Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 121712

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1212 PM CDT Sat Aug 12 2017

.SHORT TERM...(Today through Monday)
Issued at 330 AM CDT Sat Aug 12 2017

Another tranquil day on tap for the forecast area. Surface high
pressure will move east, and will allow for modest low level
warming and moisture advection. Minor H5 ridging aloft will keep
precipitation threat minimal most of the day. Shortwave dropping
southward across the northern plains, will ignite thunderstorms
along lee side trough in the western high plains and psuedo warm
front that will arc across South Dakota into Minnesota. Various synoptic
and CAM inconsistent in timing and location of stronger
convection, but in general move weakening convection into forecast
area this evening. Shortwave is slow to move east, as it
encounters channeled flow, but does help to strenghten overall wind
field. Convection looks to linger most of the night as LLJ
increases and improves theta-e advection.

Threat of convection will linger across the area Sunday, into
early Monday, as shortwave slowly trudges eastward. Likely will
see reprieve late morning Sunday into Sunday afternoon with
isentropic downglide evident. Thermodynamic forcing long remaining
synoptic and mesoscale boundaries help revive convection during
the afternoon, and it appears a weak wave moving out of central
Rockies will provide enough upper support to keep threat of
storms into Monday.

Temperatures today will be near those seen yesterday, perhaps
slightly warmer across southeast sections due to southerly flow
influence. Convective debris from storms to the west and north
could limit insolation slightly across western and northern CWA,
thus will not make much adjustment. Clouds and convective debris
will keep temperatures cooler on Sunday. A slight warm-up is
expected on Monday due to drying and upper level ridging.

.LONG TERM...(Monday night through Friday)
Issued at 330 AM CDT Sat Aug 12 2017

Upper ridging Monday night into Tuesday should keep most of the
forecast area dry. Cannot discount scattered nighttime storms due
to warm air advection/isentropic ascent, so low kept low PoPs
produced by consensus forecast.  Large upper level trough begins
to develop across western U.S., along with more pronounced frontal
system. All medium range models and GEFS drag frontal system
through the area and signal decent chances of showers and storms.
Flattening upper level flow late in the period, as aforementioned
trough dampens out. GEFS members showing spread, but depict
lingering boundary stretched somewhere across southern part of the
CWA along with quasi-permanent lee-side trough. Both could provide
focus of thunderstorm develop, but exact timing and coverage is


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1210 PM CDT Sat Aug 12 2017

VFR conditions are indicated through the TAF cycle. Showers may
affect KOFK and to a lesser extent KLNK tonight after 06Z. Have
kept out thunder wording, as instability is weak and thunder
threat quite isolated, but did include a TEMPO period for showers
at KOFK without visibility reduction. Winds at all sites will
remain southerly to southeasterly at 10kt or less.




LONG TERM...Fortin
AVIATION...Mayes is the U.S. government's official web portal to all federal, state and local government web resources and services.