Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 231441
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
841 AM MDT Sat Mar 23 2024

.UPDATE...
Quick update to add some patchy freezing drizzle to portions of
our western zones...mainly Billings to Big Timber to Judith Gap
and nearby areas. This area is also being affected by areas of fog
down to a half mile at times. So rather dangerous travel this
morning. Soundings indicate the fog and drizzle will lift around
midday...so we expect the threat to decrease around noon to 100
PM. Road temps should warm by then as well to melt any patchy icy
conditions on roads. BT

&&

.DISCUSSION...

Saturday through Sunday Night...

.Key Messages...

... Significant winter storm on track to impact the region
starting tonight with much of Southeast Montana having a greater
than 50% chance of at least 6 inches of snow.

... Strong winds (30s kts) near the Dakotas border will bring the
potential for blowing snow impacts.

... Cold temperatures come in behind the storm with much of the
 area having a 30-50% chance of getting into the single digits
 Monday morning.

... Winter highlights will be changed with Winter Weather
 Advisories for locations west of Billings and the upgrade of
 many Winter Storm Watches to Winter Storm Warnings.

There are currently snow showers making their way across the
region north of I-90 near Miles City. These snow showers are
following the right entrance region of the 500mb jet. Looking at
the RAP mesoanalysis, there is also an area of frontogenesis
forcing these showers. This frontogenesis is due to 700mb
troughing to our east and west bringing an area of convergence
from northwesterly and southwesterly winds packing isotherms. A
pool of 700mb moisture is allowing this forcing to squeeze out
some light snow. These are expected to exit the region this
morning. Winds are currently out of the east with cold air and
higher pressure over the plains and lower pressure over the higher
terrain to the west. This is bringing cool and moist air into the
western reaches of the CWA leading to fog on some of the cameras,
especially Bozeman pass. This is expected to clear by about 15Z
today.

Switching to our winter storm, I will mostly focus on some of the
changes that have occurred. The storm is close enough in time
that we can start using high resolution models. These models are
depicting a dry slot lasting longer, pushing the onset of
precipitation back for some locations in the far southeast leading
to lower snowfall totals. This change was shared with the long
range models as well. Snowfall totals have also lowered for some
locations west of Billings due to winds turning more northerly
sooner than previous model runs. There are some potential concerns
for snowfall totals for Billings and other places that may get
downsloped with a more northerly wind. It increasingly looks like
strong winds for areas near the Dakotas border will not perfectly
align with the period of heaviest snow. The most likely scenario
at this point is winds will be strongest, and blowing snow impacts
the greatest, early before decreasing throughout the event.
Looking at a historical context, CIPS analogs paints 4-8 inches of
snow across the area which aligns well with what is expected from
this system.

High temperatures today will be in the 40s for most before
temperatures fall into the 20s for tomorrow. Low temperatures
will be in the high teens to low 20s tonight before dropping into
the single digits and low teens Monday morning. Torgerson


Monday through Friday...

The upcoming winter storm will have exited, but lingering cyclonic
NW flow will bring periodic light snow showers Monday and
Tuesday, mainly over the mountains and close to the foothills.
Temps on these days will remain below normal, but a warming trend
will begin on Tuesday. In fact, sub-zero low temps are a good
possibility in our far east Monday night w/ a surface high in
place and an expectation of clear skies. There is a greater than
50% chance of low temps falling below zero in Fallon & Carter
Counties. With fresh snow cover, cannot rule out lows near zero
further west as well.

Building ridge should finally allow for more aggressive downslope
warming on Wednesday. Look for upper 40s and lower 50s most
places...but only mid 30s near Baker. Wednesday and Wednesday
night should be dry periods for most of the forecast area.

Another deepening trof over the western CONUS is anticipated for
Thursday and Friday, thus resulting in increasing chances of
rain/snow for us through late week (rain initially, then possibly
wet snow Thursday night & Friday as we advect colder Canadian
air). Plenty of uncertainty exists here, but the overall pattern
favors a period of troffing and below normal heights from Friday
through the weekend. After a seasonably mild Thursday, look for
temps to fall back to the 30s/40s for Friday-Saturday. A "too
early" look at nbm probabilities shows a 20-40% chance of at least
an inch of snow at lower elevations in the 48hr period ending
Friday night. At the very least, it will be another dose of snow
for the high elevations.

JKL
&&

.AVIATION...

Widespread low stratus, and upslope fog near the foothills, will
result in poor flying weather across the region today and tonight.
Expect persistent MVFR to LIFR conditions (VLIFR is possible in
the densest fog). Some patchy light freezing drizzle is also
possible within the fog through about 19Z including the KBIL
vicinity. Light snow will impact KMLS- KBHK this morning.
Tonight, snow will develop across much of the area as a winter
storm system moves in from the west. Mountains will be obscured.
BT/JKL

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Sun     Mon     Tue     Wed     Thu     Fri
-------------------------------------------------------
BIL 040 021/026 014/026 011/037 023/052 032/055 032/047
    4/S 9+/S    52/S    11/B    10/B    14/O    54/O
LVM 044 023/031 014/029 014/042 027/050 034/051 030/046
    5/O 98/S    33/S    13/J    21/N    37/O    64/O
HDN 046 020/029 010/027 007/036 018/053 027/056 030/047
    2/R 9+/S    72/S    11/B    10/U    14/R    64/O
MLS 039 020/025 010/023 002/026 009/041 021/048 026/039
    3/E 9+/S    51/E    00/B    00/U    01/E    43/S
4BQ 047 022/029 012/023 004/031 015/049 025/056 029/044
    0/B 8+/S    61/E    00/U    00/U    01/B    43/O
BHK 032 016/023 006/019 905/022 003/037 016/041 020/036
    7/S 9+/S    71/E    00/U    00/B    01/B    43/S
SHR 051 021/031 011/025 005/038 020/052 027/059 029/047
    1/B 7+/S    61/E    00/B    10/U    13/R    64/O

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Warning in effect from 6 PM this evening to
      midnight MDT Sunday night FOR ZONES
      29>33-36-37-57-58-138-169-173-235.
     Winter Weather Advisory in effect from noon today to midnight
      MDT Sunday night FOR ZONES
      34-40-42-56-63>66-139-141-170-172-228.
     Winter Weather Advisory in effect from midnight tonight to
      midnight MDT Sunday night FOR ZONE 171.
WY...Winter Weather Advisory in effect from midnight tonight to
      midnight MDT Sunday night FOR ZONE 198.
     Winter Weather Advisory in effect from 6 AM Sunday to
      midnight MDT Sunday night FOR ZONE 199.

&&

$$
weather.gov/billings


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