Damaging Winds in Montana, July 22, 2021

Area Forecast Discussion
National Weather Service Billings MT
1243 PM MDT Thu Jul 22 2021

.DISCUSSION...

...This afternoon through Friday night...

Broad area of weak ascent located from the Beartooth mountains
northeast into far northeast Montana early this afternoon. Ahead
of this area of scattered light showers and a few thunderstorms is
an area of clear skies under which temperatures have jumped well
into the 90s. Low level dew points are in the upper 50s to mid 60s
with these warm temperatures leading to CAPE values of 1-2000
j/kg. As the lift shifts into this unstable airmass expect
stronger storms to develop with gusty winds and locally heavy
downpours the main threat, though an isolated hail report is not
out of the question. This activity should shift east into the
Dakotas by early evening. Behind it, additional thunderstorms are
expected to develop over the western mountains mid afternoon and
move northeast in association with a jet-max and surface cold
front. This activity will move slowly across the area through late
tonight with lesser precipitation amounts and a better chance for
a strong wind gust. By sunrise this activity should have shifted
out of the area.

Friday will be sunny, dry and a few degrees cooler behind the
overnight cold front. The flow aloft becomes more zonal Friday. As
a result, winds will be a bit gusty from Billings to the west
which will lower relative humidities and increase fire weather
concerns into the foothills. Will upgrade the current Fire Weather
Watch to a Red Flag Warning with this forecast package. Chambers

Saturday through Thursday...

Zonal flow over the area through the weekend with downslope winds
keeping conditions sunny and dry. Temperatures in the low to mid
90s Saturday will climb into the triple digits for Sunday. Ridge
intensifies to the south of the area on Monday and Tuesday pushing
temperatures to near record levels once again. May need additional
Heat warnings if current forecast trends continue, possibly from
Sunday through Tuesday. By Wednesday core of the upper ridge
shifts enough to the southeast to allow southwesterly monsoonal
flow to begin working back into the area. This will take the edge
off of temperatures and bring back a daily chance for showers and
thunderstorms for the end of the week. Chambers

&&

.AVIATION...

Scattered showers and thunderstorms will persist across the area
this afternoon through the evening hours. A cold front late
tonight will shift convection into the Dakotas by 09z or so.
Locally strong wind gusts(40+kts) and heavy downpours with MVFR
conditions can be expected with the stronger cells. Outside of
convection, VFR conditions will prevail. Chambers

&&

.PRELIMINARY POINT TEMP/POPS...

    Fri     Sat     Sun     Mon     Tue     Wed     Thu
-----------------------------------------------------------
BIL 065/094 061/093 062/099 064/102 068/102 069/096 067/093
    30/H    00/U    00/U    00/G    01/G    11/B    12/T
LVM 054/092 052/093 054/096 056/099 060/099 060/092 058/090
    30/H    00/U    00/U    00/U    01/B    22/T    22/T
HDN 063/096 057/096 060/101 062/104 066/105 066/098 064/095
    20/H    00/U    00/G    00/G    00/G    11/B    11/B
MLS 068/094 061/095 063/100 066/103 070/105 071/098 067/094
    30/H    00/U    00/U    00/G    00/G    11/B    11/B
4BQ 067/094 063/094 065/098 067/101 070/105 071/098 067/092
    30/H    00/U    01/U    10/G    00/G    01/U    11/B
BHK 065/093 059/093 061/098 064/102 066/104 069/098 064/092
    31/H    00/U    01/U    10/G    00/G    01/B    11/B
SHR 060/093 056/094 058/097 059/101 062/102 064/096 061/092
    31/H    01/U    11/U    00/G    01/G    11/B    22/T

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Excessive Heat Warning in effect until 9 PM MDT this evening
      FOR ZONES 29>34-36-37-42-57-58-138-139-169-170-173-235.
     Red Flag Warning in effect from noon to 9 PM MDT Friday FOR
      ZONES 117-123>125-127.
WY...Excessive Heat Warning in effect until 9 PM MDT this evening
      FOR ZONE 199.

&&

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