Damaging Wind and High Wind in Montana, August 20, 2024

Area Forecast Discussion
National Weather Service Billings MT
223 AM MDT Tue Aug 20 2024

.DISCUSSION...
Through Wednesday night...

We are looking for yet another round of showers/thunderstorms to
develop over the higher terrain and track northeast into the
plains today. Initial develop will likely occur over SW to
central portions of Montana by mid afternoon before moving
east/northeast into the evening. Storm development will benefit
from effective bulk shear 40-50 kts associated with an upper
level jet nosing into the Rockies. Surface CAPE at mid afternoon
will range from 750 J/kg in the west to 1750 J/kg in the eastern
border zones. CAM's place an area of helicity from the Crazies to
Musselshell County and this closely corresponds to the slight risk
area on the severe weather outlook from SPC. Hail and damaging
wind are both threats in this area today. Storm activity should
track east into the evening with greatest coverage of convection
(15-35%) mainly along and north of I-90 and I-94 across east
central Montana. By midnight most of this should have weakened or
exited our forecast area to the east.

Wednesday will see more short wave energy in the SW flow break
down the upper ridge. Overall height falls will lead to widespread
ascent in the afternoon and jet dynamics nosing right over the
CWA will create unusually high effective shear (50kts plus). This
combined with steep lapse rates increases our risk of hail
Wednesday afternoon and evening with any storms that develop,
while strong winds are almost always a threat as well.

Temperatures today will be in the upper 80s to mid 90s across the
region. Wednesday will see a weak frontal passage that will drop
temperatures a few degrees west with mid to upper 80s west...and
still mid 90s over the southeast zones ahead of the front. BT

Thursday through Tuesday...

Weak ridging and southwest flow will bring warm and dry conditions
to the region on Thursday. High temperatures will be near normal,
80s to 90F. The chance for precipitation across the area will be
less than 15%, except for the southwestern mountains (up to 20%).

Friday will see warmer and breezier conditions, as the ridging and
SW flow pattern aloft become amplified by a digging upper trough
and low over the PNW. High temperatures will climb into the 90sF.
Increasing surface winds will result in gusts up to 30 mph in the
western and eastern zones. The chance for precipitation will be
10-25%, best chance in the Absaroka/Beartooths and Gallatin
mountains, as well as the far eastern zones. Relatively dry
conditions will still be felt across much of the western to
central areas, with minimum relative humidity values below 25%.
The combination of low RH values, warm temps, and breezier
conditions will be worth monitoring, with respect to fire weather.

This weekend, there is still high uncertainty in the pattern
evolution, timing, and placement, among deterministic models.
Ensemble members are generally agreeing on the aforementioned
upper low and trough in the PacNW progressing into the Northern
Rockies. Currently, ridging and SW flow looks like it will persist
into Saturday, with high temperatures in the 80s and 90sF. The
latest forecast has the chance for showers and thunderstorms
increasing from west to east, Saturday afternoon into Sunday
morning. Ensembles depict the trough pushing through the region by
Sunday, bringing cooler temperatures and a low to moderate chance
for precipitation. Cooler temperatures and zonal flow are shown
early next week, with highs in the 70s and 80sF.

With noted uncertainty in the extended forecast period, continue
to monitor the forecast for updates this week.

Matos
&&

.AVIATION...

VFR conditions will largely prevail through the period. Patchy
fog with localized MVFR conditions is possible this morning near
KMLS and KBHK. This afternoon, the chance for isolated to
scattered showers and thunderstorms will increase from KLVM-KBIL-
KMLS. Some storms may be strong enough to produce wind gusts up to
50 kts, quarter-sized hail, and heavy rainfall. Localized MVFR-IFR
conditions will be possible under storms.

Matos

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Wed     Thu     Fri     Sat     Sun     Mon
-------------------------------------------------------
BIL 095 059/089 057/088 059/094 063/090 056/078 052/080
    2/T 11/B    30/U    00/U    01/B    33/W    31/U
LVM 089 052/086 048/084 052/089 053/083 046/071 044/077
    2/T 02/T    20/U    11/N    12/W    44/W    31/U
HDN 097 058/094 056/091 060/095 061/094 054/080 051/081
    2/T 11/U    30/U    00/U    01/U    33/W    31/U
MLS 094 066/094 061/088 066/095 066/095 060/080 054/078
    0/U 21/H    40/U    01/U    00/U    23/W    31/U
4BQ 095 067/097 061/089 067/096 070/096 059/083 053/080
    0/U 02/T    20/U    01/U    00/U    22/W    21/U
BHK 092 063/094 059/087 061/091 065/094 058/082 052/078
    0/U 12/T    30/U    12/T    10/U    12/W    21/U
SHR 097 059/097 055/090 059/094 060/092 052/080 047/081
    0/U 10/U    10/U    00/B    00/U    23/W    21/U

&&

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

&&

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