020
FXUS63 KLOT 071920
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
220 PM CDT Fri Jun 7 2024

.KEY MESSAGES...

- Tomorrow will be marked by isolated to scattered rain showers.
  A repeat of the washout last Saturday is not expected.

- Pleasant conditions are expected Sunday through the middle of
  next week with limited (15% or lower) chances for rain and
  seasonable temperatures.

- A shift toward warmer temperatures and higher humidity
  appears on track to arrive after the 2nd week of June.

&&

.DISCUSSION...
Issued at 219 PM CDT Fri Jun 7 2024

Through Saturday night:

National satellite fields augmented by RAP-analyzed pressure fields
indicate a decaying low pressure system in central Ontario and an
expanding high pressure system across the middle United States
beneath broad upper-level northwesterly flow. A pair of upper-level
shortwaves are evident, first over the central Plains and the second
near the Montana and Saskatchewan border. Meanwhile, closer to home,
our area is being treated to a delightful early June day with mostly
sunny skies, a northwesterly breeze, low humidity levels, and
temperatures in the mid to upper 70s.

Tonight, upper-level clouds will increase in advance of the leading
shortwave in the Plains. Initial thunderstorms now developing in
central Kansas are poised to grow upscale into a loosely organized
convective system overnight, which will likely move along the
instability gradient well to our southwest across Missouri.
Meanwhile, a few showers may attempt to develop near the
Mississippi River after sunset associated with ephemeral
filaments of frontogenesis. A residual dry
low-level airmass will be eager to chew up initial raindrops
throughout the night, so we will continue a dry forecast. A
passing surface pressure ridge will encourage winds to become
nearly calm overnight. Lows will range from the upper 50s to
lower 60s.

Chances for isolated showers will begin to tick upward toward and
after daybreak Saturday as weak WAA approach from the west
ahead of the secondary upper-level shortwave. The continued dry
airmass may continue to prove hostile for raindrops to survive
to the surface through the morning, but felt advertising
gradually increasing PoPs toward 20 to 30% by noon was a good
idea. A slightly better push of WAA during the afternoon (and
corresponding lowering cloud bases) should be enough to support
a few areas of scattered showers through the evening hours.
Overall, limited moisture and scant instability should limit the
coverage and intensity of showers and curtail more than an
isolated rumble of thunder. (In other words, tomorrow should not
be a repeat washout like last Saturday). Overcast skies will
limit highs to the low to mid 70s.

Tomorrow night, a weak cold front will slip through the area causing
southwesterly winds to turn northwesterly. Lows will dip to the low
to mid 50s.

Borchardt

Sunday through Friday:

We are entering what looks to be a pretty quiet period through next
week. High pressure will begin building into the area on Sunday
bringing sunny skies and temperatures in the mid-to-upper 70s.
Strong northerly flow will cause temperatures to be cooler Monday
and Monday night with highs in the upper 60s and low 70s and lows
potentially dipping below 50 degrees. However, temperatures
will rebound over the following days.

On Monday, a shortwave is expected to propagate through the backside
of the trough that will be pushing off to the east, however, a very
dry moisture profile should inhibit any precipitation from forming.
The next potential for precipitation comes Wednesday as a low tracks
through Canada with a cold front draped to its south. However, model
guidance is not in good agreement about the progression of the upper-
level shortwave/low, so PoPs remain low (15% and below).

A signal continues to be present in long range ensemble guidance for
a pattern shift to warmer temperatures by the end of the forecast
period. Temperatures look poised to push into the upper 80s and
perhaps even lower 90s by the end of the work week.

Carothers

&&

.AVIATION /18Z TAFS THROUGH 00Z SUNDAY/...
Issued at 1215 PM CDT Fri Jun 7 2024

Gusty northwest winds at press time will gradually ease
throughout the afternoon as a surface high pressure system
approaches from the west. Rather than carrying multiple lines
for downward-trending gusts, will simply lower prevailing speeds
with the scheduled 21Z AMD. After sunset, winds will become
light and variable.

Tomorrow, a pair of storm systems will move through the general
region. Winds will slowly become southerly toward daybreak and
southwesterly throughout the morning as each move overhead. In
addition, upper-level (VFR) clouds will gradually thicken from
daybreak onward. A few rain showers may start as early as
tomorrow morning with the first system (10-20% chance), and
will increase (to 30 to 40%) after 18Z as warm-air advection
moves overhead with the second system. In addition, cigs may dip
into MVFR during the afternoon, as well. For now, opted to
group together MVFR and VCSH to start at 20Z at ORD/MDW in
favor of refinements in later TAF packages. Chances for thunder
appear less than 20% tomorrow.

Borchardt

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 7 PM CDT this evening for Winthrop
     Harbor IL to Gary IN.

&&

$$

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