IWX issues Area Forecast Discussion (AFD) at Jun 29, 4:31 PM EDT547
FXUS63 KIWX 292031
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
431 PM EDT Sat Jun 29 2024
.KEY MESSAGES...
- Scattered showers and thunderstorms this afternoon. A few
storms may become severe. Strong to locally damaging winds and
heavy rainfall will be the main threats.
- Dry, cooler & less humid Sunday and Monday. Highs in the 70s.
- Very warm Tuesday through Thursday (July 4th) with highs in the
80s to around 90. Chances for showers and storms each day.
&&
.DISCUSSION...
Issued at 358 PM EDT Sat Jun 29 2024
Very warm and moist airmass in place today. Instability is
definitely not lacking with around 5000 j/kg of SB CAPE present.
Dewpoint depressions were small today which allowed for mostly
cloudy conditions across most of the area with a few breaks of
sum peeking in but quickly filling in with the surface warming.
Surface dew points remained in the low to mid 70s for most of
the area. The only issue is some capping and an absence of a
decent lifting mechanism. With the late afternoon though we will
see some of that capping erode and latest CAM models indicating
some initiation of convection over the central parts of the CWA
and then moving southeastward into this evening. Any future
outflow boundaries could also spark further convective
initiation as well. Currently, SPC has removed all mention of
slight risk for our area but we are still in a marginal risk
over the entire CWA. Effective bulk shear values of 30 to 40
knots will be present later today and that could help any storms
that do develop to become organized. Storm relative helicity
values will be less than 100 m2/s2 so will make tornado chances
very low. However, with precipitable water values above 1.5
inches to around 2 inches, heavy rainfall will accompany these
storms. Some localized nuisance flooding will be possible with
these storms. Gusty winds with the additional precipitation
loading will also be possible.
As any of the storms that have developed move southeastward
through the evening a drier and cooler airmass will move into
the area in it's wake with northwesterly flow aloft on the
northeastern periphery of a broad ridge moving easterly over the
southern CONUS. Decreasing clouds on Sunday with highs only in
the 70s and even the upper 60s with a northwest wind bringing
cooler temperatures from over Lake Michigan inland to near shore
areas south and southeast of the lake. Winds will also be on
the increase with gusts around 25 mph or so possible for Sunday.
The increased winds and the northwesterly fetch will make for
dangerous conditions for the beaches of Lake Michigan. A Beach
Hazard statement will be in effect from 1 AM EDT until late
Sunday night to address this hazard.
Comfortable and drier conditions remain through at least Monday
with high temperatures in the 70s with surface ridging again
moving into the area bringing mostly clear skies and a return to
warmer conditions. Warmer temperatures for the rest of the week
will commence on Tuesday with highs back into the 80s and by
Wednesday which looks to be the warmest day next week with highs
around 90 and along with dew points back into the low 70s will
make it uncomfortable once again. The increase in moisture and
temperatures will also make for periods of increased chances of
showers and thunderstorms beginning Tuesday evening and through
Friday.
&&
.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1241 PM EDT Sat Jun 29 2024
Confidence is increasing that KSBN will be dry for the
afternoon, with thunderstorms developing southeast of there
this afternoon, eventually moving over KFWA.
Surface observations indicate a moisture rich atmosphere is in
place ahead of a cold front. Clouds are thinning over eastern IL
and western IN, likely setting the stage for additional
thunderstorms this afternoon. Convection allowing models have
been rather consistent with storms impacting KFWA in the 22z to
00z window.
Otherwise, at both sites, plenty of MVFR ceilings are noted
upstream. The duration is a little uncertain at KSBN but
ultimately hedged toward the existing forecast. Later tonight,
there is there a 50-60% chance of MVFR stratus developing.
Time-height cross sections confirm this. Medium confidence at
best on the exact timeline, however.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Beach Hazards Statement from midnight CDT tonight through late
Sunday night for INZ103.
OH...None.
MI...Beach Hazards Statement from 1 AM EDT Sunday through late
Sunday night for MIZ177-277.
MARINE...Small Craft Advisory from 1 AM Sunday to 5 AM EDT Monday for
LMZ043-046.
&&
$$
DISCUSSION...Andersen
AVIATION...Brown
Source:
IWX issues Area Forecast Discussion (AFD) at Jun 29, 4:31 PM EDT---------------
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