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fxus63 kdvn 291216 

Area forecast discussion
National Weather Service Quad Cities Iowa Illinois
716 am CDT Thu Jun 29 2017

..12z aviation update...

issued at 321 am CDT Thu Jun 29 2017

Much quieter conditions early this morning as active storms were
focusing south of the cwa with SW low level jet and attendant strong moist
advection and convergence atop surface frontal zone aiding several
convective clusters from Kansas through north MO and attendant heavy
rain/flash flooding concern with backbuilding activity. Water
vapor imagery shows digging shortwave trough through the northern
rockies, with a couple of lead impulses ejecting eastward from Wyoming
and Colorado. This energy will shift east next 24 hrs and combine with
strong moisture transport ahead of surface front lifting north
from MO to bring a renewed round of showers and storms over the
area later today and tonight.


Short term...(today and tonight)
issued at 321 am CDT Thu Jun 29 2017

Focus for convection will remain to our south this morning with
low level jet and feed into convective clusters from Kansas into MO, which
is anticipated to gradually weaken in time with waning low level jet.
However, there is some uncertainty if this occurs given emerging
Colorado shortwave into the plains which could Foster continued
development to our south. This would impact forecast negatively
in terms of reducing precipitation chances and amounts, while
also maintaining more debris cloudiness leading to lower temps and
greater uncertainties with severe weather potential for this
afternoon into evening. Having expressed the concerns, our
forecast is geared toward a decaying of am convection to our south
allowing for thinning of clouds and sufficient heating/destabilization
to result in redevelopment of at least scattered showers and
storms this afternoon into evening. There will be a slight risk
of a few severe storms with the threats being mainly large hail
and damaging winds given presence of 40+ kts of bulk shear. Again
much of what happens later today and tonight will be largely
dependant on trends of am convection to our south. Can envision
a scenario where the more robust afternoon convection could focus
across the northern cwa due to more thinning of cloudiness and
destabilization. Can also envision a scenario where the more
active clusters remain near to south of the southern cwa holding
northward progress of surface front thereby keeping more
cloudiness and limiting overall coverage and intensity of storms.
Heavy rain will again be a concern, but given all the uncertainty
leading to low confidence on just where and how much, I have not
issued any flash flood headlines. Definitely will need to keep an
eye on portions of northeast Iowa into far northern IL, and also far
northeast MO which have seen the bulk of the heaviest rains in
past 24 hrs. As for temps today, if any Delta exists believe it
could be few degrees warmer north and a few degrees cooler south.

Long term...(friday through wednesday)
issued at 321 am CDT Thu Jun 29 2017

Looks overall like a drying trend for much of the weekend with
seasonal temps as high pressure gradually builds in. A return
to another few days of active weather is suggested on tap
early next week, as cwa will reside once again in favored
juxtaposition of main belt of westerlies on northern periphery of
heat dome within strong mid level baroclinic zone from upper
Midwest to the central/Southern Plains. This could bring back a
period of active convective clusters with subsequent severe
weather and heavy rain potential.


Aviation...(for the 12z tafs through 12z Friday morning)
issued at 710 am CDT Thu Jun 29 2017

An area of low MVFR to isolated IFR cigs will affect dbq and
possibly Cid through mid morning before scattering out.
VFR conditions will be found at mli and brl this morning.
This afternoon and evening another round of showers and storms
is anticipated across the terminals. Have handled this with
tempo groups highlighting the most favored timing for this
activity. A few of the storms could once again become severe
with large hail and damaging winds.


issued at 321 am CDT Thu Jun 29 2017

Recent heavy rainfall of 2-4 inches will lead to mainly within
bank rises on northern hsa tributary rivers, with minor flooding
forecast on the wapsipinicon river near DeWitt. Initial runoff
has come in under forecast and lends to concerns that minor
flooding main not materialize but will not be quick to cancel
given routed water and potential for more locally heavy rain next
24 hours. Atmosphere remains conducive for areas of locally heavy
rain of 1-3+ inches next 24 hours, but low confidence on coverage
of storms and placement of heaviest rains precludes from issuing a
Flash Flood Watch. Will need to monitor closely northeast Iowa into
far northern Illinois tribs for any additional heavy rain, which if
occurs would be falling on saturated ground and lead to enhanced
risk of localized flash flooding and river flooding.


Dvn watches/warnings/advisories...



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