Gale Warning 92, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
145 PM AKST SAT FEB 6 2010

.ANALYSIS AND UPPER LEVELS...

HIGH AMPLITUDE TROUGH REMAINS IN PLACE WITH IMPRESSIVE COLD CORE
UPPER LEVEL LOW DIGGING SOUTHWARD NEAR BRISTOL BAY. DEFORMATION ZONE
ASSOCIATED WITH THE COLD FRONT IS POSITIONED FROM SW TO NE ACROSS
SOUTHCENTRAL ALASKA AND IS MOVING RAPIDLY NORTH. WIDESPREAD
PRECIPITATION ASSOCIATED WITH THE SURFACE FRONTAL BOUNDARY NEARING
THE COAST EARLY THIS AFTERNOON. SYNOPTIC SCALE NORTHERLY FLOW
PERSISTS ACROSS THE BERING SEA.

.MODEL DISCUSSION...SYNOPTIC FEATURES ARE IN FAIR AGREEMENT IN THE
SHORT TERM. MODELS ARE IN RELATIVE AGREEMENT ALTHOUGH RUN TO RUN
CONSISTENCY IS NOT GREAT ON AN EASTERN GULF LOW MOVING INLAND NEAR
YAKUTAT SUNDAY EVENING...ALTHOUGH THIS WILL HAVE LITTLE IMPACT ON OUR
DOMAIN. GFS AND NAM HINT AT A WEAK LOW DEVELOPING OVERNIGHT
ASSOCIATED WITH AN EMBEDDED SHORTWAVE AND REINFORCING SHOT OF COLD
AIR MOVING OUT OF SOUTHWEST ALASKA. THIS WEAK LOW WILL QUICKLY MOVE
TOWARD WESTERN PRINCE WILLIAM SOUND AND THEN INLAND SUNDAY
EVENING...BRINGING THE COOK INLET REGION ANOTHER SHOT OF LIGHT SNOW
SUNDAY. ATTENTION TURNS WEST WITH A VERY STRONG STORM SYSTEM
DEVELOPING SOUTH OF THE CENTRAL ALEUTIANS SUNDAY AFTERNOON.
DIFFERENCES IN MODEL SOLUTIONS CAN BE TRACED TO THE STRENGTH AND
POSITION OF AN UPSTREAM RIDGE OVER THE PANHANDLE EARLY NEXT WEEK. THE
FRONTAL PROGRESSION AS DEPICTED BY THE GFS APPEARS TO BE THE OUTLIER
FROM THE SLOWER ECMWF AND NAM...SO FOR THIS FORECAST PACKAGE HAVE
TRENDED TOWARD THE SLOWER SOLUTION.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...A COMPLICATED FORECAST THIS AFTERNOON...
SOUTHWEST FLOW USHERING THE COLD AIR UP COOK INLET EARLY THIS
AFTERNOON. THE WIND SHIFT FROM EAST TO SOUTHWEST ALONG THE NORTH GULF
COAST BROUGHT AN IMPRESSIVE TEMPERATURE DROP OF 12 DEGREES TO
CORDOVA...RESULTING IN HEAVY WET SNOW. COLD AIR ADVECTING NORTHWARD
WILL RESULT IN TEMPERATURES AT 850 MB DROPPING FROM APPROX -4 TO -11
THIS EVENING. THIS SCENARIO IS FAVORABLE FOR CONTINUED LIGHT SNOW
EVEN THOUGH THE MODELS ARE NOT SHOWING MUCH OF ANY ADDITIONAL QPF. IN
ANCHORAGE AND SURROUNDING AREAS...SNOW SHOULD TAPER OFF LATE TONIGHT
AND THEN AGAIN DEVELOP SUNDAY ASSOCIATED WITH THE AFOREMENTIONED WEAK
LOW MOVING INTO WESTERN PRINCE WILLIAM SOUND.

AS MENTIONED IN THE MODEL DISCUSSION...STILL SOME UNCERTAINTY
SURROUNDING THE NEXT DEVELOPING MAJOR STORM SYSTEM BUT ALL
INDICATIONS ARE THAT IT WILL BRING STORM FORCE WINDS TO THE GULF AND
POSSIBLE WARNING LEVEL WINDS TO CHANNELED TERRAIN EARLY TO MID WEEK.
FORECASTS WILL TREND TOWARD THIS VERY STRONG SYSTEM IN THE MEDIUM
RANGE.

SOUTHWEST ALASKA...WEATHER IN SOUTHWEST ALASKA IS DOMINATED BY THE
COLD CORE UPPER LOW CENTERED OVER THE LOWER KUSKOKWIM VALLEY. LIGHT
SNOW IS FALLING REGION WIDE UNDER THE BROAD SCALE CYCLONIC
CIRCULATION. THE UPPER LOW WILL MOVE INLAND SUNDAY AND AS THE STRONG
LOW DEVELOPS NEAR THE ALEUTIANS...FLOW WILL BECOME MORE NORTHEASTERLY
BRINGING AN END TO THE PRECIPITATION ACROSS THE REGION. HIGH PRESSURE
WILL DOMINATE BRIEFLY BEFORE THE STRONG FRONTAL BOUNDARY SPREADS
MOISTURE INLAND MONDAY AFTERNOON. SIMILAR TO THE SOUTHCENTRAL
FORECAST...WILL HAVE TO WATCH FOR THE POSSIBILITY OF WARNING LEVEL
WINDS THROUGH CHANNELED TERRAIN WITH THIS SYSTEM.

BERING SEA/ALEUTIANS...COLD ADVECTION SNOW SHOWERS WILL SLOWLY TAPER
OFF THROUGH SUNDAY. HIGH PRESSURE WILL BRIEFLY CALM CONDITIONS BEFORE
THE LARGE STORM TAKE SHAPE SOUTH OF THE CHAIN SUNDAY NIGHT. STORM
FORCE WINDS WITH STRONGER GUSTS ARE LIKELY WITH THIS SYSTEM AS IT
DEEPENS TO NEAR 950 MB MONDAY AFTERNOON AND THEN BEGINS TO DRIFT EAST
AND WEAKEN THROUGH MID WEEK. THE OVERALL PATTERN WILL MAKE VERY
LITTLE PROGRESS AS THE MEAN UPPER LEVEL TROUGH AXIS REMAINS NEARLY
STATIONARY THROUGH MID TO LATE NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM 170 172
         GALE WARNING...155 171 175 176 179.
         HEAVY FREEZING SPRAY WARNING...130 138 140 141 150 155
                                        160 165 179 185.
FIRE WEATHER...NONE.

AB FEB 10