Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 221058
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
458 AM MDT Fri Mar 22 2024

.DISCUSSION...

Through Saturday...

Scattered snow showers continue along a line from roughly
Livingston to Columbus, Billings and Sheridan...and there is also
some light snow near Hysham and Forsyth. The band of snow showers
closer to the foothills seems to be tied to a region of moist
instability from 750-600mb. We are seeing heights begin to slowly
rise, and flow aloft should trend toward anticyclonic, which
should allow these snow showers to diminish over the next several
hours. Meanwhile, warm advection along a mid level baroclinic zone
will produce some light snow north and northeast of Billings
through the morning and early afternoon. It seems as if the
expanding echoes in Treasure and northern Rosebud are in response
to this next phase of forcing. This is something to watch as
locations across our north have a deeper dendritic layer to work
with. Previous shift had a good handle of the evolution of pops/wx
this morning so have made minimal changes. As temps are in the
20s, the morning commute will be impacted by locally slick roads,
though snow accums from this point forward should be an inch or
less. Localized fog is a good bet as well.

Snow will taper from south to north today but cold air will remain
in place as surface high pressure remains in place north/east of
the mountains. Next ribbon of warm advection light snow will occur
across our north late tonight and Saturday morning. Again, snow
accums should be limited to an inch or less. By Saturday afternoon
we will see increasing chances of snow in our west as large scale
ascent moves into the region per approaching Pacific trof (our
main weather-maker this weekend). Temps on Saturday will range
from near 30F in the NW to the upper 40s toward Sheridan &
Broadus (a region which may see a brief surge of warmer temps
ahead of the trof, but models are likely overdone a bit here).

The probability for an inch of snow today and again late tonight
into Sunday are 20-40% across our north from roughly Roundup to
Miles City and Baker. We may also see fog in upslope areas again
tonight (20-30% chance).

JKL

Saturday night through Friday...

.Key Messages...

... Significant winter storm hitting the area Saturday night into
Sunday with warning level impacts likely (>60%) across much of
the area.

... Cold temperatures come in behind the snow storm with
widespread single digit lows and subzero lows possible (50%) for
locations along the Dakotas border Monday night.

... Wednesday through the rest of the week we return to more
seasonable temperatures.
The most significant change in the forecast has been the southward
shift of the band of heavy snow. Locations with a >50% chance of 6
inches or more of snow now includes much of the forecast area as
opposed to the more northern and eastern locations previously
favored. The same basic ingredients for this storm are still in
place with a trough to our west putting us in southwest flow aloft
and a large Colorado Low to our south bringing in Gulf moisture
with strong easterly winds. By Sunday we will enter a region of
increased Q vector convergence creating conditions for favorable
synoptic lift. Sunday afternoon into Sunday night is when lower
levels cool enough to create the best conditions for a deep DGZ
and the best timeframe for heavy snow. Winds along the border with
the Dakotas have come down as well, lessening the potential for
blizzard or near blizzard conditions. However, winds along the
border still have a chance (>70%) of gusting over 40mph leading to
significant blowing snow potential. Due to the 850mb winds being
strong out of the east and only light winds out of the north,
there will be limited upslope potential for the mountains keeping
snow totals in line with the lower elevations. The
Beartooth/Absaroka mountains have a 50-70% chance of seeing
greater than 8 inches of snow with the Bighorns only seeing 30%
chance for seeing similar amounts.

After the snow moves out of the area, a trough will make its way
down the lee of the Rockies from Canada bringing cold temperatures
25 degrees below average in some places. High tempeatures Sunday
and Monday will be in the 20s for most. Low temperatures will be
in the single digits to low teens Monday morning. Tuesday morning
will be the coldest with single digits for most and locations
along the border with the Dakotas having a 50% chance of seeing
temperatures below zero. By Wednesday ensemble clusters are in
good agreement that we will be sandwiched between troughing to the
east and west putting us in slight ridging and northwest flow
raising temperatures. There is still uncertainty in the strength of
the ridging with the ECMWF depicting a stronger ridge and
therefore higher temperatures, while the GFS is favoring a weaker
ridge and lower temperatures. Either way we will begin to warm
with some of our south central regions getting 50% probabilities
for exceeding 50 degrees by Wednesday. Torgerson

&&

.AVIATION...

Poor flying weather expected across much of the region today and
tonight, with areas of low stratus, localized fog and scattered
mainly light snow showers. Expect MVFR-IFR during much of this
time, but there should be brief improvement to VFR this afternoon
especially close to the foothills (i.e. KLVM & KSHR). Mountains
will be obscured at times. JKL

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Sat     Sun     Mon     Tue     Wed     Thu
-----------------------------------------------------------
BIL 035 025/036 021/026 013/027 009/036 019/045 027/043
    7/S 35/S    +9/S    53/S    11/B    11/B    35/S
LVM 040 027/038 023/029 013/032 016/043 025/048 031/044
    2/S 27/S    97/S    32/S    22/S    23/O    56/S
HDN 036 023/042 020/028 010/028 006/036 014/048 023/044
    8/S 33/S    +9/S    73/S    11/B    11/B    25/S
MLS 029 022/035 019/023 010/021 002/025 006/035 016/037
    6/S 54/S    99/S    61/E    00/B    00/B    13/S
4BQ 035 024/045 021/028 010/023 002/030 011/043 022/044
    3/S 31/B    89/S    72/S    00/B    00/B    13/S
BHK 029 016/031 014/023 007/020 901/023 003/034 015/039
    2/S 65/S    9+/S    72/S    00/B    00/B    12/S
SHR 042 024/049 021/031 010/028 008/038 018/049 025/047
    3/S 12/B    89/S    62/S    11/B    11/B    25/S

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Watch in effect from Saturday evening through
      Sunday evening FOR ZONES 29>34-36-37-42-57-58-138-169-173-235.
WY...None.

&&

$$
weather.gov/billings


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