039
FXAK68 PAFC 140039
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
439 PM AKDT WED AUG 13 2025
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3:
TONIGHT THROUGH SATURDAY)...
A SERIES OF SHORTWAVES MOVING INTO SOUTHCENTRAL ALASKA FROM THE
WEST WILL BRING PERIODS OF LIGHT RAIN FROM THE KENAI PENINSULA
NORTH INTO THE SUSITNA VALLEY THROUGH THURSDAY NIGHT. THE FIRST
MAIN SHORTWAVE TROUGH IS LIFTING ACROSS SOUTHCENTRAL THIS
AFTERNOON, WITH A BAND OF LIGHT RAIN PUSHING INTO ANCHORAGE AND
THE SOUTHERN SUSITNA VALLEY AS OF 330 PM. THE RAIN IS FORECAST TO
LIFT INTO THE MAT VALLEY, CLEARING OUT LATER THIS EVENING, AND
THEN LINGER IN THE NORTHERN SUSITNA VALLEY OVERNIGHT AND INTO
THURSDAY. A COUPLE TENTHS OF AN INCH OF RAIN ARE POSSIBLE FROM
WILLOW NORTHWARD, WITH HIGHER AMOUNTS IN THE TALKEETNA MOUNTAINS
ENHANCED BY UPSLOPE FLOW. A FEW HUNDREDTHS OF AN INCH ARE POSSIBLE
FOR ANCHORAGE AND THE MATANUSKA VALLEY. A SECOND SHORTWAVE TROUGH
ENTERS THE REGION ON THURSDAY, BRINGING ANOTHER CHANCE OF RAIN TO
THE NORTHERN KENAI PENINSULA, ANCHORAGE, AND MATANUSKA VALLEY IN
THE AFTERNOON, AND REINFORCING PRECIPITATION OVER THE SUSITNA
VALLEY AT LEAST THROUGH THE EVENING.
THURSDAY NIGHT, THE TROUGH AXIS SHIFTS EAST OVER THE COPPER RIVER
BASIN, WITH A STRONG UPPER LEVEL JET AND COOLER AIR MOVING IN FROM
THE WEST. HIGH PRESSURE OVER THE BERING SEA COMBINED WITH COLD AIR
ADVECTION WILL LEAD TO A NORTHWESTERLY GAP WIND EVENT WHICH WILL
CAUSE WINDS TO INCREASE TO SMALL CRAFT CRITERIA (25+ KNOTS
SUSTAINED) FOR RESURRECTION BAY AND PASSAGE CANAL, WITH GALES OUT
OF KAMISHAK GAP AND THROUGH THE BARREN ISLANDS. VALDEZ WILL ALSO
LIKELY SEE SOME GUSTY WINDS IN TOWN, WITH SOME COLDER AIR EXPECTED
TO MOVE INTO THE COPPER BASIN AS WELL AND GIVEN THE OTHERWISE
GENERALLY UNSTABLE SUMMERTIME AIRMASS. GAP WINDS WILL HOLD THROUGH
FRIDAY NIGHT AT LEAST WITH CONTINUED COLD AIR ADVECTION AND A
MODERATE PRESSURE GRADIENT. WINDS BEGIN TO DIMINISH ON SATURDAY AS
BOTH OF THESE FACTORS START TO DECREASE. THE COPPER BASIN ALSO
SEES MOISTURE MOVING IN FROM THE EAST WHICH WILL LEAD TO UPSLOPE
PRECIPITATION IN THE WESTERN PORTIONS OF THE BASIN AND ON THE
EASTERN SLOPES OF THE WRANGELL MOUNTAINS. FRIDAY NIGHT, A STRONG
SHORTWAVE BRINGS THE BEST CHANCE FOR THE COPPER VALLEY TO SEE
RAINFALL. WEAK HIGH PRESSURE ALOFT BRINGS WARMER AND DRIER
CONDITIONS HEADING INTO THE WEEKEND ACROSS SOUTHCENTRAL.
.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS
(WEDNESDAY TO FRIDAY)...
MILD RAIN SHOWERS TO CONTINUE OVER INTERIOR SOUTHWEST ALASKA THIS
AFTERNOON AND EVENING, HOWEVER DIMINISH BY THURSDAY MORNING.
THURSDAY, A STRONG RIDGE BUILDING OVER THE CENTRAL BERING WILL
BEGIN TO TAKE HOLD OF THE REGION, LENDING TO A CALMER AND DRIER
PATTERN FOR SOUTHWEST ALASKA AND MUCH OF THE ALEUTIANS. HIGH
PRESSURE BUILDING ACROSS THE BERING WILL LEAD TO WIDESPREAD FOG
AND LOW STRATUS ACROSS THE BERING SEA AND SOUTHWEST COASTLINE. AS
THE AFOREMENTIONED HIGH PRESSURE MOVES EASTWARD, NORTHWESTERLY
WINDS WILL INCREASE GAP WINDS IN THE ALASKA PENINSULA THURSDAY AND
FRIDAY RANGING FROM 25 TO 35 KNOTS. ISOLATED RAIN SHOWERS WILL
ACCOMPANY THESE STRONG GAP WINDS AS A WAVES OF MOISTURE MOVE
THROUGH THE AREA. ADDITIONALLY, COOLER TEMPERATURES ARE EXPECTED
FROM NORTHWEST FLOW IN SOUTHWEST ALASKA, THE ALEUTIANS AND THE
ALASKA PENINSULA HEADING INTO THE WEEKEND.
ON THE WESTERN PERIPHERY OF THE RIDGE, A LOW PRESSURE SYSTEM
MOVING NORTHEASTWARD IN THE NORTHERN PACIFIC WILL APPROACH THE
REGION, REMAINING SOUTH OF THE WESTERN ALEUTIANS, AND BRING RAIN
FROM AMCHITKA TO ATKA BEGINNING LATE THURSDAY. THIS SYSTEM IS
EXPECTED TO LARGELY SPIN IN PLACE, STALLED BY THE RIDGE POSITION,
CONTINUING TO BRING LIGHT RAIN TO THE CENTRAL ALEUTIANS
POTENTIALLY THROUGH THE WEEKEND.
-CL
.LONG TERM FORECAST (DAYS 4 THROUGH 7: SATURDAY THROUGH
TUESDAY)...
FORECAST MODELS ARE IN REASONABLE AGREEMENT WITH THE GENERAL
PICTURE FOR THE WEEKEND. HIGH PRESSURE IS FORECAST TO REMAIN OVER
THE EASTERN BERING WHILE A SOUTHEASTWARD MOVING WAVE OF LOW
PRESSURE INTO SOUTHCENTRAL BEGINS TO PHASE WITH A BROADER AREA OF
TROUGHING ALONG THE SOUTHEAST ALASKA COAST. RESULTANT TIGHTENING
OF THE PRESSURE GRADIENT BETWEEN HIGH PRESSURE AND LOW PRESSURE
WILL PROMOTE NORTHWESTERLY FLOW THROUGH THE WESTERN ALASKA RANGE
AND CONTRIBUTE TO GUSTY GAP WINDS THROUGH KODIAK ISLAND AND THE
BARREN ISLANDS. MEANWHILE, MUCH OF SOUTHWEST AND SOUTHCENTRAL
ALASKA LOOK TO BE ON THE DRY SIDE WITH THE DRIER NORTHERLY FLOW
OVERSPREADING THE REGIONS.
BY SUNDAY INTO MONDAY, TROUGHING ALONG THE SOUTHEAST ALASKA COAST
SLIDES SOUTHWARD WHILE THE NEXT LOW PRESSURE SYSTEM TRACKS INTO
THE CENTRAL AND WESTERN ALEUTIANS. WEAK HIGH PRESSURE BUILDS INTO
THE GULF OF ALASKA WITH A CONTINUED DRY TREND FOR BOTH SOUTHWEST
AND SOUTHCENTRAL ALASKA. THE MAIN POTENTIAL FOR ANY SHOWER
ACTIVITY SHOULD BE CONFINED TO THE ALEUTIAN CHAIN SUNDAY INTO
TUESDAY.
-BL
AVIATION
PANC...A LINE OF RAIN SHOWERS IS PASSING THROUGH THE AREAS LATE
THIS AFTERNOON. CONDITIONS SHOULD REMAIN VFR AFTER THESE SHOWERS
PASS THROUGH, BUT THERE IS A SLIGHT CHANCE FOR MARGINAL CEILINGS
LATE AFTERNOON THROUGH EARLY EVENING IN MORE STABLE AIR BEHIND THE
WAVE THAT IS CAUSING THE SHOWERS. BY MID EVENING, CONDITIONS
SHOULD BE VFR THROUGH THURSDAY. WINDS MAY TURN BRIEFLY SOUTHEAST
THROUGH EARLY EVENING, BUT SHOULD BE MAINLY SOUTHWEST TO NORTHWEST
UNDER 10 KTS.
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