Special Weather Statement, NWS Lincoln, IL

Area Forecast Discussion
National Weather Service Lincoln IL
1105 AM CDT Sat May 21 2022

.SYNOPSIS...
Issued at 1223 AM CDT Sat May 21 2022

Widespread showers likely today with heavy thunderstorms possible
along and south of I-70 through this evening. 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.

&&

.UPDATE...
Issued at 1104 AM CDT Sat May 21 2022

A wake low earlier this morning of 3-5mb pressure falls/rises
triggered some 35-40 mph gusts in east-central IL. Those have
generally weakened as pressure levels have rebounded, but the did
shake things up for a bit with the early morning band of
rain/storms.

We are currently tracking a squall line this morning that is
tracking roughly along the I-70 corridor. It is moving into an
increasingly unstable airmass as heating of the day increases
surface temps and southeast flow brings higher dewpoints in the
upper 60s northward. Instability is still not expected to become
all that high before this line of storms reaches our southeast
counties from Shelby/Effingham/Clay and eastward. SPC's latest
SWOMCD indicated a 40% chance of a watch, and a few warnings may
eventually be needed for damaging wind threat before the line
exits into Indiana.

In the northern portions of central IL, post-frontal synoptic lift
is triggering yet another wave of rain and scattered
thunderstorms. No significant impacts are expected from that wave
of rain through early afternoon. A break in the rain is projected
after this wave departs to the east, but yet another push of
showers and storms will develop late this afternoon and evening
and progress from SW to NE across central IL.

Any additional severe threat beyond the bowing complex headed for
SE IL late this morning will be from an MCV that pushes across
southern IL. That one should remain south of our counties however,
with the outflow from this midday system guiding the storm path
farther south.

Updates this morning were to fine tune the PoPs and weather to
match expected trends.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 1223 AM CDT Sat May 21 2022

Key Messages:
(1) Widespread showers and thunderstorms likely today;
(2) Severe weather possible along and south of I-70 (12pm-8pm)

Early morning WV imagery depicts deep southwest flow extending
from the Southern Plains to the Great Lakes region ahead of a low-
amplitude, positively-tilted 500 mb trough. At the surface, a
sharpening cold front is positioned from roughly Danville to
Effingham. While the main upper-level forcing is displaced well
north of the region today, model guidance suggests a pair of mid-
level shortwave troughs embedded in southwest flow will lift
across the Mid-Mississippi Valley, parallel to the cold front.
These disturbances will team up with a modest LLJ to support
multiple rounds of showers and thunderstorms across central and
southern Illinois today.

While isolated, sub-severe storms will remain a possibility north
of the cold front, the focus for severe weather comes along and
south of the front where the boundary layer will be characterized
by surface temperatures in the mid 70s, dewpoints in the mid 60s,
and MLCAPE values >1000 J/kg. While marginally unstable
conditions are modeled across the warm sector, there is at least
one limiting factor that would hinder robust storm development. Of
chief concern is any convective debris that lingers through late
morning, which would squelch SBCAPEs and keep storms elevated.

Despite some of the latest CAMs showing multiple rounds of
potentially severe storms along and south of I-70 through late
evening, it's worth noting that with every round of convection
today, the environment will become increasingly worked- over.
Given the marginal CAPE/Shear profiles across the warm sector,
it's reasonable to doubt that later rounds of storms this evening
would prove severe. Rather, the focus should be on the mid-afternoon
development when storms have the best chance of being surface-
based. It's also during this time that a belt of mid-level
westerlies will nose across the Missouri Valley, helping increase
deep-layer shear to around 35 kts. This would be enough to
support some organized multi-cell clusters given the hodograph.
Wind and hail are the primary severe weather threats for today.

Even as the surface cold front sags south of the region late this
evening, a band of light-to-moderate rain will likely persist
across central Illinois where an axis of frontogenesis will
develop amid subtle isentropic ascent.

Precip should gradually end after midnight as surface high
pressure builds in from the north. Temperatures will cool into
the upper 40s across our northern counties where skies begin to
clear overnight.

.LONG TERM...(Sunday through Friday)
ISSUED AT 1223 AM CDT Sat May 21 2022

Cooler and drier conditions are expected between Sunday and
Tuesday as surface high pressure slowly builds across the region.
The NBM is offering daily temperatures that range 5-10 degrees
below normal during this period with afternoon highs in the upper
60s and overnight lows in the upper 40s to low 50s.

Mid-range global guidance continues to resolve the next chance
for showers and thunderstorms, which appears to arrive Tuesday
evening into Wednesday as a frontal system lifts northward across
the Mid-Mississippi Valley. Unsettled weather then looks to
continue through late next week as yet another frontal system
lifts into the region. Preliminary QPF from the NBM is offering an
additional 1.50" - 2.00" of rainfall with these systems next week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 548 AM CDT Sat May 21 2022

Multiple rounds of showers and thunderstorms will lift across the
regional terminals through 00z/7pm, with breaks or lulls in
activity too challenging to indicate in the TAFs. For this reason,
we are maintaining VCTS through much of the TAF period. Flight
categories will most commonly be VFR through this afternoon, but
periods of MVFR ceilings are likely within heavier rounds of
showers and thunderstorms. It's not until after 09z/4am Sunday
that rain ends and skies clear in the wake of frontal passage.

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

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

UPDATE...Shimon
SYNOPSIS...MJA
SHORT TERM...MJA
LONG TERM...MJA
AVIATION...MJA

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Special Weather Statement
National Weather Service Lincoln IL
720 AM CDT Sat May 21 2022

ILZ045-046-055>057-062-063-068-211245-
Douglas-Coles-Vermilion-Clark-Champaign-Cumberland-Edgar-Crawford-
720 AM CDT Sat May 21 2022

...Strong thunderstorms will impact portions of eastern Coles,
northwestern Crawford, Edgar, northeastern Jasper, Clark, Vermilion,
eastern Cumberland, southeastern Champaign and eastern Douglas
Counties through 745 AM CDT...

At 720 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from Philo to near Ashmore to near Hazel Dell.
Movement was east at 60 mph.

HAZARD...Winds in excess of 40 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Strong thunderstorms will be near...
  Sidney around 725 AM CDT.
  St. Joseph, Homer and Redmon around 730 AM CDT.
  Ogden and Oliver around 735 AM CDT.
  Paris, Fairmount, Fithian, Vermilion, Muncie and West Union around
  740 AM CDT.

Other locations in the path of these storms include Danville,
Westville, Tilton, Catlin, Oakwood and Belgium.

This includes the following highways...
 Interstate 70 between mile markers 123 and 154.
 Interstate 74 between mile markers 190 and 220.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

To report severe weather, contact your nearest law enforcement
agency. They will relay your report to the National Weather Service
office in Lincoln.

&&

LAT...LON 3931 8762 3922 8757 3916 8764 3913 8795
      3917 8796 3918 8809 3949 8807 4007 8825
      4032 8753 3937 8753
TIME...MOT...LOC 1220Z 250DEG 51KT 4000 8816 3952 8798 3916 8800

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

Auten

Special Weather Statement
National Weather Service Lincoln IL
1113 AM CDT Sat May 21 2022

ILZ061-066-071-211715-
Clay-Effingham-Shelby-
1113 AM CDT Sat May 21 2022

...Strong thunderstorms will impact portions of southeastern
Christian, southern Shelby, southwestern Cumberland, northwestern
Clay and Effingham Counties through 1215 PM CDT...

At 1112 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 6 miles southwest of Pana to Brownstown to near
Salem. Movement was northeast at 50 mph.

HAZARD...Wind gusts up to 50 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Strong thunderstorms will be near...
  Altamont and Beecher City around 1125 AM CDT.
  Shelbyville around 1130 AM CDT.

Other locations in the path of these storms include Effingham,
Stewardson, Edgewood, Shumway, Iola and Watson.

This includes the following highways...
 Interstate 57 between mile markers 143 and 172.
 Interstate 70 between mile markers 79 and 100.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with these storms and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3891 8870 3891 8881 3922 8880 3922 8914
      3935 8914 3935 8903 3937 8902 3944 8847
      3917 8847 3917 8845 3881 8846 3881 8869
TIME...MOT...LOC 1612Z 233DEG 54KT 3931 8914 3902 8896 3866 8900

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH

Barnes