Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 180501
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1101 PM MDT Mon Jul 17 2017

.DISCUSSION...(This Evening Through Monday)
Issued at 119 PM MDT Mon Jul 17 2017

Water vapor shows west southwest flow aloft with potent short wave
energy to our west across WY. At the surface, low is centered over
north central South Dakota with trailing cold front extending
through southwest SD into the NEB panhandle. Convection has
initiated in the southern Blkhls within area of easterly upslope
flow.

MLCAPE expected to grow to 500-1500J/KG, strongest over south
central SD. Shear remains weak, but is expected to grow modestly
this evening as mid level winds increase ahead of approaching
short wave energy. Three area of convection of concern for this
afternoon and tonight. The first is over the Blkhls this
afternoon. These storms will be pulsy in nature given rather weak
shear, but will have the ability to produce brief severe
hail/winds. The second area is over south central SD along the
frontal boundary, but this area is where the weakest shear
resides so widespread severe storms not expected in this area.
The third area will over northeast WY early this evening as large
scale lift increases with approaching short wave. Storms that
initiate over northeast WY should become rather widespread as they
track into the Blkhls later this evening and across the SD plains
overnight. A marginally severe hail and wind threat will exist
initially, but possibly become more of a wind threat as the
evening hours progress. DCAPE in excess of 1200J/KG supports
this. Storms could continue well after midnight on the SD plains,
then end Tuesday morning.

Cold front will hang up across far southwest SD and the Blkhls on
Tuesday and will be the focus for afternoon/evening storm
development. Things should remain fairly capped on the SD plains
given cooler easterly low level flow and subsidence behind
tonight`s short wave. Temps will be noticeably cooler across much
of the area with readings struggling to get out of the 80s.

Zonal flow expected the remainder of the week with nearly daily
chances for thunderstorms. Temps should remain mainly above
average, but excessive heat not likely in this flow pattern.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Tuesday Night)
Issued At 1059 PM MDT Mon Jul 17 2017

Scattered thunderstorms will continue overnight. Expect gusty
winds in and around storms. The storms will exit the area Tuesday
morning. Area of MVFR ceilings may develop across western South
Dakota overnight and impact the KRAP terminal late tonight.

&&

.FIRE WEATHER...
Issued at 119 PM MDT Mon Jul 17 2017

Good chances thunderstorms across much of the area tonight,
especially along/north of I-90 tonight. Gusty outflow winds
possible with any storms. A bit cooler for Tuesday with easterly
winds and higher relative humidities. Temperatures expected to be
above average the rest of the week with nearly daily chances for
thunderstorms.

&&

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

$$

DISCUSSION...Johnson
AVIATION...7
FIRE WEATHER...Johnson



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