898
FXUS65 KBOI 271623
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
1023 AM MDT WED AUG 27 2025
DISCUSSION
EXTREMELY MOIST AIRMASS REMAINS OVER THE FORECAST AREA THIS
MORNING. THE MORNING SOUNDING SHOWED PRECIPITABLE WATER OF 1.53
INCHES, FIFTH HIGHEST OF ALL TIME. RADAR IS SHOWING NUMEROUS
SHOWERS OVER THE WEST-CENTRAL AND BOISE MOUNTAINS WITH
GENERALLY ISOLATED TO SCATTERED SHOWERS ELSEWHERE. HEAVY RAIN
AND LOCALIZED FLASH FLOODING IS STILL A CONCERN TODAY,
ESPECIALLY ON BURN SCARS.
AN ELONGATED SHORTWAVE TROUGH AXIS EXTENDS FORM THE CENTRAL
MOUNTAINS WEST ALONG THE OR/WA BORDER. THIS WILL CONTINUE TO
LIFT SLOWLY NORTH TODAY WITH SHOWERS AND AFTERNOON THUNDERSTORMS
CONTINUING ACROSS THE FORECAST AREA. THE BEST PRECIPITATION
POTENTIAL WILL BE ACROSS THE HIGHER TERRAIN OF SW IDAHO. DRIER
AIR SPREADING OVER THE AREA FROM THE WEST WILL LIMIT SHOWERS AND
THUNDERSTORMS OVER EASTERN OR. NO SIGNIFICANT CHANGES TO THE
FORECAST THIS MORNING.
AVIATION
MODERATE TO HEAVY SHOWERS AND ISOLATED THUNDERSTORMS
CONTINUING TODAY. GREATEST COVERAGE ACROSS SW IDAHO. LOCALIZED IFR
IN LOW CLOUDS AND FOG THIS MORNING. OUTFLOW GUSTS TO 25-35 KT, HEAVY
RAIN, AND MVFR TO LOCAL IFR CONDITIONS AND MTN OBSCURATION IN HEAVY
RAIN. VISIBILITY REDUCTIONS NEAR MTN WILDFIRES. SURFACE WINDS:
VARIABLE 5-15 KT. WINDS ALOFT AT 10KFT MSL: VARIABLE 10-20 KT.
KBOI...PERIODS OF MVFR/IFR IN LOW CLOUDS THIS MORNING. OTHERWISE
VFR. NUMEROUS SHOWERS WITH ISOLATED AFTERNOON THUNDERSTORMS.
MODERATE TO HEAVY RAIN WITH SHOWERS AND STORMS WITH GUSTY OUTFLOW
WINDS 25-35 KT. SURFACE WINDS: WEST-NORTHWEST 10 KT OR LESS.
PREV DISCUSSION
SHORT TERM...TODAY THROUGH FRIDAY NIGHT...THE MOISTURE CONTENT
OF THE CURRENT AIR MASS IS NEAR RECORD VALUES WITH THE TUESDAY
EVENING KBOI WX BALLOON MEASURING 1.57" OF PRECIPITABLE WATER.
WHILE NEARBY SHOWERS/STORMS MAY HAVE JUICED THE VALUE, IT WAS
CERTAINLY SUPPORTED BY NUMEROUS 1-3" GAUGE MEASURED RAINFALL
AMOUNTS FROM YESTERDAY'S ACTIVITY. PRECIPITATION TODAY IS
ALREADY MORE WIDESPREAD TONIGHT AND WILL CONTINUE TO BE AS AN
UPPER LOW LIFTS THROUGH CENTRAL IDAHO. SHOWERS AND THUNDERSTORMS
WILL BE CAPABLE OF PRODUCING SIMILAR RAINFALL AMOUNTS TO
YESTERDAY, EVEN ACROSS LOWER ELEVATION SITES IN THE SNAKE PLAIN.
THUS THE FLASH FLOOD WATCH REMAINS IN EFFECT FOR MUCH OF THE
AREA WITH THE POTENTIAL FOR MORE WARNINGS, ESPECIALLY AROUND
BURN SCARS OR STEEP TERRAIN THAT RECEIVED HEAVY RAIN IN THE LAST
24 HOURS. LOW LYING AREAS IN THE SNAKE PLAIN, TO INCLUDE
ROADS/INTERSECTIONS COULD ALSO SEE IMPACTS FROM HEAVIER
RAINFALL. THE BACK EDGE OF HEAVIER SHOWERS/STORMS WILL FOLLOW
THE UPPER LOW, CLEARING SOUTHEAST OREGON LATE THIS MORNING,
FOLLOWED BY THE LOWER SNAKE PLAIN THIS AFTERNOON. THE THREAT OF
SHOWERS/STORMS AND HEAVY RAIN CONTINUES ACROSS THE WESTERN MAGIC
VALLEY AND W-CENTRAL ID AND BOISE MTNS INTO THIS EVENING.
THURSDAY WILL BRING DRIER CONDITIONS TO MUCH OF SE OREGON AND
THE SNAKE PLAIN. INSTABILITY ON THE BACKSIDE OF THE LOW WILL
SUPPORT A 20-40% CHANCE OF SHOWERS AND ISOLATED THUNDERSTORMS
ACROSS ACROSS HIGHER TERRAIN. THE MOISTURE CONTENT OF THE AIR
MASS IS DOWN QUITE A BIT FROM TODAY (AROUND THE 60TH %TILE) SO
HEAVY RAINFALL WILL NOT AS MUCH OF A THREAT. WEAK UPPER RIDGING
WILL KEEP MOST AREAS DRY ON FRIDAY, WITH HIGHER TERRAIN ALONG
THE NORTHERN NV BORDER KEEPING A 15-25% CHANCE OF AFTERNOON
SHOWERS AND THUNDERSTORMS. TEMPERATURES ARE ABOUT 10 DEGREES
BELOW NORMAL TODAY UNDER THE CLOUDS/RAIN, WARMING BACK TO AROUND
NORMAL FOR THUR/FRI (MID-UPPER 80S IN LOWER VALLEYS).
LONG TERM...SATURDAY THROUGH WEDNESDAY...A BROAD UPPER RIDGE
OFF THE FOUR CORNERS REGION WILL BUILD INTO THE AREA SATURDAY
THROUGH MONDAY, BRINGING A WEAK WARMING TREND THAT WILL KEEP
PEAK VALLEY DAYTIME TEMPERATURES IN THE UPPER 80S AND LOWER 90S
THROUGHOUT THE EXTENDED FORECAST PERIOD. THERE IS SLIGHTLY
BETTER LONG-RANGE GUIDANCE AGREEMENT ON AN UPPER LOW OFF THE
PACIFIC NORTHWEST COAST TAKING AN ODD WOBBLING AND QUASI-
STATIONARY BEHAVIOR. THE SYSTEM IS PROJECTED TO STALL OFF THE
COAST OF BRITISH COLUMBIA AND WASHINGTON BEFORE MOVING BACK OUT
WEST ON TUESDAY. WEDNESDAY SEES CONSIDERABLE UNCERTAINTY OVER
WHETHER THIS SYSTEM DIGS INTO THE AREA FURTHER OR MOVES QUICKLY
BACK OUT NORTHWEST. FOR NOW, ISOLATED SHOWERS/THUNDERSTORMS ARE
MOST LIKELY OVER HIGHER ELEVATIONS MONDAY THROUGH WEDNESDAY.
BOI WATCHES/WARNINGS/ADVISORIES
ID...FLASH FLOOD WATCH THROUGH THIS EVENING IDZ011>016-028>030-033.
OR...FLASH FLOOD WATCH THROUGH THIS EVENING ORZ062>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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