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000
FXUS63 KLOT 190701
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
201 AM CDT Fri Apr 19 2024

.KEY MESSAGES...

- West winds gusting 35-40 mph with an elevated fire danger this
  afternoon.

- Patchy frost possible across the northwest cwa tonight.

- Much cooler temperatures are expected over the weekend with a
  threat for frost and sub-freezing temperatures, particularly on
  Saturday night outside of Chicago.

- The next opportunity for rain will arrive Monday night into
  Tuesday.

&&

.DISCUSSION...
Issued at 201 AM CDT Fri Apr 19 2024

Through Saturday:

Westerly winds will steadily increase after sunrise and are
expected to gust into the 35-40 mph range this afternoon and
then will diminish with sunset this evening. Dewpoints are
expected to drop into the mid 20s, possibly lower 20s and this
will allow relative humidity levels to drop into the 25-30
percent range, resulting in an elevated fire danger.

These lower dewpoints will continue tonight which will allow low
temps to drop into the mid 30s for most areas by Saturday
morning, with some lower 30s possible. This presents the
potential for frost to develop but northwest winds may remain
in the 10 mph range for most of the night which may be too
strong for frost to form. Maintained patchy frost mention across
the northwest cwa, roughly from the Fox Valley west and then
north of I-80. Confidence is low for how widespread any frost
would become and trends will need to be monitored later today.

Saturday will still be breezy, with northwest winds possibly
gusting into the 20-25 mph range. While dewpoints will generally
be in the 20s, high temps look to be a few degrees cooler,
perhaps only lower 50s for highs. Thus, relative humidity levels
look to be a little higher, in addition to the expected lower
wind speeds, thus an elevated fire danger is not expected. cms

Saturday Night through Thursday:

We`re in for a quiescent stretch of weather through the weekend
and the start of the work week as a sprawling surface high builds
across the central CONUS. While the core of the high pressure
won`t ever build directly overhead, it looks like the gradient
will relax sufficiently on Saturday night into Sunday to yield an
effective radiational cooling setup, assuming a region of high
cloud cover associated with an upper jet streak thins and
diminishes as modeled. With dewpoints in the low to mid 20s, a
potential for sub-freezing temperatures exists, particularly for
outlying areas west and north of Chicago. No headlines just yet,
but it`s possible we`ll need to consider freeze watches for this
period.

We`ll step into a brief warming trend Monday and Tuesday as the
low-level flow turns southwesterly. A slightly elevated fire
danger may evolve on Monday with breezy southwesterly winds and
afternoon RH values dipping into the 30 to 35 percent range. The
next precipitation chances arrive Monday night into Tuesday as a
fairly robust upper vort approaches, driving a notable increase in
warm advection across the region. Instability and overall
moisture quality/depth don`t look particularly impressive,
however, with activity likely in the form of scattered showers.

A reinforcing shot of cooler air will arrive in the wake of a cold
front Tuesday night and Wednesday before high temperatures once
again warm back towards and into the 60s--at least away from the
lake in northeast Illinois where persistent onshore flow will hold
temperatures in the 50s. Thereafter, while timing and amplitude
differences are evident, there seems to be a consistent signal in
the deterministic and ensemble suite of a large trough developing
across the Great Basin towards the end of next week, with embedded
shortwaves shuttling east across the central CONUS into the
weekend which could bring the next rounds of showers and storms to
the region.

Carlaw

&&

.AVIATION /06Z TAFS THROUGH 12Z SATURDAY/...
Issued at 1221 AM CDT Fri Apr 19 2024

The only aviation weather concern is the development of strong
and gusty west-northwesterly winds later this morning and
afternoon.

Northwest winds will prevail tonight, with BKN-OVC VFR cloud
cover diminishing at the Chicago-area terminals. Winds will
then increase through the morning and afternoon with gusts
around 30 knots expected. There are some indications that gusts
could approach 35 knots, particularly at RFD at times. Winds
will gradually diminish after sunset.

Carlaw

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory from 10 AM this morning to 7 PM CDT this
     evening for the IL nearshore waters.

     Small Craft Advisory until 7 PM CDT this evening for the IN
     nearshore waters.

&&

$$

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