248
FXUS65 KTFX 040058
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
658 PM MDT Thu Apr 3 2025

.KEY MESSAGES...

 - Snow diminishes for northern areas this evening, but wet,
   slushy road surfaces may refreeze and become slippery near and
   after sunset.

 - Snow shower activity and even a few rumbles of thunder
   are expected in southwest Montana by this evening, with some
   localized heavier areas of snow, especially in Madison and
   Gallatin counties.

 - Gusty northerly winds will move through Southwest Montana
   this evening, some areas will see gusts up to 40 mph at times,
   especially in the Townsend, Dillon, and Ennis areas.

 - A warming and drying trend then push temperatures back above
   average this weekend into early next week.

&&

.UPDATE...

The main change with this update was adjusting precipitation
chances to match observation trends and the latest model guidance.
Overall, the event is still on track to taper off this evening
into the overnight hours. For now, the advisory for the Southern
Rocky Mountain Front has been allowed to be expired. In the next
couple hours if snow continues to taper off ahead of schedule a
couple more zones may get cancelled a little early.

The main concern moving forward is the potential for any wet
surface to freeze overnight leading to slippery roads and
sidewalks that could impact the morning commute. Patchy fog is
also possible along portions of central and north-central Montana
although confidence in exactly where fog will form and how dense
it will be remains a bit low at this time.  -thor

&&

.DISCUSSION...
/Issued 532 PM MDT Thu Apr 3 2025/

 - Meteorological Overview:

Snow is gradually tapering off in northern areas this afternoon
while snow shower activity picks up in Southwest Montana amid weak
instability. Localized areas of heavy snow can be expected
through the evening hours, especially over Madison and Gallatin
counties where snowfall rates my exceed a half inch per hours at
times.

All areas observing wet road surfaces during the afternoon and
early evening hours will be susceptible to refreezing and becoming
slippery. Also, partial clearing of skies over the plains may
encourage patchy fog development, although most locations have
less than a 30% chance for visibility falling below a half mile.

Ridging aloft begins to build in heading into the weekend, but
northwesterly flow aloft may send some passing mid- and higher
level clouds moving through the area and keep temperatures on the
cooler side for the next day or so. Regardless, expect high
temperatures to warm 10 to 20 degrees above average by Monday.

Ensembles remain in good agreement with the ridge being flattened
some late Monday through Wednesday, allowing some unsettled
weather to pass through the Northern Rockies. Temperatures will
still be mild, it will just be windier with increasing chances for
scattered showers and some mountain snow. - RCG

 - Forecast Confidence & Scenarios:

Snow and winds this afternoon and tonight...

Snow is decreasing in a north to south fashion this afternoon and
the advisories along the Hi-Line were let go. No changes were
made to the advisories along the Southern Rocky Mountain Front and
the Little Belts with some snow still expected this afternoon in
addition to refreezing of wet surfaces around sunset. Snow over
the Little Belts fell a little below expectation, likely due to a
lower froude number in this wind set up.

Southwestern areas will be the bigger concern going forward with
the increasing snow shower activity and potential convective
enhancement. Some of the heavier snow showers will have localized
snowfall rates north of a half inch per hour. This will be
especially true in Madison and Gallatin counties where the current
winter weather advisories are going into effect this afternoon.

Southwestern areas will also see at least a brief period of
stronger winds, especially within the narrow north to south
oriented valleys, including the Dillon, Ennis, and Townsend areas
where gusts may approach and exceed 40 mph at times. - RCG

Winds Tuesday and Wednesday...

NBM probabilistic guidance indicates mostly a 50 to 80 percent
probability of 50+ mph wind gusts both days for the Rocky Mountain
Front and east into the Cut Bank area, with a 30 to 50 percent
probability of exceeding 70 mph wind gusts right along the Front.
These probabilities warrant monitoring for potential High Wind
highlights there. Elsewhere across North Central, Central, and
Southwest Montana, the probabilities of 50+ mph wind gusts
increase Tuesday into Wednesday, ranging mostly between 20 and 50
percent on Wednesday, which will also need to be watched.
- Coulston

&&

.AVIATION...
04/00Z TAF Period

Drier mid-level air moving south from Canada has brought and end
to the snow shower threat at the KCTB and KHVR terminals, with the
only potential hazard through the remainder of the 0400/0500 TAF
period being vicinity fog in the valleys below the terminals from
between 06-15z Friday. With HREF probabilities for VIS reductions
of MVFR or lower only being at a 10-20% chance I have held out
even the mention of vicinity fog at this time.

Snow chances will continue to taper off across the Central
Montana terminals of KGTF, KLWT, and KHLN through 02-05z this
evening as the aforementioned mid-level dry air work south. As was
the case with the KCTB and KHVR terminals the threat for fog will
increase beyond 06z Friday, especially at the KGTF and KLWT
terminals. Confidence was high enough at these two terminals to
prevail some low-VFR VIS due to this fog/mist, with temporary
periods of IFR/MVFR VIS/CIGS being possible near sunrise on
Friday.

For the remaining KBZN and KEKS terminals MVFR/low-VFR VIS and/or
CIGS are expected through 12-15z Friday due to snow or snow
showers, with decrease precipitation chances and improving CIGS
thereafter. At the KBZN terminal latest HREF guidance does
support a 50-60% chance for VIS to fall below 2 miles from 05-09z
Friday. Mountains obscuration will gradually decrease from north
to south through 18z Friday. - Moldan

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  18  44  23  57 /  30   0   0   0
CTB  13  42  22  54 /  10   0   0   0
HLN  20  44  23  56 /  50   0   0   0
BZN  20  39  17  51 /  80  20   0   0
WYS  13  38   7  47 /  60  10   0   0
DLN  21  41  21  53 /  80  10   0   0
HVR  16  44  20  57 /  10   0   0   0
LWT  16  38  21  52 /  40   0   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until midnight MDT tonight for Little
Belt and Highwood Mountains.

Winter Weather Advisory until 3 AM MDT Friday for Big Belt,
Bridger and Castle Mountains-Gallatin Valley-Gallatin and
Madison County Mountains and Centennial Mountains-Madison River
Valley.

&&

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