High Wind in Alaska, November 2, 2012

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
444 AM AKDT FRI NOV 2 2012

.ANALYSIS AND UPPER LEVELS...

STRONG LOW PRESSURE OVER THE NORTH PACIFIC CENTERED ABOUT 400 NM
SOUTH OF KODIAK CITY WILL REACH PEAK INTENSITY OF 949 MB LATER THIS
MORNING...THEN BEGIN A GRADUAL YET PERSISTENT WEAKENING TREND THROUGH
THE WEEKEND AS IT MOVES NORTH INTO THE CENTRAL GULF. UPPER LEVEL JET
ENERGY DIVING SOUTH ON THE UPSTREAM SIDE OF THE LOW WILL HELP TO DIG
A NEW UPPER LOW SOUTH OF THE ALASKA PENINSULA SATURDAY...WHICH WILL
PERSIST THROUGH SUNDAY NIGHT AS THE FORMER LOW BECOMES ABSORBED INTO
A DIGGING TROUGH FROM THE NORTH BETWEEN CORDOVA AND YAKUTAT. HIGH
PRESSURE WILL PERSIST OVER THE WESTERN BERING AND ALEUTIANS THROUGH
THE WEEKEND...WITH STRONG NORTHERLY FLOW CONTINUING OVER THE CENTRAL
AND EASTERN BERING SEA.

.MODEL DISCUSSION...

MODELS ARE IN GOOD AGREEMENT SYNOPTICALLY THROUGH THE WEEKEND. THE
BIGGEST QUESTION MARK IN THE FORECAST FOR THE NEXT COUPLE OF DAYS IS
THE POSSIBILITY OF ANY SNOW FALLING IN THE ANCHORAGE AREA. THE GFS
AND EC MODELS ARE HINTING AT SOME LIGHT SNOW EARLY THIS AFTERNOON
DEVELOPING IN THE VICINITY OF THE ANCHORAGE AREA. A POTENT SHORTWAVE
OVER THE NORTHERN GULF WILL BE MOVING NORTH AND WEST YET WEAKENING AS
IT APPROACHES THE AREA. WEAK UPPER LEVEL Q-VECTOR CONVERGENCE WILL
BRIEFLY COMMENCE AS A WEAK UPPER LEVEL NORTHEASTERLY JET STREAK
POSITIONS ITSELF OVER THE COOK INLET REGION AS THIS SHORTWAVE
DISTURBANCE APPROACHES. ALL OF THE USUALLY RELIABLE MODELS ALSO HINT
AT A FAIRLY MOIST SNOW GROWTH LAYER AT OR JUST ABOVE THE TEN-THOUSAND
FOOT LEVEL. IT WOULD SEEM TO REASON THAT AT LEAST A FEW SCATTERED
SNOW SHOWERS WILL DEVELOP (IF NOT A STEADY LIGHT SNOW OF BRIEF
DURATION) EARLY THIS AFTERNOON OVER THE COOK INLET REGION AS A RESULT
WITH LITTLE TO NO ACCUMULATIONS.

THE MODEL FORECASTS FOR SATURDAY MORNING INTO EARLY AFTERNOON ARE
ALSO A BIT PROBLEMATIC. THE 00Z AND 06Z NAM MODEL RUNS ARE NOTEWORTHY
BECAUSE THEY DEPICT A VERY MOIST SNOW GROWTH LAYER WITH DECENT LIFT
IN ASSOCIATION WITH A SHORTWAVE DISTURBANCE MOVING OVERHEAD FROM THE
NORTH GULF COAST NEAR PRINCE WILLIAM SOUND...ALL WHILE DEPICTING
LITTLE IN THE WAY OF DOWNSLOPE DRYING AS PARTIALLY INDICATED BY AN
ALMOST NON-EXISTENT PRESSURE GRADIENT ACROSS TURNAGAIN ARM. THE GFS
AND EC MODELS DEPICT SOMEWHAT SIMILAR CONDITIONS BUT WITH A BIT MORE
LOW-LEVEL DRYING (INCLUDING A SLIGHTLY DRIER SNOW GROWTH LAYER). THE
SATURDAY FORECAST FOR ANCHORAGE WILL ACCOUNT FOR THE UNCERTAINTY AS A
RESULT.

.SHORT TERM FORECAST...

SOUTHCENTRAL...

THE MAIN HEADLINE FOR THE REGION WILL CONTINUE TO BE THE STORM FORCE
LOW ABOUT 400 MILES SOUTH OF KODIAK CITY. A WEAKENING FRONT WILL PUSH
NORTH TOWARD THE NORTH GULF COAST THIS MORNING BUT WILL FALL APART AS
IT OUTRUNS THE UPPER LEVEL ENERGY.

MEANWHILE...SCATTERED SNOW SHOWERS OVER THE NORTHERN GULF WILL GIVE
WAY TO STEADY SNOW AND MOVE INLAND ALONG THE NORTH GULF COAST AND
PRINCE WILLIAM SOUND BY THIS AFTERNOON BEFORE WARMER TEMPERATURES
CHANGE THE PRECIPITATION OVER TO RAIN. WILL KEEP SCATTERED SNOW
SHOWERS FOR THE NORTH AND WEST SLOPES OF THE CHUGACH RANGE INCLUDING
ANCHORAGE AND THE MATANUSKA VALLEY AS A RESULT. FOR SATURDAY WE WILL
SEE A CONTINUATION OF RAINY CONDITIONS ALONG THE GULF COAST WITH A
CHANCE OF SNOW ALONG THE NORTH AND WESTERN SLOPES OF THE CHUGACH
RANGE. WILL MONITOR MODEL TRENDS FOR THE POTENTIAL OF ACCUMULATING
SNOWS IN TOWN SATURDAY...BUT FAR TOO MUCH UNCERTAINTY AT THIS POINT
IN TIME TO SAY FOR CERTAIN. THE SUNDAY FORECAST WILL LIKELY
CONSTITUTE MORE IN THE WAY OF THE SAME FOR SOUTHCENTRAL BEFORE THE
UPPER LEVEL SYSTEM BECOMES ABSORBED INTO A DIGGING TROUGH DIVING
SOUTH FROM THE INTERIOR...WHICH WILL LIKELY RESULT IN DRIER
CONDITIONS ESPECIALLY WEST OF THE CHUGACH RANGE SUNDAY NIGHT INTO
MONDAY.

SOUTHWEST ALASKA...

STRONG OFFSHORE FLOW WILL KEEP CONDITIONS MOSTLY DRY. THE EXCEPTION
MAY BE ALONG THE ALEUTIAN RANGE TODAY AND TONIGHT IN ASSOCIATION WITH
THE OUTER EDGES OF THE STRONG LOW SOUTH OF KODIAK. A POTENT SHORTWAVE
DISTURBANCE MAY ALSO BE ABLE TO SQUEEZE OUT A PERIOD OF LIGHT SNOW
OVER PARTS OF THE KUSKOKWIM VALLEY AND BRISTOL BAY ZONES TONIGHT INTO
SATURDAY MORNING.

BERING SEA/ALEUTIANS...

STORM-FORCE NORTHERLY WINDS WILL BEGIN TO SUBSIDE BY THIS AFTERNOON
AS STRONG LOW PRESSURE SOUTH OF KODIAK BEGINS TO WEAKEN AND MOVE
NORTH TOWARDS THE CENTRAL GULF OF ALASKA THROUGH SATURDAY...BECOMING
NO HIGHER THAN GALE-FORCE BY MIDNIGHT TONIGHT. A STAGNANT PATTERN
WILL PERSIST THROUGH THE WEEKEND AS HIGH PRESSURE REMAINS STATIONARY
OVER THE WESTERN BERING...AND LOW PRESSURE DRIFTS NORTH INTO THE
CENTRAL GULF AND WEAKENS...KEEPING PERSISTENTLY STRONG NORTHERLY FLOW
OVER MOST OF THE REGION. SCATTERED TO NUMEROUS SNOW SHOWERS WILL BE
COMMON IN PERSISTENT UPSLOPE AND ONSHORE AREAS SUCH AS THE EASTERLY
ALEUTIANS AND ALASKA PENINSULA. BY MONDAY THE PATTERN SHOWS SIGNS OF
CHANGING AS HIGH PRESSURE BEGINS TO MOVE TOWARDS THE CENTRAL BERING
AND A NEW WEATHER SYSTEM BEGINS TO APPROACH FROM THE SOUTHWEST
TOWARDS THE WESTERN ALEUTIANS.

.LONG TERM FORECAST...

BY EARLY NEXT WEEK MODELS SUGGEST A TRANSITION PERIOD WITH AN UPPER
LEVEL LOW/TROUGH DIGGING SOUTH AND EAST INTO THE GULF AND THEN MOVING
TOWARDS THE PANHANDLE...ALL WHILE THE STRONG UPPER LEVEL RIDGE
CURRENTLY OVER THE WESTERN BERING MOVES EAST TO THE MAINLAND AND A
LARGE UPPER LEVEL LOW DEVELOPS OVER THE NORTHERN AND/OR WESTERN
BERING SEA. THIS WOULD RESULT IN TRANSFERRING MUCH OF THE TRANQUIL
WEATHER OVER THE WESTERN BERING SEA TO THE MAINLAND ESPECIALLY BY
MIDWEEK...WHILE ALLOWING THE WESTERN AND NORTHERN BERING TO BECOME
MUCH MORE UNSETTLED.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES...140 160 165 170 171 172 179 180 185
         STORMS...120 130 132 138 150 155
         HVY FRZG SPRY...180
FIRE WEATHER...NONE.

29/CC NOV 12