361 FXUS65 KTFX 220218 AFDTFXArea Forecast Discussion National Weather Service Great Falls MT 818 PM MDT Sun Sep 21 2025
.KEY MESSAGES...
- Scattered showers and thunderstorms through tonight.
- A cooler, but seasonable day expected on Monday.
- It turns dry and warm from Tuesday into next weekend.
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.UPDATE...
Showers and a few isolated thunderstorms continue to track N/NE across much of north-central and southwest MT this evening in association with a cold front progressing east across the area. Gusty winds remain the primary weather impact this evening across much of the area from the combined effects of shower/thunderstorm downdrafts as well as pressure rises associated with the frontal passage. Areas along the Rocky Mountain Front also saw a period of mountain wave wind enhancement earlier this evening, resulting in a few isolated strong wind gusts. The probability for wind gusts in excess of 40 mph will gradually decrease through the overnight period with only areas along the immediate east slopes of the Rocky Mtn Front and portions of southern Blaine and eastern Fergus county having some potential (20-40%) for stronger gusts lingering later through the overnight period. Additional upper level energy will swing across the region overnight, maintaining a wider coverage of showers across southwest MT while precipitation across north-central MT ends from west to east overnight. A final upper level disturbance moving out of Alberta later tonight does look to bring some showers along with shift to northerly surface winds across portions of north-central MT Monday morning. Hoenisch
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.DISCUSSION... /Issued 526 PM MDT Sun Sep 21 2025/
- Meteorological Overview: A Pacific cold front is approaching the Rocky Mountain Front currently. Scattered showers and thunderstorms are developing ahead and along the cold front. The cold front will move eastward across the CWA this evening and overnight tonight. There will be a few stronger storms, with the main impact being gusty winds. By Monday morning, snow levels will fall down to about 8000 or 9000 feet, with a rain/snow mix possible at ridge tops. For Monday, afternoon temperatures will be cooler than they have been, but still close to seasonal normals. The cool air will not last long, as warmer air moves back into the CWA on Tuesday. By Wednesday, afternoon highs will be in the mid 80s to near 90 degrees, which will be about 15 to 20 degrees above normal for this time of year. The above normal temperatures, will continue into next weekend, just not as hot as the mid week temperatures though.
This system will be rather quick moving, and there will only be a few lingering showers on Monday morning, especially over the central mountains, otherwise dry conditions are expected until late next weekend.
- Forecast Confidence & Scenarios: An isolated strong wind gust is possible with the thunderstorms tonight, but the threat/possibility for any severe storms is quite low. Most areas will see rainfall less than 0.20 inches, but an isolated stronger storm could produce near a half inch of rainfall.
After this system exits the region on Monday morning, the chance for rainfall is almost near zero until late next weekend. Even the system for late next weekend only has very low chances for precip at this time.
Afternoon temperatures for Wednesday continue to increase as well. Thus some areas will once again approach 90 degrees for afternoon high temperatures.
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.AVIATION... 22/00Z TAF Period.
A Pacific cold front will continue east across north-central and southwest MT this evening with main impact to aviation being gusty and shifting winds, both with showers and thunderstorms ahead of the front and with the passage of the front itself. Showers and thunderstorms early this evening will bring some brief MVFR and mountain obscuration with a more widespread area of showers and lower cloud ceilings developing across primarily southwest MT overnight, through some showers and periods periods of MVFR ceilings are also possible for a shorter period overnight across north-central MT. Gusty west to northwest winds continue through tonight after the frontal passage before slowly diminishing Monday morning with clouds clearing by Monday afternoon. Hoenisch
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.PRELIMINARY POINT TEMPS/POPS... GTF 48 67 42 77 / 80 20 0 0 CTB 44 67 37 78 / 40 30 0 0 HLN 46 66 40 76 / 90 10 0 0 BZN 44 62 35 71 / 90 30 0 0 WYS 35 56 24 67 / 90 60 0 0 DLN 41 61 33 70 / 90 10 0 0 HVR 49 67 40 78 / 60 20 0 0 LWT 46 59 39 74 / 80 20 0 0
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.TFX WATCHES/WARNINGS/ADVISORIES... None. &&
$$ http://www.weather.gov/greatfalls
NWS TFX Office Area Forecast Discussion