Special Weather Statement, NWS Rapid City, SD

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
201 PM MDT Tue Aug 1 2017

.DISCUSSION...(This Evening Through Tuesday)
Issued at 159 PM MDT Tue Aug 1 2017

Upper level analysis shows a shortwave crossing MT
over the western CONUS ridge. Storm cluster has exited south central
SD, and a few showers/storms are moving across mainly southern
portions of the CWA. Stationary boundary stretches across SD, with
breezy easterly surface winds. Under variably cloudy skies,
temperatures are in the 80s.

Still thinking most of the activity will hold off until mid-evening
when the MT shortwave pushes into the region. MLCAPE around 1000
J/kg at 03Z will gradually diminish overnight, with sufficient shear
continuing into Wednesday. Hi-res models continue to show a
convective cluster moving into northeastern WY mid to late evening,
and then expanding across western SD overnight. Main threat with any
stronger storms will be gusty winds.

Showers/storms will continue into Wednesday morning, drying out
briefly behind this first wave, and then redeveloping in the
afternoon as a secondary wave pushes through the Dakotas. However,
best forcing and chances for precip will be across ND and eastern
SD. Decent shear and instability may support some strong to severe
storms in the afternoon, especially along the cold front, but will
also depend on morning convection. Precip will diminish towards
evening as cool high pressure sinks into the region.

Additionally on Wednesday, gusty northwest winds will be possible
with the cold front. The NAM is showing stronger 850 mb winds and
cold air advection than the ECM and GFS, and thus has highs 5 to
10 degrees lower. Highs Wednesday will be in the 70s to lower 80s,
warmer across the south.

Upper ridging and surface high will keep Thursday dry and cool, with
highs in the 70s. Thermal ridge will begin building back into the
region for Friday. Models are showing the next wave sliding through
the northern plains Friday night, bringing showers/storms to the
Dakotas. A few scattered showers/storms will be possible over the
weekend with waves moving over the ridge, but generally mild and dry
conditions are expected.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Wednesday Afternoon)
Issued At 510 AM MDT Tue Aug 1 2017

An isolated shower or storm is possible this afternoon across
southwest and south central South Dakota. For tonight, scattered
thunderstorms will redevelop early this evening and will continue
overnight across most of northeastern Wyoming and western South
Dakota. Isolated strong to severe thunderstorms are possible tonight
with large hail and damaging wind gusts. LCL MVFR CIGS are possible
near any showers or thunderstorms, otherwise VFR conditions will
prevail.

&&

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

DISCUSSION...Pojorlie
AVIATION...MLS

Hazardous Weather Outlook
National Weather Service Rapid City SD
518 AM MDT Tue Aug 1 2017

SDZ001-002-012>014-024>032-041>044-046-047-049-072>074-WYZ054>058-
071-021300-
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-
518 AM MDT Tue Aug 1 2017 /618 AM CDT Tue Aug 1 2017/

This Hazardous weather outlook is for western South Dakota and
Northeastern Wyoming.

.DAY ONE...TODAY AND TONIGHT

Scattered thunderstorms will occur this morning and again this
afternoon and tonight. Isolated severe thunderstorms are expected,
mainly this afternoon and evening, with large hail and damaging
wind gusts possible.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

There is a chance of showers and thunderstorms on Wednesday.
Isolated severe thunderstorms are expected.

.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

10

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE RAPID CITY SD
124 PM MDT TUE AUG 01 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0100 PM     HEAVY RAIN       2 WSW HAMILL            43.59N  99.71W
08/01/2017  M1.73 INCH       TRIPP              SD   COCORAHS

            1.73 INCHES IN 60 MINUTES

&&

AFOSCATO

Special Weather Statement
National Weather Service Rapid City SD
150 PM MDT TUE AUG 1 2017

SDZ042-044-012030-
Bennett SD-Oglala Lakota SD-
150 PM MDT TUE AUG 1 2017

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN OGLALA LAKOTA AND
SOUTHWESTERN BENNETT COUNTIES UNTIL 230 PM MDT...

At 150 PM MDT, Doppler radar was tracking a strong thunderstorm 10
miles south of Batesland, or 13 miles north of Gordon, moving south
at 25 mph.

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

Locations impacted include...
Batesland.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 4314 10229 4320 10223 4320 10216 4315 10208
      4300 10197 4300 10224
TIME...MOT...LOC 1950Z 338DEG 22KT 4299 10211

Foscato

Special Weather Statement
National Weather Service Rapid City SD
452 PM MDT TUE AUG 1 2017

WYZ054-055-012330-
Southern Campbell WY-Northern Cambell WY-
452 PM MDT TUE AUG 1 2017

...SIGNIFICANT WEATHER ADVISORY FOR EAST CENTRAL CAMPBELL COUNTY
UNTIL 530 PM MDT...

At 452 PM MDT, Doppler radar was tracking a strong thunderstorm near
Gillette, moving southeast at 20 mph.

Half inch hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Gillette, Rozet, and Camplex Event Facility.

This Includes Interstate 90 in Wyoming between Mile Markers 122 and
145.

LAT...LON 4417 10565 4430 10558 4430 10511 4390 10534
TIME...MOT...LOC 2252Z 295DEG 19KT 4419 10550

Eagan

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