085 
FXUS63 KIND 081756
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
156 PM EDT Thu Jul 8 2021

...Updated Aviation Discussion...

.Forecast Update...
Issued at 1000 AM EDT Thu Jul 8 2021

Scattered showers and isolated thunderstorms across mainly northern 
counties this morning...will continue to slide eastward...while 
overall convective coverage slowly expands and builds southward 
through this afternoon.  While current storms are more garden-
variety in nature, a marginal risk for strong/severe winds continues 
for this afternoon and at least early into this evening for most of 
the CWA.  Threat of heavy rainfall and very localized flooding is 
also present under stronger storms through this evening. 
Considerable cloudiness will keep temps from rebounding farther than 
the low to mid 80s for most locations amid the high humidity.

&&

.Short Term...(Today through Friday)
Issued at 301 AM EDT Thu Jul 8 2021

Scattered convection was across mainly the far northern forecast 
area, stretching back into central Illinois early this morning. 
Isolated convection was across the far southwestern forecast area. A 
surface cold front extended from lower Michigan southwest to north 
of St. Louis. An upper trough was just west of the area.

Based on recent trends, believe that at least isolated convection 
will continue through the remainder of the predawn hours, especially 
with the upper trough and front nearby. Will continue some PoPs 
before 12Z.

After 12Z, the left exit region of an upper jet will be near the 
northern forecast area. This will likely aid in the production of 
some convection by mid to late morning there. Later during the day, 
as the cold front moves through the area, it will interact with 
unstable air to produce scattered to numerous showers and 
thunderstorms. Overall, will end up going at least likely PoPs most 
areas at some point during the day.

There is enough shear around to perhaps get some isolated severe 
storms this afternoon, mainly across the eastern and southern 
forecast area ahead of the front.

The front will be exiting the area this evening, so will just keep 
some low PoPs in the east during the evening hours. 

Surface high pressure will build into the area overnight into Friday 
morning, and this will provide dry and cooler conditions. During the 
afternoon, an upper disturbance in northwest flow aloft will 
approach the area. Some lift will occur aloft with this feature by 
late afternoon. However, the surface high will still have influence 
over much of central Indiana, keeping the low levels dry. 

Thus, while some sprinkles may be possible in the far west later on 
Friday, feel that mentioning PoPs will be overdone. Will go with a 
dry forecast.

&&

.Long Term...(Friday night through Wednesday)
Issued at 301 AM EDT Thu Jul 8 2021

The long term period looks to be active, beginning with the arrival 
of leading shortwave impulses ahead of a strengthening low early in 
the weekend. This low will close off somewhere in the region, likely 
to our west per the general consensus of deterministic guidance, and 
lead to multiple potential rounds of showers and thunderstorms 
throughout the long term period.

While a marginal severe threat would not be out of the question 
given at times modest deep layer shear values, the more substantial 
concern will be hydrologic with deeply saturated/pseudotropical 
profiles (featuring deep but thin instability profiles) 
and precipitable water values continuing to be advertised at 1.8 to 
2 inches, which approaches climatological maximum for the time of 
year. This, along with wet antecedent conditions means heavy rain 
from thunderstorms, particularly if occurring in multiple rounds, 
will have little trouble causing at least nuisance flooding issues, 
if not flash flooding and renewed river flooding. OHRFC river flood 
ensembles indicate at least a 30 percent chance of renewed minor 
flooding along portions of the main stem rivers, particularly in 
southwest Indiana where river flooding has been an issue for some 
time now, and just recently ended.

The closed upper low looks to lift out of the area by mid week next 
week, although additional disturbances in the weakly cyclonic flow 
will continue to merit precip chances through the end of the period.

Given the overall pattern, temperatures should be at least a bit 
below normal, particularly early in the long term period, and the 
blend has handled this quite well.

&&

.Aviation...(18Z TAF Issuance)
Issued at 155 PM EDT Thu Jul 8 2021

IMPACTS:
- Scattered convection this afternoon will continue into early
  evening, with IFR/MVFR and gusts over 25kt in convection
- Sustained winds generally 10kt or less...except in/around storms
- Gradual wind shift to northwest this evening

DISCUSSION:
Scattered convection currently along the I-70 corridor, with 
isolated strong/severe winds...will expand in coverage through 
this afternoon and early evening along and south of the I-70 
corridor. MVFR ceilings at KIND/KLAF should lift to VFR at KIND 
late this afternoon, and KLAF early this evening. Otherwise VFR is
expected to prevail through Friday afternoon...except in and 
around today's showers/storms where brief IFR/MVFR is expected. 
Winds near stronger cells may gust as high as 25-40 kts although 
low confidence any site sees winds this intense.
 
Showers/storms will end from north to south this evening as the 
associated cold front continues to slowly cross the region.  Winds 
will veer to northwesterly early this evening...and then remain 
generally under 10 kts the remainder of the TAF period.

&&

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

$$

Update...AGM
Short Term...50
Long Term...Nield
Aviation...AGM