487
FXUS63 KIWX 180617
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
217 AM EDT Tue Jun 18 2024

.KEY MESSAGES...

- There are nearly daily low chances for showers and
  thunderstorms this week, especially in the afternoon and
  evening hours. Expect coverage to be widely scattered.

- Excessive Heat Warnings and Advisories are in effect due to
  an extended period of hot and humid conditions. Max heat
  indices this week will range from around 95 to 105, with the
  highest values in the warning area and in urban locations.
  Overnight lows in the 70s will provide little relief from the
  heat. High temperatures will be in the upper 80s and 90s.

&&

.UPDATE...
Issued at 933 PM EDT Mon Jun 17 2024

Surface dewpoints climbed to around 70F this afternoon yielding
heat indices solidly around 1-day advisory criteria of 100F and
even 1-day warning criteria of 105F in a few spots (see latest
PNS). Based on today`s performance and the latest runs of the
ECMWF showing even hotter temperatures to end the week, decided
to go ahead and extend the advisory to match the timing of all
of our neighboring offices. It is possible the warning may need
to be expanded later this week depending on how Tue/Wed evolve
but that can be a simple upgrade as needed later this week
if/when confidence increases.

&&

.DISCUSSION...
Issued at 230 PM EDT Mon Jun 17 2024

Ridging over the east coast of the CONUS along with troughing over
the west coast allows plenty of warm air and moisture to stream into
the area over the next few days at least into Saturday. Initial
placement of height anomalies is farther east in this forecast
period, but they do begin to shift more westward especially as we
head into the latter part of the work week, which indicates the
better chances for warmer temperatures and perhaps to be unscathed
by any chances for pop showers/storms during that time frame. With
the height anomalies farther east to begin the period, a vort max is
able to ride northward along its periphery and provide a chance for
showers and thunderstorms after midnight tonight into Tuesday
morning. There is some possibility for left over debris clouds that
could cut into how warm temperatures become on Tuesday, but am still
expecting a thorough stream of moist dew points into the area with
~70F degree dew points still on the table. Additionally, should the
clouds begin to break up, it wouldn`t take very long to heat back up
to advisory threshold during the late morning/afternoon time frame.
As such, have decided to hoist the advisory for areas north of US-24
and keep the warning for areas south of US-24 for Tuesday,
especially with the limited cooling off of temperatures overnight as
a result of the continued upper 60s to 70F degree dew points. One
wrinkle in this would be if dew points stay below the upper 60s from
maybe if more afternoon mixing takes place if clouds break up again.

As mentioned before, the height anomalies begin working into the
area on Wednesday and the weakening/more limited shower chances
begin to increase confidence on the mid to late week heat being the
most intense. It still looks like areas west of IN-31 have the
lowest chance to see hot heat indices based on dew points
falling back into the mid to upper 60s. Will still continue the
excessive heat warning south of US-24 where the highest heat
looks to reside during the late week period. What to do with
the areas north of US-24 will be the main question moving
forward, but continued minApT values around 75 still likely keep
the "not enough nighttime recovery" impact in play. Even still,
am not quite ready to extend the heat advisory possibility
through the period with the chance that models aren`t capturing
some vort max correctly that could bring a chance for
showers/ clouds.

There is some indication that the ridge may be able to break down
either Sunday or Monday as a cold front pushes through in concert
with a deepening upper low moving across the Northern Great Lakes/
southern Canada area. This would bring more comfortable air in for
the first half of next week. High temperatures Sunday and Monday are
in the mid 80s with dew points stepping down into the mid 60s on
Sunday and down into the 50s on Monday.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 114 AM EDT Tue Jun 18 2024

Hot and humid flow will continue through the TAF period. Daytime
wind gusts at SBN may exceed 20 kts with a little tighter
gradient there. Kept showers/storms out for now due to
uncertainty but can not rule out a TEMPO or VCNTY shower/storm
at some point today.

&&

.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.
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.
MARINE...None.

&&

$$

UPDATE...AGD
DISCUSSION...Roller
AVIATION...Skipper