058
FXUS63 KIWX 182217
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
617 PM EDT Tue Jun 18 2024

.KEY MESSAGES...

* There is a Marginal Risk for isolated severe storms in northwest
  Ohio this afternoon into early this evening. Gusty winds and heavy
  rain are the primary threats.

* Hot, humid and mainly dry conditions are expected through
  Saturday, with the hottest days Thursday and Friday. Peak
  afternoon heat indices will approach 100 degrees, hazardous to
  sensitive and vulnerable groups.

&&

.DISCUSSION...
Issued at 246 PM EDT Tue Jun 18 2024

Warm/moist southerly flow will remain in place into tonight and
Wednesday on the western periphery of a prominent upper ridge
centered over the Mid Atlantic states. This will keep clouds and low
rain/thunder chances in the forecast as Gulf of Mexico moisture
continues to stream north into a lingering mid level shear/vorticity
axis.

For this afternoon/evening, will have to monitor areas mainly east
of I-69 for widely scattered convection along a subtle convergence
zone trailing a shortwave lifting northeast through lower Michigan.
Moderate boundary layer destabilization and DCAPE up around 1200
j/kg suggests a low end threat for localized downbursts.

Additional, low, chances for widely scattered showers/storms persist
into tonight and Wednesday given the moist airmass and the potential
for additional convectively induced waves to lift through. With that
said, most locations will likely remain dry as the Mid Atlantic
States upper ridge begins to flex westward. Heat indices are forecast
to peak in the mid-upper 90s on Wednesday, but could once again be
held down a bit by cloud cover.

Confidence for PM heat indices nearing 100F increases into Thursday
and Friday as the center of the aforementioned upper ridge expands
west into the Ohio Valley. This will place the local area on the
northern fringe of the heat dome with less cloud cover and highs
well into the 90s. No changes were made to heat related headlines
through Friday.

Relief to temps/humidity more common for June still appears likely
Sunday into early next week as an upper level trough and attendant
sfc cold front swing east through the Upper Midwest and Great Lakes.
The best chance for convection will be along the cold front on
Sunday, though cannot rule out scattered convection Saturday
afternoon/night given the potential for any pre-frontal features to
sag south into an unstable/hot airmass. This and any cloud cover
will determine if headline worthy heat indices will extend into
Saturday as well. Confidence was too low to extend heat headlines
into the weekend as a result.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 614 PM EDT Tue Jun 18 2024

Only minimal changes needed for the 00Z TAFs. VFR ceilings are
expected to prevail through the entirety of the TAF forecast
period, with winds quickly diminishing after sunset tonight.
Southerly winds have been gusting 20 to 25 knots today and will
continue to do so until about 02-04Z. Once the sun sets, winds
will become very light at about 5 knots overnight. Calm, hot,
and humid conditions persist again Wednesday with cumulus
clouds expect to bubble up by the afternoon.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Heat Advisory until 8 PM EDT /7 PM CDT/ Friday for INZ005>008-
     012>015-020-022-023-103-104-116-203-204-216.
     Excessive Heat Warning until 8 PM EDT Friday for INZ009-017-
     018-024>027-032>034.
     Air Quality Alert from midnight Wednesday night to midnight
     EDT Thursday night for INZ020.
     Air Quality Alert from 11 PM this evening to 11 PM CDT
     Wednesday for INZ103-203.
OH...Excessive Heat Warning until 8 PM EDT Friday for OHZ001-002-
     004-005-015-016-024-025.
MI...Heat Advisory until 8 PM EDT Friday for MIZ078>081-177-277.
     Air Quality Alert from midnight tonight to midnight EDT
     Wednesday night for MIZ177-277.
MARINE...None.

&&

$$

DISCUSSION...Steinwedel
AVIATION...Johnson