904 
FXUS63 KUNR 052308
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
508 PM MDT Thu Jul 5 2018

.DISCUSSION...(This Evening Through Thursday)
Issued at 243 PM MDT Thu Jul 5 2018

Latest analysis shows an upper ridge building over the high
plains. At the surface, high pressure is centered over the eastern
Dakotas/Minnesota with low pressure over the Rockies. The
resulting sfc pressure gradient is producing moist southerly flow
over the forecast area. Persistent stratus over the southern part
of the forecast area has kept high temperatures cooler than the
potential, but temperatures in those areas will rise a few more
degrees late this afternoon as the cloud cover begins to
dissipate. 

Tonight, heights will continue to build expected as upper ridge 
strengthens with implied synoptic scale subsidence. However,
diurnal heating and abundant moisture suggest isolated TSRA may 
develop early this evening as a weak shortwave crosses
northeastern WY. Marginal 0-6km shear may support a robust storm.
An convection that does develop may continue across especially
northwestern South Dakota as a low level jet develops tonight.

On Friday and Saturday, very warm temperatures will develop with
the thermal ridge peaking on Saturday. MLCIN quite strong with 
deep boundary layer mixing during peak heating. While can't 
totally rule out TSRA, most areas will be in the unmentionable 
category. Heat indices will pop to 100-105F over parts of the SD 
plains on Saturday afternoon.

Saturday night/Sunday, shortwave moves across MT/ND pushing a weak 
frontal boundary into the CWA which may be the focus for some TSRA. 
Sunday's highs will be slightly cooler.

First half of next week looks hot with temperatures well into the 
90s. Limited precipitation chances into mid-week until a potential 
pattern changes develops.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Friday Evening)
Issued At 506 PM MDT Thu Jul 5 2018

Local MVFR CIGS will dissipate this evening around the Black 
Hills. Otherwise VFR conditions are expected through the period. 
Isolated thunderstorms will be possible over NE WY this evening 
and across NW SD later tonight.

&&

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

$$

DISCUSSION...10
AVIATION...JC