Brisk Wind Advisory 59, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
355 PM AKST FRI DEC 27 2013

.MODEL DISCUSSION...
GFS CONTINUES TO PERFORM POORLY AND INCONSISTENTLY WITH SIGNIFICANT
RUN TO RUN VARIABILITY AS COMPARED TO EC OR UKMET BEYOND HOUR 96
THOUGH DETAILS ARE CLOSE IN THE SHORT TERM. MODELS ARE FAIRLY
CONSISTENT IN BREAKING THE PSEUDO REX BLOCK DOWN OVER THE COMING 72
HOURS BY ROTATING THE UPPER LOW WESTWARD ALONG THE SIBERIAN ARCTIC
COAST THOUGH CUT OFF UPPER HIGH REMAINS QUASI-STATIONARY. GENERAL
FLOW EXPECTED TO DE-AMPLIFY AND BECOME MORE ZONAL FROM THE COAST OF
ASIA TO SOUTHEAST ALASKA DAY FOUR THROUGH EIGHT WITH THE LIKELIHOOD
OF A MERIDIONAL RIDGE REBUILDING AGAIN VICINITY 150W TOWARDS DAY 10.

.ANALYSIS AND UPPER LEVELS...
BROAD...COMPLEX LONG WAVE TROUGH ALONG 172W WITH MAJOR CENTER NEAR
45N HAS SEVERAL VORTICES EMBEDDED IN CIRCULATION AS EVIDENCED BY WV
IMAGERY. COMPLEX LOW SYSTEM HAS BEEN DEPRESSED SOUTHWARD UNDER PSEUDO
REX BLOCK THAT DEVELOPED OVER NORTHERN ALASKA INTO THE BEAUFORT MID
WEEK. A WEAK SURFACE LOW IS DEVELOPING ALONG TRIPLE POINT OF THE CORE
OF THE MIDDLE LATITUDE JET WHICH REMAINS SOUTH OF THE FORECAST AREA.
A SECOND LOW IS FORMING IN THE NORTHERLY BRANCH THAT WILL MOVE INTO
SOUTH CENTRAL TONIGHT.

BROAD SURFACE HIGH PRESSURE STILL THE MAIN FEATURE IMPACTING COPPER
BASIN. HOWEVER...MID LEVEL FLOW TURNING MORE WESTERLY OVER THE COPPER
BASIN HAS PUSHED IN MID CLOUDS SIGNIFICANTLY MODERATING TEMPERATURES.

NEXT UPSTREAM SYSTEM MOVING OFF THE ASIAN CONTINENT.

.SHORT TERM FORECAST...
FRONTAL SYSTEM APPROACHING SOUTH CENTRAL AND EASTERN ALASKA PENINSULA
WILL BRING MODERATING TEMPERATURES AND LIGHT SNOW TO THE REGION.
LIGHT SNOW WILL SPREAD ACROSS PRINCE WILLIAM SOUND AND THE COPPER
BASIN TONIGHT. IN BRISTOL BAY THE PRECIPITATION WILL MIX WITH LIGHT
FREEZING RAIN OVERNIGHT AS TEMPERATURES AT THE TOP OF THE BOUNDARY
LEVEL WARM ABOVE FREEZING. THE SNOW SHOULD TAPER OFF FROM THE SOUTH
OVERNIGHT AND SATURDAY MORNING. PRECIPITATION SHOULD REMAIN LIQUID
ALONG THE ALEUTIANS.

.LONG TERM FORECAST...
LOW PRESSURE SYSTEM EXITING ASIAN CONTINENT WILL DEEPEN RAPIDLY NEAR
KAMCHATKA THROUGH SATURDAY REBUILDING THE RIDGE IN ADVANCE THROUGH
THE CENTRAL ALEUTIANS. LOW EXPECTED TO RE-CURVE NORTHWESTWARD AND
FILL WITH A SECONDARY UPPER LOW EJECTING EASTWARD FLATTENING THE
FLOW SATURDAY NIGHT AND SUNDAY. SURFACE LOW SHOULD FORM ALONG THE
DEVELOPING WEATHER FRONT ON THE TRIPLE POINT ON SUNDAY.

A SERIES OF WEATHER SYSTEMS WILL SKIRT THE ALEUTIANS AND INTO THE
NORTH GULF NEXT WEEK IN THE RELATIVELY ZONAL FLOW UNTIL RUNNING INTO
THE LONG WAVE RIDGE VICINITY 140W. THIS SHOULD ENSURE NEXT WEEK WILL
BE CONSIDERABLY MORE MODERATE (TEMPERATURES) ACROSS THE AREA WITH
PERIODS OF SNOW AS THE SYSTEMS MOVE INLAND. PRECIPITATION WILL FALL
AS RAIN ALONG THE COASTAL AREAS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...WINTER WEATHER ADVISORY 131.
MARINE...GALE WARNING...119 127 130 138 177 178.
         HEAVY FREEZING SPRAY WARNING...127 139 180 181 185.
FIRE WEATHER...NONE.

CAS DEC 13