Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 01/08/24

Area Forecast Discussion

National Weather Service Indianapolis IN

 1002 PM EST Sun Jan 7 2024

.Key Messages...

- Two potentially high impact weather systems this coming week, one
early week, one late week. Confidence is high in the occurrence of
deep storm systems, but a bit lower in terms of precip types and
transitions.

- Potential for rapid burst of accumulating snow Monday night prior
to transition to all rain, mainly over northern half of central
Indiana. Precipitation transitions back to snow Tuesday night.

- Total liquid precipitation amounts in excess of one inch likely
with first system.

- Potential for additional significant precipitation late week as
well.

&&

.Forecast Update...
Issued at 1000 PM EST Sun Jan 7 2024

Enough upper level dry air has moved in, to diminish the few left
over isolated snow showers over central Indiana. Although there is
some dry air aloft, ACARS soundings shows a stable saturated layer,
of which should continue through most of the night. This will
inhibit diurnal cooling some, with lows near 30. A few areas in for
SE central Indiana could have some breaks in the clouds, enough for
lows in the upper 20s.

Otherwise, it will be an uneventful next 12 hours prior to the
arrival of a dynamic low pressure system tomorrow evening. Winds
will back as the warm front approaches from the south, with
light, easterly winds by tomorrow morning.

&&

.Short Term...(This evening through Monday)
Issued at 319 PM EST Sun Jan 7 2024

Rest of Today.

Snow has generally come to an end across central Indiana with
visibilities now greater than 6 miles across all but a few sites
across the northeast as what little forcing was remaining on the
backend of the system exits. Cloud cover remains near 100 percent
and based on upstream flow into the area, not expect anything less
than cloudy until the late evening/early overnight hours.

Tonight.

Quiet conditions are then expected tonight with cloud cover
remaining mostly cloudy but dry air will continue to erode the depth
of the clouds slowly. High pressure will slowly drift to the
northeast from Kentucky into Ohio ahead of the rapidly deepening
surface low that will impact the area Monday night into Tuesday.
With some clearing and drying temperatures will be able to cool into
the mid 20s ahead of warming temperatures tomorrow.

Monday.

Surface pressure gradients will gradually begin to tighten during
the daytime hours tomorrow with wind gusts to 20-25 mph by late into
the afternoon. Model soundings show the column will gradually
saturate through the day bringing a return to cloudy skies.  Details
on the expected rain/snow will be covered in the long term section
below.

&&

.Long Term...(Monday night through Sunday)
Issued at 319 PM EST Sun Jan 7 2024

Two potentially high impact storm systems are expected during the
long term period.

Event 1: Monday Night into Tuesday Night.

An extremely potent and rapidly-developing low pressure system will
swing northeast out of the southern Plains into the Chicagoland area
and central Great Lakes during this time frame.

Extremely strong dynamics and significant poleward moisture
transport will lead to widespread precipitation developing and
moving into the area Monday night.

Forecast profiles have come in actually a bit cooler with the most
recent runs, and despite the extremely strong meridional flow
through the mid-upper levels of the troposphere Monday night, a very
strong frontogenetic zone setting up over the area will produce
dynamic cooling and offset the associated warm advection for at
least a few hours mid to late Monday night, particularly over the
northern half of central Indiana - allowing for a quick burst of
briefly heavy snow to accumulate from roughly Indy metro northward,
before a rapid transition to rain occurs near daybreak Tuesday as
the low level frontal zone shifts northward with the low swinging
into central Illinois.

While the temperatures will still be a bit borderline, there is
surprisingly robust agreement amongst the guidance suite on this
transition/type expectation, and confidence is growing in
accumulations perhaps as much as 2-3 inches in some spots before
rapid melting occurs as rain begins and surface temperatures warm.

Rain will continue through much of the day on Tuesday, but there are
suggestions of a dry slot impacting the area Tuesday afternoon,
which would both reduce rainfall during that time and potentially
increase the wind gust threat, which is already fairly high.
Widespread and frequent gusts at or above 25-35 MPH are a near
certainty Monday night into Wednesday, with gusts near or in excess
of advisory criteria (45 MPH) still a possibility.

Rainfall amounts at or above one inch are also a virtual certainty,
which will help put a dent in long term precipitation deficits,
though will be unlikely to produce flooding. That said, some streams
may approach bankfull levels.

Minor accumulations will be possible in the wraparound precipitation
on the backside of the low Tuesday night as the low departs and
strong cold advection occurs, rapidly transitioning precipitation
back to snow.

Between Events: Wednesday night into Thursday

A quick-moving upper-wave may bring light snow and/or rain showers
to the area Wednesday night into Thursday. Deep saturation is poor
and brief, with much more than a dusting unlikely.

Event 2: Friday into Saturday

Model-to-model and run-to-run inconsistencies produce low confidence
in precipitation types, but confidence is higher that significant
precipitation amounts will occur late this week into the weekend as
another strong low pressure system moves through the region.
Ensemble probabilities do show a low to middling chance for
significant snowfall possibly over portions of central Indiana
during this time frame, but small changes will have dramatic impacts
upon this, and it is important to not seize upon one particular
model or model run, particularly the outliers, instead monitoring
model trends as we go through the week, keeping preparedness plans
in mind.

&&

.Aviation...(00Z TAF Issuance)
Issued at 616 PM EST Sun Jan 7 2024

Impacts:

-MVFR cigs through most of TAF period
-Wind shift from west to southeast after 10Z

Discussion:

Low clouds will persist through the night with brief VFR periods
between now and tomorrow afternoon. Westerly winds to 12kts
expected through the evening before winds lighten and shift to
the southeast late tonight into tomorrow morning.


&&

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

$$

Update...Updike
Short Term...White
Long Term...Nield
Aviation...Updike