Blizzard and High Wind in Alaska, December 21 to 22, 2010

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKST TUE DEC 21 2010

.MODEL DISCUSSION...
MODELS IN GOOD AGREEMENT THROUGH 120 HOURS. NAM PREFERRED EAST OF
170W DUE TO SUPERIOR HANDLING OF DETAIL. GFS PREFERRED OUT WEST DUE
TO BETTER RUN TO RUN CONSISTENCY.

.UPPER LEVELS...
UPPER LEVELS RELATIVELY FLAT AT PRESENT BUT EXPECTED TO DEVELOP INTO
A HIGH AMPLITUDE PATTERN OVER THE NEXT 36 HOURS. LOW CENTER OVER
NORTHWESTERN GULF SLIDES SOUTHWARD TO NEAR 50N 140W BY WED
AFTERNOON. RIDGE OF HIGH PRESSURE BUILDS OVER WESTERN ALEUTIANS AND
CENTRAL BERING SEA.

.ANALYSIS AND SHORT TERM FORECAST...
A 990 MB LOW SOUTH OF MIDDLETON ISLAND WILL MOVE TO SOUTHEAST OF
KODIAK ISLAND TONIGHT THEN DISSIPATE BY LATE TOMORROW MORNING.
SCATTERED SNOW SHOWERS MOVING EAST TO WEST ALONG THE GULF COAST WILL
INTERMITTENTLY REDUCE CEILINGS AND VISIBILITIES FROM CORDOVA TO
WHITTIER TO KODIAK TODAY...BUT MOST OF SOUTHCENTRAL ALASKA WILL
CONTINUE TO EXPERIENCE MOSTLY CLEAR SKIES. NORTHERLY GAP WINDS OF 30
TO 45 MPH THROUGH CHANNELED AREAS OF THE CHUGACH MOUNTAINS AND
ALEUTIAN RANGE ARE EXPECTED TO PERSIST THROUGH AT LEAST WEDNESDAY
NIGHT.
A 1006 MB LOW NORTH OF THE CENTRAL ALEUTIANS WILL PASS OVER THE
EASTERN ALEUTIANS TODAY AND DISSIPATE IN THE NORTH PACIFIC THIS
EVENING. ASSOCIATED OCCLUDED FRONT EXTENDS FROM THE SOUTHWESTERN
BERING AND THROUGH THE ALASKA PENINSULA. FRONT IS MOVING SLOWLY
EASTWARD AS IT DISSIPATES. SNOW AND RAIN SHOWERS ALONG THE FRONT
SHOULD TAPER OFF BY LATE TOMORROW MORNING.
PRESSURE GRADIENT ALONG THE ALASKA PENINSULA AND EASTERN BERING
TIGHTENS THROUGH 36 HOURS. GUSTS 45 TO 65 DEVELOPING THROUGH BAYS
AND PASSES TONIGHT AND CONTINUING THROUGH THURSDAY MORNING.
AT KODIAK...COLD AIR ADVECTING IN FROM THE NORTHWEST IN THE MID AND
UPPER LEVELS AND SNOW SHOWERS MOVING IN FROM THE EAST IN THE LOWER
LEVELS WILL COMBINE TO PRODUCE BLIZZARD OR NEAR BLIZZARD CONDITIONS
AS EARLY AS LATE THIS AFTERNOON.

.LONG TERM FORECAST...
COMPLEX LOW PRESSURE PERSISTS SOUTH OF GULF OF ALASKA. COLD AND
WINDY CONDITIONS WILL PREVAIL ACROSS SOUTHCENTRAL AND SOUTHWESTERN
ALASKA INTO THE WEEKEND.HIGH PRESSURE OVER THE ALEUTIANS AND
SOUTHERN BERING HOLDS THROUGH WEDNESDAY NIGHT THEN GIVES WAY ON
THURSDAY AS A LOW PRESSURE SYSTEM MOVES IN FROM THE WEST ON
THURSDAY.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD 171
MARINE...GALE 120 121 129 130 132 155 160 165 170 171 172 180
              351 352 413 414
         STORM 150
         HEAVY SPRAY 121 129 140 141 150 160 165 180 185 414
FIRE WEATHER...NONE.

ASB DEC 10