Small Craft Advisory 1022, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
454 AM AKST WED DEC 23 2015

.ANALYSIS AND UPPER LEVELS...
MUCH OF THE SOUTHERN MAINLAND REMAINS UNDER A FAIRLY WEAK
PATTERN...WITH THE BROAD UPPER LEVEL TROUGH SLOWLY DRIFTING
EASTWARD OVER THE SOUTHERN MAINLAND. OVER THE ALEUTIANS AND BERING
SEA...THE PATTERN BEGINS TO AMPLIFY AS AN UPPER LEVEL RIDGE BEGINS
TO BUILD OVER THE CENTRAL AND EASTERN ALEUTIANS/BERING AND AN
UPPER LEVEL LOW STARTS TO DEVELOP ON THE WESTERN FLANK OF THE
RIDGE.

AT THE SURFACE...A BROAD AREA OF LOW PRESSURE OVER THE GULF
CONTINUES TO SLOWLY SHIFT EASTWARD...WITH SHOWERS AND GUSTY WINDS
ALONG THE NORTHERN GULF COAST CONTINUING TO DIMINISH THIS MORNING.
THE DENSE FOG FROM LAST NIGHT HAS DIMINISHED TO PATCHY FOG OVER
PARTS OF SOUTHCENTRAL THIS MORNING...AS THE LOW LEVEL MOISTURE
BEGINS TO DWINDLE AND THE SURFACE INVERSIONS OVER THE AREA BEGIN
TO WEAKEN. OUT WEST...WEAK RIDGING BEGINS TO BUILD OVER THE
EASTERN ALEUTIANS AND BERING...BRINGING INSTABILITY SHOWERS AND
SOME GUSTY GAP WINDS ALONG THE ALASKA PENINSULA. SOME OF THE
INTERIOR PORTIONS OF THE SOUTHWEST MAINLAND REMAIN UNDER FOGGY
CONDITIONS AS RIDGING BUILDS IN FROM THE WEST AND LOW LEVEL
MOISTURE REMAINS TRAPPED UNDER SURFACE INVERSIONS. A WEAKENING
SURFACE LOW OVER THE KUSKOKWIM DELTA IS CURRENTLY BRINGING SOME
SNOW SHOWERS TO THE AREA AND HAS HELPED TO MIX OUT SOME OF THE FOG
THAT WAS ENVELOPING THE AREA OVERNIGHT. FURTHER WEST...A
DEEPENING NORTH PACIFIC LOW HAS STARTED TO MOVE INTO THE WESTERN
AND CENTRAL ALEUTIANS. OBSERVATIONS ALONG THESE AREAS HAVE STARTED
TO TRICKLE IN...SHOWING INCREASING WINDS AND PRECIPITATION
ASSOCIATED WITH THIS SYSTEM.

&&

.MODEL DISCUSSION...
OVERALL THE MODELS REMAIN IN GOOD SYNOPTIC AGREEMENT REGARDING
THE TRACK AND INTENSITY OF THE MAJOR FEATURES IMPACTING THE AREA
OF RESPONSIBILITY. MODELS CONTINUE TO AGREE ON THE TRACK AND
STRENGTH OF THE LOW AND ASSOCIATED FRONT TRACKING INTO THE WESTERN
AND CENTRAL ALEUTIANS. HOWEVER...THEY CONTINUE TO DIVERGE AND
STRUGGLE WITH THE TRACK AS THIS SYSTEM CROSSES INTO THE BERING
SEA THIS EVENING. THE ECMWF WAS THE MODEL OF CHOICE CONCERNING
THE ABOVE MENTIONED DIFFERENCES. AS WE HEAD INTO THURSDAY...MODELS
HAVE COME INTO BETTER AGREEMENT REGARDING A TRIPLE POINT LOW
DEVELOPING OFF THE ABOVE MENTIONED SYSTEM OVER THE SOUTHERN BERING
NEAR THE EASTERN AND CENTRAL ALEUTIANS. THE NAM AND GFS SOLUTIONS
WERE PREFERRED WITH THIS DEVELOPING SYSTEM...WITH THE EC BECOMING
THE SLOWER AND MORE NORTHERLY OUTLIER AS THE SYSTEM MOVES SLOWLY
NORTHEAST ALONG THE ALASKA PENINSULA. OVERALL FORECAST CONFIDENCE
REMAINS HIGH CONSIDERING LOW MODEL SPREAD.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE WEAK UPPER LEVEL TROUGH OVER SOUTH CENTRAL ALASKA WILL MOVE
SOUTH AND EAST OF THE AREA TONIGHT. THIS TROUGH IS NOT PRODUCING
MUCH PRECIPITATION...ONLY A FEW FLURRIES...BUT PLENTY OF CLOUDS.
SKIES SHOULD CLEAR CONSIDERABLY TONIGHT AS AN UPPER LEVEL RIDGE
BUILDS IN FROM THE WEST. OFFSHORE WINDS WILL ALSO INCREASE AT THE
FAVORABLE LOCATIONS. THIS RIDGE IS BUILDING AHEAD (EAST) OF A
POTENT LOW IN THE BERING SEA AND ALEUTIANS. WINDS WILL DIMINISH
AND CLOUDS BEGIN TO INCREASE THURSDAY NIGHT AS THE RIDGE AXIS
REACHES SOUTH CENTRAL AND A FRONT FROM THE ALEUTIAN SYSTEM MOVES
TOWARD THE AREA.

&&

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

A WEAK LOW MOVING ACROSS THE KUSKOKWIM DELTA THIS MORNING WILL
SHIFT INTO THE LOWER KUSKOKWIM VALLEY LATE THIS MORNING AND
AFTERNOON...BRINGING SNOW SHOWERS BEFORE WEAKENING BY THIS
EVENING. OTHERWISE...AREAS OF FOG WILL BE PREVALENT ACROSS THE
REMAINDER OF THE SOUTHWEST MAINLAND GIVEN RELATIVELY WEAK WINDS
AND A STAGNANT AIR MASS WITH STRONG INVERSIONS. ATTENTION QUICKLY
TURNS TO A GALE FORCE FRONT MOVING INTO THE EASTERN BERING
SEA...WHICH WILL MOVE INTO SOUTHWEST ALASKA TONIGHT AND THURSDAY.
WITH A OFFSHORE PRESSURE GRADIENT...COASTAL AREAS WILL BEGIN AS
SNOW...BEFORE CHANGING TO A RAIN AND SNOW MIX. HOWEVER...THE
STRONGEST PRESSURE GRADIENT AND POTENTIAL FOR HEAVIEST SNOW WILL
BE ACROSS THE KUSKOKWIM DELTA LATE THURSDAY NIGHT THROUGH THURSDAY
MORNING. THIS WILL SUPPORT PERIODIC BLIZZARD CONDITIONS ALONG THE
COAST FROM KIPNUK NORTHWARD...WITH REGIONS OF BLOWING SNOW INLAND
AS WELL...ALTHOUGH NOT AS SEVERE. THE FRONT WILL LIFT NORTH
THURSDAY AFTERNOON...WITH MOST AREAS ACROSS SOUTHWEST DRYING OUT
AND WARMING UP BEFORE ANOTHER FRONT MOVES IN THURSDAY NIGHT AND
EARLY FRIDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
A STORM FORCE LOW IS CURRENTLY DEVELOPING ACROSS THE SOUTHWESTERN
BERING SEA AND WESTERN ALEUTIANS THIS MORNING. RAIN AND SNOW WILL
QUICKLY TURN TO ALL RAIN AS A STRONG WARM FRONT MOVES INTO THE
REGION. THE ONLY LOCATION TO REMAIN COLD ENOUGH FOR SNOW AND SNOW
SHOWERS WILL BE ACROSS THE FAR WESTERN ALEUTIANS WHERE COLDER
ARCTIC AIR WILL WRAP AROUND THIS LOW. IMPACTS WILL BE STORM FORCE
WINDS ACROSS THE WESTERN AND CENTRAL ALEUTIANS...BUT THE STRONGEST
CORE OF WINDS LOOKS TO REMAIN IN BETWEEN ADAK AND SHEMYA...SO NO
HURRICANE FORCE WINDS ARE EXPECTED AT THIS TIME. THIS LOW WILL
REMAIN IN PLACE THEN DRIFT SOUTHEAST...EVENTUALLY MERGING WITH
ANOTHER STORM FORCE NORTH PACIFIC LOW EXPECTED TO MOVE INTO THE
EASTERN BERING LATE THURSDAY INTO FRIDAY MORNING. THE STRONGEST
CORE OF WINDS WILL SHIFT EAST TO THE CENTRAL AND EASTERN
BERING/ALEUTIANS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
GUSTY WINDS WILL LIKELY CONTINUE THROUGH FRIDAY AS THE MATURING
EXTRATROPICAL CYCLONE (THE SOUTHERN BERING TRIPLE POINT ALLUDED
TO ABOVE) WRAPS COLD AIR ALOFT AROUND ITSELF INCREASING
INSTABILITY AND THE POTENTIAL FOR WINDS ALOFT TO MIX DOWN.

FURTHER TO THE EAST...NORTH TO NORTHEASTERLY WINDS THROUGH
SHELIKOF STRAIT...COOK INLET AND ACROSS THE BARREN ISLANDS WILL
ALSO BE ENHANCED AS THE ATTENDANT FRONT APPROACHES. COLD
NORTHERLY OUTFLOW WINDS WILL INCREASE AGAIN RAPIDLY THROUGH THE
DAY FRIDAY AS THE APPROACHING FRONT TIGHTENS THE PRESSURE GRADIENT
AGAIN. ADDITIONALLY SOUTHEASTERLY GAP WINDS THROUGH TURNAGAIN ARM
AND OTHER SIMILARLY ORIENTED GAPS WILL PICK UP LATE THURSDAY NIGHT
THROUGH FRIDAY. THE COLD DRY NORTHERLY SURFACE FLOW OUT OF THE
INTERIOR AS WELL AS SOUTHEASTERLY DOWNSLOPING WINDS ACROSS THE
CHUGACH MOUNTAINS WILL BOTH MAKE IT HARD FOR THE PRECIPITATION
ASSOCIATED WITH THE INCOMING FRONT TO MAKE IT VERY FAR INLAND.

THE DEEP LOW WILL REMAIN VERTICALLY STACKED IN THE VICINITY OF
THE EASTERN ALEUTIANS AND WESTERN ALASKA THROUGH FRIDAY EVENING
BEFORE STARTING TO WEAKEN AND DRIFT EAST INTO THE WESTERN GULF
FRIDAY NIGHT AND SATURDAY AND THEN INTO THE CENTRAL GULF ON
SUNDAY. AN ACTIVE STORM TRACK IS LIKELY TO BRING ADDITIONAL STRONG
LOWS INTO THE ALEUTIANS AND BERING THROUGH THE MIDDLE OF NEXT
WEEK. STORMS ENTERING THE GULF WILL MORE LIKELY BE IN THE
WEAKENING PHASE OR REMAIN FURTHER TO THE SOUTH AND CLOSER TO THE
STRONGER JET.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...BLIZZARD WARNING...155.
MARINE...GALES...127 129 131 150 165 170-176 179-181
		 STORMS...155 177 178 185
         HVY FRZG SPRY....180 181 185.

&&

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