Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 242334

Area Forecast Discussion
National Weather Service Omaha/Valley NE
634 PM CDT Thu May 24 2018

.SHORT TERM...(Tonight through Sunday)
Issued at 340 PM CDT Thu May 24 2018

Thunderstorm chances tonight into Friday, then heat through the
weekend, are the primary forecast concerns.

A couple of areas of convection were popping up this afternoon and
will likely affect our area during the evening. One was in northeast
Nebraska where 2000-2500 J/kg of MUCAPE as focused under weak upper
level diffluence. Mid level theta-e was maximized here as well, and
persistent afternoon heating will likely translate to continued
development of storms along weak surface convergent zone. Shear
profiles are weak, thus organized storms are not expected, but a few
could pulse up rather quickly and produce some hail and gusty winds.

Another area of convection was noted in eastern Kansas and northwest
Missouri. These were bubbling up in another instability axis
characterized by MLCAPE approaching 2500 J/kg and little CINH where
dew points were in the upper 60s. Convection was aided by diffluent
mid level flow ahead of well-defined MCV in central Kansas seen on
visible satellite imagery. Cumulus cloud field was becoming more
robust-looking in southeast Nebraska and southwest Iowa adjacent
to current convection, so expect some development in those areas
late today. Much of this activity will likely die with diminishing
afternoon heating, however will maintain chances later into the
evening in far southeast Nebraska where influence of MCV may be felt
for a longer period of time.

For the overnight period, things are still a little iffy in regards
to thunderstorm coverage as short-range hi-res model output is
fairly bearish on widespread development. However there is some
overlap in solutions between hi-res and synoptic-scale models in
showing development associated with mid level shortwave and ahead of
weak surface front tracking into our area overnight. The most likely
scenario will be for storms to develop later in the evening or after
midnight in plume of highest low and mid level theta-e advection
carried along by strengthening low level jet from eastern Kansas
into northwest Iowa. Some strong storms are certainly possible
during this time as elevated MUCAPE shown on forecast soundings
reaches 2000 J/kg with little CINH.

Much of the convection will push east of the Missouri River by mid
Friday morning, and out of southwest Iowa shortly after. Light
southwest low level flow will follow, but weak surface front will
settle south into eastern Nebraska and west central Iowa during the
afternoon and evening. An isolated afternoon storm could pop along
this boundary, but better chances will focus along moisture plume
from eastern Kansas into southern Iowa.

Beyond Friday, mid level ridging is expected to build into the
region through Sunday, with temperatures on the upswing with it.
Highs in the 90s are likely both days. Dew points should only be in
the 50s to around 60 on Saturday, but increase back into the 60s by
Sunday making that day feel more humid. Still, heat indices won`t
be much higher than actual air temperatures each day.

.LONG TERM...(Sunday night through Thursday)
Issued at 340 PM CDT Thu May 24 2018

We are still looking at a more active weather pattern returning for
much of next week as upper ridge slides east with approach of upper
low from the west. That low should open up by Tuesday, keeping our
area under southwest flow aloft, and several impulses riding
through that flow could trigger convection from time to time. And
again today, there are run-to-run and model-to-model
discrepancies in timing and strength with these systems, so trying
to nail down exact timing right now is futile. Suffice it to say
periodic thunderstorm chances will rule the forecast at least
Tuesday through Thursday. Otherwise temperatures generally in the
85 to 90 degree range are expected for afternoon highs.


.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 628 PM CDT Thu May 24 2018

Unstable conditions will be widespread across the area during the
period but little in the way of any significant features to focus
convection. VFR conditions will prevail through the forecast
period with isolated storms possible.




LONG TERM...Dergan
AVIATION...Fobert is the U.S. government's official web portal to all federal, state and local government web resources and services.