Blizzard in Alaska, January 31, 2012

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
511 AM AKST TUE JAN 31 2012

.ANALYSIS AND UPPER LEVELS...

UPPER LEVEL LOW OVER THE CHUKCHI SEA WILL CONTINUE TO STRETCH
SOUTHWARD INTO THE BERING DURING THE DAY TODAY. THIS WILL HELP
CONTINUE TO ENERGIZE A LOW PRESSURE SYSTEM OVER THE CENTRAL
ALEUTIANS...WHICH WILL HELP BRING BLIZZARD CONDITIONS TODAY WITH SNOW
AND BLOWING SNOW. IN TURN A STRONG JET STREAK TO THE SOUTH WILL HELP
RAPIDLY STRENGTHEN SURFACE LOW PRESSURE ABOUT 450 MILES SOUTH OF THE
ALASKA PENINSULA BY THIS EVENING. THIS LOW WILL PEAK NEAR 943 MB
SOMETIME WEDNESDAY AFTERNOON ABOUT 125 MILES SOUTH OF KODIAK CITY
BEFORE WEAKENING AS IT MOVES NORTH TO THE KENAI PENINSULA BY THURSDAY
AFTERNOON. A STORM FORCE FRONT WILL EXTEND NORTH AND EAST ACROSS THE
GULF AND BRING A PROLONGED PERIOD OF BARRIER JET CONDITIONS TO THE
NORTH GULF COAST FOR WEDNESDAY INTO WEDNESDAY NIGHT. WITH CONTINUED
STRONG MODEL AGREEMENT THROUGH WEDNESDAY NIGHT WE HAVE ISSUED SEVERAL
NEW WATCHES WITH THE MORNING PACKAGE.

.MODEL DISCUSSION...

MODELS ARE IN GOOD SHAPE THROUGH WEDNESDAY EVENING. THE PREFERRED
EUROPEAN (EC) MODEL IS A BIT OF AN OUTLIER IN TAKING THE STRONG LOW
THAT MOVES INTO THE GULF A BIT FARTHER WEST TOWARDS THE ALEUTIAN
RANGE AND WESTERN COOK INLET. WE CHOSE THE EC MODEL DESPITE IT BEING
SOMEWHAT OF AN OUTLIER BASED ON ITS BETTER SKILL WITH SIMILAR TYPE
SYSTEMS IN THE PAST. HOWEVER...IT SHOULD BE NOTED THAT CONFIDENCE IN
THE EXACT LOW TRACK IS STILL LOW FROM EARLY THURSDAY MORNING ONWARD.
THE FARTHER WEST EC LOW TRACK WOULD BRING MUCH WARMER AIR INTO THE
UPPER COOK INLET REGION INCLUDING ANCHORAGE FOR THURSDAY.

.SHORT TERM FORECAST...

SOUTHCENTRAL...

WEAK DISTURBANCE WILL MOVE THROUGH THE UPPER COOK INLET REGION...WITH
SNOW ENDING BY NOON WEST OF THE CHUGACH RANGE BUT CONTINUING ACROSS
SOME PARTS OF THE COPPER RIVER BASIN THROUGH THIS AFTERNOON. MID
LEVEL SUBSIDENCE AND A FAIRLY MOIST LOW LEVEL ATMOSPHERE WILL LIKELY
CONTRIBUTE TO ONLY PARTIAL CLEARING TODAY FOR ANCHORAGE AND OTHER
AREAS WEST OF THE ALASKA RANGE.

AT PRESENT GIVEN THE EXPECTED TRACK OF POWERFUL LOW PRESSURE JUST
EAST OF KODIAK WEDNESDAY EVENING...EXPECTING HIGH WINDS TO DEVELOP
FOR KODIAK AND ALSO ALONG THE BARRIER JET NEAR CORDOVA. BLIZZARD
CONDITIONS WILL ALSO BE POSSIBLE FOR THOMPSON PASS AS WELL AS NEAR
PORTAGE AS MODERATE TO HEAVY SNOW DEVELOPS AND WINDS INCREASE BY
WEDNESDAY NIGHT.

ANOTHER POSSIBLE FUTURE HAZARD UNDER CONSIDERATION IS THE POTENTIAL
FOR SIGNIFICANT SNOW ACCUMULATIONS OVER THE SUSITNA VALLEY...
ESPECIALLY AREAS WEST OF THE PARKS HIGHWAY...AS WELL AS WINTER STORM
CONDITIONS POSSIBLY DEVELOPING OVER PRINCE WILLIAM SOUND...BUT WILL
LEAVE THIS FOR CONSIDERATION BY THE AFTERNOON SHIFT TODAY.

SOUTHWEST ALASKA...

MAIN CONCERN WILL BE THE TRACK OF THE POWERFUL LOW THAT DEVELOPS AND
MOVES TOWARDS THE WESTERN GULF TONIGHT THROUGH TOMORROW. STRONG WINDS
ON THE BACK SIDE OF THE LOW ALONG WITH ONSHORE FLOW WILL PRODUCE
POSSIBLE BLIZZARD CONDITIONS FOR THE ALASKA PENINSULA AND THE WESTERN
CAPES OF THE BRISTOL BAY ZONE. ADVISORY LEVEL SNOWS ARE A DISTINCT
POSSIBILITY AS WELL AS SNOW EXPANDS WEST OF THE ALEUTIAN AND ALASKA
RANGES INTO THE BRISTOL BAY AND KUSKOKWIM VALLEY ZONES. THE WIND
CHILL ADVISORY WILL REMAIN UNCHANGED FOR THE KUSKOKWIM DELTA...BUT IF
THE EC MODEL IS CORRECT THERE COULD BE SNOW AND BLOWING SNOW
POTENTIAL AS FAR WEST AS BETHEL BY WEDNESDAY EVENING.

BERING SEA/ALEUTIANS...

BLIZZARD CONDITIONS WILL AFFECT THE CENTRAL ALEUTIANS TODAY...AND
THEN SUBSIDE THIS EVENING AS LOW PRESSURE DROPS SOUTH AND BECOMES
ABSORBED INTO THE DEVELOPING POWERFUL LOW SOUTH OF THE ALASKA
PENINSULA TONIGHT. STRONG NORTHWEST FLOW AND EMBEDDED WAVES WILL KEEP
CONDITIONS COLD AND UNSETTLED OVER THE EASTERN HALF OF THE REGION
WITH BLIZZARD CONDITIONS POSSIBLE FOR THE ALASKA PENINSULA.

MEANWHILE...A MUCH WEAKER LOW PRESSURE SYSTEM WILL MOVE TOWARDS THE
WESTERN ALEUTIANS TONIGHT AND BRING SNOW...POSSIBLY MIXED WITH
RAIN...TO PARTS OF THE WESTERN ALEUTIANS TONIGHT THROUGH THURSDAY.

.LONG TERM FORECAST...

COLD ADVECTION SNOW WILL DEVELOP FRIDAY OVER THE UPPER COOK INLET
REGION INCLUDING ANCHORAGE AS LOW PRESSURE WINDS DOWN AND SLIDES
NORTH AND EAST TOWARDS THE ALCAN BORDER. AS THIS HAPPENS...ANOTHER
POWERFUL LOW WILL TAKE SHAPE NEAR THE CENTRAL AND WESTERN ALEUTIANS
AND THEN BECOME STATIONARY OVER THE CENTRAL AND/OR WESTERN BERING
SEA. THIS WILL SET UP DEEP SOUTHEASTERLY UPPER LEVEL FLOW OVER MUCH
OF SOUTHWEST AND SOUTHCENTRAL ALASKA BY THIS WEEKEND INTO EARLY NEXT
WEEK. EXPECT CONTINUED INCREASED STORMINESS WITH TEMPERATURES NEAR
NORMAL TO ABOVE NORMAL.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING...187
         BLIZZARD WATCH...125 131 161 181
         HIGH WIND WATCH...135 171
MARINE...GALES...125 140 141 160 165 170 171 172 175 179 180
         STORMS...120 130 132 138 150 155
         HVY FRZG SPRY...165 170 171
FIRE WEATHER...NONE.

29 JAN 12