551
FXUS65 KBYZ 191024
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
324 AM MST Sun Jan 19 2025

.KEY MESSAGES...

- Another round of snow for areas along and south of Interstate 90
  today into this evening. Greatest totals down along the southern
  mountains and foothills where 2 to 5 inches of snow is possible.

- Very cold temperatures through Tuesday morning. Highs will range
  from single digits below to teens above zero (coldest east).
  Monday morning wind chills are expected to reach -20 to -40
  degrees.

- High winds possible in the foothills Monday night through
  Tuesday evening along with areas of blowing snow. Much warmer
  temperatures beginning on Tuesday.

- Next chances for snow will be midweek east and south of Billings
  with areas of blowing snow, then late in the week into the
  weekend for much of the area.

&&

.DISCUSSION...

Today through Monday afternoon...

Temperatures had dropped into the single digits above zero, to
near 20 degrees below zero over the far east as of early. Weak
energy and moisture continued to produce flurries for central and
western areas at times. Another cold day can be expected, with
high temperatures in the teens over the west to the single digits
below zero over the east today as the coldest air of the season so
far settles over the region. A shortwave dropping into the area
from the north today will bring a period of snow to areas mainly
along and south of Interstate 90, starting late morning to mid day
and continuing into the evening. While most areas will likely see
an inch or less of snow accumulation, northerly upslope areas
down in the southern foothills and mountains will see greater
totals. Have issued a Winter Weather Advisory for the Beartooth
and Red Lodge foothills from 9am this morning through 10pm
tonight, where 2 to 5 inches of snowfall are possible.

Drier conditions will move into the area overnight, with
decreasing clouds for most areas. Temperatures will drop into the
teens to lower 20s below zero overnight, with widespread wind
chill values of 20 to 40 below zero by Monday morning. The Cold
Weather Advisories remain in good shape and will make no changes.
High temperatures are forecast to range from the lower teens over
western areas, to the single digits below zero over eastern areas
on Monday. If you must go outside, make sure to dress for the
temperatures during this time. STP

Monday night through Sunday...

An unsettled pattern will be over the region for the extended
period. Brief shortwave ridging will slide SE through the forecast
area Monday night. By 12Z Tuesday, NAEFS had 700 mb winds from the
WNW at 30-35 kt, while the GFS had 45-50 kt. GFS continued to run
stronger with 700 mb winds through 18z, then by 00Z both models
had 40-50 kt. This pattern sets up a strong pressure gradient that
favors high winds along the 191 corridor and over KLVM/Nye. GFS
had a 27 mb pressure gradient between IDA-LWT by 12Z Tue. Gradient
weakens to 18 mb by 00Z Wednesday, as a shortwave trough moves SE
into the area. Upper trough exits the area late Tue. night/early
Wednesday with timing differences between the models. SREF had
steep lapse rates Tue. night which will interrupt the gap flow and
create breezy conditions across the entire forecast area, but
high winds are not expected. Local studies showed a 60-70 percent
chance of high wind warning conditions for KLVM, K6S0 and K3HT
before Tue. night. Thus have issued a High Wind Watch for
KLVM/Beartooth Foothills and N. Sweet Grass from 00Z Tue. thru 06Z
Wednesday. Also issued a Watch for Wheatland County, Judith Gap
and the Melville Foothills from 06Z Tue. to 00z Wednesday. A low
chance of snow moves into areas E and S of KBIL with the trough
Tue. night and blowing snow is possible in these areas.

On Wednesday, chances for snow will be moderate E and S of KBIL
due to the trough. It will be breezy across the entire area and
blowing snow is likely in the E and S. Thursday looked dry under
upper ridging, then a trough approaches the area on Friday. PoPs
increase Thu. night into Friday. PoPs continue Sat. into Sat.
evening as the trough crosses the area. Sunday looked mainly dry
as anticyclonic flow moves into the area. Regarding snowfall
amounts, there was a 20-30% chance of at least 2 inches of snow
over the central and W each 24 hr period from 12Z Fri.-12Z Sat.
and from 12Z Sat.-12Z Sunday.

As for temperatures, Mon. night still looked unusually cold
compared to model climatology in the SE. EFI had values of .8-.9
to support this. NBM had a 90-100% chance of temps at or below
zero in the E, and a 90% chance of temps at or below -10 degs at
KBHK. That being said, forecast lows range from around -16 in the
far E to 5 to 10 degs in the W. Still looking at a warmer Tue. and
Wed. with highs in the mid 20s to mid 30s. Thursday and Friday
looked a little warmer than Tue. and Wed., before temps drop into
the 20s for the weekend due to the system. Arthur

&&

.AVIATION...

VFR will prevail for the rest of the night with some mid cloud
from KBIL W. Light snow will move SE into the area from KBIL to
KSHR W by 17z today and will be mainly out of the area by 06z
Monday. Expect mainly MVFR conditions with the snow, but localized
IFR is possible. Conditions will gradually improve to VFR after
06Z Monday. There will be fog in the vicinity of KMLS this
morning. Patchy fog is possible in the E after 06Z Monday. Arthur

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Mon     Tue     Wed     Thu     Fri     Sat
-------------------------------------------------------
BIL 010 910/010 001/030 020/034 016/035 023/036 016/028
    6/S 20/U    00/N    11/N    00/B    23/S    42/S
LVM 016 912/012 006/030 015/031 015/038 023/036 014/026
    4/S 30/N    00/N    10/B    01/N    24/S    43/S
HDN 007 915/008 908/032 020/034 010/035 018/037 013/028
    3/S 10/U    00/E    33/S    11/B    24/S    43/S
MLS 001 915/903 913/028 021/028 010/029 017/033 014/024
    0/U 00/I    01/E    34/S    11/B    22/S    21/B
4BQ 002 915/000 911/030 022/027 013/029 018/034 015/026
    0/B 00/U    00/E    35/S    21/B    22/S    32/S
BHK 902 923/907 916/026 017/025 010/026 013/031 011/022
    0/I 00/I    01/N    35/S    21/B    11/Q    11/E
SHR 011 916/005 910/036 015/029 011/035 015/038 011/026
    5/S 30/U    00/B    24/S    10/B    13/S    54/S

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Cold Weather Advisory in effect from 5 PM this afternoon to
      noon MST Monday FOR ZONES
      29>31-34-40-42-56>58-63-65>68-138-139-141-169>173-228-235.
     Cold Weather Advisory in effect until 11 AM MST Tuesday FOR
      ZONES 32-33-36-37.
     Winter Weather Advisory in effect from 9 AM this morning to
      10 PM MST this evening FOR ZONES 56-66.
     High Wind Watch in effect from Monday evening through Tuesday
      afternoon FOR ZONES 63-172-228.
     High Wind Watch in effect from Monday afternoon through
      Tuesday evening FOR ZONES 65-66-141.
WY...Cold Weather Advisory in effect from 5 PM this afternoon to
      noon MST Monday FOR ZONES 198-199.

&&

$$
weather.gov/billings