Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 250805

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
305 AM CDT MON JUL 25 2016

259 AM CDT

Through Wednesday...

A cold front bisects the county warning area along a southwest
to northeast axis. Most of the remaining precipitation is well
ahead of the front with some lighter shower activity continuing to
form along its leading edge. There are also a few showers in
southern Wisconsin associated with an upper low across west central
Ontario. Signs of a changing pattern are evident on water vapor
satellite pictures upstream of our area and at our latitude, where
the images depict a much drier story and is void of any
significant disturbances.

The leading edge of the cold front will move southeast of the area
later this morning, taking the last of the lingering showers and
thunderstorms with it. Behind the front we will welcome in a
slightly cooler and less humid airmass, along with at least a few
day period of dry weather. Comfortable dewpoints in the 60s
will make more seasonably warm but certainly more tolerable
conditions for mid-summer, as highs top out in the mid to upper
80s, or just a tad above normal, though a bit cooler at the lake
with a lake breeze expected.

Surface high pressure will take firm control Monday night and
Tuesday and possibly for most of Wednesday as well. This will
result in sunny to mostly sunny skies along with lake breeze
development each day. Lows fall into the mid 60s outlying areas to
around 70 in the city, and highs hold in the mid to possibly some
upper 80s, slightly cooler lakeside, bringing of few days of
closer to normal conditions. Expect increased cloudiness on
Wednesday ahead of northwest flow and a slow moving upper low.



259 AM CDT

Wednesday night through Sunday...

An upper level disturbance generally emanating from the Pacific
Northwest will approach the Mississippi River Wednesday night. The
leading shortwave bring increased chances of precipitation
Thursday. The main shortwave moves overhead around Friday, which
would bring continues chances for rain showers, possibly a few
thunderstorms and slightly below normal temperatures in the upper
70s to low 80s. The low will pull east late in the weekend
decreasing precipitation chances.



For the 06Z TAFs...

Welcome to quieter weather! Winds will become northwest behind the
cold front pushing southeast through the terminals early this
morning. The cirrus shield from the convection south of the
terminals will dissipate through the day. A lake breeze will
likely form but thinking it will struggle to push on shore. Have
the lake breeze impacting GYY only for now, but there is a chance
it may reach MDW. Have low confidence in the lake breeze reaching
ORD. With high pressure overhead, winds become variable this
evening under clear skies. Given all of the recent rain, fog could
develop tonight, but thinking it will form outside of the metro
and only have low to medium confidence at this time.



205 AM CDT

The cold front associated with the low over Ontario shifts southeast
of the lake early this morning.  West to northwest winds diminish as
the gradient weakens today and a lake breeze is expected.  High
pressure moves over the lake early Tuesday morning. Winds become
light and variable over the southern end of the lake and southwest
10-20 kt over the northern half.  Winds will be light and variable
Wednesday, but then become north to northeast Wednesday night as the
high shifts east.  Winds remain northeast through the end of the
week as a weak low moves over northern IL Thursday night.






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