Flash Flood Warning 1, NWS Billings, MT

Area Forecast Discussion
National Weather Service Billings MT
158 PM MDT Sun Jul 3 2022

.DISCUSSION...
Tonight through Tuesday night...

Severe weather potential remains elevated through the 4th of
July and into Tuesday. Be sure you keep an eye on the sky!
If you have outdoor activities, have a way to receive warnings and
a plan to retreat to shelter if necessary.

Satellite imagery shows an upper low along the PacNW coast and
southwest flow from the great basin to central MT.

Convection firing in SW Montana at this time thanks to short wave
lifting northeast in the mid level flow and plenty of sunshine
earlier this afternoon to help destabilize our forecast area.
All parameters continue to indicate an elevated threat of severe
thunderstorms late this afternoon through the evening. (Please see
Day 1 outlook from SPC). Cape/shear support a risk of large hail
and strong winds...and there are signs of potential 70+ mph winds
from places like Harlowton to Roundup to Miles City with a few
long track supercells possible. At least one hi-resolution model
also carries the stronger convection through Billings. Cannot rule
out a brief tornado from Harlowton to Baker (such as along the
Musselshell River valley) per elevated low level shear in this
area on north side of strong pressure falls... but overall feel
the main threat is damaging wind as there is a significant bow
echo feature showing up in hi-res models suggesting storms may
consolidate this evening east of Golden Valley County and produce
widespread damaging winds as they move east through the evening.
PWATS to an inch or higher support a risk of heavy rain as
well...but storm motion should be fast enough to prevent flash
flooding. Brisk gusty northwest winds should be expected behind
the convection as associated cold front pushes south. We should
also note...there is also a possibility of some isolated left
moving supercells in our southeast counties(Sheridan/PowderRiver
/Carter/Fallon) by evening which could potentially become severe
as they track northeast into a moisture rich environment.

So...look for large hail and downburst wind threat late this
afternoon turning to primarily wider spread damaging wind threat
with some hail and heavy rain this evening. Convection should
propagate eastward and exit our forecast area into the Dakotas
around midnight.

As severe convection ends tonight, another shortwave from the
southwest should bring another round of showers by Monday morning,
especially in our west. This activity could impact severe
potential later in the day. All models show a period of large
scale subsidence and some degree of capping in the afternoon...
but there is uncertainty with regard to how strong the cap will
be. Feel that most of Monday afternoon will remain dry (though
humid), with activity beginning over our mountains/foothills by
late afternoon. The greatest potential for severe storms may end
up being after 00z and across our north (in region of cooler mid
level temps). All of this being said, instability and shear are
definitely supportive of severe storms Monday.

Tuesday continues to have potential as pattern remains generally
unchanged from Monday, with significant instability in place and
short wave energy in the southwest flow aloft.

Temps the next couple of days will be seasonable with readings
in the mid 70s west to mid 80s east. BT

Wednesday through Sunday...

Wednesday through Saturday, an upper ridge will build
northwestward toward the Northern Rockies, however its axis looks
to stay just west of eastern MT, keeping southwest flow aloft over
the area and thunderstorm potential each day through the end of
the week. Models project that above normal atmospheric moisture
values should continue through much of this week as the low-level
flow brings moisture from the Gulf of Mexico to our area. Weak
disturbances moving through the upper flow should help to initiate
showers and thunderstorms that will be scattered Wednesday and
Thursday and then isolated Friday and Saturday. CWASP values
indicate that severe thunderstorms are less of a concern during
this time but an isolated severe thunderstorm is still possible.
These values are consistent with the overall pattern of the upper
ridge building northwestward and warmer air in the mid-levels of
the atmosphere that has a partial stabilizing effect.

Ridge breaks down late Saturday or Sunday as an upper low looks to
cut east across southern Canada, bringing slightly cooler temps
for Sunday, and a potentially better chance for storms, dependent
on the gradient of the frontal passage.

High temperatures will generally be in the 70s and 80s Tuesday and
Wednesday and 80s and 90s Thursday Saturday. RMS/Vertz

&&

.AVIATION...

Numerous thunderstorm activity still expected after 21z, with hail
up to 2", gusts up to 65 kts, and torrential rain all possible,
especially near KBIL, KMLS, and KBHK. COnfidence is high for
storms to occur at KLVM, KBIL, KMLS, and KBHK, and storms will
move from west to east. Linger, weaker thunderstorms could occur
overnight, but confidence is much lower in this occurring. Outside
of thunderstorm activity bringing about localized IFR to LIFR
conditions, VFR will persist over the next 24 hours. Vertz
&&

.PRELIMINARY POINT TEMP/POPS...

    Mon     Tue     Wed     Thu     Fri     Sat     Sun
-----------------------------------------------------------
BIL 060/081 060/079 060/085 061/086 062/090 062/092 063/083
    43/T    54/T    33/T    33/T    22/T    11/U    22/T
LVM 053/080 053/080 053/085 054/086 054/089 055/089 054/081
    45/T    45/T    34/T    44/T    22/T    11/U    12/T
HDN 058/083 058/083 060/088 059/088 060/091 060/093 061/085
    43/T    54/T    42/T    33/T    21/U    11/U    22/T
MLS 062/081 061/080 063/084 064/087 063/090 065/093 064/083
    52/T    54/T    62/W    33/T    21/U    11/U    21/U
4BQ 061/084 062/082 062/086 064/089 064/091 066/095 065/084
    32/W    43/T    52/T    23/T    21/U    10/U    11/U
BHK 060/081 058/079 060/083 063/085 062/088 065/091 062/082
    52/T    64/T    63/T    35/T    42/T    21/U    21/U
SHR 057/083 057/085 058/086 059/087 058/091 061/094 060/083
    22/T    33/T    33/T    23/T    21/U    10/U    12/T

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Severe Thunderstorm Watch 423 in effect until 8 PM MDT this
      evening FOR ZONES
      29-34-40-42-56-63>68-139-141-169>173-228-235.
WY...None.

&&

weather.gov/billings

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