Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 190837
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
337 AM CDT Tue Aug 19 2014

.SHORT TERM...(Today and tonight)
ISSUED AT 336 AM CDT TUE AUG 19 2014

Short term models have trended slower with the front and precip that
is currently supposed to be moving into the area. But will still
have chance of precip starting in the northwest parts of the CWA
this morning. Then will progress the pcpn chances southeastward
across the CWA during the day. By this evening, most of the pcpn
will be in the eastern two thirds of the area with the highest pops
in the southeast. By overnight, the pcpn should have moved southeast
of the area so most of the area should be dry overnight, though will
keep a slight chance of pops in the southeast after midnight. Could
be some additional pcpn in the southwest late tonight, but models
keep most of pcpn west of the area through 12z.

Temps will begin the slow warming tomorrow, and am expecting mid to
upper 80s throughout the area today.


&&

.LONG TERM...(Wednesday through Monday)
ISSUED AT 336 AM CDT TUE AUG 19 2014

Models still pretty consistent with the development and lift of a
boundary through the Midwest on Wednesday. Boundary will have little
reflection at the sfc with very weak flow/weak wind shift, and
thermal gradient is better represented in the mid levels.  Boundary
will provide a weak focus for waves moving through the region as the
boundary lifts to the NE through the area for Wed/Wed night.  Though
Wed is lacking signif pop for now, the timing of the progression is
better for early evening and into the overnight on Wednesday
night/shifting to the northeast for Thurs. Position of the boundary
or the remnants thereof will be where the majority of the precip
chances will be...increasing to the north, particularly north of
Interstate 74 from Thursday to Saturday. Ample sfc based instability
in the form of hot and humid conditions as the ridge over the
southwest opens and spreads signif heat into the Midwest. Models
have also shown consistency with  850 mb temps in the 19-25C range
from Wednesday through Sunday.  This will drive the temps into the
upper 80s/lower 90s with heat indices in the upper 90s/approaching
100F.  A far more summer-like pattern than much of the season so far,
and well above normal for this time of year...with breaks from the
heat provided by any thunderstorms that may have the chance to form
from more diurnal instability with any frontal forcing further to
the north. Into the extended, day 7/just into day 8, models diverge
in solutions with major difference in breaking down the upper ridge
for the Midwest.


&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 1152 PM CDT MON AUG 18 2014

Patchy fog resulting in VLIFR to MVFR conditions in place from
around K1H2-KAAA-KCMI eastward, with a line of thunderstorms
approaching northern IL from the northwest. Fog expected to
dissipate as light SSW winds ahead of the line of thunderstorms
promotes mixing. This line expected to weaken as it approaches and
mainly affect TAF sites from KPIA and KBMI northward. Have
included VCTS in central IL TAFs to address potential for
thunderstorms, but likelihood of MVFR conditions looks too low for
explicit mention at this time. A break in shower/thunderstorm
activity likely in the morning, then an upper level shortwave and
daytime heating should produce a re- intensification of storms
along the cold frontal boundary lingering over central Illinois.
Have brought VCTS and ceilings near MVFR thresholds for the
remainder of the afternoon to account for this. Starting around
00Z, conditions expected to improve as frontal boundary and upper
level shortwave moves east of the area.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...ONTON






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