Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 192342
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
642 PM CDT Fri May 19 2017

.SHORT TERM...(This evening through Saturday)
ISSUED AT 253 PM CDT Fri May 19 2017

Frontal boundary is currently located just north of the I-70
corridor this afternoon, with an extremely sharp temperature range
over the forecast area. 2 pm readings ranging from the mid 40s
north of Peoria, to the mid 80s from Flora to Lawrenceville. A
surface low which has moved into southwest Indiana should start
to drag this boundary a bit southward through the evening hours,
although the significantly colder conditions should stay north of
I-72.

Large convective complex over Kansas and eastern Oklahoma this
afternoon is now edging into western Missouri, and should start
moving into western Illinois after midnight. The area immediately
south of the I-72 corridor received 2 to 5 inches of rain last
night. This would be the area most subject to any flash flooding.
However, right now the system looks to be progressive enough, and
more in a north-south axis, to mitigate the threat of additional
flooding. This will be something we will watch closely over the
next several hours.

.LONG TERM...(Saturday night through Friday)
ISSUED AT 253 PM CDT Fri May 19 2017

Large upper low currently over Colorado will shift into the
central Plains by early Saturday, then lift northeast to near the
Iowa/Minnesota border by mid evening. The frontal boundary will
surge northward and place all of the forecast area in the warm
sector by around midday. Have not changed forecast high
temperatures much, mainly low-mid 80s except for some 70s
northwest of I-55. The GFS brings CAPE values over 1200 J/kg over
all of the forecast area by early afternoon, while the NAM limits
the higher values mainly across eastern Illinois. Main threat for
any severe weather would mainly be over the eastern CWA, where
0-6km bulk shear values reach 40-45 knots during the afternoon. By
early evening, the trailing cold front will be pushing into the
western CWA, and should largely be out of the forecast area by
sunrise Sunday.

The upper low will not be breaking any speed records early next
week, mainly loitering just northwest of Lake Superior through
Monday. By Monday night, a secondary lobe of energy will break
free, and swing southeast into the Midwest, where it will slowly
edge eastward through Thursday. In this particular pattern,
temperatures will be relatively cool during mid week, with highs
down into the 60s Tuesday and Wednesday, before starting to
recover on Thursday. Rain chances will increase quite a bit Monday
night into Tuesday as this low starts to move through, with some
wraparound showers lingering into Wednesday. May be enough
instability for a few thunderstorms on Tuesday, mainly over the
eastern CWA.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 642 PM CDT Fri May 19 2017

Central Illinois will see a continued break in the showers/storms
before the next complex reaches near SPI between 02z-03z, then
lift northeast toward PIA and BMI. Mesoanalysis tools show a much
more stable airmass across central Illinois, so the storms should
begin to weaken once they reach Illinois from eastern Missouri.
We still expect IFR to low MVFR clouds to persist ahead of the
rain, then drop to IFR across the board for late tonight into
Saturday morning. Cloud heights should improve to MVFR toward mid
morning, with VFR conditions at all TAF sites Saturday afternoon.

Storm chances will be mainly confined to this evening for western
TAF sites, then Saturday afternoon for eastern TAF sites.

Winds will be generally E-NE this eve, then shift to E-SE late
tonight and Sat morning, with southerly winds becoming established
Sat afternoon. Wind speeds should remain 10-15kt for much of this
TAF period.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Shimon



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