Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 200849
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
349 AM CDT Thu Apr 20 2017

.SYNOPSIS...
Issued at 318 AM CDT Thu Apr 20 2017

Pair of capping inversions per 00z DVN raob limited the strength
of convection and kept it elevated thereby mitigating severe
potential last evening and early this AM. Best storm coverage
occurred along the Hwy 20 corridor as that area was brushed by
main forcing attendant to shortwave trough passing through the
Upper Midwest early this AM. Meanwhile, isolated convection
occurred down to near I-80 corridor as rest of CWA split between
stronger forcing to the north and better moisture/instability
to south which accompanied by weak upper impulse aiding residual
convective cluster over southeast KS. 07z MSAS analysis places
surface low pressure near Charles City, IA with a secondary
weaker low near Independence, IA. Warm front extended SEwd to
near a Muscatine, IA to Galesburg, IL axis thermally enhanced
on cold side by ENE winds off Lake MI. Cold front is fast
on heels of warm front leading to a narrowing of the warm sector
as it approaches western CWA extending from Marshalltown, IA to
Lamoni, IA.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 318 AM CDT Thu Apr 20 2017

Surface low over northeast IA will lift through southern WI
this AM. This will lift warm front through leading to narrow
window of warm sector and rising temps for areas SE of Cedar
Rapids to Dubuque prior to daybreak. Cold front quickly on
its heels will then sweep across the CWA exiting the far SE
mid to late AM taking any rain chances with it as cooler and
drier air filter in on gusty NW winds. Plenty of cloudiness
will be found this AM with satellite imagery showing the
back edge of clouds into central NE where columnar PWATs
lower to below 0.5 inch. However, models in pretty good
agreement on drying out 1000-500 mb RH this afternoon into
evening through mixing and advection processes on gusty
westerly winds, thus anticipate a general decreasing cloud
trend for this afternoon into evening. Do have some concern
tonight, as low level flow becomes more cyclonic, that we may
see more lower clouds wrap back down into the area than
current forecast suggests, especially northeast 1/3-1/2 of CWA.

Cooler temps on tap today and tonight (near normal) with readings
slipping back into the mid 50s NW to mid-upper 60s SE today
and upper 30s to mid 40s tonight. Winds should stay up enough to
preclude any widespread frost concerns across the north tonight,
with just a low risk of patchy frost in a few sheltered areas
along/n of Hwy 20.

.LONG TERM...(Friday through Wednesday)
ISSUED AT 318 AM CDT Thu Apr 20 2017

Cooler than normal to end the week followed by moderating
temperatures.

Quiet and dry conditions will be seen across the area on Friday.
Temperatures will average below normal. Attention then turns to the
next storm system.

The WRF/GFS models have Friday night/Saturday dry while the
CMC/ECMWF models have a glancing blow across the far south. Dprog/Dt
trends with the models have shown a southward displacement with the
storm system. Thus the possibility does exist that Friday
night/Saturday will be dry for the entire area.  Right now the model
consensus has slight chance to chance pops south of an Ottumwa to
Galesburg line. Temperatures will average below normal.

Saturday night, dry but cool conditions will be seen across the area
as the next Canadian high starts building into the Midwest.

Sunday on...

Sunday through Monday the model consensus has dry conditions across
the area as the high moves into the Ohio Valley. Temperatures will
be a little warmer than normal.

Monday night another cold front will move through the area. There
are disagreements among the models regarding timing/placement of the
front. Moisture availability is also in question. Thus the model
consensus has slight chance to chance pops for the area.

Tuesday the model consensus has dry conditions for the area as the
next high pressure builds into the upper Midwest.

Tuesday night into Wednesday the models diverge on their respective
solutions. Some model solutions have another storm system moving
through the Midwest while others have dry conditions. As a result,
the model consensus has chance pops across the area late Tuesday
night and chance to likely pops for Wednesday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday Night)
ISSUED AT 1227 AM CDT Thu Apr 20 2017

Cold front will sweep through eastern Iowa and northern Illinois
through 15z/20. Ahead of the front a small organized area of
SHRA/TSRA will move through northeast Iowa into Wisconsin. Overall
VFR conditions were ahead of the front except around convection
where IFR conditions were occurring. Behind the front conditions
will deteriorate to MVFR with pockets of IFR. After 15z/20
widespread MVFR conditions will be seen with improvement to VFR
after 00z/21.

&&

.HYDROLOGY...
Issued at 318 AM CDT Thu Apr 20 2017

Rainfall was generally less than forecast for much of the area with
the exception of the highway 20 corridor west of Dubuque. This lower
rainfall is expected to result in river forecasts being lower than
previously thought.

Tributary rivers in eastern Iowa and northwest Illinois have crested
and are on a downward trend. The Mississippi river continues to
slowly rise. Refer to the latest river flood statements (FLS) and
river flood watches (FFA) for details.

&&

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

$$

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


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