Area Forecast Discussion
Issued by NWS

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FXUS64 KLUB 221713

Area Forecast Discussion
National Weather Service Lubbock TX
1213 PM CDT Tue Aug 22 2017

VFR conditions are expected at least through 03Z. A chance for Low
end MVFR to IFR cigs exists for all terminals after 03Z through at
least 12Z tomorrow morning. It is uncertain if low clouds and even
reduced vis will develop as model guidance differs with forecasted
conditions. For now the mention of low clouds and vis will be left
out of the TAFs. Showers and thunderstorms will be possible at all
terminals starting after 19Z this afternoon. While confidence in
precipitation occurring is high the coverage and location is
uncertain. Rain will be kept out of the TAFs and will be amended
as needed. Any shower or thunderstorm that moves over a terminal
will have the potential to lower flight categories.


.PREV DISCUSSION... /issued 326 AM CDT Tue Aug 22 2017/


As of 230 AM, satellite imagery showed the cold crossing central
Kansas with a reinforcing surge behind it just entering northern
Kansas. A large area of convection extended along the main frontal
boundary from eastern Kansas across to northwestern Indiana. Some
convection was attempting to backbuild into central Kansas. There is
fairly good model consensus on an 18Z entrance of the front to
our northern zones, though the GFS is, perhaps, a few hours
slower. This would delay the onset of convection. Speaking of
which, convection is expected to break out along the front as it
slowly moves southward this afternoon and evening. The combination
of diurnal heating, CAPE around 1500 J/kg and bulk shear values
reaching 30 KT should allow at least a few storms to become
strong, possibly marginally severe. Borderline severe hail will be
possible, but more likely will be damaging winds or wet
microbursts, as PWATs are around 1.5". Heavy rainfall from some
storms could lead to localized flooding.

With a ridge to our west, we`ll have favorable northwest flow
tomorrow, so where the front ends up will be important. The Euro and
GFS keep the boundary in/near our forecast area through most of
Wednesday, which will enhance rain chances. The NAM pushes it
further south, which would dry us out faster. Went with the 2 model
consensus and kept chance PoPs in for Wednesday attm. However, with
less favorable flow on Thursday, lowered PoPs to slight chance for
much of the area.

A shortwave brings rain chances back into the picture for Friday and
Saturday, maybe. TC Harvey is forecast attm to possibly make
landfall on Friday somewhere between northern Mexico and Corpus
Christi. Depending on the strength and landfall location/timing, we
could end up with subsidence that reduces our rain chances. With
about four days to go, much can change as tropical systems are
finicky beasts. We`ll be eyeing this one closely.




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