432
FXUS65 KBOI 261608
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
1008 AM MDT TUE AUG 26 2025
DISCUSSION
A VERY MOIST ATMOSPHERE IS IN PLACE AS SOUTHERLY FLOW
TRANSPORTS MONSOON MOISTURE OVER THE FORECAST AREA. THE MORNING
SOUNDING MEASURED 1.20 INCHES OF PRECIPITABLE WATER WITH LIGHT
SOUTHERLY STEERING FLOW FOR SHOWERS AND THUNDERSTORMS. THIS SETS
THE STAGE FOR LOCALLY HEAVY RAIN ONCE STORMS GET GOING.
SATELLITE SHOWS THIN OR LIMITED CLOUD COVER OVER PORTIONS OF THE
FORECAST AREA WHICH WILL AID IN SURFACE HEATING AND
DESTABILIZATION OF THE ATMOSPHERE. HIGH RESOLUTION MODELS STILL
SHOW A FOCUS FOR STORMS NEAR THE NEVADA BORDER AND EASTERN
BOISE AND VALLEY COUNTIES THIS AFTERNOON. CURRENT FORECAST LOOKS ON
TRACK.
AVIATION
ISOLATED SHOWERS/THUNDERSTORMS BECOMING SCATTERED TO
NUMEROUS THIS AFTERNOON. GREATEST COVERAGE NEAR THE NV BORDER AND
MOUNTAINS EAST OF KMYL AND KBOI. OUTFLOW GUSTS TO 25-35 KT, HEAVY
RAIN, AND SMALL HAIL POSSIBLE. MVFR CONDITIONS AND MTN OBSCURATION
IN HEAVY RAIN. VISIBILITY REDUCTIONS NEAR MTN WILDFIRES. SURFACE
WINDS: VARIABLE 5-15 KT. WINDS ALOFT AT 10KFT MSL: VARIABLE 5-15 KT.
KBOI...VFR. SCATTERED SHOWERS/THUNDERSTORMS IN TREASURE VALLEY
THIS AFTERNOON, WITH 30-40% CHANCE OF HITTING AIRPORT.
OUTFLOW GUSTS TO 25-35 KT GUSTS, MOD/HEAVY RAIN, AND SMALL HAIL
POSSIBLE. THEN, RAIN SHOWERS LIKELY (60-70% CHANCE) AT KBOI THIS
EVENING THROUGH WEDNESDAY AFTERNOON. SHOWERS MAY BE HEAVY AT TIMES
AND CREATE MVFR VISIBILITY. SURFACE WINDS: SE-S 5 KT OR LESS
BECOMING W 5 KT IN THE AFTERNOON.
PREV DISCUSSION
SHORT TERM...TODAY THROUGH THURSDAY NIGHT...DEEP MONSOON
MOISTURE WILL REMAIN OVER THE REGION THROUGH WEDNESDAY. MONDAY
EVENING'S KBOI WX BALLOON MEASURED A RECORD AMOUNT OF
PRECIPITABLE WATER FOR THE DATE (1.28 INCHES), AND THE MOISTURE
CONTENT OF THE AIR MASS IS EXPECTED TO INCREASE THIS AFTERNOON
INTO WEDNESDAY WITH FORECAST PW VALUES REACHING 1.35-1.5 INCHES.
SHOWERS AND THUNDERSTORMS WILL INITIATE OVER HIGHER TERRAIN
THROUGH THIS MORNING. MODELS ARE PICKING UP ON A SUBTLE UPPER
WAVE THAT LIFTS OUT OF NV LATE THIS AFTERNOON, THE EXTRA LIFT
FROM THIS FEATURE INCREASING COVERAGE ACROSS HIGHER TERRAIN.
SOUTHERLY FLOW ALOFT WILL GUIDE SHOWERS/STORMS INTO THE SNAKE
PLAIN, ESPECIALLY FROM MOUNTAIN HOME TO TWIN/JEROME WHERE THE
HREF SHOWS A 50-70% CHANCE OF THUNDERSTORMS THROUGH THIS
EVENING. THE MAIN SHOWER/STORM ATTRIBUTE WILL BE HEAVY RAIN,
WITH MOST CAM GUIDANCE SHOWING POTENTIAL FOR 0.75-1.25 IN/HR
RAINFALL RATES FROM STRONGER STORMS THAT DEVELOP. WHILE HIGHER
TERRAIN WILL BE QUICK TO CLOUD UP TODAY, LOWER ELEVATIONS HAVE A
CHANCE TO SEE A BIT OF SUN, ESPECIALLY AREAS ACROSS E-CENTRAL
OREGON AND THE LOWER SNAKE PLAIN. HAVE STAYED BELOW NBM GUIDANCE
WHICH HAS BEEN RUNNING TOO HOT THE LAST COUPLE OF DAYS.
AN UPPER LOW IS EXPECTED TO WRAP UP OVER S-CENTRAL IDAHO
WEDNESDAY WHICH WILL KEEP CLOUDY AND WET WEATHER OVER THE
REGION. THE 00Z MODEL SOLUTIONS KEEP THE FOCUS OF HEAVIER
PRECIPITATION EAST OF THE ID/OR BORDER, WITH THE W-CENTRAL ID
AND BOISE MTNS SEEING THE BEST CHANCE FOR AN ADDITIONAL 0.5-1.0"
THROUGH WED NIGHT. GIVEN THE CONVECTIVE NATURE THERE WILL
BE HIGH VARIABILITY IN PRECIPITATION AMOUNTS BOTH TODAY AND
WEDNESDAY. ON THE HIGHER END IT'S NOT OUT OF THE QUESTION THAT
STORM TOTALS (TODAY THROUGH WEDNESDAY NIGHT) COULD REACH THE
2-3" RANGE. THIS TYPE OF RAINFALL WILL CERTAINLY INCREASE THE
POTENTIAL FOR ROCK SLIDES AND FLASH FLOODING/DEBRIS FLOWS,
ESPECIALLY ACROSS BURN SCARS AND STEEP TERRAIN. THOUGH LIKELY
MORE LOCALIZED, AREAS OF E-CENTRAL OREGON AND THE SNAKE PLAIN
WILL SEE THE POTENTIAL FOR MODERATE TO HEAVY RAIN ON WEDNESDAY
AS WELL. AMOUNTS IN THESE AREAS WILL LIKELY TOTAL LESS THAN
0.5". WEDNESDAY WILL BE THE COOLEST DAY WITH HIGHS AROUND 10
DEGREES BELOW NORMAL.
THE UPPER LOW LIFTS NE'WARD ON THURSDAY, LEAVING A CHANCE OF
SHOWERS AND A SLIGHT CHANCE OF THUNDERSTORMS ACROSS HIGHER
TERRAIN OF SW IDAHO WHILE SE OREGON AND THE LOWER SNAKE PLAIN
IN IDAHO TREND DRIER. TEMPERATURES WILL REBOUND SOME FROM
WEDNESDAY BUT REMAIN SEVERAL DEGREES BELOW NORMAL.
LONG TERM...FRIDAY THROUGH TUESDAY...A BROAD UPPER RIDGE WILL
BUILD INTO THE REGION ON FRIDAY, RETURNING A WARMING AND DRYING
TREND. PEAK DAILY VALLEY TEMPERATURES ARE EXPECTED TO RETURN
AND MOSTLY LINGER IN THE UPPER 80S AND LOWER 90S FRIDAY TO
TUESDAY. THERE IS STRONG GUIDANCE AGREEMENT ON AN UPPER LOW
STEERING NE'WARD ALONG THE PACIFIC NW COAST AND THE N'RN IDAHO
MOUNTAINS THROUGH MONDAY. THERE IS CURRENTLY A STRONG GUIDANCE
DISAGREEMENT ON WHETHER THE AFOREMENTIONED UPPER LOW WILL EITHER
SPLIT OFF OR REMAIN QUASI- STATIONARY OVER THE NW COAST ON
TUESDAY. FOR NOW, THE POTENTIAL FOR SHOWERS/THUNDERSTORMS EARLY
NEXT WEEK REMAIN CONCENTRATED ACROSS HIGHER ELEVATIONS.
BOI WATCHES/WARNINGS/ADVISORIES
ID...FLASH FLOOD WATCH THROUGH WEDNESDAY EVENING
IDZ011>016-028>030-033.
OR...FLASH FLOOD WATCH THROUGH WEDNESDAY EVENING ORZ061>064.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
DISCUSSION...TL
AVIATION.....TL
SHORT TERM...DG
LONG TERM....JY
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