Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 090113
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
413 PM AKST MON FEB 8 2016

.ANALYSIS AND UPPER LEVELS...
UPPER LEVELS...SINCE YESTERDAY...THE UPPER LEVEL LOW THAT WAS
SOUTH OF KODIAK HAS BEEN ABSORBED INTO A NEW UPPER LOW. THE NEW
LOW AND CENTER OF CIRCULATION FOR THE NUMEROUS UPPER LEVEL WAVES
AND LOWS BOUND FOR SOUTHERN ALASKA IS NOW CENTERED SOUTH OF ADAK.
THE JET CONTINUES TO BECOME MORE ZONAL SOUTH OF THE UPPER LOW AS
IT LATERALLY TRANSLATES SOUTH. THE ZONAL JET IS PUSHING THE RIDGE
THAT HAD BEEN IN PLACE THE PAST FEW DAYS OVER THE PANHANDLE
EASTWARD...WHICH WILL HELP TO DIMINISH THE INTENSITY OF FUTURE
DISTURBANCES ROTATING NORTHWARD THROUGH THE GULF TOWARDS THE COAST
DUE TO THE LACK OF UPPER LEVEL SUPPORT.

SURFACE ANALYSIS... THE STRONG VERTICALLY STACKED LOW SOUTH OF
ADAK CONTINUES TO TRACK WELL SOUTH OF THE ALEUTIANS...WITH THE
FRONT ALONG THE NORTHERN PERIPHERY OCCASIONALLY CAUSING GALE FORCE
WINDS ON THE PACIFIC SIDE OF THE CHAIN. THE LOW THAT HAD BROUGHT
THE STRONG FRONT TO KODIAK AND THE ALASKA PENINSULA THE PAST
COUPLE DAYS HAS NOW CROSSED THE ALASKA PENINSULA INTO BRISTOL BAY.
A FEW VERY LIGHT SNOW SHOWERS ASSOCIATED WITH IT WENT THROUGH
DILLINGHAM THIS MORNING AND HAVE MOVED WESTWARD INTO THE WOOD
RIVER MOUNTAINS. WINDS WITH THIS LOW ARE LIGHT. YET ANOTHER SURFACE
LOW HAS DEVELOPED OVER THE EASTERN GULF IN ASSOCIATION WITH THE
DEPARTING JET STREAK. IT IS RACING NORTHWARD...THOUGH THE ONLY
REAL IMPACTS EXPECTED FROM IT ARE THE CONTINUATION OF COASTAL
SHOWERS NEAR PRINCE WILLIAM SOUND AND INCREASED CLOUD COVER ACROSS
THE COPPER RIVER BASIN. A FRONT IS APPROACHING SOUTHCENTRAL
ALASKA...WHICH FORMED FROM A WEAK UPPER LEVEL DISTURBANCE ROTATING
AROUND THE UPPER LOW IN BROAD SOUTHEAST FLOW. IT IS CAUSING SOME
SNOW SHOWER ACTIVITY ACROSS THE WESTERN KENAI AND WESTERN PRINCE
WILLIAM SOUND. HOWEVER...DOWNSLOPING IS LARGELY KEEPING ALL OF THE
ACTIVITY FROM REACHING ANCHORAGE AND THE WESTERN KENAI. THOUGH A
FEW OF THE STRONGER SHOWERS HAVE BEEN ABLE TO SUCCESSFULLY
TRAVERSE THE MOUNTAINS...CAUSING BRIEF PERIODS OF LIGHT
PRECIPITATION. SIGNIFICANT MOISTENING OF THE ATMOSPHERE ON THE
ANCHORAGE 12Z SOUNDING HAS BEEN NOTED SINCE YESTERDAYS 00Z
SOUNDING...WHICH EXPLAINS WHY SOME OF THE SHOWERS ARE GETTING OVER
THE CHUGACH.

&&

.MODEL DISCUSSION...
ACROSS SOUTHCENTRAL AND THE GULF...ALL OF THE MODELS HAVE COME
INTO MUCH BETTER AGREEMENT THE PAST 24 HOURS ON THE TRACK OF THE
LOW CURRENTLY DEVELOPING OVER THE EASTERN GULF. FOR THIS
FEATURE...THE NAM WAS THE PREFERRED MODEL AS ITS BETTER RESOLUTION
HANDLES THE LOCAL EFFECTS OF THE STORM BETTER THAN THE GLOBAL
MODELS. FOR THE LOW HEADED FOR THE SOUTHWESTERN GULF ON TUESDAY
NIGHT...THE GFS CONTINUES TO BE THE CHOSEN MODEL AS FOR THE PAST
FEW RUNS IT HAS BEEN THE MOST CONSISTENT. THE EC HAS BEEN THE
FASTEST/FURTHEST NORTH OF THE MODELS...BUT RUN TO RUN HAS BEEN
TRENDING SOUTH WITH THE LOW...TOWARDS THE GFS POSITION. THE GFS
SOLUTION HAS BEEN TRENDING STRONGER WITH THE WINDS AHEAD OF THE
STORM AS IT MOVES TOWARDS THE NORTHWEST...FOLLOWING THE TRACK OF
THE LOW NOW IN BRISTOL BAY.

FOR SOUTHWEST ALASKA AND THE ALEUTIANS...THE NAM WAS ALSO THE
MODEL OF CHOICE AS IT IS IN GENERAL AGREEMENT WITH THE OTHER
MODELS AND HAS BETTER DETAILS WITH THE SMALL SCALE GAP FLOWS
THROUGH THE ALEUTIANS. ALL OF THE MODELS INDICATE
BROAD...COLD...NORTHEAST SHOWERY FLOW ACROSS MUCH OF THE BERING.

FORECAST CONFIDENCE ON BOTH SIDES REMAINS HIGH CONCERNING THE
LARGER FEATURES ALREADY DISCUSSED. AS THERE REMAINS NO LARGE
SCALE CHANGES IN THE PATTERN EXPECTED FOR THE FORESEEABLE
FUTURE...IT STANDS WITH GOOD REASON THAT SMALLER SCALE FEATURES
WILL CONTINUE TO BRING CHANGEABLE WEATHER TO SOUTHERN ALASKA
BETWEEN ANY BIGGER LOWS. WHILE THERE IS HIGH CONFIDENCE THAT
THESE FEATURES WILL BE AFFECTING LOCALIZED AREAS THROUGH THE
FORECAST PERIOD...CONFIDENCE IS LOWER ON THE TIMING OF WHEN EACH
INDIVIDUAL DISTURBANCE AFFECTS THOSE AREAS.

&&

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

ONCE THE WEAK LOW IN THE EASTERN GULF TRACKS NORTH AND INLAND
OVER YAKUTAT THE LARGE BLOCKING WESTERN NORTH AMERICAN UPPER
LEVEL RIDGE WILL STRENGTHEN AND PUSH BACK ACROSS THE NORTHERN GULF
COAST TUESDAY. AS THE RIDGE BUILDS...ANY LINGERING SHOWERS WILL
END QUICKLY WITH SKIES CLEARING OVER SOUTH CENTRAL ALASKA. THE
NEXT INCOMING FRONTAL SYSTEM WILL SPREAD A FRONTAL SYSTEM INTO THE
SOUTHERN GULF TUESDAY AND TUESDAY NIGHT...BRINGING WIDE SPREAD
GALES TO THAT AREA. WINDS WILL BRIEFLY PICK UP TO STORM FORCE IN
THE FAR SOUTHWESTERN GULF AND COASTAL WATERS NEAR KODIAK ISLAND
LATE TUESDAY NIGHT. THE FRONT WILL LIFT INTO THE NORTHERN GULF
WEDNESDAY MORNING AND THEN PUSH ONSHORE WEDNESDAY AFTERNOON.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THERE IS A WEAK SURFACE LOW MOVING THROUGH THE BRISTOL BAY REGION
BEFORE MOVING INTO THE KUSKOKWIM BAY AFTER MIDNIGHT TONIGHT. THIS
SYNOPTIC FEATURE WILL THEN DIMINISH INTO A WEAK TROUGH GOING INTO
TUESDAY. AS THIS SYSTEM MOVES ALONG THE SOUTHWEST COASTLINE IT
WILL BRING PRECIPITATION THROUGH THE ALASKA PENINSULA...AND THEN
TO DILLINGHAM WESTWARD BEFORE SPREADING INTO THE KUSKOKWIM DELTA
COASTLINE. THE PRECIPITATION TYPE WILL MAINLY BE A MIXTURE OF
RAIN/SNOW FOR INLAND AREAS EXCEPT FOR ALL SNOW IN HIGHER
ELEVATIONS. WHILE ALONG THE BRISTOL BAY COASTLINE THE PRECIPITATION
WILL BE ALL RAIN.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE MAJORITY OF THE BERING IS DOMINATED BY NORTHEASTERLY WINDS
EXCEPT FOR SOUTHEASTERLY WINDS THROUGH THE EASTERN BERING. THE
CENTRAL ALEUTIANS WILL BE AFFECTED BY A NORTH PACIFIC STORM-FORCE
LOW LOCATED SOUTH OF THE CHAIN. AS THIS SYSTEM MOVES EASTWARD IT
WILL BRING GALE-FORCE EASTERLY WINDS THROUGH THE CENTRAL ALEUTIANS.
THIS WILL RESULT IN A SWATH OF PRECIPITATION ALONG THE CHAIN
BEFORE SPREADING INTO THE LOWER BERING SEA HEADING INTO TUESDAY.
BY TUESDAY EVENING THE WINDS WILL DIMINISH TO SMALL CRAFT ADVISORY
THRESHOLDS ALONG THE CHAIN AS THE LOW MOVES FARTHER EAST INTO THE
NORTHERN PACIFIC. LOOK FOR WARMER TEMPERATURES RESULTING IN MOSTLY
ALL RAIN ALONG THE CHAIN. WHILE COOLER TEMPERATURES WILL BE WEST
OF ADAK THROUGH THE WESTERN ALEUTIANS PRODUCING NUMEROUS SNOW
SHOWERS THROUGH TUESDAY.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

NOT MUCH CHANGE IN THE SYNOPTIC WEATHER PATTERN IS EXPECTED OVER
THE NEXT 7 DAYS AS THE UPPER LEVEL TROUGH THAT HAS BEEN ANCHORED
OVER THE BERING SEA AND NORTHERN PACIFIC SHOWS NO SIGNS OF
DISSIPATING. SEVERAL STRONG UPPER LEVEL LOWS AND SHORTWAVES WILL
DROP INTO THE NORTH PACIFIC OFF THE EASTERN COAST OF RUSSIA
THROUGH NEXT WEEKEND WHICH WILL HELP RE-INVIGORATE THE LONGWAVE
TROUGH AND KEEP THE WEATHER PATTERN SIMILAR TO THAT OBSERVED OVER
THE PAST MONTH. MODELS ARE IN SURPRISINGLY GOOD AGREEMENT THROUGH
THE EXTENDED PERIOD AND IT APPEARS UNSEASONABLY WARM TEMPERATURES
WILL CONTINUE THROUGH SOUTHWEST AND SOUTHCENTRAL ALASKA. THE
PLACEMENT OF THE LONGWAVE TROUGH KEEPS THE GULF OF ALASKA AND
SOUTHCENTRAL ALASKA IN THE MAIN STORM TRACK. NORMALLY FOR THIS
TIME OF THE YEAR...THIS COULD BE A FAVORABLE SET UP TO BRING
SNOWFALL TO SOUTHCENTRAL ALASKA. HOWEVER...THE AMPLIFIED TROUGH
WILL BRING LOW PRESSURE SYSTEMS FOR THE SUBTROPICS UP TOWARD
ALASKA AND ADVECT WARM AND MOIST AIR INTO THE ALASKA MAINLAND
(MORE FAVORABLE FOR RAIN ACROSS MOST LOCATIONS). TEMPERATURES
ACROSS SOUTH CENTRAL WILL BE WELL ABOVE NORMAL WITH A LOT OF
LOCATIONS SEEING NEAR OR ABOVE FREEING TEMPERATURES WHILE SOUTHWEST
ALASKA WILL SEE TEMPERATURES ANYWHERE FROM 5 TO 15 DEGREES ABOVE
NORMAL THROUGH THE EXTENDED.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 119 120 127 130 131 136 138 139 155 170-174 176.
 STORM 132 150.
         HEAVY FREEZING SPRAY 185.

&&
$$

SYNOPSIS AND MODEL DISCUSSION...JW
SOUTHCENTRAL ALASKA...JR
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PD
LONG TERM...MC


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