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000
FXAK68 PAFC 221321
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
521 AM AKDT WED OCT 22 2014

.ANALYSIS AND UPPER LEVELS...

ALASKA CONTINUES TO REMAIN UNDER THE INFLUENCE OF A LARGE AND
SPRAWLING UPPER LEVEL TROUGH...WITH THE MAIN LOW CENTER OVER THE
SOUTHERN GULF OF ALASKA. SHORTWAVE TROUGHS EMBEDDED ALONG THE
PERIPHERY OF THE LOW CAN BE SEEN ON SATELLITE...WITH THE MAIN
CENTER OF ACTION ACROSS THE GULF AS A NEAR STORM FORCE 972 MB LOW
ROTATES NORTHWESTWARD. A CYCLONICALLY CURVED 145 KT NORTH PACIFIC
JET ANCHORS THE TROUGH IN THE VICINITY OF 40-45N. SHORTWAVE
RIDGING IS BUILDING INTO THE WESTERN BERING AHEAD OF A LARGE
EASTERN SIBERIA LOW CURRENTLY TRANSITING THE KAMCHATKA PENINUSULA.
WEAK SHORTWAVE RIDGING IS BUILDING INTO MOST OF SOUTHERN
ALASKA...WITH AN OFFSHORE PRESSURE GRADIENT HELPING TO DRY THE
REGION OUT. HOWEVER...WITH A LACK OF STRONG UPPER LEVEL DOWNWARD
DESCENT AND/OR COLD AIR ADVECTION...GAP WINDS ARE A BIT WEAKER
THAN THE PRESSURE GRADIENT ALONE WOULD SUGGEST. WITH TIME...THE
LARGE SCALE TROUGH OVER THE REGION WILL BEGIN TO SHIFT EAST AS THE
RIDGING ALOFT MOVES INTO THE EASTERN BERING. THIS WILL SET IN
MOTION A CHANGE IN THE PERSISTENT WEATHER PATTERN...SHIFTING MORE
TO A PROGRESSIVE AND FAST ZONAL PATTERN THIS WEEKEND INTO NEXT
WEEK.

&&

.MODEL DISCUSSION...

THE NUMERICAL MODELS ARE IN EXCELLENT AGREEMENT THROUGH THE
WEEKEND. HOWEVER...THEY BEGIN TO DIVERGE RAPIDLY WITH MORE
SPECIFIC DETAILS EARLY NEXT WEEK AS THE PATTERN SWITCHES TO A MORE
PROGRESSIVE AND FAST ZONAL FLOW. THIS IS QUITE TYPICAL...AND WHILE
THEY ARE IN DISAGREEMENT WITH SPECIFIC WAVE PATTERNS...THEY ARE
ALL CONSISTENT IN DEPICTING A CHANGE IN THE OVERALL LONGWAVE
EVOLUTION. FORECAST CONFIDENCE IS HIGH IN THE SHORT TERM AND
MODERATE IN THE EXTENDED.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
QUIET WEATHER WILL PERVAIL ACROSS MOST OF SOUTHCENTRAL ALASKA AS
DRY OFFSHORE FLOW PERSISTS THROUGH TONIGHT. THE LACK OF A STRONG
PUSH OF DRY AIR INTO THE COPPER BASIN WILL LIKELY KEEP SOME DEGREE
OF LOW LEVEL CLOUDS AND PATCHY FOG IN THE BASIN...BUT MOST OTHER
LOCATIONS WILL STAY DRY AND LARGELY CLEAR. SOME RAIN SHOWERS
WILL IMPACT THE NORTH GULF COAST AND PRINCE WILLIAM SOUND THIS
EVENING AND TONIGHT. A FRONT MOVING IN FROM THE WEST WILL SPREAD
CLOUDS AND SCATTERED RAIN AND SNOW SHOWERS OVER SOUTHCENTRAL
FRIDAY AND SATURDAY.

SOUTHWEST ALASKA...
LARGELY QUIET WEATHER WILL PREVAIL AS THE PRESSURE GRADIENT
BECOMES OFFSHORE/OUTFLOW ACROSS THE REGION. NORTHERLY WINDS WILL
BECOME GUSTY TODAY...ESPECIALLY ACROSS THE BRISTOL BAY COAST AND
THROUGH GAPS IN THE ALASKA RANGE. A FRONT WILL PROGRESS WEST TO
EAST THURSDAY MORNING THROUGH FRIDAY MORNING...BRINGING RAIN AND
SNOW SHOWERS TO THE REGION.

BERING SEA/ALEUTIANS...
NORTHERLY WINDS AND SHOWERS WILL RAPIDLY DIMINISH TODAY AS WEAK
HIGH PRESSURE BUILDS IN OVER THE CENTRAL AND EASTERN BERING. A
FAST MOVING FRONT WILL TRACK INTO THE WESTERN ALEUTIANS AND WILL
SPREAD TO THE EASTERN BERING BY THURSDAY NIGHT.

&&

.LONG TERM FORECAST...

RUN TO RUN GUIDANCE OF THE EXTENDED MODELS HAS NOT BEEN
GOOD...AT LEAST PARTIALLY DUE TO HANDLING OF THE MOISTURE RESIDUE
FROM TROPICAL STORM ANA. EARLIER EC MODELS WERE BRINGING THE
RESIDUE ALONG WITH A DEEPENING LOW INTO THE GULF OF AK ON MON...BUT
MORE RECENT RUNS ARE SENDING THE MOISTURE FIELD EAST...WITH A MUCH
WEAKER LOW OVER THE EASTERN GULF MON THROUGH WED.

WHILE THIS IS HAPPENING...A FRONT ASSOCIATED WITH A LOW OVER
NORTHWEST AK WILL MOVE ACROSS MAINLAND AK THROUGH THE
WEEKEND...FOLLOWED BY HIGH PRESSURE EARLY NEXT WEEK. A KAMCHATKA
LOW WILL SEND A FRONTAL COMPLEX ACROSS THE BERING TO WESTERN AK
SUN THROUGH WED.

THE FORECAST UTILIZES THE WPC SOLUTION...WHICH RELIED HEAVILY ON
THE 06Z GFS ENSEMBLE FORECAST THAT PROVIDED SOME RUN TO RUN
CONSISTENCY.

-DS

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 150 155 170 172 174 178 185.
FIRE WEATHER...NONE.

&&

$$

AHSENMACHER OCT 14





000
FXAK68 PAFC 212200
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT TUE OCT 21 2014

.ANALYSIS AND UPPER LEVELS...

500 MB...THE UPPER LEVELS CONTINUE TO BE DOMINATED BY A LARGE LOW
OVER BRISTOL BAY AND A HIGH AMPLITUDE RIDGE OVER THE BERING SEA.
THE BRISTOL BAY CENTER IS EXPECTED TO DRIFT SOUTH AND WEAKEN AS A
LOW CENTER OVER THE EASTERN GULF MOVES WEST AND ANCHORS OVER THE
SOUTHERN GULF WED. THIS LOW THEN DRIFTS SOUTHEAST ON THU AS THE
RIDGE OVER THE BERING SEA MOVES OVER WESTERN ALASKA. A WAVE MOVING
ACROSS EASTERN RUSSIA SETS UP WESTERLY FLOW ACROSS THE BERING SEA
THU.

SURFACE...A WEAK DEFORMATION ZONE WAS EVIDENCED BY CLOUDS AND
SHOWERS ACROSS THE NORTHERN GULF AND KENAI PEN THIS AFTERNOON. A
LARGE 970S MB LOW WAS PRESENT  OVER THE SOUTH GULF OF ALASKA WITH
WEAK HIGH PRESSURE OVER THE MAIN LAND. A FEW SNOW SHOWERS
ASSOCIATED WITH A LOW NEAR BRISTOL BAY AND BROAD UPPER TROUGH WERE
EVIDENT OVER SW ALASKA. BRISK NORTHERLY WINDS AND COLD ADVECTION
WERE CONTINUED ACROSS MUCH OF THE CENTRAL AND EASTERN BERING SEA.
SATELLITE IMAGERY SHOWED A LARGE AREA OF OPEN/CLOSED CELL CU WITH
SHOWERS ACROSS THE BERING SEA/ALEUTIANS.

&&

.MODEL DISCUSSION...

MODELS ARE IN EXCELLENT AGREEMENT WITH THE GENERAL LARGE SCALE
PATTERN THROUGH THE LATTER PART OF THIS WEEK. MAIN DIFFERENCES
COME IN TO PLAY WITH THE HANDLING OF FRONTAL BOUNDARY MOVING
ACROSS THE BERING SEA AND IMPACTING THE SW MAINLAND THU. THE GFS
IS A LITTLE SLOW ON THE FRONTAL MOVEMENT AND PUSHES A LITTLE TOO
MUCH WARM AIR INTO THE WESTERN MAINLAND THU NIGHT.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
A BROAD BAND OF MOISTURE ASSOCIATED WITH A WEAK DEFORMATION ZONE
HEADS SOUTH AND BRINGS SOME RAIN/SNOW TO THE WESTERN GULF/KODIAK
ISLAND TONIGHT. DRY OFFSHORE FLOW AND BUILDING PRESSURE GRADIENTS
DEVELOP BEHIND THIS SYSTEM TONIGHT. IN RESPONSE BRISK GAP WINDS
ARE EXPECTED AROUND SOUTHCENTRAL...ESPECIALLY THE GULF COAST AND
EASTERN KENAI PEN. A FEW SHOWERS ARE POSSIBLE ACROSS THE NORTH
GULF AND COPPER RIVER WED NIGHT WITH A WEAK WAVE...OTHERWISE THE
NEXT SHOT AT SNOW WILL BE ON FRI.


SOUTHWEST ALASKA...
STEADY SNOW ACROSS THE DELTA THIS MORNING HAS MOVED
OFFSHORE...WITH A GENERAL DRYING TREND THROUGH WEDNESDAY AS A
NORTHERLY FLOW PATTERN DEVELOPS. A FRONT WILL APPROACH FROM THE
WEST THURSDAY AFTERNOON INTO FRIDAY...SPREADING SNOW INLAND WITH A
MIX ALONG THE COASTS. RAIN AND SNOW SHOWERS WILL INTENSIFY SOME
ACROSS THE AK PEN WAS THE UPPER TROUGH DRIFTS SOUTH. INCREASING
NORTHERLY WINDS ARE ALSO EXPECTED WITH STRONG LOWS THROUGH GAPS IN
THE PEN ON WED.


BERING SEA/ALEUTIANS...
STRONG NORTHERLY WINDS AND RAIN AND SNOW SHOWERS WILL CONTINUE
ACROSS THE EASTERN AND CENTRAL BERING AND ALEUTIANS THROUGH
WEDNESDAY. A FRONT WILL TRACK INTO THE WESTERN BERING WEDNESDAY
THEN SPREAD THROUGH THE BERING WHILE WEAKENING THURSDAY AND
FRIDAY.

&&

.LONG TERM FORECAST...

RUN TO RUN GUIDANCE OF THE EXTENDED MODELS HAS NOT BEEN
GOOD...AT LEAST PARTIALLY DUE TO HANDLING OF THE MOISTURE RESIDUE
FROM TROPICAL STORM ANA. EARLIER EC MODELS WERE BRINGING THE
RESIDUE ALONG WITH A DEEPENING LOW INTO THE GULF OF AK ON MON...BUT
MORE RECENT RUNS ARE SENDING THE MOISTURE FIELD EAST...WITH A MUCH
WEAKER LOW OVER THE EASTERN GULF MON THROUGH WED.

WHILE THIS IS HAPPENING...A FRONT ASSOCIATED WITH A LOW OVER
NORTHWEST AK WILL MOVE ACROSS MAINLAND AK THROUGH THE
WEEKEND...FOLLOWED BY HIGH PRESSURE EARLY NEXT WEEK. A KAMCHATKA
LOW WILL SEND A FRONTAL COMPLEX ACROSS THE BERING TO WESTERN AK
SUN THROUGH WED.

THE FORECAST UTILIZES THE WPC SOLUTION...WHICH RELIED HEAVILY ON
THE 06Z GFS ENSEMBLE FORECAST THAT PROVIDED SOME RUN TO RUN
CONSISTENCY.

&&


AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 150 155 170 171 172 173 174 178 179 185 351 352.
FIRE WEATHER...NONE.

$$

RMC/DS OCT 14





000
FXAK68 PAFC 212200
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT TUE OCT 21 2014

.ANALYSIS AND UPPER LEVELS...

500 MB...THE UPPER LEVELS CONTINUE TO BE DOMINATED BY A LARGE LOW
OVER BRISTOL BAY AND A HIGH AMPLITUDE RIDGE OVER THE BERING SEA.
THE BRISTOL BAY CENTER IS EXPECTED TO DRIFT SOUTH AND WEAKEN AS A
LOW CENTER OVER THE EASTERN GULF MOVES WEST AND ANCHORS OVER THE
SOUTHERN GULF WED. THIS LOW THEN DRIFTS SOUTHEAST ON THU AS THE
RIDGE OVER THE BERING SEA MOVES OVER WESTERN ALASKA. A WAVE MOVING
ACROSS EASTERN RUSSIA SETS UP WESTERLY FLOW ACROSS THE BERING SEA
THU.

SURFACE...A WEAK DEFORMATION ZONE WAS EVIDENCED BY CLOUDS AND
SHOWERS ACROSS THE NORTHERN GULF AND KENAI PEN THIS AFTERNOON. A
LARGE 970S MB LOW WAS PRESENT  OVER THE SOUTH GULF OF ALASKA WITH
WEAK HIGH PRESSURE OVER THE MAIN LAND. A FEW SNOW SHOWERS
ASSOCIATED WITH A LOW NEAR BRISTOL BAY AND BROAD UPPER TROUGH WERE
EVIDENT OVER SW ALASKA. BRISK NORTHERLY WINDS AND COLD ADVECTION
WERE CONTINUED ACROSS MUCH OF THE CENTRAL AND EASTERN BERING SEA.
SATELLITE IMAGERY SHOWED A LARGE AREA OF OPEN/CLOSED CELL CU WITH
SHOWERS ACROSS THE BERING SEA/ALEUTIANS.

&&

.MODEL DISCUSSION...

MODELS ARE IN EXCELLENT AGREEMENT WITH THE GENERAL LARGE SCALE
PATTERN THROUGH THE LATTER PART OF THIS WEEK. MAIN DIFFERENCES
COME IN TO PLAY WITH THE HANDLING OF FRONTAL BOUNDARY MOVING
ACROSS THE BERING SEA AND IMPACTING THE SW MAINLAND THU. THE GFS
IS A LITTLE SLOW ON THE FRONTAL MOVEMENT AND PUSHES A LITTLE TOO
MUCH WARM AIR INTO THE WESTERN MAINLAND THU NIGHT.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
A BROAD BAND OF MOISTURE ASSOCIATED WITH A WEAK DEFORMATION ZONE
HEADS SOUTH AND BRINGS SOME RAIN/SNOW TO THE WESTERN GULF/KODIAK
ISLAND TONIGHT. DRY OFFSHORE FLOW AND BUILDING PRESSURE GRADIENTS
DEVELOP BEHIND THIS SYSTEM TONIGHT. IN RESPONSE BRISK GAP WINDS
ARE EXPECTED AROUND SOUTHCENTRAL...ESPECIALLY THE GULF COAST AND
EASTERN KENAI PEN. A FEW SHOWERS ARE POSSIBLE ACROSS THE NORTH
GULF AND COPPER RIVER WED NIGHT WITH A WEAK WAVE...OTHERWISE THE
NEXT SHOT AT SNOW WILL BE ON FRI.


SOUTHWEST ALASKA...
STEADY SNOW ACROSS THE DELTA THIS MORNING HAS MOVED
OFFSHORE...WITH A GENERAL DRYING TREND THROUGH WEDNESDAY AS A
NORTHERLY FLOW PATTERN DEVELOPS. A FRONT WILL APPROACH FROM THE
WEST THURSDAY AFTERNOON INTO FRIDAY...SPREADING SNOW INLAND WITH A
MIX ALONG THE COASTS. RAIN AND SNOW SHOWERS WILL INTENSIFY SOME
ACROSS THE AK PEN WAS THE UPPER TROUGH DRIFTS SOUTH. INCREASING
NORTHERLY WINDS ARE ALSO EXPECTED WITH STRONG LOWS THROUGH GAPS IN
THE PEN ON WED.


BERING SEA/ALEUTIANS...
STRONG NORTHERLY WINDS AND RAIN AND SNOW SHOWERS WILL CONTINUE
ACROSS THE EASTERN AND CENTRAL BERING AND ALEUTIANS THROUGH
WEDNESDAY. A FRONT WILL TRACK INTO THE WESTERN BERING WEDNESDAY
THEN SPREAD THROUGH THE BERING WHILE WEAKENING THURSDAY AND
FRIDAY.

&&

.LONG TERM FORECAST...

RUN TO RUN GUIDANCE OF THE EXTENDED MODELS HAS NOT BEEN
GOOD...AT LEAST PARTIALLY DUE TO HANDLING OF THE MOISTURE RESIDUE
FROM TROPICAL STORM ANA. EARLIER EC MODELS WERE BRINGING THE
RESIDUE ALONG WITH A DEEPENING LOW INTO THE GULF OF AK ON MON...BUT
MORE RECENT RUNS ARE SENDING THE MOISTURE FIELD EAST...WITH A MUCH
WEAKER LOW OVER THE EASTERN GULF MON THROUGH WED.

WHILE THIS IS HAPPENING...A FRONT ASSOCIATED WITH A LOW OVER
NORTHWEST AK WILL MOVE ACROSS MAINLAND AK THROUGH THE
WEEKEND...FOLLOWED BY HIGH PRESSURE EARLY NEXT WEEK. A KAMCHATKA
LOW WILL SEND A FRONTAL COMPLEX ACROSS THE BERING TO WESTERN AK
SUN THROUGH WED.

THE FORECAST UTILIZES THE WPC SOLUTION...WHICH RELIED HEAVILY ON
THE 06Z GFS ENSEMBLE FORECAST THAT PROVIDED SOME RUN TO RUN
CONSISTENCY.

&&


AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 150 155 170 171 172 173 174 178 179 185 351 352.
FIRE WEATHER...NONE.

$$

RMC/DS OCT 14





000
FXAK68 PAFC 211227
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
427 AM AKDT TUE OCT 21 2014

.ANALYSIS AND UPPER LEVELS...

THE UPPER AIR PATTERN CONTINUES TO BE DOMINATED BY A LARGE UPPER
LOW CENTERED OVER BRISTOL BAY. A STRONG 155 KT NORTH PACIFIC JET
STREAM ANCHORS THE BASE OF THE TROUGH NEAR 42N...WITH A STRONG
LEADING SHORTWAVE TROUGH TRACKING INTO THE SOUTHEAST GULF OF
ALASKA. NUMEROUS LIGHTNING STRIKES (FROM GOES SATELLITE DATA) HAVE
BEEN NOTED ALONG AND BEHIND THE OCCLUDED FRONT WITH THIS SYSTEM. THERE
IS AN EMBEDDED SHORTWAVE TROUGH WRAPPING AROUND THE PARENT LOW
OVER THE KUSKOKWIM DELTA...WITH SLOWLY RISING HEIGHTS BUILDING
INTO SOUTHCENTRAL. EVENTUALLY...THE LOW IN THE SOUTHEAST GULF WILL
WRAP WEST-NORTHWEST TOWARD THE WESTERN GULF...WITH THE BRISTOL
BAY LOW SLOWLY TRACKING SOUTH AS RIDGING BUILDS INTO THE BERING
MIDWEEK. THIS WILL SETUP A DRY OFFSHORE FLOW PATTERN ACROSS
SOUTHERN ALASKA BY WEDNESDAY.

&&

.MODEL DISCUSSION...

MODELS ARE IN EXCELLENT AGREEMENT WITH THE GENERAL LARGE SCALE
PATTERN HEADED INTO THE WEEKEND. THERE ARE SOME REMAINING SMALL
DISCREPANCIES ASSOCIATED WITH THE EXACT TRACK OF THE GULF
LOW...BUT THEY ARE MUCH SMALLER AND LESS IMPACTFUL THAT PREVIOUS
DAYS. THE ECMWF AND GFS WERE FAVORED ACROSS THE REGION THROUGH THE
FORECAST. FORECAST CONFIDENCE IS VERY HIGH.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
A BAND OF MOISTURE CONTINUES TO SPREAD SHOWERS ACROSS PORTIONS OF
PRINCE WILLIAM SOUND...THE EASTERN KENAI...AND INTO INLAND
LOCATIONS FROM ANCHORAGE TO THE WESTERN KENAI. THIS BAND OF
MOISTURE WILL PIVOT SOUTH THROUGH THE DAY...WITH SHOWERS ENDING
FROM NORTH TO SOUTH. EVENTUALLY THIS BAND WILL PIVOT OVER KODIAK
ISLAND THIS EVENING...WITH RAIN AND SNOW IMPACTING MAINLY THE
EASTERN PORTION OF THE ISLAND BEFORE DRYING OUT BY WEDNESDAY
MORNING. FOG AND LOW STRATUS WILL REMAIN ENTRENCHED ACROSS THE
COPPER BASIN UNTIL DRIER AIR FILTERING IN FROM THE NORTH MOVES IN
THIS EVENING. A STRONG LOW MOVING NORTH INTO THE GULF WILL SET UP
A DRY OFFSHORE FLOW PATTERN THIS EVENING THROUGH THURSDAY...WITH
THE STRONGEST GAP WINDS PEAKING GENERALLY AROUND LATE TUE EVENING
THROUGH WEDNESDAY AFTERNOON.


SOUTHWEST ALASKA...
STEADY SNOW ACROSS THE LOWER KUSKOKWIM DELTA WILL DIMINISH BY MID
TO LATE MORNING...WITH A GENERAL DRYING TREND THROUGH WEDNESDAY AS
A NORTHERLY FLOW PATTERN DEVELOPS. A FRONT WILL APPROACH FROM THE
WEST LATE THURSDAY AFTERNOON INTO FRIDAY...SPREADING RAIN AND SNOW
FROM WEST TO EAST.

BERING SEA/ALEUTIANS...
STRONG NORTHERLY WINDS AND RAIN AND SNOW SHOWERS WILL CONTINUE
ACROSS THE EASTERN AND CENTRAL BERING AND ALEUTIANS THROUGH
WEDNESDAY. A FRONT WILL TRACK INTO THE WESTERN BERING WEDNESDAY
THEN SPREAD THROUGH THE BERING WHILE WEAKENING THURSDAY AND
FRIDAY.

&&

.LONG TERM FORECAST...

THE MODELS ARE IN DECENT AGREEMENT WITH THE UPPER TROUGH AS IT
MOVES OVER THE BERING STRAIT ON SATURDAY...BUT THEN QUICKLY
DIVERGE ON SUNDAY AND MONDAY. THE ECMWF IN PARTICULAR AS BEEN THE
MOST SPORADIC WITH THIS FEATURE...DIGGING DEEP TROUGHS AS FAR
SOUTH AS THE SOUTHERN GULF AND BRINGING VERY ACTIVE WEATHER TO THE
SOUTHERN MAINLAND. THE GFS AND GFS ENSEMBLE ON THE OTHER HAND HAS
BEEN MUCH MORE CONSISTENT IN KEEPING A MUCH WEAKER UPPER TROUGH
OVER THE CENTRAL INTERIOR...WITH MORE TYPICAL CLOUDY AND SHOWERY
WEATHER OVER THE SOUTHERN MAINLAND. AFTER COORDINATION WITH WPC
THIS MORNING...THE LONG TERM FORECAST AFTER SATURDAY HEAVILY USES
ENSEMBLES (EC AND NAEFS)...WHICH CURRENTLY MORE CLOSELY RESEMBLE
THE OPERATIONAL GFS. FUTURE RUNS (IN PARTICULAR OF THE EC) NEED TO
BE CLOSELY WATCHED HOWEVER...AS A DEEPER GULF LOW WOULD RESULT IN
A SIGNIFICANTLY DIFFERENT LONG TERM FORECAST INTO NEXT WEEK.

-DEK

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 150 165 170-174 178-179.
FIRE WEATHER...NONE.

&&

$$

AHSENMACHER OCT 14




000
FXAK68 PAFC 211227
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
427 AM AKDT TUE OCT 21 2014

.ANALYSIS AND UPPER LEVELS...

THE UPPER AIR PATTERN CONTINUES TO BE DOMINATED BY A LARGE UPPER
LOW CENTERED OVER BRISTOL BAY. A STRONG 155 KT NORTH PACIFIC JET
STREAM ANCHORS THE BASE OF THE TROUGH NEAR 42N...WITH A STRONG
LEADING SHORTWAVE TROUGH TRACKING INTO THE SOUTHEAST GULF OF
ALASKA. NUMEROUS LIGHTNING STRIKES (FROM GOES SATELLITE DATA) HAVE
BEEN NOTED ALONG AND BEHIND THE OCCLUDED FRONT WITH THIS SYSTEM. THERE
IS AN EMBEDDED SHORTWAVE TROUGH WRAPPING AROUND THE PARENT LOW
OVER THE KUSKOKWIM DELTA...WITH SLOWLY RISING HEIGHTS BUILDING
INTO SOUTHCENTRAL. EVENTUALLY...THE LOW IN THE SOUTHEAST GULF WILL
WRAP WEST-NORTHWEST TOWARD THE WESTERN GULF...WITH THE BRISTOL
BAY LOW SLOWLY TRACKING SOUTH AS RIDGING BUILDS INTO THE BERING
MIDWEEK. THIS WILL SETUP A DRY OFFSHORE FLOW PATTERN ACROSS
SOUTHERN ALASKA BY WEDNESDAY.

&&

.MODEL DISCUSSION...

MODELS ARE IN EXCELLENT AGREEMENT WITH THE GENERAL LARGE SCALE
PATTERN HEADED INTO THE WEEKEND. THERE ARE SOME REMAINING SMALL
DISCREPANCIES ASSOCIATED WITH THE EXACT TRACK OF THE GULF
LOW...BUT THEY ARE MUCH SMALLER AND LESS IMPACTFUL THAT PREVIOUS
DAYS. THE ECMWF AND GFS WERE FAVORED ACROSS THE REGION THROUGH THE
FORECAST. FORECAST CONFIDENCE IS VERY HIGH.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
A BAND OF MOISTURE CONTINUES TO SPREAD SHOWERS ACROSS PORTIONS OF
PRINCE WILLIAM SOUND...THE EASTERN KENAI...AND INTO INLAND
LOCATIONS FROM ANCHORAGE TO THE WESTERN KENAI. THIS BAND OF
MOISTURE WILL PIVOT SOUTH THROUGH THE DAY...WITH SHOWERS ENDING
FROM NORTH TO SOUTH. EVENTUALLY THIS BAND WILL PIVOT OVER KODIAK
ISLAND THIS EVENING...WITH RAIN AND SNOW IMPACTING MAINLY THE
EASTERN PORTION OF THE ISLAND BEFORE DRYING OUT BY WEDNESDAY
MORNING. FOG AND LOW STRATUS WILL REMAIN ENTRENCHED ACROSS THE
COPPER BASIN UNTIL DRIER AIR FILTERING IN FROM THE NORTH MOVES IN
THIS EVENING. A STRONG LOW MOVING NORTH INTO THE GULF WILL SET UP
A DRY OFFSHORE FLOW PATTERN THIS EVENING THROUGH THURSDAY...WITH
THE STRONGEST GAP WINDS PEAKING GENERALLY AROUND LATE TUE EVENING
THROUGH WEDNESDAY AFTERNOON.


SOUTHWEST ALASKA...
STEADY SNOW ACROSS THE LOWER KUSKOKWIM DELTA WILL DIMINISH BY MID
TO LATE MORNING...WITH A GENERAL DRYING TREND THROUGH WEDNESDAY AS
A NORTHERLY FLOW PATTERN DEVELOPS. A FRONT WILL APPROACH FROM THE
WEST LATE THURSDAY AFTERNOON INTO FRIDAY...SPREADING RAIN AND SNOW
FROM WEST TO EAST.

BERING SEA/ALEUTIANS...
STRONG NORTHERLY WINDS AND RAIN AND SNOW SHOWERS WILL CONTINUE
ACROSS THE EASTERN AND CENTRAL BERING AND ALEUTIANS THROUGH
WEDNESDAY. A FRONT WILL TRACK INTO THE WESTERN BERING WEDNESDAY
THEN SPREAD THROUGH THE BERING WHILE WEAKENING THURSDAY AND
FRIDAY.

&&

.LONG TERM FORECAST...

THE MODELS ARE IN DECENT AGREEMENT WITH THE UPPER TROUGH AS IT
MOVES OVER THE BERING STRAIT ON SATURDAY...BUT THEN QUICKLY
DIVERGE ON SUNDAY AND MONDAY. THE ECMWF IN PARTICULAR AS BEEN THE
MOST SPORADIC WITH THIS FEATURE...DIGGING DEEP TROUGHS AS FAR
SOUTH AS THE SOUTHERN GULF AND BRINGING VERY ACTIVE WEATHER TO THE
SOUTHERN MAINLAND. THE GFS AND GFS ENSEMBLE ON THE OTHER HAND HAS
BEEN MUCH MORE CONSISTENT IN KEEPING A MUCH WEAKER UPPER TROUGH
OVER THE CENTRAL INTERIOR...WITH MORE TYPICAL CLOUDY AND SHOWERY
WEATHER OVER THE SOUTHERN MAINLAND. AFTER COORDINATION WITH WPC
THIS MORNING...THE LONG TERM FORECAST AFTER SATURDAY HEAVILY USES
ENSEMBLES (EC AND NAEFS)...WHICH CURRENTLY MORE CLOSELY RESEMBLE
THE OPERATIONAL GFS. FUTURE RUNS (IN PARTICULAR OF THE EC) NEED TO
BE CLOSELY WATCHED HOWEVER...AS A DEEPER GULF LOW WOULD RESULT IN
A SIGNIFICANTLY DIFFERENT LONG TERM FORECAST INTO NEXT WEEK.

-DEK

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 150 165 170-174 178-179.
FIRE WEATHER...NONE.

&&

$$

AHSENMACHER OCT 14





000
FXAK68 PAFC 202154
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
154 PM AKDT MON OCT 20 2014

.ANALYSIS AND UPPER LEVELS...

TROF AXIS FROM BRISTOL BAY UPPER LOW ROTATING NORTH NORTHWEST
ACROSS SOUTH MAINLAND THIS AFTERNOON WILL PULL WESTWARD MONDAY
NIGHT AND MOVE TO THE SOUTHWEST COAST BY MID DAY TUESDAY. ANOTHER
TROF AXIS SLIPPING SOUTH ACROSS THE BERING WILL SWING ACROSS THE
ALASKA PENINSULA AND FOX ISLANDS THEN SLIDE INTO THE PACIFIC BY
10 PM MONDAY EVENING. AS THIS OCCURS MOST OF THE UPPER LOW CENTER
NOW OVER EASTERN BRISTOL BAY WILL ALSO MOVE SOUTHEAST TONIGHT AND
EASTWARD MONDAY PASSING KODIAK ISLAND BY TO THE SOUTH. THIS WILL
RESULT IN WEAK EASTERLY FLOW ALOFT TUE AFTERNOON AND NIGHT
FOLLOWED BY WEAK RIDGING WED. UPPER RIDGE FAR WESTERN ALEUTIANS
WILL REMAIN PROGRESSIVE WITH THE MAIN RIDGE AXIS ARRIVING ALONG
THE WEST COAST BY WED EVENING. THIS RIDGE WILL COLLAPSE
SOUTHEASTWARD THURSDAY AS A STRONG WEST SOUTHWEST JET DRIVES INTO
THE BERING AS UPPER LOW PRESSURE AND ARCTIC AIR EXPANDS OVER THE
RUSSIAN FAR EAST.

&&

.MODEL DISCUSSION...

THE MODELS LOOK GOOD OUT WEST AND ARE IN BASIC AGREEMENT WITH THE
MAIN FEATURES AND ORIENTATION OF THE PATTERN HEADING INTO LATE
THIS WEEK. THERE ARE SOME DIFFERENCES IN THE EXACT TRACK AND
STRENGTH OF THE 970 MB STORM NOW NEAR 51N 147W MOVING NORTH INTO
THE GULF TUESDAY AND WEDNESDAY. CURRENT TRACK APPEARS TO BE
FARTHER WEST THAN PREVIOUS RUNS. WED AFTERNOON THE THREE MODELS
SHOW THE AVERAGE LOW CENTER LONGITUDE POSITION ROUGHLY AROUND 145W
TO 148W WITH THE NAM SHOWING A 978 MB CENTER AT 56N...THE EC A 978
MB CENTER AT 54N AND THE GFS A 977 MB CENTER AT 52N. THE WAVES
FORMING FORMING ALONG THE FRONTAL BOUNDARY SHOW EVEN MORE
DISAGREEMENT.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
PRECIPITATION BECOMING MORE SHOWERY AND INTERMINTANT AS THE TROF
MOVES INLAND. A COUPLE OF MORE BANDS WILL MOVE NORTH TO THE PRINCE
WILLIAM SOUND AND THE KENAI PENINSULA THIS EVENING AND TONIGHT AND
DISSIPATE OVER SOUTHCENTRAL ALASKA TUE. AREAS OF SNOW ALONG AND
WEST OF THE ALASKA RANGE WILL MOVE WEST TO THE BERING SEA BY TUE
EVENING.




&&

.LONG TERM FORECAST...
A FRONT ASSOCIATED WITH A LOW SKIRTING THE SIBERIAN COAST THAT WILL
FIRST BRING RAIN AND GUSTY WINDS TO WESTERN ALEUTIANS ON
WEDNESDAY WILL THEN MOVE ONSHORE OVER THE SOUTHWEST MAINLAND BY
THURSDAY EVENING. THE REMNANTS OF THIS SYSTEM WILL BE THE
DOMINANT FEATURE IN THE LONG TERM FORECAST LOOKING INTO EARLY NEXT
WEEK.

THE MODELS ARE IN DECENT AGREEMENT WITH THE UPPER TROUGH AS IT
MOVES OVER THE BERING STRAIT ON SATURDAY...BUT THEN QUICKLY
DIVERGE ON SUNDAY AND MONDAY. THE ECMWF IN PARTICULAR AS BEEN THE
MOST SPORADIC WITH THIS FEATURE...DIGGING DEEP TROUGHS AS FAR
SOUTH AS THE SOUTHERN GULF AND BRINGING VERY ACTIVE WEATHER TO THE
SOUTHERN MAINLAND. THE GFS AND GFS ENSEMBLE ON THE OTHER HAND HAS
BEEN MUCH MORE CONSISTENT IN KEEPING A MUCH WEAKER UPPER TROUGH
OVER THE CENTRAL INTERIOR...WITH MORE TYPICAL CLOUDY AND SHOWERY
WEATHER OVER THE SOUTHERN MAINLAND. AFTER COORDINATION WITH WPC
THIS MORNING...THE LONG TERM FORECAST AFTER SATURDAY HEAVILY USES
ENSEMBLES (EC AND NAEFS)...WHICH CURRENTLY MORE CLOSELY RESEMBLE
THE OPERATIONAL GFS. FUTURE RUNS (IN PARTICULAR OF THE EC) NEED TO
BE CLOSELY WATCHED HOWEVER...AS A DEEPER GULF LOW WOULD RESULT IN
A SIGNIFICANTLY DIFFERENT LONG TERM FORECAST INTO NEXT WEEK

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...
MARINE...GALE 155 165 170 172 173 174 179 185. FIRE
WEATHER...NONE.

&&

$$
OCT 14




000
FXAK68 PAFC 202154
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
154 PM AKDT MON OCT 20 2014

.ANALYSIS AND UPPER LEVELS...

TROF AXIS FROM BRISTOL BAY UPPER LOW ROTATING NORTH NORTHWEST
ACROSS SOUTH MAINLAND THIS AFTERNOON WILL PULL WESTWARD MONDAY
NIGHT AND MOVE TO THE SOUTHWEST COAST BY MID DAY TUESDAY. ANOTHER
TROF AXIS SLIPPING SOUTH ACROSS THE BERING WILL SWING ACROSS THE
ALASKA PENINSULA AND FOX ISLANDS THEN SLIDE INTO THE PACIFIC BY
10 PM MONDAY EVENING. AS THIS OCCURS MOST OF THE UPPER LOW CENTER
NOW OVER EASTERN BRISTOL BAY WILL ALSO MOVE SOUTHEAST TONIGHT AND
EASTWARD MONDAY PASSING KODIAK ISLAND BY TO THE SOUTH. THIS WILL
RESULT IN WEAK EASTERLY FLOW ALOFT TUE AFTERNOON AND NIGHT
FOLLOWED BY WEAK RIDGING WED. UPPER RIDGE FAR WESTERN ALEUTIANS
WILL REMAIN PROGRESSIVE WITH THE MAIN RIDGE AXIS ARRIVING ALONG
THE WEST COAST BY WED EVENING. THIS RIDGE WILL COLLAPSE
SOUTHEASTWARD THURSDAY AS A STRONG WEST SOUTHWEST JET DRIVES INTO
THE BERING AS UPPER LOW PRESSURE AND ARCTIC AIR EXPANDS OVER THE
RUSSIAN FAR EAST.

&&

.MODEL DISCUSSION...

THE MODELS LOOK GOOD OUT WEST AND ARE IN BASIC AGREEMENT WITH THE
MAIN FEATURES AND ORIENTATION OF THE PATTERN HEADING INTO LATE
THIS WEEK. THERE ARE SOME DIFFERENCES IN THE EXACT TRACK AND
STRENGTH OF THE 970 MB STORM NOW NEAR 51N 147W MOVING NORTH INTO
THE GULF TUESDAY AND WEDNESDAY. CURRENT TRACK APPEARS TO BE
FARTHER WEST THAN PREVIOUS RUNS. WED AFTERNOON THE THREE MODELS
SHOW THE AVERAGE LOW CENTER LONGITUDE POSITION ROUGHLY AROUND 145W
TO 148W WITH THE NAM SHOWING A 978 MB CENTER AT 56N...THE EC A 978
MB CENTER AT 54N AND THE GFS A 977 MB CENTER AT 52N. THE WAVES
FORMING FORMING ALONG THE FRONTAL BOUNDARY SHOW EVEN MORE
DISAGREEMENT.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
PRECIPITATION BECOMING MORE SHOWERY AND INTERMINTANT AS THE TROF
MOVES INLAND. A COUPLE OF MORE BANDS WILL MOVE NORTH TO THE PRINCE
WILLIAM SOUND AND THE KENAI PENINSULA THIS EVENING AND TONIGHT AND
DISSIPATE OVER SOUTHCENTRAL ALASKA TUE. AREAS OF SNOW ALONG AND
WEST OF THE ALASKA RANGE WILL MOVE WEST TO THE BERING SEA BY TUE
EVENING.




&&

.LONG TERM FORECAST...
A FRONT ASSOCIATED WITH A LOW SKIRTING THE SIBERIAN COAST THAT WILL
FIRST BRING RAIN AND GUSTY WINDS TO WESTERN ALEUTIANS ON
WEDNESDAY WILL THEN MOVE ONSHORE OVER THE SOUTHWEST MAINLAND BY
THURSDAY EVENING. THE REMNANTS OF THIS SYSTEM WILL BE THE
DOMINANT FEATURE IN THE LONG TERM FORECAST LOOKING INTO EARLY NEXT
WEEK.

THE MODELS ARE IN DECENT AGREEMENT WITH THE UPPER TROUGH AS IT
MOVES OVER THE BERING STRAIT ON SATURDAY...BUT THEN QUICKLY
DIVERGE ON SUNDAY AND MONDAY. THE ECMWF IN PARTICULAR AS BEEN THE
MOST SPORADIC WITH THIS FEATURE...DIGGING DEEP TROUGHS AS FAR
SOUTH AS THE SOUTHERN GULF AND BRINGING VERY ACTIVE WEATHER TO THE
SOUTHERN MAINLAND. THE GFS AND GFS ENSEMBLE ON THE OTHER HAND HAS
BEEN MUCH MORE CONSISTENT IN KEEPING A MUCH WEAKER UPPER TROUGH
OVER THE CENTRAL INTERIOR...WITH MORE TYPICAL CLOUDY AND SHOWERY
WEATHER OVER THE SOUTHERN MAINLAND. AFTER COORDINATION WITH WPC
THIS MORNING...THE LONG TERM FORECAST AFTER SATURDAY HEAVILY USES
ENSEMBLES (EC AND NAEFS)...WHICH CURRENTLY MORE CLOSELY RESEMBLE
THE OPERATIONAL GFS. FUTURE RUNS (IN PARTICULAR OF THE EC) NEED TO
BE CLOSELY WATCHED HOWEVER...AS A DEEPER GULF LOW WOULD RESULT IN
A SIGNIFICANTLY DIFFERENT LONG TERM FORECAST INTO NEXT WEEK

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...
MARINE...GALE 155 165 170 172 173 174 179 185. FIRE
WEATHER...NONE.

&&

$$
OCT 14





000
FXAK68 PAFC 202154
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
154 PM AKDT MON OCT 20 2014

.ANALYSIS AND UPPER LEVELS...

TROF AXIS FROM BRISTOL BAY UPPER LOW ROTATING NORTH NORTHWEST
ACROSS SOUTH MAINLAND THIS AFTERNOON WILL PULL WESTWARD MONDAY
NIGHT AND MOVE TO THE SOUTHWEST COAST BY MID DAY TUESDAY. ANOTHER
TROF AXIS SLIPPING SOUTH ACROSS THE BERING WILL SWING ACROSS THE
ALASKA PENINSULA AND FOX ISLANDS THEN SLIDE INTO THE PACIFIC BY
10 PM MONDAY EVENING. AS THIS OCCURS MOST OF THE UPPER LOW CENTER
NOW OVER EASTERN BRISTOL BAY WILL ALSO MOVE SOUTHEAST TONIGHT AND
EASTWARD MONDAY PASSING KODIAK ISLAND BY TO THE SOUTH. THIS WILL
RESULT IN WEAK EASTERLY FLOW ALOFT TUE AFTERNOON AND NIGHT
FOLLOWED BY WEAK RIDGING WED. UPPER RIDGE FAR WESTERN ALEUTIANS
WILL REMAIN PROGRESSIVE WITH THE MAIN RIDGE AXIS ARRIVING ALONG
THE WEST COAST BY WED EVENING. THIS RIDGE WILL COLLAPSE
SOUTHEASTWARD THURSDAY AS A STRONG WEST SOUTHWEST JET DRIVES INTO
THE BERING AS UPPER LOW PRESSURE AND ARCTIC AIR EXPANDS OVER THE
RUSSIAN FAR EAST.

&&

.MODEL DISCUSSION...

THE MODELS LOOK GOOD OUT WEST AND ARE IN BASIC AGREEMENT WITH THE
MAIN FEATURES AND ORIENTATION OF THE PATTERN HEADING INTO LATE
THIS WEEK. THERE ARE SOME DIFFERENCES IN THE EXACT TRACK AND
STRENGTH OF THE 970 MB STORM NOW NEAR 51N 147W MOVING NORTH INTO
THE GULF TUESDAY AND WEDNESDAY. CURRENT TRACK APPEARS TO BE
FARTHER WEST THAN PREVIOUS RUNS. WED AFTERNOON THE THREE MODELS
SHOW THE AVERAGE LOW CENTER LONGITUDE POSITION ROUGHLY AROUND 145W
TO 148W WITH THE NAM SHOWING A 978 MB CENTER AT 56N...THE EC A 978
MB CENTER AT 54N AND THE GFS A 977 MB CENTER AT 52N. THE WAVES
FORMING FORMING ALONG THE FRONTAL BOUNDARY SHOW EVEN MORE
DISAGREEMENT.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
PRECIPITATION BECOMING MORE SHOWERY AND INTERMINTANT AS THE TROF
MOVES INLAND. A COUPLE OF MORE BANDS WILL MOVE NORTH TO THE PRINCE
WILLIAM SOUND AND THE KENAI PENINSULA THIS EVENING AND TONIGHT AND
DISSIPATE OVER SOUTHCENTRAL ALASKA TUE. AREAS OF SNOW ALONG AND
WEST OF THE ALASKA RANGE WILL MOVE WEST TO THE BERING SEA BY TUE
EVENING.




&&

.LONG TERM FORECAST...
A FRONT ASSOCIATED WITH A LOW SKIRTING THE SIBERIAN COAST THAT WILL
FIRST BRING RAIN AND GUSTY WINDS TO WESTERN ALEUTIANS ON
WEDNESDAY WILL THEN MOVE ONSHORE OVER THE SOUTHWEST MAINLAND BY
THURSDAY EVENING. THE REMNANTS OF THIS SYSTEM WILL BE THE
DOMINANT FEATURE IN THE LONG TERM FORECAST LOOKING INTO EARLY NEXT
WEEK.

THE MODELS ARE IN DECENT AGREEMENT WITH THE UPPER TROUGH AS IT
MOVES OVER THE BERING STRAIT ON SATURDAY...BUT THEN QUICKLY
DIVERGE ON SUNDAY AND MONDAY. THE ECMWF IN PARTICULAR AS BEEN THE
MOST SPORADIC WITH THIS FEATURE...DIGGING DEEP TROUGHS AS FAR
SOUTH AS THE SOUTHERN GULF AND BRINGING VERY ACTIVE WEATHER TO THE
SOUTHERN MAINLAND. THE GFS AND GFS ENSEMBLE ON THE OTHER HAND HAS
BEEN MUCH MORE CONSISTENT IN KEEPING A MUCH WEAKER UPPER TROUGH
OVER THE CENTRAL INTERIOR...WITH MORE TYPICAL CLOUDY AND SHOWERY
WEATHER OVER THE SOUTHERN MAINLAND. AFTER COORDINATION WITH WPC
THIS MORNING...THE LONG TERM FORECAST AFTER SATURDAY HEAVILY USES
ENSEMBLES (EC AND NAEFS)...WHICH CURRENTLY MORE CLOSELY RESEMBLE
THE OPERATIONAL GFS. FUTURE RUNS (IN PARTICULAR OF THE EC) NEED TO
BE CLOSELY WATCHED HOWEVER...AS A DEEPER GULF LOW WOULD RESULT IN
A SIGNIFICANTLY DIFFERENT LONG TERM FORECAST INTO NEXT WEEK

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...
MARINE...GALE 155 165 170 172 173 174 179 185. FIRE
WEATHER...NONE.

&&

$$
OCT 14




000
FXAK68 PAFC 201317
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
517 AM AKDT MON OCT 20 2014

.ANALYSIS AND UPPER LEVELS...

NUMEROUS UPPER LOWS AND SHORTWAVE LOW AMPLITUDE DISTURBANCES ARE
DOMINATING THE UPPER AIR PATTERN ACROSS ALASKA THIS MORNING. THE
MAIN UPPER LOW CENTER IS IN THE VICINITY OF BRISTOL BAY...WITH TWO
BASAL SHORTWAVES TRACKING ALONG ITS PERIPHERY NEAR 50N...ONE SOUTH
OF ADAK AND ANOTHER SOUTH OF KODIAK. THESE TWO SHORTWAVES ARE
PROPAGATING ALONG A STRONG 160 KT NORTH PACIFIC JET
STREAM...FORMING ALONG A SHARP BAROCLINIC ZONE AIDED BY THE
ARCTIC AIR POURING INTO THE NORTH PACIFIC FROM THE CHUKCHI SEA.
THE FIRST SHORTWAVE TROUGH HAS THE MOST POTENTIAL ENERGY
ASSOCIATED WITH IT...AND IS EXPECTED TO DEEPEN INTO A STRONG NEAR
970 HPA LOW IN THE GULF AS IT INTERACTS WITH THE ARCTIC AIR MASS
DIVING SOUTH FROM THE BERING.

IN THE NORTH GULF OF ALASKA...A WARM FRONT/ELONGATED SURFACE LOW
IS TRACKING INTO PRINCE WILLIAM SOUND THIS MORNING...WITH A
SHARPENING UPPER LEVEL TROUGH AXIS EXTENDING FROM THE BRISTOL BAY
LOW. THIS TROUGH AXIS IS BEGINNING TO INTERACT WITH THE LOW LEVEL
BAROCLINIC ZONE...WITH EXTENSIVE CONVECTIVE SHOWERS FORMING ALONG
THE LOW LEVEL FRONT AROUND PRINCE WILLIAM SOUND. COOLING CLOUD
TOPS IN THE VICINITY OF THE KENAI PENINSULA AND NORTH CORRELATE
TO INCREASING MASS ASCENT AHEAD OF THE TROUGH AXIS AS THE UPPER
LEVEL JET BECOMES INCREASINGLY DIVERGENT.

&&

.MODEL DISCUSSION...

THE MODELS ARE IN EXCELLENT AGREEMENT WITH THE LARGE SCALE
PATTERN HEADING INTO LATE THIS WEEK...BUT REMAIN IN POORER
AGREEMENT WITH BOTH THE CURRENT LOW IN THE GULF...AND ANOTHER
STRONG LOW MOVING INTO THE GULF TUESDAY AND WEDNESDAY. THE ECMWF
HAS BEEN SUPERIOR IN SIMULATING THE CURRENT DEVELOPING WINTER
PRECIPITATION EVENT ACROSS ANCHORAGE AND PRINCE WILLIAM
SOUND...AND WILL BE UTILIZED FOR THE BEGINNING OF THE FORECAST.
THE CANADIAN GDPS IS FAVORED FOR THE DEVELOPING STRONG NORTH
PACIFIC LOW EXPECTED TO MOVE INTO THE GULF AS IT REPRESENTED A
GOOD MIDDLE GROUND IN STRENGTH AND TRACK BETWEEN THE DISPARATE
ECMWF AND GFS.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
THE FIRST SIGNIFICANT WINTER EVENT OF THE SEASON IS UNFOLDING
ACROSS PORTIONS OF ANCHORAGE...TURNAGAIN ARM...AND PORTAGE VALLEY
THIS MORNING. HAVE ALREADY RECEIVED REPORTS OF 3 TO 4 INCHES IN
ANCHORAGE PROPER...AND UP TO 7 ALONG THE HILLSIDE. SNOW WILL
CONTINUE TO BE MODERATE TO HEAVY AT TIMES IN THE MORNING BEFORE
ACTIVITY TAPERS LATE MORNING THROUGH THE AFTERNOON. THERE IS A
DRASTIC CUTOFF IN PRECIPITATION NORTH OF ANCHORAGE PROPER...AND
THAT WILL LIKELY CONTINUE HEADING NORTH TOWARD THE MATANUSKA
VALLEY. LIGHTER SNOW SHOWERS WILL MOVE INTO PARTS OF THE COPPER
BASIN AND SUSITNA VALLEY LATE THIS MORNING AND AFTERNOON. LIGHT
SNOW WILL WRAP BACK AROUND THE MAIN UPPER LOW CENTER TOWARD THE
SOUTHERN KENAI PENINSULA...BUT WILL BE MUCH LIGHTER THAN THE
ACTIVITY OVER ANCHORAGE AND TURNAGAIN ARM. SHOWERS WILL DIMINISH
TUESDAY AS ANOTHER GULF LOW MOVES NORTH...SETTING UP A DRIER
OFFSHORE FLOW PATTERN INTO WEDNESDAY.

SOUTHWEST ALASKA...
SNOW AND LIGHT SNOW SHOWERS WILL IMPACT MUCH OF SOUTHWEST ALASKA
THROUGH TONIGHT AS AN UPPER LEVEL LOW ROTATES AROUND THE REGION.
SNOW WILL TAPER OFF EARLIEST FROM THE ALASKA RANGE HEADING
WEST...WITH SNOW LINGERING OVER THE SOUTHWEST COAST THROUGH MONDAY
NIGHT BEFORE TAPERING OFF. DRY OFFSHORE FLOW THEN SETS UP THROUGH
WEDNESDAY WITH INCREASING NORTH-NORTHWEST WINDS.

BERING SEA/ALEUTIANS...
RAIN AND SNOW SHOWERS WILL BECOME WIDESPREAD AS GUSTY NORTHERLY
FLOW DEVELOPS ACROSS THE CENTRAL AND EASTERN BERING SEA AND
ALEUTIANS THROUGH MOST OF WEDNESDAY BEFORE WEAK HIGH PRESSURE
BUILDS IN.

&&

.LONG TERM FORECAST...

ANOTHER LOW MOVING INTO THE GULF ON TUESDAY WILL CAUSE COLD AIR
TO SPREAD INTO THE SOUTHERN MAINLAND THROUGH MID WEEK...PRODUCING
BELOW NORMAL TEMPERATURES AND GUSTY GAP WINDS ALONG THE GULF
COAST. THIS HOWEVER APPEARS TO BE A SHORT LIVED EVENT...AS A LOW
SKIRTING THE EASTERN SIBERIAN COAST ON FRIDAY WILL BRING
INCREASED CLOUD COVER AND WARMER TEMPERATURES BY NEXT WEEKEND.
THE FRONT ASSOCIATED WITH THIS SYSTEM WILL BRING RAIN AND GUSTY
WINDS TO THE WESTERN ALEUTIANS STARTING THURSDAY....THEN SPREAD
ONTO THE MAINLAND BY THE WEEKEND. THE UPPER TROUGH FROM THIS
SYSTEM THEN LOOKS TO SLOWLY DISSIPATE OVER THE MAINLAND THROUGH
NEXT WEEKEND...LEAVING THE MAINLAND GENERALLY CLOUDY AND SHOWERY
WITH NEAR NORMAL TEMPERATURES.

-DEK

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY 101.
MARINE...GALE 155 165 170 172 173 174 179 185.
FIRE WEATHER...NONE.

&&

$$

AHSENMACHER OCT 14




000
FXAK68 PAFC 201317
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
517 AM AKDT MON OCT 20 2014

.ANALYSIS AND UPPER LEVELS...

NUMEROUS UPPER LOWS AND SHORTWAVE LOW AMPLITUDE DISTURBANCES ARE
DOMINATING THE UPPER AIR PATTERN ACROSS ALASKA THIS MORNING. THE
MAIN UPPER LOW CENTER IS IN THE VICINITY OF BRISTOL BAY...WITH TWO
BASAL SHORTWAVES TRACKING ALONG ITS PERIPHERY NEAR 50N...ONE SOUTH
OF ADAK AND ANOTHER SOUTH OF KODIAK. THESE TWO SHORTWAVES ARE
PROPAGATING ALONG A STRONG 160 KT NORTH PACIFIC JET
STREAM...FORMING ALONG A SHARP BAROCLINIC ZONE AIDED BY THE
ARCTIC AIR POURING INTO THE NORTH PACIFIC FROM THE CHUKCHI SEA.
THE FIRST SHORTWAVE TROUGH HAS THE MOST POTENTIAL ENERGY
ASSOCIATED WITH IT...AND IS EXPECTED TO DEEPEN INTO A STRONG NEAR
970 HPA LOW IN THE GULF AS IT INTERACTS WITH THE ARCTIC AIR MASS
DIVING SOUTH FROM THE BERING.

IN THE NORTH GULF OF ALASKA...A WARM FRONT/ELONGATED SURFACE LOW
IS TRACKING INTO PRINCE WILLIAM SOUND THIS MORNING...WITH A
SHARPENING UPPER LEVEL TROUGH AXIS EXTENDING FROM THE BRISTOL BAY
LOW. THIS TROUGH AXIS IS BEGINNING TO INTERACT WITH THE LOW LEVEL
BAROCLINIC ZONE...WITH EXTENSIVE CONVECTIVE SHOWERS FORMING ALONG
THE LOW LEVEL FRONT AROUND PRINCE WILLIAM SOUND. COOLING CLOUD
TOPS IN THE VICINITY OF THE KENAI PENINSULA AND NORTH CORRELATE
TO INCREASING MASS ASCENT AHEAD OF THE TROUGH AXIS AS THE UPPER
LEVEL JET BECOMES INCREASINGLY DIVERGENT.

&&

.MODEL DISCUSSION...

THE MODELS ARE IN EXCELLENT AGREEMENT WITH THE LARGE SCALE
PATTERN HEADING INTO LATE THIS WEEK...BUT REMAIN IN POORER
AGREEMENT WITH BOTH THE CURRENT LOW IN THE GULF...AND ANOTHER
STRONG LOW MOVING INTO THE GULF TUESDAY AND WEDNESDAY. THE ECMWF
HAS BEEN SUPERIOR IN SIMULATING THE CURRENT DEVELOPING WINTER
PRECIPITATION EVENT ACROSS ANCHORAGE AND PRINCE WILLIAM
SOUND...AND WILL BE UTILIZED FOR THE BEGINNING OF THE FORECAST.
THE CANADIAN GDPS IS FAVORED FOR THE DEVELOPING STRONG NORTH
PACIFIC LOW EXPECTED TO MOVE INTO THE GULF AS IT REPRESENTED A
GOOD MIDDLE GROUND IN STRENGTH AND TRACK BETWEEN THE DISPARATE
ECMWF AND GFS.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
THE FIRST SIGNIFICANT WINTER EVENT OF THE SEASON IS UNFOLDING
ACROSS PORTIONS OF ANCHORAGE...TURNAGAIN ARM...AND PORTAGE VALLEY
THIS MORNING. HAVE ALREADY RECEIVED REPORTS OF 3 TO 4 INCHES IN
ANCHORAGE PROPER...AND UP TO 7 ALONG THE HILLSIDE. SNOW WILL
CONTINUE TO BE MODERATE TO HEAVY AT TIMES IN THE MORNING BEFORE
ACTIVITY TAPERS LATE MORNING THROUGH THE AFTERNOON. THERE IS A
DRASTIC CUTOFF IN PRECIPITATION NORTH OF ANCHORAGE PROPER...AND
THAT WILL LIKELY CONTINUE HEADING NORTH TOWARD THE MATANUSKA
VALLEY. LIGHTER SNOW SHOWERS WILL MOVE INTO PARTS OF THE COPPER
BASIN AND SUSITNA VALLEY LATE THIS MORNING AND AFTERNOON. LIGHT
SNOW WILL WRAP BACK AROUND THE MAIN UPPER LOW CENTER TOWARD THE
SOUTHERN KENAI PENINSULA...BUT WILL BE MUCH LIGHTER THAN THE
ACTIVITY OVER ANCHORAGE AND TURNAGAIN ARM. SHOWERS WILL DIMINISH
TUESDAY AS ANOTHER GULF LOW MOVES NORTH...SETTING UP A DRIER
OFFSHORE FLOW PATTERN INTO WEDNESDAY.

SOUTHWEST ALASKA...
SNOW AND LIGHT SNOW SHOWERS WILL IMPACT MUCH OF SOUTHWEST ALASKA
THROUGH TONIGHT AS AN UPPER LEVEL LOW ROTATES AROUND THE REGION.
SNOW WILL TAPER OFF EARLIEST FROM THE ALASKA RANGE HEADING
WEST...WITH SNOW LINGERING OVER THE SOUTHWEST COAST THROUGH MONDAY
NIGHT BEFORE TAPERING OFF. DRY OFFSHORE FLOW THEN SETS UP THROUGH
WEDNESDAY WITH INCREASING NORTH-NORTHWEST WINDS.

BERING SEA/ALEUTIANS...
RAIN AND SNOW SHOWERS WILL BECOME WIDESPREAD AS GUSTY NORTHERLY
FLOW DEVELOPS ACROSS THE CENTRAL AND EASTERN BERING SEA AND
ALEUTIANS THROUGH MOST OF WEDNESDAY BEFORE WEAK HIGH PRESSURE
BUILDS IN.

&&

.LONG TERM FORECAST...

ANOTHER LOW MOVING INTO THE GULF ON TUESDAY WILL CAUSE COLD AIR
TO SPREAD INTO THE SOUTHERN MAINLAND THROUGH MID WEEK...PRODUCING
BELOW NORMAL TEMPERATURES AND GUSTY GAP WINDS ALONG THE GULF
COAST. THIS HOWEVER APPEARS TO BE A SHORT LIVED EVENT...AS A LOW
SKIRTING THE EASTERN SIBERIAN COAST ON FRIDAY WILL BRING
INCREASED CLOUD COVER AND WARMER TEMPERATURES BY NEXT WEEKEND.
THE FRONT ASSOCIATED WITH THIS SYSTEM WILL BRING RAIN AND GUSTY
WINDS TO THE WESTERN ALEUTIANS STARTING THURSDAY....THEN SPREAD
ONTO THE MAINLAND BY THE WEEKEND. THE UPPER TROUGH FROM THIS
SYSTEM THEN LOOKS TO SLOWLY DISSIPATE OVER THE MAINLAND THROUGH
NEXT WEEKEND...LEAVING THE MAINLAND GENERALLY CLOUDY AND SHOWERY
WITH NEAR NORMAL TEMPERATURES.

-DEK

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY 101.
MARINE...GALE 155 165 170 172 173 174 179 185.
FIRE WEATHER...NONE.

&&

$$

AHSENMACHER OCT 14





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