Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 161125
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
625 AM CDT Wed Aug 16 2017

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 313 AM CDT Wed Aug 16 2017

Eastern Iowa and points east remain in the quiet surrounded by
rather impressive waa driven bands of showers ands storms to the
north, west, and south. The storm system over western KS will move
toward Iowa today, bringing progressive showers and storms to out
region. Prior to this, a few isolated showers and storms will be
possible, especially over the central and northern CWA through 7 AM.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 313 AM CDT Wed Aug 16 2017

Today and tonight`s forecast will deal with progressive lines of
convection, that is certain.  The timing appears to be one from mid
morning in the far south to mid afternoon northeast, then the main
line this evening into the early overnight.  The coverage on the
initial line will likely be scattered as there is no real focusing
mechanism.  We will use radar trends that match the model depiction
of lift arriving in the south by mid morning. As of 2 AM, the
showers from this forcing are just south of Topeka KS, to east of
Springfield MO. Amounts from these progressive showers and storms
should be fairly light, under 0.25. I still think there are
enough dry hours in the day`s forecast for us to warm up
considerably before any widespread rains arrive. This still seems
like a day in the lower to upper 80s from north to south.

Looking at late this afternoon and this evening, the main forcing
should arrive in the form of a mature line, possibly with bowing
segments.  Winds are expected to be southerly ahead of this line,
which may reduce any squall line tornado threat, but any strong
backing of winds would allow for that potential to exist. It`s worth
keeping an eye on. In any case, this evening looks wet, as a mature
line with stratiform trailing it works through the entire CWA.  Pops
will remain in the likely to lower end categorical range until  we
are certain of the line`s timing. The mature line will most likely
have a wind threat of 40 to 60 mph winds, in bowing segments as it
moves eastward over the area. As the evening progresses, the threat
for strong winds should diminish as storms approach Illinois.
Rainfall tonight, should be generally under 1 inch, but will most
certainly have a few swaths of 1 to 2 inches where mesoscale
interaction allows for a bit of cell training.

ERVIN

.LONG TERM...(Thursday through Tuesday)
ISSUED AT 313 AM CDT Wed Aug 16 2017

Long term starts with rain and storms exiting the area on Thursday
leading to nice day.  The weather stays quiet for a short time
before the overall pattern returns to an active phase and continues
this pattern through most of the long term period.  With zonal flow
and a dearth of largescale trofs across the area, daily chances for
precip will be inextricably tied to mesoscale processes.

Thursday...surface low progged to be across southern MN will be
moving towards the east.  The actual front doesn`t look to pass the
area until the afternoon leading to chcs of precip and even a rumble
of thunder.  Main mid-level wave axis doesn`t leave the area until
near 00z Friday, so clouds could remain across the area into the
afternoon.  Friday looks like a nice dry day across the area before
the flow turns active again.

A decent wave will dig into the area for Friday into Saturday.
Current guidance has the wave south of the area.  QPF in the models
runs across the southern CWA.  The surface boundary in the GFS
suggests that the best chances for rain will be south of the CWA in
central MO.  Looks like a perfect setup for a MCS to the south of
the CWA.

The rest of the extended has weak forcing and zonal H5 flow.  Daily
chances of storms seems likely at this juncture.  Each day`s
forecast will be dependent on what occurs the night before.  As a
result, my confidence in the extended forecast solutions are low at
this time.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday Morning)
ISSUED AT 622 AM CDT Wed Aug 16 2017

A stormy day will take place across the Midwest today, and this
will bring several rounds of showers and storms north over the
area today, and a widespread line of strong storms through Iowa
and Illinois this evening. The daytime storms will be scattered
and short lived, and are handled primary with VCSH in TAF
forecasts as they will be mainly VFR in nature. South to southeast
winds will continue through the period. Tonight`s storms will
arrive from the west around 00Z and last through roughly 06Z. Low
visibility, gusty winds, and heavy rain are expected with the line
of storms.

&&

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

$$

SYNOPSIS...Ervin
SHORT TERM...Ervin
LONG TERM...Gibbs
AVIATION...Ervin



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