Storm Warning 139, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
225 PM AKDT TUES SEP 14 2010

.ANALYSIS AND UPPER LEVELS...AN OMEGA RIDGE BLOCK OVER MAINLAND
ALASKA CONTINUES TO BRING FAIR SKIES AND WARM TEMPERATURES TO
MAJORITY OF MAINLAND ALASKA. HOWEVER...OVERNIGHT STRATUS ALONG THE
WEST GULF OF ALASKA SURGED NORTHWARD ALONG THE INLET INTO ANCHORAGE.
WITH THE WEAKER SUN ANGLE AND LIGHT WINDS ALOFT UNDER THE HIGH
PRESSURE SYSTEM...THERE IS LITTLE WORKING TO BREAK OFF THE FOG. LOW
CLOUDS ARE ALSO LINGERING ALONG THE WEST COAST OF MAINLAND ALASKA
UNDER SOUTH SOUTHERLY FLOW. OFFSHORE...A FRONT STRETCHES ACROSS THE
EASTERN ALEUTIANS AND INTO THE BERING CONTINUES TO RAPIDLY DIMINISH
ALTHOUGH LIGHT RAIN WAS REPORTED IN DUTCH HARBOR THIS MORNING.

.MODEL DISCUSSION...MODELS ARE IN GREAT AGREEMENT TODAY THROUGH THE
END OF THE WEEK DUE TO THE STRONG FORCING OF THE OMEGA BLOCK. THE
NEXT MAJOR SYNOPTIC FEATURE TO APPROACH THE WEST FORECAST AREA WILL
BE A LOW PRESSURE SYSTEM THAT WILL APPROACH THE WEST ALEUTIANS BY
LATE TONIGHT. THE UPPER LEVEL LOW WILL DEVELOP RAPIDLY AND REMAIN
CONNECTED TO ITS UPPER LEVEL POTENTIAL VORTICITY SUPPORT OVER THE
NEXT SEVERAL DAYS. HOWEVER...THIS LOW WILL BEGIN TO WEAKEN BY THE END
OF THE WEEK AS IT APPROACHES THE UPPER LEVEL RIDGE AND ENCOUNTERS LOW
POTENTIAL VORTICITY AIR. MODELS THEN BEGIN TO DIVERGE ON THE
MANIFESTATION OF THIS LOW AS IT WEAKENS.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...EXPECT WARM SUNNY WEATHER AWAY FROM THE COAST THIS
AFTERNOON AS A POTENT UPPER LEVEL HIGH REMAINS OVERHEAD. WITH LITTLE
MIXING EXPECTED...STRATUS WILL REMAIN ALONG THE GULF OF ALASKA COAST
AND COOK INLET INTO WEDNESDAY. ALTHOUGH THERE MAY BE BREAKS IN THE
FOG AND STRATUS BY AFTERNOON...EXPECT CLOUDS TO REFORM TONIGHT WITH
DIURNAL COOLING.

.SOUTHWEST...STRATUS WILL PERSIST ALONG THE COAST DUE TO LIGHT
SURFACE ONSHORE FLOW OVER THE NEXT FEW DAYS.  ALTHOUGH DIURNAL
HEATING WILL ALLOW FOR BRIEF BREAKS IN THE FOG...IT WILL QUICKLY
REFORM AT NIGHT. HOWEVER...MODELS ARE INDICATING THAT STEADY OFFSHORE
FLOW WILL OCCUR ACROSS PORTIONS OF SOUTHWEST MAINLAND ALASKA WHICH
WILL HELP TO LIMIT FOG AND STRATUS COVER. INLAND AREAS EXPECT MOSTLY
CLEAR SKIES TO PERSIST WITH PATCHY FOG AT NIGHT.

.ALEUTIANS...A FRONT ACROSS THE EASTERN ALEUTIANS WILL CONTINUE TO
WEAKEN AS IT MOVES EASTWARD. MEANWHILE...A NEW SYSTEM DEVELOPING
SOUTHWEST OF THE WEST ALEUTIANS IS MOVING NORTHEAST. WINDS NEAR STORM
FORCE AND RAIN WILL REACH THE WEST AND CENTRAL ALEUTIANS BY WEDNESDAY
WHILE GALES WILL REACH THE EAST ALEUTIANS BY THURSDAY.

.LONG TERM FORECAST...RIDGING WILL PERSIST ACROSS MAINLAND ALASKA
INTO THE WEEKEND.  MODELS ARE HINTING AT A RETURN TO A MORE
PROGRESSIVE PATTERN BY EARLY NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...172 175 176
FIRE WEATHER...NONE.

ELN SEP 10