Area Forecast Discussion
Issued by NWS Chicago, IL
FXUS63 KLOT 251119
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
619 AM CDT MON JUL 25 2016
259 AM CDT
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
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 air mass, 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 12Z TAFs...
Much quieter day with high pressure shifting toward the region.
Left over clouds from yesterday`s storms will continue to push
southeast leading to clear skies by this evening. Winds will
become more northwest as the day goes on and a lake breeze is
expected. Latest hi-res guidance suggests the lake breeze will
push through ORD, MDW, and GYY this aftn. Have medium-high
confidence in the lake breeze making it that far east and timing.
Have high confidence that the lake breeze should be less than 10
kt. Winds become variable overnight as the high settles in
overhead. Given recent rainfall amounts, thinking patchy MVFR will
develop at all of the terminals except ORD and MDW.
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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