Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 210137
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
737 PM MDT Thu Jul 20 2017

.UPDATE...
Cancelled the Severe Thunderstorm Watch #425 for southeast
Montana. Strongest convection ended up just east of the state
line, in the Dakotas. Weaker convection still ongoing, but not
working with as much instability. Coordinated with SPC and decided
to drop the Watch. No changes to fire weather and existing Red
Flag Warnings, given temperatures were still up, dewpoints still
down and wind was still a little gusty. Will update again in the
next couple of hours. TWH

&&

.SHORT TERM...valid for Fri and Sat...

Convection has been forming off the Beartooth Mountains and have
already begun pushing into Big Horn County as of 230 PM. This has
been the trend that the CAMs have been advertising. Meso-analysis
shows that CAPE values along the Dakota borders are getting to
around 2000 J/kg, and shear values are 40 to 50 knots through 6
km. Recent runs of the HRRR are still pointing towards stronger
convection developing later this afternoon in eastern Montana then
moving into the Dakotas. The convection currently in Big Horn
County will increase as it moves into the better environment.

A cold front will move through overnight and should be to around
Miles City by 6 AM tomorrow. This has will keep winds breezy
across Musselshell, Treasure, and northern Rosebud counties.
Tomorrow 850mb winds remain strong out of the northwest. With
mixing tomorrow afternoon, areas from Roundup to Broadus are
going to gusty winds with relative humidity values in the teens.
Have extended the current Red Flag to until 9 PM tomorrow for
Musselshell and Northern Rosebud, and have added Custer, the rest
of Rosebud, and Powder River Counties. Saturday will be dry, as
ridging builds back into the area. Reimer

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


No significant changes. The riding continues Sunday and most of
Monday keeping conditions dry. A low in southern Canada will bring
a weak cold front across the area. This will shift the ridge to
the east. This put the area in southwesterly flow. This will
result in some scattered PoPs each afternoon. The GFS ensemble is
not showing much in the line of moisture with any of this
activity. With the increase flow of monsoonal moisture,
temperatures will be slightly cooler. Reimer
&&

.AVIATION...


Thunderstorms will move across southeast Montana and northern
Wyoming this evening impacting KBHK and KSHR. Otherwise gusty
outflow winds will move through the region producing gusts to 35
mph. Otherwise mostly clear skies expected with VFR conditions.
Borsum/TWH

&&

.PRELIMINARY POINT TEMP/POPS...

    Fri     Sat     Sun     Mon     Tue     Wed     Thu
-----------------------------------------------------------
BIL 064/090 059/090 061/095 065/095 065/092 066/090 065/092
    20/U    00/U    00/U    11/U    21/B    22/T    11/U
LVM 054/086 049/088 051/092 056/093 056/089 058/087 055/089
    00/U    00/U    00/U    01/U    21/B    22/T    22/T
HDN 064/091 058/092 058/097 062/098 063/095 064/092 062/095
    20/U    00/U    00/U    11/U    11/B    22/T    22/T
MLS 070/091 060/091 062/096 068/099 067/094 067/093 066/095
    20/U    00/U    00/U    01/U    11/B    12/T    21/U
4BQ 067/090 059/091 060/094 066/098 066/095 065/091 064/093
    30/U    00/U    00/U    01/U    11/B    12/T    22/T
BHK 068/091 056/089 056/091 063/096 062/092 062/089 061/091
    41/U    00/U    00/U    01/U    11/B    12/T    22/T
SHR 062/086 054/089 054/093 058/095 058/092 059/090 058/090
    30/U    00/U    00/U    11/U    11/B    22/T    22/T

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Red Flag Warning in effect until 9 PM MDT Friday FOR ZONES
      117-127-130.
     Red Flag Warning in effect until 9 PM MDT this evening FOR
      ZONE 124.
     Red Flag Warning in effect from 9 AM to 9 PM MDT Friday FOR
      ZONES 131-132.
WY...None.

&&

$$
weather.gov/billings


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