Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Lincoln Illinois
1045 am CDT Tue Jul 29 2014

Discussion...
issued 1045 am CDT Tue Jul 29 2014

Deep upper trough across the eastern Continental U.S. Continues to be the
dominant weather-maker across central Illinois today. Northerly
flow is providing unseasonably cool temperatures, with afternoon
highs once again expected to remain in the 70s. Main question will
be whether or not any showers will develop within the cyclonic
flow pattern aloft. Not really seeing much of anything on the
latest water vapor imagery, so am skeptical any showers will form
today. Will however hold on to just slight chance pops northeast
of I-74 as hrrr/nam12 both develop a few showers across northeast
Illinois late this afternoon. No zone updated needed at this time.

Barnes
&&

Aviation...
issued 609 am CDT Tue Jul 29 2014

VFR conditions will prevail at all central Illinois taf sites for
the next 24hrs. Mostly clear skies will continue until late
morning then scattered cloud cover will develop with daytime
heating. Cool air aloft may allow a few convective showers to
develop...mainly kprg-kgbg northward...however any MVFR
cigs/vsbys quite isolated and too low probability for mention in
tafs. After 00z...any shower activity/cloud cover diminishing.
Winds increasing to nw8-12 kts by 15z...decreasing to west up to 5
kts after 00z.

Onton
&&

Previous discussion...
issued 308 am CDT Tue Jul 29 2014
upper level ridge over the western half of the country, and trof
over the eastern half... putting much of the northern plains and
the Midwest under northwesterly flow. This pattern sticks around
for the next few days, with weak flow under a building surface
high. Forecast dominated by slowly creeping up temperatures,
though remaining below normal, and afternoon instability showers.
Best chances for precip heading into the weekend, however, with
another wave on its way as well as a kicker to shift the pattern
aloft and move the trof out of the region by the end of the
weekend. Though models are consistent with the overall trend of
the pattern, the details on timing and extent of the afternoon
showers differs here and there...as well as the
timing/impact/strength of the Fri/Friday evening wave.

Short term...today and tomorrow...
each day a degree or two warmer than the previous day.
Northwesterly winds today as the high continues to build into the
region. Tomorrows winds a bit more west/northwesterly and somewhat
lighter. Rain chances today should remain limited to the
northwest. Though a few models are coming in dry...and the GFS the
other extreme with overblown convection... the more high res model
data output in the 4km WRF and the hrrr is showing some shower
activity to the NE. Wave diving into the trof visible on WV Sat
imagery this morning will assist the diurnal afternoon development
and cannot completely rule out some isolated shower activity.
However, tomorrows afternoon showers access more instability in
the midlevels, albeit a small amount, and pops spread over much of
ilx tomorrow with the addition of thunder.

Long term...Thursday through Monday...
continued below normal temps and northwesterly flow through the
end of the week with some small impulses assisting the afternoon
showers. Models continue to enhance this activity on Thursday
night and into Friday as the impulses start moving into the West
Coast and trying to break down the ridging to the west. GFS far
more aggressive with the precip and the European model (ecmwf) is timing a little
quicker with the wave and missing the collision with the Max
afternoon heating...and therefore much less qpf. Models beginning
to signal the progression of the deep trof out of the region for
late Sunday and into Monday...which would mean a return to warmer
conditions.

Hjs

&&

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

$$

National Weather Service Glossary of Abbreviations