IWX issues Area Forecast Discussion (AFD) at May 20, 12:26 PM EDT915
FXUS63 KIWX 201626
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
1226 PM EDT Tue May 20 2025
.KEY MESSAGES...
- Passing showers and thunderstorms today. Rain may be heavy at
times.
- Wind gusts from the east today at 35 to 40 mph.
- Scattered showers and thunderstorms linger in the forecast
through at least Thursday morning.
&&
.DISCUSSION...
Issued at 415 AM EDT Tue May 20 2025
A 998mb surface low is approaching from the Kansas City area. Wind
gusts locally have been strengthening already this morning,
with wind gusts of 30-32 knots at KLAF, KVPZ, and KSBN. This is
despite soundings this hour that are rather stable. High
resolution guidance suggests this synoptic wind field will
strengthen through the morning and midday hours as the low
approaches. Wind gusts of 40 mph are expected, especially along
and west of US31. Wind will be maximized either from showers
along the incoming warm front or, should skies scatter out
briefly this afternoon in the wake of the warm front, a strong
low-level jet could be able to mix down as well. Confidence is
medium at best for how this plays out as forecast soundings are
overall rather stable, yet model agreement is high and the
existing wind field early this morning supports it.
A line of thunderstorms moving into western Indiana this hour is
exhibiting a weakening trend on infrared satellite along with a small
decline in lightning. Our local environment, with an east wind
and dew points in the low-to-mid 40s will be hostile for these
incoming storms such that a weakening trend will continue.
Showers will move through from southwest to northeast through
the morning and midday hours. As the warm sector becomes
established overhead this afternoon, scattered showers and
storms develop south of US 24 amid 500 j/kg of MUCAPE and about
40 knots of shear. Forecast soundings are generally unimpressive
locally, but small hail is a possibility from the tallest
storms and, given the strong low- level wind field, perhaps a
gusty storm collapse. Anomalously high PWATS and boundary-
parallel flow permit the risk of heavy downpours.
Scattered showers and thunderstorms taper off for a time overnight
as a dry slot attempts to move overhead. This is followed by more
shower chances Wednesday and even Thursday as the low continues its
slow trek east.
Drying out by Friday and most likely into the weekend. I've
maintained some low POPs for coordination purposes, but
guidance has shifted this weekend's low pressure center farther
south such that the best rain chances overall could be well
south of US 24. An upper-level low swirling over the eastern
Great Lakes Sunday night through Tuesday brings additional
chances for rain while keeping temperatures cooler than normal.
&&
.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1225 PM EDT Tue May 20 2025
Steadier rainfall will continue to push NE away from the TAF sites
with a brief lulls in precip possible. Cigs either side of 1000
ft will settle in behind the area of rain and linger through
the period. With regards to vsby and additional rain/storm
chances models vary on timing and coverage bouncing between more
scattered showers/isol storms or additional bands of
convection. There is no way to fully capture this in the TAFs so
a broadbrushed shower approach through 6Z will be used and
tempo groups can be added as signals hopefully become clearer.
Models diverge even more in the 6Z - 18Z Wed period as the bulk
of additional rain could push well north into MI. Have went dry
after 6Z for now.
Last but not, least, east to northeast winds will remain rather
brisk, gusting to 30 knots at times into the evening before
diminishing as the sfc low begins to approach from the west.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Gale Warning until 5 PM EDT this afternoon for LMZ043-046.
Small Craft Advisory from 5 PM this afternoon to 2 AM EDT
Wednesday for LMZ043-046.
&&
$$
DISCUSSION...Brown
AVIATION...Fisher
Source:
IWX issues Area Forecast Discussion (AFD) at May 20, 12:26 PM EDT---------------
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