Small Craft Advisory 274, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKDT TUE MAR 26 2013

.ANALYSIS AND UPPER LEVELS...

A LARGE NEGATIVE TILT UPPER VORTEX OVER THE ALASKA MAINLAND IS
CLEARLY VISIBLE ON SATELLITE IMAGERY THIS MORNING...WITH A PROMINENT
DRY AIRSTREAM ON THE BACKSIDE OF THIS FEATURE PENETRATING THROUGH THE
NORTHERN GULF OF ALASKA. A VERY WELL DEFINED PRINCE WILLIAM SOUND LOW
CAN BE SEEN ON RADAR...WITH THE LOW CURRENTLY SITUATED NEAR
HINCHINBROOK ENTRANCE. SNOW SHOWERS CONTINUE TO WRAP AROUND THIS
FEATURE ACROSS MUCH OF PWS...WITH WEAK ISOLATED SHOWERS IN COOK
INLET.

FARTHER WEST...A WEAK UPPER LOW SPLITTING FROM THE NORTHERN STREAM IS
DIGGING SOUTH OF THE ALEUTIAN CHAIN NEAR DUTCH HARBOR...WITH A
SHORTWAVE UPPER RIDGE AXIS AND ELONGATED STRETCHING DEFORMATION ZONE
PUSHING INTO THE WESTERN GULF OF ALASKA. A POWERFUL LOW IS CURRENTLY
DEVELOPING SOUTHEAST OF THE KAMCHATKA PENINSULA...WITH A STRONG WARM
FRONT/OCCLUSION SLIDING INTO THE WESTERN ALEUTIANS. THIS UPPER LOW
WILL EVENTUALLY DEVELOP INTO A LONGWAVE TROUGH WHICH WILL IMPACT ALL
OF THE BERING SEA AND SOUTHERN MAINLAND ALASKA THROUGH THE WEEKEND.

.MODEL DISCUSSION...

ALL THE NUMERICAL GUIDANCE IS IN GOOD AGREEMENT THROUGH THE END OF
THE WORK WEEK. AS USUAL...THERE ARE SMALL DIFFERENCES IN THE
DETAILS...BUT NOTHING SUBSTANTIAL. THE BIGGEST DIFFERENCES BEGIN TO
ARISE WITH THE NEXT LONGWAVE TROUGH ONCE IT REACHES THE GULF
COAST...AND THE LONGWAVE PATTERN THEREAFTER. ACROSS SOUTHERN
ALASKA...THE NAM WAS THE FAVORED MODEL OWING TO ITS HIGHER RESOLUTION
AND BETTER HANDLING OF THE PWS LOW...WHILE THE GEM GLOBAL WAS FAVORED
ACROSS THE BERING SEA AND ALEUTIANS.

.SHORT TERM FORECAST...

SOUTHCENTRAL...
A FEW SHOWERS CONTINUE TO LINGER ACROSS PORTIONS OF COOK INLET AND
THE INTERIOR MOUNTAINS INCLUDING ANCHORAGE...BUT THESE WILL BE MINOR
WITH NO ACCUMULATIONS EXPECTED. WITH SKIES GENERALLY CLEARING OUT
TODAY AND TONIGHT...TEMPERATURES ARE EXPECTED TO PLUMMET AS HIGH
PRESSURE BUILDS OVER THE REGION. TEMPERATURES WILL SLOWLY RECOVER
WEDNESDAY AS THE NEXT SYSTEM TRACKS TOWARD THE REGION.

ACROSS PRINCE WILLIAM SOUND...SNOW SHOWERS IMPACTING THE COAST WILL
BEGIN TO DIMINISH BY THE AFTERNOON AS THE LOW WEAKENS AND MOVES
INLAND. BLIZZARD CONDITIONS WILL CONTINUE THROUGH THE MORNING NEAR
WHITTIER...COMING TO AND END THIS AFTERNOON AS THE LOW TRACKS EAST
AND THE GRADIENT SLACKENS. HIGH PRESSURE BUILDS IN THIS
EVENING...WITH ALL LOCAL WINDS WEAKENING AND CLOUDS GENERALLY
CLEARING OUT.

A WARM FRONT WILL MOVE INTO THE SOUTHWEST GULF OF ALASKA ON
WEDNESDAY...BRINGING RAIN AND SNOW TO KODIAK ISLAND AND THE NORTHERN
GULF COAST INTO THURSDAY.

SOUTHWEST ALASKA/PENINSULA...
AN ARCTIC HIGH WILL SETTLE OVER THE MAINLAND TODAY...WITH WEAKENING
WINDS BRINGING AN END TO THE BITTERLY COLD WIND CHILLS. ALONG THE
PENINSULA...SNOW SHOWERS ASSOCIATED WITH A WEAKENING LOW WILL
DIMINISH TODAY...WITH ANOTHER FRONT MOVING IN WEDNESDAY WITH MORE
RAIN AND SNOW.

BERING SEA AND ALEUTIANS...
HIGH PRESSURE OVER THE EASTERN BERING AND A STRONG LOW DEVELOPING
ACROSS THE WESTERN ALEUTIANS IS HELPING SUPPORT A VERY STRONG
PRESSURE GRADIENT OVER THE CENTRAL BERING AND PRIBILOF ISLANDS. AS A
RESULT...EAST WINDS ARE ALREADY HELPING SUPPORT AREAS OF BLOWING SNOW
ACROSS THE PRIBILOFS...AND THIS WILL INCREASE THIS EVENING AND
OVERNIGHT AS A STRONG FRONT APPROACHES. BLIZZARD CONDITIONS WILL
DEVELOP AS NORTHEAST WINDS INCREASE...AIDED BY 1 TO 3 INCHES OF
ACCUMULATING SNOWFALL. ACROSS THE ALEUTIANS...THE SURFACE LOW WILL
SLOWLY TRACK WEST TO EAST...BRINGING AREAS OF RAIN AND SNOW TO THE
ENTIRE CHAIN.

.LONG TERM FORECAST...
FRIDAY AND BEYOND...THE LARGE UPPER TROUGH WILL BE TRANSLATING EAST
TOWARD THE PENINSULA...WITH A WARM FRONT PUSHING INTO THE GULF OF
ALASKA. RAIN AND SNOW WILL IMPACT THE COASTAL REGIONS...WITH ONLY
ISOLATED TO SCATTERED SHOWERS INLAND AS STRONG SOUTHEAST FLOW SHOULD
HELP DOWNSLOPE MOST INLAND LOCATIONS. THIS WILL...HOWEVER...HELP
TEMPERATURES RISE BACK TO NORMAL IF NOT SLIGHTLY ABOVE NORMAL
CLIMATOLOGICAL VALUES INTO NEXT WEEK. BEYOND MONDAY...MUCH
DISCREPANCY ARISES IN THE GLOBAL GUIDANCE WITH RESPECT TO THE EXACT
WAVE PATTERN...BUT THE GUIDANCE DOES HINT AT A DEVELOPING EASTERN
PACIFIC RIDGE FORMING INTO SOUTHERN ALASKA...WHICH WOULD BRING
QUIESCENT AND WARMER WEATHER TO THE REGION...WITH THE GENERAL STORM
TRACK STAYING ACROSS THE BERING SEA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 125 195.
MARINE...GALE 120 130 176 179 180 185 351 411 412 413 414.
         HEAVY FREEZING SPRAY 121 127 128 129 130 141 165 179 411 412
                              414.
FIRE WEATHER...NONE.

AHSENMACHER MAR 13

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1106 AM AKDT TUE MAR 26 2013

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1000 AM     SNOW             CHUGIAK                 61.39N 149.48W
03/26/2013  M6.7 INCH                           AK   NWS EMPLOYEE

            STORM TOTAL ACCUMULATION SINCE SUNDAY MORNING.

&&

CB