814
FXAK68 PAFC 060112
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
512 PM AKDT MON MAY 5 2025
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3: THIS
AFTERNOON THROUGH THURSDAY AFTERNOON)...
WITH THE LOW NEAR KODIAK ISLAND WEAKENING, MUCH OF SOUTHCENTRAL
ALASKA WILL SEE A SHIFT TOWARDS MORE DIURNALLY-DRIVEN WEATHER,
THOUGH UPPER LEVEL SHORTWAVES WILL STILL EXERT SOME INFLUENCE AS
THEY ROTATE AROUND THE LOW. THIS WILL MEAN MORE CONVECTION, WITH
SHOWERS AND PERHAPS EVEN A FEW ISOLATED THUNDERSTORMS DEVELOPING
IN THE AFTERNOON AND EVENINGS IN THE COMING DAYS. ADDITIONALLY,
EXPECT CONTINUED SOUTHEASTERLY WINDS THROUGH TERRAIN GAPS TO
AFFECT ANCHORAGE, MAT VALLEY, AND COPPER RIVER.
DIVING INTO THE DETAILS... THE PRIMARY FORECAST CHALLENGE HAS BEEN
HONING IN ON WHERE SHOWERS ARE MOST LIKELY, AS WELL AS
THUNDERSTORM POTENTIAL. OVERALL, CONDITIONS LOOK FAIRLY MARGINAL
AND NOT TOO IMPRESSIVE WHEN IT COMES TO THUNDERSTORM POTENTIAL.
THOUGH WE'LL GET SOME MORE DAYTIME HEATING UNDER CLEARER SKIES,
SURFACE-BASED INSTABILITY MAY BE LIMITED AS FORECAST HIGH
TEMPERATURES REMAIN BELOW 60 DEGREES, AND LINGERING SNOW COVER
ALONG THE MOUNTAIN SLOPES INHIBITS SURFACE WARMING. IN ADDITION,
WHILE WEAK UPPER LEVEL SHORTWAVES WILL HELP WITH CONVECTION, THE
OVERALL UPPER LEVEL VORTICITY FIELD IS RATHER CHAOTIC, WITH NO
DISTINCT AND WELL-FORMED WAVES TO REALLY DRIVE CONVECTION.
THOUGH OVERALL THUNDERSTORM POTENTIAL IS FAIRLY LOW, THE BEST DAY
FOR THUNDERSTORMS WILL LIKELY BE TOMORROW. AT LEAST ONE
THUNDERSTORM HAS ALREADY POPPED UP TODAY AROUND TALKEETNA AT
ABOUT 2 PM. HOWEVER, RADAR SHOWS THAT OTHER CONVECTIVE CELLS ARE
FIZZLING OUT BEFORE THEY CAN PRODUCE LIGHTNING, POSSIBLY BECAUSE
MID-LEVEL FLOW IS TOO FAST AND CAUSING THESE STORMS TO SHEAR
APART. CONDITIONS LOOK BETTER TOMORROW, AS MODELS ARE HINTING
TOWARDS GREATER SURFACE-BASED INSTABILITY AND MID-LEVEL FLOW IS
CLOSER TO THE HAPPY MEDIUM (10-15 KT) FOR MORE ORGANIZED
CONVECTION. AREAS WHERE THERE MIGHT BE A CHANCE FOR THUNDERSTORMS
INCLUDE MAT-SU, WESTERN KENAI PENINSULA, AND COPPER RIVER VALLEY.
BY WEDNESDAY, WEAKER STEERING FLOW AND EVEN WEAKER UPPER-LEVEL
VORTICITY BRING THUNDERSTORM CHANCES BACK DOWN. THERE'S ALSO
UNCERTAINTY WITH WHETHER A WEAK UPPER LEVEL LOW IN THE INTERIOR
WILL BRING CLOUD COVER SOUTHWARDS INTO SOUTHCENTRAL, WHICH WILL
REDUCE DAYTIME WARMING. STAY TUNED TO THE FORECAST, AND BE ON THE
LOOKOUT FOR SHOWERS AND POTENTIAL THUNDERSTORMS IF YOU'LL BE
OUTDOORS IN THE AFTERNOONS AND EVENINGS.
-CHEN
.SHORT TERM FORECAST SOUTHWEST ALASKA AND BERING SEA/ALEUTIANS
(DAYS 1 THROUGH 3: THIS AFTERNOON THROUGH THURSDAY AFTERNOON)...
SYNOPTICALLY, A SLOW MOVING LOW OFF THE COAST OF KODIAK ISLAND
WILL CONTINUE TO IMPACT THE AREA AHEAD OF A MID-WEEK FRONT
USHERING IN WARMER AIR, GUSTY WINDS AND RAIN TO THE ALEUTIANS AND
AKPEN.
WIND GUSTS ON THE SOUTHERN AK PEN AND THE PACIFIC OCEAN SIDE OF
THE ALEUTIAN CHAIN ARE IN THE 20 TO 25 MPH RANGE. HOWEVER, WIND
GUSTS ON THE NORTHERN SIDE OF THE ALEUTIANS AND AK PEN FROM EARLY
THIS MORNING THROUGH 4:00PM TODAY RANGED FROM 40 TO 52 MPH.
NORTHERLY WIND GUSTS RANGING FROM 30 TO 40 MPH ARE TO CONTINUE
INTO LATE THIS EVENING AS THE AFOREMENTIONED LOW MOVES EASTWARD.
OVERNIGHT, THE WINDS BECOME MORE NORTHWESTERLY. NORTHWESTERLY
WINDS PERSIST INTO TOMORROW THOUGH WILL CONTINUE TO DECREASE
THROUGH THE DAY. WIND GUSTS THROUGH THE GAP LOCATIONS IN THE
ALEUTIANS WILL REMAIN STRONG THROUGH THIS EVENING TOO BEFORE
DIMINISHING. WAVES OF MOISTURE BRINGING A MIX OF SNOW AND RAIN
SHOWERS TO THIS AREA CONTINUE THROUGH PREVAIL INTO LATE TOMORROW
MORNING WITH THEN TURN MORE ISOLATED DURING THE AFTERNOON. THOUGH
TRACE AMOUNTS OF SNOW HAVE BEEN REPORTED TODAY IN THE ALEUTIANS,
THE FALSE PASS AND COLD BAY OBSERVATIONS, CONFIRMED BY WEB
CAMERAS, SHOW A LIGHT COATING SNOW FALLING DURING TODAY'S BRIEF
BUT HEAVY SNOW SHOWERS AS OF 4:00PM TODAY.
ACROSS INTERIOR SOUTHWEST ALASKA, SHORTWAVES WILL CONTINUE TO BRING
RAIN SHOWERS TO THE AK PEN AND BRISTOL BAY COASTLINE THIS
AFTERNOON. THIS EVENING, A STRAY RAIN SHOWER IS POSSIBLE AS FAR
NORTH AS QUINHAGAK SOUTHEAST TO THE ALASKA RANGE WITH MOST OF THE
PRECIPITATION REMAINING SOUTH OF ALASKA RANGE. THROUGH MID-WEEK,
TEMPERATURES WILL INCREASE AND AFTERNOON CLOUDS WITH WEAK WAVES
PASSING THROUGH, RESULT IN WIDESPREAD RAIN SHOWER CHANCES. THERE
REMAINS ENOUGH INSTABILITY ACROSS THE FOOTHILLS OF THE WESTERN
ALASKA RANGE AND LOWER KUSKOKWIM VALLEY TOMORROW AFTERNOON AND
WEDNESDAY AFTERNOON TO PRODUCE A FEW LIGHTNING STRIKES SHOULD
VIGOROUS RAIN SHOWERS DEVELOP.
-DJ
LONG TERM FORECAST (DAYS 4 THROUGH 7/FRIDAY THROUGH MONDAY)
THE UPPER LEVEL FLOW WILL BE FAIRLY AMPLIFIED THROUGH THE EXTENDED
FORECAST PERIOD, BUT THE SUBTROPICAL JET STREAM WILL BE CENTERED
OVER THE NORTH PACIFIC. THIS WILL RESULT IN A FAIRLY COMMON
PATTERN FOR THIS TIME OF YEAR, WITH SOME LEVEL OF UPPER LEVEL
RIDGING PERSISTING OVER SOUTHERN AK. THIS WILL LEAD TO SOME
SUNSHINE MOST DAYS FOR SOUTHWEST AND SOUTHCENTRAL AK (ESPECIALLY
INLAND), WARMING TEMPERATURES, AND DIURNAL CONVECTION. MEANWHILE,
MORE ACTIVE WEATHER WILL PERSIST IN THE BERING SEA/ALEUTIANS AND
GULF OF ALASKA. A DEEP LOW IN THE BERING ON FRIDAY WILL GRADUALLY
WEAKEN OVER THE WEEKEND. A NEW LOW WILL MOVE OUT OF THE PACIFIC
AND TOWARD THE ALEUTIAN CHAIN ON SUNDAY, BUT MODEL SPREAD IN THE
TRACK IS LARGE. DEPENDING ON THE TRACK, THIS COULD AFFECT COASTAL
SW AK WITH RAIN AND WIND ON SUNDAY. YET ANOTHER DEEP LOW WILL MOVE
OUT OF THE NORTHWEST PACIFIC TO THE WESTERN ALEUTIANS ON MONDAY.
FOR THE GULF, A LOW WILL MOVE OUT OF THE NORTHEAST PACIFIC FRIDAY
NIGHT INTO SATURDAY, BUT WILL REMAIN OVER THE SOUTHERN GULF. AN
OCCLUDED FRONT WILL SPREAD OUT ALONG THE GULF COAST, BUT THE WORST
OF THE WEATHER WILL REMAIN OVER THE MARINE AREAS. THIS LOW WILL
THEN DISSIPATE ON SATURDAY. DEPENDING ON THE TRACK OF THE NORTH
PACIFIC LOW OUT WEST, A LOW OR FRONTAL SYSTEM COULD MOVE TO KODIAK
AND THE GULF ON MONDAY.
AVIATION
PANC...VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE CURRENT
TAF PERIOD. GUSTY TURNAGAIN ARM WINDS WITH GUST OF 25 TO 30 KTS
WILL SLOWLY DIMINISH THIS EVENING AS WINDS TURN DOWN INLET AND
DECREASE. LIGHT NORTHERLY WINDS WILL RETURN BY TUESDAY MORNING
ONLY TO BE FOLLOWED BY MORE TURNAGAIN WINDS IN THE AFTERNOON,
THOUGH THEY SHOULD BE WEAKER THAN THOSE OBSERVED TODAY.
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