National Weather Service Raw Text Product

169 
FXUS63 KIND 141903
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
303 PM EDT Wed Jul 14 2021

.Short Term...(This evening through Thursday night)
Issued at 302 PM EDT Wed Jul 14 2021

Brief period of zonal flow aloft today has helped give central 
Indiana a welcome break from what has been rather constant PoPs for 
the last month. Unfortunately this break will be short lived as 
strong frontal boundary will move toward the area Thursday. 

High pressure to the southeast helping provide southwesterly flow 
and near normal temps for mid July. Strong low pressure located 
along a frontal boundary across the plains into the upper MS Valley 
which will move toward our area on Thursday, increasing chances for 
more storms and once again a marginal severe threat along with heavy 
rain and potential flooding.  

Dry conditions should prevail through early to mid afternoon 
Thursday but with temps warming into upper 80s by mid afternoon with 
dew points in the lower 70s, instability will be increasing as well. 
NAM12 goes wild with developing convection well ahead of cold front 
in unstable environment during afternoon hours due to convective 
feedback. While a few afternoon storms are possible, better chances 
for more organized and widespread convection should develop in the 
evening and overnight hours Thursday into Friday as a weak surface 
boundary lifts north while main area of low pressure moves along 
cold front into NW IL by Friday morning. Would not be surprised if 
some type of MCV and/or outflow boundary sags into the area to aid 
convective development. Right rear quad of Great Lakes upper level 
jet will aid convective development across our north. Timing of this 
convection not good for severe weather with waning instability but 
shear profiles adequate with 30-35kts 0-3km and 35-40kts 0-6km 
shear. 

More concerned yet again with heavy rainfall and flooding 
potential with another soupy atmosphere in place as PWATs climb to 
just over 2 inches across entire region. Training storm motion 
expected with southwest to northeast oriented boundary and similar 
parallel flow with decent 850 mb flow and theta e advection. Warm 
rain processes possible with efficient rainfall rates could lead to 
1-2" per hour rainfall rates. The question though is where will this 
stronger, training convection actually develop as it could be just 
to our northwest and north or into north central Indiana. Will 
maintain mention of heavy rain and strong storm potential in HWO but 
no flood watch headlines at this time given location uncertainty.

&&

.Long Term...(Friday through Wednesday)
Issued at 302 PM EDT Wed Jul 14 2021

Ensemble means indicate an upper trough will gradually sink 
southeast across the local area over the weekend and on into early 
next week. In the wake of this trough, northwesterly upper flow will 
develop by the middle of next week, as a large heat ridge expands 
from the Rockies into the northern Plains.

The majority of the ensembles suggest the associated surface front 
will pass off the south by Saturday night, although some members 
indicate the front may linger as late as Monday. Given the amount of 
convection the models are suggesting may be linked to this feature, 
it is possible that the effective boundary may move south rather 
quickly. 

High progged precipitable waters suggest heavy rainfall is possible, 
mainly on Friday. Expecting a gradual decrease in the convective 
potential with time, as the higher precipitable waters and better 
instability get shunted off to the south. Will go with high PoPs on 
Friday, and then taper them off with time into early next week, as 
the upper trough axis exits the area.

By next Tuesday and Wednesday, ensembles overall become bearish on 
the convective potential, given the gradually rising heights. At 
this point, it appears any convective threat beyond Monday will be 
isolated in nature.

&&

.Aviation...(18Z TAF Issuance)
Issued at 1210 PM EDT Wed Jul 14 2021

IMPACTS:
-VFR prevailing through Thursday morning at all TAF sites but CU 
field could be MVFR early this afternoon
-scattered tsra possible Thu afternoon and night. 
-Local pockets of MVFR possible with any tsra 

DISCUSSION: VFR this afternoon with diurnal CU field remaining 
mostly above 3KFT. However, CU rules suggest some bases could be 
around 2500 ft early before rising. A stray shra or tsra not out of 
the question over central Indiana (5 to 10 percent chance) during 
peak heating but much too low a chance for any inclusion in 
terminals. Mostly clear tonight with light SW winds which should 
keep most sites VFR. Thu morning remains VFR but afternoon CU field 
and any TSRA development could lead to pockets of MVFR near storms 
if they develop.


&&

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

$$

Short Term...Lashley
Long Term...JAS
Aviation...Lashley