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FXAK68 PAFC 091352
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
552 AM AKDT TUE SEP 9 2025
SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3)
THE FORECAST REMAINS ON TRACK FOR A STRONG LOW NEAR THE ALASKA
PENINSULA THIS MORNING TO MOVE INTO THE GULF OF ALASKA. ITS FRONT
IS CURRENTLY OVER THE WESTERN GULF OF ALASKA AND KODIAK ISLAND
THIS MORNING. WINDS WILL GRADUALLY INCREASE THROUGHOUT THE DAY FOR
MOST PLACES ACROSS SOUTHCENTRAL AS THE FRONT CONTINUES NORTH AND
EAST. AS THE LOW APPROACHES THE GULF LATER TODAY, NORTHERLY WINDS
WILL GRADUALLY STRENGTHEN THROUGHOUT COOK INLET. NORTHEASTERLY
WINDS WILL BECOME GUSTY THROUGH THE MATANUSKA VALLEY, TO AROUND 20
TO 30 MPH. AS THE NORTHERLY WINDS BEND DOWN THE INLET, ANCHORAGE
BOWL COULD HAVE A SHARE OF THE BREEZINESS, PEAKING LATE THIS
EVENING INTO TONIGHT. AS THE FRONT LIFTS ALONG THE NORTHERN GULF
COAST, A BARRIER JET DEVELOPS A STRONG EASTERLY WIND, PARALLEL TO
THE NORTHERN GULF OF ALASKA AND PRINCE WILLIAM SOUND COASTLINES,
WITH GUSTS RANGING FROM 55 TO 65 MPH TONIGHT INTO WEDNESDAY
MORNING.
ACCOMPANYING THE WINDS WILL BE PLENTY OF RAINFALL. STREAMS AND
RIVERS ACROSS THE AREA HAVE ALREADY EXPERIENCED HIGHER WATER
LEVELS DUE TO RECENT RAINFALL EVENTS. ADDITIONAL RAINFALL WITH
THIS UPCOMING STORM WOULD LEAD TO A QUICKER RESPONSE FROM
VULNERABLE STREAMS AND RIVERS. A HYDROLOGICAL OUTLOOK HAS BEEN
ISSUED FOR ADDITIONAL DETAILS. RAINFALL AMOUNTS THROUGH WEDNESDAY
EVENING RANGE FROM 1 TO 3 INCHES FOR MOST COASTAL LOCATIONS ALONG
THE GULF AND PRINCE WILLIAM SOUND. THE HIGHEST RAINFALL TOTALS ARE
EXPECTED TO BE FOR THE WESTERN PRINCE WILLIAM SOUND COASTLINE TO
EASTERN KENAI PENINSULA NORTH OF SEWARD WHERE LOCALLY HIGHER
AMOUNTS AROUND 4 INCHES IS POSSIBLE. AMOUNTS FROM A FEW TENTHS TO
AN INCH CAN BE EXPECTED AT INTERIOR LOCATIONS INCLUDING THE COPPER
RIVER BASIN, THE MAT-SU VALLEYS SOUTH TO THE WESTERN KENAI
PENINSULA. MULTIPLE WAVES OF PRECIPITATION WILL KEEP CONDITIONS
WET FOR THE REST OF THIS WEEK.
.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS
(DAYS 1 THROUGH 3: TODAY THROUGH THURSDAY)...
THE MAIN FEATURE OF INTEREST THIS MORNING IS A LARGE LOW CURRENTLY
CENTERED TO THE SOUTH OF COLD BAY. THIS LOW IS BEGINNING TO
STEADILY WEAKEN AS IT BECOMES INCREASINGLY STACKED/OCCLUDED, AND
THE MAXIMUM WINDS ENVELOPING THE LOW HAVE NOW DIMINISHED FROM
STORM FORCE TO GALE FORCE. THE STRONGEST WINDS ARE NOW SITUATED
MAINLY TO THE WEST OF THE CENTER ACROSS THE SOUTHERN BERING SEA,
WHERE A TIGHT PRESSURE GRADIENT COMBINED WITH COLD AIR STREAMING
SOUTH INTO THE LOW IS YIELDING NORTHERLY WINDS GUSTING AS HIGH AS
50 TO 60 MPH FROM THE PRIBILOFS SOUTH TO THE EASTERN ALEUTIANS.
FARTHER NORTHEAST, THE LOW'S OCCLUDED FRONT IS MAKING HEADWAY INTO
SOUTHWEST THIS MORNING. GUSTY EASTERLY WINDS HAVE ALREADY PICKED
UP FROM THE NORTHERN AKPEN INTO BRISTOL BAY, WHILE BANDS OF LIGHT
TO MODERATE RAIN ALSO BEGIN TO LIFT NORTH INTO BRISTOL BAY ALONG
AND AHEAD OF THE FRONT. OUT TO THE WEST OF THE LOW, MUCH CALMER
CONDITIONS ARE ALREADY MAKING A RETURN TO THE WESTERN BERING AND
ALEUTIAN CHAIN AS A HIGH PRESSURE RIDGE BUILDS INTO PLACE.
FORECAST CONFIDENCE AND MOST OF THE DETAILS REMAIN IN GOOD SHAPE
THROUGH THE NEXT TWO TO THREE DAYS. BY TONIGHT, THE LOW WILL
APPROACH THE WESTERN GULF NEAR OR JUST SOUTH OF KODIAK ISLAND,
WHILE THE CORRIDOR OF STRONG NORTHERLY FLOW BETWEEN THE LOW AND
THE HIGH OUT OVER THE WESTERN BERING ADVANCES EAST INTO THE AKPEN
AND MUCH OF SOUTHWEST ALASKA. WINDS WILL BE PARTICULARLY INTENSE
WHERE FLOW FUNNELS THROUGH GAPS ACROSS THE SOUTHERN AKPEN, WHERE
GUSTS THROUGH BAYS AND PASSES ON THE PACIFIC SIDE TO AROUND 45 TO
55 MPH WILL BE POSSIBLE FROM THIS EVENING INTO WEDNESDAY NIGHT.
AREAS OF RAIN ASSOCIATED WITH THE FRONT BENDING NORTH WILL PUSH
UP INTO THE KUSKOKWIM VALLEY AND DELTA REGION THROUGH TONIGHT AS
STRONG OFFSHORE WINDS ALSO PICK UP.
BETWEEN WEDNESDAY AND THURSDAY, THE MOST INCLEMENT CONDITIONS
ACROSS THE EASTERN PARTS OF THE OUTLOOK AREA WILL SLOWLY RAMP DOWN
AS THE LOW DRIFTS FARTHER OUT INTO THE GULF. RAIN AND LOW CLOUDS
WILL CLEAR FROM WEST TO EAST AS THE UPPER LEVEL PORTION OF THE
GULF LOW BEGINS TO OPEN BACK UP INTO A TROUGH AND PARTIALLY MERGE
WITH A SEPARATE ARCTIC TROUGH DRIFTING SOUTH OVER THE WESTERN
INTERIOR. IN FACT, THIS INTERACTION WILL FAVOR QUITE A LONG FETCH
OF NORTHERLY FLOW EXTENDING ALL THE WAY UP TO THE CHUKCHI SEA,
ALLOWING SOME OF THE COLDEST AIR WE'VE SEEN IN SOUTHWEST SINCE THE
SPRINGTIME MONTHS TO MAKE IT DOWN INTO THE REGION ON THURSDAY.
MORNING LOWS FOR THURSDAY WILL LIKELY DIP INTO THE MID 30S TO LOW
40S, AND POSSIBLY EVEN A FEW DEGREES COLDER FOR ANY PLACES THAT
SEE PERSISTING NORTHWEST WINDS DECOUPLE FROM THE SURFACE.
MEANWHILE, OUT ACROSS THE BERING, A WEAK LOW WILL PUSH ANOTHER
ROUND OF RAIN SHOWERS ACROSS THE WESTERN AND CENTRAL ALEUTIANS
THROUGH THURSDAY EVENING.
AS
LONG TERM FORECAST (DAYS 4 THROUGH 7 - FRIDAY THROUGH MONDAY)
MODEL AGREEMENT BY FRIDAY IS LOOSE, HOWEVER GENERALLY A LOW IS
EXPECTED TO BE SITUATED IN THE NORTHERN GULF OF ALASKA BRINGING
RAIN TO THE SOUTHCENTRAL COASTLINE. INLAND PRECIPITATION IS
EXPECTED TO BE LIGHTER AND PRIMARILY CONFINED TO HIGHER
ELEVATIONS. VALLEYS AND THE LEE SIDE OF THE MOUNTAIN RANGES WILL
REMAIN MOSTLY DRY. OUT WEST, AGREEMENT IS WORSE WITH WEAK FEATURES
MOVING THROUGH THE REGION AND MODELS NOT COMING TOGETHER ON
PLACEMENT OR TIMING, HOWEVER A GENERALLY UNSETTLED PATTERN IS
LIKELY DUE TO THE LACK OF ANY MAJOR FEATURES SUCH AS A LOW OR
RIDGE.
BY SATURDAY, THERE IS MODERATE CONFIDENCE TOWARDS A LOW PRESSURE
SYSTEM DEVELOPING IN THE NORTHERN PACIFIC AND ADVANCING TOWARDS
THE SOUTHWESTERN GULF OF ALASKA BY LATE SUNDAY. AGREEMENT ON THE
TRACK OF THIS LOW IS POOR, WITH SOME SOLUTIONS BRINGING IT UP NEAR
THE SOUTHERN ALASKA PENINSULA AND OTHERS TOWARD SOUTHEAST ALASKA.
EITHER WAY, THIS WOULD LIKELY RESULT IN EASTERLY FLOW ACROSS THE
NORTHERN GULF COAST AND AN INCREASED RAIN POTENTIAL EARLY NEXT
WEEK FOR SOUTHERN ALASKA.
-CL
AVIATION
PANC...LOW LEVEL WIND SHEAR IS EXPECTED WITH LIGHTER NORTHERLY
FLOW AT THE SURFACE AND STRENGTHENING SOUTHEASTERLY WINDS ABOVE
1000 FEET LATE THIS AFTERNOON/EVENING. CONDITIONS OTHERWISE ARE
ANTICIPATED TO REMAIN PRIMARILY VFR. PRECIPITATION IS EXPECTED TO
BEGIN LATE THIS MORNING, BUT INCREASING SOUTHEASTERLY FLOW OVER
THE MOUNTAINS WILL HELP KEEP ANY RAINFALL RELATIVELY LIGHT.
HOWEVER, CEILINGS COULD DIP TO MVFR LEVELS DURING PERIODS OF
HEAVIER RAIN.
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