632
FXUS65 KBYZ 272040
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
240 PM MDT Sat Apr 27 2024

.DISCUSSION...
Rest of Today through Sunday Night...

Satellite imagery shows an upper low near SW Colorado with a
related northern branch trof extending from southern British
Columbia to Idaho. Radar indicated some light precipitation over
our western mtns/foothills with increasing vertical extent of
clouds...so increasing chance of measurable precipitation in the
west. Scattered clouds were observed over eastern MT.

Not much additional precipitation has occurred over our CWA so
far today, including the mountains. However, instability has
increased over the high country (6-8.5 C/km in mid layers) and
models focus scattered to numerous rain/snow showers over our very
western section from Park County northward through the Crazies
and into western Wheatland County through the evening as
differential divergence and the trof axis combine over this area.
Eastern sections will not see any precipitation overnight.

Forecast problem is what to do with the Winter Storm Warning over
the Beartooths and Crazies. Snow levels are currently around
8250-8500 ft and will slowly drop overnight to 7250-7500 ft by
Sunday morning. The heaviest precipitation is likely through
evening due to the instability where we could see some thunder
snow in the high country. Overall though...only the higher peaks
will see much snowfall accumulation with about 2-4 inches of wet
snow (25-50% chance of at least 4 inches above 8250 ft). Thus,
impacts look minimal and not worthy of a warning. We will cancel
the highlight...but folks in the high country should be prepared
for occasional heavy wet snow showers through the evening.

The easterly flow will shift to westerly overnight and into Sunday
as trof axis shifts eastward, and the upper low to our south
lifts in to the central plains. This will push some showers out
over the plains by Sunday morning, but the splitting nature of the
trof will mean generally weak showers over the plains (20-30%
coverage). Moist zonal flow and upper divergence will keep
precipitation going over the mountains Sunday, decreasing Sunday
night. Again, snow levels will generally be over 7500 ft on
Sunday, with only an additional 1-2 inches of snowfall
accumulation over the higher peaks.

Temperatures will remain seasonable. Look for lows in the 30s to
lower 40s tonight, and highs in the 55 to 65 range Sunday. BT


Monday through Saturday...

For Monday, ensembles depict a shortwave Pacific trough tracking
through MT with another shortwave passing through behind it
Wednesday. This will create an unsettled pattern for the extended
with chances (at least 20%) of precip every day. Monday, chances
for at least a quarter inch of rain is 30-60% for areas from Miles
City town to Sheridan, WY and west. With snow levels dropping to
around 3000 ft Monday night, the foothills and possibly lower
elevations could pick up some snow (15% chance of an inch for Red
Lodge and Livingston). Monday looks to be the best time for any
decent precip for the period. Models have lower chances for precip
Tuesday being in between systems. With this, post frontal winds
and daytime mixing will generate widespread wind gusts of 30-40
mph Monday night through Tuesday evening with the highest gusts
along the Dakota borders. These areas along the border have about
a 40-60% chance of seeing gusts of at least 50 mph Tuesday
afternoon. Chances for precip Wednesday are at about 20-50% for
lower elevations and 60-70% for the mountains. With regard to
mountain snow for Monday through Wednesday night, Red Lodge had a
10% chance of at least 6 inches of snow with the highest mountain
peaks at about an 80% chance. As for the latter half of the
period, ensembles are generally keeping an unsettled pattern
Friday into the weekend. With this PoPs remain at about 20-40% for
the remainder of the period.

High temperatures will be in the 50s/60s Monday, cooling down to
the 50s for the remainder of the period. TS

&&

.AVIATION...

Rain showers and mountain snow will continue to develop this
afternoon for western MT. Showers will diminish around 6Z. MVFR
conditions are possible for KLVM and mountain obscurations are
likely. Isolated showers will again develop Sunday afternoon. TS

&&

.PRELIMINARY POINT TEMP/POPS...

    Sun     Mon     Tue     Wed     Thu     Fri     Sat
-----------------------------------------------------------
BIL 044/064 043/067 038/057 035/056 036/055 037/057 037/058
    12/W    27/R    82/R    25/O    34/O    24/R    33/R
LVM 040/059 038/059 029/051 030/049 030/054 032/055 034/056
    84/W    49/T    74/O    36/O    33/O    35/O    33/O
HDN 040/066 039/069 037/059 034/059 035/057 035/060 036/061
    02/W    25/R    92/O    24/O    44/R    34/R    33/R
MLS 039/065 039/068 040/057 035/057 036/055 036/058 036/059
    01/B    01/B    82/R    13/R    22/R    23/R    32/R
4BQ 036/064 038/069 039/059 035/058 036/054 035/059 036/057
    01/B    01/B    51/N    12/R    23/R    23/R    32/R
BHK 033/059 032/068 037/055 033/057 032/052 032/056 032/057
    00/B    01/U    73/R    13/O    22/R    23/R    32/R
SHR 034/061 037/067 034/058 030/055 031/052 031/057 032/058
    03/W    13/R    83/O    24/O    44/O    33/R    33/R

&&

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

&&

$$
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