Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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888
FXUS63 KDVN 191729
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1229 PM CDT Sat Aug 19 2017

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 330 AM CDT Sat Aug 19 2017

Isolated showers and thunderstorms over the central forecast area
will gradually diminish over the next few hours. The cells were
most prevalent over parts of Rock Island, Muscatine, Louisa, and
Mercer Counties. Main threats are brief heavy rain and occasional
lightning strikes.

There is also a concern for ground fog developing early this
morning across the north. However, GOES-16 nighttime microphysics
imagery showed a batch of mixed phased clouds moving into the NW
forecast area, preventing fog there. It appears the far north-
central and NE sections of the CWA have the best chance for
localized dense fog in low-lying areas as skies clear in the next
1-3 hours. Dense fog has already formed in the river valleys to
the north - in NE Iowa and SW Wisconsin.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 330 AM CDT Sat Aug 19 2017

Today and Tonight

High pressure behind departing mid-level wave will set up a warm
day but with comfortable humidity. Highs are forecast near 80 F
NE to the upper 80s SW. For tonight, light winds and residual
boundary layer moisture may support radiation fog formation in
low-lying and river valley locations, which is typical for the
middle to end of August. Uttech

.LONG TERM...(Sunday through Friday)
ISSUED AT 330 AM CDT Sat Aug 19 2017

Warm, humid and unsettled weather with periodic rain chances will be
the story from late Sunday through early Tuesday. Dry and cooler
weather then likely for mid to late week as the area is under a
northwest flow aloft and surface high pressure.

Sunday, a warm front is expected to advance northward into the
region in the wake of the departing surface high. Latest 00z models
vary in both the location and timing of this warm front and also the
strength of an advancing shortwave, critical to the potential for
showers and thunderstorms. The NAM and ECMWF are more aggressive
with the upper level lift and have QPF reaching further east into
the region and a more southern warm front compared to the GFS and
somewhat similar Canadian that have a weaker impulse and more
northward placement of the warm front. For now, will go along with a
blended approach keeping slight chances for showers and
thunderstorms across the west in the afternoon.

Sunday night through Monday night, the setup is more favorable for
periods of showers and thunderstorms with the warm front in the
region, a very moist airmass overspreading the area and several mid
level shortwaves. Forecast precipitable water values are shown in
the range of 1.5 to 2 inches, pointing toward possible heavy
rainfall, but our forecast QPF remains low confidence this far out.
It also looks like a rather cloudy period and Monday`s forecast
highs from the lower 80s north to upper 80s south may be too warm.
High dewpoints will limit lows to the upper 60s to lower 70s.

Tuesday, the trailing cold front pushes southeast through the area
with current timing suggesting any lingering showers and cloud cover
clearing out by afternoon. This would cool highs to the upper 70s
north to lower 80s south with noticeably lower humidity in most
areas by late afternoon on northwest winds.

High pressure then provides a change to cooler, drier weather for
Wednesday through Friday. Highs are expected mainly in the 70s with
overnight lows in the 50s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday Afternoon)
ISSUED AT 1228 PM CDT Sat Aug 19 2017

Expect a light southeast breeze with some MVFR fog likely
overnight. Scattered to broken mid level clouds will overspread
the area during the morning. Showers and storms are expected to
hold off until after 18z.

&&

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

$$

SYNOPSIS...Uttech
SHORT TERM...Uttech
LONG TERM...Sheets
AVIATION...RP Kinney



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