Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 180210
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
910 PM CDT Fri Oct 17 2014

.UPDATE...
ISSUED AT 900 PM CDT FRI OCT 17 2014

Deep low pressure extending from the Great Lakes southwest to
southeast Missouri will keep clouds across much of Illinois the
rest of tonight and tomorrow. Based on satellite images of
upstream cloud cover, brief breaks in the clouds could pass by
from time to time for areas southwest of a line from Rushville to
Lawrenceville. Cloud cover will be enhanced by a couple of
shortwaves over the next 24 hours. One shortwave centered over
eastern Wisconsin will rotate southeast across NE IL from late
evening to early morning. The next wave just approaching far NW
Minnesota at 02z/9pm will move across IL on Saturday, with the
trough axis bisecting our forecast area from NE to SW around
18z/1pm. Once that wave passes, clouds will have a better chance
of clearing, especially for areas southwest of Rushville to
Robinson. Eventually, clearing should develop across all of
central IL Saturday evening as dry air overcomes the cloud layer.

Temps tonight should bottom out in the mid to upper 40s, with some
low 50s possible toward Lawrenceville. Highs tomorrow will be held
in check by cloud cover and cool NW breezes, with readings mainly
in the mid to upper 50s.

The current forecast info is on track and no formal updates will
be needed this evening.

&&

.SHORT TERM...(Tonight)
ISSUED AT 302 PM CDT FRI OCT 17 2014

18z/1pm surface map shows cold front pushing into Indiana, while
secondary front/trough axis drops southward through Wisconsin.
Brisk W/NW winds behind the front are gradually bringing cooler air
into central Illinois: however, it appears the heart of the cooler
airmass lags well behind the front and will arrive tonight into
Saturday.  Latest water vapor imagery shows upper low digging
southward into the Great Lakes, producing broad cyclonic flow across
the Upper Midwest.  As a result, widespread cloud cover is noted on
visible satellite imagery from the Dakotas to the Great Lakes
southward into central Illinois.  With continued deep N/NW flow,
think cloud cover will hold firm across the region tonight.  Thanks
to a tight pressure gradient, winds will remain brisk as well.  Due
to the clouds and wind, have gone above numeric guidance by a few
degrees, with overnight lows remaining mainly in the middle 40s.

&&

.LONG TERM...(Saturday through Friday)
ISSUED AT 302 PM CDT FRI OCT 17 2014

With another wave coming down in the continued cyclonic flow,
tomorrow morning, believe cloud cover will continue through tomorrow
early afternoon in the west, and late afternoon to early evening in
the east. Once the anti-cyclonic flow moves into the area tomorrow
evening, skies should become mostly clear and winds will become
light. With temps falling into the middle 30s tomorrow night, patchy
frost could be an issue late tomorrow night through early Sunday
morning. So have added this into the forecast. After this, surface
high pressure will build into the region for the rest of the
weekend.

Then another weather system will drop down from the northwest early
next week. All models have a low pressure area with a cold front
advecting through the area, but differ on the speed and intensity of
the system. The differences in the intensity are impacting the
amount of qpf that the models are forecasting. GFS is slower and
slightly stronger with the system, and therefore has more qpf than
the others. Despite it being the odd model out, have opted to
include some chance pops along the front for late Sunday night
through Monday. This will also bring clouds back into the region as
well.

After this system, stronger ridging will build into the region the
week. This ridging will begin to break down toward the end of the
week, but the extended models are not bringing any pcpn into the
region through Friday.

Temps will be below normal through the weekend and then around
normal for Monday. But then afternoon highs should fall to below
normal again for the rest of the week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
ISSUED AT 642 PM CDT FRI OCT 17 2014

VFR clouds continue to blanket central Illinois as northwest flow
persists over the next 24 hours. All TAF sites are OVC in the
3.5-5K FT range and those levels should continue through tomorrow
afternoon. Satellite images showed some breaks in the cloud cover
upstream in Iowa, MN and W Wisconsin, but overall trends appear to
be some filling in of those holes after mixing decreases this
evening. The upper low over the Great Lakes will slowly drift east
tonight and tomorrow, but secondary shortwaves rotating around the
west side of the low will help to reinforce our cloud cover
through much of the day tomorrow. The GFS forecast soundings show
an earlier clearing scenario tomorrow, with clouds breaking up as
early as 17z, while the NAM keeps clouds firmly in place all the
way through 00z/Oct19. Will continue with keeping VFR clouds well
into the afternoon. W/NW wind gusts have settled down from this
afternoon, and sustained 8-12kt will continue overnight and
tomorrow.


&&

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

$$

UPDATE...Shimon
SHORT TERM...Barnes
LONG TERM...Auten
AVIATION...Shimon





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