Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 221750

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1250 PM CDT FRI JUL 22 2016

Issued at 1241 PM CDT Fri Jul 22 2016

Temperatures and dew points are starting to recover across the far
western areas as clouds thin. Going on the assumption that all
areas will see clearing skies with the hot/humid air moving back
into the area, heat index values should steadily increase this
afternoon and reach a peak late this afternoon.


Issued at 330 AM CDT Fri Jul 22 2016

The latest SFC analysis was indicating a weak west-to-east boundary
extending from acrs far southern along the IA/MN border.
Ongoing elevated MCS was continuing to fester southward acrs
southeastern IA through central IL and into western IN. Resultant
large sfc cool pool was located right acrs the DVN CWA and northern
half of IL ATTM. Aloft, the northern flank of broad upper ridge was
tilting west-northwesterly flow from the Dakotas, through the GRT
LKS and down acrs the eastern OH RVR Valley. The main upstream vort
max was noted on current water vapor loop acrs NEB.


.SHORT TERM...(Today)
ISSUED AT 330 AM CDT Fri Jul 22 2016

Today...Will keep sctrd to areas of showers/storms continuing acrs
the southern third of so of the DVN CWA through 14 or 15z. the above
mentioned Neb Vort will look to ride around the periphery of the
upper ridge and elevated warm layer/cap down toward the STL area by
this afternoon. Some of this lift clipping the southwestern CWA
keeping elevated showers and storms festering this morning, but then
diurnal processes and convergence in the cloud/precip bearing layer
wanes by mid to late morning for a precip decrease. With convective
debris/llvl boundaries, marginal progged mid level cap acrs eastern
IA into NW IL, and the CWA looking to remain on northeastern,
somewhat diffluent northwest flow flank of the brunt of the upper
ridge through this evening, will keep at least slight CHC POPs acrs
much of the northern half or more of the CWA this afternoon for new
convective development. Southerly llvl flow will increase and impinge
on these areas as well. If they go, storms could be severe with
damaging wind bursts and locally heavy rain the main threats again.

As for the heat headlines, will keep consistent with neighboring
offices and let it ride for today. But convective debris and the
llvl cool pool in place will have to erode by early afternoon to
even get close to criteria. Will bank on high sfc dpts of mid 70s to
near 80 again to enhance local heat index readings this afternoon.

.LONG TERM...(Tonight through next Thursday)
ISSUED AT 330 AM CDT Fri Jul 22 2016

Little change in the synoptic pattern through Saturday night will
keep the same forecast issues in place involving excessive heat and
potential thunderstorm complexes. The current ring of fire synoptic
pattern is expected to break down Sunday with the passage of a cold
front that will return temperatures and humidity levels back closer
to late July normals and perhaps a bit below by late next week.

Tonight: Signals continue to suggest the potential for another MCS
over especially the north and northeastern portions of the forecast
area on the edge of the upper cap and have slight chances in the
evening, increasing to chance pops after midnight over much of the
forecast area. These would have the continued potential  for at
least low coverage damaging winds and heavy rainfall, which is
becoming more of a flash flood threat due to the now several day
string of rainfall events. Rain and associated cool pools may again
impact minimum temperatures and dewpoints, potentially affecting
minimum heat index values and the associated headlines. For now,
have low temperatures reflecting low rain coverage, and close to the
dewpoints, from the low 70s north to upper 70s south.

Saturday into Sunday: MCS trends will again dictate Saturday`s high
temperatures and highs from around 90 to the mid 90s are a middle of
the road compromise. With the same airmass in place and moist
surface conditions due to recent rains, dewpoints could again reach
well into the upper 70s to around 80, leading to heat index values
well above advisory criteria and potentially above the warning
criteria of 110 in the afternoon. Will thus keep the current
excessive heat warning going til 7 pm Saturday evening. Will need to
later re-evaluate a possible extension for Saturday night and
possibly into at least Sunday morning ahead of a cold front still
progged to push through during the day and lower max temperatures at
least a few degrees from Saturday. This front will also offer
another focus for thunderstorms and have carried over slight chance

A nearly zonal upper flow and a westward shift of the upper high and
warmest temperatures aloft will result in slightly cooler
temperatures next week. A Significant upper level shortwave and weak
front at the surface in the model consensus are reflected with
thunderstorm chances returning around midweek.


.AVIATION...(For the 18Z TAFS through 18Z Saturday Afternoon)
ISSUED AT 1241 PM CDT Fri Jul 22 2016

VFR conditions should now be seen through 00z/23. TSRA are
expected to develop again this afternoon and impact eastern Iowa
and northern Illinois well past 00z/23. MVFR conditions are likely
if a TSRA impacts a TAF site and IFR/LIFR are possible. After
03z/23 more widespread MVFR conditions are expected to develop
through 12z/23 and pockets of IFR conditions cannot be ruled out.
After 12z/23 conditions will slowly improve to VFR.


.DVN Watches/Warnings/Advisories...
IA...Excessive Heat Warning until 7 PM CDT Saturday for Benton-
     Buchanan-Cedar-Clinton-Delaware-Des Moines-Dubuque-Henry IA-
     Muscatine-Scott-Van Buren-Washington.

IL...Excessive Heat Warning until 7 PM CDT Saturday for Bureau-
     Carroll-Hancock-Henderson-Henry IL-Jo Daviess-McDonough-
     Mercer-Putnam-Rock Island-Stephenson-Warren-Whiteside.

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



LONG TERM...Sheets
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