Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 281758

Area Forecast Discussion
National Weather Service Lincoln IL
1258 PM CDT THU APR 28 2016

Issued at 1045 AM CDT Thu Apr 28 2016

Will update the forecast to remove patchy fog this morning and
add isolated thunderstorms to far east central IL near Danville
and Paris. Currently have showers developing with heavier rains
near Danville. Highs to range from around 60F from Galesburg to
Lacon north, to 70-75F in southeast IL. 1009 mb surface low
pressure was over central IA late thismorning with an occluded
front extending se through central IL/IN near I-74. Aloft a 554 dm
500 mb low was over nw IA. Models track upper level low into
southeast MN by sunset while surface low weakens as it tracks into
northern IL by sunset. More moisture and weak lift over northeast
CWA to continue chances of showers along with more cloud cover.
Isolated thunderstorms possible from Danville northeast from late
morning and into mid afternoon.


.SHORT TERM...(Today)
ISSUED AT 336 AM CDT Thu Apr 28 2016

Frontal boundary has edged further north across the forecast area
early this morning with several weak surface waves tracking along
the feature. Main forecast issue, at least in the short term, will
be the fog threat over west central Illinois early this morning with
several sites to our west already down to less than a mile. The
combination of the rainfall that occurred over parts of west central
Illinois overnight and the clearing skies and light wind regime will
continue the threat for at least patchy dense fog through the early
morning hours. Will add a mention of some fog in the west this
morning where skies have cleared. Forecast soundings indicate the
low clouds will return with the fog, at least across the north,
for several hours early this morning with the better rain chances
this afternoon into the evening across the north as the last of
the surface waves shifts off to our east. Another day with a wide
variation in temperatures with the cooler afternoon highs across
the far north where cloud cover will be more extensive. Highs will
struggle to reach 60 across the north with middle 70s forecast for
our southeast counties.

.LONG TERM...(Tonight through Wednesday)
ISSUED AT 336 AM CDT Thu Apr 28 2016

Upper level low that is responsible for all the weather today is
slow to move through the region tonight...but will be moving across
northern Illinois this evening.  Given the general slow trend with
the system for days...not inclined to scrub the precip out entirely
after 7 pm...and have left some slight chances in there across the
northern tier to handle any stray showers.  A break on Friday from
showers and thunderstorms, and max temperatures will be about 3-5
degrees below seasonal norms.

An almost identical situation setting up a slow moving low out to
the west in the wake of the current system. Rain chances return for
Friday night through the weekend as a warm frontal feature lifts
into the region. Warm sector showers and thunderstorms dominate
Saturday and Sat night, until the upper low finally progresses
through the region on Sunday. Sunday night will have some clearing
of the precip with drier air wrapping around the system.
Models have managed a pattern shift in the wake of the weekend low.
The deep trof over the western half of the CONUS shears out and
northwesterly flow is trying to set up in the models...but as of
yet, they are struggling with properly handling the potential trof
moving into the flow Mon night/Tuesday. Forecast still dry...banking
on drier air moving into the Midwest from the NW and robbing the
approaching trof of moisture needed for precip.  Still some
dissimilarities between ECMWF and GFS for the beginning of the week,
with the ECMWF much more further south with the piece of energy
early on.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1259 PM CDT Thu Apr 28 2016

Broken cumulus cloud field across central IL this afternoon with
bases generally 3-6k ft but at times as low as MVFR 1.5-3k ft
especially along I-74 into mid afternoon. Isolated showers
possible this afternoon mainly from I-74 northeast and isolated
coverage can be handled with VCSH if needed. Isolated
thunderstorms will stay ne of Danville. MVFR ceilings to return
tonight and linger into Friday morning with IFR ceilings possible
along i-74 overnight into early Friday morning along with MVFR
vsbys in fog. Winds stay fairly light next 24 hours with weakening
occluded front near I-74. WNW winds near 10 kts this afternoon to
veer NW tonight and then NNE Friday morning and be 4-8 kts.


.ILX Watches/Warnings/Advisories...



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