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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
738 am MDT Wednesday Jun 3 2015

Short term...today through Thursday night
issued at 237 am MDT Wednesday Jun 3 2015

Upper wave is over the central Dakotas...pushing the weakening
showers eastward. Broad trough over the West Coast continues to
put the region in southwest flow. Surface low is over southeastern
ND...and secondary cold front is passing through the County Warning Area. Winds
are northwesterly around 10kts...with temperatures in the 50s and lower
60s.

This morning will be dry...except for a few possible late morning
showers/storms over the Black Hills. Upper wave will approach the
northern plains late this afternoon. MLCAPE will be around 2000
j/kg this afternoon across northeastern Wyoming...the Black Hills...and
far southern South Dakota...with lapse rates in those areas around 7 c/km.
With 0-6 km shear of 35-40 kts...may be one or two strong to
severe storms in those areas. Overall...ingredients are not as
impressive as the past couple days...so do not expect widespread
severe weather today. Showers and thunderstorms will expand to the
northeast as wave pushes into the region tonight. Highs today will
be in the 70s...with lows tonight in the 50s.

Cold Canadian high will keep temperatures in the middle 60s to lower 70s on
Thursday. East/southeast return flow will bring in moisture...and
showers/storms will continue for much of the day before gradually
moving off to the east. Some afternoon/evening strong to severe
storms are possible across northeastern Wyoming and southwestern South Dakota with
impressive cape and marginal shear developing there by 21z...along
with another wave moving through the southwest flow. Precipitable
water Thursday into Thursday night remains around an inch and a
quarter...and so storms with heavy rainfall may aggravate flooding
conditions. Showers and storms will diminish overnight...and lows
will be in the 50s.

Long term...Friday through Tuesday
issued at 237 am MDT Wednesday Jun 3 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...with the potential for a
stronger backdoor cold front by early next week. 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 Friday/Sat as the best periods 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 Thursday morning)
issued at 735 am MDT Wednesday Jun 3 2015

An area of IFR ceilings due to St will affect far northeast Wyoming onto
the northwest/central South Dakota plains along/north of a line from about
kgcc to krap to kicr through the morning hours with improving
conditions this afternoon. VFR conds expected most places by early
afternoon. An impulse will traverse the region today...bringing
chances for shra/ts...mainly to NE Wyoming and the perhaps far western
South Dakota. Retained thunderstorms in the vicinity at kgcc with no mention at krap given low
thunder probs. Rain showers/ts chances will spread NE Wednesday night...with scattered
MVFR/IFR ceilings possible across the area then.

&&

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

$$

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

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