Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 212004

Area Forecast Discussion
National Weather Service Omaha/Valley NE
304 PM CDT Mon Aug 21 2017

.SHORT TERM...(Tonight through Thursday)
Issued at 300 PM CDT Mon Aug 21 2017

The solar eclipse is our primary forecast concerns are
storms tonight, especially before midnight and then temperatures.

The 12Z KOAX sounding showed PW at 1.70 and a K index of 42. Water
vapor imagery early this afternoon showed moisture plume extending
from Mexico and west TX northeast into KS, southeast NE and IA.
MCS that moved across southern SD had expanded down into northeast
NE, but that activity had weakened a little as of 3 pm. Mid level
trough axis extended from near the southern Saskatchewan and
southern Manitoba border back toward WY. Cold front trailed back
behind the MCS, so there should be some additional storm
development along and behind the front as it pushes through the
area tonight. Strongest height falls though will stay well to the
north, but some weak height falls will move across the area.
Storms will have some severe risk and potential for locally heavy
rain. Effective shear is 25 to 40 knots, so enough for organized
storms. MLCAPE values as of 2 pm were mainly 1000 to 2000 J/kg
ahead of the front.

After tonight, the period from mid morning Tuesday through much of
the day Wednesday looks dry. A ridge of high pressure at the
surface should build over the Dakotas and into central/eastern NE
Tuesday and Tuesday night.

Isolated storms could develop late Wednesday afternoon or
evening, mainly to our west and north. There will be some
potential Wednesday night and Thursday into parts of northeast NE
but again chances look better outside of our forecast area (to the
west for those periods).

Temperatures will be cooler Tuesday through Thursday, with mainly
mid 70s to lower 80s (possibly mid 80s southeast NE) with lows 50s
to lower 60s.

.LONG TERM...(Thursday night through Monday)
Issued at 300 PM CDT Mon Aug 21 2017

A weak mid tropospheric ridge will extend from CO up into central
Canada at the start of this period, and there will be a potential
trough from western Canada down into the Pacific Northwest. Trough
should progress east toward central Canada by Saturday night while
a ridge develops over the western US. That will cause a trough to
amplify to the west, putting us in modest north/northwest flow at
500 mb.

There will be off and on thunderstorm chances with highest
chances from Thursday night into Friday morning, and Friday night
into Saturday. Temperatures will remain below normal in this
period, highs in the mid 70s to lower 80s and lows mostly upper
50s to mid 60s.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 150 PM CDT Mon Aug 21 2017

Look for mainly VFR conditions outside of TSRA. Storms should
move across the KOFK TAF site 20Z to 23Z window with gusty winds.
Storm chances late afternoon and early evening for KOMA and KLNK,
then some SHRA could linger beyond until around 06z.




LONG TERM...Miller
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