Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Chicago/Romeoville Illinois
644 am CDT Tuesday Sep 23 2014
148 am CDT
Synopsis...dry and warming conditions are expected through the
Today through Wednesday...
high pressure is over the Ohio River valley and it will dominate
the pattern. Expecting quiet dry weather with temperatures slowly warming.
Highs today will be in the lower 70s away from the lake while a lake
breeze will keep temperatures along the lake in the upper 60s.
Light southeast winds are expected tonight and may see few to scattered
cirrus as a weakening upper level trough moves over western
Minnesota and Iowa. Lows will once again vary from the low to middle
50s downtown to the upper 40s in the outlying areas.
Wednesday looks similar to today with sunny skies and highs in the
low to middle 70s. Winds will turn off of the lake so temperatures along the
lake will top out around 70.
Wednesday night through Friday...
broad anti-cyclonic flow will continue to influence the region Wednesday
ngt-Fri...despite the ridge center being displaced well east of the
Great Lakes. Weak moisture starved middle-level trough is poised to pivot
east across the plains Wednesday ngt/thur. Expect this to produce a few
clouds...then diffluence flow aloft returns late Thursday into Friday with
a return to abundant sunshine. With the light low level flow and persistent
dry weather...the surface should easily warm into the middle 70s Thursday to
perhaps the upper 70s Friday. Afternoon lake breezes will keep the adjacent
areas cooler. Overnight lows will generally be in the low/middle
50s...with a few points dipping into the upper 40s.
Saturday through Monday...
500mb ridge arrives late week and will likely persist through the
weekend...with ensembles indicating a steady weakening to the
strength by early next week. However downstream across the Canadian
maritime a trough is prognosticated to develop...which could slow the rate
of weakening to the ridge over the Great Lakes. With the continued
dry pattern and light flow...surface temperatures will remain seasonal to a few
degrees above in the middle 70s with afternoon lake breezes keeping nearby
land slightly cooler. Overnight lows will mainly be in the low/middle
//Ord and mdw concerns...updated 12z...
* winds turning east this afternoon associated with a lake breeze.
High pressure is expected to dominate the weather pattern through
next weekend leading to a dry...VFR forecast. The only concern
today will be a lake breeze pushing through this afternoon.
Ord...mdw...and gyy will see southeast to east winds around 9 knots. Still have
limited confidence in wind speeds behind the lake breeze. Winds
then become southeast and weaken in the evening. Southeast winds pick up
to around 7 knots by late Wednesday morning and another lake breeze is
expected in the afternoon.
//Ord and mdw confidence...updated 12z...
* medium-high confidence in lake breeze timing...medium confidence
in associated wind speed.
//outlook for Ord/mdw for 00z Thursday-12z Tuesday...updated 12z...
Thursday through Sunday...VFR with afternoon lake breezes.
148 am CDT
Quiet weather continues with a lake breeze expected this afternoon
and each day through the weekend. Flow over the open waters will be
weak and out of the south through Sunday. Wind direction will vary a
bit more over the southern end of the lake where winds will be
southeast to east. Winds veer to the north Sunday night and
increase to 10-20 knots Monday.
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