Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 251735

Area Forecast Discussion
National Weather Service Lincoln IL
1235 PM CDT Thu May 25 2017

Issued at 1053 AM CDT Thu May 25 2017

Upper low over Ohio continues to shift slowly eastward this
morning: however, its associated cloud cover lingers across much
of the KILX CWA. 1530z/1030am visible satellite imagery shows the
back edge of the cloud shield along a
Effingham line. Recent satellite trends have shown the clouds
beginning to dissipate...particularly along the back edge. Expect
this to continue through the afternoon, with areas along/northeast
of a Bloomington to Paris line likely staying mostly cloudy for
the balance of the day. High temperatures will range from the
upper 60s where clouds persist the lower to middle
70s across the Illinois River Valley where skies are already
mostly sunny.


.SHORT TERM...(Today and tonight)
ISSUED AT 306 AM CDT Thu May 25 2017

The deep upper level trough that has been driving the weather for
the Midwest over the last several days is still over the Eastern
Ohio River Valley...with the axis stretching from Lake Superior
down through the Central Gulf Coast. Early this morning, patchy
stratus clouds dominated the eastern half of the state. With the
low continuing to drift eastward... expect the clouds to slowly
retreat to the east, but in areas that clear out...expect some
cumulus development to replace it. Light northwesterly winds and
high temps in the 70s. Tonight will be mild as well, with
increasing clouds as a weak wave approaches the region. Models
still not offering much in the way of consistence in handling this
wave. Pop chances very light mainly in the west tonight.

.LONG TERM...(Friday through Wednesday)
ISSUED AT 306 AM CDT Thu May 25 2017

Pop chances on Friday a little higher as the wave moves into
Central Illinois. Last few runs have been much weaker with the
wave and the resulting QPF. General lift and uncertainty with
regards to the location of the front is a cause of concern for the
forecast. Initial front on Friday can provide a focus for the weak
wave aloft...but the same front lifting northward across the state
on Saturday has the potential for some severe weather. Significant
MUCAPE across the region invof and behind the lifting warm front
throughout the day. Once again, the main concern is the location
of that boundary. By late in the afternoon, the NAM has it much
further to the south and a more southerly track of the surface
low. Same time frame in the GFS is far more dire for Central IL
and moving the front through ILX in the afternoon. SPC also
recognizes the uncertainty and still puts a slight risk in the Day
3 outlook. Not surprisingly, the temperatures/southerly breezes in
the forecast ahead of that system push max temps from the mid 70s
to the lower 80s, contributing to the overall instability of the
airmass. The storm system moves through the Midwest through the
remainder of the weekend. Parts of Sunday evening will be dry...
depending on the progress of the system... but pops return into
the forecast Monday, though weak, under cyclonic flow. GFS is far
more aggressive with precip development and at this point the
models diverge even farther with handling the exit of the precip
as the GFS lingers with the trough and a weak sfc ridge in the
Plains. Temperatures remain just below normal through the latter
half of the forecast.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1235 PM CDT Thu May 25 2017

MVFR ceilings persist along/northeast of a KPIA to KDEC line
early this afternoon, while skies have partially cleared further
southwest at KSPI. Based on satellite trends and HRRR forecast, it
appears MVFR ceilings will gradually scatter at the northeast
terminals between 21z and 23z. After that, mostly clear skies will
prevail tonight before increasing high clouds are noted by Friday
morning. Winds will initially be from the NW at 10-15kt this
afternoon, then will become light/variable overnight as high
pressure moves overhead. Light SE winds are expected on the back
side of the high by Friday morning.




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