Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 182359
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
659 PM CDT Thu May 18 2017

.SHORT TERM...(Tonight through Sunday)
Issued at 307 PM CDT Thu May 18 2017

...Near-term forecast concerns are heavy rainfall potential across
our southern counties tonight into Friday night...

A prominent mid-level cyclone was analyzed over the central
Rockies as of early afternoon with an associated vorticity lobe
and attending jet streak pivoting northeast across the central and
southern High Plains. At the surface, 19z analysis depicted an
area of low pressure over southwest KS with an accompanying
quasi-stationary front stretching northeast into northern MO.

The influence of the above-mentioned vorticity lobe and jet streak
on a strongly unstable air mass will yield widespread thunderstorm
development this afternoon within the warm sector across KS into
OK. Increasing moisture flux and warm advection along a
nocturnally strengthening LLJ will aid in the northward movement
of these storms into our area overnight. Isolated severe weather
in the form of marginally severe hail and locally strong wind
gusts is possible. However, the primary concern is flooding
rainfall given the antecedent near-saturated soil conditions. As a
result, we have issued a Flash Flood Watch from tonight into
Friday night for several of our counties in southeast NE.

We should see a break in the precipitation across much of the area
Friday morning as the stronger forcing associated with the lead
vorticity maximum lifts into the northern Plains. However, by
Friday afternoon into Friday night, the primary mid-level system
will shift east into the central Plains, contributing to
widespread showers and thunderstorms. Current indications are
that the system warm sector will remain to the south of the NE-KS
state line with the primary concern again being flooding
rainfall.

The deep-layer synoptic cyclone will develop northeast into the
upper Midwest on Saturday with drier conditions anticipated by
afternoon. By Sunday, northwest, downslope flow in the low levels
will support a warming trend with highs rising back into the 60s
areawide.

.LONG TERM...(Sunday night through Thursday)
Issued at 307 PM CDT Thu May 18 2017

Latest medium-range guidance is in reasonably good agreement in
suggesting that a substantial short-wave trough will track south
through the mid MO Valley in the Monday-Tuesday time frame,
supporting an increasing chance of showers and thunderstorms.
Thereafter, building mid-level heights will signal a drier pattern
along with gradually warming temperatures.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 654 PM CDT Thu May 18 2017

MVFR cigs and vsbys developing across the area through 06Z as
showers and thunderstorms spread north out of Kansas. Periods of
showers with cigs becoming IFR between 06Z and 12Z then continung
through remainder of the forecast period as upper low tracks into
the western high plains.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Flash Flood Watch through late Friday night for NEZ078-088>090-
     092-093.

IA...None.
&&

$$

SHORT TERM...Mead
LONG TERM...Mead
AVIATION...Fobert



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