083
FXAK68 PAFC 030105
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
505 PM AKDT FRI MAY 2 2025
SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3)
AS OF THIS AFTERNOON, A BROAD, OCCLUDED ~990 MB SURFACE LOW IS
CENTERED 130 MILES EAST OF KODIAK ISLAND. ITS FRONT HAS MOVED
ACROSS THE IMMEDIATE SOUTHCENTRAL COAST, SPREADING RAINFALL INLAND
AS PRECIPITATION RATES ARE BEING ENHANCED BY OROGRAPHIC LIFT FROM
SEWARD TO THE EASTERN KENAI MOUNTAINS TO THE SOUTH FACING SLOPES
OF THE CHUGACH FRONT RANGE AND EASTWARD. ELSEWHERE, AN AL/CAN LOW
IS ON ITS WAY OUT OF THE FORECAST ZONE, BUT LIGHT PRECIPITATION IS
STILL LINGERING ACROSS THE UPPER COPPER RIVER BASIN. WINDS ARE
GUSTY THIS AFTERNOON, PARTICULARLY IN FAVORABLE GAP REGIONS SUCH
AS THE TURNAGAIN ARM AND PASSAGE CANAL.
BREAKS IN THE CLOUDS THIS AFTERNOON HAVE ALLOWED FOR SOME WARMING
FOR LOWER ELEVATIONS AND THE VALLEYS TO HELP INITIATE ISOLATED
AREAS OF WEAK THUNDERSTORMS, ESPECIALLY IN THE LOWER MAT-SU
VALLEYS, WHERE WARMER TEMPERATURES NEAR THE SURFACE ARE
CONTRASTING WITH COOL AIR ALOFT NEAR THE UPPER LEVEL TROUGH IN
PLACE. ELSEWHERE, DESPITE FAVORABLY STEEP MID TO UPPER LEVEL
LAPSE RATES, THE LIMITING FACTOR TODAY HAS BEEN DAYTIME HEATING. A
FEW RUMBLES OF THUNDER CANNOT BE RULED OUT FOR CORDOVA AND
SURROUNDING AREAS AS A PERSISTENT ONSHORE FLOW IN A RELATIVELY
UNSTABLE AIRMASS BEHIND THE FRONT. ALOFT, AN UPPER LEVEL WAVE
ROTATING ALONG IN A DEEP LONGWAVE TROUGH TO THE WEST HAS ALIGNED
WELL WITH THE FRONT AS IT HAS MOVED INLAND.
THE TURNAGAIN ARM WIND, ALONG WITH OTHER GAP WINDS, WILL DIMINISH
TONIGHT AS THE LOW NEAR KODIAK OPENS INTO A TROUGH AND PUSHES
EASTWARD. ALSO, PRECIPITATION CHANCES WILL SIMILARLY DIMINISH AS
THE LOW FALLS APART, LEAVING LINGERING SHOWERS THROUGH SATURDAY
AS A WEAK RIDGE BUILDS IN.
FOR SUNDAY, A FRONT FROM A LOW OVER THE AK PEN DRIVES INTO THE
SOUTHCENTRAL COAST, FORCING HEAVY PRECIPITATION AND A BARRIER JET
ALONG THE COASTLINE. INLAND AREAS WILL BE SHELTERED FROM MOST
PRECIPITATION DUE TO DOWNSLOPING AND WILL SEE LOWER PRECIPITATION
CHANCES. ONCE AGAIN, HIGHER ELEVATIONS GENERALLY ABOVE 2500 FT
COULD SEE SNOWFALL, ESPECIALLY AT NIGHT. WINDS WILL BE ENHANCED AS
WELL FROM THIS FRONT. BY SUNDAY AFTERNOON, GAP WINDS WILL
INCREASE TO STORM FORCE NEAR THE BARREN ISLANDS WITH HIGH END GALE
FORCE WINDS IN THE OTHER GAP REGIONS. WIND SPEEDS ARE MORE CERTAIN
AS MODELS HAVE COME INTO CLOSER AGREEMENT, ESPECIALLY WITH THE
AFOREMENTIONED BARRIER JET. MOST GUIDANCE NOW HAS WIND GUSTS MEETING
STORM-FORCE CRITERIA.
-AM/TM/JAR
.SHORT TERM FORECAST SOUTHWEST ALASKA AND BERING SEA/ALEUTIANS(DAYS
1 THROUGH 3: TODAY THROUGH MONDAY)...
STARTING OFF THE FORECAST IS A COL THAT IS CURRENTLY OVER THE
SOUTHWEST ALASKA MAINLAND. THIS HAS ALLOWED PRECIPITATION CHANCES
TO DROP OFF AND WIND SPEEDS TO REMAIN ON THE LOW SIDE AS WELL.
HOWEVER, WINDS REMAIN BREEZY AND NORTHERLY OFF THE COAST AND DOWN
TO THE ALASKA PENINSULA AS THE PERSISTENT TONGUE OF COLD AIR
REMAINS IN PLACE. THE LOWER KUSKOKWIM VALLEY IN CONTRAST IS
RECEIVING CONVECTIVE SHOWERS WITH THE POTENTIAL FOR LIGHTNING AS
STORMS FLOW IN FROM THE NORTHWEST. FOR THE BERING, A COUPLE OF
WEAK LOWS ARE MOVING SLOWLY EASTWARD, ALLOWING FOR SHOWERS AND
SMALL CRAFT WINDS IN THE CENTRAL ALEUTIANS.
ON SATURDAY, MUCH OF THE SAME WILL OCCUR IN THE MAINLAND WITH THE
COL SLOWLY MOVING EASTWARD AND SLIGHT RIDGING BUILDING IN.
LINGERING SHOWERS WILL OCCUR IN THE LOWER KUSKOKWIM DELTA, BUT
PRECIPITATION CHANCES WILL CONTINUE TO DECREASE IN THE MAINLAND.
THE BERING WILL ALSO BE SIMILAR WITH THE MAIN REGION OF RAIN AND
WINDS MOVING INTO THE EASTERN ALEUTIANS AND ALASKA PENINSULA
REGIONS BY SATURDAY AFTERNOON.
THINGS FINALLY CHANGE ON SUNDAY WHEN THE EASTERNMOST LOW IN THE
BERING GROWS IN SIZE AND INTENSIFIES AS IT MOVES SOUTH OF THE
ALASKA PENINSULA. THE SECOND WEAKER LOW DROPS SOUTH OF ADAK AND
DISSIPATES. THE NOW BIGGER LOW WILL DRIVE PRECIPITATION CHANCES UP
IN THE ALASKA PENINSULA AND BRISTOL BAY REGIONS. THE KUSKOKWIM
DELTA REGION COULD SEE SOME SHOWERY PRECIPITATION AS THE LOW TRIES
TO ADVECT SOME MOIST AIR UP THERE. HOWEVER, THE MOUNTAINS SOUTH OF
BETHEL WILL LIMIT HOW MUCH PRECIPITATION CAN FALL. AIDED BY THIS
LOW AND THE AFOREMENTIONED TONGUE OF COLDER AIR, GAP WINDS WILL
INCREASE TO GALE FORCE IN THE EASTERN ALEUTIANS AND ALASKA
PENINSULA REGIONS. THE KAMISHAK GAP WILL SIMILARLY SEE AN INCREASE
OF WIND SPEEDS TO GALE FORCE AS THE LOW PASSES. THIS PATTERN
REMAINS ON MONDAY AS THE LOW BECOMES QUASI-STATIONARY NEAR KODIAK
ISLAND. OUT WEST IN THE WESTERN BERING, A RIDGE MOVES IN AND
SWITCHES WINDS SOUTHERLY AND DRIVES DOWN PRECIPITATION CHANCES.
-JAR
LONG TERM FORECAST (DAYS 4 THROUGH 7/TUESDAY THROUGH FRIDAY)
AT THE START OF THE EXTENDED PERIOD ON TUESDAY, A DEEP VERTICALLY
STACKED LOW WILL BE POSITIONED IN THE SOUTHERN GULF WITH A
DISSIPATING OCCLUDED FRONT WRAPPED AROUND THE GULF COAST. WITH A
HIGH AMPLITUDE RIDGE SITTING DOWNSTREAM, THE UPPER LEVEL LOW WILL
LINGER OVER THE SOUTHERN GULF THROUGH AT LEAST FRIDAY. SHORT-WAVES
ROTATING AROUND THE LOW CENTER WILL LIKELY LEAD TO DEVELOPMENT OF
MULTIPLE ADDITIONAL SURFACE LOWS, BUT ALL OF THEM WILL ULTIMATELY
END UP TRACKING TO THE POSITION OF THE UPPER CENTER. THE BULK OF
IMPACTS WILL WILL BE ALONG THE GULF COAST AND KODIAK ISLAND, WITH
OCCASIONAL RAIN OR RAIN SHOWERS. AT THIS POINT, NONE OF THE
SURFACE LOWS LOOK PARTICULARLY STRONG, SO WINDS FOR THE GULF
COASTAL WATERS LOOK TO REMAIN AT SMALL CRAFT ADVISORY LEVELS OR
LOWER. FOR SOUTHCENTRAL AND SOUTHWEST AK, THIS PATTERN WILL BRING
A MIX OF SUN AND CLOUDS, WITH SOME WEAK RIDGING AT TIMES BUT ALSO
THE LIKELIHOOD OF UPPER LEVEL SHORT-WAVES ROTATING THROUGH WITH
SOME CLOUDS AND SHOWERS. THIS TYPE OF PATTERN IS TYPICAL FOR
SPRING AND THE DETAILS OF AMOUNT OF SUNSHINE (OR CLOUDS) AND
SPECIFIC TEMPERATURES FOR EACH DAY WILL HAVE TO BE WORKED OUT AS
WE GET CLOSER AND TIME.
MEANWHILE, OUT WEST, A DEEP LOW WILL TRACK INTO THE FAR WESTERN
BERING SEA MONDAY NIGHT THROUGH TUESDAY, WITH A LEADING FRONTAL
SYSTEM PROGRESSING EASTWARD ACROSS THE BERING AND ALEUTIANS. THIS
STORM SYSTEM WILL RAPIDLY WEAKEN TUESDAY NIGHT THROUGH WEDNESDAY
AS THE DOWNSTREAM RIDGE GETS FLATTENED OUT AND UPPER JET SUPPORT
WEAKENS. A REMNANT WEAK LOW WILL EXIT TO THE PACIFIC LATE
THURSDAY. BOTTOM LINE, EXPECT LOW IMPACT WEATHER FOR THE BERING
AND ALEUTIANS NEXT WEEK.
-SEB
AVIATION
PANC...VFR CONDITIONS WINDS WILL PERSIST. THE STRONG SOUTHEASTERLY
TURNAGAIN ARM WINDS WILL PERSIST THROUGH MOST OF THE NIGHT.
HOWEVER THE STRONGEST WIND GUSTS TO NEAR 35 KT SHOULD MAINLY BE IN
THE LATE AFTERNOON THROUGH EARLY EVENING.
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