Roundup, Montana Weather Forecast Discussion

804
FXUS65 KBYZ 230059
AFDBYZ
Area Forecast Discussion
National Weather Service Billings MT
659 PM MDT Mon Sep 22 2025
.KEY MESSAGES...
- Localized valley fog tonight.
- Warming and drying trend begins Tuesday.
- High confidence of warm and dry conditions through the weekend.
&&
.UPDATE...
Upper low continues to drop thru western WY and brunt of precip
associated with it is now well to our south. There remain a few
showers in our southern upslope areas but these will diminish
entirely over the next 1-2 hours. As skies clear attention turns
to fog potential later tonight into early Tuesday. A quick shift
to downslope gradients will limit fog potential, but for
western/central areas that saw precip over the past 24 hours there
could be localized valley fog. Current dewpts are in the upper
30s to mid 40s and valley locations should fall thru these values
a bit. Have expanded coverage of patchy fog (20% chance at any
given location) from 06-15z. Low temps tonight should reach the
mid 30s to mid 40s most places. Warming trend begins Tuesday. JKL
&&
.DISCUSSION...
Today through Sunday...
Current analysis shows upper level troughing bringing a band of
showers to south central MT and north central WY. 700 mb jet
energy producing these showers will gradually move south and
weaken through this evening, with showers expected to do the same.
An additional tenth to quarter of an inch is expected through the
remainder of today. With this, southeast MT has about a 20% or
less chance for precipitation today. Additionally, the Beartooth/
Absarokas, Pryors and Bighorns can expect to see up to and inch or
two of snow above 9,000-10,000 ft. As high pressure and drying
quickly build in from behind, the pressure gradient across south
eastern MT is expected to tighten, resulting in breezy conditions
for this area through the afternoon today. Northwest wind gusts in
the 20 to 30 mph range can be expected. As precipitation exits
south shortly before midnight, there is a small chance of fog
(about 20%) for the river valley areas through about 9 am. As the
western portion of the region clears today, this will allow for
cooler overnight temperatures, giving areas of Wheatland Co about
a 30-60% chance of a frost Tuesday morning.
The main story for the remainder of the period will be warm and
dry conditions as ridging builds in over the western US and stays
put. Ensembles do have a wave moving across northern MT late
Thursday into Friday, but with most of the forcing to the north, a
weaker frontal passage with little to no precipitation is likely.
High temperatures will be in the 50s and 60s today, low 70s
Tuesday, increasing into the upper 70s to mid 80s for the
remainder of the period. TS
.AVIATION...
Given recent precipitation, clearing skies, and light winds
expect fog development before sunrise for areas along and west of
a Forsyth to Sheridan line, including in the vicinity of the
KLVM/KBIL/KSHR TAF sites. Any fog should dissipate mid to late
morning Tuesday. Chambers/Archer
&&
.PRELIMINARY POINT TEMP/POPS...
Tue     Wed     Thu     Fri     Sat     Sun     Mon
-----------------------------------------------------------
BIL 046/073 050/083 052/084 054/081 050/081 052/081 051/080
    00/U    00/U    00/U    00/U    00/U    00/U    11/U
LVM 034/073 041/082 044/083 046/079 044/081 046/078 045/078
    00/U    00/U    00/U    00/U    00/U    01/U    11/B
HDN 043/074 045/085 047/085 049/081 047/082 048/082 047/082
    10/U    00/U    00/U    00/U    00/U    00/U    11/U
MLS 046/075 048/086 049/083 052/080 048/083 050/083 051/080
    00/U    00/U    00/U    00/U    00/U    00/U    00/U
4BQ 046/072 049/082 049/083 052/079 049/081 053/082 051/080
    00/U    00/U    00/U    00/U    00/U    00/U    00/U
BHK 044/075 046/083 047/083 050/079 045/080 048/081 048/077
    00/U    00/U    00/U    00/U    00/U    00/U    00/U
SHR 040/072 042/082 046/084 048/080 045/081 048/081 046/080
    20/U    00/U    00/U    00/U    00/U    00/U    11/U
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.
&&
$$
weather.gov/billings

NWS BYZ Office Area Forecast Discussion