Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 070109
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
409 PM AKST SAT FEB 6 2016

.ANALYSIS AND UPPER LEVELS...

THE UPPER LEVEL PATTERN OVER SOUTHERN ALASKA REMAINS LARGELY
UNCHANGED THIS AFTERNOON. UPPER LEVEL TROUGHING REMAINS INTACT
ACROSS THE BERING...THUS KEEPING ANY COLD AIR OUTBREAKS LOCKED UP
OVER EASTERN RUSSIA. WHILE THE JET STREAM FOR THE MOST PART
REMAINS SOUTH OF THE AREA...A NOTABLE DIFFERENCE FROM THE ZONAL
FLOW OF WEEKS PAST IS THE CURRENT SUBTROPICAL JET STREAM PATTERN
IS FAR MORE MERIDIONAL.

AN UPPER LEVEL TROUGH WITH AN EMBEDDED VERTICALLY STACKED LOW IS
LOCATED WELL SOUTH OF THE AREA OVER THE NORTH PACIFIC. THE UPPER
LOW HAS HELPED DIG A TROUGH WELL SOUTH INTO THE
MIDLATITUDES...WHOSE AXIS IS ALONG THE 160W MERIDIAN. THIS HAS IN
TURN LED TO THE DEVELOPMENT OF UPPER LEVEL RIDGES ON BOTH THE EAST
AND WEST SIDES OF THE TROUGH. THE MORE NOTABLE RIDGE IS EAST OF
THE LOW...CAUSING THE JET STREAM TO FLOW NEARLY SOUTH TO NORTH
INTO THE EASTERN GULF AND THE PANHANDLE. VERY STRONG DIFFLUENCE
NORTHEAST OF THE UPPER LOW CENTER CORRELATES WITH THE LEFT EXIT
REGION OF A JET STREAK...HELPING INTENSIFY A STRONG FRONT MOVING
NORTHWARD TOWARDS THE GULF. THIS FRONT WILL BE THE PRIMARY WEATHER
MAKER ON THE EAST SIDE OVER THE NEXT DAY OR SO. CURRENTLY A TROUGH
MOVING THROUGH SOUTHCENTRAL AND SOUTHWEST IS BRINGING LIGHT SNOW
SHOWER ACTIVITY TO THE SUSITNA AND KUSKOKWIM VALLEYS...THOUGH
LITTLE IN THE WAY OF ACCUMULATION HAS RESULTED FROM IT. AN
EXTENSION OF THE TROUGH IS KEEPING WET WEATHER GOING THROUGH THE
EASTERN PRINCE WILLIAM SOUND AND NORTHERN GULF AREAS AS
WELL.

ACROSS THE WEST... WEAK FEATURES REMAIN THE CAUSES OF LOCAL AREAS
OF ACTIVE WEATHER. A DISSIPATING LOW OVER THE EASTERN ALEUTIANS
AND AN ASSOCIATED UPPER LEVEL DISTURBANCE ARE PUSHING NORTH ACROSS
THE EASTERN BERING...WHILE THE WESTERN BERING REMAINS IN AN
UNSTABLE...SHOWERY...COLDER WEATHER REGIME. OTHER THAN THE
AFOREMENTIONED FRONT AFFECTING THE ALASKA PENINSULA AREA...ONLY
ONE OTHER STRONG FEATURE WILL DEVELOP. A VERY STRONG 180 KT JET
CURRENTLY LOCATED OVER THE NORTHWEST PACIFIC WILL REORIENT INTO A
MORE ZONAL FLOW SOUTH OF THE WESTERN ALEUTIANS TONIGHT...MAKING
THE ENVIRONMENT IN THAT AREA MORE FAVORABLE FOR CYCLOGENESIS.

&&

.MODEL DISCUSSION...

THIS MORNINGS MODEL RUNS ARE LARGELY IN VERY GOOD AGREEMENT ABOUT
THE WEATHER FOR THE NEXT COUPLE OF DAYS. THE STORM FORCE FRONT
EXPECTED TO MOVE INTO THE GULF IS PEGGED NEARLY IDENTICALLY BY ALL
THE MODELS IN TERMS OF TIMING...WITH SOME SMALL DISCREPANCIES IN
PRECIPITATION AMOUNT ASSOCIATED WITH IT. ACROSS THE WEST
SIDE THERE ARE ONLY SMALL FEATURES OVER THE AREA CURRENTLY. THESE ARE
USUALLY NOT WELL HANDLED BY THE GLOBAL MODELS SO THE MORE
DETAILED GEM WAS USED. THE NAM...BEING ANOTHER HIGHER RESOLUTION
MODEL WAS NOT USED SINCE IT WAS A BIT SLOWER THAN THE OTHER MODELS
CONCERNING THE LOW MOVING INTO THE ALASKA PENINSULA FOLLOWING THE
FRONT. THE OTHER CONCERN IS A DEVELOPING INTENSE NORTH PACIFIC LOW
EXPECTED TO DEVELOP SOUTH OF THE WESTERN ALEUTIANS IN ABOUT A DAY
OR SO. THERE ARE MORE SIGNIFICANT DIFFERENCES BETWEEN THEM
REGARDING THE PLACEMENT OF THE CENTER...HOWEVER SINCE THEY ARE
UNANIMOUS IN KEEPING THE CENTER OF THE LOW WELL SOUTH OF THE
ALEUTIANS...ONLY THE NORTHERN PERIPHERY IS EXPECTED TO GRAZE
THROUGH THE CHAIN. THE DETAILS ON THAT ASPECT OF THE STORM ARE
LARGELY THE SAME.

ON THE EAST SIDE...A BLEND OF NAM/GFS/AND EC WERE USED TO BLEND
TOGETHER ANY SMALL DIFFERENCES BETWEEN THE MODELS. FOR THE WEST
SIDE...THE EC WAS THE GLOBAL MODEL OF CHOICE...WITH THE GEM USED
FOR THE LOCAL EFFECTS. FORECAST CONFIDENCE IS HIGH DUE TO GOOD MODEL
AGREEMENT.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...

THE TROUGH CURRENTLY STRETCHING FROM A SMALL SURFACE LOW OFF OF
THE SOUTHEAST KENAI PENINSULA COAST AND INTO PRINCE WILLIAM SOUND
WILL WEAKEN AS IT SHIFTS GRADUALLY NORTH AND INLAND TONIGHT.
SHOWERS WILL CONTINUE IN PRINCE WILLIAM SOUND AND THE SURROUNDING
AREA WITH ISOLATED TO SCATTERED SHOWERS ELSEWHERE IN SOUTH CENTRAL
ALASKA. THE NEXT SIGNIFICANT FEATURE MOVING INTO THE AREA IS THE
STRONG WEATHER FRONT LIFTING NORTH INTO THE SOUTHERN GULF TONIGHT.
THE VERTICALLY STACKED PARENT SURFACE LOW SOUTH OF KODIAK ISLAND
AROUND 47N WILL WEAKEN AND FILL AS IT TRACKS NORTH TONIGHT
THROUGH SUNDAY NIGHT BEFORE TURNING NORTHWEST AND CROSSING THE
ALASKA PENINSULA MONDAY. AFTER BRINGING STORM FORCE WINDS TO
PORTIONS OF THE SOUTHERN AND WESTERN GULF WATERS INCLUDING SHELIKOF
STRAIT AND THE EASTERN BARRENS TONIGHT AND SUNDAY MORNING...THE
FRONT WILL WEAKEN AND STALL ALONG THE NORTHERN GULF COAST SUNDAY
AFTERNOON THROUGH MONDAY.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
AN UNSTABLE AIRMASS COMBINED WITH A WEAK SHORTWAVE TROUGH ALOFT
WILL BRING SOME LIGHT SNOW TO NORTHERN PORTIONS OF THE KUSKOKWIM
VALLEY EARLY THIS EVENING BEFORE MOVING OFF TO THE NORTH. WEAK
HIGH PRESSURE WILL BUILD OVERHEAD TONIGHT AND BRING SOME PATCHY
FOG TO THE SAME AREA. OTHERWISE EXPECT NEAR NORMAL LOW TEMPERATURES
TONIGHT AND GENERALLY LIGHT AND VARIABLE WINDS THAT WILL BE
SHIFTING TO THE NORTH. ON SUNDAY AFTERNOON...A MATURE SYSTEM
SOUTH OF THE ALASKA PENINSULA WILL SWING A FRONT TOWARD THE
MAINLAND. THE MAIN IMPACT OF THIS FRONT WILL BE MIDDLE AND HIGH
CLOUDINESS AND AN INCREASE IN WINDS THROUGH THE AFTERNOON. SOME
SPOTTY LIGHT PRECIPITATION WILL BE POSSIBLE LATE SUNDAY FOLLOWED
BY GUSTY EASTERLY WINDS BEGINNING EARLY MONDAY MORNING. SHOWERY
PRECIPITATION AND EASTERLY WINDS WILL CONTINUE THROUGH LATE MONDAY
NIGHT.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
WEAK CYCLONIC FLOW CONTINUES OVER MUCH OF THE BERING SEA. THERE IS
ONE CONSOLIDATED LOW CENTER WEST OF THE PRIBILOF ISLANDS WHERE
STEADIER PRECIPITATION IS POSSIBLE. OTHERWISE EXPECT ISOLATED
SHOWERS WITH MILD TEMPERATURES. A COUPLE OF FRONTAL BOUNDARIES
WILL AFFECT THE AREA...ONE SWINGS OVER THE ALASKA PENINSULA LATE
SUNDAY WITH A WEAKENING SURFACE LOW MOVING INTO BRISTOL BAY...THE
OTHER WILL JUST REACH THE WESTERN AND CENTRAL ALEUTIANS SUNDAY
AFTERNOON. THIS FRONT WILL BE AROUND GALE FORCE WITH THE MAIN LOW
PASSING SOUTH OF THE CHAIN.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
AN ACTIVE WEATHER PATTERN WILL CONTINUE ACROSS THE GULF AND BERING
THROUGH THE BEGINNING OF NEXT WEEKEND...WITH DRIER CONDITIONS FOR
FAVORED DOWNSLOPING INLAND LOCATIONS. A WEAKENING LOW PRESSURE
SYSTEM PUSHING OVER THE ALASKA PENINSULA MONDAY EVENING WILL TRACK
INTO THE NORTHEASTERN BERING WHILE DISSIPATING TUESDAY MORNING...
KEEPING SCATTERED RAIN AND SNOW SHOWERS OVER PARTS OF THE SOUTHERN
MAINLAND THROUGH EARLY TUESDAY MORNING. AT THE SAME TIME...ANOTHER
LOW ORGANIZES SOUTH OF THE CENTRAL ALEUTIANS MONDAY EVENING...AND
TRACKS EASTWARD THROUGH TUESDAY. THE SURFACE LOW ASSOCIATED WITH
THIS SYSTEM IS EXPECTED TO BRING A STORM FORCE FRONT ACROSS THE
CENTRAL AND EASTERN ALEUTIANS OVERNIGHT MONDAY...WITH EQUALLY AS
GUSTY WINDS ALONG THE WESTERN FLANK OF THE SYSTEM AS COLDER AIR
OFF EASTERN RUSSIA ADVECTS OVER THE WESTERN ALEUTIANS AND BERING
THROUGH WEDNESDAY MORNING. THIS SYSTEM STARTS TO LOSE MOMENTUM BY
WEDNESDAY AS A RIDGE BUILDS OVER SOUTHERN ALASKA. THIS RIDGE
CURRENTLY LOOKS TO SHUNT PROGRESS OF THIS LOW AND ANOTHER LOW
TRACKING IN FROM THE EASTERN BEAUFORT SEA. THIS KEEPS TEMPERATURE
TRENDS ABOVE NORMAL FOR MUCH OF THE SOUTHERN MAINLAND THROUGH NEXT
WEEKEND. ANOTHER WEAKER SYSTEM TRACKING UP FROM THE NORTH PACIFIC
WILL BRING A FRONT THROUGH THE GULF WEDNESDAY MORNING AND SLOWLY
TRACK INTO THE NORTHERN GULF COAST BY THURSDAY MORNING. THIS WILL
BRING ANOTHER ROUND OF WET AND WINDY WEATHER TO THE AREAS
SURROUNDING THE NORTHERN GULF COAST.

OVERALL THE MODELS ARE IN FAIR AGREEMENT THROUGH MUCH OF THE
EXTENDED FORECAST...WITH THE EC AND CANADIAN MODELS HAVING THE
BEST HANDLE ON THE SYSTEMS ENTERING OUR AREA THROUGH NEXT WEEKEND.
THERE ARE THE USUAL TIMING AND STRENGTH DIFFERENCES BETWEEN THE
MODELS GIVEN HOW FAR OUT THE FORECAST GOES. HOWEVER...FORECAST
CONFIDENCE IS SLIGHTLY HIGHER THAN NORMAL GIVEN THE SYNOPTIC
AGREEMENT AMONGST THE MODELS WITH REGARDS TO THE ACTIVE WEATHER
PATTERN THAT WILL CONTINUE TO DOMINATE THE REGION THROUGH NEXT
WEEKEND.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 119 120 127 130 136 137 139 155 176 177.
 STORM 131 132 138 150.
         HEAVY FREEZING SPRAY 185.

&&
$$

SYNOPSIS AND MODEL DISCUSSION...BC
SOUTHCENTRAL ALASKA...JR
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MTL
LONG TERM...TP


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