Brisk Wind Advisory 25, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
135 PM ADT THU MAR 20 2008

.ANALYSIS AND UPPER LEVELS...ANCHOR LOW IS CENTERED JUST OFF THE
SOUTHWEST COAST THIS MORNING...DROPPING SOUTHWARD ACROSS THE EASTERN
BERING. MULTIPLE WAVES ARE EMBEDDED WITHIN THE LARGE CYCLONIC
CIRCULATION FROM THE CENTRAL BERING TO NORTH PACIFIC BACK NORTHWARD
ACROSS KODIAK ISLAND AND SOUTHWEST ALASKA. THESE WAVES ARE AIDING
IN GENERATION OF SNOW SHOWERS. MOST WIDESPREAD SNOW SHOWERS ARE
FOUND IN AREA OF COLD ADVECTION ACROSS THE BERING
SEA/ALEUTIANS/ALASKA PENINSULA. THERE ARE TWO SURFACE LOWS ON THE
MAP THIS MORNING...ONE SOUTH OF THE ALASKA PENINSULA TRACKING
EASTWARD...AND THE OTHER JUST SOUTH OF THE EASTERN GULF TRACKING
NORTHWARD. A SURFACE TROUGH EXTENDS NORTHWARD ACROSS THE GULF TO
PRINCE WILLIAM SOUND. RADAR IMAGERY SHOWS A BAND OF SNOW ALONG THIS
TROUGH HAS BEEN TRACKING WESTWARD ACROSS PRINCE WILLIAM SOUND.

.MODEL DISCUSSION...MODELS INITIALIZED WELL. THE NAM APPEARS TO BE
VERIFYING BEST IN DETAILS OF GULF TROUGH AND ASSOCIATED SNOWFALL SO
PREFER ITS SOLUTION OF PROGRESSION OF TROUGH ACROSS SOUTHCENTRAL
TONIGHT INTO FRIDAY MORNING. THERE ARE DIFFERENCES IN MODEL SOLUTIONS
AS LOW CURRENTLY SOUTH OF ALASKA PENINSULA CURVES NORTHWARD INTO THE
GULF FRIDAY NIGHT. GFS SOLUTION THEN BRINGS ANOTHER LOW INTO EASTERN
GULF SATURDAY AND THEN DEPICTS TWO GULF LOWS ROTATING AROUND EACH
OTHER. GFS IS WEAKER WITH THIS SECOND LOW THAN PREVIOUS
SOLUTIONS...BUT CONTINUES TO BE THE ODD MODEL OUT. OTHER MODELS
DEPICT A WEAKER LOW MOVING TO SOUTHEAST ALASKA. GFS ENSEMBLE HOWEVER
SUPPORTS PRESENCE OF THIS LOW AND ROTATION NORTHWESTWARD. BECAUSE
CURRENT FORECAST WAS BASED ON OLD SOLUTION DECIDED TO UPDATE USING
THE LATEST GFS.

.SHORT TERM FORECAST...SNOW WILL SPREAD WESTWARD ACROSS WESTERN
PRINCE WILLIAM SOUND THIS AFTERNOON TO ANCHORAGE AND THE WESTERN
KENAI PENINSULA TONIGHT. EXPECT SNOWFALL AMOUNTS TO BE GENERALLY
LIGHT - AND INCH OR TWO. AREAS FARTHER NORTH MAY SEE A FEW SHOWERS
WITH LITTLE OR NO ACCUMULATION. WESTERN PRINCE WILLIAM SOUND...WHICH
HAS RECEIVED 1 TO 2 FT OF SNOW THE LAST COUPLE DAYS...CAN ONCE AGAIN
EXPECT ENHANCED SNOW AMOUNTS DUE TO EASTERLY UPSLOPE FLOW AND
CONVECTION THAT WILL PERSIST BEHIND THE TROUGH. THE TROUGH WILL SWING
SOUTH AND WESTWARD FRIDAY AS THE NORTH PACIFIC LOW MOVES UP TOWARD
THE GULF...SPREADING SNOW ACROSS KODIAK ISLAND AND PORTIONS OF
SOUTHWEST ALASKA. MEANWHILE THE LOW CURRENTLY MOVING INTO THE GULF
WILL ROTATE NORTHWESTWARD AND DISSIPATE. THE NORTH PACIFIC LOW WILL
MOVE INTO THE GULF AND SPREAD MORE SNOW ALONG THE GULF COAST LAND
AREAS. UPPER JET SUPPORT AND COLD AIR FEEDING INTO BACK OF THE SYSTEM
FROM THE BERING WILL HELP STRENGTHEN THIS LOW INTO THE 970S AND
RESULT IN GALE FORCE WINDS ACROSS THE GULF WATERS. THE UNCERTAINTY
IN THE TRACK OF THIS LOW MAKES THE PRECIPITATION FORECAST VERY
TROUBLESOME...ESPECIALLY FOR KODIAK ISLAND WHICH LOOKS LIKE IT WILL
CONTINUE TO SEE SNOW THROUGH THE WEEKEND. IF THE GFS SOLUTION IS
CORRECT THERE IS POTENTIAL FOR SNOW ADVISORY AMOUNTS IN KODIAK FRIDAY
NIGHT AND SATURDAY AND AN OUTSIDE CHANCE OF BLIZZARD CONDITIONS. IT
WILL ALL DEPEND ON POSITION OF LOW OVER GULF AND WHETHER LOW LEVEL
FLOW IS OUT OF THE NORTHWEST OR NORTHEAST. FOR NOW HAVE INCREASE POPS
FOR KODIAK AND WILL KEEP SNOW AMOUNTS BELOW ADVISORY LEVEL UNTIL GET
A BETTER IDEA OF LOW POSITION.

OUT WEST HIGH PRESSURE WILL BUILD OVER THE WESTERN BERING AND WESTERN
ALEUTIANS THE NEXT COUPLE DAYS WHILE THE UPPER LOW OVER THE EASTERN
BERING DROPS SOUTHWARD AND THEN MOVES INTO THE GULF. WITH RISING
PRESSURE OUT WEST AND LOWERING PRESSURES IN THE GULF THE PRESSURE
GRADIENT WILL TIGHTEN ACROSS THE CENTRAL TO EASTERN BERING
REGION...RESULTING IN STRONGER NORTHERLY WINDS. THUS...SNOW SHOWERS
AND WINDS WILL INTENSIFY. THERE DOES NOT APPEAR TO BE ANY FEATURES
TO HELP FOCUS THE SNOW...SO DONT EXPECT SNOW SHOWERS TO BE STEADY
ENOUGH TO PRODUCE BLIZZARD CONDITIONS ANYWHERE.

.LONG TERM FORECAST...MEAN TROUGH WILL REMAIN CENTERED OVER THE GULF
THROUGH THE EXTENDED PERIOD...SO DONT EXPECT ANY SIGNIFICANT CHANGES
FROM CURRENT PATTERN.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM WARNING 120.
         GALE WARNING 121 130 132 138 140.
         HEAVY FREEZING SPRAY WARNING 130 138 140 150 155 165 170.
FIRE WEATHER...NONE.

SEB MAR 08