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000
FXUS65 KBYZ 200835
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
235 AM MDT Sat Apr 20 2024

.DISCUSSION...
Today through Sunday night...

W to E oriented upper trough continues over MT early this morning
with weak waves in the flow. Trough was producing areas of
stratocumulus/mid cloud over the forecast area. Shortwave ridge
slides E into the area this afternoon and moves E through the area
through Sunday morning. Partly cloudy skies this morning will
become mostly sunny this afternoon with below normal high temps in
the 40s to around 50 degrees. Tonight will have lows in the 20s
and dry weather.

Sunday will be a warmer day with highs near 10 degrees above
normal. RH`s will be in the upper teens to lower 20s in the
eastern part of the forecast area. Upper low will be N of the
MT/Canadian border Sun. afternoon, and models were in decent
agreement in bringing associated cold front into the NW portion
of the area in the late afternoon. It will become breezy from KBIL
W in the afternoon due to good mixing. Winds will gust to near 20
mph over KBHK and Ekalaka. There will be a 20 to 30% chance of
showers with isolated thunderstorms W of KBIL with MUCAPES up to
500 j/kg. HREF did not show any updraft helicity, but any storms
will have gusty winds due to steep lapse rates. The front should
be through most of the forecast area by 06Z Monday. Strong
frontogenesis and PWAT`s of 0.5-0.8 inches will spread 30-70%
chances of showers across the area in the evening with the highest
chances S of KBIL. There will be a slight chance of thunderstorms
from KBIL W. Chances for precipitation decrease overnight from N
to S. Wind gusts will increase across the area Sun. night behind
the front. Regarding fire weather concerns for Sun. afternoon,
will continue to watch the E due to the mild and dry conditions
with some wind. For now, will keep a headline in the FWF for
conditions surrounding the cold frontal passage. Not much QPF is
expected with this system with only a 10-20% chance of a tenth of
an inch or more of precipitation Sun. evening. Arthur

Monday through Friday...

Monday: Cooler and windy behind the frontal passage of Sunday
evening. High temperatures will be in the upper 50s to lower 60s,
which will be 5 to 10 degrees cooler than Sunday. A deep upper low
will slide southeast from southern Saskatchewan to North Dakota
by Monday evening. This will produce 850mb winds of 30-40kts
across the entire area, with the strongest winds over the east.
Cyclonic flow will keep some of these winds aloft, but enough
there for gusts of 35-45 mph, with the strongest gusts over
southeast Montana. NBM gives Miles City a 45% chance of wind gusts
of 40mph or more, with a 75% chance at Baker. Billings has a 30%
chance of a 35mph or more wind gust. The chance of showers will be
confined to northeast Montana, where the best moisture is.
Dewpoints are progged to fall to around 20F Monday afternoon,
which is generally not conducive for showers. Humidity will fall
to the lower to mid 20s, and with the strong wind gusts, could
post a concern for fire weather, although the cooler weather
should help that.

Tuesday and Wednesday: Ridging will progress through the area and
provide a dry period for Tuesday through Wednesday morning. An
upper trough moves into southwest British Columbia Wednesday
afternoon, and this system spins some energy and moisture into
western zones Wednesday afternoon for an increasing chance
(20-40%) of showers. This chance of precipitation will spread into
central zones Wednesday evening and night. Tempeatures will warm
from the lower to mid 60s on Tuesday, to the lower to mid 70s on
Wednesday.

Thursday and Friday: An upper trough will deepen over the western
United States and set up southwest flow over Montana and northern
Wyoming. A great deal of uncertainty exists on exactly how much
energy will linger in the northern part of the trough (which can
happen in these western systems). GFS ensembles do have a hint at
some northward push of energy within the trough, produces an
increase chance of showers over the area. The ECMWF ensembles were
diving the trough further south and limiting the amount of energy
lingering in the northern part of the trough. This would be a
forecast that would have a lower chance of showers. EC ensembles
have been more consistent and would thus lean more to this
solution. The GFS solution would be quite a bit wetter, with a
half inch to an inch of rainfall on the table for locations of the
western and central zones. The EC would be more in the one tenth
to a quarter inch range, with a slide toward the southeast zones
for the heavier totals. Need a few more model runs to have
confidence on where to go with this part of the forecast. High
tempeatures will slip from the mid to upper 60s on Thursday, to
the mid 50s to lower 60s on Friday. TWH
&&

.AVIATION...

A band of low to mid level clouds (3-6 thousand feet) were
present from KLVM to KBIL, and then another band from KBHK to
south of KMLS. These clouds will become more scattered by mid
morning. Otherwise, VFR flying conditions are expected today. The
mountains will have some obscurations this morning, but this will
become less impactful by late morning. TWH
&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Sun     Mon     Tue     Wed     Thu     Fri
-------------------------------------------------------
BIL 049 029/067 037/060 036/064 040/074 048/067 044/059
    0/U 01/B    51/N    00/U    01/U    35/R    44/R
LVM 049 028/067 031/057 031/062 038/071 043/062 039/055
    0/U 02/T    20/N    00/U    02/R    36/T    45/R
HDN 050 026/071 037/062 034/065 038/077 046/071 044/061
    0/U 01/B    61/N    00/U    01/U    34/R    44/R
MLS 046 026/069 039/058 036/061 040/073 048/070 045/063
    0/U 00/U    31/N    00/U    00/U    22/R    33/R
4BQ 047 025/070 039/059 036/062 040/075 048/072 045/063
    0/U 00/U    20/N    00/U    00/U    13/T    33/R
BHK 046 023/065 035/057 032/058 035/069 041/067 041/061
    0/U 00/U    21/N    01/U    00/U    13/R    33/R
SHR 046 022/067 034/057 032/062 035/073 043/068 040/058
    0/U 00/U    41/N    10/U    01/U    25/T    55/R

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.

&&

$$
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