358 
FXUS63 KOAX 051104
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
604 AM CDT Mon Jul 5 2021

...Updated Aviation Forecast Discussion...

.DISCUSSION...
Issued at 222 AM CDT Mon Jul 5 2021

At 222 AM, a weak surface front was draped across southern South 
Dakota/Minnesota, while a surface high was centered over the 
Tennessee Valley. Locally we were free of hazardous weather, with 
clear skies, light southerly winds and temperatures in the lower 
70s. 

Today:

Regional weather today will feature weak ridging aloft, a stalled 
surface front near the NE/SD border, and surface high pressure 
centered over the Tennessee Valley. Most of eastern Nebraska and 
Iowa will be positioned in the warm sector south of the front, 
and with ridging aloft producing subsidence it should be a warm 
and mostly sunny day. For those near the NE/SD border, we could 
see a couple storms bubble up along the front between 4 PM and 9 
PM. Shear along the front looks meek, but most CAMS show 
sufficient instability (MLCAPE > 2000 j/kg) for convection. With a
well mixed boundary layer and 700-500 mb lapse rates ~7 C/km, 
isolated wind gusts to 50 mph or some small hail may occur.

Highs today should range from the mid 90s along Interstate 80, to 
the upper 90s near the SD/NE border. As we will be on the western 
periphery of the aforementioned surface high, we can expect
persistent southerly winds today. 

For Tonight: 

The general trend in the CAMs suggests that any evening
thunderstorm activity in northeast Nebraska should fade with the
loss of diurnal heating. Storm dissipation may be also be 
encouraged by a slight northward drift in the front at the behest
of an approaching shortwave trough. Thus is looks like our region
should be largely dry overnight, with light southerly winds and 
overnight lows near 70 degrees.

A Front Brings Storm Chances Tuesday: 

The aforementioned shortwave trough will push the front south 
into Nebraska and Iowa Tuesday. Along and ahead of this front 
thunderstorms will be possible. Instability profiles (from the NAM
& GFS) suggest the best storm potential will be along and north 
on Interstate 80 during the day on Tuesday. Then lower storm 
chances should shift towards areas south on Interstate 80 Tuesday
evening/night. Rain potential still looks respectable (with PW 
values between 1.6 and 2.0 inches), but storm duration and 
intensity may limit totals. Most guidance now favors rain amounts
0.25 to 0.75 inches (highest totals north on Interstate 80). 
Severe weather continues to look unlikely during this period, 
with models progging meager mid level lapse rates (6.5 C/km or 
less) and anemic CAPE profiles.

Behind the Front:

A couple lingering showers or storms are possible over southeast 
Nebraska Wednesday morning. Otherwise the cooler post frontal 
airmass should result in a pleasant day Wednesday. Look for light
northeast winds, highs in the lower 80s and plenty of afternoon 
sunshine. 

Quick Late Week Warmup, & Storms Return?:

Run to run trends in the ensemble guidance have been slowly 
shifting towards a stronger shortwave trough moving into the 
Northern Plains and Great Lakes late this week. This trend has 
implications for our forecast, including the potential for a more 
rapid warm up ahead of the trough (Thursday & particularly Friday)
and increased forecaster confidence in possible thunderstorm 
activity Friday. 

Regarding warmer temperatures, it looks like surface winds should 
shift rapidly back to southerly Thursday (WAA), and remain that 
way into Friday. Leading us to forecast highs near 90 Thursday and
in the mid 90s Friday. 

The returning southerly flow should also allow surface dewpoints to 
climb over the region. We could see a shift from dewpoints near 
60 degrees on Wednesday, to dewpoints in the lower 70s Friday 
afternoon. Toss in mid level cooling with the trough, another 
front, and favorable wind profiles, and we "could" see conditions 
supportive of strong or severe storms Friday or Friday night. Of 
course it is still several days out, so we will continue to 
monitor this potential.

The Long Range Forecast:

There is no appreciable change in the long range forecast from 
this time yesterday. Ensembles still favor a strong upper level 
ridge over the Southwest and troughing out East, leaving us with 
prevailing dry northwest flow. Thus for the time being we are 
forecasting dry weather and highs in the 80s next Saturday, Sunday
& Monday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 603 AM CDT Mon Jul 5 2021

VFR conditions are forecast through Tuesday morning. Winds will
average southerly at 10kt with scattered afternoon cumulus near
FL050. Otherwise only scattered to broken high clouds are
forecast.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&

$$

DISCUSSION...Albright
AVIATION...Dergan