Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 251952

Area Forecast Discussion
National Weather Service Lincoln IL
252 PM CDT THU AUG 25 2016

.SHORT TERM...(This evening through Friday)
ISSUED AT 252 PM CDT Thu Aug 25 2016

Mesoscale Convective Vortex(MCV) associated with large cluster of
storms over the Plains last night continues to track E/NE early this
afternoon, with 19z/2pm obs/satellite data suggesting it is now
located over northeast Missouri/southeast Iowa.  Latest radar mosaic
is still not showing much activity with this feature, although some
new convective development is trying to occur across west-central
Illinois.  Most model guidance has handled this system poorly today,
with the WRF-NMM seemingly doing the best job overall.  It shows
scattered storms developing ahead of the wave over the next few
hours, primarily impacting locations along/north of I-72 between now
and 8pm.  While severe weather will be a possibility, think
widespread severe is unlikely due to strongest instability/shear not
being co-located.  SPC mesoscale analysis continues to show highest
CAPES of around 4000J/kg focused across the far SE CWA south of the
I-70 corridor and the strongest 0-6km bulk shear of 50kt setting up
further north along/north of a Jacksonville to Bloomington line.
Think the strong shear will be great enough to overcome the lack of
instability to produce scattered strong to severe thunderstorms with
damaging wind gusts across the northern half of the CWA late this
afternoon into the early evening.  Once this early convection pushes
further east, a lull in the precip chances will occur for much of
the night, with another round of showers/storms possibly approaching
from the west well after midnight.  Will therefore focus high chance
to likely PoPs along/north of I-72 into the early evening, with only
slight chances lingering after that.  Synoptic cold front will sag a
bit further southward before becoming stationary across south-
central Illinois late tonight into Friday.  With the boundary still
in the vicinity, will continue low chance PoPs across the W/SW CWA
through Friday.


.LONG TERM...(Friday night through Thursday)
ISSUED AT 252 PM CDT Thu Aug 25 2016

The cold front currently positioned from west central to northeast
Illinois looks to slowly edge southward into southern Illinois
through Friday morning then move slowly back northward as a warm
front through Saturday. This will provide a focus for an MCS
developing Friday night over northern Missouri or Iowa...potentially
crossing portions of central IL late Friday night. The highest
probability track looks to be toward northern IL so included a
period of 60% PoP`s from around the Illinois River northward late
Friday night and Saturday morning...and chance (30-40%) elsewhere.

Later in the weekend into early next week models advertise a series
of disturbances on the northern periphery of upper level high
pressure over the SE U.S. which should keep periodic chances for
thunderstorms in central IL. For the most part...the pattern looks
to be moist and unstable through the extended with little in the way
of large air mass changes. Will primarily carry chance PoPs(30-40%)
in the Sunday-Wednesday daytime periods and slight chances (20%) for
the night time periods. Most of the CWA should see highs in the 80s
for the next week, lows in the mid 60s to lower 70s.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1251 PM CDT Thu Aug 25 2016

Confidence is growing that a cluster of thunderstorms will develop
and move across the central Illinois terminals late this
afternoon/evening. Upstream satellite/radar imagery does not yet
show much additional development ahead of a disturbance over
northwest Missouri: however, HRRR has been consistently showing
storms developing over the next couple of hours then tracking
eastward through central Illinois. Based on HRRR timing, have
included TEMPO group for thunder and MVFR ceiling at KPIA between
21z and 00z...then further east to KCMI between 00z and 02z. Once
this initial wave of convection moves through, the rain will end
and winds will veer to the northwest as a cold front gets pushed
south of the area this evening.


.ILX Watches/Warnings/Advisories...


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