441
FXUS65 KBYZ 120828
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
228 AM MDT Wed Mar 12 2025

.KEY MESSAGES...

- Warm Wednesday and Thursday with highs in the 50s and 60s (near
  70 possible); showers increase over mountains Thursday
  afternoon.

- Turning colder, a period of rain and wet snow, and brisk north
  winds Thursday night and Friday; greatest chance of snow
  accumulations over the mountains and foothills.

- Unsettled weather pattern with seasonable temperatures for the
  weekend into early next week.

&&

.DISCUSSION...

Through Thursday afternoon...

Westerly flow will continue to transition into ridging for the
day today, bringing mild and mostly dry conditions. Moisture
streaming in from the Pacific will work to keep the mid and upper
levels moist, increasing cloud cover and allowing for a small
(<15%) chance of showers for areas west and south of Billings.
Conditions will be breezy for the Livingston area today with gusts
30-45 mph expected through Thursday morning. Breezy conditions
will also be prevalent for areas of the Bighorn Basin drainage up
through the 212 corridor with gusts of 20-35 mph this afternoon
through Thursday morning. High temperatures today will be in the
50s and 60s. As a low off the west coast makes landfall, most of
that energy will remain well to the south, but lowering heights
and a resulting shortwave will provide enough forcing to produce
some showers ahead of the main frontal passage Thursday night (see
discussion below for more). With models producing some
instability with these showers, a rumble of thunder cannot be
ruled out, mainly for areas of south- central MT. One factor that
could limit instability and thunderstorm potential would be cloud
cover early afternoon. Another thing to note is that model
soundings are depicting dry air near the surface, implying any
accumulations from these isolated showers will be little to
nothing. Accumulations can be expected with the main frontal
passage Thursday night into Friday. High temperatures Thursday
will also be in the 50s and 60s. TS


Thursday Night through Tuesday...

We are still looking at a period of rain to wet snow Thursday
evening to midday Friday, but there remains uncertainty in
details. The GFS and its ensembles (with a bit sharper trof)
continue to show more QPF than the EC. Given the complex
interaction between this trof and a deep low developing in the
central plains, it is not clear which way this system will swing.
A few points to make. (1) Precipitable waters will be near a half
inch (1-2 standard deviations above normal). (2) PV axis does not
exit southeast MT until 00z, so it is possible that the mid level
baroclinic zone slows its eastward progression and the area of
precip is a bit slower to exit than models show at this time. (3)
The onset of northerly winds will provide upslope enhancement in
our south. (4) Precip amounts should turn lower in the east as the
main trof continues to split and ascent weakens. All of these
items will need to be monitored.

We currently expect precipitation amounts of 0.10-0.25" at lower
elevations (greatest in upslope areas), and 0.30-0.50" over the
southern mountains. This translates to a 4-8" snowfall for the
mountains, up to 1-3" along the foothills, and an inch or less
elsewhere. Honestly, most lower elevations will not see any
accumulation with this system...it is just too warm w/o a push of
cold advection from Canada. But the precip itself will be
welcomed. The probability for 0.25" or more of precip is 5-10% in
the north and east, 20-45% central parts and 50-70% over southern
mountains/foothills.

Wet bulb zero heights look to fall to near 3500` at Billings by
09-12z Thursday night, suggesting some wet snow may fall in the
metro area, though it is doubtful there will be any accumulation
given warm surface temps (but there may be briefly over the
surrounding hills). By afternoon we will see drier downslope winds
develop from the west, and temps in the upper 30s to mid 40s.

Friday night into early Saturday should be mostly dry, but there
is another weak trof which is accompanied by cold air aloft (-30C
at 500mb) yielding diurnal instability in the afternoon and
evening. Look for isolated to scattered snow showers over the west
during this time, with an inch or two of snow over the western
mountains. Temps Saturday should max out in the mid 30s to mid 40s
(coldest east).

Look for a period of ridging Saturday night through Sunday, and
possibly into Monday, in advance of the next Pacific trof. There
is plenty of uncertainty regarding the amplitude of the ridging
and when it will break down. Sunday should see temps back to the
50s, and a cooling trend may begin Monday or may hold off until
Monday night. If the latter occurs Monday would be warmer than
Sunday. There is also increasing confidence for a period of gusty
foothills winds before the next cold front (50% chance of 50+ mph
gusts at Livingston).

A deeper (and possibly more organized) trof is expected to move
through the region sometime in the Monday through Tuesday night
time frame. A more amplified wave progression could result in
healthy snow accumulations at lower elevations, but it is far to
early to try to determine this. Cluster analyses show high spread.
Something to monitor over the coming days.

JKL

&&

.AVIATION...

VFR conditions will prevail through the taf period. Breezy SW
winds will persist through early Thursday morning at KLVM with SW
gusts of 25-40kts possible. TS

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Thu     Fri     Sat     Sun     Mon     Tue
-------------------------------------------------------
BIL 064 040/064 033/046 028/047 030/056 039/055 032/044
    1/B 02/R    83/S    12/J    21/N    34/W    46/S
LVM 055 039/054 029/040 024/040 026/051 034/045 026/037
    0/N 05/R    93/S    24/J    32/W    56/W    56/S
HDN 066 035/065 034/047 024/047 027/056 035/056 029/044
    0/B 02/R    85/S    12/J    31/B    24/W    46/S
MLS 063 035/066 035/042 020/039 023/053 035/054 027/042
    0/B 00/B    35/O    00/U    10/B    11/B    23/S
4BQ 063 036/065 035/041 021/041 025/053 034/056 029/042
    0/B 00/B    26/S    00/U    10/B    11/B    33/S
BHK 060 032/064 030/040 014/034 016/048 029/053 022/040
    0/B 00/B    15/O    00/U    00/U    11/B    22/S
SHR 061 033/061 032/040 019/042 020/054 030/053 024/040
    0/B 02/R    78/S    12/J    20/B    13/W    47/S

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.

&&

$$
weather.gov/billings