Gale Warning 990, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
100 PM AKST MON DEC 21 2009

.ANALYSIS AND UPPER LEVELS...
BROAD UPPER LEVEL LOW PRESSURE IS PRESENT OVER THE BERING SEA. A 120
KT SOUTH/SOUTHEASTERLY UPPER LEVEL JET STREAM IN THE NORTH PACIFIC
STRETCHES ACROSS KODIAK ISLAND AND THEN NORTHWEST TOWARD THE SEWARD
PENINSULA. A BUILDING UPPER LEVEL RIDGE IS PRESENT TO THE EAST OF
THIS JET OVER MOST OF THE MAINLAND.

AT THE SURFACE IS A 955 MB LOW APPROACHING SAINT MATTHEW ISLAND FROM
THE SOUTHEAST THIS AFTERNOON. THE STRONGEST WINDS BY FAR ARE ON THE
EAST SIDE OF THE LOW...WITH STORM FORCE WINDS ALONG A FRONT
EXTENDING FROM NUNIVAK ISLAND AND THE KUSKOKWIM DELTA SOUTHEAST INTO
BRISTOL BAY AND THE NORTHWEST GULF OF ALASKA. THERE HAVE BEEN SOME
HURRICANE FORCE WIND GUSTS THROUGH CHANNELED TERRAIN OF THE
SOUTHWEST MAINLAND. WARM AIR IS PRESENT TO THE EAST OF THE BERING
LOW...WITH TEMPERATURES GENERALLY ABOVE FREEZING FROM NORTON SOUND
SOUTH TO BRISTOL BAY...AND EAST TO THE NORTH/WEST IMMEDIATE GULF
COAST. PRECIPITATION...MOSTLY RAIN...IS FALLING OVER THIS SAME
AREA...AND RAIN HAS BEEN HEAVY AT TIMES TODAY AROUND KODIAK ISLAND.
THE ONLY REMAINING ARCTIC AIR IS OVER THE COPPER RIVER BASIN
STRETCHING NORTH AND EAST.

.MODEL DISCUSSION...
MODELS IN FAIRLY GOOD AGREEMENT THROUGH ABOUT WED/WED NIGHT. MAIN
MODEL CONCERN REGARDS A STRONG LOW TRACKING NORTHWEST THROUGH THE
GULF OF ALASKA TUE NIGHT/WED. MODELS HAVE COME INTO BETTER AGREEMENT
WITH THIS...BUT STILL A BIT OF DIFFERENCES IN TIMING AND EXACT
TRACK. BEST GUESS IS FOR A TRACK OVER THE NORTH END OF KODIAK ISLAND
AND INTO KAMISHAK BAY. STRONG WINDS ESPECIALLY ON THE NORTH AND EAST
SIDE OF THIS LOW AND WILL BE BUMPING UP WINDS SOME WITH THIS
FORECAST PACKAGE. FROM THURSDAY AND BEYOND...TIMING OF INDIVIDUAL
LOW PRESSURE SYSTEMS GETS NEAR IMPOSSIBLE...BUT MODELS AGREE FAIRLY
WELL ON KEEPING MEAN UPPER LEVEL LOW PRESSURE FROM THE GULF OF
ALASKA WEST TO THE ALEUTIANS AND BERING SEA...WITH A WARM AIRMASS
OVER MOST OF THE REGION. LATELY...THE REALM OF PREDICTABILITY IN
TRACKING INDIVIDUAL LOW PRESSURE SYSTEMS HAS ONLY BEEN ABOUT 48 TO
60 HOURS OUT.

.SHORT TERM FORECAST...
SOUTHCENTRAL...
A STORM FORCE FRONT OVER THE WESTERN GULF WILL MOVE NORTHEAST TO THE
NORTH/NORTHEAST GULF COAST TONIGHT AND STALL NORTH AND EAST OF
MIDDLETON ISLAND...GRADUALLY WEAKENING. HIGH WIND WARNING FOR
WESTERN TURNAGAIN ARM AND HIGHER ELEVATIONS OF ANCHORAGE IS OUT
THROUGH THIS EVENING...WITH WINDS JUST BELOW WARNING CRITERIA FOR
EASTERN TURNAGAIN ARM AND PORTAGE VALLEY. STILL THINK THIS LOOKS
REASONABLE...WITH IT BEING A LOW END WARNING EVENT. HEAVY RAIN TODAY
FOR KODIAK WILL SPREAD NORTH TONIGHT. THE HEAVIER PRECIPITATION WILL
BE OVER THE EASTERN KENAI AND THE WEST/SOUTHWEST SUSITNA VALLEY.
PRECIP SHOULD REMAIN MOSTLY RAIN AT THE LOWER ELEVATIONS OF THE
EASTERN KENAI. KENAI TO ANCHORAGE TO PALMER AND OVER INTO THE COPPER
RIVER BASIN WILL REMAIN IN THE USUAL DOWNSLOPE HOLE. PRECIPITATION
SHOULD MAKE IT TO VALDEZ AND CORDOVA LATER TONIGHT...BUT IS NOT
EXPECTED TO BE TERRIBLY HEAVY DUE TO EAST/SOUTHEAST FLOW AT LOW
LEVELS CAUSING SOME DOWNSLOPING. WITH THE FRONT STALLING ON
TUESDAY...PRECIPITATION WILL PERSIST ALONG THE NORTH GULF COAST AND
IN THE WESTERN SUSITNA...BUT WILL GRADUALLY BECOME LIGHTER. NEXT
SYSTEM IS LOOKING STRONGER THAN TONIGHTS...AND WILL BE A 980 MB LOW
TRACKING NORTHWEST THROUGH THE GULF TO AROUND KAMISHAK BAY ON
WEDNESDAY. THIS SYSTEM SHOULD HAVE STORM FORCE WINDS ON ITS
NORTH/EAST SIDE...AND WILL BRING THE POTENTIAL FOR ANOTHER HIGH WIND
EVENT FOR THE HIGHER ELEVATIONS OF ANCHORAGE...TURNAGAIN ARM...AND
PORTAGE VALLEY. PRECIP WITH THIS SYSTEM WILL BE HEAVY AT TIMES TUE
NIGHT AND WED...BUT WILL BE MOSTLY RAIN...AND WILL BE GENERALLY
CONFINED TO THE USUAL AREAS FAVORED BY SOUTHEAST FLOW.

SOUTHWEST MAINLAND...
HIGH WIND WITH THE FRONT ON THE EAST SIDE OF THE BERING LOW WILL
CONTINUE INTO EARLY THIS EVENING AND SUBSIDE AS THE FRONT PASSES
THROUGH. RAIN AND SNOW SHOULD RETURN AROUND WEDNESDAY IN ASSOCIATION
WITH THE GULF LOW MOVING TO AROUND KAMISHAK BAY...WITH THE BEST
CHANCE OF PRECIPITATION BEING OVER EASTERN/NORTHERN PORTIONS OF THE
SOUTHWEST MAINLAND. TEMPERATURES WILL REMAIN ABOVE AVERAGE THROUGH
THE NEXT SEVERAL DAYS.

BERING/ALEUTIANS...
955 MB LOW APPROACHING SAINT MATTHEW ISLAND THIS AFTERNOON WILL
ROTATE WEST TONIGHT AND BE ABSORBED INTO A COMPLEX 970 MB-ISH LOW
PRESSURE AREA OVER THE NORTHWEST BERING ON TUESDAY. THE FRONT
ASSOCIATED WITH THE SAINT MATTHEW ISLAND IS THROUGH MOST OF THE
REGION...AS THE FRONT PASSED EAST THROUGH COLD BAY AROUND 11 AM.
GENERALLY SCATTERED RAIN AND SNOW SHOWERS IN WEST TO SOUTHWEST SMALL
CRAFT TO MIN GALE FLOW IS LEFT IN THE FRONTS WAKE OVER MOST OF THE
BERING/ALEUTIANS THROUGH TUESDAY. A WEAK AREA OF HIGH PRESSURE WILL
BUILD NORTH ALONG THE ALEUTIANS TUE NIGHT AND WED AS THE COMPLEX LOW
OVER THE NORTHWEST BERING SLOWLY WEAKENS AND DRIFTS NORTHWEST.

.LONG TERM FORECAST...
AS MENTIONED IN THE MODEL DISCUSSION...TIMING INDIVIDUAL LOW CENTERS
AND SHORTWAVES BECOMES NEARLY IMPOSSIBLE THURSDAY AND BEYOND.
HOWEVER...THE MODELS ARE IN AGREEMENT FOR THE OVERALL PATTERN
THURSDAY AND BEYOND...WITH MEAN LOW PRESSURE FROM THE WESTERN GULF
OF ALASKA WEST INTO THE NORTH PACIFIC AND SOUTHERN BERING...AND
ABOVE AVERAGE TEMPERATURES...A PATTERN THAT WILL BRING DOLOROUS
FEELINGS TO SNOW LOVERS ESPECIALLY OVER THE SOUTHERN MAINLAND.
DISAGREEMENT BETWEEN THE GFS AND ECMWF FROM SUNDAY ONWARD FOR
SOUTHCENTRAL ALASKA...WITH THE GFS BRINGING BACK THE DRIER ARCTIC
AIR AND THE ECMWF KEEPING THE WARM MOIST SOUTHEAST FLOW. TEND TO
LEAN TOWARD THE ECMWF.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 101 155 161 THIS EVENING.
MARINE...STORM WARNING 120.
         GALE WARNING 125 130 132 138 140 141 160 172 175 180 185
            351 352 412 413 414.
FIRE WEATHER...NONE

FOISY DEC 09