Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 290055
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
855 PM EDT Thu Mar 28 2024

.KEY MESSAGES...

- Warmer on Friday

- Rain chances return Friday Night through Wednesday; thunderstorms
  possible at times

- Some uncertain potential for strong to severe storms early next
  week

&&

.FORECAST UPDATE...
Issued at 855 PM EDT Thu Mar 28 2024

Only minor changes needed to the forecast this evening, mainly
regarding winds and PoPs. Nudged winds upwards a bit for the next 1
to 3 hours to reflect current obs. Most short term high-res guidance
then depicts a weak boundary sagging southward this evening with
winds going light and variable along its axis. Upstream observations
are already showing this feature, so added additional weight to the
higher res guidance through 12Z. As for PoPs, current radar shows
light returns along and north of I-70. Not much reaching the ground
as of now, given a 20 degree temp dew point spread. Any precip will
be light, and scattered, so kept PoPs limited to 20-25 percent.
Added the mention of sprinkles to highlight the light nature of the
passing showers.

&&

.SHORT TERM (This evening through Friday)...
Issued at 300 PM EDT Thu Mar 28 2024

Rest of Today...

The Midwest and Great Lakes region is currently within a multi-
phased mid to upper level trough, aiding in LLJ enhancement. This
will have minimal impacts on the surface layer today, outside of a
brief 3-4hr period of increased gusting, up to 25MPH.

A lobe of vorticity on the southern edge of the upper wave is aiding
in low level pressure depletion, resulting in a weak 800-700mb wave.
This has increased mid level cloud cover over northern portions of
central Indiana. This increase in cloud cover could have minor
impacts on afternoon high temperatures, with these areas remaining
in the low 50s, vs upper 50s elsewhere.

Tonight and Tomorrow...

The aforementioned shortwave will deepen slightly into the
overnight, resulting in a slightly more elongated saturated layer
and possible even a few isolated showers and sprinkles. This should
be contained to along and north of I-70, but a few sprinkles could
stray into the rest of central Indiana. This extended cloud cover
should help limit diurnal cooling some, removing the freeze threat.
Still temperates should bottom out in the upper 30s by tomorrow
morning.

Southerly flow returns late tomorrow morning, increasing low level
warm air advection and eventually surface temperatures. This will
push highs back into 60s. The LLJ should weaken enough to mitigate
momentum transfer, keeping a modest sustained wind out of the SW at
8-12MPH
.

&&

.LONG TERM (Friday night through Thursday)...
Issued at 300 PM EDT Thu Mar 28 2024

The long term period looks quite prototypically Spring-like and
active, with warm temperatures and multiple opportunities for
showers and thunderstorms through the weekend into early next week,
including some uncertain potential for severe storms Monday into
Tuesday.

Broad quasizonal to weakly anticyclonic flow will be present across
much of the country over the weekend into early next week ahead of a
large upper level trough/closed low, which will slowly push across
the country into the middle of next week. Mid and upper level flow
ahead of this trough will be fairly stout and broadly
west/southwesterly, with lee surface cyclogenesis along a baroclinic
zone promoting sustained southerly flow and thus poleward
heat/moisture transport within the broad warm sector south of the
boundary.

Subtle leading impulses rounding the periphery of the ridge will
promote development of one or more weak surface lows Friday night
into early Monday, requiring precipitation chances to varying
degrees throughout.

Model convective indices suggest occasional low thunderstorm chances
will be required during this time frame, but the pattern suggests
little chance for organized convection over the weekend. However,
ensemble mean precipitable water values via DESI will range between
about 0.75 to 1.25 inches, which is anywhere from 75th percentile to
near climatological maximum, so hydrologic concerns will require
monitoring.

As we get into early next work week, a more substantial surface low
is expected to develop ahead of the encroaching upper level trough,
moving through the region Monday night into Tuesday. While not
necessarily a classical/textbook severe weather pattern, substantial
dynamic support in the form of 100-130KT upper level jet streak, a
50+KT 850 jet, and a broad, open warm sector with several days of
thermodynamic transport into the region will present at least some
severe weather threat, particularly if mesoscale ingredients and
timing can align in a favorable fashion. This will require
close monitoring in the coming days.

CIPS analogs and experimental CSU machine learning guidance have
been suggesting a severe threat for some time now, and outlined day
5-6 areas on SPC convective outlooks are quite reasonable per
current model solutions and these additional guidance sources.
Uncertainty remains high, of course, but we can begin messaging at
least a low severe threat early next week, primarily late Monday
into Monday night/early Tuesday.

Temperatures throughout the long term will generally be above normal
given the broad southerly flow, with the exception of a brief period
mid weekend as the boundary sags south of the area. NBM has a solid
handle on this and requires no major changes.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 747 PM EDT Thu Mar 28 2024

Impacts:

- Mid-level BKN or OVC with isolated rain showers tonight into
  Friday morning

- Low-level wind shear Friday night into Saturday

Discussion:

VFR conditions are expected through tonight, into Friday morning.

Clouds continue to stream in from the northwest. These have been
around 7000ft agl to as much as 10kft agl. A few light rain showers
are possible at times, but the best chance of rain at all terminals
is closer to sunrise.

A weak boundary may sag south far enough to allow today`s brisk
southwesterly winds to go light and variable. The greatest
likelihood of this is from IND to HUF northward and mainly during
the overnight hours. Regardless, the boundary should lift back north
Friday morning allowing southwesterly winds to resume.

A strong low-level jet should develop Friday evening, intensifying
into the night. As such, some low-level wind shear is possible
towards the end of the TAF period.


&&

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

&&

$$

UPDATE...Eckhoff
SHORT TERM...Updike
LONG TERM...Nield
AVIATION...Eckhoff


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