Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 260204
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1004 PM EDT Mon Mar 25 2024

.KEY MESSAGES...

- Wind Advisory tonight and Tuesday

- Windy with rain tonight

- Showers and few t-storms Tuesday...isolated severe storms possible

- Widespread frost/freeze possible Wednesday night

&&

.FORECAST UPDATE...
Issued at 1003 PM EDT Mon Mar 25 2024

Current radar observations show rain is beginning to move into W/SW
portions of central Indiana. Look for rain to continue overspreading
the area as low-level theta-e advection surges north ahead of an
approaching low pressure system. A steady rain is expected through
much of the overnight period before a dry slot moves in late
tonight. The dry slot is currently centered over the Ozarks and CAMs
show it moving in after 4am likely leading to an abrupt end in
precipitation for most locations before daybreak. Have decreased
POPs after 4am due to this.

A wind advisory is in effect through 6pm Tuesday for the potential
of wind gusts around 45-50 mph winds. Look for winds to pick up over
the next few hours as precipitation moves in. Models show the
aforementioned dry slot moving in late tonight may help to mix
down stronger winds potentially leading to more widespread gusts
of 45-50 mph. Strong winds and clouds will keep temperatures mild
overnight.

&&

.SHORT TERM (This evening through Tuesday)...
Issued at 251 PM EDT Mon Mar 25 2024

Rest of this Afternoon...

The winds have picked up this afternoon as mixing has commenced and
a tight surface low pressure was over central Indiana ahead of a
strong low pressure system centered near Kansas City. In the
meantime, fast southwest flow aloft was bringing waves of high
clouds per CIRA Geocolor visible loop.

Winds were blowing out of the south, off of the Gulf of Mexico, to
around 20 knots with gusts to 30+ knots. The southerly winds have
also brought in more moisture as seen in gradual rise in dew points
despite mixing down of drier air from below the 3K foot inversion.
This has kept the RH above 30 percent which precludes any other fire
mention than elevated fire danger for this afternoon. Quite
noticeably, the south and southeast winds have also caused
temperatures to drop to some 10 degrees normal to the 60s over most
locales.

Tonight...

Winds may briefly subside some at sunset due to the loss of mixing
but strong low pressure gradient and a 40 to 50 knot 925 millibar
jet, moving into the Wabash Valley, along with steep 0-3km lapse
rates may result in some near advisory criteria wind gusts for the
early evening and more toward daybreak. In between that, look for
widespread rain to develop and move east across the area as 300K
isentropic upglide kicks in and condensation pressure deficits
suggest the column will quickly saturate down.

CAMS bring the rain into the Wabash Valley after 01z Tuesday and to
the I-65 corridor around 04z. Then, as the isentropic lift moves off
to the east, a nice dry slot will move into the Wabash Valley after
around 08z. This will put an end to the widespread rain and with low
level lapse rates increasing again allow for the wind gusts to once
more pick up. With Gulf inflow continuing, overnight low
temperatures will only drop to the 50s over most locales.

Model ensemble probabilistic data suggests QPF tonight will be just
over a quarter inch on the low side to near three quarter inches on
the high side with around a half inch the most likely scenario.

Would not completely rule out a thunderstorm overnight over the
Wabash Valley as that area will be the closest to any weak elevated
instability.

Tuesday...

Tuesday morning will start off windy with potentially a lingering
shower to two around. But as the cold front gets closer and some
sunshine starts peaking through, owing to the dry slot, the
atmosphere will attempt to destabilize. If that happens, it will
have plenty of synoptic forcing including 60-80 knot deep shear and
0-1km SRH likely over 100. Probabilistic data from DESI supports
surface base CAPEs from around 250 to 500 J/kg. The combination of
shear, instability and forcing would support the potential for low
topped supercells. 100+ knot mid level jet over northern Indiana
into the Wabash Valley may also enhance low level inflow. So, the
SPC Day2 Marginal Risk for Tuesday looks good. Timing-wise, expect
some re-development over the Wabash Valley late morning to around
Noon and the activity will spread east into Ohio by late afternoon.
With very impressive low layer and deep layer shear, damaging winds
and a tornado or two are possible. Otherwise windy conditions will
continue away from convection as well with more mixing and the tight
surface pressure gradient. Temperatures should be around what they
have been today with highs in the 60s. Although, temperatures will
then drop in the wake of the front starting first over the Wabash
Valley.

&&

.LONG TERM (Tuesday night through Monday)...
Issued at 251 PM EDT Mon Mar 25 2024

Large scale mid and upper level low pressure will be the dominant
force for the latter portion of the work week as it gradually pushes
eastward across the central and eastern CONUS from the Plains to the
east coast from Tuesday night into Friday morning.

Aside from the potential of a few lingering showers in the far east
Tuesday evening, the rest of the work week will be dry, with a large
area of surface high pressure building into the Mississippi and Ohio
Valleys in the wake of the rapidly departing cold front.

The next opportunities for precipitation are likely to hold off at
least until Friday night, as a somewhat weak baroclinic zone moves
into the region and lingers through the weekend. Chances will be low
to middling much of the weekend, primarily focused along the
boundary and any subtle disturbances that may propagate along it
around the periphery of the modest upper level ridge, aided by broad
ascent associated with a 100-120KT jet streak.

A more substantial upper level wave may drop into the northern CONUS
or skirt the international border late in the weekend into early
next week, with somewhat more substantial surface low development
and higher chances for rainfall as we approach and get past the end
of the forecast period, though model differences reduce confidence
during this time frame.

Depending upon the intensity and track taken by the system toward
the end of the forecast period, there may be a non-zero severe
threat, though both CIPS analogs and CSU experimental machine
learning guidance have the focus of this modest threat more to our
west in days 7 and 8.

Temperatures will begin the long term period near to a bit below
normal in the wake of the cold front Tuesday night into Thursday
night, before quickly returning to above normal Friday onward as
heights build. Blend numbers are reasonable and will require no
significant adjustments.

A widespread frost or perhaps a light freeze will be possible
Wednesday night, with lows likely in the upper 20s to low 30s across
the area. While the growing season has still not quite officially
begun from an agricultural standpoint, significant budding has begun
on many trees and hobbyist/residential plants, and these may require
protection Wednesday night.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 740 PM EDT Mon Mar 25 2024

Impacts:

- SSE winds to 20+ knots and gusts around 30-40 knots.

- Non-convective low level wind shear possible at times between 01z-
  12z tonight into Tuesday morning

- MVFR and possibly briefly worse flying conditions
  in rain 05z-12z

- A few thunderstorms and gusts to 45+ knots can not be ruled out
  15z-19z Tuesday

Discussion:

A strong low pressure system will result in windy conditions through
the TAF period along with rain tonight and perhaps some strong to
severe thunderstorms late Tuesday morning and afternoon. Flying
conditions will also deteriorate to MVFR and possibly briefly worse
tonight and Tuesday in rain or showers.

Winds may briefly taper off slightly around or shortly after sunset,
but will quickly pick up again as rain moves in tonight. Expect SSE
winds generally around 20+ knots with gusts around 30-40 knots.
Higher gusts cannot be ruled out.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 6 PM EDT Tuesday for INZ021-028>031-035>049-
051>057-060>065-067>072.

&&

$$

UPDATE...Melo
SHORT TERM...MK
LONG TERM...Nield
AVIATION...Melo


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