Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 kilx 200218 
afdilx

Area forecast discussion
National Weather Service Lincoln Illinois
918 PM CDT Thu Sep 19 2019

Synopsis...
issued at 248 PM CDT Thu Sep 19 2019

One more day of warm weather is on tap across central and
southeast Illinois on Friday. After that, widespread clouds and
rain will result in cooler temperatures for the weekend. The front
bringing the weekend rain will be slow moving, thus the potential
exists for a couple inches of rain across the area.

&&

Update...
issued at 915 PM CDT Thu Sep 19 2019

Surface dewpoints have increased over the last 24 hours, with mid
to upper 60s in western portions of the cwa, under a light south-
southeast wind. Spurious showers and isolated storms earlier in
our SW counties have primarily dissipated. A line of convection is
starting to bubble up just north of Stark and Marshall counties. A
slight southeastward drift to those showers has lent some support
to keeping slight chance pops in our far northern County Warning Area for late
evening and a good portion of the overnight. There are widely
varying solutions from the high resolution guidance on the storm
coverage the rest of the night and Friday. The consensus appears
to be for spotty showers/storms to fester across our northern
counties, mainly from Canton to Peoria to El Paso and north.
Confidence is low on coverage of rain, so limited chance pops to a
few hours later this evening and after midnight, in our far
northern counties.

No other changes of significance were needed in the going
forecast. Updated info is already available.

&&

Short term...(this evening through friday)
issued at 248 PM CDT Thu Sep 19 2019

Outflow boundary from the early morning northern Illinois
convection has reached a Mount Sterling to Pontiac line as of 2
PM, per radar imagery. Earlier showers that had developed near
Galesburg have failed away, though there remains isolated
development back through Quincy into north central Missouri.
High-res models have been rather variable on how long this is
going to persist. There are a couple periods of concern. Initial
one is more focused along the Illinois River into early evening,
and have extended isolated pop's from the afternoon into early
evening. Second is with a convective cluster potentially forming
near the Quad Cities toward midnight, persisting into early Friday.
Have also introduced some 20-30% pop's overnight near and north
of I-74 for this area.

Later on Friday, the upper ridge will begin shifting east of the
area. Pop-up storms still possible into the afternoon, especially
where any residual boundaries happen to set up. This should also
be the last significantly warm day of this stretch, with highs
again in the mid to upper 80s.

Long term...(friday night through thursday)
issued at 248 PM CDT Thu Sep 19 2019

Main focus during this period remains with the heavy rain
potential this weekend, as the upper low currently over Nevada
lifts northeast. Strong flow off the Gulf will also combine with
some of the moisture remnants of Imelda to bring an extended
period of precipitable water values near or over 2 inches for
Saturday and Sunday. Rainfall Saturday and Saturday night will
mainly be across the central and northern cwa, gradually shifting
southward on Sunday and Sunday night. Still looks to be potential
for a couple inches of rain across most of the forecast area, with
a heavier axis currently progged to be near the Illinois River.
Given the extended period of the rain, am not currently planning
any flood headlines, though area rivers are likely to see some
decent response.

Secondary forecast concern is with a trough emerging from The
Rockies early Tuesday. The GFS is much more progressive with this
feature than either the European or Canadian models, which have a
cutoff low over the Desert Southwest or Texas into mid week.
Currently leaning more toward these two solutions, which do show a
more subtle wave moving out of the plains, so some 20-30% pop's
are warranted around midweek.

&&

Aviation...(for the 00z tafs through 00z Friday evening)
issued at 705 PM CDT Thu Sep 19 2019

VFR conditions can be expected for the next 24 hour taf period in
all of central and eastern Illinois.

Diurnal showers/T-storms that developed along an old outflow
boundary later this afternoon have all dissipated just before 00z.
Thick, cirrus cloud tops from the convection will continue to
drift over much of central Illinois...mainly north of I-72...the rest of
the evening.

Many of the convective allowing models are indicating the
development of showers and a few thunderstorms with weak to
moderate low level moisture convergence toward daybreak in
northern/northwest Illinois. Some of the remnants of this could move down into
north central Illinois into Friday morning. Thus, will keep vcsh in the
taf for kpia, but stick with no mention of rain in other areas of
central Illinois.



&&

Ilx watches/warnings/advisories...
none.
&&

$$

Update...shimon

National Weather Service Glossary of Abbreviations