Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 210205

Area Forecast Discussion
National Weather Service Lincoln IL
905 PM CDT Fri Apr 20 2018

Issued at 900 PM CDT Fri Apr 20 2018

Quiet weather will persist across central and southeast Illinois
overnight, with high pressure and an associated dry air mass
continuing to dominate the local weather. Thin high level clouds
from a developing system over the Plains will continue to stream
across the area overnight and should help keep temperatures a
little warmer than last night. Going forecast is in good shape
and only minor tweaks to the hourly trends were necessary at this


.SHORT TERM...(This evening through Saturday)
ISSUED AT 215 PM CDT Fri Apr 20 2018

High pressure to our north will slowly edge off to the east of the
region during this forecast period. That should bring another
quiet night and day to the forecast area as a storm system shifts
slowly southeast across the southern Plains. The area of high
pressure has brought some very dry air to the region and expect
that to hold through Saturday keeping the precipitation associated
with the storm away from our area.

High level clouds will be on the increase across the area tonight
which should help keep temperatures up a few degrees from last
night`s frosty lows. Across our far east and southeast counties
where the sky should remain mostly clear the longest tonight, we
may see some patchy frost but there should be enough cirrus move
in after Midnight to prevent any widespread frost threat. Lows by
Saturday morning are still expected to be in the 36 to 40 degree

.LONG TERM...(Saturday night through Friday)
ISSUED AT 215 PM CDT Fri Apr 20 2018

The storm system expected to shift well south of the area this
weekend will still influence a part of central and southeast
Illinois with some cloud cover from time to time, especially
south of I-72. As the upper low and attendant surface low track
into Arkansas on Sunday, moisture wrapping northward ahead of the
system may start to affect our far southeast counties by afternoon
with rain chances holding on in areas along and south of I-70 into
early next week. Further north, forecast soundings continue to
exhibit quite a bit of dry air in the low and mid levels of the
atmosphere as the large surface high just to our north this
afternoon will still be advecting dry air southwest into our north
and central counties Saturday and Sunday keeping any rain threat
to the south. There are some indications of a northward shift in
the rain chances on Monday as the upper low rotates northeast into
the Ohio Valley but only slight chances indicated at this point.

A series of shortwaves are then forecast to dig southeast into
the Midwest early next week which will sharpen up the longwave
trof across the eastern U.S. for the middle and latter portions of
the week. Initially, the 850 mb temperatures are not that cool for
this time of year, but as we head towards the end of the week,
models are suggesting a rather vigorous upper wave digging
southeast bringing another chilly air mass southeast into the
Midwest late next week or next weekend. Still, quite a bit of
model uncertainty with respect to how amplified the pattern will
be over the eastern Great Lakes late next week with the GFS a bit
more conservative with the 500 mb trof compared to the 12z ECMWF.

Pleasant temperatures are expected into early next week, at least
compared to what we have experienced around here over the past
several weeks. We will still be averaging just a bit below normal
on our highs and lows, but it is still a big improvement from what
temperatures have been like over the past couple of weeks. Precip
chances will increase area-wide late Tuesday into Wednesday as the
first of the southeast moving trofs dig into the Midwest, with
another chance of showers later Thursday night and Friday as a
second wave drops southeast into our area.


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 648 PM CDT Fri Apr 20 2018

Quiet/VFR aviation weather conditions will persist across the
central Illinois terminals through the 00Z TAF valid time. SCT-BKN
upper-level clouds will persist, as will easterly winds. The winds
will likely become a little gusty again Saturday afternoon.




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