379
FXUS63 KIND 240705
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
305 AM EDT Fri May 24 2024

.KEY MESSAGES...

- Patchy fog possible through daybreak

- Isolated thunderstorms possible this afternoon with more
  widespread coverage this evening/overnight. A few storms may be
  severe with strong gusty winds.

- Showers and thunderstorms likely on Sunday. Severe thunderstorms
  are possible.

- Temperatures will return to near normal next week

&&

.SHORT TERM (Today and tonight)...
Issued at 305 AM EDT Fri May 24 2024

Mostly quiet weather conditions are expected for much of the day
with ridging centered over the Ohio Valley. At the surface, weak
high pressure is aiding in optimal conditions for fog development
with mostly clear skies and light winds. Look for any patchy fog to
quickly mix out after sunrise. Increasing southerly flow ahead of an
approaching system will lead to increasing southerly flow during the
day leading to warmer temperatures in the mid 80s.

While much of the day should remain quiet, increasing moisture could
support isolated diurnal thunderstorms across W/SW portions of
central IN. Forecast soundings show deep-layer shear is weak which
suggest severe weather is unlikely. More widespread convection is
likely during the evening/overnight hours as most CAMs show a cold
front with an ongoing MCS across eastern Nebraska propagating
towards the Great Lakes Region. The main portion of this MCS may
stay to the north of the area, but low-level convergence along the
front will be sufficient to allow for scattered thunderstorm
development in a very unstable airmass across IL. New convective
development should then grow upscale as it progresses eastward.

CAMs are still not in great agreement regarding timing of the storm
complex moving into the area. In addition, there remains uncertainty
in convective organization. The main reason for this being that
effective bulk shear will be relatively weak as the line of storms
outpaces the stronger mid-level flow over IL/WI. However, the
favorable thermodynamic environment combined with weak but
sufficient deep-layer shear for loosely organized storms supports an
isolated damaging wind gust threat. Locally heavy rainfall is also
possible. The convective evolution of this system across IL will be
monitored closely later today as there is still a chance for a more
organized MCS to develop.

Given the latest trends in CAMs having a weaker MCS/cold pool, the
timing of best rain chances appears to be this late this evening
into tonight. A stronger cold pool would lead to a sooner arrival of
precipitation so this may need to be updated in future updates.
Expect temperatures generally in the upper 50s to low 60s overnight.

&&

.LONG TERM (Saturday through Thursday)...
Issued at 305 AM EDT Fri May 24 2024

The main concern for the long term will be the potential for a
severe weather outbreak including all severe weather types and heavy
rain and localized flooding Sunday and Sunday night.

Saturday through Sunday night...

The long term will start off less ominous with a cold front
sweeping east into eastern Indiana by daybreak Saturday. Behind this
front, ridging will build in late in the day and night which will
bring a brief respite to the convection over western sections and
all of central Indiana Saturday afternoon and into the night.

However, a Northern Plains trough will dig southeast and spin up a
surface low that will lift northeast across the Missouri Valley
Sunday and into the western Great Lakes Sunday night. An associated
warm front will lift northeast across central Indiana Sunday morning
and a cold front will then sweep east across the area Sunday night.
Upstream storms, potentially in the form of an MCS will likely move
through Sunday morning near the warm front and then re-development
will likely occur Sunday afternoon and night in the warm sector,
along and ahead of the quickly advancing cold front. Exact timing is
still too difficult to pinpoint all the way out to Sunday but what
is known is the combination of a potent mid to late Spring System,
potentially very unstable atmosphere along with strong 0-3km shear
present a clear severe weather outbreak possibility Sunday and Sunday
night. Model soundings are suggesting sfc based CAPEs in excess of
2000 J/kg and 0-3km Bulk Shear of 40-50 knots along with long curved
hodographs and 0-3km SRH in excess of 500 m2/s2 by Sunday afternoon.
Any discrete storm, either early near the warm front or later in the
warm sector, ahead of the cold front, could potentially develop
rapidly and rotate. Upper level winds will also steer these storms
along rather quickly to near 40 mph.

In addition to severe weather, heavy rain and localized flooding
will also be a concern as PWATs could be as high as 1.8 inches,
which is the max moving average for late May for the nearby ILN
upper air site.

Went with 30 to 50 percent morning PoPs reflecting the possibility
some of the slower end models verify and also with uncertainty if an
MCS will in fact be fully in tact and then 70 to 90 percent PoPs for
the afternoon and night when instability will be increasing and
later the cold front will be getting closer.

The southerly low level flow will also result in temperatures some 5
to 10 degrees above normal with highs in the lower to middle 80s
looking reasonable.

Memorial Day through Tuesday...

A pair of upper waves will drop down from the northwest Memorial Day
and Tuesday. Both of these will have enough moisture and instability
to work with to be able to generate at least scattered convection,
especially during the peak heating afternoon hours. Temperatures
will likely be closer to normal in the wake of the Sunday night cold
frontal passage which translates to afternoon highs mostly in the
70s.

Tuesday night through Thursday night...

Look for mostly dry and seasonable weather the remainder of the long
term as ridging builds in overhead.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 140 AM EDT Fri May 24 2024

Impacts:

- Predominately VFR conditions for much of today, Small chance of
  MVFR or worse conditions in fog or stratus 09z-13z, mainly near
  BMG/IND

- Thunderstorms with brief MVFR or worse flying conditions possible
  after 00z this evening

Discussion:

Hi-Res models suggest MVFR or worse fog is possible toward
daybreak, mainly near BMG/IND. Otherwise, ridging will result in
predominately VFR flying conditions until this evening and
overnight when a cold front will approach and interact with a very
warm, moist and unstable airmass to trigger scattered to numerous
thunderstorms. Some of these may be strong or severe with
localized gusts to 50 knots possible and frequent lightning.

Winds will be light to calm through daybreak before increasing to
around 10 knots during the day. Expect wind direction to be out of
the south.


&&

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

$$

SHORT TERM...Melo
LONG TERM...MK
AVIATION...Melo