Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 230156
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
856 PM CDT Mon May 22 2017

.UPDATE...
Issued at 855 PM CDT Mon May 22 2017

A couple of waves of precipitation are poised to affect central
Illinois the rest of the night and tomorrow. An early evening wave
produced very light rain as cloud based remained at 6K feet and
above. Better instability in NE Missouri earlier this evening
allowed for some thunderstorms to develop and progress toward
Illinois, where a more stable air mass exists this eve. We could
still get a few rumbles of thunder as the next wave of showers
affects our counties north of a line from Taylorville to Paris from
9 pm to 2 am. A break in the rain could develop for late tonight
and tomorrow morning, before a stronger line of showers and storms
develops in W Illinois and progresses across our counties tomorrow
afternoon.

All of these showers will be developing ahead of a slowly
approaching cold front, with triggers mainly associated with
shortwaves traveling through the upper level trough. Areas north
of I-70 will remain under prevailing clouds and a cold pool of
air aloft, limiting our diurnal temperature swings and keeping
temps mainly below normal.

Lows tonight look on track for the mid to upper 50s, with highs
tomorrow in the mid 60s toward Galesburg to the mid 70s south of
I-70. Updates this evening were mainly to the PoPs and weather
trends.



&&

.SHORT TERM...(This evening through Tuesday)
ISSUED AT 303 PM CDT Mon May 22 2017

A surface boundary will slowly move into the area this evening and
bring light showers to northwest parts of the CWA for tonight.
Models differ on amount of precip expected but it looks like higher
pops will be initially in the northwest and then diminish through
the night. The likelihood of precip will increase again during
the early morning hours in northwest and then continue to increase
to the east and south during the day tomorrow as the main
boundary/low pressure area finally gets into the CWA.

Clouds and precip will keep the temp spread small next 24hrs. So,
expecting lows in the 50s with highs Tuesday afternoon cooler...in
the lower to middle 60s.

.LONG TERM...(Tuesday night through Monday)
ISSUED AT 303 PM CDT Mon May 22 2017

The low pressure area that moves into the area will become
filled/vertically stacked and then slowly spin over the eastern
midwest/western OH valley through Thur morning. This will keep a
continued threat of showers and isolated thunderstorms over the CWA.
There could be a break in the precip Thur and Thur night as the
system pulls away to the east. Then another weather system will
arrive for Fri and Fri night with showers and storms possible. The
remainder of the weekend will be quite unsettled with the chance of
showers and storms continuing into Sunday night.

Temps through the period will start cool and then warm back into the
70s and lower 80s for Sat and Sunday. Overall guidance looks ok, but
may be a tad warm for Friday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 655 PM CDT Mon May 22 2017

An extended period of forcing for precipitation has set up across
central Illinois, oriented from SW to NE. A slowly approaching
cold front from the Plains will put Illinois in a persistent S-SW
flow through a deep layer. Moisture pooling ahead of the front
will support periods of rain as various shortwaves lift through
Illinois around the base of the upper trough. Thunderstorms should
remain very isolated the rest of the night, with one storm in NE
Missouri progressing toward Illinois, but generally on a weakening
trend as sunset nears.

Have kept thunder out of the TAFs until after 18z tomorrow, when a
stronger wave will arrive during peak heating and instability.

VFR conditions should prevail over the next 24 hours, except
during any thunderstorms. Have not included any tempos for MVFR at
this point, but higher potential for MVFR looks to be in the
morning near PIA, and then during the afternoon for all TAF
sites.


&&

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

$$

UPDATE...Shimon
SHORT TERM...Auten
LONG TERM...Auten
AVIATION...Shimon



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