Blizzard in Alaska, November 21, 2009

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
525 AM AKST SAT NOV 21 2009

.ANALYSIS AND UPPER LEVELS...
IN THE UPPER-LVLS A TROF IS PRESENT OVER THE BERING/ALEUTIANS AND
OVER THE GULF OF AK...WITH A RIDGE NESTLED IN BETWEEN THROUGH SW AK
AND THE AKPEN. A SHORTWAVE IS TRAVERSING BRISTOL BAY AND MOVING
NORTHEAST TOWARDS THE SUSITNA VALLEY. AT THE SURFACE A LOW SOUTH OF
MIDDLETON ISLAND IN THE GULF OF AK IS MOVING EAST AND FILLING. A
SERIES OF STORM-FORCE LOWS ARE IN THE BERING SEA. ONE LOW JUST NORTH
OF ATTU IS MOVING SOUTHEAST AND FILLING. THE OTHER WHICH IS JUST
NORTH OF ATKA IS MOVING EAST AND SLIGHTLY DEEPENING.

.MODEL DISCUSSION...
MODELS ARE SATISFACTORILY CAPTURING THE MAJOR FEATURES ACROSS THE
AOR. THE LOW SOUTH OF MIDDLETON ISLAND THIS MORNING WILL CONTINUE TO
MOVE EAST AND WEAKEN...EVENTUALLY DISSIPATING OVER THE SE GULF DURING
THE DAY SUNDAY. THE WEAKENING LOW OVER THE FAR WESTERN ALEUTIANS WILL
MOVE SOUTHEAST TODAY AND DISSIPATE AS IT SLIPS INTO THE NORTH PACIFIC
EARLY SUNDAY MORNING TO THE WEST OF ADAK. THE OTHER LOW TO THE NORTH
OF ADAK THIS MORNING WILL MOVE EAST AND APPROACH THE COAST OF BRISTOL
BAY ON MONDAY. THE ENERGY FROM THE DISSIPATING LOW OVER THE WESTERN
ALEUTIANS LOOKS TO HELP DEEPEN THE TROF IN THE BERING...AND ALSO
SLIGHTLY DEEPEN THE LOW HEADED TOWARDS BRISTOL BAY. A STORM FORCE LOW
IS DEVELOPING OVER THE NORTH PACIFIC...AND MODELS MOVE THIS INTO THE
SOUTHERN GULF SUNDAY NIGHT AND UP TOWARDS THE KENAI PENINSULA ON
MONDAY. NAM APPEARS A BIT OF AN OUTLIER IN ROTATING IT UP TOO FAR TO
THE EAST. MORNING FORECAST PACKAGE LEANS MORE ON THE GFS THROUGH THE
MID-RANGE PERIOD WITH A TRANSITION TO THE EC FOR THE LONG TERM PERIOD
BASED ON SATISFACTORY INITIALIZATION AND CONSISTENCY.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
LIGHT SNOW THROUGH THE MATANUSKA VALLEY AND ANCHORAGE BOWL SATURDAY
AS SHORTWAVE APPROACHES FROM THE WEST...AND THEN TAPERING OFF AS THE
MOISTURE FROM THE FEATURE MOVES EAST INTO THE COPPER RIVER BASIN AND
PRINCE WILLIAM SOUND SATURDAY EVENING. A STEADIER PRECIPITATION LOOKS
TO OVERSPREAD KODIAK ISLAND AND UPSLOPE AREAS OF THE SUSITNA VALLEY
ON SUNDAY AS MOISTURE AHEAD OF THE STORM-FORCE LOW MOVES INTO THE
ZONE. WARMER AIR WITH THIS LOW WILL TRANSITION SNOW TO RAIN ALONG
COASTAL AREAS OF THE KENAI PENINSULA...EASTERN KODIAK ISLAND AND
PRINCE WILLIAM SOUND AS THE PRECIPITATION CONTINUES SUNDAY INTO
MONDAY. EASTERLY 850 MB FLOW WILL HELP TO DOWNSLOPE AND RETARD
ACCUMULATING SNOWS OVER THE ANCHORAGE BOWL AND MAT-SU VALLEY ON
SUNDAY AND MONDAY...WITH MOSTLY CLOUDY CONDITIONS EXPECTED WITH
PERHAPS A FEW FLURRIES OR BRIEF SNOW SHOWERS.

.SOUTHWEST...
SNOW AND RAIN WITH THE LOW ROTATING THROUGH THE CENTRAL AND EASTERN
BERING. ARCTIC AIR STILL PREDOMINANT OVER THE KUSKOWIM DELTA/VALLEY
AND INTERIOR BRISTOL BAY WHERE SNOW LOOKS TO OVERSPREAD FROM WEST TO
EAST SATURDAY NIGHT INTO SUNDAY. STRONG WINDS ALONG THE NORTHERN
PERIPHERY OF THE LOW WILL AID IN BLOWING SNOW...WHICH COMBINDED WITH
THE FALLING SNOW MAY YIELD BLIZZARD CONDITIONS ALONG THE KUSKOWIM
DELTA COAST OVERNIGHT SATURDAY THROUGH EARLY SUNDAY. IN THE WARMER
AIR FURTHER SOUTH...SNOW WILL MIX WITH AND CHANGE OVER TO RAIN ACROSS
THE AKPEN AS THE SYSTEM WORKS EAST...AND THEN TRANSITION TO SNOW
AGAIN AS THE REMNANT LOW ENTERS BRISTOL BAY ON MONDAY.

.BERING SEA/ALEUTIANS...
NUMEROUS RAIN AND SNOW SHOWERS IN THE WAKE OF THE BERING LOWS OVER
THE REGION. STORM-LEVEL WINDS DIMINISHING OVER CENTRAL AND WESTERN
MARINE ZONES SATURDAY EVENING AS THE FAR WESTERN BERING LOW WEAKENS
AND DISSIPATES. RAIN/SNOW OVERSPREADING THE PRIBILOFFS...SATURDAY AND
TRANSITIONING BACK TO SNOW/SNOW SHOWERS AS THE LOW PASSES TO THE
SOUTH. GUSTY NORTH-NORTHWEST WINDS AIDING WITH AREAS OF BLOWING SNOW
THROUGH MONDAY...THOUGH WITH LESS AVAILABLE PRECIPITATION...BELIEVE
CONDITIONS WILL NOT REACH BLIZZARD CRITERIA WITH THIS SYSTEM OVER THE
PRIBILOFFS.

.LONG TERM FORECAST...
STAYING ACTIVE IN THE GULF AND BERING THROUGH LATE NEXT WEEK AS
PROGRESSIVE PATTERN ESTABLISHES OVER THE AOR. FORECAST CONFIDENCE IN
THE LONG RANGE REMAINS POOR DUE TO TIMING ISSUES WITH SYSTEMS AND
LESS THAN STELLAR MODEL CONSISTENCY. MORE SEASONABLE TEMPERATURES
HOWEVER AS ARCTIC AIR REMAINS OVER THE INTERIOR OF AK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WATCH...155
MARINE...STORM...352 172 175 176
         GALE...351 412 413 414 150 155 160 165 170 171 179 180 185
HEAVY FREEZING SPRAY...160 180 185

JAM NOV 09