Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Chicago/Romeoville Illinois
806 am CST Thursday Dec 25 2014
307 am CST
Storm system that had left many hopes high that it would provide
a white Christmas...but failed...is quickly moving northeast away
from Lake Huron and into Quebec. Lingering stratus in the wake of
the system continues to blanket the region early this morning but
clearing line over Iowa/Missouri should continue to make steady
progress toward and across the County Warning Area later this morning into the
afternoon. While stratus will likely clear out do anticipate high
cloudiness to stream in fast on its heels...so probably not going
to see an abundance of sunshine today...though some peaks from
time to time look like a good bet. Temperatures look to remain a bit
above average today despite the somewhat limited sunshine. Cloud
cover and a south breeze should keep the trend of unseasonably
mild nights this month going with lows closer to the normal highs
for late December.
307 am CST
Friday through Wednesday...
Another trough will begin digging into the southern rockies tonight
inducing downstream ridging over the eastern Continental U.S. And setting the
stage for a couple mild days Friday and much of Saturday. Southerly
winds will draw mild and moist air north into the region in earnest
Friday into Friday night with dewpoints inching their way up to
around 40 degrees which given the cloud cover and moderate south
wind should result in unseasonably mild temperatures Friday night.
With the warm advection and higher dewpoints surging north there
should be at least some potential for some drizzle or light fog to
Cold front expected to move across the County Warning Area Saturday...but given such
a mild start to the day have nudged high temperatures upward
some...especially in the southeast County Warning Area where frontal passage will be latest.
If the timing of the frontal passage slows any further than more of the County Warning Area
could stand a risk of temperatures making a run toward 50 degrees for a
high. Some showers will likely accompany the front...though window
of forcing doesn't look particularly large and not overly strong so
not looking like a washout. A moderate brand of cooler air of
Pacific origin follows the front knocking highs back closer to
normal Sunday and into early next week.
More substantial push of Arctic air is prognosticated to drop south out of
Canada next week...but medium range models have been advertising the
brunt of the cold air mass and associated near 1050mb high to take
aim on the plains and points west with a more moderated brand of
cold air moving into our region...though still somewhat below
average temperatures for the first time in weeks. Probably fitting as we
approach the end of 2014...a year that will likely go down as one of
the top 10 coldest in history in Rockford and probably top 20 in
//Ord and mdw concerns...updated 14z...
* MVFR ceilings 1500-2000 feet lingering this morning...scattering to
* Breezy southwest winds this morning. Gusts around 20 knots. Lighter
south winds tonight.
Weak high pressure ridge moving across forecast area this morning
in the wake of departing low pressure to the northeast. Extensive
area of MVFR stratus lingers upstream...though trailing edge
progressing steadily eastward across central/eastern Iowa and
expect this to arrive across northern Illinois terminals around 16z for
rfd and 18-19z for Chicago airports. VFR conditions with cirrus
aloft this afternoon through Friday morning.
Breezy west winds will back more southwest early this morning with
passage of ridge axis...with gusts near 20 knots at times through the
day as gradient remains relatively tight well north of surface
high pressure center over the Gulf. Winds back south 10-12 knots
//Ord and mdw confidence...updated 14z...
* high confidence in ceiling/wind trends...medium-high in details of
MVFR ceiling heights this morning and gust speeds through the day.
//outlook for Ord/mdw for 00z Saturday-12z Thursday...updated 12z...
210 am CST
Deep low pressure continues to pull away to the northeast of the
lakes into southwestern Quebec early this morning. Weak high
pressure ridging extended north from the Gulf of Mexico through the
upper Mississippi Valley...and this ridge will move to the east and
across the lake today as the low continues to move away. With the
center of the high well south of the region...winds will not drop
off too much...with 25-30 knots westerly winds backing southwest at
15-25 knots today and continuing into Friday. A weak cold frontal
trough will move slowly southeast across the lake beginning late
Friday...with a weak surface low developing along the front over the
lake Saturday morning. Winds will shift to the north behind the
front across the north portion of the lake...while remaining from
the south to the south of the low track. The low will deepen a bit
as it moves northeast across southwestern Ontario and into Quebec
through Saturday night...with winds across the lake turning
west-northwest and briefly gusting above 20 knots Saturday. Weak high
pressure will then drift east across the western lakes region
Sunday...with another weak cold front moving across the area Sunday
night. Stronger Canadian high pressure will then build across the
western Canadian prairies and will spread southeast into the plains
early next week. Gusty north-northwest winds will likely develop
ahead of the building high Tuesday-Wednesday.
Small Craft Advisory conditions will continue along the Illinois and
Indiana shores into today...with offshore flow though gusty allowing
waves to subside along the Illinois shore this morning and along the
Indiana shore this afternoon.
Lm...Small Craft Advisory...nearshore Gary to Michigan City in until 3 PM Thursday.
Small Craft Advisory...nearshore Winthrop Harbor to Gary in until 9 am
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