Lafayette, Indiana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

396
FXUS63 KIND 180547
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
147 AM EDT Sat Apr 18 2026

.KEY MESSAGES...

- Showers and thunderstorms late tonight into Saturday

- Much cooler Sunday into Monday with the potential for
  frost and near freezing temperatures early Monday morning

&&

.FORECAST UPDATE...
Issued at 1020 PM EDT Fri Apr 17 2026

Strong to severe upstream thunderstorms currently aligned over north-
central Illinois will continue their eastward progression toward
central Indiana through the late evening.  QLCS is expected to
weaken around when crossing into Indiana and reaching the CWA`s far
northwest zones around the early overnight hours...with numerous to
widespread showers and embedded, possibly strong TRWs most likely
within the 04-10Z timeframe...before a second round of numerous
showers follow across most zones through dawn.

Severe threat tonight will begin with potential isolated discrete
cells tracking SSW-NNE along/west of a line from HUF to OKK before
06Z...just ahead of the main decaying QLCS threat whose strong/
severe winds would be most likely over the Upper Wabash Valley.
Straight line winds are the prevailing threat, with noticeably
lower, non-zero chances of large hail and weak tornadoes.  Flash
flood concerns are overall low, yet on the table for any counties
that receive over 1.00 inch of rainfall from both the late
evening/early overnight cells...as well as the later overnight rains.

Winds outside of storms to continue to gust to 20-25 mph. Most
locations are progged to see 0.23-0.75 inches of rain, with heavy
amounts possible under storms over northwest counties.  Readings
will initially drop into the 60s from rain...with more staunch trend
in wee hours behind cold front...down to low 50s near Lafayette and
mid-60s for Seymour by daybreak.

&&

.MESOSCALE UPDATE...
Issued at 146 AM EDT Sat Apr 18 2026

The line of convection across the northern forecast area has become
outflow dominant. Wind gusts near 45 mph are possible with any of
the storms and with portions of the outflow boundary itself.

Satellite shows warming clouds tops, and radar trends have shown
weakening in the convection upstream in Illinois. These storms may
still be able to produce gusts of 40-45 mph when they move into the
area, but severe weather is not expected.

Given these considerations, the Tornado Watch was canceled earlier.

&&

.DISCUSSION (This evening through Friday)...
Issued at 319 PM EDT Fri Apr 17 2026

Low pressure developing over Minnesota has brought a warm front
northward through Indiana earlier today. Despite some cloud cover,
temperatures have risen once again into the 80s across much of the
area. Mixing has been quite efficient as well, especially further
east, with dew points falling to below the NBM 10th percentile. To
the west, dew points in the 50s/low 60s have been noted. These
locations are deeper within the best northward moisture advection.

Warm moist advection continues into this evening ahead of a surface
cold front extending southward from the low. Strong forcing along
this front with large-scale lift from a deepening trough is leading
to rapid convective development to our west. Mean flow roughly
parallel with the initiating boundary will allow for quick upscale
growth into a mesoscale convective system (MCS). This system should
then progress eastward this evening.

The environment ahead of the system is characterized by deep
instability to 250mb with strong easterly shear. CAPE values between
1000-2000 J/Kg are modeled to persist into the night, but with
gradual stabilization occurring after about 00z. Additionally, shear
magnitudes decrease with eastern extent especially from the IN/OH
border eastward.

Our convective threat will be determined by how strong surface cold
pools become. A stronger cold pool should allow the MCS to propagate
further east faster than most models indicate. A faster MCS would
then have access to greater CAPE and better shear. Cold pool shear
balance would be achievable longer under such a circumstance. A
slower MCS may miss the best instability and become outflow dominant
early, sparing much of central Indiana from a severe weather threat.

In terms of hazards, strong damaging winds are the primary hazard. A
QLCS tornado threat also exists, especially across our northwest CWA
during the MCS`s mature phase and where better low-level moisture is
found. The best wind/tor threat is within N/S oriented line
segments, and within surges which come parallel with an intensifying
nocturnal low-level jet. Further south and east, the threat is
reduced due to a more stable surface layer and likely a more outflow
dominant system.

Best timing for severe weather is between 11pm through 4am, from
west to east.

THIS WEEKEND

The aforementioned cold front arrives well behind the MCS, roughly
around daybreak Saturday. High temperatures for the day occur around
or before sunrise for most. Behind the front, temperatures fall from
the mid 60s into the upper 40s/low 50s by the afternoon. Brisk
northwesterly flow and occasional rain showers should make it feel
quite miserable. Though thunder probabilities remain low, under 20
percent, enough elevated instability may be present for an isolated
weak thunderstorm...mainly across our eastern CWA.

A quick rebound is likely on Sunday though not as warm as it has
been recently. Highs to near 60 are expected on Sunday. A subtle
shortwave diving southeast may bring about an isolated shower Sunday
afternoon.

NEXT WEEK

A northwesterly flow pattern sets up next week as troughing digs in
over the Great Lakes and Northeast. A stalled front Tuesday into
Wednesday may bring some precipitation, but nothing too organized at
this point. That front lifts back northward as a warm front allowing
a warming trend to begin during the second half of the week. A
return to temperatures in the 70s or even low 80s is possible again
by Wednesday.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 1254 AM EDT Sat Apr 18 2026

Impacts:

- Wind gusts up to 20-25KT continuing through most of the period
- Convective SHRA/TSRA likely...mainly within 06Z-15Z
- MVFR ceilings for 4-6 hours at any terminal, crossing NW to SE
   within 11Z-19Z
- Cold fropa will veer southerly winds to mainly SW by 12Z...and
   WNW/NW at all terminals by 17Z

Discussion:

Initial line has already impacted KLAF, and outflow from this line
may impact KIND near valid time. Convection itself may take longer
than expected to reach KIND/KHUF/KBMG as not much extends south of
the initial line. Have delayed arrival and will continue to monitor.

Eventually, showers with embedded storms will be across the sites
into the daylight morning hours. Coverage of rain will diminish by
early afternoon but scattered showers will persist into the
afternoon.

A wind shift will occur with the cold front, and gusty winds will
persist.


&&

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

$$

MESOSCALE...50
UPDATE...AGM
AVIATION...50/AGM
DISCUSSION...Eckhoff