Heavy Freezing Spray Warning 8, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ANCHORAGE AK
555 AM AKST FRI JAN 29 2016

.ANALYSIS AND UPPER LEVELS...

YESTERDAY OVER SOUTHCENTRAL...A MIXED BAG OF PRECIPITATION
DEVELOPED IN RESPONSE TO A TROUGH MOVING THROUGH THE
AREA...RESULTING IN INCREASED LIFT AND DIMINISHING SOUTHEASTERLY
DOWNSLOPING WINDS. THE DOWNSLOPING WINDS FREQUENTLY THIS WINTER
HAVE PROTECTED ANCHORAGE...THE WESTERN KENAI...AND THE MATANUSKA
AND SUSITNA VALLEYS FROM PICKING UP SIGNIFICANT PRECIPITATION IN
ANY FORM. WHILE OVERALL PRECIPITATION COVERAGE IS DIMINISHING THIS
MORNING...RAIN AND SNOW SHOWERS PERSIST PRIMARILY NORTH OF
ANCHORAGE TO THE MATANUSKA VALLEY. THE AIR MASS LEFT BEHIND FOR
THE REST OF SOUTHCENTRAL IS DRYING OUT...WITH A DRY LAYER HAVING
DEVELOPED ON THE 12Z SOUNDING FROM THE SURFACE TO ABOUT 800
MB...AND EVEN MORE SUBSTANTIAL DRYING ABOVE 700 MB.

MEANWHILE...AN AERIALLY STACKED LOW IS CENTERED RIGHT OVER
NUNIVAK ISLAND MOVING NORTH. THE LOW IS WRAPPING COLD AIR AROUND
ITS SOUTHERN FLANK WITH THE LEADING EDGE FORMING A DISTINCT
FRONT...WHICH IS MOVING THROUGH BRISTOL BAY THIS MORNING. COLD AIR
ADVECTION IS ONGOING ON BOTH SIDES OF THE FRONT...WITH MORE
COLDER AIR BEHIND IT. INSTABILITY ASSOCIATED WITH THE FRONT
REMAINS NOTABLE...WITH CONVECTIVE CUMULUS NOTED ON SATELLITE
DEMARCATING THE LEADING EDGE OF THE COLDER AIR BEHIND THE FRONT. A
DISTINCT DEFORMATION BAND OF STRATUS PERSISTS WEST OF THE LOW AND
BEHIND THE FRONT...CURRENTLY MOVING ACROSS THE PRIBILOFS AND
EASTERN BERING. THIS AREA OF SNOW DROPPED 3 INCHES OF SNOW IN
SAINT PAUL YESTERDAY.

OUT OVER THE ALEUTIANS...THE NEXT SURFACE LOW AND ASSOCIATED FRONT
ARE ENVELOPING MUCH OF THE ARCHIPELAGO WEST OF DUTCH HARBOR. GALE
FORCE WINDS AND LOCALLY HEAVY PRECIPITATION ARE ONGOING THROUGH
COMMUNITIES IN THAT AREA.

&&

.MODEL DISCUSSION...

MODEL DIFFERENCES CONCERNING THE EVOLUTION OF THE LOW MOVING
ACROSS THE ALEUTIANS PERSIST THIS MORNING...PARTICULARLY
CONCERNING HOW QUICKLY THE LOW CONSOLIDATES INTO A SINGLE
CIRCULATION CENTER. THE NAM WAS THE MODEL OF CHOICE WITH THE
MORNING PACKAGE...LARGELY AGREEING WITH THE GLOBAL
MODELS...ESPECIALLY THE EC. REGARDING THE PLACEMENT OF THE
LOW...THE NAM IS HANDLING THE WINDS WELL AND HAS A BETTER
RESOLUTION OF LOCAL FEATURES. THE CANADIAN WAS THE PRIMARY
OUTLIER...FAILING TO SHOW A CONSOLIDATED LOW CIRCULATION CENTER
EVEN BY SATURDAY AFTERNOON. ALL OF THE MODELS DEPICT A
STRENGTHENING JET STREAK FORMING EAST OF THE LOW IN RESPONSE TO
THE INCREASING TEMPERATURE GRADIENT BETWEEN THE COLD AIR
ASSOCIATED WITH THE DIGGING UPPER LEVEL TROUGH AND THE DEVELOPING
RIDGE EAST OF IT. THIS PATTERN IS FAVORABLE FOR CONSOLIDATING THE
INITIAL MULTIPLE SURFACE CIRCULATION CENTERS INTO ONE SINGLE LOW MORE
QUICKLY.

FURTHER EAST...ANY LARGE-SCALE DEFINABLE FEATURES THIS MORNING ARE
LACKING. ONLY SMALL TIMING DIFFERENCES EXIST IN THE MODELS
CONCERNING THE FRONT THAT IS CURRENTLY PUSHING ACROSS BRISTOL BAY
REACHING SOUTHCENTRAL FRIDAY EVENING. THE MODELS ALL AGREE THAT
VERY LITTLE IF ANY PRECIPITATION WILL RESULT FROM ITS PASSAGE.
FURTHER...THERE ALSO IS UNANIMOUS AGREEMENT THAT STRONG UPPER
LEVEL RIDGING WILL DEVELOP ACROSS SOUTHCENTRAL FOR THE WEEKEND.
FORECAST CONFIDENCE IS HIGH FOR THE LARGE-SCALE FEATURES DUE TO
VERY GOOD MODEL CONSENSUS.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...

WEAK COLD ADVECTION SPREADING NORTH AND EAST ACROSS SOUTHCENTRAL
THIS MORNING WILL CONTINUE THE THREAT OF SHOWERS (TRANSITIONING
FROM MIXED TO MORE SNOW THIS MORNING) INTO THE AFTERNOON HOURS.
AN UPPER TROUGH SWINGING IN FROM THE WEST TONIGHT WILL BRING
ANOTHER BRIEF PERIOD OF SNOW SHOWERS ACROSS SOUTHCENTRAL BEFORE
RIDGING BUILDS ON SATURDAY STABILIZING MOST OF THE AREA.
LOCALIZED FOG IS EXPECTED ACROSS SOUTHCENTRAL DURING THE LATE
NIGHT AND MORNING HOURS THROUGH SATURDAY...ESPECIALLY OVER THE
COPPER RIVER BASIN SATURDAY NIGHT. WEAK OUTFLOW CONDITIONS ARE
EXPECTED TO DEVELOP ACROSS THE EASTERN KENAI WITH THE FORMATION OF
A WEAK TROUGH OVER THE GULF. THESE CONDITIONS WILL BECOME SOMEWHAT
STRONGER LATE TONIGHT AND INTO SATURDAY AFTERNOON WITH PRESSURE
RISES ACROSS COOK INLET AND THE WESTERN KENAI IN THE WAKE OF THE EASTWARD
MOVING UPPER TROUGH.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A SURFACE LOW OVER NUNIVAK ISLAND PUSHES A WEAK FRONT INTO THE
SOUTHWEST COAST THIS MORNING. THIS FRONT WEAKENS AS IT MOVES EAST
THROUGH THE DAY OVER LAND. MOST OF THE AREA WILL SEE SCATTERED
SNOW SHOWERS WITH WEST-FACING SLOPES RECEIVING LIGHT
ACCUMULATIONS. THE WIND FLOW WILL GENERALLY STAY OUT OF THE
SOUTHEAST THROUGH THE WEEKEND WITH LOW PRESSURE REMAINING DOMINANT
OVER THE EAST BERING. WINDS ACROSS THE KUSKOKWIM DELTA WILL BE
GUSTY SATURDAY NIGHT AS THE NEXT FRONT MAKES LANDFALL. SNOW ON
SATURDAY LOOKS TO BE LARGELY CONFINED TO THE SOUTHWEST COAST WITH
RIDGING BUILDING FROM THE GULF TO THE KUSKOKWIM VALLEY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...

NORTHERLY FLOW CONTINUES ACROSS THE NORTHERN BERING THROUGH THIS
AFTERNOON WITH PERIODS OF MODERATE SNOW IN THE MORNING. A FRONT ACROSS
THE WESTERN AND CENTRAL ALEUTIANS EARLY THIS MORNING MAKES FAIRLY
QUICK PROGRESS TO THE NORTH AND EAST THROUGH THE DAY. THE LEADING
BOUNDARY WILL STRETCH ACROSS THE CENTRAL BERING BY THIS AFTERNOON...JUST
SOUTH OF THE PRIBILOF ISLANDS...TO THE EASTERN ALEUTIANS. WESTERLY
WINDS SHIFT BRIEFLY TO THE SOUTH AS THE BOUNDARY MOVES THROUGH.
THE WINDS ARE EXPECTED TO VARY A BIT THROUGH EARLY SUNDAY MORNING
DUE TO ANOTHER LOW THAT MOVES UP TO ADAK EARLY SATURDAY. THIS
SYSTEM BRINGS A WARM FRONT THAT NUDGES INTO THE EASTERN ALEUTIANS
FRIDAY NIGHT...THEN SPREADS INTO THE ALASKA PENINSULA ON SATURDAY
WITH NORTHWARD PROGRESS TOWARDS THE PRIBILOFS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

STRONG LOW PRESSURE IN THE CENTRAL BERING SUNDAY WILL MOVE
NORTHWEST WHILE BROADENING AND WEAKENING THROUGH SUNDAY NIGHT.
SOUTHERLY FLOW IN THE MID-LEVELS WILL CONTINUE FROM THE EASTERN
HALF OF THE BERING TO THE SOUTHWEST MAINLAND...WITH MID-LEVEL LOW
PRESSURE NEAR KAMCHATKA AND HIGH PRESSURE OVER THE PANHANDLE AND
EASTERN MAINLAND. THIS KIND OF ATMOSPHERIC PATTERN WILL ALLOW FOR
WARMER AND WETTER CONDITIONS WHERE THE SOUTHERLY FLOW
PERSISTS...WHILE UNDERNEATH THE MID-LEVEL HIGH...PLACES SUCH AS
THE COPPER RIVER BASIN AND SHELTERED VALLEYS INLAND WILL SEE THE
COLDEST TEMPERATURES AND DRIEST CONDITIONS.

BY THE MIDDLE OF NEXT WEEK THE RIDGE OVER THE EASTERN MAINLAND MAY
BREAK DOWN A BIT AS A LOW PRESSURE SYSTEM WEAKENS AND MOVES NORTH
TOWARD THE BRISTOL BAY AND SOUTHWEST ALASKA REGION. THIS MAY ALLOW
A BIT MORE ACTIVE WEATHER TO RETURN TO MUCH OF THE SOUTHERN
MAINLAND.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM 173
         GALES 150 155 160 165 170 172 174 175 176 177
               178 180 412 413 414
         HEAVY FREEZING SPRAY 185

&&

SYNOPSIS AND MODEL DISCUSSION...JPW
SOUTHCENTRAL ALASKA...BC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KH
LONG TERM...JA