Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 282348

Area Forecast Discussion
National Weather Service Lincoln IL
648 PM CDT SAT MAY 28 2016

.SHORT TERM...(Tonight)
ISSUED AT 244 PM CDT Sat May 28 2016

SPC issued a severe thunderstorm watch until 9 pm for 9 of our
northwest counties in the IL river valley. Have increased chances of
thunderstorms in this area into early evening. So far much of this
convection has been over IA and lifting NNE at 35-40 mph. But expect
this band to develop southward with time as it spreads into the IL
river valley late this afternoon and early evening until sunset.
Some sunshine helping with heating and making airmass more unstable
as CAPES are elevating to 1-2k J/kg during mid/late afternoon while
0-6 km bulk shear is 25-30 kts. This convection is developing ahead
of a frontal boundary over sw IA into central MO and expected to
track eastward across western and central IL during this evening and
eastern IL overnight. 1006 mb surface low pressure near the SD/IA
border to lift northeast into nw WI by midnight tonight helping push
the front eastward into IL this evening. Aloft a 565 dm 500 mb low
was in far southeast SD and to continue to weaken as it lifts into
western Lake Superior by dawn Sunday. Instability/CAPES to weaken
after sunset with convection also diminishing as it spreads into
eastern IL later this evening and overnight. Lows overnight mostly
in the mid 60s, with some lower 60s from Galesburg and Jacksonville
west as some drier air moves in behind the front overnight.

.LONG TERM...(Sunday through Saturday)
ISSUED AT 244 PM CDT Sat May 28 2016

Unsettled weather expected to persist across central and southeast
Illinois for much of the coming week. While the first half of the
week should still see daily highs in the 80s & daily lows in the 60s
to start the week, consensus is building that these readings will
cool to the 70s (highs) & 50s (lows) in most areas to end the week.
Main forecast concern revolves around shower/storm chances, and
looking for opportunities to remove them. Selecting dry periods is
proving difficult as the local airmass should remain fairly "juicy"
and uncapped for much of the week.

Most of Sunday is still expected to remain dry as the upper-level
low remnants, currently tracking into the upper Midwest, pushes
north/east of the area. The passage of this upper feature will push
a weak cold front through the area by early Sunday. Any stabilizing
of the atmosphere in the wake of the front will be fairly short
lived, with spotty development possible by late Monday across at
least western portions of the forecast area.

A northern stream wave and associated frontal system will impact the
area Wednesday into Thursday bringing our next chance of more
widespread showers/storms. However, scattered showers/storms are
possible as early as Tuesday areawide under pre-system WAA and
diurnal instability. Precipitation chances will lower or possibly end
for a time Friday/Saturday in the wake of the midweek system, with
temperatures trending a little cooler than normal. The operational
GFS had previously lingered precipitation chances much longer than
Thursday, but it and many of its ensemble members have trended
toward what the ECMWF & Canadian models showed yesterday.


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 648 PM CDT Sat May 28 2016

Line of broken convection extended along the IL River valley just
before 00Z. Expecting these storms to impact PIA with MVFR
conditions through 02z. For the rest of the central IL TAF sites,
the t-storms should be decreasing in intensity as we approach dusk
and as they encounter a more stable enviroment with a bit lower
shear. As a result will only put VCTS for DEC and CMI, with the
TAF sites along I-55 losing the potential for TSRA about 03-04Z.
A few showers could linger along and east of I-55 from about

Windy conditions will also wane this evening as mixing decreases
with loss of heating. Expect the wind to shift from south to
southwest and eventually west by Sunday late morning/early
afternoon with the passage of a cold front. Otherwise, VFR
conditions will prevail from early Sunday morning into Sunday


.ILX Watches/Warnings/Advisories...


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