414
FXUS65 KBYZ 301459
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
859 AM MDT Sun Jun 30 2024

.UPDATE...

Aviation personnel: See updated aviation discussion below.

&&

.DISCUSSION...

Today through Monday Night...

A hot Sunday is in store as ridging continues to build over the
Northern Rockies. Temperatures will climb into the mid 80s to 90s.
Some locations in the south and east could approach 100F. The
record high temperature for today in Sheridan, WY, is 98F. the
current forecast has them reaching 97F so tying and even breaking
the record is certainly possible.

The main story today will be the severe weather risk. A Marginal
Risk (level 1 out of 5) covers the entire forecast area, while a
Slight Risk (level 2 out of 5) covers a sizable portion of east-
central Montana. The primary risks associated within the outlooks
will be wind and hail. Heavy rainfall is a secondary risk. The
wind threat is currently a greater concern within our forecast
area with environmental parameters favoring severe to potentially
significantly severe wind gusts. The main round of severe weather
will come with an approaching upper trough and an associated cold
front. At the surface, an area of low pressure will move into
southeastern MT/ northeastern WY. The presence of this surface low
may allow for isolated convection to develop in eastern Montana
ahead of the cold front. With cold frontal passage not expected
until the late afternoon hours beginning out west, the potential
for discrete thunderstorm development cannot be entirely ruled out
as strong diurnal heating will result in higher instability. The
problem with pre-frontal convection developing and sustaining
itself is a strong cap in place. With soundings depicting warm
profiles, it will be difficult for parcels to break through strong
capping, especially when dew point depressions are 30-50F.

As for the convection expected to form with the passing cold
front, models continue to show storms firing in lee of the
Absaroka/Beartooths, Belts, Crazies, and Gallatin mountains by
mid- afternoon. HiRes soundings show MUCAPE values between
500-1000 J/kg, along with deep layer shear will be around an inch
east of Billings along with steep lapse rates in the 8-9 C/km
range, values between 40-60 knots, in the western areas. As
convection progresses east- northeast, a better environment will
allow for storms to strengthen. MUCAPE values around 2000 J/kg in
eastern MT and DCAPE values in excess of 1500 J/kg will be more
than sufficient for storms to produce wind gusts of 60-75 mph. As
for the hail potential, PWATs values around 1-1.2" will be present
east of Billings along with 8-9 C/km lapse rates. Significant
hail parameter values up to 1-1.5 indicate the potential for
severe hail, however, models are generally bullish on storms
becoming strong enough to tap into hail potential. Despite
potential limitations, large hail of 1-1.75" (quarter to golf ball
sized) is possible with the strongest storms.

Timing for convection today will be from 3pm to Midnight, with
the cold front departing the far east by the latter. The chance
for showers and thunderstorms is 60-80% west of Billings in the
afternoon. As storms move east, the highest chances will remain
just north of Billings, at 30-60%. As for Billings and locations
south-east, there is a 15-30% chance for showers and
thunderstorms.

Lingering moisture behind the cold front will bring the chance
for more showers and sub-severe thunderstorms to much of the west-
central areas Monday morning. Precipitation probabilities are
25-60%, higher in the western mountains. High temperatures on
Monday will be in the 70s to low 80s. Another round of strong to
severe storms is possible Monday afternoon, with a Marginal Risk
(level 1 out of 5) covering southeast MT and northeast WY. The
forcing mechanism for this round of storms looks to be a weak cold
front. The primary risks will be wind and hail. Matos

Tuesday through Sunday...

Although this period begins at the tail end of storms and a
strong surge of moisture producing precip for the start of the
week, that doesn`t mean we`re out of unsettled weather just yet.
Broad cyclonic flow will persist over Montana and embedded, weak
shortwaves will continue to bring off and on periods of showers
and storms to southern MT and northern WY.

Tuesday will see the weaker side of things, so while containing
small chances for showers and storms, any that form will be
relatively light, producing minor rain amounts and small hail. The
`best` shot for a stronger system still looks to be Wednesday as
a more dynamic shortwave crosses the area and brings a cold front
with it. While some moisture is brought it, it will be limited due
due not getting a good shot of moisture from the Gulf, as west to
northwest winds persist through the day, and on top of that,
shear is a bit on the low side at only 30-35 kts. Still a day to
keep an eye on, especially with it being the night before the 4th
of July.

Speaking of, the aforementioned shortwave persists into Thursday
and drags it`s storm potential with it, albeit with weaker forcing
than before. Coverage is still moderate, with the chance for
rain/storms 40-60% across southeast Montana. Current ensemble
consensus does have storms moving out of the area in the evening,
but that could easily change over the coming days. Be prepared for
rain and storm potential if you have 4th of July plans.

While ensembles are still in agreement for having a prominent
upper ridge come across the western United States for Friday and
into the weekend, there are hints within some of its members and
from deterministic models of a wave pushing down through Montana
and continuing to bring moisture and storm potential tot he area
going into the weekend (vs being hot and dry if the ridging
prevails). Something to keep an eye on over the next few days.
Vertz

&&

.AVIATION...

Building high pressure aloft will bring widespread VFR for most of
today. By mid-late afternoon, expect scattered strong to severe
thunderstorms to develop west of KBIL, possibly affecting
KLVM-K6S0-K3HT with brief MVFR and strong wind gusts before 00z.
Thunderstorms associated with a cold front will arrive around 00z
for KBIL and progress east to KMLS between 00z and 05z. Primary
hazards with these storms are strong winds and hail, potentially
impacting KBIL-KMLS-KBHK. Wind gusts of 50-65 knots are possible
with strong tstorm outflow, as well as large hail (1-1.75").
Additional showers and weaker tstorms are expected late tonight,
and mountains will be occasionally obscured.

TS POTENTIAL TIMES:
KBIL: 23z-03z (20% chance, risk of strong wind & hail)
KLVM: 21z-06z (40% chance, risk of strong wind & hail)
KMLS: 02z-06z (40% chance, risk of strong wind & hail)
KSHR: 22z-03z (10% chance, low risk of strong wind)

JKL

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Mon     Tue     Wed     Thu     Fri     Sat
-------------------------------------------------------
BIL 089 060/080 058/079 055/082 054/075 052/082 055/087
    2/T 23/T    43/T    13/T    45/T    21/U    11/U
LVM 085 053/077 048/075 047/078 046/074 046/080 050/084
    4/T 45/T    63/T    13/T    34/T    11/U    11/U
HDN 095 058/080 055/079 051/083 051/076 050/082 051/088
    2/T 23/T    54/T    13/T    55/T    21/U    11/U
MLS 092 061/079 058/078 054/083 055/074 052/081 056/086
    1/U 53/T    24/T    13/T    45/T    21/U    11/U
4BQ 096 061/080 057/077 053/086 054/075 052/079 054/084
    1/U 25/T    44/T    03/T    55/T    21/U    11/U
BHK 084 059/080 054/076 052/080 052/072 050/078 052/082
    0/N 44/T    13/T    13/T    46/T    22/W    11/U
SHR 097 055/076 050/076 048/083 048/074 046/078 048/085
    2/T 26/T    74/T    12/T    44/T    21/U    11/U

&&

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

&&

$$
weather.gov/billings