Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 281944

Area Forecast Discussion
National Weather Service Lincoln IL
244 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 18Z TAFS through 18Z Sunday afternoon)
Issued at 1258 PM CDT Sat May 28 2016

MVFR ceilings have mostly lifted to VFR early this afternoon
except at BMI with 2200 foot broken ceiling. Isolated light
showers from I-57 east next hour or two and have VCSH at CMI to
address this. A developing broken line of showers and
thunderstorms over southern IA into northeast MO was tracking NNE
at 35-40 mph and moving toward northwest IL. This convection
developing ahead of 1007 mb surface low pressure near the IA/SD
border. Also have a weakening 565 dm 500 mb low along the eastern
SD/NE border. Low pressure systems lift northeast into sw MN early
this evening and to spread this band of showers and thunderstorms
eastward toward PIA and SPI by BMI/DEC CMI by 23Z-24Z and
and to CMI from 00-02Z. Have VCTS to address this band of
convection late this afternoon and early evening over central IL.
Also have tempo groups of MVFR ceilings and vsbys for a couple
hours at western airports of PIA and SPI where thunderstorms
could be stronger with gusty winds and possible hail. Breezy SSW
winds 13-19 kts and gusts of 20-27 kts this afternoon to diminish
to 5-10 kts by mid evening. South winds this evening veer WSW
during Sunday morning at 10-15 kts.


.ILX Watches/Warnings/Advisories...


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