774 FXUS65 KTFX 091107 AFDTFXArea Forecast Discussion National Weather Service Great Falls MT 507 AM MDT Tue Sep 9 2025
Aviation Section Updated.
.KEY MESSAGES...
- There will be isolated showers and thunderstorms today through Thursday with the coverage increasing each day.
- There will be haze around North-central, Central, and Southwestern Montana through Wednesday due to wildfires in the region.
- Friday through early next week there will be showers and thunderstorms but there is great uncertainty in the total rainfall amount.
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.DISCUSSION... /Issued 252 AM MDT Tue Sep 9 2025/
- Meteorological Overview:
Today an upper-level ridge is over North-central, Central, and Southwestern Montana with an upper-level trough approaching the area. As a result it will be another warm day today. Due to the southwest flow aloft combined with monsoonal moisture, there will be isolated showers and thunderstorms this afternoon and evening across North-central, Central, and Southwestern Montana. The strongest thunderstorms will produce strong wind gusts, frequent lightning, and a brief heavy downpour. On Wednesday the upper-level ridge begins to shift eastward and the upper-level trough approaches Montana. On Wednesday it will be another warm day with isolated showers and thunderstorms across North-central, Central, and Southwestern Montana due to the upper-level ridge and approaching trough combined with monsoonal moisture. Today and Wednesday due to the Southwest flow aloft there will be hazy skies from regional wildfires across North-central, Central, and Southwestern Montana.
On Thursday the upper-level trough moves over North-central, Central, and Southwestern Montana. This will cool temperatures down and bring another round of showers and thunderstorms to the area. The strongest thunderstorms will produce strong winds, frequent lightning, and a brief heavy downpour. On Friday the upper-level trough remains over North-central, Central, and Southwestern Montana. This will cool temperatures down to near seasonal averages across the area and bring showers to the area. Saturday through Monday generally an upper-level trough persists with a few upper- level shortwaves. This will keep temperatures at about seasonal averages with daily chances for showers across North-central, Central, and Southwestern Montana Saturday through Monday.
- Forecast Confidence & Scenarios:
Today there is a 15 - 30% chance for thunderstorms across North- central, Central, and Southwestern Montana. On Wednesday there is a 10 - 30% chance for thunderstorms with the highest chances along the Rocky Mountain Front. On Thursday there is a 20 - 40% chance for thunderstorms across North-central, Central, and Southwestern Montana with the highest chances in North-central Montana. On Friday there is a 20 - 40% chance for thunderstorms across North-central, Central, and Southwestern Montana.
On Wednesday there is a 20 - 50% chance for a tenth of an inch of rain or greater across North-central, Central, and Southwestern Montana. On Thursday across North-central and Central Montana there is a 35 - 60% chance for a quarter inch of rain or greater.
Friday through Monday there is high uncertainty in the upper- level pattern. However, all four clusters have an upper-level trough affecting Montana. This upper-level trough varies significantly in amplitude and position between all four clusters Friday through Monday. This increases the confidence that temperatures will be cool Friday through Monday. Due to the various troughs that the clusters show, the spread between the 10th Percentile (reasonable low-end scenario) and the 90th Percentile (reasonable high-end scenario) rainfall from 6 am Friday through 6 am Monday is greater than an inch across North- central, Central, and Southwestern Montana. -IG
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.AVIATION... 09/12Z TAF Period
VFR conditions will prevail across all terminals during this TAF Period outside of during any thunderstorms. At the KBZN, KEKS, and KWYS terminals there is a 15 - 30% chance for showers and thunderstorms between 09/18Z and 10/03Z. At the KHLN, KGTF, and KCTB terminals there is a 15 - 40% chance for showers and thunderstorms after 09/18Z through the end of this TAF Period. At the KHVR and KLWT terminals there is a 15 - 40% chance for showers and thunderstorms after 10/00Z through the end of this TAF Period. All thunderstorms will produce frequent lightning, a brief heavy downpour, and gusty, erratic winds. Wildfire smoke will cause reductions in slantwise visibility across all terminals periodically during this TAF Period. -IG
Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information.
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.PRELIMINARY POINT TEMPS/POPS... GTF 85 53 83 54 / 30 50 10 40 CTB 81 50 79 51 / 30 40 30 50 HLN 83 53 82 54 / 40 50 20 50 BZN 82 47 82 49 / 40 40 20 30 WYS 73 38 72 38 / 50 40 30 40 DLN 74 45 78 44 / 30 30 20 20 HVR 85 55 85 55 / 10 40 40 30 LWT 82 51 83 54 / 10 30 20 40
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.TFX WATCHES/WARNINGS/ADVISORIES... None. &&
$$ http://www.weather.gov/greatfalls
NWS TFX Office Area Forecast Discussion
