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000
FXUS63 KOAX 221058
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
558 AM CDT Tue May 22 2018

.SHORT TERM...(Today through Thursday)
Issued at 315 AM CDT Tue May 22 2018

Forecast concerns over the next few days will be timing of
showers and thunderstorms and warmer temperatures.

The 00Z OAX sounding had mixed to around 815mb resulting in
temperatures warming to the mid and upper 70s with abundant
sunshine. The h5 low pressure system was centered over southern
California with the h5 low responsible for the weekend damp weather
over Minnesota. GOES-16 water vapor satellite imagery highlights
these features and the deep convection occurring over New Mexico. An
emerging 100kt jet from southern California and increased upper
level divergence combined with shortwave trough energy/deep moisture
return has a north to south corridor of storms from Mexico northward
through New Mexico into southeast Colorado and the Oklahoma
Panhandle. H85 dewpoints were around 10deg C at DDC and LBF and
15deg C in West Texas.

Latest surface observations and WSR-88D reflectivity show one
subtle surface boundary in northeast Nebraska and another in
southern Nebraska trailing back toward southwest Nebraska and
eastern Colorado closer surface low. The strengthening low level
jet to around 40kts has touched off some isolated thunderstorms.
Warm air advection continues through the day, the low level jet
decreases and the warm front lifts a little farther north.
Forecast soundings show a favorable airmass for thunderstorms and
during max heating, some could become strong to severe. While the
low level jet will be one focus, as it weakens, the focus for
storms should be more tied to the warm front. SPC had the risk for
severe storms farther north and these could clip parts of
northeast Nebraska and west central Iowa where the shear is more
supportive of stronger storms. Will include some pops for iso/sct
coverage today. The low level jet increases again tonight and
noses a bit farther north into SD and northern Iowa and this puts
the more favored area for storms northeast of the forecast area,
additional storms could develop in northeast Nebraska and west
central Iowa tonight within the moist/instability axis and could
linger into Wednesday morning.

Wednesday, the h5 closed low is over eastern Idaho and western
Wyoming with the mid h5 ridge position just east of the Missouri
River. Through Thursday, the closed H5 low lifts northeast toward
Saskatchewan and Manitoba and extends into western Kansas with a
slight eastward progression of the mean ridge to the Mississippi
River. Thunderstorms will be ongoing with warm front from South
Dakota into western Iowa Wednesday with a weakening trend during
the day Wednesday. Wednesday afternoon and Wednesday
night...upslope flow combined with the 35-45kt low level jet
increasing should resulting in thunderstorms across the western
High Plains which gradually migrate eastward overnight and into
the forecast area. Due to the weakening forcing, thunderstorm
coverage should be isolated in nature.

Highs today should be in 85 to 90 each day.

.LONG TERM...(Thursday night through Monday)
Issued at 315 AM CDT Tue May 22 2018

Thursday night through Friday the 35kt southwest low level jet
develops over central Nebraska and the upper trough deepening
through the Plains. Steep lapse rates combined with mid-level
vorticity advection utilizing 2500-3500 MUCAPE should result in
scattered thunderstorms across the forecast area Thursday night
although bulk shear vectors (0-3km and 0-6km) tend to be less than
30kts. Friday night through Tuesday, mid level ridging builds
into the area. The GFS has more thunderstorm development Friday
night and with a shortwave over the Great Lakes trailing into the
local area Sunday morning. Left isolated pops in as forecast
soundings would support thunderstorms if forcing were sufficient.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 600 AM CDT Tue May 22 2018

Spotty showers and thunderstorms will be around this morning, with
small chances this afternoon. Expect ceilings mainly above 4000
feet but isolated MVFR ceilings will be possible, especially in
precipitation. Winds will be mostly from the south or southeast 5
to 15 knots. Look for mainly VFR conditions from late afternoon
into tonight, but some fog is possible late tonight.

&&

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

$$

SHORT TERM...Zapotocny
LONG TERM...Zapotocny
AVIATION...Miller