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fxus63 kdvn 172054 
afddvn

Area forecast discussion
National Weather Service Quad Cities Iowa Illinois
354 PM CDT Wed Jul 17 2019

Synopsis...
issued at 353 PM CDT Wed Jul 17 2019

18z surface data has a squall line from northeast Iowa into south
central Iowa. A frontal boundary ran from Southern Lake Michigan
into southern Minnesota and into South Dakota. Dew points north of
the frontal boundary were in the 60s while south of the front they
were in the 70s.

&&

Short term...(this evening through thursday)
issued at 353 PM CDT Wed Jul 17 2019

Bottom line up front...will continue the current headlines as is.

Current storm complex will exit the area by late afternoon.
Lingering areas of light rain along with isolated convection will
persist through sunset.

After sunset another nocturnal storm complex is expected to develop
possibly along the Iowa/Minnesota border. Where this new complex tracks will
be important to the overall sensible weather the remainder of the
night.

Some model solutions keep the system north of the area which would
indicate dry conditions for the area.

However with the heat dome temporarily suppressed to the south,
tonights storm complex may develop across northern Iowa and move
east southeast toward northern Illinois. If this scenario occurs,
which seems more plausible, then at least the northern half of the
area would be under the gun for storms.

Internally a few of the models suggest that storms may develop and
move over the same areas. Even if this does not happen the storms
will be very efficient in producing heavy rainfall due to the high
moisture levels in the atmosphere. Rainfall rates could easily
approach 2 inches an hour and result in flash flooding.

Thursday morning the storm complex will exit the area allowing the
rain to end. Temperatures may be slow to respond due to the rain
cooled air but once clouds break up temperatures will start climbing
especially during the afternoon.



Long term...(thursday night through wednesday)
issued at 353 PM CDT Wed Jul 17 2019

Thursday night and Friday
assessment...high confidence on heat

The model consensus has hot and humid conditions with no rain for
the area.

Friday night and Saturday
assessment...medium to high confidence on heat. Low confidence on
rain.

The model consensus has slight chance pops Friday night for the
northern half of the area with slight chance to chance pops for the
northeast half of the area on Saturday.

The rain chances will be dictated on how strong and deep the layer
of warm air is is aloft. If the strength and depth are large enough
then the possibility does exist that the entire area will remain dry.

Saturday night on...

Saturday night through Sunday night
assessment...low confidence

The global models continue to push a front through the area. A
change of airmass and the forcing supplied by the front should
result in considerable rain chances. The model consensus appears to
be slowly trending this way with slight chance to chance pops
Saturday night and Sunday with slight chance pops on Sunday night.

Given the overall large scale set up, pops should continue to
increase over the next several days.

Monday through Wednesday
assessment...medium confidence

The model consensus has mainly dry conditions for the area with
temperatures around normal. However, I cannot fully rule out the
possibility of isolated diurnal convection developing during the
afternoon each day.

&&

Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 1235 PM CDT Wed Jul 17 2019

Models are not handling the current storm front moving across Iowa
toward northern Illinois. Prior to storm arrival high density
altitudes can be expected.

Outside of thunderstorms and rain and rain expected VFR conditions through 06z/18.
IFR/LIFR conditions and gusty winds are likely in thunderstorms and rain through
00z/18. After 06z/18 VFR conditions should continue but there are
questions regarding how far south into Iowa and northern Illinois
the next storm front will get.



&&

Dvn watches/warnings/advisories...
Iowa...excessive heat warning until 7 PM CDT Saturday for Benton-
Buchanan-Cedar-Clinton-Delaware-Des Moines-Dubuque-Henry Iowa-
Iowa-Jackson-Jefferson-Johnson-Jones-Keokuk-Lee-Linn-Louisa-
Muscatine-Scott-Van Buren-Washington.

Flash Flood Watch from 7 PM CDT this evening through Thursday
morning for Benton-Buchanan-Clinton-Delaware-Dubuque-
Jackson-Jones-Linn.

Illinois...excessive heat warning until 7 PM CDT Saturday for Bureau-
Carroll-Hancock-Henderson-Henry Illinois-Jo Daviess-McDonough-
Mercer-Putnam-Rock Island-Stephenson-Warren-Whiteside.

Flash Flood Watch from 7 PM CDT this evening through Thursday
morning for Carroll-Jo Daviess-Stephenson-Whiteside.

MO...excessive heat warning until 7 PM CDT Saturday for Clark-
Scotland.

&&

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