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Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
617 PM CDT Wednesday Jul 29 2015

Synopsis...
issued at 321 PM CDT Wednesday Jul 29 2015

The latest surface analysis was indicating a ridge axis settling east-
southeastward from across the west Central Plains...to the middle MS River
Valley behind a cold front pushing through the Great Lakes and western Ohio
River valley. In-building low level pressure gradient and increasing dry-
down mixing has lowered surface dewpoints into the 50s across much of the
County Warning Area...making for tolerable humidity values when combined with
ambient temperatures in the low to middle 80s. 12z upper air analysis and
especially the current water vapor loop were indicating nicely a
large wrapped up cyclone just southwest of the Hudson Bay region
spiraling east-northeastward. A weak vorticity lobe embedded in the
cyclonic flow south of this feature pressing east across the upper
Midwest...will slip across Iowa this evening but have nothing but
drying/subsiding air to act upon.

&&

Short term...(this evening through thursday)
issued at 321 PM CDT Wednesday Jul 29 2015

Tonight...a few wispy patches of cirrus traversing across the region
associated with southern flank of upper jet maximum streaking from Nebraska
to south of James Bay...otherwise clear skies tonight. With surface
winds decoupling or at least becoming light/less than 5 kts...along
with the lowered dewpoints should make for a seasonably cool night with
several areas making it into the 50s to around 60. Some River Valley
fog possible toward sunrise.

Thursday...broad/low amplitude steering flow northwesterlies take
over the upper Midwest...with lower level flow actually starting to
warm air advect from the northwest across the local area. Plenty of
sunshine and deep mixing profiles will make for widespread high
temperatures in the middle to upper 80s. Surface dewpoints will likely dry-down mix
below model guidance values again...battling the crop
evapotranspiration processes and make it back into the 50s in some
places. ..12..

Long term...(thursday night through next wednesday)
issued at 321 PM CDT Wednesday Jul 29 2015

Persistent northwest flow...near to slightly below normal
temperatures...and several windows of showers/thunderstorms
highlight the long term forecast period.

The first issue is dealing with the passage of a weak cool front
Friday...which could support a few thunderstorms during the
afternoon and early evening hours. The entire forecast area is
included in the day 3 marginal risk area. Middle/upper level forcing
looks rather anemic...but moisture pooling near the boundary with
potential for upper 60s/around 70 dewpoints...and deep layer shear
around 35 kts warrant adding a low pop. Several synoptic scale
models are generating some light quantitative precipitation forecast...mainly south...so have
limited probability of precipitation to areas along and south of a Fairfield to Galesburg
line. Surface high pressure should keep dry weather through the day
on Saturday...before a short wave trough arrives Saturday night into
Sunday morning. More widespread storms are expected with this
system...a few strong with an isolated severe storm not out of the
question.

Additional rain chances and seasonably warm temperatures continue Sunday
night through Monday night with additional short wave energy
dropping southeast through the region. By Wednesday...a more potent
trough could impact the forecast area with the best chance of
widespread rain and severe storms during the entire period.

&&

Aviation...(for the 00z tafs through 00z Thursday evening)
issued at 615 PM CDT Wednesday Jul 29 2015

VFR conditions will be seen through 00z/31 as high pressure moves
from the plains into the lower Missouri Valley.

&&

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

$$

Synopsis...12
short term...12
long term...rp Kinney
aviation...08

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