192
FXUS65 KBOI 030304
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
904 PM MDT THU OCT 2 2025
DISCUSSION
AN UPPER LEVEL TROUGH HAS SHIFTED INTO NORTHERN CA
WITH BROAD SOUTHERLY FLOW OVER THE AREA. WITH THE POSITIONING OF
THE TROUGH, UPPER LEVEL DIFFLUENCE IS FAVORABLE FOR STRONG
UPWARD MOTION FAVORING MODERATE AND LOCALLY HEAVY PRECIPITATION
LATER THIS EVENING, ESPECIALLY ACROSS SOUTHWEST IDAHO. THIS WILL
CONTINUE OVERNIGHT INTO EARLY FRIDAY BEFORE TAPERING OFF AS THE
TROUGH MOVES EASTWARD. RAINFALL AMOUNTS OF 0.50 TO 1.00 INCH
POSSIBLE WITH THIS SYSTEM, GENERALLY EAST OF A LINE FROM BURNS
OR TO MCCALL ID, WITH MINIMAL AMOUNTS IN BAKER COUNTY OR. NO
UPDATES.
AVIATION
WIDESPREAD PRECIP WITH EMBEDDED THUNDERSTORMS CONTINUING
THROUGH FRI MORNING, BECOMING SCATTERED BY FRI AFTERNOON.
MVFR/IFR AND LOCALIZED LIFR IN HEAVIER PRECIP AND LOW CLOUDS.
MTNS OBSCURED. SURFACE WINDS: VARIABLE UP TO 10KT, EXCEPT NW-W
10-20 KT WITH 25-35 KT GUSTS BETWEEN KBOI-KTWF. WINDS ALOFT AT
10KFT MSL: SW-S 10-20 KT, TRANSITIONING TO NW-NE 5-15 KT
OVERNIGHT.
KBOI...RAIN, MODERATE TO HEAVY AT TIMES. PERIODS OF MVFR/IFR IN RAIN
AND LOW CIGS, MAINLY BETWEEN 03/06Z-14Z. FOOTHILLS OBSCURED.
RAIN COVERAGE AND INTENSITY WILL DECREASE BY 03/12Z, BUT
SCATTERED SHOWERS EXPECTED THROUGH FRI EVENING. SURFACE WINDS:
W TO NW 5-12 KT. OCCASIONAL GUSTS AROUND 20 KT BEFORE 03/07Z.
WEEKEND OUTLOOK: PATCHY AM FOG FOR SHELTERED MTN VALLEYS AND
BASINS. SHOWERS CONTINUING IN CENTRAL IDAHO MTNS AND AROUND
KTWF/KJER SATURDAY. THEN, ISOLATED SHOWERS OVER CENTRAL IDAHO
MTNS SUNDAY. MVFR/IFR IN HEAVIER RAIN SHOWERS, IFR/LIFR IN SNOW.
SNOW LEVELS 6500-7500 FT MSL. MOUNTAINS OBSCURED IN PRECIP.
SURFACE WINDS: N-NW 10-20 KT GUSTING TO 20-30 KT SATURDAY, WITH
LOCALIZED GUSTS TO 40 KT IN THE SNAKE PLAIN. THEN, NW-NE 5-10 KT
SUNDAY.
PREV DISCUSSION
SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT... ISOLATED RAIN
SHOWERS ACROSS THE HIGH TERRAIN IN IDAHO ARE GRADUALLY MOVING
EAST THIS AFTERNOON AS THE MAIN AREA OF PRECIPITATION THAT WILL
AFFECT US MOVES INTO NEVADA. THE LOW OFF THE COAST OF THE
PACIFIC NORTHWEST WILL CONTINUE TO DIG INTO THE WESTERN US TODAY
AND TOMORROW. A COLD FRONT WILL MOVE INTO THE REGION BRINGING A
BAND OF HEAVY PRECIPITATION TO SOUTHWEST IDAHO THROUGH THE
NIGHT. THE HEAVIEST PRECIPITATION (0.6-1.3 INCHES) LOOKS TO
OCCUR IN A LINE FROM THE WEST CENTRAL MOUNTAINS DOWN THROUGH
IDAHO CITY, BOISE, AND THE OWYHEE MOUNTAINS. THE TREASURE
VALLEY WILL LIKELY SEE RELATIVELY LOWER AMOUNTS (0.40-0.60
INCHES OF RAIN) THANKS TO SOME SHADOWING FROM THE OWYHEE
MOUNTAINS. INTERMITTENT RAIN SHOWERS OUTSIDE OF THE BAND WILL
BRING AT LEAST A FEW HUNDREDTHS TO A WETTING RAIN (0.10 INCHES)
ACROSS THE REGION. RAIN WILL CONTINUE THROUGH FRIDAY AFTERNOON,
WITH SOME WRAPAROUND PRECIPITATION FROM A SURFACE LOW TO THE
SOUTH LIKELY IN SOUTHEAST OREGON. THIS COULD BRING HEAVIER
TOTALS UP TO AN INCH OVER HIGHER TERRAIN IN SOUTHERN
MALHEUR/HARNEY COUNTIES. EMBEDDED CONVECTION IS POSSIBLE THIS
AFTERNOON AND OVERNIGHT WITHIN THE MAIN BAND OF PRECIPITATION
WITH A FEW THUNDERSTORMS PRIMARILY IN THE SOUTHERN BOISE
MOUNTAINS AND NEAR THE NEVADA BORDER. HEAVY RAIN, ESPECIALLY IN
HIGH TERRAIN AND NEAR BURN SCARS, WILL CONTINUE THE RISK OF
FLASH FLOODING THROUGH FRIDAY AFTERNOON. THE WAPITI BURN SCAR
NEAR HIGHWAY 21 WILL CONTINUE TO BE OF PARTICULAR CONCERN, BUT
OTHER BURN SCARS IN THE AREA WILL SEE A RISK OF HIGH
PRECIPITATION TOTALS IN A RELATIVELY SHORT PERIOD OF TIME THAT
COULD LEAD TO DEBRIS FLOWS AND MUDSLIDES.
BREEZY WINDS UP TO 25 MPH WILL ALSO ACCOMPANY HEAVIER PUSHES OF
PRECIPITATION, BUT THE STRONGEST WINDS ARE ANTICIPATED ON
FRIDAY AND SATURDAY AFTERNOON AFTER THE MAIN FRONTAL PASSAGE.
SUSTAINED NORTHWESTERLY WINDS AROUND 20-25 MPH WITH GUSTS UP TO
40 MPH ARE LIKELY IN THE SNAKE RIVER VALLEY TOMORROW AND
SATURDAY AFTERNOON.
THE COOLING TREND WITH TEMPERATURES ABOUT 5-10 DEGREES BELOW
NORMAL WILL CONTINUE THROUGH SATURDAY. DRYING CONDITIONS WILL
OCCUR BY SATURDAY MORNING FOR MOST OF THE REGION, AS THE
LINGERING SHOWERS OVER HIGH TERRAIN IN SOUTHWEST IDAHO MOVE TO
THE EAST WITH THE UPPER LEVEL LOW PUSHING SOUTHEAST.
LONG TERM...SUNDAY THROUGH THURSDAY... FOLLOWING THE RAIN EVENT
IN THE SHORT-TERM, THE IDAHO WEST CENTRAL MOUNTAINS WILL
MAINTAIN A 20- 50% CHANCE OF SHOWERS (INCREASING AS YOU MOVE
NORTHEAST). THIS WILL BE THANKS TO THE PASSAGE OF A SHORTWAVE
TROUGH WHICH WILL PROPAGATE ALONG THE BACKSIDE OF THE MAIN
TROUGH THAT WILL BE EXITING OUR REGION. SNOW LEVELS LOWERING TO
6000-7000 FEET ON SUNDAY WILL MEAN THAT MOUNTAINS SEE
PRECIPITATION IN THE FORM OF SNOW/WINTERY MIX. THIS SHORTWAVE
WILL AMPLIFY AND EVENTUALLY CLOSE OFF INTO A LOW OVER
CALIFORNIA. ENSEMBLE CONSENSUS CONTINUES TO SHOW A REX BLOCK
BRIEFLY BUILDING IN WITH SLIGHT RIDGING EXTENDING NORTH OF THE
LOW OVER OUR AREA. THIS WILL ALLOW FOR A GENERAL WARMING TREND
THROUGH THE WEEK AND CHANCES OF PRECIPITATION <10% THROUGH
WEDNESDAY. MODELS GENERALLY AGREE ON A DEEP LOW FORMING OVER THE
GULF OF ALASKA LATE WEDNESDAY INTO FRIDAY AND BREAKING UP THE
REX. HOWEVER, THE EVOLUTION OF THIS LOW IS LEAVING MUCH TO BE
RESOLVED. ENSEMBLES ARE GENERALLY KEEPING IT CLOSER TO THE
SHORE, ALLOWING FOR A SLIGHT CHANCE OF PRECIPITATION ACROSS OUR
AREA COME THURSDAY AFTERNOON. TEMPERATURES WARMING FROM 5-10
DEGREES BELOW NORMAL ON SUNDAY TO NEAR NORMAL BY TUESDAY.
BOI WATCHES/WARNINGS/ADVISORIES
ID...FLASH FLOOD WATCH THROUGH FRIDAY AFTERNOON IDZ011-013.
OR...NONE.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
DISCUSSION...KA
AVIATION.....SH
SHORT TERM...SA
LONG TERM....NF
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