434
FXUS65 KTFX 161453
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
853 AM MDT Wed Jul 16 2025

.KEY MESSAGES...

 - Lingering precipitation and any fog diminishes through the
   morning and early afternoon today.

 - Temperatures trend closer to normal by the end of the week.

 - Increased chance for afternoon and evening showers and
   thunderstorms beginning Thursday.

&&

.UPDATE...

Morning update has been published, with the main adjustment being
to increase the areal coverage of low chance, 15-20%, PoPs across
portions of Fergus, Judith Basin, and Meagher Counties through the
day today. Otherwise the forecast remains on track, with recent
satellite imagery suggesting that fog will continue to dissipate
across the region through 10AM. Low clouds across Southwest
through North Central Montana, specifically over the valleys and
plains, will continue to break-up with additional heating. -
Moldan

&&

.DISCUSSION...
/Issued 334 AM MDT Wed Jul 16 2025/

 - Meteorological Overview:

The embedded wave responsible for the cooler temperatures and
precipitation is beginning to exit eastward early this morning and
should be well east of the area by the evening. Lingering
opportunities for rain and a few rain showers in the Lewistown area
and vicinity will slowly diminish through the morning. Elsewhere the
primary concern this morning will be for at least patchy fog where
clouds clear up around and just after sunrise.

Cooler temperatures remain in most areas today but begin to trend
closer to normal, especially in Southwest Montana where the cooler
air struggled to reach with this previous system.

Northwesterly flow remains heading into Thursday, with another wave
within the flow crossing northern portions of the region in
afternoon and evening. Lingering moisture, sufficiently warm
surface temperatures, and forcing from the troughing will support
scattered shower and thunderstorm development by early afternoon
across the Hi-Line. There is uncertainty as to just how supportive
the environment will be for severe weather, which will be discussed
further in the confidence section. Nonetheless, the showers and
thunderstorms that form will generally move east or southeast across
the plains through the afternoon and evening.

Flow aloft becomes slightly more zonal Friday into the weekend. That
said there appears to be several embedded waves within this flow
that will help afternoon and evening thunderstorms develop.
Temperatures continue to trend closer to normal by Saturday, which
looks to be the warmest day of the forecast period for most.

Thereafter a period of troughing is favored, though specifics as to
precipitation chances as well as how much cooling occurs is low
confidence at this time. -AM

 - Forecast Confidence & Scenarios:

Thunderstorms Thursday:

The main source of uncertainty for Thursday`s severe thunderstorm
chances is related to just how much instability develops across the
Hi-Line and vicinity. Forcing appears to be favorably timed, with
vertical wind shear near or in excess of 35 kts also supportive of a
few more organized thunderstorms. Guidance with the most instability
features afternoon temperatures on the warmer side of the envelope,
while less aggressive guidance is cooler. Neither scenario seems
unreasonable at this time.

Troughing early next week:

Ensemble support is still high for troughing early to mid next week,
with cluster guidance giving at least an 80% chance for troughing
across the Northern Rockies each of Tuesday and Wednesday. Specifics
such as how cool it looks to get as well as precipitation amounts
remain low confidence. Probabilistic guidance gives areas in and
near the Golden Triangle the best chance for a quarter of an inch of
precipitation, though that chance is only in the 20-30% range at
this time. -AM


&&

.AVIATION...
16/12Z TAF Period

The main concern this TAF period will be for precipitation winding
down across eastern areas this morning and early afternoon, in
addition to lingering low clouds and fog on the back side of the
exiting system. Low clouds and fog slowly diminish later this
morning and afternoon. -AM

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  72  50  80  53 /  10   0  10   0
CTB  67  45  73  47 /  10  10  40  10
HLN  77  49  87  54 /  20   0   0   0
BZN  75  46  89  49 /  20   0  10   0
WYS  75  39  81  40 /  10   0  10  10
DLN  77  44  87  47 /  10   0   0   0
HVR  71  49  78  52 /  10   0  30  20
LWT  65  43  78  49 /  30  10  10  20

&&

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

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