183
FXUS63 KIWX 171838
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
238 PM EDT Mon Jun 17 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.

&&

.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 /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 120 PM EDT Mon Jun 17 2024

Expansion of a scattered cu field is readily apparent across
much of Indiana as convective temperatures have been met in an
unstable atmosphere. While VFR conditions are expected to
dominate most, if not all, of the forecast there are a few
challenges that need to be monitored that are not necessarily
captured in the TAFs.

Any subtle features passing through the area could easily pop a
shower or thunderstorms at either site this afternoon and early
evening. The greatest concern at this point is an area of
persistent convection across east central IL, approaching KRZL.
While trends suggest this may stay just west of KSBN, outflow
boundaries from the convection could easily move east and
provide lift for additional showers/storms. A few of the models
actually key in on the KSBN area for one or more rounds of
storms late afternoon into the early evening, but no consistent
signals remain. For now have opted to go VCSH at both sites with
timing and duration of any shower/storm difficult to capture at
this point.

While loss of heating will bring any precip chances to an end
this evening, a weak disturbance, currently producing widely
scattered showers across portions of Kentucky, will drift north
late tonight into Tuesday morning. Think there will be at least
an increase in mid/high clouds but some question as to chances
for showers with this feature. Given the low confidence, have
introduced a broken high cloud deck for the time being late
tonight and defer to later forecasts for possible inclusion of
showers/storms.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Heat Advisory until 8 PM EDT /7 PM CDT/ Tuesday 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 Tuesday for MIZ078>081-177-277.
     Air Quality Alert until midnight EDT tonight for MIZ078-177-
     277.
MARINE...None.

&&

$$

DISCUSSION...Roller
AVIATION...Fisher