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000
FXUS65 KBYZ 221915
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
115 PM MDT Mon Apr 22 2024

.DISCUSSION...
Through Tuesday night...

Satellite imagery shows an upper low over southern SK moving into
MB and a dry NW flow over our region...though there is some
moisture wrapping southward thru northeast MT and northwest ND on
the back side of the low. This moisture and reasonably steep mid
level lapse rates may bring a few light showers/sprinkles to
Fallon County mainly this evening. Surface W-NW winds gusting
30-50 mph will continue thru most of the afternoon then diminish
as we get close to and beyond sunset. Highest gust we have seen
so far is 52 mph in northeast Rosebud County (Rock Springs DOT).
Dew points have fallen to the mid-upper teens most locations, and
if high res models are correct (upstream obs suggest they are) we
will see dew points closer to the lower teens by late afternoon,
before we begin to see moistening from northeast MT. So expect RHs
to fall into the teens before they begin to recover, with temps
in the 50s to lower 60s. All told, forecast is in good shape for
the remainder of today.

Weak shortwave in northern ID will slide to the southeast over the
next 18-24 hours. Air mass in place is obviously quite dry, but
models show a bit of moistening in the 650-550mb layer which,
along with synoptic scale ascent, could produce a few snow showers
over our southern mountains tonight through Tuesday morning. By
tomorrow, rising heights should prevent any shower activity at
lower elevations during the peak heating hours. Tuesday night will
be dry underneath upper level ridge.

Temperatures over the next 36 hours will be seasonable. Look for
lows tonight in the upper 20s to mid 30s, highs Tuesday in the
upper 50s and lower 60s, and lows Tuesday night mostly 30s.

More active weather emerges in the extended period. Keep reading
for more on that.

JKL

Wednesday through Monday...

An active weather pattern is shaping up for the second half of
this week into the weekend. Be sure to monitor the forecast over
the coming days.

Wednesday will be warm and dry as temperatures warm into the 70s
under a flat upper ridge. Luckily, winds look to be light outside
of a few 20-25 mph gusts along the western foothills, so fire
conditions are not a great concern. By Wednesday evening and
night, flow aloft will begin to back out of the SW as the upper
ridge axis slides east. This will open the door to Pacific energy
and moisture which will introduce the potential for showers across
the west late Wednesday into early Thursday morning (15-50%
chance, highest over the mountains). This will mark the beginning
of a transition period to the more active weather pattern.

Thursday will still be warm, especially in eastern MT, as
temperatures warm into the 60s to lower 70s. Lowering heights
associated with a deepening western CONUS trough will bring
increased precipitation chances to much of the region, mainly
during the afternoon (15-90% chance, highest over the mountains
and lowest over Fallon, Custer, and Northern Rosebud Counties). A
few weak thunderstorms are also possible Thursday in far
southeastern MT and along the Beartooth/Absaroka mountains and
foothills, but chances remain low. This is the point in the
forecast where the uncertainty increases.

Friday through Sunday feature periods of increased precipitation
chances (overall 30-90% chance, highest over the mountains and
lowest over Fallon, Custer, and Northern Rosebud Counties once
again). With this, how the upper level flow develops plays a
critical role in the extent of precipitation across the region.
The latest ensemble runs of the GFS and ECMWF have backed off on
precipitation over southeastern MT, but have focused in on the
heaviest precipitation falling Friday through Saturday over the
western and central mountains and foothills. Over the lower
elevations, precipitation type should be all rain, especially
during the day. Temperatures will be cooler Friday through Sunday,
but still near seasonal with highs in the 50s to lower 60s. If
the pattern does materialize in favor of the heavier
precipitation, it still looks like there will be enough cold air
aloft for all snow in the higher elevations.

Monday looks to be warmer and drier, but a lot of uncertainty
remains on how the upper level flow will respond after this
weekend. Arends

&&

.AVIATION...

W-NW winds gusting 25-40 knots (highest east) will diminish this
evening, and winds will remain much lighter late tonight through
Tuesday. A weak shortwave may produce a few light snow showers or
flurries over the Beartooth/Absaroka and Bighorn Mountains from
this evening into tomorrow, possibly obscuring the high terrain at
times. Otherwise, VFR will prevail through Tuesday as upper level
ridge builds back over the region. JKL

&&

.PRELIMINARY POINT TEMP/POPS...

    Tue     Wed     Thu     Fri     Sat     Sun     Mon
-----------------------------------------------------------
BIL 034/061 037/075 047/069 048/058 043/056 040/060 042/068
    00/U    01/U    24/R    46/R    47/R    44/R    23/R
LVM 029/059 036/071 044/066 041/054 038/052 035/057 037/062
    00/B    01/U    37/T    58/R    67/R    45/R    34/R
HDN 032/064 035/076 045/072 046/062 043/059 039/062 039/069
    00/U    00/U    13/R    45/R    46/R    44/R    23/R
MLS 034/061 038/073 046/072 046/067 043/059 039/061 040/067
    00/U    00/U    11/B    12/R    24/R    32/R    22/R
4BQ 035/061 038/074 047/073 046/066 043/057 039/061 039/067
    00/U    00/U    01/B    33/R    34/R    43/R    22/R
BHK 032/059 035/071 044/072 043/065 038/057 036/056 036/065
    00/B    00/B    02/R    22/R    24/R    33/R    22/R
SHR 030/061 033/073 042/068 043/059 038/055 037/057 035/066
    00/B    00/U    14/T    66/R    57/R    54/R    23/R

&&

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

&&

$$
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