846
FXUS65 KBOI 190837
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
237 AM MDT SAT SEP 19 2026
KEY MESSAGES
- RAIN SHOWERS IN IDAHO CONTINUE THROUGH THE DAY, SLOWLY MOVING
EASTWARD.
- GRADUAL WARMING AND DRYING TREND BEGINNING SATURDAY AND
CONTINUING THROUGH EARLY NEXT WEEK.
SHORT TERM /THROUGH MONDAY NIGHT/
BEHIND AN EXITING LOW PRESSURE SYSTEM, MOISTURE WRAPPING AROUND
THE CENTER IS STREAMING THROUGH CENTRAL AND SOUTHWESTERN IDAHO.
THE WRAP-AROUND MOISTURE IS SUPPORTING DEVELOPMENT OF STEADY
STRATIFORM RAINFALL IN THIS REGION, CLEARLY DEFINED ON SATELLITE
AND RADAR. LIGHT RAIN IN LOWER ELEVATIONS AND THE SNAKE PLAIN
WILL TAPER OFF BY THIS AFTERNOON, WITH ONLY A COUPLE HUNDREDTHS
OF AN INCH OF RAINFALL LEFT OUT OF THIS SYSTEM. AS THE CENTER OF
THE LOW MOVES EAST, WRAP-AROUND RAINFALL CONTINUES A BIT LONGER
IN CENTRAL IDAHO HIGHER TERRAIN. SHOWERS HERE WILL LAST THROUGH
THE AFTERNOON AND EARLY EVENING, WITH 0.05 TO 0.2 INCHES OF
RAINFALL POSSIBLE BY THE TIME THEY MOVE EAST. AS THE BULK OF THE
MOISTURE HAS PASSED, THESE RAINFALL AMOUNTS DON'T PRESENT MUCH
OF A FLASH FLOODING RISK. ALTHOUGH, IN VERY STEEP TERRAIN SOILS
MAY BE SATURATED AND UNSTABLE, SO A MINOR ROCKSLIDE RISK CAN'T
BE RULED OUT. BEHIND THE LOW INSTABILITY IS MEAGER, BUT ENOUGH
FOR A 10% CHANCE OF LIGHTNING THIS AFTERNOON IN HIGHER TERRAIN.
SHOWERS AND CLOUDS MOVING EAST SATURDAY NIGHT AND WET SURFACE
CONDITIONS WILL SUPPORT FOG/LOW CLOUD DEVELOPMENT THROUGH SUNDAY
MORNING IN MOUNTAIN VALLEYS.
AS THE SYSTEM DEPARTS SATURDAY EVENING, A RIDGE AXIS AND RISING
HEIGHTS ACROSS THE REGION SUPPORT DRIER AND WARMER WEATHER
HEADING INTO THE COMING WEEK. TEMPERATURES ON MONDAY WARM BACK
UP TO THE LOW/MID 80S IN LOWER ELEVATIONS AND MID 70S IN HIGH
ELEVATION VALLEYS. SKIES ARE MOSTLY CLEAR AND WINDS ARE LIGHTER.
LONG TERM /TUESDAY THROUGH SATURDAY/
A WEAK, BROAD LOW MOVING SOUTH OF THE REGION ON TUESDAY WILL
BRING A 10-20% CHANCE OF SHOWERS AND THUNDERSTORMS TO SOUTH-
CENTRAL IDAHO THAT EVENING. OVERALL SYNOPTIC FLOW OVER THE
REGION DOESN'T CHANGE TOO MUCH THOUGH, WITH ZONAL FLOW TO THE
NORTH SHIFTING IN AND OUT BUT CONTINUING A SLIGHT WARMING TREND
THROUGH THE WEEK. THE TRACK OF THE WEAK LOW SEEMS FAIRLY
CONFIDENT AMONGST MODELS, ALTHOUGH IT IS CUT OFF FROM THE
PRIMARY FLOW SO SOME CHANGE IS EXPECTED IN FUTURE MODEL RUNS.
THE ZONAL FLOW MOVES FIRMLY OVERHEAD THURSDAY NIGHT AHEAD OF AN
AMPLIFIED TROUGH OFF THE WEST COAST. CHANCES FOR PRECIPITATION
REMAIN <5% THROUGH FRIDAY, BEFORE GUIDANCE CONSENSUS BRINGS THE
TROUGH CLOSER FOR MORE FAVORABLE MOISTURE FLUX. SATURDAY
PRECIPITATION CHANCES RISE TO AROUND 10% ACROSS THE AREA, WITH
TEMPERATURES COOLING DOWN BEYOND THAT.
AVIATION /06Z SATURDAY THROUGH SUNDAY/
ISSUED 1126 PM MDT FRI SEP 18 2026
MAINLY VFR, WITH SCATTERED SHOWERS/THUNDERSTORMS CONTINUING OVER
WEST-CENTRAL ID MOUNTAINS AND MAGIC VALLEY OVERNIGHT THROUGH
SATURDAY MORNING, BEFORE TAPERING OFF IN THE AFTERNOON. LOCAL MVFR
CONDITIONS POSSIBLE IN SHOWERS. PATCHY FOG IN SHELTERED MOUNTAIN
VALLEYS OVERNIGHT THROUGH SATURDAY MORNING. SURFACE WINDS: GENERALLY
VARIABLE OR NW-SW 5-10 KT OVERNIGHT THROUGH MORNING, THEN NW-N 5-15
KT IN THE AFTERNOON. WINDS ALOFT AT 10KFT MSL: NW-N 5-15 KT.
KBOI...MAINLY VFR. SCATTERED SHOWERS OVER TERMINAL THROUGH SATURDAY
EARLY MORNING, THEN CLEARING IN THE MORNING WITH SCT CLOUDS AND
LIGHTER WINDS. SURFACE WINDS: NW 5-15 KT.
WEEKEND OUTLOOK...BRIEF MVFR AND MOUNTAIN OBSCURATION IN LINGERING
SHOWERS NEAR KMYL AND KTWF-KJER ON SATURDAY, WITH SHOWERS TAPERING
OFF BY THE LATE AFTERNOON. EXPECT VFR CONDITIONS OTHERWISE THROUGH
SUNDAY WITH VARIABLE WINDS LESS THAN 10 KT OVERNIGHT AND IN HIGH
TERRAIN AND NW 5-15 KT IN VALLEYS DURING THE 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
SHORT TERM...JM
LONG TERM....JM
AVIATION.....JY
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