Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 272046

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
346 PM CDT Sun May 27 2018

304 PM CDT

Through Monday...

In an unseasonably warm airmass, but with modest dewpoints,
temperatures are rising into the middle 90s across much of the
region.  With dewpoints still only 50s to lower 60s, temperatures
have been able to rise more rapidly than typical diurnal warming
rates with many areas seeing 90F before noon.  In the weak pressure
gradient environment, a lake breeze has formed, turning winds along
the lake front to onshore, allowing temps to moderate along the lake
front.  The boundary should push inland far enough the bring some
early cooling to the northern suburbs, but the south end of the lake
breeze is making little inland progression and the southern
portions of the Chicago Metro area will likely not be impacted.

Otherwise, main concern for the afternoon and into the early
evening is isolated thunderstorm development over central and far
western portions of the CWA.  Latest SPC mesoanalysis shows axes of
enhanced CAPE in these areas, while far nern IL/nwrn IN remain a bit
more stable.  This idea is also noted in satellite imagery where the
cu field is much more sparse.  While severe wx is not expected in a
weakly sheared environment, some cells have shown the potential to
strengthen rapidly and and produce brief heavy downpours, with small
hail possible.  In the weakly sheared environment, storm motion is
nearly stationary, with perhaps a slow south direction.  so far this
afternoon, any severe storms have remained south of the CWA, but an
isolated severe storm cannot be ruled out this afternoon for the far
southern portions of the CWA.  Convection trends should be largely
diurnal, with activity diminishing with sunset.

Monday should, largely, be a case or wash, rinse and repeat as there
will be little progression to the overall pattern.  Other than
perhaps a bit of debris cloud, mostly sunny, warm conditions are
expected for tomorrow, with temperatures once again in the middle
90s.  Lake breeze development is also likely again tomorrow,
allowing for some cooling along the lakefront by early afternoon.


337 PM CDT

Monday night through Sunday...

Relatively quiet conditions at the start of the period, with any
precip development to the north tied to surface trough likely
staying to the north. Shower/thunderstorm chances on Tuesday look
to remain low, however, can`t rule out some isolated afternoon
development. Another hot day is expected with high temps in the
90s likely over much of the area, with the exception of areas near
the lake where onshore flow will be in place. Next precip chances
Tuesday night into Wednesday will be tied to the approaching
remnants of Tropical Storm Alberto. Although chances increase
Tuesday night, highest chances arrive Wednesday when the system
lifts through the region. Thunder will be possible during this
time, and given the tropical nature of this system, will need to
monitor higher rainfall potential. This system will linger during
the middle part of the week, while another system approaches from
the west. Although some variability with the evolution of this
approaching system, could provide additional precip chances
through the end of the work week. Temps on Wednesday will be
cooler given the likely extent of the precip/cloud shield, with an
additional day of cooler temps possible on Thursday.



324 AM CDT

The following are daily record highs for Chicago and Rockford over
the next two days.

               Sunday       Monday
Chicago       97 (2012)    95 (2012)
Rockford      99 (2012)    93 (2006)



For the 18Z TAFs...

Light flow is expected through much of the day, with a lake breeze
boundary already showing up on latest radar imagery. Latest
guidance suggests lake breeze passage at arnd 21-22z with wind
shift to east 8-10 kt. There is a small chance for isolated
thunderstorms development along the lake breeze, but confidence is
to low to include mention in the TAFs. There is a slightly greater
chance for isolated thunderstorm development over ncntrl/nwrn IL
where latest satellite imagery indicates a weak convergence
boundary and TCU development. Again, due to low confidence in
occurrence and coverage, have kept the TAFs dry. Otherwise, mostly
clear skies and light and variable winds will set up again
tonight, with a chance for another lake breeze to develop tomorrow


345 PM CDT

In the near term, there has been some fog reported over the lake.
Given this possibility, have included fog in the open waters
forecast for tonight. Winds over the lake don`t appear to be
overly strong into the start of the week. Will see high pressure
build south out of Canada by late Monday night into Tuesday, with
a steadier northerly wind expected. By midweek, winds will likely
be variable as the next system approaches from the south and moves
across the lake.






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