139
FXAK68 PAFC 281401
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
601 AM AKDT FRI AUG 28 2026
SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3)
KEY MESSAGES:
- STRONG WINDS THROUGH COOK INLET TODAY, WITH LOCALIZED GUSTY
SOUTHEASTERLY GAP WINDS THROUGH TURNAGAIN ARM, ANCHORAGE, KNIK
VALLEY, AND COPPER RIVER VALLEY.
- FOR SUSITNA VALLEY, RAIN TOTALS AROUND 0.5 TO 1.5 INCHES THROUGH
SATURDAY WILL ALLOW FOR RISES ON MANY SMALL STREAMS AND RIVERS, AND
LOCALIZED PONDING IN LOW-LYING OR POOR DRAINAGE AREAS.
- FROM SATURDAY THROUGH SUNDAY, SHOWERS TAPER OFF BY SATURDAY
MORNING AND GUSTY NORTHERLY TO WESTERLY WINDS PICK UP, STRONGEST
ALONG THE COAST.
DISCUSSION:
THE FIRST PUSH OF WIDESPREAD RAIN IS MOVING ACROSS SOUTHCENTRAL THIS
MORNING, AND WILL SOON MOVE INTO THE COPPER BASIN. THIS CURRENT
ROUND OF RAIN IS ASSOCIATED WITH A FRONTAL SYSTEM LIFTING ACROSS
INTERIOR ALASKA AND GENERALLY EXTENDING OUT EAST FROM THE PARENT LOW
JUST NE OF THE SEWARD PENINSULA AND DOWN TOWARDS PRINCE WILLIAM
SOUND. WIDESPREAD RAIN WILL TAPER OFF TO SHOWERS PRETTY QUICKLY
BEHIND THIS FRONT, BUT A SECONDARY FRONT WILL COMPLICATE THE
FORECAST LATER TODAY AS SHOWERS REINVIGORATE WITH THE PASSAGE OF THE
FRONT AND ASSOCIATED TROUGH. RIGHT NOW IT APPEARS THAT THE BULK OF
THE LOWER TO MID-LEVEL FORCING WILL BE SOMEWHAT SPLIT BETWEEN THE
GULF AND FURTHER NORTH CLOSER TO THE LOW. THIS WOULD PLACE THE BEST
CHANCES FOR PRECIPITATION OVER THE NORTHERN SUSITNA VALLEY AND THE
HIGHER TERRAIN OF THE ALASKA RANGE AND TALKEETNA AND CHUGACH
MOUNTAINS, AND ANOTHER ROUND OF SHOWERS FOR THE NORTHERN AND CENTRAL
GULF. DESPITE THE SHOWERS, THERE WILL LIKELY BE SOME BREAKS IN
CLOUDCOVER.
THIS SYSTEM WILL ALSO BRING ANOTHER ROUND OF GUSTY GAP FLOW WINDS
FOR THE TURNAGAIN ARM, KNIK, AND COPPER VALLEY. SIMILAR TO THE
TUESDAY EVENT, WINDS WITH GUSTS UP TO 35-45 MPH (WITH ISOLATED GUSTS
TO 50) ARE POSSIBLE FOR WEST ANCHORAGE AND TURNAGAIN ARM, AND 40-55
MPH FOR THE HILLSIDE. EAGLE RIVER WILL ALSO SEE GUSTY WINDS WITH
GUSTS OF 25 TO 30 MPH POSSIBLE. THE WESTERN GULF WILL SEE SMALL
CRAFT TO GALES MOVE IN BEHIND THE FRONT AND THE DEVELOPMENT OF A
BARRIER JET WILL ALLOW FOR SOME HIGH END SMALL CRAFT TO EVEN GALE
FORCE WINDS ALONG THE NORTHERN GULF COAST AND INTO PRINCE WILLIAM
SOUND. THESE STRONG WINDS WILL LIKELY PUSH INLAND SOME BRINGING
GUSTY WINDS TO CORDOVA FRIDAY NIGHT.
- PP/KC
.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (DAYS
1 THROUGH 3: THIS AFTERNOON THROUGH SUNDAY MORNING)...
KEY MESSAGES:
* A WIND ADVISORY REMAINS IN EFFECT FOR THE KUSKOKWIM DELTA,
WESTERN CAPES, AND NORTHERN BRISTOL BAY COAST UNTIL 4PM FRIDAY.
SOUTH TO SOUTHWEST WINDS 25 TO 35 MPH WITH GUSTS UP TO 50 MPH
ARE EXPECTED.
* A HIGH SURF ADVISORY REMAINS IN EFFECT FOR THE KUSKOKWIM DELTA
COAST UNTIL 4PM FRIDAY FOR WATER LEVELS 1 TO 2 FEET ABOVE THE
NORMAL HIGHEST TIDE LINE.
DISCUSSION:
CURRENT SATELLITE IMAGERY AND SURFACE OBSERVATIONS SHOW A BROAD,
TRIPLE POINT SURFACE LOW MOVING INLAND ACROSS NORTHERN ALASKA FROM
THE NORTON SOUND WHILE ITS PARENT OCCLUDED LOW SPINS/FILLS ACROSS
THE CENTRAL BERING. WITH A TRAILING COLD FRONT DRAPED FROM ALONG
THE SOUTHWEST ALASKA COASTLINE AND SOUTHWESTWARD ACROSS THE
EASTERN BERING AND ALEUTIANS, CONTINUED RAIN SHOWERS CAN BE SEEN
ON RADAR MOVING ACROSS INTERIOR SOUTHWEST ALASKA. ALOFT, THE BASE
OF THE 500 MB MAIN TROUGH AXIS IS LIFTING OVER THE KUSKOKWIM
VALLEY WITH ONLY WEAK WAVES EMBEDDED WITHIN THE MEAN FLOW BEHIND
THIS SYSTEM. AS A RESULT, AND WITH COLDER AIR ALOFT MOVING IN TO
STEEPEN LAPSE RATES, RAINFALL WILL BE SHOWERY IN NATURE TODAY FOR
THE BERING AND SOUTHWEST ALASKA AS MORE STRATIFORM PRECIPITATION
COVERAGE MARCHES EASTWARD TO SOUTHCENTRAL. AREAS TO WATCH TODAY
FOR MORE COVERAGE IN SHOWERS WILL BE ALONG TERRAIN WITH AREAS OF
UPSLOPE ENHANCEMENT. WESTERLY WINDS IN THE WAKE OF THIS LARGE LOW
PRESSURE SYSTEM HAS BEEN EFFICIENT AT ADVECTING IN THE MARINE
LAYER FOR PORTIONS OF SOUTHWEST ALASKA, KEEPING MISTY CONDITIONS
AND LOW STRATUS IN THE AREA, EVEN AS THE BULK OF RAINFALL HAS BEEN
IN THE PROCESS OF CLEARING OUT OF THE REGION. ALTHOUGH RAINFALL
MOSTLY COMES TO AN END THIS MORNING, WINDS CERTAINLY WILL NOT, AND
AS SUCH, THE WIND ADVISORY AND HIGH SURF ADVISORY IS OUT UNTIL
4PM THIS AFTERNOON. THERE IS QUITE A LONG FETCH OF HIGH END SMALL
CRAFT WINDS IN THE WAKE OF THIS SYSTEM, IN PART DUE TO A STRONG
NORTH PACIFIC HIGH SOUTH OF THE ALEUTIANS ENHANCING THE PRESSURE
GRADIENT ACROSS THE BERING.
A PERIOD OF RELATIVELY QUIET WEATHER IS IN STORE FOR THE WEST FOR
MUCH OF SATURDAY AS TRANSIENT RIDGING SKIRTS ACROSS MUCH OF THE
BERING AND ALEUTIAN CHAIN. HOWEVER, DUE TO THE ORIENTATION OF THE
RIDGING AND LOWER PRESSURE INLAND ACROSS SOUTHWEST ALASKA,
NORTHWESTERLY GAP WINDS WILL PICK UP IN INTENSITY THROUGH FAVORED
BAYS AND PASSES OF THE ALASKA PENINSULA AS SOME MODELS SHOW HIGH
END SMALL CRAFT WINDS AND LOW END GALES IN THE BOUNDARY LAYER. THE
ONE EXCEPTION TO A QUIETER SATURDAY WILL BE ANOTHER LOW PRESSURE
SYSTEM RIDING AROUND THE WESTERN PERIPHERY OF THE NORTH PACIFIC
HIGH AND ARRIVING TO THE WESTERN ALEUTIANS SATURDAY MORNING WITH A
ROUND OF MODERATE RAINFALL AND SMALL CRAFT SUSTAINED WINDS. AS
THE RIDGE TRIES TO RETREAT SOUTHWARD THROUGH SUNDAY MORNING, THIS
WILL ALLOW FOR WIDESPREAD SMALL CRAFT WINDS WITH GUSTS TO GALE
FORCE TO ENCOMPASS MUCH OF THE SOUTHERN AND CENTRAL BERING. THIS
WILL ALSO BE A ROAD MAP FOR MOISTURE TRANSPORT ONCE AGAIN FROM THE
PACIFIC AS A PLETHORA OF MOISTURE RIDES AROUND THE RIDGE AND
ACROSS THE BERING THROUGH MIDDAY SUNDAY. MOST MODEL GUIDANCE SHOWS
RAINFALL RETURNING TO SOUTHWEST ALASKA BY SUNDAY AFTERNOON.
-AM
LONG TERM FORECAST (DAYS 4 THROUGH 7: MONDAY THROUGH THURSDAY)
THE PROGRESSIVE PATTERN LOOKS TO CONTINUE THROUGH LATE TUESDAY OR
EARLY WEDNESDAY AS MULTIPLE MULTIPLE UPPER-LEVEL WAVE SOUTHEAST
FROM THE CHUKCHI SEA TO THE ALASKA PANHANDLE. THIS WILL GENERALLY
BRING PERIODS OF ACTIVE WEATHER, WITH SOME LULLS BETWEEN SYSTEMS.
THE COMBINATION OF COLD AIR ADVECTION, A NORTHWESTERLY LOW-LEVEL
JET, AND A SHORTWAVE TROUGH THROUGH THE NORTHWESTERLY FLOW, WILL
LEAD TO AND INCREASE IN NORTHWESTERLY WINDS THROUGH THE BARREN
ISLANDS AND AROUND KODIAK ISLAND/THE AKPEN, AS WELL AS NORTHERLY
AND WESTERLY GAP WINDS FOR SEWARD AND WHITTIER BY LATE MONDAY.
CLOUDS AND SCATTERED SHOWERS WILL LINGER ACROSS PORTIONS OF
SOUTHCENTRAL ALASKA AS THESE WAVES MOVE THROUGH, ESPECIALLY FOR
THE HIGHER TERRAIN AND THROUGH THE COPPER RIVER BASIN.
FARTHER WEST, AN UPPER-LEVEL RIDGE WILL BUILD OVER THE NORTH
PACIFIC, EXTENDING ACROSS THE ALEUTIANS, BY LATE MONDAY. A WARM
FRONT ATTACHED TO A KAMCHATKA LOW WILL MOVE OVERTOP THE RIDGE AND
INTO THE SOUTHERN BERING FOR TUESDAY MORNING. THIS FEATURE LOOKS
TO TRANSITION INTO AN ELONGATED SURFACE LOW AS IT PHASES WITH A
SHORTWAVE TROUGH MOVING SOUTHEAST THROUGH THE Y-K DELTA, BRINING
MORE RAIN AND GUSTY WINDS FROM BRISTOL BAY TO KODIAK ISLAND.
MODEL AGREEMENT THEN FALLS APART LATE TUESDAY THROUGH THURSDAY.
THE BIGGEST QUESTION WILL BE HOW AMPLIFIED THE LONGWAVE PATTERN
GETS AS THE AFOREMENTIONED RIDGE BEGINS EXTEND NORTH AND EAST
AHEAD OF A DEEPENING TROUGH OVER THE FAR WESTERN ALEUTIANS. MOST
GUIDANCE IS BEGINNING TO ADVERTISE A RIDGE AXIS MOVING OVER
SOUTHCENTRAL WITH MULTIPLE UPPER-LEVEL WAVES AND RESULTANT SURFACE
LOWS MOVING INTO THE WESTERN HALF OF THE BERING FROM THE NORTH
PACIFIC. THE SURFACE FRONTS ASSOCIATED WITH THESE SURFACE
FEATURES LOOK TO MOVE AS FAR EAST AS WESTERN ALASKA WEDNESDAY AND
THURSDAY WITH ADDITIONAL ROUNDS OF HEAVY RAIN AND GUSTY SOUTH TO
SOUTHWEST WINDS.
- TM
AVIATION
PANC...MVFR CONDITIONS MAY BRIEFLY DIP TO IFR THIS MORNING BEFORE
IMPROVING BACK TO VFR BY 18-21Z. RAIN WILL TAPER OFF TO SHOWERS
FOR MUCH OF THE AFTERNOON BEFORE ENDING LATE TONIGHT.
SOUTHEASTERLY TURNAGAIN ARM WINDS WILL REMAIN GUSTY THROUGH ABOUT
06-09Z WITH GUSTS OF 35 TO 45 KT POSSIBLE BEFORE DIMINISHING
OVERNIGHT.
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