Scientific Forecaster Discussion
fxus64 koun 200528
Area forecast discussion
National Weather Service Norman OK
1228 am CDT Wed Sep 20 2017
the September 21-22, 2017 06 UTC taf discussion follows:
unrestricted visibility and ceilings are generally expected to
continue through the taf period.
A cold front is expected to enter northwest Oklahoma later this
morning, which will shift the wind to the north. The front will
progress southward through west-central Oklahoma before stalling.
Elsewhere, southerly winds are expected through the taf period. A
typical diurnal cycle is expected with gusty winds developing by
mid-morning before weakening in the evening.
The probability of showers and thunderstorms along the front in
the afternoon/evening is too low to include in tafs; however,
kpnc could be impacted if storms do develop.
Previous discussion... /issued 937 PM CDT Tue Sep 19 2017/
will leave chance pops going across southern Oklahoma and western
North Texas. Isolated storm development possible overnight atop
outflow boundary in weak/shallow waa regime. An isolated
strong or briefly severe storm cannot be ruled out.
Adjustments were made to temperatures and dewpoints as well.
Previous discussion... /issued 627 PM CDT Tue Sep 19 2017/
20/00z tafs. VFR conditions expected to prevail across the region
with gusty south winds ahead of approaching cold front. MVFR
restrictions will be included at ksps for the first couple of
hours due to shra/tsra near that terminal. Cold front will move
over northwest and west-central Oklahoma terminals near or shortly
after 12z with the front forecast to stall before passing over
rest of terminals. Scattered thunderstorms and rain cannot be ruled out near front
late tomorrow but will not include in this forecast.
Previous discussion... /issued 248 PM CDT Tue Sep 19 2017/
near term focus is on convective potential across far southwest
Oklahoma and western North Texas. Latest visible satellite shows
some enhancement in the vicinity of Wichita Falls over the last
hour, and some more substantial echos within the last few minutes.
Although deep layer shear is fairly weak for organized storms,
strong diabatic heating and a moist boundary layer with fairly
steep mid level lapse rates are contributing to at least moderate
instability. With such a well mixed boundary layer, isolated at
least brief strong to severe wind gusts will be the primary
Convection should wane later this evening but it's not out of the
question that isolated redevelopment may occur later tonight
across south-central Oklahoma as warm advection strengthens.
Convergence along a weak surface boundary tomorrow could be
sufficient for isolated thunderstorm development late in the day
as we destabilize once again. However the capping inversion
appears more substantial than today, owing to subsidence/mid-level
height rises seen in the models. This should limit convective
development. We've confined probabilities to the far northeast and
to the south-central portion of the area. Sref members all have
varying degrees of cin, but the general consensus is less cin and
a better chance of convective initiation over south-central
Oklahoma. This may need to be refined in the overnight forecast.
Thursday holds some potential for isolated convective development
in western Oklahoma given a subtle shortwave trough and continued
moist unstable air mass. We'll re-evaluate this further tonight
and tomorrow and may need to re-introduce low probabilities then.
Above normal temperatures will continue until deep western trough
approaches and clouds/rain chances increase. Sunday through Monday
look like potentially the wettest periods as one shortwave trough
rotates around deeper closed low. Medium range guidance varies
somewhat on character of longwave early next week so it is unclear
at the moment how long the more significant rain chances may
Fire weather is another concern over the next few days,
particularly this afternoon, Thursday and Friday afternoons, as relative humidity
falls across western Oklahoma coinciding with enhanced southerly
Preliminary point temps/pops...
Oklahoma City OK 75 91 72 89 / 10 0 10 0
Hobart OK 73 96 72 91 / 10 10 10 10
Wichita Falls Texas 76 95 73 92 / 20 10 10 10
gage OK 65 96 71 90 / 10 10 10 10
Ponca City OK 75 94 74 91 / 20 0 10 0
Durant OK 75 93 71 91 / 10 10 10 10