Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 191715
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1215 PM CDT Fri May 19 2017

.SHORT TERM...(Today through Sunday)
Issued at 347 AM CDT Fri May 19 2017

The continued chances for showers and thunderstorms through
Saturday, and the potential for heavy rain, are the primary forecast
concerns.

Upper low was still spinning in the Central Rockies this morning,
ejecting periodic shortwaves into the Plains. We will continue to
see episodic bouts of rain and potentially thunderstorms until upper
low lifts northeast of our area Saturday night.

One of those shortwaves brought widespread showers and thunderstorms
to our area overnight, but was lifting northeast this morning and
taking most of the precipitation with it. Rainfall estimates from
radar were generally around an inch over a good part of eastern
Nebraska and southwest Iowa, with a few pockets over an inch and a
half. These totals were well below 3-hour flash flood guidance
numbers. And while that flash flood guidance will come down a bit
given latest rainfall, expected additional rains through this
evening are less than what happened this morning, except for perhaps
southeast Nebraska. Thus much of our current flash flood watch will
be cancelled this morning.

The evolution of precipitation occurrences for today is a little
less defined this morning than it was yesterday at this time.
Although most of the heavier precipitation is moving off to the
north and east, pockets of showers and isolated thunder continue to
pop up from central Kansas into southern Nebraska. Thus am having a
tough time defining dry areas/periods into the early afternoon.
Therefore will maintain at least a small chance for showers all
areas today.

Better chances for precipitation will come late this afternoon and
evening when another impulse ejects through the region, sparking
convection near surface front in south central Kansas.
Showers/storms will lift north into eastern Nebraska and western
Iowa by late afternoon, becoming more elevated as it moves away from
surface instability axis ahead of Kansas front. However southeast
Nebraska and southwest Iowa will be in area where elevated
instability and layer moisture profiles will be more robust, thus a
better chance for thunderstorms and heavy rain. Meanwhile Rockies
upper low will begin to push toward the Plains, cooling mid levels
and providing forcing for showers and isolated thunder over much of
our northern CWA as well.

Upper low tracks across northeast Nebraska during the day Saturday,
maintaining shower chances over all of eastern Nebraska and
southwest Iowa at least through the morning. Dry slot pushing into
southeast Nebraska Saturday afternoon should be the beginning of the
end of this round of rain, with diminishing chances for
precipitation from south to north Saturday evening.

Temperatures will remain rather cool with clouds, precip, and
northeast to north winds keeping lows in the 40s and highs in the
50s through Saturday. More sunshine under rising heights should push
highs back into the 60s on Sunday.

.LONG TERM...(Sunday night through Thursday)
Issued at 347 AM CDT Fri May 19 2017

The dry period on Sunday will be short-lived as upper low lifts
through the Plains but then stalls just north of the Great Lakes on
Monday. Then a strong mid level trough drops south from Canada on
the west side of low and into the Plains Monday into Tuesday,
dragging upper low into the Ohio Valley region. This scenario puts
our area under the influence of cyclonic flow regime with a couple
of mid level impulses triggering shower chances the first half of
the week, with temperatures on the cool side of normal. Models
differ on evolution of low beyond Tuesday, but the trend will be for
increasing heights in the Plains, thus warmer temperatures and
a mainly dry forecast.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1215 PM CDT Fri May 19 2017

Mesoanalysis at 17z placed a surface low over northwest OK with an
associated surface front stretching through central KS into
northern MO. Persistent warm advection and isentropic upglide to
the north of this boundary have yielded widespread IFR ceilings
with areas of drizzle and fog across eastern NE. Strengthening
forcing for ascent downstream from a potent mid-level trough
edging into the central Plains will support an uptick in shower
and isolated thunderstorm activity which will spread north across
the eastern NE TAF sites later this afternoon into tonight. Expect
IFR ceilings to persist into Saturday morning with precipitation
gradually tapering off by around 15z Saturday.


&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Flash Flood Watch through late tonight for NEZ091>093.

IA...None.
&&

$$

SHORT TERM...Dergan
LONG TERM...Dergan
AVIATION...Mead



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