996 
FXUS63 KOAX 210524
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1224 AM CDT Fri Jun 21 2019

.SHORT TERM...(Tonight through Sunday)
Issued at 345 PM CDT Thu Jun 20 2019

The potential for severe thunderstorms through Saturday night 
remains the primary forecast concern.

Several rounds of potential thunderstorms over the next couple of 
days will offer chances for severe weather across eastern Nebraska 
and southwest Iowa. The first potential round is this afternoon and 
evening. We already have an unstable atmosphere in place as mid to 
upper 60s dew points continue to surge north ahead of a surface 
boundary extending from eastern South Dakota into south central 
Nebraska. MLCAPE near 2500 J/kg and effective shear at or above 50kt 
resides along frontal zone, with shear vectors nearly perpendicular 
to boundary. Some convective inhibition will still have to be 
overcome, but various convection-allowing models indicate at least 
an isolated supercell or two is likely in northeast Nebraska later 
this afternoon, with movement to the southeast into the evening. 
Given instability and shear vectors, all severe modes are possible 
including hail, wind and tornadoes.

Activity will gradually work southeast this evening, but lingering 
storms are possible along outflow/frontal boundary setting up over 
southeast Nebraska. Then the second round of potential severe comes 
overnight when a consensus of model output shows a north-south 
oriented line of storms racing east from the Highs Plains into 
eastern Nebraska and southwest Iowa after midnight. Persistent 
theta-e advection ahead of line combined with strong and diffluent
mid level flow suggests damaging wind potential will exist as 
this line marches across our area between about 2 and 7 AM.

Seasonably strong southwest mid level flow continues on Friday. 
Surface front pushed south by morning convection is forecast to mix 
northward Friday afternoon, extending from eastern South Dakota into 
south central Nebraska. MLCAPE is forecast over 3000 J/kg with 40-
50kt bulk shear vectors nearly perpendicular to front. As surface 
winds back ahead of front and below veering winds with height, low 
level shear will become increasingly conducive to tornado 
development. Again we will have convective inhibition to overcome 
during the afternoon, but expect this to wane toward 00Z. All modes 
of severe are again possible Friday evening.

Convection should move off to the northeast later Friday night with 
surface front sagging south behind it. A surge back to the north 
into southeast Nebraska and southwest Iowa is then expected again 
Saturday afternoon as shortwave rounds base of trough to our west. 
As this wave approaches through central Kansas, convection should 
become widespread by Saturday evening. Higher instability near and 
south of front along with 40kt shear vectors parallel to front 
suggest hail and wind will be primary severe threat.

Will maintain shower and thunderstorm chances through Sunday with 
approach of upper trough. Severe risk Sunday will be dependent on 
where surface front sets up after Saturday night convection, and 
models are offering varied solutions. GFS is most aggressive in 
pumping up instability with front farther northwest than ECMWF. 

.LONG TERM...(Sunday night through Thursday)
Issued at 345 PM CDT Thu Jun 20 2019

A trend toward lower precipitation chances and warmer temperatures 
is in the forecast next week. Mid level trough swinging through the 
region Sunday night will finally take most of the shower chances to 
our east by Monday afternoon. Then mid level heights rise across 
the Plains through Wednesday before a potent shortwave rides into 
the Dakotas Wednesday night and Thursday. Will have a chance for 
convection with this feature, especially in our north. Otherwise 
expect temperatures to again approach 90 degrees for highs Tuesday
through Thursday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1222 AM CDT Fri Jun 21 2019

Primary imminent concern is the convection expected at all TAF
sites within the next few hours, primarily from 08z-14z.
Preliminarily added wind gusts up to 25 knots, but will do short
term updates for higher gusts based on storm development. There 
will be break in precipitation after the morning convection, with
additional thunderstorms possible at KLNK/KOMA later in the TAF 
period 22/00-06z. MVFR ceilings also expected to develop later in 
the TAF period. 

&&

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

$$

SHORT TERM...Dergan
LONG TERM...Dergan
AVIATION...DeWald