000
FXUS63 KIND 131317
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
917 AM EDT Sat Apr 13 2024

.KEY MESSAGES...

- Warmer today and tonight with dry conditions
- Ongoing River Flooding and standing water in low-lying areas
- Multiple rounds of showers storms next week, severe weather
  possible Tuesday and Wednesday
- Cooling trend late next week.

&&

.FORECAST UPDATE...
Issued at 914 AM EDT Sat Apr 13 2024

- Sunny and Warmer this afternoon

Surface analysis late this morning shows high pressure centered over
the Gulf Coast, with a ridge axis extending north across the
Tennessee Valley into Illinois and WI. This was resulting in dry
westerly flow across Central Indiana. GOES16 shows clear skies
across Indiana and much of the region due to the influence of the
approaching ridge axis. Aloft, broad ridging was found emerging from
the Rockies to the high plains. This was resulting in lee side
subsidence across the Mississippi and Ohio valleys and the surface
area of high pressure.

Models today suggest the surface ridge will progress east and begin
crossing Indiana through the afternoon. Forecast soundings remain
dry through the afternoon with unreachable convective temperatures.
Thus we will expect a sunny afternoon. Given the warm air advection
and plentiful sunshine today forecasted highs in the upper 60s to
around 70 appear on the mark.

&&

.SHORT TERM (Today and tonight)...
Issued at 301 AM EDT Sat Apr 13 2024

Today...

Skies had cleared across central Indiana early this morning. Clear
to mostly clear skies will persist through much of the day today as
a ridge of surface high pressure moves east across the area. Some
high clouds may make an appearance later in the day ahead of a warm
front.

West/southwest winds will gradually back to the south during the
afternoon. Mixing will allow some gusts up to around 20 mph this
afternoon. Sunshine plus some warm advection will allow temperatures
to peak in the middle 60s to lower 70s this afternoon.

Tonight...

Some weak upper energy will move through the area in northwest flow
aloft. Meanwhile, a surface warm front will move northeast across
the area as low pressure moves from Wisconsin into Lower Michigan.

Isentropic lift will accompany the above features, but overall
moisture will be lacking. Thus, just expect some mid and high clouds
to move through tonight.

The pressure gradient will tighten across the area tonight as the
low moves into Michigan. In addition, a low level jet will move
through. An inversion should help keep mixing at a minimum, but if
the inversion isn`t as strong as expected, some gusts over 20 mph
may occur.

The clouds and southerly winds will keep temperatures warmer than
this morning, with lows in the 50s expected.

&&

.LONG TERM (Sunday through Friday)...
Issued at 301 AM EDT Sat Apr 13 2024

A large stacked area of low pressure and upper-level troughing is
departing to our east. This feature has brought cool and rainy
weather for the last several days. As it exits eastward, weak
ridging builds in to our west which will allow for a warming trend
over the weekend.

A weak upper-level wave looks to crest the ridge late Saturday/Early
Sunday, inducing cyclogenesis at the surface. The system should be
strong enough to induce a potent mass response and formation of a
roughly 50-60kt low-level jet. Sunday could be quite windy,
especially if any of this momentum can be mixed down to the surface.
Timing may be a limiting factor, however, as the system pulls away
and the MSLP and LLJ relax a bit during peak heating. Still, surface
wind gusts upwards of 30mph are not out of the question Sunday
morning/early afternoon.

As the system departs, it will drag a weak cold front across the
state. This front should settle somewhere in central Indiana and
lose its forward momentum. There`s a very low chance that a few
showers and thunderstorms develop on this boundary Sunday
afternoon/evening. Model soundings show instability (1000-1500 J/kg
MLCAPE), deep layer shear (40-50kt 6km bulk shear), and steep lapse
rates (7-8 C/km). The limiting factor here would be sources of lift.
The bulk of the synoptic scale forcing associated with the system is
likely out of the area by the time the front arrives. Additionally,
the front is in a weakening state and will lose its effectiveness
with time. With this in mind, the best chance of any showers and
storms or potentially severe weather would be further northeast
(closer to the departing low).

Meanwhile, out west, a trough is currently sitting off the
California coast. After spending a few days traversing the
intermountain west, this feature should eject into the Great Plains
on Monday. Guidance keeps this feature rather compact, with a strong
jet streak on its southern flank. Closer to the surface, robust low-
level flow leads to the development of a broad buoyant warm sector
which impinges into Indiana Tuesday and Wednesday. Some residual low-
level dry air over the southeastern US may get caught up in the
southerly flow ahead of the trough, which may narrow the axis of
instability somewhat.

In terms of sensible weather, enough instability should be present
for showers and thunderstorms. Lift is not an issue, as the dynamics
associated with the system are more than sufficient. Severe weather
is possible, as most guidance has shear values over 50kt. The
details of potential severe weather threats are not yet discernible
at this time. Enough spread remains within guidance regarding the
finer details despite the overall synoptic pattern showing better
agreement.

Beyond Wednesday, broad troughing returns to the Great Lakes and
Northeastern US. Ensemble guidance is trending cooler later in the
week and into next weekend. Lows may be cool enough for frost
potential late in the forecast period. Confidence remains low, but
it is worth mentioning.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 637 AM EDT Sat Apr 13 2024

Impacts:

- Non-convective low level wind shear tonight

Discussion:

VFR conditions are expected through the period. An increase in mid
and high clouds will occur tonight. Winds will become southwest to
southerly by early evening. As winds strengthen aloft this evening,
low level wind shear will develop.


&&

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

$$

UPDATE...Puma
SHORT TERM...50
LONG TERM...Eckhoff
AVIATION...50