685
FXAK68 PAFC 050038
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
438 PM AKDT SUN MAY 4 2025
SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3)
A COMBINATION OF AN UPPER LEVEL SHORTWAVE AND A POTENT FRONT IS
MOVING AWAY FROM KODIAK ISLAND AND TOWARD THE SOUTHCENTRAL COAST.
THIS IS CAUSING WINDS TO BECOME GUSTY AND PRECIPITATION CHANCES TO
INCREASE AS THE COAST IS NOW WITHIN THE OUTER FRINGES OF A BAND
OF HEAVY PRECIPITATION. SOUTHEASTERLY GAP WINDS ARE ALSO QUICKLY
MAKING THEIR WAY BACK INTO THE AREA, AND WILL ONLY PICK UP IN
INTENSITY AS THE EVENING WEARS ON AS THEY WILL BE AIDED BY STRONG
WINDS ALOFT THAT WILL LIKELY, TO A DEGREE, MIX DOWN TO THE
SURFACE. AT SOME POINT THIS AFTERNOON AND EVENING AND INTO THE
OVERNIGHT HOURS, STRONG SOUTHEASTERLY WINDS WILL SHIFT A BIT MORE
DOWN-INLET, ALLOWING FOR NORTHEASTERLY KNIK ARM WIND TO BECOME THE
DOMINANT WIND DIRECTION.
ALTHOUGH THERE ARE SUBTLE DISCREPANCIES IN SOME OF THE GUIDANCE
IN THE ORIENTATION AND STRENGTH OF THE PRESSURE GRADIENT FIELD IN
ADVANCE OF THE FRONT, THERE IS ABOVE AVERAGE CONFIDENCE OF
IMPACTFUL WIND. A SPECIAL WEATHER STATEMENT HAS BEEN ISSUED FOR
EAST TURNAGAIN ARM, INCLUDING PORTAGE AND GIRDWOOD. HERE, WINDS
ARE LIKELY TO GUST UPWARDS OF 65 TO 70 MPH AT TIMES. THERE IS
ANOTHER SPECIAL WEATHER STATEMENT ISSUED FOR THE ANCHORAGE
HILLSIDE AND EAGLE RIVER, WHERE AGAIN WINDS COULD GUST IN EXCESS
OF 50 MPH THIS EVENING, THOUGH IT'S POSSIBLE THE DOWN-INLET
GRADIENT WILL PREVAIL AND WINDS WILL BE CALM. HIGHER GUSTS FOR
BOTH SPECIAL WEATHER STATEMENT LOCATIONS ARE POSSIBLE. LIKEWISE,
POWER OUTAGES FOR THESE AFOREMENTIONED AREAS CANNOT BE RULED OUT.
LOOKING OUT EAST, THERE IS A WINTER WEATHER ADVISORY OUT FOR
THOMPSON PASS WHERE IT WILL BE COLD AND WINDY ENOUGH TO WARRANT
THE CHANCE OF BLOWING SNOW WITH THE POSSIBILITY OF REDUCED
VISIBILITY. CONFIDENCE IN BLOWING SNOW IS HIGHEST UNTIL 11AM
MONDAY WITH THE BEST CHANCE FOR ACCUMULATING SNOW ON ROADWAYS
AFTER SUNSET.
ALSO BY THIS AFTERNOON AND EVENING, BARRIER JET WINDS WILL HAVE
INCREASED TO STORM FORCE ALONG THE FRONT NEAR THE BARREN ISLANDS,
WITH HIGH END GALE FORCE WINDS OVER THE NORTHERN GULF AND
INCREASING TO STORM-FORCE SOUTH OF PRINCE WILLIAM SOUND. HURRICANE
FORCE WIND GUSTS CANNOT BE RULED OUT (64 KTS OR GREATER). THE
BARRIER JET QUICKLY COLLAPSES WITH THE FRONTAL PASSAGE MONDAY
MORNING AND NEAR SHORE WINDS SHIFT TO SOUTHERLY AS THE PARENT AREA
OF DEEP LOW PRESSURE NEARS KODIAK ISLAND.
IT WILL BE A TOTAL WASHOUT FOR COASTAL SOUTHCENTRAL, WHERE 2-4"
OF RAIN IS LIKELY TO FALL, WITH LOCALIZED AREAS THAT BENEFIT FROM
OROGRAPHIC LIFT, SUCH AS ALONG THE SOUTHERN FACING SLOPES OF THE
CHUGACH AND EASTERN FACING SLOPES OF THE KENAI MOUNTAINS, POSSIBLY
SEEING MORE THAN THAT. GUIDANCE SHOWS HEAVY PRECIPITATION WILL
START OR WILL BE ONGOING THIS AFTERNOON FOR COASTAL SOUTHCENTRAL
AND LAST THROUGH THE DAY MONDAY, AND BEGIN TO TAPER SOMEWHAT
THEREAFTER. FOR THE ANCHORAGE BOWL, ALTHOUGH THERE WILL BE STRONG
DOWNSLOPING TAKING PLACE DURING THIS EVENT, THERE IS ENOUGH
MOISTURE WITH THIS SYSTEM FOR SPRINKLES AND PERHAPS A FEW SHOWERS
TO MAKE IT OVER THE MOUNTAINS FROM THIS AFTERNOON THROUGH THE NEXT
COUPLE OF DAYS.
BY TUESDAY AFTERNOON, THERE WILL LIKELY BE ENOUGH INSTABILITY
WITH DAYTIME HEATING FROM CLEARING CONDITIONS AND UPPER LEVEL
ENERGY TO INTRODUCE THE POSSIBILITY OF CONVECTIVE SHOWERS AND
STORMS FOR THE SUSITNA VALLEY AND UPPER COPPER RIVER BASIN.
-AM/TM
.SHORT TERM FORECAST SOUTHWEST ALASKA AND BERING SEA/ALEUTIANS
(DAYS 1 THROUGH 3: TODAY THROUGH WEDNESDAY AFTERNOON)...
CURRENTLY, THERE IS A LOW WEST OF KODIAK ISLAND. THIS LOW IS
BRINGING PRECIPITATION CHANCES AND GUSTY WINDS TO MUCH OF
SOUTHWEST ALASKA INCLUDING THE EASTERN ALEUTIANS. COLD AIR
ADVECTION STRETCHING DOWNWARD ALONG THE COAST AND INTO THE EASTERN
ALEUTIANS AND ALASKA PENINSULA IS REINFORCING GUSTY GALE FORCE
WINDS ESPECIALLY IN GAP REGIONS. THE KUSKOKWIM DELTA IS BEING
DOWNSLOPED BY EASTERLY WINDS AND HAS LOWER PRECIPITATION CHANCES,
BUT RETAINS GUSTY WINDS. THESE CONDITIONS WILL LINGER THROUGH
MONDAY AS THE LOW SLOWLY MOVES EAST. MEANWHILE, THE WESTERN
ALEUTIANS ARE UNDER A RIDGE AND ARE EXPERIENCING LIGHTER WINDS AND
LOWER CHANCES FOR PRECIPITATION THROUGH MONDAY. THE RIDGE WILL
SHIFT WINDS SOUTHERLY AND ALLOW FOR WARM AIR ADVECTION THROUGH
WEDNESDAY.
BY TUESDAY, THE LOW WILL BEGIN SHIFTING EASTWARD MORE QUICKLY.
WIND SPEEDS WILL SHIFT NORTHEASTERLY IN THE MAINLAND AND DIMINISH
WHILE PRECIPITATION CHANCES WILL SIMILARLY DIMINISH. GAP WINDS IN
THE EASTERN ALEUTIANS AND ALASKA PENINSULA WILL ALSO DIMINISH,
BUT THE TONGUE OF COLD AIR WILL LINGER ON. INCREASED INSTABILITY
IN THE LOWER KUSKOKWIM VALLEY WILL ALLOW FOR THE POTENTIAL FOR
ISOLATED THUNDERSTORMS AS MOISTURE FLOWS IN FROM THE NORTHEAST.
THE WESTERN ALEUTIANS WILL HAVE THE RIDGE FLATTEN OUT AS A TROUGH
ARRIVES FROM THE WEST. A FRONT FROM THE TROUGH WILL INCREASE
CHANCES FOR PRECIPITATION AND STRENGTHEN WIND SPEEDS TO STORM
FORCE AROUND SHEMYA BY TUESDAY AFTERNOON.
BY WEDNESDAY, THE SOUTHWEST MAINLAND WILL ENTER INTO A REGION OF
WEAK HIGH PRESSURE. THIS WILL ALLOW THE REGION TO DRY OUT FURTHER
AND FOR WINDS TO BECOME LIGHT AND VARIABLE AT THE SURFACE. THERE
WILL BE LINGERING SHOWERS IN THE LOWER KUSKOKWIM DELTA WITH THE
POTENTIAL FOR SOME LIGHTNING WITHIN THEM. THIS IS UNCERTAIN
HOWEVER AND WILL DEPEND ON THE VERTICAL PROFILE OF THE ATMOSPHERE.
THE BERING WILL SEE THE FRONT WEAKEN AND DISSIPATE AS IT NEARS THE
PRIBILOFS AND EASTERN ALEUTIANS. WHAT SEEMS TO BE THE BEGINNINGS
OF A TRIPLE POINT LOW BEGINS TO PUSH IN FROM THE WEST BERING WITH
A FRONT INCREASING WIND SPEEDS AND PRECIPITATION CHANCES IN THE
WESTERN ALEUTIANS BY WEDNESDAY AFTERNOON.
-JAR
.LONG TERM FORECAST (DAYS 4 THROUGH 7/THURSDAY THROUGH
SUNDAY)...
THURSDAY, A LOW IN THE SOUTHERN GULF QUICKLY WEAKENS AND
DISSIPATES BY SATURDAY AS A HIGH AMPLITUDE RIDGE BUILDS ACROSS
NORTHWESTERN CANADA. THE FINAL SURFACE SHORTWAVE OF THIS SYSTEM LIFTS
ACROSS THE SOUTHEASTERN GULF TO THE NORTHERN GULF COAST FROM
FRIDAY MORNING THROUGH SATURDAY AFTERNOON. THE UPPER LEVEL LOW
WILL LINGER OVER THE GULF THROUGH FRIDAY BEFORE DEFORMATION CAUSES
THE REMAINING ENERGY TO DISSIPATE.
MEANWHILE, A DEEP LOW WILL TRACK INTO THE FAR WESTERN BERING SEA
THURSDAY, WITH A LEADING FRONT SWEEPING ACROSS THE PRIBILOFS AND
EASTERN ALEUTIANS THROUGH FRIDAY MORNING. DESPITE THE FRONT'S
RAPID PROGRESS, ENSEMBLE CONSENSUS DEPICTS THE LOW'S CENTER
SLOWING AS IT TRACKS INTO THE CENTRAL AND NORTHERN BERING,
REMAINING WEST OF THE PRIBILOF ISLANDS THROUGH SUNDAY. A SECOND
NORTH PACIFIC LOW LIFTS ACROSS THE ALASKA PENINSULA SUNDAY
MORNING, SPLITTING BETWEEN BRISTOL BAY AND THE GULF OF ALASKA.
AVIATION
PANC...VFR CONDITIONS WILL PERSIST. WINDS WILL ONCE AGAIN WILL BE
A CHALLENGE WITH THE POTENTIAL FOR THE STRONG TURNAGAIN ARM WINDS
TO MOVE OVER THE TERMINAL THROUGH THIS EVENING. HOWEVER, WITH THE
STRONG LOW TO THE SOUTH OF THE AREA, IT LOOKS MORE LIKELY THAT THE
SURFACE WINDS WILL INCREASE FROM THE NORTH THIS EVENING AND
OVERNIGHT WHILE WINDS ALOFT REMAIN SOUTHEASTERLY. THIS WILL
PRODUCE WIND SHEAR THROUGH MONDAY MORNING. ON MONDAY AFTERNOON, THE
TURNAGAIN ARM WINDS SHOULD BE ABLE TO MAKE IT BACK OVER THE
AIRPORT AND END THE WIND SHEAR.
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