660
FXUS63 KIND 081003
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
603 AM EDT Mon Jul 8 2024

.KEY MESSAGES...

- Partly Cloudy Today; Chances for afternoon showers/storms in the
  Wabash valley; Warm

- Increasing clouds overnight with shower/storm chances over
  mainly Western Central Indiana.

- Remnants of Beryl may bring isolated tornadoes and flooding Tuesday
  evening through Wednesday morning

- Tornado threat highest south of I-69, flood threat greatest to the
  north

&&

.SHORT TERM (Today and tonight)...
Issued at 241 AM EDT Mon Jul 8 2024

Surface analysis early this morning shows a strong and large area of
high pressure centered over NY. A ridge axis extended SW from this
high to southern Indiana and Western KY.  Winds across Central
Indiana were light and variable to calm. Water vapor imagery showed
a deepening trough axis over the northern plains states, stretching
southwest to NB and eastern CO. This was resulting in a SW flow of
moisture aloft, streaming from the southern plains toward Central
Indiana. An upper low was found over eastern MN. GOES16 shows mostly
clear skies over Indiana, however mid and high cloud were found over
MO and IL streaming northeast toward Indiana.

Today...

The upper trough axis over the plains states is expected to deepen
and begin to push east toward the Mississippi Valley. This will keep
a warm and humid SW flow in place across Central Indiana. Meanwhile
Beryl is expected to make landfall and quickly begin to turn north
and northeast within the flow ahead of this trough and begin to push
toward Central Indiana. That, however, is more of the story for
Tuesday. Meanwhile at the surface the strong surface ridging from
the high to the northeast is expected to remain in place, providing
relatively calm but warm summer weather today. Forecast soundings
show a dry column today, with a weak mid level inversion that
appears to weaken as the day progresses. HRRR suggests that as the
upper trough nudges eastward, convection over IL late in the
afternoon may reach the Wabash Valley after 21Z. Thus will keep a
dry forecast for most of the area today. However by late afternoon
introduce some low chance pops in far western Central Indiana for
this possible convection. Given the little change in the overall air
mass, will trend highs at or above persistence, in the upper 80s.

Tonight...

A change in our weather is expected to begin tonight. The protective
surface high pressure is expected to push father east, while the
trough axis to the west aloft will continue nudging toward Central
Indiana. Through the night, moist SW flow aloft is seen trending
forecast soundings toward a more saturated column. A fully saturated
column is not reached until Tuesday, but weak disturbances within
the SW flow aloft along with a warm and humid air mass results in
convection upstream drifting toward Central Indiana overnight. HRRR
suggests areal coverage of these showers and storms to be rather
limited, but still enough elements will be present to necessitate
showers and storm chances, particularly across the western parts of
the forecast area. Given the expected clouds and warm air mass, lows
near 70 or the lower 70s will be expected.

&&

.LONG TERM (Tuesday through Sunday)...
Issued at 241 AM EDT Mon Jul 8 2024

Tuesday and Wednesday.

The main focus and hazardous weather in the long term period will be
focused Tuesday evening through Wednesday morning as tropical
moisture from the remnants of Beryl impact Indiana.  There remains
quite good model agreement in the track and timing of the remnants
with the latest set of model guidance with the final details likely
to come into alignment after landfall towards daybreak today.

This system`s hazards will be two-fold.  The first and primary
threat will be the potential for tornadoes and damaging winds within
the warm sector of the final track which currently looks to set up
along and south of the I-69 corridor Tuesday evening into the early
overnight hours ahead of the surface low.  Model soundings show good
turning in the lowest 3km with 0-1 SRH in excess of 300 m^2/s^2
through 06Z Wednesday which would be more than enough to allow for
brief lower end tornadoes.  With the tropical nature, lapse rates
will be moist adiabatic which will limit the instability and higher
end threat, but with the robust low level shear, the threat is
definitely there for brief, low-end tornadoes.

The second threat will be pockets of flooding. The combination of
warm temperatures aloft which will make this a primarily warm rain
process and PWATs  near climatological records will allow for a very
efficient rain process with brief periods with rain rates of 1-2
inches per hour likely. The heaviest rain is expected just to the
northwest of the surface low which currently looks to impact mostly
Illinois and far northwestern Indiana with the swath of 3-5 inches
of rain currently forecasted to the northwest of the forecast area
along the narrow frontogenetical band, but the peripheries near
Lafayette certainly have the potential to see 2-3 inches.  Areas to
the southeast are more likely to see amounts closer to 1-2 inches
which will certainly help the ongoing drought but shouldn`t be as
impactful. A Flood Watch may end up being needed but with a
combination of recent dryness, MMEFS showing little river reponse on
even the higher end QPF scenarios, and the longer duration of the
event, will hold off for now and highlight via an ESF.

The majority of the impacts from both threats are expected to be
seen from Tuesday evening through daybreak Wednesday with lingering
showers and clouds expected for much of the daytime hours Wednesday.
The impacts from both of the main hazards may shift in the coming
days so be sure to closely follow the forecast as the exact track
details become more clear.

Thursday Through Sunday.

The pattern in the aftermath of the remnants looks fairly benign
with a weaker secondary low pressure behind the main low expected to
pass through during the daytime hours on Thursday which should bring
some light rain and help to keep temperatures cooler ahead of a warm-
up going into the weekend as the ridge tries to build back in.
Outside of the low threat for diurnally driven convection,
precipitation chances look like Friday through Sunday with highs
expected to climb back into the upper 80s to near 90 with dewpoints
climbing to back near 70 by Sunday.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 603 AM EDT Mon Jul 8 2024

Impacts:

- VFR Conditions are expected this period.
- Thunderstorms will be possible at LAF and HUF 21Z-02Z.
- More showers/storms will be possible across all TAF sites aft
09Z

Discussion:

Strong and large high pressure east of Indiana will continue to
control the weather across the TAF sites through mid afternoon. Once
again diurnal CU will be expected this afternoon as convective
temperatures are reached. Due to the developing SW flow aloft, and
mid and upper moisture across the southern plains, some high cloud
cigs will be pushed across the TAF site through the day.

As the upper trough edges eastward, some isolated convection will be
possible within the Wabash Valley late in the afternoon. HRRR
continues to show isolated convection breaking out along the IL/IN
state line, pushing northeast within the flow aloft. Confidence is
low for specific timing, thus have used a VCTS window for now.

Overnight, more showers and possibly isolated thunderstorms will be
possible as the initial surges of moisture from remnants of Beryl
arrive in Indiana.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...Puma
LONG TERM...White
AVIATION...Puma