383 
FXUS63 KIND 132317
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
717 PM EDT Tue May 13 2025

.KEY MESSAGES...

- Periodic shower and thunderstorm chances continue today and 
  Wednesday

- Conditional severe storm threat for Thursday, especially late
  day into Thursday night. Additional severe threat on Friday, 
  primarily south of I-70. 

- Warmest air of the year so far is expected Thursday-Friday...led 
  by near-record highs in the mid/upper 80s Thursday

&&

.SHORT TERM (This evening through Wednesday)...
Issued at 255 PM EDT Tue May 13 2025

A broad upper low is currently cutoff from the jet stream, allowing 
it to meander slowly eastward, although with modest subgeostrophic 
mid level flow still present. A secondary lobe of vorticity has 
developed on the NE side of the parent upper low, allowing for weak 
pressure depletion over N OH/IN and in return backed southerly flow 
across central Indiana. 

Lapse rates within the upper low are around 6.5 C/km through the 
lowest 5km, sufficient enough for modest instability to develop as 
the PBL warms slightly this afternoon. This in combination with 
broad lift below the upper low has lead to numerous showers and 
thunderstorms across the Ohio Valley. Without great shear to keep 
these storms organized, and lack of dry air aloft to locally enhance 
updrafts, the severe threat should be near zero. That said, a 
localized flood threat is present. This is due to the aforementioned 
low level backing of winds, resulting in light southerly flow below 
2km, working somewhat against the light easterly flow aloft. The 
resulting upshear storm motions are between 5-10kt; combined a 
deeply saturated troposphere could result in isolated areas seeing a 
quick 1-2" over an hour or two period of time. 

These storms should begin to falter near dusk as diurnal heating 
wanes and a local surface inversion develops. A weak surface ridge 
has been modeled to develop north of the upper low later this 
evening, of which should scatter the cloud cover some overnight 
across the southern half of the state. To the north however, the 
boundary is expected to linger leaving a highly saturated corridor 
collocated with calming winds overnight. This could allow for some 
patchy fog to develop over portions of northern central Indiana, 
especially over the northern Wabash Valley.

&&

.LONG TERM (Wednesday night through Tuesday)...
Issued at 255 PM EDT Tue May 13 2025

Wednesday through Thursday Night...

The upper low should still be on the eastern edge of the Ohio Valley 
Wednesday, and therefore similar conditions to Tuesday are likely to 
occur. That said, greatest moisture and lift will generally be east 
of central Indiana by tomorrow afternoon helping lead to less 
shower/thunderstorm coverage once proper convective heating occurs. 

A warm front will start to push through Wednesday night ahead of a 
developing negatively tilted trough. This should push some cloud 
cover and potentially a few showers through central Indiana at times 
Wednesday night. By Thursday morning, most of central Indiana should 
be in the broad warm sector with the low level trough 
strengthening to the east. Latest trends have been pushing 
greatest cyclogenesis towards the northern portion of the upper 
wave, resulting in an overall northward trend of greatest forcing.
Still, central Indiana will be well within the warm sector 
throughout the day on Thursday with a strong SW push of warm air. 

This warm air will be relatively dry aloft as it will primarily 
originate from the southern plains. The result will likely be a 
deep EML and associated cap on the environment. This non-uniform 
WAA and cool air above 5km will likely create very steep lapse rates 
between 2-5km, but should remain untapped until late in the day 
with the strong cap present. This long exposure to WAA, and mostly
clear skies, along with deep PBL mixing will push temperatures 
well above normal Thursday afternoon, likely approaching record 
temperatures for 5/14. The main limiting factor to reaching 90 
Thursday will be if diurnal cu will develop keeping the PBL from 
mixing higher. 

Given the very steep lapse rates and modest low level wind profile, 
there is a severe threat for Thursday evening and night. However, 
there is a lot of uncertainty on if the cap will erode enough 
Thursday evening for storms to initiate. If initiation does occur, 
the parameter spacing is sufficient for updrafts to become strong 
and well organized. In the event storms do develop, rotating 
updrafts are possible, and all severe hazards are on the table. The 
most likely time for convective development (if any) would be 
between 7P and 11P EDT). 

With the low pushing off to the north quickly Thursday night, the 
parent trough will remain upstream of central Indiana, leading to 
another threat for convection on Friday. Given the latest suite of 
model guidance, if widespread severe thunderstorms were to occur, 
Friday looks to be the more likely scenario for central Indiana. 
This is due to a weaker cap, and much strong jet dynamics above 5km. 
This biggest uncertainty at this point is how far north the 
instability will reach, with the ensemble variability randing from 
just north of the I-70 corridor to the Ohio River. 

Following the MCS passage on Friday, weak mesoscale high pressure 
should form in its wake, resulting in mostly dry weather on 
Saturday. There is some ensemble members that are showing some 
shallow instability ahead of a lingering pressure trough Saturday
afternoon, but uncertainty is very high at this point. Guidance 
is noting an upper ridge building over the Plains early next week 
would favor seasonable readings and low chances for 
showers/t-storms, especially over the southwestern Midwest. The 
normal max/min at Indianapolis through the long term is 74/54.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 717 PM EDT Tue May 13 2025

Impacts: 

- Scattered to numerous showers with embedded thunder diminishing 
  through mid to late evening
- Additional convection possible late tonight near KIND 
- MVFR ceilings increasing overnight mainly at KIND and KLAF. Brief 
  IFR possible as well 
- Scattered showers expected to develop Wednesday afternoon and may 
  impact KIND and KLAF

Discussion:

Scattered to numerous areas of convection continue to impact 
central Indiana early this evening. As heating is lost near sunset 
and beyond...expect showers and storms to weaken and diminish in 
coverage over the next few hours. Brief restrictions are possible at 
any of the terminals should a heavier shower or storm move over. Hi-
res models continue to try and redevelop an area of convection near 
I-70 late tonight...possibly in tandem with a lingering boundary. 
Placed a prob30 at KIND after 06Z for a few hours to account. 
Otherwise...low ceilings are likely to become the primary impact 
during the predawn hours along with the potential for visibility 
restrictions...most notably at KLAF. 

The upper low will lift north of the region Wednesday with 
redeveloping scattered afternoon convection focused primarily across 
the northeast half of central Indiana. Will carry VCSH at KIND and 
KLAF with KBMG and KHUF more likely to remain dry. Southerly winds 
up to 10kts are possible Wednesday afternoon.

&&

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

&&

$$

SHORT TERM...Updike
LONG TERM...Updike
AVIATION...Ryan