775
FXUS63 KIWX 161129
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
729 AM EDT Sun Jun 16 2024

.KEY MESSAGES...

-An excessive heat watch is in effect for portions of Northern
 Indiana and Northwest Ohio from Monday morning into Friday
 evening. Heat indices around 100 degrees are expected through
 the week. High temperatures will be in the upper 80s and 90s.

-There are low chances for intermittent showers and
 thunderstorms this week, mainly in the afternoon and evening
 hours. Severe weather is not expected.

-Today will be dry with highs in the upper 80s and low 90s.
 There are low chances for showers and thunderstorms tonight in
 Michigan counties.

&&

.DISCUSSION...
Issued at 444 AM EDT Sun Jun 16 2024

Todays main focus is the prolonged period of heat, which will last
at least through Friday, with hints of highs in the 90s for
Saturday/Sunday as well. Heat indices during peak heating each day
are expected to linger around 100 degrees for the most part, with
locations in NW Ohio/NE IN likely to see the most oppressive
heat/humidity.

Upon collaboration with the neighbors, opted to issue an excessive
heat watch for a majority of the forecast area where I am feeling
about 50% confident we may reach warning criteria in terms of Heat
index (HI) values (105 or greater)-especially in NW Ohio. However,
the main reason for the watch is the extended period of HIs around
100 degrees (warning criteria includes an exception for HIs around
100 degrees if they occur for 4 or more consecutive days). I am
around 80% confident that we`ll see values of at least 95-100
degrees through Friday, possibly even lasting beyond the headline
into early next week (depending on the model).

Why not the whole CWA? I have lower confidence further west
(especially southwest) because these areas look to be impacted most
by convection. The upper level ridge shifts slowly southeast through
the week, making us more and more susceptible to shortwaves rounding
the ridge. Further west I have more frequent chances for rain/storms
and thus greater cloud cover, which could limit things later on in
the week. I suspect that they may need to issue a heat advisory for
Monday in some areas outside of the current watch, but by Tuesday
values fall closer to the low 90s. Because most of the convection is
tied to daytime heating with no real flow beyond the occasional
shortwave, expect more isolated to scattered coverage mainly tied to
the afternoon/evening hours. This also makes pinning any specific
timing/location down for precipitation difficult, which really shows
in the wide variety of model solutions this week. Tried my best to
limit pops to the best forcing and diurnal times, but still a ton of
uncertainty. That being said, still issued for Michigan counties and
further into IN because values linger between 95-100 fairly
consistently through the week. It`s totally possible we end up
running with an advisory vs a warning-depending on how the
precipitation chances look to evolve. Have a mention in the
HWO for counties outside of the watch area for now.

In terms of models, it seems like the ECMWF/UKMET/Canadian have been
consistently warm through the past few runs (including 00z ECMWF),
whereas the GFS continues to be more consistently cooler
(significantly). For example, on Wednesday the ECMWF has highs in NW
OH around 94-96 degrees, but the GFS has highs in the upper 80s and
low 90s. Opted to stick with the higher end of guidance given the
pattern and consistency, but this is part of why we are just doing a
watch vs a warning at this point. The other thing is that with the
increased moisture advection into the area through mid week, heat
indices may still be in the mid-upper 90s.

The bottom line is this: It`s going to be hot. The time is now
to prepare: be sure your a/c is working or know local cooling
shelters, make a list of friends and family to check on and help
them prepare, and possibly reschedule outdoor work or events.
Make sure if you must work outside that you take breaks
frequently and drink a lot of water.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 725 AM EDT Sun Jun 16 2024

VFR Conditions are expected at the TAF sites, with mainly high
level cirrus and some mid level clouds to contend with. The only
exception would be some of the high resolution models are
starting to suggest that we could get passing showers/storms
between 5 and 9z. Confidence is not terribly high with this, but
if it does occur we could see a brief drop to MVFR/IFR. Added a
prob30 group to KSBN to account for the potential. Otherwise,
KFWA remains dry. Light east-southeast flow will become more
south-southwest through the period, with gusts to around 22 kts
at KSBN this afternoon.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Excessive Heat Watch from Monday morning through Friday
     evening for INZ005>009-014-017-018-024>027-032>034-104-
     116-204-216.
     Air Quality Alert until midnight EDT tonight for INZ020.
OH...Excessive Heat Watch from Monday morning through Friday
     evening for OHZ001-002-004-005-015-016-024-025.
MI...Excessive Heat Watch from Monday morning through Friday
     evening for MIZ078>081-177-277.
MARINE...None.

&&

$$

DISCUSSION...MCD
AVIATION...MCD