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Area forecast discussion...updated 
National Weather Service quadrant cities Iowa Illinois
1141 PM CDT Wednesday Jul 1 2015

Update...
issued at 622 PM CDT Wednesday Jul 1 2015

Dry midlevel was doing its job and keeping the radar returns
across northern zones limited to virga or very isolated sprinkles.
Changed the forecast to represent this. Besides this small tweak
little changes to the forecast were made. Everything else appears
T be on track for the short term period.

&&

Synopsis...
issued at 310 PM CDT Wednesday Jul 1 2015

3 PM CDT surface pressure analysis had a 1006 mb low in central
Kansas. This feature has been sliding southward through the day
and will continue to move away from east Iowa/west Illinois. Light
easterly flow has persisted into this afternoon along with several
separate layers of cloud cover. The lower level layer of stratus
has broken up substantially since this morning but as this
happened middle-level clouds filled in from the northwest.

Additionally...a relatively wide ribbon of Canadian wildfire
smoke was noted on the GOES visible satellite imagery today which
the past few days has been located between roughly 2000 to 6000
feet above ground level...mostly above the surface. A few showers were noted
across the far southern County Warning Area and the far northwest.

&&

Short term...(this evening through thursday)
issued at 310 PM CDT Wednesday Jul 1 2015

This evening and tonight...aside from some isolated to scattered
showers across the far southern and northwestern portions of the
County Warning Area...it will be a quite night with very comfortable temperatures. The
NAM has surface dewpoints slowly falling through the 50s...and the
drier air will allow temperatures to be a touch cooler than the past few
nights. Forecast min temperature gradient ranges from near 60 f across
the south to near 50 f over the northeast.

NAM forecast time-height sections expose a very dry layer between
the middle-level precipitation that is being generated west of Dubuque and
the surface with relative humidity values as low as 20 percent near 850mb. Taking
this into account it will be difficult for portions of Buchanan
and Delaware counties to receive more than a hundredth or two of
rainfall through this evening.

Thursday...lower level clouds in the morning should gradually
diminish/break up through the afternoon as we get another push of dry
air from the east/northeast. Highs in the middle to upper 70s...low
relative humidity...and light easterly flow will make for a very
nice day and a reprieve from the typically high Summer humidity.

Long term...(thursday night through wednesday)
issued at 310 PM CDT Wednesday Jul 1 2015

The long term largely consists of dealing with surface
high pressure over the Great Lakes through Saturday...followed by a
transition to return flow and moisture ahead of a seasonally strong
trough/cold front due early next week. The large scale details are
supported by both the GFS and European model (ecmwf)...as well as Gem...but there
remain significant differences on the timing and strength and
forcing along the cold front. That front is generally slower by at
least a day compared to yesterdays model runs. As mentioned
yesterday...a slower frontal passage would favor more moisture return...and
that does seem to be in the offing.

Temperatures should actually see very little real moderation in the
extended...as the flow remains weakly from the east to
northeast...with the Great Lakes tampering any real moderation of
the air mass. Since this already in place now...the real determining
factor each day will likely be cloud cover...which is difficult to
pin down accurately this far out...as models strongly suggest
sunny...but that is often not the case with low level flow off the
Great Lakes. I will keep near the cool side of guidance...and
suggest partly to mostly clear skies given no determining reason
beyond doubt to go against the model blend.

Probability of precipitation for the frontal passage Sunday have been reduced to dry...and to slight
chances for Sunday night given the slower solution trend. Probability of precipitation for
Monday and Monday through Tuesday remain in the chance range...and
until a solid forecast on frontal passage confidence can develop...the broad
range of time will continue to appear wet. In reality...it should
likely be less than a 24 hour period given a progressive front
followed by weak high pressure.

For now...next week beyond Tuesday appears mainly dry...but with
moisture and the front just south in Missouri...any pattern change
to zonal flow aloft could easily bring the mesoscale convective system track farther north.
We will have to keep a close eye on that...as climatology does not
support upper low pressures in the Great Lakes and Canada such as
the 12 GFS and older European model (ecmwf) solutions have forecasted.
Ervin

&&

Aviation...(for the 06z tafs through 06z Thursday night)
issued at 1135 PM CDT Wednesday Jul 1 2015

Ob sites on the southern tip of Lake Michigan are starting to show
a MVFR deck forming. Guidance and flow out of the east suggests
that this deck will make it to the area. As a result decided to
keep the MVFR deck in at dbq...mli...and brl. I still am not
that confident...but the signal is there for this to occur.
Otherwise...VFR conditions will prevail with light winds and
clearing skies through the period.

&&

Dvn watches/warnings/advisories...
Iowa...none.
Illinois...none.
MO...none.
&&

$$

Update...Gibbs
synopsis...uttech
short term...uttech
long term...Ervin
aviation...Gibbs

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