Scientific Forecaster Discussion
fxus63 klot 191710
Area forecast discussion
National Weather Service Chicago/Romeoville, Illinois
1110 am CST sun Nov 19 2017
121 am CST
After the soggy, windy, and cool autumn weather of the past few
days, we enter a fairly quiet and dry pattern as we head into the
Thanksgiving week. Sunday will begin on the cold side of the
temperature roller coaster in wake of yesterday's system, one that
will continue to deepen across the northeast and bring this same
messy system to that region. Nighttime satellite across the
Midwest depicts a still an area of stratus across much of
Wisconsin, northeast Illinois and northwest in. Despite some breaking up
of the clouds, which will gradually continue , the upper level
flow is still cyclonic, and thus the low clouds remain trapped
below a frontal inversion. As the morning continues, expect one
last upper wave to clear the area and the associated subsidence
will allow for better lower cloud clearing this afternoon. The
Heart of the cold air behind this first front will shift through
the western Great Lakes this morning, and with increasing higher
clouds today, highs will hold in the low to mid 30s.
Passing high clouds tonight but low level warm advection as winds
shift back to southwesterly as surface high pressure, overhead
this afternoon, will shift to the Ohio Valley tonight. Therefore
temps will fallow back to the mid 20s in our colder areas. Highs
bounce back nicely Monday, with near 50 degree readings and
plentiful sun other than some cirrus.
121 am CST
Monday through Saturday...
The general idea is high pressure will shift across
the Great Lakes, then shift off to the Ohio Valley and mid
Atlantic regions with some regularity throughout the extended. A
series of clipper like systems will bring occasional wind, clouds
and cold spells, followed by warm ups as each high pressure
departs east. This will result in several up and down swings of
temperature. No one system is expected to bring any real
precipitation, even though occasionally Tuesday night, Wednesday
night, and toward Saturday a model will try to throw out some very
light qpf, so most of the week appears dry at this point. The
first front will lead to a little cooler day Tuesday, then a
repeat of today on Wednesday with highs only in the 30s, before
readings head back closer to normal Thanksgiving day and toward
week's end before another colder shot next weekend, and maybe some
light precipitation mainly of the liquid form to accompany this
for the 18z tafs...
High pressure will build across the region today providing
primarily VFR conditions and a modest west to southwest breeze.
Late this morning through the afternoon, there will be few to
scattered stratocumulus around 030 but given the dry advection
into the region do not anticipate a broken deck to develop.
Otherwise just expect mid and high clouds to traverse the region.
Winds will be somewhat breezy during the day, with gusts to around
20kt. Winds will diminish this evening and back to the southwest
as the ridge axis moves through overnight. Winds will continue
out of the southwest Monday with gusts to around 20kt possible
once again from mid morning into the afternoon.
156 am...northwest gales have ended and will be canceling the
Gale Warning early. Northwest winds to 30 kts will slowly turn
westerly this afternoon as high pressure moves south of Lake
Michigan. Speeds may diminish further to 15-25kts tonight...
especially on the north end of the lake. Winds will turn to the
southwest Monday and are expected to increase to gales Monday
afternoon as strong low pressure moves across Ontario Monday
night. These gales will diminish Tuesday morning and shift to the
northwest as a cold front moves across the region. High pressure
will build across the plains Tuesday and then to the southern
lakes and Ohio Valley Wednesday into Thursday with westerly winds
for mid week. Cms
Lm...Small Craft Advisory...in nearshore waters until 6 PM Sunday.
Small Craft Advisory...Illinois nearshore waters until noon Sunday.
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