931
FXAK67 PAJK 130542 AAA
AFDAJK
SOUTHEAST ALASKA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JUNEAU AK
942 PM AKDT WED AUG 12 2026
UPDATE
UPDATED AVIATION SECTION FOR 6Z TAF ISSUANCE, AND
HYDROLOGY SECTION WITH UPDATED INFO.
SYNOPSIS...
KEY MESSAGES:
- SUICIDE BASIN IS RELEASING. MAJOR FLOOD STAGE ON MENDENHALL LAKE
AND RIVER EXPECTED TO BE REACHED WEDNESDAY NIGHT, WITH A CREST
EXPECTED LATER THURSDAY MORNING.
- VERY WARM TEMPERATURES TO END THE WORK WEEK WITH HIGHS IN THE
MID 70S TO LOWER 80S.
- THE WARM AND DRY CONDITIONS WILL BRING ELEVATED THREAT FOR FIRE
STARTS ACROSS MUCH OF SE AK. A FEW SMALL FIRES HAVE BEEN
OBSERVED ALREADY OVER THE PAST WEEK.
SHORT TERM.../THROUGH FRIDAY NIGHT/...WARMER TEMPERATURES,
MAINLY CLEAR SKIES AND MOSTLY DRY WEATHER WILL DOMINATE THE SHORT
TERM PERIOD. HIGH PRESSURE OUT OF THE GULF WILL SLOWLY WEAKEN AND
SHIFT WESTWARD, ALLOWING FOR WEAK SURFACE TROUGHING AND NORTHERLY
AND EASTERLY LOW-LEVEL FLOW OVER, ALLOWING FOR DRIER AND WARMER
INTERIOR AIRMASS TO BUILD INTO THE PANHANDLE. 850MB TEMPS UP TO
15C AND FULL SUN WILL ALLOW FOR VERY WARM INTERIOR TEMPS AWAY FROM
THE COAST TO CLIMB INTO THE UPPER 70S TO POSSIBLY AS HIGH AS THE
MID 80S. LOCATIONS NEAR THE COAST WILL LIKELY CLIMB INTO THE MID
AND POSSIBLY UPPER 70S BEFORE ANY SEA BREEZES KICK IN BY THE
AFTERNOON AND BRING COOLER MARINE AIR BACK INLAND. EACH
AFTERNOON/EVENING, CONVECTION WILL FIRE UP EAST OF THE COASTAL
MOUNTAINS IN WESTERN BC AND YUKON AND DRIFT WEST TOWARDS THE
BORDER. THIS AFTERNOON, SHOWERS AND FEW THUNDERSTORMS HAVE FIRED
UP EAST OF HYDER AND ARE TRYING TO DRIFT WEST INTO THE SOUTHERN
PANHANDLE. HAVE A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS FOR
HYDER THROUGH THE EVENING. THURSDAY AND FRIDAY WILL SEE A SLIGHTLY
BETTER POTENTIAL FOR SHOWERS AND THUNDERSTORMS TO DRIFT INTO THE
SOUTHERN PANHANDLE, MAINLY FOR HYDER, KETCHIKAN AND MISTY FJORDS.
ANY RAIN AMOUNTS WILL BE LIGHT AS THE WARM AND DRIER LOW LEVELS
WILL BRING HIGH CLOUD BASES AND LIMIT THE POTENTIAL FOR A WETTING
RAIN. DANGEROUS CLOUD TO GROUND LIGHTNING AND GUSTY WINDS ARE
POSSIBLE WITH ANY THUNDERSTORMS. ANY MARINE LAYER STRATUS
DEVELOPMENT WILL LIKELY BE LIMITED ALONG AND JUST OFF THE OUTER
COAST.
LONG TERM.../SATURDAY ONWARD/...SATURDAY LOOKS TO CONCLUDE OUR
PERIOD OF TEMPERATURES THAT HAVE THE POTENTIAL TO REACH HEAT
ADVISORY CRITERIA (80F), WITH 850MB TEMPERATURES EXPECTED TO BE
AROUND 12C-13C, THUS BRINGING HIGH TEMPERATURES THAT ARE LIKELY TO
BE IN THE MID TO HIGH 70S. CLOUD COVER ON SATURDAY IS EXPECTED TO
BE LESS THAN 25% IN THE MORNING AND INCREASE TO OVER 50% IN THE
NORTHERN PANHANDLE, WHICH COULD IMPACT THE TEMPERATURES THAT ARE
CURRENTLY FORECASTED. 850MB TEMPERATURES ON SUNDAY ARE NOT
EXPECTED TO BE AS WARM, SITTING AROUND 10C WHICH CAN STILL BRING
TEMPERATURES IN THE 70S TO THE PANHANDLE, BUT ARE NOT LIKELY TO
CAUSE ADVISORY LEVEL HEAT. TEMPERATURES IN THE HIGH 60S AND LOW
70S ARE EXPECTED WHICH MARKS THE START OF GRADUALLY COOLING
TEMPERATURES THROUGH THE WEEK. THE CAUSE OF THE COOLING TEMPS IS
DUE TO A SHIFT IN THE UPPER LEVEL FLOW TO AN ONSHORE DIRECTION.
THIS SHIFT WILL BRING COOLER, WETTER AIR OFF THE OCEAN WHICH WILL
CAUSE A SHIFT IN THE DRY WEATHER PATTERN WE HAVE BEEN
EXPERIENCING. THIS SHIFT IS EXPECTED TO OCCUR THROUGH THE DAY
SUNDAY, BRINGING OUR USUALLY SCHEDULED PROGRAM BACK TO PANHANDLE.
RAIN IS EXPECTED TO ARRIVE IN YAKUTAT SUNDAY EVENING WITH THE
GREATEST ACCUMULATIONS LIKELY TO OCCUR EARLY MONDAY MORNING, WITH
NO MORE THAN 0.2 IN FALLING IN A 6 HOUR PERIOD. RAIN WILL THEN
MOVE SOUTH ACROSS THE PANHANDLE THROUGH THE DAY MONDAY AND IS
LIKELY TO BE SHOWERY AND LIGHT IN NATURE DUE TO THE LOW QPF
AMOUNTS THAT MODELS ARE CURRENTLY PICKING UP. THIS PATTERN OF
DAMPER, COOLER CONDITIONS IS EXPECTETED TO LAST THROUGH MOST OF
NEXT WEEK.
AVIATION.../THROUGH THURSDAY EVENING/ VERY QUIET AVIATION WEATHER
THIS EVENING WITH VFR CONDITIONS PANHANDLE WIDE WITH MOSTLY LIGHT
WINDS. THERE ARE SOME AREAS OF 15 KT WINDS IN PLACES LIKE ICY
STRAIT, SOUTHERLY LYNN, AND NEAR YOUNG BAY BUT THAT IS THE EXTENT
OF THE WINDS. MAIN CONSIDERATION OVERNIGHT IS ANY LOW CLOUDS AND
FOG THAT DEVELOPS WHICH SHOULD NOT BE WIDESPREAD AS OFFSHORE FLOW
IS EXPECTED TO INCREASE OVERNIGHT. THE MOST LIKELY AREAS FOR IT
WILL BE THE OUTER COAST MAINLY FROM SITKA NORTHWARD AND THE
WESTERN CHANNELS OF PRINCE OF WALES ISLAND LATE TONIGHT AND EARLY
THURSDAY. EXPECT MVFR OR LOWER CONDITIONS (MAINLY CEILINGS) IN
THESE AREAS. WIDESPREAD VFR CONDITIONS EXPECTED FOR THURSDAY WITH
SOME AFTERNOON SEA BREEZES UP TO 15 KT BEING THE MAIN WIND
CONCERNS.
MARINE...
OUTSIDE: HIGH PRESSURE OVER THE GULF WILL BRING A TIGHTER
GRADIENT OVER THE EASTERN WATERS. MODERATE TO FRESH BREEZES FOR
THE OUTER COASTAL WATERS THROUGH THURSDAY, WITH STRONGEST WINDS
FROM NEAR CAPE SPENCER DOWN TO DIXON ENTRANCE. WINDS WILL DIMINISH
BY THE WEEKEND AS THE HIGH WEAKENS AND DRIFTS WEST, ALLOWING THE
GRADIENT TO RELAX. WAVE HEIGHTS WILL GENERALLY BE 4 TO 6 FT
THROUGH THE END OF THE WEEK. WAVES UP TO 7 FT THROUGH EARLY
THURSDAY OVER THE COASTAL WATERS FROM CAPE DECISION TO DIXON
ENTRANCE. MAIN MARINE CONCERN FOR OUTER AND COASTAL WATERS WILL BE
NIGHTLY RETURN OF MARINE LAYER, WITH FOG AND LOW STRATUS.
INSIDE: HIGH PRESSURE OUT IN THE GULF IS EXPECTED TO LINGER
THROUGH THE WEEK. MODERATE TO FRESH BREEZES FOR THE INNER
CHANNELS CONTINUE TONIGHT THROUGH THURSDAY. LOCALIZED WIND SHIFTS
DUE TO SEA BREEZES ARE POSSIBLE, ALONGSIDE ELEVATED GUSTS TO
15-20 KT, BUT OVERALL WIND DIRECTION IS EXPECTED TO BE FROM THE
NW. STRONGEST INNER CHANNEL WINDS UP TO 15 TO 20 KTS ARE EXPECTED
FOR THE AFTERNOON AND EVENING HOURS. WINDS ACROSS THE INNER
CHANNELS WILL WILL DIMINISH THURSDAY NIGHT AS HIGH PRESSURE
WEAKENS AND SHIFTS WEST, RELAXING THE GRADIENT ACROSS THE
PANHANDLE. LIGHT TO GENTLE WINDS ARE THEN EXPECTED BY FRIDAY AND
SHOULD CONTINUE INTO THE WEEKEND. HOWEVER N-LY WINDS OF 15 TO 20
KT ARE EXPECTED FOR NORTHERN LYNN CANAL THROUGH FRIDAY FROM A
TIGHTENED N-S GRADIENT REMAINING ACROSS THE FAR NORTHERN
PANHANDLE.
FIRE WEATHER...HIGH PRESSURE OUT THE THE GULF CONTINUES TO BRING
MOSTLY DRY AND WARM WEATHER ACROSS THE PANHANDLE. WE HAVE STARTED
TO SEE TEMPERATURES RISE INTO THE 70S WITH SOME POCKETS OF 80S
FOR THE INLAND AREAS WITH WARM TEMPERATURES EXPECTED TO CONTINUE
THROUGH THE WEEK. LOOKING AT THE PAST FEW DAYS, RELATIVE
HUMIDITIES HAVE FALLEN DOWN TO THE 30S TO 40S FOR SOME AREAS
DURING THE DAYTIME HOURS WITH REBOUNDING DURING THE OVERNIGHT
HOURS INTO THE 90S. WITH THE CONTINUED LACK OF RAIN, FINE FUELS
SUCH AS GRASSES WILL CONTINUE TO DRY. MODELS CONTINUE TO SUGGEST
THE POTENTIAL FOR ISOLATED THUNDERSTORMS ALONG THE PANHANDLE
BORDER WITH CANADA AS WELL AS THE SE PANHANDLE ON THURSDAY AND
FRIDAY. HOWEVER, DUE TO THE LACK OF LOW/MID LEVEL MOISTURE THE
CHANCE OF THUNDERSTORMS IS ONLY AROUND 15% OR LESS.
OVERALL, EXPECTING THE DRY AND WARM TREND TO CONTINUE THROUGH THE
WEEK WITH FIRE WEATHER CONDITIONS CONTINUING TO DEVELOP, THE MAIN
VARIABLE TO WATCH FOR WILL BE DAYTIME WINDS. AS OF NOW, EXPECTING
THE WORST FIRE WEATHER CONDITIONS TO BE THURSDAY AND FRIDAY
AFTERNOON, HOWEVER GIVEN THE PERSISTENT PATTERN CAN'T RULE OUT
THIS EXTENDING FURTHER INTO THE WEEKEND.
HYDROLOGY.../FLOOD WARNING IN EFFECT/
MENDENHALL LAKE GAUGE LEVELS, ALONG WITH USGS IMAGERY FROM
SUICIDE BASIN AND WATER LEVELS WITHIN THE BASIN, INDICATE THAT
A GLACIAL LAKE OUTBURST FLOOD IS ONGOING INTO MENDENHALL LAKE AND
RIVER.
AS OF 9 PM AKDT, THE MENDENHALL RIVER AND LAKE HAS CROSSED
BANKFULL STAGE (8 FT) CURRENTLY READING 8.5 FT AND RISING. IT
USUALLY TAKES AROUND 2 DAYS FROM WHEN THE BASIN RELEASE STARTS TO
WHEN YOU SEE THE HIGHEST WATER LEVELS. WATER LEVELS ON THE
MENDENHALL LAKE AND RIVER WILL RISE THROUGH THE NIGHT AS THE
RELEASE CONTINUES, WITH A FORECAST CREST BETWEEN 16.1 TO 16.6 FEET
EXPECTED THURSDAY MORNING BETWEEN 8AM AND NOON. COMPARED TO
PREVIOUS YEARS THIS IS SLIGHTLY BELOW LAST YEAR'S HIGH WATER MARK,
AND ABOVE THE HIGH WATER MARKS OF 2023 AND 2024.
VISIT WEATHER.GOV/AJK/SUICIDEBASIN FOR THE LATEST UPDATES ON THE
GLACIAL LAKE OUTBURST FLOOD FOR MENDENHALL LAKE AND RIVER. THE
WEATHER.GOV/AJK/SUICIDEBASIN WEB PAGE IS CURRENTLY UPDATED EVERY
TWO HOURS BY THE NWS JUNEAU OFFICE AND AS WE MOVE FURTHER INTO THE
EVENT, THIS CADENCE WILL INCREASE TO HOURLY UPDATES.
AJK WATCHES/WARNINGS/ADVISORIES
PUBLIC...HEAT ADVISORY UNTIL 7 PM AKDT FRIDAY FOR AKZ318-319.
HEAT ADVISORY FROM NOON THURSDAY TO 7 PM AKDT FRIDAY FOR AKZ321-
325-328-330>332.
MARINE...NONE.
SHORT TERM...DS
LONG TERM...AGP
AVIATION...EAL
MARINE...DS
FIRE...AP
HYDROLOGY...SF
VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU
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