Area Forecast Discussion
Issued by NWS Fairbanks, AK

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FXAK69 PAFG 021301
AFDAFG

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
501 AM AKDT WED SEP 2 2015

.DISCUSSION...

UPPER LEVELS... CURRENT RUNS OF THE GFS/NAM/ECMWF/GEFS ENSEMBLE
MEAN 500 MB ARE IN GOOD AGREEMENT OUT THROUGH SATURDAY.

AN UPPER LEVEL RIDGE CURRENTLY EXTENDS FROM THE CHUKOTSK
PENINSULA TO THE LOWER YUKON VALLEY THEN SOUTHWARD TO JUST WEST OF
KODIAK ISLAND AND INTO THE GULF OF ALASKA. THE RIDGE WILL MOVE
SLOWLY EASTWARD THROUGH THURSDAY NIGHT...WITH A CLOSED HIGH CENTER
FORMING NEAR BARROW LATE THURSDAY NIGHT. THE RIDGE AXIS LATE
THURSDAY NIGHT WILL EXTEND FROM THE CENTRAL BEAUFORT SEA TO PRINCE
WILLIAM SOUND AND SOUTHEASTWARD INTO THE GULF OF ALASKA. THE RIDGE
WILL REMAIN IN PLACE THROUGH FRIDAY NIGHT BUT WEAKEN SLIGHTLY.
OVER THE ALASKA INTERIOR...850 MB TEMPERATURES WILL BE NEAR OR A
LITTLE ABOVE SEASONAL NORMALS THROUGH THE WEEKEND.

A LOW AMPLITUDE SHORT WAVE TROUGH MOVING THROUGH THE WEST SIDE OF
THE RIDGE CURRENTLY EXTENDS FROM AROUND 61N/180W TO THE MCGRATH
AREA. BY LATE TONIGHT THE SHORT WAVE WILL MOVE NORTHWARD TO EXTEND
FROM THE GULF OF ANADYR TO NEAR KOTZEBUE...DECREASING SOME IN
AMPLITUDE. BY THURSDAY AFTERNOON THE SHORT WAVE WILL BE ALMOST
TOTALLY DAMPENED OUT AS IT CONTINUES ON NORTHWARD. A SURFACE LOW
PRESSURE CENTER IS ASSOCIATED WITH THE SHORT WAVE.

AN UPPER LEVEL TROUGH EXTENDING FROM 78N/160W IN THE EASTERN
ARCTIC OCEAN TO KOMAKUK BEACH WILL REMAIN IN PLACE THROUGH
TONIGHT AND BECOME REINFORCED BY AN EASTWARD MOVING SHORT WAVE
TROUGH NOW OVER THE WESTERN BEAUFORT SEA. BY FRIDAY
AFTERNOON...THE REINFORCED TROUGH WILL EXTEND ALONG 135W FROM 75N
SOUTHWARD INTO THE YUKON TERRITORY...WITH A CLOSED UPPER LOW
FORMING NEAR THE MACKENZIE RIVER DELTA AREA. BY LATE FRIDAY NIGHT
THE UPPER LOW WILL BE SPLIT OFF FROM THE WEST TO SOUTHWEST FLOW
MUCH FARTHER TO THE NORTH...AND DRIFT SOUTHWARD TO ABOUT 100 MILES
EAST OF OLD CROW. NORTHERLY FLOW ON THE WEST SIDE OF THE UPPER LOW
WILL EXPAND WESTWARD INTO THE EASTERN THIRD OF NORTHERN ALASKA.

OUT WEST...AN UPPER LOW NEAR 58N/168E...ABOUT 200 MILES EAST OF
THE NORTHERN KAMCHATKA PENINSULA...WILL MOVE EASTWARD TO THE
BRISTOL BAY AREA BY SUNDAY MORNING.

A DEEP POLAR VORTEX CENTERED NEAR 78N/142E IN THE RUSSIAN
ARCTIC OCEAN WILL MOVE TO NEAR 86N/135W IN THE NORTHERN
ARCTIC OCEAN BY LATE FRIDAY NIGHT. THIS VORTEX WILL BE TOO FAR
NORTH TO AFFECT THE NORTHERN ALASKA CWA THROUGH SUNDAY. A SHORT
WAVE ROTATING AROUND THIS VORTEX IS PROGGED TO MOVE EASTWARD TO
160-170W SOUTHWARD TO THE NORTHERN CHUKCHI SEA BY SUNDAY. THERE IS
SOME UNCERTAINTY IN THE POSITION BY SUNDAY...GEFS ENSEMBLE MEAN
SUGGESTS A MEAN TROUGH POSITION ALONG 160W...OPERATIONAL GFS PUTS
THE TROUGH AXIS NEAR 170W. BEYOND SUNDAY...THE GFS AND ECMWF
SOLUTIONS DIVERGE SUBSTANTIALLY...BUT BOTH SUGGEST THE
POSSIBILITY OF A VERY ACTIVE WEATHER PATTERN EVOLVING IN THE HIGH
ARCTIC WITH A MODERATE TO STRONG AND COLD PREDOMINANTLY NORTHWEST
FLOW ALOFT. THIS IS ALSO INDICATED BY THE GEFS AND ECMWF ENSEMBLE
MEAN 500 MB PROGS WHICH CARRY A STRONG VORTEX OVER THE HIGH ARCTIC
WITH MODERATE TO STRONG NORTHWEST FLOW ALOFT FROM THE ALASKAN
ARCTIC COAST NORTHWARD. CURRENT GFS AND CANADIAN MODELS INDICATE
THE POSSIBILITY OF A MODERATE SURFACE SYSTEM AFFECTING THE
NORTHWEST ALASKA COAST MONDAY OR TUESDAY...ECMWF SHOWS A STRONG
SHORT WAVE WHICH COULD SPAWN A SURFACE SYSTEM...BUT AT TIME THE
TRACK AND TIMING OF ANY SURFACE SYSTEMS IS VERY UNCERTAIN.

SURFACE...A BROAD 1024 MB HIGH CENTERED OVER THE ALASKA INTERIOR
WILL MOVE NORTHEASTWARD TO EXTEND FROM THE EASTERN BEAUFORT SEA TO
THE LOWER MACKENZIE RIVER REGION BY THIS AFTERNOON. BY THURSDAY
AFTERNOON THE HIGH WILL RETREAT NORTHWESTWARD WITH THE 1026-1028
MB CENTER ABOUT 200 MILES NORTH OF DEMARCATION POINT.

A DEVELOPING 1012 MB LOW 400 MILES SOUTHWEST OF COLD BAY
WILL DEEPEN TO A 1007 MB LOW OVER BRISTOL BAY BY THURSDAY
MORNING AND THEN DISSIPATE OVER THE WESTERN ALASKA
INTERIOR BY FRIDAY MORNING.

1001 MB LOW CENTERED NEAR ST MATTHEW ISLAND WILL WEAKEN TO A 1006
MB CENTER ABOUT 50 MILES NORTHWEST OF GAMBELL BY THURSDAY
AFTERNOON. THE OPERATIONAL GFS/ECMWF RUNS AGREE WELL ON THE
THURSDAY AFTERNOON CENTRAL PRESSURE AND POSITION... NAM PLACES THE
LOW CENTER ABOUT 50 MILES TO THE NORTHEAST. THE WEATHER FRONT
CURRENTLY EXTENDS FROM ST MATTHEW ISLAND TO NUNIVAK ISLAND AND
SOUTHEAST...BY LATE THIS EVENING THE FRONT WILL EXTEND FROM ST
LAWRENCE ISLAND TO ST MARYS AND SOUTHEASTWARD INTO THE SOUTHWEST
ALASKA INTERIOR.

ARCTIC SLOPE...LITTLE OR NO PRECIPITATION IS EXPECTED TODAY
THROUGH FRIDAY. WINDS MAINLY 10 MPH OR LESS TODAY...INCREASING TO
20-25 MPH BARROW EASTWARD THURSDAY. EAST WINDS 20-30 MPH BARROW
EASTWARD THURSDAY NIGHT AND FRIDAY.

CENTRAL AND EASTERN INTERIOR...PLEASANT FALL CONDITIONS
TODAY THROUGH THURSDAY WITH MAINLY CLEAR SKIES. ISOLATED
SHOWERS OVER THE SOUTHERN ZONES THURSDAY NIGHT AND FRIDAY...
SKIES BECOMING MOSTLY CLOUDY IN THE SOUTHERN ZONES BY FRIDAY.

WESTERN INTERIOR...NORTHEASTWARD MOVING WEATHER FRONT MAY BRING
SOME RAIN TO THE LOWER YUKON VALLEY TODAY...WITH A CHANCE OF SOME
LINGERING SHOWERS TONIGHT. RAIN LIKELY IN THE LOWER YUKON VALLEY
THURSDAY AFTERNOON AND THURSDAY NIGHT AND A CHANCE OF RAIN FRIDAY
WITH THE INCOMING LOW CENTER ORIGINATING SOUTH OF THE EASTERN
ALEUTIANS. RAIN LIKELY THURSDAY NIGHT AND FRIDAY OVER THE THE
UPPER KUSKOKWIM VALLEY.

WEST COAST...
RAIN OVER THE YUKON DELTA TODAY...WITH A CHANCE OF RAIN TONIGHT.
A CHANCE OF RAIN OVER THE SOUTHERN SEWARD PENINSULA COAST TODAY
THROUGH FRIDAY. RAIN LIKELY THURSDAY NIGHT AND FRIDAY MORNING
OVER EASTERN NORTON SOUND AND THE NULATO HILLS...OTHERWISE
A CHANCE OF RAIN IN THOSE AREAS THIS AFTERNOON THROUGH FRIDAY.
A CHANCE OF RAIN OR SHOWERS THIS AFTERNOON AND TONIGHT OVER THE
NORTON SOUND COAST AND NULATO HILLS. EAST TO SOUTHEAST WINDS COULD
INCREASE TO 20-25 MPH AHEAD OF THE WEATHER FRONT. THE WEATHER
FRONT WILL BE WEAKENING TONIGHT.

ST LAWRENCE ISLAND...
RAIN AND EAST WINDS INCREASING TO 25-35 MPH TODAY AHEAD OF THE
WEATHER FRONT. RAIN WILL TAPER OFF LATER TONIGHT...WITH WINDS
SHIFTING TO SOUTH AND THEN TO SOUTHWEST AND DECREASING.


COASTAL HAZARD POTENTIAL DAYS 3 AND 4...NONE.

&&

.HYDROLOGY...
THE CHENA RIVER FROM THE MOOSE CREEK DAM DOWNSTREAM REMAINS
ELEVATED...BUT WATER LEVELS WILL CONTINUE TO FALL SLOWLY. THE
STAGE OF THE CHENA RIVER AT FAIRBANKS IS CURRENTLY ABOUT 7.2
FEET...AND IS FORECAST TO FALL TO ABOUT 5.9 FEET BY MIDNIGHT
FRIDAY NIGHT. ELSEWHERE...NO HYDROLOGIC ISSUES.


&&

.AFG WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY FOR PKZ210.

&&

$$



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