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Area forecast discussion
National Weather Service Omaha/valley NE
625 am CDT Tue Sep 17 2019

Short term...(today through thursday)
issued at 253 am CDT Tue Sep 17 2019

The region remains under strong southwesterly flow aloft between
amplified ridging to our east and a deepening trough across the
western Continental U.S.. this pattern will continue to allow monsoonal
moisture to stream northeastward over the area. Through the week,
pwat's are forecast around 200% of normal for this time of the
year.

For today, temperatures and wind will be the primary concerns. We
are starting the day off well above normal with highs reaching
the low 90s once again for most areas. Breezy southerly winds
will allow decent mixing with late morning/afternoon surface gusts
near 30mph. Have continued a small chance for thunderstorms in
our far northern counties late this evening as a potent shortwave
moves northeast across the western Dakotas allowing a surface
cold front to move southeast across the forecast area overnight. A
nocturnal 40-50kt veered low-level jet should help sustain
convection across our eastern counties through daybreak. By
Wednesday afternoon, the frontal boundary is forecast to extend
southwest to northeast across the forecast area while a series of
embedded shortwaves move northeast across the area. With pw's
around 1.5-2" and storms possibly training along the frontal
zone, we do think it is quite possible to see heavy rain Wed
night through Thursday morning, primarily along the boundary with
a focus toward southwest Iowa. A few scattered showers could
linger through the day Thursday, especially in our eastern
counties, but much of the day should remain mostly dry.

Long term...(thursday night through monday)
issued at 253 am CDT Tue Sep 17 2019

Late Thursday into early Friday looks mostly dry but
precipitation chances increase for the early part of the weekend
as a large mid/upper level trough moves into the High Plains
region and eventually turns northeast toward the eastern Dakotas
and Minnesota on Saturday. Ahead of this trough a moisture-rich
environment will reside with pwat's still about 200% of normal.
Strong isentropic lift ahead of the system will likely produce
widespread showers Friday night with the better forcing lifting
to our northeast with the upper wave.

Cooler and drier air moves over the area later in the weekend and
into the early part of next week.

&&

Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 617 am CDT Tue Sep 17 2019

VFR conditions are expected to continue through the majority of
the taf period. A few showers and storms will move through after
06z tonight as a cold front drifts into the region. However,
confidence was too low to include at this time. Otherwise strong
winds will remain out of the south today, sustained at 10-20 kts,
gusting up to 20-30 kts. Expect winds to gradually decrease
overnight.

&&

Hydrology...
issued at 253 am CDT Tue Sep 17 2019

Flood warnings remain in place for the Missouri River from around
Sioux City south past Rulo. Water from heavy rainfall over South
Dakota last week continues to flow into the Missouri River basin.
This has led to Rising River levels over the last 48 hours,
especially north of Omaha. The trend of Rising River levels should
continue this week, with crests expected from north to south
between the 18th and 22nd. Flooding could impact travel along
portions of interstates 29 and 680 in Iowa by Wednesday. Other low
lying areas may be re-flooded depending on the repair status
levee breaches from earlier flooding.

Additional rainfall is anticipated over the region between Tuesday
and Saturday, with the heaviest rain expected Wednesday night
through Saturday. Model guidance suggest some potential for
additional heavy rainfall during this period. However, confidence
in rainfall amounts and timing is low with fronts pushing into the
region and stalling before moving south out of the area. This
potential for additional rainfall will need to be monitored with
future forecasts. Current River level forecasts only take into
account the rainfall forecast for the next 24 hours.

&&

Oax watches/warnings/advisories...
NE...none.
Iowa...none.
&&

$$

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