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000
FXUS63 KIND 110129
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
929 PM EDT Wed Apr 10 2024

.KEY MESSAGES...

- Rain Tonight and Thursday; Cool
- Minor Flooding possible
- Rainfall in the next 48 hours will may prolong ongoing river
flooding at a minimum, and lead to some renewed lowland flooding
along main stem rivers.
- Active weather pattern continues into next week with numerous
chances for rain and storms.
- Above normal temperatures in the 70s Sunday into most of next week.

&&

.MESOSCALE UPDATE...
Issued at 928 PM EDT Wed Apr 10 2024

Broad area of rain continues to lift across Central Indiana this
evening. Some pockets of moderate to heavy rain is located within a
corridor of Sullivan county to Marion county, where more robust
collision and coalescence is taking place to parcels and allowing
for larger more efficient hydrometeors to reach the surface. This
area is also still seeing isentropic ascent to parcels through a
moist column, further aiding in the efficiency to the steady
rainfall. Surface OBS indicating some reduced VSBY within the
steadier rain along and south of the I-70 corridor. Satellite
imagery is indicating some cooling to cloud tops along the Ohio
River and lifting north, while underneath radar reflectivity has
some pockets of convection that has developed.

&&

.SHORT TERM (This evening through Thursday)...
Issued at 300 PM EDT Wed Apr 10 2024

Synopsis:

Surface analysis this afternoon shows a frontal boundary stretching
from north of Richmond to Columbus and then south of Vincennes.
Surface high pressure was found over Lake Huron and Lake Erie. Cool
easterly surface flow was in place across much of the forecast area
and dew points across northern Central Indiana were in the 40s,
while the southern half of the forecast areas had recovered with dew
points in the mid 50s. Radar mosaics show an area of showers over
southwest Indiana and west Central KY pushing northeast within the
flow aloft. Aloft, water vapor imagery showed a deep upper trough
over the southern plains states. This was resulting in moist
southwest flow streaming northeast into the Ohio Valley. The upper
trough was producing much stronger storms over LA and Arkansas.

Tonight...

The upper trough over the southern plains is expected to push
northeast, becoming negatively tilted in the process. Forcing
dynamics ahead of the system are suggested to push in to the Ohio
Valley and Central Indiana as the evening progresses. The lingering
lower level boundary will act as an area of lower level convergence
while the forcing provided aloft provides additional lift.
Isentropic surfaces also remain in play. The 300K GFS Isentropic
surface shows some lift surging into the area this evening and
specific humidities are over 6 g/kg. Forecast soundings also show a
saturated column through much of the night across Central Indiana
with pwats over 1.3 inches. Finally, HRRR shows a shield of rain
showers expected to develop and surge into Central Indiana this
evening and early overnight. CAPE is limited with this feature, but
given the warm and moist air and lapse rates that are marginal
unstable, a stray embedded thunderstorm cannot be ruled out. Thus
expect the main precipitation to be rain showers.

Given the clouds, precipitation and steady easterly flow, nearly
steady state or slightly cooling temps toward wet bulbs will be
expected. Expect lows in the lower to middle 50s.

Thursday...

Models show the negatively tilted upper trough slowly swinging
through Indiana and the Ohio Valley through the day. The mid levels
keep a saturated trough in place over Central Indiana through the
day, as the surface low is expected to quickly push east of the
state. This will allow the winds to become northwesterly. The
associated tight pressure gradient across the area will allow for
gusty winds of 20-30 mph also. Strong lower level cyclonic flow will
also remain in place, allowing for the development of scattered wrap
around rain showers. Forecast soundings are not as saturated on
Thursday as they were previously, as dry air begins to intrude into
the system, however still plenty of lower level moisture will still
remain present. Pwats on Thursday start over 1 inch and by late
afternoon fall to around 0.75. HRRR suggests scattered showers
through the day, gradually diminishing by late afternoon. Thus will
again use high pops on Thursday for scattered rain showers, with
lessening pops through the afternoon as dry air intrudes from the
northwest.

Given the expected clouds, rain, and cold air advection, little
temperature movement will be expected through the day. Look for high
temperatures only a few degrees warmer than the previous lows, in
the middle to lower 50s.

&&

.LONG TERM (Thursday night through Wednesday)...
Issued at 300 PM EDT Wed Apr 10 2024

An active pattern continues through the end of the work week and
into next week with numerous chances for rainfall and storms;
however temperatures remain largely above normal for this time of
year through the period.

.Thursday night and Friday...

A strengthening surface low, aided by phasing jet energy aloft,
tracks NE through the state Thursday then slowly away to the
northeast into Quebec on Friday. Guidance is in great agreement with
a strong upper wave diving SE into the state behind the departing
low Thursday night into Friday morning, keeping the chance for
convective showers around. By 12z Friday, a negatively tilted upper
trough axis is right on top of the state with Indiana in the left
exit region of an 110kt jet streak over IL and MO. Steepening low
and mid level lapse rates from CAA on the backside of the surface
low in addition to saturated low levels and 20-30 kt 0-1km and 0-3km
shear will result in an environment conducive for convective showers
late Thursday night into the first half of the day on Friday. With
such a strong 35-45 kt low level jet overhead and steep low level
lapse, expect breezy conditions during this time as well with
frequent gusts over 40 mph likely. Higher wind gusts are also
possible in any convective shower as well. Would not be surprised to
see small hail or graupel as well with the strongest showers as
freezing levels lower to around 3,000 ft by Friday morning.

Drying trend expected through the daytime hours Friday as higher
pressure and much drier air advect into the region. Friday will
likely be the coolest day over the next week with afternoon highs
struggling to even reach the 60 degree mark.

.This Weekend into Next Week...

An extended period of well above average temperatures and storm
chances arrives this weekend and persists into next week. Ridging at
the surface and aloft will expand into the Ohio Valley for the
weekend. Ridge axis remains over the Plains through Monday placing
Indiana with an upper level northwesterly flow pattern. Longer range
guidance does show the potential for waves of energy within the NW
flow to bring storm chances Late Sunday night and then again on
Monday night. This is a classic late Spring to early summertime
pattern with southerly flow and a warm, humid airmass at the surface
with waves of energy flowing NW to SE along the jet. Unfortunately,
guidance does not handle the smaller details such as timing and
placement of these waves of energy very well. While high confidence
exists in well above average temperatures in the 70s (and maybe
80s!) next week, lower confidence exists on storm track, timing, and
location. Will have to watch where the upper level storm track sets
up, which will determine where these potential clusters of storms
set up and track. Some guidance has these storm clusters pushing
into Indiana, while others keep the storms further north. For now
keeping only 20-30 POPs in the Sunday - Monday forecast and will
adjust up or down in future forecast packages as timing and location
become clearer. This will not be a wash out type event, so expect
most of these days to remain dry before and after the storms. Not
ruling out the threat for a strong to potentially severe storm
associated with these thunderstorm complexes.

Upper ridging shifts eastward mid week with numerous stronger storm
systems moving through the Plains. This places Indiana within a
warm, southwest flow pattern within the warm sector of storm systems
to the west. While much warmer, above normal temperatures continue,
the threat for more storms remains in the forecast. At the moment,
the current storm track looks to remain west of the Ohio Valley
midweek as dying frontal systems and associated storms push into the
region. There are some hints in the guidance that the storm track
does move further east over the Ohio Valley by late week bringing
more frequent and widespread chances for rain and storms, but
confidence this far out on details remains low.

For now, high confidence exists in a much warmer weather pattern
with periodic to daily chances for storms. Do not expect any
particular day to be a washout this weekend into the first half of
next week; however will keep a close eye on the weather pattern
later next week for potential repeated rounds of heavy rain and
storms. Lower confidence exists with timing and placement of daily
threats for storms. It is too early to talk about the severe or
flooding threat with storms mid to late next week, however not
ruling out the possibility.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 755 PM EDT Wed Apr 10 2024

Impacts:

- IFR/possible LIFR ceilings to prevail through at least 18Z
Thursday...although MVFR at KLAF to begin period
- Mainly IFR/MVFR visibility into THursday morning...with low-IFR/
brief LIFR possible in heavier rain
- Isolated non-severe TSRA are possible overnight, with best chances
 at KBMG

Discussion:

A storm system centered over the Lower Mississippo Valley early this
evening will intensify while lifting towards the Midwest tonight...
before crossing the region Thursday morning.  Scattered to
widespread light to moderate rain showers will fall under mainly IFR
ceilings tonight, with generally IFR/MVFR visibility lowered in
heavier rains and any subsequent fog formation.  Non-severe TSRA are
possible tonight, but chances too low outside of KBMG to include in
TAF.

Winds will remain sustained around 10 knots overnight from easterly
directions...except more norhteast at KLAF.  Wind directions will
change through the early Thursday timeframe as the surface
circulation crosses the region.  Gustier northwest flow will then
advance across the region from west to east Thursday afternoon
behind the deepening, departing system...with gusts to at least 20-
30KT after 18Z Thursday.

Kept VCSH for Thursday with low confidence on location and timing
for the few to scattered showers that will accompany the passing
system, although periods of steadier rain will certainly be
possible.  Conditions should improve quickly from IFR to VFR during
the afternoon for KLAF/KHUF...and probably towards sundown at
KIND/KBMG.


&&

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

$$

MESOSCALE...Beach
SHORT TERM...Puma
LONG TERM...CM
AVIATION...AGM