992 FXUS65 KTFX 160138 AFDTFXArea Forecast Discussion National Weather Service Great Falls MT Issued by National Weather Service Glasgow MT 738 PM MDT Mon Sep 15 2025
Aviation Section Updated.
.KEY MESSAGES...
- Unsettled with near average temperatures expected today and Tuesday. - Warmer and drier weather returns for Thursday and Friday. - Shower and thunderstorm chances return for Saturday.
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.DISCUSSION... /Issued 128 PM MDT Mon Sep 15 2025/
- Meteorological Overview:
Broad upper level toughing over the area today has resulted noticeably cooler temperatures across the area compared to yesterday, with many locations around 5 to 10 degrees cooler than they were yesterday at this time. With the upper level low around, expect a mix of clouds and sun this afternoon, with a few rain showers developing later this afternoon and evening. This trough will shift eastward a bit overnight tonight and Tuesday, but northerly flow will keep us on the cool side on Tuesday.
Upper level ridging building into the area on Wednesday will bring an end to the showers and will allow temperatures to climb back above average a little bit for the second half of the week. The warmth will peak on Saturday as southerly flow develops ahead of our next upper level trough, which will bring renewed chances for showers along with some breezy winds for the weekend and early next week.
- Forecast Confidence & Scenarios:
Low chance for heavy downpours through Tuesday:
As our upper level trough continues to slowly push through the area today and Tuesday, expect a few showers and possibly thunderstorms to develop, especially later during the afternoon hours today and Tuesday. For the most part, these showers and storms should not be overly heavy today since they will be driven primarily by large scale lift, but model soundings tomorrow afternoon suggest some convective instability will develop tomorrow afternoon as daytime heating contrasts with cold air advection occurring aloft. This could bring some localized heavy rainfall, which could result in some ponding of water in low lying or poor drainage areas.
Winds Saturday night - early next week:
As our next upper level ridge breaks down over the weekend, zonal upper level flow along with a developing lee trough will result in the development of a modest pressure gradient that results in some gusty winds across the area Sunday and Monday. While winds dont look overly strong, the NBM is currently showing generally a 25-40% chance of 45 mph across most of the area north of I-90. While not unseasonable, it will be a noted change from the relatively light winds we have been experiencing as of late. Ludwig
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.AVIATION... 16/00Z TAF Period
A low pressure system will continue to bring scattered shower and thunderstorm activity for much of the TAF period, most widespread along the Continental Divide and Southwest Montana tonight and Tuesday morning. MVFR and lower conditions and mountain obscuration will be most widespread between 16/09 and 16/18Z over Southwest Montana due precipitation, low stratus, and patchy fog. - RCG
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.PRELIMINARY POINT TEMPS/POPS... GTF 52 74 47 79 / 60 20 0 0 CTB 49 73 44 78 / 40 10 0 0 HLN 50 72 48 78 / 60 40 0 0 BZN 44 67 43 74 / 70 60 10 0 WYS 32 62 31 68 / 30 40 10 0 DLN 40 66 40 72 / 20 20 0 0 HVR 52 77 48 77 / 20 10 0 0 LWT 48 69 46 74 / 70 60 20 10
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.TFX WATCHES/WARNINGS/ADVISORIES... None. &&
$$ http://www.weather.gov/greatfalls
NWS TFX Office Area Forecast Discussion