710
FXUS63 KIWX 150000
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
800 PM EDT Sun Jul 14 2024

.KEY MESSAGES...

- There are periodic chances for showers and storms (20 to 60%) tonight
  through Tuesday night, with one or more rounds of strong to
  severe storms possible during this timeframe.

- Best chances for severe weather will be on Monday late
  afternoon into the evening, when there is an Enhanced Risk
  (level 3 of 5) for severe weather. Damaging winds 60-75+ mph
  and a few tornadoes possible.

- Alongside the severe threat, flooding is also possible in any
  storms, especially in areas that remain saturated from the
  remnants of Beryl.

- Hot and humid Monday, depending on storm coverage, timing, and cloud
  cover. Afternoon heat indices mid 90s to near 100 degrees.

- Cooler, drier weather is anticipated midweek through next
  weekend.

&&

.DISCUSSION...
Issued at 231 PM EDT Sun Jul 14 2024

Multiple rounds of storms are expected over the next 48 hours, with
one or more rounds being strong to severe. Our CWA is on the
periphery of a building ridge in the Plains, and with northwest
steering flow, this puts the Upper Midwest and Great Lakes regions
in a very favorable zone for storms. Several strong shortwaves that
drop into the Midwest in the coming days may help to sustain several
rounds of MCSs. SPC has us in a Day 1 Slight Risk (level 2 of 5), a
Day 2 Enhanced Risk (level 3 of 5), and a Day 3 Marginal Risk (level
1 of 5). The next 48 hours come with a lot of uncertainty in the
coverage, timing, and number of rounds of storms. Alongside the
severe threat, flooding is also possible with any of the MCSs. Many
locations, especially in the Wabash and St Joseph river basins, have
had 5 to 8 inches of rain this week. With saturated ground and
elevated rivers, it won`t take much for these areas to experience
more flooding. High PWATS of  and the potential for storms to
backbuild along outflow boundaries has me concerned about flooding
potential in addition to the multi-day severe threat.

As the initial round of storms today has now exited the area,
dry conditions will return for the next several hours before yet
another chance for storms. Hi-res models have yet to come to a
strong consensus, but it is looking more plausible (medium
confidence) that an MCS will develop over eastern IA/northwest
IL late this evening and move eastward into our CWA between 10
PM to 12 AM EDT tonight. With ample MLCAPE 2000-3000 J/kg and
DCAPE 1000+ J/kg, damaging winds would be the main hazard
overnight. The greatest confidence in severe weather is along
and west of US 31, as the MCS should weaken as it pushes
eastward overnight.

There is increasing confidence in severe weather Monday late
afternoon and into the evening. SPC has introduced 30% hatched wind
probabilities into the Day 2 Outlook, prompting the need for a
Enhanced Risk (level 3 of 5) upgrade across northern Indiana.
Another progressive MCS/bow-echo could develop upstream of a much
more favorable environment and ride along the highest theta-e axis
through southern WI, northern IL, and into northern IN. Strong
buoyancy, increasing vertical shear, and favorable thermodynamics
(dewpoints low 70s, highs upper 80s to low 90s, MLCAPE of 4000
to 5000 J/kg) could certainly yield a high-end impact damaging
wind event. A derecho is possible with organized damaging winds
60-75+ mph and a few tornadoes possible.

Heat and humidity build on Monday, with highs in the low 90s and
heat indices potentially in the upper 90s to low 100s. Heat Advisory
headline could be needed. Uncertainty in storm coverage, timing, and
lingering cloud cover could all result in temperatures being lower
than what is currently forecasted.

An upper level trough will pivot through the Great Lakes on Tuesday,
resulting in chances for storms ahead of and along the front. A
continental, cooler airmass from Canada will sink south midweek,
resulting in seasonable highs in the 70s, a stark decrease in
humidity, and dry conditions.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 755 PM EDT Sun Jul 14 2024

Temporary stabilizing effects from earlier convective complex
have allowed for mainly dry conditions through early this
evening. However, stronger westerly upstream flow will
overspread northern Indiana over the next several hours in
advance of next upstream mesoscale convective vortex across NW
Illinois. This will allow for recovery in instability via
advection. Convection has already initiated with this feature
with moderate to strong instability across these areas. This
showers and storms should encounter some instability gradient as
they reach into northwest Indiana, but localized stronger
shear/forcing with the small scale vort max should allow for
another round of thunderstorms at the terminals in the 04Z-08Z
timeframe. Strongest gusts to around 40 knots expected at KSBN
with these potential storms with brief IFR vsbys possible. These
showers and storms should wane late tonight, with next upstream
possible convectively enhanced short wave arriving toward end of
this valid period with more thunderstorm chances. Given a good
deal of uncertainty at that forecast distance in this pattern,
will omit mention in TAFs for now.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Flood Watch from 11 PM EDT /10 PM CDT/ this evening through
     late Monday night for INZ012>015-020-022-103-104-203-204.
OH...None.
MI...Flood Watch from 11 PM EDT this evening through late Monday
     night for MIZ078-177-277.
     Air Quality Alert until midnight EDT tonight for MIZ177-277.
MARINE...None.

&&

$$

DISCUSSION...Johnson
AVIATION...Marsili