Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 230935

Area Forecast Discussion
335 AM CST Tue Dec 23 2014

.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 06Z TAFS through 06Z Tuesday night)

Clouds continue over the area with rain lifting north. Pcpn will
end, but with lower clouds, light pcpn could hang around for
awhile, so will keep VCSH at all sites overnight. Cig heights will
also lift some as well and become lower level MVFR overnight.
Satellite trends do show clearing across MO and based on HRRR
forecast the clearing gets into the area. But believe mid level
clouds will move into the area behind the clearing area. By
tomorrow afternoon, cigs will drop more and then finally drop back
to MVFR levels ahead of the next system. Winds will be southerly
overnight and then become light and variable tomorrow afternoon
and evening.





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