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012
FXUS63 KDVN 200439
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1139 PM CDT Mon Jun 19 2017

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 308 PM CDT Mon Jun 19 2017

A cyclonic NW flow aloft along the edge of an upper level trough
over the Great Lakes was seen over the forecast area this
afternoon. Vort maxima embedded in this flow were triggering
scattered showers and thunderstorms over eastern WI into
northeast IL and southeast MN into central IA. The central IA
convection, spreading east-se into eastern IA, has had a history
of producing small hail due to the cold air aloft and steep mid
level lapse rates. At the surface, a mild and seasonably dry
airmass was in place with dewpoints only in the lower to mid 50s.

&&

.SHORT TERM...(This Evening through Tuesday)
ISSUED AT 308 PM CDT Mon Jun 19 2017

Main challenges center on convective trends through the rest of
today, then temperatures and potential for at least scattered
showers and thunderstorms with a cold front dropping through
Tuesday.

SPC mesoanalysis at 2 pm showed a pocket of steeper mid level
lapse rates over southeast IA, while an upstream area of 35 kt
effective shear was approaching from central IA. This may be
enough to lead a few storms capable of at least pea to dime sized
hail and wind gusts over 40 mph over east central and southeast IA
over the next couple hours. Elsewhere, isolated to scattered
showers and thunderstorms will continue to fire. All this should
dissipate by early evening as the triggering mid level feature
passes into central IL and the daytime instability wanes.

Overnight will see mostly clear skies and a weak surface ridge
passing through. With the dry air in place, temperatures should cool
to near current dewpoints, into the mid to upper 50s.

Tuesday, a stronger shortwave over eastern Saskatchewan is expected
to rotate through WI into the Great Lakes around midday, sending a
cold front south across the forecast area. While mid level forcing
looks stronger than today, mid level lapse rates by then will be
much weaker than today as the pocket of colder air aloft shifts
eastward. Thus will go with lower coverage than today, with mainly
slight chance pops for showers and thunderstorms along and behind
the cold front that passes north to south during the afternoon. The
south will end up being near or warmer than today, with highs in the
lower 80s, while the north only reaches the mid 70s with morning
frontal passage.

.LONG TERM...(Tuesday Night through Monday)
ISSUED AT 308 PM CDT Mon Jun 19 2017

Warm for the remainder of the work week with a cool down for the
weekend. The overall weather pattern looks to remain fairly active
with several chances for rain.

Tuesday night/Wednesday a weak cool front will move into the area
and dissipate. Forcing is weak along the front and there are
questions regarding moisture availability. Based on these factors,
dry conditions are now expected. Temperatures should be close to
normal.

Wednesday night return flow allows moisture to start moving back
into the area. A cold front will interact with that moisture on
Thursday. Nocturnal convection will develop Wednesday night in the
return moisture that has the potential to grow upscale into an
organized thunderstorm complex. The north half of the area has the
better chances of seeing rain Wednesday night and Thursday.

Thursday night on...

Thursday night the cold front moves through the area. Moisture
moving up from the south should give the best chances of seeing rain
across the area. Internally, the models are indicating the
convection will grow upscale into an organized thunderstorm complex.
As a result the model consensus has likely pops for the area.

If storms grow upscale into an organized thunderstorm complex, rain
should continue into Friday morning before ending from north to south
across the area. The model consensus has slight chance to chance
pops for the area.

Starting Friday night the model solutions begin to diverge. High
pressure building into the Great Lakes should keep most of the area
dry. The model consensus has mainly dry conditions for the area
except for the extreme south which has slight chance pops.

Over the weekend the flow aloft will be coming from the northwest
resulting in cooler than normal temperatures.

Saturday into Sunday there is a respectable upper level disturbance
that will move through the Midwest. There are differences on the
timing of this system between the models. However, the forcing
produced by this disturbance combined with what moisture is
available should be enough to produce some showers and
thunderstorms. The current model consensus has chance pops
Saturday/Saturday night and slight chance pops on Sunday. The
possibility does exist that Sunday could be dry.

Dry conditions will be seen Sunday night as high pressure moves
through the Midwest.

On Monday, another upper level disturbance will move through the
western Great Lakes. There are differences between the models
regarding the track of this disturbance. However, cool temperatures
aloft combined with daytime heating should be enough to generate
diurnal showers and possibly a few thunderstorms. As such the model
consensus has slight chance to chance pops for the northeast third
of the area.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday Night)
ISSUED AT 1137 PM CDT Mon Jun 19 2017

VFR conditions to persist next 24 hours with fair skies as high pressure
continues. Winds will be westerly to northwesterly at 5 to 15 MPH with
some higher gusts mid day on Tuesday, then become light westerly after
sunset.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.

&&

$$

SYNOPSIS...Sheets
SHORT TERM...Sheets
LONG TERM...08
AVIATION...Nichols