094
FXUS65 KMSO 210751
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
151 AM MDT TUE JUL 21 2026
DISCUSSION
KEY MESSAGES:
- PERIODS OF HAZE AND SMOKE PERSIST ACROSS THE REGION INTO
TONIGHT. LOW RAIN SHOWER AND STORM CHANCES.
- MONSOON MOISTURE SURGE RETURNS TUESDAY THROUGH THURSDAY.
LOCALIZED FLASH FLOODING AND A FEW SEVERE THUNDERSTORMS
POSSIBLE.
- HOT TEMPERATURES ARE EXPECTED THIS WEEK, WITH HIGHS REACHING
THE 90S UP TO 106 DEGREES IN THE LOWER ELEVATIONS OF IDAHO.
UPPER LEVEL MONSOONAL MOISTURE WILL CONTINUE TO STREAM ACROSS THE
NORTHERN ROCKIES TODAY, BRINGING PERSISTENT HIGH AND MID-LEVEL
CLOUD COVER AND ISOLATED LIGHT SHOWERS. SMOKE AND HAZE FROM
WILDFIRES IN OREGON AND WASHINGTON WILL INTERMITTENTLY DEGRADE AIR
QUALITY.
ATMOSPHERIC MOISTURE DEEPENS SIGNIFICANTLY THIS AFTERNOON, WITH
PRECIPITABLE WATER (PWAT) VALUES CLIMBING TO 200-250% OF NORMAL
FOR THE REGION. HOWEVER, ABUNDANT MORNING CLOUD COVER WILL LIKELY
LIMIT SURFACE INSTABILITY AND OVERALL THUNDERSTORM POTENTIAL. BY
THE AFTERNOON, HIGH-RESOLUTION GUIDANCE INDICATES SCATTERED
THUNDERSTORM DEVELOPMENT FROM LEMHI COUNTY INTO SOUTHWEST MONTANA,
WHERE BRIEF HEAVY RAINFALL AND ERRATIC WIND GUSTS EXCEEDING 40
MPH WILL BE THE PRIMARY THREATS.
BY WEDNESDAY AFTERNOON, THE THREAT SHIFTS SLIGHTLY NORTHWARD.
AREAS SOUTH OF U.S. HIGHWAY 12 WILL SEE AN INCREASED RISK OF
LOCALLY HEAVY RAINFALL CAPABLE OF TRIGGERING DEBRIS FLOWS OR FLASH
FLOODING. THE OVERALL MAGNITUDE OF THIS THREAT REMAINS HIGHLY
CONDITIONAL ON MORNING CLEARING AND THE RESULTING REALIZED
INSTABILITY.
IT WILL ALSO BE QUITE WARM TO HOT. NBM TEMPERATURES ARE ON THE
WARMER SIDE COMPARED TO MOST GUIDANCE AND WOULD BRING
TEMPERATURES NEAR HEAT ADVISORY LEVELS TO THE LOWER ELEVATIONS OF
NORTH-CENTRAL IDAHO. HOWEVER, THERE IS CONSIDERABLE UNCERTAINTY
REGARDING HOW MUCH CLOUDS AND SMOKE MAY IMPACT THE HIGH
TEMPERATURE FORECAST. STILL ADVISORIES MAY BE NEEDED FOR THE
WEDNESDAY/THURSDAY ATMOSPHERIC MOISTURE DEEPENS SIGNIFICANTLY ON TUESDAY, WITH
PRECIPITABLE WATER (PWAT) VALUES CLIMBING TO 200-250% OF NORMAL
FOR THE REGION. HOWEVER, ABUNDANT MORNING CLOUD COVER WILL LIKELY
LIMIT SURFACE INSTABILITY AND OVERALL THUNDERSTORM POTENTIAL. BY
TUESDAY AFTERNOON, HIGH-RESOLUTION GUIDANCE INDICATES SCATTERED
THUNDERSTORM DEVELOPMENT FROM LEMHI COUNTY INTO SOUTHWEST MONTANA,
WHERE BRIEF HEAVY RAINFALL AND ERRATIC WIND GUSTS EXCEEDING 40
MPH WILL BE THE PRIMARY THREATS.
BY WEDNESDAY AFTERNOON, THE THREAT SHIFTS SLIGHTLY NORTHWARD.
AREAS SOUTH OF U.S. HIGHWAY 12 WILL SEE AN INCREASED RISK OF
LOCALLY HEAVY RAINFALL CAPABLE OF TRIGGERING DEBRIS FLOWS OR FLASH
FLOODING. THE OVERALL MAGNITUDE OF THIS THREAT REMAINS HIGHLY
CONDITIONAL ON MORNING CLEARING AND THE RESULTING REALIZED
INSTABILITY.
IT WILL ALSO BE QUITE WARM TO HOT. NBM TEMPERATURES ARE ON THE
WARMER SIDE COMPARED TO MOST GUIDANCE AND WOULD BRING
TEMPERATURES NEAR HEAT ADVISORY LEVELS TO THE LOWER ELEVATIONS OF
NORTH-CENTRAL IDAHO. HOWEVER, THERE IS CONSIDERABLE UNCERTAINTY
REGARDING HOW MUCH CLOUDS AND SMOKE MAY IMPACT THE HIGH
TEMPERATURE FORECAST. STILL ADVISORIES MAY BE NEEDED FOR THE
WEDNESDAY/THURSDAY TIME PERIOD IF CONFIDENCE INCREASES.
THURSDAY THROUGH THE WEEKEND...THURSDAY PRESENTS A MORE DYNAMIC
SETUP AS THE REGION TRANSITIONS FROM DEEP MONSOONAL MOISTURE TO A
DRIER, MORE SHEARED SOUTHWESTERLY FLOW. THIS COMBINATION OF
ENHANCED VERTICAL WIND SHEAR AND INCREASED INSTABILITY COULD
SUPPORT STRONG TO SEVERE THUNDERSTORMS, MAKING THURSDAY A KEY
PERIOD TO MONITOR.
BY FRIDAY AND INTO THE WEEKEND, THE SYNOPTIC PATTERN SHIFTS
TOWARD NEAR-CRITICAL FIRE WEATHER CONDITIONS. INCREASING WESTERLY
WINDS, A DRYING AIR MASS, AND A SHARP DECLINE IN SHOWER ACTIVITY
WILL COMBINE TO ELEVATE FIRE DANGER ACROSS THE REGION.TIME PERIOD
IF CONFIDENCE INCREASES.
THURSDAY THROUGH THE WEEKEND...THURSDAY PRESENTS A MORE DYNAMIC
SETUP AS THE REGION TRANSITIONS FROM DEEP MONSOONAL MOISTURE TO A
DRIER, MORE SHEARED SOUTHWESTERLY FLOW. THIS COMBINATION OF
ENHANCED VERTICAL WIND SHEAR AND INCREASED INSTABILITY COULD
SUPPORT STRONG TO SEVERE THUNDERSTORMS, MAKING THURSDAY A KEY
PERIOD TO MONITOR.
BY FRIDAY AND INTO THE WEEKEND, THE SYNOPTIC PATTERN SHIFTS
TOWARD NEAR-CRITICAL FIRE WEATHER CONDITIONS. INCREASING WESTERLY
WINDS, A DRYING AIR MASS, AND A SHARP DECLINE IN SHOWER ACTIVITY
WILL COMBINE TO ELEVATE FIRE DANGER ACROSS THE REGION.
AVIATION
VFR CONDITIONS WILL PREVAIL THROUGH TODAY. MONSOONAL
MOISTURE OVERSPREADING THE REGION WILL MAINTAIN WIDESPREAD HIGH
AND MID- LEVEL CLOUD COVER AND ISOLATED LIGHT SHOWERS. BY THIS
AFTERNOON, SCATTERED THUNDERSTORMS ARE POSSIBLE ACROSS LEMHI
COUNTY AND SOUTHWEST MONTANA; HOWEVER, CONVECTIVE DEVELOPMENT
REMAINS HIGHLY CONDITIONAL ON THE CLEARING OF MORNING CLOUD COVER.
IF THESE STORMS MATERIALIZE, BRIEF MVFR CEILINGS AND VISIBILITIES
MAY IMPACT KSMN AND KBTM AFTER 21/2200Z. WINDS WILL REMAIN
RELATIVELY LIGHT AND DIURNALLY DRIVEN THROUGH THIS AFTERNOON. AN
EASTERLY PRESSURE GRADIENT WILL DEVELOP ACROSS WESTERN MONTANA
TONIGHT INTO TUESDAY MORNING, BUT PEAK GUSTS ARE EXPECTED TO
REMAIN UNDER 20 KNOTS.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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