003
FXUS65 KBOI 100341
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
941 PM MDT TUE SEP 9 2025
DISCUSSION
SHOWERS AND THUNDERSTORMS STRADDLED THE REGION
TODAY BRINGING LOCALLY HEAVY RAIN TO THE BLUE MTNS, AND CENTRAL
IDAHO MTNS. ANOTHER ROUND OF SHOWERS MOVING UP FROM NV WILL PUSH
INTO SE OREGON LATE TONIGHT AND COULD PRODUCE A FEW RUMBLES OF
THUNDER. THERE IS A LOW CHANCE THAT A LINE OF SHOWERS AND
POSSIBLE THUNDERSTORMS EXTENDS INTO SW IDAHO THROUGH EARLY
WEDNESDAY MORNING. THAT SAID THE MORE ACTIVE WEATHER ACROSS SW
IDAHO AND PORTIONS OF SE OREGON WILL COME WEDNESDAY AFTERNOON
WITH A ROUND OF THUNDERSTORMS. STRONG THUNDERSTORMS ARE POSSIBLE
AND WOULD BRING HEAVY RAIN, SMALL HAIL AND GUSTY WINDS.
AVIATION
VFR. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
POSSIBLE FOR MOST AREAS OVERNIGHT, WITH A FOCUS ON EASTERN
OREGON. OTHERWISE PARTLY CLOUDY. SHOWERS AND THUNDERSTORMS
AREA-WIDE AFTER 19Z WEDNESDAY. SOME STORMS COULD CONTAIN WIND
GUSTS GREATER THAN 30 KT. SFC WINDS VARIABLE 5-15 KT. WINDS
ALOFT AT 10KFT MSL: SSW 5-15 KT.
KBOI...VFR WITH INCREASING CLOUDS AND ISOLATED SHOWERS AND
THUNDERSTORMS POSSIBLE 06-12Z. BETTER CHANCE FOR STORMS, ALONG
WITH GUSTY OUTFLOW WINDS (30% OF 40 MPH OR GREATER) AFTER 20Z
WEDNESDAY. WINDS BECOME SE LESS THAN 10 KT, BEFORE TURNING TO
THE NORTHWEST WEDNESDAY AFTERNOON.
PREV DISCUSSION
SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT...ACTIVE WEATHER IS
EXPECTED THROUGH THE SHORT TERM. THIS WILL BE THE RESULT OF AN
UPPER LEVEL LOW CURRENTLY CENTERED OVER FAR NORTHERN CALIFORNIA
THAT WILL SLOWLY DRIFT EAST THROUGH THURSDAY. THE LOW WILL BE
ACCOMPANIED BY ABUNDANT MOISTURE WITH PRECIPITABLE WATER VALUES
RISING TO THE 80TH TO 90TH PERCENTILE. AHEAD OF THIS LOW,
SHOWERS AND ISOLATED THUNDERSTORMS WILL DEVELOP OVER THE CENTRAL
ID MOUNTAINS THIS EVENING BEFORE TAPERING OFF. ISOLATED
ACTIVITY WILL CONTINUE OVERNIGHT ACROSS THE AREA AS A SHORTWAVE
LIFTS NORTH.
ON WEDNESDAY, SHOWER AND THUNDERSTORM COVERAGE WILL EXPAND WITH
DAYTIME HEATING. MODELS ARE DEPICTING TWO PRIMARY AREAS OF
DEVELOPMENT. THE FIRST WILL BE NEAR THE LOW CENTER ACROSS
CENTRAL OREGON, WHERE COOLER TEMPERATURES WILL ALLOW FOR
WIDESPREAD SHOWERS AND EMBEDDED THUNDERSTORMS CAPABLE OF HEAVY
RAINFALL. THE SECOND AREA IS EXPECTED TO DEVELOP ACROSS FAR SE
OREGON AND SW IDAHO LATE AFTERNOON AND EVENING AS AN EMBEDDED
SHORTWAVE ROTATES AROUND THE MAIN UPPER LOW INTO OUR AREA AND
PROVIDES LIFT FOR MORE ORGANIZED DEVELOPMENT. PARTIAL CLEARING
IS EXPECTED DURING THE AFTERNOON TOMORROW IN THIS AREA ALLOWING
FOR WARM SURFACE TEMPERATURES AND INCREASING INSTABILITY. ENOUGH
SHEAR WILL ALSO BE PRESENT FOR STRONGER STORMS TO DEVELOP WITH
HEAVY RAIN, HAIL, AND GUSTY WINDS IN EXCESS OF 50 MPH POSSIBLE.
HEAVY RAIN OVER RECENT BURN SCARS MAY ALSO CREATE POTENTIAL FOR
FLASH FLOODING AND DEBRIS FLOWS, ALTHOUGH CONFIDENCE IN THIS IS
LOW.
SHOWERS AND THUNDERSTORMS WILL CONTINUE OVER OUR AREA WEDNESDAY
NIGHT AND THURSDAY AS THE LOW SLOWLY MOVES OVERHEAD. THE FOCUS
FOR SIGNIFICANT PRECIPITATION SHOULD BE NEAR THE LOW CENTER
ACROSS SE OREGON, AS WELL AS THE MOUNTAINS OF SW IDAHO. THIS
WILL ALSO COOL TEMPERATURES TO 5-10 DEGREES BELOW NORMAL.
PRECIPITATION CHANCES WILL DIMINISH THURSDAY NIGHT WITH THE LOSS
OF DAYTIME HEATING.
LONG TERM...FRIDAY THROUGH TUESDAY...THE PATTERN WILL REMAIN
ACTIVE THROUGH THE EXTENDED PERIOD. THE UPPER LOW WILL CONTINUE
TO SLOWLY DRIFT ACROSS OUR AREA ON FRIDAY AND WEAKEN. THIS WILL
BRING A 40-70% CHANCE OF SHOWERS AND EMBEDDED THUNDERSTORMS
FRIDAY AFTERNOON, AIDED BY DAYTIME HEATING. SHOWER CHANCES WILL
DECREASE ON SATURDAY, WITH MOST ACTIVITY IN THE MOUNTAINS. AN
UPPER LEVEL RIDGE WILL BRIEFLY MOVE OVERHEAD SATURDAY NIGHT
BEFORE THE NEXT UPPER LEVEL LOW MOVES INTO THE PACIFIC NORTHWEST
ON SUNDAY. THIS WILL BRING A 30-50% CHANCE OF SHOWERS AND
SLIGHT CHANCE OF THUNDERSTORMS SUNDAY AND MONDAY, THEN DECREASE
ON TUESDAY AS THE LOW MOVES EAST. THIS PATTERN WILL KEEP
TEMPERATURES NEAR TO SLIGHTLY BELOW NORMAL THROUGH THE PERIOD.
BOI WATCHES/WARNINGS/ADVISORIES
ID...NONE.
OR...NONE.
WWW.WEATHER.GOV/BOISE
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DISCUSSION...DG
AVIATION.....MC
SHORT TERM...ST
LONG TERM....ST
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