Blizzard in Alaska, December 20 to 21, 2011

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
230 PM AKST TUE DEC 20 2011

.ANALYSIS AND UPPER LEVELS...

.AT THE SURFACE...A 978 MB LOW IS MOVING QUICKLY ACROSS BRISTOL BAY
TOWARDS THE KUSKOKWIM DELTA. WHILE THIS LOW HAS ALREADY REACHED ITS
MAXIMUM STRENGTH...IT HAS BEEN SUPPORTING WIND GUSTS ACROSS THE
ALASKA PENINSULA SINCE THIS MORNING. ITS ASSOCIATED FRONT IS BRINGING
RAIN AND SNOW ACROSS MUCH OF THE SOUTHCENTRAL AREA AND GUSTS TO OVER
70 MPH AT GLEN ALPS. STRONG GUSTS ARE EXPECTED THROUGH THE EVENING
HOURS. OUT WEST...CONDITIONS ARE RATHER QUIET WITH A WEAK LOW IN THE
WESTERN BERING.

.UPPER LEVELS...
A BROAD UPPER LEVEL TROUGH ENCOMPASSES THE BERING AND WESTERN
MAINLAND ALASKA. A JET IS CURRENTLY SUPPORTING THE SURFACE LOW NEAR
BRISTOL BAY...BUT THIS JET IS CONTINUING TO WEAKEN.  FURTHER
WEST...THE JET STREAM IS SEVERAL HUNDRED MILES SOUTH OF THE ALEUTIAN
ISLANDS.  AS A RESULT...NO NEW STRONG LOW PRESSURE SYSTEMS ARE POISED
TO IMPACT ALASKA THE NEXT FEW DAYS.

.MODEL DISCUSSION...MODELS ARE IN GOOD AGREEMENT IN THE SHORT TERM IN
THE PROGRESSION OF THE BRISTOL BAY LOW TOWARDS THE KUSKOKWIM VALLEY
THROUGH WEDNESDAY MORNING. MODELS BEGIN TO DIVERGE MORE SUBSTANTIALLY
TOWARDS THE END OF THE WEEK AS ONE LOW APPROACHES THE GULF OF ALASKA
AND A SECOND LOW APPROACHES THE EASTERN ALEUTIANS. THE ECMWF HAS
REMAINED THE MOST CONSISTENT MODEL AND WAS THE FAVORED SOLUTION.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...GUSTY WINDS HAVE ALREADY BEGUN TO PICK UP AHEAD
OF THE FRONT ACROSS THE ANCHORAGE BOWL AND ARE EXPECTED TO CONTINUE
THROUGH THE EVENING HOURS. THE COMBINATION OF GUSTY WINDS AND SNOW
WILL SUPPORT BLIZZARD CONDITIONS IN THE GAP WIND REGIONS ACROSS
PORTAGE VALLEY AND THROUGH THOMPSON PASS. LIGHT SNOW WILL CONTINUE TO
BE POSSIBLE LATE THIS EVENING AS AN UPPER WAVE PROGRESSES ACROSS THE
REGION BEHIND THE FRONT. GUSTY WESTERLY WINDS WILL ALSO DEVELOP
BEHIND THE FRONT ALONG COOK INLET LATE TONIGHT.

SOUTHWEST ALASKA...A LOW IN BRISTOL BAY WILL CONTINUE TO SUPPORT
GUSTY WINDS ACROSS THE BRISTOL BAY REGION THROUGH THIS EVENING AS IT
MOVES TOWARDS THE KUSKOKWIM DELTA. THIS LOW AND ITS FRONT HAVE BEEN
SUPPORTING SNOW SHOWERS ACROSS MUCH OF SOUTHWEST ALASKA THIS MORNING.
AS A RESULT...VISIBILITIES SHOULD BE REDUCED THROUGH THE AFTERNOON
HOURS NEAR BRISTOL BAY...UNTIL THIS SYSTEM HAS WEAKENED. CONDITIONS
WILL THEN REMAIN RATHER QUIET ACROSS THE REGION UNTIL A NEW SYSTEM
APPROACHES LATE THURSDAY NIGHT.

BERING SEA/ALEUTIANS...THE UPPER LEVEL JET WILL REMAIN WELL SOUTH OF
THE ALEUTIANS FOR THE NEXT FEW DAYS.  AS A RESULT...WEAK LOW PRESSURE
SYSTEMS WILL DOMINATE THE BERING.  COLD AIR ADVECTION ACROSS MUCH OF
THE BERING WILL SUPPORT INSTABILITY SHOWERS ACROSS MUCH THE BERING
OVER THE NEXT FEW DAYS.

.LONG TERM FORECAST...MODELS DIVERGE SUBSTANTIALLY IN THE LONG TERM
SO THERE IS STILL A LOT OF UNCERTAINTY IN THE LONG TERM FORECAST.
MODELS CONTINUE TO INDICATE AN ACTIVE PATTERN...BUT THE JET STREAM
WILL REMAIN MAINLY SOUTH OF THE ALEUTIANS. AS A RESULT...A SERIES OF
WEAKER LOWS WILL IMPACT THE REGION.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING...ZONE 125 131
        HIGH WIND WARNING ZONE 101.
MARINE...GALE WARNING...120 125 132 138 140 150 155 160
         HEAVY FREEZING SPRAY WARNING...185
FIRE WEATHER...NONE.

ELN DEC 11

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1245 PM AKST TUE DEC 20 2011

AKZ101-210600-

...STRONG WINDS EXPECTED ACROSS ALL OF ANCHORAGE THIS AFTERNOON
THROUGH EARLY EVENING...

ANOTHER STRONG CHINOOK WIND EVENT WILL AFFECT ANCHORAGE THIS
AFTERNOON AND EVENING. HOWEVER...WINDS WILL NOT BE QUITE AS
STRONG AS SYSTEMS THAT AFFECTED ANCHORAGE THE PAST FEW WEEKENDS.

WINDS HAVE BEGUN TO INCREASE ACROSS THE ANCHORAGE AREA EARLY THIS
AFTERNOON AHEAD OF A STRONG FRONT MOVING UP COOK INLET AND THE
KENAI PENINSULA. EAST TO SOUTHEAST WINDS WILL CONTINUE TO INCREASE
THE NEXT FEW HOURS WITH THE STRONGEST WINDS EXPECTED BETWEEN 3 PM
THIS AFTERNOON AND 7 PM THIS EVENING. A HIGH WIND WARNING IS IN
EFFECT FOR TURNAGAIN ARM AND THE ANCHORAGE HILLSIDE. EXPECT WIND
GUSTS UP TO 90 MPH ABOVE HILLSIDE DRIVE AND GUSTS TO AROUND 60 MPH
LOWER DOWN THE HILLSIDE AS WELL AS FOR LOWER ELEVATIONS OF ANCHORAGE
RIGHT ALONG THE MOUNTAINS. THE REST OF THE ANCHORAGE BOWL CAN ALSO
EXPECT TO SEE STRONG SOUTHEAST WINDS GUSTING UP TO 45 MPH.

THE FRONT IS EXPECTED TO PASS THROUGH ANCHORAGE EARLY THIS EVENING.
SOUTHEAST WINDS WILL THEN DIMINISH THROUGH LATE EVENING.
HOWEVER...GUSTY SOUTH WINDS OF 15 TO 30 MPH WITH LOCAL GUSTS
TO 40 MPH WILL MOVE BACK INTO ANCHORAGE OVERNIGHT AND PERSIST
THROUGH WEDNESDAY MORNING. WINDS WILL FINALLY LIGHTEN UP ACROSS
THE AREA WEDNESDAY AFTERNOON.

AFTER THIS STORM MOVES THROUGH THE WEATHER PATTERN WILL UNDERGO A
SHIFT. STORMS WILL BEGIN TO TRACK TO OUR SOUTH AND INTO THE GULF.
THIS WILL BRING AN END TO THE SERIES OF CHINOOK WIND EVENTS AND
ALLOW COLDER AIR TO SETTLE BACK OVER THE REGION. TEMPERATURES ARE
FORECAST TO DROP DOWN INTO THE SINGLE DIGITS TO TEENS BY THE END
OF THE WEEK.

SEB

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
130 PM AKST TUE DEC 20 2011

AKZ101-210600-

...STRONG WINDS EXPECTED ACROSS ALL OF ANCHORAGE THIS AFTERNOON
THROUGH EARLY EVENING...

ANOTHER STRONG CHINOOK WIND EVENT WILL AFFECT ANCHORAGE THIS
AFTERNOON AND EVENING. HOWEVER...WINDS WILL NOT BE QUITE AS
STRONG AS SYSTEMS THAT AFFECTED ANCHORAGE THE PAST FEW WEEKENDS.

WINDS HAVE BEGUN TO INCREASE ACROSS THE ANCHORAGE AREA EARLY THIS
AFTERNOON AHEAD OF A STRONG FRONT MOVING UP COOK INLET AND THE
KENAI PENINSULA. EAST TO SOUTHEAST WINDS WILL CONTINUE TO INCREASE
THE NEXT FEW HOURS WITH THE STRONGEST WINDS EXPECTED BETWEEN 3 PM
THIS AFTERNOON AND 7 PM THIS EVENING. A HIGH WIND WARNING IS IN
EFFECT FOR TURNAGAIN ARM AND THE ANCHORAGE HILLSIDE. EXPECT WIND
GUSTS UP TO 90 MPH ABOVE HILLSIDE DRIVE AND GUSTS TO AROUND 70 MPH
LOWER DOWN THE HILLSIDE AS WELL AS FOR LOWER ELEVATIONS OF ANCHORAGE
RIGHT ALONG THE MOUNTAINS. THE REST OF THE ANCHORAGE BOWL CAN ALSO
EXPECT TO SEE STRONG SOUTHEAST WINDS GUSTING UP TO 45 MPH.

THE FRONT IS EXPECTED TO PASS THROUGH ANCHORAGE EARLY THIS EVENING.
SOUTHEAST WINDS WILL THEN DIMINISH THROUGH LATE EVENING.
HOWEVER...GUSTY SOUTH WINDS OF 15 TO 30 MPH WITH LOCAL GUSTS
TO 40 MPH WILL MOVE BACK INTO ANCHORAGE OVERNIGHT AND PERSIST
THROUGH WEDNESDAY MORNING. WINDS WILL FINALLY LIGHTEN UP ACROSS
THE AREA WEDNESDAY AFTERNOON.

AFTER THIS STORM MOVES THROUGH THE WEATHER PATTERN WILL UNDERGO A
SHIFT. STORMS WILL BEGIN TO TRACK TO OUR SOUTH AND INTO THE GULF.
THIS WILL BRING AN END TO THE SERIES OF CHINOOK WIND EVENTS AND
ALLOW COLDER AIR TO SETTLE BACK OVER THE REGION. TEMPERATURES ARE
FORECAST TO DROP DOWN INTO THE SINGLE DIGITS TO TEENS BY THE END
OF THE WEEK.

SEB

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
415 PM AKST TUE DEC 20 2011

AKZ101-210300-

...STRONG WINDS ACROSS ANCHORAGE...

WINDS HAVE INCREASED ACROSS THE ANCHORAGE BOWL AHEAD OF A STRONG
WEATHER FRONT MOVING UP COOK INLET. AS OF 4 PM...THE HIGHEST WINDS
REPORTED WHERE AT GLENN ALPS (UPPER HILLSIDE) WITH SOUTHEAST GUSTS TO
77 MPH. STRONG WINDS ARE ALSO EVIDENT ALONG PORTIONS OF EAST AND
SOUTH ANCHORAGE AS WELL AS THE GLENN HIGHWAY. WIND GUSTS OF 55 MPH
WERE REPORTED AT THE S CURVES ALONG THE GLENN HIGHWAY. STRONG WINDS
ARE ALSO PRODUCING LOCALIZED AREAS OF BLOWING SNOW ALONG THE
MOUNTAINS AND PORTIONS OF THE GLENN HIGHWAY.

THE FRONT IS EXPECTED TO PASS THROUGH ANCHORAGE EARLY THIS EVENING.
SOUTHEAST WINDS WILL THEN DIMINISH THROUGH LATE EVENING.
HOWEVER...GUSTY SOUTH WINDS WILL PERSIST THROUGH WEDNESDAY MORNING
BEFORE FINALLY TAPERING OFF WEDNESDAY AFTERNOON.

AFTER THIS STORM MOVES THROUGH THE WEATHER PATTERN WILL UNDERGO A
SHIFT. STORMS WILL BEGIN TO TRACK TO OUR SOUTH AND INTO THE GULF.
THIS WILL BRING AN END TO THE SERIES OF CHINOOK WIND EVENTS AND
ALLOW COLDER AIR TO SETTLE BACK OVER THE REGION. TEMPERATURES ARE
FORECAST TO DROP DOWN INTO THE SINGLE DIGITS TO TEENS BY THE END
OF THE WEEK.

RMC