Fishtail, Montana Weather Forecast Discussion

356
FXUS65 KBYZ 092104
AFDBYZ
Area Forecast Discussion
National Weather Service Billings MT
304 PM MDT Tue Sep 9 2025
.KEY MESSAGES...
- Above normal temperatures through Thursday.
- Daily chance of showers and thunderstorms over portions of the
  area today through Thursday, best chance over the mountains and
  foothills.
- Good chance of more significant precipitation (20-70% chance
  widespread >0.5in) and cooler temps Friday into Sunday.
&&
.DISCUSSION...
Through Thursday night...
The weather pattern through Thursday will be dominated by the
gradual eastward movement of an upper level ridge axis over
eastern Montana and a large low pressure system over the western
United States. Under the influence of the upper level ridge,
temperatures will remain above normal with highs in the upper 70s
to lower 90s. While the core of the low pressure system will
remain to our west through Thursday, multiple waves of energy and
moisture ejecting northeastward out of the low will allow for the
daily chance of showers and thunderstorms over portions of the
region today through Thursday. As far as today goes, scattered
showers and isolated thunderstorms are expected to remain mainly
over the mountains and foothills of south-central Montana and
northern Wyoming. By Wednesday into Thursday, look for the daily
chance of precipitation to increase in percentage and coverage as
better upper level support moves into our region from the low
pressure system gradually approaching our region. With that said,
the chance of precipitation is around 15 to 40 percent Wednesday
and 20 to 70 percent Thursday, greatest over the mountains and
foothills both days. Over far eastern Montana, where the chance of
precipitation is the lowest, increased atmospheric moisture will
lead to increased instability. While mid-level capping will likely
limit convection in this area under the upper level ridge, hence
the lower chance of precipitation, if a storm is able to break the
cap Wednesday or especially Thursday, it could become strong to
severe in this area. Across the rest of the area, thunderstorms
are expected to remain below severe limits today through Thursday.
By Friday into Saturday, the aforementioned low pressure system
looks to move into and through our region in some fashion,
potentially bringing widespread moderate to heavy rainfall to
portions of the area. See the long term discussion for more
information on this.
Wildfire smoke...Look for smoke concentrations to decrease from
south to north tonight through Wednesday as the south to
southwesterly flow aloft increases. Arends
Friday through Tuesday...
Friday and Saturday continue to look the most promising for
widespread precipitation in the long term as an upper level trough
moves across the region. Currently, for at least 0.5" of precip,
there is a 20-40% chance over the Absaroka/Beartooth mountains and
foothills and a 40-70% chance, highest near the Dakota border,
over the rest of the region. Additionally, near the Dakota border
there is a 30-40% of more than 1.5". There is still uncertainty in
the exact track of this system, so stay tuned to the forecast.
Enough instability will be present Friday and Saturday for
thunderstorms in the afternoon and evening, with a 50-70% chance
of CAPE values greater than 500 J/kg, highest near the Dakota
border. At this time, it is still uncertain if enough ingredients
will align for stronger storms to develop.
On Sunday, the trough will exit the region. There is still
disagreement on how quickly the trough will exit, with some models
leaning towards early Sunday and others towards late Sunday. As a
result, the NBM currently has a 10-30% chance of precip through
the day. If the trough exits earlier in the day, this will allow
a brief window of dry conditions for Sunday afternoon into Monday
morning before another disturbance enters the region. Monday
through at least the middle of next week are then expected to
remain unsettled as the disturbance moves through, although the
exact details are still uncertain.
Highs will be in the mid 70s to near 80 Friday, decreasing to low
to mid 70s for the weekend. Then, highs will warm back to mid 70s
to near 80 to start the next week. Archer
&&
.AVIATION...
Scattered showers and isolated thunderstorms are expected over
the mountains and foothills of south-central Montana and northern
Wyoming this afternoon into tonight. While the plains look to
remain dry under VFR conditions, a low level jet could bring a
period of low level wind shear to areas around and east of KBIL
this evening into tonight, but uncertainty remains on the strength
of these winds. Otherwise, wildfire smoke will continue to reduce
slant range visibility today. Smoke concentrations then look to
decrease from south to north through the day Wednesday. Arends
&&
.PRELIMINARY POINT TEMP/POPS...
Wed     Thu     Fri     Sat     Sun     Mon     Tue
-----------------------------------------------------------
BIL 057/087 060/083 054/079 055/072 054/076 053/079 054/075
    11/K    24/T    34/T    66/T    32/W    12/W    33/W
LVM 047/084 051/078 044/075 045/071 045/074 044/076 045/073
    31/B    26/T    35/T    56/T    33/W    23/T    44/T
HDN 055/089 056/086 051/081 052/071 051/076 049/080 051/077
    11/K    22/T    34/T    76/T    42/W    11/U    33/W
MLS 059/091 061/089 058/083 057/073 055/075 053/080 054/077
    11/K    21/B    32/W    77/T    63/W    21/U    22/W
4BQ 059/089 063/090 057/081 056/071 054/074 052/079 054/076
    11/K    11/B    22/T    76/T    52/W    11/U    22/W
BHK 053/087 059/090 055/081 054/073 051/075 050/078 051/077
    11/N    21/B    21/B    77/T    63/T    21/U    22/W
SHR 051/088 054/085 049/079 048/070 047/075 046/080 048/075
    21/B    12/W    25/T    76/T    42/W    11/U    34/W
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.
&&
$$
weather.gov/billings

NWS BYZ Office Area Forecast Discussion