Blizzard and High Wind in Alaska, November 15 to 16, 2010

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 PM AKST MON NOV 15 2010

.ANALYSIS AND UPPER LEVELS...
A COLD CORE UPPER TROUGH IS DROPPING EAST ACROSS MAINLAND ALASKA
USHERING IN BELOW AVERAGE TEMPERATURES TO THE REGION. A LARGE AREA OF
HIGH PRESSURE IS BUILDING OVER THE CENTRAL BERING SEA. AT THE
SURFACE...A 1014 MB LOW IS DEVELOPING IN THE NORTHERN GULF WHICH IS
HELPING TO TIGHTEN THE PRESSURE GRADIENT. THE COMBINATION OF THE
BUILDING HIGH TO THE WEST AND DEVELOPING LOW IN THE GULF WILL RESULT
IN VERY STRONG WINDS THROUGH CHANNELED TERRAIN.

.MODEL DISCUSSION...
MODELS CONTINUE TO BE IN EXCELLENT AGREEMENT THROUGH THE SHORT TERM.
ONLY MINOR ADJUSTMENTS ARE NEEDED TODAY TO THE FORECASTS.

.SHORT TERM FORECAST...
THE FOCUS FOR THE DAY IS THE UPCOMING WIND STORM ACROSS SOUTH CENTRAL
ALASKA. COLD AIR IS FILTERING SOUTH AND EAST OVER THE REGION WHILE
THE PRESSURE GRADIENT INCREASES. GAP WINDS HAVE ALREADY BEGUN TO
INCREASE...BUT THE STRONGEST WINDS ARE EXPECTED LATE TONIGHT THROUGH
WEDNESDAY. THESE WINDS WILL INCREASE AS A RESULT OF THE UPPER TROUGH
SWINGING THROUGH SOUTHCENTRAL TONIGHT AND ADDING UPPER LEVEL SUPPORT.

WARNING LEVEL WINDS ARE POSSIBLE IN MANY ZONES. SINCE THERE IS AN
ABUNDANCE OF TRANSPORTABLE SNOW THROUGH THOMPSON PASS...WE ARE
EXPECTING A GROUND BLIZZARD LATER THIS AFTERNOON THROUGH TUESDAY
AFTERNOON. AT THAT POINT...THE TROUGH AXIS MOVES THROUGH AND WINDS
INCREASE AND WILL BEGIN MIXING DOWN TO VALDEZ.

MOST OTHER AREAS HAVE RECENT LIGHT SNOW FALL SO BLOWING AND DRIFTING
SNOW IS POSSIBLE...ALTHOUGH BLIZZARD CONDITIONS ARE NOT EXPECTED
OUTSIDE OF THOMPSON PASS.

BY WEDNESDAY THE AREA OF HIGH PRESSURE WILL BE CENTERED OVER THE
MAINLAND...JUST NORTH OF THE ALASKA RANGE. AT THIS POINT...THE GULF
OF ALASKA LOW WILL WEAKEN AND MERGE WITH ANOTHER LOW TOWARD THE
PANHANDLE. AS THAT LOW DISSIPATES...THE PRESSURE GRADIENT WILL WEAKEN
SO WIND SPEEDS WILL DIMINISH LATE WEDNESDAY. TEMPERATURES WILL SLOWLY
REBOUND MIDWEEK IN RESPONSE TO THE RELATIVELY WARM AIRMASS UNDER THE
RIDGE OF HIGH PRESSURE...SO NEAR CLIMATOLOGICAL NORMS FOR HIGHS AND
BELOW AVERAGE FOR OVERNIGHT LOW TEMPERATURES LATE IN THE WEEK.

SOUTHWEST ALASKA...A 5000 FOOT STRATUS DECK IS BLANKETING THE
SOUTHWEST MAINLAND. ONLY A FEW FLURRIES ARE FALLING AROUND THIS AREA
TODAY. WINDS WILL GENERALLY INCREASE DURING THE AFTERNOON AS THE
RIDGE BUILDS TO THE WEST. DRIER AIR WILL ALSO FILTER ACROSS THE
REGION RESULTING IN A FEW CLEAR AND COLD DAYS. THE BRISK NORTHERLY
WINDS WILL ALSO REDUCE WIND CHILL READINGS.

HIGH CLOUDS WILL INVADE THE COAST TUESDAY AFTERNOON BUT THE RIDGE
WILL MAINTAIN THE HOLD OF THE REGION THROUGH THE END OF THE WEEK.

BERING SEA/ALEUTIANS...A VERY QUIET PATTERN OUT WEST THANKS TO THE
BUILDING RIDGE OF HIGH PRESSURE. A FRONT IS APPROACHING THE FAR
WESTERN ALEUTIANS BUT THE RIDGE WILL PROVE TO BE TOO
STRONG...STALLING THE FRONT OVER THE WESTERN BERING. LATER IN THE
WEEK AS THE RIDGE AXIS MOVES TO SOUTHWEST ALASKA...A REINVIGORATED
FRONTAL BOUNDARY WILL PUSH INTO THE WESTERN AND CENTRAL ALEUTIANS.

.LONG TERM FORECAST...
THE BLOCKING UPPER RIDGE IN THE BERING SLOWLY MOVE EAST TO THE
MAINLAND LATE IN THE WEEK. THIS LOOKS TO HELP BREAK THE COLD-SNAP
OVER THE MAINLAND. RESULTING ONSHORE FLOW HOWEVER BRINGS INCREASED
MOISTURE AND CHANCES OF PRECIPITATION.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 131
         HIGH WIND WATCH 111 131 135.
MARINE...STORM 126 127 128 130 150
         GALE 120 121 129 132 138 155 160 172 175 176 185.
FIRE WEATHER...NONE.

AB NOV 10