Gale Warning 1084, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 PM AKST SAT DEC 25 2010

.MODEL DISCUSSION...SYNOPTIC INITIALIZATIONS WERE IN GENERALLY GOOD
AGREEMENT AMONG THE MODELS THIS MORNING. FORECAST SOLUTIONS THROUGH
THE SHORT TERM STILL VARY CONSIDERABLY OVER THE GULF OF ALASKA AND SW
OF THE ALEUTIANS. THE NAM SEEMED TO INITIALIZE THE BEST OVER THE SE
GULF AND IS IN GENERALLY GOOD AGREEMENT WITH THE ECMWF THROUGH SUN
AFTERNOON. IT IS HARD TO FIND A CONSENSUS IN THE GULF AFTER THIS BUT
IT DOES APPEAR THAT A A MORE CONSOLIDATED CENTER WILL FORM AND MOVE
INTO THE SOUTHERN GULF TUE. FOR NOW WILL LEAN WITH THE NAM IN THE
NEAR TERM AND ONLY MAKE SLIGHT ADJUSTMENTS FOR THE REMAINDER OF THE
SHORT TERM IN THE GULF.

FURTHER WEST THE MODELS SEEM REASONABLE OVER THE SW MAINLAND AND
EASTERN BERING SEA. ALTHOUGH THE STRENGTH AND POSITION OF THE LOW
COMPLEX SOUTH OF THE WEST ALEUTIANS VARIES AMONG SOLUTIONS THE
RESULTANT PRESSURE GRADIENTS APPEAR IN GOOD AGREEMENT.

.ANALYSIS

UPPER LEVELS...LITTLE CHANGE IN THE OVERALL SYNOPTIC PATTERN FROM
YESTERDAY. AN UPPER LEVEL TROUGH ENCOMPASSES MUCH OF THE MAINLAND
WITH A WEAK CUT-OFF LOW AT THE BASE OF THE TROUGH OVER THE CENTRAL
GULF. A STRONG BLOCKING HIGH PRESSURE RIDGE IS ANCHORED OVER THE
SOUTHERN AND WESTERN BERING SEA. THE 100 KT UPPER LEVEL JET TRAVERSES
THE PERIPHERY OF THE RIDGE AND PLUNGES SOUTHWARD ACROSS THE EASTERN
BERING SEA.

AT THE SURFACE...
A BROAD LOW PRESSURE COMPLEX OVER THE GULF OF ALASKA CONTINUES TO
PERSIST. A WEAK TROUGH MOVED WEST ACROSS THE GULF OVERNIGHT AND IS
CURRENTLY WEAKENING AND MOVING OVER COOK INLET AND TOWARD KODIAK
ISLAND. THIS TROUGH BROUGHT SNOW AND SNOW SHOWERS TO THE KENAI
PENINSULA AND ANCHORAGE BOWL. THE PATTERN WILL CONTINUE TO BE FAIRLY
COMPLEX OVER THE GULF AND WILL PRESENT A FORECAST CHALLENGE
THROUGHOUT THE SHORT TERM.

A CONTINUED WEAK CYCLONIC OFFSHORE FLOW PATTERN IS DRAWING DRIER AND
COOLER AIR FROM THE INTERIOR INTO THE SOUTHERN MAINLAND. SNOW SHOWERS
ARE PREVALENT ACROSS MUCH OF THE EASTERN BERING AND AKPEN...DRIVEN BY
THE COLD AIR INTERACTING WITH THE RELATIVELY WARM OCEAN WATERS.
WIDESPREAD NORTHERLY GALE FORCE WINDS PERSIST ACROSS THE EASTERN
BERING IN CONJUNCTION WITH THE UPPER LEVEL JET. THE CENTRAL BERING
REMAINS RELATIVELY CALM UNDER A SURFACE HIGH PRESSURE CELL WHILE A
WEATHER FRONT IS STALLED OVER THE FAR WESTERN ALEUTIANS...UNABLE TO
PROGRESS EASTWARD DUE TO THE BLOCKING HIGH.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
.SOUTHCENTRAL...A WEAK TROUGH OVER THE NORTHERN GULF OF ALASKA IS
PRODUCING SOME SNOW SHOWERS AND TRACKING WEST. DO NOT EXPECT THIS TO
BE A MAJOR IMPACT ON SOUTHCENTRAL. A 980S CENTER OVER THE EASTERN
GULF THIS AFTERNOON MOVES SOUTH KENAI PEN SUN MORNING...THEN WEAKENS
AND DRIFTS SOUTH LATER SUN. THIS CENTER WILL SPREAD SNOW ACROSS THE
GULF AND BRING A SHOT OF SNOW TO THE ANCHORAGE BOWL BEGINNING LATE
TONIGHT. SNOW SHOULD TAPER OFF OVER INLAND AREAS OF SOUTHCENTRAL AS
UPPER SUPPORT FOR THIS FEATURE MOVES WEST. THE THREAT OF SNOW SHOWERS
WILL CONTINUE OVER MUCH OF THE GULF AND TO A LESSER EXTENT INLAND
THROUGH MON. WIND CHILLS WILL REMAIN NEAR ADVISORY LEVELS THROUGH
THOMPSON PASS INTO SUN AFTERNOON. ADVISORY MAY HAVE TO BE CONTINUED
THROUGH SUN NIGHT AS A SIGNIFICANT SLACKING OF THE GRADIENT AND
WARMING DOES NOT OCCUR UNTIL MON.

.SOUTHWEST MAINLAND...VERY COLD AIRMASS MOVING TO THE SOUTHWEST TODAY
AND WILL MOVE OUT INTO THE BERING TOMORROW. WINDS SHOULD BE STRONG
ENOUGH TO SUPPORT MINIMUM WIND CHILL ADVISORY CRITERIA FOR THE DELTA
AND TO A LESSER EXTENT THE BRISTOL BAY ZONE. SO WILL CONTINUE
EXISTING ADVISORY FOR ZONE 155 AND CANCEL FOR 161. TEMPERATURES
MODERATE A BIT MONDAY...BUT OVERALL WEATHER PATTERN REMAINS
UNSEASONABLY CALM THROUGH MIDWEEK.

.BERING SEA AND ALEUTIANS...STATIONARY HIGH PRESSURE OVER THE CENTRAL
BERING MEANS GUSTY NORTHERLY WINDS WILL CONTINUE OVER THE EASTERN
BERING. MEANWHILE...STALLED FRONT OVER THE WESTERN BERING WILL WEAKEN
AND SLOWLY DROP SOUTHWARD THROUGH MONDAY.

.LONG TERM FORECAST...
LONG RANGE MODELS ARE CONTINUING TO SUGGEST A PATTERN SHIFT BY NEXT
WEEKEND...WITH ACTIVE WEATHER RETURNING TO THE BERING SEA. EXTREME
COLD OVER SOUTHWEST ALASKA SHOULD CONTINUE TO SHIFT OVER TO THE
BERING SEA REGION...WHILE TEMPERATURES OVER SOUTHCENTRAL ARE LIKELY
TO REBOUND SIGNIFICANTLY TO NEAR SEASONAL NORMS WITH A MORE
PROGRESSIVE OVERALL WEATHER PATTERN.

.AER/ALU...WATCH/WARNING/ADVISORY SUMMARY
PUBLIC...WIND CHILL ADVISORIES ZONES 131 AND 155.
MARINE...GALES...155 160 165 170 176 179 180 185
         HEAVY FREEZING SPRAY...121 129 138 140 141 150 155 160 165
179 180 185
FIRE WEATHER...NONE.

RMC DEC 10