Gale Warning 192, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
1230 PM AKST FRI MAR 12 2010

.ANALYSIS AND UPPER LEVELS...LONG-WAVE TROUGH EXTENDS FROM EASTERN
ASIA TO WESTERN CANADA AND AS FAR SOUTH AS 30 TO 35N LATITUDE.
A SHORT-WAVE IS LIFTING NORTHEAST ACROSS SOUTHCENTRAL THIS
MORNING...PRODUCING SNOW SHOWERS ALONG UPSLOPE AREAS OF THE
CHUGACH AND TALKEETNA MOUNTAINS...FROM ANCHORAGE AND THE MAT
VALLEY TO VALDEZ AND CORDOVA. THE MAIN CONCERN FOR THE SHIRT-TERM
IS A MAJOR STORM  SOUTH OF THE EASTERN ALEUTIANS. SATELLITE IMAGERY
SHOWS THAT A TRIPLE POINT LOW HAS DEVELOPED SOUTH OF THE ALASKS
PENINSULA AND THIS LOW WILL CONTINUE TO DEEPEN UNDER GOOD UPPER
SUPPORT WHILE THE PARENT LOW WILL QUICKLY WEAKEN. BLIZZARD WARNINGS
ARE IN EFFECT FOR THE CENTRAL AND EASTERN ALEUTIANS. THE DEEP
MOISTURE IS BEGINNING TO EXIT THIS REGION AS THE TRIPLE POINT
LOW BECOMES DOMINANT AND THE PARENT LOW SINKS SOUTHWARD...SO PRECIP
WILL BECOME SHOWERY VERY SHORTLY AND PLAN TO CANCEL THE WARNINGS.

.MODEL DISCUSSION...SOLUTIONS ARE ALL A LITTLE DIFFERENT WITH
LOCATION AND STRENGTH OF THE TWO LOW CENTERS SOUTH OF THE EASTERN
ALEUTIANS AND ALASKA PENINSULA. THE GFS/NAM APPEAR TO BETTER DEPICT
THE DOUBLE BARREL STRUCTURE...BUT THESE DIFFERENCES HAVE LITTLE
IMPACT ON THE FORECAST. ALL SOLUTIONS ARE GROUPED IN THE SAME AREA
AND SHOW THE SAME IDEA OF STRENGTHENING TRIPLE POINT LOW SOUTH THE
NEXT 24 HOURS. MORE SIGNIFICANT DIFFERENCES ARISE WITH HANDLING OF
OCCLUDED FRONT AS IT MOVES NORTHWARD ACROSS THE GULF SATURDAY.
THE GFS IS FASTEST IN SWINGING THIS FRONT WESTWARD TOWARD KODIAK
ISLAND...ALTHOUGH THE UKMET AND EC ARE NOT FAR BEHIND. HOW FAR
WESTWARD THIS FRONT PROGRESSES WILL HAVE A SIGNIFICANT IMPACT
ON KODIAK'S WEATHER AND WILL BE THE DIFFERENCE BETWEEN A LOT OF
SNOW AND WIND AND MOSTLY DRY WITH A LOT OF WIND. RIGHT NOW WE
ARE LEANING TOWARD THE MORE AGGRESSIVE GFS/ECMWF/UKMET. MODELS
ALSO SHOW OTHER WEAK TRIPLE POINT LOWS FORMING...BUT DON'T EXPECT
THESE TO DEVELOP INTO ANYTHING MORE THAN WEAK FRONTAL LOWS.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...HAVE ALREADY UPDATED KODIAK FORECAST TO
TREND TOWARD SNOWIER CONDITIONS. PLAN TO ISSUE A BLIZZARD WATCH
WITH THE AFTERNOON PACKAGE...RECOGNIZING THAT IF THE OCCLUDED
FRONT IS A LITTLE FURTHER EAST THAN CURRENTLY INDICATED BY THE
MODEL CONSENSUS THE WILL STILL SEE STRONG WINDS...BUT SNOWFALL
WOULD BE MUCH LESS AND THEREFORE BLIZZARD WOULD LIKELY NOT HAPPEN.
THEREFORE...WILL HAVE TO CLOSELY MONITOR MODEL TRENDS THIS
AFTERNOON AND EVENING AND MAKE ADJUSTMENTS IF WARRANTED. EXPECT
FRONTAL PRECIP TO EXTEND UP TO THE PRINCE WILLIAM SOUND REGION
BY SATURDAY NIGHT. WITH EXTENSIVE OFFSHORE FLOW AHEAD OF THE
FRONT PRECIP WILL GENERALLY BE LIGHT. WILL ALSO HAVE TO WATCH
OUT FOR USUAL THREAT OF A BLIZZARD THROUGH THOMPSON PASS...BUT
AT THIS POINT WINDS LOOK BORDERLINE AND SNOW LOOKS LIKE IT WILL
BE LIGHT...SO NOT ENOUGH EVIDENCE TO ISSUE ANYTHING YET. THE REST
OF SOUTHCENTRAL CAN EXPECT A CHANCE OF SNOW SUNDAY INTO MONDAY AS
MOISTURE PUSHES INLAND...BUT IF SNOW DOES FALL IT SHOULD BE LIGHT.

SOUTHWEST ALASKA...THE BULK OF THE PRECIP ASSOCIATED WITH THE
STORM SYSTEM WILL REMAIN SOUTH AND EAST OF THE ALASKA PENINSULA.
HOWEVER...EXPECT A BAND OR TWO OF SNOW TO SPREAD NORTHWEST ACROSS
BRISTOL BAY LATE TONIGHT INTO SATURDAY. SNOWFALL WILL BE LIGHT AND
SHORT-LIVED. OTHERWISE...THE REST OF SOUTHWEST ALASKA WILL REMAIN
DRY WITH INCREASING NORTHERLIES DUE TO THE TIGHTENING PRESSURE
GRADIENT. A WIND CHILL ADVISORY WILL BE ISSUED FOR THE KUSKOKWIM
DELTA BEGINNING THIS EVENING. WINDS AND BELOW ZERO TEMPERATURES
WILL LAST THROUGH THE WEEKEND WITH IMPROVING CONDITIONS BY MONDAY.

BERING SEA/ALEUTIANS...STRONG WINDS AND COLD ADVECTION ON THE
BACK SIDE OF THE STORM WILL PRODUCE WIDESPREAD SNOW SHOWERS
WITH OCCASIONALLY LOW VISIBILITIES...ESPECIALLY FROM THE CENTRAL
ALEUTIANS TO SOUTHERN ALASKA PENINSULA. CONDITIONS WILL GRADUALLY
IMPROVE FROM WEST TO EAST LATE SATURDAY THROUGH MONDAY AS THE
STORM MOVES INTO THE GULF AND HIGH PRESSURE BUILDS IN FROM THE
WEST. RIGHT BEHIND THIS RIDGE A STRONG FRONT WILL MOVE INTO THE
WESTERN ALEUTIANS SUNDAY. FLOW ALONG THE FRONT WILL BE
SOUTHERLY...BUT TEMPERATURES WILL ONLY BE MARGINALLY WARMER...SO
EXPECT SNOW PERHAPS MIXED WITH RAIN.

.LONG TERM FORECAST...RIDGE MOVING ACROSS BERING SUNDAY AND MONDAY
WILL BECOME HIGHLY AMPLIFIED AHEAD OF A DIGGING WESTERN BERING
SYSTEM...SO MUCH SO THAT IT WILL LIKELY SET UP A BLOCKING PATTERN
BY MID WEEK CENTERED OVER THE EASTERN BERING AND WESTERN ALASKA.
THIS WOULD RESULT IN DRY AND SEASONABLE WEATHER FROM THE EASTERN
BERING TO MAINLAND ALASKA AND ISOLATE ANY STORMS TO THE WESTERN
BERING AND ALEUTIANS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WATCH 171 (WITH AFTERNOON FORECAST).
MARINE...STORM WARNING...132 150 155.
         GALE WARNING...120 130 138 140 160 165 170 171 172 175 176
                        179 180.
FIRE WEATHER...NONE.

SEB MAR 10