Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/23/24

Area Forecast Discussion

National Weather Service Indianapolis IN

 942 PM EDT Fri Mar 22 2024

.KEY MESSAGES...

- Isolated light rain showers will continue through shortly past
  midnight
- Hard freeze possible again Saturday night
- Gusty southerly winds Monday to around 40 mph
- Potential for heavy rainfall Monday night-Tuesday night

&&

.FORECAST UPDATE...
Issued at 942 PM EDT Fri Mar 22 2024

As steady light rain moves out of far southeast portions of central
Indiana...a weakening band of showers is moving into the northern
Wabash Valley immediately following a cold front. In between across
much of the forecast area it was mainly cloudy and dry with winds
gradually shifting to northerly as the boundary moves in. 0130Z
temperatures ranged from the upper 30s over northeast counties to
near 50 in the lower Wabash Valley.

Overall...the ongoing forecast remains solid for the rest of the
night. The band of showers has begun to show a weakening trend and
expect that to continue as it moves into the region over the next
few hours. ACARS soundings from KIND show a column with limited
moisture and the shift to north-northeast flow in the boundary layer
is advecting drier air into the region already. Will maintain chance
pops for the next few hours focused especially across the northeast
half of the forecast area...but any amounts will be just a couple
hundredths at best.

Of greater impact will be a return to gusty winds in the wake of the
frontal passage highlighted by a brief period of 1-2 hours with
gusts potentially pushing 35-40mph immediately after the boundary
passes as noted by obs across central and eastern Illinois over the
last couple hours. With a tight surface pressure gradient trailing
the boundary and cold advection in play as well...winds have not had
trouble getting to the surface within a narrow axis just behind the
boundary. This is likely to impact the Wabash Valley in particular
with sounding data showing an inversion present further east across
central Indiana which should mitigate some of the stronger winds to
the surface. The strongest gusts will come through 06Z then slide
back to 25-30mph for the rest of the night.

Nudged lows up a degree or two with clouds holding for much of the
night. Still anticipate lows to drop into the upper 20s to mid 30s
from northeast to southwest. Zone and grid updates out.

&&

.SHORT TERM (This evening through Saturday)...
Issued at 312 PM EDT Fri Mar 22 2024

Clouds have almost complete encompassed central Indiana as of 1730Z,
with a mid level saturated layer advecting northward. Deeper
saturation has allowed for isolated light showers across locations
along and south of I-70, despite the surface layer remaining quite
dry with dew point depressions of of 15-20 degrees. This should
slowly increase throughout the afternoon and evening, eventually
leading to greater coverage of light showers. Given the lack of a
southerly wind component and extended cloud cover, temperatures are
failing to reach previously forecasted levels. Highs in the mid to
upper 40s look much more likely for central Indiana.

By midnight, a larger upper level wave will push out the shortwave
along with an associated weak frontal boundary. This will end any
remaining light showers and shift winds from ENE to N. The pressure
gradient behind the wave in much greater; this along with the
typical nocturnal LLJ increase should lead to breezy conditions. The
current expectation is for sustained winds between 10-15MPH with
gusts up to 30MPH.

Marginally cooler air will usher into the Ohio Valley with the
moderate northerly flow, leading to below normal temperatures for
Saturday. Winds are likely to stay elevated throughout the morning,
but should die down in the afternoon as the wave`s influence wanes
with its progression eastward. Expect cloud cover to also decrease
throughout the day, with mostly clear skies by the evening.

&&

.LONG TERM (Saturday night through Friday)...
Issued at 312 PM EDT Fri Mar 22 2024

The long term period will start off dry with near normal
temperatures. An upper trough with associated surface low
progressing through the lower 48 will approach the area early in
the week bringing rain, winds, and warmer temperatures, into the
60s, on Monday. Rain is expected to last through the day Tuesday
and should bring a healthy amount of rain to the region as
moisture surges up from the Gulf of Mexico. Current models are
showing PWATs of 1 to 1.5 inches over several hours and the
potential for QPF to be over 1 inch with this system. The rain
will be ahead and along the associated front which should pass
through central Indiana Tuesday night. Ahead of the front will
also include tight pressure gradients and breezy winds on Monday
and potentially Tuesday. Max gusts Monday are expected to be
around 40 mph. Rain will quickly come to an end behind the front
as a dry surface high will quickly follow. This high will linger
over the area through the rest of the forecast period allowing for
dry weather as well as temperatures to drop briefly Wednesday
with highs only reaching the the mid 40s to low 50s. Lows for the
latter half of the week will stay around freezing with the dry
conditions allowing greater cooling overnight.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 642 PM EDT Fri Mar 22 2024

Impacts:

- Scattered light showers possible through the evening and early
overnight
- MVFR ceilings developing overnight into Saturday morning
- Northerly wind gusts up to 25kts later this evening through
Saturday afternoon

Discussion:

Much of the widespread light rain from earlier has shifted closer to
the Ohio River and southeast of all terminals early this evening. A
narrow axis of drier air lingers between the broader moisture plume
to our southeast and the approaching cold front across northern
Illinois. An area of showers is currently accompanying immediately
behind the boundary but as it moves into the area over the next few
hours...the drier air lingering over central Indiana will likely
serve to minimize precip coverage to scattered light showers at best
later this evening into the early overnight.

Of greater impact to aviators will be a backing of winds to
northerly with a quick burst of gusts potentially in excess of 25kts
for brief periods this evening into the overnight as the front
passes by. Gusts will drop back slightly during the predawn hours as
the pressure gradient subtly relaxes but expect them to linger well
into Saturday as boundary layer mixing develops during the day.

A period with MVFR ceilings will also expand across the terminals in
the post-frontal environment late tonight into Saturday morning
before mixing out as drier air advects in. Mostly clear skies are
expected by the afternoon with gusts dropping off late day as the
influence of a high pressure ridge is felt.

&&

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

&&

$$

UPDATE...Ryan
SHORT TERM...Updike
LONG TERM...KF
AVIATION...Ryan