Heavy Freezing Spray Warning 63, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
310 PM AKST WED FEB 01 2012

.ANALYSIS AND UPPER LEVELS...AN IMPRESSIVE LOW PRESSURE SYSTEM
CENTERED SOUTHEAST OF CHIGNIK DOMINATES THE WEATHER MAP TODAY. THIS
LOW IS EXPECTED TO REACH ITS PEAK INTENSITY AT 944 MB AS IT MOVES
TOWARDS KODIAK ISLAND BY THIS AFTERNOON. A 160 KT JET IS TRANSPORTING
A COPIOUS AMOUNT OF MOISTURE AND WARM AIR NORTHWARDS FROM THE
TROPICS. THIS MOISTURE AND WARM AIR ADVECTION IS SUPPORTING THE
DEVELOPMENT OF AN IMPRESSIVE RIDGE AHEAD OF THIS LOW.
MEANWHILE...WEAK TROUGHING ALOFT COVERS THE BERING. THIS WILL SUPPORT
A WEAK LOW PRESSURE SYSTEM AS IT MOVES FROM SHEMYA NORTHEASTWARD OVER
THE NEXT FEW DAYS.

.MODEL DISCUSSION...MODELS ARE IN GREAT AGREEMENT ON BOTH THE
INTENSITY AND TRACK OF THE LOW PRESSURE SOUTHEAST OF CHIGNIK...AS IT
MOVES ACROSS KODIAK ISLAND THIS EVENING AND INLAND NORTHWEST OF
KODIAK THURSDAY MORNING. MODELS BEGIN TO DIVERGE SIGNIFICANTLY BY
THURSDAY EVENING AS A NEW...MUCH WEAKER LOW APPROACHES FROM THE
EASTERN GULF. CURRENTLY THE MORE WESTERN TRACK...AS INDICATED BY THE
GFS MODEL...WAS FAVORED.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...A 944 MB LOW NEAR KODIAK ISLAND AND ITS ASSOCIATED
FRONT WILL CONTINUE TO IMPACT MUCH OF SOUTHCENTRAL INTO THURSDAY. A
TROPICAL FETCH ASSOCIATED WITH THIS SYSTEM IS PROVIDING PLENTY OF
MOISTURE AND STEADY SNOW ACROSS THE REGION. IN ADDITION...THIS LOW
AND ITS ASSOCIATED FRONT ARE SUPPORTING STRONG PRESSURE GRADIENTS.
AS A RESULT...BLIZZARD CONDITIONS ARE OCCURRING ACROSS SEVERAL LOCAL
GAPS. WINDS HAVE ALREADY REACHED 74 MPH IN PORTAGE VALLEY THIS
MORNING...WITH VISIBILITY DOWN TO A QUARTER MILE. WINDS ARE EXPECTED
TO PEAK THIS AFTERNOON AND EVENING THROUGH WESTERN TURNAGAIN ARM AND
HIGHER ELEVATIONS...THEN QUICKLY RELAX BY TONIGHT AS THE FRONT MOVES
INLAND. HOWEVER...GUSTY WINDS ARE POSSIBLE AGAIN BY EARLY THURSDAY
MORNING AS THE LOW ITSELF APPROACHES COOK INLET AND INTENSIFIES THE
PRESSURE GRADIENT. A MUCH WEAKER LOW WILL APPROACH THE REGION FRIDAY
AND BRING A CHANCE FOR SNOW...HOWEVER...THERE IS STILL A SIGNIFICANT
AMOUNT OF UNCERTAINTY IN THE MODELS.

.SOUTHWEST ALASKA...
A POTENT LOW PRESSURE SYSTEM SOUTH OF CHIGNIK WILL CONTINUE TO
SUPPORT BLIZZARD CONDITIONS ACROSS THE REGION AS MOISTURE STREAMS
NORTHWARD...AND PRESSURE GRADIENTS REMAIN STRONG. THIS LOW WILL
GRADUALLY MOVE NORTHEASTWARD AND WEAKEN AS IT MOVES INLAND THURSDAY
MORNING. DUE TO THE INTENSITY OF THIS LOW...AND ITS SLOW
PROGRESSION...BLIZZARD CONDITIONS ARE EXPECTED TO PERSIST INTO EARLY
THURSDAY MORNING. A REINFORCING SHOT OF COLD AIR WILL SURGE SOUTHWARD
BEHIND THIS LOW...BRINGING A BRIEF COLD SPELL BEFORE THE NEXT LOW
PRESSURE SYSTEM APPROACHES FRIDAY.

.ALEUTIANS/BERING SEA...
A WEAK LOW PRESSURE SYSTEM THAT BROUGHT SNOW SHOWERS TO SHEMYA EARLY
THIS MORNING CONTINUES TO SKIRT TO THE NORTH AND FURTHER INTO THE
BERING. THIS LOW AND ITS ASSOCIATED FRONTS ARE EXPECTED TO MOVE
EASTWARD OVER THE NEXT FEW DAYS...BUT NO SIGNIFICANT WINDS OR
PRECIPITATION ARE EXPECTED. A MUCH MORE SUBSTANTIAL LOW WILL APPROACH
THE WESTERN ALEUTIANS BY LATE THURSDAY NIGHT.

.LONG TERM FORECAST...
INCREASINGLY AMPLIFIED PATTERN BEGINS TO TAKE SHAPE WITH RAPIDLY
STRENGTHENING LOW OVER THE NORTH PACIFIC BY WEDNESDAY WHICH MOVES
NORTH TOWARDS THE GULF COAST THURSDAY. WITH INCREASINGLY STRONG
SOUTHERLY FLOW WE SHOULD EXPECT TEMPERATURES AT LEAST NEAR NORMAL AND
PRECIPITATION ABOVE NORMAL BY LATE THIS WEEK INTO THE WEEKEND OVER
SOUTHCENTRAL ALASKA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC....BLIZZARD WARNING...101 121 125 131 155 161 181 185
MARINE...STORMS...120 130 155 160 165 170 171 180
         GALES...125 129 132 138 140 141 150 172 175 176 179
         HEAVY FREEZING SPRAY...127 130 132 138 141 150 155 165 170
FIRE WEATHER...NONE.

ELN JAN 12