Area Forecast Discussion
Issued by NWS Chicago, IL
FXUS63 KLOT 140822
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
222 AM CST Sat Jan 14 2017
222 AM CST
On the front burner this morning is potential for a period of some
light wintry precip over our far southern CWA this morning. Short
range guidance continues to show the northern flank of an swath of
mainly light precip providing a glancing blow portions of Ford,
Benton, and Iroquois counties, mainly south of US 24. Forecast
soundings would suggest more of a sleet threat than freezing rain,
which given the very light amounts could pose less of a travel
hazard. At this point, not planning any headlines, but will
continue to monitor trends this morning for any signs of a more
substantial icy threat.
Otherwise, the remainder of the weekend looks dry and uneventful
until Sunday night. In fact, it would appear as though we could
see some clearing take place over especially northern CWA later
this afternoon. That same clearing could allow temps to get colder
than previous thought tonight. Cloudiness will increase and
thicken Sunday ahead of the next round of precip slated to arrive
after dark Sunday.
222 AM CST
Sunday night through Friday...
As the big upper low over the southwest begins to lift out into
the plains, guidance suggests a band of light precip will move
across our CWA later Sunday night into Monday morning. Forecast
soundings suggest precip could briefly start as some snow, before
transitioning over to mostly light freezing rain and/or sleet.
Amounts at this distance look to be light, though the threshold
for impact with wintry mix events (particularly freezing rain) is
quite low and would anticipate a winter wx advisory eventually
becoming necessary if current trends in model guidance holds.
It appears as though could be a break in the precip for a time
Monday morning, during which time temps will likely inch up above
freezing most locations, setting the stage for appears to be
primarily a rain event by the time the main precip shield arrives
with the system Monday afternoon and especially Monday evening.
Rain with this system should end overnight Monday or early Tuesday
morning, but a northern stream shortwave fast on its heels could
provide for at least a threat of some of isolated showers Tuesday
as lapse rates steepen.
The quick transition to zonal flow and an extended period of above
average temps still looks quite likely through the rest of the
week into next weekend. In the latest medium range models, there
are more differences in the smaller scale features later in the
week and over the weekend, which will impact how extreme the late
week warmth will be and dictate precip chances. At this distance,
the pattern evolution looks pretty complex and confidence is low
in the details, but confidence is high in above (probably much
above) average temperatures Thur through the weekend.
For the 06Z TAFs...
Mvfr cigs earlier this evening across the Chicago terminals have
shifted west and northwest as winds have turned more easterly...
and are still across parts of northern IL and southeast WI. These
are expected to scatter and dissipate through the early morning
hours but may linger at rfd for a few hours. Otherwise mid clouds
around 8kft will lower to 5kft by morning and scatter out Saturday
afternoon. High pressure will remain across the western Great
Lakes region this weekend...centered north of the terminals. Light
easterly winds will become variable Saturday morning and then
shift northwesterly Saturday afternoon...but speeds are expected
to remain below 10kts through the period. cms
230 PM CST
As high pressure moves from Wisconsin over the lake later tonight,
the northeast winds will lighten and become east. Waves should
slowly continue to ease along the Illinois and Indiana nearshores.
A quick-moving low across Canada will tighten the pressure
gradient across the northern part of the lake Saturday, with a
brief increase in gusts to around 25 kt near the northern
straits. A prolonged period of southerly flow is forecast Sunday
afternoon through most of next week (at times southwest and others
southeast). While gales are not presently forecast, there does
look to be possible 30 kt winds during midweek as low pressure
passes the western/central Lakes.
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