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000
FXUS63 KDVN 172015
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
315 PM CDT Thu Aug 17 2017

.SYNOPSIS...
Issued at 313 PM CDT Thu Aug 17 2017

18Z surface data indicates the cold front runs from eastern
Wisconsin, down to KSTL, and then into northeast Oklahoma. Dew
points along and ahead of the front were in the 70s with 60s behind
the front.

&&

.SHORT TERM...(This Evening through Friday)
ISSUED AT 313 PM CDT Thu Aug 17 2017

Through sunset, expect isolated to scattered rain showers to persist
mainly along and north of highway 30.

After sunset, dry conditions will be seen along with clearing skies
as high pressure moves through the area. Temperatures should be
slightly below normal.

On Friday the dry conditions will continue during the morning hours
as another storm system approaches from the west. Attention then
turns to Friday afternoon.

There are many questions regarding how the sensible weather will
evolve Friday afternoon. The models loosely agree that one and
probably two upper level disturbances will move through the area.
This scenario does have support based on water vapor imagery over
the northern Rockies. The first disturbance would arrive roughly
during peak heating. However, the models disagree on the
track/timing of the surface low and the position/timing of any
related fronts.

Therefore, a broad brush approach has been done regarding rain
chances Friday afternoon. It may be initially dry early Friday
afternoon but as the forcing increases with the approach of the
upper level disturbance, convection should begin developing west of
the Mississippi and increase in areal coverage through late
afternoon.

Given the initial dryness of the atmosphere, some of the stronger
storms would be capable of producing small hail from mid to late
Friday afternoon.

.LONG TERM...(Friday Night through Thursday)
ISSUED AT 313 PM CDT Thu Aug 17 2017

Forecast focus on zonal flow and several opportunities for rain then
a cool/dry northwest flow later next week.

Friday night: Significant short wave/cold front will move across the
cwa, with showers and thunderstorms (some possibly strong) in the
evening. The rain will end overnight with the passage of the front.

This weekend: Models quickly return a zonal flow to the area, with
warmer temperatures but dry conditions, as weak high pressure will
be over the area. Maximum temperatures will push in the upper 70s to
mid 80s on Saturday, and then well into the 80s to around 90 on
Sunday.

Monday: Low confidence in timing of thunderstorms but temperatures
look to be on the hot side. Highs will rise into the lower 90s,
especially south of Interstate 80 with dewpoints rising into the
lower 70s. This will soar heat index values into the mid to upper
90s, especially in our southern counties.  This warming will be
ahead of a significant upper level trough/strong cold front that
will be diving southeast towards the area.

Monday night through Tuesday: Likely pops for showers and
thunderstorms as strong forcing and plentiful moisture will be in
place. Too early to determine the severe weather threat.

Wednesday through Thursday: Northwest flow aloft and surface high
pressure should bring pleasant temperatures/comfortable humidity.
Highs should be in the 70s to lower 80s with lows in the 50s to
lower 60s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday Afternoon)
ISSUED AT 1232 PM CDT Thu Aug 17 2017

MVFR conditions associated with wrap around clouds from the
departing storm system will slowly exit eastern Iowa and northern
Illinois through 01z/18. After 01z/18 expect VFR conditions as
high pressure moves through the Midwest.


&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

SYNOPSIS...08
SHORT TERM...08
LONG TERM...Haase
AVIATION...08