IWX issues Area Forecast Discussion (AFD) at Jul 27, 2:47 PM EDT
480
FXUS63 KIWX 271847
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
247 PM EDT Sun Jul 27 2025
.KEY MESSAGES...
- A Heat Advisory is in effect for today for heat indices from
95 to 100 degrees.
- Hot and humid weather is expected Monday and Tuesday with
afternoon heat indicies between 100 and 110 degrees.
- Isolated to scattered thunderstorms are possible today through
Tuesday. Severe weather is not expected.
&&
.DISCUSSION...
Issued at 245 PM EDT Sun Jul 27 2025
Between the eventual position of the outflow boundary from
yesterday's storms and a theta-e boundary bisecting our area from
west to east, storms will likely continue to fire across our
southern 2 to 3 tiers of counties: at least south of a line from
Starke to Henry county. Still, 70+ degree dew points at the surface
pair with 15C dew points at 850 mb, deep warm cloud depths, and 1.5
to 2.5 inch PWATs to create a moist environment. Today, we have less
shear and so severe weather appears to be a low threat, but flooding
would be an issue with slow storm motion, training of storms, and
relatively weak MBE vectors. There was some discussion around a
flood watch today, but precipitation has generally been evenly
distributed across the area, even if there has been above normal
precip observed south of US-30 and west of I-69. As the
aforementioned boundary sinks southward this afternoon and tonight,
the storm threat shifts southward, which may also remove the
residence time of rainfall over a single area. The more widespread
storms seem to be south of the area between 00 and 03z, but short
range guidance wants to continue chances overnight. This seems a
little odd with better forcing shifting southward. Have retained a
token 15 to 20 PoP for now.
For Monday, a shortwave rides atop the ridge during the morning and
hours, and models appear to have an MCS dive southward around this
area. There is some question around if it dives southward through
the Mississippi Valley or dies into this area. Both cases may allow
debris clouds to stay around the area. If the MCS comes into the
CWA, it may create some localized shear to be able to sustain
updrafts and cause some gusty to damaging winds. This may also
affect the potential to see high heat. It was also noticed that
the NBM is way too high with dew points yesterday for today and
Monday and have slackened back dew points away from upper 70s
to mid 70s for peak heating time frame as a result. This allows
for more of a heat advisory scenario than a heat warning
scenario. As a result, have issued a heat advisory for the area
for Monday.
Yet another shortwave pushes into the area for Tuesday from the
Northern Plains (at least as the low res guidance depicts), which
puts Tuesday's chances for high heat in question with showers and
storms possible. 850 mb temperatures for both Monday and Tuesday are
in the low 20s C would allow highs in the low 90s if maximum mixing
is allowed. So the potential is there, we'd just need to realize
maximum mixing which is hard with higher dew points and chances for
showers/storms as well as lingering debris clouds again for Tuesday.
A cold front approaches for Wednesday as an upper low positions
itself over eastern Canada, and this brings another chance for
showers and thunderstorms. This time, models do bring some shear
into the area, and with some instability to work with severe weather
could be had. With mid level lapse rates also surpass 7C/km, we
could have a hail. This would also be contingent on favorable timing
though. 850 mb temps begin to collapse during the day to either side
of 20C and this should keep heat indices in the 90s, below heat
advisory criteria.
Behind the cold front, a cooler and drier pattern is forecast as a
1025 mb high comes in from Canada. Highs on Thursday and Friday are
only in the 70s and dew points are in the 50s and 60s. The dry
weather is expected to continue through the weekend. However, we'll
be watching down towards the Gulf for our next disturbance as a
shortwave approaches the west, we get a taste of the tropical air
again and showers and storms could arrive for the next work week.
&&
.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 155 PM EDT Sun Jul 27 2025
Low level theta-e boundary appears to be a focal point for
renewed shower/isolated thunderstorms early this afternoon.
Current axis of shower activity is situated south of KFWA, but
some weak veering of low level flow is expected later this
evening that could allow a few of these showers and storms to
reach KFWA vicinity. With a good deal of uncertainty on coverage
given less distinct mid/upper level forcing today, will hold
off on thunder mention under greater confidence can be attained
with PROB30 SHRA. Cannot discount isolated showers and storms at
KSBN also given proximity to stronger instability gradient, but
point probabilities appear to be too low at this time. Some
stratus fog/potential exists tonight given weak wind profiles,
near sfc moisture availability from recent rain, scattering
clouds. Greatest potential of IFR appears to be at KFWA and for
points east-southeast. Will maintain a dry forecast through this
period as upstream potential convective system is expected to
diminish across the Mid MS Valley Monday AM. Remnant outflows
could spark isolated convective potential Monday late
AM/afternoon, but confidence too low for inclusion at this time.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Heat Advisory until 9 PM EDT /8 PM CDT/ this evening for
INZ005>009-012>015-017-018-020-022>027-032>034-103-104-
116-203-204-216.
Heat Advisory from 1 PM EDT /noon CDT/ to 9 PM EDT /8 PM CDT/
Monday for INZ005>009-012>015-017-018-020-022>027-032>034-
103-104-116-203-204-216.
OH...Heat Advisory until 9 PM EDT this evening for OHZ001-002-004-
005-015-016-024-025.
Heat Advisory from 1 PM to 9 PM EDT Monday for OHZ001-002-004-
005-015-016-024-025.
MI...Heat Advisory until 9 PM EDT this evening for MIZ078>081-177-
277.
Heat Advisory from 1 PM to 9 PM EDT Monday for MIZ078>081-177-
277.
MARINE...None.
&&
$$
DISCUSSION...Roller
AVIATION...Marsili
Source: IWX issues Area Forecast Discussion (AFD) at Jul 27, 2:47 PM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202507271847-KIWX-FXUS63-AFDIWX)
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