Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 kilx 250217 

Area forecast discussion
National Weather Service Lincoln Illinois
817 PM CST Fri Feb 24 2017

issued at 817 PM CST Fri Feb 24 2017

Colder air continues to spill across all of central and southeast
Illinois this evening in the wake of a strong cold front. The
spotty Post-frontal convection that had been impacting parts of
the forecast area near the Indiana border has pushed east of the
region. The remaining precipitation risk for the rest of the night
will be spotty rain showers/sprinkles in the wrap around moisture
field that quickly transition to light snow showers/flurries as
the vertical column cools. This wrap-around precipitation is not
expected to be significant locally as the system continues to lift
northeast away from the area and keeps the deeper moisture north
of the forecast area. However, while we will avoid the more
substantial precipitation on the back side of the system, we will
still see the pressure gradient increasing overnight for a time,
with many areas seeing west to northwest winds gusting over 30
mph at times.

Have already made a couple forecast updates for the nighttime
weather/pop trends, and have also beefed up wind speeds/gusts
overnight. Otherwise, only minor tweaks were needed to the hourly


Short term...(this evening through saturday)
issued at 256 PM CST Fri Feb 24 2017

By late this afternoon, the cold front responsible for some
scattered showers today has made its way almost to the Indiana
border. Deeper thunderstorms are just beginning to develop on the
boundary and will keep some pops in the southeast through the early
evening. Otherwise, the cold air moving into place will drop the
temperatures into far more seasonable temps the 20s for
most locations. Moisture that has wrapped around the storm system
will move into the Midwest overnight, and fall as snow. Generally a
dusting is anticipated...with areas in the northern portions of ilx
seeing maybe a tenth to a quarter of an inch. Warm ground will
likely limit any further accumulations. Some slick spots on the least on elevated surfaces and bridges...will be a concern
as the frigid air moves into place with wet roads. Gusty winds
expected to continue through the overnight hours with a tightening
pressure gradient. Cold airmass moving in will keep saturdays Max
temps in the 30s.

Long term...(saturday night through friday)
issued at 256 PM CST Fri Feb 24 2017

A chunk of high pressure will break off from the northern plains
and northern rockies and settle into the mid MS River Valley by
sunset Saturday and into the eastern Tennessee Valley by sunrise Sunday.
This will provide fair/dry weather to the area from Sat afternoon
thru Sunday morning. A seasonably cold night in the low to mid 20s
is expected Sat night with less clouds and lighter winds with
nearby high pressure. Clouds will increase NW of Illinois River later
Sat night and spread east across central and eastern Illinois during
Sunday. A short wave off the Pacific northwest coast will dive
into the Central Plains by midday Sunday and spread light rain
chances NE into SW County Warning Area during Sunday afternoon and over areas
southeast of the Illinois River Sunday evening, and continue small
chances in southeast Illinois overnight Sunday night. Best chances of
light rain will be from I-72 south and light snow could mix in on
northern fringe of precipitation during Sunday night, but no snow
accumulations expected. The short wave trof will press into
southeast Illinois on Monday and lingered small chances of light rain
showers south of I-72. Temps climb a good 10 degrees on Sunday
with breezy south-southwest winds 10-20 mph and gusts to 25 mph with highs in
the mid to upper 40s. Lows Sunday night range from around 30f NW
of the Illinois River, to the mid 30s in southeast Illinois. Milder highs
Monday of 50-55f.

Rain chances increase on Monday night with likely chances, as low
pressure ejects from eastern Colorado into NE Kansas by dawn Tue and into
southern WI by sunset Tue. Central Illinois will be on the milder side of
this storm system with rain expected Monday night with warm front
and becoming more isolated to scattered on Tue in warm sector.
Isolated thunderstorms possible in southeast/east central Illinois Tue
afternoon into Tue evening as cold front moves east over Illinois. Tue
will be the mildest day with highs in the upper 50s and lower 60s,
with mid 60s from Highway 50 south.

An upper level trof will dig southeast into Illinois by Wed and continue
more clouds and chances of light rain showers. Thermal profiles
could be cool enough Wed morning for light rain/light snow chances
NW of the Illinois River. Temperatures will also be cooler in the wake of
the frontal passage. Highs Wed range from mid 50s over northern cwa,
to 50-55f in southeast Illinois. After isolated light rain/snow showers on
Wed evening, expect dry conditions returning from overnight Wed
night thru Thu. Highs Thu in the mid to upper 40s, with areas south
of I-70 around 50f. A weak northern stream short wave will dive into
the Midwest by Thu evening of next week and bring isolated light
rain/snow showers again. This system should be east of Illinois by next
Fri with dry wx and similar highs to Thu of 45-50f.


Aviation...(for the 00z tafs through 00z Saturday evening)
issued at 545 PM CST Fri Feb 24 2017

Gusty westerly winds will persist across the central Illinois
terminals for most of the 00z taf valid time in the wake of a
strong cold front. Moisture wrapping in behind the cold front
supports MVFR cigs more often than not into midday Saturday, along
with a few snow showers. VFR conditions will return to the area
Saturday as drier air works into the area.


Ilx watches/warnings/advisories...


National Weather Service Glossary of Abbreviations