924
FXAK68 PAFC 181305
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
505 AM AKDT FRI SEP 18 2026
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3:
TODAY THROUGH SUNDAY EVENING)...
DISCUSSION:
THE PATTERN ACROSS THE SOUTHERN MAINLAND THIS MORNING IS DOMINATED
BY A NEGATIVELY TILTED UPPER-LEVEL TROUGH EXTENDING FROM THE
KUSKOKWIM DELTA COAST SOUTHEAST TO KODIAK ISLAND. FOR
SOUTHCENTRAL, SHOWERS ARE CONTINUING TO STREAM WESTWARD FROM THE
NORTHERN GULF ACROSS PRINCE WILLIAM SOUND AND THE KENAI
PENINSULA. THIS AREA OF SHOWERS IS BECOMING MORE PRONOUNCED AND
WIDESPREAD DUE TO A STRENGTHENING SOUTHEASTERLY FLOW ALOFT,
MOISTURE ADVECTION, AND LIFT OUT AHEAD OF AN UPPER-LEVEL SHORTWAVE
AND SURFACE TROUGH MOVING NORTHEAST FROM KODIAK ISLAND. SHOWER
ACTIVITY WILL REDEVELOP THIS MORNING ACROSS COOK INLET, ANCHORAGE,
AND PARTS OF THE MAT-SU VALLEYS AS THESE FEATURES CONTINUE TO
TRACK TOWARD NORTHWARD.
AS THE UPPER-LEVEL TROUGH DIGS SOUTH OF KODIAK ISLAND THIS
MORNING, A ROBUST SHORTWAVE WILL ROUND THE BASE OF THE TROUGH
THEN DRIVE NORTH AND INTENSIFY DUE TO GOOD JET SUPPORT. THIS WILL
DRIVE THE DEVELOPMENT OF A SURFACE LOW OVER THE NORTH PACIFIC THAT
WILL QUICKLY LIFT NORTHWARD OVER THE EASTERN GULF REACHING
MIDDLETON ISLAND AS A 992MB LOW BY LATE THIS AFTERNOON. THIS
SYSTEM, AND THE ASSOCIATED SHORTWAVE WILL MOVE INTO EASTERN
PRINCE WILLIAM SOUND THEN INLAND TOWARD THE EASTERN TALKEETNA
MOUNTAINS FOR SATURDAY MORNING. THERE IS BETTER MODEL CONSENSUS
THAT THE LOW WILL TAKE THIS SLIGHTLY MORE WESTWARD TRACK. AS SUCH,
THERE IS INCREASING CONFIDENCE FOR A PERIOD OF HEAVY RAIN AND
STRONG EASTERLY WINDS FROM CAPE SUCKLING TO HITCHINBROOK
ENTRANCE, INCLUDING CORDOVA, BEGINNING LATER THIS AFTERNOON. A
PERIOD OF GUSTY EASTERLY WINDS COULD ALSO MOVE OVER VALDEZ LATE
TONIGHT. STEADY RAIN WILL ALSO FALL FROM PRINCE WILLIAM SOUND
NORTH ACROSS MUCH OF THE COPPER RIVER BASIN. MOISTURE ALSO LOOKS
TO GET PULLED WESTWARD TOWARD THE TROUGH MOVING THROUGH COOK INLET
NORTH INTO THE SUSITNA VALLEY. THIS WILL LIKELY RESULT IN ANOTHER
ROUND OF RAIN FROM KENAI TO TALKEETNA THROUGH EARLY SATURDAY
MORNING BEFORE THE PRECIPITATION BECOMES MORE SCATTERED AND
SHOWERY. IT MY ALSO BE COLD ENOUGH OVERNIGHT FRIDAY INTO SATURDAY
MORNING FOR THE PRECIPITATION TO FALL AS SNOW, OR A RAIN/SNOW MIX
FROM EUREKA WEST TOWARD SHEEP MOUNTAIN.
MODELS THEN SHOW A ROBUST, DIGGING SHORTWAVE 500 MB TROUGH RIDING
SOUTH OF THE ALEUTIAN CHAIN AND BEGINNING TO TRANSLATE OVER THE
SOUTHERN GULF BY SATURDAY MORNING. THE PROGRESSION OF THIS FEATURE
WILL AID TO DEVELOP AND DEEPEN A LARGE SURFACE LOW PRESSURE
SYSTEM AS IT MOVES NORTHWARD ACROSS THE GULF SATURDAY MORNING.
MODELS DEEPEN THIS LOW IN THE 975 TO 985 MB RANGE, WHICH IS STRONG
ENOUGH FOR POTENTIAL GALES AS THE LOW LIFTS NORTHWARD. RAIN
AMOUNTS AND INTENSITY WILL ALSO BE SOMETHING TO WATCH, AS THE
NORTHERN GULF COAST (INCLUDING PRINCE WILLIAM SOUND AND EASTERN
KENAI PENINSULA) COULD SEE A LONG DURATION OF MODERATE RAIN.
LASTLY, WE ARE ARRIVING TO THE TIME OF YEAR WHERE SNOW LEVELS ARE
LOW ENOUGH IN THE MORNING FOR SOME AREAS TO WHERE WE CAN SEE SOME
HIGHER ELEVATION SNOWFALL. IN SAYING THAT, PLACES LIKE EUREKA LOOK
TO SEE SOME FLAKES FLY (40-60% CHANCE) SATURDAY MORNING, BUT VERY
LITTLE TO NO ACCUMULATION IS EXPECTED AT THIS TIME AND
TEMPERATURES ARE ON TRACK TO REBOUND INTO THE MID 40S FOR SATURDAY
AFTERNOON. NOW MAY BE THE TIME TO START THINKING ABOUT
WINTERIZING, ESPECIALLY AS TEMPERATURES BEGIN TO TREND COOLER
HEADING INTO NEXT WEEK.
-TM/AM
.SHORT TERM FORECAST SOUTHWEST ALASKA AND BERING SEA/ALEUTIANS
(DAYS 1 THROUGH 3)...
SATELLITE IMAGERY DEPICTS A LOW PRESSURE SYSTEM WITH A HIGH END
SMALL CRAFT FRONT MOVING EASTWARD ACROSS THE CENTRAL BERING WHILE
UPPER LEVEL CLOUD COVER CAN BE SEEN STREAMING NORTHWARD FROM A
NORTH PACIFIC LOW THAT IS APPROACHING THE ALASKA PENINSULA.
NESTLED IN BETWEEN THESE TWO SYSTEMS IS A FOG AND LOW STRATUS BANK
LOCKED IN ACROSS THE EASTERN BERING, NORTH PACIFIC, AND ALSO
ACROSS THE KUSKOKWIM DELTA REGION FOR AREAS LIKE BETHEL.
MEANWHILE, OUTSIDE OF AREAS OF FOG ACROSS SOUTHWEST ALASKA,
ISOLATED TO WIDELY SCATTERED SHOWERS AND THUNDERSTORMS HAVE
DEVELOPED WITH DAYTIME HEATING AND FROM WEAK WAVES EMBEDDED WITHIN
THE 500 MB MEAN FLOW FROM A RIDGE OF HIGH PRESSURE ANCHORED
ACROSS THE COOK INLET REGION OF SOUTHCENTRAL. THE FOCUS AND
HIGHEST CONFIDENCE OF THUNDERSTORM ACTIVITY THIS AFTERNOON THROUGH
EARLY TOMORROW MORNING WILL ALONG THE SLOPES OF THE KILBUCK
MOUNTAINS AND NEAR LIME VILLAGE, WITH CONVECTION MOVING NORTH-
NORTHEASTWARD WITH TIME. THIS WILL BE THE LAST DAY OF THUNDERSTORM
POTENTIAL FOR SOUTHWEST ALASKA DUE TO THE NORTH PACIFIC LOW
MOVING NORTHWARD THROUGH THE SHORT TERM FORECAST PERIOD, WHICH
WILL BRING IN A MORE STABLE AIRMASS AND DISPLACE ANY INSTABILITY
POTENTIAL FARTHER NORTH AND OUT OF THE REGION.
BY MID WEDNESDAY MORNING, THE BERING LOW NEARS THE PRIBILOF
ISLANDS AS ITS FRONT SLOWLY WEAKENS. TO THE SOUTHEAST, THE NORTH
PACIFIC LOW CONTINUES TO LIFT NORTHWARD. ITS LEADING FRONT WILL BE
CAPABLE OF SOUTHEASTERLY SMALL CRAFT WINDS, WITH EVEN STRONGER
WINDS FLOWING THROUGH FAVORED GAPS, BAYS, AND PASSES OF THE ALASKA
PENINSULA AND ACROSS THE BRISTOL BAY WATERS. THE MOVEMENT OF THE
NORTH PACIFIC LOW WILL NUDGE THE RIDGE FARTHER NORTHEASTWARD AND
THE FLOW BECOMES MORE DIFLUENT ACROSS SOUTHWEST ALASKA HEADING
INTO WEDNESDAY AFTERNOON.
-LM
LONG TERM FORECAST (DAYS 4 THROUGH 7: MONDAY THROUGH THURSDAY)
LONGWAVE TROUGH PATTERN DOMINATES SOUTHERN ALASKA EARLY NEXT WEEK.
THE MAIN LOW SITS IN THE GULF OF ALASKA THAT WILL MERGE WITH AN
A NORTH PACIFIC LOW AS IT MOVES TOWARDS THE SOUTHERN GULF OF
ALASKA ON TUESDAY. THERE IS RELATIVELY FAIR MODEL CONFIDENCE FOR
THIS LOW TRACKING INTO THE GULF, WEAKENING AND SHIFTING BACK SOUTH
THROUGH MID-WEEK NEXT WEEK. WIDESPREAD RAINFALL IS LIKELY ACROSS
SOUTHERN ALASKA, INCLUDING THE ALASKA PENINSULA AND ALEUTIAN
CHAIN, EARLY NEXT WEEK. AS THE INITIAL LOW FADES INTO THE NORTH
PACIFIC LOW AND THEN MOVES AWAY FROM THE SOUTHCENTRAL COAST,
PRECIPITATION WILL DIMINISH INLAND, LINGERING ALONG THE COAST
THROUGH WEDNESDAY MORNING.
MODEL CONFIDENCE IS STEADILY INCREASING FOR A LARGE LOW TO ENTER
THE BERING SEA MID TO LATE WEEK NEXT WEEK.
KM
AVIATION
PANC...LIGHT RAIN WILL ONCE AGAIN DEVELOP OVER THE TERMINAL THIS
MORNING ALONG WITH LIGHT AND VARIABLE WINDS. CEILINGS LOOK TO
REMAIN VFR THROUGH THIS MORNING; HOWEVER, CEILINGS MAY FALL BELOW
5,000 FT OR VERY BRIEFLY TO MVFR IN ANY HEAVIER RAIN SHOWERS.
MVFR CEILINGS ARE EXPECTED THIS AFTERNOON AS AN AREA OF LOW
PRESSURE MOVES INTO PRINCE WILLIAM SOUNDS AND A STEADIER RAIN
MOVES WEST FROM THE LOW AND OVER THE TERMINAL. ANY HEAVIER RAIN
LATE THIS AFTERNOON OR EVENING COULD ALSO LEAD TO MVFR
VISIBILITIES. A LIGHT NORTH WIND WILL SHIFT TO THE SOUTHWEST BY
THIS EVENING THEN TO A GUSTY SOUTHEAST WIND OUT OF TURNAGAIN ARM
AS THE LOW TRACKS INLAND AND NORTH OF THE REGION. AS THE LOW
WEAKENS AND CONTINUES TO MOVE NORTH, THE GUSTY WINDS WILL AND RAIN
WILL BOTH DIMINISH. THE LIGHT AND VARIABLE WINDS OVERNIGHT AND
INTO SATURDAY, COMBINED WITH LINGERING LOW-LEVEL MOISTURE, COULD
RESULT IN PATCHY FOG NEAR OR OVER THE TERMINAL.
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