553
FXUS65 KBYZ 200802
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
202 AM MDT Sat Jul 20 2024

.DISCUSSION...

Through Sunday Night...

Upper level flow is expected to become more northerly, bringing
wildfire smoke down from Canada, some of which may reach the
surface. As a result, high temperatures may be a couple degrees
cooler than initially forecast if smoke in the upper levels
becomes thick enough to act as partial cloud cover. Currently,
highs are expected in the upper 80s to low 90s for today and
Sunday.

Energy dropping through the flow this weekend will bring a 30-50%
chance of showers and thunderstorms over the mountains and a
15-30% chance over the plains today and a 15-30% chance over the
mountains and east of Billings on Sunday. PWATs continue to be
near to slightly above normal with values around 0.75-1 inch, so
brief, locally heavy rain may occur under thunderstorms. Archer

Monday through Friday...

WPC 500 mb clusters show that ensemble model solutions are in good
agreement through about Thursday, and then some differences exist
for Friday. Overall 500 mb flow evolution consists of a ridge
over western North America Monday that slowly moves eastward
through the week. On Friday, the differences amongst clusters
involve how far eastward to slide the pattern, with an upper
trough somewhere over western Canada/Pacific Northwest an upper
ridge somewhere over central/eastern North America.

Monday through Wednesday, look for a warming trend with high
temperatures Monday generally in the 80s and 90s, then 90s Tuesday
and upper 90s to lower 100s Wednesday. Isolated to scattered
showers and thunderstorms (20-30% chance) will occur in and near
the mountains in the afternoon to early evening each day.
Otherwise, much of the area away from the mountains should be dry
with a lack of moisture aloft.

Thursday will be another hot day with high temperatures mainly in
the upper 90s to lower 100s. Models are hinting that isolated-
scattered showers and thunderstorms (20-40% chance, greatest in
Beartooth/Absaroka Mountains) will occur over more of the
forecast area Thursday as upper flow becomes more southwesterly
and increased moisture aloft moves in.

Friday, despite some differences in trough/ridge placement,
overall pattern shown by ensemble model solutions favors
southwesterly flow over our area, which should support an
increased chance of thunderstorms across the area in the afternoon
to evening period. In accord with this conceptual model, NBM shows
a 20-60% chance of showers and thunderstorms across the area,
greatest again in the Beartooth/Absaroka Mountains, but with
increased probability values over the lower elevations of south
central MT too. NBM shows high temperatures probably will drop a
bit to the 80s and 90s, though uncertainty is greater this day
with the NBM 10th to 90th percentile range at Billings being 87F
to 100F.

More on high temperatures...NBM shows that the probability of
temperatures reaching 100F on Wednesday is 50-80% over the lower
elevations of south central MT and north central WY, then
probability values decrease in southeast MT to 20% or less for
much of Fallon and Carter Counties. On Thursday, this probability
rises to 40-80% for much of the lower elevations including
Fallon/Carter Cos. For Friday this probability reaches 50% in the
valleys east of Billings with lower values elsewhere, which is
consistent with the pattern evolving to SW flow and the increased
chance of showers and thunderstorms.

The heat might support a heat advisory...will be monitoring this
as we go into next week. RMS

&&

.AVIATION...

Smoke from wildfires may reduce slantwise visibility at times.
Scattered showers and thunderstorms are possible near all TAF
sites beginning around 18z and continuing until 0z near KLVM and
KBIL and 5z near KSHR and KMLS. Within storms, conditions may
temporarily lower to MVFR at times. Archer

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Sun     Mon     Tue     Wed     Thu     Fri
-------------------------------------------------------
BIL 093 064/092 064/093 063/097 066/103 068/103 067/095
    1/U 10/U    00/U    00/U    00/G    01/G    12/W
LVM 090 054/090 053/091 055/097 059/101 058/098 058/091
    2/U 10/U    00/U    01/U    11/G    12/T    23/T
HDN 094 060/092 059/093 060/098 062/103 063/104 063/096
    1/U 21/U    00/U    00/U    00/G    00/G    21/B
MLS 091 064/090 064/090 064/095 066/100 067/102 071/096
    2/T 21/H    01/U    00/U    00/U    00/G    11/B
4BQ 091 063/090 061/090 063/096 064/099 066/102 070/098
    1/U 11/H    01/U    00/U    00/U    00/G    11/B
BHK 089 060/088 060/088 060/092 062/097 064/099 066/096
    2/U 12/T    11/U    00/U    00/U    00/U    11/B
SHR 090 057/088 055/090 056/096 059/100 059/101 061/095
    3/T 22/T    11/U    00/U    00/U    00/G    12/T

&&

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

&&

$$
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