786
FXUS63 KIWX 060436
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
1236 AM EDT Mon May 6 2024

.KEY MESSAGES...

- Primarily dry conditions will persist through Monday night but
there is a low chance of rain south of US-30 late Monday.

- Several rounds of thunderstorms are possible Tuesday through
Wednesday night. Some of these storms may be capable of producing
large hail and damaging winds. However, confidence in timing,
placement, and strength remains low.

- Cooler weather returns to end the week with periodic
  additional chances for light rain.

&&

.UPDATE...
Issued at 830 PM EDT Sun May 5 2024

Low clouds have largely eroded across the area, all but the far
northeast. Low clouds have been replaced by high clouds with more
extensive high cloudiness lifting into the area overnight. Near term
guidance low level RH progs do suggest some potential of some
stratus redevelopment downstream of the eastern Great Lakes with
good deal of lingering low level moisture beneath subsidence
inversion. Previous forecast has these trends in hand and no major
changes to near term will be made this evening.

&&

.DISCUSSION...
Issued at 250 PM EDT Sun May 5 2024

Dry/tranquil weather will persist through Mon morning. Weak/diffuse
cold front has largely cleared our area with stubborn postfrontal
stratus deck holding in our northern counties. Can`t entirely rule
out a sprinkle in our far E/SE but best chances remain outside of
our area. Overnight cloud forecast is tricky with most guidance
suggesting clearing by sunset. However, models have struggled with
this cloud cover over the past 12 hours and confidence is not
high. Will therefore hold with partly cloudy skies and lows
generally around 50F. Cooler temps possible if clouds scatter
entirely.

Broad midlevel shortwave will lift into the Ohio Valley tomorrow but
sharp midlevel ridging/AVA will maintain strong subsidence over the
Great Lakes. Still some uncertainty exactly how far north showers
survive tomorrow. General trend has been to keep precip just to our
south given weak 850mb theta-e advection in our area. There are a
few outliers though that suggest light showers sneaking to about the
US-30 corridor. Have therefore stayed very close to inherited low
PoP`s confined to our south. No impacts expected either way as
profiles appear too stable to support thunder and any rain will be
very light.

Primary focus continues to be on Tue-Wed for potential severe
weather and heavy rain concerns as deep western CONUS upper low
lifts NE toward the Great Lakes. This will actually occur in
piecemeal fashion as another strong Pacific jet/trough comes onshore
Monday and forces the development of a very large upper low over the
Northern Plains/Rockies that will also eject eastward in a piecemeal
fashion later this week. Unsurprisingly models are struggling with
exact details in this complicated pattern and confidence remains on
the low side.

Still expect the initial wave and associated warm front to lift
through the area late morning-early afternoon Tue. Models have
slowed this initial wave a bit which complicates the severe weather
forecast. A later arrival could result in that being the primary
"show" (which could itself feature large hail and damaging winds
given steep midlevel lapse rates, moderate instability of 2000 J/kg
SBCAPE, and a strongly sheared environment). Early arrival
could limit the instability but if the slower trends continue
that will increase the risk with round 1. If that is the case
that will in turn limit our potential for a second round during
the evening hours though with primary focus for severe storms
well to our south.

After a break Tue night into early Wed we will watch the potential
for another round of storms Wed evening-overnight as the primary
upper low finally releases east. All ingredients for severe weather
and flooding remain favorable given ample moisture advection on
strong LLJ, high instability, and very strong shear. The question
for Wed will be where exactly these ingredients come together with
track of surface low dependent on exact evolution of upper low and
likely some mesoscale influences from the day before. It is possible
the surface low and associated highest severe risks remain to our
south as suggested by the 12Z deterministic GFS and reflected in
the SWODY4. However several models suggest a further north track
that would impact our CWA.

Bottomline...the ingredients are in place for potentially
several rounds of strong/severe storms but details regarding
exact timing, placement, and strength remain low. Continue to
monitor the forecast closely as we narrow down these details in
the coming days.

Negative height anomalies persist over eastern Canada for much of the
Thu-Sat period. This will result in cooler temps with periodic
chances for light rain. Better moisture and associated instability
is shunted out of our region though. Chances for generic
thunderstorms (let alone strong storms) appear very low.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1236 AM EDT Mon May 6 2024

Dry and mainly VFR through the period as easterly winds pick up
to around 10 knots today north of a warm front. An upper level
system tracking east-northeast through the Ohio Valley will
continue to spread plenty of high cloud cover into northern
Indiana, with some cigs near 5 kft likely at KFWA during the day
today. There also remains a non-zero chance for a high MVFR
stratocu deck to briefly work into KFWA toward daybreak.

&&

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

&&

$$

UPDATE...Marsili
DISCUSSION...AGD
AVIATION...Steinwedel