416 
FXUS63 KOAX 191724
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1224 PM CDT Sat Jun 19 2021

...Updated Aviation Forecast Discussion...

.DISCUSSION...
Issued at 400 AM CDT Sat Jun 19 2021

Departing shortwave had produced some large hail across parts of
southwestern Iowa overnight, but the area is now dry in its wake.
Expect morning lows near seasonal norms.

Saturday will remain dry through the afternoon with high temps 
again near 90F. For a second consecutive day, a relatively 
stationary front will halve the CWA and leave areas north of the 
Platte River with perceptibly lower humidity. 

Are we in for a repeat later tonight? Another shortwave 
approaches on Saturday evening, ejecting out of the Desert 
Southwest. Models have been consistent on producing a bowing line 
of storms along the KS/NE state line overnight. This threat would 
primarily be damaging wind gusts. Of more interest, to me anyway, 
is the possible convection ahead of the shortwave. Significant 
theta-e advection along the warm front will help drive it 
poleward. Surface based cape isn't all that impressive, but 
forecast sounding show elevated convection could tap into 2500 
J/kg of MUCAPE. Elevated storms capable of producing large hail 
will be the threat for the second consecutive night. (There was 
some tennis ball sized hail in Pottawattamie County Friday night.)
The area under the threat may be a bit further north than Friday 
night's storms as the front meanders that direction and the 40kt 
LLJ overrides it. 

Locally heavy rain is possible and generally welcomed over areas
where drought is reclaiming territory. PWAT and water vapor
transport are over the 90th percentile in eastern Nebraska and
western Iowa. QPF values of 0.50 to 1"+ are forecast. 

A strong cold front will sweep through the area over Sunday's
second half, bringing another chance of storms across Iowa and,
behind it, much cooler temps. Monday's highs will be relegated to
the 70s for the first time this month.

Northwest mid-level flow brings back occasional chances for
shortwaves and associated showers for the second half of the week.
Until then, the sprinkler will have to suffice once again. 

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1217 PM CDT Sat Jun 19 2021

Main aviation concern will be thunderstorms moving into eastern
Nebraska overnight. Storms are forecast to develop in western and
central Nebraska this afternoon, then approach eastern Nebraska
TAF sites by 05Z or so, before moving east by 12Z. MVFR cigs are
forecast to spread across northeast Nebraska in the wake of
thunderstorms, but KOMA and KLNK should remain VFR through the
period outside of thunderstorms. Generally an easterly component
to surface winds is anticipated through the day before turning
southeasterly with approach of convection this evening. A turn to
northwest winds mid to late Sunday morning will follow.

&&

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

$$

DISCUSSION...Nicolaisen
AVIATION...Dergan