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Area forecast discussion 
National Weather Service Lincoln Illinois
1136 am CST Tuesday Dec 1 2015

issued at 1003 am CST Tuesday Dec 1 2015

Back edge of the lower cloud deck was roughly along the Indiana
border late this morning. Still getting a fair amount of mid and
high level clouds streaming up from the Southern Plains and
affecting mainly the southeast half of the forecast area, but this
should start to thin out with time. Latest visible satellite
imagery showing some stratus advecting eastward into areas near
Galesburg, ahead of a shortwave rotating around the upper low that
is centered just southeast of Sioux Falls South Dakota. This should continue
to spread across the far northern forecast area over the next few

Made some refinements to the sky trends over the next few hours,
which required some adjustments to the zone forecasts. However,
temperatures and winds generally on track and required little


Short term...(today)
issued at 327 am CST Tuesday Dec 1 2015

09z/3am surface analysis shows 1005mb low over southwest Minnesota
with occluded frontal boundary arcing southeastward into
east-central Illinois. While most of the showers associated with
the system have departed the kilx cwa, low clouds and drizzle
persist across much of the area early this morning. Latest
satellite imagery continues to show the back edge of the cloud
shield marching steadily northeastward toward the Mississippi
River as a dry slot wraps into the system. Based on satellite
timing tools, the clearing line should reach a Peoria to
Springfield line by 12z/6am and further east to the Indiana border
by around 17z/11am. Mostly sunny skies are then expected for the
balance of the day across most of the area, with the exception
being locations northwest of the Illinois River where wrap-around
moisture will result in increasing cloudiness by mid to late
afternoon. Thanks to a good deal of sunshine and southwesterly
winds gusting to around 25mph, high temperatures will rise into
the middle to upper 40s...with a few readings around 50 degrees
south of I-70.

Long term...(tonight through monday)
issued at 327 am CST Tuesday Dec 1 2015

As a deep upper low currently over southwest Minnesota tracks slowly
eastward over the next 24 hours, clouds will spread back into
central Illinois and some light precipitation will be possible
across the north. Models are in good agreement with the track of
the low and its expected quantitative precipitation forecast across the area. Based on both NAM and
GFS output, will carry chance pops for light snow along/north of the
I-74 corridor tonight, with a chance for flurries as far south as a
Paris to Taylorville line. As the low slowly slides by to the
north, light snow/flurries will continue into Wednesday as well.
Snowfall will be quite light with this system, with perhaps a couple
tenths of an inch along/north of I-74 late tonight into Wednesday
morning. Despite continued light snow or flurries into Wednesday
afternoon, surface temperatures rising into the middle to upper 30s
will prevent further accumulation and may even result in the light
snow mixing with rain.

Once the low departs the region, upper heights will rise
significantly by the end of the week. Both the GFS and European model (ecmwf)
indicate unseasonably high 500mb heights of 582 to 585dm by
Saturday. These heights along with a southerly low-level flow and
plenty of sunshine will yield high temperatures around 10 degrees
above normal for this time of year in the lower to middle 50s over
the weekend.

After that, model solutions begin to diverge somewhat early next
week. Previous runs of the GFS/European model (ecmwf) had tracked an upper low
across the Midwest on Monday, resulting in rain chances across
central Illinois. The 00z Dec 1 run of the GFS now features a much
weaker open wave with no precip tracking through the area, while the
European model (ecmwf) still shows a stronger closed system but also keeps things
dry. Given the trend toward a weaker/drier wave, have decided to
drop mentionable pops in favor of just a slight chance for showers
Monday/Monday night.


Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 1135 am CST Tuesday Dec 1 2015

Main concern will be with development of MVFR conditions
overnight. A fast moving disturbance, associated with an upper
level low tracking slowly east across Iowa, will bring a period
of snow showers to central Illinois. Greatest potential for a
significant reduction in visibility will be closer to kpia/kbmi
and northward, but ceilings expected to lower below 3000 feet at
all taf sites during the 06-12z period. With the low expected to
begin tracking southeast during the day Wednesday, the lower
clouds and periodic show showers will persist the remainder of the
taf period.


Ilx watches/warnings/advisories...


short term...Barnes
long term...Barnes

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