819 
FXUS63 KOAX 041113
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
613 AM CDT Sun Jul 4 2021

...Updated Aviation Forecast Discussion...

.DISCUSSION...
Issued at 300 AM CDT Sun Jul 4 2021

At 3 AM, skies were covered in thin cirrus generated by overnight
convection in the Sandhills. A few midlevel cumulus stretched 
from Hasting to around Sioux Falls, and a couple showers were 
ongoing near Neligh. Given current instability profiles on the SPC
Mesoanalysis page, these showers were mostly elevated. Surface 
winds were light out of the south and temperatures were hovering 
around 70 degrees.

Today:

For today we have two primary weather concerns, heat and 
thunderstorm activity. Both will primarily affect northeast 
Nebraska, so areas like Lincoln, Omaha and western Iowa should be 
weather hazard free today. 

Regarding the heat, a Heat Advisory remains in place for portions of 
northern Nebraska and South Dakota (including Cedar and Knox 
Counties). This region should see temperatures climb to around 100 
degrees this afternoon as 850 mb temps spike to 25-28 C and the 
boundary layer mixes. Fortunately dewpoints should only be in the
upper 60s, limiting heat indicies to the 100 to 106 degree range.
Be sure to stay hydrated if you have outdoor plans. Further south
(Lincoln and Omaha) high temperatures should only reach the lower
90s.

A weak shortwave tracking through the Dakotas and frontal boundary 
may bring the forcing required for thunderstorm activity in 
northeast Nebraska between 4 PM and 11 PM. CAM soundings suggest 
effective shear of 25 to 30 kt, MLCAPE > 2000 J/kg and 700 to 500
mb lapse rates > 7 C/km, sufficient for a couple strong/severe 
storms if convection can get going. Primary hazards would be 
nickel to quarter sized hail and/or wind gusts to 60 mph.

Tonight: 

Any ongoing storms should weaken post sunset with the loss of 
diurnal heating and subsequent reduction in available 
instability. This should limit the better storm chances to 
northeast Nebraska prior to 11 PM. Once any thunderstorms activity
fades, we should see quiet weather prevail overnight. Expect 
light south winds and lows in around 70 degrees.

This Weeks Highlights

As we head into the workweek we can anticipate dry and warm weather 
on Monday (widespread highs in the mid to upper 90s). Then 
attention turns to a trough and frontal passage Tuesday that 
should bring more widespread thunderstorm chances to the region. 
Guidance continues to suggest deep moisture (PW values 1.6 to 1.9 
inches) ahead of the front, though the deepest moisture has 
shifted toward Minnesota and northern Iowa in recent model runs. 
This suggest at least some potential for solid rains. Ensembles 
are supportive of rain as well with the ensemble mean QPF hovering
around 0.5 inches. Local amounts to 2 inches are suggested by 
some ensemble members. For now, instability and shear profiles in 
the models aren't particularly supportive of severe weather. 

After Tuesday's frontal passage it looks like Wednesday will be 
the coolest day of the week, with forecast highs in the mid 80s. 
Then temperatures should trend upward Thursday and Friday. 
Thunderstorms may return to the region Friday, with most guidance
suggesting the arrival of another shortwave trough. 

Long Range Trends, Friday and Beyond

The longer range forecast from the global ensembles is relatively
unchanged over the last 24 hour. There remains a robust trend 
towards strong ridging (around 600 DM!) over the Southwest, while
troughing is favored over the Eastern U.S. This places us in the 
"in between" zone where northwest flow aloft is favored. So any 
rain chances from Friday to next Tuesday will likely depend on 
weak disturbances riding the prevailing northwest flow. These 
features are generally poorly resolved at this time range, so
predictability is low. The large scale pattern would also favor 
near average temperatures (upper 80s or lower 90s).

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 609 AM CDT Sun Jul 4 2021

VFR conditions are forecast through Monday morning. South to
southwest winds will increase into the 12 to 20kt range during the
afternoon. There is a small chance for thunderstorms between 21Z
and 06Z near KOFK, however because of the expected isolated
coverage, will not mention in TAF at this time.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Heat Advisory from 1 PM this afternoon to 8 PM CDT this evening 
     for NEZ011-012.

IA...None.
&&

$$

DISCUSSION...Albright
AVIATION...Dergan