775
FXAK68 PAFC 161332
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
532 AM AKDT WED SEP 16 2026
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3:
WEDNESDAY THROUGH FRIDAY EVENING)...
KEY MESSAGES:
- WIND ADVISORIES REMAIN IN EFFECT FOR ANCHORAGE BOWL AND COASTAL
PORTIONS OF WESTERN KENAI PENINSULA THROUGH NOON TODAY.
- A HYDROLOGIC OUTLOOK REMAINS IN EFFECT FOR SUSITNA VALLEY, AS
STEADY RAIN FROM YESTERDAY MAY RESULT IN RIVERS REACHING
BANKFULL CONDITIONS.
- TOWARDS THE END OF THE WORKWEEK, TRENDING LESS STORMY WITH
LIGHTER WINDS, SCATTERED RAIN SHOWERS, AND COOLER OVERNIGHT LOW
TEMPERATURES.
DISCUSSION:
AS OF 4 AM THIS MORNING, A LARGE, OCCLUDED SURFACE LOW SITS NEAR
GALENA, MOVING EAST ACROSS INTERIOR ALASKA. A COLD FRONT
ASSOCIATED WITH THIS LOW IS SWEEPING EAST ACROSS THE COPPER RIVER
BASIN, WITH ANY LINGERING RAINFALL QUICKLY TAPERING OFF IN THE
WAKE OF THE FRONT. AREAS OF LOW STRATUS AND FOG PERSIST THIS
MORNING ACROSS PRINCE WILLIAM SOUND, PARTS OF THE COPPER RIVER
BASIN, AND FROM NORTH OF ANCHORAGE INTO THE SUSITNA VALLEY. THE
BIGGER STORY, HOWEVER, IS THE REDEVELOPMENT OF STRONG SOUTHERLY
WINDS ACROSS COOK INLET AND THE ANCHORAGE BOWL NORTH TO TALKEETNA
AS COLDER AND DRIER AIR ADVECTS OVER THE REGION BEHIND THE COLD
FRONT. A PEAK GUST OF 43 MPH HAS BEEN RECORDED AT KENAI AND
NIKISKI WITH A GUST TO 48 MPH AT THE PORT OF ANCHORAGE.
RAINFALL WITH THIS SYSTEM WAS ALSO QUITE IMPRESSIVE, WITH 36 HOUR
TOTALS OF OVER 1" FOR ANCHORAGE, NEAR 2" FOR TALKEETNA, AND OVER
2" FOR CORDOVA. FOR ANCHORAGE, THE 1.16" OF RAIN RECORDED
YESTERDAY IS A NEW DAILY RECORD, BREAKING THE OLD RECORD OF 0.94"
SET IN 2015. MOREOVER, IT WAS THE 11TH WETTEST DAY IN SEPTEMBER
AND THE WETTEST SEPTEMBER DAY SINCE SEPTEMBER 29TH, 2015.
THERE IS HIGH CONFIDENCE (>90%) THAT THE GUSTY SOUTHERLY WINDS
ACROSS COOK INLET, ANCHORAGE, AND THE SUSITNA AND COPPER RIVER
VALLEYS WILL PERSIST INTO THE AFTERNOON HOURS TODAY AS THE LOW
CONTINUES TO TRACK INLAND AND COLDER AIR ALOFT ADVECTS OVER
SOUTHCENTRAL. THERE IS ALSO HIGH CONFIDENCE (>90%) THAT GUSTS
FROM THE WESTERN KENAI PENINSULA NORTH TO ANCHORAGE EXCEED 40 MPH
AT TIMES WITH A LOWER PROBABILITY (20-30%) OF GUSTS REACHING OR
EXCEEDING 50 MPH. FOR TALKEETNA AND GLENNALLEN, THERE IS HIGH
CONFIDENCE (80-90%) FOR GUSTS 25 TO 35 MPH.
THERE REMAINS A HIGH LIKELIHOOD THAT THESE WINDS DIMINISH IN
INTENSITY BY LATER THIS EVENING AS THE LOW OVER THE INTERIOR
FURTHER WEAKENS AS IT MOVES OVER THE YUKON FLATS, EXITS THE
STATE, AND THE COLD AIR ADVECTION SUBSIDES. SHOWERS LIKELY
(60-70%) LINGER AT HIGHER ELEVATION TODAY DUE TO THE INSTABILITY
FROM THE COLD AIR ALOFT.
MODEL CONSENSUS SUPPORTS A HIGHER LIKELIHOOD (60-70%) OF RAIN
EXTENDING FROM PRINCE WILLIAM SOUND WEST INTO THE SUSITNA VALLEY
LATE TONIGHT INTO THURSDAY MORNING AS SHORTWAVE TROUGH LIFTS NORTH
OVER THE REGION. THERE IS A CHANCE (30-40%) THAT ANCHORAGE COULD
SEE A BRIEF PERIOD OF RAIN WITH THIS SYSTEM.
BY THURSDAY AFTERNOON, ANOTHER LOW MOVES FROM THE BERING SEA INTO
SOUTHWEST ALASKA, BRINGING A RETURN OF SHOWERS TO KODIAK ISLAND.
CONFIDENCE IS INCREASING THAT THE SHORTWAVE TROUGH ASSOCIATED
WITH THIS SYSTEM BECOMES NEGATIVELY TILTED AS IT MOVES SOUTH
ACROSS THE ALASKA PENINSULA. THIS EVOLUTION SUPPORTS A DEVELOPING
SOUTHEASTERLY WIND FLOW ALOFT OUT AHEAD OF THE TROUGH WITH A
SHORTWAVE UPSTREAM MOVING NORTH TOWARD THE KENAI PENINSULA WITH A
SURFACE LOW MOVING INTO PRINCE WILLIAM SOUND. THIS SOLUTION
RESULTS IN A HIGH LIKELIHOOD (70-80%) OF RAIN SHOWERS SPREAD
ACROSS MOST OF THE SOUTHCENTRAL MAINLAND LATE THURSDAY INTO
FRIDAY.
ONE THING TO WATCH LATER THIS WEEK WILL BE THE POTENTIAL FOR
STRONGER CONVECTION, AND PERHAPS EVEN THUNDERSTORMS. THE UPPER
LEVEL SETUP WILL HAVE LOTS OF EMBEDDED SHORTWAVES; THAT, COUPLED
WITH COLD AIR ADVECTION AND STILL-WARM OCEAN TEMPERATURES, COULD
LEAD TO A CHANCE FOR HEAVIER SHOWERS AND SOME LIGHTNING AROUND
PRINCE WILLIAM SOUND AND KODIAK ISLAND. IT'S HARD TO SAY FOR NOW
EXACTLY WHERE AND WHEN THUNDERSTORMS MIGHT OCCUR, SO THAT ASPECT
OF THE FORECAST MAY BE SOMETHING TO MONITOR AS WE SLOWLY HONE IN
ON LIGHTNING POTENTIAL.
-TM/KC
.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS
(DAYS 1 THROUGH 3: TODAY THROUGH SATURDAY MORNING)...
KEY MESSAGES:
* A COASTAL FLOOD ADVISORY IN EFFECT UNTIL 10AM THIS MORNING FOR
THE KUSKOKWIM DELTA COAST. WATER LEVELS ARE EXPECTED TO RISE
ANYWHERE FROM 1.5 TO 4.0 FEET ABOVE THE NORMAL HIGH TIDE LINE.
* A FLOOD ADVISORY IN EFFECT FOR THE KUSKOKWIM RIVER NEAR BETHEL
UNTIL 1PM THIS AFTERNOON AS WATER LEVELS MAY RE-ENTER MINOR
FLOOD STAGE WITH THIS MORNING'S HIGH TIDE CYCLE.
DISCUSSION:
THE STRONG LOW PRESSURE SYSTEM THAT BROUGHT WATER LEVEL RISES
ALONG THE KUSKOKWIM DELTA COAST AND UP THE KUSKOKWIM RIVER TO
BETHEL CONTINUES TO MOVE INLAND OF NORTON SOUND THIS MORNING.
SHOWERS CONTINUE THROUGH TODAY AND THE REST OF THE SHORT-TERM
THROUGH SATURDAY MORNING AS ADDITIONAL SHORTWAVES MOVES ACROSS THE
AREA FROM THE BERING SEA. A MORE CONSOLIDATED LOW PRESSURE SYSTEM
MOVES ACROSS THE BERING TO SOUTHWEST ALASKA BY THURSDAY MORNING
WHICH WILL ALSO AID IN THE CONTINUATION OF SHOWERY CONDITIONS
ACROSS THE AREA. THIS LOW IS EXPECTED TO BE QUITE WEAK COMPARED TO
THE LOW THAT BROUGHT IMPACTS YESTERDAY AND THIS MORNING TO THE
KUSKOKWIM DELTA. SOUTHERLY TO SOUTHWEST WINDS ARE LIKELY (60 TO
90% CHANCE) TO GO UP KUSKOKWIM BAY AND KUSKOKWIM RIVER THROUGH
THURSDAY. HOWEVER, INSTEAD OF 50 TO 60 MPH WINDS LIKE THE SYSTEM
YESTERDAY, ANTICIPATE 20 TO 30 MPH WINDS GOING UP THE BAY. THIS
SYSTEM WILL LINGER ALONG THE COAST THROUGH FRIDAY AS IT WEAKENS.
MOVING INTO FRIDAY EVENING AND SATURDAY, A TROUGH FROM THE ARCTIC
BEGINS TO DIG SOUTH INTO THE NORTHERN BERING BRINGING A BATCH OF
COLD AIR WITH IT. SHORTWAVES EMBEDDED IN THE NORTHERLY FLOW AHEAD
OF THIS TROUGH WILL KEEP SHOWERS GOING ACROSS THE ALEUTIAN CHAIN,
ALASKA PENINSULA (AKPEN), AND SOUTHWEST ALASKA. ONE OF THE
FORECAST CHALLENGES THIS WEEKEND WILL BE TO GAUGE HOW STRONG THE
COLD AIR PUSH SOUTH THROUGH THE BERING WILL BE WITH RESPECT TO
STRENGTH OF NORTHERLY GAP WINDS THROUGH THE ALEUTIAN CHAIN AND
AKPEN. STAY TUNED FOR FORECAST UPDATES AS THE UNSETTLED WEATHER
PATTERN CONTINUES.
LONG TERM FORECAST (DAYS 4 TO 7, SATURDAY THROUGH TUESDAY)
GOING INTO THE WEEKEND, A LONGWAVE UPPER LEVEL TROUGH WILL BE
OVER MAINLAND ALASKA WITH A DEEPENING LOW AT THE BASE OF THE
TROUGH IN THE NORTH PACIFIC. THE LOW MOVES NORTHEASTWARD INTO THE
GULF ON SATURDAY, WITH GUIDANCE SHOWING LOWEST SURFACE PRESSURE
AROUND 980 MB EARLY SUNDAY MORNING. A TIGHTENING PRESSURE GRADIENT
WILL PROMOTE SMALL- CRAFT TO GALE-FORCE WINDS THROUGHOUT THE GULF AROUND
THE LOW, AS WELL AS ACCELERATE GAP WINDS IN FAVORABLE AREAS
(NORTHWEST WINDS THROUGH THE AKPEN, SOUTHEAST WINDS IN TURNAGAIN
ARM AND COPPER RIVER VALLEY). MOISTURE PULLED IN FROM THE PACIFIC
WILL PROMOTE RAINFALL FOR THE NORTHERN GULF COAST THROUGH THE
WEEKEND, WITH THE HEAVIEST RAIN EXPECTED SATURDAY NIGHT THROUGH
MONDAY MORNING. LIGHTER RAIN MAY SPILL OVER INTO INTERIOR
LOCATIONS OF SOUTHCENTRAL THROUGHOUT THE WEEKEND, WITH HIGHEST
CHANCES IN THE SUSITNA VALLEY. OUT WEST, PERSISTENT SHORTWAVES
WILL MAINTAIN OVERCAST SKIES WITH OCCASIONAL SHOWERS FOR
SOUTHWEST, THE BERING, THE ALEUTIANS AND THE AKPEN THROUGH MONDAY
MORNING. WITH THE AKPEN BEING CLOSEST TO THE LOW, CHANCES FOR
SHOWERS WILL BE HIGHEST THERE.
BEGINNING MONDAY MORNING, A RIDGE LOOKS TO BUILD IN THE BERING AS
LONGWAVE TROUGHING CONTINUES OVER THE MAINLAND. SHOWERS ARE
EXPECTED TO LINGER ACROSS COASTAL SOUTHCENTRAL AND PARTS OF THE
AKPEN, WITH SOME SMALL CRAFT WINDS POSSIBLE THROUGH GAPS IN THE
AKPEN AS WELL GIVEN COLD AIR ADVECTION ON THE WEST SIDE OF THE
LOW. FORECAST CONFIDENCE DECREASES MONDAY AS MODELS DIVERGE ON
SOLUTIONS. IN GENERAL, MODELS HINT AT THE RIDGE SLOWLY MOVING
EAST ON TUESDAY TO THE EASTERN BERING. THIS MAY TAPER OFF
LINGERING SHOWERS FOR THE AKPEN AND GULF COAST ON TUESDAY AND
PROMOTE QUIETER WEATHER ACROSS SOUTHERN ALASKA. DETAILS WILL
BECOME MORE CLEAR IN THE COMING DAYS.
- PA
AVIATION
PANC...THERE IS HIGH CONFIDENCE (>90%) THAT STRONG SOUTHERLY WINDS
PERSIST ACROSS THE TERMINAL TODAY WITH GUSTS UP TO 35 KT THROUGH
MID AFTERNOON. WINDS DIMINISH THIS EVENING AND BECOME LIGHTER
OVERNIGHT. A HIGH LIKELIHOOD (70-80%)THAT VFR CONDITIONS PERSIST
THROUGH MUCH OF THE TAF PERIOD, THOUGH VICINITY SHOWERS ARE
POSSIBLE (20-30% CHANCE) THIS AFTERNOON AND EVENING. CEILINGS
LOWER AGAIN THURSDAY MORNING WITH LIGHT RAIN DEVELOPING AND MVFR
CONDITIONS LIKELY (60%) BY LATE THURSDAY MORNING. SOUTHERLY WINDS
ALSO INCREASE THURSDAY MORNING WITH GUSTS AROUND 20 KT.
LM/TM
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