Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 160844

Area Forecast Discussion
National Weather Service Lincoln IL
344 AM CDT Sun Jul 16 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 318 AM CDT Sun Jul 16 2017

Through most of the forecast, there isn`t much of a change
overall. Still a shift from a more northwesterly flow pattern with
embedded waves to broad ridging aloft expanding over much of the
southern two thirds of the country. Shorter term forecast is
dominated by a wave within that NW flow pattern and the surface
front making its way through the forecast area this morning.
Mostly anticipated by midday in prev forecasts...the overnight
convection has stayed together working through fairly unstable
air. With southward progression, the instability reduces
considerably, but still enough fuel to potentially be showers and
thunderstorms for the nrn tier of the CWA later this morning. HRRR
and RAP both eroding the majority of the precip as it moves
through nrn IL. The front is masked somewhat by the mesoscale
impacts of the storms and their outflow...and models/MOS are
persistent with an arrival of the boundary midday. Precip and
thunder expected to light up along the boundary again
later...possibly after a brief break. To that end, the 07Z run of
the HRRR looks like it is trying to spin up precip later on both
the front, as well as the outflow from this mornings storms to the
north. With such a warm airmass in place, plenty of CAPE
available, although subsident air behind the boundary may be
enough inhibition to eventually chip away at the Marginal Risk for
the forecast area later this evening in the north. Overnight, the
precip slowly makes its way out of southeastern IL...with another
evenings lows dropping into the 60s.


.LONG TERM...(Monday through Saturday)
ISSUED AT 318 AM CDT Sun Jul 16 2017

The slightly cooler air and associated cloud cover may keep
Monday`s high temps in the low to mid 80s, with a northeasterly
component to the winds...but the cooler air will not stay in place
too long before the broadening area of the upper ridge eventually
results in plenty of warm air from the SW shifting over the Miss
River Basin and into the Midwest. A general warming trend kicks in
again, resulting in another hot week. The ECMWF and the GFS are a
still conflicted as to the strength and northern extent of the
ridging aloft as a series of quick waves top the ridge. This
difference will be the difference between some off and on precip
chances...and the showers potentially being shifted off to the
northeast. Either way, the mid levels maintain a warming trend
throughout...and have continued to bump the temps in the latter
half of the week a degree or two above most guidance...which will
result in heat indices back into the low 100s.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1246 AM CDT Sun Jul 16 2017

Not much of a shift in the forecast...revolves around a cold front
dropping into the region later today. Mainly a southwesterly flow
with relatively light flow ahead of it... switching around to more
northerly behind the boundary and a chance of scattered showers
and thunderstorms about midday. One adjustment to the forecast
right now is a result of some convection along that same boundary
to the north. The outflow and the thunderstorms may be masking the
actual location of the boundary through the near term...and
hesitate to change too much of the midday timing of the boundary.
May shift thinking by 12z run...but for now, remaining




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