Small Craft Advisory 837, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
130 PM AKDT TUE OCT 28 2008

.ANALYSIS AND UPPER LEVELS...HIGH AMPLITUDE TROUGHS ARE POSITIONED
OVER THE GULF OF ALASKA /NE PACIFIC AND OVER THE SEA OF OKHOTSK WITH
A STRONG RIDGE IN BETWEEN...CENTERED WELL SOUTH OF THE ALEUTIANS. A
165 KT UPPER JET EXTENDS FROM THE NW PACIFIC UP AND OVER TOP OF THE
RIDGE (INTO THE SOUTHERN BERING SEA) AND THEN DIVES SOUTHWARD INTO
THE NE PACIFIC BEFORE RETURNING NORTHWARD TOWARD SOUTHEAST ALASKA.
THERE ARE TWO DEEP VERTICALLY STACKED LOWS CURRENTLY AFFECTING THE
FORECAST AREA. THE FIRST IS OVER THE EASTERN GULF AND HEADED NNE
TOWARD SOUTHEAST ALASKA. THE PRESSURE GRADIENT HAS TIGHTENED ALONG
THE NORTH GULF COAST...RESULTING IN GUSTY GAP WINDS. THE DIFFERENCE
IN AIRMASS TEMPERATURE BETWEEN INLAND AND AIR OVER THE GULF IS ALSO
CONTRIBUTING TO STRONG WINDS. THE SECOND MAJOR LOW IS TRACKING ACROSS
THE NORTHERN BERING (OVER TOP OF THE RIDGE) WHILE AN OCCLUDED FRONT
PUSHES ONSHORE OF SOUTHWEST ALASKA. THE COMBINATION OF A SHORT-WAVE
RIDGE OUT AHEAD OF THE FRONT AND LITTLE PUSH BEHIND THE FRONT MEANS
THE INLAND PROGRESSION OF PRECIPITATION IS VERY SLOW. SNOW AND
BLOWING SNOW HAS IS OCCURRING ALONG THE IMMEDIATE COAST WHERE
TEMPERATURES ARE IN THE UPPER 20S AND WINDS ARE GUSTING 40 TO 50 MPH.

WITH THE EXCEPTION OF CAPE NEWENHAM OBSERVATIONS ALONG THE COAST
INDICATE VISIBILITY HAS REMAINED 1 MILE OR MORE. SLOWLY WARMING
TEMPERATURES WILL PREVENT ANY POSSIBILITY OF SUSTAINED BLIZZARD
CONDITIONS. A STRONG PRESSURE GRADIENT IS PRODUCING WIDESPREAD
GALE FORCE WINDS BEHIND THE FRONT.

.MODEL DISCUSSION...MODELS INITIALIZED WELL AND SHOW GOOD AGREEMENT
THROUGH THE SHORT-TERM FORECAST PERIOD. MODEL RUN-TO-RUN CONSISTENCY
IS ALSO GOOD...SO WILL STICK CLOSE TO CURRENT FORECAST WITH JUST
SOME MINOR ADJUSTMENTS.

.SHORT TERM FORECAST...

SOUTHCENTRAL...LOCALLY GUSTY WINDS WILL GRADUALLY DIE DOWN TONIGHT
AS THE EASTERN GULF LOW WEAKENS AND MOVES INLAND OVER SOUTHEAST
ALASKA. IT WILL BE ANOTHER VERY COLD NIGHT ACROSS THE REGION UNDER
CLEAR SKIES. THE OCCLUDED FRONT OUT WEST WILL APPROACH KODIAK ISLAND
LATE TONIGHT AND FALL APART AS IT MOVES TOWARD THE KENAI PENINSULA
WEDNESDAY. THE BERING LOW WILL THEN CROSS THE ALASKA PENINSULA TO
SOUTH OF KODIAK ISLAND WEDNESDAY NIGHT...CAUSING FLOW OVER
SOUTHCENTRAL TO SHIFT TO THE NORTH. IN ADDITION TO THESE FACTORS
THERE IS ALSO A DEEP LAYER OF COLD DRY AIR CURRENTLY OVER
SOUTHCENTRAL. THEREFORE...EVERYTHING POINTS TOWARD A DRY FORECAST
FOR INTERIOR SOUTHCENTRAL WITH JUST A PERIOD OF CLOUDINESS. EXPECT
SOME LIGHT PRECIPITATION TO MAKE IT TO COASTAL SECTIONS WEDNESDAY
NIGHT AND THURSDAY. CONDITIONS WILL THEN DRY OUT AS THE LOW PULLS
AWAY THURSDAY NIGHT AND FRIDAY.

SOUTHWEST ALASKA...THE NORTHERN PORTION OF THE FRONT WILL FALL
APART FAIRLY QUICKLY TONIGHT INTO WEDNESDAY AS THE LOW BEGINS TO
TRACK SOUTHEASTWARD TOWARD BRISTOL BAY. IT WONT MAKE MUCH MORE
PROGRESSION INLAND...SO MOST OF THE KUSKOKWIM VALLEY AS WELL AS
FAR INLAND BRISTOL BAY WILL REMAIN DRY. ONSHORE FLOW ALONG THE
IMMEDIATE COAST TONIGHT AND WEDNESDAY WILL PROVIDE JUST ENOUGH
WARM AIR TO CHANGE SNOW TO RAIN AND END THE ONGOING BLOWING SNOW.
AN UPPER LEVEL SHORT-WAVE BEHIND THE BERING LOW WILL MAINTAIN A
THREAT FOR A FEW SHOWERS WEDNESDAY NIGHT AND THURSDAY BEFORE
DRYING OUT ON FRIDAY.

ALEUTIANS...STRONG WINDS WILL CONTINUE WEST OF THE LOW CENTER...THEN
DIMINISH FROM WEST TO EAST WEDNESDAY THROUGH THURSDAY AS THE BERING
LOW WEAKENS AND TRACKS ACROSS THE ALASKA PENINSULA. THERE IS LITTLE
IN THE WAY OF THERMAL ADVECTION ON THE BACK SIDE OF THE LOW...SO
WINDS WILL DIMINISH IN STEP WITH THE PRESSURE GRADIENT. A RIDGE WILL
BUILD OVER THE BERING OUT AHEAD OF THE SYSTEM MOVING OUT OF
RUSSIA...BUT WILL QUICKLY MOVE EASTWARD AS A STRONG JET PUSHES A
FRONT EASTWARD ACROSS THE BERING ON THURSDAY THROUGH FRIDAY.

.LONG TERM FORECAST...THE TROUGH CROSSING THE BERING AT THE END OF
THE WEEK WILL JOIN UP WITH THE GULF TROUGH OVER THE WEEKEND.
THUS...IF THERE IS ANY CHANCE OF PRECIPITATION OVER SOUTHCENTRAL IT
WILL COME FROM THE SOUTHEAST...WHICH IS WHAT THE MEDIUM RANGE MODELS
INDICATE. A SPLIT JET OUT WEST WILL MAKE IT DIFFICULT TO DETERMINE
TIMING AND LOCATION OF FEATURES...BUT IT DOES NOT LOOK LIKE ANY
MAJOR SYSTEMS WILL AFFECT THE REGION THROUGH EARLY NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING 165 170 176 179 180 185.
FIRE WEATHER...NONE.

SEB OCT 08