013
FXUS65 KBYZ 131903
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
103 PM MDT Thu Aug 13 2026

.KEY MESSAGES...

- Widespread precipitation is forecast today through Saturday.
  Locally heavy rainfall is possible during this period, with a
  slight risk of exceeding flood guidance for areas east of a
  Roundup to Billings to Sheridan line.

- Temperatures will be well below normal today through Saturday,
  and possibly Sunday.

- Return to average temperatures next week.

&&

.DISCUSSION...
Next 7 Days...

An upper level low pressure system / trough axis remains centered
over the Great Basin today. This is allowing for our region to get
repeated vort maxes as they migrate northeastwards. Several more
weak waves of energy will move up from the Great Basin into
Montana through the day Saturday. This will result in rounds of
showers and thunderstorms over the next 2-3 days with periods of
relatively dry conditions in the areas of AVA behind these
shortwaves.

Now that we are firmly under the shield of clouds there will be
little severe threat with any of these storms due to the lack of
CAPE and increased CIN. What remains a threat though the the
potential for locally heavy rainfall. While no storm is forecast
to have overly impressive rainfall rates, repeated showers over
the same areas could cause some localized flooding. That being
said, we have been quite dry over the past month which means that
the ground should be able to hold most of this moisture just fine
with minimal flooding concerns on a region-wide scale.

Due to the relative weak steering flow the upper level low will be
allowed to naturally retrograde over the next several days before
merging with a secondary advancing low pressure system. This will
put our area back under a ridge as it builds back in from the
Great Plains. The good news with this feature though is that it
will not be nearly as hot as the previous ridging pattern. Surface
winds will remain primarily out of the plains, limiting any
downslope effects and keeping the neer-surface environment
decently moist. Additionally, the apex of this ridge will be
roughly along the MT/SK border meaning that we could see
shortwaves ride along the ridge bringing chances for brief
cooldowns and / or precipitation. One such trough could impact the
area this time next week. WMR


.AVIATION...

18z Aviation Discussion....

Stratus deck is slowly lifting and eroding over the western and
central portions of the forecast area at 18z. Do not expect this
IFR/MVFR deck to completely dissipate today, but an approaching
shortwave trof will help to lift and scatter it out in most
locations by 21z. Light showers will continue across the forecast
area this afternoon with general weak lift over the area. After 2z
shower and isolated thunderstorm activity will develop over the
mountains as the shortwave trof moves into the area. A broad area
of light to moderate precipitation with embedded thunderstorms and
localized pockets of heavy rain will slowly cross the area this
evening, exiting to the northeast in the early morning hours
tonight. In the wake of the trof, expect light upslope winds and
a saturated low levels to result in fog development across much of
the area through 16z Friday morning. While periods of VFR are
expected this afternoon, especially over the eastern half of the
forecast area, MVFR/IFR conditions will prevail over the next 4
hours with widespread precipitation through this evening, and
fog/stratus overnight into the day Friday. Chambers

&&

.PRELIMINARY POINT TEMP/POPS...

    Fri     Sat     Sun     Mon     Tue     Wed     Thu
-----------------------------------------------------------
BIL 058/072 057/074 055/082 058/085 058/083 058/083 058/083
    95/T    64/W    41/U    11/B    12/T    22/W    21/B
LVM 048/072 046/076 045/081 047/083 048/081 047/080 047/080
    89/T    95/T    51/U    22/T    22/T    23/W    33/W
HDN 054/074 052/076 050/083 053/087 054/085 054/085 053/085
    94/T    64/T    21/U    12/W    22/T    22/W    21/B
MLS 058/074 054/075 052/083 057/087 058/085 057/084 056/084
    87/T    22/W    13/W    23/W    34/T    43/W    32/W
4BQ 059/076 057/076 054/082 058/086 059/084 059/085 059/084
    96/T    33/T    35/T    44/T    43/T    33/W    32/W
BHK 055/075 051/075 047/081 053/086 054/083 052/083 052/083
    89/T    31/E    01/U    33/W    34/T    43/W    33/W
SHR 053/073 051/073 049/079 050/083 051/082 051/083 052/082
    84/T    77/T    52/T    22/T    22/T    22/T    22/T

&&

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

&&

$$
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