Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 250452

Area Forecast Discussion
National Weather Service Lincoln IL
1152 PM CDT TUE MAY 24 2016

Issued at 902 PM CDT Tue May 24 2016

Most of current forecast looks ok and doesn`t need to be adjusted.
However, pops/wx need to be lowered over most of the area since
not seeing any development near the Mississippi river as some
short range models were showing earlier this afternoon. So have
lowered pops to slight chance or all the way to none. Still have
lots of high clouds over the area and these will continue the
remainder of the night. Will leave late tonight forecast as is
since lots of uncertainty as to what will be happening overnight
given the current ongoing convection in KS/OK and AR. Updated
forecast will be coming out shortly.


.SHORT TERM...(Tonight)
ISSUED AT 240 PM CDT Tue May 24 2016

Mostly sunny, breezy, and warm conditions prevailed across central
Illinois this afternoon as the area remained under the influence of
surface/upper ridging.  A short-wave trough evident on water vapor
imagery over western Missouri will be the primary weather-maker over
the next 24 hours as it slowly tracks eastward.  Most models suggest
widely scattered thunderstorms will develop ahead of this feature
along the Mississippi River late this afternoon then will push into
west-central Illinois during the evening.  With plenty of dry air
evident at mid/low-levels, the environment will remain hostile to
widespread precip.  The HRRR has been consistently showing these
showers/storms dissipating toward midnight as they slowly track
toward the I-55 corridor.  Will therefore carry highest PoPs across
the Illinois River Valley tonight, with locations further east
around Champaign/Danville only seeing slight chance PoPs after
midnight.  Thanks to continued southerly flow and increasing surface
dewpoints, overnight low temperatures will remain in the lower to
middle 60s.

.LONG TERM...(Wednesday through Tuesday)
ISSUED AT 240 PM CDT Tue May 24 2016

Southwest flow aloft will prevail across the Midwest through this
forecast period bringing very warm and humid weather to the region
with the difficult part of the forecast trying to pin down rain
chances ahead of rather weak low amplitude shortwaves that are
forecast to eject northeast from the main longwave trof over the
western U.S.  With the persistent southwest flow aloft, any frontal
boundary and main forcing mechanism is expected to remain well west
and northwest of our area through the week. The next shortwave over
the southern Rockies is expected to push across the central Plains
tonight and into the northern Plains on Wednesday bringing another
round of convection to our west. Just how far east these storms
move towards the mid-Mississippi River valley and away from the
better forcing remains to be seen with most of the deterministic
models and even a few of the CAM solutions not doing very well
with the current convection to our west and south.

With the aforementioned shortwave approaching on Wednesday, we
should see a weak boundary/warm front develop and shift north across
the area during the day, with most model solutions having this
feature to our north by late tomorrow afternoon where the better
forcing/low level convergence will be located. Overnight, it still
appears convection will fire on the nose of the 850 mb low level jet
and along and just north of the 850 boundary which suggests the
better threat for more organized storms will be closer to the 850
front which with this model run is to our north. Based on the 1000-
500 mb thickness diffluence across our area, it appears the
storms may dive southeast into parts of our area early Thursday
morning where the better instability would be located. Still not
worth much more than 40 to 50 POPs at this point. Yet another
shortwave will approach the area from the southern Plains later
Friday and into Saturday possibly bringing another round of
convection to parts of the Midwest.

Warm weather is expected to continue through the holiday weekend
with daily chances for showers and storms. The 12z GFS ensemble
and ECMWF solutions indicate a transition to an increase in 500
mb heights over the Midwest, with the stronger flow and thunderstorm
chances shifting into the northern Rockies east thru the upper Great
Lakes during the first week of June.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1152 PM CDT Tue May 24 2016

VFR conditions will prevail at all TAF sites remainder of the
night. Then question is will any pcpn reach into the area and if
so, what time. COnvection out in the plains not being handled well
by convective short-term models...which is normal. Models differ
on how to handle the possible incoming pcpn. Newest HRRR model
brings some pcpn toward the sites beginning around 15z. These
seems somewhat plausible so will add a VCTS for all sites
beginning around 15z at SPI and then advecting it eastward,
starting last at CMI around 18z. Since remainder of the afternoon
and into the evening is uncertain, will keep the VCTS going just
until early evening and then have drier weather for remainder of
the TAF period. Will keep VFR conditions throughout. Winds will
light out of the south tonight and then be southerly tomorrow
with some gusts to around 20kts.


.ILX Watches/Warnings/Advisories...


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