National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KIND 121954 AAA
AFDIND

Area Forecast Discussion...UPDATED
National Weather Service Indianapolis IN
354 PM EDT Fri Apr 12 2024

.KEY MESSAGES...

- Scattered showers/isolated storms until early evening; small
  hail possible
- Mostly Sunny and warmer on Saturday;
- Ongoing River Flooding and standing water in low-lying areas
- Multiple rounds of showers storms next week, severe weather
  possible Tuesday and Wednesday

&&

.MESOSCALE UPDATE...
Issued at 354 PM EDT Fri Apr 12 2024

Surface heating, residual PBL moisture, and relatively steep
low- to mid-level lapse rates has resulted in scattered
convection across central Indiana. Thermal profile is supportive
of both charge separation for occasional lightning and small
hail. Mean cloud-bearing wind supports southeasterly storm motions
at around 45 mph.

Although some momentum transfer may occur with convective cells,
lower tropospheric winds are generally no higher than around 40
knots per model soundings. Only the most intense convective cells
would be capable of >40 knot winds which won`t be much of an
enhancement from gradient winds observed now. Severe gusts will
be unlikely. Narrowing ECAPE profile into the hail growth zone
suggests hail size will be limited to sub-severe.

&&

.SHORT TERM (This evening through Saturday)...
Issued at 233 PM EDT Fri Apr 12 2024

Synopsis:

Surface analysis this afternoon shows deep low pressure over Ontario.
A moderate cyclonic pressure gradient remained across Central
Indiana late this afternoon, resulting in some wind gusts to around
30 mph. A strong ridge of high pressure was found over Plains
states. GOES16 shows the back edge of the cloud shield associated
with the departing low found over the Wabash valley, with clear
skies in place over IL and WI. Radar shows the morning showers have
exited central Indiana to the south and east. Isolated
showers/storms were trying to develop across the northeast parts of
the forecast area due to heating and weak instability.

The pattern aloft was high amplitude, with strong ridging in place
over the Rockies and a deep trough over the eastern Great Lakes and
Appalachia. Northwest flow was in place across across the upper
midwest, spilling into Indiana.

Tonight...

The strong ridging aloft to the west is expected to continue to
build eastward. This will allow continued subsidence across
Mississippi valley building east into Indiana overnight. The
associated surface ridge over the plains is also expected to build
across Indiana overnight. Forecast soundings and time height
sections show the arrival of a dry column. Thus as heating is lost
this evening and the low continues to depart, clouds will exit the
area this evening and wind gusts will diminish. Overall, look for
decreasing cloudiness tonight along with clearing overnight.

Weak cold air advection will be in place, so look for cooler lows
around 40 to the lower 40s.

Saturday...

A quiet weather day is in store for Saturday. Models show the strong
surface ridge in place west of Indiana and slowly moving across the
state through the day. Forecast soundings again show a very dry
column with unreachable convective temperatures. Northwest flow
aloft on the lee side of the approaching ridge will continue to
provide subsidence. Thus a sunny day is in store.

Some warm air advection is in play on Saturday afternoon as the 850
ridge axis arrives late in the day over Central Indiana. This will
allow 850mb temps to rise to 8-10C by late afternoon. Given this and
the abundant sunshine, highs in the upper 60s to near 70 will be
expected.

&&

.LONG TERM (Saturday night through Friday)...
Issued at 233 PM EDT Fri Apr 12 2024

Saturday Night Through Monday.

The brief break in the precipitation will continue Saturday night
into Sunday with high pressure building across the Central Plains
and with northwesterly flow aloft across central Indiana. A weak
shortwave will push across the Great Lakes Region Sunday morning,
but based on the current orientation of the upper level jet, not
expecting any precipitation to reach as far south as central Indiana
with impacts to Michigan and Ohio. On Monday the ridge will shift
eastwards ahead of the arrival of more impactful weather Tuesday
through the rest of the week.  Precipitation may begin as early as
Monday night along a subtle warm front towards the Ohio River, but
there remains a significant amount of uncertainty as to whether the
front will be strong enough to generate lift.

Tuesday Through Friday.

Focus then shifts on Tuesday to a strong closed low as it exits the
Rockies and tracks from Kansas into the Upper Midwest through the
daytime hours Tuesday. As a response to the approaching system, the
LLJ will begin to ramp up with a good moisture fetch from the Gulf
of Mexico extending into the Ohio Valley and bringing temperatures
to near 80 with dewpoints to near 60.  As the LLJ ramps up, model
soundings show good daytime mixing which will bring wind gusts in
excess of 40 mph and the potential for winds greater than 50 mph.
Models have a pretty good handle on the synoptics of the system when
it comes to track and strength, but details on the mesoscale
environment remains low.

That being said, highest confidence in timing for thunderstorms will
be in the evening to overnight hours Tuesday into Wednesday with the
frontal passage during the daytime hours Wednesday.  Instability
will be highest during the daytime hours Wednesday and across south
central Indiana where the frontal passage may not occur until the
evening hours.  Confidence in severe weather is low but with the
strong dynamics associated with this intense early spring low
pressure system, isolated to scattered severe weather looks probable
across portions of the Ohio Valley.  There looks to be a brief dry
period Thursday before a secondary low associated with the polar jet
moves in from the northwest bringing additional rainfall to Indiana
on Friday.  Little to no instability is expected which will keep
hazards limited to the heavy rain and associated flooding.

Total QPF between this weekend and next week may exceed 1-1.5 inches
in spots which would allow for rivers to remain in minor flood stage
through next week.  A high end scenario of 1.5-2 inches along the
White River basin would lead to moderate flooding across much of the
basin with lower chances elsewhere based on latest MMEFS ensemble
runs.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 1256 PM EDT Fri Apr 12 2024

Impacts:

- MVFR Cigs improving to VFR by 00Z
- Gusty winds diminishing by 00Z
- VFR on Saturday

Discussion:

GOES16 shows the back edge of cyclonic cloud shield over the Wabash
Valley, while clear skies were found over IL. The cloud shield was
making steady progress east, with clearing and VFR conditions
expected to arrive at LAF and HUF within the next few hours. VFR
should arrive at IND and HUF by late afternoon.

Strong ridging aloft over the plains will lead to subsidence along
with a ridge of surface high pressure building across the TAF sites
tonight and on Saturday. Forecast soundings trend toward a dry
column. Thus VFR is expected to arrive overnight, and persist on
Saturday as the surface high dominates at that time.

Gusty winds this afternoon will also diminish as the low to the
northeast departs farther and the pressure gradient gradually
lessens and daytime heating is lost.


&&

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

$$

MESOSCALE...BRB
SHORT TERM...Puma
LONG TERM...White
AVIATION...Puma