Hail and Damaging Wind in Wyoming, June 29, 2018

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1055 AM MDT Fri Jun 29 2018

.UPDATE...
Issued at 934 AM MDT Fri Jun 29 2018

Current surface analysis shows low pressure over south central SD,
with cold front now over Tripp County. Upper level analysis shows
large scale trough centered over the Northern Rockies, with
southwest flow over the Northern Plains. Skies are variably cloudy
across the area, mostly clear over northeast WY into far western
SD, with partly to mostly cloudy skies to the east. Temps right
now are mostly in the upper 60s to near 80. Lingering showers
have exited eastern areas, with the forecast area clear on the
radar for the time being.

Main forecast change was to remove pops over western areas until
around midday as latest short range models show showers holding
off until at least that time. A favorable severe weather threat
is still in place for later today, starting off early to mid
afternoon over northeast WY and the Black Hills, spreading east
across the rest of the area through at least the early evening.
A good amount of moisture in the low to mid levels remains across
the area, with SBCAPE values progged to range from around 1000
j/kg over northeast WY to over 2000 j/kg over parts of southwest
and south central SD. Shear looks adequate for at least shorter-
lived supercells, especially across southern portions of the CWA.
Cap looks to remain strong to the east of the Black Hills this
afternoon, with most of the activity developing further west with
shortwave energy this afternoon. There is a strong likelihood that
the activity will consolidate into a MCS as it moves into/through
western SD late today and this evening. Main threats with severe
storms will be large hail and strong wind gusts, but an isolated
tornado threat is also expected from northeast WY to southwest SD.
May need to adjust high temps a bit through the day, with a
fairly wide spread expected across the area. 70s across northeast
WY to around 90 over south central SD.

&&

.DISCUSSION...(Today Through Thursday)
Issued at 311 AM MDT Fri Jun 29 2018

Upper trough is slowly crossing the Cascades into the northern
Rockies with active southwest flow across the northern High Plains.
At the surface, low pressure center is over KPHP at this time, with
a strong cold front crossing the western South Dakota plains.
Dewpoints in the upper 60s to low 70s is making for a warm and humid
night across central SD. KUDX radar shows the cold front crossing
Custer to Oglala Lakota counties, with gusts to near 50 mph. Surface
low will push eastward today, with breezy northwest winds continuing
across the area. Temps will be lower across the CWA...but with a
wide range as cooler air filters in from the northwest. Highs across
northeast WY will be in the low to mid 70s while highs across south
central SD will near 90. The next major convective activity will
occur this afternoon and evening as the next series of upper waves
cross the region. While there could be some lingering showers and
storms this morning, today's activity is expected to develop along
the Bighorns in the early afternoon, then push into NE WY. Other
activity will develop over the Black Hills, but the main activity
will be moving in from the west, and then develop into a line across
western SD this evening. There will be sufficient instability and
shear for severe thunderstorms with large hail and damaging winds as
the main threats.

Drier air will filter into the region through Saturday as the main
trough axis crosses the region. As the trough moves through, storms
are expected to develop Saturday afternoon mainly from the Black
Hills into southern portions of the CWA. Instability and shear will
both be weaker, so severe weather is not expected. Zonal flow aloft
will develop Sunday and Monday with dry weather expected to start
the week. Much warmer weather is expected toward the middle of the
week southerly flow restrengthens.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Saturday)
Issued At 1055 AM MDT Fri Jun 29 2018

Lingering MVFR CIGS over far southwestern SD and northwestern SD
will decrease early this afternoon; otherwise, mostly VFR
conditions will continue through the period. The exception will
be local IFR/MVFR conditions with scattered thunderstorms that
move west-to-east across the forecast area from roughly 19z-07z.
Also, after 08z some MVFR CIGS are expected to develop across far
southwestern into south-central SD.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

Update...26
DISCUSSION...13
AVIATION...Bunkers

Hazardous Weather Outlook
National Weather Service Rapid City SD
238 AM MDT Fri Jun 29 2018

SDZ001-002-012>014-024>032-041>044-046-047-049-072>074-WYZ054>058-
071-301300-
Harding-Perkins-Butte-Northern Meade Co Plains-Ziebach-
Northern Black Hills-Northern Foot Hills-Rapid City-
Southern Foot Hills-Central Black Hills-Southern Black Hills-
Custer Co Plains-Pennington Co Plains-Haakon-Fall River-
Oglala Lakota-Jackson-Bennett-Mellette-Todd-Tripp-
Sturgis/Piedmont Foot Hills-Southern Meade Co Plains-
Hermosa Foot Hills-Northern Campbell-Southern Campbell-
Western Crook-Wyoming Black Hills-Weston-Northeastern Crook-
238 AM MDT Fri Jun 29 2018 /338 AM CDT Fri Jun 29 2018/

This Hazardous Weather Outlook is for western South Dakota and
northeastern Wyoming.

.DAY ONE...Today and Tonight

Numerous thunderstorms will move across the area this afternoon
into tonight. There is a slight risk of severe thunderstorms with
large hail and damaging winds.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

There is a chance of thunderstorms Saturday, mainly south of
Interstate 90. Severe thunderstorms are not expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed today.

&&

Stay tuned to NOAA weather radio for further updates...or check
our web site at weather.gov/rapidcity

Special Weather Statement
National Weather Service Rapid City SD
120 PM MDT FRI JUN 29 2018

WYZ054-291945-
Northern Campbell WY-
120 PM MDT FRI JUN 29 2018

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN CAMPBELL COUNTY
UNTIL 145 PM MDT...

At 120 PM MDT, Doppler radar was tracking a strong thunderstorm 8
miles west of Echeta, or 30 miles northwest of Gillette, moving
northeast at 40 mph.

Dime size hail and wind gusts up to 50 mph will be possible with this
storm.

Locations impacted include...
Spotted Horse and Echeta.

A severe thunderstorm watch remains in effect until 800 PM MDT for
northeastern Wyoming.

LAT...LON 4453 10600 4463 10601 4478 10578 4440 10562
      4438 10602
TIME...MOT...LOC 1920Z 241DEG 36KT 4448 10603

Bunkers