928
FXUS65 KBYZ 252029
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
229 PM MDT Tue Jun 25 2024

.DISCUSSION...
Through Wednesday night...

Added low PoPs to the SW mountains after 21Z today, given webcams
were showing growing cumulus there. There was also some cumulus
over SE MT, but deeper clouds were moving SE out of the area.
Upper ridge remains over the area tonight with some weak jet
energy and shortwaves moving through the ridge. Model consensus
just kept some low PoPs over the SW mountains through 03Z. Low-
level flow will turn ESE overnight and bring Gulf of Mexico
moisture into the area Wednesday into Wed. night. Shortwave
energy will move E into the upper ridge Wed. afternoon and cross
the area Wed. night, allowing SW flow aloft to move over the
region. Weak cold front will move through the western part of the
area Wed. night. PWAT`s will climb to 1-1.25 inches over the area
during Wed. with highest values in the E. MLCAPE will be around
500 J/kg with higher values in the far SE. Bulk Effective Shear
will range from 40 to 50 kt.

Given the above, PoPs will increase over and near the western
mountains to 20-40% Wed afternoon. Low PoPs will be over the NE
Bighorns and far SE MT as well. 30-40% PoPs will overspread most
of the forecast area Wed. evening, and will move E overnight,
affecting KMLS, KBHK and Ekalaka late at night. CAPE`s were not
that high, but shear will produce a few helicity tracks SW of KBIL
per the HREF. Cannot rule out possible heavy rainfall with the
storms due to high PWAT`s. High temps will be in the 80s to lower
90s on Wednesday. Arthur

Thursday through Tuesday...

There is good model agreement that a trough will make its way
across the region Thursday. This will bring shower and
thunderstorm chances (40-80%) to the region. An upper low to our
north will bring southerly winds wrapping in moisture from the
plains. Ensembles are currently showing PWAT values of over an
inch for much of the region with some locations in the east seeing
PWAT values over 1.25 inches. These values are around 150% of
normal providing plenty of moisture for precipitation. The forcing
mechanism for these storms will be a cold front associated with
the low moving through Thursday afternoon. Looking at both ECMWF
and GFS deterministic soundings, the ECMWF shows the more
favorable solution at this time with steeper lapse rates through
the lower half of the atmosphere. This equates to MUCAPE values
approaching 2,000 J/kg with 0-6km shear values in the 40s kts
creating a favorable environment for thunderstorms. Due to these
factors the Storm Prediction Center has put our eastern CWA into a
slight risk of severe weather with the main threats being strong
wind gusts and large hail. NBM gives most of the area a 30-50%
chance of seeing >0.25 inches of precipitation. Though high PWAT
values and the scattered nature of thunderstorms will bring about
the potential for localized heavy rainfall.

Late Sunday into Monday there is good ensemble agreement in
another Pacific trough entering the region bringing more
precipitation chances. There is much more uncertainty with this
system due to it being at the end of the forecast period.

Thursday and Friday will be windy as lapse rates will be steep
leading to mix down winds. Both days will see a >50% chance of
getting a gust over 40mph across the region.

Temperatures Thursday will be in the low 80s in the west with much
warmer temperatures in the low to mid 90s in the east.
Temperatures will drop Friday into the 70s for most due to the
troughing and cold front. Temperatures will warm over the weekend
with low to mid 90s returning in the east by Sunday. Another
trough early next week drops temperatures back into the 70s for
most Monday and Tuesday. Torgerson

&&

.AVIATION...

VFR will prevail over the next 24 hours. A few isolated showers
or thunderstorms are possible over the southwest mountains late
this afternoon and evening (after 21z). Tomorrow will see
increasing cloud cover throughout the day across the region with
showers and thunderstorms starting to make their way in from the
west. STP/LT


&&

.PRELIMINARY POINT TEMP/POPS...

    Wed     Thu     Fri     Sat     Sun     Mon     Tue
-----------------------------------------------------------
BIL 056/087 062/088 054/073 047/079 054/087 058/078 054/079
    01/U    26/T    41/B    10/B    13/T    65/T    31/U
LVM 050/085 056/082 045/070 042/078 049/083 050/074 046/075
    03/T    47/T    42/T    10/B    25/T    76/T    32/W
HDN 054/089 059/091 052/074 045/081 053/091 056/079 051/080
    00/B    36/T    51/B    10/U    12/W    66/W    32/W
MLS 054/086 064/090 056/074 048/075 056/089 059/081 056/078
    00/U    35/T    51/N    10/U    22/W    64/W    32/W
4BQ 056/089 064/095 056/076 049/078 055/095 059/081 055/078
    01/U    34/T    41/U    10/U    21/U    44/W    31/U
BHK 051/084 061/091 054/071 046/074 050/087 057/081 053/076
    00/U    35/T    61/N    10/B    23/T    64/T    32/W
SHR 052/089 059/091 050/073 044/081 052/092 055/079 049/079
    00/B    24/T    31/N    10/U    11/U    34/T    21/U

&&

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

&&

$$
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