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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
212 am MDT Tuesday Jun 2 2015

Short term...today through Wednesday night
issued at 208 am MDT Tuesday Jun 2 2015

Upper wave continues to push showers and storms through the
northern plains...mainly across Montana and ND...and drier air is
moving in. With the surface low over the Montana/ND/SD borders...the
stationary front is draped through our County Warning Area. Winds are southerly
around 10 kts...and temperatures are remaining in the 60s.

The northern plains will be under southwest flow as the upper trough
continues to move on shore. Ahead of the surface low...warm and
moist air will advect into the region. Temperatures will warm well into the
80s across much of the County Warning Area...with dew points in the 60s. Slightly
cooler highs are expected over the northwestern County Warning Area as a cold front
sweeps through. MLCAPE values will reach 3000-4000 j/kg across
central South Dakota and around the southern Black Hills by middle afternoon with
near 30 j/kg cin. Forecast soundings indicate capping may inhibit
thunderstorm development across central South Dakota...but the cap may break
over the Southern Hills by middle afternoon. With near 45 kts 0-6km
shear over the hills by evening...would not be surprised if a
supercell were to develop there. However...the potential exists for
strong to severe storms with large hail and damaging winds to
develop across most parts of the County Warning Area. Precipitable water values are
near an inch around and east of the Black Hills again...and the
possibility remains that heavy rain may aggravate flooding
conditions. However...storm motion is a bit stronger today at 15-
20kts...so would not expected storms to be as stationary as on
Monday.

Upper low over the West Coast will continue to eject energy into the
region Wednesday...with chances of showers and thunderstorms
continuing. With around 2500 j/kg MLCAPE and 35 kts effective shear
across southern South Dakota...may be a few strong to severe storms
there...but expect the majority of the severe weather to be farther
south. Highs Wednesday behind the cold front will be in the 70s.

Long term...Thursday through Monday
issued at 208 am MDT Tuesday Jun 2 2015

Closed upper low expected over the western Continental U.S. By the
end of the week. This will set the stage for split flow with an
active northern stream reinforcing a ll baroclinic zone across the
region through much of the period. Ejecting impulses emanating from
the western Continental U.S. Upper trough as well as passing northern stream
waves will support an active flow pattern for the region as ll east-southeast
flow retains appreciable ll moisture in vicinity of the region. This will
allow for near daily chances for rain showers/ts in most if not all of the
forecast area through most of the period. Mean forecast models continue to
favor Thursday/Friday as the best period for more widespread precipitation chances
given the ejection of two appreciable jet streaks. Retained the
highest probability of precipitation in this period...with generally low to slight chances
through the remainder of the period. Periodic chances for severe
storms can also be expected especially given faster flow aloft with
sufficient ll moisture and east-southeast upslope flow. Seasonal to slightly
below seasonal temperatures on track thorough the period.

&&

Aviation...for the 12z tafs through 12z Wednesday morning issued at
208 am MDT Tuesday Jun 2 2015

Scattered rain showers will persist across NE Wyoming and northwest South Dakota. VFR conditions
expected through this morning. Scattered thunderstorms and rain will redevelop across northestern Wyoming
and the Black Hills this afternoon...then spread into western South Dakota this evening...with
mfvr/IFR conditions in heavier precipitation.

&&

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

$$

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

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