Indiana’s Weather For Sunday

HEADLINES
– Widespread rain today with isolated thunder in the south this afternoon.
– Temperatures hovering around normal through the middle of next week before warm up begins.
– Much warmer and wetter pattern setting up end of the week and into next weekend.

TODAY’S MAP

NWS TECHNICAL DISCUSSION

A surface ridge is moving away from the region to the east as low
pressure organizes over the southern Plains. Mid and high clouds
were steadily increasing across the forecast area this morning in
advance of the surface low...with clusters of convection across much
of the southern half of Missouri west into eastern Kansas.
Temperatures varied from the low 30s over the northeast to near 40
in the lower Wabash Valley.

The surface low over the southern Plains will lift northeast today
becoming gradually absorbed by a stronger surface wave to the north
over the upper Midwest. The approach of the storm system with an
associated frontal boundary will bring a wet...windy and dreary end
to the weekend with widespread rain expected by mid morning and
continuing for much of the day. Stronger wind gusts will linger into
tonight as the surface low pivots across the Great Lakes.

Today

Clouds will continue to thicken and lower through the predawn hours
with the leading edge of the convection ongoing across the mid
Mississippi Valley arriving in southwest counties by 10-11Z.
Initially...dry air and southeast winds will stunt northeast
expansion of the rainfall through daybreak with ACARS soundings at
KIND showing little to no moisture present below 500mb currently. An
initial surge of isentropic lift through the upper portions of the
boundary layer associated with the leading edge of the showers will
aid in kickstarting the saturation process near and just after
daybreak. That will spread northeast with rain steadily expanding in
coverage through the second half of the morning.

This will serve as the appetizer for a broader and stronger area of
isentropic lift located at the nose of the low level jet. The jet
will pivot around the base of the 850mb trough axis and across the
area for the first half of the afternoon...with a widespread steady
rain encompassing the forecast area for the first half of the
afternoon ahead of the frontal boundary. By late afternoon...the
primary area of rainfall will shift east with convection developing
behind it immediately ahead of the front. The MLCAPE axis will
primarily remain to the south of the forecast area but soundings do
show a narrow ribbon of weak instability aloft across the southern
half of the forecast area...likely sufficient enough to warrant an
isolated thunder mention until the front passes by early evening.
Despite an inversion present around 800mb by mid to late
afternoon...likely to see showers mix down some of the stronger
winds within the low level jet. Peak gusts of 30 to perhaps as high
as 35mph will be possible sporadically through the afternoon and
early evening.

Rainfall amounts by this evening will range from around 0.25 inches
in the northern Wabash Valley to between 0.75 to 1 inch over the far
south where the potential for some convection along and ahead of the
front may produce brief heavier rainfall in some locations.

Tonight

The airmass will dry out rapidly in the wake of the frontal passage
with most of the rain east of the forecast area by 00Z or shortly
after. The focus for the remainder of the evening and likely into
the first part of the overnight as well will be the winds. The
combination of decent cold advection in the post frontal airmass
with continued 850mb flow at 50-60kts will support a period of
several hours with wind gusts occasionally reaching 40mph focused
especially across the northern half of the forecast area. Peak gusts
will gradually drop back during the second half of the night as the
surface low lifts into the northern Great Lakes and away from
central Indiana...but brisk winds will persist with boundary layer
flow remaining elevated all night.

Clouds will scatter with increasing subsidence behind the front by
late evening...although lower stratus may pivot back across far
northern counties overnight as the cold pool aloft settles over the
lower Great Lakes. The day to day variability in temperatures and
weather that we so commonly experience in mid to late March will
continue.

Temps...while subfreezing temps exist currently over northeast
counties...expect them to rise prior to daybreak and then further
prior to the arrival of rainfall later this morning. Leaned towards
the cooler end of guidance today for highs as the rain and cloud
cover will keep readings down. Expect upper 40s for the northern
half of the forecast area with lower to mid 50s further south. Lows
tonight will fall into the mid and upper 30s.

&&

.LONG TERM (Monday through Saturday)...
Issued at 312 AM EDT Sun Mar 23 2025

The extended range features near normal temperatures and periodic
chances for showers through much of the week. A much warmer and
wetter weather pattern sets up for the end of the week and into
early April with greater chances for thunderstorms.

A general northwest flow pattern sets up for the Great Lakes region
Monday through Thursday, keeping near normal temperatures around and
periodic chances for light precipitation due to weak passing systems
within the upper jet. Monday looks mainly dry and breezy compared to
the weekend. Indiana will be on the backside of a departing low in
the upper Great Lakes with cold air advection filtering in aloft.
Steepening low level lapse rates and mixing into a 30-40 kt low
level jet will result in windy conditions with gusts over 40 mph at
times. If mixing heights end up higher than what models suggest,
temperatures could exceed forecast highs while min RH falls
significantly below guidance. Updated the temperature and RH
forecasts to reflect this. Despite wind and RH thresholds
potentially being met for fire weather concerns, recent rainfall
will likely keep any fire weather threat relatively low.

The next chance for rain arrives Tuesday as a weak upper level
disturbance drops southeastward from Canada. Lowered PoPs for
Tuesday as the latest trends has weakened the disturbance and
therefore have more sporadic chances for showers. Keeping low Pops
in the forecast through Wednesday morning as some guidance is
suggesting additional weak disturbances within the northwest flow
pattern sliding into the region. Confidence remains low on exact
details as these features are so subtle that guidance will likely
struggle to resolve them this far out. Not expecting a washout of a
week whatsoever, but isolated scattered showers are certainly
possible almost each day through mid to late week in this type of
pattern. This weather pattern and below normal 850mb temperature
anomalies support highs and low at or just below average for this
time of year. Keeping highs in the mid 50s with lows around or just
above freezing.

Thursday through next weekend...

Details toward the end of the week and into the weekend become muddy
as longer range guidance disagrees with evolution of a major pattern
shift going into April. While confidence is high in a much warmer
and wetter pattern setting up, low confidence exists in timing and
track of specific features. Beginning Thursday, The northwest flow
pattern transitions into ridging with the main storm track pushing
further north as well. Lower pressure develops along the front range
of the Rockies by the end of the week; however discrepancies appear
in the timing and placement of the warm front and associated waves
of energy riding along it. There is higher confidence Indiana will
be on the warm side of these systems, but currently uncertain with
how close the front will be to the region. This front will be the
main focus for thunderstorm development, Therefore, keeping chance
PoPs in for much of the weekend. Will raise or lower PoPs in later
forecast issuances as agreement builds regarding exact details of
these features. This pattern also supports to possibility of
increased severe weather chances for the Ohio Valley...so will be
keeping an eye on the end of the month and into early April for
severe weather threats. Nonetheless, temperatures are expected to be
above normal with daily highs likely reaching the 70s.

NWS CHARTS FOR TODAY/TONIGHT