Winter Weather Advisory 3, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
518 AM AKST TUE FEB 2 2016

.ANALYSIS AND UPPER LEVELS...

THE NARROW UPPER RIDGE THAT HAD BEEN SITUATED FROM THE NORTHWEST
MAINLAND THROUGH THE SOUTHEAST PANHANDLE CONTINUES TO ERODE FROM
BOTH DIRECTIONS WITH THE COMBINATION OF A WEAK UPPER LEVEL LOW
OVER THE YUKON AND NUMEROUS SHORTWAVE DISTURBANCES PUSHING INTO
SOUTHERN ALASKA FROM THE SOUTH. THE PRIMARY LONGWAVE UPPER TROUGH
CONTINUES IN A WEST-EAST FASHION FROM RUSSIA EAST ACROSS KAMCHATKA
TO THE WESTERN ALEUTIANS...THEN EXTENDS EAST-SOUTHEAST TO A NEARLY
STACKED LOW SOUTH OF THE AKPEN AND KODIAK NEAR 50N LATITUDE. THE
JET STREAM IS SOUTH OF THIS TROUGH/LOW COMBO RUNNING ZONALLY FROM
JAPAN TO JUST NORTH OF HAWAII. THERE IS A FRONT FROM THE PREVIOUS
SET OF WEAK LOWS THAT STRETCHES FROM NEAR THE BERING STRAIT
THROUGH THE GULF OF ALASKA. THIS FRONT CONTINUES TO DISSIPATE
LARGELY IN PLACE WITH THE MAIN DEFORMATION AREA OVER THE LOWER
KUSKOKWIM VALLEY. THE STRONG SURFACE LOW THAT IS SOUTH OF THE
ALASKA PENINSULA IS NEAR PEAK STRENGTH AND WILL GRADUALLY BEGIN TO
OCCLUDE AS IT DECOUPLES FROM THE UPPER LEVEL SUPPORT BEFORE
APPROACHING ALASKA OVER THE NEXT FEW DAYS.

&&

.MODEL DISCUSSION...
MODELS REMAIN IN GOOD SYNOPTIC AGREEMENT. THE STACKED LOW PRESSURE
SYSTEM SOUTH OF THE AKPEN WILL DRIFT NORTH TO THE AKPEN
WEDNESDAY...AND THEN LARGELY REMAIN STATIONARY OVER THE REGION AS
A BROAD CENTER OF ACTION FOR THE REMAINDER OF THE WEEK. WHERE
MODELS DIFFER IS WITH A STRENGTHENING SHORTWAVE LOCATED IN A
DUAL-JET REGION ABOUT 42N 180 THAT WILL MOVE EAST AND THEN QUICKLY
WRAP AROUND THE CYCLONIC CIRCULATION OF THE LOW NEARING THE AKPEN
WEDNESDAY NIGHT INTO THURSDAY. THERE WILL LIKELY BE A TRIPLE POINT
LOW FORMING FROM THIS FEATURE AT THAT TIME...BUT MODELS DIFFER ON
THE STRENGTH AND LOCATION...WITH SOME MODELS BRINGING IT SOUTH AND
WEST OF KODIAK (EC) AND CONSOLIDATING INTO THE MAIN LOW NEAR THE
AKPEN...WHILE OTHERS SUGGEST A MOVEMENT INTO THE BARREN ISLANDS
REGION AND THEN INTO THE BRISTOL BAY AREA BEFORE WEAKENING (NAM
AND GEM MODELS). THIS WILL HAVE A LARGE ROLE AS TO WIND SPEEDS AND
DIRECTION FOR THIS REGION. FOR THE OVERNIGHT PACKAGE THE EC AND
GFS WERE PREFERRED WITH THIS FEATURE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE UPPER LEVEL FRONT OVER THE NORTHERN GULF WILL MOVE ONSHORE
TODAY AND DISSIPATE AS IT MOVES INTO THE ALASKAN RIDGE. ALMOST
ALL OF THE PRECIPITATION FROM THIS SYSTEM WILL FALL ALONG THE GULF
COAST AND COASTAL MOUNTAINS...WITH ALMOST NONE GETTING INLAND. THE
NEXT FRONT WILL MOVE INTO THE GULF TUESDAY NIGHT AND REACH THE
NORTH GULF COAST ON WEDNESDAY. THIS FRONT WILL HAVE STRONGER WINDS
AND MORE PRECIPITATION THAN THE PREVIOUS ONE. CROSS BARRIER FLOW
WILL ACT TO LIMIT PRECIPITATION GETTING INLAND. THERE IS AT LEAST
A LITTLE HOPE OF SOME PRECIPITATION INLAND AS THIS SYSTEM HAS
MORE MOISTURE THAN THE PREVIOUS ONE...AND THE THE ALASKAN RIDGE
WILL RETREAT TO THE NORTH. SOUTHERLY FLOW ALOFT WILL KEEP
CONDITIONS RATHER MILD FOR THIS TIME OF YEAR.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE MAINLAND LIES BETWEEN WEATHER SYSTEMS AT THE MOMENT. LINGERING
MOISTURE AND LIGHT WINDS HAVE PROMOTED AREAS OF FOG AND LOW
STRATUS ACROSS THE AREA. EXPECT THESE CONDITIONS TO HOLD THROUGH
LATE MORNING WHEN NORTHERLY WINDS AHEAD OF THE APPROACHING FRONT
WILL MIX AND DRY THE LOW LEVELS. LOW CLOUDS WILL DISSIPATE TODAY
WHILE A FRESH BATCH OF HIGH CLOUDS WILL STREAM IN FROM THE SOUTH.
THESE ARE ASSOCIATED WITH AN APPROACHING FRONT OVER THE NORTH
PACIFIC THAT WILL IMPACT THE AREA ON WEDNESDAY. THE FRONT WILL BE
WEAKENING AS IT MOVES OVERHEAD AND THE LOW LEVELS WILL BE DRIER
FROM STRONG CROSS BARRIER FLOW SO IT LOOKS AS IF IT WILL MAINLY
BRING CLOUDS BUT VERY LITTLE PRECIPITATION...SPRINKLES OR FLURRIES
IF ANYTHING. AFTER TODAY EXPECT INCREASING CLOUDS AND NORTHERLY
WINDS. TEMPERATURES WILL GET A LITTLE COLDER THAN WHAT HAS BEEN
RECENTLY EXPERIENCED FOR THE KUSKOKWIM DELTA AND VALLEY WHILE THE
GREATER BRISTOL BAY AREA WILL HOVER NEAR NORMAL.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
WEAK CYCLONIC CIRCULATION WILL KEEP THE WESTERN BERING IN A
SCATTERED SNOW SHOWER REGIME TODAY. A FRONT AND LOW PRESSURE
SYSTEM WILL MOVE INTO THE CENTRAL AND EASTERN BERING SEA TODAY
BRINGING A MIX OF RAIN AND SNOW ALONG WITH INCREASING EASTERLY
WINDS. PRECIPITATION WILL BE OCCASIONAL OVER THE EASTERN
BERING...BUT OVER THE WESTERN/CENTRAL BERING A DEFORMATION BAND
WILL FORM AND BRING SOME STEADIER LIGHT SNOW. THIS SYSTEM IS IN A
WEAKENING PHASE...SO NORTHERLY WINDS WILL NOT GET MUCH STRONGER
THAN SMALL CRAFT CRITERIA.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7...THU THROUGH MON)...
ANOTHER DEEP BUT WEAKENING NORTH PACIFIC LOW AND ITS ASSOCIATED
ELONGATED FRONT STRETCHING FROM THE NORTHERN GULF AND INTO THE
EASTERN BERING SEA WILL KEEP PRECIPITATION MAINLY ALONG UPWIND
PORTIONS OF LARGE MOUNTAIN BARRIERS NEAR THE GULF COAST...AND
ACROSS THE BERING SEA AND KODIAK ISLAND. AN ARCTIC HIGH NORTH OF
THE NORTH SLOPE WILL TRY TO KEEP COLDER AIR FILTERING DOWN INTO
INTERIOR LOCATIONS...BUT MOST LOCATIONS AROUND THE SOUTHERN
MAINLAND (ESPECIALLY ALONG THE COAST) WILL EXPERIENCE ENOUGH INFLUENCE
FROM THE PACIFIC FRONT TO BECOME WARMER THAN AVERAGE.
THEREAFTER...THE SPRAWLING NORTH PACIFIC LOW WILL SLOWLY WEAKEN
AND DRIFT INTO THE EASTERN BERING SEA THROUGH LATE FRIDAY. THIS
WILL BRING SOME SHOWERY ACTIVITY INLAND...BUT KEEP A BULK OF THE
ACTIVITY ACROSS COASTAL LOCATIONS.

BY THE WEEKEND...THE ACTIVE NORTH PACIFIC JET PATTERN WILL SEND
ANOTHER STRONG LOW AND ASSOCIATED WARM FRONT INTO THE GULF OF
ALASKA AND EASTERN BERING...WITH THAT SURGE OF WARMER AIR POSSIBLY
PENETRATING INLAND SOMETIME LATE SUNDAY INTO MONDAY. THIS
POTENTIAL CHINOOK SCENARIO WOULD USHER IN DRASTICALLY WARMER THAN
AVERAGE TEMPERATURES OVER THE SOUTHERN MAINLAND FOR THE EARLY PART
OF NEXT WEEK. HOWEVER...THERE REMAINS SOME UNCERTAINTY WITH THAT WHICH
WE WILL CONTINUE TO MONITOR CLOSELY. WE CAN SAY WITH HIGHER
CONFIDENCE THAT A WARMING TREND WILL BE UNDERWAY... BRINGING
WARMER THAN AVERAGE TEMPERATURES ACROSS LARGE PORTIONS OF SOUTHERN
ALASKA. A STRONG HIGH OVER THE ARCTIC WILL CONTINUE TO DOMINATE
INTO THE MIDDLE OF NEXT WEEK ALONG WITH THE VERY ACTIVE PACIFIC
JET STREAM WELL SOUTH OF THE STATE. THIS ACTIVE PACIFIC PATTERN
WILL KEEP WINTER AT BAY FOR MOST OF SOUTHERN ALASKA.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...HEAVY FREEZING SPRAY WARNING 180 181 185
         GALE WARNING 119 120 130 131 132 136 137 138 139 150 155 160 165
         176 180

&&

SYNOPSIS AND MODEL DISCUSSION...CC
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MTL
LONG TERM...TP