Area Forecast Discussion
Issued by NWS Central Illinois
FXUS63 KILX 060556
Area Forecast Discussion
National Weather Service Lincoln IL
1156 PM CST Thu Dec 5 2013
ISSUED 915 PM CST Thu Dec 5 2013
Plan to continue the winter storm warning through Friday south of
I-70 (Clay, Richland, Lawrence, Jasper and Crawford counties) and
continue the winter weather advisory for through Friday for
Shelby, Effingham, Cumberland, Clark, Coles and Edgar counties.
Updated forecast for quicker changeover to snow over southeast IL
as colder air arrived quicker in southeast IL with most of the
mixed precipitation changing to all snow early this evening.
Therefore increased snowfall accumulations to 2 to 4 inches for
the rest of the night, with another 2 to 4 inch expected Friday
giving a storm total of 5 to 8 inches south of I-70.
Radar mosaic shows steady area of light to moderate snow along and
southeast of a St Louis to just se of a Shelbyville to Charleston
to Paris line. Some patches of light snow and flurries nw of this
line to near I-55 like at Springfield. The freezing rain and sleet
over far southeast IL has changed to all snow during early this
evening. Had reports of as much as a tenth to quarter inch of ice
and sleet south of I-70 with locally as much as quarter to half
inch of ice and sleet. Snowfall ranges from a 1 to 3 inches so far
with an observer 4 miles southeast of Clay City up to 3.2 inches.
Frontal boundary extends from central WV into se TN into central MS/LA.
1046 mb arctic high pressure over alberta and ridging se into the
central plains was ushering in cold air into central IL. Temps
were 20-25F with Galesburg down to 19F. NW winds of 10 to 15 mph
was giving wind chills in the upper single digits and teens. Temps
to stay nearly steady in the low to mid 20s over southeast IL and
cool a few more degrees over the IL River valley where mid level
cloud bases higher above 12K feet.
Short waves ejecting ne from the southern plains into the Ohio
Valley Friday to keep snow going over southeast IL overnight and
Friday and diminish by Friday evening. Seeing 3-4 inch snowfall
accumulations upstream in sw IL into parts of MO and feel need to
increase snowfall amounts by at least an 1 inch tonight with 2 to
4 inches of new snow over southeast IL from I-70 south and 1-3 inches
in the advisory area. Expect another 2 to 4 inches of snow Friday
over southeast IL and 1 to 3 inches over the advisory area south
of I-72 to along I-70.
ISSUED 1155 PM CST Thu Dec 5 2013
Brunt of accumulating snows along with winter storm to stay
southeast of central IL airports through Friday closer to a frontal
boundary over central WV into se TN and central MS/LA. VFR
conditions expected through Friday nw of I-55 with MVFR vsbys
and ceilings developing with light snow along I-72 late tonight into
Friday with ceilings lowering to 2-3k ft with vsbys as low as 2-4
miles Friday as short wave riding ne along the frontal boundary
tugs the light snow further nw into parts of central IL,
especially along I-72 on Friday. IFR conditions should stay se of
SPI/DEC/CMI overnight and Friday. Clouds to scattered our or clear
from nw to se between 01Z-04Z happening first at PIA and last at
CMI. NNW winds around 10 kts tonight to be 10-13 kts on Friday and
7-10 kts Friday evening.
ISSUED 331 PM CST Thu Dec 5 2013
Main concerns this package revolve around the winter storm for
tonight through tomorrow and then another chance of snow for
Sunday through Sun night. GFS/ECMWF/GEM look to be in fairly good
agreement all around, while the NAM-WRF looks ok but spreads too
much pcpn further north tonight and tomorrow. Temp profiles in the
models look ok too, so current pcpn type forecast for tonight
looks ok. Most models with weekend system look ok, again except
for the NAM having too little pcpn at the onset. So, overall,
prefer the GFS/ECMWF/GEM solution.
Long term models look in fairly good agreement and
using the blended model forecast looks good for now sine main
focus is in the shortly term.
SHORT TERM...Tonight through Sunday night
Precip occurring across mainly southeast IL at the moment and pcpn
type is a mix of snow and sleet, with some freezing rain. This
will likely continue for next 5-6 hours. Then as temps in the
lower layers cool after sunset, pcpn type will change to all snow,
likely by 8-9pm. Snowfall amounts by morning should reach to
around 3 inches in the extreme southeast, where the warning will
remain. Further north, amounts will be less, to where there will
be just a dusting along I-72. Tomorrow, snow will continue across
the southeast with another 3-4 inches possible. Winter storm
warning will then remain until 6pm tomorrow night. North of I-70,
2-4 inches is expected through tomorrow, so the advisory will
continue as well.
There will be a break in the pcpn as a very cold high pressure
area moves into the midwest. As the high pressure shifts to the
east another weather system will develop in the plains and spread
more pcpn across the area Sunday through Sunday night. Temps will
be quite cold through the period so pcpn type should be all snow.
However, there is a concern as to the pcpn type during the
afternoon. Model soundings in the southeast suggest that pcpn
could be falling as liquid given the warm air advection sounding
and that temps will be just below freezing in the cloud layer. So
have included a mix of freezing rain with the snow in the
southeast during the afternoon. Remainder of the area should be
Temps will get very cold as the first real Arctic blast comes into
the area. Temps are expected to remain below freezing through the
period with coldest lows being early Sat morning; where temps will
be in the single digits. Wind chills through the period will also
be below zero as winds will be out of the north at 10-15mph.
LONG TERM...Monday through Thursday
Dry weather is expected through the extended period as a large
high pressure area drops into the area and sits over most of the
US through next Thursday. The upper level trough that finally
moves across the area this weekend will become more zonal for next
week. Very cold temperatures are expected through the extended
period with some possible warming toward the end of next week. So,
expect lows in the single digits Mon night through Wed night and
highs remaining below freezing.
WINTER STORM WARNING until 6 PM CST Friday FOR ILZ067-068-
WINTER WEATHER ADVISORY until 6 PM CST Friday FOR ILZ056-057-