121
FXUS65 KBOI 200553
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
1153 PM MDT WED AUG 19 2026
UPDATE
UPDATED AVIATION DISCUSSION.
KEY MESSAGES
- HEAT ADVISORY THURSDAY AFTERNOON THROUGH FRIDAY IN THE
TREASURE VALLEY, WESTERN MAGIC VALLEY, AND UPPER WEISER
RIVER VALLEY.
- INCREASED CHANCE OF AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS OVER HIGHER TERRAIN FRIDAY THROUGH SUNDAY.
- ABOVE NORMAL TEMPERATURES NEXT WEEK WITH A CHANCE OF
AFTERNOON THUNDERSTORMS EACH DAY OVER THE MOUNTAINS OF
SOUTHWEST IDAHO.
SHORT TERM /THROUGH FRIDAY NIGHT/
ISSUED 200 PM MDT WED AUG 19 2026
HEAT ADVISORY CONTINUES IN EFFECT THURSDAY AFTERNOON THROUGH FRIDAY
SUNSET AS ORIGINALLY ISSUED FOR THE SNAKE BASIN AND UPPER WEISER RIVER
VALLEY EVENING. HOWEVER, HIGH TEMPS FRIDAY HAVE BEEN ADJUSTED DOWN
A COUPLE DEGREES DUE TO INCREASING CLOUDS, ESPECIALLY ON THE OREGON
SIDE. PATCHY SMOKE FROM WILDFIRES WILL CONTINUE IN EASTERN OREGON
AND NORTHERN MOUNTAINS IN IDAHO WITH FRIDAY MORNING THE WORST,
ALTHOUGH NOT NEARLY AS SMOKY AS 10 TO 15 DAYS AGO. THE FIRST MINOR
INFLUX OF MONSOON MOISTURE WILL BRING ISOLATED THUNDERSTORMS TO
NORTHEAST NV LATE TODAY. STORMS SHOULD STAY SOUTH OF ID BUT GUSTY
OUTFLOW WINDS MAY REACH SOUTHERN TWIN FALLS COUNTY. A SLIGHTLY
STRONGER MOISTURE SURGE WILL BRING A 20% CHANCE OF SHOWERS AND
THUNDERSTORMS TO TWIN FALLS COUNTY THURSDAY AFTERNOON AND EVENING.
HOWEVER, FRIDAY IS THE DAY TO WATCH AS MONSOON MOISTURE INCREASES
FURTHER UNDER STRONGER SOUTHWESTERLY FLOW ALOFT, DUE TO A PACIFIC
UPPER TROUGH NEARING THE NORTHWEST COAST. ON THAT DAY AFTER A VERY
HOT AFTERNOON THERE WILL BE A 20-30 PERCENT CHANCE OF THUNDERSTORMS
IN EASTERN-MOST IDAHO ZONES, AND WITH LOWER ATMOSPHERIC LAYERS STILL
DRY THESE STORMS WILL AGAIN FEATURE GUSTY WINDS AND LITTLE RAIN.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
ISSUED 200 PM MDT WED AUG 19 2026
AN UPPER TROUGH MOVING ACROSS THE PACNW ON SATURDAY WILL BRING A
COLD FRONT AND ASSOCIATED STRONG WINDS AND INCREASED THUNDERSTORM
CHANCES. WIND GUSTS ON SATURDAY INCREASE TO 20-35 MPH ACROSS THE
AREA, HIGHEST IN SE OREGON WHERE MINIMUM RELATIVE HUMIDITIES AROUND
10-20% WILL CAUSE ELEVATED FIRE WEATHER CONDITIONS EVEN THOUGH
TEMPERATURES ARE COOLER THAN FRIDAY. INCREASED MOISTURE AHEAD OF
THE TROUGH IS AMPLIFIED AS IT APPROACHES, SUPPORTING A 20-50%
CHANCE OF AFTERNOON AND EVENING THUNDERSTORMS ACROSS WEST CENTRAL
AND SOUTH CENTRAL IDAHO, ESPECIALLY OVER THE MOUNTAINS. STORM
CHANCES STRETCH INTO THE BLUE MTNS OF EASTERN OREGON AS WELL.
STORMS COULD PRODUCE LIGHTNING, STRONG GUSTY WINDS, AND BRIEF
HEAVY RAINFALL.
THE REMAINDER OF THE EXTENDED PERIOD WILL BE DEFINED BY THE
PERSISTENT FOUR CORNERS RIDGE WHICH WILL PLACE OUR REGION UNDER
SOUTHWEST FLOW. NEAR NORMAL TEMPERATURES SUNDAY, WILL BE ON THE
RISE NEXT WEEK AS THE RIDGE REBOUNDS. LATENT MONSOONAL MOISTURE
CIRCLING THE RIDGE MAINTAINS A 10-20% CHANCE OF STORMS AND SHOWERS
IN SOUTH CENTRAL IDAHO SUNDAY THROUGH WEDNESDAY.
AVIATION /06Z THURSDAY THROUGH FRIDAY/
ISSUED 1126 PM MDT WED AUG 19 2026
VFR WITH INCREASING HIGH CLOUDS IN THE AFTERNOON. SOME
REDUCTION IN VISIBILITY DUE TO WILDFIRE SMOKE. SURFACE WINDS:
LESS THAN 10 KT, BECOMING SW-NW 5-15 KT AFTER 18Z. WINDS ALOFT
AT 10KFT MSL: SW 10-20 KT.
KBOI...VFR WITH INCREASING HIGH CLOUDS IN THE AFTERNOON. HAZY
CONDITIONS DUE TO WILDFIRE SMOKE. LIGHT SURFACE WINDS THROUGH
THURSDAY NIGHT.
BOI WATCHES/WARNINGS/ADVISORIES
ID...HEAT ADVISORY FROM NOON THURSDAY TO 9 PM MDT FRIDAY FOR IDZ012-
014-016-033.
OR...HEAT ADVISORY FROM NOON MDT /11 AM PDT/ THURSDAY TO 9 PM MDT
/8 PM PDT/ FRIDAY FOR ORZ064.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
AVIATION.....DG
SHORT TERM...LC
LONG TERM....JM
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