799
FXUS63 KIND 151900
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
300 PM EDT Wed May 15 2024

.KEY MESSAGES...

- Scattered showers and a few rumbles of thunder through early
  evening across the south.

- Fog possible overnight to early tomorrow morning.

- Rain and storm chances return at times late Thursday through
  Saturday.

- Above normal temperatures for this weekend through the middle of
  next week.

&&

.SHORT TERM (This evening through Thursday)...
Issued at 259 PM EDT Wed May 15 2024

The low pressure system that has brought ample rain since yesterday
is slowly making its way eastward leaving scattered showers across
the southern portion of the forecast area this afternoon. The rain
should fully exit central Indiana by late this evening. Brief upper
ridging will then move through, allowing a quick break in
precipitation before the next system moves in for the end of the
week.

Clouds will likely stick around for much of the night tonight with
model soundings showing persistent saturation at the top of the
boundary layer, but will have to keep an eye out for any locations
that do begin to clear as the recent rains will help to
supersaturate the low levels and may allow for some fog formation.
The low confidence that things will clear out enough for widespread
fog makes a Dense Fog Advisory seem a bit overdone at this time, but
will have to monitor things going into this evening.

Warmer temperatures are expected tomorrow with highs back into the
mid 70s to near 80. Another upper short wave behind the ridging will
bring additional rain later in the day tomorrow. Time of arrival is
still not clear but could arrive from the west as early as the 2 to
8pm timeframe.

&&

.LONG TERM (Thursday night through Wednesday)...
Issued at 259 PM EDT Wed May 15 2024

Thursday night through Saturday...

An approaching southern stream shortwave will keep elevated rain or
storm chances in the forecast towards the end of this week. The best
chance for rain looks to be late Thursday night through Friday
evening when the best forcing/moisture move across the Ohio Valley.
Anomalous moisture and warm rain processes could potentially lead to
another round of locally heavy rain. Considering grounds are already
saturated from heavy rain over the past 24 hours, there are elevated
flooding concerns if this scenario plays out. The one caveat to this
is that a strong MCS will likely move across the Gulf coast states
late Thursday into Friday morning which could limit deeper moisture
return further north. A few models have recently trended lower on
precipitation amounts for this reason.

Rain chances persist into Saturday as the aforementioned system
should still be centered near the Ohio Valley. Confidence is
somewhat limited on how long precipitation lingers Saturday due to
model discrepancies. The GFS is noticeably slower compared to other
guidance keeping elevated rain chances into Saturday night. Decided
to stick with the larger suite of models showing a more progressive
pattern with the system departing Saturday evening and decreasing
rain chances overnight.

Sunday onward...

Brief ridging building in Sunday should provide mostly dry
conditions, but can`t rule isolated diurnal convection, mainly over
SE counties as there could still be sufficient PBL moisture in
place. Confidence decreases some towards next week with model
solutions diverging. However, guidance is in general agreement that
upper level pattern switch from split-flow to more full-latitude
troughing across the western CONUS. The pattern looks to remain
active with multiple embedded shortwaves potentially moving through
next week. Look for rain chances to return late Monday PM and
persist through at least midweek.

At least a low end severe weather threat looks possible
Tuesday/Tuesday night as increasing instability and deep-layer shear
ahead of an approaching surface low could support organized
convection. CIPS Analogs and CSU machine learning are showing
increasing severe weather probabilities during this period. It is
still too early for exact details, but this will be monitored
closely over the coming days. Strengthening southerly flow should
help to warm temperatures well into the 80s early next week.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 1259 PM EDT Wed May 15 2024

Impacts:

- MVFR/TEMPO IFR conditions through the afternoon.

- IFR or worse visibilities developing late tonight in fog.

- A few lingering showers, possibly a thunderstorm.

Discussion:

As low pressure slowly departs the area, low clouds remain expansive
across the region, with widespread MVFR and pockets of IFR. Will
carry prevailing MVFR/TEMPO IFR ceilings at all sites through about
22Z, with VFR thereafter.

A few showers are lingering across the area, and an isolated
thunderstorm cannot entirely be ruled out, but will be far too low
probability for a mention. Will carry VCSH for the next few hours to
account for showers.

Clearing skies and lighter winds tonight will promote fog
development, with IFR visibilities likely everywhere. Dense fog is a
possibility, and will hint at this with a BCFG mention. Could easily
see 1/4-1/2SM visibility for a time near daybreak, given
preconditioning of widespread significant rainfall in the past 24-36
hours.

Fog will dissipate in typical diurnal fashion tomorrow morning, with
a SCT-BKN low end VFR cumulus deck likely to develop on Thursday.

Winds will be around 10-11KT or less throughout the period, likely
becoming light and variable or calm overnight tonight. Winds will
primarily be northerly early, becoming southerly during the day on
Thursday.


&&

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

$$

SHORT TERM...KF
LONG TERM...Melo
AVIATION...Nield