Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 120237

Area Forecast Discussion
National Weather Service Billings MT
837 PM MDT Fri Aug 11 2017


No update to the short term forecast this evening. AAG


.SHORT TERM...valid for Sat and Sun...

Upper Low over Saskatchewan is tracking SE into NE Montana by
evening. There is a nice little cold front associated with this
feature being pushed south/southeastward toward our CWA. At this
time it appears situated from west of Lewistown curving back to
Malta in northern Montana. There is a nice low level
convergent/upper level divergent couplet along the front and
decent bulk shear dropping southward as well. This generally looks
to target the northern sections of our CWA from Judith Gap to
Baker, but the southward push could very well extend across
Yellowstone County and into the Hardin vicinity. There is also a
low level jet that develops in the east later tonight. Instability
remains moderate and shear is adequate for some sustained
updrafts. So will keep mention of storms in the far east all
night. Saturday appears a bit more stable for much of the CWA.
However, remnants of the upper system and some low level
convergence suggest strong to severe storm potential right along
the southeast corner of Montana. Otherwise, convection will
generally be limited to the higher elevations this weekend.
Temperatures will be a little warmer than today both Saturday and
Sunday, but still considered seasonal. BT

.LONG TERM...valid for Mon...Tue...Wed...Thu...Fri...

A large trough and upper low will be positioned over southern
British Columbia on Monday. This will flatten the ridge and shift
its axis that was over the state Sunday eastward toward the
Dakotas, as well as bring a southwest flow aloft across the
forecast area. Models bring a Pacific front across the forecast
area during the day. A surface trough will set up across the
eastern half of our forecast area. The best shear, CAPE and
moisture look to be across southeast Montana. We will continue to
have a chance for showers/thunderstorms Monday, possibly strong to
severe, to develop west of Billings by early afternoon and spread
eastward during the afternoon and evening.

The system shifts east Tuesday. Models diverge Tuesday into
Wednesday with the GFS placing mainly a zonal flow aloft across
the forecast area with the ECMWF putting an upper low across the
Montana/North Dakota/Canadian border resulting in a cooler and
possible unstable northwest flow aloft. Models then bring mainly a
westerly flow aloft Wednesday into Friday resulting in mainly dry
conditions and seasonal temperature. Hooley



Scattered showers and thunderstorms will develop this afternoon
and continue through the evening hours. Most of the activity will
be along and east of a Roundup-KBIL-KSHR line with any activity
expecting to end by 06z. The exception will be along the North
Dakota border south to the South Dakota/Wyoming borders where the
activity may last past 06z with a few thunderstorms possibly being
strong to severe. MVFR to IFR conditions will be possible in any
thunderstorm activity. In addition, some mountain obscuration will
be possible. Otherwise, VFR conditions will prevail for the
remainder of the afternoon through the overnight hours. Hooley



    Sat     Sun     Mon     Tue     Wed     Thu     Fri
BIL 058/085 056/088 060/082 057/085 058/084 058/086 058/086
    31/U    01/U    23/T    31/B    10/U    00/U    00/U
LVM 051/087 050/088 053/079 049/083 050/084 049/085 049/086
    21/U    12/T    24/T    22/T    00/U    01/U    10/U
HDN 058/086 054/090 058/086 056/086 058/087 056/088 056/088
    31/U    01/U    22/T    31/B    10/U    00/U    00/U
MLS 059/082 055/086 060/087 060/087 060/087 059/088 059/087
    21/B    10/U    12/T    41/B    10/U    00/U    00/U
4BQ 057/084 053/086 058/089 059/085 059/087 058/087 057/087
    22/T    10/U    12/T    42/W    10/U    02/U    00/U
BHK 055/077 051/080 054/084 058/085 057/085 055/085 055/083
    34/T    20/U    12/T    42/T    11/B    02/U    00/U
SHR 054/082 050/086 054/086 054/084 053/084 052/085 052/085
    12/T    12/T    23/T    32/T    21/U    11/U    00/U




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