153
FXUS63 KLOT 170941
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
441 AM CDT Mon Jun 17 2024

.KEY MESSAGES...

- Hot and muggy conditions will prevail through the end of the
  week. Periodic chances for thunderstorms will continue, though
  many hours will remain dry.

&&

.DISCUSSION...
Issued at 238 AM CDT Mon Jun 17 2024

Through Tuesday Night:

Today will be another warm day as a sprawling ridge begins to
build across the Mid Atlantic. 850-500 mb thicknesses will
increase a bit over where they were on Sunday, so temperatures may
end up warmer by a few degrees. A glance at forecast soundings
shows a little in the way of drying in the mid-levels, so it
seems like dewpoints may mix out a bit more. Favored the warmest
guidance for high temperatures today given the expected strong and
deep PBL mixing with highs in the urban Chicago core near 96-98
degrees. With dewpoints largely expected to mix out into the mid
60s, heat indices look to be in the 95-105 degree range, with
values at the higher end of that range more limited in coverage.

We`ll be uncapped by midday in most locations given the forecasted
temperatures and dewpoints. However, there don`t seem to be any
well-defined impulses to drive notable large scale forcing for
ascent in the region this afternoon. There is perhaps a low-
amplitude disturbance visible in moisture channel loops across
central Missouri which will lift northeastward today but that
looks to be about it with the remnant convective vortex from
Sunday expected to push east across Lake Erie. Slight chance
(15-20%) PoPs look reasonable for this afternoon with any activity
expected to remain few and far between. An isolated strong/gusty
downburst wind threat can`t be ruled out given how hot and
deeply mixed it`ll be.

Tonight, a plume of deeper moisture emanating from the central
and western Gulf of Mexico will surge northward. Mid-level lapse
rates will trend towards moist adiabatic which will lessen the
amount of instability available, but several embedded
disturbances/vort lobes within the plume may be enough to crank
out some showers or a few storms and have added some low precip
chances to account for this.

While the core of the moist plume will pivot east of us through
Tuesday, overall increased tropospheric moisture looks like it
might limit mixing a bit compared to Monday. With thickness
values at or even a bit under Monday`s levels, air temperatures
are expected to come down a few degrees although dewpoints may not
drop as significantly. All of this nets peak heat indices Tuesday
afternoon in the 95-100 degree range. Additional very isolated
showers or storms once again can`t be ruled out with peak heating.

Carlaw


Wednesday through Sunday:

Hot and humid conditions will continue to be the primary focus
through the end of the week and into the weekend as a broad
ridge and high pressure system over the eastern CONUS continues
to build and remain stagnant. Southwesterly flow will allow
temperatures to routinely be in the low-to-mid 90s Wednesday
through Saturday. Dew points in the upper 60s will bring heat
indices into the upper 90s with some areas occasionally pushing
100 degrees. This will keep us below Heat Advisory criteria
(>105 degrees for a single day or >100 degrees for 4+ days),
however, caution should still be exercised during long periods
of time outdoors by taking breaks and hydrating. Overnight lows
won`t bring much relief as temperatures are only expected to
drop into the low- to-mid 70s due to the high moisture content.

Although the heat is the main story through the extended, there
are several chances for showers/storms. A synoptic
cold/stationary front will be situated across Wisconsin on
Wednesday. Convection will initiate ahead of this front and may
sneak into the northwest portion of the CWA Wednesday afternoon,
so have left some chance PoPs in the forecast.

On Thursday, this front will move further southeast, potentially
reaching the northern periphery of the CWA bringing another
chance for showers and storms to the northwestern CWA. There is
also a signal in the long range models for the front to push
down Lake Michigan and enhance a lake breeze Thursday afternoon,
setting the stage for a possible backdoor cold front scenario.
Depending on the timing of this front, areas near the lakeshore
may see an early high temperature with cooling temperatures
through the afternoon, however, confidence in occurrence and
timing is low at this time.

Towards the end of the work week, the ridge will begin to
flatten out and be pushed south by a trough moving across
Canada bringing zonal flow to the area. Ensemble guidance shows
a consistent signal for a shortwave to move across the area
sometime this weekend, with a surface cold front bringing an end
to this extended period of heat and humidity. This will also
bring a chance for showers and storms with the passing of this
front, however, confidence is very low on the timing.

Carothers

&&

.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 1221 AM CDT Mon Jun 17 2024

Current satellite imagery shows a MCV moving away from the area and
into Michigan. Some mid-level clouds associated with this MCV will
stick around overnight, but VFR conditions are expected to
persist. Tomorrow looks generally quiet with the exception of
some gusty (around 25 kts) southwest winds in the afternoon.
Mid-level moisture will allow some diurnal low-to-mid level
clouds to develop tomorrow afternoon. A few of the CAMs hint at
the possibility of some isolated storms tomorrow, but
confidence in this actually occurring is too low to include in
the TAFs.

Carothers

&&

.CLIMATE...
Issued at 441 AM CDT Mon Jun 17 2024

Several temperature records will be threatened over the next few
days. The records that appear to be in greatest jeopardy are
today`s (June 17) record high for Chicago and several record
warmest low temperatures for both Chicago and Rockford through
Saturday, June 22nd.

Here are the daily high and warmest low temperature records
for Chicago and Rockford for each day through June 22nd:

                  Chicago
--------------------------------------------
Day:           6/17 6/18 6/19 6/20 6/21 6/22
--------------------------------------------
Record High:     96   98  102  104  101   97
Record Warm Low: 78   77   78   78   74   76

                  Rockford
--------------------------------------------
Day:           6/17 6/18 6/19 6/20 6/21 6/22
--------------------------------------------
Record High:     99   99   99  101  100   97
Record Warm Low: 75   74   76   73   71   73

Ogorek

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Air Quality Alert until midnight CDT tonight for ILZ005-ILZ006-
     ILZ012-ILZ013-ILZ020-ILZ021-ILZ103-ILZ104-ILZ105-ILZ106-
     ILZ107-ILZ108.

IN...None.
LM...None.

&&

$$

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