Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 260453
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1153 PM CDT MON APR 25 2016

.UPDATE...
Issued at 922 PM CDT Mon Apr 25 2016

Boundary is finally moving through the CWA this evening. Will need
to update pop/wx grids to account for current situation and
trends. Based on radar, isolated showers and thunderstorms will
continue to move through the CWA, mainly east of I-55. Boundary is
hard to see in the observations but it can be seen on radar just
passing the NWS office and is just east of I-55. This movement
will continue through the night, which means the showers could as
well. Other updates will be needed to account for the scattered
clouds in the west behind the boundary. Update forthcoming.

&&

.SHORT TERM...(Tonight)
ISSUED AT 242 PM CDT Mon Apr 25 2016

Main concern in the short term remains with the severe weather
potential. CAPE values already in excess of 1000 J/kg across areas
northwest of the Illinois River, where the cumulus field has only
recently started to fill in. Best wind fields are further north
across Wisconsin and far northern Illinois, but some modest 0-6km
bulk shear values of around 30 knots were analyzed on the 18Z SPC
mesoscale analysis. Boundary located just ahead of the thinning band
of stratocumulus and seen as a fine line on the Davenport Doppler
radar just northwest of the Quad Cities as of 2 pm. This will likely
be the trigger for storm development over the next couple hours,
with latest HRRR model showing development by around 3 pm. Bulk of
that particular line progged to mainly be north of us with it
scraping the northern parts of the CWA through sunset, but with
further development a bit further south along the I-55 corridor
toward 6-7 pm. Severe threat will be on the wane by mid evening,
although a few stronger storms will still be possible over east
central Illinois.

With more of a multi-cell configuration this far south, have kept
PoP`s in the 30-40% range, with the threat shifting southward with
time. By about midnight, the northern CWA should be dry, with the
higher PoP`s continuing to spread into southeast Illinois.

.LONG TERM...(Tuesday through Monday)
ISSUED AT 242 PM CDT Mon Apr 25 2016

Latest models have remained fairly consistent regarding their
guidance over the next several days, and forecast does not require
significant changes at this time. Forecast area will continue to be
impacted by predominantly southwest upper-level flow with systems
ejecting toward the region from the southwest U.S. every couple of
days. Downstream blocking pattern over eastern Canada & Greenland is
forecast to persist at least until the weekend which will tend to
deflect the disturbances on a more southerly track than their
original trajectory. This storm track will keep forecast area a
little cooler than was anticipated a few days ago (although still
near seasonal normals), and push the main severe weather threat
south of the area as well.

Tuesday should start out mostly dry across the forecast area, except
in the southeast where a front will still be hanging around. Then,
precipitation chances will ramp up, especially Tuesday night into
Wednesday, as vigorous wave (currently moving into Four Corners
region) approaches the Midwest. Thursday into Friday should be
mostly dry as we lie between systems. A final system, at least for
this forecast package, is expected to bring showers/storms to the
area for the weekend. This system is larger and slower moving than
the ones earlier in the week, and will likely result in a more
widespread/drawn out precipitation event.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1153 PM CDT Mon Apr 25 2016

VFR conditions will prevail at all TAF sites next 24hrs. Sct to
bkn clouds at around 5-6kft will continue over the area and then
become all scattered in a few hours at all sites. However,
additional moisture will increase along the boundary that is
slowly moving through the area. By morning this will bring broken
cigs around 4kft at all sites. These broken cigs will continue
over the area through remainder of the forecast period. With the
frond just south of sites, any pcpn along the front should remain
south of the TAF sites as well. Winds will be tricky as the front
will be fairly stationary near I-72, so PIA/BMI and then CMI will
see winds become more northeast after FROPA. SPI and DEC should
see variable winds through most of the period, but then become
more southwest for the afternoon and evening periods.

&&

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

$$

UPDATE...Auten
SHORT TERM...Geelhart
LONG TERM...BAK
AVIATION...Auten



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