930
FXUS63 KIWX 051733
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
133 PM EDT Sun May 5 2024

.KEY MESSAGES...

- Mostly dry today into Monday night, with only low chances for
  showers and thunderstorms south of US 24 Monday afternoon and
  evening. Severe weather is not expected. Highs will range from
  55 near Lake Michigan into the 60s and 70s inland today, then
  warm up slightly on Monday into the upper 60s and 70s.

- There is potential for severe weather Tuesday into Tuesday
  evening. Damaging winds, large hail, and heavy rain will be
  the primary threats with any storms. Chances for stronger
  storms may return Wednesday evening into Thursday morning, but
  confidence is low.

- Cooler with chances for showers and storms this weekend. Highs
  will be in the 60s, with lows in the 40s and low 50s. Severe
  weather is not expected.

&&

.DISCUSSION...
Issued at 507 AM EDT Sun May 5 2024

Dry conditions will prevail through Monday afternoon, with surface
high pressure and weak mid level ridging aloft. There is potential
for showers and storms south of US 24 Monday afternoon as a
shortwave ripples through the flow aloft, but much of the higher-res
guidance available keeps the precipitation further south. Lowered
pops slightly from yesterday, sticking around 20-30 percent at
maximum around 18-21z, then tapering off shortly after sunset.
Otherwise, expect decreasing clouds today with quite the temperature
gradient. Highs north of US 24 will range from 55 to 65, then along
and south of US 24 highs will be in the mid to upper 60s and low 70s
(warmest near Lima, OH; coldest near Lake Michigan). Highs on Monday
will be in the upper 60s and low to mid 70s. Lows will be in the 40s
and 50s.

The storm prediction center has most of our CWA in a slight
risk for severe weather on day 3 (Tue into Tue Evening), which
is reasonable given the latest model guidance. There are still
differences in the event specifics, but generally expect a
surface low to develop in response to a broad upper low in the
northern plains Tuesday, lifting a warm front through during the
afternoon. The low will occlude as it lifts ENE, bringing the
cold front in Tuesday evening. Where the exact sfc low develops
tracks is not for certain beyond it moving through the Great
Lakes region. The NAM has the low further northwest, and is
slightly slower than the GFS/ECMWF/GEM to start (fastest to move
precipitation out),however all have the warm front lifting
across from SW to NE from roughly 12z Tue to 00z Wed, with the
occluding front/cold front shifting across the south and east
through about 21z Tue-03z Wed. Split the difference for pops,
with chances beginning in the SW around 12z, then increasing to
widespread for the afternoon/evening. Kept low-end chances for
late Tuesday night in the event the slower exiting model
solutions are correct.

As far as severe weather is concerned, if things work out as models
suggest as of this writing, think we have a decent shot. As far as
ingredients go, it looks like we`ll have decent moisture transport
in the low/mid levels with flow off the gulf of mexico on a decent
LLJ. PWATS end up around 1.4 to 1.6, which is about 200 percent of
normal for this time of year. Obviously with the warm front lifting
northward in the morning we could see some marginal severe weather-
likely hail, as we have mid level lapse rates around 6-7C (8C if the
GFS is correct!). Towards the afternoon hours we build our surface
instability to around 1500-2400 J/kg, and 0-6 km bulk shear
magnitudes are in the 55 to 75 knot range (Depends on the model);
which is plenty to work with as far as severe weather is concerned-
so the probability of all threats increases into the afternoon and
evening. The best chances will probably be closer to 00z as we get
the increase in shear around sunset and the cold front is
progressing eastward/occluding. This certainly warrants watching
over the next couple of days. Highs on Tuesday will reach into the
mid to upper 70s, with lows in the 50s and 60s.

BUT WAIT! THERE`S MORE! Models are starting to suggest an additional
surface low moving through the CWA after a lull in precipitation
chances from Wednesday morning. This low develops in the central
plains Wed AM and lifts ENE into IN/OH by Thursday morning, exiting
the forecast area into the Lower Great Lakes by Thu Evening (00z
Fri). Once again, plenty of moisture to work with, with an even
better moisture transport off the gulf than the Tuesday system. The
warm front lifts up through Wed evening, with the cold front (and
the low pressure center) overhead by around 6-12z Thu. Again the 0-6
km bulk shear is on the order of 50-70 knots at times Wed afternoon
into Thursday, with possibly as much as 1000 J/kg of CAPE (depends
on the model). It is possible that the best storms stay south of our
area, but I wouldn`t be surprised to see a few strong/severe ones
(mainly along/south of US 30) with the cold front as the system
moves overhead (or just north). SPC has our area in a Day 4 outlook
for severe potential, but it`s low confidence at this point being
further out and dependent on the earlier convection that day/exact
low placement.

The upper low settles overhead for the weekend, so we see continued
low-mid range chances for showers and storms, in addition to cooler
temperatures. Highs will be in the 60s, warming closer to 70 by
Monday. Lows will be in the 40s and low 50s.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 133 PM EDT Sun May 5 2024

Surface high pressure moving through today provides a reprieve from
the rainfall for this TAF period. It moves in on the heels of an
area of cold air advection that brought clouds to the area last
night into this morning. This afternoon started with MVFR and IFR
CIGs around, but they are expected to rise with the diurnal curve
not too long into this TAF period. West winds today become more
easterly overnight with the high pressure system to our north, and
that is expected to provide more cloud cover into Monday. There
is still quite a bit of variance in model output of CIG heights,
but with the NBM having 30 to 40 percent chance of less than 3
kft CIGs will put a tempo group in there to indicate the
possibility. Future shifts will want to continue to investigate this
possibility further.

&&

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

&&

$$

DISCUSSION...MCD
AVIATION...Roller