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Area Forecast Discussion (AFD)

Issued by Omaha/Valley, NE (OAX)

                            
000
FXUS63 KOAX 200922
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
422 AM CDT Thu Jun 20 2019

.SHORT TERM...(Today through Saturday)
Issued at 350 AM CDT Thu Jun 20 2019

The primary forecast concerns will be the potential for severe 
weather each day. Some fog in southwest Iowa this morning and
parts of the area again Friday morning.

High temperatures Wednesday ranged from the upper 70s to the mid 
80s.  Skies were variably cloudy with some build ups during the day. 
Falls City, Lincoln, and Wahoo reported a trace with 0.16" at
Clarinda. Isolated thunderstorms developed over central South 
Dakota and central Nebraska during the late afternoon with a 
shortwave trough. These dropped south and even southwest and 
dissipated west of the forecast area. 

The 00Z OAX sounding showed around 700 J/kg of SBCAPE with just over 
an inch of precipitable water.  Low level lapse rates were close to 
7.5 deg C/km.  The KLBF 00Z sounding has 0.65 PWAT with low level 
and mid level lapse rates from 7 to 8.5 C/km.

Showers and thunderstorms will shift southeast from SD and 
central Nebraska this morning as a seasonably strong 120kt h3 jet 
over the northwest U.S. dives eastward acros Idaho into Montana 
and a shortwave trough lifts northeast across the Northern Plains.
A low level jet of 25 to 35kts maintains itself, then weakens 
around 18Z. his afternoon, the environment has steep midlevel 
lapse rates to work with with h85 dewpoints pooling to around 10 
to 15 deg C. Meanwhile...seasonably strong westerly mid level 
winds 50 to 60kts will overspread the area. SBCAPE is around 500 
to 1000J/kg early today...then increases to 2000 to 3000J/kg by 
18Z and 3000-5000J/kg by 00Z. Deep layer shear increases to 
55-65kts at 18Z. The cams suggest that showers and thunderstorms 
will move through this morning with the stronger activity north 
into South Dakota or farth northeast Nebraska through 18Z. Between
18Z-21Z an isolated supercell/s may develop toward SUX/Mapleton 
dropping southward/southeast across western Iowa. A few of the 00Z
runs of the cams showed a track slightly west more along the 
Missouri River and along the surface boundary. The better forcing
shifts to the east, so it appears isolated activity is possible
due to the moisture and instability in place and marginally warm
mid level temps in place.  Additional development could occur 
across southern Nebraska/Iowa during the evening, and is also 
expected overnight into Friday as the next shortwave pushes across
the Central Plains...and again Friday night. There is a boundary 
in the area Friday afternoon and Friday night with much warmer 
mid- level temperatures over the region...very steep lapse rates 
of 9.0/9.5 deg C are progged Friday afternoon with effective shear
between 40 and 60kts. Storms would initially be elevated with 
plenty of instability and shear to work with. Parts of the cwa are
in a slight risk each day. Large hail, damaging winds and 
isolated tornadoes would be possible due to the favorable 
instablity and shear.

High temperatures today dependent on the precipitation and clouds,
but have highs in the mid to upper 70s north to the upper 80s
south with similar readings for Friday and Saturday.

.LONG TERM...(Saturday night through Wednesday)
Issued at 350 AM CDT Thu Jun 20 2019

Sunday...The longwave trough over the western High Plains will 
swing through the Mississippi Valley. An area of scattered showers
and thunderstorms Sunday will generally shift eastward with it. 
There are some timing differences as to how fast the system will 
exit the area and if Monday will remain dry, or if there will be 
some isolated shower activity lingering. Mid level ridging builds 
in for Tuesday and Wednesday and these increasing heights should 
result in warmer, more seasonal temperatures in the 85 to 90 
degrees range. Thunderstorm trends with this pattern will be 
spotty Monday through Wednesday. Normal highs are around 85 
degrees.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1125 PM CDT Wed Jun 19 2019

VFR conditions and light/variable winds will prevail through 10Z 
Thursday. Scattered thunderstorms are possible after 10Z in 
northeast Nebraska, with storms shifting to the south and east 
through 16Z Thursday. Brief impacts possible at KOMA, KLNK, and 
KOFK between 11Z and 15Z Thursday. Moderate up/downdrafts 
possible in the vicinity of any storms. Storms may redevelop along
the Missouri River Valley between 19Z and 22Z Thursday, possibly 
impacting KOMA.


&&

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

$$

SHORT TERM...Zapotocny
LONG TERM...Zapotocny
AVIATION...Albright