Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/22/22

Area Forecast Discussion

National Weather Service Indianapolis IN

 1149 PM EDT Sun Aug 21 2022

...Updated Aviation Discussion...

.Forecast Update...
Issued at 1007 PM EDT Sun Aug 21 2022

Cyclonic low-level flow behind departing shortwave trough and
residual moisture has resulted in isolated showers continuing into
late evening. These are decreasing with loss of diabatic surface
heating, however. Latest ACARS at IND shows deep moist layer still,
beneath warming/capping midlevel subsident layer. This has kept
shallow and no lightning has been observed over the last several
hours.

With weakening winds and good radiative conditions at least briefly
early tonight, T/Td depressions will decrease and patchy fog could
form. Later in the night, stratus is expected to spread into at
least portions of the area limiting a more significant fog event.

Previous forecast remains in good shape.

&&

.Short Term...(This evening through Monday night)
Issued at 251 PM EDT Sun Aug 21 2022

* Scattered showers and storms come to an end this evening.
* Dry and relatively mild for the time of year this week.

Upper level trough axis is overhead this afternoon, and while water
vapor imagery shows the deeper moisture axis has shifted well south
and east of the area, MLCAPE of 1000-1500 J/kg has developed owing
to breaks in the clouds, lingering low level moisture, and cooler
temperatures aloft with the trough. Poor effective shear values will
limit updraft organization, and thus expect little more than a few
heavy downpours and perhaps a few wind gusts/small hail events with
the strongest updrafts near peak heating this afternoon.

This activity is strongly diurnally driven and will dissipate
rapidly with sunset this evening, thus will carry only slight chance
pops in the east for an hour or so past 00Z.

Low level moisture will linger through the night, and subsidence on
the back side of the trough looks to produce some low stratus and
perhaps some patchy fog near daybreak Monday, and have made grid
adjustments to reflect this.

Convective temperatures will be reachable tomorrow, however a
strengthening midlevel subsidence inversion looks likely to prevent
any significant precipitation, and will carry a dry forecast. Cannot
rule out an isolated sprinkle, but this will be too inconsequential
for a mention. Have increased daytime cloud cover to account for
likely ample cumulus development.

Low clouds in the morning and a milder, drier airmass in general
should limit highs to the upper 70s to low 80s on Monday after
morning lows not far above overnight dewpoints in the low to mid
60s. Lows across the area look good to get down into the mid 50s to
low 60s Monday night as skies clear and dewpoints continue to
decrease.

&&

.Long Term...(Tuesday through Sunday)
Issued at 251 PM EDT Sun Aug 21 2022

Surface high pressure and a dry column per BUFKIT soundings should
keep next work week mostly dry despite a slow moving trough that
will migrate over eastern Canada, the Great Lakes and Ohio Valley.
This system is expected to force a cool front through central
Indiana early in the weekend before it returns northeast as a warm
front late next weekend as upper ridging builds in from the west.
Would not rule out a few thunderstorms during the weekend with
soundings showing moisture increasing through the column a bit,
and instability increasing and frontal forcing. That said, the
ridge over the area will tend to suppress convection.

In general, combo of limited sky cover and low level moisture, low
level thermals and afternoon mixing support seasonable temperatures
with afternoon highs in the 80s and overnight lows mostly in the
60s.

&&

.Aviation...(06Z TAF Issuance)
Issued at 1149 PM EDT Sun Aug 21 2022

Impacts:

* IFR ceilings developing at least temporarily early this morning.

Discussion:

Residual moisture in northwesterly flow behind the departing wave
may result in low stratus later tonight, especially across east-
central Indiana. Ceiling heights per forecast soundings and hi-res
model guidance would likely be in the IFR range so we have adjusted
the TAFs for this and confined to a window for temporary coverage.
IFR ceilings would likely diminish by mid-morning once
heating/mixing commence. Where stratus does not occur, or before it
forms, radiative conditions may result in patchy fog. We have lowest
visibilities confined to HUF where stratus may be less likely, or
shorter duration that other TAF sites.

&&

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

$$

Update...BRB
Short Term...Nield
Long Term...MK
Aviation...BRB