472
FXUS65 KBOI 020041
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
641 PM MDT TUE SEP 1 2026
UPDATE
UPDATED AVIATION DISCUSSION.
KEY MESSAGES
- ISOLATED TO SCATTERED THUNDERSTORMS TONIGHT THROUGH WEDNESDAY
MORNING, MAINLY ACROSS THE MOUNTAINS OF CENTRAL IDAHO.
- WIDESPREAD SHOWERS AND EMBEDDED THUNDERSTORMS ACROSS MUCH OF
SOUTHEAST OREGON AND WEST-CENTRAL IDAHO WEDNESDAY NIGHT
THROUGH THURSDAY WITH SIGNIFICANT RAINFALL TOTALS POSSIBLE.
- MUCH COOLER THIS WEEK, WITH HIGHS 10-20 DEGREES BELOW NORMAL
BY THURSDAY WITH PERIODS OF GUSTY WINDS.
- ADDITIONAL WET AND COOL WEATHER ANTICIPATED LATE THIS WEEKEND
INTO EARLY NEXT WEEK.
SHORT TERM /THROUGH THURSDAY NIGHT/
ISSUED 237 PM MDT TUE SEP 1 2026
A DEEP UPPER LEVEL LOW WILL APPROACH THE PACIFIC NORTHWEST
TONIGHT INTO WEDNESDAY, PLACING OUR AREA IN SOUTHERLY FLOW
ALOFT. MONSOONAL MOISTURE IN PLACE OVER IDAHO AND A WEAK
SHORTWAVE TROUGH WILL BRING SCATTERED SHOWERS AND THUNDERSTORMS
TO THE MAGIC VALLEY NORTH THROUGH THE CENTRAL IDAHO MOUNTAINS
THROUGH THIS EVENING. STORMS MAY PRODUCE OUTFLOW GUSTS TO 50
MPH, BRIEF HEAVY RAIN, AND SMALL HAIL.
AFTER A BRIEF BREAK IN STORM ACTIVITY, A SHORTWAVE TROUGH AHEAD
OF THE MAIN UPPER LOW WILL ROTATE ACROSS OUR AREA LATE TONIGHT
THROUGH WEDNESDAY MORNING. THERE WILL BE ENOUGH MOISTURE AND
INSTABILITY IN PLACE ACROSS WEST- CENTRAL IDAHO AND EAST-CENTRAL
OREGON FOR SHOWERS AND A 10-30% CHANCE OF THUNDERSTORMS. THE
HIGHEST RAINFALL TOTALS AND BEST CHANCE OF THUNDERSTORMS WILL BE
ACROSS THE CENTRAL IDAHO MOUNTAINS WHERE 0.10-0.25" OF RAIN IS
EXPECTED, EXCEPT HIGHER AMOUNTS POSSIBLE IN THUNDERSTORMS.
TEMPERATURES WILL BE AROUND 10 DEGREES LOWER THAN TODAY AS
COOLER AIR ACCOMPANIES THE SHORTWAVE PASSAGE. WINDS WILL BE
GUSTY TONIGHT SOUTH OF THE SNAKE RIVER, WITH GUSTS 20-35 MPH
EXPANDING TO MOST HIGHER ELEVATION LOCATIONS BY WEDNESDAY
AFTERNOON. LOCALLY LOW RELATIVE HUMIDITY NEAR THE IDAHO/NEVADA
BORDER AND GUSTY WINDS WILL LEAD TO ELEVATED FIRE WEATHER
CONDITIONS.
AS THE LOW CENTER APPROACHES THE COAST, MOIST SOUTHWESTERLY FLOW
WILL SET UP ACROSS SOUTHEAST OREGON AND WEST-CENTRAL IDAHO
WEDNESDAY NIGHT INTO THURSDAY. SHOWERS WILL BECOME WIDESPREAD
IN THESE AREAS, BUT PRECIPITATION CHANCES WILL BE LOWER TO THE
EAST WITH A LESS THAN 10% CHANCE OF RAIN IN THE MAGIC VALLEY.
WEAK INSTABILITY WILL SUPPORT A 10-20% CHANCE OF THUNDERSTORMS,
HIGHEST THURSDAY AFTERNOON WITH THE ADDITION OF DAYTIME HEATING.
SUSTAINED MOIST SOUTHWEST FLOW, OROGRAPHIC LIFT, AND A NEUTRAL
TO WEAKLY UNSTABLE ATMOSPHERE IN ADDITION TO DYNAMIC FORCING
AHEAD OF THE UPPER LOW WILL PRODUCE SIGNIFICANT RAINFALL TOTALS
ACROSS MUCH OF SOUTHEAST OREGON INTO WEST- CENTRAL IDAHO.
AMOUNTS OF 0.25-0.75" ARE EXPECTED ACROSS MUCH OF SOUTHEAST
OREGON (TAPERING TO NEAR ZERO NEAR THE OREGON/IDAHO/NEVADA
TRIPLE POINT), WITH 0.5-1.5" ACROSS THE WEST-CENTRAL IDAHO AND
EAST- CENTRAL OREGON MOUNTAINS. LOCALLY HEAVIER AMOUNTS ARE
POSSIBLE FROM THUNDERSTORMS. THE TREASURE VALLEY LOOKS TO PICK
UP LESS THAN A TENTH OF AN INCH OF RAIN, EXCEPT SLIGHTLY HIGHER
TOWARDS THE WEST END OF THE VALLEY. WINDS WILL REMAIN GUSTY NEAR
THE NEVADA BORDER, AND TEMPERATURES WILL DIP 5-10 DEGREES
COOLER THAN WEDNESDAY WHERE RAIN IS PERSISTENT, WITH HIGHS 10-20
DEGREES BELOW NORMAL ACROSS THE AREA.
LONG TERM /FRIDAY THROUGH TUESDAY/
ISSUED 237 PM MDT TUE SEP 1 2026
THE PATTERN WILL REMAIN COOLER AND RELATIVELY WET THROUGH EARLY
NEXT WEEK AS THE UPPER LOW WOBBLES ACROSS THE PACIFIC
NORTHWEST. A 20-60% CHANCE OF SHOWERS AND 10-20% CHANCE OF
THUNDERSTORMS WILL CONTINUE INTO FRIDAY AS THE LOW CENTER LIFTS
TO THE NORTH. PRECIPITATION CHANCES THEN DECREASE SATURDAY INTO
EARLY SUNDAY AS THE LOW PIVOTS BACK TO THE WEST, BUT WILL STILL
REMAIN AROUND 10-30%. THE LOW IS THEN FAVORED TO MOVE TO THE
EAST LATE SUNDAY INTO MONDAY, INCREASING PRECIPITATION CHANCES
TO 30-60% ONCE AGAIN BEFORE DECREASING TUESDAY. HOWEVER,
FORECAST CONFIDENCE IS LOWER DURING THIS PERIOD AS TROPICAL
ACTIVITY OFF THE COAST OF BAJA CALIFORNIA WILL HAVE DOWNSTREAM
FORECAST IMPLICATIONS. EVEN IF TROPICAL ACTIVITY STAYS OFFSHORE,
THERE IS POTENTIAL FOR ENTRAINMENT OF TROPICAL MOISTURE INTO
THE INTERIOR WEST, WHICH WOULD INCREASE THE RISK FOR HEAVY
RAINFALL. TEMPERATURES WILL GRADUALLY WARM TO ONLY A FEW DEGREES
BELOW NORMAL BY SATURDAY, THEN COOL ONCE AGAIN EARLY NEXT WEEK
AS SHOWERS INCREASE.
AVIATION /00Z WEDNESDAY THROUGH THURSDAY/
ISSUED 619 PM MDT TUE SEP 1 2026
SCATTERED SHOWERS/THUNDERSTORMS OVER CENTRAL IDAHO MTNS
PRODUCING MVFR-IFR IN HEAVY RAIN AND HAIL UNDER THE CORES, AND
GUSTS UP TO 40 KT. CELLS WILL EXIT TO THE N-NE LATE THIS
EVENING, THEN SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
REGENERATING IN EARLY MORNING HRS ACROSS EAST OREGON AND
W-CENTRAL IDAHO. SURFACE WINDS: SE-SW 5-15 KT, AREAS OF GUSTS
20-25 KT. WINDS ALOFT AT 10KFT MSL: S-SW 10-20 KT.
KBOI...VFR. A 30 PERCENT CHANCE OF LIGHT RAIN SHOWERS DURING
EARLY TO MID WED MORNING HOURS. SURFACE WINDS: NW 5-10 KT, THEN
SE 5-10 KT AFTER WED/03Z. RETURNING TO LIGHT NW OR VARIABLE
AROUND WED/10Z.
BOI WATCHES/WARNINGS/ADVISORIES
ID...OR...NONE.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
AVIATION.....SH
SHORT TERM...ST
LONG TERM....ST
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