Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 190802

Area Forecast Discussion
National Weather Service Lincoln IL
302 AM CDT WED OCT 19 2016

.SHORT TERM...(Today and tonight)
ISSUED AT 301 AM CDT Wed Oct 19 2016

The cold front has finally slipped south of Lawrenceville as of 200
am and will continue to edge a bit further south before stalling out
over far southern Illinois into southern Indiana. To the north of
the front, temperatures and dew points have lowered considerably
from the past few mornings with temperatures in the upper 40s to
lower 50s across our northern counties to the upper 60s over the
I-70 corridor. Radar was indicating some isolated showers starting
to develop along the front from near Mount Vernon to just south of
Mount Carmel and were tracking mainly to the east.

The main challenge today will be timing of the showers back into our
area as an upper level trof moves across the Plains inducing a
surface low along the frontal boundary to our south. Most of the
guidance now was keeping the frontal boundary and surface wave just
south of the I-70 corridor late this afternoon through this evening
with the better instability axis along and just south of the front
with MUCAPEs around 1000 J/KG over extreme southeast Illinois for
a brief time late this afternoon into early this evening. Plenty of
deep layered shear as well near the frontal boundary with 0-6km
shear values around 50 kts. With the warm sector expected to remain
just south of the I-70 corridor, it appears the more organized
severe weather threat will be south of our area, however, a few of
the storms could produce some gusty winds and hail before the threat
wanes early this evening. Most areas today should be in the 70s with
a few locations in far southeast Illinois possibly approaching the
80 degree mark.

As the surface wave shifts east-northeast along the frontal boundary
tonight, widespread showers and isolated thunderstorms will occur
over far east central and especially southeast Illinois with the
potential for some significant rainfall over southeast Illinois
where up to 1.50 inches of rain may fall by later tonight into
early Thursday morning. Further north, precipitation chances start
to lower but it appears there should be enough forcing for at least
some scattered showers through the evening before the POPs begin to
decrease late tonight from northwest to southeast.


.LONG TERM...(Thursday through Tuesday)
ISSUED AT 301 AM CDT Wed Oct 19 2016

Upper trough will sharpen as it moves into the Mississippi Valley on
Thursday, helping to boot the cold front and rain off to our east.
Behind it, quiet weather will dominate into the weekend as a surface
high pressure drifts across the Midwest into the southeast states.
Some patchy frost is possible late Thursday night across the
northwest corner of the CWA around Peoria and Galesburg, as
temperatures dip into the upper 30s. However, temperatures will
recover nicely over the weekend across central Illinois, with more
of a zonal flow setting up as the trough shifts to the east.

As an upper ridge begins to build across the Plains early in the
week, the dry weather pattern will continue over our area. Latest
runs of the GFS and ECMWF models focus most of the precipitation
with the mid-week system more over the upper Mississippi Valley on
Tuesday, with more of an impact in our CWA on Wednesday, just beyond
the current forecast period.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1144 PM CDT Tue Oct 18 2016

The cold front and all associated light rain showers continue to
drift farther south of I-70 this evening. Winds have continued to
veer from NW toward N, and will eventually become NE before
sunrise. A generally weak pressure gradient is expected during the
next 24 hours, as high pressure builds into Illinois from the
west. Winds should remain NE through the day tomorrow, with speeds
generally remaining less than 10kt.

The cold front will stall out roughly along a line oriented along
the southern border of Indiana late tonight, then begin a slow
shift back northward tomorrow afternoon in response to a weak
shortwave lifting NE along the front. That will bring increasing chances
of showers into central and SE IL. Showers and a few storms will
become likely by evening for SPI, DEC and CMI with chances
including PIA and BMI through the evening. Storm chances should
generally remain south of I-72, but we included VCTS for SPI, DEC
and CMI for the evening time frame to coincide for the passage of
the low pressure to the south of our counties. In general, we kept
prevailing conditions in the VFR category for this TAF period,
but any storms could produce MVFR cloud heights or visibility for
short periods of time if they move over any terminal sites
tomorrow evening.


.ILX Watches/Warnings/Advisories...


LONG TERM...Geelhart
AVIATION...Shimon is the U.S. government's official web portal to all federal, state and local government web resources and services.