Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 231116

Area Forecast Discussion
National Weather Service Omaha/Valley NE
616 AM CDT Wed Aug 23 2017

.SHORT TERM...(Today through Friday)
Issued at 317 AM CDT Wed Aug 23 2017

Quiet, cooler, and drier weather continues today. Subjective 00Z
upper-air analysis indicates a deepening upper-level trough in the
eastern US and ridging in the west, with northwesterly flow across
the central US. Frontal passage had brought much drier and slightly
cooler mid-level air to the central US, with 12C+ dewpoints at 850mb
confined to the southern Plains to TN River valley area and
southward. A pocket of cooler 850mb temperatures was noted in ON,
but in the central Plains, temps were still 10-20C from east to
west. Surface high at 06Z was centered in eastern NE/western
IA/northeast KS/northwest MO.

Main forecast concern is potential for an isolated shower or storm
tonight, with increasing chances Friday and especially Friday night
into Saturday. Fair weather should continue today as high pressure
slides to the east, with return flow developing through the day.
Temperatures should be able to gain a few degrees on Tuesday`s
highs. As mid-level warm/moist air advection continues into tonight,
a few showers/storms could develop on the nose of the low-level jet;
this would be mainly in central NE to southeast SD and mostly out of
the area, but a stray shower/storm or two could clip central to
northeast NE.

A shortwave trough should round the ridging in the Rockies on
Thursday, making its way toward the central Plains through Friday.
With continued warm/moist air advection ahead of it, convective
development is likely on the High Plains by Thursday
afternoon/evening, with a chance of weakening showers/storms
reaching eastern Nebraska to northwest Iowa later in the night.
Activity probably will wane a bit diurnally on Friday, with another
round of High Plains convective development on Friday
afternoon/evening again rolling east on Friday night and into
eastern NE/western IA. The showers/storms should continue into
Saturday, especially in northeast NE to northwest IA, as the surface
front finally reaches those areas. Overall, confidence is on the low
side for timing and coverage of showers/storms for any of these
potential rounds of activity, with a range of possibilities from a
few isolated showers/storms here and there to a couple of larger
convective complexes.

.LONG TERM...(Friday night through Tuesday)
Issued at 317 AM CDT Wed Aug 23 2017

Another upper-level low digging into the Great Lakes should help
force a cold front through the area on Saturday night/Sunday/Sunday
night, bringing the final round of precipitation during the more
active period. Instability axis does shift eastward through the
period; after residing over central NE to the High Plains earlier
in the week, it is likely to shift toward eastern NE on Saturday.
This may make Saturday afternoon/evening the most likely day in
the week for more coverage of thunderstorms and for stronger
thunderstorms. Instability decreases markedly on Sunday, and any
lingering precipitation is likely to be more showers than storms.
Drier and cooler weather then should follow for Monday and Tuesday
as a surface to mid-level high builds into the area.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 615 AM CDT Wed Aug 23 2017

VFR conditions through the period. There may be some patchy fog
this morning in southwest IA, but should not impact the KOMA TAF.
There may also be some low level wind shear at KOFK 24/10-12z at
the end of the TAF period.




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