516
FXUS65 KBYZ 290258
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
858 PM MDT Sun Apr 28 2024

.UPDATE...

Just a quick update to adjust precipitation chances overnight
into tomorrow morning as additional shower activity is expected to
develop over the southwest mountains and push northeast
overnight. Precipitation amounts will be light (under a tenth of
an inch), with snow adding up to less than 4 inches in the highest
portions of the Beartooth/Absaroka mountains. Added a mention of
fog in for the eastern state line zones. This may be short lived
as westerly winds should get in there before sunset which will
quickly disperse the low level moisture. Better chances for
precipitation arrive for tomorrow afternoon/evening as a stronger
disturbance crosses the region. Chambers

&&

.DISCUSSION...

Tonight through Monday night...

Satellite imagery shows a dynamic low in the central plains and a
zonal flow moving thru the PacNW and northern Rockies with
embedded weak short waves. The short waves and associated
frontogenesis were producing showers over mainly our southern
higher terrain (mtns and foothills) today. None of this precip
is or will be heavy, and diurnal instability is too bother
mentioning "thunder" the rest of the day, though an isolated
rumble is not out of the question. Mountains may be picking up a
little snow through evening above 8000 ft. Lows tonight will range
from lower 30s along the Dakota borders to upper 30s and lower 40s
elsewhere.

Westerly downslope winds and pre-frontal warming ahead of a
stronger Pacific shortwave will boost temps into the 60-70 degree
range for Monday. SW winds will increase (gusts 25-35 mph
expected along western foothills). A few showers may spread over
our western mountains/foothills and nearby plains in the morning,
but the much better chance of showers (30-80%) will be in the
afternoon as large scale ascent increases from the west. Dew
points in the low-mid 30s will limit instability but sbcapes
should reach 100-300 j/kg, so we may see a few weak thundershowers
near the front, which isn`t expected to reach our west until late
afternoon. The cold front/convection combo has the potential to
produce gusty winds (up to 45 mph) late in the day, starting in
our west of course. Something to watch if you have outdoor plans
late Monday afternoon & evening.

Showers will continue to spread east Monday evening with most
areas seeing measurable precipitation as favorable jet dynamics
target our CWA (Pops from 30% in SE to 90% over mountains and
western sections). After midnight...showers will become less
robust and shift east with the better frontogenesis and upper
support. While most areas will see precipitation, the chance of
seeing a tenth (0.10) of an inch or more of liquid will range
from just 10% in the east to 70 percent in the W/NW portions of
our CWA for this event.

As for snowfall...snow levels will be over 7500 ft Monday
afternoon, falling to about 6500 ft by the end of the event. Our
foothills could see some wet snow mixed in, but its more likely
only the higher elevations see any snowfall accumulations,
generally ranging from 4 to 8 inches over the higher Beartooth peaks.
The Big Horns may see 1 to 4 inches over higher west facing
slopes Monday night. BT

Tuesday through Sunday...

For Tuesday, subsidence behind the frontal passage will create dry
and windy conditions for the region. Winds in the low/mid levels
will mix down, allowing for wind gusts of 35-45 mph Monday night
through Tuesday afternoon. The probability of hitting 45 mph is
best Tuesday afternoon for north and east of Miles City and along
the Dakota borders. PoPs remain limited for the mountains (50%)
with a few inches of snow expected. Wednesday and Thursday,
another piece of energy associated with the cyclonic flow to our
NE will bring a chance for precip (20-50% chance). More than a
quarter inch of rain/SWE is most likely for areas to the west of
Billings, especially in the higher terrain. As for mountain
snowfall through Friday morning, the Beartooth/Absarokas and
Bighorns have about a 40-60% chance of getting 6 inches for the
highest peaks with Red Lodge and Story, WY at about a 15% chance.
Ensembles have another piece of energy moving through Friday with
possible ridging for the weekend.

High temperatures will be in the 50s through Thursday, 50s/60s
Friday-Saturday and 60s/70s Sunday. TS

&&

.AVIATION...

Isolated to scattered showers will be present through the period.
VFR conditions are expected with MVFR possible under any showers
(mainly for KLVM late this evening). Showers will become more
widespread tomorrow afternoon and evening moving west to east starting
around 21Z and lasting into the overnight. TS/LT

&&

.PRELIMINARY POINT TEMP/POPS...

    Mon     Tue     Wed     Thu     Fri     Sat     Sun
-----------------------------------------------------------
BIL 045/066 037/056 035/056 036/057 037/059 036/061 040/071
    24/T    72/R    15/O    44/O    24/R    32/R    12/R
LVM 038/060 028/049 028/048 030/055 034/055 032/059 038/067
    48/T    83/S    36/O    43/O    25/T    22/R    13/R
HDN 041/068 037/058 034/058 035/057 034/062 036/064 039/075
    33/T    82/R    14/O    55/R    24/R    32/R    11/B
MLS 039/066 040/057 035/057 036/055 035/061 036/062 039/072
    11/B    71/N    02/R    34/R    12/R    22/R    01/B
4BQ 039/067 040/057 034/058 035/054 033/059 036/059 039/075
    01/U    41/N    01/B    34/R    22/R    32/R    00/U
BHK 033/066 037/055 032/056 032/052 030/056 031/058 034/068
    01/U    42/R    02/R    24/R    12/R    32/R    11/U
SHR 037/066 034/056 030/054 031/053 030/059 032/059 036/072
    22/R    63/O    24/O    55/O    24/R    32/R    11/B

&&

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

&&

$$
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