Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 241959

Area Forecast Discussion
259 PM CDT Tue Mar 24 2015

.SHORT TERM...(Tonight)

19z/2pm surface analysis shows 1007mb low centered over southeast
Kansas, with nearly stationary frontal boundary extending eastward
into Kentucky.  North of the front, a cool easterly flow continues
with current temps across central Illinois only in the upper 30s and
lower 40s.  Meanwhile south of the boundary, temps have soared well
into the 70s from southwest Missouri to the Gulf Coast.  As a
vigorous short-wave trough evident on the latest water vapor imagery
over central Kansas tracks eastward and interacts with the low,
thunderstorms are expected to rapidly develop in the warm sector
along a trailing cold front/dryline this afternoon.  Rapid Refresh
has been consistently showing storms forming from southwest Missouri
into northern Arkansas after 21z/4pm, then spreading northeastward
this evening as the surface low tracks from its current position
near Kansas City to southern Lake Michigan by early Wednesday
morning.  Based on Rapid Refresh timing, broken line of storms will
approach the W/SW KILX CWA around Winchester/Rushville after 8pm,
then will spread across the remainder of the area between 9pm and
3am.  Despite punching into the warm sector as the surface low
approaches, think waning instability in the warmer airmass after
dark will inhibit a widespread severe threat.  Given strong winds
within the profile and strong upper dynamics approaching from the
west, a few of the storms will be capable of producing gusty winds
of 40 to 50 mph and small hail.  Total rainfall from this event will
generally range from one quarter to one half an inch.


.LONG TERM...(Wednesday through Tuesday)

Next upstream short-wave within the progressive zonal flow pattern
across the CONUS will rapidly approach from the west on Wednesday.
Brief surface/upper ridging will produce dry conditions with high
temperatures ranging from the upper 50s north to the upper 60s south
of I-70.  As the wave currently located over the Northern Rockies
drops southeastward into the Plains, surface low pressure will
develop over the Texas/Oklahoma panhandle on Wednesday, then track
northeastward into the Ohio River Valley by Thursday morning.  This
particular track is a bit further south than previous model runs
indicated, so think the best chance for strong/severe storms will be
shifted southward into the Ozarks/Lower Ohio River Valley with the
next convective outlook update from SPC.  The main threat with the
low as it passes just south of the area Wednesday night will likely
be heavy rainfall, as the latest QPF guidance suggests as much as
1.50 to 2 inches of rain south of the I-70 corridor.  This heavy
rainfall on top of what will occur tonight and the already
moist/saturated soil conditions across southeast Illinois could lead
to flash flooding.  A Flood Watch may be required for the SE CWA as
the heaviest rainfall axis becomes better defined, but for now will
hold off and issue an SPS instead.  Have also increased PoPs to 100
percent and mentioned heavy rain in the forecast along/south of
I-70.  Rain chances will decrease further northwest, with only
chance PoPs for showers from the Peoria area northward.

Once the Wednesday night system departs, cooler weather will prevail
through the balance of the extended as a northwesterly flow pattern
establishes itself.  Several weak impulses will track through the
Midwest Thursday night into Friday, but none are expected to
significantly impact the weather across central Illinois.  The next
weather-maker will be a cold front expected to pass through the
region late Saturday night into Sunday.  Will carry low chance PoPs
at that time, followed by a return to cool/dry weather early next


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)

Quasi stationary boundary at the surface just south of Central
Illinois terminals slow to move this afternoon, delaying the onset
of the MVFR/IFR stratus deck in PIA BMI and CMI. SPI BKN012
now...DEC soon to follow suit. Showers moving along SPI to DEC
path as well, with more rain to the west. Afternoon showers and
thunderstorms late remaining possible, though coverage anticipated
to be rather sparse...keeping the mention to VC since the warm
sector of the approaching low is delayed until after sunset.
Tightening pressure gradient however, will result in some rather
gusty winds after sunset/before midnight gusting to 30kts...mainly
out of the SE. IFR through the overnight hours. Clearing in the
morning with the llvl moisture trapped/enhanced may be delayed
considerably and since the operational models are not clearing
until closer to holding off mention of improvement
just yet.




LONG TERM...Barnes
AVIATION...HJS is the U.S. government's official web portal to all federal, state and local government web resources and services.