Heavy Freezing Spray Warning 33, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
510 AM AKST TUE JAN 10 2012

.ANALYSIS AND UPPER LEVELS...
A STRONG PACIFIC SYSTEM IS THE DOMINANT FEATURE ACROSS THE AOR. THE
PARENT LOW IS 350 MILES SOUTH OF DUTCH HARBOR MOVING EAST. A FRONT
EXTENDS NORTHEAST TOWARDS THE AKPEN AND THE SOUTHWESTERN GULF...WITH
A HUGE SLUG OF PRECIPITATION AND STRONG WINDS. SNOW WAS PARTICULARLY
HEAVY ACROSS KODIAK ISLAND OVERNIGHT...WHERE WARM AIR DID NOT PUSH
NORTH AS QUICKLY AS EXPECTED...THOUGH RAIN IS BEGINNING TO MIX IN
NOW. A TRIPLE POINT ALONG THE FRONT NEAR CHIGNIK IS MOVING NORTH TO
BRISTOL BAY BRINGING A REINFORCING SHOT OF SNOW. NORTH AND WEST OF
THE FRONT...COLD ADVECTION IS BLEEDING SOUTHEAST...WITH MIXED
PRECIPITATION HAVING TURNED BACK TO ALL SNOW AROUND DUTCH HARBOR...
AND ON THE DOORSTEP OF THE AKPEN.

.MODEL DISCUSSION...
IN GENERAL...THE ECMWF APPEARS TO HAVE DONE THE BEST JOB CAPTURING A
MORE VIGOROUS TRIPLE POINT MOVING TO BRISTOL BAY...AND WITH THE
PARENT LOW SOUTH OF DUTCH HARBOR. IN THE EAST...THE NAM HOWEVER HAS
SOME UTILITY FOR THE STRONG GAP WINDS ACROSS TURNAGAIN ARM/PORTAGE
VALLEY. THE LOW SOUTH OF DUTCH HARBOR WILL TRACK TO AROUND 200 MILES
SOUTH OF SITKINAK WEDNESDAY MORNING...THEN UP TOWARDS THE SOUTHERN
KENAI PENINSULA ON THURSDAY. THE ECWMF AND NAM CAPTURE THIS THE MOST
CONSISTENTLY AND HAVE BEEN EMPLOYED IN THE MORNING FORECAST PACKAGE.
FURTHER WEST...THERE ARE SOME DIFFERENCES REGARDING A TROUGH OF LOW
PRESSURE THAT SWINGS THROUGH THE FAR WESTERN CHAIN AND BERING ON
WEDNESDAY. THE GFS/NAM SHOW A SMALL CLOSED LOW PINWHEELING UP TO JUST
NORTH OF SHEMYA WEDNESDAY AFTERNOON. SATELLITE IMAGERY THIS MORNING
DOES NOT SEEM TO SHOW MUCH IN THE WAY OF STRONG UPPER-SUPPORT FOR
THIS LOW UPSTREAM IN THE WEST CENTRAL PACIFIC. AS SUCH...HAVE TENDED
TO STAY CLOSER TO THE ECMWF WHICH SHOWS A WEAKER FEATURE. ALL MODELS
HOWEVER AGREE ON A DEEP LOW AND STORM FORCE FRONT ADVANCING TO THE
WESTERN CHAIN WEDNESDAY NIGHT INTO THURSDAY.

.SHORT TERM FORECAST...
SOUTHCENTRAL...
HIGH WIND WARNING FOR ZONE 101 (ALONG TURNAGAIN ARM AND HIGHER
ELEVATIONS) HAS VERIFIED AS THE PRESSURE GRADIENT AHEAD OF THE GULF
FRONT IS BEING SQUEEZED. THE FRONT WILL MOVE TOWARDS THE NORTHERN
COAST THIS AFTERNOON/EVENING AND WEAKEN...ALLOWING THE GRADIENT TO
RELAX A BIT. DOWNSLOPED AREAS SUCH AS THE ANCHORAGE BOWL AND
MATANUSKA VALLEY LOOK TO SEE SOME PERIODS OF LIGHT SNOW DEVELOP LATE
THIS EVENING AS THIS OCCURS. THE APPROACH OF THE PACIFIC LOW WILL
ONCE AGAIN INCREASE THE EAST TO SOUTHEAST FLOW ACROSS THE CHUGACH
RANGE...NOT TO WARNING LEVEL...BUT SUFFICIENT TO BEGIN DOWNSLOPING
FAVORED AREAS AGAIN DURING THE DAY WEDNESDAY. AS THE PACIFIC LOW
MOVES TOWARDS PRINCE WILLIAM SOUND WEDNESDAY NIGHT INTO THURSDAY...
LOOK FOR A STEADIER AND MORE MEASURABLE SNOW TO DEVELOP.

ELSEWHERE...MULTIPLE BLIZZARDS FROM THE SOUTHWESTERN KENAI PENINSULA
TO EASTERN PRINCE WILLIAM SOUND WILL END FROM SOUTHWEST TO NORTHEAST
CONCURRENT WITH THE WEAKENING GRADIENT. IN THE INTERIM...A GENEROUS
FETCH OF MOISTURE WILL CONTINUE TO PRODUCE MODERATE TO HEAVY
INTENSITY SNOW OVER THE REGION. THE SUSITNA VALLEY WILL ALSO
EXPERIENCE SUBSTANTIAL SNOW AS SOUTHEAST FLOW SHOVES MOISTURE UP THE
VALLEY WHILE COLD AIR FROM THE SW ALASKA BEGINS TO FILTER SOUTHEAST.
WE HAVE INCREASED STORM TOTALS TO HIGH END ADVISORY LEVELS...WITH THE
HEAVIEST AMOUNTS WEST OF THE PARKS HIGHWAY.

SOUTHWEST...
BLIZZARD CONDITIONS TO PERSIST NORTH OF KING SALMON IN BRISTOL BAY
AND ALONG THE KUSKOKWIM DELTA COAST THROUGH MID-DAY. WINDS WILL BE
SLOWEST TO DIMINISH OVER THE DELTA WHERE COLD ADVECTION IS QUICKLY
FILTERING SOUTHEAST...WITH WIND CHILLS 30 TO 40 BELOW EXPECTED OVER
THE DELTA. EXPECT SEVERAL INCHES OF ACCUMULATION PARTICULARLY OVER
INTERIOR AREAS OF BRISTOL BAY AND THE KUSKOKWIM VALLEY. COLD AIR IS
NOSING SOUTH TOWARDS THE AKPEN AS WELL...WHERE RAIN WILL GIVE WAY TO
SNOW OR SNOW SHOWERS BY THIS AFTERNOON ALONG WITH GALE FORCE WINDS
AND STORM FORCE GUSTS OUT OF BAYS AND PASSES.

BERING SEA/ALEUTIANS...
LOOK FOR A QUICK SHOT OF SNOW AS A WEAK TROUGH OF LOW PRESSURE SWINGS
TOWARDS THE FAR WESTERN CHAIN ON WEDNESDAY. HOT ON IT'S HEELS A
STRONG FRONT WILL APPROACH WEDNESDAY NIGHT...WITH SOUTHERLY FLOW AND
WARM AIR POKING NORTHWARD TO ALLOW RAIN TO MIX IN WITH THE SNOW AS
THE PRECIPITATION OVERSPREADS THE CHAIN.

.LONG TERM FORECAST...
MODELS AGREE ON AN AMPLIFIED LONG-WAVE PATTERN THIS WEEKEND INTO
EARLY NEXT WEEK. A QUASI BLOCKING RIDGE LOOKS TO BUILD OVER THE
CENTRAL TO EASTERN BERING...WITH CONDITIONS ON THE UPSTREAM SIDE
STAYING UNSETTLED AND WET THROUGH THE WESTERN ALEUTIAN CHAIN.
SOUTHCENTRAL AND SOUTHWEST AK MEANWHILE LOOK TO BE COOL AND
DRY...WITH STRONG GAP WINDS ALONG THE COASTS AS THE INLAND AIRMASS
FILTERS SOUTH.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING...121 125 131 135 155 161
         HIGH WIND WARNING...101
         WINTER WEATHER ADVISORY FOR SNOW...145
MARINE...STORM...120 125 172 351 352
         GALE...127 129 130 132 140 141 150 155 160 165 170 171 179
                180 412 413 414
         HEAVY FREEZING SPRAY...129 140 150 155 165 170 171 172 179
                                411 412 413 414
FIRE WEATHER...NONE

JAM