154
FXUS65 KBYZ 171927
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
127 PM MDT Thu Jul 17 2025

.KEY MESSAGES...

- A few strong thunderstorms are possible over northeastern
  areas, including Miles City and Baker this evening. Strong winds
  and large hail are the main threats.

- Seasonal temperatures Friday, becoming above normal for the
  weekend. Isolated to scattered mainly afternoon and evening
  thunderstorms are possible each day through the weekend.

- Early next week is trending cooler (80s) and more unsettled
  with another storm system working into the region.

&&

.DISCUSSION...

Through Friday night...

Stratus and fog have yielded to sunny skies across the forecast
area this afternoon. Temperatures should reach the mid 80s for
most of the area for highs this afternoon.

There is an upper level system dropping southeast out of Canada
this afternoon that will cross far NE Montana tonight. A surface
cold front is trailing this system through the area with winds
turning northerly behind it. The northerly winds will clash with
southeast winds already in place across eastern Montana this
afternoon setting up a focus for thunderstorm development late
today into late tonight. The most likely scenario is for one or
two strong storms to move into and across northern Rosebud,
Custer, and Fallon county between 9pm and 3am tonight. 12z HREF
continues to advertise strong long track helicity tracks moving
into this area, possibly impacting Miles City and Baker late
tonight. Strong wind gusts and large hail are the main threats
with these storms. The latest model runs are showing a low
probability for an earlier arrival for a strong storm into eastern
Musselshell county moving southeast into Forsyth area by 6pm this
evening, with strong wind gusts the main threat.

The fly in the ointment for strong storms reaching SE Montana is
the timing and the strength of the nocturnal inversion that will
develop once the sun sets. The further into the night we go before
storms arrive the stronger this inversion will get and it will
lock up a good deal of the moisture and helicity that is below the
inversion, preventing the storms from utilizing this energy.
Models are kind of hinting at this with storms dying out pretty
quickly before getting halfway through Custer/Fallon counties.
Also, only expecting a couple of cells to make it this far south,
so not a widespread threat. That said these storms may arrive
after 10 pm with the latest HRRR moving storms through Baker
around 2am, so be prepared and have a way to receive alerts in the
middle of the night tonight.

Northerly flow turns back to the southeast during the day on
Friday. So despite the cold front tonight, temperatures will be
back into the 80s Friday afternoon. There is a weak disturbance
that moves west to east across the forecast area during the
afternoon that models are generating isolated convection along,
starting off in the western mountains late afternoon and moving
into central zones by mid evening before fizzling out late
evening. These storms have good CAPE but less shear compared to
tonight and mid level temperatures are warmer so more of a cap to
overcome. As a result the chance of organized severe storms looks
low for tomorrow. Precipitable water values are over an inch and
storm motion looks slow enough to support locally heavy downpours
with storms tomorrow as likely the main threat with storms for
the day. Storms should end late evening for a clearing and quiet
Friday night. Lows will drop into 50s and lower 60s. Chambers

Saturday through Thursday...

This weekend is shaping up to be warm with highs pushing into the
90s most areas due to stronger southwest winds aloft advecting
Great Basin heat into the area. Despite the heat there is plenty
of atmospheric moisture hanging out over the area, especially from
Billings eastward where PWAT values stay near to above an inch
through the weekend. This moisture and the heat will bubble up
afternoon and evening thunderstorms each day, with areas from
Billings east seeing the best chance for a heavier downpour.

Monday into Thursday still shows a decent amount of uncertainty. A
Pacific trof developing is a near certainty, but the location and
track of this feature is still up in the air. The most likely
scenario shows the trof digging east of the Cascades and pushing
into western Montana by Tuesday, and then retrograding to the west
later in the week as a strong ridge builds into the northern
plains. This pattern would keep our area under southwest flow
aloft providing energy for convection each afternoon and evening,
but also hold temperatures down with the lower heights aloft into
Tuesday, then a warming trend Wed/Thu but continued chances for
late day showers/thunderstorms. NBM seems to be trending this way
with cooler temperatures for Monday and Tuesday compared to
previous forecasts with highs in the mid 80s Monday and lower 80s
Tuesday. Temperature spreads start to increase Wednesday with
lower 90s starting to show up on the high end of the reasonable
temperature range, and this upward trend continues into Thu/Fri.

There are other less likely but still reasonable scenarios
regarding the system for next week including one with a cooler and
wetter solution and another dry and hot, so take the current
forecast for next week with moderate confidence. Chambers

&&

.AVIATION...

18z Discussion...
All FG and low stratus (CIGs) have eroded with the sunrise or
will do so within the next hour. VFR conditions will prevail
throughout the period. Areas near KMLS/KBHK have the potential to
see strong thunderstorms between 00z and 09z tonight. The main
hazard with these storms will be wind gusts potentially up to
50kts and large hail. Localized FG is possible again tomorrow
morning, especially in low lying areas. All FG should erode by
15z. WMR

&&

.PRELIMINARY POINT TEMP/POPS...

    Fri     Sat     Sun     Mon     Tue     Wed     Thu
-----------------------------------------------------------
BIL 058/085 061/094 061/092 061/088 059/083 058/085 059/091
    10/U    21/U    21/U    22/T    22/T    31/B    21/U
LVM 049/088 051/091 051/088 053/084 049/082 050/085 050/089
    02/T    21/U    11/U    12/T    23/T    22/T    21/U
HDN 056/086 060/095 059/093 060/089 058/085 056/085 056/092
    10/U    21/U    21/U    22/T    21/B    31/B    21/U
MLS 057/083 062/094 063/092 063/090 061/084 059/084 059/091
    30/U    13/T    31/U    32/T    32/T    31/B    21/U
4BQ 058/083 064/092 064/091 063/091 061/086 061/083 061/090
    20/U    32/T    21/U    21/U    21/B    31/B    31/U
BHK 050/079 056/085 059/088 059/086 057/083 056/081 056/087
    30/U    23/T    41/B    21/B    32/T    42/T    31/B
SHR 055/085 055/092 056/091 056/090 054/085 053/084 053/089
    11/U    31/U    11/U    11/U    11/U    22/T    21/B

&&

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

&&

$$
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