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000
FXAK68 PAFC 190048
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
348 PM AKST THU DEC 18 2014

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LEVEL LOW OVER THE GULF OF ALASKA WITH A FRONT
STRETCHED EAST TO WEST ACROSS THE NORTHERN GULF. THERE IS ANOTHER
LOW SOUTH OF THE WESTERN ALEUTIANS WITH A LEADING FRONT OVER THE
CENTRAL ALEUTIANS. HIGH PRESSURE SITS OVER CENTRAL ALASKA.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS CONTINUE TO STRUGGLE WITH THE LOCATIONS OF
VARIOUS SURFACE LOWS...ESPECIALLY BETWEEN FORECAST HOURS 24 AND 42
AS THE TWO MAIN UPPER LOWS MERGE. BY 84 HOURS (SUNDAY AFTERNOON)
THE MODELS ARE ACTUALLY IN DECENT AGREEMENT...BUT THAT IS MAINLY
DUE TO THE LARGER SCALE OF WEATHER FEATURES AT THAT TIME.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3)...
THE GENERAL PATTERN THROUGH SUNDAY CONSISTS OF A LOW (USUALLY A
COMPLEX LOW...THAT IS MULTIPLE CENTERS) IN THE GULF WITH WEAK HIGH
PRESSURE INLAND. THUS IT WILL BE MAINLY DRY INLAND WITH SURGES OF
PRECIPITATION IN THE COASTAL AREAS. THE FIRST OF THESE "SURGES"
WILL PUSH TO THE NORTH GULF COAST LATE TONIGHT INTO FRIDAY MORNING
WITH THE NEXT ONE DUE FRIDAY NIGHT. BY THE TIME THE THIRD ONE
PUSHES NORTH ON SUNDAY...THE TWO UPPER LOWS WILL BE MERGING. THIS
WILL SEND THE MAIN UPPER LEVEL GULF LOW NORTHWARD...WHICH WILL
COMBINE WITH AN EASTWARD MOVING TROUGH THAT IS OVER WESTERN ALASKA
ON SUNDAY.

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
GENERAL EASTERLY OR SOUTHEASTERLY FLOW WILL CONTINUE ACROSS THE
AREA THROUGH THE SHORT TERM (84 HR) FORECAST PERIOD. TWO WEAK
SHORTWAVES WILL MOVE THROUGH THE REGION...THE FIRST TONIGHT AND
THE SECOND ON SATURDAY OR SATURDAY NIGHT...BUT BOTH WILL BE WEAK
WITH ONLY A DUSTING OF SNOW (AT MOST) FOR MUCH OF THE AREA.
TEMPERATURES WILL REMAIN FAIRLY STEADY THROUGH THE START OF THE
WEEKEND BEFORE A MORE PRONOUNCED COOLING TREND SETS IN STARTING
SUNDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE VERY STRONG ZONAL JET COMING OUT OF EASTERN ASIA WILL KEEP A
SERIES OF FAIRLY WEAK DISTURBANCES MOVING EASTWARD ALONG OR JUST
SOUTH OF THE CHAIN OVER THE NEXT FEW DAYS. STARTING THIS
WEEKEND...WINDS WILL BECOME MORE PREVAILING OUT OF THE NORTH AS
SEASONABLY COOL AIR STARTS TO FILTER DOWN MORE SIGNIFICANTLY FROM
THE BERING STRAIT. AS COOL AIR INCREASINGLY SPREADS ACROSS THE
RELATIVELY WARM OCEAN WATERS THE ATMOSPHERE WILL CONTINUE TO
SLOWLY DESTABILIZE AND SHOULD RESULT IN AN INCREASE IN SHOWER
ACTIVITY ACROSS MUCH OF THE AREA BY THE END OF THE WEEKEND.

&&

.LONG TERM FORECAST (DAYS 4 THROUGH 7)...
A PATTERN CHANGE WILL OCCUR MONDAY AND TUESDAY. A LARGE UPPER LOW
WILL SET UP OVER THE WESTERN BERING SEA AND WESTERLY/SOUTHWESTERLY
FLOW ALOFT WILL DEVELOP ACROSS THE BERING/ALEUTIANS AND SOUTHERN
ALASKA. THE WPC USED A BLEND THAT CONSISTS OF 50 PERCENT 00Z ECMWF
AND ECMWF ENSEMBLE MEAN...WITH THE OTHER 50 PERCENT CONSISTING OF
THE 06Z GFS/PARALLEL GFS AND ENSEMBLE MEAN.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES...119 120 127 130-132 138 177 178
  HEAVY FREEZING SPRAY...180 181.
FIRE WEATHER...NONE.

&&

$$




000
FXAK68 PAFC 190048
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
348 PM AKST THU DEC 18 2014

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LEVEL LOW OVER THE GULF OF ALASKA WITH A FRONT
STRETCHED EAST TO WEST ACROSS THE NORTHERN GULF. THERE IS ANOTHER
LOW SOUTH OF THE WESTERN ALEUTIANS WITH A LEADING FRONT OVER THE
CENTRAL ALEUTIANS. HIGH PRESSURE SITS OVER CENTRAL ALASKA.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS CONTINUE TO STRUGGLE WITH THE LOCATIONS OF
VARIOUS SURFACE LOWS...ESPECIALLY BETWEEN FORECAST HOURS 24 AND 42
AS THE TWO MAIN UPPER LOWS MERGE. BY 84 HOURS (SUNDAY AFTERNOON)
THE MODELS ARE ACTUALLY IN DECENT AGREEMENT...BUT THAT IS MAINLY
DUE TO THE LARGER SCALE OF WEATHER FEATURES AT THAT TIME.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3)...
THE GENERAL PATTERN THROUGH SUNDAY CONSISTS OF A LOW (USUALLY A
COMPLEX LOW...THAT IS MULTIPLE CENTERS) IN THE GULF WITH WEAK HIGH
PRESSURE INLAND. THUS IT WILL BE MAINLY DRY INLAND WITH SURGES OF
PRECIPITATION IN THE COASTAL AREAS. THE FIRST OF THESE "SURGES"
WILL PUSH TO THE NORTH GULF COAST LATE TONIGHT INTO FRIDAY MORNING
WITH THE NEXT ONE DUE FRIDAY NIGHT. BY THE TIME THE THIRD ONE
PUSHES NORTH ON SUNDAY...THE TWO UPPER LOWS WILL BE MERGING. THIS
WILL SEND THE MAIN UPPER LEVEL GULF LOW NORTHWARD...WHICH WILL
COMBINE WITH AN EASTWARD MOVING TROUGH THAT IS OVER WESTERN ALASKA
ON SUNDAY.

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
GENERAL EASTERLY OR SOUTHEASTERLY FLOW WILL CONTINUE ACROSS THE
AREA THROUGH THE SHORT TERM (84 HR) FORECAST PERIOD. TWO WEAK
SHORTWAVES WILL MOVE THROUGH THE REGION...THE FIRST TONIGHT AND
THE SECOND ON SATURDAY OR SATURDAY NIGHT...BUT BOTH WILL BE WEAK
WITH ONLY A DUSTING OF SNOW (AT MOST) FOR MUCH OF THE AREA.
TEMPERATURES WILL REMAIN FAIRLY STEADY THROUGH THE START OF THE
WEEKEND BEFORE A MORE PRONOUNCED COOLING TREND SETS IN STARTING
SUNDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE VERY STRONG ZONAL JET COMING OUT OF EASTERN ASIA WILL KEEP A
SERIES OF FAIRLY WEAK DISTURBANCES MOVING EASTWARD ALONG OR JUST
SOUTH OF THE CHAIN OVER THE NEXT FEW DAYS. STARTING THIS
WEEKEND...WINDS WILL BECOME MORE PREVAILING OUT OF THE NORTH AS
SEASONABLY COOL AIR STARTS TO FILTER DOWN MORE SIGNIFICANTLY FROM
THE BERING STRAIT. AS COOL AIR INCREASINGLY SPREADS ACROSS THE
RELATIVELY WARM OCEAN WATERS THE ATMOSPHERE WILL CONTINUE TO
SLOWLY DESTABILIZE AND SHOULD RESULT IN AN INCREASE IN SHOWER
ACTIVITY ACROSS MUCH OF THE AREA BY THE END OF THE WEEKEND.

&&

.LONG TERM FORECAST (DAYS 4 THROUGH 7)...
A PATTERN CHANGE WILL OCCUR MONDAY AND TUESDAY. A LARGE UPPER LOW
WILL SET UP OVER THE WESTERN BERING SEA AND WESTERLY/SOUTHWESTERLY
FLOW ALOFT WILL DEVELOP ACROSS THE BERING/ALEUTIANS AND SOUTHERN
ALASKA. THE WPC USED A BLEND THAT CONSISTS OF 50 PERCENT 00Z ECMWF
AND ECMWF ENSEMBLE MEAN...WITH THE OTHER 50 PERCENT CONSISTING OF
THE 06Z GFS/PARALLEL GFS AND ENSEMBLE MEAN.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES...119 120 127 130-132 138 177 178
  HEAVY FREEZING SPRAY...180 181.
FIRE WEATHER...NONE.

&&

$$





000
FXAK68 PAFC 181316
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
416 AM AKST THU DEC 18 2014

.ANALYSIS AND UPPER LEVELS...
SATELLITE IMAGERY SHOWS TWO LARGE STORM SYSTEMS IN THE
REGION...BOTH CENTERED OVER THE NORTH PACIFIC WHERE PROGRESSIVE
UPPER LEVEL FLOW DOMINATES. A VERY LARGE AND MATURE STORM FORCE
LOW IS CENTERED SOUTH OF THE GULF OF ALASKA WITH THE OCCLUDED
FRONT SLOWLY LIFTING NORTHWARD BRINGING GALE FORCE WINDS AND RAIN
TO THE GULF AND KODIAK ISLAND. OUT HEAD OF THIS A SHORT-WAVE RIDGE
IS MOVING OVER THE SOUTHERN MAINLAND RESULTING IN QUIET
CONDITIONS. THERE SOME AREAS OF FOG OVER SOUTHCENTRAL...BUT AS
PRESSURE GRADIENTS TIGHTEN WITH THE APPROACHING FRONT AND OFFSHORE
FLOW STRENGTHENS EXPECT MOST OF THIS TO DISSIPATE. MEANWHILE A
200+ KT JET IS DRIVING EASTWARD ACROSS THE NORTHWEST PACIFIC AND
INTO THE NORTH-CENTRAL PACIFIC CAUSING RAPID CYCLOGENESIS WITH A
SERIES OF LOWS STRUNG OUT JUST TO THE SOUTH OF THE BERING SEA AND
ALEUTIANS. THE LOW CLOSEST TO THE WESTERN ALEUTIANS AND ASSOCIATED
OCCLUDED FRONT ARE LIFTING NORTHWARD TOWARD THE ALEUTIANS...SO
GALE FORCE WINDS AND RAIN ARE ON THE WAY.

&&

.MODEL DISCUSSION...MODELS SEEM TO BE CONVERGING ON A COMMON
SOLUTION WITH TRIPLE POINT LOW FORMING OVER THE FAR NORTHEAST
PACIFIC THURSDAY MORNING AND ROTATING WESTWARD ACROSS THE
SOUTHERN GULF THURSDAY AFTERNOON THROUGH THURSDAY NIGHT. ALL
SOLUTIONS EXCEPT THE NAM ARE GROUPED FAIRLY CLOSE TOGETHER...SO
WILL UPDATED FORECAST TO REFLECT THIS LOW (WHICH IT DOES NOT
PRESENTLY). THE ENTIRE SYSTEM NOW LOOKS LIKE IT WILL REMAIN
FARTHER SOUTH THAN PRIOR GUIDANCE INDICATED...MEANING WINDS OVER
THE NORTHERN GULF/PRINCE WILLIAM SOUND AREA WILL BE A LITTLE
LIGHTER THAN CURRENTLY ADVERTISED.

NUMERICAL GUIDANCE CONTINUES TO STRUGGLE WITH HANDLING OF MULTIPLE
LOWS SOUTH OF THE ALEUTIANS. CURRENT FORECAST SEEMS A FAIR
REPRESENTATION OF THE GENERAL WINDS AND WEATHER EXPECTED.
HOWEVER...THERE MAY BE SOME DIRECTIONAL ISSUES DEPENDING ON WHERE
THE CURRENT LOW ALONG THE ALEUTIANS STALLS OUT. WITH MULTIPLE WEAK
LOWS IN PLACE SOUTH OF THE ALEUTIANS/ALASKA PENINSULA/KODIAK
ISLAND THROUGH THE WEEKEND FORECAST CONFIDENCE IN THIS AREA IS
BELOW AVERAGE. FORECAST CONFIDENCE FARTHER NORTH IS GENERALLY
HIGH.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
IMPACTS OF THE LARGE NORTHEAST PACIFIC LOW WILL INITIALLY REMAIN
DOWN OVER THE GULF AND KODIAK ISLAND. WHEN THE TRIPLE POINT LOW
CROSSES THE GULF THIS AFTERNOON AND TONIGHT THE UPPER RIDGE WILL
BE PUSHED NORTHWARD INTO INTERIOR ALASKA ALLOWING SOME PRECIP TO
MAKE IT UP TO THE NORTH GULF COAST. SOME COMPONENT OF OFFSHORE
FLOW WILL PERSIST IN THE LOW LEVELS SO PRECIP WILL BE LIGHT.

MEANWHILE LOCALIZED OUTFLOW WINDS WILL SET UP THROUGH MAJOR GAPS
TODAY AS PRESSURE GRADIENTS TIGHTEN AND LOW LEVEL FLOW BECOMES
MORE UNIFORMLY OFFSHORE. THE AIR MASS IN THE COPPER RIVER BASIN IS
COLDER THAN THE REST OF SOUTHCENTRAL...BUT THERE REALLY ISN`T MUCH
IN THE WAY OF ADVECTION OF THIS AIR. THUS EXPECT THIS TO BE A WEAK
EVENT.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A COUPLE WEAK UPPER LEVEL WAVES MOVING OVER TOP OF THE LARGE LOW
OVER THE NORTHEAST PACIFIC WILL CROSS SOUTHWEST ALASKA THE NEXT
COUPLE DAYS. THIS WILL BRING A COUPLE QUICK SHOTS OF PRECIP...BUT
WHATEVER DOES FALL WILL BE LIGHT AND BRIEF. WITH THE EXCEPTION OF
THE ALASKA PENINSULA...THE AIR MASS IN PLACE WILL REMAIN COLD
ENOUGH TO SUPPORT SNOW.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE BULK OF ACTIVE WEATHER WILL BE CONFINED TO THE ALEUTIANS AND
ALASKA PENINSULA THE NEXT COUPLE DAYS AS LOWS PASS JUST TO THE
SOUTH. A GENERALLY UNSTABLE AIR MASS OVER THE BERING SEA WILL
CONTINUE TO PRODUCE SOME SHOWERS...BUT NOTHING VERY WELL
ORGANIZED.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
CONFIDENCE IN THE GENERAL EVOLUTION OF THE LARGE SCALE PATTERN AS
WE HEAD INTO THE EARLY TO MIDDLE PART OF NEXT WEEK IS HIGH...WITH
VERY GOOD RUN-TO-RUN CONTINUITY. CONFIDENCE IN SOME OF THE
SPECIFICFEATURES INVOLVED IS NOT QUITE AS A HIGH...BUT LATEST
SOLUTIONS ARE NOT TERRIBLY DIFFERENT...SO CONFIDENCE IS GROWING.

AS HAS BEEN ADVERTISED IN PREVIOUS DISCUSSIONS THE SERIES OF LOWS
STRUNG OUT ACROSS THE NORTH PACIFIC AND GULF OF ALASKA THIS
WEEKEND WILL ALL CONSOLIDATE INTO ONE VERY LARGE CYCLONIC
CIRCULATION CENTERED SOMEWHERE OVER THE WESTERN GULF OF ALASKA
PENINSULA BY EARLY NEXT WEEK. AS THE SYSTEMS PROGRESS A LITTLE
FURTHER NORTH THIS WEEKEND WARMER LOW LEVEL AIR WILL MOVE BACK
INTO SOUTHCENTRAL AS WELL AS THE BRISTOL BAY AREA. THEREFORE THE
THREAT OF FREEZING RAIN WILL RETURN ONCE AGAIN...ALTHOUGH THE BULK
OF PRECIP SHOULD REMAIN ALONG THE COAST

A TRANSITION IN PATTERN WILL COMMENCE NEXT WEEK AS A DEEP TROUGH
MOVES OUT OF ASIA AND INTO THE BERING SEA. A BUILDING RIDGE OUT
AHEAD OF THIS TROUGH WILL HELP PROVIDE A QUICK SHOT OF COLD
ADVECTION DOWNSTREAM OF THE TROUGH...OVER THE BERING SEA THIS
WEEKEND SPREADING TO MAINLAND ALASKA EARLY NEXT WEEK. THERE COULD
EVEN BE A QUICK SHOT OF SNOW OVER SOUTHCENTRAL DEPENDING ON WHAT
HAPPENS TO THE REMNANTS OF THE CONSOLIDATED LOW MENTIONED ABOVE.

THE GFS/ECMWF ARE BOTH DEPICTING DEVELOPMENT OF A DEEP SURFACE LOW
ON THE FRONT EDGE OF THE TROUGH MOVING OUT OF ASIA. ITS HARD TO
SAY EXACTLY HOW DEEP IT WILL BE...BUT WITH A STRONG UPPER LEVEL
JET IN AMPLIFIED FLOW CONDITIONS LOOK FAVORABLE FOR A RAPID
DEEPENING. WITH THE DOWNSTREAM RIDGE CONTINUING TO BUILD THE STORM
WILL BE FORCED NORTHWARD ACROSS THE BERING SEA. THIS TRACK IS
VERY IMPORTANT TO THE FORECAST OVER MAINLAND ALASKA BECAUSE IT
MEANS THE BULK OF WARM PACIFIC AIR WILL REMAIN OVER THE BERING
SEA. THEREFORE...AS THE UPPER TROUGH CONTINUES TO PROGRESS
EASTWARD TO MAINLAND ALASKA THE MIDDLE OF NEXT WEEK THE AIR MASS
WILL LIKELY REMAIN COLD ENOUGH TO SUPPORT ALL SNOW OVER INTERIOR
SOUTHWEST ALASKA AND OVER MUCH OF SOUTHCENTRAL ALASKA. IT IS WAY
TOO EARLY TO HAVE MUCH CONFIDENCE IN THIS SINCE DYNAMIC PATTERNS
OFTEN PRODUCE SOME SURPRISES...BUT THERE IS DEFINITELY SOME
POTENTIAL FOR SOME FRESH SNOW ACROSS THE SOUTHERN MAINLAND OF
ALASKA IN TIME FOR CHRISTMAS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING...119 120 127 130 131 132 136 137 138 139
                        150 176 177 178.
HEAVY FREEZING SPRAY WARNING...185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...SEB
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...SEB
LONG TERM...SEB




000
FXAK68 PAFC 181316 CCA
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
416 AM AKST THU DEC 18 2014

.ANALYSIS AND UPPER LEVELS...
SATELLITE IMAGERY SHOWS TWO LARGE STORM SYSTEMS IN THE
REGION...BOTH CENTERED OVER THE NORTH PACIFIC WHERE PROGRESSIVE
UPPER LEVEL FLOW DOMINATES. A VERY LARGE AND MATURE STORM FORCE
LOW IS CENTERED SOUTH OF THE GULF OF ALASKA WITH THE OCCLUDED
FRONT SLOWLY LIFTING NORTHWARD BRINGING GALE FORCE WINDS AND RAIN
TO THE GULF AND KODIAK ISLAND. OUT HEAD OF THIS A SHORT-WAVE RIDGE
IS MOVING OVER THE SOUTHERN MAINLAND RESULTING IN QUIET
CONDITIONS. THERE SOME AREAS OF FOG OVER SOUTHCENTRAL...BUT AS
PRESSURE GRADIENTS TIGHTEN WITH THE APPROACHING FRONT AND OFFSHORE
FLOW STRENGTHENS EXPECT MOST OF THIS TO DISSIPATE. MEANWHILE A
200+ KT JET IS DRIVING EASTWARD ACROSS THE NORTHWEST PACIFIC AND
INTO THE NORTH-CENTRAL PACIFIC CAUSING RAPID CYCLOGENESIS WITH A
SERIES OF LOWS STRUNG OUT JUST TO THE SOUTH OF THE BERING SEA AND
ALEUTIANS. THE LOW CLOSEST TO THE WESTERN ALEUTIANS AND ASSOCIATED
OCCLUDED FRONT ARE LIFTING NORTHWARD TOWARD THE ALEUTIANS...SO
GALE FORCE WINDS AND RAIN ARE ON THE WAY.

&&

.MODEL DISCUSSION...MODELS SEEM TO BE CONVERGING ON A COMMON
SOLUTION WITH TRIPLE POINT LOW FORMING OVER THE FAR NORTHEAST
PACIFIC THURSDAY MORNING AND ROTATING WESTWARD ACROSS THE
SOUTHERN GULF THURSDAY AFTERNOON THROUGH THURSDAY NIGHT. ALL
SOLUTIONS EXCEPT THE NAM ARE GROUPED FAIRLY CLOSE TOGETHER...SO
WILL UPDATED FORECAST TO REFLECT THIS LOW (WHICH IT DOES NOT
PRESENTLY). THE ENTIRE SYSTEM NOW LOOKS LIKE IT WILL REMAIN
FARTHER SOUTH THAN PRIOR GUIDANCE INDICATED...MEANING WINDS OVER
THE NORTHERN GULF/PRINCE WILLIAM SOUND AREA WILL BE A LITTLE
LIGHTER THAN CURRENTLY ADVERTISED.

NUMERICAL GUIDANCE CONTINUES TO STRUGGLE WITH HANDLING OF MULTIPLE
LOWS SOUTH OF THE ALEUTIANS. CURRENT FORECAST SEEMS A FAIR
REPRESENTATION OF THE GENERAL WINDS AND WEATHER EXPECTED.
HOWEVER...THERE MAY BE SOME DIRECTIONAL ISSUES DEPENDING ON WHERE
THE CURRENT LOW ALONG THE ALEUTIANS STALLS OUT. WITH MULTIPLE WEAK
LOWS IN PLACE SOUTH OF THE ALEUTIANS/ALASKA PENINSULA/KODIAK
ISLAND THROUGH THE WEEKEND FORECAST CONFIDENCE IN THIS AREA IS
BELOW AVERAGE. FORECAST CONFIDENCE FARTHER NORTH IS GENERALLY
HIGH.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
IMPACTS OF THE LARGE NORTHEAST PACIFIC LOW WILL INITIALLY REMAIN
DOWN OVER THE GULF AND KODIAK ISLAND. WHEN THE TRIPLE POINT LOW
CROSSES THE GULF THIS AFTERNOON AND TONIGHT THE UPPER RIDGE WILL
BE PUSHED NORTHWARD INTO INTERIOR ALASKA ALLOWING SOME PRECIP TO
MAKE IT UP TO THE NORTH GULF COAST. SOME COMPONENT OF OFFSHORE
FLOW WILL PERSIST IN THE LOW LEVELS SO PRECIP WILL BE LIGHT.

MEANWHILE LOCALIZED OUTFLOW WINDS WILL SET UP THROUGH MAJOR GAPS
TODAY AS PRESSURE GRADIENTS TIGHTEN AND LOW LEVEL FLOW BECOMES
MORE UNIFORMLY OFFSHORE. THE AIR MASS IN THE COPPER RIVER BASIN IS
COLDER THAN THE REST OF SOUTHCENTRAL...BUT THERE REALLY ISN`T MUCH
IN THE WAY OF ADVECTION OF THIS AIR. THUS EXPECT THIS TO BE A WEAK
EVENT.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A COUPLE WEAK UPPER LEVEL WAVES MOVING OVER TOP OF THE LARGE LOW
OVER THE NORTHEAST PACIFIC WILL CROSS SOUTHWEST ALASKA THE NEXT
COUPLE DAYS. THIS WILL BRING A COUPLE QUICK SHOTS OF PRECIP...BUT
WHATEVER DOES FALL WILL BE LIGHT AND BRIEF. WITH THE EXCEPTION OF
THE ALASKA PENINSULA...THE AIR MASS IN PLACE WILL REMAIN COLD
ENOUGH TO SUPPORT SNOW.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE BULK OF ACTIVE WEATHER WILL BE CONFINED TO THE ALEUTIANS AND
ALASKA PENINSULA THE NEXT COUPLE DAYS AS LOWS PASS JUST TO THE
SOUTH. A GENERALLY UNSTABLE AIR MASS OVER THE BERING SEA WILL
CONTINUE TO PRODUCE SOME SHOWERS...BUT NOTHING VERY WELL
ORGANIZED.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
CONFIDENCE IN THE GENERAL EVOLUTION OF THE LARGE SCALE PATTERN AS
WE HEAD INTO THE EARLY TO MIDDLE PART OF NEXT WEEK IS HIGH...WITH
VERY GOOD RUN-TO-RUN CONTINUITY IN NUMERICAL GUIDANCE. CONFIDENCE
IN SOME OF THE SPECIFIC FEATURES IS NOT QUITE AS HIGH...BUT
LATEST SOLUTIONS ARE NOT TERRIBLY DIFFERENT...SO CONFIDENCE IS
GROWING.

AS HAS BEEN ADVERTISED IN PREVIOUS DISCUSSIONS THE SERIES OF LOWS
STRUNG OUT ACROSS THE NORTH PACIFIC AND GULF OF ALASKA THIS
WEEKEND WILL ALL CONSOLIDATE INTO ONE VERY LARGE CYCLONIC
CIRCULATION CENTERED SOMEWHERE OVER THE WESTERN GULF OR NEAR THE
ALASKA PENINSULA BY EARLY NEXT WEEK. AS THE SYSTEMS PROGRESS A
LITTLE FURTHER NORTH THIS WEEKEND WARMER LOW LEVEL AIR WILL MOVE
BACK INTO SOUTHCENTRAL AS WELL AS THE BRISTOL BAY AREA. THEREFORE
THE THREAT OF FREEZING RAIN WILL RETURN ONCE AGAIN...ALTHOUGH THE
BULK OF PRECIP SHOULD REMAIN ALONG THE COAST.

A TRANSITION IN PATTERN WILL COMMENCE NEXT WEEK AS A DEEP TROUGH
MOVES OUT OF ASIA AND INTO THE BERING SEA. A BUILDING RIDGE OUT
AHEAD OF THIS TROUGH WILL HELP PROVIDE A QUICK SHOT OF COLD
ADVECTION DOWNSTREAM OF THE TROUGH...OVER THE BERING SEA THIS
WEEKEND SPREADING TO MAINLAND ALASKA EARLY NEXT WEEK. THERE COULD
EVEN BE A QUICK SHOT OF SNOW OVER SOUTHCENTRAL DEPENDING ON WHAT
HAPPENS TO THE REMNANTS OF THE CONSOLIDATED LOW MENTIONED ABOVE.

THE GFS/ECMWF ARE BOTH DEPICTING DEVELOPMENT OF A DEEP SURFACE LOW
ON THE FRONT EDGE OF THE TROUGH MOVING OUT OF ASIA. ITS HARD TO
SAY EXACTLY HOW DEEP IT WILL BE...BUT WITH A STRONG UPPER LEVEL
JET IN AMPLIFIED FLOW CONDITIONS LOOK FAVORABLE FOR RAPID DEEPENING.
WITH THE DOWNSTREAM RIDGE CONTINUING TO BUILD THE STORM WILL BE
FORCED NORTHWARD ACROSS THE BERING SEA. THIS TRACK IS VERY
IMPORTANT TO THE FORECAST OVER MAINLAND ALASKA BECAUSE IT MEANS
THE BULK OF WARM PACIFIC AIR WILL REMAIN OVER THE BERING SEA.
THEREFORE...AS THE UPPER TROUGH CONTINUES TO PROGRESS EASTWARD TO
MAINLAND ALASKA THE MIDDLE OF NEXT WEEK THE AIR MASS WILL LIKELY
REMAIN COLD ENOUGH TO SUPPORT ALL SNOW OVER INTERIOR SOUTHWEST
ALASKA AND OVER MUCH OF SOUTHCENTRAL ALASKA. IT IS WAY TOO EARLY
TO HAVE MUCH CONFIDENCE IN THIS SINCE DYNAMIC PATTERNS OFTEN
PRODUCE SOME SURPRISES...BUT THERE IS DEFINITELY POTENTIAL FOR
SOME FRESH SNOW ACROSS THE SOUTHERN MAINLAND OF ALASKA IN TIME
FOR CHRISTMAS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING...119 120 127 130 131 132 136 137 138 139
                        150 176 177 178.
HEAVY FREEZING SPRAY WARNING...185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...SEB
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...SEB
LONG TERM...SEB





000
FXAK68 PAFC 181316 CCA
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
416 AM AKST THU DEC 18 2014

.ANALYSIS AND UPPER LEVELS...
SATELLITE IMAGERY SHOWS TWO LARGE STORM SYSTEMS IN THE
REGION...BOTH CENTERED OVER THE NORTH PACIFIC WHERE PROGRESSIVE
UPPER LEVEL FLOW DOMINATES. A VERY LARGE AND MATURE STORM FORCE
LOW IS CENTERED SOUTH OF THE GULF OF ALASKA WITH THE OCCLUDED
FRONT SLOWLY LIFTING NORTHWARD BRINGING GALE FORCE WINDS AND RAIN
TO THE GULF AND KODIAK ISLAND. OUT HEAD OF THIS A SHORT-WAVE RIDGE
IS MOVING OVER THE SOUTHERN MAINLAND RESULTING IN QUIET
CONDITIONS. THERE SOME AREAS OF FOG OVER SOUTHCENTRAL...BUT AS
PRESSURE GRADIENTS TIGHTEN WITH THE APPROACHING FRONT AND OFFSHORE
FLOW STRENGTHENS EXPECT MOST OF THIS TO DISSIPATE. MEANWHILE A
200+ KT JET IS DRIVING EASTWARD ACROSS THE NORTHWEST PACIFIC AND
INTO THE NORTH-CENTRAL PACIFIC CAUSING RAPID CYCLOGENESIS WITH A
SERIES OF LOWS STRUNG OUT JUST TO THE SOUTH OF THE BERING SEA AND
ALEUTIANS. THE LOW CLOSEST TO THE WESTERN ALEUTIANS AND ASSOCIATED
OCCLUDED FRONT ARE LIFTING NORTHWARD TOWARD THE ALEUTIANS...SO
GALE FORCE WINDS AND RAIN ARE ON THE WAY.

&&

.MODEL DISCUSSION...MODELS SEEM TO BE CONVERGING ON A COMMON
SOLUTION WITH TRIPLE POINT LOW FORMING OVER THE FAR NORTHEAST
PACIFIC THURSDAY MORNING AND ROTATING WESTWARD ACROSS THE
SOUTHERN GULF THURSDAY AFTERNOON THROUGH THURSDAY NIGHT. ALL
SOLUTIONS EXCEPT THE NAM ARE GROUPED FAIRLY CLOSE TOGETHER...SO
WILL UPDATED FORECAST TO REFLECT THIS LOW (WHICH IT DOES NOT
PRESENTLY). THE ENTIRE SYSTEM NOW LOOKS LIKE IT WILL REMAIN
FARTHER SOUTH THAN PRIOR GUIDANCE INDICATED...MEANING WINDS OVER
THE NORTHERN GULF/PRINCE WILLIAM SOUND AREA WILL BE A LITTLE
LIGHTER THAN CURRENTLY ADVERTISED.

NUMERICAL GUIDANCE CONTINUES TO STRUGGLE WITH HANDLING OF MULTIPLE
LOWS SOUTH OF THE ALEUTIANS. CURRENT FORECAST SEEMS A FAIR
REPRESENTATION OF THE GENERAL WINDS AND WEATHER EXPECTED.
HOWEVER...THERE MAY BE SOME DIRECTIONAL ISSUES DEPENDING ON WHERE
THE CURRENT LOW ALONG THE ALEUTIANS STALLS OUT. WITH MULTIPLE WEAK
LOWS IN PLACE SOUTH OF THE ALEUTIANS/ALASKA PENINSULA/KODIAK
ISLAND THROUGH THE WEEKEND FORECAST CONFIDENCE IN THIS AREA IS
BELOW AVERAGE. FORECAST CONFIDENCE FARTHER NORTH IS GENERALLY
HIGH.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
IMPACTS OF THE LARGE NORTHEAST PACIFIC LOW WILL INITIALLY REMAIN
DOWN OVER THE GULF AND KODIAK ISLAND. WHEN THE TRIPLE POINT LOW
CROSSES THE GULF THIS AFTERNOON AND TONIGHT THE UPPER RIDGE WILL
BE PUSHED NORTHWARD INTO INTERIOR ALASKA ALLOWING SOME PRECIP TO
MAKE IT UP TO THE NORTH GULF COAST. SOME COMPONENT OF OFFSHORE
FLOW WILL PERSIST IN THE LOW LEVELS SO PRECIP WILL BE LIGHT.

MEANWHILE LOCALIZED OUTFLOW WINDS WILL SET UP THROUGH MAJOR GAPS
TODAY AS PRESSURE GRADIENTS TIGHTEN AND LOW LEVEL FLOW BECOMES
MORE UNIFORMLY OFFSHORE. THE AIR MASS IN THE COPPER RIVER BASIN IS
COLDER THAN THE REST OF SOUTHCENTRAL...BUT THERE REALLY ISN`T MUCH
IN THE WAY OF ADVECTION OF THIS AIR. THUS EXPECT THIS TO BE A WEAK
EVENT.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A COUPLE WEAK UPPER LEVEL WAVES MOVING OVER TOP OF THE LARGE LOW
OVER THE NORTHEAST PACIFIC WILL CROSS SOUTHWEST ALASKA THE NEXT
COUPLE DAYS. THIS WILL BRING A COUPLE QUICK SHOTS OF PRECIP...BUT
WHATEVER DOES FALL WILL BE LIGHT AND BRIEF. WITH THE EXCEPTION OF
THE ALASKA PENINSULA...THE AIR MASS IN PLACE WILL REMAIN COLD
ENOUGH TO SUPPORT SNOW.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE BULK OF ACTIVE WEATHER WILL BE CONFINED TO THE ALEUTIANS AND
ALASKA PENINSULA THE NEXT COUPLE DAYS AS LOWS PASS JUST TO THE
SOUTH. A GENERALLY UNSTABLE AIR MASS OVER THE BERING SEA WILL
CONTINUE TO PRODUCE SOME SHOWERS...BUT NOTHING VERY WELL
ORGANIZED.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
CONFIDENCE IN THE GENERAL EVOLUTION OF THE LARGE SCALE PATTERN AS
WE HEAD INTO THE EARLY TO MIDDLE PART OF NEXT WEEK IS HIGH...WITH
VERY GOOD RUN-TO-RUN CONTINUITY IN NUMERICAL GUIDANCE. CONFIDENCE
IN SOME OF THE SPECIFIC FEATURES IS NOT QUITE AS HIGH...BUT
LATEST SOLUTIONS ARE NOT TERRIBLY DIFFERENT...SO CONFIDENCE IS
GROWING.

AS HAS BEEN ADVERTISED IN PREVIOUS DISCUSSIONS THE SERIES OF LOWS
STRUNG OUT ACROSS THE NORTH PACIFIC AND GULF OF ALASKA THIS
WEEKEND WILL ALL CONSOLIDATE INTO ONE VERY LARGE CYCLONIC
CIRCULATION CENTERED SOMEWHERE OVER THE WESTERN GULF OR NEAR THE
ALASKA PENINSULA BY EARLY NEXT WEEK. AS THE SYSTEMS PROGRESS A
LITTLE FURTHER NORTH THIS WEEKEND WARMER LOW LEVEL AIR WILL MOVE
BACK INTO SOUTHCENTRAL AS WELL AS THE BRISTOL BAY AREA. THEREFORE
THE THREAT OF FREEZING RAIN WILL RETURN ONCE AGAIN...ALTHOUGH THE
BULK OF PRECIP SHOULD REMAIN ALONG THE COAST.

A TRANSITION IN PATTERN WILL COMMENCE NEXT WEEK AS A DEEP TROUGH
MOVES OUT OF ASIA AND INTO THE BERING SEA. A BUILDING RIDGE OUT
AHEAD OF THIS TROUGH WILL HELP PROVIDE A QUICK SHOT OF COLD
ADVECTION DOWNSTREAM OF THE TROUGH...OVER THE BERING SEA THIS
WEEKEND SPREADING TO MAINLAND ALASKA EARLY NEXT WEEK. THERE COULD
EVEN BE A QUICK SHOT OF SNOW OVER SOUTHCENTRAL DEPENDING ON WHAT
HAPPENS TO THE REMNANTS OF THE CONSOLIDATED LOW MENTIONED ABOVE.

THE GFS/ECMWF ARE BOTH DEPICTING DEVELOPMENT OF A DEEP SURFACE LOW
ON THE FRONT EDGE OF THE TROUGH MOVING OUT OF ASIA. ITS HARD TO
SAY EXACTLY HOW DEEP IT WILL BE...BUT WITH A STRONG UPPER LEVEL
JET IN AMPLIFIED FLOW CONDITIONS LOOK FAVORABLE FOR RAPID DEEPENING.
WITH THE DOWNSTREAM RIDGE CONTINUING TO BUILD THE STORM WILL BE
FORCED NORTHWARD ACROSS THE BERING SEA. THIS TRACK IS VERY
IMPORTANT TO THE FORECAST OVER MAINLAND ALASKA BECAUSE IT MEANS
THE BULK OF WARM PACIFIC AIR WILL REMAIN OVER THE BERING SEA.
THEREFORE...AS THE UPPER TROUGH CONTINUES TO PROGRESS EASTWARD TO
MAINLAND ALASKA THE MIDDLE OF NEXT WEEK THE AIR MASS WILL LIKELY
REMAIN COLD ENOUGH TO SUPPORT ALL SNOW OVER INTERIOR SOUTHWEST
ALASKA AND OVER MUCH OF SOUTHCENTRAL ALASKA. IT IS WAY TOO EARLY
TO HAVE MUCH CONFIDENCE IN THIS SINCE DYNAMIC PATTERNS OFTEN
PRODUCE SOME SURPRISES...BUT THERE IS DEFINITELY POTENTIAL FOR
SOME FRESH SNOW ACROSS THE SOUTHERN MAINLAND OF ALASKA IN TIME
FOR CHRISTMAS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING...119 120 127 130 131 132 136 137 138 139
                        150 176 177 178.
HEAVY FREEZING SPRAY WARNING...185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...SEB
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...SEB
LONG TERM...SEB




000
FXAK68 PAFC 181316 CCA
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
416 AM AKST THU DEC 18 2014

.ANALYSIS AND UPPER LEVELS...
SATELLITE IMAGERY SHOWS TWO LARGE STORM SYSTEMS IN THE
REGION...BOTH CENTERED OVER THE NORTH PACIFIC WHERE PROGRESSIVE
UPPER LEVEL FLOW DOMINATES. A VERY LARGE AND MATURE STORM FORCE
LOW IS CENTERED SOUTH OF THE GULF OF ALASKA WITH THE OCCLUDED
FRONT SLOWLY LIFTING NORTHWARD BRINGING GALE FORCE WINDS AND RAIN
TO THE GULF AND KODIAK ISLAND. OUT HEAD OF THIS A SHORT-WAVE RIDGE
IS MOVING OVER THE SOUTHERN MAINLAND RESULTING IN QUIET
CONDITIONS. THERE SOME AREAS OF FOG OVER SOUTHCENTRAL...BUT AS
PRESSURE GRADIENTS TIGHTEN WITH THE APPROACHING FRONT AND OFFSHORE
FLOW STRENGTHENS EXPECT MOST OF THIS TO DISSIPATE. MEANWHILE A
200+ KT JET IS DRIVING EASTWARD ACROSS THE NORTHWEST PACIFIC AND
INTO THE NORTH-CENTRAL PACIFIC CAUSING RAPID CYCLOGENESIS WITH A
SERIES OF LOWS STRUNG OUT JUST TO THE SOUTH OF THE BERING SEA AND
ALEUTIANS. THE LOW CLOSEST TO THE WESTERN ALEUTIANS AND ASSOCIATED
OCCLUDED FRONT ARE LIFTING NORTHWARD TOWARD THE ALEUTIANS...SO
GALE FORCE WINDS AND RAIN ARE ON THE WAY.

&&

.MODEL DISCUSSION...MODELS SEEM TO BE CONVERGING ON A COMMON
SOLUTION WITH TRIPLE POINT LOW FORMING OVER THE FAR NORTHEAST
PACIFIC THURSDAY MORNING AND ROTATING WESTWARD ACROSS THE
SOUTHERN GULF THURSDAY AFTERNOON THROUGH THURSDAY NIGHT. ALL
SOLUTIONS EXCEPT THE NAM ARE GROUPED FAIRLY CLOSE TOGETHER...SO
WILL UPDATED FORECAST TO REFLECT THIS LOW (WHICH IT DOES NOT
PRESENTLY). THE ENTIRE SYSTEM NOW LOOKS LIKE IT WILL REMAIN
FARTHER SOUTH THAN PRIOR GUIDANCE INDICATED...MEANING WINDS OVER
THE NORTHERN GULF/PRINCE WILLIAM SOUND AREA WILL BE A LITTLE
LIGHTER THAN CURRENTLY ADVERTISED.

NUMERICAL GUIDANCE CONTINUES TO STRUGGLE WITH HANDLING OF MULTIPLE
LOWS SOUTH OF THE ALEUTIANS. CURRENT FORECAST SEEMS A FAIR
REPRESENTATION OF THE GENERAL WINDS AND WEATHER EXPECTED.
HOWEVER...THERE MAY BE SOME DIRECTIONAL ISSUES DEPENDING ON WHERE
THE CURRENT LOW ALONG THE ALEUTIANS STALLS OUT. WITH MULTIPLE WEAK
LOWS IN PLACE SOUTH OF THE ALEUTIANS/ALASKA PENINSULA/KODIAK
ISLAND THROUGH THE WEEKEND FORECAST CONFIDENCE IN THIS AREA IS
BELOW AVERAGE. FORECAST CONFIDENCE FARTHER NORTH IS GENERALLY
HIGH.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
IMPACTS OF THE LARGE NORTHEAST PACIFIC LOW WILL INITIALLY REMAIN
DOWN OVER THE GULF AND KODIAK ISLAND. WHEN THE TRIPLE POINT LOW
CROSSES THE GULF THIS AFTERNOON AND TONIGHT THE UPPER RIDGE WILL
BE PUSHED NORTHWARD INTO INTERIOR ALASKA ALLOWING SOME PRECIP TO
MAKE IT UP TO THE NORTH GULF COAST. SOME COMPONENT OF OFFSHORE
FLOW WILL PERSIST IN THE LOW LEVELS SO PRECIP WILL BE LIGHT.

MEANWHILE LOCALIZED OUTFLOW WINDS WILL SET UP THROUGH MAJOR GAPS
TODAY AS PRESSURE GRADIENTS TIGHTEN AND LOW LEVEL FLOW BECOMES
MORE UNIFORMLY OFFSHORE. THE AIR MASS IN THE COPPER RIVER BASIN IS
COLDER THAN THE REST OF SOUTHCENTRAL...BUT THERE REALLY ISN`T MUCH
IN THE WAY OF ADVECTION OF THIS AIR. THUS EXPECT THIS TO BE A WEAK
EVENT.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A COUPLE WEAK UPPER LEVEL WAVES MOVING OVER TOP OF THE LARGE LOW
OVER THE NORTHEAST PACIFIC WILL CROSS SOUTHWEST ALASKA THE NEXT
COUPLE DAYS. THIS WILL BRING A COUPLE QUICK SHOTS OF PRECIP...BUT
WHATEVER DOES FALL WILL BE LIGHT AND BRIEF. WITH THE EXCEPTION OF
THE ALASKA PENINSULA...THE AIR MASS IN PLACE WILL REMAIN COLD
ENOUGH TO SUPPORT SNOW.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE BULK OF ACTIVE WEATHER WILL BE CONFINED TO THE ALEUTIANS AND
ALASKA PENINSULA THE NEXT COUPLE DAYS AS LOWS PASS JUST TO THE
SOUTH. A GENERALLY UNSTABLE AIR MASS OVER THE BERING SEA WILL
CONTINUE TO PRODUCE SOME SHOWERS...BUT NOTHING VERY WELL
ORGANIZED.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
CONFIDENCE IN THE GENERAL EVOLUTION OF THE LARGE SCALE PATTERN AS
WE HEAD INTO THE EARLY TO MIDDLE PART OF NEXT WEEK IS HIGH...WITH
VERY GOOD RUN-TO-RUN CONTINUITY IN NUMERICAL GUIDANCE. CONFIDENCE
IN SOME OF THE SPECIFIC FEATURES IS NOT QUITE AS HIGH...BUT
LATEST SOLUTIONS ARE NOT TERRIBLY DIFFERENT...SO CONFIDENCE IS
GROWING.

AS HAS BEEN ADVERTISED IN PREVIOUS DISCUSSIONS THE SERIES OF LOWS
STRUNG OUT ACROSS THE NORTH PACIFIC AND GULF OF ALASKA THIS
WEEKEND WILL ALL CONSOLIDATE INTO ONE VERY LARGE CYCLONIC
CIRCULATION CENTERED SOMEWHERE OVER THE WESTERN GULF OR NEAR THE
ALASKA PENINSULA BY EARLY NEXT WEEK. AS THE SYSTEMS PROGRESS A
LITTLE FURTHER NORTH THIS WEEKEND WARMER LOW LEVEL AIR WILL MOVE
BACK INTO SOUTHCENTRAL AS WELL AS THE BRISTOL BAY AREA. THEREFORE
THE THREAT OF FREEZING RAIN WILL RETURN ONCE AGAIN...ALTHOUGH THE
BULK OF PRECIP SHOULD REMAIN ALONG THE COAST.

A TRANSITION IN PATTERN WILL COMMENCE NEXT WEEK AS A DEEP TROUGH
MOVES OUT OF ASIA AND INTO THE BERING SEA. A BUILDING RIDGE OUT
AHEAD OF THIS TROUGH WILL HELP PROVIDE A QUICK SHOT OF COLD
ADVECTION DOWNSTREAM OF THE TROUGH...OVER THE BERING SEA THIS
WEEKEND SPREADING TO MAINLAND ALASKA EARLY NEXT WEEK. THERE COULD
EVEN BE A QUICK SHOT OF SNOW OVER SOUTHCENTRAL DEPENDING ON WHAT
HAPPENS TO THE REMNANTS OF THE CONSOLIDATED LOW MENTIONED ABOVE.

THE GFS/ECMWF ARE BOTH DEPICTING DEVELOPMENT OF A DEEP SURFACE LOW
ON THE FRONT EDGE OF THE TROUGH MOVING OUT OF ASIA. ITS HARD TO
SAY EXACTLY HOW DEEP IT WILL BE...BUT WITH A STRONG UPPER LEVEL
JET IN AMPLIFIED FLOW CONDITIONS LOOK FAVORABLE FOR RAPID DEEPENING.
WITH THE DOWNSTREAM RIDGE CONTINUING TO BUILD THE STORM WILL BE
FORCED NORTHWARD ACROSS THE BERING SEA. THIS TRACK IS VERY
IMPORTANT TO THE FORECAST OVER MAINLAND ALASKA BECAUSE IT MEANS
THE BULK OF WARM PACIFIC AIR WILL REMAIN OVER THE BERING SEA.
THEREFORE...AS THE UPPER TROUGH CONTINUES TO PROGRESS EASTWARD TO
MAINLAND ALASKA THE MIDDLE OF NEXT WEEK THE AIR MASS WILL LIKELY
REMAIN COLD ENOUGH TO SUPPORT ALL SNOW OVER INTERIOR SOUTHWEST
ALASKA AND OVER MUCH OF SOUTHCENTRAL ALASKA. IT IS WAY TOO EARLY
TO HAVE MUCH CONFIDENCE IN THIS SINCE DYNAMIC PATTERNS OFTEN
PRODUCE SOME SURPRISES...BUT THERE IS DEFINITELY POTENTIAL FOR
SOME FRESH SNOW ACROSS THE SOUTHERN MAINLAND OF ALASKA IN TIME
FOR CHRISTMAS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING...119 120 127 130 131 132 136 137 138 139
                        150 176 177 178.
HEAVY FREEZING SPRAY WARNING...185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...SEB
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...SEB
LONG TERM...SEB




000
FXAK68 PAFC 181316 CCA
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
416 AM AKST THU DEC 18 2014

.ANALYSIS AND UPPER LEVELS...
SATELLITE IMAGERY SHOWS TWO LARGE STORM SYSTEMS IN THE
REGION...BOTH CENTERED OVER THE NORTH PACIFIC WHERE PROGRESSIVE
UPPER LEVEL FLOW DOMINATES. A VERY LARGE AND MATURE STORM FORCE
LOW IS CENTERED SOUTH OF THE GULF OF ALASKA WITH THE OCCLUDED
FRONT SLOWLY LIFTING NORTHWARD BRINGING GALE FORCE WINDS AND RAIN
TO THE GULF AND KODIAK ISLAND. OUT HEAD OF THIS A SHORT-WAVE RIDGE
IS MOVING OVER THE SOUTHERN MAINLAND RESULTING IN QUIET
CONDITIONS. THERE SOME AREAS OF FOG OVER SOUTHCENTRAL...BUT AS
PRESSURE GRADIENTS TIGHTEN WITH THE APPROACHING FRONT AND OFFSHORE
FLOW STRENGTHENS EXPECT MOST OF THIS TO DISSIPATE. MEANWHILE A
200+ KT JET IS DRIVING EASTWARD ACROSS THE NORTHWEST PACIFIC AND
INTO THE NORTH-CENTRAL PACIFIC CAUSING RAPID CYCLOGENESIS WITH A
SERIES OF LOWS STRUNG OUT JUST TO THE SOUTH OF THE BERING SEA AND
ALEUTIANS. THE LOW CLOSEST TO THE WESTERN ALEUTIANS AND ASSOCIATED
OCCLUDED FRONT ARE LIFTING NORTHWARD TOWARD THE ALEUTIANS...SO
GALE FORCE WINDS AND RAIN ARE ON THE WAY.

&&

.MODEL DISCUSSION...MODELS SEEM TO BE CONVERGING ON A COMMON
SOLUTION WITH TRIPLE POINT LOW FORMING OVER THE FAR NORTHEAST
PACIFIC THURSDAY MORNING AND ROTATING WESTWARD ACROSS THE
SOUTHERN GULF THURSDAY AFTERNOON THROUGH THURSDAY NIGHT. ALL
SOLUTIONS EXCEPT THE NAM ARE GROUPED FAIRLY CLOSE TOGETHER...SO
WILL UPDATED FORECAST TO REFLECT THIS LOW (WHICH IT DOES NOT
PRESENTLY). THE ENTIRE SYSTEM NOW LOOKS LIKE IT WILL REMAIN
FARTHER SOUTH THAN PRIOR GUIDANCE INDICATED...MEANING WINDS OVER
THE NORTHERN GULF/PRINCE WILLIAM SOUND AREA WILL BE A LITTLE
LIGHTER THAN CURRENTLY ADVERTISED.

NUMERICAL GUIDANCE CONTINUES TO STRUGGLE WITH HANDLING OF MULTIPLE
LOWS SOUTH OF THE ALEUTIANS. CURRENT FORECAST SEEMS A FAIR
REPRESENTATION OF THE GENERAL WINDS AND WEATHER EXPECTED.
HOWEVER...THERE MAY BE SOME DIRECTIONAL ISSUES DEPENDING ON WHERE
THE CURRENT LOW ALONG THE ALEUTIANS STALLS OUT. WITH MULTIPLE WEAK
LOWS IN PLACE SOUTH OF THE ALEUTIANS/ALASKA PENINSULA/KODIAK
ISLAND THROUGH THE WEEKEND FORECAST CONFIDENCE IN THIS AREA IS
BELOW AVERAGE. FORECAST CONFIDENCE FARTHER NORTH IS GENERALLY
HIGH.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
IMPACTS OF THE LARGE NORTHEAST PACIFIC LOW WILL INITIALLY REMAIN
DOWN OVER THE GULF AND KODIAK ISLAND. WHEN THE TRIPLE POINT LOW
CROSSES THE GULF THIS AFTERNOON AND TONIGHT THE UPPER RIDGE WILL
BE PUSHED NORTHWARD INTO INTERIOR ALASKA ALLOWING SOME PRECIP TO
MAKE IT UP TO THE NORTH GULF COAST. SOME COMPONENT OF OFFSHORE
FLOW WILL PERSIST IN THE LOW LEVELS SO PRECIP WILL BE LIGHT.

MEANWHILE LOCALIZED OUTFLOW WINDS WILL SET UP THROUGH MAJOR GAPS
TODAY AS PRESSURE GRADIENTS TIGHTEN AND LOW LEVEL FLOW BECOMES
MORE UNIFORMLY OFFSHORE. THE AIR MASS IN THE COPPER RIVER BASIN IS
COLDER THAN THE REST OF SOUTHCENTRAL...BUT THERE REALLY ISN`T MUCH
IN THE WAY OF ADVECTION OF THIS AIR. THUS EXPECT THIS TO BE A WEAK
EVENT.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A COUPLE WEAK UPPER LEVEL WAVES MOVING OVER TOP OF THE LARGE LOW
OVER THE NORTHEAST PACIFIC WILL CROSS SOUTHWEST ALASKA THE NEXT
COUPLE DAYS. THIS WILL BRING A COUPLE QUICK SHOTS OF PRECIP...BUT
WHATEVER DOES FALL WILL BE LIGHT AND BRIEF. WITH THE EXCEPTION OF
THE ALASKA PENINSULA...THE AIR MASS IN PLACE WILL REMAIN COLD
ENOUGH TO SUPPORT SNOW.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE BULK OF ACTIVE WEATHER WILL BE CONFINED TO THE ALEUTIANS AND
ALASKA PENINSULA THE NEXT COUPLE DAYS AS LOWS PASS JUST TO THE
SOUTH. A GENERALLY UNSTABLE AIR MASS OVER THE BERING SEA WILL
CONTINUE TO PRODUCE SOME SHOWERS...BUT NOTHING VERY WELL
ORGANIZED.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
CONFIDENCE IN THE GENERAL EVOLUTION OF THE LARGE SCALE PATTERN AS
WE HEAD INTO THE EARLY TO MIDDLE PART OF NEXT WEEK IS HIGH...WITH
VERY GOOD RUN-TO-RUN CONTINUITY IN NUMERICAL GUIDANCE. CONFIDENCE
IN SOME OF THE SPECIFIC FEATURES IS NOT QUITE AS HIGH...BUT
LATEST SOLUTIONS ARE NOT TERRIBLY DIFFERENT...SO CONFIDENCE IS
GROWING.

AS HAS BEEN ADVERTISED IN PREVIOUS DISCUSSIONS THE SERIES OF LOWS
STRUNG OUT ACROSS THE NORTH PACIFIC AND GULF OF ALASKA THIS
WEEKEND WILL ALL CONSOLIDATE INTO ONE VERY LARGE CYCLONIC
CIRCULATION CENTERED SOMEWHERE OVER THE WESTERN GULF OR NEAR THE
ALASKA PENINSULA BY EARLY NEXT WEEK. AS THE SYSTEMS PROGRESS A
LITTLE FURTHER NORTH THIS WEEKEND WARMER LOW LEVEL AIR WILL MOVE
BACK INTO SOUTHCENTRAL AS WELL AS THE BRISTOL BAY AREA. THEREFORE
THE THREAT OF FREEZING RAIN WILL RETURN ONCE AGAIN...ALTHOUGH THE
BULK OF PRECIP SHOULD REMAIN ALONG THE COAST.

A TRANSITION IN PATTERN WILL COMMENCE NEXT WEEK AS A DEEP TROUGH
MOVES OUT OF ASIA AND INTO THE BERING SEA. A BUILDING RIDGE OUT
AHEAD OF THIS TROUGH WILL HELP PROVIDE A QUICK SHOT OF COLD
ADVECTION DOWNSTREAM OF THE TROUGH...OVER THE BERING SEA THIS
WEEKEND SPREADING TO MAINLAND ALASKA EARLY NEXT WEEK. THERE COULD
EVEN BE A QUICK SHOT OF SNOW OVER SOUTHCENTRAL DEPENDING ON WHAT
HAPPENS TO THE REMNANTS OF THE CONSOLIDATED LOW MENTIONED ABOVE.

THE GFS/ECMWF ARE BOTH DEPICTING DEVELOPMENT OF A DEEP SURFACE LOW
ON THE FRONT EDGE OF THE TROUGH MOVING OUT OF ASIA. ITS HARD TO
SAY EXACTLY HOW DEEP IT WILL BE...BUT WITH A STRONG UPPER LEVEL
JET IN AMPLIFIED FLOW CONDITIONS LOOK FAVORABLE FOR RAPID DEEPENING.
WITH THE DOWNSTREAM RIDGE CONTINUING TO BUILD THE STORM WILL BE
FORCED NORTHWARD ACROSS THE BERING SEA. THIS TRACK IS VERY
IMPORTANT TO THE FORECAST OVER MAINLAND ALASKA BECAUSE IT MEANS
THE BULK OF WARM PACIFIC AIR WILL REMAIN OVER THE BERING SEA.
THEREFORE...AS THE UPPER TROUGH CONTINUES TO PROGRESS EASTWARD TO
MAINLAND ALASKA THE MIDDLE OF NEXT WEEK THE AIR MASS WILL LIKELY
REMAIN COLD ENOUGH TO SUPPORT ALL SNOW OVER INTERIOR SOUTHWEST
ALASKA AND OVER MUCH OF SOUTHCENTRAL ALASKA. IT IS WAY TOO EARLY
TO HAVE MUCH CONFIDENCE IN THIS SINCE DYNAMIC PATTERNS OFTEN
PRODUCE SOME SURPRISES...BUT THERE IS DEFINITELY POTENTIAL FOR
SOME FRESH SNOW ACROSS THE SOUTHERN MAINLAND OF ALASKA IN TIME
FOR CHRISTMAS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING...119 120 127 130 131 132 136 137 138 139
                        150 176 177 178.
HEAVY FREEZING SPRAY WARNING...185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...SEB
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...SEB
LONG TERM...SEB





000
FXAK68 PAFC 181316
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
416 AM AKST THU DEC 18 2014

.ANALYSIS AND UPPER LEVELS...
SATELLITE IMAGERY SHOWS TWO LARGE STORM SYSTEMS IN THE
REGION...BOTH CENTERED OVER THE NORTH PACIFIC WHERE PROGRESSIVE
UPPER LEVEL FLOW DOMINATES. A VERY LARGE AND MATURE STORM FORCE
LOW IS CENTERED SOUTH OF THE GULF OF ALASKA WITH THE OCCLUDED
FRONT SLOWLY LIFTING NORTHWARD BRINGING GALE FORCE WINDS AND RAIN
TO THE GULF AND KODIAK ISLAND. OUT HEAD OF THIS A SHORT-WAVE RIDGE
IS MOVING OVER THE SOUTHERN MAINLAND RESULTING IN QUIET
CONDITIONS. THERE SOME AREAS OF FOG OVER SOUTHCENTRAL...BUT AS
PRESSURE GRADIENTS TIGHTEN WITH THE APPROACHING FRONT AND OFFSHORE
FLOW STRENGTHENS EXPECT MOST OF THIS TO DISSIPATE. MEANWHILE A
200+ KT JET IS DRIVING EASTWARD ACROSS THE NORTHWEST PACIFIC AND
INTO THE NORTH-CENTRAL PACIFIC CAUSING RAPID CYCLOGENESIS WITH A
SERIES OF LOWS STRUNG OUT JUST TO THE SOUTH OF THE BERING SEA AND
ALEUTIANS. THE LOW CLOSEST TO THE WESTERN ALEUTIANS AND ASSOCIATED
OCCLUDED FRONT ARE LIFTING NORTHWARD TOWARD THE ALEUTIANS...SO
GALE FORCE WINDS AND RAIN ARE ON THE WAY.

&&

.MODEL DISCUSSION...MODELS SEEM TO BE CONVERGING ON A COMMON
SOLUTION WITH TRIPLE POINT LOW FORMING OVER THE FAR NORTHEAST
PACIFIC THURSDAY MORNING AND ROTATING WESTWARD ACROSS THE
SOUTHERN GULF THURSDAY AFTERNOON THROUGH THURSDAY NIGHT. ALL
SOLUTIONS EXCEPT THE NAM ARE GROUPED FAIRLY CLOSE TOGETHER...SO
WILL UPDATED FORECAST TO REFLECT THIS LOW (WHICH IT DOES NOT
PRESENTLY). THE ENTIRE SYSTEM NOW LOOKS LIKE IT WILL REMAIN
FARTHER SOUTH THAN PRIOR GUIDANCE INDICATED...MEANING WINDS OVER
THE NORTHERN GULF/PRINCE WILLIAM SOUND AREA WILL BE A LITTLE
LIGHTER THAN CURRENTLY ADVERTISED.

NUMERICAL GUIDANCE CONTINUES TO STRUGGLE WITH HANDLING OF MULTIPLE
LOWS SOUTH OF THE ALEUTIANS. CURRENT FORECAST SEEMS A FAIR
REPRESENTATION OF THE GENERAL WINDS AND WEATHER EXPECTED.
HOWEVER...THERE MAY BE SOME DIRECTIONAL ISSUES DEPENDING ON WHERE
THE CURRENT LOW ALONG THE ALEUTIANS STALLS OUT. WITH MULTIPLE WEAK
LOWS IN PLACE SOUTH OF THE ALEUTIANS/ALASKA PENINSULA/KODIAK
ISLAND THROUGH THE WEEKEND FORECAST CONFIDENCE IN THIS AREA IS
BELOW AVERAGE. FORECAST CONFIDENCE FARTHER NORTH IS GENERALLY
HIGH.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
IMPACTS OF THE LARGE NORTHEAST PACIFIC LOW WILL INITIALLY REMAIN
DOWN OVER THE GULF AND KODIAK ISLAND. WHEN THE TRIPLE POINT LOW
CROSSES THE GULF THIS AFTERNOON AND TONIGHT THE UPPER RIDGE WILL
BE PUSHED NORTHWARD INTO INTERIOR ALASKA ALLOWING SOME PRECIP TO
MAKE IT UP TO THE NORTH GULF COAST. SOME COMPONENT OF OFFSHORE
FLOW WILL PERSIST IN THE LOW LEVELS SO PRECIP WILL BE LIGHT.

MEANWHILE LOCALIZED OUTFLOW WINDS WILL SET UP THROUGH MAJOR GAPS
TODAY AS PRESSURE GRADIENTS TIGHTEN AND LOW LEVEL FLOW BECOMES
MORE UNIFORMLY OFFSHORE. THE AIR MASS IN THE COPPER RIVER BASIN IS
COLDER THAN THE REST OF SOUTHCENTRAL...BUT THERE REALLY ISN`T MUCH
IN THE WAY OF ADVECTION OF THIS AIR. THUS EXPECT THIS TO BE A WEAK
EVENT.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A COUPLE WEAK UPPER LEVEL WAVES MOVING OVER TOP OF THE LARGE LOW
OVER THE NORTHEAST PACIFIC WILL CROSS SOUTHWEST ALASKA THE NEXT
COUPLE DAYS. THIS WILL BRING A COUPLE QUICK SHOTS OF PRECIP...BUT
WHATEVER DOES FALL WILL BE LIGHT AND BRIEF. WITH THE EXCEPTION OF
THE ALASKA PENINSULA...THE AIR MASS IN PLACE WILL REMAIN COLD
ENOUGH TO SUPPORT SNOW.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE BULK OF ACTIVE WEATHER WILL BE CONFINED TO THE ALEUTIANS AND
ALASKA PENINSULA THE NEXT COUPLE DAYS AS LOWS PASS JUST TO THE
SOUTH. A GENERALLY UNSTABLE AIR MASS OVER THE BERING SEA WILL
CONTINUE TO PRODUCE SOME SHOWERS...BUT NOTHING VERY WELL
ORGANIZED.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
CONFIDENCE IN THE GENERAL EVOLUTION OF THE LARGE SCALE PATTERN AS
WE HEAD INTO THE EARLY TO MIDDLE PART OF NEXT WEEK IS HIGH...WITH
VERY GOOD RUN-TO-RUN CONTINUITY. CONFIDENCE IN SOME OF THE
SPECIFICFEATURES INVOLVED IS NOT QUITE AS A HIGH...BUT LATEST
SOLUTIONS ARE NOT TERRIBLY DIFFERENT...SO CONFIDENCE IS GROWING.

AS HAS BEEN ADVERTISED IN PREVIOUS DISCUSSIONS THE SERIES OF LOWS
STRUNG OUT ACROSS THE NORTH PACIFIC AND GULF OF ALASKA THIS
WEEKEND WILL ALL CONSOLIDATE INTO ONE VERY LARGE CYCLONIC
CIRCULATION CENTERED SOMEWHERE OVER THE WESTERN GULF OF ALASKA
PENINSULA BY EARLY NEXT WEEK. AS THE SYSTEMS PROGRESS A LITTLE
FURTHER NORTH THIS WEEKEND WARMER LOW LEVEL AIR WILL MOVE BACK
INTO SOUTHCENTRAL AS WELL AS THE BRISTOL BAY AREA. THEREFORE THE
THREAT OF FREEZING RAIN WILL RETURN ONCE AGAIN...ALTHOUGH THE BULK
OF PRECIP SHOULD REMAIN ALONG THE COAST

A TRANSITION IN PATTERN WILL COMMENCE NEXT WEEK AS A DEEP TROUGH
MOVES OUT OF ASIA AND INTO THE BERING SEA. A BUILDING RIDGE OUT
AHEAD OF THIS TROUGH WILL HELP PROVIDE A QUICK SHOT OF COLD
ADVECTION DOWNSTREAM OF THE TROUGH...OVER THE BERING SEA THIS
WEEKEND SPREADING TO MAINLAND ALASKA EARLY NEXT WEEK. THERE COULD
EVEN BE A QUICK SHOT OF SNOW OVER SOUTHCENTRAL DEPENDING ON WHAT
HAPPENS TO THE REMNANTS OF THE CONSOLIDATED LOW MENTIONED ABOVE.

THE GFS/ECMWF ARE BOTH DEPICTING DEVELOPMENT OF A DEEP SURFACE LOW
ON THE FRONT EDGE OF THE TROUGH MOVING OUT OF ASIA. ITS HARD TO
SAY EXACTLY HOW DEEP IT WILL BE...BUT WITH A STRONG UPPER LEVEL
JET IN AMPLIFIED FLOW CONDITIONS LOOK FAVORABLE FOR A RAPID
DEEPENING. WITH THE DOWNSTREAM RIDGE CONTINUING TO BUILD THE STORM
WILL BE FORCED NORTHWARD ACROSS THE BERING SEA. THIS TRACK IS
VERY IMPORTANT TO THE FORECAST OVER MAINLAND ALASKA BECAUSE IT
MEANS THE BULK OF WARM PACIFIC AIR WILL REMAIN OVER THE BERING
SEA. THEREFORE...AS THE UPPER TROUGH CONTINUES TO PROGRESS
EASTWARD TO MAINLAND ALASKA THE MIDDLE OF NEXT WEEK THE AIR MASS
WILL LIKELY REMAIN COLD ENOUGH TO SUPPORT ALL SNOW OVER INTERIOR
SOUTHWEST ALASKA AND OVER MUCH OF SOUTHCENTRAL ALASKA. IT IS WAY
TOO EARLY TO HAVE MUCH CONFIDENCE IN THIS SINCE DYNAMIC PATTERNS
OFTEN PRODUCE SOME SURPRISES...BUT THERE IS DEFINITELY SOME
POTENTIAL FOR SOME FRESH SNOW ACROSS THE SOUTHERN MAINLAND OF
ALASKA IN TIME FOR CHRISTMAS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING...119 120 127 130 131 132 136 137 138 139
                        150 176 177 178.
HEAVY FREEZING SPRAY WARNING...185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...SEB
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...SEB
LONG TERM...SEB




000
FXAK68 PAFC 181316
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
416 AM AKST THU DEC 18 2014

.ANALYSIS AND UPPER LEVELS...
SATELLITE IMAGERY SHOWS TWO LARGE STORM SYSTEMS IN THE
REGION...BOTH CENTERED OVER THE NORTH PACIFIC WHERE PROGRESSIVE
UPPER LEVEL FLOW DOMINATES. A VERY LARGE AND MATURE STORM FORCE
LOW IS CENTERED SOUTH OF THE GULF OF ALASKA WITH THE OCCLUDED
FRONT SLOWLY LIFTING NORTHWARD BRINGING GALE FORCE WINDS AND RAIN
TO THE GULF AND KODIAK ISLAND. OUT HEAD OF THIS A SHORT-WAVE RIDGE
IS MOVING OVER THE SOUTHERN MAINLAND RESULTING IN QUIET
CONDITIONS. THERE SOME AREAS OF FOG OVER SOUTHCENTRAL...BUT AS
PRESSURE GRADIENTS TIGHTEN WITH THE APPROACHING FRONT AND OFFSHORE
FLOW STRENGTHENS EXPECT MOST OF THIS TO DISSIPATE. MEANWHILE A
200+ KT JET IS DRIVING EASTWARD ACROSS THE NORTHWEST PACIFIC AND
INTO THE NORTH-CENTRAL PACIFIC CAUSING RAPID CYCLOGENESIS WITH A
SERIES OF LOWS STRUNG OUT JUST TO THE SOUTH OF THE BERING SEA AND
ALEUTIANS. THE LOW CLOSEST TO THE WESTERN ALEUTIANS AND ASSOCIATED
OCCLUDED FRONT ARE LIFTING NORTHWARD TOWARD THE ALEUTIANS...SO
GALE FORCE WINDS AND RAIN ARE ON THE WAY.

&&

.MODEL DISCUSSION...MODELS SEEM TO BE CONVERGING ON A COMMON
SOLUTION WITH TRIPLE POINT LOW FORMING OVER THE FAR NORTHEAST
PACIFIC THURSDAY MORNING AND ROTATING WESTWARD ACROSS THE
SOUTHERN GULF THURSDAY AFTERNOON THROUGH THURSDAY NIGHT. ALL
SOLUTIONS EXCEPT THE NAM ARE GROUPED FAIRLY CLOSE TOGETHER...SO
WILL UPDATED FORECAST TO REFLECT THIS LOW (WHICH IT DOES NOT
PRESENTLY). THE ENTIRE SYSTEM NOW LOOKS LIKE IT WILL REMAIN
FARTHER SOUTH THAN PRIOR GUIDANCE INDICATED...MEANING WINDS OVER
THE NORTHERN GULF/PRINCE WILLIAM SOUND AREA WILL BE A LITTLE
LIGHTER THAN CURRENTLY ADVERTISED.

NUMERICAL GUIDANCE CONTINUES TO STRUGGLE WITH HANDLING OF MULTIPLE
LOWS SOUTH OF THE ALEUTIANS. CURRENT FORECAST SEEMS A FAIR
REPRESENTATION OF THE GENERAL WINDS AND WEATHER EXPECTED.
HOWEVER...THERE MAY BE SOME DIRECTIONAL ISSUES DEPENDING ON WHERE
THE CURRENT LOW ALONG THE ALEUTIANS STALLS OUT. WITH MULTIPLE WEAK
LOWS IN PLACE SOUTH OF THE ALEUTIANS/ALASKA PENINSULA/KODIAK
ISLAND THROUGH THE WEEKEND FORECAST CONFIDENCE IN THIS AREA IS
BELOW AVERAGE. FORECAST CONFIDENCE FARTHER NORTH IS GENERALLY
HIGH.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
IMPACTS OF THE LARGE NORTHEAST PACIFIC LOW WILL INITIALLY REMAIN
DOWN OVER THE GULF AND KODIAK ISLAND. WHEN THE TRIPLE POINT LOW
CROSSES THE GULF THIS AFTERNOON AND TONIGHT THE UPPER RIDGE WILL
BE PUSHED NORTHWARD INTO INTERIOR ALASKA ALLOWING SOME PRECIP TO
MAKE IT UP TO THE NORTH GULF COAST. SOME COMPONENT OF OFFSHORE
FLOW WILL PERSIST IN THE LOW LEVELS SO PRECIP WILL BE LIGHT.

MEANWHILE LOCALIZED OUTFLOW WINDS WILL SET UP THROUGH MAJOR GAPS
TODAY AS PRESSURE GRADIENTS TIGHTEN AND LOW LEVEL FLOW BECOMES
MORE UNIFORMLY OFFSHORE. THE AIR MASS IN THE COPPER RIVER BASIN IS
COLDER THAN THE REST OF SOUTHCENTRAL...BUT THERE REALLY ISN`T MUCH
IN THE WAY OF ADVECTION OF THIS AIR. THUS EXPECT THIS TO BE A WEAK
EVENT.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A COUPLE WEAK UPPER LEVEL WAVES MOVING OVER TOP OF THE LARGE LOW
OVER THE NORTHEAST PACIFIC WILL CROSS SOUTHWEST ALASKA THE NEXT
COUPLE DAYS. THIS WILL BRING A COUPLE QUICK SHOTS OF PRECIP...BUT
WHATEVER DOES FALL WILL BE LIGHT AND BRIEF. WITH THE EXCEPTION OF
THE ALASKA PENINSULA...THE AIR MASS IN PLACE WILL REMAIN COLD
ENOUGH TO SUPPORT SNOW.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE BULK OF ACTIVE WEATHER WILL BE CONFINED TO THE ALEUTIANS AND
ALASKA PENINSULA THE NEXT COUPLE DAYS AS LOWS PASS JUST TO THE
SOUTH. A GENERALLY UNSTABLE AIR MASS OVER THE BERING SEA WILL
CONTINUE TO PRODUCE SOME SHOWERS...BUT NOTHING VERY WELL
ORGANIZED.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
CONFIDENCE IN THE GENERAL EVOLUTION OF THE LARGE SCALE PATTERN AS
WE HEAD INTO THE EARLY TO MIDDLE PART OF NEXT WEEK IS HIGH...WITH
VERY GOOD RUN-TO-RUN CONTINUITY. CONFIDENCE IN SOME OF THE
SPECIFICFEATURES INVOLVED IS NOT QUITE AS A HIGH...BUT LATEST
SOLUTIONS ARE NOT TERRIBLY DIFFERENT...SO CONFIDENCE IS GROWING.

AS HAS BEEN ADVERTISED IN PREVIOUS DISCUSSIONS THE SERIES OF LOWS
STRUNG OUT ACROSS THE NORTH PACIFIC AND GULF OF ALASKA THIS
WEEKEND WILL ALL CONSOLIDATE INTO ONE VERY LARGE CYCLONIC
CIRCULATION CENTERED SOMEWHERE OVER THE WESTERN GULF OF ALASKA
PENINSULA BY EARLY NEXT WEEK. AS THE SYSTEMS PROGRESS A LITTLE
FURTHER NORTH THIS WEEKEND WARMER LOW LEVEL AIR WILL MOVE BACK
INTO SOUTHCENTRAL AS WELL AS THE BRISTOL BAY AREA. THEREFORE THE
THREAT OF FREEZING RAIN WILL RETURN ONCE AGAIN...ALTHOUGH THE BULK
OF PRECIP SHOULD REMAIN ALONG THE COAST

A TRANSITION IN PATTERN WILL COMMENCE NEXT WEEK AS A DEEP TROUGH
MOVES OUT OF ASIA AND INTO THE BERING SEA. A BUILDING RIDGE OUT
AHEAD OF THIS TROUGH WILL HELP PROVIDE A QUICK SHOT OF COLD
ADVECTION DOWNSTREAM OF THE TROUGH...OVER THE BERING SEA THIS
WEEKEND SPREADING TO MAINLAND ALASKA EARLY NEXT WEEK. THERE COULD
EVEN BE A QUICK SHOT OF SNOW OVER SOUTHCENTRAL DEPENDING ON WHAT
HAPPENS TO THE REMNANTS OF THE CONSOLIDATED LOW MENTIONED ABOVE.

THE GFS/ECMWF ARE BOTH DEPICTING DEVELOPMENT OF A DEEP SURFACE LOW
ON THE FRONT EDGE OF THE TROUGH MOVING OUT OF ASIA. ITS HARD TO
SAY EXACTLY HOW DEEP IT WILL BE...BUT WITH A STRONG UPPER LEVEL
JET IN AMPLIFIED FLOW CONDITIONS LOOK FAVORABLE FOR A RAPID
DEEPENING. WITH THE DOWNSTREAM RIDGE CONTINUING TO BUILD THE STORM
WILL BE FORCED NORTHWARD ACROSS THE BERING SEA. THIS TRACK IS
VERY IMPORTANT TO THE FORECAST OVER MAINLAND ALASKA BECAUSE IT
MEANS THE BULK OF WARM PACIFIC AIR WILL REMAIN OVER THE BERING
SEA. THEREFORE...AS THE UPPER TROUGH CONTINUES TO PROGRESS
EASTWARD TO MAINLAND ALASKA THE MIDDLE OF NEXT WEEK THE AIR MASS
WILL LIKELY REMAIN COLD ENOUGH TO SUPPORT ALL SNOW OVER INTERIOR
SOUTHWEST ALASKA AND OVER MUCH OF SOUTHCENTRAL ALASKA. IT IS WAY
TOO EARLY TO HAVE MUCH CONFIDENCE IN THIS SINCE DYNAMIC PATTERNS
OFTEN PRODUCE SOME SURPRISES...BUT THERE IS DEFINITELY SOME
POTENTIAL FOR SOME FRESH SNOW ACROSS THE SOUTHERN MAINLAND OF
ALASKA IN TIME FOR CHRISTMAS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING...119 120 127 130 131 132 136 137 138 139
                        150 176 177 178.
HEAVY FREEZING SPRAY WARNING...185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...SEB
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...SEB
LONG TERM...SEB





000
FXAK68 PAFC 181316
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
416 AM AKST THU DEC 18 2014

.ANALYSIS AND UPPER LEVELS...
SATELLITE IMAGERY SHOWS TWO LARGE STORM SYSTEMS IN THE
REGION...BOTH CENTERED OVER THE NORTH PACIFIC WHERE PROGRESSIVE
UPPER LEVEL FLOW DOMINATES. A VERY LARGE AND MATURE STORM FORCE
LOW IS CENTERED SOUTH OF THE GULF OF ALASKA WITH THE OCCLUDED
FRONT SLOWLY LIFTING NORTHWARD BRINGING GALE FORCE WINDS AND RAIN
TO THE GULF AND KODIAK ISLAND. OUT HEAD OF THIS A SHORT-WAVE RIDGE
IS MOVING OVER THE SOUTHERN MAINLAND RESULTING IN QUIET
CONDITIONS. THERE SOME AREAS OF FOG OVER SOUTHCENTRAL...BUT AS
PRESSURE GRADIENTS TIGHTEN WITH THE APPROACHING FRONT AND OFFSHORE
FLOW STRENGTHENS EXPECT MOST OF THIS TO DISSIPATE. MEANWHILE A
200+ KT JET IS DRIVING EASTWARD ACROSS THE NORTHWEST PACIFIC AND
INTO THE NORTH-CENTRAL PACIFIC CAUSING RAPID CYCLOGENESIS WITH A
SERIES OF LOWS STRUNG OUT JUST TO THE SOUTH OF THE BERING SEA AND
ALEUTIANS. THE LOW CLOSEST TO THE WESTERN ALEUTIANS AND ASSOCIATED
OCCLUDED FRONT ARE LIFTING NORTHWARD TOWARD THE ALEUTIANS...SO
GALE FORCE WINDS AND RAIN ARE ON THE WAY.

&&

.MODEL DISCUSSION...MODELS SEEM TO BE CONVERGING ON A COMMON
SOLUTION WITH TRIPLE POINT LOW FORMING OVER THE FAR NORTHEAST
PACIFIC THURSDAY MORNING AND ROTATING WESTWARD ACROSS THE
SOUTHERN GULF THURSDAY AFTERNOON THROUGH THURSDAY NIGHT. ALL
SOLUTIONS EXCEPT THE NAM ARE GROUPED FAIRLY CLOSE TOGETHER...SO
WILL UPDATED FORECAST TO REFLECT THIS LOW (WHICH IT DOES NOT
PRESENTLY). THE ENTIRE SYSTEM NOW LOOKS LIKE IT WILL REMAIN
FARTHER SOUTH THAN PRIOR GUIDANCE INDICATED...MEANING WINDS OVER
THE NORTHERN GULF/PRINCE WILLIAM SOUND AREA WILL BE A LITTLE
LIGHTER THAN CURRENTLY ADVERTISED.

NUMERICAL GUIDANCE CONTINUES TO STRUGGLE WITH HANDLING OF MULTIPLE
LOWS SOUTH OF THE ALEUTIANS. CURRENT FORECAST SEEMS A FAIR
REPRESENTATION OF THE GENERAL WINDS AND WEATHER EXPECTED.
HOWEVER...THERE MAY BE SOME DIRECTIONAL ISSUES DEPENDING ON WHERE
THE CURRENT LOW ALONG THE ALEUTIANS STALLS OUT. WITH MULTIPLE WEAK
LOWS IN PLACE SOUTH OF THE ALEUTIANS/ALASKA PENINSULA/KODIAK
ISLAND THROUGH THE WEEKEND FORECAST CONFIDENCE IN THIS AREA IS
BELOW AVERAGE. FORECAST CONFIDENCE FARTHER NORTH IS GENERALLY
HIGH.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
IMPACTS OF THE LARGE NORTHEAST PACIFIC LOW WILL INITIALLY REMAIN
DOWN OVER THE GULF AND KODIAK ISLAND. WHEN THE TRIPLE POINT LOW
CROSSES THE GULF THIS AFTERNOON AND TONIGHT THE UPPER RIDGE WILL
BE PUSHED NORTHWARD INTO INTERIOR ALASKA ALLOWING SOME PRECIP TO
MAKE IT UP TO THE NORTH GULF COAST. SOME COMPONENT OF OFFSHORE
FLOW WILL PERSIST IN THE LOW LEVELS SO PRECIP WILL BE LIGHT.

MEANWHILE LOCALIZED OUTFLOW WINDS WILL SET UP THROUGH MAJOR GAPS
TODAY AS PRESSURE GRADIENTS TIGHTEN AND LOW LEVEL FLOW BECOMES
MORE UNIFORMLY OFFSHORE. THE AIR MASS IN THE COPPER RIVER BASIN IS
COLDER THAN THE REST OF SOUTHCENTRAL...BUT THERE REALLY ISN`T MUCH
IN THE WAY OF ADVECTION OF THIS AIR. THUS EXPECT THIS TO BE A WEAK
EVENT.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A COUPLE WEAK UPPER LEVEL WAVES MOVING OVER TOP OF THE LARGE LOW
OVER THE NORTHEAST PACIFIC WILL CROSS SOUTHWEST ALASKA THE NEXT
COUPLE DAYS. THIS WILL BRING A COUPLE QUICK SHOTS OF PRECIP...BUT
WHATEVER DOES FALL WILL BE LIGHT AND BRIEF. WITH THE EXCEPTION OF
THE ALASKA PENINSULA...THE AIR MASS IN PLACE WILL REMAIN COLD
ENOUGH TO SUPPORT SNOW.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE BULK OF ACTIVE WEATHER WILL BE CONFINED TO THE ALEUTIANS AND
ALASKA PENINSULA THE NEXT COUPLE DAYS AS LOWS PASS JUST TO THE
SOUTH. A GENERALLY UNSTABLE AIR MASS OVER THE BERING SEA WILL
CONTINUE TO PRODUCE SOME SHOWERS...BUT NOTHING VERY WELL
ORGANIZED.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
CONFIDENCE IN THE GENERAL EVOLUTION OF THE LARGE SCALE PATTERN AS
WE HEAD INTO THE EARLY TO MIDDLE PART OF NEXT WEEK IS HIGH...WITH
VERY GOOD RUN-TO-RUN CONTINUITY. CONFIDENCE IN SOME OF THE
SPECIFICFEATURES INVOLVED IS NOT QUITE AS A HIGH...BUT LATEST
SOLUTIONS ARE NOT TERRIBLY DIFFERENT...SO CONFIDENCE IS GROWING.

AS HAS BEEN ADVERTISED IN PREVIOUS DISCUSSIONS THE SERIES OF LOWS
STRUNG OUT ACROSS THE NORTH PACIFIC AND GULF OF ALASKA THIS
WEEKEND WILL ALL CONSOLIDATE INTO ONE VERY LARGE CYCLONIC
CIRCULATION CENTERED SOMEWHERE OVER THE WESTERN GULF OF ALASKA
PENINSULA BY EARLY NEXT WEEK. AS THE SYSTEMS PROGRESS A LITTLE
FURTHER NORTH THIS WEEKEND WARMER LOW LEVEL AIR WILL MOVE BACK
INTO SOUTHCENTRAL AS WELL AS THE BRISTOL BAY AREA. THEREFORE THE
THREAT OF FREEZING RAIN WILL RETURN ONCE AGAIN...ALTHOUGH THE BULK
OF PRECIP SHOULD REMAIN ALONG THE COAST

A TRANSITION IN PATTERN WILL COMMENCE NEXT WEEK AS A DEEP TROUGH
MOVES OUT OF ASIA AND INTO THE BERING SEA. A BUILDING RIDGE OUT
AHEAD OF THIS TROUGH WILL HELP PROVIDE A QUICK SHOT OF COLD
ADVECTION DOWNSTREAM OF THE TROUGH...OVER THE BERING SEA THIS
WEEKEND SPREADING TO MAINLAND ALASKA EARLY NEXT WEEK. THERE COULD
EVEN BE A QUICK SHOT OF SNOW OVER SOUTHCENTRAL DEPENDING ON WHAT
HAPPENS TO THE REMNANTS OF THE CONSOLIDATED LOW MENTIONED ABOVE.

THE GFS/ECMWF ARE BOTH DEPICTING DEVELOPMENT OF A DEEP SURFACE LOW
ON THE FRONT EDGE OF THE TROUGH MOVING OUT OF ASIA. ITS HARD TO
SAY EXACTLY HOW DEEP IT WILL BE...BUT WITH A STRONG UPPER LEVEL
JET IN AMPLIFIED FLOW CONDITIONS LOOK FAVORABLE FOR A RAPID
DEEPENING. WITH THE DOWNSTREAM RIDGE CONTINUING TO BUILD THE STORM
WILL BE FORCED NORTHWARD ACROSS THE BERING SEA. THIS TRACK IS
VERY IMPORTANT TO THE FORECAST OVER MAINLAND ALASKA BECAUSE IT
MEANS THE BULK OF WARM PACIFIC AIR WILL REMAIN OVER THE BERING
SEA. THEREFORE...AS THE UPPER TROUGH CONTINUES TO PROGRESS
EASTWARD TO MAINLAND ALASKA THE MIDDLE OF NEXT WEEK THE AIR MASS
WILL LIKELY REMAIN COLD ENOUGH TO SUPPORT ALL SNOW OVER INTERIOR
SOUTHWEST ALASKA AND OVER MUCH OF SOUTHCENTRAL ALASKA. IT IS WAY
TOO EARLY TO HAVE MUCH CONFIDENCE IN THIS SINCE DYNAMIC PATTERNS
OFTEN PRODUCE SOME SURPRISES...BUT THERE IS DEFINITELY SOME
POTENTIAL FOR SOME FRESH SNOW ACROSS THE SOUTHERN MAINLAND OF
ALASKA IN TIME FOR CHRISTMAS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING...119 120 127 130 131 132 136 137 138 139
                        150 176 177 178.
HEAVY FREEZING SPRAY WARNING...185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...SEB
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...SEB
LONG TERM...SEB





000
FXAK68 PAFC 180036
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
336 PM AKST WED DEC 17 2014

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LEVEL LOW IN THE SOUTHWEST GULF OF ALASKA. THERE
IS ANOTHER LOW OVER THE NORTHERN BERING SEA. THERE IS A LOW
CENTERED SOUTH OF THE KAMCHATKA PENINSULA...AND ASSOCIATED WITH IT
IS A 200 KT JET AT AROUND 35 TO 40 DEGREES NORTH LATITUDE POKING
INTO THE MID PACIFIC (AROUND 170 DEGREES EAST LONGITUDE). THERE IS
AN UPPER LEVEL RIDGE BEGINNING TO BUILD OVER SOUTHERN ALASKA.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE NOT IN VERY GOOD AGREEMENT TODAY. THEY
QUICKLY BEGIN TO DIVERGE ON SOLUTIONS FOR A COMPLEX LOW SOUTH OF
THE ALEUTIANS (24 TO 36 HOURS INTO THE FORECAST) AND ALSO WITH THE
LOW IN THE GULF OF ALASKA AS IT BECOMES COMPLEX. SOME OF THE
MODELS STRUGGLES PROBABLY ARE RELATED TO THE 200 KT JET...WHERE
SMALL PERTURBATIONS IN THE FLOW CAN QUICKLY DEVELOP INTO LARGE
DIFFERENCES. THEREFORE FORECAST CONFIDENCE IS BELOW NORMAL TODAY.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3)...
THERE IS A WEAK FRONT OVER SOUTH CENTRAL ALASKA THAT WILL
DISSIPATE TONIGHT AS RIDGING BUILDS AHEAD OF THE LOW APPROACHING
FROM THE SOUTHWEST. THIS LOW (CURRENTLY OVER THE SOUTHWEST GULF)
WILL PUSH EAST INTO THE SOUTH CENTRAL GULF TONIGHT...TURN
NORTHWARD ON THURSDAY...THEN PUSH WESTWARD TO THE WESTERN
GULF/ALASKA PENINSULA WHERE IT WILL SETTLE IN THROUGH SATURDAY. A
STRONG FRONT ASSOCIATED WITH THIS LOW WILL PUSH INTO THE NORTH
GULF TONIGHT THEN STALL OFF THE GULF COAST. THIS IS WHERE THE
MODELS BEGIN TO DISAGREE...BUT ESSENTIALLY A TRIPLE POINT LOW WILL
FORM ON THE FRONT THURSDAY NIGHT THEN MOVE NORTHWARD THROUGH
FRIDAY. FOR FRIDAY NIGHT AND SATURDAY...VARIOUS SURFACE LOW
CENTERS WILL BE SPINNING AROUND THE MAIN UPPER LOW.


&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE REMAINDER OF TODAY WILL BE FAIRLY QUIET ACROSS THE MAINLAND AS
THE AREA REMAINS BETWEEN WEATHER SYSTEMS. HIGHER CLOUDS WILL
CONTINUE TO STREAM OVERHEAD FROM THE SOUTH TONIGHT AS A FRONTAL
BOUNDARY SWINGS UP TOWARD THE ALASKA PENINSULA ASSOCIATED WITH A
LOW PRESSURE SYSTEM IN THE NORTH PACIFIC. SOME WEAK DISTURBANCES
IN THE FLOW COULD BRING AREAS OF RAIN MIXED WITH SNOW TO MAINLY
SOUTHERN AREAS OF INTERIOR BRISTOL BAY ALONG WITH NORTHERLY WINDS
OF 10 TO 20 MPH. TEMPERATURES WILL CONTINUE TO RUN ABOVE NORMAL
WITHOUT A DEEP ARCTIC AIR MASS IN THE INTERIOR. THE PATTERN HOLDS
THROUGH FRIDAY WITH ANY POTENTIAL PRECIPITATION CHANCES STAYING
IN INTERIOR BRISTOL BAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE BERING SEA ALSO CURRENTLY SITS BETWEEN THREE SYSTEMS. A
FRONTAL BOUNDARY CLOSE TO THE ALASKA PENINSULA WILL KEEP RAIN
SHOWERS IN THE FORECAST...BUT CLOUD COVER SHOULD BE ON THE
DECREASE TONIGHT. MOST OF THE BERING SEA SITS UNDER AN UNSTABLE
SHOWERY REGIME LEFT OVER BY THE LAST SYSTEM. THESE CONDITIONS
WILL TAPER TONIGHT AS A NEW FRONT FORMS SOUTH OF THE CHAIN
BRINGING AN INCREASE IN EASTERLY WINDS AND SNOW.

&&

.LONG TERM FORECAST (DAYS 4 THROUGH 7)...
THE MAIN STORY IS THAT THE UPPER LEVEL PATTERN WILL BECOME MORE
PROGRESSIVE NEXT WEEK. THE LOW OVER THE WESTERN GULF/ALASKA
PENINSULA WILL BE PUSHED EASTWARD ON SUNDAY AND MONDAY AS A LARGE
UPPER LOW DEVELOPS OVER THE WESTERN BERING SEA. STRONG WESTERLY
FLOW ALOFT WILL PROGRESSIVELY PUSH EAST UNTIL ALL OF THE BERING
SEA AND SOUTHERN ALASKA ARE INVOLVED BY WEDNESDAY NIGHT. THE WPC
FORECAST FAVORS THE 00Z ECMWF AND 00Z ECMWF ENSEMBLE MEAN...WITH
SOME 12Z GFS SPRINKLED IN.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES...119 120 127 130-132 138 139 150 175-178
FIRE WEATHER...NONE.

&&

$$




000
FXAK68 PAFC 171311
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
411 AM AKST WED DEC 17 2014

.ANALYSIS AND UPPER LEVELS...
ALASKA REMAINS FIRMLY ENTRENCHED WITHIN A LONG-WAVE TROUGH. A
CLOSED LOW IS NEARLY STATIONARY OVER THE NORTH CENTRAL BERING SEA
WHILE A STRONG AMPLIFIED SUBTROPICAL JET IS PRODUCING AN ACTIVE
STORM TRACK ACROSS THE NORTH PACIFIC. THE STORM TRACK CURVES
NORTHWARD AS IT REACHES THE EAST PACIFIC THANKS TO A STRONG
BLOCKING RIDGE DOWNSTREAM OVER WESTERN CANADA. SATELLITE IMAGERY
SHOWS A LARGE INTENSE STORM SOUTH OF THE EASTERN ALEUTIANS AND
ALASKA PENINSULA JUST BEGINNING TO CURVE NORTHEASTWARD.
SCATTEROMETER DATA SHOWS A LARGE AREA OF STORM FORCE WINDS WITH
THIS LOW...BUT IT IS TOO FAR SOUTH TO HAVE MUCH IMPACT ON ALASKA.
MEANWHILE ANOTHER LARGE AND DEEP STORM SYSTEM IS MAKING ITS WAY
ACROSS THE FAR NORTHWEST PACIFIC.

WITH WEAK FEATURES NORTH OF THE SUBTROPICAL JET THE WEATHER
ACROSS ALASKA IS GENERALLY ON THE QUIET SIDE. A SERIES OF WEAK
UPPER LEVEL SHORT-WAVE TROUGHS ARE LIFTING NORTHWARD ACROSS THE
GULF AND SOUTHCENTRAL. PRECIPITATION IS GENERALLY ON THE LIGHT
SIDE...ALTHOUGH LOW TO MID-LEVEL INSTABILITY IS PRODUCING SOME
LOCALIZED HEAVY SHOWERS. A LOW LEVEL ABOVE FREEZING WARM NOSE
PERSISTS FROM THE WESTERN KENAI PENINSULA TO ANCHORAGE AND PARTS
OF THE MATANUSKA VALLEY...ALTHOUGH THE 00Z SOUNDING FROM ANCHORAGE
SHOWS THE WET BULB DOWN IS NOW DOWN AROUND ZERO. THEREFORE...IF
ENOUGH QPF FALLS INTO THE ABOVE FREEZING LAYER PRECIP WILL QUICKLY
CHANGE TO ALL SNOW AND THERE MAY BE SOME VERY LIGHT ACCUMULATION.
ON THE OTHER HAND...IF PRECIP REMAINS LIGHT THEN IT WILL TAKE
LONGER TO CHANGE TO ALL SNOW AND THERE LIKELY WILL NOT BE ANY
SNOW ACCUMULATION.

&&

.MODEL DISCUSSION...
MODELS CONTINUE TO STRUGGLE WITH SMALL SCALE FEATURES MOVING
THROUGH SOUTHCENTRAL CREATING A CHALLENGING PRECIPITATION FORECAST
FOR THE REMAINDER OF TONIGHT THROUGH WEDNESDAY MORNING. WILL MAKE
HEAVY USE OF RADAR AND SATELLITE TRENDS FOR THE EARLY PORTION OF
THE FORECAST.

THERE IS INITIALLY EXCELLENT AGREEMENT WITH STRONG PACIFIC LOW
TRACKING TOWARD GULF...BUT RAPIDLY DIVERGE LATE THURSDAY WITH
SHORT-WAVE ROUNDING THE LOW AND FORMING A SECONDARY LOW. ECMWF
SHOWS SOME RUN-TO-RUN CONSISTENCY AND IS A NICE MIDDLE GROUND
SOLUTION. WILL TREND FORECAST THAT DIRECTION RECOGNIZING THERE IS
A LARGE DROP OFF IN FORECAST CONFIDENCE BEGINNING THURSDAY NIGHT.

MEANWHILE...MODELS ARE REALLY STRUGGLING WITH SYSTEMS SOUTH OF
THE ALEUTIANS BEGINNING WEDNESDAY NIGHT. WITH A 200+ KNOT
SUBTROPICAL JET POISED TO CROSS THE NORTH PACIFIC THIS IS A
FAVORABLE ENVIRONMENT FOR RAPID CYCLOGENESIS...WITH LOWS FORMING
IN SUCCESSION AS THE JET HEADS EASTWARD. A DYNAMIC SITUATION SUCH
AS THIS IS HARD FOR THE NUMERICAL GUIDANCE TO CAPTURE. THERE IS A
TREND IN THE LATEST SOLUTIONS TOWARD BRINGING PRECIP AND GALE
FORCE WINDS FARTHER NORTH. WILL APPLY THIS TREND TO THE FORECAST.
DUE TO THE COMPLEXITY OF THE SITUATION FORECAST CONFIDENCE ALONG
THE ALEUTIANS IS BELOW AVERAGE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE LAST OF A SERIES OF WEAK UPPER LEVEL SHORT-WAVES WILL EXIT TO
THE NORTH TODAY WHILE A SHORT-WAVE RIDGE BUILDS IN AHEAD OF THE
STRONG PACIFIC STORM SYSTEM. THUS...EXPECT PRECIPITATION TO
TAPER OFF FOR ALL BUT THE GULF COAST WHERE CONTINUE LOW LEVEL
INSTABILITY WILL KEEP A FEW SHOWERS AROUND. LOW LEVEL FLOW WILL
SHIFT AROUND TO THE NORTH WEDNESDAY NIGHT AND THURSDAY AS THE
STORM MAKES ITS WAY TOWARD THE GULF....WHICH SHOULD PREVENT ANY
WIDESPREAD FOG PROBLEMS. WITH DECREASING CLOUDS TEMPERATURES WILL
SLOWLY RETURN TO SOMEWHERE CLOSER TO SEASONAL NORMALS. WITH THE
STORM REMAINING WELL TO THE SOUTH PRECIP AND WINDS WILL BE
CONFINED TO THE GULF COAST WHILE INLAND AREAS WILL STAY DRY.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
SOUTHWEST ALASKA WILL REMAIN ON THE OUTER PERIPHERY OF MAJOR
FEATURES. THUS WEATHER WILL REMAIN QUITE BENIGN OVER THE NEXT
COUPLE DAYS WITH JUTS A FEW PASSING SHOWERS. THERE ARE SOME AREAS
OF FOG OUT THERE RIGHT NOW...BUT DRY LOW LEVEL OFFSHORE FLOW WILL
DEVELOP THIS AFTERNOON AND EVENING WHICH SHOULD HELP ERODE MOST
IF NOT ALL OF THE FOG.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE ALEUTIANS WILL BE ON THE NORTH END OF STRONG STORMS TRACKING
ACROSS THE NORTH PACIFIC. THUS...EXPECT OCCASIONAL WINDY AND RAINY
CONDITIONS. OTHERWISE RELATIVELY BENIGN CONDITIONS WILL PERSIST
ACROSS THE BERING SEA.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
ALTHOUGH THERE ARE SOME DIFFERENCES WITH HANDLING OF PARTICULAR
STORM SYSTEMS IN THE FRIDAY THROUGH TUESDAY TIME PERIOD NUMERICAL
GUIDANCE IS IN GOOD AGREEMENT ON THE EVOLUTION OF THE LARGE SCALE
PATTERN. THE UPPER FLOW WILL UNDERGO AMPLIFICATION LATE THIS WEEK
THROUGH THE WEEKEND AS A TROUGH DIGS OUT OF ASIA CAUSING A RIDGE
TO BUILD OVER THE WESTERN BERING. THIS WILL THEN CAUSE DOWNSTREAM
TROUGH TO AMPLIFY...WITH LOWS CONSOLIDATING INTO A SINGLE LOW
SOMEWHERE OVER THE WESTERN GULF OR BRISTOL BAY AREAS. THUS...THERE
WILL BE A SHIFT FROM SYSTEMS MOVING RAPIDLY FROM WEST TO EAST
ACROSS THE NORTH PACIFIC AND INTO THE GULF TO A MORE STAGNANT
PATTERN WITH ONE LARGE CYCLONIC CIRCULATION DOMINATING THE
WEATHER. PRIOR TO AND DURING THE CHANGE IN PATTERN ACTIVE WEATHER
WILL BE FOCUSED ALONG THE SOUTHERN TIER OF THE FORECAST
AREA...ALONG THE ALEUTIANS AND ALASKA PENINSULA AND INTO THE GULF
OF ALASKA. THE BERING SEA AND MUCH OF SOUTHWEST AND SOUTHCENTRAL
ALASKA WILL REMAIN ON THE DRY SIDE...WITH JUST AN OCCASIONAL
CHANCE OF PRECIP AS UPPER WAVES MOVE THROUGH. LOW LEVEL WARM AIR
WILL CONTINUE TO PENETRATE SOUTHCENTRAL ALASKA AND PORTIONS OF
SOUTHWEST ALASKA...SO TEMPERATURES WILL GENERALLY REMAIN ABOVE
NORMAL AND THERE WILL BE A THREAT OF FREEZING RAIN IF ANY PRECIP
DOES MAKE IT INLAND.

LOOKING OUT TO EARLY NEXT WEEK MORE SIGNIFICANT CHANGES ARE LIKELY
AS THE UPPER LEVEL WAVES PROGRESS EASTWARD...WITH THE HIGHLY
AMPLIFIED TROUGH WHICH MOVES OUT OF ASIA HEADING INTO THE BERING
SEA MONDAY AND TUESDAY. CONDITIONS WILL BE EXTREMELY FAVORABLE FOR
DEVELOPMENT OF DEEP SURFACE LOWS. THUS EXPECT MUCH MORE ACTIVE
WINTER-LIKE WEATHER TO RETURN TO THE BERING SEA AND
ALEUTIANS...AND MOST LIKELY SOUTHWEST AND SOUTHCENTRAL ALASKA BY
NEXT WEDNESDAY AND THURSDAY.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING...119 120 127 130 131 132 136 137 138 139
                        150 155 175 176 177 178 185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...SEB
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...SEB
LONG TERM...SEB





000
FXAK68 PAFC 171311
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
411 AM AKST WED DEC 17 2014

.ANALYSIS AND UPPER LEVELS...
ALASKA REMAINS FIRMLY ENTRENCHED WITHIN A LONG-WAVE TROUGH. A
CLOSED LOW IS NEARLY STATIONARY OVER THE NORTH CENTRAL BERING SEA
WHILE A STRONG AMPLIFIED SUBTROPICAL JET IS PRODUCING AN ACTIVE
STORM TRACK ACROSS THE NORTH PACIFIC. THE STORM TRACK CURVES
NORTHWARD AS IT REACHES THE EAST PACIFIC THANKS TO A STRONG
BLOCKING RIDGE DOWNSTREAM OVER WESTERN CANADA. SATELLITE IMAGERY
SHOWS A LARGE INTENSE STORM SOUTH OF THE EASTERN ALEUTIANS AND
ALASKA PENINSULA JUST BEGINNING TO CURVE NORTHEASTWARD.
SCATTEROMETER DATA SHOWS A LARGE AREA OF STORM FORCE WINDS WITH
THIS LOW...BUT IT IS TOO FAR SOUTH TO HAVE MUCH IMPACT ON ALASKA.
MEANWHILE ANOTHER LARGE AND DEEP STORM SYSTEM IS MAKING ITS WAY
ACROSS THE FAR NORTHWEST PACIFIC.

WITH WEAK FEATURES NORTH OF THE SUBTROPICAL JET THE WEATHER
ACROSS ALASKA IS GENERALLY ON THE QUIET SIDE. A SERIES OF WEAK
UPPER LEVEL SHORT-WAVE TROUGHS ARE LIFTING NORTHWARD ACROSS THE
GULF AND SOUTHCENTRAL. PRECIPITATION IS GENERALLY ON THE LIGHT
SIDE...ALTHOUGH LOW TO MID-LEVEL INSTABILITY IS PRODUCING SOME
LOCALIZED HEAVY SHOWERS. A LOW LEVEL ABOVE FREEZING WARM NOSE
PERSISTS FROM THE WESTERN KENAI PENINSULA TO ANCHORAGE AND PARTS
OF THE MATANUSKA VALLEY...ALTHOUGH THE 00Z SOUNDING FROM ANCHORAGE
SHOWS THE WET BULB DOWN IS NOW DOWN AROUND ZERO. THEREFORE...IF
ENOUGH QPF FALLS INTO THE ABOVE FREEZING LAYER PRECIP WILL QUICKLY
CHANGE TO ALL SNOW AND THERE MAY BE SOME VERY LIGHT ACCUMULATION.
ON THE OTHER HAND...IF PRECIP REMAINS LIGHT THEN IT WILL TAKE
LONGER TO CHANGE TO ALL SNOW AND THERE LIKELY WILL NOT BE ANY
SNOW ACCUMULATION.

&&

.MODEL DISCUSSION...
MODELS CONTINUE TO STRUGGLE WITH SMALL SCALE FEATURES MOVING
THROUGH SOUTHCENTRAL CREATING A CHALLENGING PRECIPITATION FORECAST
FOR THE REMAINDER OF TONIGHT THROUGH WEDNESDAY MORNING. WILL MAKE
HEAVY USE OF RADAR AND SATELLITE TRENDS FOR THE EARLY PORTION OF
THE FORECAST.

THERE IS INITIALLY EXCELLENT AGREEMENT WITH STRONG PACIFIC LOW
TRACKING TOWARD GULF...BUT RAPIDLY DIVERGE LATE THURSDAY WITH
SHORT-WAVE ROUNDING THE LOW AND FORMING A SECONDARY LOW. ECMWF
SHOWS SOME RUN-TO-RUN CONSISTENCY AND IS A NICE MIDDLE GROUND
SOLUTION. WILL TREND FORECAST THAT DIRECTION RECOGNIZING THERE IS
A LARGE DROP OFF IN FORECAST CONFIDENCE BEGINNING THURSDAY NIGHT.

MEANWHILE...MODELS ARE REALLY STRUGGLING WITH SYSTEMS SOUTH OF
THE ALEUTIANS BEGINNING WEDNESDAY NIGHT. WITH A 200+ KNOT
SUBTROPICAL JET POISED TO CROSS THE NORTH PACIFIC THIS IS A
FAVORABLE ENVIRONMENT FOR RAPID CYCLOGENESIS...WITH LOWS FORMING
IN SUCCESSION AS THE JET HEADS EASTWARD. A DYNAMIC SITUATION SUCH
AS THIS IS HARD FOR THE NUMERICAL GUIDANCE TO CAPTURE. THERE IS A
TREND IN THE LATEST SOLUTIONS TOWARD BRINGING PRECIP AND GALE
FORCE WINDS FARTHER NORTH. WILL APPLY THIS TREND TO THE FORECAST.
DUE TO THE COMPLEXITY OF THE SITUATION FORECAST CONFIDENCE ALONG
THE ALEUTIANS IS BELOW AVERAGE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE LAST OF A SERIES OF WEAK UPPER LEVEL SHORT-WAVES WILL EXIT TO
THE NORTH TODAY WHILE A SHORT-WAVE RIDGE BUILDS IN AHEAD OF THE
STRONG PACIFIC STORM SYSTEM. THUS...EXPECT PRECIPITATION TO
TAPER OFF FOR ALL BUT THE GULF COAST WHERE CONTINUE LOW LEVEL
INSTABILITY WILL KEEP A FEW SHOWERS AROUND. LOW LEVEL FLOW WILL
SHIFT AROUND TO THE NORTH WEDNESDAY NIGHT AND THURSDAY AS THE
STORM MAKES ITS WAY TOWARD THE GULF....WHICH SHOULD PREVENT ANY
WIDESPREAD FOG PROBLEMS. WITH DECREASING CLOUDS TEMPERATURES WILL
SLOWLY RETURN TO SOMEWHERE CLOSER TO SEASONAL NORMALS. WITH THE
STORM REMAINING WELL TO THE SOUTH PRECIP AND WINDS WILL BE
CONFINED TO THE GULF COAST WHILE INLAND AREAS WILL STAY DRY.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
SOUTHWEST ALASKA WILL REMAIN ON THE OUTER PERIPHERY OF MAJOR
FEATURES. THUS WEATHER WILL REMAIN QUITE BENIGN OVER THE NEXT
COUPLE DAYS WITH JUTS A FEW PASSING SHOWERS. THERE ARE SOME AREAS
OF FOG OUT THERE RIGHT NOW...BUT DRY LOW LEVEL OFFSHORE FLOW WILL
DEVELOP THIS AFTERNOON AND EVENING WHICH SHOULD HELP ERODE MOST
IF NOT ALL OF THE FOG.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE ALEUTIANS WILL BE ON THE NORTH END OF STRONG STORMS TRACKING
ACROSS THE NORTH PACIFIC. THUS...EXPECT OCCASIONAL WINDY AND RAINY
CONDITIONS. OTHERWISE RELATIVELY BENIGN CONDITIONS WILL PERSIST
ACROSS THE BERING SEA.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
ALTHOUGH THERE ARE SOME DIFFERENCES WITH HANDLING OF PARTICULAR
STORM SYSTEMS IN THE FRIDAY THROUGH TUESDAY TIME PERIOD NUMERICAL
GUIDANCE IS IN GOOD AGREEMENT ON THE EVOLUTION OF THE LARGE SCALE
PATTERN. THE UPPER FLOW WILL UNDERGO AMPLIFICATION LATE THIS WEEK
THROUGH THE WEEKEND AS A TROUGH DIGS OUT OF ASIA CAUSING A RIDGE
TO BUILD OVER THE WESTERN BERING. THIS WILL THEN CAUSE DOWNSTREAM
TROUGH TO AMPLIFY...WITH LOWS CONSOLIDATING INTO A SINGLE LOW
SOMEWHERE OVER THE WESTERN GULF OR BRISTOL BAY AREAS. THUS...THERE
WILL BE A SHIFT FROM SYSTEMS MOVING RAPIDLY FROM WEST TO EAST
ACROSS THE NORTH PACIFIC AND INTO THE GULF TO A MORE STAGNANT
PATTERN WITH ONE LARGE CYCLONIC CIRCULATION DOMINATING THE
WEATHER. PRIOR TO AND DURING THE CHANGE IN PATTERN ACTIVE WEATHER
WILL BE FOCUSED ALONG THE SOUTHERN TIER OF THE FORECAST
AREA...ALONG THE ALEUTIANS AND ALASKA PENINSULA AND INTO THE GULF
OF ALASKA. THE BERING SEA AND MUCH OF SOUTHWEST AND SOUTHCENTRAL
ALASKA WILL REMAIN ON THE DRY SIDE...WITH JUST AN OCCASIONAL
CHANCE OF PRECIP AS UPPER WAVES MOVE THROUGH. LOW LEVEL WARM AIR
WILL CONTINUE TO PENETRATE SOUTHCENTRAL ALASKA AND PORTIONS OF
SOUTHWEST ALASKA...SO TEMPERATURES WILL GENERALLY REMAIN ABOVE
NORMAL AND THERE WILL BE A THREAT OF FREEZING RAIN IF ANY PRECIP
DOES MAKE IT INLAND.

LOOKING OUT TO EARLY NEXT WEEK MORE SIGNIFICANT CHANGES ARE LIKELY
AS THE UPPER LEVEL WAVES PROGRESS EASTWARD...WITH THE HIGHLY
AMPLIFIED TROUGH WHICH MOVES OUT OF ASIA HEADING INTO THE BERING
SEA MONDAY AND TUESDAY. CONDITIONS WILL BE EXTREMELY FAVORABLE FOR
DEVELOPMENT OF DEEP SURFACE LOWS. THUS EXPECT MUCH MORE ACTIVE
WINTER-LIKE WEATHER TO RETURN TO THE BERING SEA AND
ALEUTIANS...AND MOST LIKELY SOUTHWEST AND SOUTHCENTRAL ALASKA BY
NEXT WEDNESDAY AND THURSDAY.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING...119 120 127 130 131 132 136 137 138 139
                        150 155 175 176 177 178 185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...SEB
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...SEB
LONG TERM...SEB




000
FXAK68 PAFC 170104
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
404 PM AKST TUE DEC 16 2014

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LEVEL LOW CENTERED OVER THE EASTERN BERING SEA.
THERE ARE SEVERAL TROUGHS ASSOCIATED WITH THIS LOW. ONE OF THESE
IS JUST ALONG THE NORTH GULF COAST...WITH ANOTHER OVER THE
NORTHERN GULF PARALLEL TO THE FIRST...AND ANOTHER IN THE SOUTHERN
GULF. THERE IS A DEVELOPING LOW SOUTH OF THE CENTRAL ALEUTIANS AND
ANOTHER ONE CENTERED OVER HOKKAIDO (ISLAND OF JAPAN).

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN GOOD AGREEMENT THROUGH ABOUT HOUR 60
OF THE FORECAST (3PM AKST THURSDAY)...THEN BEGIN TO SHOW
INCREASING GREATER SPREAD THROUGH 84 HOURS. THE MAIN DIFFERENCES
ARE HOW THEY HANDLE THE SPEED/DEPTH OF A LOW SOUTH OF THE
ALEUTIANS THURSDAY NIGHT/FRIDAY AND THE VARIOUS CENTERS OF A
COMPLEX LOW IN THE GULF.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE TROUGH ALONG THE GULF COAST WILL RAPIDLY MOVE INLAND AND
DISSIPATE EARLY THIS EVENING. THE SECOND TROUGH WILL OVERTAKE THE
PREVIOUS ONE DURING THE EVENING AND SHOULD PROVIDE ENOUGH DYNAMICS
TO PRODUCE PRECIPITATION FOR INLAND AREAS. PRECIPITATION WILL
CONTINUE OVERNIGHT AND INTO WEDNESDAY...PROLONGED A LITTLE BY THE
THIRD TROUGH THAT MOVES ONSHORE EARLY WEDNESDAY AFTERNOON.
PRECIPITATION TYPE WILL PROBABLY START AS RAIN OR A RAIN/SNOW
COMBINATION THEN SWITCH TO ALL SNOW OVERNIGHT. NOT A LOT OF
ACCUMULATION IS EXPECTED AS THE WINDS ALOFT NEVER BECOME VERY
FAVORABLE...BUT SOME IS POSSIBLE. ON WEDNESDAY NIGHT AND THURSDAY
THE LOW THAT IS CURRENTLY SOUTH OF THE CENTRAL ALEUTIANS WILL PUSH
NORTHWESTWARD INTO THE GULF. THIS WILL PUT US IN A PATTERN WHERE
WE HAVE PRECIPITATION IN COASTAL AREAS AND LITTLE OR NONE INLAND.

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
CONDITIONS LOOK TO BE IMPROVING ACROSS THE MAINLAND THIS
EVENING INTO TOMORROW. THE SYSTEM RESPONSIBLE FOR THE PREVIOUS
FRONT WILL SLOWLY DRIFT NORTH IN THE BERING AND
DISSIPATE...HOWEVER...DEEP COLD AIR ALOFT WILL BRING A SHOWERY
REGIME THROUGH TOMORROW MORNING FOR MOST LOCATIONS. EXPECT
WIDESPREAD LOW AND MID-LEVEL CLOUDS TO DISSIPATE AND MOVE OUT OF
THE AREA WHILE INTERMITTENT CLOUDS AND SNOW SHOWERS TO AFFECT MOST
AREAS. WEDNESDAY INTO THURSDAY A SYSTEM PROGRESSING SOUTH OF THE
ALASKA PENINSULA WILL SPREAD SOME HIGHER CLOUDS OVER INTERIOR
BRISTOL BAY...BUT THE AREA SHOULD STAY DRY UNTIL THURSDAY WHEN THE
CHANCE FOR SNOW RETURNS...MAINLY ALONG THE ALASKA PENINSULA. ABOVE
AVERAGE TEMPERATURES AND LIGHT WINDS WILL PREVAIL FOR THE NEXT
COUPLE DAYS.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE ALEUTIANS CURRENTLY SIT BETWEEN THE UNSTABLE SHOWERY REGIME OF
THE PREVIOUS SYSTEM IN THE BERING AND A NEW SYSTEM DEVELOPING TO
THE SOUTH. THE CENTRAL AND EASTERN ALEUTIANS WILL REMAIN IN
SCATTERED SNOW SHOWERS WHILE THE TIP OF THE ALASKA PENINSULA WILL
SEE SOME RAIN AND SNOW AS THE FRONTAL BOUNDARY FROM THE SOUTHERN
SYSTEM MOVE OVERHEAD. GENERAL TROUGHINESS CONTINUES OVER THE
BERING SEA THROUGH THURSDAY AS ANOTHER FRONT WASHES OUT OVER THE
WESTERN/CENTRAL ALEUTIANS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE GENERAL PATTERN FROM THE SHORT TERM WILL CONTINUE THROUGH
FRIDAY AND SATURDAY. THE GULF LOW WILL PUSH WESTWARD ACROSS
KODIAK ISLAND WHILE LOWS IN THE BERING AND ALEUTIANS WILL SPIN
SOUTH/SOUTHEAST. THE PATTERN WILL BEGIN TO SHIFT ON SUNDAY...WITH
STRONG ZONAL (STRONG WESTERLY) FLOW BEGINNING TO PUSH INTO THE
WESTERN BERING SEA. THIS ZONAL FLOW WILL PUSH EASTWARD FOR THE
NEXT FEW DAYS AND ENCOMPASS THE ENTIRE AREA BY TUESDAY AFTERNOON.
WPC IS AGAIN GOING WITH ALL ENSEMBLE MEANS...A BASICALLY EVEN
SPLIT OF GFS...EC...AND NAF (WHICH IS A COMBINATION OF THE
CANADIAN MODELS AND THE GFS).

&&



.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES...119 120 131 132 150 178 179 185
FIRE WEATHER...NONE.

&&

$$




000
FXAK68 PAFC 170104
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
404 PM AKST TUE DEC 16 2014

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LEVEL LOW CENTERED OVER THE EASTERN BERING SEA.
THERE ARE SEVERAL TROUGHS ASSOCIATED WITH THIS LOW. ONE OF THESE
IS JUST ALONG THE NORTH GULF COAST...WITH ANOTHER OVER THE
NORTHERN GULF PARALLEL TO THE FIRST...AND ANOTHER IN THE SOUTHERN
GULF. THERE IS A DEVELOPING LOW SOUTH OF THE CENTRAL ALEUTIANS AND
ANOTHER ONE CENTERED OVER HOKKAIDO (ISLAND OF JAPAN).

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN GOOD AGREEMENT THROUGH ABOUT HOUR 60
OF THE FORECAST (3PM AKST THURSDAY)...THEN BEGIN TO SHOW
INCREASING GREATER SPREAD THROUGH 84 HOURS. THE MAIN DIFFERENCES
ARE HOW THEY HANDLE THE SPEED/DEPTH OF A LOW SOUTH OF THE
ALEUTIANS THURSDAY NIGHT/FRIDAY AND THE VARIOUS CENTERS OF A
COMPLEX LOW IN THE GULF.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE TROUGH ALONG THE GULF COAST WILL RAPIDLY MOVE INLAND AND
DISSIPATE EARLY THIS EVENING. THE SECOND TROUGH WILL OVERTAKE THE
PREVIOUS ONE DURING THE EVENING AND SHOULD PROVIDE ENOUGH DYNAMICS
TO PRODUCE PRECIPITATION FOR INLAND AREAS. PRECIPITATION WILL
CONTINUE OVERNIGHT AND INTO WEDNESDAY...PROLONGED A LITTLE BY THE
THIRD TROUGH THAT MOVES ONSHORE EARLY WEDNESDAY AFTERNOON.
PRECIPITATION TYPE WILL PROBABLY START AS RAIN OR A RAIN/SNOW
COMBINATION THEN SWITCH TO ALL SNOW OVERNIGHT. NOT A LOT OF
ACCUMULATION IS EXPECTED AS THE WINDS ALOFT NEVER BECOME VERY
FAVORABLE...BUT SOME IS POSSIBLE. ON WEDNESDAY NIGHT AND THURSDAY
THE LOW THAT IS CURRENTLY SOUTH OF THE CENTRAL ALEUTIANS WILL PUSH
NORTHWESTWARD INTO THE GULF. THIS WILL PUT US IN A PATTERN WHERE
WE HAVE PRECIPITATION IN COASTAL AREAS AND LITTLE OR NONE INLAND.

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
CONDITIONS LOOK TO BE IMPROVING ACROSS THE MAINLAND THIS
EVENING INTO TOMORROW. THE SYSTEM RESPONSIBLE FOR THE PREVIOUS
FRONT WILL SLOWLY DRIFT NORTH IN THE BERING AND
DISSIPATE...HOWEVER...DEEP COLD AIR ALOFT WILL BRING A SHOWERY
REGIME THROUGH TOMORROW MORNING FOR MOST LOCATIONS. EXPECT
WIDESPREAD LOW AND MID-LEVEL CLOUDS TO DISSIPATE AND MOVE OUT OF
THE AREA WHILE INTERMITTENT CLOUDS AND SNOW SHOWERS TO AFFECT MOST
AREAS. WEDNESDAY INTO THURSDAY A SYSTEM PROGRESSING SOUTH OF THE
ALASKA PENINSULA WILL SPREAD SOME HIGHER CLOUDS OVER INTERIOR
BRISTOL BAY...BUT THE AREA SHOULD STAY DRY UNTIL THURSDAY WHEN THE
CHANCE FOR SNOW RETURNS...MAINLY ALONG THE ALASKA PENINSULA. ABOVE
AVERAGE TEMPERATURES AND LIGHT WINDS WILL PREVAIL FOR THE NEXT
COUPLE DAYS.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE ALEUTIANS CURRENTLY SIT BETWEEN THE UNSTABLE SHOWERY REGIME OF
THE PREVIOUS SYSTEM IN THE BERING AND A NEW SYSTEM DEVELOPING TO
THE SOUTH. THE CENTRAL AND EASTERN ALEUTIANS WILL REMAIN IN
SCATTERED SNOW SHOWERS WHILE THE TIP OF THE ALASKA PENINSULA WILL
SEE SOME RAIN AND SNOW AS THE FRONTAL BOUNDARY FROM THE SOUTHERN
SYSTEM MOVE OVERHEAD. GENERAL TROUGHINESS CONTINUES OVER THE
BERING SEA THROUGH THURSDAY AS ANOTHER FRONT WASHES OUT OVER THE
WESTERN/CENTRAL ALEUTIANS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE GENERAL PATTERN FROM THE SHORT TERM WILL CONTINUE THROUGH
FRIDAY AND SATURDAY. THE GULF LOW WILL PUSH WESTWARD ACROSS
KODIAK ISLAND WHILE LOWS IN THE BERING AND ALEUTIANS WILL SPIN
SOUTH/SOUTHEAST. THE PATTERN WILL BEGIN TO SHIFT ON SUNDAY...WITH
STRONG ZONAL (STRONG WESTERLY) FLOW BEGINNING TO PUSH INTO THE
WESTERN BERING SEA. THIS ZONAL FLOW WILL PUSH EASTWARD FOR THE
NEXT FEW DAYS AND ENCOMPASS THE ENTIRE AREA BY TUESDAY AFTERNOON.
WPC IS AGAIN GOING WITH ALL ENSEMBLE MEANS...A BASICALLY EVEN
SPLIT OF GFS...EC...AND NAF (WHICH IS A COMBINATION OF THE
CANADIAN MODELS AND THE GFS).

&&



.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES...119 120 131 132 150 178 179 185
FIRE WEATHER...NONE.

&&

$$





000
FXAK68 PAFC 161303
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
403 AM AKST TUE DEC 16 2014

.ANALYSIS AND UPPER LEVELS...
A LONG-WAVE TROUGH IS CENTERED OVER THE BERING SEA AND NORTH
PACIFIC WITH A SEMI-PERMANENT DOWNSTREAM RIDGE OVER WESTERN
CANADA. A SPOKE OF THIS RIDGE EXTENDS WESTWARD INTO NORTHERN
ALASKA. THUS...THE MAIN STORM TRACK IS EASTWARD ACROSS THE NORTH
PACIFIC THEN NORTHWARD UP THE WEST WIDE OF THE RIDGE INTO MAINLAND
ALASKA.

THERE IS A HOST OF GENERALLY WEAK FEATURES EMBEDDED WITHIN THE
UPPER FLOW WITH FAIRLY BENIGN CONDITIONS ACROSS ALASKA FOR THIS
TIME OF YEAR. THE ONE EXCEPTION IS A FAIRLY COMPACT GALE FORCE LOW
WHICH IS TRACKING NORTHWARD ACROSS THE CENTRAL GULF AND HEADED
TOWARD SOUTHCENTRAL ALASKA. OUT AHEAD OF THIS LOW STRONG EASTERLY
FLOW ACROSS THE KENAI AND CHUGACH MOUNTAINS HAS LARGELY MAINTAINED
DRY CONDITIONS FROM THE WESTERN KENAI PENINSULA UP TO ANCHORAGE
AND THE MAT-SU...WITH THE EXCEPTION OF A FEW BRIEF PERIODS OF RAIN
OR FREEZING RAIN AS UPPER WAVES MOVE THROUGH AND TEMPORARILY
WEAKEN THE FLOW ACROSS THE MOUNTAINS. THE APPROACHING LOW COULD
PROVIDE ANOTHER ONE OF THOSE BRIEF SPILL-OVERS OF PRECIP. THE
CHALLENGE IS IN DETERMINING WHETHER THERE WILL BE ENOUGH
PRECIPITATION TO WARRANT A FREEZING RAIN ADVISORY FOR ANCHORAGE OR
THE SUSITNA VALLEY (WHERE SURFACE TEMPERATURES REMAIN AT OR BELOW
FREEZING). DISSIPATION OF THE CROSS MOUNTAIN FLOW WILL ALSO ALLOW
LOW LEVEL TEMPERATURES TO COOL...BUT IN THE ABSENCE OF COLD AIR
ADVECTION IT WILL TAKE QUITE A WHILE TO COOL THE ANCHORAGE
SOUNDING ENOUGH FOR ALL SNOW.

THE SECOND IMPORTANT PIECE TO THE SOUTHCENTRAL ALASKA FORECAST IS
A TROUGH WHICH EXTENDS FROM NORTHWEST TO SOUTHEAST ALONG THE
SOUTHWEST ALASKA COAST AND INTO THE WESTERN GULF. THIS TROUGH IS
LIFTING NORTHWARD AND BRINGING WITH IT SOME MARGINALLY COLDER
AIR. THIS WEAK COLD ADVECTION SHOULD BE ENOUGH TO TRANSITION
PRECIP BACK TO MOSTLY SNOW ACROSS THE SOUTHERN MAINLAND OF ALASKA
OVER THE NEXT 12 TO 18 HOURS.

&&

.MODEL DISCUSSION...
WITH THE EXCEPTION OF THE GFS SOLUTION...MODELS HAVE COME INTO MUCH
BETTER AGREEMENT WITH THE TRACK AND STRENGTH OF THE LOW OVER THE
GULF. THE BIGGER QUESTION IS NOW THE DEPICTION OF THE TROUGH
MOVING IN BEHIND THE LOW. PRIOR SOLUTIONS INDICATED A NICE CLEAN
TROUGH AXIS WITH LOW LEVEL SOUTHWESTERLY FLOW (FAVORABLE FOR
PRECIP IN ANCHORAGE AND THE MAT-SU). THE MODELS NOW DEVELOP A WAVE
OVER THE CENTRAL GULF WHICH CHANGES THE ORIENTATION OF THE TROUGH
AS IT MOVES THROUGH SOUTHCENTRAL AND RESULTS IN LOW LEVEL SOUTHERLY
(OR EVEN SOUTHEASTERLY) FLOW. ALTHOUGH THERE ARE DIFFERENCES IN
THE DETAILS...WILL BUY INTO THIS NEW DEPICTION. THIS CREATES A
MUCH MORE CHALLENGING QPF FORECAST...SO FORECAST CONFIDENCE FOR
TUESDAY AFTERNOON THROUGH TUESDAY NIGHT IN THE POPULATION CENTERS
OF SOUTHCENTRAL IS NOW BELOW AVERAGE.

ELSEWHERE...MODELS ARE IN GOOD AGREEMENT WITH LARGE SCALE FEATURES
THROUGH WEDNESDAY AND FORECAST CONFIDENCE IS GENERALLY ABOVE
AVERAGE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
FREEZING RAIN WILL REMAIN A THREAT TO ANCHORAGE AND THE SUSITNA
VALLEY THROUGH EARLY THIS MORNING AS A WEAK UPPER LEVEL WAVE MOVES
THROUGH. RIGHT NOW DO NOT THINK PRECIP WILL BE WIDESPREAD ENOUGH TO
WARRANT A FREEZING RAIN ADVISORY...BUT IT IS A VERY TOUGH CALL. AS
THE GULF LOW REACHES THE KENAI PENINSULA THIS AFTERNOON THE STRONG
CROSS MOUNTAIN FLOW WILL COME TO AN END AND THE COLUMN WILL BEGIN
TO COOL. THUS...BY THE TIME PRECIP ARRIVES AHEAD OF THE UPPER TROUGH
THIS EVENING EXPECT PRECIP TO BE MAINLY IN THE FORM OF SNOW. THERE
WILL BE AN AREA OF STRONGER LIFT AHEAD OF AN AMPLIFYING WAVE ALONG
THE TROUGH...WHICH WILL PRODUCE LOCALLY HEAVIER SNOWFALL. THE
PRINCE WILLIAM SOUND AREA SEEMS TO BE BEST POSITIONED TO SEE A
BRIEF PERIOD OF HEAVIER PRECIP...BUT THERE IS A POSSIBILITY SOME
OF THIS MAY MAKE IT INTO ANCHORAGE AND THE MAT VALLEY. FOR NOW
WILL STICK WITH MINOR SNOW ACCUMULATION...WHICH IS WHAT MOST OF
THE REGION WILL SEE AS THIS FAIRLY WEAK TROUGH MOVES THROUGH.

THE MODELS ARE NOW RESOLVING ANOTHER WEAK UPPER TROUGH APPROACHING
SOUTHCENTRAL ON WEDNESDAY. THIS COULD PROLONG SNOW IN SOME
AREAS...THOUGH IT WILL BE LIGHT. LOW LEVEL FLOW WILL BEGIN TO
SHIFT AROUND TO THE NORTH LATE WEDNESDAY AS A LARGE AND DEEP
PACIFIC LOW APPROACHES THE GULF. THIS WILL LEAD TO A DRYING AND
COOLING TREND.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A SERIES OF WEAK UPPER LEVEL TROUGHS WILL MOVE THROUGH SOUTHWEST
ALASKA THE NEXT COUPLE DAYS BRINGING NO MORE THAN A FEW SHOWERS.
AIR MASS HAS BEEN COOLING OVERNIGHT WITH THE 12Z SOUNDING FROM
KING SALMON ALMOST ALL BELOW FREEZING...SO PRECIP TYPE WILL BE
PRIMARILY SNOW. WITH BREAKS IN THE CLOUDS IN BETWEEN SHORT-WAVES
CONDITIONS ARE FAVORABLE FOR FOG.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE ALEUTIANS AND SOUTHERN ALASKA PENINSULA WILL BE ON THE
NORTHERN PERIPHERY OF SYSTEMS TRACKING ACROSS THE NORTH PACIFIC
AND ON THE SOUTHERN PERIPHERY OF A NEARLY STATIONARY LOW OVER THE
NORTH-CENTRAL BERING SEA. THUS...EXPECT CONTINUED VERY BENIGN
WINTER-TIME CONDITIONS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE LARGE SCALE PATTERN WILL REMAIN ESSENTIALLY THE SAME OVER THE
NEXT WEEK WITH PROGRESSIVE FLOW ACROSS THE NORTH PACIFIC AND A
DOWNSTREAM BLOCK FORCING STORMS NORTHWARD INTO THE GULF WHERE
THEY WILL WEAKEN. THIS MEANS WARMER AIR WILL ONCE AGAIN MOVE INTO
THE SOUTHERN MAINLAND OF ALASKA...AND FREEZING RAIN WILL REMAIN A
POSSIBILITY WITH EACH OF THESE SYSTEMS. MODELS ARE ALL INDICATING
AMPLIFICATION OF THE FLOW OVER THE NORTH PACIFIC AND BERING SEA
EARLY NEXT WEEK AS A DEEP TROUGH MOVES OUT OF ASIA. THIS WOULD
BRING A RETURN TO MORE WINTER-LIKE CONDITIONS ACROSS THE BERING
AND ALEUTIANS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM WARNING...119.
         GALE WARNING...125 179 185.
         HEAVY FREEZING SPRAY WARNING...185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...SEB
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...SEB
LONG TERM...SEB





000
FXAK68 PAFC 161303
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
403 AM AKST TUE DEC 16 2014

.ANALYSIS AND UPPER LEVELS...
A LONG-WAVE TROUGH IS CENTERED OVER THE BERING SEA AND NORTH
PACIFIC WITH A SEMI-PERMANENT DOWNSTREAM RIDGE OVER WESTERN
CANADA. A SPOKE OF THIS RIDGE EXTENDS WESTWARD INTO NORTHERN
ALASKA. THUS...THE MAIN STORM TRACK IS EASTWARD ACROSS THE NORTH
PACIFIC THEN NORTHWARD UP THE WEST WIDE OF THE RIDGE INTO MAINLAND
ALASKA.

THERE IS A HOST OF GENERALLY WEAK FEATURES EMBEDDED WITHIN THE
UPPER FLOW WITH FAIRLY BENIGN CONDITIONS ACROSS ALASKA FOR THIS
TIME OF YEAR. THE ONE EXCEPTION IS A FAIRLY COMPACT GALE FORCE LOW
WHICH IS TRACKING NORTHWARD ACROSS THE CENTRAL GULF AND HEADED
TOWARD SOUTHCENTRAL ALASKA. OUT AHEAD OF THIS LOW STRONG EASTERLY
FLOW ACROSS THE KENAI AND CHUGACH MOUNTAINS HAS LARGELY MAINTAINED
DRY CONDITIONS FROM THE WESTERN KENAI PENINSULA UP TO ANCHORAGE
AND THE MAT-SU...WITH THE EXCEPTION OF A FEW BRIEF PERIODS OF RAIN
OR FREEZING RAIN AS UPPER WAVES MOVE THROUGH AND TEMPORARILY
WEAKEN THE FLOW ACROSS THE MOUNTAINS. THE APPROACHING LOW COULD
PROVIDE ANOTHER ONE OF THOSE BRIEF SPILL-OVERS OF PRECIP. THE
CHALLENGE IS IN DETERMINING WHETHER THERE WILL BE ENOUGH
PRECIPITATION TO WARRANT A FREEZING RAIN ADVISORY FOR ANCHORAGE OR
THE SUSITNA VALLEY (WHERE SURFACE TEMPERATURES REMAIN AT OR BELOW
FREEZING). DISSIPATION OF THE CROSS MOUNTAIN FLOW WILL ALSO ALLOW
LOW LEVEL TEMPERATURES TO COOL...BUT IN THE ABSENCE OF COLD AIR
ADVECTION IT WILL TAKE QUITE A WHILE TO COOL THE ANCHORAGE
SOUNDING ENOUGH FOR ALL SNOW.

THE SECOND IMPORTANT PIECE TO THE SOUTHCENTRAL ALASKA FORECAST IS
A TROUGH WHICH EXTENDS FROM NORTHWEST TO SOUTHEAST ALONG THE
SOUTHWEST ALASKA COAST AND INTO THE WESTERN GULF. THIS TROUGH IS
LIFTING NORTHWARD AND BRINGING WITH IT SOME MARGINALLY COLDER
AIR. THIS WEAK COLD ADVECTION SHOULD BE ENOUGH TO TRANSITION
PRECIP BACK TO MOSTLY SNOW ACROSS THE SOUTHERN MAINLAND OF ALASKA
OVER THE NEXT 12 TO 18 HOURS.

&&

.MODEL DISCUSSION...
WITH THE EXCEPTION OF THE GFS SOLUTION...MODELS HAVE COME INTO MUCH
BETTER AGREEMENT WITH THE TRACK AND STRENGTH OF THE LOW OVER THE
GULF. THE BIGGER QUESTION IS NOW THE DEPICTION OF THE TROUGH
MOVING IN BEHIND THE LOW. PRIOR SOLUTIONS INDICATED A NICE CLEAN
TROUGH AXIS WITH LOW LEVEL SOUTHWESTERLY FLOW (FAVORABLE FOR
PRECIP IN ANCHORAGE AND THE MAT-SU). THE MODELS NOW DEVELOP A WAVE
OVER THE CENTRAL GULF WHICH CHANGES THE ORIENTATION OF THE TROUGH
AS IT MOVES THROUGH SOUTHCENTRAL AND RESULTS IN LOW LEVEL SOUTHERLY
(OR EVEN SOUTHEASTERLY) FLOW. ALTHOUGH THERE ARE DIFFERENCES IN
THE DETAILS...WILL BUY INTO THIS NEW DEPICTION. THIS CREATES A
MUCH MORE CHALLENGING QPF FORECAST...SO FORECAST CONFIDENCE FOR
TUESDAY AFTERNOON THROUGH TUESDAY NIGHT IN THE POPULATION CENTERS
OF SOUTHCENTRAL IS NOW BELOW AVERAGE.

ELSEWHERE...MODELS ARE IN GOOD AGREEMENT WITH LARGE SCALE FEATURES
THROUGH WEDNESDAY AND FORECAST CONFIDENCE IS GENERALLY ABOVE
AVERAGE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
FREEZING RAIN WILL REMAIN A THREAT TO ANCHORAGE AND THE SUSITNA
VALLEY THROUGH EARLY THIS MORNING AS A WEAK UPPER LEVEL WAVE MOVES
THROUGH. RIGHT NOW DO NOT THINK PRECIP WILL BE WIDESPREAD ENOUGH TO
WARRANT A FREEZING RAIN ADVISORY...BUT IT IS A VERY TOUGH CALL. AS
THE GULF LOW REACHES THE KENAI PENINSULA THIS AFTERNOON THE STRONG
CROSS MOUNTAIN FLOW WILL COME TO AN END AND THE COLUMN WILL BEGIN
TO COOL. THUS...BY THE TIME PRECIP ARRIVES AHEAD OF THE UPPER TROUGH
THIS EVENING EXPECT PRECIP TO BE MAINLY IN THE FORM OF SNOW. THERE
WILL BE AN AREA OF STRONGER LIFT AHEAD OF AN AMPLIFYING WAVE ALONG
THE TROUGH...WHICH WILL PRODUCE LOCALLY HEAVIER SNOWFALL. THE
PRINCE WILLIAM SOUND AREA SEEMS TO BE BEST POSITIONED TO SEE A
BRIEF PERIOD OF HEAVIER PRECIP...BUT THERE IS A POSSIBILITY SOME
OF THIS MAY MAKE IT INTO ANCHORAGE AND THE MAT VALLEY. FOR NOW
WILL STICK WITH MINOR SNOW ACCUMULATION...WHICH IS WHAT MOST OF
THE REGION WILL SEE AS THIS FAIRLY WEAK TROUGH MOVES THROUGH.

THE MODELS ARE NOW RESOLVING ANOTHER WEAK UPPER TROUGH APPROACHING
SOUTHCENTRAL ON WEDNESDAY. THIS COULD PROLONG SNOW IN SOME
AREAS...THOUGH IT WILL BE LIGHT. LOW LEVEL FLOW WILL BEGIN TO
SHIFT AROUND TO THE NORTH LATE WEDNESDAY AS A LARGE AND DEEP
PACIFIC LOW APPROACHES THE GULF. THIS WILL LEAD TO A DRYING AND
COOLING TREND.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A SERIES OF WEAK UPPER LEVEL TROUGHS WILL MOVE THROUGH SOUTHWEST
ALASKA THE NEXT COUPLE DAYS BRINGING NO MORE THAN A FEW SHOWERS.
AIR MASS HAS BEEN COOLING OVERNIGHT WITH THE 12Z SOUNDING FROM
KING SALMON ALMOST ALL BELOW FREEZING...SO PRECIP TYPE WILL BE
PRIMARILY SNOW. WITH BREAKS IN THE CLOUDS IN BETWEEN SHORT-WAVES
CONDITIONS ARE FAVORABLE FOR FOG.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE ALEUTIANS AND SOUTHERN ALASKA PENINSULA WILL BE ON THE
NORTHERN PERIPHERY OF SYSTEMS TRACKING ACROSS THE NORTH PACIFIC
AND ON THE SOUTHERN PERIPHERY OF A NEARLY STATIONARY LOW OVER THE
NORTH-CENTRAL BERING SEA. THUS...EXPECT CONTINUED VERY BENIGN
WINTER-TIME CONDITIONS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE LARGE SCALE PATTERN WILL REMAIN ESSENTIALLY THE SAME OVER THE
NEXT WEEK WITH PROGRESSIVE FLOW ACROSS THE NORTH PACIFIC AND A
DOWNSTREAM BLOCK FORCING STORMS NORTHWARD INTO THE GULF WHERE
THEY WILL WEAKEN. THIS MEANS WARMER AIR WILL ONCE AGAIN MOVE INTO
THE SOUTHERN MAINLAND OF ALASKA...AND FREEZING RAIN WILL REMAIN A
POSSIBILITY WITH EACH OF THESE SYSTEMS. MODELS ARE ALL INDICATING
AMPLIFICATION OF THE FLOW OVER THE NORTH PACIFIC AND BERING SEA
EARLY NEXT WEEK AS A DEEP TROUGH MOVES OUT OF ASIA. THIS WOULD
BRING A RETURN TO MORE WINTER-LIKE CONDITIONS ACROSS THE BERING
AND ALEUTIANS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM WARNING...119.
         GALE WARNING...125 179 185.
         HEAVY FREEZING SPRAY WARNING...185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...SEB
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...SEB
LONG TERM...SEB




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