Blizzard in Alaska, February 13, 2012

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
1215 PM AKST SUN FEB 12 2012

CORRECTED TYPOS

.ANALYSIS AND UPPER LEVELS...HIGH AMPLITUDE LONG-WAVE TROUGH IS
CENTERED OVER THE BERING SEA AND NORTHWEST PACIFIC WITH AN EMBEDDED
CLOSED LOW JUST EAST OF THE KAMCHATKA PENINSULA. A SHORT-WAVE
TROUGH EXTENDING FROM THE PRIBILOF ISLANDS TO THE NORTHERN GULF
IS LIFTING NORTHWARD. STRONG SOUTHEASTERLY LOW LEVEL WINDS HAVE
BEEN PRODUCING DOWNSLOPE DRYING ACROSS PORTIONS OF THE SOUTHERN
MAINLAND. HOWEVER...THESE WINDS WILL DROP OFF SIGNIFICANTLY AS THE
UPPER TROUGH GOES THROUGH GIVING THESE AREAS A QUICK SHOT OF PRECIP.

PRECIP TYPE IS ALL SNOW OVER SOUTHWEST ALASKA...BUT SOUTHCENTRAL
HAS SOME LAYERS OF ABOVE FREEZING TEMPERATURES (AS INDICATED BY
THE 12Z ANCHORAGE SOUNDING) AND BOTH RAIN AND SNOW IS BEING OBSERVED
ACROSS THE REGION. IN ANY CASE PRECIPITATION WILL GENERALLY BE
LIGHT AS THE UPPER TROUGH MOVES THROUGH...WITH LITTLE OR NO SNOW
ACCUMULATION.

A 974 MB LOW JUST SOUTH OF THE ALASKA PENINSULA IS TRACKING
NORTHWARD ALONG THE EAST SIDE OF THE UPPER TROUGH WITH THE
FRONTAL SYSTEM HEADED FOR THE GULF OF ALASKA. OTHER WEAK LOWS
ARE EMBEDDED WITHIN THE UPPER TROUGH OVER THE BERING SEA AND
ALONG THE ALEUTIANS.

.MODEL DISCUSSION...THE NAM INITIALIZED TOO FAR WEST WITH THE
LOW APPROACHING THE ALASKA PENINSULA...BUT IS IN LINE WITH
NAM/ECMWF/GEMGLB/UKMET AS THIS LOW MOVES INTO BRISTOL BAY.
GFS BECOMES AN OUTLIER WITH A MORE EASTERLY TRACK OF THE MAIN
LOW...ACTUALLY TRACKING IT INTO THE NORTHERN GULF. THEREFORE...
WILL LEAN HEAVILY TOWARD THE NAM SOLUTION FOR THIS SYSTEM. MODELS
CONTINUE TO SHOW RUN-TO-RUN INCONSISTENCIES WITH TRACK OF A DEEP
PACIFIC LOW TO THE ALEUTIANS TUESDAY AND THEN INTO THE BERING SEA.
THERE IS A GENERAL TREND TOWARD A MORE EASTERLY TRACK COMPARED TO
THE MODEL RUNS OVER THE LAST COUPLE DAYS...SO WILL TREND IN THAT
DIRECTION.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...AS UPPER TROUGH MOVING ACROSS THE AREA EXITS
TO THE NORTH THIS EVENING FRONTAL SYSTEM FROM LOW ALONG THE ALASKA
PENINSULA WILL QUICKLY MOVE IN. STRONG DOWNSLOPE WINDS WILL DEVELOP
ONCE AGAIN OUT AHEAD OF THIS FRONT INITIALLY CONFINING THE BULK OF
THE PRECIP TO THE GULF COAST AND PRINCE WILLIAM SOUND. THERE WILL
BE VERY LITTLE TEMPERATURE ADVECTION WITH THIS SYSTEM...SO THE
RAIN/SNOW LINE WILL REMAIN RIGHT ALONG THE COAST WITH SOME AREAS
SWITCHING BACK AND FORTH. AS THE FRONT REACHES THE NORTH GULF COAST
LATE TONIGHT A BARRIER JET WILL SET UP...BUT IT SHOULD NOT LAST VERY
LONG AS STRONG UPPER FLOW WILL HELP PUSH THE FRONT ONSHORE WHERE
IT WILL FALL APART IN THE MOUNTAINS. WITH THE FRONT PUSHING ONSHORE
EXPECT STRONG WINDS TO MAKE IT TO THOMPSON PASS AND PRODUCE BLIZZARD
CONDITIONS. OTHER PLACES IN THE PRINCE WILLIAM SOUND WILL BE TOO
WARM TO SEE MUCH IN THE WAY OF BLOWING SNOW.

ALTHOUGH THE MAIN LOW WILL TRACK INLAND ACROSS THE BRISTOL BAY AREA
MODELS INDICATE A MUCH WEAKER SECONDARY LOW FORMING NEAR AUGUSTINE
ISLAND MONDAY MORNING. THIS LOW MAY MOVE INTO THE INLET OR ACROSS
THE NORTHERN GULF. A MORE TYPICAL SCENARIO IS TO HAVE A WEAK LOW
IN BOTH LOCATIONS. MEANWHILE A STRONG UPPER LEVEL SHORT-WAVE WILL
MOVE ACROSS THE KENAI PENINSULA AND COOK INLET. THE COMBINATION OF
THE SURFACE LOW DEVELOPMENT AND UPPER WAVE WILL WEAKEN THE DOWNSLOPE
WINDS AND ALLOW PRECIP TO MOVE INTO THE WESTERN KENAI PENINSULA. THE
UPPER TROUGH WILL THEN LIFT NORTHEAST ACROSS SOUTHCENTRAL MONDAY
NIGHT BRINGING AN END TO DOWNSLOPE WINDS AND BRINGING A QUICK SHOT
OF PRECIP TO MOST AREAS. ONCE AGAIN...WITH THE EXCEPTION OF THE
IMMEDIATE COAST PRECIP WILL BE LIGHT AND ANY SNOW ACCUMULATION WILL
BE MINOR.

THERE WILL BE ANOTHER BRIEF BREAK IN THE WEATHER OVER SOUTHCENTRAL
ON TUESDAY BEFORE A FRONT ASSOCIATED WITH A STRONG ALEUTIAN LOW
MOVES INTO THE REGION TUESDAY NIGHT AND WEDNESDAY. THERE IS QUITE A
BIT OF UNCERTAINTY WITH THE TIMING AND STRENGTH OF THIS FRONT...BUT
EXPECT IMPACTS WILL BE SIMILAR TO CURRENT SYSTEMS WITH THE BULK OF
PRECIP ALONG THE COAST AND DOWNSLOPE EASTERLY WINDS INLAND.

SOUTHWEST ALASKA...CONDITIONS OVER SOUTHWEST ALASKA WILL RAPIDLY
CHANGE AS LOW MOVES ACROSS BRISTOL BAY ZONE AND INLAND TONIGHT AND
MONDAY. PRECIPITATION WILL BE PRIMARILY IN THE FORM OF SNOW...BUT
DON'T EXPECT IT TO LAST VERY LONG IN ANY ONE LOCATION. THUS SNOW
TOTALS WILL BE LIGHT. HIGH PRESSURE WILL PROVIDE A BRIEF BREAK
BEFORE A STRONG FRONT ARRIVES FROM SOUTHWEST ON TUESDAY. THERE IS
POTENTIAL FOR BLOWING SNOW OR BLIZZARD ISSUES WITH THIS FRONT...
PRIMARILY ALONG THE KUSKOKWIM DELTA COAST. HOWEVER...THERE IS STILL
QUITE A BIT OF UNCERTAINTY IN THE TIMING AND STRENGTH OF THIS FRONT
TO HAVE MUCH CONFIDENCE.

BERING SEA/ALEUTIANS...A LOW JUST BEGINNING TO DEVELOP DOWN OVER
THE NORTH PACIFIC WILL RAPIDLY DEEPEN INTO THE 950S AS IT CURVES
NORTHWARD TOWARD THE CENTRAL ALEUTIANS TONIGHT AND MONDAY. AT THIS
POINT THERE IS QUITE A BIT OF UNCERTAINTY IN THE TRACK OF THIS
STORM. THERE IS ALWAYS POTENTIAL FOR HIGH IMPACT WEATHER WITH A
LOW THIS STRONG...BUT THE EXACT TRACK WILL DETERMINE WHICH AREAS
OBSERVE THE WORST CONDITIONS.

.LONG TERM FORECAST...DEEP UPPER LOW/TROUGH WILL PERSIST OVER THE
BERING SEA THROUGH THE DAY 4 THROUGH 7 TIME PERIOD. THEREFORE...
EXPECT LITTLE CHANGE IN THE TYPE OF WEATHER BEING OBSERVED ACROSS
THE ALASKA REGION.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 131.
MARINE...STORM WARNING 172.
         GALE WARNING...120 125 130 132 138 150 155 165 170 171.
FIRE WEATHER...NONE.

SEB FEB 12