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Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
325 PM CDT Tuesday Jul 28 2015

issued at 256 PM CDT Tuesday Jul 28 2015

Active weather regime across the area this afternoon will lead to
a difficult forecast for the short term. A warm front was draped
across the S Minnesota into S WI and north Illinois. Showers and thunderstorms from
overnight convection were still ongoing across the area. Numerous
outflow boundaries are located across the area. An outflow
boundary of specific concern is across the central to southern
portions of the area. A strong July cold front was across NE...SW
Minnesota and northwest Iowa. This cold front is expected to push through the area
tonight and lead to showers...and thunderstorms.


Short term...(this evening through wednesday)
issued at 256 PM CDT Tuesday Jul 28 2015

Main forecast problem are the showers and thunderstorms the rest of
today and into tonight across the area. Severe weather...and
flash flooding are possible tonight across the area.

Convective debris from today has limited warming across the far
northern County Warning Area. Areas north of i80 have been in the middle to upper
70s. To the south across southern Iowa and northern MO...temperatures are
in the low to middle 90s. This has created quiet the thermal gradient
across our County Warning Area. Current gut feeling is that we will continue to
see showers and thunderstorms slowly move in from the west over
Benton and Linn counties. This training could lead to flash
flooding...especially with precipitable waters near 2 inches. These storms
appear to be elevated and will stay that way until the front
approaches. The front may then push these showers and storms to
the south and east and intensify them. If they can become surface
based...there is threat for severe wind and tornadoes with them.
At this time they appear to be remain elevated and will stay that

Off to the west in SW Iowa and southeast NE...cumulus was being monitored for
thunderstorm development. If these storms can initiate and then
become surface based the potential for severe weather will be
increased. Surface winds are backed and all indications are that surface
based storms would have a wind and tornado threat. Rain rates this
morning were very high and areas with rather benign convection had
1 to 2 inches of rain quickly. Since areas south of i80 have seen
significant rainfall recently and precipitable waters are near 2
inches....decided to go with a flash Flood Advisory for much of the central and
southern parts of the County Warning Area. South of i80....widespread rainfall of
one to 1.5 inches are possible. Isolated pockets of training
convection could see up to 4 inches of rain.

The cold front should move out of the area near 12z.

Long term...(wednesday night through tuesday)
issued at 256 PM CDT Tuesday Jul 28 2015

A few Post frontal showers may linger Wednesday morning...but for
the most part by a northwest breeze with cooler and less humid
conditions. Through late week...the forecast area will be situated
in northwest flow...between a western Continental U.S. Ridge and eastern Continental U.S.
Upper trough. Expect dry conditions with seasonably warm
temperatures through Friday...although dewpoints will be in the 60s
for the most part rather than the 70s of late.

Looking ahead...will carry low probability of precipitation...generally in the 20 to 30
percent range...from Saturday night through Tuesday. There will
likely be more dry periods than wet ones...but with a number of
subtle short wave troughs in the northwest flow that are difficult
to time...cannot rule out any one period for some rain at this
point. Seasonably warm temperatures are forecast to continue...with
an absence of extreme heat and humidity.


Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 256 PM CDT Tuesday Jul 28 2015

VFR conditions are forecast throughout the taf period with the
exception possible thunderstorms early this evening and into
tonight. I have low confidence that Cid and dbq will see thunder
again. MVFR visibilities and ceilings are possible during these storms. Once
the storms move through...everything will clear out and winds will
be out of the northwest tomorrow morning.


Dvn watches/warnings/advisories...
Iowa...Flash Flood Watch through Wednesday morning for Benton-Cedar-Des
Moines-Henry Iowa-Iowa-Jefferson-Johnson-Keokuk-Lee-Linn-
Louisa-Muscatine-Scott-Van Buren-Washington.

Heat advisory until 7 PM CDT this evening for Des Moines-Henry
Iowa-Jefferson-Keokuk-Lee-Louisa-Van Buren-Washington.

Illinois...Flash Flood Watch through Wednesday morning for Hancock-
Henderson-Henry Illinois-McDonough-Mercer-Rock Island-Warren.

Heat advisory until 7 PM CDT this evening for Hancock-Henderson-

MO...Flash Flood Watch through Wednesday morning for Clark-Scotland.

Heat advisory until 7 PM CDT this evening for Clark-Scotland.



short term...Gibbs
long term...rp Kinney

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