706
FXUS65 KBOI 211741
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
1141 AM MDT MON SEP 21 2026
UPDATE
UPDATED AVIATION DISCUSSION.
KEY MESSAGES
- MOSTLY DRY WITH WARMING TEMPERATURES THROUGH THURSDAY.
- CHANCE OF SHOWERS AND THUNDERSTORMS TUESDAY, MOSTLY ACROSS
HIGHER TERRAIN OF SOUTHWEST IDAHO.
- COOLER TEMPERATURES HEADING INTO THIS WEEKEND WITH A CHANCE
OF PRECIPITATION ACROSS SE OREGON AND PORTIONS OF SW IDAHO
FRIDAY.
SHORT TERM /THROUGH WEDNESDAY NIGHT/
ISSUED 245 AM MDT MON SEP 21 2026
BROAD UPPER RIDGING WILL KEEP WARM AND DRY CONDITIONS OVER THE
REGION ON MONDAY. THIS MORNING, SOME MOUNTAIN VALLEY FOG IS
POSSIBLE IN CENTRAL IDAHO HIGH TERRAIN. BUT AS THE SUN RISES IN
CLEAR SKIES TEMPERATURES REACH 5-10 DEGREES ABOVE NORMAL, OR
ABOUT 5 DEGREES WARMER THAN SUNDAY. AN EASTWARD SHIFT IN THE
RIDGE AXIS ON TUESDAY WILL ALLOW FOR A CLOSED LOW TO LIFT
NORTHEASTWARD THROUGH THE GREAT BASIN. THIS WILL BRING A 20-30%
CHANCE OF SHOWERS AND THUNDERSTORMS TO HIGHER TERRAIN ALONG THE
IDAHO/NEVADA BORDER, THE CENTRAL IDAHO MOUNTAINS AND THE
MOUNTAINS IN BAKER COUNTY TUESDAY AFTERNOON. TEMPERATURES MAY BE
A DEGREE OR TWO COOLER ON TUESDAY COMPARED TO MONDAY, BUT A
GENERAL WARMING TREND CONTINUES INTO WEDNESDAY AS THE CUT OFF
LOW MOVES EAST, HEIGHTS RISE, AND STRONGER WARM SOUTHWESTERLY
FLOW ALOFT MOVES IN.
LONG TERM /THURSDAY THROUGH MONDAY/
ISSUED 245 AM MDT MON SEP 21 2026
A RIDGE WILL REMAIN OVER THE AREA ON THURSDAY. THURSDAY WILL BE
THE HOTTEST DAY IN THE 7-DAY PERIOD, WITH TEMPERATURES NEAR 90
DEGREES IN LOWER ELEVATIONS AND 80 DEGREES IN HIGHER ELEVATIONS.
A TROUGH MOVES INTO THE PACIFIC NW FRIDAY/SATURDAY WITH COOLER
TEMPERATURES AND INCREASED CHANCES (15 TO 25 PERCENT) OF
PRECIPITATION THIS WEEKEND. PRECIPITATION CHANCES WILL BE
HIGHEST IN NORTHEASTERN OREGON AND WEST-CENTRAL IDAHO, WITH
GENERALLY DRY CONDITIONS AS ONE APPROACHES THE NEVADA BORDER.
TEMPERATURES FALL TO NEAR NORMAL ON FRIDAY, AND 5 TO 10 DEGREES
BELOW NORMAL ON SATURDAY AND SUNDAY. THE TEMPERATURE DROP MAY
SHIFT FULLY TO FRIDAY OR SATURDAY AS SYNOPTIC MODELS COME INTO
BETTER AGREEMENT ON THE COLD FRONT PASSAGE, CAUSING A SHARPER
COOL OFF ON FRIDAY OR PROLONGED WARMNESS ON FRIDAY RESPECTIVELY.
COOLER TEMPERATURES REMAIN THROUGH THE WEEKEND INTO NEXT MONDAY
AS A TROUGH AXIS ENTRENCHES ITSELF ALONG THE COAST AND THE JET
STREAM STAYS OVERHEAD.
AVIATION /18Z MONDAY THROUGH TUESDAY/
ISSUED 1141 AM MDT MON SEP 21 2026
VFR WITH HIGH CLOUDS INCREASING THIS AFTERNOON. SURFACE WINDS:
GENERALLY VARIABLE OR S-SE 5-10 KT. WINDS ALOFT AT 10KFT MSL: S
5-10 KT
KBOI...VFR WITH INCREASING HIGH CLOUDS THIS AFTERNOON. SURFACE
WINDS: SE UNDER 10 KT, WITH A BRIEF PERIOD OF LIGHT W-NW WINDS
THIS AFTERNOON.
BOI WATCHES/WARNINGS/ADVISORIES
ID...NONE.
OR...NONE.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
AVIATION.....NF
SHORT TERM...JM
LONG TERM....JM
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