691 
FXUS63 KOAX 091128
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
628 AM CDT Tue Jul 9 2019

.SHORT TERM...(Today through Thursday)
Issued at 331 AM CDT Tue Jul 9 2019

Rain and thunderstorms this morning, another chance this afternoon 
and tonight, then cooler temperatures for a couple of days, are the 
primary highlights of the forecast.

Well-defined MCV on radar was spinning into our western CWA just 
after 2 AM this morning, with line of scattered thunderstorms arcing 
south and southwest into central Kansas. This line will continue 
pushing east into east central and southeast Nebraska where juicy 
atmosphere exists, characterized by lower 70s surface dew points. 
Short-range mesoscale model output suggests storms will weaken 
rather rapidly around 12Z, and intensity trends have been downward 
as of late. There is still 500-1000 J/kg of MLCAPE available for 
convection ahead of line, so would expect only a gradual weakening 
trend through sunrise. To the north of the MCV, widespread rain with 
a few embedded lightning strikes should continue across northeast 
Nebraska into west central Iowa this morning. All activity is 
forecast to be moving east of our western Iowa counties between 15Z 
and 18Z today. 

Behind this system, atmosphere is expected to recover during the 
afternoon as low level moisture remains in place despite 
southwesterly surface wind component. Upper level forcing and low 
level convergence are weak during the afternoon when MLCAPE again 
exceeds 2500 J/kg, and nearly all model output keeps a lid on 
afternoon redevelopment. However with high instability and remnant 
low level convergent boundaries from morning convection, would not 
be surprised if a few storms could get going a couple of counties 
either side of Interstate 80. 

A more likely area of afternoon storm development is in the Nebraska 
Panhandle or southwest South Dakota where strong mid level jet 
streak and shortwave will steepen lapse rates and increase forcing. 
Models are fairly consistent in breaking out convection there, with 
a southeast propagation into central Nebraska during the evening, 
and eventually eastern Nebraska overnight. Strong layer wind fields 
suggest a damaging wind threat with this activity, mainly west of 
our area as diurnal cooling stabilizes boundary layer this far east.

Any overnight convection should move out of southeast Nebraska early 
Wednesday, with cooler northwesterly flow to follow as surface high 
pressure settles into the region. 850 temps drop 5-7C, pointing to 
highs only in the low to mid 80s Wednesday, and lows close to 60 
Wednesday night. There is some potential for afternoon showers 
Wednesday in western Iowa where steep lapse rates will exist. 
Otherwise a dry forecast takes us into Thursday when southerly low 
level flow returns in the afternoon, boosting temps a degree or two 
higher than Wednesday.

.LONG TERM...(Thursday night through Monday)
Issued at 331 AM CDT Tue Jul 9 2019

Warmer and more humid weather returns to the region for the weekend 
as mid level ridge in the Southwest pushes closer to the Plains. 
However main storm track around northern periphery of ridge is 
expected to remain close to the South Dakota and Nebraska border 
region much of the weekend. Thus perturbations in the flow will 
likely affect at least our northern CWA from time to time. These 
occurrences should favor the late night periods when mid level 
capping weakens and low level jet strengthens. Otherwise expect high 
temperatures in the 90s each day, with heat indices close to 100.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 623 AM CDT Tue Jul 9 2019

Line of TSRA is pushing out of ERN NE and into WRN IA. Activity
should be moving out of KOMA within an hour or so. Otherwise, VFR 
conditions will prevail thru the fcst pd.

&&

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

$$

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