Heavy Freezing Spray Warning 150, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
145 PM AKDT WED MAR 28 2012

.ANALYSIS AND UPPER LEVELS...THE JET STREAM REMAINS WELL SOUTH OF
ALASKA KEEPING THE MAJORITY OF THE ACTIVITY OVER THE NORTH PACIFIC.
THE ZONAL FLOW IS SENDING WAVE AFTER WAVE TOWARD THE COAST OF
WASHINGTON AND OREGON. MEANWHILE UP NORTH...A BROAD TROUGH PERSISTS
OVER THE EASTERN BERING SEA WHILE AN UPPER LEVEL RIDGE NOSES OVER THE
EASTERN HALF OF ALASKA EXTENDING FROM CANADA.

AN OLD FRONTAL BOUNDARY REMAINS NEAR KODIAK AND OVER THE SOUTHWEST
MAINLAND. SOUTHEASTERLY WAVES FLOWING AROUND THE BASE OF TROUGH ARE
LINING UP FROM THE PANHANDLE THROUGH SOUTHCENTRAL AND SOUTHWEST AK.

PRECIPITATION CONTINUES TO FALL OVER KODIAK ISLAND AND ALONG THE
NORTH GULF COAST AS WELL AS LIGHT RAIN AND SNOW OVER BRISTOL BAY. THE
STRONGEST OF THE SHORTWAVES IS HEADING TOWARD KODIAK ISLAND THIS
AFTERNOON SO EXPECTING PRECIP TO GET ENHANCED AS THIS APPROACHES.

.MODEL DISCUSSION...NO MAJOR CHANGES EXPECTED AS MODELS CONTINUE TO
BE IN FAIR AGREEMENT AND CONSISTENT WITH PREVIOUS RUNS. THE EXCEPTION
IS THE 12Z NAM WHICH AGAIN HAS INITIALIZED VERY POORLY OFF OF THE 18Z
SATELLITE AND IS A CLEAR OUTLIER VS THE OTHER OPTIONS.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
12Z SOUNDING OVER ANCHORAGE SHOWS THE WARM-UP IS UNDERWAY WITH 925
MB TEMPS 7 DEG CELCIUS WARMER THAN MONDAY MORNING. EVEN WITH THE
CLOUD COVER...TEMPERATURES ARE APPROACHING 40 DEGREES EARLY THIS
AFTERNOON. WE ARE WATCHING AN AREA OF CLEARING DIRECTLY AHEAD OF THE
APPROACHING SHORTWAVE THAT COULD GIVE US A PARTLY CLOUDY AFTERNOON.
IF THIS HAPPENS...TEMPERATURES WILL LIKELY JUMP UP INTO THE MID 40S
VERY QUICKLY.

BESIDES THE CHALLENGES OF CLOUD COVERAGE AND TEMPERATURES...A FAIRLY
STRAIGHT FORWARD FORECAST THROUGH THE REST OF THE WEEK. THE GRADIENT
ACROSS THE GULF COAST WILL GRADUALLY DIMINISH AS THE LOW IN THE
NORTHEAST PACIFIC FILLS AND A SLIGHTLY COOLER AIRMASS FILTERS BACK IN
OVER THE REGION. THE REMNANTS OF THE PARENT LOW WILL STILL REMAIN AT
THE END OF THE WEEKEND AS THE CENTRAL PRESSURE INCREASES FROM THE
970S TO THE 990S WITH LITTLE CHANGE IN THE POSITION. THIS WILL ALLOW
A FEW MORE SHORTWAVES TO TRAVERSE SOUTHCENTRAL BRINGING RAIN AND SNOW
TO THE COAST AND INCREASED CLOUDS AND A SLIGHT CHANCE OF PRECIP
INLAND. THE BEST CHANCE OF PRECIP OVER THE INTERIOR LOOKS TO BE
FRIDAY EVENING ASSOCIATED WITH ONE OF THE MORE POTENT WAVES MOVING
FROM EAST TO WEST.

SOUTHWEST ALASKA AND ALEUTIANS...
LIGHT PRECIPITATION CONTINUES TO FALL OVER MANY AREAS OF SOUTHWEST
ALASKA. THE DEFORMATION ZONE EXTENDING FROM THE LOW IN THE PACIFIC TO
THE DECAYING LOW IN THE BERING IS SERVING AS THE FOCUS FOR LIFT
ACROSS THE REGION. ONE CHALLENGE TO THE SHORT TERM FORECAST INCLUDES
THE ADVECTION OF WARMER AIR ALOFT LATE TONIGHT OVER THE SOUTHWEST.
THE KODIAK ISLAND SHORTWAVE WILL CROSS THE ALASKA RANGE LATE TONIGHT
AND INTRODUCE WARMER TEMPERATURES ALOFT TO BRISTOL BAY AND THE LOWER
KUSKOKWIM VALLEY. SURFACE TEMPERATURES TOWARD THE KUSKOKWIM VALLEY
ARE STILL EXPECTED TO BE NEAR OR BELOW FREEZING SO THE POTENTIAL FOR
FREEZING RAIN EXISTS BRIEFLY THURSDAY MORNING. SINCE PRECIPITATION IS
EXPECTED TO BE VERY LIGHT...IF THIS HAPPENS WE ARE ONLY EXPECTING A
FEW HOURS OF FREEZING DRIZZLE SO NO ADVISORIES ARE EXPECTED AT THIS
TIME.

OTHERWISE CONDITIONS WILL GRADUALLY IMPROVE FROM MARGINAL TO VFR BY
FRIDAY WITH LOCAL AREAS OF STRATUS AND FOG IN THE MORNING. AS SKIES
BECOME PARTLY CLOUDY TO CLEAR THIS WEEKEND...EXPECTING TEMPERATURES
TO ONCE AGAIN DROP BACK DOWN BELOW CLIMATOLOGICAL NORMAL FOR THIS
TIME OF YEAR.

VERY BENIGN WEATHER PATTERN PERSISTS OVER THE ALEUTIANS AND BERING
SEA. COLD AIR ADVECTION WRAPPING AROUND THE EASTERN BERING LOW WILL
BRING GALE FORCE WINDS TO THE CENTRAL ALEUTIANS ALONG WITH THE
NUMEROUS SNOW SHOWERS. FLOW GRADUALLY DIMINISHES OVER THE WEEKEND AS
THE NEXT SEVERAL LOW PRESSURE SYSTEMS DEVELOP WELL SOUTH OF OUR
DOMAIN. IT IS NOT UNTIL LATE IN THE WEEKEND THAT THE NEXT SURGE OF
WARM AIR ASSOCIATED WITH A DEVELOPING NORTH PACIFIC LOW BRINGS GALE
TO STORM FORCE WINDS TO THE WESTERN ALEUTIANS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...130 170 172 412 413.
FIRE WEATHER...NONE.

AB MAR 12