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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
307 PM MDT sun Jul 5 2015

Short term...this evening through Monday night
issued at 305 PM MDT sun Jul 5 2015

Current surface analysis shows cold front from northeast ND
through north central to southwest South Dakota...and into central Wyoming. Weak
low pressure along the front is located over west central South Dakota.
Upper level analysis shows low pressure over central Canada...with
zonal flow across the northern plains. One shortwave has exited
north and east of the area...while the next wave is moving across
eastern Wyoming into western South Dakota now. Kudx radar shows showers and a few
thunderstorms increasing in coverage over eastern Wyoming into far
western South Dakota...with scattered showers and storms further east toward
north central South Dakota. Skies range from mostly sunny over south central
South Dakota to mostly cloudy over northeast Wyoming and far western South Dakota. A fairly
wide range of temperatures across the area right now...ranging from 60s
over parts of northeast Wyoming to the lower 90s over south central South Dakota.
Winds are breezy from the northwest behind the front...with south
to southeast winds ahead of the front over south central South Dakota.

Active weather is expected across at least eastern portions of the
region late this afternoon and especially this evening. Clouds and
somewhat faster movement of the cold front across western South Dakota today
has kept atmosphere more stable and capped over this area. Some
uncertainty at this point on how far north and west the threat for
severe weather will be across the County Warning Area...but areas near and east of the
front... especially across south central South Dakota...should see the highest
risk into the evening hours. The best instability and shear will be
in place across this area...with strong shear near and just behind
the frontal boundary. Supercells are possible late this afternoon
and early evening...with a line of storms potentially developing
along the front later this evening...likely to the east of the County Warning Area.
Large hail will be the main threat with any severe storms into the
early evening...possibly turning into more of a wind trheat later in
the evening. An isolated tornado cannot be ruled out along the front
over southwest into south central South Dakota late today. Heavy rainfall
could be an issue as well...especially over south central South Dakota...as
rotating storms will likely be slower movers near the front and
precipitable water values will be 1.5 to 2 inches there.

Further north and west...instability lowers...especially into
northeast Wyoming...where clouds and cooler airmass have kept temperatures down.
The severe risk over the Black Hills area and much of far western South Dakota
will be somewhat less...with the front having passed by.
However...isolated strong to severe storms are certainly possible
through the late afternoon and possibly early evening. Overall...
activity should diminish in intensity and move south and east of the
County Warning Area overnight.

Monday will be partly cloudy and on the cooler side...with highs in
the upper 60s and 70s. Will keep a slight chance for a shower or
thundershower over the Black Hills in the afternoon..
otherwise...dry and cooler weather is expected into early Tuesday.

Long term...Tuesday through Sunday
issued at 305 PM MDT sun Jul 5 2015

Generally dry weather will continue into Tuesday as strong high
pressure shifts east into the upper Midwest. Return flow across
northeast Wyoming and far western South Dakota will bring chances of
showers/storms Tuesday aftn/night. Broad cyclonic flow is prognosticated to
develop across the region Wednesday and Thursday with daily chances for
storms. Temperatures will be near average. Models are still
diverging greatly for the end of the week with how an upper low
over California will phase back into the main flow. The wetter
solution is the GFS which has most of the energy pushing within
the southwest flow into the northern plains. The European model (ecmwf) keeps
strong upper ridging centered across the Southern Plains which
keeps the remnant low pushing northeast through the northern
rockies...keeping the forecast area mainly dry under the ridge. At
this time...kept the current forecast going with a chance for
storms through the weekend and temperatures around average.

&&

Aviation...for the 00z tafs through 00z Monday evening
issued at 305 PM MDT sun Jul 5 2015

A strong cold front will continue to cross the area today. With
this front...numerous rain showers/thunderstorms and rain will develop and some storms will
be severe. MVFR/IFR conditions are expected with the strong storms
as well as strong and erratic wind gusts. Storm activity will end
through the night as cooler and drier air moves in from the
northwest...leading to VFR conditions.

&&

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

$$

Short term...26
long term...mls
aviation...mls

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