183
FXUS63 KIWX 081043
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
643 AM EDT Wed May 8 2024

.KEY MESSAGES...

-Dry conditions expected today, with increasing chances for
 showers and thunderstorms after 8 pm EDT. Chances for showers
 and storms continue through most of the week, with highs in the
 70s and 80s today dropping into the 50s and 60s Thursday into
 Saturday. We warm back into the upper 60s and low to mid 70s by
 Sunday.

-Isolated strong to severe storms are possible this evening,
 mainly south and west of a line from LaPorte, Indiana to Lima,
 Ohio. The primary hazards with any strong to severe storms that
 develop would be heavy rain and localized flooding, damaging
 winds, and large hail. Confidence in severe weather occurring
 is low at this time.

&&

.DISCUSSION...
Issued at 528 AM EDT Wed May 8 2024

Quiet weather today with high pressure in control, just some morning
fog to contend with-which seems to be shallow or at least not
widespread. There could be a few dense spots, with Angola and Goshen
and Elkhart bouncing between 4-6 miles and down to 1/4 mile. Opted
to hold off on any SPS for now given the patchy nature and
intermittent duration. Expect improvement after sunrise, with highs
climbing into the 70s and low 80s under partly to mostly sunny
skies. Clouds will be on the increase from south to north through
the late afternoon as our next system approaches.

The SPC Day 1 Outlook has roughly the southwest half of our CWA in a
marginal risk for isolated strong to severe storms this evening
(southwest of a line from LaPorte, IN to Lima, OH). Not too
impressed with this set up for our area, and I suspect that severe
weather will pass us just barely to the south this evening-so
confidence is low. A cold front extends through central Lower
Michigan into central IN (over our office, actually), and
southwestward into IL/MO/OK, and it will continue eastward through
the late morning (out of our area). A surface low developing along
the front over MO will lift northeast through the afternoon into IL
by 00z, lifting a warm front up to about our southern border
(depends on the model). Have pops increasing from south to north
starting at 8 pm EDT, which is better in line with the higher
resolution guidance (hrrr/Rap). Expect the window between 8 pm and 2
am will be our best chance for severe weather, as this is when we
have some surface based instability (300-700 J/kg, best early on),
stronger forcing from the approaching mid level trough, a coupled
upper level jet structure (west of the CWA, shifting east), and the
bulk shear profiles are still decent (35-55 knots). The issue is
that models are conflicted as to how far north the surface low gets,
and then whether or not some discrete cells develop ahead of the
main line early on (HRRR, RAP, NAM show this) then the convection
along the cold front really takes off just to the south, which I
suspect will limit the deeper moisture necessary for the higher
continued pops (a lull). When the stronger jet coupling moves in,
the surface low splits--which I suspect is where models are
struggling--with the broader low remaining over IA/IL and the (I
suspect) more mesoscale induced low moves along our southern border
heading eastward. Some of the guidance has stronger mid-level lapse
rates of around 7C/km, but per the latest HRRR/RAP/NAM they look to
be around 5-6C/km, which is another strike against severe weather.
The primary hazards with any strong to severe storms that develop
would be heavy rain and localized flooding, damaging winds, and
large hail. By 2 am, the instability wanes and we are limited as far
as forcing goes (some stability behind the stronger line to the
south), so the severe threat will wane significantly as well.

As the LLJ kicks in and we get better moisture transport, expect
showers to redevelop along the warm front either in the central or
northern CWA (E-W orientation). Rain will continue through Thursday
night, with isolated thunderstorms when we can get some instability.

By Friday into the weekend, the entire Great Lakes is beneath an
upper level trough, with a parade of rapidly alternating
ridges/shortwaves that each bring chances for showers and maybe
thunderstorms to our area on and off through the week. Today and
Friday are the driest days, though this weekend into early next week
we mainly have 20-40 percent chances (low confidence). Temperatures
drop into the 50s and 60s until Sunday, when we see upper 60s and
low 70s for highs. Temperatures warm into the low to mid 70s by
early next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 635 AM EDT Wed May 8 2024

The front moved through last night, although winds have become
light southwest early today. A small band of dense fog had
formed near the Mich border. SBN had dropped down to 1/4SM,
although conditions have improved to 3SM. The latest satellite
showed the fog drifting north with improvement south of the SBN
terminal. Conditions should improve early with a break before
more rain arrives tonight as the warm front moves north. Expect
basically MVFR conditions with IFR possible with the embedded
storms/heavier rain.

&&

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

&&

$$

DISCUSSION...MCD
AVIATION...Skipper