197
FXUS63 KIND 011916
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
316 PM EDT Mon Sep 1 2025

.KEY MESSAGES...

- Quiet and dry weather through Tuesday

- Rain and isolated thunderstorms late Wednesday ending by early
  Thursday morning

- Another round of cooler/drier air late week into next weekend.

&&

.SHORT TERM (This evening through Tuesday)...
Issued at 314 PM EDT Mon Sep 1 2025

Another quiet short term forecast, thanks to the fairly stagnant
pattern in place with a longwave trough over the eastern U.S at mid
and upper levels and surface ridging over the Great Lakes into the
eastern seaboard.

Mostly clear skies will allow for another night of below normal
temperatures in the 50s across Central Indiana thanks to low PWAT
values from 0.6-0.7 inch (near 25% of climo) and light winds.
There will be some mid-high clouds that skirt the SW portions of
central Indiana associated with a weak shortwave moving southeast
across the MS valley.

Temperatures and PWATs will gradually rise tomorrow owing to a
slight increase in low level moisture as surface ridging fades and
winds become southeast by the afternoon. Skies will be mostly
sunny most areas, except for the far south where mid-high clouds
early will be replace with lower cumulus clouds in the afternoon.
Models have backed off on precip chances in far southern portions
of the forecast area for tomorrow afternoon. This seems reasonable
given the deeper moisture and mass convergence lift are well
southeast of the forecast area and primarily terrain driven
today, so pops have been removed from the forecast.

&&

.LONG TERM (Tuesday night through Monday)...
Issued at 314 PM EDT Mon Sep 1 2025

The pattern of a longwave trough in the east will continue through
the period. Additional shortwave energy riding along the northern
edge of a ridge across NW Canada will intensify as it progresses
southeast towards the Great Lakes region/Hudson Bay. Diabatic
processes from the interaction of seasonably warm water
temperatures underlying cold advection aloft does suggest some
rapid intensification of shortwave energy and models indicate
fairly deep/strong cold core low developing by late Wednesday
over the northern Great Lakes region and persisting into the
weekend.


As a result of the approaching/deepening shortwave, surface pressure
falls and increasing south-sw winds will usher in a more
moist/unstable airmass into central Indiana Wednesday ahead of an
associated cold front moving through the western Great Lakes. NAM
forecast soundings for late Wednesday look more reasonable
considering the source region of dewpoints in the upper 50s/lower
60s is as close as Missouri. These dewpoint values generate between
500-1000 j/kg of MUCAPE. Deep layer wind fields are fairly strong
and oriented about 60 degrees to the cold front. As a result a line
of heavy showers with at least isolated thunderstorms is expected to
develop late Wednesday afternoon just NW of central Indiana.  NBM
pops in the categorical range over 80 percent seems very reasonable
for Wednesday night. Given the aforementioned meager instability,
the threat for severe thunderstorms appears fairly low, but a few
strong wind gusts can not be ruled out given the kinematic
environment.

The fast movement of the front will aid in a quick cessation of
precip by early Thursday, likely by sunrise for all of central
Indiana. High temperatures about 10 degrees below normal will
occur Thursday, as a weak area of high pressure moves in behind
the cold front. Another deepening shortwave moves across the area
Friday phasing with the closed low over the Great Lakes.
Thermodynamic fields suggest FGEN forcing kicks in during the day
Friday which will lead to an increase in mid clouds and potential
for light rain by Friday afternoon.

In the wake of this shortwave, drier and cooler weather will
continue for the remainder of the forecast with highs 5-10
degrees below normal through the weekend. A larger amount of
uncertainty exists with the forecast as we move towards early next
week. Euro ensembles suggest a persistence of the east coast long
wave pattern albeit somewhat diminished, with the GEFS indicating
a more zonal pattern setting up across the region by Monday
thanks to increasing waa ahead of upper level ridging building
over the Rockies. Based on the degree of diabatic feedback
expected with the Great Lakes and the strength of the closed low
circulation, I am leaning towards the drier/cooler Euro solution
which is also reflected in the NBM output.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 118 PM EDT Mon Sep 1 2025

Impacts:

- None

Discussion:

VFR Conditions are expected through the TAF period. Back side of
long wave trough combined with high pressure over the Great Lakes
will continue to provide for mostly clear skies today except for
some high clouds that move out of the MS valley towards KBMG, KHUF
this afternoon. E-NE winds will gradually drop off this evening and
the possibility of some slight visibility reductions at KLAF towards
morning. High clouds will thicken somewhat overnight, so have
carried a period of broken ceilings for both KHUF and KBMG. Tomorrow
looks like a repeat performance, except for weaker winds during the
afternoon.


&&

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

$$

SHORT TERM...Crosbie
LONG TERM...Crosbie
AVIATION...Crosbie