Gale Warning 588, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
1250 PM AKDT TUE SEP 7 2010

.ANALYSIS AND UPPER LEVELS...STRONG MID-LEVEL SHORT-WAVE WHICH
BROUGHT A BRIEF PERIOD OF MODERATE TO HEAVY RAINFALL TO THE
SOUTHERN MAINLAND OVERNIGHT IS NOW RAPIDLY EXITING TO THE
NORTH AND EAST. SURFACE OCCLUDED FRONT HAS ALSO CROSSED MOST OF
THE REGION. HOWEVER...A TRIPLE POINT LOW DEVELOPED SOUTH OF THE
KENAI PENINSULA SO THIS LOW AND ITS FRONTAL SYSTEM ARE STILL
BACK OVER THE CENTRAL GULF AND WILL CONTINUE TO TRACK EASTWARD
THROUGH THE DAY. THE LARGE PARENT LOW IS NOW OVER THE NORTHERN
BERING TRACKING SLOWLY EASTWARD. SHORT-WAVES EMBEDDED IN WESTERLY
FLOW SOUTH OF THE LOW CENTER CONTINUE TO BRING RAIN TO SOUTHWEST
ALASKA. WIDESPREAD GALES CONTINUE ACROSS THE BERING SEA DUE TO A
TIGHT PRESSURE GRADIENT BETWEEN THE BERING LOW AND A STRONG RIDGE
OVER THE NORTH CENTRAL PACIFIC. GUSTY WINDS ARE ALSO MAKING IT
INLAND ACROSS SOUTHWEST ALASKA...PARTLY DUE TO STRONG PRESSURE
RISES BEHIND THE OCCLUDED FRONT. LOOKING TO THE WEST A RIDGE IS
BUILDING OVER THE WESTERN BERING OUT AHEAD OF STRONG LOW OVER THE
FAR NORTHWEST PACIFIC.

.MODEL DISCUSSION...MODELS CONTINUE TO HAVE A GOOD HANDLE ON
SYNOPTIC SCALE FEATURES. DIFFERENCES IN SOLUTIONS LIE PRIMARILY
IN THE TIMING AND PLACEMENT OF MID-LEVEL SHORT-WAVES ROTATING
AROUND THE MAIN UPPER LOW. FORECASTS WILL CONTINUE TO BE FINE-TUNED
TO REFLECT THE LATEST CHANGES IN HANDLING OF THESE FEATURES.

.SHORT TERM FORECAST...

SOUTHERN MAINLAND...THE LOW OVER THE BERING WILL CONTINUE TO TRACK
EASTWARD TO AROUND NORTON SOUND WEDNESDAY MORNING AND THEN DIVE
SOUTHEASTWARD TO THE GULF BY THURSDAY AS A RIDGE BUILDS TO THE
NORTH AND WEST OF THE LOW. AS IT MAKES THIS TRANSITION SHORT-WAVES
EMBEDDED IN THE FLOW WILL CONTINUE TO PRODUCE AREAS OF RAIN OR
RAIN SHOWERS. SOUTHWEST ALASKA WILL SEE THE BRUNT OF THE RAIN
TONIGHT AND WEDNESDAY AND SOME FAIRLY STRONG SHORT-WAVES TRACK
THROUGH...ENHANCED BY ONSHORE FLOW. SOUTHCENTRAL WILL SEE MORE
OF A SHOWERY REGIME WITH THE BULK OF SHOWERS IN SOUTHWEST UPSLOPE
FLOW AREAS. CONDITIONS WILL BEGIN TO DRY OUT ACROSS THE REGION
DURING THE DAY THURSDAY AS FLOW BECOME NORTHERLY ON THE BACK SIDE
OF THE LOW. THE WEAK RIDGE MOVING IN FROM THE WEST WILL FLATTEN
OUT AS IT REACHES SOUTHWEST ALASKA THURSDAY NIGHT DUE TO PRESENCE
OF DOWNSTREAM TROUGH AND APPROACH OF ANOTHER TROUGH FROM THE WEST.
STILL...EXPECT MOSTLY DRY WEATHER THURSDAY NIGHT INTO FRIDAY WITH
THE EXCEPTION OF THE SOUTHWEST COAST WHICH MAY SEE SOME RAIN ON
FRIDAY AS A WEAKENING BERING FRONT ARRIVES.

BERING SEA/ALEUTIANS...THE STRONG LOW OVER THE NORTHWEST PACIFIC
WILL LIFT NORTHWARD TO UP THE WEST SIDE OF THE BUILDING DOWNSTREAM
RIDGE AND INTO EASTERN RUSSIA. THE FRONT WILL MARCH SLOWLY EASTWARD
ACROSS THE BERING SLOWLY WEAKENING AS THE FRONT ELONGATES. THERE
LIKELY WON'T BE MUCH WIND OR RAIN LEFT WITH THE FRONT BY THE TIME
IT REACHES THE SOUTHWEST ALASKA COAST ON FRIDAY. ANOTHER RIDGE WILL
BUILD IN BEHIND THE FRONT RESULTING IN GENERALLY BENIGN CONDITIONS
ACROSS THE BERING SEA FOR THE END OF THE WEEK.

.LONG TERM FORECAST...THE DISSIPATING FRONT ALONG THE SOUTHWEST
COAST ON FRIDAY WILL LIKELY BE COMPLETELY GONE BY SATURDAY WITH
A STRONG SHORT-WAVE RIDGE BUILDING IN FROM THE WEST. THIS MEANS
THE SOUTHERN MAINLAND WILL REMAIN MOSTLY DRY THROUGH THE WEEKEND.
UPSTREAM OF THIS RIDGE THE MEDIUM RANGE MODELS INDICATE A STRONG
STORM TRACKING FROM THE PACIFIC INTO THE BERING WITH THE FRONT
PUSHING EASTWARD TO THE MAINLAND EARLY NEXT WEEK. AT THIS POINT
CONFIDENCE IN THE STRENGTH AND TRACK OF THIS SYSTEM IS VERY LOW.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...160 175 176 180.
FIRE WEATHER...NONE.

SEB SEP 10