461
FXUS65 KBYZ 300845
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
245 AM MDT Tue Apr 30 2024

.DISCUSSION...
Today through Wednesday...

Showers associated w/ a fairly dynamic Pacific trof continue to
move west to east thru the forecast area tonight. The back edge is
nearing Billings at 08z. Precip over the last six hours has been
a tenth of an inch or less across the north and east, but a
heavier area of precip associated with the trof axis itself has
resulted in 0.10-0.25" from the foothills to Billings. A nice
drink of water indeed. The Beartooth-Absarokas saw a period of
heavy snow, and Snotels are suggesting something like 3-6". Wet
snow has also fallen along the foothills but with little
accumulation below ~5kft. Showers will move through southeast MT
over the next several hours and should end by 12-15z as subsidence
arrives from the west.

Gusty well-mixed west winds will develop across the region today.
Mid level flow around 35kts suggests peak gusts in the 30-45 mph
range. By afternoon we will see pressure falls to the west, i.e.
the isallobaric wind will work against the westerly flow, so don`t
see a risk of 50+ mph gusts (probability of this is only 10%
across our north). Pwats falling to 0.20" or less will yield
dewpts in the teens. Even with the cooler temps we should see
afternoon humidity down to the upper teens to mid 20s most places.

An upper low w/ cold air aloft exists over southern BC, and
satellite imagery shows the next shortwave of interest along the
WA coast. Despite the large scale subsidence today, the cooling
aloft (near -30C at 500mb) will yield enough diurnal/shallow
instability to produce isolated to scattered rain/snow showers
(maybe graupel?) mainly near the western and southern mountains &
foothills (but these could reach Billings by late afternoon). Then
tonight as next wave approaches, we should see greater potential
for showers especially from Billings westward and southward
(30-50% chance). Shower coverage should increase Wednesday as the
trof passes thru. Given the steep lapse rates through the period,
the Beartooth Absarokas will see a few more inches of snow
(probability of 3+ inches is ~60%). Lower elevation precip will be
a tenth of an inch or less. Winds on Wednesday will remain breezy
but not to the extent of today. Expect 20-30 mph gusts tomorrow.

One thing to note is that with the dry boundary layer, wet bulb
zero heights will be low enough to produce some wet snow along and
near the foothills with any heavier shows tonight thru Wednesday.
This will not be necessarily impactful (per warm surface temps)
but may result in localized poor visibility. Something to watch if
you will be out and about.

We are entering a stretch of cooler than normal days. Look for
highs in the upper 40s and 50s both today and Wednesday.

JKL

Wednesday night through Monday...

Cyclonic flow over northeast MT will continue to bring periods of
precipitation to the region through Friday. Chances for at least
a tenth of an inch are most likely for the central and western
portions of the region through Friday evening. The chance of
precipitation for most of the region remains at around 30-50% with
the best time being the afternoon hours. With snow levels around
5000 ft during this same time period, the foothills have about a
50% chance of getting an inch of snow, with the mountains likely
to get a few inches. Ensembles are in agreement that ridging will
build in for the weekend allowing for warm and dry conditions.
Agreement between ensembles is also strong for a Pacific low to
enter the region Sunday night into Monday. However, there is
variance on the track of this system, so this will be something to
watch as that time approaches. There does appear to be a strong
push of moisture with above average precipitable water values.
Chances for at least a quarter inch of precip Monday look to be
around 25% for the region with precip chances likely to continue
through the week.

High temperatures will be in the 50s through Friday, warming into
the 60s/low 70s for the remainder of the period. TS

&&

.AVIATION...

Showers w/ local MVFR will shift eastward thru the remainder of
the night...ending at KBIL by 09z, KMLS by 13z and the Dakotas
border by 15z this morning. Today will be windy with VFR
prevailing. Look for westerly wind gusts of 25-35kts across lower
elevations, affecting all TAF sites. Winds will decrease by
evening. This afternoon through tonight, a weak disturbance from
the west will bring scattered rain/snow showers west of KMLS and
K00F. Mountains will be frequently obscured in snow showers. JKL

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Wed     Thu     Fri     Sat     Sun     Mon
-------------------------------------------------------
BIL 056 035/055 037/053 034/054 033/065 042/073 046/069
    2/W 23/W    35/W    34/W    11/U    02/W    34/W
LVM 050 029/049 033/049 030/052 030/063 039/066 041/064
    4/W 45/W    45/W    44/W    11/B    13/T    34/W
HDN 058 033/057 034/054 032/055 030/067 040/078 045/071
    2/W 23/W    37/W    34/W    11/U    02/W    34/W
MLS 057 035/058 035/052 032/052 031/062 041/076 047/069
    2/W 02/W    25/W    23/W    11/U    01/B    34/W
4BQ 057 033/057 034/053 032/053 031/064 040/078 047/068
    2/W 02/W    25/W    23/W    11/U    01/B    33/W
BHK 056 030/057 031/051 029/050 029/059 036/073 045/067
    3/W 01/B    25/W    23/W    11/U    01/B    34/W
SHR 056 030/053 030/052 029/051 027/064 037/075 043/067
    2/W 24/W    45/W    35/W    21/U    02/T    34/W

&&

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

&&

$$
weather.gov/billings