Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 121628
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
1128 AM CDT Sat Aug 12 2017

.DISCUSSION...
Have made a few adjustments to rain chances, temperatures, etc.
for today to account for current trends and expectations. Expect
widespread rain to continue into the afternoon, with gradual
decrease in intensity/coverage...except along the southern edges,
where moist inflow and isentropic lift will continue to support
development. MUCAPE values appear to diminish fairly quickly from
north to south late this afternoon into the evening, presumably as
the overall heaviest rain area shifts south into the moisture
supply and the areas to the north stabilize. This is somewhat at
odds with such forecasts as the HRRR and HRRRX, which keep rather
tough-looking storms near the Red River well into the evening. The
extensive cloud cover does appear to be farther south than
originally planned, so it seems a little more likely that the
stronger storms will tend to be farther south than previously
forecast...although elevated strong/severe storms will still be
a possibility this afternoon over about the southern half of
Oklahoma and into parts of north Texas.

CmS
&&

.PREV DISCUSSION... /issued 546 AM CDT Sat Aug 12 2017/

AVIATION...12/12Z TAF ISSUANCE...
An area of showers and thunderstorms continues to evolve across
much of western into central Oklahoma, impacting KOKC/KOUN and
airfields to the west and northwest. Overall, this activity will
be the primary concern for aviation through the day. Attempted to
keep the TAFs simple, but sufficient to cover the time-frames
through the day when impacts from shower, thunderstorms, and MVFR
to IFR ceilings are likely to occur. The greatest rain chances and
impacts to aviation are likely to occur across southern Oklahoma
into north Texas this afternoon and evening, as a complex of
storms is expected to develop this evening and overnight.
Generally, winds will remain out of the east and southeast.
Ceilings will be tricky, at times, given any influence from
thunderstorms, but overall, VFR with bouts of MVFR possible, the
same can be said for visibilities.

Kurtz

PREV DISCUSSION... /issued 344 AM CDT Sat Aug 12 2017/

DISCUSSION...
Primary forecast focus, this morning, is on the convection over the
Panhandles and its evolution through today.

This morning, a complex of thunderstorms over the Panhandles and
along the northern reach of the Llano Estacado will continue to
slowly evolve and build gradually eastward through sunrise. Overall,
the strongest convection has continued to be focused between
Amarillo and Lubbock, just west of I-27, nearest a weak MCV. Latest
(230 AM) GOES-16 IR imagery reveals a steady focus of colder cloud
tops on the Caprock associated with this convection. Expect this
activity to continue to slowly build eastward through the morning,
into western Oklahoma and portions of western north Texas.

Elsewhere this morning, isolated showers have started to develop
over northwestern Oklahoma. Forcing for this activity appears to be
associated with a weak 950 or 850mb baroclinic zone which is right
along the edge of an axis of 300 to 500 J/Kg CAPE. With some
assistance from the weak 500mb short wave, expect this activity to
continue to gradually increase in coverage across western and
northwestern Oklahoma through the morning.

After sunrise, expect coverage of thunderstorms across western and
northwestern Oklahoma to continue. The HRRR, overall, has had a
decent handle on evolution early this morning, although it usually
struggles in weakly forced environments. To the south, we`ve
continued to watch a subtle surface boundary on KFDR, well south of
the Red River. Through 3 AM, this boundary has continued to slowly
lift northward, back toward the Red River. It`s anticipated, this
boundary, will be a focus for additional thunderstorm development
through the afternoon. So far, this morning, cirrus coverage across
much of north Texas and southern Oklahoma has been minor, and if it
stays that way, strong differential heating could result in
increasing instability along the Red River valley region. Short
range guidance suggests a modest build of instability through the
afternoon, 1500 nearing 2000 J/Kg possible, with decent deep layer
shear. Any initial convection will hold a hail and wind risk, but
with the increasing low level jet into the evening, expect any
persisting convection to develop into a complex with heavy rainfall
and damaging winds possible. Similar to yesterday, we expect this
system to be an efficient rain producer, leading to an increased
risk of flash flooding.

Overnight, the expected complex will continue to advance east, with
a continuing risk for heavy rainfall and damaging winds, traversing
southern Oklahoma and northern Texas, toward the Ouachitas by
sunrise, Sunday.

Thunderstorms remain in the forecast, near daily for much of the
work week. The best chances, at the moment, appear to be Sunday
night into Monday as another thunderstorm complex is expected to
move across the southern plains.

Kurtz

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  77  68  84  71 /  90  80  50  50
Hobart OK         78  68  87  72 /  90  70  30  50
Wichita Falls TX  84  72  91  74 /  80  70  30  50
Gage OK           73  63  83  66 /  90  60  20  50
Ponca City OK     79  65  80  69 /  50  40  40  50
Durant OK         89  72  87  73 /  70  80  60  50

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Flood Watch through Sunday morning for OKZ004>048-050>052.

TX...None.
&&

$$

23/03



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