Storm Warning 136, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKDT TUE SEP 8 2009

.ANALYSIS AND UPPER LEVELS...
ALOFT...THE UPPER LOW SOUTH OF THE AKPEN CONTINUES TO WEAKEN WHILE AN
ARCTIC UPPER LOW DIGS SOUTHWARD. THIS LOW WILL DEEPEN THE LONGWAVE
TROUGH OVER MAINLAND ALASKA AND BECOME ONE OF THE MAIN FEATURES OF
INTEREST AS WE HEAD THROUGH THE COMING WEEK.

AT THE SURFACE...A WEAKENING LOW IS IN THE CENTRAL GULF OF AK WITH AN
ASSOCIATED WEATHER FRONT WASHING OUT ALONG THE NORTHERN GULF COAST.
THE OLD PARENT LOW IS STATIONARY OVER THE AKPEN...AND WILL EVENTUALLY
BE ABSORBED INTO A DEVELOPING NORTH PACIFIC LOW LATE WEDNESDAY.
ELSEWHERE...HIGH PRESSURE IS IN PLACE OVER THE WESTERN ALEUTIANS.
BETWEEN THESE TWO SYSTEMS...STRONG NORTHERLY WINDS ARE OCCURRING
ACROSS THE EASTERN BERING SEA AND ALEUTIANS.

.MODEL DISCUSSION...
MODELS ARE IN GENERAL AGREEMENT ON THE OVERALL FEATURES THROUGH LATE
THURSDAY...ALTHOUGH DETAILS REMAIN CLOUDY WITH REGARDS TO INTENSITY
AND POSITIONING OF INDIVIDUAL SURFACE LOWS. EXPECT THE DIGGING UPPER
LOW TO MOVE INTO THE GULF...DEEPENING THE DEVELOPING NORTH PACIFIC
SURFACE LOW MOVING INTO THE GULF OF ALASKA ON THURSDAY. THIS LOW WILL
THEN FILL IN THE GULF THROUGH THE REMAINDER OF THE WEEK. THE NEXT
AREA OF CONCERN PERTAINS TO THE REMNANTS OF FORMER TROPICAL CYCLONE
DUJUAN AS IT MOVES INTO THE BERING SEA LATE WEEK. MODEL DISAGREEMENT
CONTINUES WITH THIS FEATURE...BUT ANOTHER ROUND OF RAIN AND GALE TO
STORM FORCE WINDS CAN BE EXPECTED FOR THE WESTERN ALEUTIANS BY THE
END OF THE WORKWEEK.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
THE WEAKENING WEATHER FRONT WILL CONTINUE TO SPREAD SHOWERS ACROSS
COASTAL AREAS THIS AFTERNOON INTO TONIGHT...WITH THE HEAVIEST RAIN
ALONG THE IMMEDIATE GULF COAST. THE AFOREMENTIONED LOW WILL MOVE
NORTHWEST TO NEAR KODIAK ISLAND BEFORE DISSIPATING...RESULTING IN A
TIGHTENING GRADIENT AND GUSTY WINDS FOR THE NORTHERN GULF COAST AND
COOK INLET REGION THIS EVENING AND TONIGHT. AMPLE MOISTURE AND
VARIOUS SHORTWAVES ROTATING AROUND THE DIGGING UPPER LOW WILL KEEP
PRECIPITATION ALONG THE COAST TOMORROW AS WELL. BY LATE WEDNESDAY THE
DEEPENING SURFACE LOW MOVING INTO THE GULF WILL BEGIN TO IMPACT THE
REGION. MAIN CONCERNS INCLUDE GALE TO STORM FORCE WINDS ALONG THE
COASTAL AND OFFSHORE WATERS WITH HEAVY PRECIPITATION AS WELL. INLAND
LOCATIONS WILL REMAIN RELATIVELY DRY...WITH TYPICAL DOWNSLOPED AREAS
EXPERIENCING MINIMAL PRECIPITATION. THURSDAY IS EXPECTED TO BRING THE
MOST IMPACT TO THE REGION...WITH KODIAK ISLAND TAKING THE BRUNT FOR
LAND AREAS. STRONG WINDS CAN BE EXPECTED THROUGH CHANNELED AND HIGH
TERRAIN FARTHER INLAND WITH THIS SYSTEM AS WELL.

.SOUTHWEST...
SHOWERS WILL CONTINUE ACROSS THE REGION THROUGH EARLY THURSDAY AS THE
DIGGING UPPER LOW AND VARIOUS WAVES ROTATE AROUND THE AREA. AS THE
LOW MOVING INTO THE GULF SLIPS EASTWARD...BRISK NORTHERLY FLOW WILL
BE DEVELOPING ON THURSDAY. THIS WILL LEAD TO A DRYING TREND ACROSS
THE AREA THROUGHOUT THE DAY THURSDAY...WITH GUSTY WINDS POSSIBLE
PARTICULARLY ALONG THE AKPEN.

.BERING SEA AND ALEUTIANS...
STRONG NORTHERLY FLOW CONTINUES ACROSS THE EASTERN BERING AND
ALEUTIANS AS THE LOW WEAKENS IN THE GULF. EXPECTING THE GRADIENT TO
STRENGTHEN ONCE AGAIN TOMORROW AS THE LARGE NORTH PACIFIC LOW MOVES
INTO THE GULF. SUBSEQUENTLY...COLD AIR WILL BE FILTERING INTO THE
REGION WITH SCATTERED SHOWERS THROUGH THURSDAY. PROGRESSIVE HIGH
PRESSURE CURRENTLY OVER THE WESTERN ALEUTIANS WILL SLIDE
SOUTHEASTWARD THROUGH THURSDAY...KEEPING LOW CLOUDS AND FOG OVER THE
AREA. EARLY THURSDAY FOCUS SHIFTS TOWARDS THE REMNANTS OF TROPICAL
CYCLONE DUJUAN. WHILE THE DETAILS ARE DIFFICULT TO RESOLVE AT THIS
POINT...EXPECT UNSETTLED WEATHER AND STRONG WINDS TO RETURN TO THE
WESTERN BERING BY LATE WEEK.

.LONG TERM FORECAST...
UPPER FLOW IS EXPECTED TO BECOME MORE ZONAL ACROSS THE REGION THIS
WEEKEND. THERE IS ALSO GENERAL AGREEMENT ON AN UPPER LOW DIGGING FROM
BRISTOL BAY INTO THE GULF OF ALASKA...WHICH MEANS CONTINUED UNSETTLED
WEATHER AND SLIGHTLY BELOW NORMAL TEMPERATURES ACROSS MAINLAND ALASKA
AS WE HEAD INTO NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE 120 130 132 150 155 165 170 171 172 176 179 180
         STORM 170
FIRE WEATHER...NONE

NRH SEP 09