Area Forecast Discussion
Issued by NWS Central Illinois

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163
FXUS63 KILX 251943
AFDILX

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

.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 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1217 PM CDT Mon Apr 25 2016

Not a lot of change to the previous TAF set in regards to
scattered convection developing later today, but have made some
minor adjustments to the timing. Coverage is still uncertain
enough to go more than a VCTS mention, but will amend later once
it becomes more clear. Gusty south-southwest winds to around 25-30
knots this afternoon should subside toward 00Z. As a frontal
boundary settles southward late tonight, a trend toward the west
will occur, and areas near KPIA/KBMI likely to go more north or
northeast by late in the forecast period. With the frontal
boundary settling over the area, there are some indications of
potential MVFR ceilings after 12Z, especially north of this
boundary. Right now, will keep ceilings just above 3000 feet until
this becomes a bit more clear.


&&

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

$$

SHORT TERM...Geelhart
LONG TERM...BAK
AVIATION...Geelhart



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