Area Forecast Discussion
Issued by NWS Central Illinois

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727
FXUS63 KILX 281744
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1244 PM CDT Sun May 28 2017

.UPDATE...
Issued at 918 AM CDT Sun May 28 2017

14z/9am surface analysis shows 1007mb low just south of
KIKK...with cold front extending southwestward between the I-55
and I-57 corridors. Aloft...vigorous short-wave is noted on water
vapor imagery over northern Wisconsin. The trailing vort lobe
associated with this feature is providing enough lift to trigger a
line of showers across southern Wisconsin/northern Illinois this
morning, and latest HRRR suggests isolated to scattered showers
and thunderstorms will develop further south into central Illinois
as the day progresses. Have updated hourly PoPs to better reflect
current and expected trends. It appears the showers will become
most numerous along/northeast of a KBMI to K1H2 line by early to
mid afternoon. After that, the upper wave will gradually pass to
the east and the showers will end from west to east by early
evening. High temperatures today will generally be in the middle
to upper 70s...with a few lower 80s south of I-70.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 250 AM CDT Sun May 28 2017

Large MCS continues to sink into the lower Mississippi Valley with
cirrus blowoff extending northward, although cloud tops are
warming over our area and some thinning is taking place over the
far northern CWA. Meanwhile, water vapor imagery shows a well
defined upper wave from Minnesota into Nebraska, and the latest
surface map shows our frontal boundary roughly along I-70 with a
surface low near Effingham. As the low lifts northeast and the
upper wave approaches, CAPE`s over the eastern CWA are progged to
reach 1000-1500 J/kg by midday, enough to trigger some scattered
showers and storms. Bulk of the activity will be east of I-55, but
main chances should generally be focused on only a couple hour
period, as the front is progged to be in western Indiana by mid
afternoon. Behind the front, skies will quickly clear from west
to east.

.LONG TERM...(Monday through Saturday)
ISSUED AT 250 AM CDT Sun May 28 2017

Upper low currently near Lake Winnipeg will slowly wobble
southeast and east into mid week, keeping the Midwest in a cooler
weather pattern. While Monday will still see some 80 degree highs,
mid 70s will be more common into mid week. By late in the week,
model discrepancies lead to some uncertainties, as the GFS and
Canadian models bring down another upper low into the same area,
while the ECMWF is warmer with the low staying north of the Great
Lakes.

With the broad low/upper trough in place for a couple days,
periodic shortwaves will rotate around it and bring isolated
showers and storms at times, mainly Monday and Tuesday afternoons.
Better chances are expected later in the week as Gulf moisture
starts to arrive. However, trends during the weekend are more
uncertain, with the ECMWF featuring a rather prominent shortwave
passage on Saturday with much better storm chances, and the GFS
hanging up a surface boundary to our south with more of a cool
rain. Tried to blend the two together and downplay some of the
thunder chances in the northern CWA for now.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1243 PM CDT Sun May 28 2017

1730z/1230pm radar imagery shows widely scattered showers
developing in the vicinity of a slow-moving cold front from KCMI
southwestward to KSPI. HRRR suggests showers/thunder will continue
to develop in this corridor over the next couple of hours before
pulling into Indiana later this afternoon. Based on latest trends,
have included VCTS at KBMI/KDEC/KCMI through the 20-22z time
frame. Ceilings have risen to VFR and are expected to gradually
scatter as the day progresses. Mostly clear skies will prevail
tonight through Monday morning before an approaching trough
once again triggers scattered showers/thunder by Monday
afternoon. Winds will remain W/NW through the entire 18z TAF
period.

&&

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

$$

UPDATE...Barnes
SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Barnes



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