Damaging Winds in Montana, May 11, 2025

Area Forecast Discussion
National Weather Service Billings MT
142 PM MDT Sun May 11 2025

.KEY MESSAGES...

- Showers and thunderstorms return to much of the area this
  afternoon into the evening (20-50% chance), with the main hazard
  being strong wind gusts to 65 mph.

- Above normal temperatures through Monday, with highs forecast
  to be in the upper 70s to lower 90s.

- Expect additional rises on rivers and streams due to mountain
  snowmelt through early this week.

- Confidence increasing for a cool and wet weather system during
  the middle of this week. There is a 40-80% chance of at least 1
  inch of precipitation (greatest over southern mountains &
  foothills) and a 80% chance of at least a foot of snow in the
  mountains above 7000 feet.

- Midweek precipitation may add to elevated water levels on rivers
  and streams along the foothills.

&&

.DISCUSSION...

Today through Monday night...

For today, southwest flow will usher in weak energy allowing for
light showers and strong to potentially severe thunderstorms.
Given the dry low levels of the atmosphere, the main threat with
these storms will be strong winds up to 65 mph. Any showers that
develop could also produce gusty winds even without any thunder,
but likely being less than 60 mph. One factor that could inhibit
instability and stronger thunderstorms this afternoon and evening
would be the cloud cover over south- central MT. Higher confidence
exists for areas across southeast MT given the surface heating
from lack of cloud cover. Dry conditions will also limit any kind
of precipitation accumulation to less than a tenth of an inch.
Showers will diminish late this evening as dryer air builds in for
the day Monday. Breezy conditions will be present across the
western foothills as a 700 mb jet moves over. Gusts 30-40 mph can
be expected through the afternoon. A frontal passage ahead of the
approaching trough is set to move through late Monday evening,
mainly bringing gusty northwest winds and little precipitation. A
blend of high resolution models is depicting gusts of 30 to 45 mph
after sunset into the overnight hours. High temperatures Monday
will range from the mid 70s west to low 90s in southeast MT.
Additionally, as warm temperatures persist through Monday,
continue to use caution as rises is small streams and rivers are
expected. TS

Tuesday through Sunday...

Wet midweek system is still poised to impact us, but there remains
plenty of uncertainty with regard to the track of the mid level
low and associated precipitation.

What we know: (1) Cooling trend begins Tuesday followed by temps
in the 50s to lower 60s Wednesday & Thursday (Wed probably coolest
day). (2) Heavy snow for the mountains above 7kft with 1-2 feet
possible. Impacts to snow removal ops over Beartooth Highway are
likely. (3) Widespread rain for lower elevations w/ 0.50" or more
everywhere (>80% chance).

Uncertainties: (1) The exact track of the low. The EC continues
to favor heavy precip with a low moving slowly thru northern WY
before reaching the Dakotas. Meanwhile the GFS is staying its
course with a weaker low lifting thru eastern MT, thus an overall
drier and shorter-lived event. (2) Impacts of precip on river and
stream levels which are running higher due to current snowmelt.
Larger rivers are currently expected to remain below flood stage
through the week, thanks in large part to the fact that snow will
accumulate above 7000 feet, but smaller streams and low-lying
areas, and perhaps burn scar locations, will need to be monitored.
The western two-thirds of our forecast area have been quite wet
over the past several weeks. The east has been dry and the ground
can definitely take on a good amount of water. All told, the
greatest water concerns will be close to the mountains and
foothills.

A few notable probabilities:
1+ Inches of rain: 40-80% (greatest central & south)
2+ Inches of rain: 10% north to 50% southern foothills
3+ Inches of rain: 10% south of Billings
1+ feet of snow above 7000 feet: 80%
2+ feet of snow above 7000 feet: 30%

For Billings, a good estimate at this time is around 1.50" of rain
from Tuesday night through Thursday. Of course, this is subject
to change pending the track of the low.

Secondary wave in WNW flow will bring a continuation of shower
activity through Thursday, regardless of the fate of the initial
low. After a short break w/ ridging Thursday night into Friday,
more Pacific energy arrives bringing a likelihood of showers
(50-80% chance) each day from Friday afternoon through the
weekend. In fact, there is potential for a deeper trof or
evolving low (i.e. stronger forcing), by late in the weekend and
into the following Monday. Another period of moderate to heavy
rain is possible, though this is of high uncertainty at this time
and will need to be watched. Temps Friday through next weekend
should be seasonable with highs mostly upper 50s to mid 60s. Temps
at high elevations will be cold enough for snow showers and
possible accumulation. At the very least, we expect little to no
high elevation snow melt from Tuesday through the weekend.

JKL

&&

.AVIATION...

18Z Update

Multiple rounds of scattered showers and thunderstorms will begin
this afternoon and track southwest to northeast through the
evening. Storms this afternoon have a 40-60% chance of producing
gusts to 50 kts with a small chance for small hail at all TAF
sites. See below for potential thunderstorm timing. TS

SITE  TIMING
-----------------
KLVM  19Z-00Z
KBIL  20Z-04Z
KSHR  21Z-04Z
KMLS  23Z-06Z

&&

.PRELIMINARY POINT TEMP/POPS...

    Mon     Tue     Wed     Thu     Fri     Sat     Sun
-----------------------------------------------------------
BIL 056/084 050/067 046/054 046/061 042/063 045/064 045/063
    41/B    34/W    99/R    78/T    23/T    46/T    67/T
LVM 049/076 043/058 040/053 040/057 038/060 040/062 039/058
    21/N    58/T    99/T    67/T    24/T    58/T    77/T
HDN 053/088 049/070 046/054 045/060 040/063 043/065 044/065
    41/B    22/W    9+/R    88/T    33/T    46/W    67/T
MLS 055/089 055/075 050/058 046/059 041/062 041/064 044/065
    30/B    20/U    89/R    88/W    31/B    24/W    45/W
4BQ 057/089 054/072 049/056 045/056 042/060 041/064 044/063
    20/U    00/U    89/R    88/W    41/B    24/W    46/T
BHK 054/090 051/077 047/062 041/055 038/060 035/063 039/061
    30/U    00/U    79/R    88/W    41/B    12/W    44/W
SHR 053/086 048/069 042/052 040/056 037/060 038/062 039/062
    20/B    13/W    9+/T    89/T    43/T    36/T    68/T

&&

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

&&

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