346
FXUS65 KBYZ 171623
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
1023 AM MDT Fri May 17 2024

.UPDATE...

Showers were already moving into the NW zones on radar ahead of a
weak cold front. Adjusted PoPs for this early start and used CAMS
to adjust PoPs into the evening. There will be two rounds of
precipitation, 1st one exiting by 22Z and then the second one
behind it starting around KBIL and moving E through the evening.
MUCAPES were not that high, 250-500 J/kg, but there was at least
40 kt of Bulk Effective Shear, mainly E of KBIL. Hodographs mainly
supported splitting cells, but some were curved suggesting a few
supercells. In addition, there were a few decent helicity tracks E
of KBIL. SPC has a marginal over areas E and S of KBIL with a
slight risk for severe over Carter and Fallon Counties. Main
threat is strong wind gusts, but cannot rule out hail given the
above, and freezing levels in the 6000-7500` range. PWAT`s will be
up to .8 inches over parts of the E, so expect some heavy rain
with thunderstorms. Regarding winds, mountain wave potential did
not look at good as it did yesterday, but cannot rule it out. Deep
mixing and the convection will support gusty winds, so wind
highlights were in good shape. Arthur

&&

.DISCUSSION...
Today through Saturday night...

Upgraded High Wind Watches to Warnings and added the Beartooth
Foothills to the going Wind Advisory mainly for areas just south
of Big Timber. These areas show NBM probabilities over 60 percent
for gusts around 60 mph with the best timing for a strong gust
between 4 and 8pm. With trees leafing out the chances for
tree/power line damage resulting in power outages is increased
compared to earlier in the Spring. Westerly winds will favor
strong crosswinds along US-191 and other north/south oriented
roadways, with I-90 experiencing mainly a strong head/tail wind.

The other area favored for some stronger wind gusts today will be
areas east of Billings where convective gusts could reach 50 mph
in a few locations across SE Montana, and an isolated warning gust
is not out of the question (~10 percent). Convection gets going
early (around noon) in central areas and gets a bit stronger over
SE Montana in the late afternoon/early evening hours. SPC has
upgraded to a slight risk over far SE Montana and expanded the
marginal risk west to Rosebud/E Big Horn county to cover this wind
threat.

Synoptic Pattern...Core of the upper level low that will impact
our area is located well north of the border in west central
Canada. A lobe of energy pivoting east around this low is
currently moving through the Pacific NW and will push into the
forecast area by late morning. By this evening the upper trof will
be exiting the area to the east with zonal flow building in behind
it. Zonal downslope flow continues through the day Saturday and
into Saturday evening. The next Pacific wave moves into the area
late Saturday night into Sunday, sticking around through at least
Monday afternoon.

Today will be unsettled with periods of strong winds west, and
convection central and east. Temperatures will be moderated by
cloud cover and convection, with highs mainly in the 65 (west) to
75 (east) degree range. NBM has trended lower with overall
precipitation amounts, particularly for central areas from
Billings/Roundup and west. This downward trend makes sense given
the gusty westerly winds in the forecast. Expect areas that will
see around 0.20 or more inches of precipitation to be confined to
scattered thunderstorms which will be moving pretty quickly to the
east. This time of year just about any thunderstorm can produce
small hail, to go along with the gusts potential around 50 mph.

Tonight will be windy with post frontal winds gusting 40 to 60 mph
in the west, 25 to 40 mph elsewhere outside of convective gusts.
Convection will diminish overnight, but winds will likely hold on
into Saturday morning.

Westerly winds will bring mostly sunny and dry conditions to the
area Saturday. Winds will be strongest in the morning, trending
lighter in the afternoon. Highs will be mainly in the 60s.

Saturday night will start off mostly clear, but will transition to
cloudy as the next system begins to impact the area. By Sunday
morning expect 30 to 50 percent precipitation chances from
Billings to the east. Chambers


Sunday through Friday...

Unsettled weather will continue through next week. Sunday into
Monday, a trough will impact the region, bringing a 40-60% chance
(highest over the mountains and foothills) of at least 0.25" of
precipitation from Sheridan to Forsyth and west.

For Tuesday, the trough is expected to move south of the region
before brief riding builds in. Enough energy will linger for a
50-60% chance of precip over the mountains and foothills and a
20-30% chance over lower elevations.

Late Wednesday into early Thursday, another trough is expected to
move in. The exact timing varies between models, but widespread
precip is expected, with a 50-80% chance (highest over the west
and mountains) by Thursday evening.

High temperatures will be in the 60s to low 70s through the
period. Archer

&&

.AVIATION...

Scattered showers and thunderstorms will spread from west to east
this afternoon and evening. When thunderstorms occur, brief
MVFR/IFR conditions are possible. Beginning this afternoon,
expect gusts up to 45 kts near KLVM, K6S0 and K1KM. Archer

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Sat     Sun     Mon     Tue     Wed     Thu
-------------------------------------------------------
BIL 071 042/067 044/063 041/060 042/064 043/066 045/063
    8/T 40/U    16/W    45/T    23/T    14/T    46/T
LVM 067 035/066 042/057 035/057 037/061 040/062 041/059
    6/T 10/N    28/T    56/T    23/W    26/T    67/T
HDN 073 039/068 042/067 040/060 040/064 042/069 044/066
    8/T 70/U    15/W    45/T    23/T    13/T    45/T
MLS 072 042/067 041/068 042/061 040/062 042/068 045/066
    8/T 50/N    12/W    33/W    12/W    12/W    34/W
4BQ 078 042/066 042/070 042/060 041/061 041/068 044/067
    6/T 50/U    02/W    33/W    23/W    12/W    24/T
BHK 077 039/065 039/069 040/061 038/061 038/066 040/064
    6/T 40/N    11/B    33/W    12/W    12/W    23/W
SHR 077 035/068 040/068 037/056 037/059 038/065 040/064
    4/T 40/U    04/T    45/T    44/T    23/T    35/T

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...High Wind Warning in effect until midnight MDT tonight FOR
      ZONES 63-141-172-228.
     Wind Advisory remains in effect until midnight MDT tonight
      FOR ZONES 65-66.
WY...None.

&&

$$
weather.gov/billings