792
FXUS63 KLOT 110731
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
231 AM CDT Sun Aug 11 2024

.KEY MESSAGES...

- Seasonably cool conditions will persist through Monday, with a
  low (20-40%) chance of light rain toward central Illinois on
  Monday.

- Period or two of showers and t-storms appearing increasingly
  likely Wednesday night through Thursday night time frame

&&

.DISCUSSION...
Issued at 231 AM CDT Sun Aug 11 2024

Through Monday:

Another day with seasonably cool conditions and mostly sunny
skies is expected today with high pressure building in from the
west. Temps this afternoon will rise into the mid to upper 70s
while WNW winds settle around 10-15 mph. With light west winds
tonight and periods of passing upper-level clouds, expect low
temps tonight in the mid 50s inland and low 60s near the lake.

A seasonably strong upper-level jet stretching across much of
the CONUS today will consolidate into a pair of 100-110 knot jet
streaks across the northern Great Plains and Ohio Valley by
Monday. Meanwhile, a weak mid-level wave within modest WNW flow
aloft will track across most of Illinois and into Missouri on
Monday. Guidance remains highly split on how the mid and upper-
level dynamics interact with Pacific-based moisture aloft and
Gulf moisture slowly advecting northeastward across Missouri,
with global deterministic guidance favoring more of an open wave
and precip expanding well into the CWA, CAM guidance favoring
loosely organized convection well southwest of the area, and
ensemble guidance split between both solutions. Overall,
expectations are that a round of two of convection should shift
southeast across Missouri along a more pronounced theta-e
gradient while lighter mid-level precip spreads into at least
central Illinois and possibly northern Illinois and northwest
Indiana. With little low-level moisture advection into the
antecedent air mass over our area, precip chances (20-40%) seem
limited to a couple periods of light rain or sprinkles eroding
from west to east through the day on Monday. It is entirely
possible that the entire forecast area remains dry on Monday,
especially for areas north of the Illinois/Kankakee River
valleys.

Kluber

Monday Night through Saturday:

Our stint of below average temperatures will come to an end
Tuesday and Wednesday as transient short wave ridging moves
across the region allowing high temps to rebound back into the
80s. Humidity levels will remain quite comfortable by August
standards with dry conditions expected.

Next trough is still slated to move across the region Wednesday
night through early Friday time frame, likely resulting in a
bout or two of showers and thunderstorms. After days of
southerly flow from the Gulf transporting moisture northward,
this system looks to pose a greater risk of a meaningful
rainfall and thunderstorms. There remains a lot of variability
in the details among the medium range models and their
respective ensemble members, but there is enough of consensus
to support the high chance/low end likely pops in the NBM.

Low confidence in the forecast next weekend as there is
considerable spread in location and depth of a trough that is
expected to be over the Great Lakes or New England. A more
progressive solution, weaker trough would likely allow for a
mostly dry weekend with seasonable temps. Conversely, if the
slower, more amplified solutions pan out, then there could be
some scattered showers and storms around at times, particularly
during the afternoon/early evening.

- Izzi

&&

.AVIATION /06Z TAFS THROUGH 12Z MONDAY/...
Issued at 1238 AM CDT Sun Aug 11 2024

VFR conditions are expected through this TAF forecast cycle.
West to west-northwest winds will pick up a bit this morning to
around 10kt. There will probably be a few sporadic gusts in the
upper teens late this morning into the afternoon, but
prevailing gustiness is unlikely. Winds will ease toward sunset.

- Izzi

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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