Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 kilx 221042 

Area forecast discussion
National Weather Service Lincoln Illinois
542 am CDT Sat Jul 22 2017

Short term...(today and tonight)
issued at 245 am CDT Sat Jul 22 2017

One more brutal day of heat on tap, as widespread heat index
values of 110-115 are likely over a good portion of the County Warning Area this
afternoon. Some thicker clouds along and north of the I-74
corridor may help keep temperatures down a tad, but heat index of
105+ still likely there as well. High temperatures should still
reach the mid-upper 90s, hottest from Jacksonville southeast to

Late night satellite imagery showing several mcs's from eastern
south Dakotas into central Indiana. Bulk of the rain from these
features has been staying to our north so far, but some storms
will begin moving into the northwest County Warning Area shortly. Latest hrrr
indicates the northern County Warning Area will see the most threat through about
9 am or so. After that, leftover outflows and a weak frontal
boundary settling southward will be the focus for any renewed
development later this afternoon. NAM/GFS continue to show
tremendous instability this afternoon, with cape values around
5000 j/kg, although the shear remains weak south of I-74 where
there is more influence from the upper ridge. The front will slow
down as it moves into the southern cwa, so will maintain some
chance pop's into the night south of I-72.

Long term...(sunday through friday)
issued at 245 am CDT Sat Jul 22 2017

Upper low currently just west of Lake Winnipeg will open up a bit
as it swings into the Great Lakes on Sunday, helping to finally
break down the ridge over the Midwest. Drier air will be a bit
slower to spread into our area, but it currently appears that
with 60s dew points arriving in the afternoon, this should keep
the heat index below 100 degrees in most of the County Warning Area on Sunday.
Thus, will allow the current heat headlines to expire on schedule
this evening.

Cold front is expected to arrive in the northwest County Warning Area during the
afternoon, and push southeast through the evening. Forecast
soundings over the southern County Warning Area are a bit on the dry side, and
have some concerns that the Storm Prediction Center day2 convective outlook of a
slight risk pushes too far south. The GFS is most favorable for
any strong/severe storms in the southeast cwa, but most of the
other models are dry in the evening over that area.

A couple nice days of drier air on tap, as high pressure drifts
east across the Great Lakes. Unfortunately, the upper ridge
starts to build eastward toward mid week, spreading more 90s back
into the area by Wednesday. Main question will again be with the
placement of the ridge periphery, which is closer to our County Warning Area than
the recent couple days. The GFS is fastest in bringing
precipitation with a frontal boundary southward, as early as
Wednesday afternoon, while the European model (ecmwf) is favoring more of a
Thursday arrival with associated rain chances. Late in the week,
both models favor more of a ridge position over The Rockies into
the first part of the weekend, returning temperatures close to


Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 542 am CDT Sat Jul 22 2017

Showers and thunderstorms have been developing southward as the
convective complex moves out of Iowa. Will start off with
prevailing thunderstorms and rain at kpia and tempo one in at kbmi for the first
couple hours. Further south, some scattered showers/storms have
been occurring from kspi-kcmi along an outflow boundary, but these
should be gone in a few hours.

Cold front moving through late afternoon and evening between
about 22-03z will result in some scattered storms. Have added a
thunderstorms in the vicinity mention from kspi-kcmi for about a 3-4 hour period to cover
this. Areas further north are more uncertain with the prospects,
and have not added them at this time.


Ilx watches/warnings/advisories...
excessive heat warning until 8 PM CDT this evening for

Heat advisory until 8 PM CDT this evening for ilz030-031-038-



National Weather Service Glossary of Abbreviations