880
FXUS63 KIND 010520
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
120 AM EDT Wed Apr 1 2026

.KEY MESSAGES...

- Wind gusts of 30 to 40 MPH at times again Thursday.

- Wet pattern through the week and into the weekend, with multiple
  rounds of showers and storms expected, which may produce renewed
  flooding along area waterways

- A few strong to severe storms and locally heavy rainfall are
  possible mainly northern portions of central Indiana tonight.

- Potential for additional heavy rainfall and severe weather for
  late Thursday and again late Saturday.

- Drier and cooler weather for early next week.

&&

.FORECAST UPDATE...
Issued at 948 PM EDT Tue Mar 31 2026

Some showers and thunderstorms have finally entered portions of the
northwest forecast area this evening. These are along a cold front,
with convection now stretching southwest into central Illinois.
Temperatures in northwest Indiana behind the front were in the mid
40s, but ahead of the front readings were in the lower and middle
70s.

With convergence continuing along the front, along with some
instability (MUCAPEs less than 1000 j/kg), expect showers and
thunderstorms to become more widespread into the overnight. Current
trends indicate that the northern forecast area will have the most
coverage, so kept PoPs high there. Did tighten the gradient from the
high PoPs north to the chance PoPs south based on latest trends seen
in guidance. (Did not cut as much as the HRRR would suggest, as its
coverage looks underdone based on what`s on radar now).

With the instability and weak shear, a strong to potentially severe
storm cannot be ruled out into the early overnight. Have seen gusts
near 50mph in central Illinois with the convection this evening but
nothing severe. As instability weakens overnight, odds of strong
convection will decrease.

Locally heavy rain from storms remains a threat, mainly across the
northern forecast area where multiple rounds of convection are
possible.

Temperatures will get into the 40s in the northwest behind the
front, with readings remaining in the 60s south ahead of it.

&&

.MESOSCALE UPDATE...
Issued at 806 PM EDT Tue Mar 31 2026

Central Indiana remains convection free near 00Z this evening, with
convection across northern Indiana and across portions of Illinois.

Some weak CIN remains across the local area, with MLCAPE below 1000
J/kg. Better shear remains across northern Indiana, where convection
there is being assisted by an upper wave.

Convection to the north and northwest of central Indiana is firing
along a cold front, which with assistance from cold advection from
Lake Michigan has pushed south of KRZL. At least scattered
convection should continue to fire along the front thanks to deeper
convergence and the available instability.

This convection hasn`t become severe, and with the better shear off
to the east and north, feel that any severe threat across the
northern forecast area in the next couple of hours would be
isolated.

&&

.SHORT TERM (This evening through Wednesday)...
Issued at 329 PM EDT Tue Mar 31 2026

Rest of this afternoon...

Subtle shortwave trough will continue to push east through the lower
Great Lakes. Ample elevated instability (MUCAPE around 1000 j/kg)
and limited instability will support a threat for scattered
thunderstorms with small hail, gusty winds up to 45 mph and locally
heavy rain for the next 1-3 hrs before weakening and ending from the
west by 22Z.

Tonight...

Thunderstorms have begun to develop along a line from the western
Chicago Suburbs back towards the Quad Cities. This activity is
forming in a region of deep moisture convergence ahead of the main
frontal boundary. Expected storm motions and current location agree
with bulk of CAM guidance which moves this activity into far NW
portions of central Indiana around 00Z. Similar to this mornings
activity, threat will initially be large hail thanks to steep mid
level lapse rates up to 7.5 C/KM. Elevated TS activity that moved
through NW portions of the forecast area in the last 1-2 hrs has
stabilized the BL. However, sufficient heating should redevelop
before 00Z that near surface based parcels will support an
additional threat for damaging winds. Activity will also be working
with around 1.3 inch PWAT, which combined with slow storm motions
will lead to threat for locally heavy rainfall. The threat for
severe down to I-70 per recent SPC day 1 outlooks seems a little too
far south given the slow storm motions and increasing cinh with
southward extent. However the WPC day 1 marginal location looks
reasonable. As the cold front accelerates southward later tonight,
aided by CAA of Lk. Michigan, expect the greatest the for heavy rain
to gradually shift south towards I-70 by 12Z Wednesday.

Wednesday...

Given strong convective overturning and weakening mid level lapse
rates owing to building heights and latent heat processes,
thunderstorm activity will continue to weaken and diminish in
coverage during the morning. However, strong deep convectively
enhanced frontal convergence aided by 30-40 kt 850mb jet will
support the threat for multiple rounds of heavy showers along the
frontal boundary during the day. Uncertainty exists on the exact QPF
amounts, so decided to not hoist a Flood Watch, but over 1 inch of
QPF is possible between 12-00Z. Expecting the frontal boundary to
push much further south than NBM guidance and thus have undercut
highs by 1-2 categories, remaining in the 40s/50s along and north of
I-70.

Wednesday night...

Frontal boundary will lift northward as a warm front as strong
pressure falls develop associated with another shortwave trough
digging southward through the rockies and surface low pressure
intensifying over the high plains. Showers and isolated TS chances
will end quickly from the south early in the period as the front
moves north of the CWA by 06Z. In fact Wednesday`s high temps for
most areas north of I-70 will occur just before 04Z.

Thursday and Thursday night...

As the next shortwave kicks eastward into the plains into the
western Great Lakes, an associated frontal zone will push eastward
to near the upper MS river by Thursday afternoon. Early morning TS
over the Ozarks may move far enough east to aid in a convective
outflow boundary ahead of the primary frontal forcing to support
renewed convection along this boundary by afternoon just west of
central IN. With little to no mid level height falls, soundings
indicate substantial inversion centered around 500 mb robbing a
deeper CAPE profile. Thus the slight risk has a lot of conditional
nature to it, with many negatives limiting the threat at the moment.
NBM Pops were lowered some, but possibly not enough given the
limited deep forcing and marginal instability.

&&

.LONG TERM (Wednesday night through Tuesday)...
Issued at 329 PM EDT Tue Mar 31 2026

Unseasonably warm and anomalously humid pattern to continue into the
late week amid continued chances of rain/thunder..before mid-weekend
transition to dry and much cooler conditions early next week.
Indiana`s position, Friday and into Saturday, in the subtropical
warm sector south of a rather quick zonal mid-level flow near the
CONUS-Canada border...will provide a quasi-continuous ribbon of
anomalously high precipitable water off the Gulf, separated by
perhaps a shorter period of drier mid-levels between passing. rounds
of forcing.  Steady S/SSW surface flow will hold 55-65F dewpoints
over the CWA, promoting high-POPs of low-QPF around the Friday
timeframe.  Overall breezy conditions will likely include one more
windy day Thursday where gusts to at least 25-35 mph will be
possible.

Final period of steadier rainfall is expected to precede a regime-
changing cold front expected to cross Indiana around the late
Saturday-Saturday night timeframe.  Widespread moderate rainfall and
isolated to scattered thunder would be the most likely solution,
with potential for an additional 1.00-2.00 inches of rainfall under
heavier downpours/storms...as the boundary takes a slower passage
across the region.  This final round of rain may be the one to take
a few local creeks and river points from Action Stage into Minor
Flooding, or at least prolong ponding of low-lying areas into early
next week.

A distinct transition to below normal temperatures will follow into
Sunday, with rain-free conditions and dewpoints falling to around
30F as seasonably strong surface high pressure builds into the Great
Lakes/Midwest into Monday.  Current NBM timing would only allow
maximums 10 degrees below normal Sunday...with subsequent clearing
and diminishing winds promoting frost late Sunday night.  Any
moderation into the mid-week to be modest and towards near normal
conditions.  The normal max/min at Indianapolis through the long
term is 60/40.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 118 AM EDT Wed Apr 1 2026

Impacts:

- Showers with some embedded thunder, particularly at LAF

- Ceilings deteriorating through MVFR to IFR at all but BMG through
  daybreak

Discussion:

A boundary continues to slowly sag into the area, with winds
shifting to the north and then northeast behind it. The majority of
precipitation and thunderstorm activity are elevated north of the
boundary, and this will largely remain the case, though more shower
activity will overspread the sites as the boundary pushes south.

A stout frontal inversion north of the boundary will promote
deteriorating ceilings and perhaps visibilities, with IFR likely to
dominate most of the sites by daybreak and through much of the rest
of the period. BMG may remain MVFR once it falls to that level but
the gradient between IFR and VFR may be tight, so uncertainty is
high there.

Will only mention thunder at LAF, though a low chance for embedded
thunder cannot be ruled out at the other sites. Uncertainty is too
high for too long to narrow down a particular time frame at this
point for a PROB30.

Winds will gradually shift to the north and northeast through the
period, becoming easterly this evening. This boundary will begin to
push back northward as a warm front beyond the TAF period.

&&

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

&&

$$

UPDATE...50
SHORT TERM...Crosbie
LONG TERM...AGM
AVIATION...Nield