Area Forecast Discussion
Issued by NWS Chicago, IL

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS63 KLOT 290752

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

252 AM CDT

Through Monday...

The remnants of the line of storms that impacted northern Illinois
yesterday evening has abated to only a few spotty showers entering
northwestern Indiana at this hour. A weak surface cold front will
move across the area this morning. In spite of this cold frontal
passage...temperatures today will not be more than a couple degrees
cooler than Saturday. As such...another day in the low 80s looks in
store for the region.  The main difference today will be the
humidity. With dew points in the wake of this front expected to
settle down into the upper 50s...although it will still be mild will feel more comfortable than Saturday.

Overall I have opted to go with a dry forecast area wide today with
the drier air moving over the area. However...following the passage
of the main upper trough this morning...guidance is suggesting that
another...much weaker mid level disturbance...currently over
NE...will shift eastward across northern IL this afternoon. Guidance
is not suggesting any precip will occur with this disturbance...and
this may very well end up being the case. However...I cant totally
rule out an isolated shower or thunderstorm developing over northern
Illinois later this afternoon...but due to low confidence in this
actually occurring...I have kept a dry forecast with partly cloudy
to mostly sunny skies.

Memorial day looks to be another decent day...though could be a bit
warmer in the middle 80s...especially inland from Lake Michigan.
Weaker westerly winds on Monday could allow for lake breeze
development...and slightly cooler conditions on the lake shores.

There will also be a small chance of thunderstorms over western
Illinois late tonight into early Monday as better moisture tries to
shift eastward atop a surface ridge over the south central CONUS.
This small chance of thunderstorms will extend farther east over
northern Illinois Monday afternoon as diurnal instability builds. does not appear that there will be much low-level or
upper level support for widespread thunderstorm development Monday
afternoon. However...due to weak capping an isolated storm or two
cannot be ruled out...though I tend to think most areas will stay



204 PM CDT

Sunday night through Friday...

The upper low will dampen and shift east of the region Sunday night.
Broad surface high pressure will form in its wake and bring a
generally drier start to the extended period. A subtle trough/weak
cold front will move through overnight with weak energy sliding
southeast in slightly more progressive WNW flow aloft. Most
guidance is dry with its passage but we cannot rule out an
isolated shower.

Memorial Day is shaping up to at least start off fairly nice
and stay that way for most areas in spite some increasing clouds.
After the weak trough passage, a ever so slightly cooler and less
humid air mass will remain in place. To our west warm moist
advection will resume after the gulf of Mexico is temporarily cut
off by the transient surface high. Most of the convection looks to
be tied to daytime heating. Some guidance including the GFS/GEM
attempt to bring some of this into our area. The NAM shoves the
moist air mass south suggesting a better push with the front, and
the EC keeps convection to our west. Given the mixed signals but
favoring a drier solution as is currently forecast, have trended
that direction.

Model guidance does show a diurnal weakening Monday evening, but
suggests some overnight development again to our west that will
attempt to push into our area into early Tuesday, but chances
remain tempered given the weak ridging, southeasterly drier
surface flow. Better chances for showers and thunderstorms returns
Tuesday through midweek in response to a storm system that will
move east through the Dakotas Tuesday. A warm and humid air mass
will return in the southwest flow ahead of this system with an
undisturbed feed from the gulf of Mexico. Shower and thunderstorm
chances appear highest Wednesday and Wednesday night as forcing
from the low is much closer to the region. Cooler and drier
weather will eventually take hold for the latter half of the week
as a modest cold front shifts in with dewpoints dropping back
through the 50s making it feel comfortably and seasonably cool.



For the 06Z TAFs...

Only aviation weather concerns through Sunday night is a brief
period of showers and possibly an isolated embedded thunderstorm in
the next 1-2 hours for Chicago terminals...then breezy west-
southwest winds through the day Sunday.

Low pressure was over the upper Midwest at midnight...with a cold
front trailing southward across east-central Iowa and into
Missouri. A decaying area of showers and a few lingering
thunderstorms was well ahead of the front across far eastern WI
and eastern IL. Activity has shown a marked downward trend in
lightning over the past couple of hours...with most of the
remaining thunder located in the vicinity of KBMI. An area of
showers roughly from KARR-KJOT-KIKK was lifting northeast...and
will likely bring a brief period of light rain to the Chicago area
terminals prior to about 07z. Once this passes...dry weather is
expected to persist through the remainder of the taf period.

South winds near 10 kts expected for the remainder of the night...
becoming west and gusting 20-25 kt by mid-morning as cold front
moves east across the area and boundary layer mixing deepens after
sunrise. Breezy westerly winds to continue through the afternoon.



204 PM CDT

While fog has lifted across the lake, it is expected to return
again tonight into early Sunday, and the marine dense fog advisory
will be extended until tomorrow.

A warm front has pushed north of the lake this afternoon with
breezy southerly winds in place. The low will shift to western
Lake Superior by Sunday night, which will maintain southwest winds
to 25 kt today and to 20 kt Sunday with elevated waves on the
north half. The low will strengthen as it moves northeast to James
Bay Monday morning. A weak cold front will moves across the lake
Monday morning which will shift winds only slightly to the west
southwest, with a secondary potentially stronger cold front will
allow for a wind shift to northeast at least for the north half.
Lighter winds remain place through Tuesday before strengthening
out of the southeast in response to low pressure that will cross
the Dakotas Tuesday and move to western Lake Superior late






WWW.YOUTUBE.COM/NWSCHICAGO is the U.S. government's official web portal to all federal, state and local government web resources and services.