Severe Thunderstorm Warning 76, NWS Billings, MT

Area Forecast Discussion...Updated
National Weather Service Billings MT
358 PM MDT Thu Jun 7 2018

.UPDATE...

Quick update to add Severe Thunderstorm Watch 161 from Rosebud,
Treasure, Big Horn, and Sheridan counties, and areas to the east.
The Severe Thunderstorm Watch is in effect through 11 pm MDT. STP

&&

.SHORT TERM...valid for Tdy and Fri...

Very minor changes to the short term forecast, as convective setup
continues to support strong to severe thunderstorms across the
region today.

High dewpoints support CAPES 1500 to 2500 j/kg for most of the
area with even higher amounts along the Montana/Dakota border.
Shear looks sufficient for some storm organization with 100m2/s2
storm relatively helicity over western half of the area and it
really climbs to 250m2/s2 along the eastern border.

Best estimate of timing for activity looks pretty consistent,
beginning in the early afternoon in the western high terrain.
Activity will spread eastward into central zones, around Billings,
between 4 and 8pm, and into eastern zones, Miles City and Baker,
after 8pm.

Overnight the approaching trof begins to pull drier air over the
region and the surface trof shifts east of the area by Friday so
convective chances are decreased. This will point to a mainly dry
day for Friday. Increased sunlight and downslope flow will be
offset by slightly cooler air aloft on Friday, resulting in
similar temps as Thurs.

Cooler air aloft goes away for Saturday, but downslope flow and
sunlight persist, so expect temperatures Saturday to be much
warmer, with high back into the 90s, and continued dry. AAG

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

Cooler weather is in store for the first part of the extended
forecast. This cool weather will come behind a strong cold frontal
passage Saturday night. This front will be driven along by a deep
upper trough moving across the northern Rockies through early
next week. This will set up a breezy day for Sunday with post
frontal winds gusting throughout the day. High temperatures will
be suppressed into the lower to mid 70s on Sunday and even upper
60s by Monday. Cyclonic flow will provide a slight chance of
showers, but coverage will be limited.

Warmer temperatures will move back in for the middle of the week
as a flat ridge slides into the northern Rockies. TWH

&&

.AVIATION...

Showers and thunderstorms are beginning to develop over the high
terrain this afternoon. Activity coverage is expected to continue
to increase, and spread eastward through the afternoon and evening.
Some storms may be severe with large hail, strong wind gusts to
50 kt, frequent lightning, and torrential rainfall. MVFR to LIFR
conditions will occur with the storms. Expect areas of obscuration
over all mountains this afternoon and evening. AAG

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Fri     Sat     Sun     Mon     Tue     Wed
-------------------------------------------------------
BIL 083 056/082 057/092 059/076 047/068 046/074 050/079
    4/T 41/U    21/U    03/T    31/N    21/N    01/U
LVM 079 049/080 049/089 050/066 041/061 041/070 045/076
    5/T 41/U    20/N    03/T    32/T    21/N    01/B
HDN 085 055/084 058/093 058/079 048/069 046/076 049/080
    3/T 31/U    21/U    02/T    31/B    21/U    01/U
MLS 082 059/083 060/092 063/081 051/069 048/074 052/079
    3/T 61/U    11/U    12/T    30/B    20/U    00/U
4BQ 084 058/083 060/093 062/085 050/071 047/076 049/080
    3/T 41/U    11/U    12/T    30/U    20/U    01/U
BHK 079 056/082 058/088 062/085 050/069 045/073 047/079
    4/T 61/U    11/U    11/N    20/B    10/N    00/U
SHR 083 054/080 055/091 056/079 045/069 041/073 045/078
    3/T 31/U    21/U    03/T    31/U    20/U    01/U

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Severe Thunderstorm Watch 161 in effect until 11 PM MDT this
      evening FOR ZONES 30>33-36>38-57-58.
WY...Severe Thunderstorm Watch 161 in effect until 11 PM MDT this
      evening FOR ZONES 98-99.

&&

weather.gov/billings

Hazardous Weather Outlook
National Weather Service Billings MT
232 PM MDT Thu Jun 7 2018

MTZ028>042-056>058-063>068-WYZ098-099-080300-
Southern Wheatland-Musselshell-Treasure-Northern Rosebud-Custer-
Fallon-Northern Stillwater-Yellowstone-Powder River-Carter-
Southern Big Horn-Eastern Carbon-Northern Park-
Northern Sweet Grass-Golden Valley-Red Lodge Foothills-
Northern Big Horn-Southern Rosebud-Judith Gap-Paradise Valley-
Livingston Area-Beartooth Foothills-Absaroka/Beartooth Mountains-
Crazy Mountains-Northeast Bighorn Mountains-Sheridan Foothills-
232 PM MDT Thu Jun 7 2018

This Hazardous Weather Outlook is for portions of central
Montana...south central Montana...southeast Montana and north
central Wyoming.

* WHAT...Strong to severe thunderstorms possible.

* WHERE...Southern Montana and north-central Wyoming.

* WHEN...This afternoon and evening.

* ADDITIONAL DETAILS...The main hazards are large hail and damaging
  winds. Also these storms could produce heavy rainfall.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Hazardous Weather Outlook is issued when hazardous weather could
impact the region within the next week. Be sure to stay tuned for
future updates as locations, timing, and impacts could change.
Begin preparations to mitigate any impacts that could result from
the hazardous weather.

&&

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