Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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830
FXUS63 KDVN 310246
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
946 PM CDT TUE AUG 30 2016

.UPDATE...
Issued at 932 PM CDT Tue Aug 30 2016

Cold front draped just northwest of a Freeport to Quad Cities to
Washington axis at 9 pm, and will continue to sag southward
through rest of cwa tonight. An isolated shower is possible ahead
of the front, but stabilizing boundary layer and weak convergence
along with a lack of a trigger aloft will preclude mentionable
precipitation chances. Developing light northerly winds post-
frontal will bring a gradual draw down of dew points overnight
into the 60s with some upper 50s possible north of Hwy 30 by
sunrise. Until this drying arrives expect some pockets of fog to
form next several hours that could become dense in patches,
especially south of I-80 where it will take a while for the drier
air to arrive. Lows could be a few degrees cooler into the upper
50s north, but this will depend on how much thinning or clearing
takes place, as satellite suggests some more high cloudiness to
move in overnight. Lows elsewhere look to be in the 60s.

&&

.SYNOPSIS...
Issued at 304 PM CDT Tue Aug 30 2016

Analysis at 2 PM shows leading edge of a broad front not into the northwest
1/3 of the forecast area. A spotty line of showers has developed in
the the past hours with no significant forcing center noted beyond normal
diurnal heating. Copious mid and high clouds are keeping area temperatures
within a couple degrees of 80 degrees. Upstream energy shows a
large early fall Canadian high pressure to overspread the entire
region tonight and Wednesday bringing splendid early fall weather.

&&

.SHORT TERM...(This Evening through Wednesday)
ISSUED AT 304 PM CDT Tue Aug 30 2016

Short Term Forecast Confidence Assessment...Fair or average with main
issue the coverage of showers and possibly embedded storms to pass across
the region the next 6 hours. Local tools support no severe risk with
some localized 1+ inch amounts possible between 4 and 9 PM mainly along
and especially south of the I-80 corridor.

Tonight...Chance/slight chance POPS this evening south 1/2 or so of
the region to move south by midnight with light north winds and slow
clearing along with lower dewpoints into morning. NW 1/4 of the area
should clear well before daybreak allowing for area mins to fall into
the upper 50s with lower to middle 60s rest of the region.

Wednesday...A nice early fall day with fair skies and northerly winds
of 5 to 15 MPH. Highs should be cooler, within a couple degrees of normal
with upper 70s north to lower 80s south. Area dewpoints will fall into
the upper 50s to lower 60s by afternoon.

.LONG TERM...(Wednesday Night through Tuesday)
ISSUED AT 304 PM CDT Tue Aug 30 2016

Quiet weather through the end of the week with temperatures slightly
below normal.

Quiet and dry conditions will be seen Wednesday night through Thursday
night as high pressure settles across the Great Lakes. Temperatures
will be slightly below normal.

Friday on...

The quiet and dry conditions will continue Friday through Saturday
as high pressure slowly moves into the eastern Great Lakes.
Temperatures should average slightly below normal.

Starting Saturday night and continuing into Sunday, some model
solutions start bringing rain back into the far western areas. Other
model solutions keep Saturday night and Sunday dry. As a result, the
model consensus has slight chance pops generally west of a line from
Guttenberg, IA to Ottumwa.

Sunday night through Tuesday, the weather pattern starts turning
active again. There are disagreements among the models on the
overall timing but the large scale picture suggests at least two
upper level disturbances moving through the area bringing more
showers and thunderstorms.

As a result of the model differences, the model consensus has slight
chance to chance pops for most of the area Sunday night, and chance
pops Monday through Tuesday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
ISSUED AT 634 PM CDT Tue Aug 30 2016

A cold front will continue exiting the region this evening, with
isolated showers and storms possible near MLI and BRL. Some fog is
then possible overnight with decreasing clouds, but confidence is
low given at least some northerly wind ushering in gradual drying.
For now though, I have kept previous shifts mention of a period of
mvfr visibilities at terminals, but delayed the mention until
after 06z. Otherwise, gradually drier air will bring fair skies
into Wednesday with northerly winds 4-10 kts.

&&

.HYDROLOGY...
Issued at 304 PM CDT Tue Aug 30 2016

Changes:
The flood watch for New Boston on the Mississippi River has been
upgraded to a warning. A flood warning has been issued for the
Green River near Geneseo. A flood watch has been issued for the
Wapsipinicon river near Dewitt.

Upstream of Dewitt the river continues to rise. The flood watch
has been issued to indicate a higher level of confidence that the
river may reach flood stage in the next 3 to 4 days.

&&

.DVN Watches/Warnings/Advisories...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

UPDATE...McClure
SYNOPSIS...Nichols
SHORT TERM...Nichols
LONG TERM...08
AVIATION...McClure
HYDROLOGY...08



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