Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 231635

Area Forecast Discussion
1035 AM CST Tue Dec 23 2014

Weak low pressure center at the sfc moving NE from east central IA
this morning, as a dry slot built into Central Illinois resulting
in long absent sunshine for the area. Cirrus building in from the
south will slowly cloud back over and the day should wrap up
rather cloudy again. Temperatures on track for the afternoon with
southwesterly winds. Quiet weather expected through the afternoon,
with a break between the two systems. Forecast looking good and no
updates are anticipated in the short term.


.SHORT TERM...(Today)

Initial shortwave associated with a closed low at 500 mb early this
morning was tracking across north central Illinois. Backedge of the
rain has shifted into our east and northeast counties...soon to exit
our area for this morning. Mid level dry slot seen on satellite data
tracking east into parts of west central Illinois. Most of the short
term models shift the lower clouds to our northeast this morning
allowing some breaks to develop. HRRR and RUC soundings showing
the low level moisture slowly lifting with time this morning, but
that shouldn`t last long as mid and high level clouds start to stream
northeast into our area ahead of the second shortwave that will bring
another round of rain, then snow to our area starting tonight. Air
mass in the wake of the weak frontal passage today not very cold at
all, in fact, 925-850 mb temperature forecasts suggests highs this
afternoon will range from the upper 40s north to the middle 50s


.LONG TERM...(Tonight through Monday)

Will be issuing a Special Weather Statement to address the 1-3inch
snow accumulations with locally 3 to 4 inches west of I-57 to near
the IL river on Wed and Wed evening. 00Z models have trended
further west (especially NAM model) up Indiana Wed with
deformation/trowal setting up over central and northeast IL on Wed.
Rain spread back northward across se IL this evening and over rest
of central IL overnight with chance of light snow late tonight
west of the IL river. But appears warm enough for most areas
tonight to just get rain. Lows tonight in mid 30s from I-55 nw to
upper 30s to around 40F in eastern/southeast IL.

Surface low pressure to deepen and lift nne from the nw Gulf of
Mexico across central Indiana Wed and into eastern lower MI by Wed
evening. Strong upper level low to pivot across IL Wed afternoon
and expect rain to change to wet snow from west to east during the
day Wed. Snow to diminish from west to east during Wed night. Best
snow accumulations to occur over western IL Wed morning with 1
inch or less while snow accumulations 1-3 inches from IL river
east toward I-57 Wed afternoon/evening with locally 3-4 inches
near I-55 and into ne IL. Morning highs Wed in mid to upper 30s
central IL and lower 40s eastern/se IL and then slipping into low
to mid 30s by end of day Wed as strong west/nw winds kick in
during day Wed into Wed night with gusts 25 to 35 mph.

Christmas day still looks dry with return of some sunshine
especially sw counties as strong low pressure exits into Quebec
and 1025 mb surface high pressure sets up over southeast states.
A southerly flow sets up by Thu afternoon with highs in the upper
30s to lower 40s so any snow that fall Wed/Wed evening will likely
melt on Thu afternoon.

Another area of low pressure ejects ne from CO into WI by Fri
evening and swings a cold front se across central IL Fri night and
near southeast IL Sat. Milder highs in mid to upper 40s on Friday
with IL getting in warm sector. Then precipitation chances
increasing during Friday night into Sat especially over southeast
IL. Southeast IL looks warm enough for mainly rain (turning to mix
during day on Sat) with mix of light rain/snow central IL but
little accumulations. Highs Sat range from lower 30s nw of IL
river to lower 40s along the Wabash River.

ECMWF model is further north with southern low pressure system and
qpf into southeast IL Sat night through Sunday eve and drawing in
colder air and cold enough for light snow. Have chance of light
snow southeast IL Sat night and Sunday with slight chances over
central IL. Seasonably cold highs in the low to mid 30s on Sunday.
Quieter weather returns early next work week with seasonable temps
for late Dec.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)

MVFR and local IFR cigs will become VFR this morning with PIA on
the edge of some wrap around moisture from the departing storm
system. Forecast soundings showing despite the loss of the low
level moisture, quite a bit of mid and high level cloud cover
will affect the TAF sites this morning into the afternoon hours
before more MVFR cigs approach the area for late this evening and
into the overnight hours ahead of the next storm system. As the
next storm system approaches from the south tonight, rain will
overspread the area from south to north after 04z with CMI and
DEC the first to see the rain followed by SPI and BMI aftr 06z
and then PIA during the early morning hours. Once the rain begins
it appears the cigs will quickly drop to MVFR and then eventually
IFR once again, but at this time will hold off bringing cigs and
or vsbys down too much in this forecast period as it appears the
IFR and LIFR cigs will be during the day Wed. Surface winds will
be out of the southwest today at 10 to 15 kts, and the gradually
turn into a light northwest to north direction tonight at 4 to
9 kts.




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