970
FXAK68 PAFC 160147
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
547 PM AKDT TUE SEP 15 2026
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3:
THIS AFTERNOON THROUGH FRIDAY AFTERNOON)...
KEY MESSAGES:
- A STRONG FALL STORM MOVING INTO WESTERN ALASKA WILL BRING GUSTY
SOUTHERLY WINDS AND PERIODS OF HEAVY RAIN TO SOUTHCENTRAL FROM
NOW THROUGH TOMORROW AFTERNOON.
- WIND ADVISORIES REMAIN IN EFFECT FOR ANCHORAGE BOWL AND COASTAL
PORTIONS OF WESTERN KENAI PENINSULA THROUGH NOON TOMORROW.
- A HYDROLOGIC OUTLOOK REMAINS IN EFFECT FOR SUSITNA VALLEY, AS
STEADY RAIN COULD CAUSE LOCALIZED PONDING AND 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:
THE FORECAST REMAINS VERY MUCH ON TRACK, WITH THE SURFACE LOW OUT
WEST SLOWLY OCCLUDING AS IT APPROACHES THE SEWARD PENINSULA THIS
AFTERNOON. A STRONG SOUTHEAST TO NORTHWEST PRESSURE GRADIENT
BETWEEN THE LOW AND HIGHER PRESSURE LINGERING OVER THE GULF IS
PRODUCING ROBUST SOUTHERLY FLOW ACROSS SOUTHCENTRAL ALASKA. GAP
WINDS KICKED IN EARLIER THIS MORNING AND WILL BE PEAKING LATER
THIS AFTERNOON. CURRENT TOP GUSTS ARE 42 MPH ALONG THE GLENN
HIGHWAY S CURVES NEAR EAGLE RIVER, 41 MPH NEAR GLENNALLEN, 37 MPH
IN SELDOVIA, AND 35 MPH AT TED STEVENS IN WEST ANCHORAGE.
OVERALL, THE WIND FORECAST LOOKS FAIRLY ON TRACK FOR ALL BUT
PALMER, WHERE WINDS HAVE BEEN SLOW TO INCREASE AND MAY NOT QUITE
REACH THE HIGHER SPEEDS THAT WE'VE BEEN PREDICTING.
ASIDE FROM WINDS, RAIN AMOUNTS AND INTENSITY HAVE REALLY PICKED UP
AS A TRAILING COLD FRONT BEGINS TO SWEEP ACROSS SOUTHCENTRAL FROM
WEST TO EAST, SENDING ANOTHER BATCH OF MODERATE TO HEAVY RAINFALL
THROUGH THE REGION AS IT PASSES THROUGH. GAP WINDS ACROSS THE MAT
VALLEY AND TURNAGAIN ARM WILL SHUT OFF QUICKLY BEHIND THE FRONTAL
PASSAGE BY TUESDAY NIGHT. HOWEVER, A SECOND CORRIDOR OF STRONG
WINDS, AIDED BY COLD AIR ADVECTION AND A TRAILING SHORTWAVE, WILL
EXTEND FROM KAMISHAK BAY UP THE COOK INLET, SENDING ANOTHER ROUND
OF STRONG SOUTH WINDS INTO ANCHORAGE AND MUCH OF THE COASTLINE OF
THE KENAI PENINSULA, WITH GUSTS AGAIN TOPPING OUT AROUND THE 40 TO
50 MPH RANGE OVERNIGHT TONIGHT INTO EARLY TOMORROW MORNING. GUSTS
OF 30 TO 40 MPH ARE ALSO POSSIBLE ACROSS THE SUSITNA VALLEY TO
TALKEETNA. IT'S WORTH NOTING THAT WE STILL HAVE YET TO SEE MOST OF
OUR TREES TRULY START TO TURN YELLOW, SO THEY WILL BE MORE
SUSCEPTIBLE TO DAMAGE FROM THE GUSTY WINDS THAN WHAT WE WOULD
EXPECT LATER IN THE FALL.
BY EARLY TOMORROW MORNING, RAIN WILL BEGIN TO TAPER OFF AS A
DRIER AND COOLER AIR MASS WORKS IN BEHIND THE FRONT AS IT EXITS TO
THE EAST. A FEW LINGERING SHOWERS COULD CONTINUE ON AND OFF
THROUGHOUT THE DAY, BUT OVERALL IT SHOULD BE MUCH DRIER COMPARED
TO TODAY. GUSTY SOUTH TO SOUTHWEST WINDS WILL SLOWLY RELAX
THROUGH TOMORROW AFTERNOON AS COLD AIR ADVECTION WANES AND AS A
TRANSIENT UPPER LEVEL RIDGE BEGINS TO BUILD BACK OVERHEAD. SHOWERS
WILL LINGER MOSTLY AT HIGHER ELEVATION, BUT AN INCOMING SHORTWAVE
COULD PRODUCE A BROADER REGION OF RAIN AROUND PRINCE WILLIAM
SOUND TOMORROW NIGHT INTO THURSDAY. BY THURSDAY AFTERNOON,
ANOTHER LOW MOVES FROM THE BERING SEA INTO SOUTHWEST ALASKA,
BRINGING A RETURN OF SHOWERS TO KODIAK ISLAND. SHOWERS SPREAD
ACROSS THE SOUTHCENTRAL MAINLAND AS THE LOW MOVES INTO THE GULF
LATER ON 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)...
KEY MESSAGES:
* A WIND ADVISORY IS IN EFFECT UNTIL 1AM WEDNESDAY FOR THE
KUSKOKWIM DELTA COAST AND INTERIOR KUSKOKWIM DELTA FOR WINDS OF
35 TO 45 MPH WITH GUSTS TO 60 MPH EXPECTED.
* A COASTAL FLOOD ADVISORY IN EFFECT UNTIL 10AM WEDNESDAY 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.
DISCUSSION:
A STRONG LOW THAT TRAVERSED THE BERING SEA THE PAST 48 HOURS
MOVED NORTHWARD AND OUT OF THE REGION THIS AFTERNOON. IN ITS WAKE,
A FAST- MOVING RIDGE MOVES ACROSS THE BERING SEA TOMORROW MORNING
FOLLOWED BY WEAK LOWS MOVING THROUGH THE BERING SEA THROUGH THE
LATTER PART OF THIS WEEK.
ALONG THE SOUTHWEST ALASKA COASTLINE, SOUTHWESTERLY/SOUTH WIND
GUSTS RANGING FROM 50 TO 60 MPH THROUGH EARLY THIS AFTERNOON WILL
SLOWLY SUBSIDE OVERNIGHT WITH A 25% CHANCE OF WIND GUSTS EXCEEDING
55 MPH BY 10 PM AND A LESS THAN 5% CHANCE BY 3 AM. WINDS ACROSS
SOUTHWEST ALASKA BECOME MORE ZONAL WITH EAST- WEST FLOW BY MID-
MORNING TOMORROW. HOWEVER, A RETURN TO A MORE SOUTHWESTERLY WIND
DIRECTION BY THE LATE AFTERNOON HOURS WITH GUSTS ABOVE 40 MPH
ALONG THE COAST AT A 10% CHANCE FROM TOMORROW AFTERNOON INTO LATE
THURSDAY MORNING. THIS CHANGE IN WIND DIRECTION SIGNALS THE
ARRIVAL OF THE FIRST WEAK LOW PRESSURE SYSTEM. AS THIS LOW MOVES
ACROSS THE BERING SEA, NORTHWESTERLY TO NORTHERLY WINDS IN ITS
WAKE ARE EXPECTED THURSDAY THROUGH THE CENTRAL ALEUTIANS. A BRIEF
PERIOD OF AFTERNOON GUSTS TO 40 MPH TOMORROW FROM ADAK TO UNALASKA
IS 35% LIKELY. IN ADDITION TO THE WIND GUSTS THE NEXT FEW DAYS,
SHOWERY CONDITIONS WILL PERSIST ACROSS THE ALEUTIANS AND SOUTHWEST
ALASKA AS SHORTWAVES FROM THIS LOW MOVE ACROSS THE BERING SEA. A
SECOND LOW MOVES INTO THE NORTH PACIFIC LATTER THIS WEEK.
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...SOUTHEASTERLY WINDS WILL INCREASE RAPIDLY TUESDAY MORNING,
WITH GUSTS REACHING 30 KT BY 15Z AND 40 KT BY 20Z. VFR CONDITIONS
WILL PREVAIL INITIALLY, WITH LIGHT RAIN SHOWERS DEVELOPING AROUND
08Z. CEILINGS WILL LOWER TO MVFR BY 20Z AS STEADIER RAIN
DEVELOPS, WITH MVFR CONDITIONS PERSISTING THROUGH THE REMAINDER OF
THE TAF PERIOD. WINDS BECOME MORE SOUTHERLY TUESDAY EVENING WHILE
REMAINING GUSTY.
LM
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