762
FXUS63 KIWX 211037
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
637 AM EDT Sat Sep 21 2024

.KEY MESSAGES...

- Dense fog early this morning will mix out by mid-morning.

- Very warm again today with high temperatures near 90 degrees.


- Frequent chances of showers and thunderstorms Sunday through
  at least Tuesday.

&&

.DISCUSSION...
Issued at 319 AM EDT Sat Sep 21 2024

Dense fog developed rapidly early this morning where stratus
departed. Stratus lingers over a majority of northwest Ohio, south-
southwest to Jay County, IN, where visibility remains unimpeded. Fog
still has a few more hours to develop there, so will continue to
monitor the need for a dense fog advisory in northwest Ohio (or an
early cancellation for any IN counties).  Forecast guidance favors
fog mixing out in the 9a to 10a EDT window.

Unseasonably warm yet again this afternoon. High resolution guidance
indicated 850mb temperatures could be 2C greater than yesterday (19C
this afternoon) with a subtle poleward shift in the 582dm isoheight.
Thus, despite a foggy start, I`ll swing toward the high-end of
guidance such that 89-90 degrees will be common today. There were a
few sites that reached 90 or greater yesterday while others were
inhibited by rain. The inherited forecast ranked as the 25th
percentile of bias-corrected guidance (favoring bias correction here
based on the stagnant, hot pattern) with an average CWA temperature
of 87. The updated forecast is just beyond the 75th percentile of
guidance.

A large swatch of the US-24 corridor missed out on Friday
rainfall. Those folks (and the rest of the forecast area) will try
again Sunday and Sunday night, followed by additional rain chances
into midweek. An upper-level low currently over far northwest North
Dakota will track east into the western Great Lakes and interact
constructively with shortwave energy riding atop a ridge centered
over Texas and Oklahoma. Moisture return from the Gulf improves
through Sunday as the ridge is displaced east in response to a
trough ejecting from the Four Corners. This trough may spread rain
through central Indiana Monday, thus favoring the US 24 Corridor
locally by that time before renewed cyclogenesis over the Midwest
could result in more rain area-wide into Tuesday. During this time,
high temperatures will be seasonally appropriate; mid-70s.

Beyond Tuesday, there is enormous difference among ensemble systems
with respect to how the Four Corners trough evolves by the time it
reaches the eastern US. The speed and magnitude of the trough varies
notably, thus it was difficult to stray much from the in-house blend.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 637 AM EDT Sat Sep 21 2024

Dense fog is widespread but appears to be relatively shallow
and expect it will mix out quickly around 14Z. This is largely
based on the speed of mixout with similar fog events earlier
this week but some variation is possible. Otherwise VFR
conditions and light winds will persist through the period. Any
rain or impacts associated with the next approaching system will
not arrive until after 12Z Sunday.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Dense Fog Advisory until 10 AM EDT /9 AM CDT/ this morning for
     INZ005>009-012>015-017-018-020-022>027-032>034-103-104-
     116-203-204-216.
OH...Dense Fog Advisory until 10 AM EDT this morning for OHZ001-002-
     004-005-015-016-024-025.
MI...Dense Fog Advisory until 10 AM EDT this morning for MIZ078>081-
     177-277.
MARINE...None.

&&

$$

DISCUSSION...Brown
AVIATION...AGD