Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 200236

Area Forecast Discussion
National Weather Service Lincoln IL
836 PM CST Sun Nov 19 2017

Issued at 836 PM CST Sun Nov 19 2017

High pressure ridge axis extends from the southern Mississippi
region into east central IL this evening as it moves eastward.
This is already allowing enough gradient for 5-10 mph of SW wind
over western Illinois which will limit temperature falls
overnight. Over eastern Illinois, a few more degrees of
temperature drop can be expected before winds increase. Overall,
lows look about right with mainly upper 20s, perhaps a few mid 20s
over east central or southeast IL. Winds and gusts have been
increased a bit for tonight and tomorrow to account for the
pressure gradient between the high moving into the southeast and a
low moving into the upper Midwest/southern Canada region. Boundary
layer momentum of 25+ kts Monday afternoon should result in gusts
25-30 mph.


.SHORT TERM...(This evening through Monday)
ISSUED AT 246 PM CST Sun Nov 19 2017

West northwest winds that dominated the day are coming around to
more southwesterly as the evening wears on...once the ridge axis
slips to the east. High pressure will keep the Midwest dry through
Monday...even as the temperatures warm slightly with the more
southwesterly flow ushering warmer temps into Central IL. However,
tonights winds will not be quite strong enough to counter the
radiational cooling under mostly clear skies. Temps tonight will
once again drop into the upper 20s, maybe a degree or two above
last night. By tomorrow, winds back to more south/southwesterly
and the warm air advection kicks in. Temps warm into the 50s with
plenty of sunshine to start the week.

.LONG TERM...(Monday night through Sunday)
ISSUED AT 246 PM CST Sun Nov 19 2017

Going into the longer term forecast, very little to talk about for
Central IL. Mondays warm up involving a shift to an almost zonal
flow aloft before the next wave dives into the Upper
Midwest...setting up a more amplified flow aloft and a temperature
rollercoaster btwn dry cold fronts and short warming trends. 12Z
runs of GFS/NAM/ECMWF all digging that wave a little further south
of the Great Lakes than prev runs. Still spawning a piece of that
energy down into the southeastern CONUS, NAM stronger with a
closed low...less so in this run for ECMWF and GFS. Either way,
energy passing through the region on each run is increasing, as is
surface convergence along the front. This run, precip is reaching
back further into IN, at the IL border with precip for Tues
afternoon/evening. Soundings still a bit dry... and portion of the
forecast to watch will be how much moisture can get into the
region from the southerly/southwesterly flow over the next couple
days ahead of the currently dry cold front for Tuesday. Problem
with that... the high pressure over the south cutting off any
moisture feed from the Gulf, and the general dry airmass over the
desert SW. So for now... dry forecast continues. Cooler air moves
in behind a dry cold front to cool temps through Wednesday. Ridge
axis slips east and southerly winds start to set up again, warming
the Midwest briefly through Friday early and repeating the pattern
with another dry (for now) cold front Friday overnight/Sat


.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 518 PM CST Sun Nov 19 2017

VFR conditions, with increasingly breezy SSW Winds over the next
24 hours for the central IL terminals. As high pressure slips
eastward into the southeast U.S. and a low moves toward southern
Canada/upper Midwest region, pressure gradients will increase
tonight into tomorrow promoting a gradual increase in SSW winds
overnight, becoming 15-20 kts with gusts to 25 kts by Monday
afternoon. Cloud cover will be of minimal impact as it will be
high cirrus.




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