Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 201836

Area Forecast Discussion
National Weather Service Quad Cities IA IL
136 PM CDT WED JUL 20 2016

Issued at 130 PM CDT Wed Jul 20 2016

The back edge of the convection moving into IL fits nearly
perfectly with the 10C 700 mb temperature isotherm. At 1 pm this
isotherm extended from just east of Dubuque to the Quad Cities to
east of Macomb. This is where the strengthening cap is spreading
eastward and by late this afternoon or early this evening the
thunderstorms will have exited the cwa. Have updated the grids to
remove the pops west of this line.

To our west across central IA and into the Plains current
temperatures were in the lower to mid 90s with dewpoints well into
the 70s to lower 80s. SBCAPES in central IA were 6000 J/KG but
this was under a strong capping inversion.

UPDATE Issued at 1205 PM CDT Wed Jul 20 2016

Regarding heat headlines: The excessive heat watch has been
upgraded to a warning. See NPW product for details.

In the meantime: Scattered thunderstorms continue in extreme
eastern IA into far nw IL on the edge of the strengthening cap.
This cap will continue to spread slowly eastward as the afternoon
progresses with the storms pretty much shutting down by early this
evening. Then the hot and oppressive weather will be in full
force through Saturday.

Temperatures will be a challenge depending on amount of cloud
cover and have already lowered afternoon highs in our ne cwa.


Issued at 344 AM CDT Wed Jul 20 2016

A few storms have recently developed into southeast Iowa attendant
to secondary wing of moisture transport near 850 mb. Another
stronger moisture transport axis extends from north central and
northeast Nebraska through southwest Minnesota where recent
convection has developed though it has been struggling across
portions of Minnesota where evidence of some mid level capping.
Nebraska portion of convection is also being aided by mid level
shortwave, and this wave looks to crest upper ridge and slide
SSE though Mid-Mississippi Valley to maintain storm chances next
12-18 hours.


.SHORT TERM...(Today and Tonight)
ISSUED AT 344 AM CDT Wed Jul 20 2016

Shortwave and warm, moist advection north of warm front will
provide at least scattered storms today. Will have to watch
convective trends to our northwest as cwa remains in favorable
850 mb thermal gradient for genesis/track of mesoscale convective
system should convection grow upscale. For now though will
maintain moderate to high chance pops for warm advection wing
with highest pops central and north. Models suggest bulk shear
plenty with 0-6km 30-40 kts, which would support some risk of
organized storms with mainly a wind threat along with very heavy
rain with PWATs in excess of 2 inches. Heights aloft build a bit
more tonight with veering jet, elevated moisture transport and
thermal gradient more conducive for convection to our northeast
thus have kept precip chances below mention by mid evening through

Temps will be challenging today, with areas north and east most
favorable to maintain clouds and convection, and have highs
mid to upper 80s but potential to be cooler. Meanwhile, southwest
cwa most favored for some sunshine and hotter temperatures, and
have highs around 90 or lower 90s. These temps combined with dew
points climbing into the 70s will make it feel like 100 or lower
100s southwest cwa and 90s elsewhere.

.LONG TERM...(Thursday through Tuesday)
ISSUED AT 344 AM CDT Wed Jul 20 2016

Main forecast concern remains the heat and the potential for
convection through the period.  Confidence is lower in potential
excessive heat warnings as dewpoints are suspect along with the
potential for convection each day.  At this time, the best chance
for excessive heat warning criteria will be due to 4 days in a row
of heat advisory criteria.

Still have low confidence in the rest of the CWA meeting excessive
heat warning criteria due to convection potential and concerns over
whether or not the models are accurately producing BL moisture.
Looking at the model soundings, dry air exists aloft and with
daytime heating, this could cause our dewpoints to be lower.  This
coupled with convective temperatures being met, suggests that we may
have diurnal convection.  If the ridge was more over our CWA then we
would have higher confidence in this verifying.  Regardless, its
going to be hot and people will need to take safety precautions for

Friday the boundary has accelerated south in the latest runs,
suggesting that convection will be possible during peak heating.
This will further complicate matters, especially across eastern
portions of the CWA.

Through the weekend, we should gradually cool down into more normal
temperatures with the boundary somewhere across the area.  This
will lead to schc to chc pops through the extended.


.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
ISSUED AT 1205 PM CDT Wed Jul 20 2016

VFR conds for the most part through this taf cycle. Scattered
thunderstorms along and east of the MS River can be expected this
afternoon into early this evening. MVFR/brief IFR conds in
thunderstorms due to heavy rainfall. South to southeast winds
around 10 knots through tonight, then south 10 to 20 knots


.DVN Watches/Warnings/Advisories...
IA...Excessive Heat Warning from 7 AM Thursday to 7 PM CDT Saturday
     for Buchanan-Cedar-Clinton-Delaware-Dubuque-Jackson-Jones-

     Excessive Heat Warning until 7 PM CDT Saturday for Benton-Des
     Moines-Henry IA-Iowa-Jefferson-Johnson-Keokuk-Lee-Louisa-
     Van Buren-Washington.

IL...Excessive Heat Warning from 7 AM Thursday to 7 PM CDT Saturday
     for Bureau-Carroll-Henry IL-Jo Daviess-McDonough-Mercer-
     Putnam-Rock Island-Stephenson-Warren-Whiteside.

     Excessive Heat Warning until 7 PM CDT Saturday for Hancock-

MO...Excessive Heat Warning until 7 PM CDT Saturday for Clark-



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