Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 220657

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
157 AM CDT Sat Oct 22 2016

235 PM CDT

Through Saturday...

High pressure continues to nose in from the west this afternoon.
Cloud cover across northwest Indiana and east Central Illinois is
a result of lake effect process with additional diurnally driven
clouds moving in from the northwest. Lake effect rain showers
continue to shift east of the area though still remain possible
along the lake and on the Porter/Laporte county border and
eastward. Convergence in observation is decreasing as a boundary
from the northwest moves southeast and is scouring out the
easterly component to winds over the lake. There have been a few
funnel cloud reports over the southern tip of the lake today, but
no reported waterspouts. Will maintain the mention this afternoon
across the nearshore but then with expected decrease in lift and
more uniform wind field the threat will shift east and diminish.

Expect that this lower cloud field will erode after sunset with
the exception of lingering lake effect clouds in nw Indiana. With
warm advection aloft we will have some mid and higher clouds
rolling through tonight. In spite of high pressure leading to some
clearing and light winds, have held off on a frost advisory
tonight with the uncertainties in cloud cover as temperatures are
forecast to be in the 34-38 degree range for most areas away from
the urban corridor. Therefore, patchy frost is possible with
local areas of frost in any sheltered areas and could be more
widespread if clouds are thin.

High pressure will shift east Saturday and return southwest flow
will allow for a mix of sun and some clouds with highs back near
normal - upper 50s to low 60s, warmest southwest.




Saturday night through Friday...

216 pm...Two main forecast concerns this period...first high temps
Sunday with a cold front late afternoon/early evening...second is
precip/thunder chances with a storm system middle of next week.

High pressure will be departing to the southeast Saturday night as
low pressure moves from the Dakotas Saturday night to lower MI by
Sunday evening. A trailing cold front will move across the area
Sunday afternoon into Sunday evening. Timing of this front will
have a large impact on temperatures...with possible quickly
falling temps behind the front but also how warm temps rise Sunday
afternoon. Ahead of this front...temps will warm well into the 60s
and some lower 70s are also possible especially across the
southern cwa. Possible front may accelerate down the lake into
far northeast IL with a wind shift more off the lake. An earlier
arrival would limit how much high temps rise across the north.

A fast moving high pressure will build across the area Monday into
Monday night with high temps Monday/Tuesday near seasonal levels...
upper 50s/lower 60s. Another low will develop over the central
plains Monday and Tuesday and move across the area Wednesday
afternoon into Wednesday night. This timing and track has been
fairly consistent for several runs now. There is a chance of
precip along a warm front Tuesday afternoon/Tuesday night which
sets up mainly over southern WI...possibly affecting far northern
IL. But the bulk of the precip will hold off until Wednesday and
Wednesday evening as the low moves across the area. Chance of
thunderstorms also likely Wednesday along with gusty southeast
winds as the low approaches. Flow quickly turns back southerly
Thursday night into Friday with high temps possibly remaining in
the 60s for the end of the week. cms


For the 06Z TAFs...

VFR conditions expected through the TAF period with winds
generally less than 10kt.



157 AM CDT

Ridge axis will move east of the lake today allowing winds to back
to southwest. Low pressure will move across the lake late Sunday
with a brief period of moderately strong northerlies developing
behind the low, late Sunday afternoon spreading to southern
portions of the lake early Sunday evening. Winds should begin to
subside by late Sunday night and Monday as high approaches from
the west. Strong low pressure is forecast to develop the central
plains Tuesday and track east toward the mid-Mississippi Valley
region midweek. Current models suggest the low will track south of
the lake setting the stage for strong easterly winds developing
Tuesday night and continuing into Thursday. Depending on eventual
track of the system, could see a period of easterly gales midwee,
but confidence is still fairly low.



LM...Small Craft Advisory...INDIANA NEARSHORE WATERS UNTIL 4 AM Saturday.




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