Gale Warning 119, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
300 PM AKST MON FEB 9 2009

.ANALYSIS AND UPPER LEVELS...A COLD UPPER VORTEX OVER THE ARCTIC
CONTINUES TO SINK SOUTHWARD TOWARD THE BERING STRAIT. A TROUGH
EXTENDS SOUTHWARD FROM THIS LOW TO THE KUSKOKWIM VALLEY AND IS
MOVING EASTWARD TOWARD SOUTHCENTRAL ALASKA. THERE IS LITTLE IN
THE WAY OF MID OR UPPER LEVEL CLOUDS AHEAD OF THIS TROUGH...BUT
THERE IS QUITE A BIT OF LOW LEVEL MOISTURE IN PLACE IN THE FORM
OF STRATUS AND PATCHY FOG. SO IT WON'T TAKE A WHOLE LOT OF LIFT
TO GENERATE LIGHT SNOW OR FLURRIES.

HEADING SOUTH TO THE NORTH PACIFIC IS A PROGRESSIVE SOUTHERN STREAM.
A STRONG JET EXTENDS ALL THE WAY ACROSS ASIA OUT INTO THE WEST
PACIFIC. A WEAK SHORT-WAVE JUST EAST OF JAPAN IS EXPECTED TO BE
THE NEXT IN A LINE OF STRONG STORMS TO MOVE TO THE WESTERN ALEUTIANS.
THE CURRENT SYSTEM IS WEST OF SHEMYA WITH FRONT HEADING NORTH AND
EAST ACROSS THE ALEUTIANS AND SOUTHERN BERING. THE REMNANTS OF THE
PREVIOUS FRONT TO MOVE THROUGH ARE LYING ACROSS THE CENTRAL BERING
AND SOUTHEASTWARD ACROSS THE SOUTHERN ALASKA PENINSULA TO A SURFACE
LOW SOUTH OF KODIAK ISLAND. THIS LOW IS BEING PUSHED SOUTHWARD INTO
THE PACIFIC AS AN UPPER RIDGE BUILDS JUST TO THE WEST OF IT AHEAD
OF THE WESTERN ALEUTIANS SYSTEM.

.MODEL DISCUSSION...MODELS ARE IN DECENT AGREEMENT THROUGH 12Z
THURSDAY. THERE ARE SOME DIFFERENCES IN POSITION AND STRENGTH OF
LOW NEAR SHEMYA...BUT NOT ENOUGH TO MAKE ANY MAJOR DIFFERENCES IN
THE FORECAST. ALSO...THE GFS IS STRONGER THAN OTHER SOLUTIONS IN
DEVELOPMENT OF A TRIPLE POINT LOW NORTH OF SAINT PAUL TUESDAY
AFTERNOON AND MAINTAINS THIS STRENGTH AS IT MOVES INLAND ACROSS
THE KUSKOKWIM DELTA. WILL GO WITH THE WEAKER CONSENSUS OF THE
ECMWF/NAM/UKMET. MORE SIGNIFICANT DIFFERENCES IN THE MODELS BEGIN
TO SHOW UP AS NEXT MAJOR LOW TRACKS ACROSS THE BERING SEA MID TO
LATE WEEK...ALTHOUGH THEY ARE ALL TRENDING TOWARD A MORE SOUTHERLY
TRACK. THE OPERATIONAL GFS DEPICTS A STRONGER LOW THAN OTHER
SOLUTIONS AND IS 10 MB OR MORE DEEPER THAN THE ENSEMBLE MEAN.
ECMWF SOLUTION SEEMS MORE REASONABLE AND RUN-TO-RUN CONSISTENCY
IS BETTER. THEREFORE...WILL UPDATE THE EXTENDED FORECAST BASED ON
THE 12Z ECMWF. SIMILARLY...PREFER THE MORE CONSISTENT ECMWF WITH
WEAK LOW IN THE GULF TUESDAY NIGHT THROUGH THURSDAY.

.SHORT TERM FORECAST...

SOUTHCENTRAL...THE UPPER SHORT-WAVE OVER THE KUSKOKWIM VALLEY WILL
DIG A BIT SOUTHWARD AND MOVE ACROSS SOUTHCENTRAL TONIGHT AND EXIT
INTO THE YUKON TUESDAY MORNING. WEAK LIFT FROM THIS AS WELL AS WEAK
COLD ADVECTION ACCOMPANYING THE SHORT-WAVE WILL BE ENOUGH TO PRODUCE
AREAS OF LIGHT SNOW OR FLURRIES ACROSS LAND AREAS AND A FEW SHOWERS
OVER THE GULF WATERS...WITH LITTLE OR NO ACCUMULATION. THERE IS A
DECENT UPPER JET STREAK RIGHT BEHIND THE TROUGH AXIS...SO AS THE
TROUGH MOVES THROUGH EXPECT THIS WILL AID COLD ADVECTION IN
GENERATING GUSTY WINDS...ESPECIALLY FOR THE BARREN ISLANDS
REGION...RESURRECTION BAY AND PASSAGE CANAL...WESTERN PRINCE
WILLIAM SOUND...AND THE THOMPSON PASS/VALDEZ AREA. THEREFORE...WILL
INCREASE WINDS TO SMALL CRAFT OVER THE MENTIONED MARINE AREAS.
THIS TROUGH ALSO LOOKS LIKE IT IS STRONG ENOUGH TO CLEAR OUT MOST
OF THE STRATUS AND FOG THAT HAS BEEN SITTING OVER THE REGION THE
LAST COUPLE DAYS. THE PASSAGE OF THIS TROUGH WILL THEN ALLOW THE
NEXT SHORT-WAVE OVER THE BERING TO TRACK FARTHER NORTH TOWARD
MAINLAND ALASKA. AS THE NEXT FRONT MOVING ACROSS THE BERING REACHES
KODIAK ISLAND EXPECT A TRIPLE POINT LOW TO DEVELOP AND MOVE ACROSS
THE NORTHERN GULF WHILE THE UPPER TROUGH MOVES ACROSS SOUTHCENTRAL.
THIS WILL PROVIDE A VERY GOOD CHANCE OF SNOW TUESDAY NIGHT THROUGH
THURSDAY. THERE IS SOME UNCERTAINTY IN TRACK OF SURFACE LOW...SO WILL
KEEP INLAND POPS AT CHANCE FOR NOW AND GO WITH HIGHER LIKELY POPS
ALONG THE COAST.

SOUTHWEST ALASKA...AS UPPER TROUGH EXITS TO THE EAST THIS AFTERNOON
AND EVENING MOST OF THE CLOUDS SHOULD GO ALONG WITH IT. COLD
ADVECTION AND MOSTLY CLEAR SKIES WILL CAUSE TEMPERATURES TO DROP
QUICKLY TONIGHT. HOWEVER...THIS WON'T LAST TOO LONG. A BERING SEA
FRONT WILL MOVE TO THE SOUTHWEST COAST TUESDAY AFTERNOON AND MOVE
INLAND TUESDAY NIGHT AND WEDNESDAY. WITH VERY COLD TEMPERATURES IN
PLACE AS THE FRONT REACHES THE COAST THERE IS POTENTIAL FOR LOW
VISIBILITIES IN SNOW AND BLOWING SNOW. THE FRONT WILL BE MOVING
ALONG AT A GOOD CLIP AND WINDS DON'T LOOK LIKE THEY WILL BE STRONG
ENOUGH TO WARRANT A BLIZZARD WARNING...BUT WILL HAVE TO RE-EVALUATE
AS THE FRONT GETS CLOSER.

BERING SEA/ALEUTIANS...THE AIR ALONG THE FRONT NEAR THE WESTERN
ALEUTIANS IS WARMER THAN THE LAST FRONT THAT PUSHED THROUGH...SO
EXPECT MORE RAIN TO MIX IN THIS TIME. HOWEVER...THE FRONT WILL
OCCLUDE AS IT REACHES THE EASTERN ALEUTIANS AND SOUTHERN ALASKA
PENINSULA...SO STILL EXPECT PRECIP TO FALL MAINLY AS SNOW IN THOSE
LOCATIONS. THE PRIBILOFS WILL ONCE AGAIN SEE LOW VISIBILITIES IN
SNOW AND BLOWING SNOW...PERHAPS EVEN BLIZZARD CONDITIONS...BUT DUE
TO THE SPEED OF THE FRONT THESE CONDITIONS SHOULD BE SHORT-LIVED
AND WILL NOT ISSUE A BLIZZARD WARNING.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM WARNING...176 411.
         GALE WARNING...155 170 172 175 179 185 412 413 414.
         HEAVY FREEZING SPRAY WARNING...121 125 129 130 140 160 179.
FIRE WEATHER...NONE.

SEB FEB 09