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352
FXUS65 KBYZ 240343
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
943 PM MDT Thu May 23 2024

.UPDATE...

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Snow has decreased over the Bighorn and Pryor mountains this
evening as the low pressure system gradually shifts east.
Additional snow accumulations in the mountains are expected to be
minor. Therefore, have gone ahead and cancelled the Winter Storm
Warning. The forecast remains on track. STP
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&&

.DISCUSSION...

Today through Friday night...

...Key Messages...

- Heavy precipitation for lower elevations and heavy snow for
  mountains today lingering early this evening.

- Heavy rain will cause rises on area rivers and streams.
Active day of weather across the region with heavy rain in the
lower elevations and heavy snow in the mountains. There is an
upper jet passing to the south putting the region in the favorable
left exit region. RAP mesoanalysis is also depicting strong upper
divergence and frontogenesis. This strong upper forcing
combined with soundings that are saturated through a deep layer
of the atmosphere is leading to efficient rain production and
heavy rain in a short amount of time. Winds are wrapping around
the backside of the low bringing north/northwest winds through
the western areas of the CWA. Some of our northwestern counties
such as Wheatland have started to clear out. Locations in far
southeast Montana have been dry-slotted today leading to higher
temperatures and surface heating. This has allowed these areas to
remain dry so far. Precipitation will continue to spread into
these areas of southeast Montana this afternoon into evening. CAPE
will be lilted in these areas to about 500J/kg or less but 0-6km
shear will be strong with values in the 50s and 60s kts. HREF is
showing 2-5km updraft helicity tracks for locations mainly in
Powder River and Carter Counties. Due to these factors, the Storm
Prediction Center has put these areas into a marginal risk for
severe weather with the main threats being hail and wind. Most of
the region east of a line from Red Lodge to Miles City will see
additional rainfall of an inch or more. Locations to the west of
that line will begin to clear out this afternoon and receive 0.10
inches or less of additional rainfall.

Due to the heavy rainfall amounts saturating soils, there is a
risk of water ponding and localized minor flooding conditions.
This will be more pronounced in cities and towns were development
prevents water absorption or in locations with already saturated
soils. We have gotten some reports of localized street flooding on
low lying roadways in Billings. Stream and river levels are
expected to rise although there are currently no major concerns
for stream and river flooding. The Little Bighorn River near
Hardin is no longer expected to reach minor flood stage.

This afternoon and evening will continue to be windy with most
locations having a 30-60% chance of getting a wind gust over
40mph. The strongest winds will be in Sheridan County where
probabilities will be 60-90%.

Temperatures will be cool tomorrow morning with most locations
being in the low to high 30s. Some locations west of Billings
generally have a 20-50% chance of getting a freeze. Tomorrow we
will move more into a more downsloped pattern leading to warmer
temperatures in the low to mid 60s. There will be isolated showers
around tomorrow from a low pressure system to our north. Most
locations north of Billings have a 20-30% chance for
precipitation. Torgerson

Saturday through Thursday...

Next trough approaches the region on Saturday, and moves through
the area on Sunday. Low PoPs in the western mountains Sat.
morning, will increase and spread E in the afternoon. Highest PoPs
will be W of KBIL (60-80%). The high PoPs will traverse the area
from W to E Sat. night. While a few thunderstorms will occur into
Sat. night, CAPE/shear values were weak. Chances for at least 0.25
inches of precipitation will be 29% in KLVM and 21% in KBIL for
Sat. night. Temps will be near or a little below normal on
Saturday. On Sunday, PoPs will range from 30% W to 60% E. Chances
for thunderstorms will be confined E and S of KBIL. Again,
CAPE/shear looks weak. Sunday will be slightly cooler than
Saturday. Chances for at least 0.25 inches of precipitation on
Sunday were 20% in many areas.

Monday through Tuesday will be mainly dry with a warming trend due
to upper ridging. Highs on Tue. will be in the upper 70s to lower
80s. SW flow moves in on Wednesday ahead of the next trough. This
flow will bring scattered (30-40%) showers and thunderstorms into
the area in the afternoon through Wed. night. Warm weather
continues on Wednesday. Uncertainty in the pattern increases for
Thursday as ensembles have different solutions regarding the
trough. Forecast has a 20-30% chance of showers and thunderstorms,
with temps in the 70s. Arthur

&&

.AVIATION...

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Moderate to heavy rain will move W to E through the forecast area
through this evening. Snow will occur in the foothills and
mountains above around 5000 ft. Expect scattered showers and
thunderstorms from Rosebud County E. Conditions will be MVFR/IFR
with areas of LIFR. Mountains will be obscured. VFR will return
to the area after 06Z, but scattered stratus and patchy fog cannot
be ruled out. Chances of showers and thunderstorms will move into
the area from the N after 18z Friday, with MVFR/IFR conditions
and areas of mountain obscuration. Arthur
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&&

.PRELIMINARY POINT TEMP/POPS...

    
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Fri     Sat     Sun     Mon     Tue     Wed     Thu
-----------------------------------------------------------
BIL 036/065 042/068 046/064 044/074 048/080 053/079 052/074
    01/U    15/T    74/W    10/U    00/U    13/T    43/T
LVM 031/061 036/062 039/061 039/071 044/078 049/077 047/073
    01/U    18/T    73/T    00/U    01/U    14/T    33/T
HDN 034/066 039/070 045/065 042/074 044/082 050/081 050/076
    21/U    03/T    75/W    10/U    00/U    12/T    42/W
MLS 038/065 041/070 047/064 045/073 046/079 053/082 052/076
    52/T    11/B    55/T    10/U    00/U    11/U    42/W
4BQ 039/065 042/070 047/063 045/071 046/079 053/082 054/077
    +1/U    01/B    56/T    10/U    00/U    01/U    32/W
BHK 037/062 038/071 044/065 042/070 043/077 049/079 049/075
    +3/T    01/B    36/T    10/U    00/U    01/U    32/W
SHR 033/064 038/067 041/061 040/071 044/078 049/080 049/076
    50/U    02/T    66/T    10/U    00/U    02/T    32/T
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&&

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

$$
weather.gov/billings