Wind Chill Advisory 12, NWS Anchorage, AK

656 
WWAK42 PAFC 281217
WSWALU

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE ANCHORAGE AK
317 AM AKST MON NOV 28 2011

AKZ155-281330-
/X.CAN.PAFC.WC.Y.0012.000000T0000Z-111128T1400Z/
KUSKOKWIM DELTA-
INCLUDING THE CITIES OF...BETHEL...HOOPER BAY...NUNIVAK ISLAND
317 AM AKST MON NOV 28 2011

...WIND CHILL ADVISORY IS CANCELLED...

THE NATIONAL WEATHER SERVICE IN ANCHORAGE HAS CANCELLED THE WIND
CHILL ADVISORY. 


$$

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
1120 AM AKST SUN NOV 27 2011

.ANALYSIS AND UPPER LEVELS...A PROGRESSIVE PATTERN IS IN PLACE
ACROSS THE NORTH PACIFIC THIS MORNING WITH A NEARLY ZONAL UPPER
LEVEL JET. A LOW IS BOTTOMING OUT NEAR THE SOUTH TIP OF KODIAK
ISLAND AROUND 979 MB AND WILL BEGIN TO WEAKEN AS IT TRACKS INTO
THE GULF WHILE THE JET SUPPORT MOVES OFF TO THE EAST. THE FAST
UPPER FLOW MEANS THE LOW WILL BE QUICK TO TRACK ACROSS THE GULF
AND THE BULK OF WINDS AND PRECIP WITH THE LOW WILL BE FELT ALONG
THE COASTAL REGION. THE BULK OF WARMER AIR WITH THE SYSTEM WILL
ALSO HEAD EAST ACROSS THE GULF MEANING PRECIP-TYPE WILL REMAIN
PREDOMINANTLY SNOW ACROSS KODIAK ISLAND AND THE SOUTHCENTRAL COAST.

A VERTICALLY STACKED LOW IS NEARLY STATIONARY OVER THE WESTERN
BERING SEA...IN THE ARCTIC AIR NORTH OF THE SUBTROPICAL JET. A
WEAK LOW OVER THE NORTHWEST PACIFIC WILL DEVELOP RIGHT ALONG THE
JET TONIGHT WHICH WILL AMPLIFY THE UPPER LEVELS AND FORCE THE
BERING LOW SOUTHWARD WITH TIME.

.MODEL DISCUSSION...THE NAM IS BOUT 80 NAUTICAL MILES TOO FAR WEST
WITH THE 18Z POSITION OF THE LOW JUST SOUTH OF KODIAK ISLAND AND
IT CONTINUES TO BE AN OUTLIER FOR THE ENTIRE MODEL RUN. THE
GFS/ECMWF/UKMET ALL SEEM TO BE VERIFYING WELL WITH THE CURRENT
SYSTEM AND SHOW GOOD AGREEMENT WITH MAJOR LOW MOVING TO BRISTOL
BAY LATE TUESDAY. THE RUN-TO-RUN CONSISTENCY WITH THIS SECOND LOW
IS ALSO GOOD SO FORECAST CONFIDENCE IS GROWING.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...GULF LOW WILL TRACK TOWARD THE NORTHEAST GULF
TONIGHT AND MONDAY WITH FRONTAL SYSTEM REMAINING OFFSHORE. OFFSHORE
LOW LEVEL FLOW WILL STRENGTHEN AS THE LOW PASSES BY WHICH MEAN SNOW
WILL GENERALLY BE ON THE LIGHT SIDE. AS THIS SYSTEM EXITS TOWARD
CANADA ON MONDAY AND MONDAY NIGHT AN UPPER LEVEL SHORT-WAVE
TROUGH WILL CROSS SOUTHCENTRAL. IT WILL BE WEAK AND QUICK TO MOVE
THROUGH...BUT LOOKS LIKE THERE IS JUST ENOUGH VERTICAL MOTION TO
PRODUCE LIGHT SNOW. ANY ACCUMULATION THAT DOES OCCUR WILL BE VERY
MINOR (LESS THAN 1 INCH). A PATTERN CHANGE IS IN STORE FOR MID WEEK
AS A DEVELOPING PACIFIC STORM AMPLIFIES THE DOWNSTREAM PATTERN.
THIS IN TURN WILL CAUSE THE LOW TO TURN NORTHWARD TOWARD WESTERN
ALASKA SETTING UP A LONG FETCH OF SOUTHERLY FLOW...WHICH MEANS
TRANSPORT OF MOISTURE AND WARMER AIR FROM THE TROPICS. THIS SET-UP
IS FAVORABLE FOR HEAVY PRECIPITATION IN PRINCE WILLIAM SOUND AS WELL
AS THE SUSITNA VALLEY. THIS IS ALSO FAVORABLE FOR HIGH WINDS THROUGH
WESTERN TURNAGAIN ARM AND HIGHER ELEVATIONS OF ANCHORAGE. ALTHOUGH
WARMER AIR WILL ACCOMPANY THIS SYSTEM IT APPEARS THE WARMEST AIR
WILL BE SHUNTED EASTWARD WITH THE TRIPLE POINT. THE INTENSITY OF THE
PRECIPITATION WILL ALSO TEND TO FAVOR MAINTAINING SNOW. WITH THIS IN
MIND MAY ALSO NEED TO KEEP AN EYE ON BLIZZARD POTENTIAL FOR PORTAGE
VALLEY AND EASTERN TURNAGAIN ARM ON WEDNESDAY WHEN SNOW AND WINDS
FIRST ARRIVE. IT IS TOO EARLY TO ISSUE WATCHES BUT WILL RE-ISSUE
A SPECIAL WEATHER STATEMENT TO HIGHLIGHT THE POTENTIAL FOR SEVERE
WEATHER.

SOUTHWEST ALASKA...AREAS OF LIGHT SNOW WILL PERSIST ACROSS THE
BRISTOL BAY REGION TONIGHT WITH MOISTURE ON THE BACK SIDE OF THE
GULF LOW AND AN UPPER LEVEL SHORT-WAVE MOVING THROUGH. THE KUSKOKWIM
VALLEY WILL ALSO LIKELY SEE SOME LIGHT SNOW AS THIS MOVES
THROUGH...BUT WITH LESS MOISTURE TO WORK EXPECT LITTLE OR NO
ACCUMULATION. A STRONG LOW MOVING OUT OF THE NORTH PACIFIC WILL
BE THE NEXT SYSTEM TO AFFECT SOUTHWEST ALASKA. BASED ON THE CURRENT
EXPECTED TRACK OF THIS SYSTEM THE MAIN THREAT WILL BE STRONG WINDS
ALONG THE ALEUTIAN AND ALASKA RANGES AND A POTENTIAL FOR BLIZZARD
CONDITIONS OVER WESTERN BRISTOL BAY AND THE KUSKOKWIM DELTA. MUCH
WARMER AIR WILL ACCOMPANY THE SYSTEM...SO ANY SMALL CHANGE IN TRACK
WILL GREATLY AFFECT WHAT TYPE OF WEATHER IS OBSERVED. WILL CONTINUE
TO FINE TUNE THE FORECAST AS WE GET CLOSER TO THE EVENT.

BERING SEA/ALEUTIANS...LATEST MODELS HAVE TRENDED A BIT STRONGER AND
FURTHER WESTWARD WITH DEVELOPING PACIFIC SYSTEM. WITH ALL SOLUTIONS
HEADED THIS WAY WILL UPDATE WIND FORECAST TO REFLECT A TRACK CLOSER
TO DUTCH HARBOR ON TUESDAY AS WELL AS STRONGER WINDS THAN CURRENTLY
FORECAST. AS THIS SYSTEM MOVES TO SOUTHWEST ALASKA WEDNESDAY ANOTHER
SYSTEM WILL MOVE TO THE ALEUTIANS. THE JET WILL QUICKLY PASS BY THIS
SECOND SYSTEM SO DON'T EXPECT IT TO BE AS POWERFUL AS THE FIRST
STORM.

.LONG TERM FORECAST...EXPECT NEW PATTERN TO BECOME EVEN MORE
AMPLIFIED AS WE HEAD THROUGH THE EXTENDED PERIOD WITH A STRONG
RIDGE CENTERED NEAR 140W LONGITUDE AND A TROUGH OVER THE BERING
SEA/NORTH-CENTRAL PACIFIC. THE STORM TRACK WILL BE FROM THE
NORTH-CENTRAL PACIFIC NORTHWARD TO WESTERN ALASKA. THIS MEANS
SOUTHCENTRAL ALASKA AND THE GULF WILL BECOME PROGRESSIVELY WARMER
AS WE HEAD THROUGH THE WEEK. ON THE OPPOSITE SIDE ARCTIC AIR WILL
PERSIST OVER THE CENTRAL TO WESTERN BERING SEA AND ALEUTIANS. IN
BETWEEN OVER SOUTHWEST ALASKA WILL BE THE FOCUS OF A CLASH BETWEEN
TWO VERY DIFFERENT AIR MASSES...AND THESE WILL LIKELY FLUCTUATE
BACK AND FORTH AS SYSTEMS PASS THROUGH.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...120 130 132 138 140 155 170 171 172 175
                        176 185.
         HEAVY FREEZING SPRAY WARNING...140 180 185.
FIRE WEATHER...NONE.

SEB NOV 11