675
FXUS63 KIWX 291915
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
315 PM EDT Mon Apr 29 2024

.KEY MESSAGES...

- Showers and a rumble of thunder possible this afternoon east of I-69.

- Additional chances for showers and thunderstorms expected Friday.

- Unseasonably warm through the week with temperatures 70s being
  attainable.

&&

.DISCUSSION...
Issued at 312 PM EDT Mon Apr 29 2024

This afternoon`s pattern is characterized by a strong moisture
stream into the area with a connection to the Gulf, which allows
60+F degree dew points to remain across the area into tonight. With
the morning showers creating debris clouds, getting 1000 J/kg of
MUCAPE and decent low level lapse rates will likely be difficult.
Shear appears to be present, but only with pockets of 30 kts of
effective shear at best. It`s obvious on the NAM, but the ECWMF
shows shades of this as well, that there`s a sort of pre-frontal/
differential heating trough that also helps to limit any
thunderstorm production to east of I-69. If we can get some
instability to form, perhaps there could be some stronger storms
that develop as the NAM and to some extent the HRRR shows mainly
east of I-69. The main threat looks to be damaging winds and heavy
rain with the moisture loading present.

Mid level height rises signal the return of surface high pressure
for Tuesday providing a dry day. For Wednesday, a front passes
through with forcing dissipating and moisture being a little lower.
Perhaps a shower or storm could form, but don`t quite have
confidence on where with model disagreement still existing on timing
and moisture content. During this midweek period from Tuesday into
Thursday, a subtropical southeast CONUS ridge builds and the pattern
slows down allowing a trough across the Western CONUS and for
showers and storms across the Plains States and Mississippi River
Valley. As vorticity from the Western CONUS ejects northeast, it
wouldn`t be completely out of the question that a few counties could
receive a shower, but think much more of the messaging for this
period should be on it being dry. Highs will also be trending warmer
with low to mid 70s on Tuesday achieving highs securely into
the 80s on Thursday.

A resurgence of 60F degree dew points will be possible on Thursday
allowing it to feel more humid again, but a better chance of that
will be on Friday just out in front of a cold frontal moving in. The
ECMWF has 500 to 1000 J/kg, but the shear appears to be lower, which
may lessen the severity of it. The front appears to stall out along
US-24 or just south of the forecast area, call it in the
vicinity if you want, so am not quite ready to remove PoPs in
that area quite yet with some lingering instability noted on the
ECMWF. Sunday has a better chance to remain dry with mid level
height rises taking over and surface high pressure coming in
behind the now departing cold front.

That departing cold front looks to have stunted the southeast CONUS
ridge to some extent even if it still exists for Monday and Tuesday.
As such, with a cold front pushing through during this period and
60F degree dew points, we`ll have to watch for another chance for
showers and storms as long it times out favorably.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 209 PM EDT Mon Apr 29 2024

An upper level vort lobe lifting northeast across the Upper MS
Valley will continue to shift off to the northeast this evening.
The movement of this forcing will result in a slow eastward
advance of trailing cold front across the southern Great Lakes.
A fairly respectable low level moist tongue is preceding this
front into northeast Indiana. While mid level lapse rates are
meager, combination of sfc temperatures in mid-upper 70s and
this low level moist axis will produce surface based CAPEs on
the order of 500-1000 J/kg. This better instability should set
up just east of KFWA and thus will limit thunder mention to VCTS
in the 21Z-00Z timeframe. Storm development could also be aided
by a differential heating boundary setting up along IN/OH
stateline. Slow movement of this front should prolong rain
chances through around 03Z this evening. Conditions dry out from
west to east tonight with perhaps a brief period of some MVFR
cigs tonight near the cold front. No major weather concerns
anticipated for Tuesday with mostly clear skies and west-
northwest winds of around 10 knots.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.

&&

$$

DISCUSSION...Roller
AVIATION...Marsili