Small Craft Advisory 149, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
1235 PM AST WED FEB 20 2008

.ANALYSIS AND UPPER LEVELS...THE LAST IN A STEADY PROGRESSION OF
LOWS OVER THE PAST WEEK IS CURRENTLY MOVING INTO THE SOUTHERN
GULF...FOLLOWING ALMOST THE SAME EXACT TRACK AS THE LOW FROM
YESTERDAY. THE BIG DIFFERENCE IS THIS LOW HAS BOTTOMED OUT
YESTERDAY AROUND 960 MB AND HAS BEGUN TO SLOWLY WEAKEN WITH A
CURRENT CENTRAL PRESSURE AROUND 970 MB. IT IS ALSO MOVING FAIRLY
SLOW SO THAT THE INCREASE IN WINDS AND PRECIPITATION ACROSS THE
GULF WATERS IS HAPPENING MUCH SLOWER THAN YESTERDAY. WINDS ACROSS
SOUTHCENTRAL HAVE BEEN DIMINISHING THIS MORNING AS THE PRESSURE
GRADIENT LOOSENS BETWEEN THE DEPARTING LOW (WHICH IS CURRENTLY
TRACKING NORTHWARD ALONG THE WESTERN ALASKA COAST) AND THE NEW GULF
LOW. TAMDAR DATA INDICATES LOW LEVEL WIND SHEAR IS STILL PRESENT
FROM ANCHORAGE TO SOUTHWEST ALASKA WITH SURFACE WINDS BECOMING LIGHT
WHILE WINDS A COUPLE THOUSAND FEET OFF THE GROUND REMAIN QUITE
STRONG. THE OTHER FEATURE OF INTEREST THIS MORNING IS A SHORT-WAVE
TROUGH ORIENTED NORTHWEST TO SOUTHEAST ABOUT HALF WAY BETWEEN COLD
BAY AND DUTCH HARBOR. A WEAK CIRCULATION IS ALSO VISIBLE IN SATELLITE
IMAGERY JUST SOUTH OF UNIMAK PASS. SNOW..HEAVY AT TIMES IS BEING
OBSERVED IN DUTCH HARBOR WHILE LIGHT SNOW IS BEING OBSERVED ACROSS
THE SOUTHERN ALASKA PENINSULA. ANOTHER VERY SHORT-WAVELENGTH TROUGH
IS NOTED IN WATER VAPOR IMAGERY OVER THE WESTERN BERING. MODERATE
COLD ADVECTION IS OCCURRING ALONG AND BEHIND THIS AND RESULTING IN
WIDESPREAD SNOW SHOWERS.

.MODEL DISCUSSION...MODELS INITIALIZED WELL WITH ALL OF THE FEATURES
MENTIONED ABOVE AND ARE IN GOOD AGREEMTN THROUGH MUCH OF THE
SHORT-TERM PERIOD. THERE CONTINUES TO BE DIVERGENCE IN SOLUTIONS
WITH TRACK OF LOW APPROACHING WESTERN ALEUTIANS FRIDAY...SO WILL
CHANGE CURRENT FORECAST.

.SHORT TERM FORECAST...

SOUTHERN MAINLAND...THE EAST-WEST PRESSURE GRADIENT WILL CONTINUE
TO SLACKEN THIS AFTERNOON...BUT EASTERLY WINDS WILL INCREASE AHEAD
OF THE OCCLUDED FRONT MOVING NORTHWARD ACROSS THE GULF. THE STRONGEST
WINDS ARE EXPECTED OVER THE NORTHERN GULF WHERE A STORM WARNING IS
IN EFFECT. STRONG WINDS WILL ALSO PUSH INTO PRINCE WILLIAM SOUND
TONIGHT AS THE FRONT MOVES ONSHORE AND WEAKENS. THE STRONGEST WINDS
OVER LAND ARE EXPECTED FROM CORDOVA TO PORTAGE VALLEY AND EASTERN
TURNAGAIN ARM. WINDS ARE EXPECTED TO REMAIN BELOW HIGH WIND WARNING
LEVELS. WESTERN TURNAGAIN ARM WINDS WILL INCREASE AGAIN THURSDAY AS
THE LOW CENTER REACHES THE BARREN ISLANDS AREA JUST NORTH OF KODIAK
ISLAND AND THE EAST-WEST PRESSURE GRADIENT PICKS UP ONCE AGAIN.
THERE WILL ALSO BE A DECENT SHORT-WAVE MOVING ACROSS SOUTHCENTRAL
THURSDAY AND THIS WILL ALSO CONTRIBUTE TO AN INCREASE IN WINDS.
THE LOW WILL STALL IN THE BARREN ISLANDS REGION THURSDAY DUE TO
BUILDING RIDGE OUT WEST. THE LOW WILL SLOWLY WEAKEN THROUGH
FRIDAY...SO WINDS WILL GRADUALLY TREND DOWNWARD. PRECIPITATION
PATTERNS WILL BE VERY SIMILAR TO TUESDAYS STORM WITH MOST OF
PRECIPITATION FALLING IN UPSLOPE AREAS IN THE FORM OF RAIN. SOME
RAIN AND SNOW WILL ALSO BACK INTO SOUTHWEST ALASKA...MAINLY ACROSS
BRISTOL BAY. COLD ADVECTION AND SNOW SHOWERS WILL MOVE INTO THE
SOUTHWEST COAST THURSDAY AFTERNOON AND SPREAD EASTWARD FRIDAY. EXPECT
REDUCED VISIBILITIES DUE TO BLOWING SNOW...MAINLY ALONG THE COAST.

BERING SEA/ALEUTIANS/ALASKA PENINSULA...THE LOW/SHORT-WAVE BETWEEN
THE EASTERN ALEUTIANS AND ALASKA PENINSULA WILL SINK SOUTHWARD THIS
EVENING...SO THE INTENSE SNOW BEING OBSERVED IN DUTCH HARBOR WILL
COME TO AN END. HOWEVER...WINDS WILL INCREASE AND SNOW SHOWERS WILL
MOVE IN...SO LOW VISIBILITIES WILL CONTINUE DUE TO BLOWING SNOW.
COLD ADVECTION SNOW SHOWERS WILL DOMINATE MUCH OF THE BERING
SEA/ALEUTIANS/ALASKA PENINSULA THROUGH THURSDAY AND HANG IN OVER
EASTERN AREAS FRIDAY WHILE A RIDGE BUILDS OVER THE CENTRAL BERING
AND BRINGS CALMER WEATHER. A PACIFIC STORM WILL APPROACH THE WESTERN
ALEUTIANS FRIDAY BRINGING GALE TO STORM FORCE SOUTHEASTERLIES TO
THE CENTRAL TO WESTERN ALEUTIANS.

.LONG TERM FORECAST...MEDIUM RANGE MODELS INDICATE BERING SEA UPPER
RIDGE WILL BE CUT OFF AT ITS BASE OVER THE WEEKEND AND RETREAT UP TO
THE CHUKCHI SEA WHERE IT WILL REMAIN THROUGH NEXT WEEK. THIS WILL
KEEP MOST OF THE MAINLAND DRY WITH SEASONABLE TEMPERATURES. THE
PERSISTENT NORTHERLY FLOW ALOFT OVER MAINLAND ALASKA WILL SET UP
THE POTENTIAL FOR STRONG NORTHERLY WINDS THROUGH CHANNELED AREAS OF
SOUTHCENTRAL. STORMINESS WILL BE HELD TO THE SOUTHERN PORTION OF THE
FORECAST AREA FROM THE ALEUTIANS TO KODIAK ISLAND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM WARNING 120.
         GALE WARNING 125 130 140 170 172.
         HEAVY FREEZING SPRAY 165 179 185.
FIRE WEATHER...NONE.

SEB FEB 08