Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 101101

Area Forecast Discussion
National Weather Service Lincoln IL
601 AM CDT Thu Aug 10 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 330 AM CDT Thu Aug 10 2017

1024 mb high pressure over VA/PA and ridging westward into central
IL was providing another fair and seasonably cool night with light
to calm winds. The 3 AM temperatures were in the mid 50s to lower
60s across central and southeast IL, coolest near the IN border.
Very patchy fog noted near the Wabash river with Robinson vsby at
3/4 miles. Clouds were increasing from the west early this morning
with ceilings ranging from 5-12k ft.

A 1012 mb surface low pressure was over east central MN at 08Z/3
am and has a cold front extending sw into central Nebraska. The
00Z model suite has trended slower with arrival of convection
chances today and most of CWA should stay dry this morning, with
chances of showers and thunderstorms spreading east over central
IL during the afternoon and evening, and not reaching areas east
of I-57 until this evening. SPC day1 outlook has marginal risk of
severe storms over the IL river valley late this afternoon into
mid evening. There is a 5% risk of large hail and damaging wind
gusts and 2% risk of tornadoes over the IL river valley during
that time. CAPES rise to 1-1.5k j/kg from 23-04Z while 0-6km bulk
shear is 30-35 kts over this area. Stronger forcing still appears
to pass north of central IL closer to low pressure track which
tracks across northern WI today and into south central upper MI
and northern Lake MI this evening. Convection chances should
diminish overnight over the IL river valley as cold front moves
toward I-55 by 12Z/7 am Fri. Highs in the low to mid 80s today.
Dewpoints currently in the mid to upper 50s at predawn should
climb into the low to mid 60s today, so a bit more humid than past
few days. Lows tonight in the low to mid 60s, with coolest
readings nw of the IL river.

.LONG TERM...(Friday through Wednesday)
ISSUED AT 330 AM CDT Thu Aug 10 2017

Cold front to push through se half of CWA on Friday with chances
of showers and thunderstorms lingering se of I-55 and isolated
convection se of I-70 on Friday evening mainly until dusk/9 pm.
Highs Friday mostly in the lower 80s, ranging from near 80F from
Peoria north to near 85F by Lawrenceville. Lows Fri night range
from mid 50s by Galesburg to lower 60s in southeast IL.

1021 mb high pressure settling over the upper MS river valley on
Saturday should return dry conditions across CWA from overnight
Friday night through most of Saturday night. GFS model is showing
some qpf over east central IL on Saturday especially during Sat
afternoon but other models are dry and followed that route. Partly
to mostly sunny skies Saturday with highs in the upper 70s and
lower 80s.

Models have trended further south with passage of a southern
stream wx system on Sunday and carried just slight pops sw CWA
late Sat night, over most of area on Sunday and lingering small
pops in southeast IL Sunday evening. Highs Sunday 75-81F with
mildest readings by Lawrenceville. Another weak high pressure
ridge settles into the upper MS river valley by Monday and returns
dry wx from Monday through Wednesday night. Highs in the lower
80s Monday slowly modify into the low to mid 80s by middle of next
week as humidity levels gradually rise too with upper level
ridging into IL by Wed. Next chance of showers and thunderstorms
appears to be from next Thu afternoon through Friday Aug 18.


.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 555 AM CDT Thu Aug 10 2017

Scattered to broken clouds of 6-12k ft over central IL early this
morning and should stay VFR ceilings today. Isolated showers over
ne MO drifting east toward the MS river/west central IL border
are forecast to weaken as they move east into central IL during
this morning. The latest HRRR model shows isolated convection
developing between 18-19Z over central IL and then dissipating by
00Z/7 pm. Have included VCTS with 5k ft broken ceilings for this
possibility, but most of the day should be dry. Light to calm
winds early this morning will veer SW and increase to near 10 kts
with gusts around 15 kts this afternoon. A cold front extending
from 1012 mb low pressure over along the nw WI and east central MN
border and into nw corner of IA and southeast Nebraska will move
se into toward the IL river around midnight and to DEC and CMI
later tonight. This may be accompanied by more isolated showers
and possible thunderstorms, and included VCSH for about 4 hours
along and ahead of cold front. Winds veer west to WSW behind the
front less than 10 kts.





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