Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 221301
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
801 AM CDT Sat Jul 22 2017

.UPDATE...
Issued at 758 AM CDT Sat Jul 22 2017

The nocturnal heavy rain MCS is about to exit the area. There are
some lingering showers and thunderstorms south of I-80 thatshould
dissipate by 10 AM.

With only a hour left for the flash flood watch, the current plan
is to let it expire at 9 AM.

&&

.SYNOPSIS...
Issued at 405 AM CDT Sat Jul 22 2017

06Z surface data has the effective boundary running from just south
of Lake Michigan west to near KOMA. Dew points were in the 60s from
the Great Lakes into the northern Plains with 70s along and south of
the boundary.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 405 AM CDT Sat Jul 22 2017

A hydrology section regarding area rivers will be available around
5 AM.

First off, the current headlines will remain as is. In terms of the
heat headlines, the possibility does exist that parts of the
advisory and warning areas may see heat index readings below 100 due
to the cloud cover and cooler temperatures from the overnight storms.

Through sunrise, the heavy rain thunderstorm complex over the area
will continue but slowly weaken. Boundaries from this storm complex
will generate isolated to scattered thunderstorms across the south
third of the area.

After sunrise, the thunderstorm complex will slowly dissipate during
the morning. The effective boundary will get pushed into the
southern third of the area.

Starting around mid day and continuing into the afternoon,
differential heating along the effective boundary across the south
third of the area will provide the focus for new convection to
develop that will continue into the early evening.

Once sunset occurs tonight, any lingering convection will dissipate
leaving the area quiet but humid through sunrise Sunday.

.LONG TERM...(Sunday through Friday)
ISSUED AT 405 AM CDT Sat Jul 22 2017

Another cold front will move through the area on Sunday afternoon.
After a dry morning, showers and thunderstorms are possible across
the southeast half of the area during the afternoon. The warm and
humid conditions will continue with temperatures averaging above
normal.

Sunday night through Monday night, quiet and dry conditions will be
seen across the area as high pressure moves through the Midwest. Dew
points will drop Sunday night with much lower dew points across the
entire area Monday and Monday night. Temperatures will average
slightly below normal.

Tuesday on...

Quiet and dry conditions will continue on Tuesday as high pressure
moves into the Ohio Valley. Temperatures should be close to normal.

Late Tuesday night into Wednesday the next front drops down into the
area and eventually stalls. The model consensus has slight chance to
chance pops late Tuesday night into Wednesday. Temperatures should
be around or above normal.

Wednesday night through Thursday night the weather pattern becomes
active again. The key to the overall forecast is the location of the
stalled frontal boundary. Here the models disagree on the location
but suggest it will be somewhere over the area. As a result, the
model consensus has chance pops for essentially the entire area.

On Friday, the models bring the next high pressure into the Great
Lakes but disagree on the timing and location of the high. As a
result, the model consensus has slight chance to chance pops over
roughly the northeast half of the area. Temperatures should be close
to normal.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday Morning)
ISSUED AT 638 AM CDT Sat Jul 22 2017

Thunderstorm complex across eastern Iowa and northern Illinois
will slowly dissipate through 18z/22 with conditions varying
between IFR in TSRA and VFR. After 18z/22 expect VFR conditions
with isolated TSRA that may or may not affect a TAF site. The
potential for high density altitudes will continue through 01z/23.
After 06z/23 conditions are expected to deteriorate to MVFR due to
fog development.


&&

.HYDROLOGY...
Issued at 412 AM CDT Sat Jul 22 2017

Overnight updates focused on minor adjustments to forecasts on the
Rock, Pecatonica, Wapsi, and Maquoketa Rivers. Based on routed and
recent rainfall, Freeport, Moline and Joslin are all forecast to
surpass major flood stage. Como has already shot up quickly into
major flood, faster than previously forecast.

On the faster responding Maquoketa River, sharp rises are
underway, but there is still uncertainty as to the eventual crest.
Have continued the flood watch at Manchester and Maquoketa.
Forecast crests on the Wapsi are early next week, plenty of time
to maintain flood watches and reevaluate.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Flash Flood Watch until 9 AM CDT this morning for Benton-
     Buchanan-Cedar-Clinton-Delaware-Dubuque-Iowa-Jackson-
     Johnson-Jones-Linn-Muscatine-Scott.

     Excessive Heat Warning until 8 PM CDT this evening for Cedar-Des
     Moines-Henry IA-Iowa-Jefferson-Johnson-Keokuk-Lee-Louisa-
     Muscatine-Scott-Van Buren-Washington.

     Heat Advisory until 8 PM CDT this evening for Benton-Clinton-
     Jones-Linn.

IL...Flash Flood Watch until 9 AM CDT this morning for Bureau-Carroll-
     Henry IL-Jo Daviess-Putnam-Rock Island-Stephenson-Whiteside.

     Excessive Heat Warning until 8 PM CDT this evening for Hancock-
     Henderson-Henry IL-McDonough-Mercer-Rock Island-Warren.

     Heat Advisory until 8 PM CDT this evening for Bureau-Putnam-
     Whiteside.

MO...Excessive Heat Warning until 8 PM CDT this evening for Clark-
     Scotland.

&&

$$

UPDATE...08
SYNOPSIS...08
SHORT TERM...08
LONG TERM...08
AVIATION...08
HYDROLOGY...RP Kinney



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