504
FXAK68 PAFC 210026
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
426 PM AKDT SAT JUN 20 2026
SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3)
KEY MESSAGES:
* SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH LATE THIS
EVENING, PRIMARILY FOR THE COPPER RIVER BASIN. COVERAGE OF
THUNDERSTORMS IS EXPECTED TO BE BE LESS THAN WHAT THEY WERE
YESTERDAY. IF YOU HEAR THUNDER OR SEE LIGHTNING, SEEK SHELTER.
* CONVECTION CHANCES DECREASE OVER THE NEXT FEW DAYS. A LOW
APPROACHING KODIAK WILL BRING RAIN TODAY THROUGH MONDAY. THERE
IS LOW CONFIDENCE WITH HOW FAR NORTH THE FRONT WILL AFFECT
MAINLAND SOUTHCENTRAL AND WHEN IT WOULD ARRIVE.
DISCUSSION:
WITH A MARINE LAYER RESIDING OVER MUCH OF THE COOK INLET THIS
MORNING AND EARLY AFTERNOON, COASTAL LOCATIONS ALONG THE WESTERN
KENAI PENINSULA AND NORTHWARD TO ANCHORAGE HAVE STRUGGLED TO WARM
UP TODAY. THE FOG FROM EARLIER HAS MOSTLY LIFTED, THOUGH A NARROW
CORRIDOR OF LOW STRATUS STILL REMAINS IN PLACE FROM TYONEK TO JUST
NORTH OF ANCHOR POINT. ALTHOUGH SATELLITE IMAGERY SHOWS THAT THIS
LOW STRATUS DECK IS SHRINKING AND SCATTERING OUT, THESE LOCATIONS
HAVE LESS TIME FOR DAYTIME HEATING - SO TODAY'S HIGH TEMPERATURES
HAVE BEEN LOWERED QUITE A BIT FOR THIS AFTERNOON WITH THIS
FORECAST PACKAGE FOR THESE AREAS.
ELSEWHERE, WHERE IT HAS BEEN ABLE TO WARM AS EXPECTED TODAY,
RADAR RETURNS AS OF 3PM AKDT DEPICT ISOLATED SHOWERS AND
THUNDERSTORMS ONGOING ACROSS THE CENTRAL/SOUTHERN COPPER RIVER
BASIN FROM CHITINA TO GLENNALLEN. 500 MB VORTICITY ANALYSIS
DEPICTS A SHORTWAVE MOVING OVER THIS REGION AND ROTATING
NORTHEASTWARD AROUND THE NORTHERN FLANK OF A VERTICALLY STACKED
COASTAL RIDGE SITUATED OVER THE EASTERN GULF. THERE ARE ALSO A
COUPLE OF ISOLATED STORMS FORMING ACROSS THE NORTHERN SUSITNA
VALLEY, THOUGH THERE IS MEDIUM TO HIGH (70-80%) CONFIDENCE THAT
THIS AREA WILL SEE LESS STORM COVERAGE THIS AFTERNOON GIVEN MUCH
OF THE UPPER LEVEL SUPPORT/STEEPER LAPSE RATES ARE LOCATED OVER
THE COPPER RIVER BASIN.
MEANWHILE, A WEAK NORTH PACIFIC LOW IS LIFTING A FRONT NORTHWARD
ACROSS THE WESTERN GULF, BRINGING RAINFALL TO KODIAK ISLAND THIS
AFTERNOON. THE MODELS SHOW THAT KODIAK ISLAND WILL SEE PERIODS OF
RAIN SHOWERS LASTING INTO EARLY NEXT WEEK.
AT THE SURFACE, MODELS INDICATE THAT THE COASTAL RIDGE CURRENTLY
IN PLACE CONTINUES TO BUILD THROUGH SUNDAY AFTERNOON. THIS WILL
SET UP AN EAST TO WEST ORIENTED PRESSURE GRADIENT FROM WHITTIER TO
ANCHORAGE AND DEVELOP A RELATIVELY WEAK TURNAGAIN ARM WIND SUNDAY
AFTERNOON. THIS JET WILL LIKELY TAKE A SLIGHT BEND TO THE NORTH
AS THE FLOW IS REDIRECTED BY LOWER PRESSURE FROM DAYTIME HEATING
ACROSS THE MATANUSKA AND SUSITNA VALLEY. THERE IS A CHANCE THAT
BREEZY CONDITIONS CLIP WEST ANCHORAGE SUNDAY AFTERNOON, BUT THAT
AS OF NOW IS OF LOWER CONFIDENCE (20-30%).
MODEL AGREEMENT HAS IMPROVED SOMEWHAT FOR MONDAY AS A COMPLEX LOW
APPEARS TO FORM AS A LOW PRESSURE SYSTEM DIPPING SOUTHWARD ACROSS
THE EASTERN BERING SEA INTERACTS WITH THE NORTH PACIFIC LOW. THE
GLOBAL MODELS ARE STARTING TO CONVERGE ON THE IDEA THAT THE
COMPLEX LOW ENTERS THE GULF OF ALASKA WHERE BROAD TROUGHING SETS
UP. RAIN SHOWERS ARE EXPECTED TO LIFT NORTHWARD ACROSS THE GULF
THIS WEEKEND THROUGH MONDAY. THERE IS GROWING CONFIDENCE THAT RAIN
SHOWERS REACH COASTAL AREAS OF SOUTHCENTRAL (FROM HOMER TO SEWARD
TO CORDOVA) AS EARLY AS MONDAY MORNING. BY LATE MONDAY, MODEL
CONSENSUS DEGRADES, BUT BIG PICTURE WISE, TROUGHING ACROSS THE
GULF WILL LIKELY SEND WAVES OF MOISTURE TOWARDS COASTAL
SOUTHCENTRAL, THOUGH THERE IS LOW CONFIDENCE ON HOW MUCH RAINFALL
AND THE TIMING/DURATION. STAY TUNED.
-AM/RUX
.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS
(DAYS 1 THROUGH 3: TODAY THROUGH TUESDAY AFTERNOON)...
GENERALLY UNSETTLED WEATHER CONTINUES. RAIN SHOWERS AND
THUNDERSTORM POTENTIAL CONTINUE IN INTERIOR SOUTHWEST ALASKA AND
KUSKOKWIM DELTA THROUGH EARLY NEXT WEEK. FOR BRISTOL BAY, ALASKA
PENINSULA, AND ALONG THE BERING SEA, EXPECT AREAS OF FOG AND LOW
CLOUDS TO LINGER, WITH SOME STEADY RAIN ARISING FROM A LOW NEAR
KODIAK ISLAND. FOR ADAK/ATKA AND WEST, A FRONT WILL BRING
SUSTAINED WINDS 25 TO 35 KT FROM EARLY TOMORROW MORNING THROUGH
MONDAY. NO MAJOR HAZARDS ARE ANTICIPATED AT THIS TIME.
DIVING INTO THE DETAILS... THUNDERSTORM POTENTIAL REMAINS THE
BIGGEST CHALLENGE WITH THE FORECAST. FOR THIS AFTERNOON AND
EVENING, HAVE EXPANDED COVERAGE OF ISOLATED THUNDERSTORMS AND
EXTENDED THUNDERSTORM POTENTIAL THROUGH LATE TONIGHT. CURRENTLY,
SATELLITE SHOWS CONVECTION DEVELOPING ALONG THE WESTERN ALASKA
RANGE NEAR LIME VILLAGE AND ALONG KUSKOKWIM RIVER AS POCKETS OF
CLEAR SKY COMBINE WITH ROBUST UPPER LEVEL SHORTWAVES MOVING OVER
SOUTHWEST ALASKA. WHILE CLOUD COVER MAY INHIBIT SURFACE HEATING IN
KUSKOKWIM DELTA TODAY, THE THINKING IS THAT THIS WILL BE
COMPENSATED FOR BY LIFT FROM ROBUST SHORTWAVES ROTATING AROUND THE
UPPER LOW IN THE EASTERN BERING. AND AS WE'RE RIGHT ON THE CUSP
OF THE SUMMER SOLSTICE, LONG DAYS COULD LEAD TO THUNDERSTORM
ACTIVITY CONTINUING WELL INTO THE EVENING AND OVERNIGHT HOURS, AS
WAS SEEN YESTERDAY. OVERALL, TODAY'S THUNDERSTORMS WON'T HAVE AS
MUCH INSTABILITY TO DRAW ON AS YESTERDAY'S, SO LIGHTNING INTENSITY
WILL LIKELY BE LESS. GENERALLY EXPECT THE FOOTPRINT OF
THUNDERSTORMS TO DECREASE THROUGH THE NEXT FEW DAYS TOO, AS A LOW
LINGERING NEAR KODIAK ISLAND WILL LIKELY BRING CLOUDS AND REDUCE
SURFACE HEATING.
-KC
.LONG TERM FORECAST (DAYS 4 THROUGH 7: WEDNESDAY THROUGH
SATURDAY)...
AN UNSETTLED PATTERN IS EXPECTED TO PERSIST ACROSS SOUTHCENTRAL
ALASKA AND THE ALEUTIANS THROUGH MUCH OF NEXT WEEK. A BROAD UPPER
TROUGH AND SURFACE LOW PRESSURE OVER THE GULF OF ALASKA WILL
MAINTAIN EXTENSIVE CLOUD COVER AND PERIODIC SHOWER ACROSS
SOUTHCENTRAL. THE GREATEST PRECIPITATION CHANCES WILL GENERALLY BE
ALONG THE COASTAL MOUNTAINS AND WINDWARD TERRAIN, THOUGH SCATTERED
INLAND SHOWERS ARE ALSO EXPECTED DURING THE AFTERNOON AND EVENING
HOURS. TEMPERATURES SHOULD REMAIN NEAR TO SLIGHTLY BELOW SEASONAL
NORMALS UNDER THE PERSISTENT CLOUD COVER.
FARTHER WEST, A BERING SEA LOW WILL GRADUALLY TRACK EASTWARD
TOWARD THE ALEUTIANS, BRINGING PERIODS OF RAIN AND LOCALLY GUSTY
WINDS TO THE ISLAND CHAIN THROUGH MIDWEEK. AS THE SYSTEM MOVES
INTO THE WESTERN MAINLAND, IT WILL BECOME ABSORBED INTO A MORE
ZONAL WESTERLY FLOW ALOFT, ALLOWING PRECIPITATION CHANCES TO
SPREAD EASTWARD WHILE KEEPING GENERALLY UNSETTLED CONDITIONS IN
PLACE.
MEANWHILE, A RIDGE CENTERED OVER THE CENTRAL BERING WILL PROMOTE
COMPARATIVELY QUIETER WEATHER ACROSS THE ALASKA PENINSULA AND
PORTIONS OF SOUTHWEST ALASKA. HOWEVER, DAYTIME HEATING AND WEAK
INSTABILITY MAY STILL SUPPORT ISOLATED AFTERNOON SHOWERS
PARTICULARLY ALONG THE WESTERN SLOPES OF HIGHER TERRAIN.
FORECAST CONFIDENCE DECEASES TOWARD THE LATTER HALF OF NEXT WEEK
AS MODEL SOLUTIONS DIVERGE ON THE EVOLUTION AND PLACEMENT OF THE
BERING LOW AND ASSOCIATED UPPER-LEVEL FEATURES. DESPITE THESE
DIFFERENCES, CONFIDENCE REMAINS MODERATE THAT MUCH OF SOUTHERN
ALASKA WILL REMAIN IN A COOLER, SHOWERY, AND GENERALLY UNSETTLED
PATTERN THROUGH THE END OF THE FORECAST PERIOD.
LM
AVIATION
PANC...VFR CONDITIONS EXPECTED TO PERSIST THROUGH THE PERIOD. MID
AND UPPER LEVEL CLOUD COVER SHOULD MITIGATE FOG AND STRATUS
DEVELOPMENT OVER COOK INLET OVERNIGHT. TURNAGAIN ARM WINDS WILL
INCREASE SUNDAY AFTERNOON...PERIODICALLY BENDING INTO THE TERMINAL
WITH GUSTS UP TO 20 KTS.
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