Heavy Freezing Spray Warning 1, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
417 PM AKST FRI JAN 15 2016

.ANALYSIS AND UPPER LEVELS...

A VERTICALLY STACKED LOW IS CENTERED A COUPLE HUNDRED MILES SOUTH
OF THE ALASKA PENINSULA THIS AFTERNOON. AN ASSOCIATED UPPER LEVEL
FRONT IS MOVING ACROSS SOUTHERN KODIAK ISLAND AND STRETCHING WEST
OVER THE SOUTHERN ALASKA PENINSULA. THIS FRONT IS PRODUCING
WIDESPREAD CLOUDINESS WITH SOME RAINFALL AFFECTING THE SOUTHERN
ALASKA PENINSULA AND EASTERN ALEUTIANS. UPPER LEVEL RIDGING ALONG
THE WEST COAST OF MAINLAND ALASKA IS SETTING UP A REX BLOCK...
PREVENTING LARGE INFLUXES OF LOW-LEVEL WARM AIR FROM OFF THE GULF
INTO SOUTHERN ALASKA. RECENTLY UPPER LEVEL FRONTS SUCH AS THE ONE
IMPACTING THE ALASKA PENINSULA HAVE BEEN STALLING OUT BEFORE
REACHING MAINLAND ALASKA. THE UPPER LEVEL WARM AIR ASSOCIATED WITH
THE RIDGE OVER SOUTHERN ALASKA HAS CREATED A STABLE VERTICAL
PROFILE...TRAPPING LOW LEVEL MOISTURE OVER SOUTHCENTRAL AND
PROMOTING THE RECENT BOUTS OF FREEZING FOG ACROSS THE AREA. THIS
IS IN ADDITION TO THE NEW SNOW COVER AROUND PORTIONS OF
SOUTHCENTRAL PROMOTING ADDITIONAL COOLING OF THE SURFACE
LAYER...WHICH ONLY FURTHER ENHANCES THE STRENGTH OF THE INVERSION.
THE LACK OF WIND WITH THE HIGH PRESSURE OVER THE AREA HAS ALLOWED
TEMPERATURES IN ANCHORAGE PARTICULARLY TO FALL TO THEIR LOWEST
LEVELS SINCE CHRISTMAS DAY.

&&

.MODEL DISCUSSION...

THE MODELS ARE IN EXCELLENT AGREEMENT THROUGH 60 HOURS IN THE
POSITIONS OF THE SYNOPTIC LOWS AND ASSOCIATED FRONTS. AS WITH THIS
MORNINGS RUNS...THE SMALL DIFFERENCES IN THE MODELS ARE THAT THE
EC IS SLIGHTLY FASTER IN TIMING...AND THE NAM IS SOMEWHAT SLOWER.
THUS THE GFS WAS USED AS THE MIDDLE GROUND SOLUTION ONCE AGAIN.
THE SMALL DIFFERENCES IN THE MODELS THROUGH THE SHORT TERM LEND
TOWARDS HIGHER FORECAST CONFIDENCE ACROSS THE DOMAIN.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
AN INTENSE LOW IS PUSHING ITS ASSOCIATED FRONT NORTH ACROSS THE
GULF OF ALASKA TO THE NORTH GULF COAST. AMPLE MOISTURE AND WARM
AIR HAS MOVED OVER KODIAK ISLAND. THE INCREASING PRESSURE GRADIENT
IN ADVANCE OF THIS FRONT WILL SERVE TO MIX OUT THE LOWER LAYERS OF
THE ATMOSPHERE BREAKING UP THE FOG OVER THE SOUTH CENTRAL REGION.
THIS WILL TAKE A BIT LONGER FOR THE COPPER RIVER BASIN AS THE
INVERSION IS STRONGER AND IT WILL TAKE LONGER FOR THE WIND TO
BREAK THROUGH THE INVERSION MIXING DOWN TO THE SURFACE. FOG WILL
REMAIN AN ISSUE FOR THE COPPER RIVER BASIN THROUGH EARLY SATURDAY.

PRECIPITATION ASSOCIATED WITH THE FRONT IS EXPECTED TO REMAIN
ALONG THE COASTAL REGIONS NOT MAKING MUCH PROGRESS INLAND.

&&

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

RAINFALL FROM THE NORTH PACIFIC FRONT AND WINDS CAN BE EXPECTED
TONIGHT ALONG THE SOUTH SIDE OF THE AKPEN...WITH DRY CONDITIONS
AND INCREASING HIGH CLOUDS OVER INTERIOR ZONES. AS THE FRONT MOVES
OVER THE ALEUTIAN RANGE IT WILL SPREAD MOISTURE INLAND ON SATURDAY
IN THE FORM OF INCREASING CLOUDS. AN UPPER LEVEL SYSTEM MOVING
FROM THE NORTH WILL INTERACT WITH THIS INCREASED MOISTURE AND
SPREAD SOME SNOW SHOWERS...ESPECIALLY OVER THE BRISTOL BAY
ZONE...SATURDAY NIGHT INTO SUNDAY.

&&

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

RAIN FROM THE NORTH PACIFIC FRONT WILL PERSIST OVER THE EASTERN
ALEUTIANS AND ALASKA PENINSULA ZONES THROUGH SUNDAY. RAIN AND SNOW
OVER THE WESTERN AND CENTRAL ALEUTIANS WILL TAPER OFF THROUGH
SATURDAY AND THEN BE ENHANCED BY AN UPPER WAVE MOVING ACROSS THE
BERING LATER ON SUNDAY.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
A BROAD UPPER LEVEL TROUGH STRETCHING FROM THE GULF OF ALASKA
ACROSS THE ALEUTIANS AND INCLUDING PORTIONS OF THE NORTH PACIFIC
AND SOUTHERN BERING WILL PERSIST IN THAT GENERAL LOCATION THROUGH
THE FIRST HALF OF NEXT WEEK. INDIVIDUAL AREAS OF LOW PRESSURE WILL
CONTINUE TO ROTATE AROUND THE BROADER CIRCULATION. FOR THE GULF
COASTAL AREAS THIS WILL RESULT IN A SERIES OF WEAKENING FRONTAL
SYSTEMS AND TROUGHS ROTATING FROM THE SOUTHEAST GULF UP ALONG THE
NORTHERN GULF COAST. FURTHER WEST...WEAK TROUGHS WILL ROTATE
THROUGH SOUTHWEST ALASKA AND OUT OVER BRISTOL BAY. AS WE MOVE INTO
MID TO LATE NEXT WEEK SOME ADDITIONAL BIGGER SYSTEMS WILL SPIN UP
ALONG THE STRONG JET STREAM TO THE SOUTH AND PERHAPS START A
GRADUAL PATTERN SHIFT BRINGING THE STORM TRACK FURTHER NORTH.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 119 120 127 130 131 136 137 139 160 170-174 178-185.
		 STORM 132 138 150 155 165.
         HEAVY FREEZING SPRAY 180-185.
&&

SYNOPSIS AND MODEL DISCUSSION...RMC
SOUTHCENTRAL ALASKA...SAM
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DS
LONG TERM...JR