305
FXAK68 PAFC 251346
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
546 AM AKDT TUE AUG 25 2026
SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3)
KEY MESSAGES:
- SPECIAL WEATHER STATEMENT HAS BEEN ISSUED FOR STRONG WINDS
TOMORROW, TUESDAY FOR ANCHORAGE, ANCHORAGE HILLSIDE, PALMER AND
BUTTE.
- SEVERAL ROUNDS OF WIDESPREAD RAINFALL ACROSS THE SUSITNA VALLEY
THIS WEEK WILL ALLOW FOR RISES ON MANY SMALL STREAMS AND RIVERS, AND
LOCALIZED PONDING IN LOW-LYING OR POOR DRAINAGE AREAS.
DISCUSSION:
SEVERAL FEATURES OF NOTE THIS MORNING. A SHORTWAVE RIDGE OVER THE
GULF WILL CONTINUE TO FLATTEN TODAY AS SEVERAL SYSTEMS MOVE IN FROM
THE WEST. THE FIRST OF THESE SYSTEMS IS A SMALL SHORTWAVE TROUGH
THAT IS RIDING OVER THE RIDGE. THE SYSTEM BROUGHT SOME RAIN TO THE
SOUTHERN KENAI PENINSULA OVERNIGHT AND HAS SINCE MOVED OUT INTO THE
GULF AS IT WEAKENS AND GETS ABSORBED INTO THE FLOW.
THE NEXT SYSTEM OF NOTE IS THE MORE SUBSTANTIAL TROUGH POSITIONED
NEAR THE BERING STRAIT THIS MORNING WITH FRONT SWEEPING ACROSS
SOUTHWEST AK. BROAD ISENTROPIC ASCENT AHEAD OF THIS FRONT COMBINED
WITH MODEST MOISTURE TRANSPORT ON SOUTHWESTERLY FLOW HAS RESULTED IN
A BROAD REGION OF SCATTERED RAIN SHOWERS OVER INLAND BRISTOL BAY AND
INTO THE CENTRAL INTERIOR. ANOTHER AREA OF RAIN WAS ALSO NOTED NEAR
THE SURFACE LOW NEAR THE Y-K DELTA REGION. THE SURFACE LOW WILL LIFT
TO THE NE TODAY WITH RAIN BECOMING MORE FOCUSED ALONG AND NEAR THE
FRONT AS THE TROUGH BECOMES MORE NEGATIVELY TILTED AND FORCING
INCREASES ALONG THE FRONT. LEE TROUGHING WILL ALSO BECOME MORE
PRONOUNCED JUST OFF THE EASTERN KENAI PENINSULA, HELPING TO INCREASE
RAIN CHANCES FOR PRINCE WILLIAM SOUND AND THE NORTHERN GULF COASTAL
ZONES. GREATEST RAIN AMOUNTS STILL LOOK TO BE FOCUSED OVER THE
SUSITNA VALLEY, WHERE A HALF INCH TO AROUND AN INCH OF RAINFALL IS
POSSIBLE FOR AREAS FROM PETERSVILLE EAST TO TALKEETNA AND ALONG THE
TALKEETNA MOUNTAINS TO HATCHER PASS. GIVEN RECENT RAINFALL EVENTS
OVER THE PAST FEW MONTHS, RISES ALONG AREAS CREEKS AND RIVERS CAN BE
ANTICIPATED, ALONG WITH PONDING IN LOW-LYING AND POOR DRAINAGE
AREAS. THIS SYSTEM WILL DEPART FAIRLY QUICKLY WITH RAINFALL
GENERALLY ENDING FROM WEST TO EAST BY LATE TONIGHT INTO WEDNESDAY
MORNING.
IN ADDITION TO WIDESPREAD RAINFALL, WINDS WILL BEGIN TO INCREASE
THIS MORNING ALONG THE TURNAGAIN ARM AND ANCHORAGE HILLSIDE AND THE
PRESSURE GRADIENT TIGHTENS ALONG THE CHUGACH MOUNTAINS. GUSTS AROUND
40 MPH ARE POSSIBLE FOR PORTIONS OF SOUTH AND WEST ANCHORAGE,
INCLUDING THE AIRPORT, PARTICULARLY THIS AFTERNOON AND EARLY
EVENING. STRONG WINDS ARE ALSO EXPECTED THROUGH THE KNIK VALLEY AND
COPPER RIVER BASIN GAPS AS THE FRONT MOVES THROUGH. WINDS WILL BEGIN
TO SUBSIDE TONIGHT AS THE GRADIENT STARTS TO RELAX WITH THE PASSAGE
OF THE FRONT.
LOOKING TOWARDS LATER IN THE WEEK... WEDNESDAY AFTERNOON AND
THURSDAY BRING A BRIEF RESPITE FROM WIND AND RAIN BEFORE ANOTHER
BERING LOW BRINGS ANOTHER ROUND OF WIDESPREAD RAINFALL TO SOUTHWEST
AND SOUTHCENTRAL.
- PP
.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS
(DAYS 1 THROUGH 3: THIS AFTERNOON THROUGH FRIDAY MORNING)...
RAIN SHOWERS ARE ONGOING THIS MORNING ACROSS MUCH OF SOUTHWEST
ALASKA AS A FRONT FROM A SURFACE LOW MOVING OUT OF THE REGION AND
ACROSS NORTHERN ALASKA CONTINUES TO TREK EASTWARD. ALOFT, THE BASE
OF A NEUTRALLY TILTED 500 MB TROUGH IS CROSSING OVER SOUTHWEST
ALASKA. AS THE UPPER TROUGH TAKES A NEGATIVE TILT AND LIFTS OUT OF
THE REGION AND OVER SOUTHCENTRAL BY THIS AFTERNOON, EXPECT
CONDITIONS TO TREND DRIER AND FOR OVERALL WEATHER CONDITIONS TO
IMPROVE FOR SOUTHWEST ALASKA. ELSEWHERE, A NORTH PACIFIC HIGH
REMAINS ANCHORED IN PLACE SOUTH OF THE CENTRAL AND EASTERN
ALEUTIANS WITH RIDGING EXTENDING NORTHWARD ACROSS THE ALEUTIAN
CHAIN AND CENTRAL BERING. MEANWHILE, FARTHER WEST, RAINFALL
ASSOCIATED WITH A FRONT FROM A KAMCHATKA LOW IS APPROACHING THE
WESTERN ALEUTIANS.
LOOKING AHEAD TO WEDNESDAY MORNING, TRANSIENT UPPER LEVEL RIDGING
WILL MOST LIKELY ENCOMPASS MUCH OF THE BERING SEA, WHICH WILL
RESULT IN A SHORT LIVED PERIOD OF QUIETER WEATHER (OUTSIDE OF FOG
AND LOW STRATUS) FOR THE BERING AND ALEUTIAN CHAIN. MOS GUIDANCE
IS STILL HINTING AT FOG AND LOW STRATUS MAKING ITS WAY ONSHORE
WEDNESDAY MORNING FOR COASTAL PORTIONS OF SOUTHWEST ALASKA,
EXTENDING AS FAR INLAND AS BETHEL. IN THE WAKE OF THE RIDGE, THE
KAMCHATKA FRONT WILL BEGIN TO LIFT NORTHEASTWARD ACROSS THE BERING
SEA WEDNESDAY MORNING. WARM, MOIST, TROPICAL AIR WILL BE
TRANSPORTED NORTHWARD FROM THE PACIFIC AND INTO THE BERING SEA
DURING THIS TIME AS AN ATMOSPHERIC RIVER WILL ALSO ACCOMPANY THIS
SYSTEM AS MODERATE TO HEAVY RAIN MOVES INTO SHEMYA WEDNESDAY
MORNING. THE HEAVY RAIN AXIS SHIFTS EAST BY WEDNESDAY AFTERNOON
AND EVENING AS RAIN MOVES INTO THE PRIBILOF ISLANDS BY THEN.
ON THE WIND SIDE OF THINGS, LOW END SOUTHWESTERLY GALES WITH THIS
SYSTEM ARE EXPECTED TO TRAVERSE THE BERING AND ALEUTIAN CHAIN
BEGINNING AS EARLY AS LATE WEDNESDAY MORNING. THESE WINDS ARE ON
TRACK TO REACH THE PRIBILOF ISLANDS BY THURSDAY MORNING. FROM
HERE, GALES TRANSLATE EASTWARD ACROSS THE EASTERN BERING THURSDAY
AFTERNOON. THE ONE NOTABLE CHANGE OVERNIGHT IS THAT THE CORRIDOR
OF STRONGEST WINDS HAS TRENDED SOUTHWARD WITH OVERNIGHT MODEL
RUNS, MOST NOTICEABLY ON THE GFS. WHAT INITIALLY LOOKED LIKE A
KUSKOKWIM DELTA COAST THREAT FOR PROLONGED GUSTY WINDS HAS SHIFTED
SOUTHWARD TO THE WESTERN CAPES AND THE BRISTOL BAY REGION. THE
SYSTEM AS A WHOLE ALSO LOOKS TO BE TRENDING MARGINALLY WEAKER WITH
GALES NOW ANTICIPATED TO BE LESS EXPANSIVE. REGARDLESS, A ROUND
OF HEAVY RAINFALL IS ON TRACK TO ARRIVE THURSDAY MORNING TO
SOUTHWEST ALASKA AND CONTINUE ON THROUGH FRIDAY, POTENTIALLY
ADDING UP TO 1 TO 2 INCHES OF RAINFALL FOR SOME AREAS. STAY TUNED.
-AM/DN
LONG TERM FORECAST (DAYS 4 THROUGH 7: FRIDAY THROUGH MONDAY)
AN ACTIVE, PROGRESSIVE PATTERN CONTINUES THROUGH THE END OF THE
WEEK AND INTO EARLY NEXT WEEK AS MULTIPLE SYSTEMS QUICKLY TRACK
FROM WEST TO EAST. THIS WILL GENERALLY BRING PERIODS OF ACTIVE
WEATHER, WITH BRIEF LULLS IN BETWEEN FOR MOST LOCATIONS.
BY FRIDAY MORNING, A 990 MB LOW WILL HAVE TRACKED JUST EAST OF ST.
LAURENCE ISLAND AND BEGINS TO MOVE INLAND NEAR THE NORTON SOUND,
BRINGING MODERATE TO HEAVY PRECIPITATION ACROSS MUCH OF
SOUTHWESTERN ALASKA. CONCURRENTLY, SOUTHWESTERLY SMALL-CRAFT TO
GALE- FORCE WINDS WILL CONTINUE TO PUSH INTO BRISTOL BAY AND THE
KUSKOKWIM DELTA COAST. WIDESPREAD PRECIPITATION WILL ALSO FILTER
INTO SOUTHCENTRAL, AND WILL BE PARTICULARLY HEAVY FOR THE
NORTHERN GULF COAST AND TALKEETNA MOUNTAINS. TURNAGAIN/KNIK GAPS
WINDS WILL LIKELY RETURN FRIDAY, BRINGING POTENTIAL FOR GUSTY
CONDITIONS AROUND ANCHORAGE AND PALMER. RIVER LEVELS ACROSS THE
SUSITNA VALLEY, SUCH AS THE YENTNA RIVER AT LAKE CREEK WILL HAVE
TO BE MONITORED CLOSELY WITH THIS SYSTEM FOR POTENTIAL FLOODING
CONCERNS.
BY SATURDAY MORNING, THE TROUGH EJECTS A SURFACE LOW INTO THE
GULF, CAUSING RAINFALL TO TAPER OFF FROM WEST TO EAST ACROSS THE
MAINLAND AS THIS LOW CONTINUES TOWARD THE ALASKAN PANHANDLE. SOME
SHOWERS MAY LINGER IN SPOTS, PARTICULARLY FOR PRINCE WILLIAM
SOUND AND THE WESTERN/CENTRAL CHUGACH, THOUGH CONDITIONS WILL
GRADUALLY IMPROVE AS RIDGING REBUILDS OVER THE REGION. A SEPARATE
NORTH PACIFIC LOW MOVES INTO THE WESTERN BERING BY SATURDAY WHICH
WILL LIKELY BRING ANOTHER WAVE OF PRECIPITATION TO THE
WESTERN/CENTRAL ALEUTIANS.
DETERMINISTIC SOLUTIONS BEGIN TO DIFFER SUBSTANTIALLY BY MONDAY.
HOWEVER, ENSEMBLE MEANS SHOW A BROAD RIDGE AMPLIFYING JUST SOUTH
OF THE ALEUTIANS, WHICH COULD SET UP A PERIOD OF MOIST FLOW.
ANOTHER SHORTWAVE APPEARS TO WORK DOWN THE MAINLAND BY MONDAY. IF
THIS FEATURE CAN TAP INTO THIS MOISTURE, ANOTHER ROUND OF
WIDESPREAD PRECIPITATION COULD BE ON TRACK FOR MUCH OF THE
SOUTHERN ALASKA EARLY NEXT WEEK.
-CW
AVIATION
PANC...SOUTHERLY WINDS PICK UP THIS MORNING WITH GUSTS TO 25 KTS
AND INCREASE WITH GUSTS TO 30 KTS LATER THIS MORNING (AFTER 18Z).
LIGHT RAIN EXPECTED OVER THE TERMINAL THROUGH TODAY. CLOUD
CEILINGS WILL DROP BELOW 5000 FT AFTER 18Z.
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