Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 191744
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1244 PM CDT Tue Aug 19 2014

.UPDATE...
ISSUED AT 923 CDT TUE AUG 19 2014

Area of showers and thunderstorms associated with an upper-level
wave is currently crossing the Mississippi River into west-central
Illinois. 1417z radar imagery shows leading edge of precip extending
from Galesburg...to Rushville...to Bowling Green Missouri. Based
on timing tools, showers/thunder will arrive along the I-55
corridor by midday. HRRR and other high-res models generally show
the precip area weakening as it pushes eastward through the
morning, then potentially re-developing across east-central
Illinois later this afternoon. Made some adjustments to hourly
PoPs today, mainly to increase to categorical along/west of I-55
during the morning. Once the wave passes, rain chances will come
to an end across the Illinois River Valley by mid to late
afternoon, followed by a return to partly to mostly sunny skies.
Further east, rain chances will linger throughout the day before
coming to an end by evening.

&&

.SHORT TERM...(This evening through Wednesday)
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 night through Tuesday)
ISSUED AT 347 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 18Z TAFS through 18Z Wednesday afternoon)
ISSUED AT 1244 PM CDT TUE AUG 19 2014

17z surface analysis shows cold front across eastern Iowa
approaching the Mississippi River. Earlier convection that pushed
into the Illinois River Valley ahead of the front continues to
diminish as it tracks toward the I-57 corridor. Based on latest
satellite/radar trends, it appears chances for additional
convection at KPIA are slim to none, so have gone with a dry
forecast there. Further southeast at the remaining terminals, will
carry either VCTS or a TEMPO group for thunder this afternoon.
Atmosphere has been temporarily stabilized due to clouds/showers
this morning, but as skies partially clear, think scattered
showers/storms will develop east of the Illinois River through the
afternoon. Any convection that fires up will push into Indiana by
early evening, followed by clearing skies tonight. Given clear
skies and light winds, think areas of fog will once again develop.
Have dropped visbys lowest at KPIA where quite a bit of rain fell
earlier, but have gone with 2-3 miles everywhere between 07z and
14z. After that, mostly clear skies with a light W/SW wind will
prevail by Wednesday morning.

&&

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

$$

UPDATE...BARNES
SHORT TERM...AUTEN
LONG TERM...HJS
AVIATION...BARNES






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