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FXUS65 KBYZ 221730
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
1030 AM MST Fri Nov 22 2024

.KEY MESSAGES...

- Low risk (10-20%) of light freezing rain this morning in
  Wheatland, Golden Valley, and Musselshell Counties. A glaze of
  ice is possible so heads up for morning travelers.

- Next best chance of precipitation across the area in the form of
  rain then snow arrives for most of the area Saturday evening
  into Sunday. Snow amounts will be light on the plains.

- Sunday and Monday will be cooler and the pattern will remain
  unsettled through the week.

&&

.DISCUSSION...

Today through Saturday...

Satellite imagery shows a ridge axis over the northern high
plains, troffing off the Pacific coast and resultant dirty SW flow
extending into our region. There is a Canadian cold front sagging
thru MT and Judith Gap is now reporting a north wind, as well as a
temp of 24F (down from 35F in the late evening). This post-frontal
cooling combined with potential for light precip associated with
a mid level warm front brings a low (10-20%) risk of light
freezing rain along the Musselshell valley (Harlowton and Judith
Gap to Ingomar) this morning from roughly 13-19z. Precip chances
are much greater north of our cwa today so at worst we are looking
at a light glaze of ice. Heads up for any morning travelers on
US-12 in this area.

Backdoor front will bring notably cooler temps today, even along
the western foothills where we expect the east winds to reach this
morning. Conceptually, this is a scenario that could advect low
stratus, but neither upstream obs nor recent models suggest this.
Something to watch. HRRR does show some fog development in the
upper Musselshell valley by early Saturday. Other than the warm
advection precip in our north today, it will be dry across the
region through tonight under this period of ridging as we await
the upstream trof.

Tricky wind forecast exists for Livingston over the next 30-36
hours. We are seeing gap gusts to 40 mph currently, and these will
linger thru ~15z, then the fropa will shift winds quickly to the
east. Some guidance has winds returning to the SW later today but
pressures suggest easterly winds should hold through this
afternoon and even tonight. This of course removes any risk of
high gusts. By Saturday afternoon there should at least be a few
hours where mixed SW winds are observed. 700mb flow up to near 40
knots suggests gusts near 50 mph are possible (60% chance).

Height falls w/ a Pacific shortwave will bring a 30-60% chance of
rain/snow showers over our west on Saturday, with highest chances
late in the day. Any precip for Billings should hold off until the
evening.

Temps today will range from the mid 30s north to lower 50s along
the foothills. Saturday should be a bit milder (40s to mid 50s)
in west/central parts in a pre-frontal regime, while the east and
far north hold in the 30s.

JKL


Saturday night through Friday...

The best chance of precipitation will be Saturday evening,
gradually becoming snow over lower elevations and tapering off
overnight through Sunday afternoon. The highest accumulations are
possible over the western mountains, with a 50% chance of at
least 6 inches of snow over the Absaroka/Beartooth mountains. Over
the plains, snow accumulations are expected to remain fairly
light, with the highest chance for locations west of Rosebud
county only around 20-40% for 1 inch or more of snow.

Brief ridging is expected to build in Monday before upper level
flow becomes northwesterly through the end of the week. With this
unsettled pattern, daily chances for light snow are possible. The
mountains have a 25-45% chance and lower elevations have a 10-25%
chance.

Highs will be in the 20s and 30s Sunday and Monday, increasing
slightly to the mid 30s to mid 40s Tuesday. More uncertainty
exists for the end of the week, although confidence is trending
towards cooler temperatures for Thanksgiving into the weekend.
From Billings east, there is a 50-80% (highest east) of highs at
or below freezing by Thanksgiving day. Archer

&&

.AVIATION...

18z TAF Update...
General VFR conditions will prevail through this evening. Chances
for localized fog/stratus (MVFR to local IFR) will increase after
midnight as surface/frontal inversion strengthens with easterly
upslope winds underneath. Can`t rule out light shower activity
this afternoon into this evening over western foothills, with more
likely precipitation potential over the mountains (occasional
obscuration). Do not expect this activity to change flight
categories over the lower elevations. KLVM will see persistent low
level wind shear, as the easterly surface winds will be shallow
through tonight with gusty (30kt) southwest winds over the top.
Expect any fog/stratus to lift around 17z Saturday. Chambers

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Sat     Sun     Mon     Tue     Wed     Thu
-------------------------------------------------------
BIL 038 023/040 022/032 012/034 019/042 021/038 018/033
    1/B 01/E    63/S    10/B    01/B    11/B    22/S
LVM 048 027/052 023/040 017/042 022/042 020/039 017/036
    1/B 05/W    73/S    10/U    12/S    21/B    22/S
HDN 041 020/040 019/031 009/033 014/041 018/037 014/032
    0/B 01/E    64/S    10/U    11/B    12/S    22/S
MLS 036 021/039 017/027 006/027 011/036 014/032 010/027
    0/B 00/B    21/B    00/B    00/B    01/B    11/B
4BQ 042 022/044 021/031 010/032 014/040 018/036 013/030
    0/B 00/B    11/B    10/U    00/B    01/B    11/B
BHK 037 015/034 014/026 002/026 006/035 011/032 007/025
    0/B 00/E    11/B    00/B    00/B    00/B    11/B
SHR 049 022/049 020/036 012/040 016/044 017/039 014/034
    0/U 00/B    44/S    10/U    01/B    12/S    22/S

&&

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

&&

$$
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