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fxus63 koax 180806 

Area forecast discussion
National Weather Service Omaha/valley NE
306 am CDT sun Aug 18 2019

Short term...(today through tuesday)
issued at 305 am CDT sun Aug 18 2019

The main forecast concerns are in regards to potential for some
severe storms and heavy rain Tuesday night into Wednesday morning.

Temperatures yesterday topped out mostly in the mid and upper 80s
in the local area. Today will be cooler, with the most noticeable
cooling in the northern part of the forecast area.

Upper air charts from last evening showed fairly strong mid
tropospheric flow, for this time of year, across the northern and
central parts of the plains. At 500 mb, the strongest 12 hour
height falls (around 60 meters) last evening were noted near the
border of Mt, ND and Saskatchewan. These height falls continue to
move eastward. Water vapor imagery indicated the axis of a mid
level trough extending from southern Manitoba into western NE
early this morning. Two main clusters of storms have been ongoing
the in the past 6 hours, with the most coverage to our north,
south and east. We may still see some isolated to scattered
showers and thunderstorms for parts of our area. Will keep some
20-30 percent chances for precipitation going this morning. As of
about 3 am, a cold front (at least partially enhanced by
thunderstorm outflow) stretched from Minnesota across northwest IA,
parts of eastern NE and then into northwest Kansas. Temperatures in
the 40s were noted in eastern Montana and western ND.

The previously mentioned front should continue to push southeast
through the region today. Look for high temperatures in the upper
70s and lower 80s across northeast NE, with lower and mid 80s
elsewhere in our forecast area. Will keep a dry forecast going for
tonight and Monday. High pressure at the surface will build in
tonight, then shift off to the east Monday. Some moisture should
start to return aloft Monday night, thus will include a slight
chance for showers and thunderstorms. A weak front is forecast to
slide into our area from the north Tuesday.

Long term...(tuesday night through saturday)
issued at 305 am CDT sun Aug 18 2019

Storm chances should be higher for Tuesday night, with a frontal
boundary in the vicinity, development of a low level jet and an
influx of deeper moisture. Precipitable water (pw) values may
increase to around two inches with bulk shear increasing to over
40 knots. This may result in some severe storms (see the Storm Prediction Center
day 3 outlook) and areas of locally heavy rain for Tuesday night
into Wednesday morning.

In general, the large scale pattern should feature a ridge across
the southern part of the US at the beginning of the long term
period, with closed lows off the coast of British Columbia and
over northern Ontario. Through the week, there will be some subtle
changes. What is expected to happen by Friday and Saturday is that
moderately strong zonal flow will spread from the Pacific northwest
eastward toward the northern half of the plains. This should keep
intermittent chances for showers and thunderstorms going for our
area. The highest chances (outside of Tuesday night) are currently
expected from Wednesday into Wednesday night. High temperatures
should vary from the upper 70s to the upper 80s, with lows mostly
in the 60s.


Aviation...(for the 06z tafs through 06z Sunday night)
issued at 1126 PM CDT Sat Aug 17 2019

An mesoscale convective system is in progress as of 11 PM from southwest Minnesota into northwest
Iowa and southeast South Dakota with trailing isolated thunderstorms
stretching west to near konl. That latter convection could pass
near or to the north of kofk within the next couple of hours.
Thereafter, a cold front will move through the area with south
winds switching to northwest at around 10 kt. Models continue to
indicate a swath of MVFR ceilings behind the front which will most
likely impact kofk and klnk into Sunday morning. Some low-level
wind shear is also possible overnight at koma and klnk.


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