Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 190147

Area Forecast Discussion
National Weather Service Lincoln IL
847 PM CDT Fri May 18 2018

Issued at 840 PM CDT Fri May 18 2018

A slow moving upper level low was pushing into extreme southern
Illinois this evening with a band of showers and thunderstorms to
its east over central, east central and southeast Illinois. As the
low continues to edge to the east and northeast, the better chances
for showers will move along with the feature into the eastern part
of the forecast area overnight. The upper wave will shift to our
east by Saturday afternoon with the residual low clouds, patchy
fog and rain threat moving out as well. The clouds should gradually
lift in the afternoon allowing sunshine to return which should push
our temperatures back into the 80s most areas. Widespread cloud
cover and higher dew points across the entire forecast area will
lead to warmer temperatures overnight with most areas in the 60 to
65 degree range by Saturday morning.

Have made some minor adjustments to the precipitation trends for
the rest of the evening, especially across the east. Otherwise,
the rest of the forecast is in good shape. We should have the
updated zones out by 9 pm.


.SHORT TERM...(This evening through Saturday)
ISSUED AT 325 PM CDT Fri May 18 2018

A weak 575 dm 500 mb low over southeast MO at mid afternoon will
slowly lift into central IL by 06Z/1 am tonight, and weaken/open
up as it lifts into the central Great Lakes by sunset Saturday.
Increasing moisture from the se ahead of this disturbance has
brought isolated to scattered showers nw into central and
southeast IL, with a few thunderstorms along the MS river valley
from St Louis to Paducah, and more thunderstorms over KY and
southeast MO where airmass is more unstable. Fairly stable airmass
over our CWA so mainly getting showers here. Extensive cloud cover
over CWA keeping temps closer to seasonable levels, with 70s.
Showers were cooling temps into the mid to upper 60s over west
central IL from Jacksonville west.

Latest CAM models showing scattered showers persisting into this
evening with isolated thunderstorms possible south of I-72, then
isolated to scattered showers mainly east of Peoria and
Springfield overnight, and lingering east of I-57 Sat morning.
Added patchy fog overnight into early Sat morning over western
half of CWA as winds become light and variable with lingering low
level moisture. Lows overnight around 60F northern CWA and mid 60s
in southeast IL. Warmer highs of 80-85F Saturday as some sunshine
appears during the afternoon with most areas being dry, aside from
isolated showers east of I-57 during early/mid Sat morning.

.LONG TERM...(Saturday night through Friday)
ISSUED AT 325 PM CDT Fri May 18 2018

Another upper level low will emerge near the CO/KS border by
sunset Saturday and a warm front to set up over central IL during
Sat night into Sunday ahead of this upper level low. This will
likely develop showers and thunderstorms over the IL river valley
later Sat evening and overnight Sat night, with a chance of
showers and thunderstorms overnight Sat night over eastern/se IL.
SPC updated day2 outlook has expanded marginal risk of severe
storms further east to areas west of I-57, mainly overnight Sat
night hours for strong winds and hail a threat.

Good chance of showers and thunderstorms across CWA on Sunday
afternoon and evening with warm front lifting toward northern
CWA. SPC day3 has marginal risk of severe thunderstorms across
area, mainly from mid afternoon into mid evening, with strong
winds and large hail again a threat. More of a north to south temp
gradient across the warm front on Sunday with highs in the upper
70s/lower 80s from Peoria and Bloomington north, to the upper 80s
to near 90F from Springfield and Paris south. Convection chances
lower during overnight Sunday night into Monday morning, but
redevelop again Monday afternoon/evening especially east of I-55.
Could be a few strong thunderstorms in eastern IL from mid Monday
afternoon into early Mon evening. Highs near 80F by Galesburg on
Monday and mid 80s along and east of I-55 with upper 80s in
southeast IL.

Summertime pattern expected to continue during middle and later
part of next work week as upper level ridge builds over the area.
Could be some short waves/MCSs ridging over top of the ridge and
mainly passing north of central IL during mid and late week.
Isolated showers and thunderstorms possible in southeast IL on Tue
afternoon. Highs Tue of 80-85. The best chances of convection
next work week are in sw CWA on Wed afternoon/evening and over
central and western CWA next Friday. Warm highs in the low to mid
80s Wed thru Friday with lows in the low to mid 60s.


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 610 PM CDT Fri May 18 2018

Main forecast concern this period will be the timing of the
MVFR/IFR cigs late tonight as a weather system tracks across
the region. Currently, widely scattered showers and isold
TSRA are occurring over parts of central IL late this afternoon
and we expect the coverage to gradually diminish after dark this
evening. However, low level moisture will continue to increase
overnight with most areas going down to MVFR with at times IFR
cigs Saturday morning before we see a gradual decrease in the
clouds in the afternoon. Surface flow will remain from an east
to northeast direction tonight at 10 kts or less and then swing
into a west to northwest direction at 10 kts or less by Saturday




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