Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 261036
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
636 AM EDT Tue Mar 26 2024

.KEY MESSAGES...

- First round of rain exits this morning with a few 40 mph wind
gusts possible.

- Second round of showers this afternoon (1-8pm EDT) may include
isolated thunderstorms with a few damaging wind gusts possible.

- Dry weather Wednesday through Friday with slowly warming
  temperatures.

&&

.DISCUSSION...
Issued at 303 AM EDT Tue Mar 26 2024

First round of rain already well underway...forming on the nose of
an incredible 70+ kt LLJ. Precip also aided by approach of deep
upper low with associated ~990mb surface low now drifting into WI.
Wind speeds have behaved as predicted so far with just a few
sporadic 40 kt gusts over southern IN/IL where LLJ was strongest and
momentum transport was aided by initial saturation. Expect generally
30-35 kts around here through the early morning due to very stable
profiles limiting mixing. While a stray 40 kt gust can`t be ruled
out...confidence in duration and coverage is too low to justify an
advisory. Water vapor imagery shows midlevel dry slot already
pushing into our area and will bring an end to steady precip by
sunrise though some SCT showers will likely persist through late
morning as the dry slot isn`t particularly strong.

Attention then turns to primary cold front crossing our area this
afternoon. Timing is a little more consistent in the latest guidance
with the front entering our west around 18Z and exiting our east
around 00Z. While timing is ideal to maximize instability...trend in
latest guidance has been for slightly lower instability values.
Surface dewpoints (which have been running consistently below most
guidance) struggle to get much above 50F and steep lapse rates can
only compensate so much for poor low level moisture quality and some
lingering capping from morning rainfall. However, the kinematic
environment remains quite strong and models still suggest a few
hundred J/kg of CAPE. Thunderstorms may be very isolated but even
showers will be capable of mixing down some 40-50 kt winds gusts in
this type of setup. There is also some concern for 40 kt gusts to
linger for a few hours behind the front given better mixing/downward
momentum transport in region of isentropic descent. This is also not
a high confidence scenario either as gradient weakens quickly behind
the front and isentropic analysis indicates wind directions largely
parallel to a relatively broad isobar gradient (not the typical
setup necessary for a high wind event). Will therefore plan to hold
off on advisory during the afternoon as well. Day shift can decide
to issue in the late morning with the benefit of 12Z obs/guidance or
just handle with SPS`s/SVR`s as necessary (the more likely
scenario given brief/convective nature of strongest gusts).

Rest of the forecast remains relatively tranquil. Dry conditions
return by tonight and persist through Fri as upper low drifts over
Ontario and maintains dry WNW flow. Broad, low amplitude ridging
develops over much of the CONUS by the end of the week with a few
shortwaves zipping through the region. Still some uncertainty but
appears best chances for rain will be with a shortwave Fri night
into early Sat and again Sun night into Mon (and Tue) as next large-
scale trough ejects out of the southwest CONUS. After a cool start
on Wed, temps slowly climb through Sat.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 624 AM EDT Tue Mar 26 2024

A strong low level jet was over northern Indiana and had
translated east over FWA where wind speeds aloft were up to 75
knots. The stronger winds will move east out of the area this
morning, but the jet will persist over the area until the front
moves through this afternoon. Kept the mention of a TEMPO group
at FWA around 20Z for a line of convection that is expected to
develop with the FROPA (HRRR). Placed wind gusts there to 43
kts, but can not rule out a wind gust up to 48 kts at the FWA
airport. Otherwise, the large area of rain had moved east with
lingering showers over the area. Some post-frontal clouds are
likely to develop and bring MVFR ceilings.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory until 11 AM EDT this morning for LMZ043-
     046.
     Gale Warning from 11 AM this morning to 8 PM EDT this evening
     for LMZ043-046.

&&

$$

DISCUSSION...AGD
AVIATION...Skipper


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