Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 202037 CCB
AFDOAX

Area Forecast Discussion...CORRECTED
National Weather Service Omaha/Valley NE
337 PM CDT WED JUL 20 2016

.SHORT TERM...(tonight through Saturday)
Issued at 330 PM CDT Wed Jul 20 2016

...The heat wave continues...with some relief by Sunday...

For this update there were no changes in the excessive heat
warning. The 19Z MSAS/Satellite data shows virtually clear skies
across the area with surface low pressure centered near KPIR. Heat
index values today reached warning criteria as dew points soared
well into the mid to upper 70s under a southerly surface flow.
Weather stations from southwest Iowa even reported a few 81 degree
dew points, which is extreme. Of course this humidity is the
reason for the misery. Actual air temperatures are rather
unimpressive, only in the low to mid 90s. Normal temperatures for
this time of year are 88 at Omaha, 89 at Lincoln and 87 at
Norfolk. Aloft we are under the influence of strong high pressure.
500mb heights were observed at 596 decameters on the morning
sounding and have risen throughout the day. This ridge will
strengthen through tomorrow, allowing high temperatures to climb
even higher on Thursday. 100 degrees will be common across
Nebraska by this time tomorrow, with upper 90s expected in western
Iowa. Continued high dew points means the misery will continue for
Thursday and likely into Friday if we can keep the clouds and
precipitation away.

Aside from temperatures, a weak shortwave trough will move into
northeast Nebraska late tonight and could spark a few showers
across central Nebraska. While these showers could leak into our
area, decided to go with a dry forecast tonight given the low
probability. A strong shortwave will move over the ridge on
Thursday, yielding a better chance of precipitation as the upper
ridge begins to slowly break down. Associated with this feature
is also a marginal risk for severe weather. Though instability is
high given the moisture in place, the environmental shear is
negligible and best placed over northeast Nebraska and areas of
western Nebraska. The best opportunity for storms will likely be
in the evening hours.

Beyond Thursday the area remains in a favorable regime for
some precipitation as the upper ridge flattens. This will allow
more shortwave energy to traverse the area, yielding a slight
chance of showers and thunderstorms going into the weekend.

.LONG TERM...(Saturday night through Wednesday)
Issued at 330 PM CDT Wed Jul 20 2016

A stronger cold front will push through the Central Plains on
Saturday night. Temperatures behind this feature should drop a
bit, but not substantially. The latest guidance points to high
temperatures on Sunday in the upper 80s, this coupled with dew
points in the 60s should feel better than days past but still not
great. We do however expect an increased potential for
precipitation associated with this front. This feature is slow
moving and may even stall as it traverses the forecast area, thus
have opted to keep showers and thunderstorms through Sunday and
Monday associated with it.

By Tuesday a potent shortwave is progged to move out of Wyoming
and Colorado on its way to eastern Nebraska by Tuesday night. This
feature looks to drag a lot of moisture into it as precipitable
water values skyrocket well above two inches. This system will be
a significant precipitation producer if it comes to fruition.
Long-range guidance differs enough on placement and timing to not
get too excited yet. This feature exits the region on Wednesday
allowing drier conditions to prevail by later in the day.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1221 PM CDT Wed Jul 20 2016

VFR conditions through the period. Southerly winds at 14 to 24
knots, with gusts diminishing by 23-01z. Non convective LLWS
develops 05-06z...then diminishes by 14-15z.

&&

.OAX Watches/Warnings/Advisories...
NE...Excessive Heat Warning until 8 PM CDT Friday for NEZ011-012-
     015>018-030>034-042>045-050>053-065>068-078-088>093.

IA...Excessive Heat Warning until 8 PM CDT Friday for IAZ043-055-056-
     069-079-080-090-091.

&&

$$

SHORT TERM...Pearson
LONG TERM...Pearson
AVIATION...DeWald


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