Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 130532

Area Forecast Discussion
National Weather Service Lincoln IL
1232 AM CDT Sun Aug 13 2017

Issued at 835 PM CDT Sat Aug 12 2017

Very pleasant weather conditions to continue tonight and Sunday
as high pressure, currently stretching from Lake Superior south
to northern Illinois, will drift slowly off to our east through
Sunday. The combination of a mostly clear sky, light winds and
residual low level moisture may lead to some patchy ground fog
towards dawn Sunday. Convection currently over Nebraska will
continue to move east overnight but as it approaches the surface
ridge in our area will dissipate with just some residual clouds
tracking across the region Sunday with afternoon temperatures once
again around the 80 degree mark. Other than including some patchy
fog for a few hours towards dawn on Sunday, no other changes were
made to the grids for the overnight hours. We should have the
updated zones out by 9 pm.


.SHORT TERM...(This evening through Sunday)
ISSUED AT 259 PM CDT Sat Aug 12 2017

High pressure is keeping mild and quiet weather in place for the
weekend in the Midwest. Todays highs are mainly in the upper
70s/near 80 for most of Central IL. Fair weather cumulus clouds
across the sky and light northerly winds on the east side of the
surface ridge. Overnight, winds light and variable as the ridge
remains anchored in the region. Clear skies and cool again
tonight. Radiational cooling overnight will be relatively
efficient and areas to the north could see some patchy fog with
the more significant lull in the surface winds. Not enough
confidence in the guidance to go with a mention, but may need to
adjust after the sun sets and a better idea of where the xover
temps land. Tomorrow, the quiet weather continues with some diurnal
cu and light easterly winds. Temps very similar to today.

.LONG TERM...(Sunday night through Saturday)
ISSUED AT 259 PM CDT Sat Aug 12 2017

Quiet weather continues at least through midday Monday. Previous
models brought a quick wave just to the south of the FA on Sun
night but have since evened out. However, the GFS maintains the
threat of the second wave Monday night/Tuesday for the potential
of at least some weak showers/TS, although at this point the
blends are barely catching it, so it remains the lowest of slights
in the forecast. Into midweek remains mild and dry for Central IL
as a slow warming trend kicks in Wednesday/Thursday as the winds
slowly come around to more southerly to end the forecast. Btwn the
GFS and the ECMWF, the surface parameters look suspiciously
similar compared to their far more divergent 500mb charts. Almost
zonal flow aloft in the ECMWF and a much more amplified pattern in
the GFS point to something being worked out a bit. And to that
end, the GFS has made some progress phasing in a southern
shortwave into the more significant trough over the western half
of the CONUS. Even so, the models still producing copious
potential storms from a series of shortwaves through at least the
end of the week. Confidence in the precipitation forecast beyond
Wednesday is far from optimal.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1230 AM CDT Sun Aug 13 2017

Only real concern for this TAF set is the potential for some fog
around dawn. Forecast soundings suggest if any occurs, it will be
very shallow. This was observed Saturday morning in similar
conditions. Have included a TEMPO group at all sites for the
10-12Z period for some patchy, shallow fog. Otherwise, diurnal
cumulus field is expected to start forming late morning once
again, mainly from KPIA-KCMI, starting around 3500 feet and edging
upward. The clouds should mostly fade before early evening.




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