IWX issues Area Forecast Discussion (AFD) at Jul 5, 1:54 PM EDT192
FXUS63 KIWX 051754
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
154 PM EDT Fri Jul 5 2024
.KEY MESSAGES...
- A chance for showers and thunderstorms exist today with the
greatest chance occurring during the afternoon. Gusty winds
and locally heavy rain are the main threats from storms.
- More comfortable humidity levels and leaning dry for this
weekend.
- Our next chance for showers and thunderstorms occurs between n
later Monday afternoon and much of Tuesday.
&&
.DISCUSSION...
Issued at 309 AM EDT Fri Jul 5 2024
With a Pacific jet across the mid and northern tier of the CONUS, an
upper low and associated strong vort max enter the Great Lakes
region today. This increased forcing pushes a cold front through the
area. With a subtropical high pressure system in the Gulf States,
the cold front is cut off from better moisture and that keeps
greater than 70s dew points south of the area today. Even still, the
ECMWF has greater than 1000 J/kg of MUCAPE and 30 kts of effective
shear for storms to work with. In looking at soundings and
hodographs on the NAM3k and HRRR, gusty to near-damaging winds could
be possible with DCAPE over 1000 J/kg, along with some small hail
likely made smaller as a result of the wetter low levels of the
sounding. Shear appears straight likely eliminating the tornado
potential. Locally heavy rainfall will also be possible. Look for
showers and potentially a few thunderstorms to arrive this morning
as an initial area of vorticity comes in from the southwest. But the
better storm chance appears to be after 18z between our western
border and IN-15, just out in front of the cold front, through
around 3z in our east. Still looks like one of the better areas for
stronger storms based on ingredients is in the I-69 corridor.
The better moisture is gutted behind the cold front for Saturday and
that likely keeps the rain chances on the low side to
potentially dry despite some delayed areas of vorticity moving
through in the flow. A cooler air mass comes in, but models
develop showers more in the morning, which is before the better
low level lapse rates develop in the afternoon. So this would
likely restrict the rain intensity and keep thunderstorms at
bay. High temperatures are expected to be in the mid 70s to
around 80 degrees, which is slightly below average for this time
of year.
Surface high pressure begins edging into the area Saturday afternoon
and evening and moves east of the area Sunday morning and this
provides a time of dry weather through this period. Then, from
Sunday afternoon to Monday morning, weak areas of vorticity move
southwest to northeast with our Lake MI-adjacent counties
potentially on the eastern periphery of their cross-hairs. Will have
slight to chance PoPs in this area during this time period, but am
not expecting any substantial rain from these opportunities given
how weak the forcing is.
Finally, better forcing arrives Monday afternoon into Tuesday as a
Pacific wave deepens the trough. The best time for instability is
Monday evening and Tuesday morning so will allow for thunderstorms
during that time frame. The aforementioned trough departs for
Wednesday and Thursday, which points to low chances for rain, if
at all. Aside from Monday, which has highs slightly above
normal, in the upper 80s, highs in the low to mid 80s will be
common Tuesday through Thursday, which is right around normal.
&&
.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 154 PM EDT Fri Jul 5 2024
Some light showers continue early this afternoon across
northeast Indiana in pre-frontal forcing zone. Best low level
moisture resides in this pre-frontal forcing region, and deeper
moisture should be exiting to the east over the next few hours.
Surface cool front working in from northeast Illinois will
likely become active with isolated showers and a few storms as
primary upper trough interacts with this front. Instability is
somewhat on the limited side however, which leads to low
confidence in coverage of thunder with this front. While thunder
is possible for a brief time later this afternoon at terminals,
point probabilities and confidence are increasingly on the low
side given instability limitations. Threat of showers should end
at KFWA after 23 or 00Z. Some brief MVFR cigs are possible at
KFWA/KSBN through around 20Z, but otherwise mainly VFR
conditions expected through remainder of afternoon into the
evening.
Primary upper level low center will track across the northern
Great Lakes tonight, but fairly strong low level cold advection
will overspread the southern Great Lakes. Some cold advection
induced stratocu is expected, particularly across KSBN area late
tonight into Saturday morning. Lower confidence exists at KFWA
regarding Saturday morning low clouds as better diurnal mixing
may begin by expected time of arrival.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Roller
AVIATION...Marsili
Source:
IWX issues Area Forecast Discussion (AFD) at Jul 5, 1:54 PM EDT---------------
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