563
FXUS65 KBOI 201737
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
1137 AM MDT THU AUG 20 2026
UPDATE
UPDATED AVIATION DISCUSSION.
KEY MESSAGES
- HEAT ADVISORY THURSDAY AFTERNOON THROUGH FRIDAY IN THE
TREASURE VALLEY, WESTERN MAGIC VALLEY, AND UPPER WEISER
RIVER VALLEY.
- INCREASED CHANCE OF AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS OVER HIGHER TERRAIN FRIDAY THROUGH SUNDAY.
- ABOVE NORMAL TEMPERATURES NEXT WEEK WITH A CHANCE OF AFTERNOON
THUNDERSTORMS OVER THE MOUNTAINS OF SOUTHWEST IDAHO EARLY IN
THE WEEK.
SHORT TERM /THROUGH SATURDAY NIGHT/
ISSUED 358 AM MDT THU AUG 20 2026
THE HEAT IS ON FOR THE THE NEXT COUPLE OF DAYS AS AN UPPER RIDGE
INTENSIFIES OVER THE AREA. MOST LOWER ELEVATION SITES WILL SEE
HIGH TEMPERATURES TOP OUT BETWEEN 96 AND 104 TODAY AND FRIDAY.
A COUPLE OF CAVEATS WILL BE SMOKE AND CLOUD COVER, ESPECIALLY AS
WE GET INTO FRIDAY. FOR NOW IT DOESN'T LOOK LIKE SMOKE GETS
THICK ENOUGH TO IMPACT TEMPERATURES (OF COURSE DEPENDENT ON ANY
NEW FIRE ACTIVITY). HIGH CLOUD COVER LATER TODAY AND MORE SO ON
FRIDAY WILL LIKELY TAKE A COUPLE OF DEGREES OFF OF HEATING
POTENTIAL WHICH PUTS WIDESPREAD 100-103 TEMPERATURES IN THE
TREASURE VALLEY. ELEVATED MOISTURE ON FRIDAY WILL FEED AFTERNOON
SHOWER AND THUNDERSTORM DEVELOPMENT OVER HIGHER TERRAIN ALONG
THE NV BORDER WHICH THEN PROPAGATES NORTHWARD THROUGH THE
EVENING. A SLIGHT CHANCE OF THUNDERSTORMS IS MAINTAINED ACROSS
MUCH OF THE AREA THROUGH FRIDAY NIGHT DUE TO THE PASSAGE OF A
SHORTWAVE TROUGH. A DEEPER LOW OFFSHORE LIFTS THROUGH THE PAC
NW ON SATURDAY, COOLING TEMPERATURES 5-10 DEGREES FROM FRIDAY
WHILE KEEPING A CHANCE OF SHOWERS AND THUNDERSTORMS IN PLACE FOR
MOST SITES. GUSTY OUTFLOW WINDS ARE THE DOMINATE STORM THREAT
FRIDAY AND SATURDAY WITH GREATER MOISTURE ON SATURDAY INCREASING
THE HEAVY RAIN POTENTIAL ACROSS SW IDAHO. WINDS WILL RAMP UP
SATURDAY AFTERNOON BRINGING 25-35 MPH GUSTS TO SE OREGON. A COLD
FRONTAL PASSAGE SATURDAY NIGHT WILL SHIFT WINDS TO THE
NORTHWEST.
LONG TERM /SUNDAY THROUGH THURSDAY/
ISSUED 358 AM MDT THU AUG 20 2026
DRY AIR BEHIND THE FRONT WILL LIMIT SHOWER AND THUNDERSTORM
DEVELOPMENT TO THE ID/NV BORDER AREA AND EASTERN BOISE MTNS ON
SUNDAY. TEMPERATURES WILL RUN 4-8 DEGREES COOLER THAN SATURDAY,
PLACING LOWER ELEVATIONS AROUND 90 DEGREES, WHICH IS NEAR NORMAL
HEADING INTO LATE AUGUST. FOR NEXT WEEK, WE'LL REMAIN ON THE
NORTHWEST FRINGE OF A BROAD RIDGE CENTERED OVER NM. EARLY IN THE
WEEK FLOW AROUND THE RIDGE WILL KEEP MOISTURE OVER SOUTHERN AND
EASTERN AREAS, SUPPORTING A 20-40% CHANCE OF SHOWERS AND
THUNDERSTORMS OVER HIGHER TERRAIN OF SOUTHWEST IDAHO. BY
WEDNESDAY DRIER AIR WILL CUT OFF PRECIPITATION CHANCES FOR MOST
AREAS. TEMPERATURES ARE BACK ABOVE NORMAL NEXT WEEK.
AVIATION /18Z THURSDAY THROUGH FRIDAY/
ISSUED 1130 AM MDT THU AUG 20 2026
VFR. INCREASING CLOUDS AOA 15 KFT MSL. SOME REDUCTION IN
VISIBILITY DUE TO WILDFIRE SMOKE. ISOLATED HIGH-BASED
SHOWERS/STORMS NEAR THE ID/NV BORDER 20/21Z - 21/01Z.
SURFACE WINDS: SW-NW 5-15 KT UNTIL 21/01Z THEN VARIABLE
LESS THAN 8 KT. WINDS ALOFT AT 10KFT MSL: SW 15-25 KT.
KBOI...VFR, INCREASING HIGH CLOUDS AOA 18 KFT MSL. SOME
REDUCTION IN VISIBILITY DUE TO WILDFIRE SMOKE. LIGHT
DIURNAL SURFACE WINDS THROUGH FRIDAY.
WEEKEND OUTLOOK...SCATTERED SHOWERS AND THUNDERSTORMS LATE
FRIDAY THROUGH SATURDAY. GUSTY OUTFLOW WINDS AND LOCALLY HEAVY
RAIN IN STORMS. DRIER SUNDAY. LOCAL REDUCTIONS IN VISIBILITY
DUE TO WILDFIRE SMOKE THROUGH THE WEEKEND. GUSTY SW WINDS
SATURDAY ACROSS SE OREGON. BREEZY W-NW WINDS ALL AREAS ON
SUNDAY.
BOI WATCHES/WARNINGS/ADVISORIES
ID...HEAT ADVISORY UNTIL 9 PM MDT FRIDAY FOR IDZ012-014-016-033.
OR...HEAT ADVISORY UNTIL 9 PM MDT /8 PM PDT/ FRIDAY FOR ORZ064.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
AVIATION.....LC
SHORT TERM...DG
LONG TERM....DG
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