964
FXUS65 KBYZ 040327
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
927 PM MDT Mon Jun 3 2024

.UPDATE...

Reports of whiteout conditions on the highest portions of Beartooth
Highway have resulted in MTDOT closing the pass on the Montana
side this evening. Expect an additional 3 to 5 inches on the pass
tonight, along with strong wind gusts around 50 mph and a few
evening thunderstorms. Near whiteout conditions are likely to
persist after snow ends late tonight, likely into the day Tuesday.
Freezing levels drop to around 7500 feet overnight and
temperatures on top of the pass look to be in the mid 20s tonight.
Put out a winter weather advisory for this area until 9 am
tomorrow morning.

Line of showers and thunderstorms has traversed the forecast area
this afternoon/evening. winds gusting mainly in the 30 to 50 mph
range have been the main impact from this activity, with a few
gusts over 50 mph. Expect this activity to shift into the Dakotas
by midnight. Additional light shower activity will shift through
the area tonight, before ending tomorrow morning as the stronger
downslope synoptic winds develop. A windy day remains on tap for
Tuesday with some strong gusts likely in the western foothills.
Going wind highlites are in good shape, no changes planned to
those this evening. Chambers

&&

.DISCUSSION...

Rest of Today through Wednesday...

Satellite imagery showed a strong upper trough pushing into the
northern Rockies from Washington state while several minor
perturbations could be seen in the W/SW flow over Montana. Sct
showers and some thundestorms had developed over SW Montana and
were spreading east into the central sections of the state.

Upper low will track across Canadian border and push/drag cold
front across our CWA this evening providing forcing for
convection. Look for frontal passage between 7 pm and 9 pm at
Billings shifting winds to NW with increasing chance of
showers/thunderstorms along this boundary as it pushes E/SE.

Latest analysis indicated around 500 J/kg CAPE values over our
western and central zones attm which are progged to possibly
reach over 750 J/kg by evening as convection spreads into our CWA.
This is sufficient for some stronger thunderstorms capable of
producing brief heavy rain and gusty winds early this evening.
A few hundredths of an inch of QPF is expected for most
locations. However, higher amounts are possible with stronger
cells, with some local spots seeing 0.1-0.2". Main threat though
seems to be local wind gusts 50-55 mph early this evening in our
west (Billings west to Livingston) associated with cells along
cold front.

The cold front is expected to depart the region after midnight
with the upper low pushing into the Dakota/SW Saskatchewan area
overnight. Strong subsidence associated with a powerful 125kt
250mb jet will fill in behind the upper low over our western
zones. Corresponding 700mb winds will increase across our western
zones. Low level lapse rates are progged to be 6.5-8 C/km creating
a mix down scenario Tuesday. Wind is expected to increase early
Tuesday and spread east as we mix out with diurnal heating. The
strongest winds are expected in our western foothills. We have
upgraded our high wind watch to a warning, and also added a wind
advisory from Livingston to the Beartooth foothills. Keep in mind,
high winds like this are not typical this time of year (more of a
Fall and Winter feature), so there is uncertainty how this will
play out. Here is a breakdown of wind potential per each unique
section of our CWA.

Wheatland County (Harlowton vicinity)...Forecast soundings suggest
a very shallow weak inversion forms after midnight which may delay
onset of strong winds...but we could still see strong winds as
early as midnight. Strongest will be during the middle to latter
part of Tuesday. Winds may back off Tuesday night before
increasing again Wednesday as even strong 700mb winds develop
overhead. Models all want to hit strongest gusts (60-65 mph)
Tuesday...but strongest 700mb winds are Tuesday night into
Wednesday but may not be as bad due to a somewhat more shallow
mixing layer.

Big Timber Vicinity...Strongest winds expected Tuesday with
diurnal heating, but strong winds may continue Tuesday night into
Wednesday morning as 700 mb speeds are even stronger during this
time frame (60-70kts). Again, significant uncertainty with onset
and duration of winds (will it be that strong into Wednesday?).

Livingston Area...Wind Advisory from 600 AM to 1200 AM Wed. Wind
directions (westerly) do not favor true gap flow nor does the
seasonality. However...very strong 850-700mb winds with deep
mixing per Bufkit soundings on both GFS/NAM suggest max wind gusts
50-60 mph a good bet (60 mph Prob 55%). Wind gusts should peak
midday. Wednesday does not look as favorable as 700mb wind max is
a little further north and mixing not as deep...but gusts 35-45
mph still expected. This will need to be monitored though...in
case 700mb wind forecast shifts a bit further south on subsequent
model runs.

Eastern Plains...Biggest question mark. We may see some locally
strong winds this evening and overnight with frontal passage and
some showers around (gusts 45-50 mph). Look for brisk winds
Tuesday, increasing by Tuesday night. Powerful 700mb wind max over
east central Montana late Tuesday night into Wednesday. We
currently expect sub warning winds (gusts 45-55 mph) from Rosebud
eastward on Wednesday. Strongest will be Wednesday over Baker
vicinity (Prob 25% for 60 mph gust at Baker).

The downslope winds and subsidence will mean dry conditions
Tuesday through Wednesday. Highs will be in the 70s while
overnight lows range from 40s tonight to mid 50s Tuesday night.
BT


Wednesday Night through Monday...

The long term will generally see a calm pattern persist with above
average temperatures and dry conditions. Thursday and Friday have
good model agreement that ridging will be over the region bringing
temperatures in the high 70s to mid 80s. Once we get into the
weekend, there is more uncertainty in the WPC clusters. For
Saturday, about 50% of the clusters have ridging remaining in
place and the other 50% show a trough sliding along the north of
the ridge bringing cooler temperatures. Sunday is similar with
about 60% of models maintaining ridging and the other 40% showing
the ridging breaking down. Once we get out to Monday there is
even less ensemble agreement in the pattern but about 25% of
models are showing a trough to our west bringing the potential for
widespread precipitation over the region again.

Temperatures over the weekend will be in the 80s for most with
inherent uncertainty given the potential patterns. Temperatures
look to drop a few degrees on Monday into the mid 70s to low 80s.
Given these above average temperatures and a snowpack that is near
freezing and ready to melt, we will be watching area rivers and
streams for any potential rises. All river and stream gauges are
currently well below any flood stage indicating they can handle
increased water flows. Due to this there are currently no
flooding concerns. Torgerson

&&

.AVIATION...

Showers and embedded weak thunderstorms from KBIL S and E, with
rain and snow over the mountains, will decrease from NW to SE
through the night. MVFR is expected in the precipitation, and
mountain obscuration will decrease through the night. Wind gusts
to 50-55 mph are possible near stronger storms, especially E of
KBIL.

Late tonight behind this system, strong westerly winds may develop
in our foothills. Look for gusts of 25-45 kts along the western
foothills tonight. The potential for strong winds 30-45 kts will
spread east on Tuesday.

TS POTENTIAL TIMES:
KMLS: through 07Z
KSHR: Slight chance through 12Z

Arthur
&&

.PRELIMINARY POINT TEMP/POPS...

    Tue     Wed     Thu     Fri     Sat     Sun     Mon
-----------------------------------------------------------
BIL 047/074 055/078 049/081 056/085 057/084 059/086 059/079
    50/N    00/N    00/U    01/U    11/U    12/T    33/T
LVM 042/071 054/077 047/084 054/085 054/084 054/083 052/077
    10/N    00/N    00/U    02/T    11/U    13/T    45/T
HDN 047/075 053/077 046/081 054/085 055/085 056/088 057/080
    70/N    00/N    00/U    00/U    10/U    11/U    33/T
MLS 049/074 054/072 046/079 052/085 055/083 056/086 057/080
    60/N    00/N    00/U    00/U    00/U    01/U    32/T
4BQ 051/072 055/073 047/079 054/086 055/084 057/087 057/080
    50/N    00/N    00/U    00/U    11/U    11/U    33/T
BHK 048/071 051/071 044/078 049/082 050/080 052/082 054/078
    40/N    00/N    00/U    00/U    00/U    00/U    22/T
SHR 044/074 049/076 046/081 053/085 053/083 054/086 054/079
    61/U    00/N    00/U    01/B    11/B    12/T    34/T

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...High Wind Warning in effect until noon MDT Wednesday FOR
      ZONES 63-228.
     Wind Advisory in effect from 6 AM Tuesday to midnight MDT
      Tuesday night FOR ZONES 65-66.
     High Wind Warning in effect from 6 AM Tuesday to noon MDT
      Wednesday FOR ZONES 141-172.
WY...None.

&&

$$
weather.gov/billings