859
FXAK68 PAFC 290028
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
428 PM AKDT THU MAY 28 2026
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3/TONIGHT
THROUGH SUNDAY)...
A NEARLY STATIONARY VERTICALLY STACKED LOW ANCHORS A HIGH AMPLITUDE
TROUGH IN THE GULF OF ALASKA. A SHORT-WAVE EXTENDS FROM THIS LOW
NORTHEASTWARD TO THE YUKON AND IT IS ROTATING WESTWARD TOWARD THE
COPPER RIVER BASIN. AN AREA OF ORGANIZED SHOWERS HAS FORMED AHEAD
OF IT AND ARE MOVING WEST-SOUTHWEST ACROSS THE WRANGELL MOUNTAINS,
SOUTHEASTERN COPPER RIVER BASIN, AND TOWARD THE VALDEZ-CORDOVA
AREA. PARTLY TO MOSTLY SUNNY SKIES HAVE PREVAILED FOR THE FIRST
HALF OF THE DAY ACROSS THE REST OF SOUTHCENTRAL. WEAK VORTICITY-
MAXIMA EMBEDDED IN THE FLOW AHEAD OF THE AFOREMENTIONED SHORT-WAVE
ARE ACTING ON A WEAKLY UNSTABLE AIRMASS TO PRODUCE ISOLATED TO
SCATTERED AFTERNOON SHOWERS ACROSS THE REMAINDER OF SOUTHCENTRAL.
STEERING FLOW IS GENERALLY NORTHERLY, WITH SHOWERS TRACKING FROM
NORTH TO SOUTH. HAVE REMOVED THUNDERSTORMS FROM THE FORECAST TODAY
DUE TO MARGINAL INSTABILITY AND A LACK OF STRONGER UPPER LEVEL
FORCING. THE SHIFT IN PATTERN HAS BROUGHT AN END TO THE STRONG AND
GUSTY SOUTHEASTERLY GAP WINDS. INSTEAD, A MORE SUMMER-LIKE
PATTERN IS IN PLACE, WITH SEA BREEZES DEVELOPING ALONG THE COAST
AND LIGHT WINDS INLAND.
THE SHORT-WAVE ENTERING THE EASTERN COPPER RIVER BASIN WILL ROTATE
SOUTHWESTWARD TONIGHT AND WEAKEN AS IT REACHES PRINCE WILLIAM
SOUND ON FRIDAY. SHOWERS THIS AFTERNOON WILL GRADUALLY TRANSITION
TO A STEADY LIGHT RAIN OVERNIGHT FROM CHITINA AND COPPER CENTER
SOUTHWARD TO VALDEZ AND CORDOVA. SHOWERS ELSEWHERE WILL DIMINISH
WITH THE LOSS OF DAYLIGHT AND SURFACE HEATING TONIGHT, THOUGH A
FEW VERY LIGHT SHOWERS COULD CONTINUE THROUGH THE NIGHT-TIME
HOURS AS VORTICITY-MAXIMA CONTINUE TO PASS OVERHEAD.
THE CONVECTIVE FORECAST FOR TOMORROW POSES SOME CHALLENGES. FIRST
OFF, DEBRIS CLOUDS FROM THE WEAKENING SHORT-WAVE WILL LIMIT
SURFACE HEATING AND ABILITY TO DESTABILIZE THE ATMOSPHERE OVER
THE SOUTHERN TIER OF SOUTHCENTRAL. SECOND, THE UPPER LEVEL
FEATURES ARE QUITE COMPLEX, WITH A PLETHORA OF SHORT-WAVES AND
VORTICITY MAXIMA MOVING THROUGH A SHORT-WAVE RIDGE. CONTINUED
NORTHERLY FLOW ACROSS THE ALASKA RANGE WILL LEAD TO MORE UNSTABLE
CONDITIONS OVER INTERIOR SOUTHCENTRAL, ESPECIALLY ACROSS THE
NORTHERN SUSITNA VALLEY AND TALKEETNA MOUNTAINS. THE COMPLEXITY
OF THE SET-UP MAKES IT DIFFICULT TO PINPOINT AREAS OF CONVECTIVE
INITIATION. BASED ON OVERALL LEVEL OF INSTABILITY (AND TAKING INTO
ACCOUNT CLIMATOLOGY PREFERRED AREAS FOR INITIATION) THE MOST
LIKELY AREAS FOR CONVECTION ARE THE NORTHERN PORTIONS OF THE
SUSITNA VALLEY AND COPPER BASIN AS WELL AS THE TALKEETNA MOUNTAINS
SOUTHWARD TO THE FRONT RANGE CHUGACH NEAR ANCHORAGE. SIMPLE
ADVECTION COULD CAUSE SOME OF THESE TO MOVE OVER POPULATED AREAS
OF THE MATANUSKA VALLEY AND ANCHORAGE FRIDAY AFTERNOON AND
EVENING. THUNDERSTORMS AREA FAVORED OVER THE INTERIOR THEN
SOUTHWARD ACROSS THE TALKEETNA MOUNTAINS TO THE MAT VALLEY.
CONDITIONS WILL BE MORE UNSTABLE THAN TODAY, THOUGH KEY PARAMETERS
ARE STILL ON THE LOW END FOR THUNDERSTORMS, SO ANY STORMS THAT
DO FORM WILL BE ISOLATED IN NATURE.
AS WE HEAD TO THE WEEKEND, THE WEAK UPPER LEVEL SHORT-WAVE RIDGE
WILL SIT OVERHEAD WHILE A WEAK SHORT-WAVE DROPS SOUTHWARD FROM
THE INTERIOR AND STALLS ALONG/NEAR THE ALASKA RANGE. IT'S LOOKING
INCREASINGLY LIKELY THAT MOISTURE WILL BE TRAPPED BENEATH THE
RIDGE AND LEAD TO MOSTLY CLOUDY SKIES OVER THE WEEKEND (WITH JUST
AN OCCASIONAL BREAK OF SUN). A LOSS OF NORTHERLY FLOW WILL LEAD
TO A SLIGHT COOLING OF THE AIRMASS AND MORE STABLE CONDITIONS.
THIS WILL LEAD TO LOWER COVERAGE OF SHOWERS AND GENERALLY LIGHTER
RAINFALL IN ANY SHOWERS. INCREASING SOUTHERLY FLOW UP COOK INLET
WILL KEEP THE POPULATION CENTERS DRY (OR MOSTLY DRY). THE CLOUD
COVER AND COOLISH AIRMASS MEANS TEMPERATURES WILL MAX OUT IN THE
50S FOR MOST AREAS.
LASTLY, IT IS WORTH HIGHLIGHTING THAT MUCH WARMER AND SUNNIER
WEATHER REMAINS ON TRACK FOR NEXT WEEK.
-SEB
.SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA/ALEUTIANS
(DAYS 1 THROUGH 3)...
SURFACE OBSERVATIONS, SATELLITE IMAGES AND WEATHER CAMERAS ACROSS
THE SOUTHWEST AND BRISTOL BAY COASTLINE SHOWED VISIBILITY IN THE
FOG RANGING FROM 1/4 OF A MILE TO 3 MILES THROUGH LATE THIS
MORNING. THE THICKEST FOG WAS ALONG THE COAST AND LOW LYING AREAS
ALONG THE KUSKOKWIM RIVER TO BETHEL. FOG REDEVELOPS OVERNIGHT
INTO FRIDAY MORNING IN THESE AREAS.
THROUGH THE NEXT 48 TO 72 HOURS, THE SYNOPTIC WEATHER PATTERN WILL
SHIFT AND CHANGE TO A MORE SUMMER TIME PATTERN. CURRENTLY THROUGH
TOMORROW EVENING, A DEEP NW-SE ORIENTED TROUGH LOCATED IN THE
BERING SEA WEST OF THE PRIBILOF ISLANDS WILL ALLOW FOR A LOW TO
MOVE THROUGH THE WESTERN BERING BRINGING RAIN AND SMALL CRAFT
WINDS FROM ADAK TO SHEMYA. IN ITS WAKE, HIGH PRESSURE BUILDS IN
FROM RUSSIA AND MOVES EASTWARD. THIS BRINGS A FAST-MOVING LOW,
AND ITS RAIN AND WIND, THROUGH THE CENTRAL ALEUTIANS FRIDAY
EVENING. EASTERLY TO NORTHEASTERLY WINDS BRING WAVES OF MOISTURE
TO THE ALEUTIANS SATURDAY AS THE HIGH DEEPENS AND SHIFTS TO TOWARD
THE BERING STRAIT.
ON THE MAINLAND, SCATTERED RAIN SHOWERS PERSIST INTO LATE THIS
EVENING AS WAVES OF MOISTURE MOVE WESTWARD OVER THE AREA. THEY
WILL DIMINISH WITH THE DEPARTURE OF A GULF OF ALASKA LOW GRADUALLY
MOVING SOUTHWARD TODAY. AS THE AFOREMENTIONED HIGH PRESSURE
BUILDS, ITS NORTHEASTERLY TO NORTHERLY WIND FLOW BRINGS MORE
ROBUST SHORTWAVES ACROSS THE SOUTHWEST ALASKA TOMORROW AND
SATURDAY. THIS WILL ALLOW FOR WIDESPREAD SCATTERED AFTERNOON AND
EVENING THUNDERSTORMS FROM ALONG THE ALASKA RANGE TO THE KUSKOKWIM
VALLEY SOUTH TO THE BRISTOL BAY COASTLINE. TEMPERATURES WILL
CONTINUE TO INCREASE THROUGH SATURDAY.
-DJ
LONG TERM FORECAST (DAYS 4 THROUGH 7: SUNDAY THROUGH WEDNESDAY)
A HIGH PRESSURE RIDGE WILL DOMINATE ACROSS THE BERING SEA AND
EXTEND INTO THE WESTERN MAINLAND ALASKA WEDNESDAY THROUGH
SATURDAY, KEEPING CONDITIONS GENERALLY STABLE AND DRY OVER WESTERN
ALASKA, THE ALEUTIAN ISLANDS AND THE BERING SEA. MARINE ACTIVITY
SHOULD REMAIN FAIRLY QUIET UNDER THIS SETUP, WITH LITTLE CHANCE OF
WIDESPREAD PRECIPITATION OR SIGNIFICANT WEATHER IMPACTS IN THOSE
FAR WESTERN ZONES.
MEANWHILE, A BROAD UPPER LEVEL LOW WILL STAY ANCHORED WELL SOUTH
OVER THE SOUTHERN GULF OF ALASKA, LIMITING ANY DEEP MOISTURE REACH
INTO SOUTHCENTRAL COASTAL AREAS. EXPECT ONLY LIGHT OR ISOLATED
SHOWERS AT TIMES RATHER THAN HEAVIER OR ORGANIZED RAINFALL ALONG
THE SOUTHCENTRAL COAST FROM THE ALASKA PENINSULA THROUGH THE KENAI
PENINSULA AND PRINCE WILLIAM SOUND REGION. OVERALL THE PATTERN
POINTS TO A RELATIVELY QUIET STRETCH OF WEATHER ACROSS
SOUTHCENTRAL AND WESTERN ALASKA, WITH NO MAJOR PRECIPITATION
EVENTS OR HAZARDS HIGHLIGHTED THROUGH THE WEEKEND.
-DD
AVIATION
PANC...VFR CONDITIONS WILL PERSIST THROUGH FRIDAY. A RAIN SHOWER
COULD DEVELOP IN THE VICINITY OF THE TERMINAL THIS AFTERNOON, BUT
CHANCES WILL BE LOW AND A NORTHWESTERLY FLOW ALOFT SHOULD KEEP
THE BULK OF ANY SHOWER ACTIVITY CLOSER TO THE FOOTHILLS OF THE
WESTERN CHUGACH. THERE IS LOW CONFIDENCE THAT A CEILING BETWEEN
3,500 AND 5,000 FT COULD DEVELOP FOR A FEW HOURS OVERNIGHT INTO
EARLY FRIDAY MORNING, A RESULT OF LINGERING CLOUDS FROM THE
SHOWERS OVER THE MOUNTAINS TODAY MOVING OVER THE ANCHORAGE BOWL
AND TERMINAL AS THE NORTHWESTERLY FLOW ALOFT BECOMES MORE NORTH-
NORTHEASTERLY AND WEAKENS.
A SOUTHEASTERLY TURNAGAIN ARM WIND WILL REDEVELOP FOR FRIDAY
AFTERNOON AND EVENING WITH GUSTS UP TO 25 KT POSSIBLE. A CHANCE
FOR SHOWERS ALSO RETURNS FOR FRIDAY AFTERNOON.
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