604
FXUS63 KIND 081900
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
300 PM EDT Mon Jul 8 2024

.KEY MESSAGES...

- There is a chance of thunderstorms over the Wabash Valley into the
  early overnight.

- Additional convection associated with Beryl will move in from
  the southwest Tuesday. Isolated tornadoes, gusty winds, heavy
  rain and flooding will be possible Tuesday evening through
  Wednesday morning.

- Tornado threat highest south of the I-70 corridor, flood threat
  greatest over the upper Wabash Valley.

&&

.SHORT TERM (This evening through Tuesday)...
Issued at 259 PM EDT Mon Jul 8 2024

The main concern for the short term will be the potential for brief
tornadoes associated with the remnants of Beryl, toward Tuesday
evening. Beryl is expected to move from southeastern Texas to the
the Missouri bootheel by Tuesday evening as an upper trough moves
from the western Great Lakes and Rockies to near the Mississippi
Valley. Meanwhile, tropical moisture associated with Beryl should be
moving into the lower Wabash Valley during the morning and points
northeast toward evening. Low level winds will shift to the
southeast as Beryl gets closer and combined with seasonable strong
southwest flow aloft, ahead of the trough, will result in long
curved hodographs in the lowest 2km and SRH over 300 m2/s2. The
tropical airmass will lead to deep moist adiabatic lapse rates and
combined with thick cloud cover limit the visibility and
consequently lightning strikes. That said, with its tropical
origins, brief tornadoes will be definitely be possible by late
afternoon, anywhere to the right of the remnant`s track. Going by
the preferred official NHC forecast, this would mean areas near and
south of the I-70 corridor per the new SPC Day2 Severe Weather
Outlook. Additionally, CAMS are all hinting at rotating convection
after 20z. Believe the best chances for spin-ups will be toward 00z
as the warm front moves in and provides convergence along with
supplemental helicity to the already favorable low level ambient
shear.

Current indications based on Hi-Res moisture profiles, CAMS, the
approaching upper trough and remnants of Beryl along with WPC, DESI
and model data are that the heaviest rainfall will hold off until
Tuesday night. However, by late in the day Tuesday, the rain should
be becoming widespread, especially over southwestern sections. Any
shift on the track of Beryl will shift to the tornado threat area,
keep up with the latest track projections.

Prior to Beryl`s impact, upper disturbances in the southwest flow
aloft ahead of the upper trough along with increasing moisture and
weak instability supports isolated to scattered thunderstorms
tonight, over the Wabash Valley, and the latest radar loop was
showing thunderstorms developing just north and west of Warren
county.

&&

.LONG TERM (Tuesday night through Monday)...
Issued at 259 PM EDT Mon Jul 8 2024

The primary focus of the early long range continues to be Hurricane
Beryl and its remnants.

Hurricane Beryl has made landfall as a hurricane earlier today along
the Texas Gulf Coast as a category 1 storm. The system is tracking
northward over eastern Texas, and is expected to turn northeast
towards Indiana. Guidance is in decent agreement regarding the track
of the cyclone, though some differences remain.

SYNOPTIC OVERVIEW

As a quick synoptic overview, we see a positively-tilted trough over
the Great Plains with ridging along the east and west coasts. The
trough will effectively capture Beryl and bring the storm
northeastward with increasing speed. As it does so, the system will
undergo extratropical transition. A few members of guidance (NAM)
take a piece of the trough and phase it into the transitioning
cyclone, allowing it to strengthen slightly as it passes through
Illinois and Indiana. If this phasing does not occur, or is slower,
then a weaker system with a more southerly track is possible (the
bulk of guidance currently resides here).

HAZARDS AND IMPACTS

The primary hazards with Beryl are wind, rain, and isolated
tornadoes. All hazards may be present across central Indiana based
on the current model consensus and expected storm track (NHC).
Timing of these hazards is Tuesday night into Wednesday.

Tornadoes: despite weak lapse rates and low instability within the
warm tropical air mass associated with the storm, plenty of shear
exists within the warm sector. Model hodographs show strong
curvature and over 300 m^2/s^2 0-3km SRH, 0-1km shear over 20kt, and
effective shear over 40kt. Model soundings show weak overall lapse
rates (6 C/Km) but slightly steeper rates near the surface (7 C/Km).
This, combined with high near-surface moisture, may lead to a
tornado threat even into the nighttime hours.

Rainfall: As mentioned above, model soundings show weak lapse rates
but high moisture levels. LCLs are low, and freezing levels are
high, and thus warm rain processes will contribute greatly to
rainfall production. Flash flooding is possible in locations that
see sustained heavy rainfall rates, especially in areas of training
convection. A swath of heavy rainfall, coincident with 700mb
frontogenetic forcing, will occur just northwest of the surface low.
Rainfall in this region may end up totaling 2 to 4 inches, with
isolated higher amounts. Note: a stronger surface low may shift the
swath of heavy rain northwest into Illinois / northern Indiana and
mostly out of our area.

Wind: In a stronger surface low scenario, we`ll see a tighter
pressure gradient and potentially stronger surface wind gusts. High-
res guidance shows wind gusts between 30 to 40 knots at times, with
the highest values just to the northwest of the surface low center.

Thursday Onward

The synoptic pattern for the remainder of the period will be
characterized by strong western ridging with weak east coast
troughing. This may lead to shower/storm chances at times as pockets
of energy / waves crest the ridge and dive southeastward. Surface
high pressure over the southeastern US should promote a generally
west-southwesterly flow allowing for hot and occasionally humid
conditions to prevail. Temperatures may run a bit above average
(upper 80s or low 90s) through the week and into the weekend, and
perhaps beyond.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 1224 PM EDT Mon Jul 8 2024

Impacts:

- Can not rule out a thunderstorm or two after 21z at KLAF and
  KHUF and at KIND and KBMG after 10z.

Discussion:

Mid and high clouds will continue to stream northeast across the
terminals and scattered to broken diurnal cu is also expected to
develop. Meanwhile, as the upper trough gets gradually closer,
isolated convection is possible starting late in the day, in the
vicinity of KLAF and KHUF. Overnight and Tuesday, all sites have the
potential to see convection as moisture starts streaming in from the
remnants of Beryl. With very limited instability if any, introduced
VCSH, an isolated lightning strike or two are still
possible.

Winds will be light from the southwest.


&&

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

&&

$$

SHORT TERM...MK
LONG TERM...Eckhoff
AVIATION...MK