483
FXUS65 KBOI 211733
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
1133 AM MDT TUE JUL 21 2026
UPDATE
UPDATED AVIATION DISCUSSION.
KEY MESSAGES
- ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS TODAY, MAINLY
OVER THE HIGHER TERRAIN.
- SHOWERS/THUNDERSTORMS INCREASE WEDNESDAY WITH HEAVY RAINFALL
POSSIBLE ESPECIALLY OVER THE CENTRAL IDAHO MOUNTAINS.
- HOT TEMPERATURES AND AREAS OF SMOKE THROUGH THE WEEK.
SHORT TERM /THROUGH THURSDAY NIGHT/
ISSUED 329 AM MDT TUE JUL 21 2026
WEAK SOUTHERLY FLOW ALOFT ASSOCIATED WITH AN UPPER RIDGE
CENTERED OVER THE SOUTH-CENTRAL U.S. WILL CONTINUE TO TRANSPORT
MONSOONAL MOISTURE INTO OUR AREA TODAY AND WEDNESDAY.
PRECIPITABLE WATER WILL CLIMB WELL OVER 1 INCH, RISING ABOVE THE
95TH PERCENTILE TODAY AND CLOSER TO THE 99TH PERCENTILE ON
WEDNESDAY, INDICATING A VERY MOIST AIRMASS. A BAND OF LIGHT
SHOWERS WILL MOVE NORTH ACROSS OUR AREA THIS MORNING WITH ABOUT
A 10% CHANCE OF EMBEDDED LIGHTNING. DESPITE THE MOISTURE,
INSTABILITY THIS AFTERNOON AND EVENING WILL BE LIMITED AND
FOCUSED OVER THE HIGHER TERRAIN, WHERE A 20-40% CHANCE OF
SHOWERS AND THUNDERSTORMS WILL DEVELOP. STORMS MAY PRODUCE
BRIEF HEAVY RAIN AND GUSTS TO 45 MPH. SHOWERS AND ISOLATED
STORMS WILL CONTINUE TONIGHT NEAR THE NEVADA BORDER AS AN
IMPULSE LIFTS NORTH. THE INCREASING MOISTURE AND CLOUD COVER
WILL BRING A FEW DEGREES OF COOLING TODAY IN MOST AREAS, BUT IT
WILL STILL BE HOT. SIMILAR TO YESTERDAY, SMOKE SHOULD DECREASE
IN THE AFTERNOON AS DAYTIME HEATING MIXES OUT SMOKE NEAR THE
SURFACE. OUTSIDE OF STORMS, WINDS WILL BE LOCALLY BREEZY WITH
GUSTS 15-25 MPH. NORTHWEST SURFACE WINDS WILL TRANSPORT SMOKE
FROM WILDFIRES IN OREGON BACK ACROSS THE AREA TONIGHT.
ON WEDNESDAY, A SHORTWAVE TROUGH WILL AID CONVECTION IN THE
AFTERNOON AND EVENING ACROSS THE CENTRAL IDAHO MOUNTAINS, WHERE
THE CHANCE OF SHOWERS AND THUNDERSTORMS WILL RISE TO 40-80%.
DEEP MOISTURE AND EXPECTED SLOW STORM MOTION WILL RESULT IN THE
POTENTIAL FOR HEAVY RAIN AND FLASH FLOODING, ESPECIALLY OVER
BURN SCARS AND STEEP TERRAIN, INCLUDING THE WAPITI BURN AREA.
MODELS ALSO INDICATE THE POTENTIAL FOR GUSTY OUTFLOW WINDS AS A
COLD POOL FORMS OVER THE MOUNTAINS. ELSEWHERE, A 20-40% CHANCE
OF SHOWERS AND THUNDERSTORMS WILL DEVELOP ACROSS THE HIGHER
TERRAIN WITH A LESS THAN 20% CHANCE IN THE LOWER ELEVATIONS.
INCREASED CLOUDS/SHOWERS WILL COOL MOST AREAS SLIGHTLY, WITH UP
TO 10-15 DEGREES OF COOLING ACROSS THE CENTRAL IDAHO MOUNTAINS.
AN UPPER LEVEL TROUGH OFF THE PACIFIC NORTHWEST COAST ON
THURSDAY WILL TRANSITION THE FLOW ALOFT TO SOUTHWESTERLY. THIS
WILL BEGIN TO PUSH MONSOONAL MOISTURE TO THE EAST, BUT THERE
WILL STILL BE ENOUGH MOISTURE AND INSTABILITY FOR A 10-20%
CHANCE OF SHOWERS AND THUNDERSTORMS. DECREASING MOISTURE WILL
ALLOW TEMPERATURES TO RISE WITH LOWER VALLEY HIGHS ONCE AGAIN
NEAR 100 DEGREES. BREEZY CONDITIONS WILL DEVELOP ACROSS
SOUTHEAST OREGON IN RESPONSE TO THE SOUTHWEST FLOW. SMOKE MAY
CONTINUE TO IMPACT THE AREA WEDNESDAY AND THURSDAY WITH
IMPROVEMENT EACH AFTERNOON.
LONG TERM /FRIDAY THROUGH TUESDAY/
ISSUED 329 AM MDT TUE JUL 21 2026
AN UPPER LEVEL TROUGH WILL REMAIN IN PLACE ALONG THE PACIFIC
NORTHWEST COAST THROUGH THE PERIOD WITH AN UPPER LEVEL RIDGE
TO THE EAST. THE RESULTING SOUTHWEST FLOW WILL CONTINUE TO
USHER IN A MUCH DRIER AIRMASS. SHOWER/STORM CHANCES WILL
GENERALLY BE LESS THAN 20% AND CONFINED TO THE HIGHER TERRAIN
AND ALONG THE IDAHO/NEVADA BORDER. THE PATTERN WILL BRING HOT,
DRY, AND BREEZY CONDITIONS THROUGH THE WEEKEND AND INTO EARLY
NEXT WEEK. LOWER VALLEY HIGHS WILL REMAIN IN THE UPPER 90S TO
AROUND 100 DEGREES. WINDS EACH DAY WILL GUST 15-30 MPH,
STRONGEST IN OPEN, ELEVATED AREAS INCLUDING THE HIGH DESERT OF
SOUTHEAST OREGON AND SOUTHWEST IDAHO SOUTH OF THE SNAKE RIVER.
SMOKE MAY IMPACT THE AREA THROUGH THE PERIOD, ESPECIALLY ACROSS
SOUTHEAST OREGON.
AVIATION /18Z TUESDAY THROUGH WEDNESDAY/
ISSUED 1132 AM MDT TUE JUL 21 2026
GENERALLY VFR. AREAS MVFR- IFR VISIBILITY DUE TO WILDFIRE
SMOKE, GRADUALLY IMPROVING THIS AFTERNOON AND EVENING.
BROKEN CLOUDS AOA 15 KFT MSL. SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS NEAR THE NV BORDER AND IN THE CENTRAL ID MOUNTAINS.
HIGH DENSITY ALTITUDE DURING AFTERNOON HEAT. BROKEN CLOUDS AOA
12 KFT MSL INCREASING FROM THE SOUTH AFTER 22/00Z. AFTER 22/06Z
SCATTERED SHOWERS AND THUNDERSTORMS NEAR THE NV/ID BORDER WITH
BRIEF HEAVY RAIN AND OUTFLOW WINDS TO 40 KT. SURFACE WINDS:
W-NW 5-15 KT WITH LOCAL GUSTS AROUND 25 KT. WINDS ALOFT AT 10KFT
MSL: NW AROUND 10 KT.
KBOI...VFR. BROKEN CLOUDS AOA 15 KFT MSL UNTIL 20Z THEN DECREASING
TO SCATTERED. HIGH DENSITY ALTITUDE DURING AFTERNOON HEAT.
SURFACE WINDS: NW 5-10KT UNTIL 21Z, THEN NW 10-15 KT WITH GUSTS
20-25 KT UNTIL 22/01Z. BROKEN-OVERCAST CLOUDS AOA 15 KFT SPREADING
IN FROM THE SOUTH AFTER 22/05Z.
BOI WATCHES/WARNINGS/ADVISORIES
ID...AIR QUALITY ALERT UNTIL 3 PM MDT WEDNESDAY FOR IDZ011-012-014-
033.
FLASH FLOOD WATCH FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY
EVENING FOR IDZ013.
OR...AIR QUALITY ALERT UNTIL 1 PM MDT /NOON PDT/ WEDNESDAY FOR
ORZ061>064.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
AVIATION.....LC
SHORT TERM...ST
LONG TERM....ST
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