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Area forecast discussion 
National Weather Service Sioux Falls South Dakota
620 PM CDT Wednesday Jul 30 2014

Short term...(this evening through thursday)
issued at 318 PM CDT Wednesday Jul 30 2014

The few to scattered diurnal cumulus out there will dissipate once again
with sunset. Will see a weak middle level wave and surface low drop
south across the northern plains tonight into tomorrow. Thetae
advection associated with this system should result in some
scattered to broken middle level cloudiness tonight around 700
mb...spreading from northwest to southeast. Soundings suggest very
limited cape originating from this level so despite the quantitative precipitation forecast signal
in some of the models...will keep the overnight forecast dry for
now. As it seems like it might be tough to get much more than a
sprinkle. Lows tonight will be warmer than last night but still
chilly...generally middle 50s to around 60.

The wave will continue to sink south tomorrow. Just enough large
scale forcing and cooling aloft that looks increasingly likely we
will be able to generate isolated to scattered showers and
thunderstorms from late morning through the afternoon. Given the
expected wave and weak boundary coverage will probably
end up south of Interstate 90 across northwest Iowa and extreme
southeast South Dakota. Cape is pretty weak and thin...likely
staying below 1000 j/kg. Thus not expecting anything strong or
severe...just some rain and a few lightning strikes. We warm about
another 1c at 850 mb tomorrow...but with more cloud cover
likely...we will probably only realize 1f or maybe 2f degrees warmer
surface readings than today...ending up in the 78 to 84 range.

Long term...(thursday night through wednesday)
issued at 318 PM CDT Wednesday Jul 30 2014

Seasonally cool and dry conditions are expected Thursday night
through Saturday as the area remains in northwest flow between an
upper level ridge and an exiting trough. Will keep some small probability of precipitation
in northwest Iowa on Thursday evening but the activity will likely
be waning or at least remain fairly sparse. Will keep temperatures
at or below seasonal normals with lows mainly in the 50s and highs
from the upper 70s to middle 80s.

In the outer periods (sunday through wednesday)...upper level
ridging over the West Coast is expected to gradually build westward
onto the plains. However...a weak trough along the top of the ridge
is pretty consistently forecast by each model to weaken the ridge
and keep the area from getting into a hot Dry Ridge. While Monday
and Tuesday have the best chance to be above normal an extended
period of how weather looks unlikely. The chances for rainfall
during this time will likely be the typical hit and miss Summer time
variety however if this trough does round the ridge then there could
be a bit better chances Tuesday night into Wednesday.


Aviation...(for the 00z tafs through 00z Thursday afternoon)
issued at 620 PM CDT Wednesday Jul 30 2014

VFR conditions expected through the period. A weak low pressure
system dropping south should bring an increase in middle level
cloudiness sometime later tonight into tomorrow. Could also see an
isolated shower or thunderstorm...but probability too low to include
in tafs at this time.


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


Short term...chenard
long term...08

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