High Wind Watch 12, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTH CENTRAL AND SOUTHWEST ALASKA
500 PM AKDT MON OCT 20 2008

.MODEL DISCUSSION...MODEL INITIALIZATIONS ARE REASONABLE. THE STORM
CENTER THAT MOVES INTO THE GULF OF ALASKA TUE IS HANDLED WELL BY THE
GFS/ECMWF MODELS. ALTHOUGH THE MODELS ARE CONVERGING ON INTENSITY OF
STORM CENTER APPROACHING THE ALEUTIANS TUE...THERE ARE STILL ISSUES
WITH SPEED. THE GFS CONTINUES TO SHOW A FASTER MOVEMENT. CONSIDERING
THE PROGRESSIVENESS OF CURRENT PATTERN...WE FEEL THAT THE GFS SPEED
IS PROBABLY CLOSER TO REALITY.

.UPPER LEVELS...
PROGRESSIVE PATTERN CONTINUES ACROSS THE REGION. THE TROUGH OVER THE
GULF MOVES INTO CANADA TONIGHT. A SHARPENING TROUGH EXTENDING FROM A
LOW NEAR SAINT MATTHEW ISLAND TO 45N 160W AND SOUTHWARD WILL ROTATE
EAST TO EXTEND SE ACROSS THE MAINLAND TO OVER SE ALASKA WED
AFTERNOON. AT THIS TIME A NEARLY ZONAL FLOW IS EVIDENT OVER THE NORTH
PACIFIC WITH SHORT WAVES MOVING ACROSS THE ALEUTIANS AND AK PEN. BY
THU...A COLD LOW SETS UP OVER THE MAINLAND WITH TROUGHS EXTENDING SW
ACROSS THE BERING SEA AND SOUTH OVER THE GULF OF ALASKA.

.SHORT TERM FORECAST...
.EAST...A WEAK TROUGH OVER BRISTOL BAY THIS AFTERNOON WILL MOVE INTO
SOUTH CENTRAL TONIGHT AND BRING RAIN AND SNOW SHOWERS THIS EVENING
AND SHOW SHOWERS AFTER MIDNIGHT. THE GULF LOW CONTINUES TO WEAKEN
THROUGH TONIGHT AND WILL SLOWLY RETROGRADE WEST AS DEVELOPING LOW
OVER THE NE PACIFIC APPROACHES THE GULF. THIS STORM CENTER IS HANDLED
WELL BY THE MODELS AND THE 12Z GFS WILL BE USED WITH THIS SYSTEM. A
STRONG LOW CENTER WILL MOVE TO THE EASTERN GULF TUE NIGHT WITH A
PRESSURE IN THE 960S. THIS LOW WILL THEN WEAKEN AS IT MOVES INLAND
NEAR YAKUTAT WED AFTERNOON. GALES TO STORM FORCE WINDS ARE EXPECTED
IN ADVANCE OF LOW AND ASSOCIATED FRONT AND GALES TO STORMS/STORM
GUSTS ARE EXPECTED ON THE BACKSIDE OF CENTER WITH COLD ADVECTION OVER
MARINE AREAS TUE NIGHT AND WED. THERE WILL ALSO BE FAIRLY STRONG GAP
FLOWS OVER SOUTH CENTRAL AND THE NORTH GULF DURING THIS TIME FRAME.

.WEST...A WEAK TROUGH WILL MOVE THROUGH THE SW INTERIOR THIS EVENING
AND BRING LIGHT SNOW OR SNOW SHOWERS. A WEAK FRONTAL TROUGH AND
ASSOCIATED LOW WILL PROVIDE SOME LIGHT SNOW TO COASTAL SW
ALASKA/BRISTOL BAY TONIGHT. A LOW CENTER OVER THE NORTHEAST BERING
SEA WILL MOVE TO NEAR UNIMAK PASS TUE AFTERNOON. BRISK WINDS ARE
EXPECTED ON THE BACKSIDE OF THIS CENTER AS IT PROGRESSES SOUTH.
SATELLITE IMAGERY SHOWS OPEN/CLOSED CELL CUMULUS CLOUDS WITH THIS
SYSTEM...SO EXPECT ENHANCED SHOWER ACTIVITY OVER THE EASTERN
ALEUTIANS AND WESTERN AK PEN TUE. A DEVELOPING W PACIFIC LOW WILL
DROP INTO THE LOWER 950S AS IT CROSSES THE DATE LINE NEAR 49N TUE
AFTERNOON. THE 12Z GFS LOOKS LIKE IT HAS THE OVERALL BEST
SOLUTION...WITH A FASTER TRACK PREFERRED. THIS LOW WEAKENS AS IT
TRACKS SOUTH OF THE AK PEN WED NIGHT. STORM/HURRICANE FORCE WINDS ARE
EXPECTED ALONG THE ALEUTIANS WITH POTENTIAL FOR HIGH WIND WARNING
CONDITIONS PUBLIC ZONES 191 AND 187. FOR NOW WILL GO WITH A HIGH WIND
WATCHES STARTING TUE AFTERNOON/EVE AND CONTINUE INTO WED. ANY BLOWING
SNOW SHOULD BE SHORT LIVED WITH WARM ADVECTION IN ADVANCE OF LOW
CENTER.

.LONG TERM FORECAST...A LOW SOUTH OF AK PEN WED NIGHT MOVES INTO THE
GULF THU WITH A FAIRLY SIGNIFICANT TRIPLE POINT MOVING INTO THE NE
GULF THU AFTERNOON. STRONG PRESSURE GRADIENTS AND COLD ADVECTION OVER
THE WESTERN GULF THU WILL PRODUCE STRONG WINDS OVER MUCH OF THE
WESTERN GULF AND GAP FLOWS OVER SOUTH CENTRAL/GULF THU THROUGH EARLY
FRI. COOLER TEMPS ARE EXPECTED OVER THE MAINLAND THU AND FRI AS COLD
AS COLD UPPER LOW MOVES OVER THE REGION.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WATCH ZONES 187 185 AND 191 TO BE INITIATED AT 4PM
MONDAY.
MARINE...HURRICANE FORCE 175. STORMS 172 176. GALES 120 130 132 170.
FIRE WEATHER...NONE.

RMC OCT 08