579
FXUS65 KBYZ 022117
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
317 PM MDT Thu May 2 2024

.DISCUSSION...

Tonight through Saturday night...

500 mb low centered over southern Saskatchewan/northeastern MT is
producing northwesterly and cyclonic flow over our area late this
afternoon. This pattern favors marginal instability and associated
scattered showers (20-60% chance) and isolated thunderstorms (20%
chance). Any rainfall amounts should be light, generally less
than 0.10 inch. The pattern also favors general windy conditions
with northwesterly winds 15-25 mph gusting to 40 mph through early
this evening. A few isolated gusts to 45-50 mph are possible from
showers and thunderstorms.

Near and after sunset tonight, the lower atmosphere will
stabilize with the loss of solar heating. The increased stability
will cause much of the shower/storm activity and general windy
conditions to diminish tonight, with a few exceptions. There will
be another 500 mb disturbance that will move southeastward over
MT tonight and produce isolated to scattered showers (20-50%
chance, greatest near Judith Gap) for areas north of Big Timber-
Billings-Colstrip.

An area of concern is the Red Lodge area where the higher
resolution models are projecting a period of snow from late this
afternoon into tonight, ending around midnight MDT. A combination
of ascent from a weak 500 mb disturbance, low-level winds turning
northerly favoring upslope precipitation, and mid-level
frontogenesis support about 1 to 2 inches of snow in Red Lodge
tonight. The mid-level atmosphere will be conditionally unstable
which could support heavier snow amounts if the wind direction
were to favor upsloping over a deep enough layer, but the depth
of the upslope appears unimpressive at this time. So, currently
not expecting much in the way of impacts...but will need to be
monitored.

On Friday, the 500 mb low will be over the northern Plains with
northwesterly flow over our area. Instability looks weaker on
Friday, as mid-level temperatures rise a bit and mid-level lapse
rates decrease with the upper low moving farther away from our
area. Isolated to scattered showers (20-40% chance) will occur but
areal coverage should be less than that of today.

Friday night into Saturday night, 500 mb shortwave ridge will move
over the region, bringing dry weather. In addition, low-level
southeasterly flow on the western side of surface high pressure
centered over the northern Plains will cause warming on Saturday
via warm air advection and compressional warming. While the
shortwave ridge will dominate our weather during this period, it
will be moving eastward. So, for Saturday night, the ridge will
have moved far enough eastward that an upper low will begin to
affect the far western part of our area with the mountains and
foothills in Park County, MT having a 15-20% chance of showers
(rain/snow showers in the mountains).

Low temperatures will generally be in the 20s and 30s tonight and
Friday night and 40s Saturday night. High temperatures will
mainly be in the upper 40s to 50s Friday then 60s Saturday. RMS

Sunday through Thursday...

The extended period remains active with the potential for a
dynamic weather system impacting the region early next week from
Sunday into at least Wednesday. Potential impacts include strong
winds, moderate to heavy precipitation, and cooler temperatures.
Note: we are NOT looking at a significant rain on snow event
during this time as snow is expected in the mountains. However,
these conditions will likely create hazardous outdoor conditions,
especially for young livestock. Make sure to stay up to date with
the latest forecast as details will continue to change.

Sunday will start out dry and warm with highs in the upper 60s to
lower 80s. In the east, where the warmest temperatures are
forecast, strong southeasterly winds will develop by the
afternoon, with the NBM giving a 60-90% chance for gusts of 40 mph
or more. Along with this, chances of precipitation, with a rumble
of thunder or two, will increase across the region Sunday
afternoon and evening (40-80% chance, highest over the mountains).
This will mark the beginning of a potentially active week ahead.

This active weather will come from a dynamic upper low that is
forecast to move into the western CONUS this weekend and up
through Montana and the Dakotas Monday into Wednesday. Uncertainty
remains on how long the impacts from this low stick around, but
cluster analysis suggests continued lower heights over the Pacific
NW will allow for impacts to remain through at least mid- week.
Uncertainty also remains in the initial track of the low, which
plays a major role in the potential impacts across our region. If
the track of the low follows a favorable path, we could be in for
a good event with rain, snow and wind across the region. At this
time, the NBM gives a 60-80% chance for wind gusts of at least 40
mph Monday and Monday night across the area and a 70-90% chance
Tuesday (highest chances in the east). The NBM also gives a 50-70%
chance of at least a half inch of rain across the region Sunday
through Wednesday morning. One thing to note, these probabilities
increased slightly over the last 24 hours. As far as snow goes, we
are expecting mainly snow in the mountains as snow levels drop
quickly Sunday evening into Monday. With the main snow pack
estimated to be above 7000 feet and snow levels having a high
chance of dropping below that, we are NOT expecting a rain on snow
event this time around. While rain is forecast in the east with
the warmer temperatures, dynamic cooling with the deep upper low
could cause temperatures to remain cooler than expected Tuesday
and Wednesday. With this, there are a few members in the ensembles
putting impactful snow in the east, likely due to them picking up
on cooler temperatures. This will be something to watch going
forward. Arends
&&

.AVIATION...

Scattered showers and isolated weak thunderstorms will continue
to impact the region this afternoon before diminishing in coverage
this evening. This activity has the potential to produce local
MVFR conditions, a combination of rain, snow and graupel, and wind
gusts up to about 40 kts. With the light snow showers, frequent
mountain obscurations will occur through the evening into tonight.
Along with the showers, the 20-30 kt NW wind gusts occuring today
will decrease this evening. Expected isolated showers to impact
the region once again Friday. Arends/JKL.
&&

.PRELIMINARY POINT TEMP/POPS...

    Fri     Sat     Sun     Mon     Tue     Wed     Thu
-----------------------------------------------------------
BIL 031/053 031/067 043/075 045/055 042/055 041/053 039/057
    22/W    00/U    03/R    67/R    34/R    46/R    56/R
LVM 028/053 028/064 041/066 038/049 037/050 035/050 035/055
    31/B    00/B    16/T    88/R    45/O    56/O    56/O
HDN 029/053 027/070 042/080 044/057 040/056 039/053 038/057
    22/W    00/U    03/R    67/R    54/R    56/R    56/R
MLS 031/051 028/065 045/080 048/062 040/051 038/052 039/057
    41/B    00/U    01/N    67/T    65/R    55/R    54/R
4BQ 029/051 028/068 045/080 048/060 040/054 038/050 038/055
    31/B    00/U    01/N    57/T    64/R    55/R    44/R
BHK 028/050 026/063 039/072 048/062 038/052 035/052 034/055
    51/N    00/U    01/N    67/T    75/R    55/R    44/R
SHR 026/051 026/067 041/076 041/055 038/057 037/052 034/054
    32/W    00/U    02/R    67/T    44/R    55/O    56/R

&&

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

&&

$$
weather.gov/billings