Snow Advisory 23, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 PM AST MON DEC 3 2007

.ANALYSIS AND UPPER LEVELS...
UPPER LEVEL CUT OFF HIGH CONTINUES TO HOLD STRONG NORTH OF THE STATE
THIS MORNING WITH A RIDGE EXTENDING DOWN OVER THE BERING SEA.
MEANWHILE IN THE NORTHERN PACIFIC A BAROTROPIC LOW IS SLOWLY MOVING
EASTWARD INTO SHELIKOF STRAIT THIS MORNING.  STRONG WINDS CAUSED BY
THE INCREASED GRADIENT AND COLD AIR ADVECTION HAVE TAPERED OFF THIS
MORNING...HOWEVER AS THE LOW PROGRESSES FURTHER NORTHEASTWARD THE
WINDS ARE EXPECTED TO INCREASE AGAIN.  MEANWHILE IN THE ALEUTIANS THE
NORTHERLY FLOW ON THE EAST SIDE OF THE RIDGE IS BRINGING COLD
TEMPERATURES AND SOME GUSTY WINDS.  THIS IS EXPECTED TO CONTINUE
UNTIL THE LOW IN NORTH PAC MOVES INTO SHELIKOF STRAIT THIS AFTERNOON
AND THE GRADIENT WEAKENS OUT WEST.

.MODEL DISCUSSION...
12Z RUNS OF THE MODELS HAVE COME TOGETHER ON THE SOLUTIONS FROM THE
SHORT TERM THROUGH THE MID RANGE.  PREVIOUS MODEL RUN OF THE GFS AND
NAM DIFFERED BETWEEN THE ORIENTATION OF THE ISOBARS IN THE GULF OF AK
AS THE N PAC LOW MOVES INTO SHELIKOF STRAIT.  HOWEVER THE NEW RUN
SHOWS VERY SIMILAR SOLUTIONS...AND CLOSER TO THE 06Z RUN OF THE GFS.
WITH THE CONSISTENCY OF THE GFS IT IS THE MODEL OF CHOICE AGAIN
TODAY.

.SHORT TERM FORECAST...
EAST OF THE AK RANGE...
WITH THE COLD AIR POOLING IN THE COPPER RIVER BASIN GUSTY WINDS WILL
CONTINUE ACROSS THE MAT VALLEY AND THE SOUTHCENTRAL REGION TODAY.
THESE WILL TAPER OFF A LITTLE THIS AFTERNOON BUT ARE EXPECTED TO PICK
UP AGAIN OVERNIGHT AS THE LOW MOVES NORTHWARD AND THE GRADIENT
TIGHTENS.  NORTHERLY WINDS THROUGH THE GAPS AND DOWN COOK INLET ARE
CONTINUING TO CAUSE GALE AND EVEN STORM FORCE WINDS FOR THESE AREAS
TODAY. COLD TEMPERATURES MEAN THAT HEAVY FREEZING SPRAY IS ALSO
PREVALENT IN SMALLER MARINE AREAS LIKE RESURRECTION BAY. NORTHWARD
PROGRESSION OF THE LOW IN THE GULF WILL BRING A FRONT TO THE
SOUTHCENTRAL REGION...WHILE WINDS WITH THIS FRONT ARE NOT TOO STRONG
THERE IS A FAIR AMOUNT OF LIFT ASSOCIATED WITH THE SYSTEM AND
SIGNIFICANT SNOWFALLS ARE EXPECTED ALONG THE COASTAL AREAS.  THIS MAY
CREATE A SNOWFALL ADVISORY FOR THE HOMER BLUFF AREA TOMORROW AND
POSSIBLY 8 TO 10 INCHES OF SNOW IN THE VALDEZ AREA TOMORROW NIGHT.
ELSEWHERE THE SNOW WILL BE BRIEF AND SIGNIFICANT SNOWFALLS ARE NOT
EXPECTED.

WEST OF THE AK RANGE INCLUDING THE ALEUTIANS...
GUSTY WINDS WILL CONTINUE TO TAPER OFF TODAY AS THE LOW IN THE NORTH
PAC MOVES NORTHEASTWARD AND THE RIDGE MOVES IN BEHIND IT.  COLD AIR
ADVECTION WILL BRING SNOW SHOWERS TO THE ALEUTIANS IN PARTICULAR BUT
SIGNIFICANT SNOWFALL IS NOT EXPECTED.  THESE CONDITIONS ARE EXPECTED
TO CONTINUE FOR THE CENTRAL ALEUTIANS AND EASTWARD THROUGH THE SHORT
TERM. OVER THE WESTERN MAINLAND AND AK PEN A BRIEF SHOT OF SNOW IS
EXPECTED AS THE LOW IN SHELIKOF STRAIT BRINGS AN INVERTED TROUGH
THROUGH THE REGION TODAY AND TOMORROW.  IN THE WESTERN ALEUTIANS
CONDITIONS ARE CHILLY BUT CALM TODAY BUT ARE EXPECTED TO DETERIORATE
AS A LOW APPROACHES FROM THE SEA OF JAPAN.  MODELS ARE FORECASTING A
CENTRAL PRESSURE OF 955 MB ON THIS LOW AND HURRICANE FORCE WINDS ARE
EXPECTED IN THE MARINES STARTING TUESDAY AFTERNOON.  A HIGH WIND
WATCH FOR THE LAND AREAS WILL ALSO BE ISSUED THIS AFTERNOON.

.LONG TERM FORECAST...
MODELS HAVE BEEN VARIABLE IN THE LONG TERM SO NOT A LOT OF CONFIDENCE
IN THE FORECAST.  HOWEVER AT THIS POINT IT LOOKS LIKE A RETURN TO
WARMER WINDY WEATHER IS IN STORE FOR THE STATE. THE STRONG LOW
ENTERING THE WESTERN ALEUTIANS TUESDAY EVENING WILL CONTINUE TO
STRENGTHEN AND MOVE EASTWARD INTO THE CENTRAL BERING BY WEDNESDAY
AFTERNOON.  THIS WILL BRING A FRONT WITH SOUTHEASTERLY FLOW ONTO THE
WEST COAST ON THURSDAY AND INTO THE SOUTHCENTRAL REGION THURSDAY
AFTERNOON.  GFS IS FORECASTING A SECOND LOW TO FORM ALONG THIS FRONT
AND MOVE INTO THE SOUTHCENTRAL REGION ON FRIDAY.  WHETHER THIS WILL
OCCUR AND EXACTLY HOW WARM THE TEMPERATURES GET BY THE END OF THE
WEEK IS STILL UNCERTAIN AT THIS POINT.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WATCH 191
         HEAVY SNOW ADVISORY 121
MARINE...HEAVY FREEZING SPRAY 121 125 130 140 141
         GALE 125 130 132 138 141 150 155 165 180 170 172 185
         STORM 120 140 175
         HURRICANE FORCE 176
FIRE WEATHER...NONE

LEWF DEC 07