IND issues Area Forecast Discussion (AFD) at May 13, 7:17 PM EDT383
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
Source:
IND issues Area Forecast Discussion (AFD) at May 13, 7:17 PM EDT---------------
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