Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 230522

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1222 AM CDT Wed May 23 2018


Issued at 305 PM CDT Tue May 22 2018

A passing short wave trof provided plenty of low clouds this
morning but this afternoon these clouds were thinning. Mid
afternoon temperatures were in the upper 60s to mid 70s.


.SHORT TERM...(This Evening through Wednesday)
ISSUED AT 305 PM CDT Tue May 22 2018

Forecast focus on thunderstorm chances and possible fog.

Tonight: Weak high pressure will be centered near Chicago
providing light winds to the area. With dewpoints near 60 there
will be plenty of low level moisture. Depending on the amount of
cloud cover (or lack of) this would set up the potential for
patchy or areas of fog, possibly dense. As of now, the most likely
area for fog would be east of the MS River closer to the surface
high, and less cloud cover. Later shifts will need to monitor the
situation for any headlines. Lows should range from the mid 50s to
the lower 60s.

Convection: Models suggest a low level jet increasing after
midnight, especially west of the dvn cwa. The more organized
storms look to remain across extreme northern IA/southern MN, on
the nose of this jet. However, an elevated THETA-E/WAA wing of
possible showers and a few thunderstorms may graze our nw cwa late
tonight. The most likely area to be affected would be along
Highway 20, from Independence to Dubuque. However, can`t rule out
at least isolated activity as far south as Highway 30 in eastern
IA. None of the storms look to be severe as both shear and
instability will be weak. SPC has a marginal risk well to our
west. The high anchored to our east should prevent the
precipitation from reaching our IL counties.

Wednesday: Any lingering convection should lift northward out of
the cwa by mid morning. This will leave the remainder of the day
with partly to mostly sunny skies and warm temperatures. Highs
should push into the 80s at most locations. It should be humid
especially west of the MS River as dewpoints rise into the mid 60s.

.LONG TERM...(Wednesday Night through Tuesday)
ISSUED AT 305 PM CDT Tue May 22 2018

The developing summer-like weather pattern setting up later this
week is expected to persist through the holiday weekend. This will
feature well above normal temperatures, mid-summer humidity levels
and daily chances for thunderstorms. An upper level ridge axis over
the central U.S. and upstream low over the west or southwest is
progged to develop into a blocking pattern. The resulting thermal
ridge is shown pushing 850 mb temperatures into the upper teens to
near 20 Celsius by the weekend into early next week. At the same
time, returning Gulf moisture and low level moisture pooling will
push surface dewpoints into the mid to upper 60s. This setup will be
favorable for highs reaching the 80s to possibly near 90, depending
on the timing and coverage of potential thunderstorm complexes and
related cloud cover.

Wednesday night through Thursday night: A weak upper level system
topping the upper level ridge is shown triggering a nocturnal storm
complex that may enter the far north in a weakening stage late Wed
night, where slight chances are mentioned. A better potential for
sunshine and deeper mixing should push highs into the mid 80s after
overnight lows only drop into the upper 50s to lower 60s as
dewpoints remain seasonably high.

Friday through Memorial Day: Highs could reach the upper 80s to
around 90 through this period, depending trends with convection and
cloud cover, which is low confidence this far out. Combined with
dewpoints in the mid to upper 60s, resulting heat index readings may
reach the lower 90s, making it feel more like the 4th of July
instead of Memorial Day. During this stretch, Friday appears to have
the greatest potential for scattered thunderstorms as model
consensus has a shortwave trough topping the upper level ridge. The
rest of this period features mainly slight chance pops, centered on
the afternoon hours each day.

Little change is expected into Tuesday as the blocky upper level
holds with high pressure aloft even less favorable for
thunderstorms. Current forecast highs in the mid 80s may be several
degrees too cool and would need to be raised if there is consistency
and greater confidence in this forecast scenario.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday Night)
ISSUED AT 1216 AM CDT Wed May 23 2018

VFR conditions expected to largely dominate the TAF cycle. Light
winds and moisture will result in some patchy fog with
visibilities 2-5sm after 23/10z to 23/14z. Also, watching an area
of showers and storms over north central IA attendant to elevated
warm, moist advection. Some of this activity may drift and/or
develop into eastern IA toward 12z through mid morning before
diminishing. KCID would appear to have best chances for seeing
some of this activity, but spotty coverage limits mention to just
VCSH for now. Any shower and storms will have potential for MVFR




LONG TERM...Sheets
AVIATION...McClure is the U.S. government's official web portal to all federal, state and local government web resources and services.