Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 270815
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
315 AM CDT SAT AUG 27 2016

.SHORT TERM...(Today and tonight)
ISSUED AT 315 AM CDT Sat Aug 27 2016

The latest satellite and radar loops show a well-defined shortwave
lifting northeast through eastern Iowa and northwestern Illinois.
The wave will continue to trigger showers and storms early this
morning, with locally heavy rainfall possible due to PWAT values of
2 to 2.25". The latest HRRR actually pushes the bulk of the rain
east of our area by 16z, with little to no redevelopment through
22z/5pm. While there should be a break in the rain behind this
initial wave, the GFS/NAM/GEM/EC all point toward some redevelopment
in central IL during the day today along a trailing surface
boundary, especially east of I-55 where the theta-e ridge axis will
be focused. Those additional showers will also be fueled in part by
a warm front lifting north through IL this afternoon. Instability
and moisture content appear sufficient for that next phase of storm
development.

Have used a mix of likely and high chance PoPs in the near term this
morning to coincide with the latest radar trends. Areas east of I-57
appear to have likely chances at some point early this afternoon, so
have confined likely PoPs to that area for now, with 30-50 percent
chances in the remainder of the area into early afternoon. Later
this afternoon, chances should begin to wane west of I-55 at least.

High temperatures today will be closely tied to the amount of
sunshine that develops between periods of rain. Yesterday, some low
90s developed south of I-70, and could see that same scenario today
after the early morning storms clear out of areas east of I-57. Have
included around 90 for LWV. Less sunshine and more periods of rain
north of I-70 should help to keep highs in the lower to mid 80s.

&&

.LONG TERM...(Sunday through Friday)
ISSUED AT 315 AM CDT Sat Aug 27 2016

A 594 dm 500 mb subtropical ridge over the mid Atlantic states will
ridge westward toward the mid MS river valley Sunday through Tuesday
and provide very warm and humid conditions over central and
southeast IL. Highs in the mid 80s to near 90F while dewpoints of
70-75F expected during this time frame and will make for rather
uncomfortable humidity levels for a few days. Expect a daily
chance of showers and thunderstorms Sunday through Tuesday
especially during the afternoon and early evening hours with
frontal boundary nw of CWA and our area in the tropical airmass
with precipitable water values of 1.60-2.20 inches prevailing.

Upper level flow becomes nw during midweek and brings a cool front
southeast over NW IL by Tue afternoon and into southeast IL on
Wednesday and keeps at least slight chances of showers and
thunderstorm going from Tuesday night through Wed evening. Highs
in the lower 80s from I-74 north and mid 80s south of I-74 on Wed
and still rather humid with dewpoints at least around 70F.
Somewhat cooler and drier air filters into CWA on Thu/Fri with
surface high pressure over the central Great Lakes around lower MI
and bringing northeast flow into IL Wed night and Thursday and
dewpoints slipping into the lower 60s with some upper 50s from
I-74 northeast by Thu night.

Upper level ridge building back east into IL Friday night and
Saturday and keeping it dry with temperatures starting to modify.
Highs Thursday of 79-83F and back in the low to mid 80s by
Saturday. Extended models have 500 mb heights building over IL
between 588-594 dm during Labor Day weekend which would support
summerlike warmth returning.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1100 PM CDT Fri Aug 26 2016

A stationary front to the south of the TAF sites late this
evening is expected to push north late tonight as a warm front
with showers and thunderstorms most numerous to its north. As a
result, we look for deteriorating conditions during the early
morning hours as cigs and vsbys drop to MVFR with local IFR
conditions in rain and TSRA along with fog. These conditions will
persist into the mid morning hours of Saturday before we see a
gradual improving trend by afternoon as the front shifts north.
Forecast soundings indicate cigs should improve to sct-bkn MVFR
and then to VFR after between 15 and 18z. With the boundary north
of our area by afternoon, there still could be a shower or
thunderstorm during peak heating but as it appears now, coverage
will be too limited to include in TAFs. Surface winds will be
light east to southeast during the early morning hours at 6 to 10
kts and then as the warm front lifts north of the area by late
tomorrow morning, we look for winds to veer more into the south at
8 to 13 kts. Winds will be variable in direction and speed and and
near any of the stronger thunderstorms overnight and Saturday
morning.


&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...Shimon
LONG TERM...07
AVIATION...Smith



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