Heavy Freezing Spray Warning 137, NWS Anchorage, AK

SOUTH CENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKDT TUE MAR 13 2012

.MODEL DISCUSSION...

MODELS REMAIN IN GOOD AGREEMENT INTO THE WEEKEND AND EXPECT TO MAKE
MINIMAL CHANGES TO THE SHORT TERM FORECASTS. A BIT OF A DIFFERENCE
COMES UP IN THE GFS AND ECMWF BY EARLY NEXT WEEK WITH RESPECT TO A
STRONG STORM MOVING INTO THE GULF OF ALASKA EARLY NEXT WEEK.

.SHORT AND MID TERM FORECAST WITH ANALYSIS...

THE UPPER LOW OVER SOUTHWEST ALASKA WILL INTENSIFY AS IT CONTINUES TO
MOVE TO THE WEST SOUTHWEST THROUGH THURSDAY AFTERNOON WHILE THE
WHILE A WEAK UPPER LEVEL RIDGE BUILDS FROM BRITISH COLUMBIA INTO THE
EASTERN INTERIOR. FLOW WILL REMAIN NEARLY ZONAL ACROSS THE NORTH
PACIFIC. SEVERAL SHORT WAVES EMBEDDED IN THE CYCLONIC FLOW
SURROUNDING THE UPPER LOW CENTER WILL TRIGGER PERIODS OF LIGHT SNOW
OR SCATTERED SNOW SHOWERS ACROSS BOTH SOUTH CENTRAL AND SOUTHWESTERN
ALASKA THROUGH THE REMAINDER OF THE WEEK.

AT THE SURFACE...A BROAD AREA OF COMPLEX AREA OF LOW PRESSURE EXTENDS
FROM THE NORTHERN GULF OF ALASKA ACROSS KODIAK ISLAND TO A LOW JUST
NORTH OF UNALASKA. THE LOW NORTH OF UNALASKA WILL DROP SOUTH ACROSS
THE CHAIN THIS EVENING AND BECOME THE MAIN CENTER SOUTHWEST OF KODIAK
ISLAND BY WEDNESDAY AFTERNOON. WEAK LOW PRESSURE WILL ROTATE AROUND
THE NORTH SIDE OF THIS LOW INTO THE BRISTOL BAY ZONE BY WEDNESDAY
AFTERNOON. THIS WILL RESULT IN PERIODS OF TIGHTENING AND THEN
RELAXING OF THE GRADIENT ACROSS THE SOUTHERN MAINLAND. GUSTY NORTH
WINDS PRESENTLY BLOWING THROUGH CHANNELED AREAS OF THE CHUGACH AND
ALASKA RANGES WILL DIMINISH BY LATE THIS AFTERNOON BUT ARE EXPECTED
TO REDEVELOP EARLY WEDNESDAY. AN EASTERLY BARRIER JET OF 25 TO
40 MPH DEVELOPS ALONG THE NORTHERN AND EASTERN GULF COAST WEDNESDAY
MORNING THEN FALLS APART THURSDAY MORNING. BRISK NORTHEAST WINDS
ACROSS THE KUSKOKWIM DELTA COMBINED WITH UNSEASONABLY LOW
TEMPERATURES WILL KEEP WIND CHILLS NEAR 40 BELOW AT TIMES. WIND
CHILLS WILL MODERATE IN THE AFTERNOON BUT RE INTENSIFY LATE TONIGHT.

AS THE LOW OUT WEST DROPS SOUTH ACROSS THE EASTERN ALEUTIANS THE FLOW
WILL BECOME MORE NORTH TO NORTHEAST ACROSS THE BERING SEA AND
ALEUTIANS ISLANDS TO THE ALASKA ALASKA PENINSULA. THIS WILL RESULT IN
THE TYPICAL SNOW SHOWER REGIME AN THE BERING SEA SIDE OF THE CHAIN
AND ALASKA PENINSULA.

BY WEDNESDAY NIGHT AND THURSDAY MORNING THE MAIN LOW PRESSURE CENTER
WILL BE OVER THE KODIAK ISLAND AREA WITH A TROUGH EXTENDING WEST TO
THE WESTERN ALEUTIANS. THIS WILL KEEP THE SOUTHWEST PORTION OF THE
STATE IN THE UNSEASONABLY COLD AIRMASS FOR THE REMAINDER OF THE WEEK.

.EXTENDED OUTLOOK...
BEGINNING THIS WEEKEND THE DOMINANT UPPER LOW OVER SOUTHWEST ALASKA
WILL SPLIT WITH A PORTION DROPPING SOUTHEAST INTO THE GULF OF ALASKA
WHILE ANOTHER PORTION MOVES TO THE NORTH CENTRAL BERING SEA SATURDAY.
BY SUNDAY THE BERING SEA UPPER LOW WILL BECOME THE DOMINANT CENTER
AND DIG A TROUGH SOUTH INTO THE NORTH PACIFIC WHILE A RIDGE BUILDS
INTO THE SOUTHERN GULF OF ALASKA. EARLY NEXT WEEK THE MAIN UPPER LOW
WILL BE OVER THE MAINLAND WITH A RIDGE INTO THE BERING SEA AND A DEEP
UPPER LOW JUST OFF THE KAMCHATKA PENINSULA. UNSEASONABLY COLD
TEMPERATURES CAN BE EXPECTED TO CONTINUE ACROSS MAINLAND PORTIONS OF
THE STATE THROUGH THE WEEKEND. OVER THE BERING AND ALONG THE CHAIN
WARMER SHOWERY CONDITIONS WILL SET UP BY EARLY NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...HEAVY SPRAY...138 140 150 155 165 170 411 412 413 414
FIRE WEATHER...NONE

SAM MAR 12