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000 
FXUS63 KDVN 202345
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
645 PM CDT Wed Sep 20 2017

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 256 PM CDT Wed Sep 20 2017

18Z surface data has the cold front from northwest Wisconsin, 
through central Iowa and into northeast Kansas. Although not 
indicated in the surface data, satellite suggests a weak low in the 
cloud fields moving northeast along the front in Iowa. Dew points 
ahead of the front were in the 60s to lower 70s. Behind the front 
dew points were in the 40s and 50s.

&&

.SHORT TERM...(This Evening through Thursday)
ISSUED AT 256 PM CDT Wed Sep 20 2017

Convection has initiated just prior to peak heating along the front 
in northeast Iowa with additional storms developing further south 
into central Iowa.

Through late afternoon convection should be confined near the front. 
However, the instability that had developed in the full sun ahead of 
the front should result in another band of convection developing 
along or just west of the Mississippi just prior to sunset.

The inferred wave in satellite should aid in convection expanding in 
areal coverage during the evening. However, overall coverage should 
remain scattered.

The severe potential still looks low. However, the inferred wave in 
satellite data may help to enhance storm development and allow a few 
severe storms to develop. If this does occur, the primary risk would 
be wind and possibly hail.

Late tonight convection will slowly decrease in areal coverage as 
the front washes out across the area. The light winds combined with 
the humid airmass should allow patchy fog to develop that may 
increase in areal coverage prior to sunrise. Clouds across the area 
may help to limit how thick the fog gets but some patchy dense fog 
is possible in river valleys and low lying areas.

On Thursday, any lingering rain/fog will dissipate during the 
morning and skies will slowly clear. How long the clouds hold during 
the morning will dictate how warm it gets during the afternoon. 
However, it does look to be another very warm and humid day.

Refer to the climate section for record highs over the next few 
days.

.LONG TERM...(Thursday Night through Wednesday)
ISSUED AT 256 PM CDT Wed Sep 20 2017

Little change in the long term forecast with this iteration as 
guidance continues ridging and above normal temps into the weekend. 
Later in the period a chance for showers and storms returns as a the 
ridge breaks down and the L/W trof advects east.

Friday through the Weekend...After today's high temperatures 
guidance with highs in the 90s look likely Friday into Saturday 
before lower H85 temps advect into the area.  Saturday looks to 
possibly set new record highs at a couple of sites.  Spread in the 
high temperature guidance has decreased in the latest run of the 
synoptic models leading to higher confidence in forecast highs. 
Regardless, these temperatures are going to feel more like July than 
late September.

Into next week, agreement between guidance is for the L/W trof to 
shift back to the east across our area.  With it a series of 
shortwaves are forecast to affect the central Plains starting 
Monday.  Each of these waves will lead to summer like convection. 
Eventually all of the guidance has a robust wave with cold front 
moving in.  Temperatures are expected to drop to more seasonable 
later in the period.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
ISSUED AT 630 PM CDT Wed Sep 20 2017

Brief periods of MVFR/IFR in or near thunderstorms this
evening/early tonight - Gusty winds, heavy downpours, and 
lightning strikes are primary threats. Areal coverage will remain
scattered. The only terminal where storms are likely is at KDBQ.

After 05Z/Thursday, fog is possible with best chances at 
KCID/KDBQ. Low confidence on how thick fog becomes at this lead 
time, so will have to reassess for 06Z TAF issuance. Uttech

&&

.CLIMATE...
ISSUED AT 256 PM CDT Wed Sep 20 2017

Record Highs for September 20...

Moline.........92 in 1931
Cedar Rapids...93 in 1931
Dubuque........92 in 1895
Burlington.....93 in 1940

Record Highs for September 21...

Moline.........92 in 2007
Cedar Rapids...93 in 1920
Dubuque........94 in 1891
Burlington.....94 in 1908

Record Highs for September 22...

Moline.........95 in 1937
Cedar Rapids...94 in 1930
Dubuque........92 in 1937
Burlington.....94 in 1937 and other years

&&

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

$$

SYNOPSIS...08

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