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Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
1145 PM CDT Friday Jul 25 2014

Synopsis...
issued at 322 PM CDT Friday Jul 25 2014

12z upper air analysis had an inferred 850mb low near kabr with a warm
front extending southeast into eastern Missouri. A low level jet ran from West
Texas into the middle Missouri Valley. Satellite/radar trends through
middle afternoon show the nocturnal mesoscale convective system decaying as it moves into the
lower Ohio Valley with low clouds across Wisconsin.

18z surface analysis has a low at kofk with a warm front southeast to
kstl. A cold front ran from northwest Minnesota into southeast
Colorado. Dew points were in the 50s across the Great Lakes and Ohio
Valley with 60s and 70s ahead of the cold front in the plains.

&&

Short term...(this evening through saturday)
issued at 322 PM CDT Friday Jul 25 2014

Based on satellite trends through middle afternoon...mainly dry
conditions are expected through late afternoon due to the lack of an
apparent trigger. Slight chance probability of precipitation were included east of the
Mississippi this evening as a weak disturbance aloft might initiate
some isolated showers or storms. However...the possibility of
remaining dry through sunset is fairly high.

Late this evening and through sunrise Saturday dry conditions are
expected. Warm and moist air will surge into the area ahead of the
front resulting in muggy conditions.

Dry conditions will be seen across the area Saturday morning.
Moisture will pool ahead of the front and create very warm and humid
conditions.

Saturday afternoon...heat index readings will climb well into the
90s across the area with the far southern areas being right around
100 degrees. The situation is marginal for a heat advisory across
the extreme south and temperatures close to 90 may not be realized
as energy will go into drying out the wet ground.

As convective temperatures are achieved Saturday afternoon...
thunderstorms will break out along and ahead of the front. If the
high instability suggested by the models is realized...severe storms
will be possible. Individual storms may evolve upscale into a larger
severe storm complex.

Right now it appears the south half of the area is most favored for
thunderstorms Saturday afternoon with the north half potentially
remaining dry behind the front.

Long term...(saturday night through friday)
issued at 322 PM CDT Friday Jul 25 2014

The main forecast concern in the long term period is potential for
severe weather/locally heavy rain Saturday night.

Deterministic models appear to be converging on similar timing
regarding a potential mesoscale convective system impacting the southern portion of the
forecast area Saturday. However...there is still some question about
if...or how long...the threat will linger past 00z Saturday night.
The 18z 12km NAM and the 12z nmm/arw runs would suggest the mesoscale convective system will
still be in the forecast area during the evening hours...and have
opted to continue the higher probability of precipitation south into the evening...and
account for the potential for additional storms into the late night
hours. Looking at the set-up for the event...a cool front is
forecast to move southeast and reinforce an existing boundary in vicinity of
northern Missouri through central Illinois. The 12km NAM is
advertising precipitable water values at or above 2.5 inches...which seems to be rather
extreme...but there will be substantial moisture and instability.
Increasing west/northwest winds aloft will also provide favorable deep layer
shear. Another quick shot of heavy rain could also pose a flash
flood threat in the south...especially hard hit areas this morning
from Sigourney/Fairfield/Keosauqua into far northeast Missouri.

On Sunday...expect a brisk northwest wind and afternoon
showers/isolated storms in cyclonic flow...especially in far east
central Iowa and northwest Illinois.

Monday through Wednesday...a large upper trough will be in place
with unseasonably cool and mainly dry conditions forecast. Expect
afternoon highs mainly in the 70s. The next potential rain will be
Thursday or Friday.

&&

Aviation...(for the 06z tafs through 06z Saturday night)
issued at 1143 PM CDT Friday Jul 25 2014

Post convective low clouds of MVFR to low end VFR will gradually
break up by early morning bringing mostly VFR conditions under a
partly cloudy sky toward morning with patchy light aviation fog
of 4-6 miles possible. Partly cloudy skies on Saturday are expected
with few-broken bases at or above 4k above ground level. After 26/20z...prob30 group for
storms with isolated mvr/IFR conditions as convective temperature
reached at mli and brl terminals with stalled front nearby. Light
southeast winds will become variable to light NE on Saturday.

&&

Dvn watches/warnings/advisories...
Iowa...none.
Illinois...none.
MO...none.

&&

$$

Synopsis...08
short term...08
long term...rp Kinney
aviation...Nichols

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