Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Lincoln Illinois
819 PM CST Wed Dec 11 2013
issued 818 PM CST Wed Dec 11 2013
Only minor grid tweaks required this evening.
High pressure ridging northeast of 1040mb high over northern
Missouri will continue to decrease gradient and allow winds to
diminish a bit more over the next few hours. In addition, some
mid/high clouds associated with jet streak over northern plains
will steady temperature fall over the advisory area.
Wind chills have fallen as low as -16 degrees at gbg with -8
degrees at pia and -12 at Bloomington this evening. With
diminishing winds and scattered clouds, wind chills may actually
rise over next few hours. However, once the ridge gets past
central Illinois an increase in the gradient should allow sfc
winds to become southwest and once again increase into the 5-15
knot range and allow wind chills to once again fall to -15 or
below in the advisory area by sunrise.
issued 456 PM CST Wed Dec 11 2013
High pressure centered over northwest Missouri will continue to
drift southeast. With the surface ridge across Illinois through
the night, winds will decouple early on and winds should become
light and variable shortly. In the fast progression in northwest
flow, pressure gradient already begins to pick up by morning as
ridge passes into Ohio Valley.
Strong jet aloft over the prairie provinces will keep periods of
scattered VFR clouds moving across region late tonight through Thursday.
issued 257 PM CST Wed Dec 11 2013
Main concerns today is the wind chill conditions overnight tonight
and then the Friday to Saturday storm.
Short term...tonight through Friday night.
Morning upper air shows the minor clipper shortwave that moved
across northern Illinois this morning. Through the day today, tail end
of the wave has produced some snowshowers over the County Warning Area in left
over moisture behind the front, and the deep cold air aloft in
strong cold advection at 850mb.
Main concern focused on today is the developing upper system that
moves through the southern rockies and comes out by Friday.
Surface inverted trough sets up from OK over MO into northwest Illinois
by midday on Friday, with isentropic lift over MO. Models now
coming together better on the timing of the lift and pcpn
development over MO, spreading slowly into western Illinois by late
afternoon on Friday. Have modified the quantitative precipitation forecast some for the location
of the pcpn moving into western IL, which should be all snow. Best
lift overnight Friday night as the upper wave comes out of rockies
through the Southern Plains, increasing the moist flow and lift
into the mid MS valley region. Inverted trough moves east
overnight, with the main snow over cwa during the 00-12z
timeframe. Have kept a mixture in the southeast area Friday
afternoon and into the evening, dropping the mixture Friday night
due to latest sounding profiles. Modified the HPC quantitative precipitation forecast some, with
the result being a general 2.5 to 4 inch range for region.
Long term...Saturday through Wednesday.
Trough moves off to the east in the morning Saturday and so the
quantitative precipitation forecast will go also, with some light pcpn possible into afternoon
before ending. Dry period for the following few days, remaining
cold with only a couple minor fronts moving through, but being too
dry for any real pcpn.
Wind Chill Advisory until 8 am CST Thursday for ilz027>031-037-