National Weather Service Raw Text Product

797 
FXUS63 KOAX 071120
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
620 AM CDT Mon May 7 2018

.SHORT TERM...(Today through Wednesday)
Issued at 306 AM CDT Mon May 7 2018

A return of showers and thunderstorms later tonight through 
Wednesday is the primary forecast concern.

High pressure was settling over Iowa and eastern Nebraska at early 
morning, and is forecast to drift off to the east during the day. 
Meanwhile mid level trough riding through the Northern Rockies will 
push toward the Northern Plains this afternoon. Lowering surface 
pressures ahead of wave will promote a return to increasing 
southerly flow across the Plains today. Flow strengthens overnight
as trough closes off a low center in the Dakotas, resulting in 
modest low and mid level theta-e increases from central through 
northeast Nebraska and South Dakota. Elevated instability on the 
order of 500-800 J/kg in zone of 40-50kt low level jet should 
result in scattered convection after midnight, affecting parts of 
northeast Nebraska. Activity will expand southeast a bit during 
the morning, but decreasing in intensity and coverage as we head
through Tuesday morning.

Attention then turns to the west again in the afternoon. Surface 
front attendant to Dakota's low is forecast into northeast Nebraska 
in the afternoon. Continued low level theta-e advection under cool 
mid level trough will result in MUCAPE values approaching 2000 J/kg 
in a modest bulk shear environment of 30-35kt. Waning inhibition
should allow convection to fire along frontal zone in the heat of
the day from eastern South Dakota into northeast and central 
Nebraska. Severe potential appears to come with initial storm 
development when updrafts are most robust, and should wane with 
time during the evening as instability and shear both decrease as 
front and convection shifts eastward across the the rest of 
eastern Nebraska and southwest Iowa. More general showers and 
thunderstorm activity will be the rule much of the night before 
shifting east of our area by Wednesday morning.

Northwest flow at the surface and aloft follows for Wednesday, 
allowing for clearing skies and a relatively pleasant afternoon. 
Temperatures Monday through Wednesday should remain above normal, 
averaging the upper 70s and lower 80s each day.

.LONG TERM...(Wednesday night through Sunday)
Issued at 306 AM CDT Mon May 7 2018

An active weather pattern develops for the end of the week and 
weekend as upper flow becomes southwesterly over the Plains ahead of 
developing western trough. Shortwave ridging will begin the period 
Wednesday night, with a weak mid level impulse quickly to follow. 
Warm advection regime overspreading our area with building shortwave 
ridge will bring an initial chance for showers/thunder late Wednesday
night. Then shortwave trough will become increasingly influential
beginning Thursday afternoon. Broad theta-e increase ahead of 
wave should result in scattered convection Thursday night as well,
with best shot of stronger thunderstorms coming Friday afternoon 
as surface front attendant to shortwave swings through eastern 
Nebraska and western Iowa. GFS and ECMWF indicate substantial 
instability and shear profiles at that time. 

Cooler conditions are expected for the weekend with surface front 
settling south of our area. However southwest flow aloft and 
ejecting trough/low will provide for continued chances for 
overrunning showers into Sunday. Highs for the weekend will likely 
hold in the 60s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 616 AM CDT Mon May 7 2018

VFR conditions will prevail thru the fcst pd.

&&

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

$$

SHORT TERM...Dergan
LONG TERM...Dergan
AVIATION...DEE