Area Forecast Discussion
Issued by NWS Central Illinois

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696
FXUS63 KILX 062318
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
618 PM CDT FRI MAY 6 2016

.SHORT TERM...(Tonight)
ISSUED AT 255 PM CDT Fri May 6 2016

As high pressure drifts east of the region, a cold front currently
extending from northern Minnesota to South Dakota will drop slowly
southward tonight.  The boundary will reach far northern Illinois by
12z Sat, keeping the KILX CWA in the warm sector tonight.  The
pressure gradient ahead of the approaching front will support
westerly winds of 5 to 10 mph, which will keep overnight lows
several degrees warmer than in recent nights, with readings
remaining in the middle to upper 50s.  Skies will initially be
clear: however, mid-level clouds will be on the increase toward
dawn, particularly north of the I-72 corridor.

.LONG TERM...(Saturday through Friday)
ISSUED AT 255 PM CDT Fri May 6 2016

A surface low near Lake Winnipeg this afternoon will sweep along the
Canadian border and lift into northern Ontario tonight. In response
to that, a cold front extending southwest of the low will progress
south through central Illinois Saturday afternoon. Severe parameters
have been increasing in the short term models, with MUCAPES expected
to climb into the 1500-2000 J/kg range in central IL Saturday
afternoon and evening. Bulk shear values climb into the 35-40kt
range, with unidirectional shear. SPC Day 2 slight risk now includes
a narrow portion of far eastern Illinois along the Wabash river,
with Marginal expanded westward to include all of our forecast area.
We could see a few stronger storms approach severe levels with hail
and some strong downbursts possible. Have expanded the likely PoPs
Saturday after 4 pm in east-central IL, as well as Sat night along
and south of I-72.

A break in the storms should develop Sunday morning as the front
sags south into the Ohio River Valley. The break may be short-lived
however, as the long wave trough in the Rocky Mountains shifts
eastward and draws the front back northward as a warm front. Model
consensus shows the front is expected to lift through our forecast
area on Monday. That will result in likely precip chances as early
as Sunday night ahead of the front, and west of I-55 on Monday
closer to the better moisture return. At this point, severe
potential should be focused west of IL on Monday.

Likely precip chances will continue Monday night and Tuesday as the
front stalls across north-central IL and low pressure moves toward
Illinois along the front. The Canadian and GFS take the low all the
way across IL Tuesday night, while the ECMWF washes out the low
before it reaches IL, and lifts the warm front to near the Wisconsin
border. In general, we should still see decreasing precip chances
later Tuesday night into Wednesday. The GFS even keeps most of our
forecast area dry the rest of the week, except for Thurs morning
south of I-72. The ECMWF delays the passage of a stronger mid-level
wave until Wednesday, with a cold fropa Wed night, and precip
lingering into Thursday. The influence of the much wetter 12z
ECMWF in the blended extended initialization kept chance PoPs in
the forecast each period through Thursday, with slight chances
Thur night and Friday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 618 PM CDT Fri May 6 2016

VFR conditions will prevail until around 18z then a cold front
currently extending from Lake Superior to western Nebraska will
sag southward into the area...bringing scattered thunderstorms
with a possibility of isolated MVFR conditions and gusty winds.
Skies will initially be clear this evening, then increasing mid-
level moisture along/ahead of the approaching boundary suggests
scattered cloud cover around 12000ft developing at KPIA by
08z...spreading southward through the early morning. Winds will
remain W through 18Z...shifting to northerly late in the forecast
period. Wind speeds will be 5-10 kts overnight...increasing to
10-15 kts with gusts to around 20 kts during the daytime. 40 kt
westerly wind at around 2 kft AGL is expected to develop
overnight...and this will lead to low level wind shear exceeding
30 kts after 8-9Z.

&&

.ILX Watches/Warnings/Advisories...
NONE.

&&

$$

SHORT TERM...Barnes
LONG TERM...Shimon
AVIATION...Onton



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