239
FXAK67 PAJK 121814
AFDAJK
SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
1014 AM AKDT WED AUG 12 2026
UPDATE
TO THE AVIATION SECTION FOR 18Z TAF ISSUANCE AS WELL AS
AN UPDATE TO THE HYDROLOGY SECTION...
AVIATION.../THROUGH THURSDAY MORNING/
THE MAIN AVIATION
CONCERN FOR TODAY WILL BE THE EFFECTS OF THE MARINE LAYER ON THE
OUTER COASTAL TAF SITES LINGERING THIS MORNING AND TOMORROW
MORNING. SOME SOUTHERN SITES STRUGGLED TO BREAK OUT OF LIFR/IFR
CONDITIONS, THOUGH ARE NOW EXPECTED TO PERSIST IN VFR THROUGH THE
TAF PERIOD. THE EXCEPTION BEING PAKW, WHICH COULD LIKELY SEE THE
RETURN OF LOW CLOUDS TOMORROW MORNING IMPACTING BOTH CIG/VIS.
NORTHERN/CENTRAL COAST SITES AND INTO CROSS SOUND (ELFIN COVE)
ALSO SEEING LOW CLOUDS AND MVFR/IFR CONDITIONS CURRENTLY, WITH
HIGHER CONFIDENCE IN CIGS AOA 2000FT UNTIL THE AFTERNOON. VFR
ANTICIPATED FOR THESE SITES AROUND 21Z TO 00Z, BREAKING OUT FROM
SOUTH TO NORTH.EVERYWHERE ELSE IN THE PANHANDLE IS SEEING VFR
CONDITIONS TODAY WITH LIGHT WINDS TO START, INCREASING THROUGH THE
AFTERNOON DUE TO SEA BREEZES. HIGHEST WINDS WILL LIKELY REACH 15
TO POSSIBLY 20 KTS AT MOST. LATE TONIGHT, OFFSHORE FLOW WILL
DOMINATE THE PATTERN SO LOW CLOUDS, POSSIBLY DOWN TO IFR OR MVFR,
WILL KEEP MOSTLY TO THE OUTER COAST WITH ALL OTHER AREAS REMAINING
GENERALLY VFR.
PREV DISCUSSION......ISSUED AT
805 AM AKDT WED AUG 12 2026
SYNOPSIS...
KEY MESSAGES:
- SUICIDE BASIN IS RELEASING. MAJOR FLOOD STAGE ON MENDENHALL LAKE
AND RIVER EXPECTED TO BE REACHED WEDNESDAY NIGHT.
- WARMING TREND FOR THE WEEK WITH HIGHS IN THE 70S. LOWER 80S
WILL BE POSSIBLE, ESPECIALLY ACROSS INTERIOR LOCATIONS ACROSS
THE SOUTH AND FAR NORTHERN INTERIOR FOR MID TO LATE WEEK.
- 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...RIDGE OF HIGH PRESSURE WILL BUILD OVER THE GULF
THROUGH TODAY, LINGERING THROUGH THE REST OF THE WEEK TO THE WEST OF
THE PANHANDLE. WARM TEMPERATURES AND DRY WEATHER IS EXPECTED TO
CONTINUE ACROSS THE PANHANDLE TODAY THROUGH THE END OF THE WEEK,
WITH THE WARMEST TEMPERATURES EXPECTED THURSDAY AND FRIDAY AFTER THE
RIDGING STRENGTHENS OVER THE GULF AS WESTERLY FLOW TRANSITIONS TO A
NORTHWESTERLY OFFSHORE FLOW. SOME MARINE LAYER CLOUDS WILL STILL
DEVELOP IN THE GULF WITH THIS RIDGE PLACEMENT, HOWEVER ANY LOW
STRATUS CLOUDS ARE EXPECTED TO STAY JUST OFFSHORE AND ALONG THE
OUTER COAST.
THE MAJORITY OF THE PANHANDLE WILL SEE CLEARING SKIES
WITH THE OFFSHORE FLOW, AND BY THE END OF THE WEEK MOST OF THE
PANHANDLE IS EXPECTED TO SEE WARMER TEMPERATURES WITH HIGHS REACHING
MID TO HIGH 70S THURSDAY AND FRIDAY. INLAND AREAS ALONG THE KLONDIKE
AND HAINES HIGHWAYS MAY SEE HIGH TEMPERATURES IN THE HIGH 70S TO LOW
80S THROUGH THE END OF THE WEEK WITH THESE CLEAR SKIES. THE SOUTHERN
PANHANDLE IS ALSO EXPECTED TO SEE TEMPERATURES REACH NEAR 80 INTO
THE LOW 80S THURSDAY AND FRIDAY, WITH AREAS FURTHER FROM THE WATER
HAVING POTENTIAL TO SEE DAYTIME HIGHS IN THE MID 80S.
THERE STILL IS POTENTIAL FOR SOME CONVECTIVE ACTIVITY IN THE SE
CORNER OF THE PANHANDLE THURSDAY AND FRIDAY AFTERNOON/EVENING, WITH
THE INSTABILITY PRESENT AND OVERALL SETUP SUGGESTING A VERY LOW
CHANCE FOR EASTERLY THUNDERSTORMS MOVING INTO THE AREA. THE MOISTURE
STILL IS NOT IDEAL HOWEVER, AND ANY DEVELOPMENT IS LIKELY TO BE
ISOLATED OVER THE SE PANHANDLE AND ALONG THE COASTAL RANGE. SOME
MODEL GUIDANCE SHOWS 60-70% RH AT THE LOW/MID LEVELS WITH A BIT OF
WESTERLY COMPONENT TO LOWER LEVEL WINDS TO BRING MOISTURE INTO THE
AREA, BUT CONFIDENCE IS STILL LACKING AS TO IF THESE INGREDIENTS
ALIGN FOR THUNDERSTORM DEVELOPMENT.
LONG TERM...CORRECTED THE RIGHT LONG TERM SECTION / FRIDAY
THROUGH MONDAY/...ENSEMBLE MODELS AGREEING ON AN UPPER LEVEL RIDGE
DISSIPATING AND BEING REPLACED BY A WEAK TROUGH OVER THE SOUTHERN
PANHANDLE BY FRIDAY, WITH THE RIDGE REBUILDING EARLY NEXT WEEK.
THIS SHIFT WILL BRING POSITIVE VORTICITY ADVECTION AND SOME
LIFTING, WHILE MOISTURE ADVECTION ARRIVES VIA AN EASTERLY WAVE IN
THE 700MB LEVEL. ADDITIONALLY, A SURFACE MARITIME RIDGE FORMING IN
THE EASTERN GULF WILL GENERATE NORTHWESTERLY WINDS ACROSS THE
PANHANDLE WHICH COULD WORK IN CONJUNCTION WITH DIURNALLY DRIVEN
SEA BREEZES TO PROMOTE WEAK ONSHORE FLOW TOWARD THE END OF THE
WEEK.
REGARDING SEVERE WEATHER POTENTIAL FOR END OF WEEK/EARLY WEEKEND,
GUIDANCE IS KEYING IN ON SEASONABLY HIGH CAPE VALUES IN PARTS OF
THE CENTRAL AND SOUTHERN REGIONS, THOUGH FORECASTER CONFIDENCE
REMAINS LOW DUE TO DRIER CONDITIONS IN MANY OF THE ATMOSPHERIC
PRESSURE LEVELS AND A LACK OF SUPPORT FOR SUSTAINING STORMS
MOVING IN FROM CANADA. CUMULUS FIELDS ARE MORE LIKELY THAN STORMS,
AS A LACK OF A CAP AND SIGNIFICANT MOISTURE INHIBITS POTENTIAL
CONVECTION. WHILE WESTERLY FLOW ON FRIDAY MIGHT DRIVE SOME
LOCALIZED CONVECTION THROUGH UPSLOPING, MARINE INFLUENCES WILL
LIKELY STABILIZE THE SURFACE LAYER AND CHOKE OFF DEVELOPMENT.
MEANWHILE, LIGHT WINDS AND CLEARING SKIES ARE EXPECTED TO BOOST
TEMPERATURES, WITH FRIDAY AND SATURDAY CONTINUING THIS WARM SPELL
AS TEMPERATURES REACH THE UPPER 70S TO LOW 80S, BEFORE COOLING
RETURNS SUNDAY INTO MONDAY AS THE SURFACE HIGH PRESSURE WEAKENS.
THERE IS STILL A LOT OF SPREAD IN THE TRACK OF A LOW PRESSURE
CENTER MOVING INTO THE CENTRAL GULF NEXT WEEK, AND IF LINGERING
HIGH PRESSURE WILL BLOCK PRECIPITATION FROM MOVING IN. WE WILL
CONTINUE TO MONITOR THIS NEXT SYSTEM AND ASSOCIATED RAINFALL
ACCUMULATION.
MARINE...
OUTSIDE: MARINE FORECAST REMAINS ON TRACK. HIGH PRESSURE OVER THE
GULF WILL STRENGTHEN AND SHIFT EASTWARD, TIGHTENING THE GRADIENT
OVER THE EASTERN GULF. GENTLE TO MODERATE NORTHWEST BREEZES WILL
BECOME FRESH FOR THE OUTER COASTAL WATERS FROM NEAR CAPE SPENCER
DOWN TO DIXON ENTRANCE. WAVE HEIGHTS OF 3 TO 4 FT WILL INCREASE
TO 4 TO 6 FT BY MIDWEEK AND REMAIN THROUGH THE END OF THE WEEK.
WINDS WILL DIMINISH BY THE WEEKEND AS THE HIGH WEAKENS. MAIN
MARINE CONCERN FOR OUTER AND COASTAL WATERS WILL BE NIGHTLY RETURN
OF MARINE LAYER, WITH FOG AND LOW STRATUS IMPACTING VISIBILITY.
INSIDE: HIGH PRESSURE OUT IN THE GULF IS EXPECTED TO LINGER
THROUGH THE WEEK, WITH LIGHT TO GENTLE W/NW-LY WINDS OVERNIGHT
SHIFTING TO A NW-LY MODERATE TO FRESH BREEZE FOR THE INNER
CHANNELS BY THIS AFTERNOON. 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
ALSO DIMINISH THURSDAY AND FRIDAY AS THE RIDGE BEGINS WEAKENING,
HOWEVER N-LY WINDS OF 15 TO 20 KT ARE EXPECTED FOR NORTHERN LYNN
CANAL FROM A TIGHTENED N-S GRADIENT REMAINING ACROSS THE NORTHERN
PANHANDLE THE END OF THE WEEK.
FIRE WEATHER...HIGH PRESSURE CONTINUES TO SIT OVER THE AREA WITH
NO REAL SIGNAL OF A PATTERN CHANGE LIKELY UNTIL THE UPCOMING
WEEKEND. WITH THE PERSISTENT DRY WEATHER, 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 10AM AKDT, THE MENDENHALL RIVER IS AT 5.85 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 TODAY AS THE RELEASE
CONTINUES, WITH A FORECAST CREST BETWEEN 16.1 TO 16.6 FEET
EXPECTED EARLY THURSDAY MORNING. 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 THURSDAY FOR AKZ318-319.
HEAT ADVISORY FROM NOON THURSDAY TO 7 PM AKDT FRIDAY FOR AKZ328-
330>332.
MARINE...NONE.
SHORT TERM...CONTINO
LONG TERM...BAS
AVIATION...BAS
MARINE...CONTINO
HYDROLOGY...SF
VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU
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