939
FXAK68 PAFC 181249
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
449 AM AKDT THU SEP 18 2025
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3: TODAY
THROUGH SATURDAY NIGHT)...
THE RESPITE IN GLOOMY WEATHER HAS ENDED AS MORE QUINTESSENTIALLY-
SEPTEMBER ALASKA WEATHER HAS RETURNED. SATELLITE IMAGERY REVEALS
CLOUD COVER HAS SPREAD BACK ACROSS MUCH OF SOUTHCENTRAL ALASKA
AMID SOUTHWESTERLY CYCLONIC FLOW. RADAR SHOWS SHOWERY ACTIVITY
ACROSS MUCH OF THE NORTHERN GULF OF ALASKA, AS WELL AS INTO THE
KENAI PENINSULA AND NORTH/WEST SUSITNA VALLEY.
THIS WILL BE THE CASE AS CONTINUE THROUGH THE END OF THE WEEK AS
MOIST SOUTHERLY FLOW PREVAILS WITH A SERIES OF WEAK FEATURES
TRAVERSING THE GULF OF ALASKA INTO SOUTHCENTRAL. THIS WILL PROMOTE
PERIODS OF RAINFALL OVER THE GULF WITH UPSLOPE SHOWERS ALONG MUCH
OF THE NORTH GULF COAST TODAY AND FRIDAY. PERIODS OF LIGHT RAIN
ARE ALSO POSSIBLE FOR INLAND LOCATIONS AS MORE POTENT SHORTWAVES
LIFT PAST THE MOUNTAINS. SHOWERS MAY ALSO SPREAD INLAND THURSDAY
NIGHT AS A WEAK FRONT LIFTS PAST THE COASTAL MOUNTAINS.
ACCUMULATIONS WOULD BE FAIRLY LIGHT.
FRIDAY NIGHT INTO SATURDAY, MORE COHERENT LOW PRESSURE TRACKS
ACROSS THE SOUTHERN GULF, WEAKENING THE SOUTHERLY FLOW ALONG THE
NORTH GULF COAST OR EVEN SHIFTING FLOW TO WEAK NORTHERLY ACROSS
SOUTHCENTRAL. THIS REVERSAL OF FLOW WILL RESULT IN A DRYING TREND
BOTH ALONG THE COAST AND INLAND FOR AT LEAST SOME PORTION OF THIS
WEEKEND.
-BROWN/QUESADA
.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (DAYS
1 THROUGH 3)...
THE FORECAST CONTINUES TO REMAIN LOW IMPACT AND ON TRACK.
CURRENTLY, A VERTICALLY STACKED ~990 MB LOW CENTERED ACROSS THE
WESTERN ALEUTIANS CONTINUES TO WEAKEN AND ELONGATE THIS MORNING.
ITS UPPER LEVEL ENVIRONMENT CONSISTS OF A RELATIVELY DEEP UPPER
LEVEL LOW ENVELOPED IN A LONGWAVE AND POSITIVELY TILTED TROUGH. AS
THE LONGWAVE TROUGH CONTINUES TO DIG SOUTHWARD, IT WILL DEEPEN
AND SOMEWHAT AMPLIFY THE UPPER LEVEL PATTERN. FARTHER EAST, A
SHORTWAVE TROUGH IS LIFTING AND DECAYING AS IT MOVES OVER THE AK
PEN, BUT HAS PROVIDED ENOUGH FORCING TO DEVELOP A WEAK AREA OF LOW
PRESSURE WELL SOUTH OF THE AK PEN AND KODIAK ISLAND THAT IS
MOVING INTO THE GULF OF ALASKA. MEANWHILE, THERE IS STILL AN
OCCLUDED FRONT AND SURFACE TROUGH DRAPED FROM THE CENTRAL BERING
SEA SOUTHEASTWARD ACROSS THE AK PEN, WHICH HAS BEEN THE MAIN FOCAL
POINT FOR AREAS OF RAIN SHOWERS. ACROSS SOUTHWEST ALASKA, MOSTLY
CLEAR SKIES EARLIER THIS MORNING BEFORE CLOUDS ROLLED IN AND LIGHT
WINDS FOR THE INTERIOR KUSKOKWIM VALLEY ALLOWED LOW TEMPERATURES
TO BOTTOM OUT IN THE MID TO UPPER 30S FOR MOST, WHICH WAS A BIT
COLDER THAN GFS/NAM MOS GUIDANCE. MUCH OF THE REGION HAS OBSERVED
TEMPERATURES WARMING BY AT LEAST A COUPLE OF DEGREES DUE TO CLOUDS
AND EVEN SOME ISOLATED AREAS OF FOG.
THROUGH FRIDAY MORNING, THE SURFACE LOW ACROSS THE WESTERN
ALEUTIANS TREKS EASTWARD ACROSS THE SOUTHERN BERING SEA AND STOPS
JUST SHORT OF BRISTOL BAY, BREAKING DOWN INTO A COMPLEX LOW AS IT
DOES SO. MODELS ARE IN FAIR AGREEMENT OF THIS EVOLUTION, ALTHOUGH
THE EURO IS MORE BULLISH ON RAINFALL AND KEEPS THE TROUGH/LOW
ENVELOPE A TICK STRONGER THAN THE GFS AND NAM. LOOKING THROUGH
MIDDAY FRIDAY, THE UPPER LEVEL TROUGH TAKES A NEGATIVE TILT AND
THE SURFACE LOW NEAR BRISTOL BAY PHASES WITH A NEW SURFACE LOW IN
THE WESTERN GULF OF ALASKA. BY SATURDAY MORNING, A ROBUST 500 MB
SHORTWAVE RIPPLES INTO THE CENTRAL BERING FROM THE NORTH, WHILE
THE MAIN LONGWAVE TROUGH RIDES SOUTH OF THE ALEUTIAN CHAIN WITHIN
THE UPPER JET. THESE TWO FEATURES ALSO LOOK TO PHASE SUNDAY
MORNING. THE SYNOPTIC FORCING WILL LIKELY RESULT IN INCREASED
NORTHWESTERLY SURFACE WINDS ACROSS THE BERING SEA, ALEUTIANS, AND
AK PEN THROUGH THE WEEKEND ALONG WITH INCREASED RAIN CHANCES.
ALONG WITH COLD AIR ADVECTION FOR THE REGION, WINDS UP TO 30 KTS
OR SO WILL BE POSSIBLE THROUGH FAVORED BAYS AND PASSES OF THE
CENTRAL ALEUTIANS TO THE AK PEN.
-AM
LONG TERM FORECAST (DAYS 4 THROUGH 7: SUNDAY THROUGH WEDNESDAY)
UPPER LEVEL LOW PRESSURE IS EXPECTED TO LINGER IN THE GULF OF
ALASKA FROM THE WEEKEND THROUGH MID-WEEK. SHORTWAVE TROUGHS AND
EMBEDDED SURFACE LOWS WILL BRING ENHANCED PERIODS OF RAIN AND WIND
TO THE NORTH GULF COAST. THE HEAVIEST RAIN AND STRONGEST WINDS
LOOK TO STAY IN THE PANHANDLE, BUT PRINCE WILLIAM SOUND AND THE
EASTERN KENAI PENINSULA WILL SEE PLENTY OF MOISTURE AND WIND IN
COASTAL WATERS AS WELL. THERE IS SOME UNCERTAINTY IN THE
ORIENTATION OF THE LOW AS IT PROGRESSES THROUGH THE BEGINNING OF
THE WEEK, WHICH WILL GREATLY IMPACT THE ABILITY FOR SHOWERS TO
DEVELOP ACROSS INLAND AREAS. THE SUGGESTION OF SOUTHWESTERLY
UPPER LEVEL FLOW WOULD BE FAVORABLE FOR PRECIPITATION UP COOK
INLET AND INTO THE MAT-SU VALLEYS, THOUGH RAIN SHOULD REMAIN
RELATIVELY LIGHT IN THESE AREAS IF IT DOES DEVELOP.
PERSISTENT NORTHERLY FLOW ACROSS WESTERN ALASKA AND THE BERING
SEA WILL BRING A COOLING TREND TO THE REGION AS OVERNIGHT LOWS ARE
EXPECTED TO DIP INTO THE 30'S FOR PORTIONS OF SOUTHWEST ALASKA.
THE COMBINATION OF COLD AIR ADVECTION AND A TIGHT PRESSURE
GRADIENT WILL BRING GUSTY WINDS THROUGH GAPS AND PASSES OF THE
ALASKA PENINSULA AND EASTERN ALEUTIANS ON SUNDAY AND MONDAY. THE
ALEUTIAN CHAIN WILL SEE ANOTHER ROUND OF RAIN AND WIND ON TUESDAY
WHILE THE REST OF SOUTHWEST REMAINS DRY FOR THE REMAINDER OF THE
LONG TERM FORECAST PERIOD.
AVIATION
PANC...VFR CONDITIONS WILL PERSIST THROUGH THE DAY TODAY BEFORE
POSSIBLE DEGRADATION TONIGHT. SOUTHEAST WINDS WILL CONTINUE
THROUGH THE MORNING AS THE AIRPORT SITS ON THE NORTHERN PERIPHERY
OF STRONGER SOUTHEAST WINDS OUT OF THE TURNAGAIN ARM. OCCASIONAL
HIGHER GUSTS MAY REACH THE AIRPORT, BUT THE STRONGEST WINDS ARE
EXPECTED TO REMAIN SOUTH. THIS WILL SHIFT LATER TODAY AS WINDS
BECOME LIGHT AND OUT OF THE NORTH. ISOLATED SHOWERS WILL BE IN THE
AREA THROUGH THE MORNING AND AFTERNOON BEFORE AN INCREASE IN
COVERAGE OVERNIGHT. CEILINGS SHOULD LOWER TONIGHT AS WELL INTO
MVFR OR POSSIBLY EVEN IFR TERRITORY AS THE LOWER ATMOSPHERE
SATURATES.
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