Heavy Freezing Spray Warning 177, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 PM AKDT SAT NOV 3 2012

.ANALYSIS AND UPPER LEVELS...
MAIN FEATURE OF INTEREST THIS AFTERNOON IS THE LARGE VERTICALLY
STACKED LOW PRESSURE SYSTEM OVER THE CENTRAL GULF OF ALASKA...WHICH
CONTINUES TO PRODUCE STRONG WINDS AND RAIN SHOWERS OVER MARINE AREAS
AND THE NORTHERN GULF COAST AS IT MOVES NORTHWARD AND WEAKENS.
PRECIPITATION REMAINS MOSTLY CONFINED TO COASTAL PORTIONS OF
SOUTHCENTRAL AK...WITH INLAND AREAS SEEING GENERALLY CLOUDY SKIES
WITH A FEW BREAKS OF SUNSHINE. THE SOUTHWEST MAINLAND REMAINS UNDER
THE INFLUENCE OF A FAIRLY BENIGN PATTERN...WITH OFFSHORE FLOW
YIELDING CLEAR SKIES OVER MUCH OF THE REGION. HIGH PRESSURE PERSISTS
OVER THE EASTERN RUSSIA AND THE WESTERN BERING...WITH STRONG
NORTHERLY FLOW BETWEEN THIS FEATURE AND THE GULF LOW BRINGING SNOW
SHOWERS AND GUSTY WINDS TO THE EASTERN BERING/ALEUTIANS.

.MODEL DISCUSSION...
MODELS ARE IN DECENT AGREEMENT WITH RESPECT TO THE OVERALL SYNOPTIC
PATTERN THROUGH THE SHORT TERM. THE STACKED LOW CURRENTLY OVER THE
CENTRAL GULF WILL MOVE TO THE NORTHERN COAST INTO SUNDAY MORNING. THE
LOW WILL TRANSITION TO AN OPEN UPPER LEVEL DISTURBANCE AND MOVE
INLAND SUNDAY AS THE NEXT DISTURBANCE RIDES INTO THE PANHANDLE.
DESPITE THE OVERALL SYNOPTIC AGREEMENT...DISCREPANCIES REMAIN
REGARDING PLACEMENT OF MESOSCALE FEATURES...WITH SEVERAL UPPER LEVEL
DISTURBANCES ROTATING AROUND THE GULF LOW CONTRIBUTING TO FORECAST
UNCERTAINTIES IN THE LIKELIHOOD AND TIMING OF PRECIPITATION OVER
SOUTHCENTRAL ALASKA INTO THE BEGINNING OF THE WEEK.

.SHORT TERM FORECAST...
SOUTHCENTRAL...THE STACKED LOW IN THE GULF REMAINS THE PROBLEM
THROUGH TONIGHT. THIS LOW WILL LIFT TO THE COAST EAST OF CORDOVA
TONIGHT AS ANOTHER LOW MOVES INTO THE PANHANDLE. A COUPLE UPPER
DISTURBANCES WILL ENCIRCLE THE LOW TONIGHT WITH SOME SHOWERS
REMAINING MAINLY ALONG THE COASTAL LOCATIONS. SOME SNOW WILL SPREAD
INLAND OVER THE COPPER RIVER BASIN BUT REMAIN MAINLY OVER THE HIGHER
ELEVATIONS. MODERATE WINDS WILL REMAIN OVER THE AREA AS THE LOW
REMAINS IN THE NORTHERN GULF THROUGH SUNDAY. GAP WINDS ALONG THE
COAST WILL PICK UP SUNDAY AS THE FLOW ALOFT BECOMES MORE NEUTRAL
ALLOWING FOR WESTERLY AND NORTHERLY GAP FLOWS TO DEVELOP. IN
ADDITION...THE GRADIENT BECOMES MORE FAVORABLE.

IN THE MEANTIME...AN UPPER TROUGH SINKS INTO THE REGION AND SLOWLY
MOVES THROUGH THE AREA SUNDAY NIGHT THROUGH TUESDAY. AS THE FLOW
ALOFT TURNS MORE SOUTHWEST SUNDAY NIGHT INTO MONDAY...SUSPECT CHANCES
OF PRECIPITATION WILL INCREASE OVER THE REGION. THE PRECIP WILL BE IN
THE FORM OF SNOW SINCE THE TROUGH IS BRINGING COLDER ARCTIC AIR. AS
THE TROUGH MOVES THROUGH TUESDAY...NORTHERLY FLOW WILL PICK UP AND
THE GAP FLOWS WILL INCREASE IN INTENSITY.

SOUTHWEST ALASKA...STRONG PRESSURE GRADIENT DUE TO LOW IN THE GULF
AND DEVELOPING HIGH IN THE WESTERN BERING. MODERATE WINDS INLAND AND
STRONG WINDS ALONG THE AKPEN AND THE BERING SEA COASTLINE. THE LOW IN
THE GULF WILL CONTINUE TO WEAKEN AND MOVE A BIT EAST TOMORROW AND
MONDAY AS THE HIGH PRESSURE MOVES IN THE EASTERN BERING. WINDS WILL
DIMINISH SUNDAY NIGHT INTO MONDAY. THE TROUGH MOVING SOUTH THROUGH
NORTHERN AND WESTERN ALASKA IS PRODUCING SCATTERED SNOW SHOWERS OVER
THE KUSKOKWIM DELTA AND VALLEY AREAS AS WELL. THIS ACTIVITY WILL
CONTINUE TO SLIDE SOUTH TONIGHT WITH ISOLATED SHOWERS MOVING INTO
BRISTOL BAY TOMORROW AFTERNOON AND NIGHT. THE TROUGH AXIS MOVES
THROUGH THE AREA SUNDAY NIGHT INTO MONDAY WITH WINDS DIMINISHING AND
SKIES CLEARING MONDAY INTO TUESDAY.

BERING SEA AND ALEUTIANS...COLD AIR ADVECTION CONTINUES OVER THE
BERING IN MODERATE TO STRONG NORTHERLY FLOW. OVER THE
WATER...CONVECTIVE SNOW SHOWERS WILL REMAIN THE RULE THROUGH TONIGHT
AND INTO TOMORROW FOR THE CENTRAL AND EASTERN BERING. HIGH PRESSURE
OVER THE WESTERN BERING TO SLOWLY MOVE INTO THE CENTRAL BERING MONDAY
WITH WINDS AND SHOWERS DIMINISHING OVER THE BERING. A DEVELOPING LOW
IN THE NORTH PACIFIC WILL BRING SOME HIGHER EAST/SOUTHEAST WINDS TO
THE WESTERN ALEUTIANS BEGINNING TUESDAY. THE LOW WILL REMAIN FAR
ENOUGH SOUTH TO ONLY PROVIDE A SLIGHT CHANCE OF PRECIPITATION.

.LONG TERM FORECAST...THE PATTERN IS IN FOR A CHANGE. THE TROUGH OVER
THE MAINLAND INTO THE GULF IS EXPECTED TO SWING TO THE PANHANDLE
WEDNESDAY AS THE RIDGE OVER THE BERING MOVES OVER THE MAINLAND. THERE
IS TO BE A TROUGH MOVING OUT OF RUSSIA INTO THE NORTHERN BERING
PHASING WITH A LOW MOVING OUT OF THE NORTH PACIFIC WEDNESDAY INTO
THURSDAY. THIS PHASING OF ENERGIES IS THE CAUSE FOR A LOT OF
UNCERTAINTY MID TO LATE NEXT WEEK. OVERALL...BY LATE NEXT WEEK THE
PATTERN WILL BE MORE ACTIVE FOR THE MAINLAND AND BERING.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE WARNING 120 127 128 160 165 170 179 180
FIRE WEATHER...NONE

CB/JN NOV 12