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FXAK68 PAFC 031254
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
454 AM AKDT TUE JUN 3 2025
SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3)
A STRONG SHORTWAVE ROUNDING THE BASE OF A DEEP UPPER LOW OVER THE
EASTERN BERING WILL MOVE OVER SOUTHCENTRAL TODAY, BRINGING
WIDESPREAD LIGHT TO MODERATE RAIN AND WINDY CONDITIONS.
WHILE SOME SOUTHEASTERLY GAP WINDS HAVE WEAKENED A BIT OVERNIGHT,
ANOTHER ROUND OF STRONG WINDS ARE EXPECTED THROUGH TURNAGAIN AND
KNIK ARMS AND THE COPPER VALLEY. WINDS ALOFT ARE OUT OF THE SOUTH-
SOUTHEAST, WHICH WILL FOCUS THE BULK OF THE PRECIPITATION ONTO
THE GULF COAST, PARTICULARLY SEWARD, IN ADDITION TO THE SUSITNA
VALLEY. MOST OF THE FORECAST GUIDANCE SHOWS A SLIGHT DOWNSLOPE
HOLE FROM ANCHORAGE NORTH TO PALMER, THOUGH SOME LIGHT RAIN OR
SPRINKLES ARE STILL EXPECTED THIS AFTERNOON AS THE MAIN SHORTWAVE
MOVES OVERHEAD.
ON WEDNESDAY A SURFACE LOW WILL DEVELOP ALONG THE BASE OF THE
UPPER TROUGH AND MOVE OVER KODIAK ISLAND EARLY IN THE MORNING.
THE LOW WILL THEN MOST LIKELY TRACK THROUGH THE BARREN ISLANDS
BEFORE DEVIATING AND MOVING INTO OR NEAR THE SOUND. THIS LOW TRACK
IN COMBINATION WITH THE UPPER TROUGH NOW SLOWLY MOVING THROUGH
SOUTHERN ALASKA WILL LEAD TO WIDESPREAD LIGHT RAIN THROUGHOUT
SOUTHCENTRAL WEDNESDAY AND THURSDAY.
.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS
(DAYS 1 THROUGH 3: TODAY THROUGH THURSDAY)...
EXPECT GENERALLY UNSETTLED WEATHER WITH LOWER-END IMPACTS. TWO
WEAKER LOWS INFLUENCE WEATHER ACROSS THE EASTERN BERING AND
SOUTHWEST ALASKA THROUGH THURSDAY. MEANWHILE, QUIETER WEATHER IS
EXPECTED FOR THE REMAINDER OF THE BERING SEA AND ALEUTIAN ISLANDS
AS A RIDGE OF HIGH PRESSURE BUILDS IN. THE ONLY HAZARD BEING
MONITORED IS THE POTENTIAL FOR ISOLATED AFTERNOON THUNDERSTORMS IN
THE KUSKOKWIM VALLEY TODAY AND TOMORROW.
DIVING INTO THE DETAILS... AN OCCLUDING BERING SEA LOW IS MOVING
TOWARDS SOUTHWEST ALASKA THIS MORNING. THIS WILL BRING WIDESPREAD
RAIN THROUGH MUCH OF TODAY, WITH RADAR CURRENTLY SHOWING LIGHT TO
MODERATE PRECIPITATION ACROSS MUCH OF BRISTOL BAY AND KUSKOKWIM
DELTA. BREEZY CONDITIONS PERSIST, BUT WINDS WILL CONTINUE TO
DIMINISH THROUGH TODAY.
THE BIGGEST QUESTION WITH THIS FORECAST WILL BE THE POTENTIAL FOR
ISOLATED THUNDERSTORMS ACROSS SOUTHWEST ALASKA. OVERALL,
CONDITIONS DON'T LOOK PARTICULARLY FAVORABLE FOR THUNDERSTORMS.
SATELLITE IMAGERY SHOWS OVERCAST SKIES ASSOCIATED WITH THE LOW,
AND FORECAST HIGH TEMPERATURES FOR SOUTHWEST ALASKA ARE EXPECTED
TO TOP OUT IN THE MID 50S. THIS CALLS INTO QUESTION WHETHER
DAYTIME HEATING WILL BE SUFFICIENT TO SUPPORT ROBUST CONVECTION.
AT THE SAME TIME, COLDER AIR ALOFT WILL LEAD TO A MORE UNSTABLE
ENVIRONMENT, AND THERE WILL BE A DECENT AMOUNT OF MIDLEVEL
VORTICITY. ISOLATED THUNDERSTORMS ARE POSSIBLE TODAY, BUT OVERALL
LIKELIHOOD IS LOW SINCE NOT ALL THE INGREDIENTS ARE QUITE THERE.
FOR TOMORROW, FEWER CLOUDS, SLIGHTLY WARMER MAXIMUM TEMPERATURES,
AND LINGERING VORTICITY COULD ALSO LEAD TO THE POTENTIAL FOR
ISOLATED THUNDERSTORMS. HOWEVER, UNCERTAINTY WITH THE PLACEMENT OF
THE UPPER LEVEL LOW AND, THEREFORE, UNCERTAINTY WITH WHERE THE
VORTICITY WILL BE, IS LEADING TO LOWER CONFIDENCE WITH WHERE
ISOLATED THUNDERSTORMS MAY BE EXPECTED.
FURTHER WEST, MUCH OF THE BEING SEA AND ALEUTIAN ISLANDS WILL SEE
CALMER CONDITIONS. LIGHT NORTHWESTERLY WINDS DEVELOP BEHIND THE
LOW, THEN A RIDGE STRENGTHENS ACROSS THE WESTERN AND CENTRAL
ALEUTIANS THROUGH THURSDAY. IT MIGHT BE A BIT EARLY IN THE SEASON
(I.E. SEA SURFACE TEMPERATURES MAY STILL BE A LITTLE TOO COLD FOR
THIS) BUT SUMMERTIME RIDGING OVER THE BERING SEA MAY PROVIDE A
FAVORABLE PATTERN FOR LOW STRATUS AND FOG. AS SUCH, THIS COULD BE
SOMETHING TO KEEP AN EYE ON.
-CHEN
LONG TERM FORECAST (DAYS 4 THROUGH 7: FRIDAY THROUGH MONDAY)
NO SIGNIFICANT CHANGE FROM PREVIOUS DISCUSSION. THE PERSISTENT
LONGWAVE TROUGH ACROSS THE BERING AND ALEUTIANS WILL BECOME MORE
ZONAL AND LIFT ACROSS SOUTHCENTRAL WITH SEVERAL EMBEDDED
SHORTWAVES ROTATING AROUND THE MAIN TROUGH AXIS. THE POSITIONING
AND ORIENTATION OF THE TROUGH WILL KEEP A FAVORABLE STORM TRACK
FOR SOUTHCENTRAL, WHICH WILL CONTINUE TO SUPPORT COOLER AND WETTER
THAN AVERAGE WEATHER CONDITIONS FOR THE LONG TERM. MODEL GUIDANCE
SUGGESTS ONE WAVE OF LOW PRESSURE MOVES INTO SOUTHCENTRAL
WEDNESDAY AFTERNOON. A BREAK FROM PRECIPITATION MAY OCCUR ON
FRIDAY FOR THE REGION BETWEEN SYSTEMS, THOUGH ANY CLEARING/DAYTIME
HEATING WILL PRESENT A CHANCE FOR AFTERNOON THUNDERSTORMS.
ANOTHER SYSTEM WORKS INTO THE AREA FOR SATURDAY AND SUNDAY.
-DD
AVIATION
PANC...VFR CONDITIONS WILL PERSIST THIS MORNING WITH MVFR
CONDITIONS POSSIBLE THIS AFTERNOON SHOULD RAIN BECOME HEAVY ENOUGH
TO LOWER CIGS. CURRENT THINKING IS WINDS WILL PROVIDE ENOUGH
DOWNSLOPING TO KEEP CIGS ABOVE 3000FT DUE TO SOME LOW LEVEL DRYING.
SOUTHEAST WINDS OUT OF THE TURNAGAIN ARM WILL CONTINUE THIS
MORNING WITH GUSTS UP TO 30 KTS. A FEW GUSTS TO 35 KT CAN'T BE
RULED OUT. WINDS WILL WEAKEN SLIGHTLY THIS EVENING, HOWEVER
DIRECTION IS EXPECTED TO PREVAIL FROM THE SOUTHEAST INTO WEDNESDAY
MORNING.
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