IWX issues Area Forecast Discussion (AFD) at Jul 31, 4:06 AM EDT357
FXUS63 KIWX 310806
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
406 AM EDT Thu Jul 31 2025
.KEY MESSAGES...
- Showers and isolated thunderstorms will persist into late
morning. Locally heavy rainfall and isolated flooding remain
the primary threats.
- Cooler and less humid weather Friday into this weekend.
- Dangerous swim conditions are expected along the beaches of
southeastern lake Michigan primarily in LaPorte county into
the start of the weekend.
&&
.DISCUSSION...
Issued at 406 AM EDT Thu Jul 31 2025
Rather disjointed radar mosaic as a weak deformation zone band
of lighter precip extended from Gary, IN northeast into
southern lower Michigan with overall precip rates under a tenth
per hour as lowering dewpoints (low 60s) continue to advect in
from the NE. Further south, an area of rain/rainshowers and an
embedded storm or 2 (most recently east of Marion) was rooted in
the deeper moisture (upper 60s to low 70s) with highly variable
rainfall rates (mainly a quarter inch or less, but stronger
returns across Grant to Jay counties upwards of 0.5 to 1"/hr.
CAMs continue to show an uptick in coverage should occur, but
confidence is lessening as dewpoints across NW Ohio are already
starting to drop (mid 60s) and this should shift SW into the
larger area of precip. Pops have been adjusted to reflect trends
and thunder chances confined to southern areas although models
all agree on negligible instability by 12Z and beyond. Stratus
is likely to linger for a while, but clearing should commence in
NW areas and progress SE through the day. Although dewpoints
will be slowly lowering, 850 mb temps will only drop slightly
with the main push of colder and drier air not arriving till
tonight into the weekend. As a result, the faster clearing may
allow NW areas to end up warmer for highs today than SE spots
under the cloud cover.
Over the next days a long overdue transition to cool and much
less humid conditions will occur as high pressure builds from
the north. Overnight lows tonight will bottom out in the low to
mid 50s, with temperatures this "cold" not having been felt
since the first half of June. Afternoon highs will even end up
near to slightly below normal in the mid 70s to lower 80s into
Sunday. The upper level trough will linger through much of the
upcoming week. possibly shifting eastward toward the end of the
period. Although local model blend introduces some slgt chc to
chc pops as early as Tuesday, skeptical on these coming to
fruition as deeper moisture will remain well to our south.
&&
.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 134 AM EDT Thu Jul 31 2025
A band of light rain/showers extends from KORD into southern
Lower MI. This will slowly expand and pivot over KSBN over the
next several hours and linger through 12Z or so. MVFR cigs are
in place with upstream obs showing periodic IFR conditions. Have
adjusted for these anticipated trends. At KFWA...impacts from
heavier rainfall and IFR cigs (already in place and likely to
persist) as a expanding area of showers edges in at the start of
the period with CAMs showing expansion of the precip overnight
into Thursday morning before weakening/shifting east. Have opted
for a more aggressive approach here with a tempo group for some
potential LIFR cigs based on observations. Thus far, thunder has
remained in central IN, but can't rule out a few storms at KFWA
overnight (not currently in TAF). Will monitor for possible
addition if upward trends occur in lightning.
Flight conditions will improve first at KSBN with VFR cigs and
vsbys arriving by 16Z, but likely to be delayed at KFWA until
closer to the 21-23Z time frame.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Beach Hazards Statement through late tonight for INZ103.
OH...None.
MI...Air Quality Alert until midnight EDT tonight for MIZ078>081-
177-277.
MARINE...Small Craft Advisory until 5 AM EDT Friday for LMZ046.
&&
$$
DISCUSSION...Fisher
AVIATION...Fisher
Source:
IWX issues Area Forecast Discussion (AFD) at Jul 31, 4:06 AM EDT---------------
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