Area Forecast Discussion

FXUS63 KILX 180957
Area Forecast Discussion
National Weather Service Lincoln IL
357 AM CST Sun Feb 18 2018
.SHORT TERM...(Today and tonight)
ISSUED AT 355 AM CST Sun Feb 18 2018
Updated the forecast a few hours ago to increase coverage of 
freezing fog (locally dense) through mid morning especially north 
of Peoria and also south of I-72. Also cooled low temperatures 
over snow covered northern CWA early this morning with far 
northern CWA near 10F again. The 3 am temps ranged from 12F at 
Galesburg to 29F at Lawrenceville and the Mount Carmel airport. 
1028 mb high pressure over the lower Ohio river valley in 
southeast IL, southern IN and western KY was ridging northward 
into central IL and providing fair skies and light to calm winds. 
Patchy freezing fog noted north of Peoria and south of I-72 with 
pockets of dense freezing fog observed at times at Galesburg, 
Olney and Taylorville. 
Latest HRRR model has been trending more widespread with freezing
fog and locally dense into a larger part of central IL, and less 
coverage over east central IL. Will continue to monitor for 
possible dense fog advisory. Models diminish the fog during 
mid/late morning as south winds pick up to breezy levels as high 
pressure over lower Ohio river valley quickly moves over WV at 
1030 mb high by 18Z/noon today and 1032 mb high off the mid 
Atlantic coast by sunset. Ample sunshine through increasing thin 
cirrus clouds and breezy south winds with gusts 20-30 mph by 
afternoon. Milder highs in the upper 40s and lower 50s today, 
coolest over northern/ne CWA. Clouds increase during this evening
with isolated rain showers western CWA late evening, then
widespread showers and isolated thunderstorms moving in during
overnight as 1000 mb low pressure emerges over central KS by dawn
Mon with a frontal boundary just nw of IL. South breezes to keep 
temps from falling too much tonight, with lows in the upper 30s 
to mid 40s, coolest from I-74 ne. 
.LONG TERM...(Monday through Saturday)
ISSUED AT 355 AM CST Sun Feb 18 2018
Will update the ESF product to continue to highlight the heavy
rain and increasing flooding threat Mon thru Wed morning. A flash
flood or flood watch may eventually be needed for a good chunk of
our area. Widespread 1.5-3 inches of rain expected over CWA 
during this time frame with locally 3-4 inches east of the IL 
river with heaviest rain expected Tue afternoon into Tue night. 
Potential exists for another round of moderate to heavy rainfall 
Friday thru Saturday, especially se of i-55. 
Low pressure to eject ne from central KS into northern IL by
sunset Monday, and bring more rain showers and isolated
thunderstorms, though becoming more scattered in coverage Mon
afternoon. Rainfall amounts from overnight Sunday night through
sunset Monday average a half to three quarter inches north of i-70
and lighter amounts from I-70 south. Unseasonably warm highs 
Monday in the 60s with areas from Springfield and Lawrenceville sw
near 70F with stronger south winds gusting 25-35 mph. 
A deepening upper level trof over the Rockies early this week
while a 500 mb high of 595 dm strengthens off the southeast
Atlantic coast. This to eject another surface low pressure into 
central/southern KS by sunrise Tue and eject ne into nw/northern 
IL by early Tue evening. A subtropical jet and plume of moisture
coming from baja into the ohio river valley has precipitable water
values going up to 1.3-1.6 inches which is near the climatological
max for late winter. Showers with some thunderstorms and moderate 
to heavy rains sets up over area Tue with heaviest rains over IL 
river valley Tue and shifting into southeast IL during Tue night 
as cold front pushes se across CWA and toward the ohio river by 
dawn Wed. Highs Tue range from upper 50s/lower 60s nw of the IL 
river to mid/upper 60s over heart of CWA and lower 70s over 
southeast IL. 
As much colder air arrives behind the strong cold front during Tue
night, rain will change to freezing rain and sleet nw of IL river
late Tue evening and east to along I-55 during overnight Tue night
while IL river valley has mixed pcpn eventually change to snow
before ending. Could be some ice accumulations up to a tenth inch
from I-55 west overnight Tue night and will need to watch this
possible winter wx advisory. Continued chances of rain showers
from I-72 south on Wed with likely pops se of I-70 Wed morning as
cold front pushes into the TN river valley. Highs Wed range from
low to mid 30s over the IL river valley, to the low to mid 40s in
southeast IL. 
Models differ with how far north qpf gets Wed night with ECMWF
further north with qpf/mixed pcpn into central IL while GFS is
drier and GEM is in between. Stayed close to consensus with 
chance pops over CWA, highest in southeast IL. A period of dry wx 
expected Thu and Thu night as a strong high pressure over 1040 mb 
pushes east over the GReat lakes region. Models then show another 
wx system ejecting ne across the frontal boundary to our southeast
late this week, spreading qpf ne over area, though some timing 
issues (ECMWF is faster than GFS model). Went with consensus for 
pops Friday through Sat and threat is there again for moderate to 
heavy rains se of I-55.
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1150 PM CST Sat Feb 17 2018
VFR cigs will continue overnight and through most of tomorrow. 
There is still the possibility of some light fog at the TAF sites,
though lower vis could be north of PIA overnight. Temp/dwpt
spreads look ok for light fog, but only SPI has gone there with
3sm br. So will add TEMPO group for tomorrow morning for all sites
of 3sm, but back to p6sm by 14z. Some high cirrus is possible 
tomorrow afternoon and into the evening. Winds will be light and
variable overnight as high pressure ridge moves east, then
southerly winds return for tomorrow. Wind speeds will increase
tomorrow with gusts around 22-24 kts possible tomorrow afternoon.
Should loose the gusts tomorrow evening, but thinking LLWS could
be possible at about 45 kts.