264
FXUS65 KBOI 040025
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
625 PM MDT THU SEP 3 2026
UPDATE
UPDATED AVIATION DISCUSSION.
KEY MESSAGES
- INTERMITTENT SHOWERS AND EMBEDDED THUNDERSTORMS ACROSS MUCH OF
SOUTHEAST OREGON AND WEST-CENTRAL IDAHO THROUGH FRIDAY WITH
SIGNIFICANT RAINFALL TOTALS POSSIBLE THIS EVENING.
- TEMPERATURES 10 TO 20 DEGREES BELOW NORMAL THIS WEEK.
- COOL AND UNSETTLED CONDITIONS CONTINUE INTO EARLY NEXT WEEK.
SHORT TERM /THROUGH SATURDAY NIGHT/
ISSUED 232 PM MDT THU SEP 3 2026
PERIODS OF RAIN WILL CONTINUE IN VARIED COVERAGE THIS AFTERNOON
THROUGH TONIGHT, AS THE UPPER LOW REMAINS POSITIONED OVER THE
PACIFIC NORTHWEST COAST. A COLD FRONT APPROACHING FROM WEST-
CENTRAL OREGON THIS AFTERNOON WILL CROSS THE FORECAST AREA
OVERNIGHT INTO FRIDAY MORNING. THIS FRONT WILL BRING ANOTHER
WAVE OF WIDESPREAD RAIN AND EMBEDDED THUNDERSTORMS TONIGHT,
ALONG WITH BREEZY WESTERLY WINDS. THE FRONT WILL PUSH OUT EAST
EARLY FRIDAY, CLEARING CLOUD COVERAGE BY THE AFTERNOON. THE
RESULTING SURFACE HEATING WILL INTRODUCE WEAK DAYTIME
INSTABILITY, TRIGGERING ANOTHER ROUND OF ISOLATED TO SCATTERED
THUNDERSTORMS ON FRIDAY.
THE AFOREMENTIONED AFTERNOON/EVENING STORMS ON FRIDAY WILL BE
CAPABLE OF PRODUCING LOCALLY HEAVY DOWNPOURS ESPECIALLY OVER
HIGHER TERRAIN AREAS, ELEVATING FLASH FLOOD POTENTIAL OVER
RECENT BURN SCARS ACROSS SOUTHEAST OREGON AND THE CENTRAL IDAHO
MOUNTAINS, WHERE FLASH FLOOD WATCHES REMAIN IN EFFECT (INCLUDING
THE WAPITI BURN SCAR). TOTAL RAINFALL ACCUMULATIONS THROUGH
FRIDAY EVENING ARE FORECAST TO RANGE FROM 1.0 TO 1.5 INCHES IN
MOUNTAIN AREAS, WITH LOCALIZED HIGHER TOTALS IN CORE STORM
CENTERS. PEAK TEMPERATURES THROUGH FRIDAY WILL STAY 10 TO 20
DEGREES BELOW NORMAL.
ON SATURDAY, THE UPPER LOW CENTER WILL REMAIN QUASI-STATIONARY
OVER THE PACIFIC NORTHWEST COAST. WHILE LINGERING ATMOSPHERIC
MOISTURE WILL SUPPORT ONGOING SHOWER CHANCES, SPATIAL COVERAGE
WILL DECREASE AS DYNAMIC FORCING TEMPORARILY WEAKENS FROM THE
COOLER TEMPERATURES. TEMPERATURES ON SATURDAY WILL BEGIN A
SLIGHT RECOVERY, WARMING BACK CLOSER TO SEASONAL AVERAGES UNDER
PERSISTENT SOUTHWEST FLOW ALOFT.
LONG TERM /SUNDAY THROUGH THURSDAY/
ISSUED 232 PM MDT THU SEP 3 2026
THE LARGE PACIFIC UPPER LOW WILL SLOWLY STEER INLAND ONTO THE
COASTS OF WASHINGTON/OREGON ON SUNDAY AND THE LOW CORE WILL
PASS DIRECTLY OVER OUR AREA THROUGH MONDAY, RETURNING MODERATE
TO WIDESPREAD PRECIPITATION LATE SUNDAY INTO MONDAY. GUIDANCE
CONTINUES TO TRACK THE LOW STEERING MOISTURE FROM HURRICANE
MARIE INTO THE UPPER GREAT BASIN AND NEAR OUR AREA COME MONDAY.
THE MOISTURE WILL REMAIN CLOSE ENOUGH FOR SOUTH-CENTRAL IDAHO TO
EXPERIENCE HEIGHTENED CHANCES FOR HEAVIER RAINFALL, ESPECIALLY
THE CENTRAL MOUNTAINS. SNOW LEVELS ARE STILL EXPECTED TO DROP
LOW ENOUGH OVER THE HIGHEST PEAKS FOR A RAIN AND SNOW MIX,
MAINLY ON MONDAY.
BELOW-NORMAL TEMPERATURES WILL PERSIST THROUGH EARLY NEXT WEEK
DUE TO UPPER TROUGHING AND WIDESPREAD CLOUD COVER. LATEST
LONG-RANGE GUIDANCE SUGGESTS ANOTHER PACIFIC UPPER LOW STEERING
INTO THE REGION TUESDAY THROUGH THURSDAY, BUT WITH CONSIDERABLE
UNCERTAINTY OVER ITS MAGNITUDE AND BEHAVIOR TOWARDS LATE WEEK.
FOR NOW, DRIER CONDITIONS AND WARMER TEMPERATURES ARE EXPECTED
TUESDAY THROUGH LATE NEXT WEEK. THE APPROACHING LOW MAY RETURN
SCATTERED PRECIPITATION ON THURSDAY, DEPENDING ON THE AMOUNT OF
PACIFIC MOISTURE STEERED INTO OUR AREA.
AVIATION /00Z FRIDAY THROUGH SATURDAY/
ISSUED 546 PM MDT THU SEP 3 2026
MOSTLY VFR. NUMEROUS RAIN SHOWERS THROUGH FRIDAY MORNING, THEN
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS FRI AFTERNOON.
AREAS OF MVFR/IFR WITH HEAVIEST PRECIP. MTNS OBSCURED. SNOW
LEVELS LOWERING TO 6.5K-7.5K FEET MSL IN E OREGON THIS EVENING,
AND 8K-9K FEET IN W-CENTRAL ID BY FRI AM. SURFACE WINDS: SW-NW
5-15 KT WITH AREAS OF 20-30 KT GUSTS, THEN VARIABLE UP TO 10 KT
EARLY FRI MORNING. WINDS ALOFT AT 10KFT MSL: SW 10-30 KT.
KBOI...GENERALLY VFR. SHOWERS THIS EVENING, TAPERING OFF AFTER
FRI/12Z. BRIEF MVFR POSSIBLE DURING MODERATE SHOWERS. THEN, A
20% CHANCE OF SHOWERS AND THUNDERSTORMS FRIDAY AFTERNOON.
SURFACE WINDS: NW 6-12 KT. OCCASIONAL GUSTS TO 20 KT UNTIL EARLY
FRI AM. BECOMING LIGHT AND VARIABLE AS SHOWERS EXIT MID-MORNING.
WEEKEND OUTLOOK...MOSTLY VFR. SCATTERED SHOWERS SATURDAY
MORNING. ACTIVITY DECREASING TOWARD THE NORTHEAST LATE
MORNING/AFTERNOON. THEN, SHOWERS INCREASING AGAIN SUNDAY, WITH
HIGHEST CHANCES (50-70%) OVER EAST OREGON AND W-CENTRAL IDAHO.
LOCALIZED MVFR/IFR AND MTN OBSCURATION IN HEAVIEST PRECIP. FOG
DEVELOPMENT IN MOUNTAIN VALLEYS AND HIGH BASINS POSSIBLE SAT/SUN
MORNINGS. SW-NW SURFACE WINDS 5-10 KT WITH PM GUSTS TO 15-20 KT.
BOI WATCHES/WARNINGS/ADVISORIES
ID...FLASH FLOOD WATCH THROUGH FRIDAY EVENING FOR IDZ011-013.
OR...FLASH FLOOD WATCH THROUGH FRIDAY EVENING FOR ORZ061>063.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
AVIATION.....SH
SHORT TERM...JY
LONG TERM....JY
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