Heavy Freezing Spray Warning 172, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT MON OCT 29 2012

.MODEL DISCUSSION...
GUIDANCE AGAIN IN FAIRLY GOOD AGREEMENT IN THE SHORT TERM. THE NAM
AGREES WELL WITH THE ECMWF ON THE SURFACE LOW PLACEMENT IN THE
NORTHERN GULF OF ALASKA. BASED ON THIS AND THE BETTER HANDLING
OF SMALL SCALE AND TERRAIN EFFECTS THE NAM WAS THE PREFERRED
MODEL...WITH SOME ECMWF MIXED IN FOR THE WESTERN MARINE ZONES.

.ANALYSIS AND UPPER LEVELS...
UPPER LEVEL HIGH PRESSURE OVER THE BERING SEA IS RETROGRADING AS A
DEEP UPPER LOW OVER NORTHERN ALASKA MOVES SOUTH. AT LOWER LEVELS
SURFACE HIGH PRESSURE IS BUILDING INTO ALASKA FROM THE WEST WITH THE
COLD ADVECTION ASSOCIATED WITH THE UPPER LOW MOVES INTO THE AREA.

.SHORT TERM FORECAST...
AS THE BERING SEA HIGH RETROGRADES INTO EXTREME NORTHEAST RUSSIA THE
UPPER LOW OVER NORTHERN ALASKA WILL CONTINUE TO MOVE TOWARD THE
SOUTH-SOUTHEAST THROUGH TUESDAY AND THEN SETTLE INTO THE NORTHERN
GULF OF ALASKA BY TUESDAY NIGHT. MOISTURE IS SOMEWHAT LIMITED WITH
THIS SYSTEM AND CHANCES OF PRECIPITATION WILL BE MAINLY OVER HIGHER
ELEVATIONS OF SOUTHERN ALASKA AS WELL AS EAST OF A LINE THAT RUNS
FROM ABOUT TALKEETNA THROUGH MONTAGUE ISLAND. SURFACE WINDS WILL
INCREASE IN MOST AREAS AS LOW LEVEL COLD ADVECTION SETS IN. A
SURFACE LOW WILL DEVELOP IN THE GULF OF ALASKA SOUTH OF SEWARD THIS
AFTERNOON AND THEN STRENGTHEN AS IT MOVES TO JUST SOUTH OF CAPE
SUCKLING BY TUESDAY MORNING. THIS LOW WILL THEN DRIFT SLOWLY
EASTWARD AND WEAKEN THROUGH WEDNESDAY NIGHT.

.LONG TERM FORECAST...
THE UPPER LOW SHOULD BE GENERALLY IN THE GULF OF ALASKA FOR THE
EXTENDED PORTION OF THE FORECAST. GLOBAL MODELS DISAGREE SOMEWHAT AS
TO THE ORIENTATION OF THE LOW AND HOW MUCH MOISTURE AND WARMTH WRAP
AROUND IT. CURRENT FORECASTS HAVE SLIGHTLY ABOVE NORMAL TEMPERATURES
IN SOUTH CENTRAL ALASKA AND SLIGHTLY BELOW IN SOUTHWEST...WITH
PRECIPITATION CHANCES NEAR NORMAL SOUTH CENTRAL AND BELOW NORMAL
SOUTHWEST.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING 121 127 128 130 132 140 150 170 172 175.
FIRE WEATHER...NONE.

LUDWIG OCT 12