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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
507 am MDT Wednesday Jul 27 2016

Short term...(today through Thursday night)
issued at 153 am MDT Wed Jul 27 2016

Impulse laden NW flow will persist in the period, bringing rounds
of shra/ts to much of the fa. Weak cool front has settled across
the region, stalling across the far western fa. Weak shortwave
trough now traversing the northern plains supporting sct shra/ts
activity over western areas. This wave should support sct showers
over much of the western third through morning...possible edging
into the eastern fa by late morning. Otherwise...diurnal heating
will support shra/ts over the fa this afternoon, mainly the
western third, and esp over the Black Hills. Mean ml cape around
1500 j/kg with 40 knots of deep layer shear will support the
chance for a couple supercells over the western third. Otherwise,
mostly isold activity expected on the SD plains given weak
subsidence and associated cin. Strong impulse will begin to push
into the region tonight, supporting precip chances in a pos
Theta-E adv regime. This system will slowly traverse the region
Thursday, supporting a good chance of diurnal convection thurs
over much of the area, esp invof the Black Hills. Lack of
applicable cape and marginal shear thur, will highly limit severe
threat. Overall slow flow aloft will allow some areas to see
appreciable rains where cells develop, given pw/S in excess of
1.25 inches. Carried precip chances through thur night, although a
drying trend is likely overnight.

Seasonal temps expected today, with even cooler conds thurs given
clouds, moisture, and rain. Mainly places will see highs in the
70s thurs.

Long term...(friday through tuesday)
issued at 153 am MDT Wed Jul 27 2016

Chances for showers and thunderstorms will continue
Friday, mainly over the eastern County Warning Area where upper energy will be
focused. Highs will be in the 80s.

With weak upper ridging briefly over the region this weekend, warmer
and drier conditions are expected. Towards the end of the weekend,
the European model (ecmwf) and GFS agree that a Canadian low pressure system will
push the ridge eastward, placing the northern plains back in more
active zonal to southwest flow. Above average temperatures will
continue into early next week.


Aviation...(for the 12z tafs through 12z Thursday morning)
issued at 507 am MDT Wed Jul 27 2016

A band of showers/storms continues to move across northeastern
Wyoming/southwestern South Dakota this morning, with MVFR conditions. MVFR
conditions also expected through early morning for portions of the
western South Dakota plains, as some low clouds/fog have developed there.
Additional strong storms are expected this afternoon/evening, with
IFR visibilities in stronger storms.


Unr watches/warnings/advisories...
South Dakota...none.


Short term...jc
long term...pojorlie

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