Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 181111
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
611 AM CDT Tue Apr 18 2017

.SHORT TERM...(Today through Thursday)
Issued at 328 AM CDT Tue Apr 18 2017

Main issue to contend with is convection this morning then
possible severe storms Wednesday aftn.

88D mosaic already showing narrow line of storms advancing eastward
across cntrl SD/n-cntrl Neb along a surface trof associated with low
pressure centered in cntrl SD. Sfc obs were showing a decent
moisture feed fueling the convection with Tds in the low/mid 50s.
RAP13/HRRR indicated storms will hold together as they push into the
CWA later this morning. As of now..it appears that the nrn CWA will
see the brunt of accumulations with around a quarter inch possible
before dissipating by early aftn.

Next round of pcpn comes after midnight tonight with the approach of
shortwave energy ejecting out of the cntrl Rockies. Increasing DPVA
induces leeside low over ern CO early Wednesday morning with
convection developing along attendant warm front extending across
Neb into IA...but quickly dissipate by aftn with onset of CAP.
Sfc low is progged to move into wrn IA by late aftn with a
trailing cold front sweeping in. Environment quickly destabilizes
with continuing influx of llvl moisture...MLCAPES 1200 J/kg.
NAM/GFS/NMM are in quite good agreement storms will begin popping
along/south of I-80 on nose of steep llvl lapse rates coincident
to axis of llvl theta-E convergence. Regarding severe storm
development...is reasonable to assume a few large hail producing
storms will form over SE Neb/SW IA given steep mid lvl lapse rates
atop moist bndry layer will be in place. However...appears that
the environment will be more favorable to support widespread
severe just east of the CWA where sfc-6km shear/ML SRH/instability
will be most prevalent in addition to nose of llvl jets
trajectory into srn IA.

Dry and cooler conditions then late Wednesday night thru Thursday
night.

.LONG TERM...(Thursday night through Monday)
Issued at 328 AM CDT Tue Apr 18 2017

GFS/CMC/ECM are in reasonable agreement a Pacific NW shortwave will
strengthen as it digs toward the cntrl Plains and bring the next
round of pcpn Friday aftn thru Saturday. Given the track of the
system will be across KS/OK...will focus higher POPs generally over
the srn CWA. Severe potential looks minimal at best.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 611 AM CDT Tue Apr 18 2017

A band of showers and thunderstorms stretching from northwest IA
to central NE as of 11z will spread east this morning, affecting
all three TAF sites. Prevailing conditions should remain VFR, but
a brief period of MVFR ceilings is possible with the passage of
the heaviest precipitation, especially at KOFK. The precipitation
should move to the east of the TAF sites by mid morning with gusty
south winds gradually shifting to west and then northwest with the
arrival of a weak front into the area. The front will stall later
today into tonight and serve as the focus for shower and
thunderstorm development late tonight into Wednesday morning.

&&

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

$$

SHORT TERM...DEE
LONG TERM...DEE
AVIATION...Mead



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