Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 181650

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1150 AM CDT Fri Aug 18 2017

Issued at 1150 AM CDT Fri Aug 18 2017

Will keep a slight chance of thunderstorms for parts of southwest
Iowa and southeast Nebraska, but chances look higher farther to
the east in southern Iowa and northern Missouri. Made minor
adjustments to sky cover, winds, temps.


.SHORT TERM...(Today through Sunday)
Issued at 335 AM CDT Fri Aug 18 2017

A shortwave trough over SD early this morning will translate east
into MN today ahead of an amplifying upstream impulse and
associated upper-level jet streak which will track from the
eastern Dakotas into the mid-MS Valley by tonight. Forcing for
ascent attendant to the former has fostered a loosely organized
MCS over the mid-MO Valley, which will likely decrease in areal
coverage as it continues southeast across our CWA this morning.
An isolated strong storm is possible, though severe weather is not

A weak cool front will move through the area this afternoon with
winds shifting to northwest with its passage. It appears that
generally weak convergence along this boundary will limit the
potential for the redevelopment of storms later today. High
pressure will build south into the mid-MO Valley tonight,
potentially leading to patchy fog. This is especially the case
across eastern parts of the forecast area where surface winds will
remain light through 12z/Saturday.

A quasi-zonal, mid-level flow pattern is forecast to develop
across the northern tier of states this weekend, supporting
southerly low-level winds, increasing moisture content and warmer
temperatures. The low-level warming/moistening will yield a low-
probability chance of showers and thunderstorms Saturday night
into Sunday.

.LONG TERM...(Sunday night through Thursday)
Issued at 335 AM CDT Fri Aug 18 2017

The primary focus in the long-term period is weather conditions
for the total-solar eclipse on Monday. Latest medium-range model
guidance is consistent in suggesting that a subtropical-branch
shortwave trough over CO Sunday night will be drawn northeast into
the mid-MO Valley on Monday where it will be entrained into a belt
of higher-momentum flow present across the north-central states.
Forcing for ascent associated with this feature will likely foster
scattered clouds and at least an isolated chance of showers and
thunderstorms across southeast NE and southwest IA on Monday

From Monday night into the middle of next week, considerable
amplification of a mid-level trough is forecast from eastern
Canada into the Great Lakes. This upper-air pattern evolution will
support the movement of a cold front through the forecast area
Monday night into Tuesday when a good chance of measurable
precipitation will exist. The cold front will usher a cooler,
continental air mass into the region with near or slightly below-
normal high temperatures expected through the middle to latter
part of the upcoming week.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1150 AM CDT Fri Aug 18 2017

Generally look for VFR conditions through much of the period, with
some fog possible toward sunrise. Winds will become light and
variable this evening and then turn to the southeast Saturday.




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