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fxus63 koax 191705 

Area forecast discussion
National Weather Service Omaha/valley NE
1205 PM CDT Thu Sep 19 2019

Short term...(today through saturday)
issued at 333 am CDT Thu Sep 19 2019

Main forecast concern centers around heavy rain this morning and
localized flash flooding across portions of northeast Nebraska and
west-central Iowa.

Convection containing very heavy rain continues to backbuild along a
quasi-stationary front extending across northeast Nebraska and into
west-central Iowa. Radar rainfall estimates show on average around 3-
5" in the heaviest bands, with some localized radar estimates on
the order of 7-9". While we don't have confirmation or any ground
truth as of yet, we don't doubt that there are isolated high
amounts on this order that we will hear about later this morning,
especially in northern Stanton, northern Cuming and southeastern
Wayne counties, mostly in the Elkhorn River Valley. Will need to
monitor the Elkhorn for drastic rises. A few reports are coming
in already of some flash flooding in Stanton and Thurston counties
and can only imagine there is more ongoing flash flooding that we
just haven't heard about yet. This area of convection is expected
to continue near the boundary this morning aided by a 35kt llvl
jet. The area may also expand in coverage in advance of a weak
shortwave impulse and associated upper-level jet streak.
Instability remains moderate with MUCAPE on the order of 1500-2000
j/kg in addition to steep mid- level lapse rates. Pwat's continue
to pool near the boundary and area near 200% of normal for this
time of the year. Of note, the 19/00z oax sounding broke a precipitable water
record at 1.81". The previous record for that time was 1.72.
Expect the convection along the boundary to diminish after sunrise
as the low-level jet wanes, however scattered convection further
south may continue in association with forcing for ascent
associated with the above mentioned weak shortwave impulse and
associated upper-level jet streak. Will continue the Flood Watch
that was issued yesterday for areas along and east of the Missouri
River where river flooding is already ongoing and additional
rainfall will only aggravate area rivers and tributaries.

A few scattered showers could linger through the day but a majority
of the day looks fairly dry with highs generally in the 80s.

The next good chance for rain will come Friday night into Saturday
across northeast Nebraska ahead of a large mid/upper level trough
moving northeast across the the High Plains. Ahead of this trough
will reside a moisture-rich environment with pwat's still about 200%
of normal. Much of the activity looks to be nocturnal in association
with the forcing from a veered low-level jet.

Long term...(saturday night through wednesday)
issued at 333 am CDT Thu Sep 19 2019

Additional chances for heavy rain arrive in the forecast Saturday
night into Sunday, generally south of Interstate 80 as the
previously mentioned upper trough axis swings through the Central
Plains. Day 3 excessive rainfall outlook has areas south of i80
in a slight risk as does the severe outlook.


Aviation...(for the 18z tafs through 18z Friday afternoon)
issued at 1204 PM CDT Thu Sep 19 2019

Convection continues to push east, having cleared out at kofk,
koma, and klnk. VFR conditions will hold through the taf period.


Oax watches/warnings/advisories...
NE...Flood Watch until 1 PM CDT this afternoon for nez034-045-052-053-

Iowa...Flood Watch until 1 PM CDT this afternoon for iaz043-055-056-069-


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