868 
FXUS63 KIND 142235
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
635 PM EDT Wed May 14 2025

.KEY MESSAGES...

- Chances for showers and storms into tonight

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

- Near record highs possible Thursday and remaining very warm on 
  Friday

&&

.SHORT TERM (This evening through Thursday night)...
Issued at 241 PM EDT Wed May 14 2025

Rest of This Afternoon....

Clouds from this morning's convection have thinned, allowing 
temperatures to rise into the 70s. Where sunshine has been present 
all day, temperatures were around 80. 

In between, a weak pressure trough was moving slowly northeast. 
Isolated showers have been developing along this trough. This will 
continue as the trough drifts northeast. Thunderstorms will also be 
possible as instability grows, but not expecting any severe weather 
given the expected parameter space.

Warm and humid conditions will persist.

Tonight...

Warm advection aloft will kick in tonight, with the leading edge of 
the stronger advection moving southwest to northeast during the 
night. The boundary layer will cool, but instability will remain 
aloft. Forcing from the warm advection will work with the 
instability aloft to create some scattered showers and thunderstorms.

Instability will be high enough that some potentially severe hail 
will be possible in a few storms. The best instability will remain 
across the southwest forecast area, so that is where the main threat 
will be. 

As the forcing moves away from the best instability in the 
southwest during the night, coverage may decrease. Will have highest 
PoPs (chance) southwest with lower PoPs northeast.

Thursday...

For the severe threat, please see the section below.

A cap should keep much of the day dry. Can't rule out something 
breaking through though if an area of the cap is weaker than the 
rest, so will keep some slight chance PoPs in the afternoon.

The air will be very warm for mid-May. Given the expected lack of 
convection, there will be enough sunshine to boost temperatures to 
near record levels. However, some areas that saw a lot of rain 
Wednesday may have a harder time reaching these levels thanks to the 
wet ground. Will go mid 80s to around 90 for highs.

Forcing will be enough for chance PoPs all areas Thursday night.

---Severe potential on Thursday---

A pronounced and pristinely maintained elevated mixed layer capping 
a warm/moist PBL will lead to strong instability across our region 
tomorrow. This EML is being carried eastward from its source region 
in the central Rockies by strengthening westerlies at the base of 
closed/deep low migrating across the northern Plains. There is about 
a 75-mile spread in the position of the attendant Pacific front that 
will serve as an initiating boundary and this is one element of 
uncertainty in tomorrow's severe thunderstorm risk. The other is 
whether or not the trough's geometry, position, and timing will be 
enough to effectively lift the capping EML this far south. If 
convection does form, the parameter space would support severe 
thunderstorms, including supercells with the potential for 
significant severe. Scenarios, and reasonable best- and worst-case 
scenarios are covered below. 

Scenario #1 Little/no convection forms this far south precluding a 
convective hazard threat. 

Subjective estimate of occurrence: 30%

Analysis: Either, (1) diurnal destabilization and frontal 
convergence are not a match for the magnitude of the capping EML, 
and/or (2) trough lags and is less amplified (there has been a 
slight multi-run trend toward this).

Scenario #2 Convection initiates, likely well west of our area near 
the Mississippi River, and sustains eastward into central Indiana. 

Subjective estimate of occurrence: 55%

Analysis: Once convection initiates, as midlevel thermal ridge moves 
eastward and slight ascent/cooling overspread the area, residual 
strong instability into the evening would sustain convection. There 
may be a tendency for storm mode to be less organized and rooted 
within moist/ascent layer aloft, atop the EML, thereby limiting the 
severe magnitude some. With any convection that can overcome 
inhibition from strong capping EML and remain deeply rooted in the 
PBL, a more substantive severe threat would be possible with very 
large hail the primary threat, though all hazards are possible.

Scenario #3 Intense/mature supercells sustain into central Indiana 
during the evening with accompanying significant magnitude severe. 

Subjective estimate of occurrence: 15%

Analysis: If strong capping EML weakens sufficiently and supercells 
are more easily able to deeply root in the PBL traversing central 
Indiana well into the evening, all severe hazards are possible, 
including a tornado threat. Elongated middle portion of the 
hodograph favor very large hail in this scenario. This is a less 
likely scenario since ascent needed to lift the capping EML appears 
insufficient given the characteristics and timing of the parent 
trough and so the higher-end scenario will likely be confined to the 
Great Lakes region, north of our area.

In scenario #2 or #3, convection may persist into late evening or 
even overnight along the trailing and decelerating Pacific front 
across roughly the southern one half to one third of Indiana. Later 
in the night, convection should mostly or completely diminish as 
forcing for ascent isn't particularly robust and some capping may 
remain. Further, the front will become ill-defined as low-level flow 
veers, and there is a weak warm/moist advection signal at best. 
There is a low probability scenario of warm/moist advection being 
just sufficient enough to interact with trailing boundary keeping 
some convection going over southern Indiana into the pre-dawn hours.

&&

.LONG TERM (Friday through Wednesday)... 
Issued at 241 PM EDT Wed May 14 2025

Friday and Friday Night...

Forcing from an upper low will interact with lingering moisture and 
instability to produce the threat for showers and thunderstorms once 
again Friday. Timing remains uncertain, but later Friday afternoon 
into Friday evening look best. With rain not likely not arriving 
until later in the day, highs in the mid 80s look reasonable. 

--- Severe Potential Friday ---

Models generally agree on a slow-moving closed low moving toward 
Lake Superior by late in the day. The mean westerlies on the 
equatorward side of this low are about +2-sigma in magnitude and 
particularly broad, contributing to strong deep layer shear across 
our entire region. When coupled with at least moderate instability, 
the threat for severe thunderstorms is present with significant 
severe a possibility, particularly if an organized MCS/wind threat 
evolves. Some of the models are more suppressed with the warm sector 
and focus a potential intense MCS and high-end wind event further 
south closer to the Ohio River, though this evolution and placement 
is uncertain. Even then, some severe threat would occur this far 
north with all convective modes and severe types possible. Once the 
characteristics/timing of the mid-upper trough are more clear, and 
its influence on the warm sector's northward return, we will be able 
to convey more certainty.

Saturday and Sunday...

Cooler and drier air will move in behind a cold front on Saturday, 
and then high pressure will build in for Sunday. This should keep 
the area dry for the weekend and bring seasonable temperatures.

Monday into Wednesday...

Uncertainty increases for early next week as an upper low ejects out 
of the southwestern USA and moves into the Upper Mississippi Valley. 
Questions remain on the strength and timing of the upper low as it 
moves northeast, as well as the development of its associated 
surface low pressure system. This leads to lower confidence in PoPs 
through the period.

On Monday the surface warm front will try to move north, but upper 
ridging will building in aloft. Will have some low PoPs, but the 
ridge may be able to squash any convection that tries to form. 

PoPs will continue Tuesday and Wednesday as the system itself moves 
in and through. Right now it looks like Tuesday night has the best 
chances.

Temperatures will depend on the coverage of rain and timing of the 
warm front, but highs in the 70s look reasonable.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 635 PM EDT Wed May 14 2025

Impacts: 

- Narrow band of scattered convection may impact the terminals for a 
  few hours late tonight
- MVFR ceilings possible for a short time Thursday morning
- Gusty S/SW winds Thursday afternoon

Discussion:

Scattered diurnal convection has moved largely to the northeast of 
the terminals early this evening and will be even further off to the 
northeast by 00Z issuance time. Slightly drier air following will 
lead to a lessening of cloud coverage this evening before an 
increase in mid level ceilings associated with the approach of a 
warm front from the southwest. The boundary will lift across the 
terminals overnight and may generate scattered convection for a few 
hours with it. Confidence is highest in brief impacts at KBMG and 
KHUF and will employ 3 hour tempo groups. Could see a few rumbles of 
thunder but coverage will be sparse enough to keep mention out of 
the forecast at this time.

Any showers associated with the warm front will be north of the 
region by or shortly after 12Z Thursday. Moisture will persist 
within the boundary layer through midday with the possibility for 
brief periods with MVFR stratocu before mixing out into a VFR cu 
field for the afternoon. S/SW winds will increase with peak gusts 
around 25kts in advance of a frontal boundary moving into the area 
by Thursday evening. 

A well noted capping inversion will keep a lid on any convective 
development until the evening hours but as the boundary layer cools 
and the inversion weakens...there is potential for isolated to 
scattered robust convection to develop by mid evening Thursday. 
Trends will continue to be closely monitored tonight and into 
Thursday.

&&

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

&&

$$

SHORT TERM...50/BRB
LONG TERM...50/BRB
AVIATION...Ryan