Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 171104
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
604 AM CDT Sun Aug 17 2014

.SHORT TERM...(Today and tonight)
ISSUED AT 324 AM CDT SUN AUG 17 2014

MCV just north of St. Louis early this morning with a band of
showers and storms to its east which encompasses our southeast
counties. Further to the north and west of the vort center, areas
of rain and drizzle, along with some fog, were observed over the
past several hours.

Main forecast concern in the short term is with coverage of rain
today and affect of widespread low clouds on afternoon temperatures.
Then the fog potential over a larger area tonight, especially if we
see more clearing that what is anticipated. MCV will continue to edge
slowly southeast today with the highest POPs along and to the east
of the track of the vort center, which will be in our southeast
counties. Further north, short term models have various solutions as
to how far north the showers will rotate around the mid level
circulation. Most models suggest due to the slow movement of the
vort center, and with the circulation passing to our south, most of
our area will see an extensive area of low cloudiness and widely
scattered showers from time to time today with the threat for
thunder mainly over southeast IL. Any hope for some breaks in the
clouds will be along and south of Interstate 70 and that may bring
Cape values up sufficiently to support at least scattered
thunderstorms into the evening hours.

As the upper wave shifts further off to our southeast this evening,
we should see the POPs diminish from northwest to southeast but
forecast soundings not showing much in the way of clearing. Even if
we did clear out later tonight, it would be temporary, as the
abundant low level moisture from the rainfall will be enough for
some fog to develop overnight. At this point, will add patchy but if
we see any widespread clearing in the wake of the shortwave, we may
have to deal with some widespread dense fog towards Monday morning.

With the cloud cover expected to hold over our area and a light east
to northeast flow, will stay on the cool side of guid numbers today
with most areas once again struggling to reach 80 degrees.

&&

.LONG TERM...(Monday through Saturday)
ISSUED AT 324 AM CDT SUN AUG 17 2014

The low will move off to the east bringing precip mainly just north
of the Ohio River Valley by Monday with some lingering slight chance
pops in the extreme southeast.  Warming trend continues for the
region with the temps still in the low 80s for a mostly dry Monday.
Until Monday night when another wave passes just to the north and
into the Great Lakes, bringing back chance pops for Monday overnight
into Tuesday.  Better chances to the north and the ECMWF and the NAM
are starting to show signs of drying out the SW sooner on Tuesday
and have trended the pops in that direction.  Separate wave passing
a little further south along the 850 mb front/developing baroclinic
zone.  SFC representation is little more than a very diffuse wind
shift and not convinced where this feature will set up and how much
of an impact it will have... but all models are creating some sort
of precip along this disparity through Wed night, with better
clarity/agreement for the day on Wed night as the boundary lifts
northward.  Pops remaining in the region with this particular
feature and a series of short waves moving along it.  Temps climbing
in a slow warm up, with highs approaching 90 and heat indices
reaching into the upper 90s on Thursday...but all temps are
contingent on the behavior of the boundary and associated timing of
precip. Next weekend dry in the GFS, wet in the ECMWF with a quicker
approach with the next trof to amplify the flow pattern over the
CONUS.  Forecast trended more to the dry GFS, but confidence is low
with next weekend.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
ISSUED AT 600 AM CDT SUN AUG 17 2014

Cigs and Vsbys will continue to deteriorate over the next several
hours to IFR or even lower across the northwest portion of the
forecast area. Weak low pressure just east of St. Louis will track
south of all TAF sites this morning keeping the area under a low
deck of clouds with areas of lower vsbys in fog. The lower vsbys
look to affect SPI, PIA and possibly into BMI by 13z before we
see a very slow improvement in cigs and vsbys as we head into
early afternoon, but still expecting all of our area to see mainly
MVFR cigs this afternoon. Will be watching for the redevelopment
of low clouds and fog for later tonight which could become
widespread, especially if we see any clearing this evening. Surface
winds today will be from the east and northeast at 5 to 10 kts and
turn more northerly this evening with wind speeds of 5 kts or less.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...SMITH
LONG TERM...HJS
AVIATION...SMITH



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