Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 191053

Area Forecast Discussion
National Weather Service Lincoln IL
553 AM CDT Tue Oct 19 2021

Issued at 256 AM CDT Tue Oct 19 2021

Another pleasant fall day is expected today with highs in the mid
70s, southerly winds gusting up to 20 mph, and scattered cirrus
clouds. A weather system will move across the Midwest on
Wednesday, with scattered showers and isolated thunderstorms ahead
of the cold front.


.SHORT TERM...(Today and tonight)
ISSUED AT 256 AM CDT Tue Oct 19 2021

No major changes to the short term forecast as we remain under the
influence of high pressure and pleasant fall weather continues
through Tuesday. Overall, conditions today will be similar to
Monday, with the main differences being the addition of scattered
cirrus clouds and an uptick in wind speeds. Southerly wind gusts
of 15-20 mph are expected in the afternoon. Temperatures will be
roughly 5 degrees above average, with highs in the low 70s and
lows near 50.

.LONG TERM...(Wednesday through Monday)
ISSUED AT 256 AM CDT Tue Oct 19 2021

A cut-off upper low located over Utah early Tuesday morning will
track into the Midwest by Wednesday. The deterministic model suite
has remained rather consistent in the overall track and timing of
this system. A narrow band of weak instability will be present
ahead of the front, allowing a corridor of scattered showers and
isolated thunderstorms to develop, though a warm nose at 850 mb
will limit the development of surface-based convection. Model
soundings for Wednesday afternoon indicate a well-mixed boundary
layer up to 1 km, with downdraft CAPE of 800-1000 J/kg, suggesting
that despite the weak instability a few strong to severe wind
gusts are possible in the afternoon. Most of the precip activity
should remain west of the Illinois River through early evening,
then track eastward from there as the cold front sweeps across IL
late Wed night/early Thurs morning.

Cooler air advects into the area on Thursday following the frontal
passage, dropping high temperatures into the low to mid 60s for
most of the area, and brisk west-northwesterly winds will keep a
chill in the air. A deeper upper low will continue to swirl over
eastern Canada into the weekend, with several weak shortwaves
expected to track from the upper Plains towards central IL late
this week. Ascent from these shortwaves will act to increase cloud
cover, but precip chances appear fairly limited due to dry low
level air beneath cloud base. A few pockets of light rain or
drizzle are in the realm of possibility both Thursday and Friday,
but for now kept the forecast dry as precip chances are too low
for mention. The next appreciable chance of precipitation comes on
Sunday as an approaching system lifts a warm front into central
IL. However, model differences and inconsistency from run to run
reduce confidence in both the timing of precip and the temperature
forecast for Day 6 and beyond.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 551 AM CDT Tue Oct 19 2021

VFR conditions will persist through the period. Winds start off
southerly, then shift to southwesterly during the day and become
gusty in the afternoon. An area of high clouds will progress
through the area from west to east, resulting in scattered cirrus
over the terminals through mid-afternoon. After sunset, gusts
subside and winds return to southerly or south-southeasterly.




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