307
FXUS63 KIND 110101
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
901 PM EDT Fri May 10 2024

.KEY MESSAGES...

- Increasing clouds tonight, with a brief period of rain overnight
- Breezy on Saturday
- Showers and storms return Monday into Monday night
- Near normal temperatures for next week

&&

.FORECAST UPDATE...
Issued at 901 PM EDT Fri May 10 2024

Forecast is in very good shape this evening, with no substantive
change required.

A compact upper level shortwave and weak surface boundary will sweep
through the area late tonight, with a band of showers along it.
Rainfall will be light and fairly quick, with the band clearing the
area shortly after daybreak. Going forecast handles this very well
and was minimally adjusted.

Low temperatures also are tracking well with latest guidance and
were left in the lower 50s.

&&

.SHORT TERM (This evening through Saturday)...
Issued at 257 PM EDT Fri May 10 2024

Rest of This Afternoon...

Cumulus will continue across central Indiana through much of the
afternoon. Satellite has been showing some enhanced cumulus as well,
so still wouldn`t rule out an isolated shower. However, odds remain
too low to mention in the forecast.

Tonight...

Cumulus will dissipate with mainly some patchy mid and high clouds
around this evening, with high pressure ridging into the area.

Overnight, an upper shortwave will move through. A surface cold
front will accompany the shortwave. Moisture will be confined to
mainly north of the area, but there will be enough for the system to
produce up to around a tenth of an inch in the far north. However,
lack of moisture to the southwest should keep the far southwest part
of the area dry.

Will go with likely PoPs at some point overnight in the north,
tapering to dry PoPs in the far southwest.

Temperatures will dip into the lower 50s for lows tonight.

Saturday...

The vast majority of the forcing will be east of central Indiana by
the start of the Saturday period (12Z, 8AM EDT). Will only go with
some chance PoPs far east through mid-morning.

Cold advection will aid in mixing on Saturday, bringing wind gusts
up to around 30 mph at times. Some cumulus will form in the cold
advection, but skies will still be partly to mostly sunny.

Some models are keeping a surface trough across the northeast
forecast area Saturday afternoon, with a few even generating rain
with it. However, looking at ensembles, these seem like a low
probability. Will keep it dry but increase sky cover some in the
northeast Saturday afternoon.

Even with cold advection, temperatures will peak in the upper 60s to
lower 70s.

&&

.LONG TERM (Saturday night through Friday)...
Issued at 257 PM EDT Fri May 10 2024

An active weather pattern continues into next week with multiple
chances for additional rain and thunderstorms. It won`t be a
complete washout of a week though with a couple dry days in between
systems. While there will be rain and storm chances throughout the
extended, the threat for severe weather appears much lower than it
has been over the past week.

Sunday...

High pressure sets up just south of the region late Saturday night
while upper ridging builds in through Monday resulting in a brief
period of drier and warmer weather across the Ohio Valley.
Subsidence under the high in addition to warm air advection through
the column will result in a beautiful, warm day across the entire
region. Model soundings indicate a well mixed boundary layer and
steep low level lapse rates leading to highs well into the 70s and
potentially reaching 80 for portions of SW Indiana.

Monday through Tuesday...

Another warm day expected Monday; however an approaching trough and
associated surface low over Kansas will bring the next chance for
rain across the region. Increasing moisture advection through the
column and lift ahead of the system will result in increasing clouds
Monday with rain beginning to develop during the afternoon and
evening hours. Currently some discrepancies among guidance with
timing of arrival for precipitation with the GFS bringing in rain by
early Monday afternoon and the EC holding off until Monday night.
Will have to watch how much dry air mixes down to the surface Sunday
and how quickly the column saturates on Monday. Historically, models
are too quick to saturate the column after a few days of dry weather
and bring in rainfall too early at times. This would also affect
high temperatures, with a later arrival of rain allowing for more
daytime heating. Despite lower confidence in rainfall chances Monday
afternoon, high confidence exists in showers Monday night into
Tuesday morning as the surface low pushing into Southern
Missouri/Illinois on Tuesday.

Model soundings show very skinny, elevated CAPE Monday night with
better instability values on Tuesday in the immediate vicinity of
the surface low. Lightning will likely be few and far between
initially with the best chance for any thunder and lightning closer
to the surface low Tuesday afternoon in South Central Indiana.

Model soundings show PW values rising to between 1.25 and 1.50
inches late Monday night into Tuesday with deep moisture present
throughout the depth of the column. The setup supports the potential
for pockets of heavy rainfall, particularly on Tuesday with any slow
moving convection. Ensemble means show low probability for greater
than an inch of rainfall with 90th percentile QPF totals ranging from
1.00" to 1.30" across Central Indiana. It is likely lower resolution
guidance is not taking into account the potential for heavier
convection. So values over an inch appear certainly probably in this
scenario, especially for areas that get repeated heavier showers.
South Central Indiana looks to have a better potential for those
higher rainfall totals being closer to the low and having better
moisture advection and higher instability values.

Despite increased clouds, warm air advection ahead of the system
will support highs in the 70s on Monday, with the potential for a
few areas to near the 80 degree mark if rain holds off until the
evening and nighttime hours. Expect Tuesday to be a little cooler in
the mid 60s to lower 70s due to more widespread showers and storms.

Wednesday through Thursday...

Troughing begins to slide eastward on Wednesday while ridging builds
back in over the Midwest. With high pressure settling in from the NW
Wednesday morning and the trough still influencing weather locally,
low stratus may stick around through the first half of the day as
moisture is trapped under a subsidence inversion. Expect a drying
trend through the day Wednesday persisting into Thursday with highs
still near to above average in the low to mid 70s. High pressure
centered over Southern Canada and the Northeast CONUS will result in
another mainly dry day on Thursday for Indiana.

Friday into Next Weekend...

Another deep trough and potent storm system is expected to develop
and push into the region sometime this weekend bringing another
round of unsettled weather conditions. Longer range guidance
diverges quite a bit on the exact evolution of the system, timing,
and track. Despite lower confidence in details, ensembles have been
consistent in showing signals for a strong storm system during this
time frame potentially leading to another round of showers and
thunderstorms and cooler weather on the backside of it. Will be
watching this timeframe closely through the week as details become
clearer on the evolution of things and associated impacts.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 620 PM EDT Fri May 10 2024

Impacts:

- Wind gusts 23-27KT Saturday from 290-310 degrees.

- Brief period of showers late tonight/around daybreak Saturday at
  LAF/IND.

Discussion:

A broken high based cumulus field will dissipate somewhat this
evening, though midlevel clouds may make up the difference prior to
the passage of a compact system late tonight that looks to bring a
quick band of showers to primarily LAF/IND. Cannot rule out brief
visibility restrictions in the showers, but these are too low
probability/transient for inclusion at this time. Ceilings should
largely remain VFR.

During the day on Saturday, a few high based cumulus will remain,
along with a bit of high cloudiness. The primary concern will be
winds, with sustained winds of 15-18KT gusting to 23-27KT from
around 290-310 degrees from mid morning through the evening. These
gusts will dissipate in typical diurnal fashion near sunset.

&&

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

&&

$$

UPDATE...Nield
SHORT TERM...50
LONG TERM...CM
AVIATION...Nield