289
FXUS63 KIND 030636
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
236 AM EDT Mon Jun 3 2024

.KEY MESSAGES...

- Potential for patchy fog this morning

- Warmer today/tuesday periodic thunderstorm chances.
  The best chances will be Wednesday.

- Below normal temperatures in the 70s late week into the weekend

&&

.SHORT TERM (Today and tonight)...
Issued at 236 AM EDT Mon Jun 3 2024

Early This Morning...

Late evening cirrus has dissipated, with mid-lvl water vapor
indicating the channel is knocking on the door steps of Central
Indiana. The big concern overnight revolves around potential for fog
development. Dewpoints are still in the low 60s for much of the
area, and we never observed good afternoon/diurnally driven mixing
to provide any subsidence once the shallow stratus deck departed.
With a weak isallobaric gradient overhead from weak ridging, it
would appear favorable for seeing patchy fog to develop. Earlier in
the evening KIND VWP would equally support this with most targets
within 1000ft agl being less than 5kts; however, since 3Z we are
seeing targets return at 2-5kft agl from the southwest at roughly 10-
15kts. This would suggest we may be on the backside of the weak
ridge, and could inhibit the fog potential due to induced friction
within the boundary layer. While this appears to be the case for
Indy metro and points west/northwest, the same may not be for the
southeast forecast area. Surface OBS are indicating a few points are
seeing fog develop with some reduction to VSBYs being observed;
however, the duration for the lowest VSBYs does appear to be minimal
which is supportive of the shallow ground fog type and easily
fluctuates with any little bit of wind. Have opted at this time to
issue an SPS to highlight the nuisance hazard that could be
encountered early this morning across Central Indiana. Should
conditions deteriorate in the next few hours we may need to go with
a dense fog advisory, but at this time that does not appear to be
needed.

Remainder of today... Once sunrise hits, we should observe a steady
diurnal swing with temps. The caveat will be the increased heat
capacity to surface parcels due to the continued moist nature of the
boundary layer. So that should slow the rate of warmth late morning,
but with minimal cloud cover overhead and a weak gradient in the
pressure fields, temps should easily be flirting with 80 degrees by
noon or shortly after. Then through the afternoon hours temps will
continue to warm, but expect a cirrus shield to be arriving from the
west as the axis of higher mid-lvl moisture begins to drift east. So
expect a dry day, although there is a possibility that a few
isolated showers could develop late in the afternoon for the far
west/southwest portions of Central Indiana. Confidence is very low
in this scenario though.

Tonight...Slowly thickening cloud cover aloft from west to east
overnight. Guidance has continued to hint that some very weak
instability could nudge east overnight, and coupled with the moist
layer overhead could translate into an isolated shower/thunderstorm.
Have held onto low POPs as not all solutions are in agreement which
suggests a lower confidence forecast for precip tonight. With
thickening clouds expect temps to not radiate much below the middle
60s.

&&

.LONG TERM (Tuesday through Sunday)...
Issued at 236 AM EDT Mon Jun 3 2024

Highlights of extended continue to be the active weather mid-week,
with the anomalous shortwave that parks itself over the Great Lakes
region later in the week.

Tuesday... Some amplification to the 500mb wave ahead appears to be
favored for the Ohio Valley. With any amplification to heights, it
should aid the lower levels that remain moist with a channel of
water vapor present from the West GOMEX stretching north through the
Western Ohio Valley into the Great Lakes. Guidance is still leaning
towards perhaps weak mid-lvl diffluence in the morning, but the
downstream ridge should be drifting east and allow this moist
channel to arrive across Indiana by afternoon hours. As a result
there does appear to be some marginal instability, but nothing
organized from a vorticity maxima or presence of robust shear, so at
the moment feel that any convection should not grow upscale or more
organized within the moist column. In addition to the precip chances
Tue increasing, it does appear dewpoints will equally be elevated in
the mid/upr 60s and likely result in a humid afternoon with max
apparent temps nearing 90. The wildcard will be if upstream precip
develops earlier in the day and helps introduce solar shielding by
midday and holds temps down in the low 80s.

Tue ngt-Wed... there continues to be some disagreement amongst
guidance with respect to timing/placement of an upstream developing
shortwave. The 500mb flow does appear to be quasi-zonal, which
should help to shove the overhead amplified ridge east and as a
result increase the precip chances overnight into Wed. Parcels will
continue to be influenced by a warm/moist southerly flow, which will
only further aid in perhaps more organized precip coverage but the
timing appears to be around daybreak Wed. This will all hinge on the
upstream arrival to the shortwave. Should the ridging persist
longer, this will likely delay the precip channel until later Wed
and also produce a more humid/warm day Tue. Subsequently it could
also elevate the surface instability Tue aftn/eve, so several
elements remain in place.

As Wed progresses, a few things will be ongoing further upstream as
well as over the Central CONUS. Guidance for several days has
continued to place a shortwave sliding along the Northern CONUS
while further upstream a steadily growing ridge should continue to
amplify. Viewing the DESI 500mb/vort for mid-week and confidence
remains high in placement out west of a robust ridge, which should
result in a long trough period for the Great Lakes region and
further support the broad vort max providing added clouds and precip
chances to the Ohio Valley through weeks end.

Thur-Sat...With a northwest flow arriving later in the week, the
current projection is that the placement to the upper level
shortwave will be displaced to the north of Indiana and perhaps far
enough that precip coverage will likely be north/northeast.
Ensembles also lean towards weak lower lvl ridging, which could
assist with subsidence at the surface and pleasant temps in the 70s
for Thur/Fri.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 146 AM EDT Mon Jun 3 2024

Impacts:

- Patchy fog after 06z, MVFR and IFR conditions possible

Discussion:

Shallow stratus has dissipated; however, the next challenge is if we
will observe fog develop overnight. There have been a few locations
already report shallow fog development, and the setup appears to be
favorable. A few things that may help to inhibit fog develop are
that the KIND wind profile is suggesting the winds aloft have
increased from the southwest and could be enough friction to prevent
widespread fog development. Still feel that some fog may develop in
the more typical low/bowl like airfields that are more protected.
Otherwise those locations would see occasional reductions bouncing
between one half mile and several miles, and with ground fog that is
common.

Elsewhere winds will turn southerly overnight or just prior to
daybreak. This will help to further inhibit fog development with
mainly VFR conds prevailing right at daybreak. A cirrus shield
should start to arrive from the west midday/afternoon, but no
impacts to flying conditions.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...Beach
LONG TERM...Beach
AVIATION...Beach