Small Craft Advisory 168, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
420 PM AKST WED FEB 20 2013

.ANALYSIS AND UPPER LEVELS...
A CLOSED UPPER HIGH REMAINS IN PLACE OVER THE CHUKCHI SEA THIS
AFTERNOON...WITH A LARGE UPPER LOW LOCATED TO ITS SOUTHWEST NEAR THE
SOUTHERN KAMCHATKA PENINSULA AND ZONAL FLOW SPANNING MUCH OF THE
NORTHERN PACIFIC. A PAIR OF UPPER LOWS ARE LOCATED OVER THE GULF OF
ALASKA...WITH ONE LOCATED OVER THE NORTHERN GULF NEAR KODIAK ISLAND
AND THE OTHER MOVING RAPIDLY EASTWARD TOWARD THE PANHANDLE AS IT
TRANSITIONS INTO AN OPEN WAVE. A 979 MB LOW IS PRESENT OVER THE
NORTHERN GULF WITH AN ASSOCIATED FRONT EXTENDING EASTWARD FROM THE
CENTER AS THESE FEATURES CONTINUE TO BRING SNOW SHOWERS TO AREAS
ALONG THE COAST.

.MODEL DISCUSSION...
DESPITE SOME VARIATIONS IN STRENGTH AND TIMING OF SYSTEMS...MODELS
ARE IN REASONABLE AGREEMENT THROUGH THE SHORT TERM WITH RESPECT TO
THE OVERALL SYNOPTIC PATTERN. THE CHUKCHI SEA HIGH/KAMCHATKA LOW WILL
BOTH REMAIN IN PLACE THROUGH LATE THURSDAY NIGHT AS A SERIES OF WAVES
CONTINUE TO MOVE RAPIDLY EASTWARD ACROSS THE NORTHERN PACIFIC. THE
KAMCHATKA LOW WILL THEN BEGIN TO WEAKEN ON FRIDAY AS A STRONG NORTH
PACIFIC LOW RAPIDLY DEVELOPS ALONG ITS EASTERN PERIPHERY AND MOVES
INTO THE WESTERN/CENTRAL ALEUTIANS...BRINGING STRONG WINDS AND
PRECIPITATION TO THOSE AREAS. MEANWHILE...THE CHUKCHI HIGH WILL
RETREAT POLEWARD INTO THE ARCTIC AS A CLOSED UPPER LOW DEVELOPS OVER
NORTHERN ALASKA AND SLIDES SOUTHWESTWARD TOWARD THE BERING STRAIT BY
THE END OF THE WEEK.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
SNOW WILL BEGIN TO SPREAD INLAND OVER SOUTHCENTRAL ALASKA TONIGHT AND
PERSIST THROUGH THURSDAY NIGHT AS THE LOW OVER THE NORTHERN GULF
BECOMES NEARLY STATIONARY AND THEN MOVES SLOWLY NORTHWARD TOWARD THE
KENAI PENINSULA. SNOW WILL BEGIN TO TAPER OFF ON FRIDAY MORNING AS
THE LOW WEAKENS...HOWEVER A CHANCE OF PRECIPITATION WILL REMAIN IN
THE FORECAST THROUGH THE WEEKEND AS ANOTHER FRONT MOVES INTO THE
GULF.

SOUTHWEST ALASKA...
SCATTERED SNOW SHOWERS WILL CONTINUE THROUGH THURSDAY AND THEN BEGIN
TO TAPER OFF BY FRIDAY MORNING AS TRANSITORY RIDGING MOVES OVERHEAD.
THE BREAK IN PRECIPITATION WILL BE SHORT LIVED AS A FRONT ASSOCIATED
WITH THE STRONG LOW MOVING OVER THE ALEUTIANS WILL REACH THE AKPEN ON
FRIDAY AND APPROACH THE SOUTHWEST MAINLAND ON FRIDAY NIGHT.

ALEUTIANS/BERING SEA...
PERIODS OF RAIN AND SNOW WILL CONTINUE THROUGH THURSDAY ACROSS THE
ALEUTIANS AS ANOTHER SYSTEM TRAVERSES THE NORTHERN PACIFIC. A
POWERFUL LOW WILL THEN MOVE OVER THE WESTERN AND CENTRAL ALEUTIANS BY
FRIDAY MORNING...BRINGING WIDESPREAD PRECIPITATION AND STRONG WINDS
TO THE SOUTHERN BERING AS THE SYSTEM ADVANCES EASTWARD.

.LONG TERM FORECAST...
AN ACTIVE PATTERN WILL CONTINUE INTO THE EXTENDED TERM AS A LONG WAVE
TROUGH REMAINS IN PLACE OVER THE BERING AND SYSTEMS MOVING ACROSS THE
NORTHERN PACIFIC CONTINUE TO BRING PERIODIC CHANCES OF PRECIPITATION
TO SOUTHERN ALASKA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE WARNING 130 132 136 137 138 150 155
         HEAVY FREEZING SPRAY 130 140 141
FIRE WEATHER...NONE

CB FEB 13