052
FXUS65 KTFX 060218
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
818 PM MDT Tue Aug 5 2025

.KEY MESSAGES...

- Isolated showers and thunderstorms this afternoon and evening
  across the North Central MT plains.

- An increased risk for showers and storms Thursday and Friday.

- A cooler weekend, and decreasing chances for precipitation
  early next week.

&&

.UPDATE...

Isolated showers and thunderstorms that developed this afternoon,
mainly along the Hi-line region, will continue to dissipate
through the rest of this evening. Subtle shortwave ridging in the
general WSW flow aloft will shift across the Northern Rockies and
MT overnight, providing mainly clear and dry conditions for the
area through Wednesday morning. Dewpoints remain elevated (55-60F)
across the Hi-line area, which may allow for some patchy fog
development later tonight, particularly across Hill and Blaine
counties where some precipitation fell this evening winds are
most likely become light by early Wednesday morning. Hoenisch

&&

.DISCUSSION...
/Issued 510 PM MDT Tue Aug 5 2025/

 - Meteorological Overview:

An upper-level wave aloft moving east along the Hi-line this
afternoon and evening will keep isolated chances for showers and
thunderstorms through the evening across the North-Central MT
plains. Wednesday, zonal flow aloft transitions to southwest flow
aloft ahead of a digging upper-level trough along the west coast.
This will bring another round of isolated to scattered showers
Wednesday. Low instability will keep thunderstorms limited. Better
chances arrive for thunderstorms Thursday. The upper-level trough
continues to propagate to the east, and forms a closed upper-
level low. A shortwave and a Pacific cold front ahead of this
upper-level low will bring scattered showers and thunderstorms.
Instability remains low, but an increase in deep layer shear will
bring a strong to severe threat, though there remains a little
uncertainty with timing of storms. This closed low will keep
scattered precipitation Friday. This system brings wetter and
cooler conditions Friday, with best chances for wetting rain
across the Hi-Line.


Behind that system, we transition to a northwest flow aloft pattern
through the beginning of next week. Temperatures are expected to
warm up back to near or slightly below averages. Although models
show the weekend and beginning of next week to remain drier.
However, PWATs of around 0.75" or greater and weak waves diving
south from Canada may keep low end chances for precipitation.

 - Forecast Confidence & Scenarios:

Thunderstorms with afternoon, despite having 1,000 j/kg of CAPE,
will remain weaker with no deep layer shear. Some high resolution
models have 1 to two storms produce a 40-50 mph wind gust.
Tomorrow, CAPE remains limited again, which will keep
thunderstorms isolated and on the weaker side.

Thursday still remains a little uncertain in terms of timing of
the storms. Recent model runs are starting to trend towards late
afternoon to early evening for initiation, which will allow for
better chances for strong to severe thunderstorms. Though I would
like for more run to run consistency before having good confidence.
CAPE remains rather low for convection, under 1,000 J/kg. Though,
strong deep layer shear suggests some storms can become more
organized, and mix down the stronger winds aloft to the surface.

Moisture wrapping around the occluding surface low in southern
Canada will keep wetting rain more confined to the Hi-line Friday.
Though, there will be slight chances for showers and thunderstorms
elsewhere across the region. There`s a 50-60% chance for 0.25" of
rain along the Hi-line Friday and a 30-40% chance for 0.5".
Although the flooding threat remains low with precipitation,
already saturated soils from last week`s rain may cause minor
flooding issues for typical trouble spots (poor drainage areas).
We are already seeing effects of this in some country roads in
Blaine County, where a few areas are having trouble draining the
precipitation from over the weekend and still have some roadway
flooding. -Wilson

&&

.AVIATION...
06/00Z TAF Period

Isolated showers and thunderstorms track east across portions of
north-central MT from near KCTB east to the KHVR and KLWT
terminals through early this evening. These should dissipate by
03z with cumulus decreasing for mostly clear skies overnight with
VFR conditions prevailing. Hoenisch

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  54  86  57  80 /  10  10  20  40
CTB  50  77  53  71 /  20  10  10  30
HLN  55  87  57  79 /   0  10  10  60
BZN  50  89  52  83 /   0   0  10  40
WYS  38  81  42  77 /   0   0   0  20
DLN  47  85  50  80 /   0  10   0  40
HVR  55  86  57  81 /  30   0  10  20
LWT  52  83  52  77 /  10  10  30  40

&&

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

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