Area Forecast Discussion
Issued by NWS Central Illinois
FXUS63 KILX 110508
Area Forecast Discussion
National Weather Service Lincoln IL
1108 PM CST Tue Dec 10 2013
ISSUED 824 PM CST Tue Dec 10 2013
Only minor tweaks to grids this evening. No changes anticipated
for the worded forecasts.
Clipper system approaching northern Illinois tonight remains on
track to bring several inches of snow just north of ILX forecast
area. With increasing clouds, temperatures should be near
overnight lows northwest of I-72 and Danville. May be a flurry or
two later tonight, but still looks like any measurable snow should
be confined to the area north of Peoria.
ISSUED 1108 PM CST Tue Dec 10 2013
Southern edge of moisture associated with clipper system moving
across Iowa having problems saturating lower levels. Associated
cold front should cross the area Wednesday morning. MVFR
conditions will likely be post-frontal associated with strong
cold advection. Will be removing pcpn from KPIA terminal forecast,
but will retain MVFR ceilings for several hours after frontal
passage per NAM time height plots. Subsidence of dry air should
finally clear residual boundary layer moisture by 21-24Z.
Cold front will also shift 190-220 degree winds to 300-330 degrees
and increase gusts. Highest winds will likely just after clearing
as mixing of higher momentum air allow winds to gust to near 25
kts before winds decouple in very cold and mostly clear air mass
ISSUED 310 PM CST Tue Dec 10 2013
Main challenges this forecast period include the weather
associated with the clipper system coming through the northern
part of the area late tonight and early tomorrow, then the next
system Friday afternoon through Saturday morning. In addition, the
non-diurnal temperature trends in the short term can be a
challenge. Models look similar through the end of the week and the
weekend. So a good blend of the models looks in order. This also
leads to higher than normal confidence in the forecast.
SHORT TERM...Tonight through Friday
A clipper system is moving through the northern plains and will
bring snow to northern IL beginning late tonight and through
tomorrow morning. The best dynamics with this system looks to be
north of the cwa, but believe accumulating snow could affect the
northern 3 counties of the cwa tonight. So will have likely snow
in the north, mainly north of the Peoria area. Snowfall totals
will likely range from one half inch to close to an inch in the
extreme north of our cwa. Higher totals will be see toward I-80.
After a dry and cold period for tomorrow afternoon through
Thursday night, another stronger system will move out of the
southern plains and toward the southeastern US. An inverted trough
associated with this system will move across IL beginning Friday
afternoon. Models have trended slower with the onset of pcpn
Friday so will have chance pops for snow in the southwest part of
the cwa. Precip chances increase Friday night...in the extended.
Another shot of Arctic air will move into the area tomorrow night.
Northwest winds of around 10mph will also be occurring tomorrow
night. So looks like wind chills of around -15 will be possible.
Will not issue a wind chill advisory just yet, but let later shift
take a look and decide. The remainder of the short term period
should warm some as high pressure slides to the southeast,
allowing southwest winds to bring some warmer air into the region,
though it will still be below normal.
LONG TERM...Friday night through Tuesday
The inverted trough will move through the area Friday night into
Saturday morning. Model forecast sounding (temperature profiles)
indicate that pcpn should start as light snow. However, as some of
the lower layers warm about 1-2 degrees above zero, the pcpn could
become a mix of snow and sleet. Then by afternoon, it appears the
pcpn will begin to end, but temps on the sfc will warm to just
above freezing in the southeast and we will loose our ice
crystals. So, precip type for Sat afternoon could be a mix of
rain, snow and sleet. But not much expected as the pcpn should be
ending at this point and moving east. Snowfall/sleet totals
through the event over the area looks to be in the 2-3 inch range.
The remainder of the extended forecast will be dry, though there
is a couple of systems that could bring some pcpn to the area. For
now, will just keep slight chance in the grids and wait and see
what models do with them.
Temps will remain cold through the period. Some areas could see
temps above freezing Sat and then again Tuesday. Sunday night
could be very cold, likely seeing single digits over most of the
area, given light winds and fresh snow cover.