216
FXUS63 KIND 280106
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
906 PM EDT Mon Jul 27 2026

.KEY MESSAGES...

- SEVERE THUNDERSTORM WATCH for Much of western central Indiana
  UNTIL 11 PM.

- Thunderstorms ending this evening. Damaging winds are the
  primary hazard. Secondary hazards of large hail, tornadoes, and
  flooding also possible.

- Rain free Tuesday-Thursday amid near to slightly below normal
  temperatures/humidity...with northerly breezes Tuesday, Wednesday

&&

.FORECAST UPDATE...
Issued at 904 PM EDT Mon Jul 27 2026

Convection across the area is expected to wane over the next several
hours and mainly be contained to western Central Indiana. Radar this
evening shows the strongest storms within the Wabash valley pushing
south. Favorable instability remains in place across SW Central
Indiana ahead of the storms. Elsewhere a more stable column has
arrived due to the previously passed convection and limited showers
continue to suggest a diminishing trend.

Overnight, HRRR suggests a overall diminishing trend to an end for
the precipitation. The weak surface trough associated with this
feature will have exited to the south, resulting in diminishing
forcing. Thus will focus pops mainly in the west over the next few
hours before ending entirely. Overnight, lingering lower level
moisture and high dew points in the upper 60s may lead to some fog
or stratus development.

Overall, expect storm and rain chances to end by 04Z-05Z, with cloud
and possibly fog development overnight.

&&

.DISCUSSION (This evening through Monday)...
Issued at 256 PM EDT Mon Jul 27 2026

Satellite and radar imagery shows a large complex of showers and
thunderstorms over the Chicago area as of 2pm. This cluster of
storms is likely going to impact our area to some extent this
afternoon and evening. At the surface, a distinct axis of greater
instability (3000-4000 J/Kg MLCAPE) extends NW to SE through most of
central Indiana. Surface winds are generally southwesterly to the
west of this boundary. Along it, light and variable conditions are
noted. To the east, a southeasterly wind is observed.

Aloft, strong southeasterly shear between 45-55kt extends over most
of Illinois, Indiana and Ohio. This mean shear vector is almost
exactly parallel to the instability axis. Further to the north, a
potent mid-level vort max is shown which was the catalyst to ongoing
convection. Now that storms have initiated, the immediate mesoscale
concern is how storms evolve coming into our CWA in the next few
hours.

One scenario is that the storms develop a strong cold pool and begin
propagating southeastward along the instability axis. This is
plausible since the shear vector points southeastward along this
axis, and cold pool shear balance will be easier to achieve. In this
scenario, severe winds will be the primary hazard. However, embedded
supercells, as have been seen over Chicago this afternoon, would be
capable of all hazards including large hail and tornadoes.
Additionally, a QLCS tornado threat may develop if the low-level jet
ramps up significantly this evening.

A second scenario is similar to the one above, but the low-level jet
ramps up a bit earlier and storms propagate more southward owing to
greater upshear growth. This would send the storm cluster over our
western CWA with similar hazards to scenario one. All in all, the
main difference is timing and influence from the low-level jet.
Guidance shows the low-level jet increasing substantially around 02z
to between 30-40kt at 925mb. However, the storms may already be
through our area by that point. Renewed development on the western
edge could occur if a residual cold pool lingers over the area.
Flooding could occur if storms begin redeveloping over the same
areas as the initial round of activity.

After tonight, the vort max and associated surface low depart
eastward with a cold front sweeping through by dawn. Northern winds
usher in cooler and drier air with temperatures falling towards
normal for the remainder of the week. Another vort max may arrive
this weekend, embedded within weak westerlies aloft, bringing
precipitation chances back by Friday. Given the weak flow and
likewise weak vort max it would seem prudent to keep precipitation
chances capped at chance (40 percent). Model uncertainty is high, and
such weak/subtle features can be hard to pin point this far out.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 702 PM EDT Mon Jul 27 2026

Impacts:

- Strong to severe thunderstorms possible through 04Z.

- Potential for fog or low ceilings near daybreak Tuesday.

Discussion:

Radar shows convection pushing across Central Indiana poised reach
BMG within the next hour. Favorable set-up remains for ongoing
convection especially at the TAF sites as they remain within a very
moist airmass as a weak surface trough passes. HRRR continues to
suggest southward propagation with best set-up for additional storms
over western and southern Indiana which has not been too
significantly impacted as of yet and continues to have the best
instability in place.

After 04-06Z, best forcing and instability will be be lost and
convection will end. Forecast soundings show the arrival of
subsidence and HRRR shows diminishing and ending convection early
overnight.

Other than the possibility of some morning fog, a return the VFR is
expected on Tuesday as the column is expected to remain unsaturated.


&&

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

$$

UPDATE...Puma
AVIATION...Puma
DISCUSSION...Eckhoff