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FXUS63 KOAX 212315

Area Forecast Discussion
National Weather Service Omaha/Valley NE
615 PM CDT Mon Oct 21 2019

...Updated Aviation Forecast Discussion...

Issued at 305 PM CDT Mon Oct 21 2019

Through Tuesday Morning...
Very impressive storm system is driving our weather today with a
986 surface low centered over south central MN at 3 PM Monday. The
low appears to be nearing its peak intensity, although pressure
falls may continue for a few more hours as it remains nearly
stationary. Pressure rises are also occurring over western and
central Nebraska, with a substantial pressure gradient in place
across the local forecast area which will lead to increasing wind
speeds through the rest of this afternoon and into the evening. 
Wind gusts in the North Platte area have exceeded 60 mph several 
times today, and while the conditions are not quite as favorable
locally, there appears to be some potential for wind gusts to
reach 60 mph, especially in northeast Nebraska and west central
Iowa. Current indications are that the strongest boundary layer
flow will be over the forecast area this evening between 6-10 PM.
At the same time, cold advection at the top of the boundary layer
is strong enough to maintain very steep lapse rates and even some
shallow convection at the top of the BL. Winds at the top of the
steep lapse rate layer are in the 50-55 kt range which may promote
some occasional downward mixing of 50 kt gusts to the surface.
However, at this time, it is a borderline setup so have not issued
a high wind warning but will need to closely monitor through the
evening hours. As we progress into the early morning hours, it
appears that a layer of warmer air aloft will wrap around the low
and effectively mitigate low level mixing, thus letting gusts
taper off. Those winds will increase again by mid morning with
sunshine and resumed mixing, so have continued the wind advisory
through noon, but may be able to trim some areas out of the
advisory during the overnight hours as the strongest winds on
Tuesday will probably be in far northeast NE and western Iowa with
occasional morning gusts in the 40-45 mph range.

Other than wind, will continue to see light to moderate rain
through this evening, especially across the northern half of the
forecast area where moisture advects around the back side of the
low and experiences isentropic upslope through a TROWAL and 
frontogenesis region. Temperatures will remain warm enough to keep
it all rain.

Tuesday through Thursday Night...
Winds die down by late Tuesday and sunny skies will allow
temperatures to climb into the 50s to around 60 along the KS
border. A quick clipper moves across the area on Wednesday with a
cold front and at least a few hours of wind gusts greater than 30
mph by Wednesday afternoon. There is some potential for light
precipitation in far northeast NE with this system but the airmass
is quite dry so could end up more as sprinkles or virga. Thursday
will find the area under surface high pressure once again, and
with this being behind a reinforcing short of cold air, this will
probably be the coldest day of the week as temperatures are likely
to hold in the 40s to perhaps lower 50s. 

Friday through Monday...
Warm advection returns to the area for Friday and Saturday as a
trough develops into the western CONUS and southwest flow returns
across the Plains. Currently expect to be well into the 60s by 
Saturday before another cold front crashes through on Sunday. 
Early next week appears likely to be very unsettled as a series of
storm systems cross the Plains, but the details of this are very 
much in question other than a seemingly high potential for 
precipitation in the Monday or Tuesday time frame.


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 604 PM CDT Mon Oct 21 2019

Strong westerly and northwesterly wind gusts up to 40 knots will
continue overnight. Strong winds aloft will also cause low level
wind shear of 45 knots at FL020 for a few hours Tuesday morning.
Winds will decrease at all sites after 12z. Lingering evening
showers will diminish and ceilings will become VFR at all sites 
in the next few hours. Clear skies are expected by Tuesday 


NE...Wind Advisory until noon CDT Tuesday for NEZ011-012-015>018-

IA...Wind Advisory until noon CDT Tuesday for IAZ043-055-056-069-079-


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