632
FXUS65 KBYZ 260037
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
637 PM MDT Fri Apr 25 2025

.KEY MESSAGES...

- Warmer Saturday and Sunday (60s and 70s).

- Scattered showers and isolated thunderstorms possible over
  south-central Montana Saturday afternoon and evening (10 to 30
  percent chance).

- Another spring storm system is taking shape for later Sunday
  into Monday. This system could produce significant
  precipitation across much of the area (30-60 percent chance of
  at least 1 inch of rain / snow water equivalent).

- Flooding in low lying areas, rises in creaks and streams, and
  impacts to recent burn scar areas are possible with this next
  system.

&&

.UPDATE...
Satellite imagery shows a weak shortwave lifting from northern NV
into southern ID, and there are some showers & weak t-storms in
southeast ID. Some benign activity may spread into the Beartooth-
Absarokas later this evening into the overnight hours. Most of the
cwa will be dry tonight, but the advection of low cloud into far
southeast MT may yield spotty drizzle later tonight, but the risk
of fog is low per the breezy southerly winds. Something to watch.
Better chance of upslope stratus and perhaps localized fog is west
of Billings and in particular the east side of the Crazy
Mountains. Look for low temps tonight in the mid 30s to lower 40s
most places. Current forecast has all of this covered well. JKL

&&

.DISCUSSION...

Through Saturday Night...

Mostly dry conditions under partly to mostly cloudy skies will
continue into tonight as a weak upper low progresses through the
region. With that said, an isolated shower or two are possible
this afternoon and evening over the higher terrain to the south of
Billings, but the chance of precipitation remains low (5 to 20
percent). As we progress into tonight, the breezy winds over
south-central Montana look to taper off. With this, localized
patchy fog is possible once again into the morning hours.
Therefore, if you commute on Highway 191 from Big Timber through
Harlowton, stay alert for patchy fog Saturday morning. East of
Billings over south-eastern Montana, breezy winds will continue
into tonight with gusts generally around 20 to 35 mph.

Saturday will be a mostly dry day as our next weather system
moves inland over California. While the core of this system will
still be far away, divergent south-west flow along with modest
instability will allow scattered showers and isolated
thunderstorms to develop during the afternoon and evening over
south-central Montana. Any thunderstorm that does develop will
generally be weak, but small hail and gusty winds are possible.
Temperatures Saturday will also be warmer than today with highs in
the 60s and 70s (F). Arends

Sunday through Friday...

The synoptic forecast remains on track with a strong upper level
low progressing eastward during the day Sunday bringing precip
across the area to start the work week.

Rain/snow showers will fill into the mountains through the day
Sunday, and as we progress into Sunday afternoon and evening the
chance for thunderstorms develops across the eastern half of the
CWA. NBM has forecast SFC CAPE values over 800J/Kg in some
locations in southeast Montana with widespread 500+ J/Kg.
Additionally, very steep lapse rates will be the theme for the
region as a GFS forecast sounding pulled near KMLS shows SFC-3KM
lapse rates approaching 9C/KM. The other thing that caught my eye
with this sounding is that the lowest levels show northeasterly
winds with a sickle shaped hodograph. This will allow for good
moisture advection and WAA into the region which could also help
increase some SB CAPE. The primarily inverted-V soundings will
make strong winds the primary hazard, however some modest hail is
also possible with some of the stronger storms.

Snow levels for the event have also changed slightly. The start of
the event will see levels near 8,500ft with gradual falls to near
6,000ft. This has cautiously decreased the concern for flooding
of the Elk Fire burn scar as most of the heaviest precip should
fall as snow. That being said, the lowest elevations of the scar
could see rain for a little longer into Monday morning leading to
localized flooding. Once the snow begins in the Absaroka/Beartooth
mountains snow could be heavy at times totaling 18"+ at the
highest peaks by Tuesday AM as the system makes a rapid exit to
our east.

The next chance for precip will be Wednesday afternoon as a
speedy shortwave moves in from the NW. This could give us another
chance for some showers and thunderstorms Wednesday afternoon and
evening region-wide with mountain snow. After that shortwave
exits to the east, there is great consensus in a building ridge
towards the end of the week. The specifics of whether this ridge
will be more neutrally oriented or flopped over a quasi-cutoff
low is yet to be determined. Regardless, clear skies and temps in
the 70s seem likely late next week. WMR

&&

.AVIATION...

The scattered to broken MVFR clouds over south-central and
eastern Montana this afternoon will continue to break up into this
evening. With easterly surface winds continuing into tonight,
areas along the western foothills (KLVM, K6S0, K3HT) could see low
clouds linger through tonight (10 to 50 percent chance) and the
development of isolated fog into Saturday morning. While the
breezy winds around and west of KBIL will taper off tonight, winds
around KSHR, KMLS, and KBHK look to remain breezy this evening
into tonight out of the southeast. With that said, uncertainty
remains on the strength and duration of these winds at the surface
as the inversion develops tonight. Arends

&&

.PRELIMINARY POINT TEMP/POPS...

    Sat     Sun     Mon     Tue     Wed     Thu     Fri
-----------------------------------------------------------
BIL 038/072 044/075 044/054 038/069 047/064 042/072 045/076
    01/B    26/T    +8/W    21/B    64/W    21/U    00/U
LVM 036/069 041/069 040/053 037/064 040/061 037/071 041/073
    12/T    18/T    +8/W    03/W    64/W    11/U    01/U
HDN 038/072 042/077 042/054 035/069 045/064 040/071 042/077
    01/B    25/T    +9/W    21/B    65/W    21/B    00/U
MLS 042/073 043/078 046/056 035/068 046/065 041/070 043/077
    00/B    22/T    98/W    11/B    44/W    11/U    00/U
4BQ 043/073 045/078 046/053 036/065 045/062 041/067 043/074
    01/B    12/T    89/W    20/B    34/W    11/U    00/U
BHK 040/065 041/078 043/052 029/064 041/063 036/067 038/073
    11/N    12/T    88/W    20/U    33/W    11/U    00/U
SHR 035/069 041/076 040/050 031/066 039/058 035/068 037/073
    11/B    13/T    8+/W    31/U    46/W    31/B    01/U

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Watch in effect from Sunday evening through
      Monday afternoon FOR ZONES 67-68.
WY...None.

&&

$$
weather.gov/billings