221 
FXUS63 KOAX 242047
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
347 PM CDT Tue Aug 24 2021

...Updated Forecast Discussion...

.DISCUSSION...
Issued at 346 PM CDT Tue Aug 24 2021

Main forecast concern going forward remains heat and shower/storm 
chances. Early afternoon analysis showed an outflow boundary along a 
line including Columbus, NE, to Harlan, IA. Additional sporadic 
showers and storms were developing along said boundary through much 
of the day as well as just ahead of some weak shortwave energy 
sliding through north-central Nebraska. For tonight, expect 
additional development along an incoming cold front as a low level 
jet strengthens and a slightly stronger shortwave moves in 
(currently seen in northeast Colorado). Latest guidance suggests 
MUCAPE values of right around 2000 J/kg on either side of midnight, 
roughly when initiation is progged by most short term CAMs. That 
said, tend to lean toward slightly earlier initiation given the 
aforementioned incoming shortwave energy and low level jet. In that 
case, would expect a little bit more instability, but deeper layer 
shear still looks fairly weak, so not anticipating much in the way 
of storm organization. Still, can't rule out some stronger to severe 
storms along the boundary, given favorable low level shear and 
decent instability. Damaging wind and localized heavy rain would 
likely be the main threats.

The aforementioned cold front will remain oriented roughly west to 
east near or across the area through the next several days, 
providing a focus for more thunderstorm potential each day. Expect 
sufficient instability for stronger to severe storms through at 
least Thursday, with shear likely being the main question mark in 
regards to a more widespread severe weather threat.

Regarding heat, clouds and showers have kept heat index values in 
check across northeast Nebraska, so elected to cancel portion of the 
Heat Advisory. For Wednesday, the front looks to remain over far 
southern portions of the forecast area, keeping most under easterly 
to northeasterly surface flow. Still looks to be warm, but not quite 
as favorable for Heat Advisory criteria, at least for areas north of 
the boundary. Clouds/showers/storms could limit heat as well, so 
confidence in temperature forecast isn't super high. For now, going 
with a Heat Advisory for those areas south of the boundary where 
winds are more likely to be southerly.

Heat looks to continue into at least Saturday, with widespread highs 
in the 90s and heat index values over 100, though boundary location 
and associated clouds/precip will play a large role each day. 
Eventually expect the front to sweep through the area and provide at 
least some brief relief Sunday/Monday, as high temperatures look to 
"only" be in the 80s those days.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1220 PM CDT Tue Aug 24 2021

VFR conditions are expected for the most part with a chance for
thunderstorms moving through parts of the area this afternoon and
again overnight (04-10z) . Conditions in and around thunderstorms
could be variable down to IFR at times in addition to gusty and 
variable surface winds. Forecaster confidence on these
thunderstorms is low. 


&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Heat Advisory until 8 PM CDT this evening for NEZ030>034-042>045-
     050>053-065>068-078-088>093.

     Heat Advisory from noon to 8 PM CDT Wednesday for NEZ066-068-078-
     088>093.

IA...Heat Advisory until 8 PM CDT this evening for IAZ043-055-056-069-
     079-080-090-091.

&&

$$

DISCUSSION...CA
AVIATION...Kern