Heavy Freezing Spray Warning 178, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
130 PM AKST SUN NOV 4 2012

.ANALYSIS AND UPPER LEVELS...
ALASKA AND THE NORTH PACIFIC REMAIN IN A HIGHLY AMPLIFIED UPPER LEVEL
PATTERN FEATURING A RIDGE ACROSS THE WESTERN BERING SEA AND A BROAD
LONGWAVE TROUGH GENERALLY CENTERED SOUTH OF THE ALASKA PENINSULA. JET
STREAM ENERGY IS CONSOLIDATED INTO A SINGLE 130 KNOT BRANCH THAT IS
WELL SOUTH OF OUR AREA AND IS SUPPORTING THE LONGWAVE TROUGH. STRONG
NORTHERLY WINDS OVER THE WEST COAST OF ALASKA ARE USHERING COLD AIR
INTO THE REGION THROUGH THE BERING STRAIT AND BRINGING GUSTY WINDS AS
FAR SOUTH AS THE EASTERN ALEUTIANS AND ALASKA PENINSULA. COLD AIR IS
ALSO POOLED OVER INTERIOR ALASKA AND IS BEGINNING TO FILTER THROUGH
THE MOUNTAINS INTO SOUTHCENTRAL AND ON TO THE COAST. IN
RESPONSE...GUSTY WINDS HAVE INTENSIFIED THROUGH THE NORMAL TERRAIN
GAPS FROM THOMPSON PASS TO WHITTIER AND RESURRECTION BAY. IN
ADDITION...AN UPPER LEVEL TROUGH THAT HAS BEEN NEARLY STATIONARY OVER
THE INTERIOR FOR THE LAST 36 HOURS IS POISED TO BEGIN MOVING
SOUTHWARD AS WELL. WHILE GENERALLY STARVED FOR MOISTURE...THIS TROUGH
HAS MANAGED TO DROP SEVERAL INCHES OF SNOW IN THE FAIRBANKS AREA DUE
TO ITS VERY SLOW MOVEMENT.

.MODEL DISCUSSION...
MODELS ARE IN GOOD OVERALL AGREEMENT THROUGH THE FIRST 84 HOURS
(SHORT TERM) OF THE FORECAST PERIOD. CONFIDENCE IS HIGH THAT A
SUSTAINED PERIOD OF COLD OUTFLOW WINDS ACROSS COASTAL SOUTHCENTRAL
WILL CONTINUE THROUGH TUESDAY NIGHT. LESS CERTAIN IS THE IMPACT OF
THE UPPER LEVEL TROUGH CURRENTLY STRETCHING ACROSS INTERIOR ALASKA.
THE MODELS AGREE THAT THIS TROUGH WILL SLOWLY MAKE ITS WAY THROUGH
THE ANCHORAGE BOWL ON TUESDAY. THE LINGERING QUESTION IS HOW MUCH
ATMOSPHERIC MOISTURE IS AVAILABLE TO DEVELOP CLOUDS AND SNOW ACROSS
THE REGION. GENERALLY SPEAKING...COLD UPPER LEVEL TROUGHS DROPPING
DOWN FROM THE NORTH ARE STARVED FOR MOISTURE AND STRUGGLE TO PRODUCE
MORE THAN FLURRIES. HOWEVER...SINCE THIS FEATURE WILL BE MOVING SO
SLOWLY...AND WITH LIGHT SOUTHERLY FLOW IN FRONT OF THE TROUGH...THERE
REMAINS A CHANCE SOME AREAS AROUND COOK INLET COULD SEE SOME MINOR
SNOW ACCUMULATIONS ON TUESDAY.

.SHORT TERM FORECAST...
SOUTHCENTRAL...A TROUGH ALONG THE NORTH GULF COAST CONTINUES WITH A
WEAK CIRCULATION EMBEDDED IN THE MEAN FLOW CURRENTLY NEAR MIDDLETON
ISLAND. THIS FEATURE IS KEEPING SHOWER ACTIVITY AROUND PRINCE WILLIAM
SOUND AND CORDOVA...WHICH SHOULD GRADUALLY DIMINISH THIS EVENING. AS
MENTIONED ABOVE...EXPECT GAP OUTFLOW WINDS TO REALLY ESTABLISH THIS
EVENING AS THE COLD ADVECTION PROCESS INTENSIFIES. THE ARRIVAL OF THE
COLD AIR WILL ALSO HELP REDEVELOP A LOW IN THE NORTHERN GULF BY
MONDAY AFTERNOON...WHICH WILL ACT TO TIGHTEN PRESSURE GRADIENTS
ACROSS THE REGION EVEN MORE. INLAND...LIGHT NORTHERLY WINDS WILL
ACCOMPANY THE REINFORCING SHOT OF COLD AIR...AND KEEP AFTERNOON HIGH
TEMPERATURES IN THE 20S AT MOST LOCATIONS THROUGH THE START OF THE
WEEK. AS DISCUSSED IN THE MODEL DISCUSSION...STILL A CHANCE THAT COOK
INLET REGION MAY SEE A BIT OF SNOW FROM THE UPPER TROUGH MOVING
THROUGH ON TUESDAY. BETTER CHANCES FOR SNOW OVER WESTERN PRINCE
WILLIAM SOUND TUESDAY NIGHT WITH HIGHER CONFIDENCE IN AVAILABLE
ATMOSPHERIC MOISTURE.

SOUTHWEST...WITH A RIDGE TO THE WEST AND TROUGH TO THE EAST...EXPECT
COLD DRY AND WINDY CONDITIONS TO CONTINUE ACROSS MUCH OF THE REGION
TO BEGIN THE WEEK. NORTH/NORTHWESTERLY WINDS WILL GRADUALLY BECOME
MORE NORTHEASTERLY AS THE LOW IN THE NORTHERN GULF DRIFTS TOWARD
KODIAK ISLAND TUESDAY. ONCE THIS HAPPENS....THE LOCATION OF THE
STRONGEST WINDS WILL LIKELY SHIFT FROM ALONG THE KUSKOKWIM DELTA
COAST TO INLAND BRISTOL BAY. THE GUSTIEST WINDS WILL LIKELY SHOW A
DIURNAL TREND (HIGHER DURING THE DAY...LOWER AT NIGHT) AS THE SUN IS
STILL STRONG ENOUGH TO GENERATE SOME MIXING IN THE LOWER ATMOSPHERE.

BERING SEA AND ALEUTIANS...HIGH PRESSURE WILL KEEP WEATHER
UNSEASONABLY TRANQUIL OVER THE CENTRAL AND WESTERN BERING THROUGH
TUESDAY. FURTHER EAST...STRONG NORTHERLY WINDS CURRENTLY OVER THE
EASTERN ALEUTIANS WILL GRADUALLY SHIFT TOWARD THE MAINLAND BEFORE
DIMINISHING MONDAY NIGHT INTO TUESDAY. A LARGE AND SLOW-MOVING
PACIFIC LOW WILL GRADUALLY NUDGE NORTHWARD OVER THE NEXT FEW
DAYS...GRADUALLY SWITCHING WINDS AROUND TO THE EAST AND INCREASING TO
GALE FORCE BY TUESDAY ACROSS THE WESTERN 1/2 OF THE ALEUTIANS.

.LONG TERM FORECAST...
A PATTERN CHANGE LOOKS LIKELY BY MIDWEEK AS THE CURRENT
HIGH-AMPLITUDE PATTERN BECOMES MORE PROGRESSIVE WITH FEATURES MORE
FREELY MOVING AROUND THE REGION. THE LONG-RANGE MODELS ALSO SEEM TO
BE SUGGESTING THAT THE PATTERN MAY TRANSITION BY NEXT WEEKEND INTO A
TROUGH OVER THE BERING SEA AND A RIDGE OVER THE GULF. IF THIS WERE TO
HAPPEN...IT COULD SET MUCH OF MAINLAND ALASKA UP WITH WINDY AND MOIST
SOUTHERLY FLOW...REMINISCENT OF SEPTEMBER.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE 130 132 150 155 160 165 170 171 180 175 176
         HEAVY FREEZING SPRAY 150 160 180
FIRE WEATHER...NONE

DIXON NOV 12