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Area forecast discussion 
National Weather Service Lincoln Illinois
103 PM CDT Sat may 30 2015

issued at 1112 am CDT Sat may 30 2015

Widespread clouds/showers blanket the western half of the kilx County Warning Area
this morning...while some peeks of sunshine are occurring further
east across east-central and southeast Illinois. Due to the
partial sunshine and a continued southerly flow...temperatures
have risen well into the 70s and even the lower 80s in some
locations along/east of the I-57 corridor. This is the area we
will be watching for potential strong to severe thunderstorm
development later today as low pressure currently over southeast
Missouri tracks across southern Illinois. Enhanced low-level wind
shear near the low will interact with a moderately unstable
environment to trigger widespread thunderstorms. Latest day 1
outlook from Storm Prediction Center highlights locations along/southeast of a
Champaign to Shelbyville line with a slight risk for severe later
today. Based on hrrr appears the primary time frame
will be between 2 PM and 8 PM. Made a few minor adjustments to the
going forecast...but overall trend is right on track.


Short term...(today)
issued at 328 am CDT Sat may 30 2015

Low pressure is projected to track in a northeast direction across
southeast Illinois today, with a cold front pushing across Illinois
from northwest to southeast during the day. Both features will provide a focus for
an extended period of rain showers and scattered thunderstorms in
central and southeast Illinois. An intensifying southerly low level
jet will progress across southern Illinois ahead of the low...with speed
convergence maximized on an axis from SW to NE across our forecast
area. That low level jet will aid in moisture transport pushing precipitation water
values into the 1.5 to 2 inch range. Flash flood guidance for one
hour is generally 2 to 2.5 inches in areas that are expected to see
the higher precipitation totals. Some concern for a Flash Flood Watch
southeast of the Illinois River, but most of that area should be
able to handle the rainfall that occurs with this system. Peak
instability this afternoon is forecast to reach to around 1500 j/kg
MUCAPE southeast of I-55, which will increase rainfall rates with stronger
updraft development. Severe storms are not expected, but a few
storms closer to the track of the low southeast of I-55 could see some
small hail and gusty winds.

High temperatures will be held in check by the widespread cloud cover and
periodic rain. Highs will struggle to reach 70 around Galesburg,
with low 80s for 80s southeast of I-70 where some peeks of sun may occur
this morning to help boost temperatures.

Long term...(tonight through friday)
issued at 328 am CDT Sat may 30 2015

Surface low projected to ride just north of the Ohio River and then
into central Indiana tonight...with most of the models favoring a
position in east central Indiana by Sunday morning. Some heavier
rains should continue to affect eastern Illinois into the first part
of the evening with this track...where categorical pop's will be in
place for the first few hours. With the changes to the track...have
had to re-Orient the original pop grids to favor a more west-east
tapering of the rain vs a clearing from the northwest. Thus...pop's
will linger east of I-57 past midnight. Total quantitative precipitation forecast for today and
tonight expected to be in the 1.5 inch range in areas from Effingham
northeast to Danville. Stiff north/northeast wind will drive in much
cooler air into the area...although there will be a tight
temperature gradient across the far east depending on the speed of
the departing low.

Much quieter weather expected Sunday and Monday in the wake of the
departing system. Surface high to build southward through the Great
Lakes...and will not be in any particular hurry to leave. GFS and
European model (ecmwf) take until late Wednesday/early Thursday to push this system
into the eastern Great Lakes region...resulting in dry conditions
for our area. In fact...they basically keep things dry until late
Thursday or Friday as upper level heights build due to high pressure
in the plains. Temperatures will start off rather cool with highs in
the 60s to around 70 Sunday and Monday...but 80s should return by
middle week as the high pushes farther east.


Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 103 PM CDT Sat may 30 2015

Occasional showers will persist at the kilx terminals through the
afternoon as low pressure tracks across southern Illinois. Model
consensus brings the rain to an end at kpia by around 23z...then
further east to kcmi by 05z. Ceilings will generally be in the
MVFR category through the afternoon...however as winds swing
around to the north/NE on the back side of the departing low...a
period of VFR ceilings is likely from late afternoon through the
evening. Strong/gusty winds will develop as well...with forecast
soundings suggesting gusts of 20 to 25kt. Pressure gradient will
remain tight through the strong north/NE winds will
continue through 18z.


Ilx watches/warnings/advisories...


short term...shimon
long term...geelhart

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