Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 221940

Area Forecast Discussion
National Weather Service Lincoln IL
240 PM CDT Thu Mar 22 2018

.SHORT TERM...(This evening through Friday)
ISSUED AT 240 PM CDT Thu Mar 22 2018

Extremely moist system progged to develop over the Missouri Valley
late tonight and move east into Illinois Friday. Although upper
dynamics is somewhat limited low level isentropic lift (295K-300K)
is very impressive as Gulf moisture lifts over nearly stationary
boundary anchored over Missouri. Friday will see the advection of
precip northeast into the southwest half of the forecast area.
Highs should be only slightly below normal due to the cloudcover,
but as precip begins evaporative cooling should allow temps to


.LONG TERM...(Friday night through Thursday)
ISSUED AT 240 PM CDT Thu Mar 22 2018

Big challange this package is precip type and any potential
accumulations friday Night into Saturday. Models are consistent in
producing storng isentropic lift and mixing ratios as high as 8.0
g/kg advecting northeast into Illinois. Much of the forecast area
should have a prolonged period of rain which will be occasionally
moderate. Thunder may also be a possibility. Rain and easterly
flow should keep temps well below normal.

For those areas north of I-74 there remains an above average
uncertainty in precip type and any accumulations. Several
different ptype techniques produce slightly different scenarios. A
difference of a degree or two at the surface or even 2-4kft aloft
will make a big difference. Throw in the increased mid-March
insolation and warm ground temperatures combined with impressive
snowfall rates and you have a large range in potential solutions.

Having said that the most likely scenario suggest pcpn beginning
as rain Friday evening and then mixing with or changing to snow
well after midnight and continuing into Saturday. The best chance
of significant snowfall will likley be across northeast
Stark...northeast Marshall...and extreme northeast Woodford
Counties where a period of moderate snow will be possible during
the early morning Saturday. Forecast accumulations may reach to
around 6 inches. However, with warm surface temps the snow may
slowly melt from underneath which may limit the amount of snow on
the ground at any one time. Will also need to keep an eye on
northern Vermilion as some techniques they should also see amounts
approaching warning criteria. Given the uncertainty, will retain
headlines as a watch at this time.

The next system will move into the region Monday Night with more
dyanmical support. Precipitation amounts may reach a one to one
and a half inches with this sytem as well as Gulf moisture is
tapped. This system will be much warmer and precip type is not an
issue. GFS forecasted surface-based CAPE of 300-500 J/kg Tuesday
suggests some thunder will likely accompany the cold front
associated with this system.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1259 PM CDT Thu Mar 22 2018

VFR conditions are forecast to continue across the central IL
airports through 18Z/1 pm on Friday. Mid level clouds with bases
of 5-10k ft will spread se across SPI this afternoon, and reach
as far east at BMI and CMI early this evening. Isolated light rain
showers should stay sw of SPI next 24 hours and removed vcsh.
Winds generally stay under 10 kts through Friday morning,
starting NW this afternoon, and veering ENE overnight, and east to
ESE during Friday and increase to 7-12 kts on Friday.


Winter Storm Watch from Friday evening through Saturday
afternoon for ILZ028-030-031-038-046.



LONG TERM...Barker
AVIATION...07 is the U.S. government's official web portal to all federal, state and local government web resources and services.