUESDAY/TUESDAY EVENING. BOTH THE NAM
AND GFS PUSH A LOT OF MOISTURE UP AHEAD OF THIS BOUNDARY BUT I AM
HAVING A HARD TIME SEEING THESE HIGH DEWPOINTS. WE ARE CURRENTLY IN
THE 30S WITH DEWPOINTS AS FAR DOWNSTREAM AS KANSAS AND CENTRAL
MISSOURI ONLY IN THE MID 40S. DID A MODIFIED SOUNDING IN AWIPS TO
LOWER THE DEWPOINTS JUST A FEW DEGREES FROM MODEL FORECAST WHICH
EFFECTIVELY KILLED THE CAPE. SO MOISTURE RETURN WILL OBVIOUSLY BE
KEY TO WHETHER WE SEE THUNDER AT ALL. CONVERGENCE IS ALSO PRETTY
WEAK ALONG THE BOUNDARY. HAVING SAID THAT I DID NOT REDUCE POPS AT
THIS POINT SINCE SOME MOISTURE RETURN WILL OCCUR...JUST NOT SURE HOW
MUCH...AND THERE COULD BE SOME DEVELOPMENT ALONG THE FRONT. I DID
HOWEVER TRY AND TIE THE PRECIP TO THE BOUNDARY SO I NARROWED THE
AREA OF POPS WITH WHERE I FELT THE FRONT WOULD BE.
WEAK HIGH PRESSURE STILL ON TAP FOR LATER TUESDAY NIGHT THROUGH
WEDNESDAY NIGHT. THIS WILL RESULT IN A DRY PERIOD WITH SLIGHTLY
COOLER TEMPS...THOUGH IT WILL STILL BE ABOVE NORMAL.
THURSDAY THROUGH THE REMAINDER OF THE EXTENDED FORECAST IS STILL A
BIT TOUGH TO FORECAST. THE RIDGE AXIS IS NEARLY ABOVE THE REGION
THURSDAY AND BEGINS TO SHIFT TO THE EAST THURSDAY NIGHT AND FRIDAY.
WARM ADVECTION BEGINS OVER THE WEST THURSDAY NIGHT BUT AGAIN
MOISTURE RETURN IS QUESTIONABLE AT BEST DUE TO BEING UNDER THE
RIDGE. ADD TO THIS THAT NOW THE MODELS JUST DO NOT HAVE A GOOD
HANDLE ON WHERE THE SHORTWAVE WILL COME ACROSS AND THE FRONTAL
BOUNDARY WILL BE AND THE RESULT IS A VERY LOW CONFIDENCE POP
FORECAST. IT DOES APPEAR THAT CHANCES IMPROVE SOME LATER THURSDAY
NIGHT WEST OF THE CWA AND WORKING ITS WAY TOWARDS THE WESTERN CWA
WITH THE DEVELOPMENT OF A LOW LEVEL JET WHICH WILL IMPINGE ON THE
BOUNDARY BUT THAT WOULD AFFECT OUR WESTERN FORECAST AREA TOWARDS
FRIDAY MORNING.
FOR FRIDAY THROUGH SATURDAY...CHANCES GRADUALLY INCREASE FOR
THUNDERSTORMS AS THE UPPER RIDGE SHIFTS EAST AND DEEPER RETURN FLOW
BRINGS UP MOISTURE ACROSS OUR FORECAST AREA. A SLOW MOVING FRONTAL
BOUNDARY WILL GRADUALLY SAG INTO THE CWA SATURDAY THROUGH SUNDAY
NIGHT WHICH WILL BRING OUR BEST CHANCES FOR THUNDERSTORMS...AND A
FEW SEVERE STORMS AT THAT. I BUMPED POPS UP TO CHANCE BUT WILL
REFRAIN FROM TOO STRONG A WORDING AT THIS POINT SINCE THE FRONT IS
SO SLOW MOVING.
&&
.AVIATION...15/06Z
CEILINGS WILL REMAIN VFR WITH HIGH PRESSURE PULLING SOUTH OF THE
REGION. WINDS WILL REMAIN PRIMARILY FROM THE SOUTHWEST. A COLD FRONT
WILL PUSH ACROSS THE REGION LATE IN THE PERIOD WITH WINDS SHIFTING
TO THE NORTH TO NORTHWEST. COULD SEE SOME PRECIPITATION ASSOCIATED
WITH THE FRONT ESPECIALLY ACROSS KMCW/KALO AND KOTM...BUT NOT
ENOUGH CONFIDENCE TO INCLUDE MENTION ATTM...AND CEILINGS WILL REMAIN
VFR.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...DONAVON
LONG TERM...FAB
AVIATION...AWB
000
FXUS63 KDVN 142339
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
639 PM CDT MON MAY 14 2012
.AVIATION...
HIGH PRESSURE SOUTHEAST OF THE REGION WILL CONTINUE THE VFR
CONDITIONS WITH CLEAR SKIES AND LIGHT WEST WINDS THROUGH TUESDAY
MORNING. TUESDAY MORNING WINDS WILL INCREASE OUT OF THE SOUTHWEST
AT 10 TO 15KTS WITH GUSTS UP TO 20KTS. THERE IS A CHANCE OF
THUNDERSTORMS AFTER 21Z AS A COLD FRONT SLOWLY DROPS INTO THE
REGION. COVERAGE AND PROBABILITY IS STILL SOMEWHAT LOW...AS THERE
MAY BE MORE DRY AIR WHICH WOULD ACT TO SUPPRESS STORMS.
THUS...HAVE LEFT PRECIPITATION OR THUNDER OUT OF FORECAST FOR NOW
UNTIL THESE DETAILS CAN BE BETTER DETERMINED. LE
&&
.PREV DISCUSSION... /ISSUED 308 PM CDT MON MAY 14 2012/
SYNOPSIS...
RIDGE OF HIGH PRESSURE EXTENDING FROM EASTERN KS TO LOWER MI
CONTINUED TO PROVIDE SUNNY SKIES...LIGHT WINDS AND WARM TEMPERATURES
OVER THE FORECAST AREA THIS AFTERNOON. THE DVN FORECAST SOUNDING
FROM THIS MORNING INDICATED A VERY DRY ATMOSPHERE...WITH A PW
VALUE OF ONLY .29...OR 40 PERCENT OF NORMAL. GULF MOISTURE
CONTINUES TO BE CUT OFF BY A SPLIT FLOW PATTERN THAT FEATURES
UPPER LEVEL SYSTEMS MOVING ALONG A WEAK SOUTHERN JET STREAM FROM
TX EAST ALONG THE GULF COAST...WHILE THE STRONGER NORTHERN JET
STREAM EXTENDED IN A SLIGHTLY CYCLONIC CONFIGURATION ACROSS SOUTH
CENTRAL INTO SOUTHEAST CANADA. THIS IS KEEPING A WEAK AND
SOMEWHAT SUBSIDENT FLOW IN BETWEEN INFLUENCING THE LOCAL AREA.
SHORT TERM...TONIGHT AND TUESDAY...
PRIMARY FOCUS IS ON CHANCES FOR THUNDERSTORMS TUESDAY AFTERNOON AS A
SHORTWAVE IN THE NORTHERN STREAM BEGINS TO CARVE OUT A LONGWAVE
UPPER LEVEL TROUGH TO OUR EAST...SENDING A CANADIAN COLD FRONT SOUTH
THROUGH THE FORECAST AREA DURING PEAK HEATING. 12Z MODELS HAVE
MAINTAINED SIMILAR TIMING WITH THE FRONT BISECTING THE FORECAST AREA
FROM SW TO NE BY 00Z. OVERALL...THE AMERICAN AND EUROPEAN MODELS
APPEAR OVERDONE WITH DEWPOINTS...SUGGESTED IN THE UPPER 50S TO
AROUND 60 ALONG AND AHEAD OF THE FRONT BY LATE AFTERNOON. 12Z
MOS...INCLUDING THE GFS/MAV AND NAM/MET APPEAR TO HAVE MORE
REALISTIC VALUES...IN THE 40S TO LOWER 50S...SIMILAR TO THE PAST
COUPLE DAYS. THESE LOWER VALUES LOOK MORE REALISTIC GIVEN THE
DEPTH OF MIXING EXPECTED IN THE SOUTHWEST PREFRONTAL FLOW. USING
THE MORE CONSERVATIVE SURFACE DEWPOINTS AND LIMITED MOISTURE
THROUGH 850 MB...CAPES WILL LIKELY BE IN THE UPPER HUNDREDS TO
JUST OVER 1000 J/KG...WITH INSTABILITY PARAMETERS AVERAGING IN A
MODERATE RANGE BASED ON SEVERAL PARAMETERS. SHEAR IS MODERATE AS
WELL...AND APPEARS TO BE HIGHEST OVER NW IL. SPC HAS ROUGHLY THE
NORTHEAST HALF OF THE FORECAST AREA IN DAY 2 SLIGHT RISK. LOCAL
SEVERE WEATHER ASSESSMENT SUGGESTS A POTENTIAL FOR SMALL HAIL AND
WIND GUSTS BELOW 50 KTS WITH POSSIBLE BOWING SEGMENTS ALONG THIS
FRONT DURING PEAK HEATING. HAVE INCREASED POPS TO AN AXIS OF 30
PERCENT ACROSS EASTERN IA INTO NW IL FOR LATE AFTERNOON...WITH
SLIGHT CHANCES ELSEWHERE.
TONIGHT...THERE SHOULD BE ENOUGH OF A SURFACE PRESSURE GRADIENT AS
THE SURFACE HIGH SHIFTS SOUTH AND THE FRONT IN SOUTHERN CANADA DROPS
SOUTH INTO MN AND WI. THIS SHOULD LIMIT THE LOCAL DRAINAGE EFFECTS
THAT RESULTED IN THE COOL TEMPERATURES THIS MORNING. HOWEVER...WITH
THE VERY DRY AIR IN PLACE AND ENHANCED DIURNAL EFFECTS...WILL STAY AT
THE LOW END OF GUIDANCE...THAT WAS TOO WARM FOR THIS
MORNING...AND FORECAST MINS FROM AROUND 50 TO THE MID 50S IN THE
FAR SOUTH. WOULD NOT BE SURPRISED TO STILL SEE A SITE OR TWO DIP
INTO THE UPPER 40S. TUESDAY...DEEP MIXING TO AT LEAST 850 MB AHEAD
OF THE LATE DAY FROPA SHOULD DRIVE TEMPERATURES IN THE LOWER 80S.
SHEETS
LONG TERM...TUESDAY NIGHT THROUGH NEXT MONDAY...
THE SCENARIO THAT APPEARS TO BE SETTING UP FOR LATE THURSDAY
AFTERNOON AND EVENING IS ONE OF TYPICAL DIURNAL CONVECTION. THE MAIN
QUESTION IS MOISTURE AVAILABILITY. IF THERE IS NOT ENOUGH MOISTURE
THEN THE WEAK CONVERGENCE ALONG THE FRONT WILL ONLY RESULT IN
CONVECTIVE CLOUDS THAT WILL DISSIPATE SHORTLY AFTER SUNSET. ASSUMING
THERE WILL BE JUST ENOUGH MOISTURE AVAILABLE...WILL CONTINUE THE
SCHC POPS FOR TUESDAY EVENING BUT SHIFT THEM FURTHER SOUTH BASED ON
THE EXPECTED FRONTAL POSITION AT 00Z.
QUIET AND DRY CONDITIONS ARE EXPECTED LATE TUES NIGHT THROUGH WED
EVENING AS HIGH PRESSURE MOVES THROUGH THE WESTERN GREAT LAKES.
THERE COULD BE QUITE A GRADIENT IN TEMPERATURES FROM NORTHEAST TO
SOUTHWEST ACROSS THE CWFA ON WEDNESDAY WITH THE DRY LOW LEVEL
EASTERLY FLOW.
LATE WED NIGHT INTO THURSDAY BECOMES MORE INTERESTING. A RESPECTABLE
LLJ WITH MOISTURE TRANSPORT SETS UP WELL WEST OF THE CWFA WED
EVENING. MCS TOOL IN COMBINATION WITH LIFT AND HEAVY RAIN TOOLS ARE
SUGGESTING A NOCTURNAL MCS WILL DEVELOP POSSIBLY ALONG THE IA/MN
BORDER. IF THIS IS THE LOCATION OF DEVELOPMENT...CORFIDI VECTORS
WOULD TAKE THE MCS GENERALLY EAST WITH POSSIBLY A SLOW DRIFT TO THE
SOUTH THAT MAY AFFECT THE EXTREME NORTHERN CWFA AROUND SUNRISE
THURSDAY. YESTERDAY...THE SAME INTERNAL SIGNALS SUGGESTED AN MCS
DEVELOPING FURTHER SOUTH. SO...THE THEME OF AN MCS DEVELOPING WEST
OF THE CWFA WED NIGHT WILL BE FOLLOWED. HOWEVER...GIVEN CURRENT
MODEL TRENDS WILL GO WITH THE IDEA OF IT DEVELOPING IN SOUTHWEST
MINNESOTA AND MOVING EAST OVERNIGHT. A POSSIBLE WAA WING OF PRECIP
MAY COME CLOSE TO THE HWY 20 CORRIDOR AROUND DAWN BUT FOR NOW WILL
CONTINUE TO KEEP THE CWFA DRY WED NIGHT.
IF THE MCS DEVELOPS IN SOUTHWEST MN...OUTFLOW AND A GRADUAL
PROPAGATION SOUTH OF THE DEVELOPING WAA WING OF PRECIP MAY CATCH THE
HWY 20 CORRIDOR FROM DUBUQUE EAST AFTER SUNRISE THURSDAY. THIS
SCENARIO IS ALL PREDICATED ON THE WARM FRONT MOVING INTO THE
NORTHERN CWFA SHORTLY AFTER SUNRISE. ALL MODELS PROG THE FRONT
THROUGH THE AREA BY MID DAY SO THE AFTERNOON HOURS SHOULD BE DRY.
THURSDAY NIGHT ON...
MODEL CONSENSUS HAS SCHC POPS FROM THURS NIGHT THROUGH SATURDAY. ANY
FORCING PRESENT IS WEAK WITH THE 500MB RIDGE BUILDING OVER THE
EASTERN CONUS. ALTHOUGH CONVECTION WILL BE POSSIBLE...THERE WILL BE
MANY HOURS OF DRY WX ACROSS THE AREA. THE OVERALL SIGNALS FROM THE
MODELS INDICATE DIURNAL CONVECTION DEVELOPING DURING THE AFTERNOON
HOURS AND DISSIPATING AFTER SUNSET.
STARTING SATURDAY NIGHT AND CONTINUING THROUGH MONDAY THINGS BECOME
MORE INTERESTING. A FRONT APPROACHES FROM THE WEST AND SLOWLY MOVES
ACROSS THE AREA SUNDAY THROUGH MONDAY. ALTHOUGH THE FRONT WILL NOT
BE PARALLEL TO THE FLOW ALOFT IT WILL NOT BE FAR FROM IT SO THE
FORWARD MOVEMENT WILL BE SLOW. THE MODEL CONSENSUS HAS SCHC POPS
SATURDAY NIGHT THAT EVOLVES INTO PROGRESSIVELY HIGHER CHC POPS
SUNDAY THROUGH MONDAY. IF THE SLOW MOVING FRONT SCENARIO PLAYS OUT
THEN THESE POPS WILL SLOWLY INCREASE AS THE WEEKEND GETS CLOSER.
PRIOR TO THE ARRIVAL OF THE FRONT TEMPERATURES SHOULD AVERAGE ABOVE
NORMAL. ..08..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
000
FXUS63 KDMX 142320 AAA
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
620 PM CDT MON MAY 14 2012
...UPDATED AVIATION DISCUSSION...
.SHORT TERM /TONIGHT/...
BROAD NORTHWEST FLOW WILL STEEPEN A BIT OVERNIGHT ACROSS THE CENTRAL
AND NORTHERN PLAINS. SASKATCHEWAN SHORT WAVE AND ASSOCIATED
ANOMALIES WILL DROP SOUTHEAST AND BE OVER WESTERN LAKE SUPERIOR BY
12Z TUESDAY AND WILL DRAG A COLD FRONT INTO SOUTHERN MN...POSSIBLY
INTO FAR NW IA BY THIS TIME. A DEEP DRY COLUMN WILL PRECLUDE ANY
POPS OVERNIGHT THOUGH A FEW MID LEVEL CLOUDS MAY REACH THE IA/MN
BORDER LATE. WARM ADVECTION IN ADVANCE OF THE APPROACHING BOUNDARY
AND SOUTHWEST WINDS OVERNIGHT WILL HELP KEEP TEMPERATURES MILD AND
WILL BE GENERALLY IN THE LOW TO MID 50S BY 6 AM.
.LONG TERM /TUESDAY THROUGH MONDAY/...
THE MODELS ARE STILL IN FAIRLY GOOD AGREEMENT ON THE PASSAGE OF A
COLD FRONT LATE IN THE DAY TUESDAY/TUESDAY EVENING. BOTH THE NAM
AND GFS PUSH A LOT OF MOISTURE UP AHEAD OF THIS BOUNDARY BUT I AM
HAVING A HARD TIME SEEING THESE HIGH DEWPOINTS. WE ARE CURRENTLY IN
THE 30S WITH DEWPOINTS AS FAR DOWNSTREAM AS KANSAS AND CENTRAL
MISSOURI ONLY IN THE MID 40S. DID A MODIFIED SOUNDING IN AWIPS TO
LOWER THE DEWPOINTS JUST A FEW DEGREES FROM MODEL FORECAST WHICH
EFFECTIVELY KILLED THE CAPE. SO MOISTURE RETURN WILL OBVIOUSLY BE
KEY TO WHETHER WE SEE THUNDER AT ALL. CONVERGENCE IS ALSO PRETTY
WEAK ALONG THE BOUNDARY. HAVING SAID THAT I DID NOT REDUCE POPS AT
THIS POINT SINCE SOME MOISTURE RETURN WILL OCCUR...JUST NOT SURE HOW
MUCH...AND THERE COULD BE SOME DEVELOPMENT ALONG THE FRONT. I DID
HOWEVER TRY AND TIE THE PRECIP TO THE BOUNDARY SO I NARROWED THE
AREA OF POPS WITH WHERE I FELT THE FRONT WOULD BE.
WEAK HIGH PRESSURE STILL ON TAP FOR LATER TUESDAY NIGHT THROUGH
WEDNESDAY NIGHT. THIS WILL RESULT IN A DRY PERIOD WITH SLIGHTLY
COOLER TEMPS...THOUGH IT WILL STILL BE ABOVE NORMAL.
THURSDAY THROUGH THE REMAINDER OF THE EXTENDED FORECAST IS STILL A
BIT TOUGH TO FORECAST. THE RIDGE AXIS IS NEARLY ABOVE THE REGION
THURSDAY AND BEGINS TO SHIFT TO THE EAST THURSDAY NIGHT AND FRIDAY.
WARM ADVECTION BEGINS OVER THE WEST THURSDAY NIGHT BUT AGAIN
MOISTURE RETURN IS QUESTIONABLE AT BEST DUE TO BEING UNDER THE
RIDGE. ADD TO THIS THAT NOW THE MODELS JUST DO NOT HAVE A GOOD
HANDLE ON WHERE THE SHORTWAVE WILL COME ACROSS AND THE FRONTAL
BOUNDARY WILL BE AND THE RESULT IS A VERY LOW CONFIDENCE POP
FORECAST. IT DOES APPEAR THAT CHANCES IMPROVE SOME LATER THURSDAY
NIGHT WEST OF THE CWA AND WORKING ITS WAY TOWARDS THE WESTERN CWA
WITH THE DEVELOPMENT OF A LOW LEVEL JET WHICH WILL IMPINGE ON THE
BOUNDARY BUT THAT WOULD AFFECT OUR WESTERN FORECAST AREA TOWARDS
FRIDAY MORNING.
FOR FRIDAY THROUGH SATURDAY...CHANCES GRADUALLY INCREASE FOR
THUNDERSTORMS AS THE UPPER RIDGE SHIFTS EAST AND DEEPER RETURN FLOW
BRINGS UP MOISTURE ACROSS OUR FORECAST AREA. A SLOW MOVING FRONTAL
BOUNDARY WILL GRADUALLY SAG INTO THE CWA SATURDAY THROUGH SUNDAY
NIGHT WHICH WILL BRING OUR BEST CHANCES FOR THUNDERSTORMS...AND A
FEW SEVERE STORMS AT THAT. I BUMPED POPS UP TO CHANCE BUT WILL
REFRAIN FROM TOO STRONG A WORDING AT THIS POINT SINCE THE FRONT IS
SO SLOW MOVING.
&&
.AVIATION...15/00Z
CEILINGS WILL REMAIN VFR WITH HIGH PRESSURE PULLING SOUTH OF THE
REGION. WINDS WILL REMAIN PRIMARILY FROM THE SOUTHWEST. A COLD FRONT
WILL PUSH ACROSS THE REGION LATE IN THE PERIOD WITH WINDS SHIFTING
TO THE NORTH TO NORTHWEST. COULD SEE SOME PRECIPITATION ASSOCIATED
WITH THE FRONT ESPECIALLY ACROSS THE NORTHEASTERN AND SOUTHERN
SITES...BUT NOT ENOUGH CONFIDENCE TO INCLUDE MENTION ATTM.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...DONAVON
LONG TERM...FAB
AVIATION...AWB
000
FXUS63 KDMX 142023
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
323 PM CDT MON MAY 14 2012
.SHORT TERM /TONIGHT/...
BROAD NORTHWEST FLOW WILL STEEPEN A BIT OVERNIGHT ACROSS THE CENTRAL
AND NORTHERN PLAINS. SASKATCHEWAN SHORT WAVE AND ASSOCIATED
ANOMALIES WILL DROP SOUTHEAST AND BE OVER WESTERN LAKE SUPERIOR BY
12Z TUESDAY AND WILL DRAG A COLD FRONT INTO SOUTHERN MN...POSSIBLY
INTO FAR NW IA BY THIS TIME. A DEEP DRY COLUMN WILL PRECLUDE ANY
POPS OVERNIGHT THOUGH A FEW MID LEVEL CLOUDS MAY REACH THE IA/MN
BORDER LATE. WARM ADVECTION IN ADVANCE OF THE APPROACHING BOUNDARY
AND SOUTHWEST WINDS OVERNIGHT WILL HELP KEEP TEMPERATURES MILD AND
WILL BE GENERALLY IN THE LOW TO MID 50S BY 6 AM.
.LONG TERM /TUESDAY THROUGH MONDAY/...
THE MODELS ARE STILL IN FAIRLY GOOD AGREEMENT ON THE PASSAGE OF A
COLD FRONT LATE IN THE DAY TUESDAY/TUESDAY EVENING. BOTH THE NAM
AND GFS PUSH A LOT OF MOISTURE UP AHEAD OF THIS BOUNDARY BUT I AM
HAVING A HARD TIME SEEING THESE HIGH DEWPOINTS. WE ARE CURRENTLY IN
THE 30S WITH DEWPOINTS AS FAR DOWNSTREAM AS KANSAS AND CENTRAL
MISSOURI ONLY IN THE MID 40S. DID A MODIFIED SOUNDING IN AWIPS TO
LOWER THE DEWPOINTS JUST A FEW DEGREES FROM MODEL FORECAST WHICH
EFFECTIVELY KILLED THE CAPE. SO MOISTURE RETURN WILL OBVIOUSLY BE
KEY TO WHETHER WE SEE THUNDER AT ALL. CONVERGENCE IS ALSO PRETTY
WEAK ALONG THE BOUNDARY. HAVING SAID THAT I DID NOT REDUCE POPS AT
THIS POINT SINCE SOME MOISTURE RETURN WILL OCCUR...JUST NOT SURE HOW
MUCH...AND THERE COULD BE SOME DEVELOPMENT ALONG THE FRONT. I DID
HOWEVER TRY AND TIE THE PRECIP TO THE BOUNDARY SO I NARROWED THE
AREA OF POPS WITH WHERE I FELT THE FRONT WOULD BE.
WEAK HIGH PRESSURE STILL ON TAP FOR LATER TUESDAY NIGHT THROUGH
WEDNESDAY NIGHT. THIS WILL RESULT IN A DRY PERIOD WITH SLIGHTLY
COOLER TEMPS...THOUGH IT WILL STILL BE ABOVE NORMAL.
THURSDAY THROUGH THE REMAINDER OF THE EXTENDED FORECAST IS STILL A
BIT TOUGH TO FORECAST. THE RIDGE AXIS IS NEARLY ABOVE THE REGION
THURSDAY AND BEGINS TO SHIFT TO THE EAST THURSDAY NIGHT AND FRIDAY.
WARM ADVECTION BEGINS OVER THE WEST THURSDAY NIGHT BUT AGAIN
MOISTURE RETURN IS QUESTIONABLE AT BEST DUE TO BEING UNDER THE
RIDGE. ADD TO THIS THAT NOW THE MODELS JUST DO NOT HAVE A GOOD
HANDLE ON WHERE THE SHORTWAVE WILL COME ACROSS AND THE FRONTAL
BOUNDARY WILL BE AND THE RESULT IS A VERY LOW CONFIDENCE POP
FORECAST. IT DOES APPEAR THAT CHANCES IMPROVE SOME LATER THURSDAY
NIGHT WEST OF THE CWA AND WORKING ITS WAY TOWARDS THE WESTERN CWA
WITH THE DEVELOPMENT OF A LOW LEVEL JET WHICH WILL IMPINGE ON THE
BOUNDARY BUT THAT WOULD AFFECT OUR WESTERN FORECAST AREA TOWARDS
FRIDAY MORNING.
FOR FRIDAY THROUGH SATURDAY...CHANCES GRADUALLY INCREASE FOR
THUNDERSTORMS AS THE UPPER RIDGE SHIFTS EAST AND DEEPER RETURN FLOW
BRINGS UP MOISTURE ACROSS OUR FORECAST AREA. A SLOW MOVING FRONTAL
BOUNDARY WILL GRADUALLY SAG INTO THE CWA SATURDAY THROUGH SUNDAY
NIGHT WHICH WILL BRING OUR BEST CHANCES FOR THUNDERSTORMS...AND A
FEW SEVERE STORMS AT THAT. I BUMPED POPS UP TO CHANCE BUT WILL
REFRAIN FROM TOO STRONG A WORDING AT THIS POINT SINCE THE FRONT IS
SO SLOW MOVING.
&&
.AVIATION...14/18Z
VFR CONDITIONS WILL PERSIST THROUGH THE PERIOD. WIND SHIFTS DICTATE
FORECAST WITH SOME DIRECTIONAL CHANGES FROM THIS AFTERNOON AND
EVENING THEN ON TUESDAY IN ADVANCE OF APPROACHING COLD FRONT. CLOUDS
WILL BE A NON FACTOR WITH SOME VFR CUMULUS POSSIBLE OVER THE SOUTH
TODAY AND POSSIBLE MID LEVEL CLOUDS LATE TUESDAY MORNING.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...DONAVON
LONG TERM...FAB
AVIATION...DONAVON
000
FXUS63 KDVN 142008
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
308 PM CDT MON MAY 14 2012
.SYNOPSIS...
RIDGE OF HIGH PRESSURE EXTENDING FROM EASTERN KS TO LOWER MI
CONTINUED TO PROVIDE SUNNY SKIES...LIGHT WINDS AND WARM TEMPERATURES
OVER THE FORECAST AREA THIS AFTERNOON. THE DVN FORECAST SOUNDING
FROM THIS MORNING INDICATED A VERY DRY ATMOSPHERE...WITH A PW
VALUE OF ONLY .29...OR 40 PERCENT OF NORMAL. GULF MOISTURE
CONTINUES TO BE CUT OFF BY A SPLIT FLOW PATTERN THAT FEATURES
UPPER LEVEL SYSTEMS MOVING ALONG A WEAK SOUTHERN JET STREAM FROM
TX EAST ALONG THE GULF COAST...WHILE THE STRONGER NORTHERN JET
STREAM EXTENDED IN A SLIGHTLY CYCLONIC CONFIGURATION ACROSS SOUTH
CENTRAL INTO SOUTHEAST CANADA. THIS IS KEEPING A WEAK AND
SOMEWHAT SUBSIDENT FLOW IN BETWEEN INFLUENCING THE LOCAL AREA.
&&
.SHORT TERM...TONIGHT AND TUESDAY...
PRIMARY FOCUS IS ON CHANCES FOR THUNDERSTORMS TUESDAY AFTERNOON AS A
SHORTWAVE IN THE NORTHERN STREAM BEGINS TO CARVE OUT A LONGWAVE
UPPER LEVEL TROUGH TO OUR EAST...SENDING A CANADIAN COLD FRONT SOUTH
THROUGH THE FORECAST AREA DURING PEAK HEATING. 12Z MODELS HAVE
MAINTAINED SIMILAR TIMING WITH THE FRONT BISECTING THE FORECAST AREA
FROM SW TO NE BY 00Z. OVERALL...THE AMERICAN AND EUROPEAN MODELS
APPEAR OVERDONE WITH DEWPOINTS...SUGGESTED IN THE UPPER 50S TO
AROUND 60 ALONG AND AHEAD OF THE FRONT BY LATE AFTERNOON. 12Z
MOS...INCLUDING THE GFS/MAV AND NAM/MET APPEAR TO HAVE MORE
REALISTIC VALUES...IN THE 40S TO LOWER 50S...SIMILAR TO THE PAST
COUPLE DAYS. THESE LOWER VALUES LOOK MORE REALISTIC GIVEN THE
DEPTH OF MIXING EXPECTED IN THE SOUTHWEST PREFRONTAL FLOW. USING
THE MORE CONSERVATIVE SURFACE DEWPOINTS AND LIMITED MOISTURE
THROUGH 850 MB...CAPES WILL LIKELY BE IN THE UPPER HUNDREDS TO
JUST OVER 1000 J/KG...WITH INSTABILITY PARAMETERS AVERAGING IN A
MODERATE RANGE BASED ON SEVERAL PARAMETERS. SHEAR IS MODERATE AS
WELL...AND APPEARS TO BE HIGHEST OVER NW IL. SPC HAS ROUGHLY THE
NORTHEAST HALF OF THE FORECAST AREA IN DAY 2 SLIGHT RISK. LOCAL
SEVERE WEATHER ASSESSMENT SUGGESTS A POTENTIAL FOR SMALL HAIL AND
WIND GUSTS BELOW 50 KTS WITH POSSIBLE BOWING SEGMENTS ALONG THIS
FRONT DURING PEAK HEATING. HAVE INCREASED POPS TO AN AXIS OF 30
PERCENT ACROSS EASTERN IA INTO NW IL FOR LATE AFTERNOON...WITH
SLIGHT CHANCES ELSEWHERE.
TONIGHT...THERE SHOULD BE ENOUGH OF A SURFACE PRESSURE GRADIENT AS
THE SURFACE HIGH SHIFTS SOUTH AND THE FRONT IN SOUTHERN CANADA DROPS
SOUTH INTO MN AND WI. THIS SHOULD LIMIT THE LOCAL DRAINAGE EFFECTS
THAT RESULTED IN THE COOL TEMPERATURES THIS MORNING. HOWEVER...WITH
THE VERY DRY AIR IN PLACE AND ENHANCED DIURNAL EFFECTS...WILL STAY AT
THE LOW END OF GUIDANCE...THAT WAS TOO WARM FOR THIS
MORNING...AND FORECAST MINS FROM AROUND 50 TO THE MID 50S IN THE
FAR SOUTH. WOULD NOT BE SURPRISED TO STILL SEE A SITE OR TWO DIP
INTO THE UPPER 40S. TUESDAY...DEEP MIXING TO AT LEAST 850 MB AHEAD
OF THE LATE DAY FROPA SHOULD DRIVE TEMPERATURES IN THE LOWER 80S.
SHEETS
.LONG TERM...TUESDAY NIGHT THROUGH NEXT MONDAY...
THE SCENARIO THAT APPEARS TO BE SETTING UP FOR LATE THURSDAY
AFTERNOON AND EVENING IS ONE OF TYPICAL DIURNAL CONVECTION. THE MAIN
QUESTION IS MOISTURE AVAILABILITY. IF THERE IS NOT ENOUGH MOISTURE
THEN THE WEAK CONVERGENCE ALONG THE FRONT WILL ONLY RESULT IN
CONVECTIVE CLOUDS THAT WILL DISSIPATE SHORTLY AFTER SUNSET. ASSUMING
THERE WILL BE JUST ENOUGH MOISTURE AVAILABLE...WILL CONTINUE THE
SCHC POPS FOR TUESDAY EVENING BUT SHIFT THEM FURTHER SOUTH BASED ON
THE EXPECTED FRONTAL POSITION AT 00Z.
QUIET AND DRY CONDITIONS ARE EXPECTED LATE TUES NIGHT THROUGH WED
EVENING AS HIGH PRESSURE MOVES THROUGH THE WESTERN GREAT LAKES.
THERE COULD BE QUITE A GRADIENT IN TEMPERATURES FROM NORTHEAST TO
SOUTHWEST ACROSS THE CWFA ON WEDNESDAY WITH THE DRY LOW LEVEL
EASTERLY FLOW.
LATE WED NIGHT INTO THURSDAY BECOMES MORE INTERESTING. A RESPECTABLE
LLJ WITH MOISTURE TRANSPORT SETS UP WELL WEST OF THE CWFA WED
EVENING. MCS TOOL IN COMBINATION WITH LIFT AND HEAVY RAIN TOOLS ARE
SUGGESTING A NOCTURNAL MCS WILL DEVELOP POSSIBLY ALONG THE IA/MN
BORDER. IF THIS IS THE LOCATION OF DEVELOPMENT...CORFIDI VECTORS
WOULD TAKE THE MCS GENERALLY EAST WITH POSSIBLY A SLOW DRIFT TO THE
SOUTH THAT MAY AFFECT THE EXTREME NORTHERN CWFA AROUND SUNRISE
THURSDAY. YESTERDAY...THE SAME INTERNAL SIGNALS SUGGESTED AN MCS
DEVELOPING FURTHER SOUTH. SO...THE THEME OF AN MCS DEVELOPING WEST
OF THE CWFA WED NIGHT WILL BE FOLLOWED. HOWEVER...GIVEN CURRENT
MODEL TRENDS WILL GO WITH THE IDEA OF IT DEVELOPING IN SOUTHWEST
MINNESOTA AND MOVING EAST OVERNIGHT. A POSSIBLE WAA WING OF PRECIP
MAY COME CLOSE TO THE HWY 20 CORRIDOR AROUND DAWN BUT FOR NOW WILL
CONTINUE TO KEEP THE CWFA DRY WED NIGHT.
IF THE MCS DEVELOPS IN SOUTHWEST MN...OUTFLOW AND A GRADUAL
PROPAGATION SOUTH OF THE DEVELOPING WAA WING OF PRECIP MAY CATCH THE
HWY 20 CORRIDOR FROM DUBUQUE EAST AFTER SUNRISE THURSDAY. THIS
SCENARIO IS ALL PREDICATED ON THE WARM FRONT MOVING INTO THE
NORTHERN CWFA SHORTLY AFTER SUNRISE. ALL MODELS PROG THE FRONT
THROUGH THE AREA BY MID DAY SO THE AFTERNOON HOURS SHOULD BE DRY.
THURSDAY NIGHT ON...
MODEL CONSENSUS HAS SCHC POPS FROM THURS NIGHT THROUGH SATURDAY. ANY
FORCING PRESENT IS WEAK WITH THE 500MB RIDGE BUILDING OVER THE
EASTERN CONUS. ALTHOUGH CONVECTION WILL BE POSSIBLE...THERE WILL BE
MANY HOURS OF DRY WX ACROSS THE AREA. THE OVERALL SIGNALS FROM THE
MODELS INDICATE DIURNAL CONVECTION DEVELOPING DURING THE AFTERNOON
HOURS AND DISSIPATING AFTER SUNSET.
STARTING SATURDAY NIGHT AND CONTINUING THROUGH MONDAY THINGS BECOME
MORE INTERESTING. A FRONT APPROACHES FROM THE WEST AND SLOWLY MOVES
ACROSS THE AREA SUNDAY THROUGH MONDAY. ALTHOUGH THE FRONT WILL NOT
BE PARALLEL TO THE FLOW ALOFT IT WILL NOT BE FAR FROM IT SO THE
FORWARD MOVEMENT WILL BE SLOW. THE MODEL CONSENSUS HAS SCHC POPS
SATURDAY NIGHT THAT EVOLVES INTO PROGRESSIVELY HIGHER CHC POPS
SUNDAY THROUGH MONDAY. IF THE SLOW MOVING FRONT SCENARIO PLAYS OUT
THEN THESE POPS WILL SLOWLY INCREASE AS THE WEEKEND GETS CLOSER.
PRIOR TO THE ARRIVAL OF THE FRONT TEMPERATURES SHOULD AVERAGE ABOVE
NORMAL. ..08..
&&
.AVIATION...
HIGH PRESSURE OVER THE CENTRAL PLAINS WILL CONTINUE VFR CONDITIONS
WITH CLEAR SKIES AND LIGHT WEST WINDS THROUGH TONIGHT. WINDS WILL
INCREASE TO 10 TO 20 KTS AND BECOME GUSTY BY LATE TUESDAY MORNING.
BEYOND THE FORECAST PERIOD THERE WILL BE A CHANCE OF THUNDERSTORMS
LATE TUESDAY AFTERNOON AS A COLD FRONT DROPS SOUTH THROUGH THE
REGION.
SHEETS
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
SHEETS/08
000
FXUS63 KDMX 141728 AAA
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1228 AM CDT MON MAY 14 2012
...UPDATE FOR THE 18Z AVIATION DISCUSSION...
.SHORT TERM /TODAY/...
NOT MUCH CHANGE IN THE PATTERN FROM YESTERDAY. SURFACE RIDGE HAS
MOVED TO SOUTHERN IA. WINDS WILL TURN SOUTHWEST AND WITH LITTLE
CHANGE IN THE AIRMASS OTHER THAN SOME WARMING ALOFT WILL GO WITH A
P+3 TO P+5 MOST AREAS FOR HIGHS TODAY.
.LONG TERM /TONIGHT THROUGH SUNDAY/...
AS A SURFACE HIGH DEPARTS TO THE SOUTHEAST TONIGHT WE WILL SEE A
RETURN OF LIGHT SOUTHWESTERLY FLOW WITH SLIGHTLY WARMER OVERNIGHT
TEMPERATURES. MEANWHILE A 500 MB VORTICITY MAXIMUM WILL ROUND THE
BASE OF A LARGE GYRE OVER HUDSON BAY...MOVING ACROSS NORTHERN MN/WI
ON TUESDAY. THIS FEATURE WILL COINCIDE WITH THE PASSAGE OF A SURFACE
TROUGH ACROSS OUR CWA ON TUESDAY AFTERNOON AND EVENING. GIVEN AMPLE
WARMING AHEAD OF THE TROUGH IT APPEARS LIKELY THAT INCREASING
MID-LEVEL LAPSE RATES AND MODEST LOW-LEVEL CONVERGENCE ALONG THE
BOUNDARY WILL BE SUFFICIENT TO POP A FEW THUNDERSTORMS...EVEN WITH
MOST OF THE FORCING ALOFT TO OUR NORTHEAST AND LIMITED ATMOSPHERIC
MOISTURE. HAVE MAINTAINED JUST SOME SLIGHT POPS ON TUESDAY AFTERNOON
AND EVENING MAINLY ACROSS OUR NORTHEAST AND EAST TO ACCOUNT FOR
THESE STORMS. GIVEN THE LACK OF MOISTURE INSTABILITY WILL BE
SOMEWHAT LIMITED AND WOULD EXPECT FAIRLY HIGH BASED STORMS WITH SOME
VERY SLIGHT RISK OF HAIL GIVEN THE ANTICIPATED STEEP LAPSE RATES.
THE CURRENT SPC DAY 2 OUTLOOK CONVEYS THIS SMALL THREAT WELL. AT ANY
RATE ANY THUNDERSTORMS SHOULD BE DIURNALLY DRIVEN AND DISSIPATE
RAPIDLY LATE IN THE EVENING.
BEHIND THE LATE TUESDAY TROUGH A COOL SURFACE HIGH WILL BUILD IN
QUICKLY FROM MN BEFORE SHUNTING OFF TO THE EAST ON WEDNESDAY NIGHT.
BEYOND THIS POINT THE FORECAST BECOMES MORE COMPLEX. CURRENTLY A
LARGE 500 MB RIDGE IS BUILDING INTO THE PACIFIC U.S. COAST...BUT
WITH A CUTOFF LOW STRANDED BENEATH THE RIDGE AND EXPECTED TO MOVE
OVER NORTHERN CA LATER TODAY. AS THE LARGER SCALE RIDGE MOVES
EASTWARD ACROSS THE U.S. THIS WEEK THE CUTOFF LOW WILL STEADILY
WEAKEN BUT PERSIST...APPROACHING OUR AREA BY THURSDAY MORNING
COINCIDENT WITH THE AFOREMENTIONED SURFACE HIGH MOVING AWAY AND A
RETURN OF SOUTHERLY LOW-LEVEL FLOW AND ASSOCIATED MOISTURE. GIVEN
THE WEAK STEERING FLOW BENEATH THE 500 MB RIDGE THE PROGNOSTIC
MODELS ARE HAVING DIFFICULTY PINNING DOWN THE TIMING AND DEPTH OF
THE REMNANTS OF THE CUTOFF LOW. THE RESULT IS THAT WE EXPECT A
GRADUAL WARMING TREND AS THE 500 MB RIDGE BUILDS IN DURING THE
LATTER HALF OF THE WEEK...BUT WITH PERIODS OF ISOLATED THUNDERSTORMS
POSSIBLE. HAVE ATTEMPTED TO NARROW DOWN THE RESULTING SLIGHT POPS
AND CONFINED THEM TO THE THURSDAY NIGHT PERIOD FOR NOW AS THAT
APPEARS TO BE THE MOST LIKELY TIME FOR THE WEAK 500 MB WAVE TO MOVE
OVERHEAD. IT IS DIFFICULT TO TELL WHAT DAMPER THIS MAY HAVE ON THE
EXPECTED WARMING TREND AS IT WILL DEPEND ON COVERAGE AND DIURNAL
TIMING OF CLOUDS...AND WE WILL BE REVISITING THIS OVER THE NEXT FEW
DAYS.
BY FRIDAY IN THE WAKE OF THE REMNANTS OF THE 500 MB CUTOFF LOW WE
WILL SEE UNABATED RIDGING BUILD IN ALONG WITH CONSIDERABLY WARMER
WEATHER. CURRENTLY FORECAST CALLS FOR HIGHS IN THE LOW TO MID 80S ON
FRIDAY BUT THESE MAY NEED TO BE INCREASED IF CONFIDENCE INCREASES IN
THE STRENGTH OF THE RIDGING AND WARM AIR ADVECTION ALOFT. MEANWHILE
ON FRIDAY A LONGWAVE 500 MB TROUGH WILL BE MOVING FROM THE WEST
COAST INTO THE ROCKIES...AND WILL SUBSEQUENTLY BUTT UP AGAINST THE
RIDGE AND BE SHUNTED SOMEWHAT NORTHEASTWARD ACROSS THE MIDWESTERN
STATES OVER THE WEEKEND. LONG RANGE MODELS REMAIN INCONSISTENT IN
THE EVOLUTION OF THE TROUGH DURING THIS TIMEFRAME...BUT IT APPEARS
LIKELY THAT WE WILL REMAIN CAPPED AND LARGELY DRY ON SATURDAY WITH
ANY PRECIP ASSOCIATED WITH THE TROUGH MORE LIKELY MOVING THROUGH
DURING THE LATTER HALF OF THE WEEKEND WHEN WE ARE MAINTAINING 20 TO
40 POPS.
&&
.AVIATION...14/18Z
VFR CONDITIONS WILL PERSIST THROUGH THE PERIOD. WIND SHIFTS DICTATE
FORECAST WITH SOME DIRECTIONAL CHANGES FROM THIS AFTERNOON AND
EVENING THEN ON TUESDAY IN ADVANCE OF APPROACHING COLD FRONT. CLOUDS
WILL BE A NON FACTOR WITH SOME VFR CUMULUS POSSIBLE OVER THE SOUTH
TODAY AND POSSIBLE MID LEVEL CLOUDS LATE TUESDAY MORNING.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...MS MAY 12
LONG TERM...LEE
AVIATION...DONAVON
000
FXUS63 KDVN 141709
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1209 PM CDT MON MAY 14 2012
.AVIATION...
HIGH PRESSURE OVER THE CENTRAL PLAINS WILL CONTINUE VFR CONDITIONS
WITH CLEAR SKIES AND LIGHT WINDS THIS AFTERNOON THROUGH TONIGHT.
WINDS WILL BECOME WEST AROUND 10 TO 20 KTS BY LATE TUESDAY
MORNING. BEYOND THE FORECAST PERIOD THERE WILL BE A CHANCE OF
THUNDERSTORMS LATE TUESDAY AFTERNOON AS A COLD FRONT DROPS SOUTH
THROUGH THE REGION. SHEETS
&&
.PREV DISCUSSION.../ISSUED 327 AM CDT MON MAY 14 2012/
SYNOPSIS...
ELONGATED SFC RIDGE AXIS EXTENDS FROM MI THROUGH NRN IL AND MUCH
OF IA INTO THE CENTRAL PLAINS PROVIDING TRANQUIL CONDITIONS
EARLY THIS AM. TEMPS HAVE PLUMMETED WELL INTO THE 40S IN SOME
FAVORED COLD DRAINAGE OR LOW LYING AREAS WITH CLEAR SKIES...CALM
WINDS AND DRY AIR. TEMPS ELSEWHERE WHILE HOVERING AROUND 50F
OR THE LOWER 50S ARE DESTINED FOR THE 40S AS WELL. 00Z SUBJECTIVE
UPPER AIR ANALYSIS AND LATEST WATER VAPOR IMAGERY REVEAL BROAD
TROUGHING OVER SOUTH CENTRAL AND SOUTHEAST CONUS WITH A SHORTWAVE
DROPPING SWD THROUGH NM... AND ANOTHER LIFTING NEWD FROM THE TN
VLY. MEANWHILE OUR AREA IS BASKING IN NW FLOW ALOFT BETWEEN
THESE ENERGY CENTERS... AND A RATHER VIGOROUS CANADIAN SHORTWAVE
PLOWING ACROSS HUDSON BAY. ATTENDANT COLD FRONT IS JUST CROSSING
THE BORDER INTO NW MN EARLY THIS AM.
SHORT TERM...TODAY AND TONIGHT...
MORE STELLAR WX ON TAP COMPLIMENTS OF SFC RIDGE AXIS... WHICH WILL
REMAIN IN CONTROL TDY THOUGH BEGIN SAGGING SWD LATER TDY INTO TNGT
IN ADVANCE OF COLD FRONT PROGGED TO REACH NEAR A MINNEAPOLIS MN TO
SIOUX FALLS SD LINE BY 12Z TUE. FOR TDY... ABOVE NORMAL WARMTH
COUPLED WITH LOW HUMIDITY AND SUNNY SKIES TO RESULT IN NEAR PERFECTION.
NAM AND GFS BUFR SOUNDINGS SHOW MIXING DEPTH NEARLY IDENTICAL TO
THAT OF YSTDY... WHICH WAS JUST ABOVE 800 MB PER 00Z/14 KDVN RAOB.
HOWEVER... ADDING SW WINDS OF 5-10 MPH AND CONTINUED DRYING BELIEVE
LIKELY TO MIX DEEPER TO NEAR 750 MB OR SO CENTRAL AND NORTH SECTIONS.
BRINGING THIS TO THE SFC YIELDS HIGHS IN GENERAL RANGE OF 77-82F.
SOUTHERN SECTIONS NOT LIKELY TO MIX AS DEEP BEING IN CLOSE PROXIMITY
TO SFC RIDGE AND THUS LIGHT WINDS MOST OF DAY. HOWEVER... TO
COMPENSATE THEY WILL BE STARTING OFF A BIT WARMER AND SO IN THE
END EXPECT SIMILAR ACHIEVEMENT ON HIGH TEMPS WITH U70S TO AROUND 80F.
TNGT... AREA WILL RESIDE IN PRE-FRONTAL ENVIRONMENT CHARACTERIZED
BY LIGHT SW WINDS... MAINLY CLEAR SKIES AND DRY AIR THUS FAVORED LOWS
NEAR THE COOL SIDE OF GUIDANCE WITH GENERAL RANGE OF 50-55F.
05
LONG TERM...TUESDAY THROUGH NEXT SUNDAY...
TUESDAY AND WEDNESDAY...LATEST SUITE OF 00Z RUN MODELS ARE IN GOOD
AGREEMENT OF NORTHWEST FLOW AND UPPER LEVEL TROFFINESS SWEEPING A
FRONT THROUGH THE REGION FROM THE NORTHWEST TUE AFTERNOON AND
EVENING. THE LATEST RUNS HAVE ALSO SEEMED TO SPEED UP THIS PROCESS
SOME. BIG QUESTION REMAINS MOISTURE RETURN UP INTO THIS FEATURE AND
ALTHOUGH THE AMERICAN MODELS HAVE TRENDED DRIER THIS RUN...THE
EUROPEAN SOLUTIONS STILL SEEM TO BE HANDLING THE MOISTURE RETURN/OR
LACK OF IT/ AND DRIER SFC LAYER MOISTURE MIX-OUT BETTER. PRE-FRONTAL
WARM DRAW AND MIXING SHOULD ZOOM TEMPS INTO THE LOW TO MID 80S CWA-
WIDE...BUT DPTS DRY DOWN-MIXED INTO THE UPPER 40S TO LOWER 50S. EVEN
MID 50 DPTS ONLY YIELD SBCAPES OF 1000-1400 J/KG OR SO BY LATE TUE
AFTERNOON. DEEPER LAYER SHEAR VALUES MARGINAL TO ADEQUATE TO SUPPORT
SOME ISOLATED TO SCTRD SHOWER AND STORM DEVELOPMENT ALONG THE FRONT
LATER TUE AFTERNOON AND INTO THE EVENING WITH THE FORCING OVERCOMING
THE WEAK CAP IN PLACE. BUT AGAIN IT APPEARS THAT ONLY MARGINAL
THERMODYNAMICS/BUOYANCY IN PLACE TO FUEL A MORE ORGANIZED SVR WX
EVENT AND MAYBE JUST A CHANCE FOR A STORM PRODUCING NEAR SVR SIZE
HAIL AND A LOCALIZED DOWNBURST TYPE PHENOMENA TUE EVENING ESPECIALLY
IN NORTHWEST IL. THE BOUNDARY FEATURE IS PROGRESSIVE AND CLEARS TO
THE SOUTH AS A LLVL ANTICYCLONE DUMPS DOWN THE UPPER MS RVR VALLEY
AND WESTERN GRT LKS INTO WED. NOW MOST OF THE 00Z RUN MEDIUM RANGE
SOLUTIONS AGREE OR HAVE SIDED WITH EARLIER ECMWF RUNS OF SHUNTING
THE BOUNDARY WELL ENOUGH TO THE SOUTH OF THE LOCAL FCST AREA TO
ENSURE A DRY FCST WED AND WED NIGHT. NORTHEAST LAKE-ENHANCED
BOUNDARY LAYER FETCH ON WED SUGGESTS A COOLER DAY IN STORE WITH
HIGHS BACK IN THE 70S...ALTHOUGH THE DRY AIRMASS MAY WARM TO AROUND
80 AGAIN IN THE FAR SOUTH AND SOUTHWEST. WED NIGHT...ELEVATED RETURN
FLOW FORCING AND MOISTURE FEED TAKE AIM AT THE DAKOTAS AND INTO MN
WITH A LOW CHANCE FOR SOME OF THE RESULTANT MCS TO FEED DOWN
SOUTHEASTWARD ENOUGH TO GET INTO THE NORTHERN DVN CWA BY EARLY THU
MORNING.
THURSDAY AND FRIDAY...LATEST RUN OF SOLUTIONS GENERALLY AGREE
THAT WARM FRONTAL RETREAT PROCESS WILL SUPPORT MORE THUNDERSTORM
DEVELOPMENT OR MCS SUSTENANCE OUT OF WED NIGHT ACRS MN AND WI WITH
THE ONGOING LOW POTENTIAL OF SOME OF THIS ACTIVITY MOVING ACRS THE
NORTHERN CWA ON THU. WILL GO WITH SLIGHT CHC POPS IN THE NORTHEAST
FOR THIS POSSIBILITY BUT DOES NOT APPEAR TO WARRANT HIGHER
PROBABILITIES AT THIS TIME. THU NIGHT INTO FRI WILL SIDE WITH THE
CONSISTENT ECMWF AND UKMET WHICH CONTINUE TO FOCUS THE MAIN WARM
FRONT UNDER BUILDING UPPER RIDGE COMPLEX OVER THE UPPER MIDWEST FROM
THE DAKOTAS...EASTWARD ACRS MN...WI AND MI. THESE SHOULD BE THE
FAVORED CONVECTION ZONES ESPECIALLY AT NIGHT WITH NORMAL MCS
GENERATION PROCESSES TAKING PLACE. THE DVN CWA MAY BE MAINLY SOUTH
OF THE ACTION AND INCREASINGLY IN THE WARM SECTOR WITH FRI HIGHS
WELL UP IN THE 80S.
SATURDAY THROUGH SUNDAY...CONTINUING TO SIDE WITH THE EURO
SOLUTIONS...AS UPPER RIDGE AXIS MIGRATES ACRS THE GRT LKS THE CWA
WILL CONTINUE TO BE UNDER THE INFLUENCE IT/S WEST SIDE WARM SECTOR
WITH EARLY PROJECTED THERMAL PROFILES SUPPORTING HIGHS IN THE MID
TO UPPER 80S FOR SAT. EXTENT OF WARM WEDGE ALOFT AND LACK OF ANY
FORCING WOULD KEEP THE AREA DRY THROUGH EARLY SUNDAY. LONGER RANGE
SIGNALS SUGGEST L/W TROF ENERGY PIVOTING ACRS THE NORTHERN PLAINS
AND CENTRAL CANADA WILL EVENTUALLY TRY TO SHUNT AN ASSOCIATED SFC
FRONT TOWARD THE AREA SOMETIME LATE IN THE EXTENDED PERIOD WITH
SOME MOISTURE RETURN OFF THE WESTERN GULF. THIS THINKING WOULD
SUPPORT AN INCREASING CHC OF SHOWERS AND STORMS FROM THE WEST LATER
SUNDAY AND SUNDAY NIGHT...BUT TIMING AN HANDLING OF THIS FEATURE AS
WELL AS PHASING WITH THE BROAD SCALE FORCING STILL UNCERTAIN AND
HARD TO DEFINE AT THIS POINT. ANY SLOW DOWN OF THESE PROCESSES WOULD
MEAN A WARM AND MAINLY DRY SUNDAY. 12
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
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