159 
FXUS63 KILX 190453
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1153 PM CDT Tue Mar 18 2014

.DISCUSSION...
ISSUED 930 PM CDT Tue Mar 18 2014

Low pressure at the surface will move from west central Missouri
at 02z to south central Wisconsin by 12z. Rain showers will
develop ahead of the low as the warm sector passes across
Illinois. A few thunderstorms will be possible closer to the
triple point as the dry mid-level air punches into Illinois.
showers are already approaching far western IL as of 0215z. We
will keep chance PoPs will be this evening with likely PoPs across
the north from 03z to 09z during the best omega. Any thunder
chances will end with the cold fropa between 09z and 12z, with
lingering light rain showers changing to snow showers in the cold
advection. The precipitation after 12z will be mainly trace
amounts, behind the departing low pressure. Brisk northwest winds
will gust to 25-30 mph on Wed, adding a wintry chill to the air.

Updates this evening were to cloud, PoPs, and weather to match the
current trends. Also some minor adjustments to the temps and
dewpoints. Updated forecast info will be available shortly.

Shimon

&&

.AVIATION...
ISSUED 1153 PM CDT Tue Mar 18 2014

Low pressure will track across northern IL overnight, bringing a
quick push of moisture and lift across C IL. Instability
parameters show favorable conditions for a few thunderstorms as
the warm sector passes over the terminals. Thunderstorms are
already in progress in east-central Missouri, moving northeast
toward SPI. The best window of opportunity for thunder should be
in the hours between 06z and 11z from SW to NE. The rain chances
should diminish after 12z from the west as the cold front passes
across the terminals. Lingering spotty showers may continue after
sunrise as rain mixes with or changes to snow. No snow
accumulation is expected. We ended VCSH at 15z as additional dry
air arrives above the cloud layer on very strong NW winds.

Southeast winds at 10 to 20 kt late this evening will generally
continue in that range the rest of the night as the low pressure
reaches the IL/WI border by 12z. Winds will sustain in the 14-17kt
range behind the low and cold front as winds shift to south
between 12-15z and then become northwest Wed morning. NW winds will
increase to 20g30kt by Wed afternoon in the strong cold advection.

Cloud heights will most likely dip to MVFR as the rainfall
develops, then remain MVFR through much of the day Wed in the cold
low level air. 

Shimon
&&

.PREV DISCUSSION...
ISSUED 255 PM CDT Tue Mar 18 2014

The main focus through the period is with the deep low pressure 
system which will move across the area tonight, with the potential 
for showers and a few thunderstorms which will exit the area early 
Wednesday. Farther out, another low will track north of the forecast 
area Thursday night into Friday with a warm up ahead of it, then a 
chance of showers and a trend toward colder temperatures especially 
late in the weekend into early next week.

Surface low pressure was over eastern Kansas this afternoon. This 
low is progged to lift northeast across far northern Illinois after 
midnight tonight, and northeast of the state after sunrise Wednesday 
in response to a strong mid-level short wave propagating out of the 
plains. Low level moisture return with this system is initially 
blocked by the southern extent of high pressure over the Gulf Coast 
states, though moisture was beginning to surge north across east 
Texas at 19z. Strong dynamics associated with the approaching short 
wave and surface low will spread across the forecast area this 
evening, though moisture will be slow to catch up with this deeper 
forcing. Guidance continues to depict blossoming of precipitation 
over the region during the late evening/overnight hours however, 
though with relatively low qpf given late moisture arrival. Some 
potential for isolated to scattered thunder exists, with a pocket of 
steep mid-level lapse rates arriving with the main short wave trough 
axis overnight. Breezy south-southeast winds should help keep 
temperatures from falling off too tonight, with mos numbers looking 
a bit too cool given warm advection and winds. System exits to the 
northeast Wednesday morning with a few spotty showers lingering into 
mid-day. Cool pocket aloft swings across mainly northern IL where 
rain may mix with some wet snow, though low level thickness progs 
and surface temps warming back into the mid 40s to near 50 by 
afternoon suggest little potential for any persistent rain/snow mix 
across central IL. Gusty west winds up to 30 mph linger into the 
afternoon as pressure gradient only slowly relaxes as low pulls away 
to the northeast. Winds will diminish Wednesday night and Thursday 
as surface high pressure ridge builds in from the west.

Warm advection redevelops Thursday afternoon/night as the ridge 
moves off to the east...and broad upper ridging develops with 90+ 
meter height rises behind departing eastern CONUS trough. Models 
indicate another short wave trough propagating along the US/Canadian 
border Thursday, with an area of low pressure and troughing 
extending south across the plains. Winds become south again by 
Friday as the low passes over Northern IL, with temps expected to 
warm into the 60s in most areas before the trailing cold front 
pushes through later in the afternoon. Some potential for showers 
ahead and along the cold front Friday and Friday evening, though 
moisture again remains somewhat limited and thus only low chance 
pops mentioned. Column cools enough for a mention of a rain/snow mix 
north of SPI area overnight...though mainly as precip ends.

Cool Canadian high pressure will build southeast across the Midwest 
over the weekend, with a secondary push of colder air keeping temps 
in the 30s/lower 40s by Sunday. Another upper trough will bring the 
potential for some light snow and a reinforcing push of cold air 
late Monday into Tuesday. 

Ratzer


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$