131
FXUS65 KTFX 162045
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
245 PM MDT Wed Jul 16 2025

.KEY MESSAGES...

 - Reduced visibilities due to fog are once again possible tonight
   through Thursday morning, mainly over the plains of Central and
   North Central Montana.

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

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

&&

.DISCUSSION...

 - Meteorological Overview:

Transient ridging within overall northwest flow aloft was moving
over the Northern Rockies this afternoon, with surface high pressure
centered over Southern Saskatchewan, Northeast Montana, and Northern
North Dakota. Dry conditions have and will continue to prevail
through the overnight hours as the aforementioned ridge and surface
high slowly slide and move, respectively, further east towards the
Upper Mississippi River Valley through Thursday morning. An
abundance of boundary layer moisture thanks to recent precipitation
and/or overall low level flow from the southeast to northeast
combined with clearing skies will help to set the stage for another
night for fog development. Overnight low temperatures will once
again fall well below normal, with most locations falling into the
40s while some cold prone valleys in Central and Southwest Montana
dip into the 30s. - Moldan

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:

Fog Tonight through Thursday morning :

Hi-Res Ensemble Forecast (HREF) guidance supports increasing chances
(i.e. greater than 10%) for reduced visibilities (i.e. 6 miles or
less) due to fog development beyond 3AM MDT (09z) Thursday along and
northeast of a Browning, to Choteau, to Carver, to Roy line; with
the highest probabilities of 30-50% for reduced visibilities (i.e. 6
miles or less) occurring near Browning and Cut Bank between 6AM and
9AM MDT (12-15z) Thursday. Furthermore, HREF probabilities support a
10-30% chance for visibilities to fall to or below 1/4 mile between
5AM and 9AM MDT (11-15z) Thursday from Browning to Cut Bank, with
generally a 10-20% chance within the Milk River Valley across
Western Hill County and in Eastern Pondera County over this same
timeframe. For now we will hold off on issuing any Dense Fog
Advisories given low confidence on when skies will clear enough to
support fog development (earlier clearing would allow for the best
chance of seeing the lowest visibilities), but satellite trends will
need to be monitored and a short notice Dense Fog Advisory may be
needed. - Moldan

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...
16/18Z TAF Period

Marginal VFR conditions across central Montana continue to
improve. Ceiling becomes scattered through afternoon, then
clearing overnight.

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  47  80  52  80 /   0  10  10   0
CTB  45  71  48  75 /  10  40  30   0
HLN  47  87  51  86 /   0   0   0   0
BZN  44  88  47  88 /  10   0   0  10
WYS  37  80  39  80 /   0   0  10  20
DLN  43  86  46  87 /   0   0   0  20
HVR  49  78  51  80 /  10  30  20   0
LWT  42  77  49  77 /   0  10  10  10

&&

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

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