Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 050445
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1145 PM CDT WED MAY 4 2016

.UPDATE...
Issued at 808 PM CDT Wed May 4 2016

Upper low over northeast Indiana this evening will continue a
southward movement overnight with shortwaves rotating around the
feature...providing areas of cloud cover through early
morning...especially for the eastern half of Illinois. Some light shower
activity should pass southward through Indiana late in the
night...reaching to around the Illinois border and have included
slight chances for showers in eastern Illinois counties bordering
Indiana. Have also updated the forecast this evening for cloud
cover trends. The cold air mass associated with the upper low will
provide for below normal temperatures in the low 40s across
central IL...but fortunately a persistent north wind around 10
mph and cloud cover will keep temperatures warm enough to prevent
frost overnight.

&&

.SHORT TERM...(Tonight)
ISSUED AT 257 PM CDT Wed May 4 2016

Cu field developed through the day in response to cold air aloft and
diurnal heating. Enough moisture and instability to trigger
scattered showers over the east and southeast sections. Though no
lightning strikes so far, one report of pea size hail. Will continue
to be chance of this convection next 3 hours, then heating drop off
will allow showers to dissipate with the CU field also clearing and
yielding mostly clear skies overnight.

Upper level low center seen in IR imagery over southwest MI will
drop slowly to the south overnight, with weak upper wave rotating
around it. short range models advect moisture and low clouds with
this wave south southwestward, reaching the eastern parts of central
IL for 2-3 hours around 12z on Thursday. Expect the winds to
gradually diminish also overnight.

.LONG TERM...(Thursday through Wednesday)
ISSUED AT 257 PM CDT Wed May 4 2016

The closed 500 mb upper low will be located over northern Kentucky
by tomorrow morning with our area still under some decent low and
mid level cyclonic flow, at least through early afternoon.
Forecast soundings suggest we should see a decent cumulus field
develop again tomorrow afternoon over the east before temps aloft
start to warm and our flow becomes increasingly anticyclonic by
mid to late afternoon. After that, some quiet weather expected
through Friday night with temperatures warming back into the 60s
all areas tomorrow afternoon, and from 75 to 80 on Friday.

The blocky pattern will start to slowly break down Friday night into
Saturday as a rather vigorous northern stream shortwave dives
southeast over the upper Great Lakes. This will drive another cold
front into our area by Saturday afternoon and at least along or just
south of the Ohio River Saturday night into Sunday. This remains the
main forecast challenge for the weekend as models were suggesting
the trof amplifying to our east late Saturday into Sunday
significantly enough to push the front well south of the Ohio River.
Now, several deterministic models indicate the boundary may not get
much of a push south Saturday night and be close enough to our area
to keep at least mentionable POPs going through Sunday. Still feel
the combination of convection expected to develop in our area
Saturday afternoon and evening and the vigorous upper wave digging
southeast should be enough to push the boundary south of the Ohio
River. As a result, the higher POPs will remain roughly south of
I-72 on Sunday with the further south boundary position, but
start to push back into our area Sunday night into Monday as the
front edges back into our forecast area.

The active weather pattern is expected to hold into at least the
first half of the new work week as the southwest upper low finally
gets close enough to our area Monday night through at least early
Wednesday to warrant high chance to likely POPs, especially over
the western forecast area. Temperatures starting on Sunday and thru
the remainder of the forecast period are going to be tricky as the
front is expected to drift north as the upper wave from the southwest
approaches central Illinois late Tuesday into Wednesday. Temperatures
will be close to or a bit above normal during this time frame.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1145 PM CDT Wed May 4 2016

Upper low centered over east-central Indiana will continue to
produce cloud cover primarily over eastern portions of Illinois
overnight as disturbances wrap around the feature. A period of
MVFR cigs continues to look likely for KCMI in the morning
starting around 12Z. With daytime heating a scattered cumulus
layer around 4000 ft AGL should develop after 16Z across central
IL. Winds N-NNW around 5 kts overnight...becoming 10-15 kts with
gusts as high as 20 kts after 16Z. Winds decreasing after 00Z.

&&

.ILX Watches/Warnings/Advisories...
NONE.

&&

$$

UPDATE...Onton
SHORT TERM...Goetsch
LONG TERM...Smith
AVIATION...Onton



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