660
FXUS63 KIWX 021533
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
1133 AM EDT Tue Jul 2 2024

.KEY MESSAGES...

- There is a marginal to slight risk for strong to severe storms
  on Wednesday between 2 and 8 pm EDT. The best chance will be
  along and south of US 24. Damaging winds and heavy rain are
  the main threats. Highs Wednesday will be in the mid to upper
  80s, with locations south of US 24 seeing heat indices in the
  low 90s.

- Mostly dry today and tonight, with highs in the 80s and
  variable cloud cover. There are low chances for showers this
  morning and maybe an isolated thunderstorm west near Lake
  Michigan this morning and then again late tonight. Highs will
  be in the 80s and lows in the 60s.

- There are chances for showers and thunderstorms most days
  Thursday into early next week, with potential for a couple of
  strong to severe storms Friday. Confidence is low at this
  time, but monitor the forecast for the latest. Highs will be
  in the upper 70s and 80s through the week, with lows in the
  60s.

&&

.UPDATE...
Issued at 1124 AM EDT Tue Jul 2 2024

Previous forecast is in good shape this morning with main
forecast uncertainty in low chances of rain showers across far
northwest portions of the area. Moisture advection has been
mainly mid level in variety today with dry low level air
persisting as evident on ILX 12Z RAOB this morning. Weak MUCAPE
of around 250 J/kg with this elevated moisture return could
allow a few showers or sprinkles to work into southwest Lower
Michigan through mid afternoon, but otherwise dry conditions
across the area. Clouds should gradually thin toward evening as
focus for additional convective initiation this evening shifts
back across the Mid MS Valley.

&&

.DISCUSSION...
Issued at 435 AM EDT Tue Jul 2 2024

Mid level ridging extending from high pressure anchored over the SE
CONUS today will keep us dry through tonight, then drift eastward
Wed AM as a trough works to break it down from the west. Highs today
will be in the low to mid 80s, warmest east of I 69 and along/south
of US 24. A warm front will lift northward across the area tonight,
bringing an increase in clouds and a wind shift from ESE to SW
overnight. Lows tonight will be around 70 degrees.

A cold front moves through from west to east Wednesday into Thursday
morning, bringing our next chances for showers and thunderstorms. A
few strong to severe storms are possible n the afternoon between 2
pm-8 pm EDT, mainly along and south of US 24. SPC Has our forecast
area mostly in a marginal risk, but there is a slight risk from near
Lima, OH to Portland, IN.

Coverage looks pretty isolated/scattered as the front initially
moves into our western CWA, but then as we get into better daytime
heating expect we`ll see sfc based instability along/south of US 24
in the 800-1600 J/Kg range. This should be enough to pop heavier
showers and storms, in addition to the increased moisture
convergence. 0-6 Km Bulk shear appears to be in the 20-30 knots
range at best, so don`t expect coverage of severe weather to be
widespread. The primary concern with any storms would be damaging
winds and heavy rain. Don`t expect much in the way of flooding
except maybe far southeast (near Lima, OH) where the front could be
slow to exit (some of the guidance stalls the front and has it
exiting closer to 11 pm EDT)-we could see some ponding of water on
the road and in fields. Otherwise, expect high temperatures to climb
into the mid to upper 80s, warmest along and south of US 24. Heat
indices may climb into the low and perhaps even mid 90s for areas
south of US 24. Lowered temps and heat indices a little bit from
previous forecast as it looks like the afternoon/evening will be
cloudier with higher pops. If we are drier or warmer than expected,
we may see heat indices in the upper 90s at times.

Less confidence as we go into Thu-Fri as models disagree on how far
south to take the cold front before it stalls and lifts back north
as a warm front. The ECMWF has the front stalling further north
than the others, and has a couple weak shortwaves ride along
the fairly zonal flow aloft and kick off convection Thursday.
Most models, however, sink the front further south and thus keep
any chances for precipitation out of our area save for areas
south of US 30. For now, have the best pops (30-60 percent)
south of US 30 and then 15- 30 percent north in the event the
more aggressive ECMWF is correct. It`s possible (if the GFS is
right) we are mostly dry on Thursday. High temperatures will be
in the low to mid 80s, and then lows will be in the upper 60s
and low 70s.

Meanwhile, as we are dealing with the potentially stalled front, a
deeper upper level trough swings into the Dakotas/MN. This feature
will slowly drift eastward into Upper MI/Lake Superior by 12z
Saturday as it weakens, and then into James Bay by Sat Eve. This
will push our frontal boundary north Thursday evening, extending W-E
across Lower MI from roughly Holland, MI through Detroit, MI and
southern Ontario by 12z Fri. The occluding surface low at that time
will be centered over WI/IA/IL, with the cold front extending along
the IL/IN border and the triple point just over the IL/WI State Line
on the Lake Michigan shoreline. The low lifts into eastern Upper
Michigan by Saturday morning, with a weak trough swinging through
our forecast area in it`s wake. Have high chance/likely pops
starting Friday morning and continuing through the day, then low
chances to account for the exiting front in the east, and the
incoming trough behind it. There could be a few stronger storms with
this system as we have around 35-55 knots of 0-6km shear and around
500-1000 J/kg sfc based CAPE. There is still uncertainty at this
point, but something to keep an eye on. Highs will be in the low to
mid 80s.

By next weekend, highs will be in the 70s and low to mid 80s. Lows
will be in the 60s. We`ll have the lingering trough over the Great
Lakes through at least Saturday night, then a brief ridge builds for
Sunday-Monday as the next system approaches. Have some chances for
showers and thunderstorms Saturday (especially in the afternoon),
then dry Saturday night into much of Sunday. The only exception will
be far west in the late afternoon as a cold front approaches our
area. The front slowly moves eastward through Tuesday, bringing
additional chances for showers and storms. Highs will be in the 80s
Monday and Tuesday, with lows in the 60s.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 630 AM EDT Tue Jul 2 2024

Theta-e advection aloft will bring ample mid/high clouds and
perhaps a sprinkle at KSBN but dry low levels will maintain VFR
conditions through the period. A weak cold front will wash out
across the area Wed morning. Aviation impacts are unlikely but
if they do occur they will be after 12Z. Light winds will
steadily veer ahead of the approaching front.

&&

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

&&

$$

UPDATE...Marsili
DISCUSSION...MCD
AVIATION...AGD