Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 131739
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1239 PM CDT Sun Aug 13 2017

.SHORT TERM...(Today through Tuesday)
Issued at 349 AM CDT Sun Aug 13 2017

Remnants of MCS continue to track across the CWA this morning.
ESRL HRRR depicting location adn intensity the best, and will
use it a primary guide in very short term portion of the
forecast as far as PoP. Expect spotty showers to linger
into late morning across northeast Nebraska/northwest Iowa, but
rest of the forecast area will see a lull as isentropic downglide
inhibits development through midday.

Slow moving upper level trough will provide enough dynamic forcing
to regenerate convection along instability axis in advance of
surface trough that will extend from north central Nebraska into
the Texas panhandle. Another area of focus will be along weak warm
front that will extend from surface low in south central South
Dakota into northwest Iowa. Mid-level lapse rates will be steepen
as compared to Saturday, with models depicting 6-7C/km by 21-00Z
and MUCAPES 2000-3500 J/kg. Bulk shear 35-40kts is on the marginal
side, but sufficient to sustain updrafts that could produce large
hail. CAM and Synoptic models showing variability in convective
initiation and evolution, but have most confidence of development
further north, where dynamics will be stronger. As is the case
this morning, convection will linger through the overnight into
the morning hours of Monday. After convection moves east, feel
most of the area will remain mostly late morning until late
afternoon Monday afternoon, as upper ridging builds over central
plains.

Break in precipitation threat is short-lived, as models again
spark thunderstorm development due to thermodynamic forcing along
quasi- stationary boundary that will arc from Black Hills into
Iowa on Monday night. Given storms will be diurnally driven,
expect activity to wane by late evening, especially as upper ridge
amplifies somewhat in response to trough diving into western U.S.
Will keep low chance PoP in place Monday night into Tuesday and
warm advection and increasing LLJ could generate elevated
convection.

.LONG TERM...(Tuesday night through Saturday)
Issued at 349 AM CDT Sun Aug 13 2017

More pronounced dynamic and surface forcing being depicted
by medium range models Tuesday night into through Wednesday as
more amplified upper trough moves across central U.S. Consequence
will be decent chance of precipitation for most of the forecast
area. Broad cyclonic flow remains across central U.S. through
the end of the week per medium range models, though EC/GEM little
faster building upper ridge into northern Rockies. As of now,
Thursday looks to be the dry and warmest day; however given
variance depicted by GEFS members from Thursday onward, that could
change. Temperatures will be seasonal and will be dependent on
amount of convective debris from storm development.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1227 PM CDT Sun Aug 13 2017

Main concern is possible TSRA later tonight. All this ahead of a weak
frontal boundary dropping out of SD and into nern Neb sometime toward
midnight. Activity is expected to increase in areal coverage as
it pushes southward overnight...moving into KOFK around 04Z...and
KOMA/KNLK around 06Z. Activity should be clear of all TAF sites by
12Z Monday morning.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&

$$

SHORT TERM...Fortin
LONG TERM...Fortin
AVIATION...DEE



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