Flash Flood and Hail in South Dakota, July 31, 2016

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
158 PM MDT SUN JUL 31 2016

.SHORT TERM...(This Evening Through Monday Night)
Issued at 155 PM MDT Sun Jul 31 2016

19z surface analysis had low over eastern MT with warm front into
western NE, dry-line into central WY, and another frontal boundary
into southwest MT. 2-3KJ/kg MLCAPE is developing ahead of warm
front with 1-2KJ/kg MLCAPE between dry-line and warm front. MLCIN
eroding evidenced by CU field forming across parts of the area and
TCU/isolated TSRA over the Black Hills. Water vapour showed
impulse over southwest WY heading east-northeast. Upper ridge
peaking over the CWA, and then heading east by this evening. Main
belt of westerlies north of CWA, but enough flow aloft to give
15m/s 0-6km bulk shear. Active to severe convection should develop
this afternoon and evening with multiple modes possible. Greatest
threat of supercells will be over northwest SD with greatest
threat of high winds across eastern WY into southwest SD given
moderate DCAPE values. Hail threat most places. Activity will
congeal into a couple of convective complexes and shift east later
this evening with some patchy fog left behind over central SD
given T/Td spreads and rain moistened air. Temperatures will be
near guidance.

Monday, surface trough/cold front slides through western SD
during the day with instability ahead of front supporting pops for
TSRA over portions of central SD and the Black Hills. Conditions
will be slightly cooler in the west and muggy in the east with
heat advisory possible depending on how high dew points end up.

Monday night, weak high pressure brings quieter weather with
pleasant temperatures.

.LONG TERM...(Tuesday Through Sunday)
Issued at 155 PM MDT Sun Jul 31 2016

Zonal flow aloft early in the week will give way to southwesterly
flow Wednesday as an upper level low moves across the Pacific NW
and eventually into the southern Canadian Prairie Provinces. Above
average temperatures can be expected across the area Tuesday and
Wednesday, before a cold front moves through Wednesday afternoon
and evening, bringing more seasonable temperatures for the rest of
the week. Weak disturbances in the flow will bring mostly isolated
thunderstorm activity Tuesday and Wednesday. The more widespread
coverage looks to be on Wednesday with the cold front passage.
Drier westerly flow late in the week should result in mainly dry
conditions Thursday and Friday. Both GFS and EC show developing
southwesterly flow over the weekend and this pattern would bring
increasing chances for thunderstorms.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Monday)
Issued At 155 PM MDT Sun Jul 31 2016

Another round of isolated to scattered thunderstorms will move
across the area through the evening hours. MVFR conditions and
gusty winds expected in and near any storms. Otherwise, VFR
conditions expected across the area.

&&

.UNR Watches/Warnings/Advisories...
SD...None.
WY...None.
&&

SHORT TERM...Helgeson
LONG TERM...26
AVIATION...26

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RAPID CITY SD
1246 PM MDT SUN JUL 31 2016

WYZ054>058-071-011300-
NORTHERN CAMPBELL-SOUTHERN CAMPBELL-WESTERN CROOK-
WYOMING BLACK HILLS-WESTON-NORTHEASTERN CROOK-
1246 PM MDT SUN JUL 31 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST
WYOMING...AND THE BLACK HILLS OF WYOMING.

.DAY ONE...THIS AFTERNOON AND TONIGHT

ISOLATED THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON AND EVENING.
ORGANIZED SEVERE THUNDERSTORMS ARE NOT EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

THERE IS A SLIGHT CHANCE OF THUNDERSTORMS ON TUESDAY. 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 DETAILS OR UPDATES...
OR CHECK OUR WEB SITE AT WEATHER.GOV/RAPIDCITY

SDZ001-002-012>014-024>032-041>044-046-047-049-072>074-011300-
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-
1246 PM MDT SUN JUL 31 2016 /146 PM CDT SUN JUL 31 2016/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTH CENTRAL
SOUTH DAKOTA...THE BLACK HILLS OF SOUTH DAKOTA...AND WESTERN
SOUTH DAKOTA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

THERE IS A CHANCE FOR THUNDERSTORMS THIS AFTERNOON INTO TONIGHT.
THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER NORTHWEST
SOUTH DAKOTA AND A MARGINAL RISK OVER SOUTH WEST INTO SOUTH
CENTRAL SOUTH DAKOTA. LARGE HAIL AND DAMAGING WINDS ARE POSSIBLE.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

THERE ARE CHANCES FOR THUNDERSTORMS MONDAY THROUGH WEDNESDAY.
ORGANIZED 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 DETAILS OR UPDATES...
OR CHECK OUR WEB SITE AT WEATHER.GOV/RAPIDCITY

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