Heavy Freezing Spray Warning 82, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKST THU MARCH 3 2011

.UPPER LEVEL/SURFACE ANALYSIS...HIGH PRESSURE CENTERED OVER NORTHERN
CANADA NEAR INUVIK CONTINUES TO DOMINATE MUCH OF MAINLAND ALASKA THIS
MORNING WITH CLEAR SKIES ACROSS MUCH OF THE STATE. TO THE SOUTH A
WEAKENING LOW HAS CONTINUED TO SPREAD SNOW SHOWERS ACROSS MUCH OF THE
GULF OF ALASKA WITH THE MAIN IMPACT BEING FELT ACROSS KODIAK ISLAND.
CLOUD COVER HAS CLEARED OUT ACROSS THE EASTERN BERING OVERNIGHT AS A
SHOT OF DRY AIR FROM THE MAINLAND HAS PUSHED WEST TOWARDS THE
PRIBILOFS. STRATUS CONTINUES TO MAKE ITS WAY WESTWARD ACROSS THE
CENTRAL INTO THE WESTERN BERING IN ANTICYCLONIC FLOW UNDERNEATH A
LARGE RIDGE CENTERED OVER THE NORTHERN BERING. FARTHER WEST A 986 MB
LOW SOUTHWEST OF ATTU IS PUSHING AN OCCLUDED FRONT INTO THE WESTERN
ALEUTIANS BRINGING STRONG WINDS ALONG WITH RAIN AND SNOW.

.MODEL DISCUSSION...A RELATIVELY SIMPLE PATTERN INITIALLY MAKES FOR
GOOD MODEL AGREEMENT IN BRINGING THE NEXT LOW NORTH INTO THE GULF OF
ALASKA BY LATE TONIGHT. THERE ARE MINOR POSITIONAL DIFFERENCES WITH
THE NEXT STORM SYSTEM THAT IMPACTS THE WESTERN ALEUTIANS SATURDAY
EVENING BUT THE GENERAL PICTURE REMAINS SIMILAR. DIFFERENCES BEGIN TO
BECOME MORE PRONOUNCED ON SUNDAY REGARDING THE TIMING OF A
TROUGH/TRIPLE POINT LOW THAT SWINGS NORTH INTO THE AKPEN LATER IN THE
WEEKEND. THE NAM/GFS BOTH FAVOR AN OPEN TROUGH WHEREAS THE ECMWF/GEM
FAVOR A DEEPER AND SLOWER CLOSED LOW. THE MORNING FORECAST PACKAGE IS
GOING WITH THE NAM/GFS SOLUTION IN THE WEST. MODEL AGREEMENT BREAKS
DOWN BY EARLY NEXT WEEK AS THERE ARE SIGNIFICANT DIFFERENCES IN THE
TRACK AND TIMING OF THE NEXT BIG LOW THAT MOVES INTO THE WESTERN
ALEUTIANS...NOT SURPRISING AS THE OVERALL PATTERN BECOMES ZONAL AND
MORE PROGRESSIVE. WENT WITH A BLEND OF THE GFS AND ECMWF IN THE
MIDRANGE TO SPLIT THE DIFFERENCE FOR NOW WITH HPC BEING THE CHOICE IN
THE THE LONGER RANGE...DAYS 6-7.

.SHORT TERM FORECAST...
.SOUTHCENTRAL ALASKA...THE GRADIENT BETWEEN THE HIGH OVER THE
INTERIOR AND LOW PRESSURE IN THE GULF WILL KEEP GUSTY NORTH WINDS
BLOWING THROUGH THE USUAL GAPS THROUGH THE WEEKEND...THOUGH THE LACK
OF UPPER LEVEL SUPPORT MEANS THAT WINDS SHOULD NOT BE NEARLY AS
STRONG AS THEY HAVE BEEN OVER THE LAST FEW DAYS. STRONG WIND
HEADLINES WILL STILL BE NECESSARY THROUGH SATURDAY THROUGH THOMPSON
PASS AND THE COPPER RIVER DELTA THOUGH AS THE SURFACE PRESSURE
GRADIENT IS ENHANCED BY A STRONG LOW THAT MOVES INTO THE CENTRAL GULF
BY SATURDAY. THE TIGHTENED GRADIENT IS EXPECTED TO RESULT IN STORM
FORCE WINDS ACROSS PORTIONS OF THE NORTH CENTRAL GULF SATURDAY. MOST
AREAS CAN COUNT ON CONTINUED DRY AND SUNNY WEATHER WELL INTO NEXT
WEEK. THE PRIMARY EXCEPTION WILL BE KODIAK ISLAND WHERE SNOW SHOWERS
SHOULD BE ONGOING FOR MUCH OF TODAY BEFORE DIMINISHING TONIGHT AS THE
LOW PRESSURE IN THE GULF MOVES SOUTH AND FALLS APART. THE RESPITE FOR
KODIAK SHOULD BE BRIEF THOUGH AS THE NEXT LOW MOVES INTO THE GULF AND
SNOW RETURNS BY SATURDAY NIGHT. THERE MAY BE A PERIOD OF HEAVY SNOW
WITH THIS NEXT SYSTEM HOWEVER IT SHOULD QUICKLY MIX WITH RAIN SUNDAY
AS WARMER AIR MOVES ACROSS THE ISLAND.

.SOUTHWEST ALASKA...VERY QUIET PATTERN THROUGH THE WEEKEND OVERALL
WITH CONTINUED OFFSHORE FLOW. DID GO WITH CHANCE POPS FOR BRISTOL BAY
LATE SATURDAY NIGHT AND SUNDAY AS THERE IS THE POSSIBILITY THAT SOME
MOISTURE MAY BE IT OVER THE ALEUTIAN RANGE FROM THE LOW IN THE
GULF...BUT OTHERWISE MUCH OF THE SAME.

.ALEUTIANS AND BERING SEA...HIGH PRESSURE OVER THE CENTRAL BERING SEA
BECOMES CUT OFF AND RETREATS NORTHEASTWARD OVER THE WEEKEND OPENING
UP THE ALEUTIANS TO THE STORM TRACKS ONCE AGAIN. A FRONT MOVES INTO
THE WESTERN ALEUTIANS TODAY BRINGING GALES ALONG WITH SNOW AND RAIN
BEFORE FALLING APART TONIGHT. THE NEXT MAJOR STORM LOOKS POISED TO
AFFECT THE WESTERN AND CENTRAL ALEUTIANS BY SATURDAY BRINGING RAIN
AND WIND. FOR NOW JUST GOING WITH CHANCE POPS FOR THE AKPEN THIS
WEEKEND DUE TO THE UNCERTAINTY IN THE POLEWARD EXTENT OF THE
TROUGH/POSSIBLE LOW THAT DEVELOPS IN THE SECOND HALF OF THE WEEKEND.

.LONG TERM FORECAST...STORM TRACKS WILL CONTINUE TO STAY SOUTH OF
MUCH OF THE AOR WITH THE EXCEPTION OF THE ALEUTIANS THANKS TO HIGH
PRESSURE THAT WILL REMAIN FIRMLY ENTRENCHED OVER MAINLAND ALASKA
THROUGH NEXT WEEK. RESULTING DRY NORTHERLY FLOW WILL KEEP SKIES SUNNY
ACROSS SOUTHCENTRAL AND SOUTHWEST ALASKA WITH HIGHS NEARLY NORMAL IN
SPITE OF THE NORTHERLY FLOW DUE TO PLENTY OF SUNSHINE.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...120 130 132 138 176
         HEAVY FREEZING SPRAY WARNING...121 140 165 170 179 185
FIRE WEATHER...NONE.

WOOD FEB 11