Scientific Forecaster Discussion
fxus63 klot 122049
Area forecast discussion
National Weather Service Chicago/Romeoville, Illinois
249 PM CST Tue Nov 12 2019
220 PM CST
Through Wednesday night...
Record cold continues across the area this afternoon, with high
temperatures as of this writing in the mid to upper teens area-
wide. The previous record for the coldest high temperature for
today was 28 and 27 in Chicago and Rockford, respectively, so
these values will be broken by 8 to 10 degrees.
Surface high pressure will move eastward across central and
southern Illinois early this evening. As it does so surface winds will
continue to weaken across the area, and this should allow
temperatures, with a fresh snow cover, to radiate efficiently by
early this evening. In fact, it is not out of the question that
some of the favored cold spots across north central Illinois could make
a run at 0 this evening. It does appear though that temperatures
should bottom out this evening, then slowly rise overnight as low
level warm air advection takes place on the back side of the
surface high shifting to our southeast. High level cloudiness
will also develops later tonight. While temperatures will remain
cold on Wednesday, we should see temperatures rebound back into
the mid to upper 20s for daytime highs.
Mainly cloudy skies are expected on Wednesday as we remain in a
warm air advection pattern ahead of a weak clipper type system
that will be shifting eastward over the northern plains and upper
Midwest. This disturbance will shift across our area Wednesday
night, resulting in our next chance for some light snow. While
this is not looking like much of snow producer for the area, there
could be some accumulations up to an inch near the WI state line.
Otherwise, amounts should remain well under an inch for most
areas, especially along and south of I-88. Expect the light snow
to end prior to daybreak Thursday morning.
249 PM CST
Thursday through Tuesday...
The unseasonably cool pattern will persist into the weekend and
early next week with a progressive upper flow through the period.
While temperatures will moderate by Thursday from the record cold of
today... continued moderation over the weekend and early next week
will be only slight and gradual... with Max temps by Monday-Tuesday
still running 5 to 8 degrees below average.
The surface and boundary layer flow will turn anti-cyclonic Thursday
in the wake of the departing cold front. This will allow subsidence
to overspread the area from the northwest ahead of high pressure
that will ridge over the area Friday. With a chilly northwest wind
on Thursday... and only a slow clearing trend from the northwest...
Max temps will struggle to get to the lower to mid 30s. Despite
abundant sunshine Friday... temps will only warm only into the mid
and maybe upper 30s in a few spots
The next chance of rain or snow then comes back into the area late
Saturday night through Sunday night as short wave energy races
across the area ahead of a more vigorous progressive upper trough.
Moisture in the low levels remains lacking however... and soundings
showing vertical temperature profiles that are marginal for snow.
Hence only low chance pops warranted and these futures will continue
to be monitored.
Medium range models suggest a more amplified upper level shortwave
trough to move into the area later Monday into Tuesday... bringing
the potential for another brief period of light rain or light
rain/snow mixed Monday afternoon into Monday night.
Record minimum temperature for November 12th
-chicago: 8 in 1986
-rockford: 7 in 1986
Record low maximum temperature for November 12th
-chicago: 28 in 1995
-rockford: 27 in 1940
Record minimum temperature for November 13th
-chicago: 6 in 1986
-rockford: 3 in 1986
for the 18z tafs...
Overall quiet, but very cold, weather is expected over the area
through the period. Winds will remain west-northwesterly this
afternoon, before backing more south-southwest early this evening
as a surface high tracks south of the area. Winds will then
increase out of the south-southwest on Wednesday morning as the
pressure gradient strengthens on the western periphery of the
surface high. This should result in gusty winds up to around 24 kt
during the day. Any precipitation and low clouds associated with
our next approaching weather disturbance should hold off until
early Wednesday evening. This is currently just beyond the end of
the current taf period.
In...Lakeshore Flood Warning...inz001-inz002 until 4 PM Tuesday.
Lm...Small Craft Advisory...Illinois nearshore waters until 3 PM Tuesday.
Small Craft Advisory...in nearshore waters until 10 PM Tuesday.
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