961
FXUS65 KBYZ 020313
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
913 PM MDT Tue Apr 1 2025

.KEY MESSAGES...

- Periods of mountain and foothill snow through Wednesday. Several
  inches of snow accumulation can be expected (8 to 16" mountains;
  2 to 5" foothills), with light snow accumulations over the lower
  elevations. Main impacts will be slushy/slick roads and reduced
  visibility in snow, mainly over the mountains and foothills.

- Clipper system brings next shot of lower elevation snow and
  colder temps Thursday night and Friday.

- High confidence of building high pressure this weekend; expect
  warmer and dry conditions into next week.

&&

.UPDATE...

Updated the forecast to adjust PoPs and cloud cover to radar
imagery and latest model data. There is a lull in the
precipitation from about Park County, MT east/southeastward to
Sheridan County, WY this evening. This break in the precipitation
will end overnight as bands of rain and snow move southward into
the area. Did lower some precipitation amounts for this evening
but the rest of the precipitation forecast looks on track.

Also, added some fog to the forecast, first over southeast MT,
especially near Treasure, Big Horn and Rosebud Counties (Lame Deer
Divide MT DOT web cam shows fog) this evening, then to much of the
area after midnight MDT into Wednesday morning. HRRR suggests the
more persistent fog should occur near eastern Big Horn County
tonight. Elsewhere, fog should be patchy. Any fog should diminish
from north to south during the day Wednesday. RMS

&&

.DISCUSSION...

Through Thursday afternoon...

A large upper trough situated over the western US continues to
bring southwest flow and upper diffluence over the region. Within
this large upper trough, an embedded shortwave trough is moving
northeast through Wyoming this afternoon. As this shortwave moves
into the Dakotas this evening and night, it is expected to
strengthen into an upper level low. While these upper level
features are the main driving force for the forecast, the broad
nature of the large upper trough continues to introduce
uncertainty to the precipitation forecast through Wednesday.

With that said, a broad north-south band of precipitation is
currently situated over south- eastern Montana, east of Billings,
this afternoon. By this evening into tonight, precipitation is
expected to build back in over south-central Montana as the upper
level low develops in the Dakotas. This will also bring wrap
around precipitation to areas in far eastern Montana. As we go
through tonight into Wednesday, the area of precipitation in
south-central Montana is expected to sink south into the mountains
and foothills south of Billings before tapering off mid-day
Wednesday. The wrap around precipitation in far eastern Montana
also looks to taper off through mid-day Wednesday. After this,
unstable northwest flow looks to keep isolated to scattered
rain/snow showers in the forecast for south-central Montana
through Wednesday evening. As far as precipitation type goes for
this event, all snow is expected in the mountains. Over the lower
elevations, a rain/snow mix can be expected during the day, with
mostly snow expected at night.

With this event, the overall precipitation totals have remained
similar to last nights forecast. Currently, precipitation amounts
of 0.25 to 0.75 inches are forecast from Harlowton to Billings to
Sheridan, with much less precipitation expected around Miles
City, Baker, and Ekalaka. While the western foothills will
continue to be downsloped most of today, around 0.15 to 0.50
inches are still forecast in this region. With regards to snow, a
few inches of snow are possible for foothill locations, with
generally an inch or less for the lower elevations. Greatest
accumulations will be on grassy surfaces and near the mountains.
Several inches are possible in the mountains with up to 16 inches
total in the Beartooth- Absaroka and Crazy mountains, and up to 12
inches total in the Bighorn and Pryor mountains. With that said,
the winter weather products across our area remain in good shape.

Look for temperatures to remain in the 40s Wednesday and 40s to
lower 50s Thursday. After a break in the precipitation Wednesday
night through Thursday morning, another weather system will bring
the chance of precipitation back to the region Thursday evening.
See the long term discussion for more information. Arends

Thursday night through Tuesday...

Western U.S. troughiness continues over the area Thursday night
and Friday, but will become more organized during the period. The
N portion of the trough will affect the forecast area as it moves
E. Decent 700 mb frontogenesis drops SE through the area Thursday
night through Friday morning. Surface cold front moves S through
the area Thursday night, or Thu. night through Friday morning,
with ECMWF having the fastest movement. QPF amounts and placement
differed between the models, but all of them indicated upslope
flow. NBM PoPs were a reasonable solution based on the above.
Expect moderate to high PoPs over the area Thu. night with a
rain/snow mix changing to all snow. PoPs were in the 20% to 60%
range Friday morning, with the highest PoPs over Sheridan County.
The probabilities of 2 or more inches of snowfall were 20-30% over
KBIL and KSHR, with 40-90% over the upslope areas. Chances for at
least 6 inches over the NE Bighorns were 10-30%. Precipitation
chances decrease quickly Fri. afternoon.

With a strong pressure gradient and the frontal passage Thu.
night, have increased wind speeds/gusts by 30% toward the NBM 90th
percentile. Cold advection over the E through the day on Friday
will create breezy conditions in this area. Lows Thu. night will
be in the 20s with highs on Friday below normal in the mid 30s to
lower 40s. There was a 30-40% chance of highs reaching only 32
degrees W of KBIL and over KSHR.

Region will be on the E side of an upper ridge on Saturday under
northerly flow. This pattern continues on Sunday. Expect dry
weather and a warming trend with temps in the 50s to lower 60s on
Sunday. Upper ridge will be over the forecast area on Monday, but
Clusters differed in the depiction of the ridge. Temps will
continue to moderate with dry weather over the area. Clusters had
either SW flow aloft or upper ridging on Tuesday. NBM gave some
low PoPs over and near the mountains in the afternoon.

Keep an eye on the forecast for any changes to the system early in
the period and for changes late in the period with the
uncertainty in the pattern. Arthur

&&

.AVIATION...

Band of rain showers with some snow showers will affect areas from
KBIL to KSHR E through this evening. There will be scattered
rain/snow showers W of KBIL. Scattered to widespread rain and snow
showers continue overnight through Wednesday 18Z, with the best
chances from KBIL S. Expect MVFR to IFR conditions in the
precipitation. Surface wind gusts will be in the 30s kts W of KBIL
through this afternoon. Expect widespread mountain obscurations
through the period. Arthur


&&

.PRELIMINARY POINT TEMP/POPS...

    Wed     Thu     Fri     Sat     Sun     Mon     Tue
-----------------------------------------------------------
BIL 035/047 029/050 028/041 023/055 032/061 035/068 040/068
    78/W    24/W    73/S    10/U    00/U    00/U    01/B
LVM 030/044 027/046 026/039 021/051 031/058 035/063 038/061
    67/W    24/J    73/S    10/U    00/U    00/U    12/R
HDN 032/047 027/051 027/042 020/053 028/061 031/068 036/069
    88/W    24/W    73/S    10/U    00/U    00/U    01/U
MLS 033/045 027/050 026/039 021/051 029/056 030/066 037/069
    33/W    13/W    51/B    00/U    00/U    00/U    00/U
4BQ 032/042 027/050 028/038 020/049 029/054 029/064 036/067
    66/W    12/W    63/S    10/U    00/U    00/U    01/U
BHK 028/040 024/048 023/038 017/047 024/050 024/060 033/065
    55/J    12/W    62/S    10/U    00/U    00/U    00/U
SHR 026/041 022/047 023/036 014/048 025/055 028/064 033/063
    58/W    24/W    66/S    21/U    00/B    00/U    01/U

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory in effect until 6 PM MDT Wednesday
      FOR ZONES 40-56-63>66-141-171-172-228.
     Winter Storm Warning in effect until 6 PM MDT Wednesday FOR
      ZONES 67-68.
     Winter Weather Advisory in effect until 3 PM MDT Wednesday
      FOR ZONE 138.
WY...Winter Weather Advisory in effect until 6 PM MDT Wednesday
      FOR ZONE 198.
     Winter Weather Advisory in effect until 3 PM MDT Wednesday
      FOR ZONE 199.

&&

$$
weather.gov/billings