835
FXUS65 KBYZ 151839
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
1239 PM MDT Sun Jun 15 2025

.KEY MESSAGES...

- Enhanced risk (3/5) of severe thunderstorms today. Main threats
  are strong winds, large hail, and heavy rain. A small chance
  for tornadoes.

- There is daily potential for thunderstorms into Tuesday; some
  severe thunderstorms are possible. Monitor the forecast.

- Quieter weather pattern for the second half of the week.

&&

.DISCUSSION...
Through Monday Night...

Severe weather is a threat yet again this afternoon into the
overnight hours with all severe hazards possible.

A vorticity maximum is forecast to move through ID into Western
MT this afternoon brining with it a large area of ascent which
will be conducive for a large area of convection. Winds across the
eastern 2/3 of the CWA remain out of the east which continues to
bring climatologically very high dew points to much of the region.
As of this hour, even places as far west as Livingston have
managed to reach a dew point of 50F with Billings and points
eastwards eclipsing the 60F mark. CAPE is also not going to be any
issue today with ML-CAPE values over Big Horn County already over
1500 J/Kg and the SPC guidance showing that places in the far
eastern reaches of the CWA could approach 3000 J/Kg before the
convection reaches these locations. And in terms of shear, there
will be plenty of that with the whole region forecast to be over
40kts of effective bulk sheer by late afternoon with the
approaching shortwave with pockets of over 50kts.

The 12z GGW observed sounding already shows an area of skinny
CAPE with a sfc temp of 64F. As temps warm by 20F into the
afternoon, it appears that the CAPE profile will be well
distributed throughout the column. Mid to upper level wind speed
and wind sheer will increase as the shortwave moves into the
region, with 300hPa wind speeds forecast to be 50kts by the most
recent RAP run. The CAPE distribution along with wind sheer
tilting the updrafts later today will be conducive for large to
very large hail to fall out of these storms. Keeping with the
theme of sounding analysis, even though our dew points are quite
high climatologically, during peak daytime heating in mid June,
the high temps will easily top 80F. This will create inverted-V
soundings in places such as Miles City. As these strong updrafts
collapse and storms become outflow dominant wind gusts of 70-80mph
are very well within the realm of possibility.

In terms of tornado potential today, there is a possibility,
however, the other threats remain the primary concern. Any right
moving storm could take advantage of the ample sheer that we have
present at all levels, including sfc-3km. The biggest limiting
factor is that LCL heights will likely be too high during the
daytime hours for any meaningful tornado potential. As the sun
sets though, and temps cool off just a bit, the LCL may lower to
3kft in far Southeast Montana which could amount to a tornado
threat for a short period of time. It is also worth noting that
the LCLs will be lowing at the same time that the nocturnal LLJ
begins to strengthen. This threat remains highly conditional and
several questions remain at this time.

There is a small severe threat yet again on Monday, however, it
is less impressive than today`s event. All parameters wil be
significantly lower in addition to there being limited forcing as
the main shortwave moves through the region this evening.
Nevertheless, an isolated severe storm remains possible Monday
afternoon and evening.
WMR

Tuesday through Saturday...

Models are in good agreement that we will be transitioning to a
drier and warmer pattern in the extended. A weak short wave
embedded in weak zonal flow will track over the region Tuesday
with scattered showers possible through the day, and some
thunderstorm activity also possible. PWAT progs still show
readings above 0.80 inches Tuesday, so some locally heavy rain is
possible. MUCAPE values Tuesday afternoon range from 500-1250
J/kg, so some small hail and gusty winds remain a possibility as
temps reach the 70s.

Ridging then builds over the inter-mountain west Wednesday and
Thursday with weak downslope flow pushing the bulk of low level
moisture east. So we should see limited if much of any convection
at midweek. Temps will push above normal reaching mid to upper
80s with some 90 degree readings possible by Thursday and Friday.
The ridge axis shifts east over the high plains late in the week
with an upper trough moving into the Pacific NW. This may lead to
another period of daily scattered thunderstorm activity by the
weekend with temps dropping back to around normal by Sunday. BT
&&

.AVIATION...

18z Discussion...

The low clouds at KBIL are expected to move out of the area within
the hour. After these clouds clear the whole region will prevail
with VFR conditions. Most of the forecast area could see TS this
afternoon and evening, some storms could be strong to severe.
While exact storm location remains uncertain, there was enough
confidence to include TEMPO lines in most TAFs. The strongest of
these storms could produce very large hail and wind gusts as high
as 60kts. Additionally, some low lying areas could see some FG
development as well as points eastwards near ND. WMR
&&

.PRELIMINARY POINT TEMP/POPS...

    Mon     Tue     Wed     Thu     Fri     Sat     Sun
-----------------------------------------------------------
BIL 056/079 055/076 054/084 057/087 059/084 057/080 052/066
    65/T    66/T    10/U    00/U    22/T    22/T    54/T
LVM 049/078 049/075 048/082 051/087 052/082 048/076 042/062
    57/T    55/T    10/U    01/U    33/T    23/T    65/T
HDN 055/080 055/074 051/084 055/089 059/086 056/083 052/066
    85/T    78/T    20/U    00/U    22/T    31/U    54/T
MLS 060/080 056/074 053/083 056/089 060/085 059/083 054/067
    43/T    67/T    30/U    00/U    42/T    41/U    64/T
4BQ 058/078 057/071 053/081 057/088 060/086 059/087 054/066
    63/T    88/T    30/U    00/U    11/U    21/U    43/T
BHK 056/078 053/072 051/080 054/087 057/081 056/081 054/068
    72/T    56/T    41/U    00/U    31/B    31/B    53/T
SHR 052/078 051/071 049/080 053/089 056/087 054/085 048/065
    55/T    79/T    20/U    00/U    11/U    11/U    44/T

&&

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

&&

$$
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