Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 172017
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
317 PM CDT Mon Jul 17 2017

.SHORT TERM...(Tonight through Thursday)
Issued at 315 PM CDT Mon Jul 17 2017

Forecast concerns in the short term will be the chance for
thunderstorms tonight through Tuesday night and temperatures and
excessive heat headlines through the work week.

Our 12Z OAX sounding had dried out a little with pwat of 0.90".
The h3 jet extended from northern CA into the Northern Plains and
southern Canada. Ht falls over 100m were noted over Manitoba and
these trailed southward to around 20m toward KLBF. Water vapor
satellite imagery and h7 dewpoints showed mid level moisture with
the weakening h5 low pressure system.

The latest surface map hat temperatures in the 90s across the
local area with most dewpoints in the 60s with a few in the 70s.
Any cool air was northeast east of the boundary in central Iowa
and north of the front in North Dakota.

The WSR-88D radar mosaic showed a cluster of storms in west
central Nebraska...lifting to the northeast.

Through the afternoon...the RAP/HRRR develop showers and
thunderstorms mostly in central Nebraska with the weak h5 wave and
some weak upper level support. The main storm track in the short
term remains to our north across the Dakotas into
MN/IA/MN...however the is some chance that the southwest extent of
an MCS could affect parts of our area Tuesday night.

Tonight...the low level jet increases to 40kts into central
Nebraska and is more in the 20 to 25kt range as it spreads east
into the local forecast area. By 12Z the weak h5 wave is over
eastern Nebraska shifts into northern Missouri by Tuesday night.
The clouds are forecast to increase with the chance for isolated
to scattered thunderstorms into parts of northeast/east central
Nebraska tonight and toward the Missouri River Tuesday morning.
There should be a diurnal lull and then the coverage increases in
the afternoon. The slips southward into northeast Nebraska Tuesday
afternoon and this could provide an additional focus. Due to the
limited coverage isolated to scattered pops...however these can
be refined per radar trends Tuesday.

Highs Tuesday will again be in the 90s and with higher dewpoints
the highest heat indices should be 98 to 105. A heat advisory may
be need for parts of the area Tuesday depending of the
clouds/precip/resultant temps.

The effects of any MCSs in the area Tuesday night could affect
temperatures for Wednesday or delay /modify the warm up. At this
time with highs in the 90s and a few 100 or higher with higher
dewpoints expected will issue and excessive heat watch for
Wednesday through Friday for all but northeast Nebraska. It is
uncertain how far south the front will make it, however this
seemed like a good starting point.  More broad 105 to 112 heat
index values are forecast across the area for these days and have
a cumulative effect with the mild low temperatures and little
relief overnight.

.LONG TERM...(Thursday night through Monday)
Issued at 315 PM CDT Mon Jul 17 2017

Thursday night into Friday convection will be ongoing mainly from
the Dakotas into MN and northern Iowa. The GFS is hinting that
some storms from the Black Hills could make it into the forecast
Friday night and a weak shortwave in the flow aloft/front could
move in Friday night. The trend for the weekend is cooler.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1240 PM CDT Mon Jul 17 2017

Generally expect VFR conditions are expected through the period,
outside of any TSRA. At this time, did mention VCTS at KOFK and
KLNK but confidence is not overly high. Ceilings would most likely
be above 5000 feet.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Excessive Heat Watch from Wednesday afternoon through Friday
     evening for NEZ015-033-034-042>045-050>053-065>068-078-
     088>093.

IA...Excessive Heat Watch from Wednesday afternoon through Friday
     evening for IAZ043-055-056-069-079-080-090-091.

&&

$$

SHORT TERM...Zapotocny
LONG TERM...Zapotocny
AVIATION...Miller



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