Heavy Freezing Spray Warning 83, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
1200 PM AKDT MON MAR 14 2011

.ANALYSIS AND UPPER LEVELS...IN THE UPPER LEVELS A REX BLOCK IS
IN PLACE WITH A HIGH CENTERED OVER THE BERING STRAIT AND A LOW
ALONG THE ALASKA PENINSULA. THERE ARE THREE SURFACE LOWS IN THE
GULF...TWO JUST TO THE SOUTHEAST OF KODIAK ISLAND AND ANOTHER OVER
THE SOUTHEASTERN GULF. THE SOUTHERLY FLOW ALOFT ON THE EAST SIDE
OF THE UPPER LOW IS BEGINNING TO SPREAD MOISTURE NORTH AND WESTWARD
ACROSS THE GULF. THIS WILL BRING SNOW TO KODIAK ISLAND BY THIS
AFTERNOON. A TIGHT SURFACE PRESSURE GRADIENT BETWEEN THESE LOWS
AND MAINLAND ALASKA IS PRODUCING LOCALIZED GAP WINDS OVER
SOUTHCENTRAL AND SOUTHWEST ALASKA. OTHERWISE CALM AND CLEAR
CONDITIONS PERSIST ACROSS THE REGION. OUT WEST THE UPPER JET
COMING OUT OF ASIA IS STEERING A SURFACE LOW SOUTH OF KAMCHATKA
TOWARD THE WESTERN ALEUTIANS.

.MODEL DISCUSSION...MODELS HAVE NOT RESOLVED THE DUAL LOWS SOUTHEAST
OF KODIAK ISLAND...BUT THE GENERAL EVOLUTION OF SPREADING MOISTURE
NORTH AND WEST ACROSS KODIAK ISLAND LOOKS GOOD. THERE ARE ALSO MINOR
POSITION DIFFERENCES WITH ALEUTIAN LOW AS WELL AS LOW MOVING INTO
THE EASTERN GULF. PLAN TO GO WITH AN AVERAGE POSITION ON THESE.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...THE UPPER HIGH WILL REMAIN CENTERED OVER THE
BERING STRAIT THE NEXT FEW DAYS BUT WILL CONSTANTLY CHANGE SHAPE AS
SHORT-WAVES MOVE AROUND IT. THE UPPER LOW OVER THE ALASKA PENINSULA
WILL TRACK WESTWARD UNDERNEATH THE HIGH. AS IT EXITS ENERGY OVER THE
GULF WILL CONTINUE TO MAKE NORTHWARD PROGRESS TOWARD SOUTHCENTRAL
WITH THE SURFACE LOW OVER THE EASTERN GULF TRACKING TO EAST OF
KODIAK ISLAND BY WEDNESDAY. EXPECT MID TO HIGH CLOUDS TO SPREAD
OVER AT LEAST THE SOUTHERN HALF OF SOUTHCENTRAL BEGINNING TUESDAY.
THE IMMEDIATE COAST COULD SEE SOME SNOW OR RAIN ALTHOUGH DRY
LOW-LEVEL OFFSHORE FLOW WILL TEND TO LIMIT WHAT REACHES THE GROUND.
BOTTOM LINE...CONTINUED DRY MOST PLACES...BUT WITH SOME CLOUDS.

SOUTHWEST ALASKA...LITTLE CHANGE IS EXPECTED FOR SOUTHWEST ALASKA
AS WELL. AS THE UPPER LOW MOVE OVERHEAD TONIGHT AND TUESDAY THERE
MIGHT BE A FEW SHOWERS ALONG THE BRISTOL BAY COAST AND ALONG THE
ALASKA PENINSULA...BUT FOR THE MOST PART CONDITIONS WILL REMAIN
CALM AND MOSTLY CLEAR.

BERING SEA/ALEUTIANS...UNDER NEAR ZONAL FLOW ALONG AND SOUTH OF
THE ALEUTIANS THE LOW SOUTH OF KAMCHATKA WILL WEAKEN AS IT MOVES
EASTWARD ALONG THE ALEUTIANS TUESDAY INTO WEDNESDAY. MODELS ARE
CONSISTENT IN DEPICTING A RAPIDLY INTENSIFYING LOW OVER THE
NORTHWEST PACIFIC TUESDAY NIGHT AND WEDNESDAY THANKS LARGELY
TO A 200KT+ JET STREAK. THIS WILL ARRIVE IN THE BERING SEA AND
ALEUTIANS WEDNESDAY AFTERNOON THROUGH THURSDAY AFTERNOON AND
HELP TRIGGER A PATTERN CHANGE ACROSS THE REGION AS WE HEAD THROUGH
THE END OF THE WEEK.

.LONG TERM FORECAST...AS A MAJOR STORM MOVES INTO THE BERING SEA
LATE IN THE WEEK THE HIGH OVER THE BERING STRAIT WILL MERGE WITH
AN AMPLIFYING SHORT-WAVE RIDGE OUT AHEAD OF THE STORM TO FORM A
HIGH AMPLITUDE RIDGE OVER MAINLAND ALASKA THURSDAY NIGHT. THIS
NEWLY FORMED RIDGE WILL LIKELY KEEP THE FRONTAL SYSTEM FROM
PROGRESSING INTO INTERIOR ALASKA. SO THE SOUTHWEST COAST WILL
SEE PRECIPITATION BY FRIDAY BUT INTERIOR SOUTHWEST ALASKA AND
SOUTHCENTRAL COULD REMAIN COMPLETELY DRY...DEPENDING ON THE EXACT
POSITION OF THE UPPER RIDGE. THE LOW ITSELF WILL WEAKEN AS IT
MOVES INTO THE BERING SEA AND THE UPPER TROUGH LIFTS NORTHWARD
DUE TO THE PRESENCE OF THE DOWNSTREAM RIDGE.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...127 172 175 176.
FIRE WEATHER...NONE.

SEB MAR 11