629
FXUS65 KTFX 152323
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
523 PM MDT Tue Jul 15 2025

Aviation Section Updated.

.KEY MESSAGES...

 - Precipitation will gradually decrease from northwest to
   southeast through the overnight hours tonight

 - Clearing skies and light winds where recent precipitation has
   fallen will set the stage for the potential of fog Wednesday
   morning.

 - Temperatures trend closer to normal toward the weekend, with a
   few showers and thunderstorms Thursday near the Hi-Line.

 - At least a low-end risk for showers and thunderstorms each
   afternoon and early evening Friday through Sunday.

&&

.DISCUSSION...
/Issued 253 PM MDT Tue Jul 15 2025/

 - Meteorological Overview:

A compact, but potent, upper level shortwave will continue to dig
southeast over the Northern Rockies and eventually Northern High
Plains through Wednesday morning. At the surface a cold front has
pushed through much of Southwest Montana before stalling just short
of the Idaho/Montana border. Cool, with temperatures more closely
resembling that of late September, conditions exist across all of
North Central through Southwest Montana in wake of the
aforementioned front; with the coolest conditions occurring over the
plains of Central and North Central Montana where persistent, and
mostly stratiform, precipitation has been falling for much of the
day today. Further south near the Idaho border where late
morning/afternoon clearing has occurred scattered (strong)
thunderstorms were developing over Northeast Idaho, with these
thunderstorms lifting northeast across Southwest Montana,  generally
along and southeast of a MonIDA to Bozeman Pass line. By this
evening the precipitation shield over the plains of Central and
North Central Montana will gradually begin to pivot to the
southeast as the best forcing associated with the upper level
shortwave shifts east of the Northern Rockies. Additional showers
and thunderstorms lifting northeast across Southwest Montana will
be possible through the evening hours, with the expectation that
the threat for strong/severe thunderstorms will gradually wane
through 03z this evening due to the loss of heating. As
precipitation ends from northwest to southeast during the
overnight hours some breaks in the cloud cover will occur, most
notably along the Hi-Line. These breaks in the cloud cover and
decreasing winds near sunrise on Wednesday will set the stage for
fog development, especially along and just west of the western
edge of the stratus cloud deck. - Moldan

Temperatures during the day Wednesday begin to trend a touch
warmer, but still look to be well below average.

A zonal to slightly northwesterly flow aloft continues heading into
Thursday, with a weak wave passing across northern areas in the
afternoon. This should result in a few showers and thunderstorms
near the Hi-Line.

Thereafter guidance struggles with the specifics of the pattern
Several waves within a zonal to slightly northwesterly flow aloft
look to pass across the Northern Rockies Friday into early next
week, but the timing of any individual wave is uncertain still.
Temperatures look to trend closer to normal for this weekend, but
there is growing confidence in another cooler spell for the middle
of next week. -AM

 - Forecast Confidence & Scenarios:

Late week into the middle of next week:

Deterministic guidance does agree that there will be a zonal to
slightly northwesterly flow aloft across the Northern Rockies Friday
into the weekend. Although there is agreement in the general pattern
setup, there is not a lot of agreement on the timing of any embedded
waves traversing this flow. Each wave will be capable of producing
scattered showers and thunderstorms. The when and where for each
wave remains uncertain.

Heading toward early next week, cluster guidance reveals better
agreement on the evolution of the pattern, with around 90% of
ensemble members favoring a period of troughing. This would result
in another cooler period, with increased chances for rain. -AM

&&

.AVIATION...
16/00Z TAF Period

Widespread IFR-MVFR conditions continue through the rest of this
evening at most terminals in low clouds, showers and mist with a
few isolated thunderstorms possible through 03z near SW MT
terminals. Precipitation decreases from NW to SE across the region
after 06z but low cloud ceilings are likely to persist at many
terminals. Breaks in the lower clouds could also promote the
development of fog, particularly across N-central MT terminals
later in the overnight period. Hoenisch

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  48  70  46  80 /  70  10   0  10
CTB  40  67  45  73 /  30   0   0  30
HLN  48  75  47  87 /  60  10   0   0
BZN  50  74  43  89 /  70  10   0  10
WYS  41  74  37  81 /  60  10   0  10
DLN  44  76  42  87 /  30   0   0  10
HVR  46  71  48  78 /  50  10   0  10
LWT  45  63  41  78 / 100  30   0  10

&&

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

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