FXUS64 KOUN 210238

Area Forecast Discussion
National Weather Service Norman OK
938 PM CDT Thu Jul 20 2017

Aviation discussion for the 06 UTC TAFs is below.


VFR conditions and generally south surface winds are
expected to continue at all TAF sites.



.PREV DISCUSSION... /issued 125 PM CDT Thu Jul 20 2017/


Heat will continue to be the the main weather impact. We have
extended the Heat Advisory through Saturday which encompasses the
period when the most dangerous combination of heat and humidity
is expected. Thereafter, a slightly cooler pattern should result
in heat indices below thresholds, although some caution will still
need to be exercised through much of next week to avoid heat
related illness. We ask our partners to continue to help message
the danger of heat related illness.

An elongated mid-upper ridge will deamplify late tomorrow into
Saturday as a shortwave trough moves east-southeast into the
northern Plains. This will send a weak front south into Kansas
that should move into the area late Saturday into Sunday,
probably augmented at least somewhat by convection to our north.
The speed and southward progression will depend on how the
convection evolves Sunday afternoon into the night. The forecast
then becomes a little more challenging as synoptic boundary
becomes even more diffuse and convective outflow may become the
main focus for additional diurnally driven convection on Monday,
which could be just about anywhere across the area. We have
assigned low chance (30-40 percent) for most locations Monday
afternoon and evening, with the highest values across the north in
case convective coverage is underwhelming on Sunday and the
remnant synoptic boundary ends up being the primary focus again.

Severe thunderstorms during this period will be unlikely given
weak effective shear values of around 15 knots not being
supportive of organized/sustained updrafts. When storms initially
develop, in an environment that likely be well mixed, some brief
strong/severe wind gusts will be possible as they collapse, but
this threat should be very isolated. Despite the moist
environment (PWATs approaching 2"), short lived nature of the
convection should preclude a flood threat.

As western mean ridging amplifies on Tuesday, convection chances
decrease and by mid-week mid-level heights continue to steadily
build and the thermodynamic profiles in forecast soundings become
even less favorable for convection. 10 to maybe 20 percent
coverage is possible Wednesday with very weak small scale
perturbations in a band of northerly high level flow on the
eastern edge of the ridge. After a slight cool down Sunday through
early next week, temperatures look to return to above normal
levels for the latter half of the week.



OK...Heat Advisory until 8 PM CDT Saturday for OKZ007-008-012-013-



Back to Main Forecast Discussion Page