604 
FXUS63 KILX 061754
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1154 AM CST Tue Mar 6 2018

.UPDATE...
Issued at 1154 AM CST Tue Mar 6 2018

Deep upper level low pressure will drop southeast across Illinois
this afternoon, bringing and expanding area of rain or snow
showers to the area. Forecast soundings indicate that wet bulb
temperatures above the ground are below freezing, which should
allow for evaporative cooling to change rain over to snow sooner
than some models are indicating. Surface temps may be into the
upper 30s, but snow could still be reaching the ground. Have still
included a chance of rain in the W-NW portions of the CWA this
afternoon because of the warm surface air mass, but would could
end up seeing more snow showers than rain. Even with that, snow
accumulations should remain just a few tenths of an inch at most,
and mainly on grassy areas. Slippery conditions could develop on
secondary and untreated roads, especially tonight when the temps
drop below freezing across the entire forecast area.

Strong W-SW winds are the other concern today. Mixing heights and
momentum transfer are pointing toward our sustained winds
remaining below the 30 mph wind advisory levels, but gusts of 35
to 40 mph are still likely, especially south of I-72 where the LLJ
will be maximized.

Precipitation should come to an end overnight, from west to east
as the low pressure system pulls away, and drier air returns to 
the area.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 316 AM CST Tue Mar 6 2018

The upper low currently centered over NW Iowa will make its way 
southeastward today centering over central Illinois by this evening. 
A strong cold pocket aloft characterized by -30 C 500 mb temps and 
-8 C 850 mb temps will accompany the upper low. Preceding the low,
 dry 0.25 inch precipitable water values and dewpoints as low as
 the mid 20s are poised south of the low to wrap into central IL.
 The combination of cold temperatures aloft and relatively dry
 boundary layer will allow snow to reach the ground at slightly
 warmer temperatures than usual due to evaporational cooling
 effects, so have included a mix of rain and snow in the forecast
 with temperatures as high as the upper 30s this afternoon and
 tonight. Through afternoon have chance-likely rain/snow mix
 southeastward to around I-72, and tonight have a chance of snow 
 showers throughout central and southeast Illinois. Nevertheless, 
 precipitation amounts are expected to be light and temperatures 
 fairly warm so accumulations should be hard to come by until 
 after sunset. Overnight, have accumulations of a tenth or two 
 tenths southward to near I-70. Highs today are expected to range 
 from 39 in Galesburg to 53 in Lawrenceville, starting to cool off
 in the afternoon. Lows tonight should reach 23 in Galesburg to 
 31 in Lawrenceville.

Winds associated with today's storm system will be strongest south 
of the central IL forecast area, but have 15-22 mph sustained WSW 
winds from I-72 southward late this morning through afternoon, and 
gusts 30 to 35 mph. To the north, still breezy but only 10 to 18 mph 
with less significant gusts.

.LONG TERM...(Wednesday through Monday)
ISSUED AT 316 AM CST Tue Mar 6 2018

A long wave trough will linger over the Great Lakes region Wednesday 
through Thursday keeping conditions largely dry and cool with highs 
in the mid and upper 30s and lows in the low to mid 20s. With 
cyclonic flow over Illinois can't rule out some flurries, but 
nothing too significant looks on track and timing would be uncertain 
at this point.

The next chance for precipitation looks to be Friday into Saturday 
morning as a frontal boundary sets up from the central Plains across 
southern Illinois. Precipitation type will likely vary from rain in 
daytime periods to snow at night, as highs reach to 40s to lower 50s 
and lows reach the upper 20s to mid 30s. Any snow amounts look to 
remain light at this point. 

The next potential system is progged for Saturday night into Sunday 
as a wave propagates southeastward out of the northern Plains. 
Again, a mix of rain and snow looks to take place with this storm 
system, and amounts light.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1154 AM CST Tue Mar 6 2018

VFR conditions will start out the 18z TAF period, but cloud
heights will eventually drop to MVFR this evening as the upper 
low progresses across Illinois. These MVFR cigs will last through
the night, then VFR conditions should begin to develop Wednesday
morning. 

Scattered snow or rain showers will increase in coverage from west
to east this afternoon and evening. Forecast soundings and 
upstream observations are pointing toward more snow than rain, so 
some slippery travel surfaces could develop. Scattered rain or
snow showers will continue to around 06z at all sites given how 
slow the system is moving east. Winds will be west-southwest and
quite gusty for SPI/DEC/CMI. Gusts of 35kt could occur. PIA and 
BMI will not see the stronger winds, due to a looser pressure
gradient. As system passes over north-central Illinois, winds 
will become west to northwesterly, especially this evening and 
then all sites will see gusty winds over 25kts for a good portion
of the night.

&&

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

$$

UPDATE...Shimon
SHORT TERM...37
LONG TERM...37
AVIATION...Shimon

639 
FXUS63 KILX 061754
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1154 AM CST Tue Mar 6 2018

.UPDATE...
Issued at 1154 AM CST Tue Mar 6 2018

Deep upper level low pressure will drop southeast across Illinois
this afternoon, bringing and expanding area of rain or snow
showers to the area. Forecast soundings indicate that wet bulb
temperatures above the ground are below freezing, which should
allow for evaporative cooling to change rain over to snow sooner
than some models are indicating. Surface temps may be into the
upper 30s, but snow could still be reaching the ground. Have still
included a chance of rain in the W-NW portions of the CWA this
afternoon because of the warm surface air mass, but would could
end up seeing more snow showers than rain. Even with that, snow
accumulations should remain just a few tenths of an inch at most,
and mainly on grassy areas. Slippery conditions could develop on
secondary and untreated roads, especially tonight when the temps
drop below freezing across the entire forecast area.

Strong W-SW winds are the other concern today. Mixing heights and
momentum transfer are pointing toward our sustained winds
remaining below the 30 mph wind advisory levels, but gusts of 35
to 40 mph are still likely, especially south of I-72 where the LLJ
will be maximized.

Precipitation should come to an end overnight, from west to east
as the low pressure system pulls away, and drier air returns to 
the area.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 316 AM CST Tue Mar 6 2018

The upper low currently centered over NW Iowa will make its way 
southeastward today centering over central Illinois by this evening. 
A strong cold pocket aloft characterized by -30 C 500 mb temps and 
-8 C 850 mb temps will accompany the upper low. Preceding the low,
 dry 0.25 inch precipitable water values and dewpoints as low as
 the mid 20s are poised south of the low to wrap into central IL.
 The combination of cold temperatures aloft and relatively dry
 boundary layer will allow snow to reach the ground at slightly
 warmer temperatures than usual due to evaporational cooling
 effects, so have included a mix of rain and snow in the forecast
 with temperatures as high as the upper 30s this afternoon and
 tonight. Through afternoon have chance-likely rain/snow mix
 southeastward to around I-72, and tonight have a chance of snow 
 showers throughout central and southeast Illinois. Nevertheless, 
 precipitation amounts are expected to be light and temperatures 
 fairly warm so accumulations should be hard to come by until 
 after sunset. Overnight, have accumulations of a tenth or two 
 tenths southward to near I-70. Highs today are expected to range 
 from 39 in Galesburg to 53 in Lawrenceville, starting to cool off
 in the afternoon. Lows tonight should reach 23 in Galesburg to 
 31 in Lawrenceville.

Winds associated with today's storm system will be strongest south 
of the central IL forecast area, but have 15-22 mph sustained WSW 
winds from I-72 southward late this morning through afternoon, and 
gusts 30 to 35 mph. To the north, still breezy but only 10 to 18 mph 
with less significant gusts.

.LONG TERM...(Wednesday through Monday)
ISSUED AT 316 AM CST Tue Mar 6 2018

A long wave trough will linger over the Great Lakes region Wednesday 
through Thursday keeping conditions largely dry and cool with highs 
in the mid and upper 30s and lows in the low to mid 20s. With 
cyclonic flow over Illinois can't rule out some flurries, but 
nothing too significant looks on track and timing would be uncertain 
at this point.

The next chance for precipitation looks to be Friday into Saturday 
morning as a frontal boundary sets up from the central Plains across 
southern Illinois. Precipitation type will likely vary from rain in 
daytime periods to snow at night, as highs reach to 40s to lower 50s 
and lows reach the upper 20s to mid 30s. Any snow amounts look to 
remain light at this point. 

The next potential system is progged for Saturday night into Sunday 
as a wave propagates southeastward out of the northern Plains. 
Again, a mix of rain and snow looks to take place with this storm 
system, and amounts light.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1154 AM CST Tue Mar 6 2018

VFR conditions will start out the 18z TAF period, but cloud
heights will eventually drop to MVFR this evening as the upper 
low progresses across Illinois. These MVFR cigs will last through
the night, then VFR conditions should begin to develop Wednesday
morning. 

Scattered snow or rain showers will increase in coverage from west
to east this afternoon and evening. Forecast soundings and 
upstream observations are pointing toward more snow than rain, so 
some slippery travel surfaces could develop. Scattered rain or
snow showers will continue to around 06z at all sites given how 
slow the system is moving east. Winds will be west-southwest and
quite gusty for SPI/DEC/CMI. Gusts of 35kt could occur. PIA and 
BMI will not see the stronger winds, due to a looser pressure
gradient. As system passes over north-central Illinois, winds 
will become west to northwesterly, especially this evening and 
then all sites will see gusty winds over 25kts for a good portion
of the night.

&&

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

$$

UPDATE...Shimon
SHORT TERM...37
LONG TERM...37
AVIATION...Shimon