Area Forecast Discussion
Issued by NWS Chicago, IL

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641
FXUS63 KLOT 291947
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
247 PM CDT SUN MAY 29 2016

.SHORT TERM...
232 PM CDT

Through Monday...

Hi-res models hint at light rain showers west of I-55 this afternoon
and tonight, but thinking we will continue to see dry conditions.
Scattered storms are forming over northern Iowa and southern WI.
Scattered convection has a better chance of forming north of the
vort max currently over Iowa and thus north of the CWA. If any
convection does get going, thinking locations will only see
sprinkles given dewpoint depressions around 20 degrees.

Clouds clear tonight and winds diminish.  Lows will be in the lower
60s.  A few clouds are expected tomorrow with lighter winds and
highs in the low to mid 80s. Limited highs south of I-80 where there
may be more cloud cover, but if cloud cover is less than forecast,
could see high temps above 85.  The weak surface flow allows a lake
breeze to form in the afternoon.  The lake breeze looks like it will
push onshore later than normal so thinking lake side locations have
a good chance of seeing 80. Models suggest precip will spread west
of I-39 late Monday afternoon, but thinking the precip will hold off
til Monday evening when the vort max gets closer to the CWA.  Did
include a slight chance of showers and storms east of I-39 late
Monday aftn in the off chance precip does form.

JEE

&&

.LONG TERM...
246 PM CDT

Monday night through Sunday...

Monday night through Wednesday night:
Mid-lev diffluence will begin to shift East slightly Monday evening;
however, some guidance members continue to indicate enough
ridging/diffluence will hold through Monday evening to hold precip
to the West of the area. Have adjusted POPs to account for better
chance for POPs not arriving until closer to daybreak Tue. Upper
level trough will remain well West through Mon ngt, meanwhile a
displaced surface wave will be trying to develop over the Central
Plains late Monday. This may be strong enough to send a lobe of
vorticity Northeast towards the western Illinois area. Low level
feed of moisture will steadily increase Monday night, helping to
bring dew points back into the lower 60s across Northern Illinois by
Tuesday. With a continued feed of moisture Tuesday, and steady
growth of instability, the periodic chances for
showers/thunderstorms will likely continue Tuesday. Temps Tue will
return to the lower to perhaps middle 80s across much of Northern
Illinois and Northwest Indiana.

Heading into tuesday night, the 500mb trough axis will begin to
pivot east of the Rockies and increasing the forcing along the lee-
side through the Plains. This should likely increase POPs chances
through the mid-sections of the CONUS towards the Western Great
Lakes late Tue into Wed. With the trough axis being slow to arrive
over the forecast area Wed eve, a persistent chance of
showers/thunderstorms is possible. Then the frontal boundary
continues to be progged to arrive late Wed, which will usher in
drier air and bring an end to the precip chances for later in the
week.

Thursday through Saturday: Ensembles continue to point towards a
ridge developing along the western CONUS late in the week into next
weekend. Thursday through Friday look to remain dry with weak
surface ridging arriving, then with the upstream ridge progged to
develop this will likely usher in a quasi-northwest flow for the
upcoming weekend and a return to periodic showers/thunderstorms.
Temps for late week through next weekend will return to the middle
to upper 70s, with overnight lows in the 50s.

Beachler

&&

.AVIATION...
For the 18Z TAFs...

Gusty southwest to west winds dissipate this afternoon. Low end
VFR cigs will also continue to thin into this evening with clear
skies expected overnight. High pressure continues Monday with
west winds and VFR conditions. Some guidance members suggest
precip is possible south of the terminals. Have low confidence in
precip actually occurring and high confidence that precip will be
well south of the terminals if it does occur. The weak flow will
allow a lake breeze to form. Thinking the lake breeze will not
reach the eastern terminals until late in the afternoon/early
evening and will be less than 10 kt.

JEE

&&

.MARINE...
232 PM CDT

Will let the fog advisory expire this afternoon as fog has
dissipated over the northern end of the lake. Drier air is also
moving over the lake.  Low pressure over Ontario continues northeast
while high pressure just south of the lake spreads north.  West to
southwest winds become south Monday.  The high shifts east Tuesday
allowing winds to become southeast. A low shifts east over the
northern plains and upper Mississippi valley Wed and south winds
increase to around 20 kt.  High pressure spreads over the lake late
in the week as the low continues northeast over Quebec.  Light winds
become north by late Thursday night/early Friday morning. Another
low is forecast to impact the northern Great Lakes early next week.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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