Heavy Freezing Spray Warning 112, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
145 PM AKDT THU MAR 29 2012

.ANALYSIS AND UPPER LEVELS...BROAD CYCLONIC CIRCULATION CENTERED OVER
THE GULF OF ALASKA AND MOST OF MAINLAND ALASKA WHILE A RIDGE PERSISTS
OVER THE WESTERN BERING SEA. THE PARADE OF EASTERLY SHORTWAVES
CONTINUES TO TRAVERSE THE NORTHERN GULF AND TRACK ACROSS SOUTHWEST
ALASKA BRINGING RAIN AND SNOW TO THE COASTAL SECTIONS AND SCATTERED
SHOWERS TO THE SOUTHWEST INTERIOR. COLD AIR ADVECTION AND ASSOCIATED
SHOWER ACTIVITY ON THE BACKSIDE OF THE UPPER LOW PERSISTS OVER THE
EASTERN BERING SEA...ALASKA PENINSULA...AND EASTERN ALEUTIANS.

.MODEL DISCUSSION...NO MAJOR CHANGES EXPECTED AS MODELS CONTINUE TO
BE IN FAIR AGREEMENT AND CONSISTENT WITH PREVIOUS RUNS.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
NO CHANGES TO THE ONGOING FORECAST OF A MIX OF CLOUDS AND SUN INLAND
WITH PERIODS OF RAIN AND SNOW EFFECTING COASTAL COMMUNITIES. THE
PRESSURE GRADIENT HAS DIMINISHED SIGNIFICANTLY OVER THE LAST TWO DAYS
THANKS TO A WEAKENING LOW IN THE EASTERN BERING SEA. A 970 MB LOW
ROUNDING THE BASE OF THE TROUGH THIS MORNING WILL MEANDER AROUND THE
SOUTHERN GULF THROUGH THE WEEKEND. THE CENTRAL PRESSURE BY THE END OF
THE WEEKEND IS EXPECTED TO BE IN THE MID 990S WHILE A COOLER AIRMASS
SETTLES OVER THE REGION.

THE SOUTHEASTERLY WAVES CONTINUE TO MOVE ACROSS THE REGION BUT IT
APPEARS THE TEMPERATURE ADVECTION IS NOW RELATIVELY NEUTRAL AND WILL
REMAIN SO UNTIL FRIDAY NIGHT WHEN 925 TEMPERATURES AGAIN DROP BELOW
FREEZING. UNTIL THEN...AFTERNOON HIGH TEMPERATURES WILL RANGE FROM 5
TO 10 DEGREES ABOVE NORMAL WITH MOST PRECIPITATION FALLING IN THE
FORM OF RAIN.

THE ONE CHALLENGE IN THE SHORT TERM FORECAST IS THE POTENTIAL FOR
LIGHT PRECIPITATION AROUND SOUTHCENTRAL FRIDAY NIGHT AS THAT COLD AIR
BEGINS TO ARRIVE. AN INVERTED TROUGH WILL SET UP OVER THE REGION
WHICH SHOULD HELP ORGANIZE AN AREA OF STRATIFORM PRECIPITATION. AT
THIS POINT WILL ONLY ADVERTISE A CHANCE ALTHOUGH CONFIDENCE IS
GROWING IN A PERIOD OF LIGHT RAIN OR SNOW FRIDAY NIGHT OVER MUCH OF
SOUTHCENTRAL.

SOUTHWEST ALASKA AND ALEUTIANS...
NO CHANGES ANTICIPATED OVER SOUTHWEST ALASKA WITH ONLY PERIODS OF
LIGHT RAIN OR SNOW FALLING OVER BRISTOL BAY AND THE LOWER KUSKOKWIM
VALLEY. DRIER AIR SHOULD BEGIN TO FILTER OVER THE REGION AS THE
EASTERLY SHORTWAVES STOP TRAVERSING THE ALASKA RANGE AND INSTEAD TAKE
A TURN SOUTH TOWARD KODIAK ISLAND. A RESIDUAL AREA OF DEFORMATION
WILL BE EVIDENT OVER THE REGION SO HARD TO RULE OUT LIGHT
PRECIPITATION BUT OVERALL CLOUDY SKIES OVERNIGHT WILL GIVE WAY TO
PARTLY CLOUDY AND FAIR WEATHER CONDITIONS DURING THE DAY. AS
ALWAYS...A CHANCE OF FOG AND STRATUS WILL PERSIST ESPECIALLY IN THE
LOWER VALLEYS AND ALONG THE COAST WHERE MOISTURE AND COLD ALWAYS
SEEMS TO POOL.

ALEUTIANS AND BERING SEA...
THE REMNANTS OF A LOW THAT HAS BEEN OVER THE EASTERN BERING SEA SINCE
THE WEEKEND IS FINALLY MOVING SOUTH...APPROACHING THE ALASKA
PENINSULA THIS AFTERNOON. THIS LOW IS BRINGING COLD AIR AND GUSTY
WINDS AROUND THE WESTERN PERIPHERY. THE SHOWERS ASSOCIATED WITH THIS
SYSTEM ALSO SEEM TO BE A BIT MORE WIDESPREAD THAN ANTICIPATED WITH
THE CENTRAL AND EASTERN ALEUTIANS REPORTING PERSISTENT SNOW SHOWERS
AND WINDS GUSTING CLOSE TO 60 MPH THROUGH CHANNELED TERRAIN. THE
BROAD NORTHWESTERLY FLOW WILL CONTINUE THROUGH THE WEEKEND ALTHOUGH
THE MAGNITUDE WILL BE SIGNIFICANTLY LESS BY SATURDAY AND SUNDAY WITH
THE LACK OF ANY UPPER LEVEL SUPPORT ROLLING THROUGH.

HIGH PRESSURE BUILDS OVER THE WESTERN BERING WITH THE NEXT GALE TO
STORM FORCE FRONTAL BOUNDARY DEVELOPING WAY OUT WEST AND IMPACTING
THE WESTERN ALEUTIANS LATE IN THE WEEKEND. THE MODELS HAVE NOT BEEN
TOO CONSISTENT WITH THIS FEATURE SO CONFIDENCE IS DIMINISHED BEYOND
SATURDAY.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...155 170 172
FIRE WEATHER...NONE.

AB MAR 12