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Area forecast discussion 
National Weather Service Lincoln Illinois
640 am CDT Wed Aug 20 2014

Short term...(today and tonight)
issued at 333 am CDT Wednesday Aug 20 2014

Storms have developed along a boundary in northeast MO and southeast
Iowa early this morning. These storms should move into western and
southwest Illinois in the next several hours. These could get into western
parts of the County Warning Area so will have some chance pops in the west this
morning. However, all models seem to indicate this area will not
travel very far and should dissipate during the morning hours. The
associated boundary will then slowly lift northeast as a warm front
through the cwa, and though convergence along this boundary will be
weak, some isolated showers or thunderstorms will remain possible in
the early afternoon. By late afternoon and into the evening and
overnight hours, the warm front will remain across the central part
of the County Warning Area so the chance of showers and thunderstorms will continue
during the evening and overnight hours.

Temperatures will be a few degrees warmer than yesterday, with some
areas in the west and south getting to around 90. Overnight lows
will also be warmer as most of the County Warning Area will be in the warm sector


Long term...(thursday through tuesday)
issued at 333 am CDT Wednesday Aug 20 2014

Position of the boundary after lifting through the forecast area today and
tonight will have a signif impact on the location of the showers and
thunderstorms. Though most recent models are lifting the boundary
further to the northeast, some chance pops thurs and slight chance
pops remain in place at least over the northeastern portions of the
County Warning Area from Thursday night through Friday night. Pops increasing
somewhat for Saturday as models are collapsing the ridge somewhat as
a wave moves over the ridge and into the Ohio River valley. Though
the precip chances are scattered at best and low confidence...the
models have been very persistent with the very hot temperatures for
some Summer like conditions that are well above normal for this time
of year. Models have also shown consistency with 850 mb temps in
the 19-25c range through Sunday. This will drive the temps into the
upper 80s/lower 90s with heat indices in the upper 90s/low 100s.
Forecast dwpts into the low to mid 70s may be over representing llvl
relative humidity enhancement from widespread precip in the models that may not
quite come to fruition as widespread. Todays heat indices are more
borderline for heat advisory criteria...but far more likely to see
from Thursday into Sunday with subsequent forecasts, should the
trend continue. Into the extended, day 7/just into day 8, models
actually beginning to diverge into a solution to break down the
ridge with an upper system pushing a return of precip in for tues
night into Wed.


Aviation...(for the 12z tafs through 12z Thursday morning)
issued at 640 am CDT Wednesday Aug 20 2014

Showers and thunderstorms are moving across the western portion of
the state, but not currently affecting any of the taf sites on
station. However, they could affect spi so will have thunderstorms in the vicinity to start
the taf. Bmi has had some fog this am so will have a tempo group
for that. In addition, cmi has been done with 1/4sm vv002 all
night. Believe this fog is not very thick, given the trends of the
observations from sites that have experienced fog this morning. By
14-15z all sites should be VFR with cumulus developing during the day
and high cirrus overspreading from the storms west of the area.
These clouds should dissipate toward the evening hours and then
just leave scattered ac around 12kft at all sites for the evening.
Then overnight high SC develops over the area and should become
broken. Could be some pcpn with this as the clouds will be
associated with the warm front that lifts through the area today,
but believe only vcsh warranted at this point. Later forecasts can
get a better handle on things later today. Winds will become
southwesterly during most of the day and then southerly tonight.


Ilx watches/warnings/advisories...


Short term...auten
long term...hjs

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