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-- Discussion containing changed information from previous version are highlighted. --
229
FXUS63 KOAX 240825
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
325 AM CDT Sat Jun 24 2017

.SHORT TERM...
-- Changed Discussion --
(Today through Monday)
Issued at 321 AM CDT Sat Jun 24 2017

A dry and mild weekend will remain in the forecast, with rain
chances returning later Sunday night and Monday.

Northwest flow aloft will continue in the Plains until Monday as
mean trough position lingers in the Great Lakes area. A couple of
shortwaves are forecast to drop through that flow. The first will
dive southeast across Minnesota and Wisconsin today, triggering
scattered afternoon showers as far southeast as central Iowa.
Affects here should be limited to afternoon cumulus and gusty
northwest winds in our north and east, then a reinforcement of
cooler airmass as cool advection follows shortwave for later
tonight and Sunday. Thus highs today may be a few degrees higher
than Sunday, but still looking at max temps in the 70s for the
most part each day.

The second shortwave of note is forecast to spread vorticity channel
under 90-100kt upper level jet into eastern Nebraska late Sunday
night into Monday morning. Moisture will remain somewhat limited
before this time, but a modest increase is forecast by GFS and
Canadian models in the 850 to 700mb layer. Increasing forcing
under jet combined with increasing moisture suggests at least a
few showers will develop after midnight Sunday night and continue
into Monday evening before jet tracks to the east. GFS is a bit
more aggressive with moisture return and thus instability. Have
sided more with Canadian in regards to instability, so expect only
isolated areas of thunder potential.

.LONG TERM...(Monday night through Friday)
Issued at 321 AM CDT Sat Jun 24 2017

Things get a little more interesting next week with mid level
ridging briefly building into the Plains before more zonal
configuration sets in Wednesday and Thursday. By Friday, flow begins
to buckle somewhat as upper low settles southeast into the southern
Canadian Plains, suggesting at least shallow troughing in our part
of the CONUS.

The first chance for convection in this scenario will be Tuesday as
warm/moist advection occurs under building ridge. This should affect
areas mainly to our west, but there is a chance storms could skirt
western and northern sections of eastern Nebraska. Mid level
shortwave quickly moves into the Plains Tuesday night, effectively
breaking down short-lived ridging, and likely triggering convection
over much of our area as robust theta-e advection occurs on
increasing low level jet. A weak frontal boundary will follow
shortwave and settle across eastern Nebraska and western Iowa, then
remain in our area through Thursday and offering low level focus
for convection those days. While the exact configuration of
frontal boundaries and thus instability maxima will have to be
determined as we get closer to mid week, a good majority of
longer-term model solutions show 2000-3500 J/kg of MLCAPE and
strong shear, with Thursday offering the highest numbers on both
parameters, and thus the greatest threat of severe convection. By
Friday, it appears surface front will be south of our area, but
potentially close enough to keep thunder chances in our south.
-- End Changed Discussion --


&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1132 PM CDT Fri Jun 23 2017

High pressure will prevail across the central plains through the
period with VFR conditions at all TAF sites.


&&

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

$$

SHORT TERM...Dergan
LONG TERM...Dergan
AVIATION...Fobert