Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 231126

Area Forecast Discussion
National Weather Service Omaha/Valley NE
626 AM CDT Sun Oct 23 2016

.SHORT TERM...(today through Tuesday night)
Issued at 325 AM CDT Sun Oct 23 2016

Thunderstorm and heavy rain chances on Tuesday remain the primary
forecast concerns for the shorter term period.

Mid level flow pattern was featuring a broad ridge across much of
the center of the country this morning, with strong trough moving
east off the East Coast and another settling toward the West Coast.
Western trough will deepen through Monday as it shifts toward the
coast, then eject a significant shortwave into the Plains on
Tuesday. Ahead of this wave, ridge will amplify briefly over our
area on Monday.

At the surface, a cold front, tied to mid level shortwave moving
through southern Manitoba this morning, had entered northeast
Nebraska just past midnight, and will continue southeast through the
rest of eastern Nebraska and southwest Iowa by noon. North winds
will follow the front along with cooler and drier air for this
afternoon and tonight as high pressure settles into the region.
Despite this cool advection regime, plenty of sunshine and decent
low level mixing will help temperatures rebound into the 60s most
areas with some lower 70s in southeast Nebraska and southwest Iowa
this afternoon. Light winds and clear skies will allow most lows
tonight to drop into the 30s.

Winds will begin to turn southeasterly Monday as surface high slides
to the east and pressures lower in the High Plains with approach
of Tuesday shortwave. Low level airmass will change little as
neutral temperature advection is noted Monday, but filtered
insolation will help chilly morning temperatures reach the 60s
in the afternoon. Warm advection regime sets up Monday night as
low level jet kicks in after midnight, bringing higher theta-e air
to mid levels. Models continue to suggest isolated showers are
possible in eastern Nebraska before sunrise, but maximum
lift/convergence occurs north of Nebraska.

Rain/thunder chances will increase markedly during the day Tuesday
and especially Tuesday night as surface low attendant to mid level
wave deepens in central Nebraska. Gulf moisture return appears to be
robust at this time as GFS has been indicating precipitable water
values at or above the 90th percentile of seasonal norms, on the
order of 1.33 inches representing almost 200 percent of normal.
Moisture along with cooling aloft and surging low level temperatures
ahead of low combine to produce over 1000 j/kg of MLCAPE as per GFS
over at least the southern half of our area Tuesday afternoon and
evening. Moderate bulk shear of 30kt or so is also expected. All of
this suggests a fairly high chance for preciptation, with some
potential for strong thunderstorms along with heavy rain. Finer
details will have to be worked out with time, but strongest storms
will likely occur over southeast Nebraska and southwest Iowa. High
precip chances will continue much of the night, gradually tapering
from west to east as trough axis moves east of our CWA by 12Z

.LONG TERM...(Wednesday through Saturday)
Issued at 325 AM CDT Sun Oct 23 2016

We return to a more tranquil weather pattern for the last half of
the week when temperatures will average at or just above seasonal

Northwest mid level flow will follow Tuesday`s exiting shortwave
before weak ridging sets up late in the week. At the surface,
northerly winds and cool advection will rule Wednesday behind
Tuesday system, then winds turn to some form of southerly component
for the rest of the week. Layer relative humidity progs suggest
plenty of sunshine each day as well. There is some divergence in
model forecasts by Saturday when ECMWF swings a potent system
through the region while the GFS is much less amplified. Neither
paints significant precipitation across our area, so will maintain
a dry forecast through Saturday.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 558 AM CDT Sun Oct 23 2016

VFR conditions expected thru the fcst pd.




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