Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 232324

Area Forecast Discussion
National Weather Service Lincoln IL
524 PM CST Thu Nov 23 2017

.SHORT TERM...(This evening through Friday)
ISSUED AT 258 PM CST Thu Nov 23 2017

High pressure ridge over the Ohio River Valley this afternoon, and
southwesterly winds will become more southerly as the evening
progresses, decreasing as the boundary layer decouples for the
overnight. Relatively warm air over the region and southerly winds
will counter radiational cooling somewhat under mostly clear
skies. As a result, tonight will only drop into the 30s. As a mid
level thermal ridge slips into the Midwest going into Friday,
tomorrow 850 mb temps surge to 9-13C. Between the warm advection
and ample sunshine, can expect temperatures to climb into the
lower 60s and upper 50s for Central IL. Pressure gradient
increasing at the surface will result in the potential for some
gusty winds in advance of a developing cold front to the

.LONG TERM...(Friday night through Thursday)
ISSUED AT 258 PM CST Thu Nov 23 2017

Upper level trof dropping into the Midwest tomorrow evening is
starting to look vigorous enough to look similar to the overnight
trough this past Tuesday. With that in mind, and plenty of warm
air and increasing RH ahead of the boundary...have put in the
chance for at least some sprinkles late Friday. For now, confining
them to before midnight. However, timing of the boundary likely to
get some fine tuning through the next few runs. Cold front brings
cooler temperatures to wrap up the weekend, then the pattern
repeats. Winds come around to more southerly Sunday night, Monday
gets warmer again (and have pulled forecast above blended MOS as a
result). Front is dragged back through the region with cooler air
and slight chance pops late Tues/Tuesday night. Models having
issues resolving available moisture for fropa and precip...but
picks up on the Tues/Tuesday night least in the GFS.
Both ECMWF and GFS break the energy off from the northern stream
and spin up a h5 closed low across the midsection of the country.
GFS brings the low along with the parent trough for Tues/Tues
night precip. The ECMWF is slower with the momentum of the closed
low and with the reduced forward motion, precip is delayed into
day 7, which coincidentally becomes a precip type issue. Forecast
confidence beyond day 4 is lower until the models produce better


.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 518 PM CST Thu Nov 23 2017

VFR conditions are expected through this forecast period. Light
southerly flow expected tonight under a mostly clear sky will
increase to 15 to 25 kts after 16z Friday with gusts up to 30 kts
possible in the afternoon.




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