Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 212001

Area Forecast Discussion
National Weather Service Lincoln IL
301 PM CDT Sat May 21 2022

Issued at 301 PM CDT Sat May 21 2022

Periodic showers and thunderstorms will remain possible through
this evening across central Illinois, with the better chances
south of I-70. A cooler and drier air mass will settle into the
region Sunday into Monday, before showers and thunderstorms return
by the middle of next week.


.SHORT TERM...(This evening through Sunday)
ISSUED AT 301 PM CDT Sat May 21 2022

The main concern in the short term is the potential of any more
severe storms this evening. Modified soundings show that the
morning convection has turned over the boundary layer airmass
quite a bit. However, we still see a 7.5C/km mid-level lapse rate
present across the SPC slight risk area. While marginal
instability will limit severe potential, we could still see a few
updrafts become strong, producing 50-60 mph gusts. The better
chances of strong storms in our CWA will be along and south of
I-70, but possible as far north as the I-72 corridor.

The other concern that has entered the picture could be some flash
flooding potential, due to the rains that have hit our SE counties
the last 48 hours. The axis of convection across Missouri that is
approaching our SE counties appears poised to dump another 1 to 2
inches of rain on already saturated ground. WPC just issued a Meso
Precip Discussion for our SE 6 counties, south of Effingham to
Robinson. Have increased the QPF amounts in that area for the
afternoon update.

Once this last light of convection shifts east late this evening
and overnight, an expansive area of surface high pressure will
arrive bringing cooler and drier air to the region. Sunday will
see northerly breezes at 10 to 20 mph with high temps limited to
the mid 60s.


.LONG TERM...(Sunday night through Saturday)
ISSUED AT 301 PM CDT Sat May 21 2022

A period of dry and cool weather will start out the extended
forecast, as Canadian high pressure progresses across the Midwest
into the Great Lakes. Starting Monday afternoon, a shortwave will
begin to carve an upper level trough into the central and
southern Plains. That action will work to shift the Canadian high
off to the NE CONUS on Tuesday, initiating the return of deeper
layer moisture toward Illinois. An additional shortwave entering
the Pacific Northwest on Monday night will quickly dive into that
trough on Tuesday night, increasing the upper toughs
amplification and ejecting the first shortwave toward the Upper
Mississippi River Valley. As a result, rain chances will increase
to categorical Tuesday night across our entire CWA. A dry slot
should provide a break in the rain for a time on Wednesday,
especially for areas west of I-57. However, the upper trough axis
will remain west of Illinois, allowing southerly low level flow to
continue a moisture feed into the system. That will spell rain
chances continuing through Thursday. There may be some flooding
concerns again in our SE counties, where the higher QPF totals are
projected (2 o 2.5" rainfall possible south of I-70). A flash
flood watch may be needed for portions of our SE counties if those
projected numbers continue to be indicated by the suite of
extended and ensemble models.

Temperatures in the extended forecast look to remain below normal
until possibly next Saturday, when high temps return to the upper
70s to low 80s.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1258 PM CDT Sat May 21 2022

The back edge of the morning wave of showers/storms will exit the
terminal areas in the next couple of hours. Rain just ended at PIA
and SPI before 18z. There are still additional rounds of showers
and thunderstorms expected to lift across our terminals through
04z/10pm, with breaks or lulls in activity too challenging to
indicate in the TAFs. For this reason, we are continuing to
maintain VCTS through much of the first half of the 18z TAF
period. Flight categories through 20z could dip to IFR in vis and
cigs, but some improvement back to VFR is expected. High res
guidance point toward MVFR ceilings developing this afternoon,
even outside of rainy periods. Have included MVFR cigs at all TAF
sites for several hours this afternoon into evening. The end of
rain chances looks to come after 09z/4am Sunday as the skies
clear in the wake of frontal passage.

Surface winds will generally blow from from the north through the
TAF period with sustained speeds near 10 kts, occasionally
gusting near 20 kts this evening.




LONG TERM...Shimon
AVIATION...Shimon is the U.S. government's official web portal to all federal, state and local government web resources and services.