Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 261753
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1253 PM CDT Fri May 26 2017

.UPDATE...
Issued at 1054 AM CDT Fri May 26 2017

MCV noted on latest satellite/radar imagery over eastern Iowa will
continue to track eastward across north-central Illinois this
afternoon. A cluster of convection is ongoing with this system
and will brush the far northern KILX CWA around Galesburg and
Lacon over the next 2-4 hours. Based on radar timing tools, it
appears the bulk of the storms will remain just north of the CWA,
but additional scattered development south of the main system
appears likely. Both the NAM and HRRR show convection associated
with the MCV becoming widespread as it tracks along/just south of
the I-80 corridor this afternoon...with widely scattered
thunderstorms developing as far south as I-72. With 12z KILX
upper air sounding already showing a strong mid-level cap and
upstream 700mb temps rising to 12C at KSGF, think capping will
greatly limit the southern extent of the convection today. As a
result, will maintain just slight chance PoPs across the southern
two-thirds of the area...with high chance PoPs confined to
locations along/north of I-74.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 322 AM CDT Fri May 26 2017

Early this morning, a weak ridge stretched from the western Gulf
Coast up through the Upper Midwest. However, the weak ridge is
losing ground to clouds filtering in ahead of the next system
moving into the region. For today, generally the cooler temps
associated with clouds between the clouds streaming in from the
west and the cu that will develop in any clear spots. A couple of
weak waves on sat imagery moving through the forecast area this
morning along with a very weak boundary...bringing some showers
to the region, with increasing chances later this
afternoon/evening. Models still differ with how far north the
stronger wave will move later this afternoon. Models have trended
north...but wave on sat imagery is a little further south in the
water vapor. Either way...chance for showers and later
thunderstorms today will linger into the evening and overnight
hours. Thunderstorms are contingent on breaking a relatively weak
cap with weak warm air advection into the region...as well as whether
or not the region will get an assist from outflow from convection
upstream this morning. Overnight lows are limited to the upper
50s to mid 60s.

.LONG TERM...(Saturday through Thursday)
ISSUED AT 322 AM CDT Fri May 26 2017

Next wave moves into the region with a sfc low from the SW as the
upper trough moves through the Midwest. Last couple synoptic runs
of the models tracking significantly further south with the low
itself...keeping much of the warm frontal feature out of Central
IL. Significant MUCAPE across the region invof and behind the
lifting warm front throughout the day...but once again, further
south...leaving the uncertainty of the track a concern for Central
IL. Either way, SPC has kept Central IL in a slight risk,
partially due to some uncertainty...but also as the storms may be
focused further to the south, but more than enough instability
will be in place to warrant the threat. Easterly flow for much of
Saturday is actually keeping the temperatures mainly in the
70s and lower 80s. The storm system moves through the Midwest
through the remainder of the weekend slowing as the front moves
east of ILX...lingering the pops in the southeastern portions of the
state. Sunday evening will dry out...but pops return into the
forecast Monday, though weak and in the northern portions of the
state under cyclonic flow. Pops through the end of the week are
relatively low and sporadic until Thursday as another frontal
boundary stretches across the Midwest, providing a focus for
showers and thunderstorms. Mild and seasonal temperatures are
expected in the extended.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1253 PM CDT Fri May 26 2017

A cluster of thunderstorms has developed across west-central
Illinois early this afternoon and will continue tracking eastward
over the next several hours. Based on radar trends, have included
TEMPO thunder at KPIA between 18z and 20z. Further east, have
only gone with VCTS at KBMI and KCMI until convective certainty
and timing become better established. Once this wave passes, it
will push a weak cold front southward into the area this evening.
Isolated convection may develop along the boundary, so have
included VCTS at both KSPI and KDEC between 21z and 01z. After
that, winds will become light/variable and fog development will
become an issue. HRRR suggests fog will first develop along the
I-74 corridor where rain will be most prevalent this afternoon by
around 06z...then will develop/spread southward toward dawn. Have
therefore reduced visbys around midnight, with widespread IFR
ceilings and visbys down to around 2 miles between 09z and 13z.

&&

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

$$

UPDATE...Barnes
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...Barnes



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