Dillon, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

401
FXUS65 KTFX 141308
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
708 AM MDT Wed May 14 2025

.KEY MESSAGES...

 - Mainly mountain snow and valley rain continues through the day today
   across Southwest Montana. Across northern areas, showers and a
   few thunderstorms will be around this afternoon.

 - Remaining unsettled through the remainder of the week, with
   showers and a few thunderstorms in most areas in the
   afternoon.

 - Although the details are murky, a more widespread precipitation
   event is looking likely early next week.

&&

.UPDATE...

7:08 AM Update : Expanded the Winter Weather Advisory to included
the Boulder and Elkhorn Mountains through noon MDT today as
increasing light has revealed snow covered roadways on the Montana
Department of Transportation webcams at Elk Park and Boulder Hill
in Jefferson County. - Moldan

6:39 AM Update : Morning update has been published, with the main
focus being to lower snow levels an additional 500 to 1000 feet
across Beaverhead and Western Madison County where sufficient
cooling due to heavy precipitation rates has changed precipitation
at the valley floors over to all snow. These lowered snow levels
has resulted in snow accumulations of generally 1 to 3 inches for
the I-15 corridor in Beaverhead County, including the city of
Dillon. With surface temperatures only marginally supporting snow
across these areas, and with the approach of increasing solar
insolation which should limit additional accumulations on road
surfaces, I have elected to issue a Special Weather Statement to
cover the slushy snow accumulations through the late morning hours
vs a Winter Weather Advisory. Main impact from the snow across
the valley floors here will be to elevated surfaces like bridges
and overpasses, along with where roads are shaded from hills and
tress, with these areas becoming slippery. - Moldan


&&

.DISCUSSION...
/Issued 639 AM MDT Wed May 14 2025/

 - Meteorological Overview:

Upper level troughing across the interior west with an
intermittently closed upper low pivoting through will be the driver
of impactful weather through the day today into tonight, mostly
across Southwest Montana. There remains a few discrepancies between
guidance in the mid levels with respect to the magnitude of forcing,
though all members favor banded precipitation stretching from the
Bozeman area southwestward toward Dillon and vicinity through the day
today. Magnitude of forcing and resulting precipitation rates looks
to play a role in how far snow levels fall today within this
banding. More aggressive guidance results in at least brief snow at
valley floors between the Bozeman and Dillon areas this morning,
while the lighter members favor all rain at lower elevations. The
most aggressive guidance shows a rather potent H7 low over SW MT or
eastern ID this morning. So far the analyses aren`t trending quite
that potent, so I have not dropped snow levels to valley floors for
too long this morning. Trends will need to be closely monitored for
stronger forcing, as that would be enough for impactful snow at
lower elevations this morning.

Moderate to heavy mountain snow is still on track south of I-90
today. Given impacts to roadways do not appear to be major at this
time, no upgrades are needed to the ongoing Winter Weather
Advisories, though once again, trends will need to be closely
monitored. I did end up extending the advisories through noon to
catch any lingering impacts and expanded it to include the Big
Belts and Bridgers. A few slushy inches of snow near pass level
seems plausible, with amounts greater than 6 inches above pass
level.

Further north today the relative lack of cloud cover will result
in afternoon showers and perhaps a few thunderstorms as well. The
overall environment is not conducive to stronger thunderstorms,
however.

Heading into the rest of the week, an unsettled westerly to
northwesterly flow will keep shower opportunities in place in the
afternoon and early evening hours.

Late weekend into early next week another robust trough moves in
across the west. Details are murky, but this will bring another
opportunity for widespread precipitation, with snow levels likely
dropping to at least pass level. -AM


 - Forecast Confidence & Scenarios:

The greatest piece of uncertainty continues to be how far snow
levels fall this morning. Heavy precipitation rates will drive
cooling at the surface, but it remains unclear how heavy
precipitation rates will ultimately get, as well as the exact
location of the greatest rates. Those across Southwest Montana
valleys should be prepared for brief transitions to snow, dependent
on precipitation rates. Impacts to roadways where lower elevation
snow falls is even more uncertain, given how warm the roads are from
recent warm weather.

For early next week areas across Southwest and Central Montana are
most favored for precipitation at this time. Areas along and south
of a line from Great Falls to Lewistown have a greater than 50%
chance for 0.50" precipitation. -AM

&&

.AVIATION...
14/12Z TAF Period

Widespread lower elevation rain and mountain snow will affect
Central and Southwest MT through 00z Thu before slowly starting to
change to more scattered showers after 00z Thu. Expect low
ceilings and IFR conditions. At this time, I do not expect
impactful snowfall at the TAF sites, but through 15z today it
would be possible at times for the rain does change to snow for
some southwest valley locations. Mountains/passes will be obscured
across much of the CWA through the period. Brusda

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  60  43  55  39 /  70  70  90  30
CTB  64  40  52  35 /  50  70  80  20
HLN  59  43  57  40 /  90  70  80  40
BZN  50  36  54  36 / 100  80  80  30
WYS  46  28  48  27 / 100  80  80  40
DLN  50  33  52  34 / 100  50  40  20
HVR  62  41  62  38 /  60  30  60  20
LWT  48  38  52  36 / 100  80  80  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until noon MDT today for Big Belt,
Bridger and Castle Mountains-Elkhorn and Boulder Mountains-
Gallatin and Madison County Mountains and Centennial Mountains-
Northwest Beaverhead County-Ruby Mountains and Southern
Beaverhead Mountains.

&&

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