Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/27/23

Area Forecast Discussion

National Weather Service Indianapolis IN

 1000 PM EDT Thu Oct 26 2023

.Forecast Update...
Issued at 1000 PM EDT Thu Oct 26 2023

305K Isentropic data is showing lower condensation pressure deficits
late this evening and overnight, spreading east across central
Indiana. This implies, the atmosphere will be moistening down which
in combination with radar trends upstream, across central Illinois,
CAMS trends and weak embedded impaules in southwest flow aloft is
enough to keep at least chances PoPs in through the overnight.

Temperatures will not budge much with the continued warm advection.
Overnight lows will be mostly in the lower to mid 60s.

&&

.Short Term...(This evening through Friday)
Issued at 308 PM EDT Thu Oct 26 2023

* Near record warm low temperatures tonight
* Isolated to scattered showers overnight into Friday

A warm, cloudy, and breezy weather pattern continues today and
tomorrow for the state of Indiana as a strong baroclinic zone
remains parked over the region. Current satellite imagery clearly
depicts a ridge of high pressure over the Southeast CONUS with
tropical moisture streaming northward on its western periphery. At
the surface, high pressure is centered over North Carolina with an
elongated area of low pressure/frontal boundary from the Front Range
to Minnesota. Over the next few days, mid and upper level waves will
ride along the baroclinic zone periodically bringing increased
clouds and showers to the region. See the Long Term Forecast for
details on when the heaviest rain is expected for Central Indiana
this weekend. Currently, the best forcing for ascent and moisture
advection is located just north and west of the region, however
everything shifts eastward tonight and tomorrow with increasing rain
chances for Central Indiana.

.This evening and tonight...

Current satellite imagery clearly depicts broad southwest flow over
the entire region with thickest cloud cover and convection located
from Arkansas to Southern Wisconsin. Mainly dry conditions have been
reported across Central Indiana this afternoon and evening so far
with temperatures in the mid 70s. Short term guidance shows
southwest flow increasing at all levels this evening and overnight
as the baroclinic zone slowly pushes eastward over the region with
an upper wave passing through. Increasing moisture advection aloft
will result in the atmospheric profile becoming more saturated in
the lower levels. Current IND ACARS sounding shows a very dry
environment not supportive of any shower activity before at least
sunset. The presence of such a large dry layer will likely keep any
showers light and widely scattered overnight until deeper saturation
occurs. PoPs remain under 30 percent through around 09z tonight
across the region, then begin to increase in the southern half of
the state closer to sunrise tomorrow morning.

With this weather pattern in place, warm, southerly flow and cloud
cover will keep temperatures from falling much overnight. Forecast
lows are in the mid 60s across the entire region. In fact, a few
locations could set daily record warm low temperatures by Friday
morning.

.Friday...

A strong 35-45 kt low level jet will continue to pump moisture into
the region on Friday resulting in overcast skies much of the day and
the chance for showers. As mentioned above, showers will have a lot
of dry air to overcome, which will likely keep convective
development more isolated with lower rainfall amounts. Friday
morning into early Friday afternoon, Southwest and South Central
Indiana have the best threat at seeing more widespread showers as
the environment will likely saturate quicker in that area. Not
expecting a wash out of a day though as there likely be a break in
the showers during the afternoon and evening before heavier rain
pushes in Friday night. Potential is there for an isolated lightning
strike or rumble of thunder across the south, but any instability
amounts look quite low. Keeping isolated thunderstorm wording in the
forecast to account for this, but not overly impressed with what
guidance is showing.

Highs Friday were lowered towards the NBM25th percentile as the
presence of scattered showers and thicker cloud cover will likely
limit boundary layer heating despite strong warm air advection.
Still kept highs in the low to mid 70s everywhere, which is well
above average for this time of October anyway.

&&

.Long Term...(Friday night through Thursday)
Issued at 308 PM EDT Thu Oct 26 2023

* Heavy rainfall possible over the weekend
* Unseasonably cold temperatures next week with near record values
  possible (resulting in a widespread hard freeze)

A trough will be approaching at the beginning of the long term
period while a blocked ridge persists in the SW. This will allow for
the leading edge of the trough to stall near or over the region,
setting up SW flow from around Texas to the Great Lakes, with
moisture advecting into the area with it. Associated rain and
thunderstorms will begin around or prior to the start of the period
with best chances for rain and heavy rain being Saturday late
afternoon through Sunday night. Models show that an extra surge of
moisture may ride along the leading edge sometime this weekend, due
to remnants from Hurricane Otis tracking northward. Exact timing and
locality of heavy rain as well as higher QPFs remain uncertain as
models vary on where the stalled trough sets up. Best chances for
those higher amounts will be over southern Indiana but the bullseye
has the potential to set up anywhere from central Indiana down to
south and/or west of the Ohio River. At least a half an inch over
the weekend is likely across our forecast area with amounts
potentially reaching near 2 inches or higher for some areas.
Luckily, the ground is dry and river and creek basins are low, so
there is the capacity for several inches over a few days. The
flooding concern will come from the potential of higher rain rates
dumping a lot of rain in one area over a short amount of time, so it
is still a hazard to watch for.

Eventually, the ridge will break down sometime early next week
allowing for the large upper trough to progress eastward and rain to
exit to the east. In its wake expect much colder temperatures for
Halloween and the start of November.

High temperatures this weekend will be in the 50s and 60s before
dropping into the 40s for next work week. Behind the front,
overnight lows are forecasted to be in the 20s for next week as
well.

&&

.Aviation...(00Z TAF Issuance)
Issued at 703 PM EDT Thu Oct 26 2023

Impacts:

- SSW wind gusts to 20+ knots after 14z Friday

- MVFR flying conditions possible in showers mainly after 09z-11z
  Friday

Discussion:

Mostly VFR flying conditions are expected through at least the
early overnight, then some MVFR ceilings and visibilities possible in
rain showers and possibly an isolated thunderstorm Friday as warm
and moist air continues to move in from the southwest in between
east coast high pressure and an frontal system to the northwest.


&&

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

$$

Update...MK
Short Term...CM
Long Term...KH
Aviation...MK