Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 231030
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
530 AM CDT Fri Aug 23 2019

.SHORT TERM...
212 AM CDT

Through Tonight...

Pleasant and quiet apparent weather for the area today, although
breezy northeast winds near Lake Michigan will continue dangerous
swimming conditions due to high waves and rip currents.

Satellite water vapor imagery this morning reveals subsidence
and drying in the mid and even lower levels moving in over the
Lower Great Lakes from the north. Resulting surface high pressure
of 1025 mb over central Ontario this morning will gradually expand
southward through the day. Much of the CWA and Lake Michigan will
remain in the gradient around this, with a tightened clockwise
flow and thus northeast winds with occasional gusts to 20 mph.
Near the lake front, the sustained winds at times will approach 20
mph, and these will help to sustain the ongoing high wave action.
While this is not to the level of lakeshore flooding, some higher
waves can cause dangers for those walking near the lakeshore. The
perpendicular flow to much of the shore will continue the rip
current risk and wind direction and speed look enough for this
threat to go into this evening. There may be a brief lull late
this morning in wave action due to slightly veered winds, but that
looks temporary.

Otherwise today should realize high temperatures at or a couple
degrees below yesterday given the cold advection at the top of the
mixed layer that has occurred in the past 12 hours and will
continue through midday. With a clear sky by tonight and weakening
flow, though maybe not completely calm until late, low
temperatures look to drop into the lower 50s in outlying areas and
suspect a few of the typical cool spots touch upper 40s.

MTF

&&

.LONG TERM...
321 AM CDT

Saturday through Thursday...

A large, sprawling area of surface high pressure will be centered
over the upper Great lakes region Saturday morning and will slowly
slide east, centered over New England by Sunday morning.  Conditions
across the local area will be unseasonably cool and dry, with highs
on Saturday in the middle to upper 70s and upper 70s to lower 80s
for Sunday. Given the continental-polar origin of the associated air
mass, dewpoints will also be relatively low, mainly in the middle
50s.  Overall, this is expected to result in pleasant weather with
ample across the area.

For Sunday night and into early next week, the longer range model
guidance remains in good agreement with a well defined southern
stream shortwave lifting through the Missouri Valley and into
central Illinois late Sunday night and Monday morning and lift
across southern lake Michigan and into Lower Michigan Monday night.
Also, a northern stream short wave is expected to track across
Northern Plains/Canadian border area while dragging a cold front
across the Upper Mississippi Valley.  During this period from Sunday
night through Tuesday, the large sfc high will move off the New
England coast.  This will set up a period of unsettled weather
across the region, with periods of showers and thunderstorms
expected as a return flow of deep layer moisture sets up as the sfc
high moves east and the double-barreled system approaches from the
west and crosses the region.  Conditions should settle down as the
system moves off to the east and high pressure builds out of the
Central Plains and across the Middle Mississippi Valley. Another
northern stream shortwave rotating around the base of a deep upper
low expected to develop over Central Canada by mid week could bring
the next chance for some scattered showers or thunderstorms for
Wednesday afternoon into Wednesday night.

&&

.AVIATION...
For the 12Z TAFs...

For the Chicago area TAFs today the main story is northeast
winds, with high confidence in these being 10+ kt from 14Z-01Z.

High pressure gradually building into the Upper Great Lakes will
continue to result in northeast winds over the area. Early this
morning there is 20 kt flow just 2,000 ft aloft per radar VWP.
This is indication there will very likely be some gusts to that
magnitude especially mid-late morning as mixing ensues and before
that channel of winds eases in speed some. There will be
fluctuation in wind direction between mainly 030 and 060 degrees
at Chicago airports today. Winds will gradually ease in the 00Z-
03Z time similar to last evening.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Beach Hazards Statement...ILZ006-ILZ014 until 4 AM Saturday.

IN...Beach Hazards Statement...INZ001-INZ002 until 4 AM Saturday.

LM...Small Craft Advisory...nearshore waters
     until 4 AM Saturday.

&&

$$

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