Winston, Montana Weather Forecast Discussion

582
FXUS65 KTFX 131735
AFDTFX
Area Forecast Discussion
National Weather Service Great Falls MT
1135 AM MDT Sat Sep 13 2025
Aviation Section Updated.
.KEY MESSAGES...
- Near to above normal temperatures to continue for much of the
   next week.
- Daily chances for showers and thunderstorms through the
   weekend and first half of the upcoming work week.
&&
.DISCUSSION...
/Issued 444 AM MDT Sat Sep 13 2025/
- Meteorological Overview:
Longwave troughing, with embedded waves sliding east/lifting
northeast from the Pacific Northwest/Great Basin and over the
Northern Rockies, will remain over the Western CONUS through the
first half of the upcoming work week before transient upper level
ridging over the Eastern Pacific amplifies and builds east on
Wednesday. This longwave troughing pattern will help to maintain
daily chances for showers and thunderstorms across Southwest through
North Central Montana through the first half of the upcoming work
week, with temperatures running near to above normal. Shower and
thunderstorm coverage today and tonight will be greatest along and
east of a Bozeman to Havre line, but even isolated showers and
storms will be possible west of this line and up to the Continental
Divide. While severe thunderstorms are not expected through this
timeframe given weak shear, sufficient instability and PWATs will
support the potential for gusty/erratic winds and brief periods of
heavy rainfall beneath the strongest storms. Sunday will largely see
dry conditions through the morning and early afternoon hours as the
Northern Rockies resides between embedded wave, with increasing
coverage of showers and thunderstorms thereafter into the evening
and overnight hours as the next embedded wave pivots over the
region. Shower and thunderstorms chances will continue through the
day on Monday, with a weak cold fronts pushing south and across
Montana during the afternoon and evening hours. This cold front will
help to bring the "coolest" conditions of the unsettled pattern,
with temperatures rebounding on Wednesday as the aforementioned
upper level ridge builds eastward and over the Northern Rockies.
After a brief period of transient ridging on Wednesday a potent
shortwave over the Gulf of Alaska/Eastern Pacific will begin to lift
northeastward and over Western Canada and the Pacific Northwest.
This lifting shortwave will help to flatten the ridge over the
Northern Rockies through the remainder of the work week, with quasi-
zonal developing over Southwest through North Central Montana from
Thursday/Friday and persisting into next weekend. Near to slightly
above normal temperatures will continue beneath this quasi-zonal
pattern, with additional chances for precipitation occurring across
most locations. - Moldan
- Forecast Confidence & Scenarios:
Heavy Rainfall Today/Tonight :
Latest HREF (Hi-Res Ensemble Forecast) guidance supports a 10%
chance for hourly rainfall rates to reach or exceed 0.25" across
mainly Blaine and Fergus Counties from the late morning through
afternoon hours, with 90th Percentile 24hr rainfall accumulations of
0.5" to 1" over the Island ranges of these two counties. While an
isolated storm or two producing brief periods of heavy rainfall
leading to ponding of water in low-lying or poor drainage areas
(i.e. urban locations like Lewistown) can`t be ruled out...the
overall threat for heavy rainfall leading to flooding is quite low
given the available probabilistic data. - Moldan
&&
.AVIATION...
13/18Z TAF Period
VFR conditions prevail. Mountain obscuration is likely east of a
KEKS, to KBZN, to KLWT line through 13/21z to 14/03z as mid-level
cloud cover pivots from east to west across portions of Southwest
through North Central Montana. Isolated showers initiating over
higher terrain across Southwest and Central MT could affect
routing into some terminals, particularly KLWT.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF  78  48  80  53 /  10  10  10  10
CTB  77  45  78  50 /  10  10  10  10
HLN  76  48  79  52 /  20  10  10  30
BZN  71  42  77  46 /  20  10  10  20
WYS  62  32  66  35 /  40  10  10  20
DLN  71  40  73  43 /  10  10  10  30
HVR  77  50  81  51 /  20  10  10  10
LWT  67  48  76  49 /  40  20  10  10
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
http://www.weather.gov/greatfalls

NWS TFX Office Area Forecast Discussion