Four Corners, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

467
FXUS65 KTFX 291721
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1121 AM MDT Tue Jul 29 2025

Aviation Section Updated.

.KEY MESSAGES...

- Another round of showers and thunderstorms this afternoon, with
  strong to severe storms possible in Central and Southwest
  Montana.

- Daily chances for showers and thunderstorms, with localized
  heavier rainfall possible through the rest of the week.

&&

.UPDATE...
/Issued 835 AM MDT Tue Jul 29 2025/

Minor adjustments were made to the precipitation chances based on
updated NBM guidance. Otherwise, the rest of the forecast remains
on track.  -thor

&&

.DISCUSSION...
/Issued 835 AM MDT Tue Jul 29 2025/

 - Meteorological Overview:

Southwest flow aloft continues to bring an active pattern through
the forecast period. For this afternoon and evening, an upper
level shortwave moving from Idaho through Southwest MT will bring
scattered showers and thunderstorms. Sufficient CAPE of up to
1,500 j/kg and deep layer shear of 35kts will support the threat
for another round of strong to severe thunderstorms. DCAPE of
~1,000 j/kg or greater, deep inverted V profiles, and decent mid
level lapse rates of ~8 degrees C/km support a severe wind and
hail threat. The best chances for thunderstorms will be in
Southwest MT to Central MT, where that shortwave travels through.
Coverage in North-Central MT remains more isolated, as there is
uncertainty in the northern extent of where the shortwave travels
before dissolving. PWATs will be high again today, nearing an inch
across North- Central Montana. This will cause concern for
localized areas of heavy rainfall with storms. Thunderstorm
coverage being more isolated will keep the heavy rainfall more
localized with storms. In Southwest MT, PWATs aren`t as high
(~0.75"), so heavy rainfall will remain more localized down there
as well.

Heading into Wednesday, steering flow aloft decreases which will
slow down storm propagation. A skinnier CAPE profile and high PWATs
again will help aid in the threat for heavier rainfall again. The
primary concern will be for burn scars and urban areas. Since this
threat is mainly driven by convection, it`ll be hard to pinpoint
exactly where the heavy rainfall will set up. As a result, flood
watches aren`t anticipated as of right now. This moisture will
stick around through the end of the week. Thursday looks to be the
day with the highest PWATs (reaching 1"-1.25" across North-
Central MT). Ensembles hint at southwest flow aloft will keep low
end chances for precipitation during the beginning of next week
as well.

 - Forecast Confidence & Scenarios:

Models have been consistent with the threat for some strong to
severe thunderstorms across parts of Southwest and Central
Montana today. Recent model guidance has this shortwave aloft
struggling to go north of a Helena to southern Fergus County line.
As a result, lesser forcing farther north will keep precipitation
this afternoon and evening isolated. Though with high moisture,
any further movement north of this forcing will increase the heavy
rainfall threat today. -Wilson

&&

.AVIATION...
29/18Z TAF Period

VFR conditions will prevail at all terminals during this TAF Period
outside of during any thunderstorms. The primary concern will be
showers and thunderstorms in Southwestern Montana. These showers
and thunderstorms will produce heavy downpours, frequent
lightning, small hail, and gusty, erratic winds. Isolated
thunderstorms in Southwestern Montana will produce large hail and
wind gusts in excess of 40 kts. At the KCTB terminal there is a
15 - 25% chance for showers and thunderstorms between 29/22Z and
30/06Z. At the KHVR terminal there is a 25% chance for showers and
thunderstorms between 29/21Z and 30/00Z. There will be periods of
mountain obscuration during thunderstorms. -IG

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  81  57  82  58 /  10  20  20  20
CTB  76  54  78  55 /  20  20  10  10
HLN  83  57  84  58 /  30  30  40  20
BZN  85  52  83  53 /  70  70  40  20
WYS  82  41  80  41 /  40  20  50  20
DLN  83  49  81  49 /  50  40  40  20
HVR  82  54  83  56 /  30  10  10   0
LWT  76  52  75  54 /  50  40  50  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$
http://www.weather.gov/greatfalls