Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 190834 CCA

Area Forecast Discussion...corrected typo in long term
National Weather Service Quad Cities IA IL
321 AM CDT FRI AUG 19 2016

Issued at 307 AM CDT Fri Aug 19 2016

Active and wet pattern continues with quasi-zonal flow aloft.  Water
vapor satellite shows next wave of interest dropping into western
Montana this morning. At the surface, slow moving cold front extends
from the upper peninsula of Michigan across western Iowa and into
western Kansas. MCS has tracked south out of the area, continuing to
follow the CAPE gradient across central Illinois.  Elevated
convection that initially triggered on the MCS outflow boundary
continues to move slowly east across Carroll County, fortunately
north of where the heavier rain fell earlier in Whiteside County.


.SHORT TERM...(Today and Tonight)
ISSUED AT 307 AM CDT Fri Aug 19 2016

Forecast focus is thunderstorm chances throughout the short term.

Short range models are of little use this morning as they have not
been handling the track or evolution of the ongoing convection. With
boundaries lingering over area and without a cap, expect lingering
isolated to scattered convection to fester today.  Have introduced
low precip chances for the northern half of the forecast area. By
evening, there is a possibility for a more focused area of storms as
the upper level energy and surface cold front approach.

By tonight, widespread thunderstorms are expected as the main energy
drops into the base of the trough over the plains and the whole
system begins to move out.  There is some concern for severe wind
depending on the timing of the line as instability will be adequate
and low level lapse rates could support strong winds in surface-
based storms near the front.

Temperature forecasts today are also somewhat problematic.  With
increased cloud cover expected, have shaved a few degrees off of
today`s high temperatures. However, high temperatures may still be
too warm in some areas where the clouds stick.

.LONG TERM...(Saturday through Thursday)
ISSUED AT 307 AM CDT Fri Aug 19 2016

Seasonably strong cold front will bring much cooler conditions
with a hint of fall by late in the weekend into early next
week. Strong dynamics aided by anomalously deep upper trough
and divergence with entrance region of jet, along with DCVA
in concert with frontal convergence will lead to widespread
showers and some storms Saturday morning tapering off during
the day from west to east. Still appears to be some substantial
differences with deterministic models on strength and placement
of surface low on Saturday. NAM and GEM appear to be unrealistic
strong outliers on strength of closed surface low with a more
fall-type cyclogenesis and intensification, not supported by the
upper jet structure, as the system lifts from the MN/WI/IA border
region on Saturday. Some re-intensification of storms is possible
by afternoon mainly eastern cwa ahead of the cold front with
bulk shear 0-6km of 30+ kts, but a conditional risk of strong to
possibly isolated severe storms dependent on amount of

In the wake of the front, a much cooler airmass will settle in
for the latter half of the weekend through Monday with below
normal temperatures and lower humidity making for quite pleasant
late summer weather. Some models show 850 mb temperatures as low
as 10C, which if occurs with strong inversion would be supportive
of some lows in the 40s possibly by Monday morning.

Tuesday through Thursday, an upper level wave and return of low to
mid level warm, moist air will lead to near normal temperatures
(around 80/lower 80s for highs) and increasing rain chances into
Thursday. May then see another decent cold front with a return of
dry and cool conditions yet again late next week into the weekend.


.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
ISSUED AT 1131 PM CDT Thu Aug 18 2016

Scattered thunderstorms remain possible over eastern Iowa and
northwest Illinois overnight, and again Thursday evening. Many
hours will be dry in between showers, and VFR conditions should
dominate the over all weather at all sites. Winds will be light
east to south overnight, followed by southerly tomorrow around 8
to 10 kts. This pattern will remain in place through late Friday
night, when a cold front will approach eastern Iowa.


.DVN Watches/Warnings/Advisories...


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