604
FXUS65 KBOI 271136
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
536 AM MDT SUN SEP 27 2026
UPDATE
UPDATED AVIATION DISCUSSION.
KEY MESSAGES
- VIRGA AND LIGHT RAIN TODAY THROUGH EARLY MONDAY, WITH HIGHEST
RAIN CHANCES ACROSS EAST OREGON AND THE WEST-CENTRAL IDAHO
MOUNTAINS.
- WARM AND DRY CONDITIONS EXPECTED TUESDAY THROUGH NEXT
WEEKEND, WITH MAX TEMPERATURES PEAKING WEDNESDAY AND THURSDAY.
SHORT TERM /THROUGH TUESDAY NIGHT/
ISSUED 230 AM MDT SUN SEP 27 2026
SOUTHEAST OREGON AND SOUTHWEST IDAHO RESIDE UNDER SOUTHWEST
FLOW ALOFT THIS MORNING AHEAD OF A WEAK TROUGH OVER THE WEST
COAST. THIS TROUGH IS SPREADING A SWATH OF MID-LEVEL MOISTURE
ACROSS THE AREA TODAY THROUGH EARLY MONDAY, BRINGING CLOUDY
SKIES, WIDESPREAD VIRGA, AND LIGHT RAIN. WHILE PRECIPITATION IS
EXPECTED TO BE SPORADIC AS MOISTURE EXPANDS NORTHWARD, THE
HIGHEST PROBABILITIES OF MEASURABLE RAINFALL ARE OVER EAST
OREGON AND WEST-CENTRAL IDAHO (20-40%) MAINLY IN THE AFTERNOON
AND EVENING...WITH LOWER CHANCES (5-15%) ELSEWHERE. SOUTHWEST TO
NORTHWEST SURFACE WINDS WILL BECOME BREEZY THIS AFTERNOON
ACROSS SOUTHEAST OREGON AND PORTIONS OF THE WESTERN SNAKE PLAIN.
AS THE TROUGH HEADS EASTWARD OVERNIGHT INTO EARLY MONDAY, THE
MOISTURE WILL ALSO DEPART TOWARD THE EAST. AS A RESULT, SKIES
WILL BEGIN TO CLEAR AND TEMPERATURES WILL TREND WARMER FOR
MONDAY COMPARED TO PREVIOUS DAYS. WESTERLY FLOW ALOFT WILL
ESTABLISH OVER THE REGION BEGINNING TUESDAY, WITH DRY AND WARM
CONDITIONS ANTICIPATED.
LONG TERM /WEDNESDAY THROUGH SUNDAY/
ISSUED 230 AM MDT SUN SEP 27 2026
FORECAST MODELS DEPICT A BUILDING RIDGE OVER THE SOUTHWESTERN
U.S. FROM TUESDAY THROUGH THURSDAY, DRIVING LOWER-ELEVATION
TEMPERATURES INTO THE UPPER 70S/LOW 80S BY WED AND THU.
THEREAFTER, A WEAK SHORTWAVE TROUGH WILL ENTER THE PACIFIC
NORTHWEST ON FRIDAY, BRIEFLY FLATTENING THE RIDGE AND DROPPING
TEMPERATURES BY A FEW DEGREES FRIDAY THROUGH SATURDAY. MOISTURE
ASSOCIATED WITH THIS TROUGH IS LIKELY TO REMAIN NORTH, KEEPING
SOUTHEAST OREGON AND SOUTHWEST IDAHO IN A DRIER AIRMASS. THE
RIDGE IS EXPECTED TO REBOUND ON SUNDAY AS THE TROUGH CONTINUES
EAST, SUPPORTING THE RETURN OF ABOVE NORMAL TEMPERATURES.
AVIATION /12Z SUNDAY THROUGH MONDAY/
ISSUED 529 AM MDT SUN SEP 27 2026
GENERALLY VFR. VIRGA AND ISOLATED/SCATTERED LIGHT RAIN SHOWERS
WILL EXPAND NORTH ACROSS THE AREA TODAY. SURFACE WINDS: VARIABLE
LESS THAN 10 KT THROUGH MORNING. BECOMING SW-NW 5-15 KT, WITH
GUSTS TO 25 KT SOUTH/EAST OF KBOI AFTER SUN/21Z. WINDS ALOFT AT
10KFT MSL: SW 10-20 KT.
KBOI...VFR. VIRGA OR LIGHT RAIN IN THE VICINITY THROUGH MORNING.
A 15% CHANCE OF RAIN REACHING THE GROUND AT THE TERMINAL.
SURFACE WINDS: LIGHT SE OR VARIABLE THROUGH MORNING, BECOMING
NW 7-14 KT THIS AFTERNOON, WITH GUSTS TO AROUND 20 KT MID-
AFTERNOON THROUGH EARLY EVENING.
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.....SH
SHORT TERM...SH
LONG TERM....SH
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