Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 211637

Area Forecast Discussion
National Weather Service Norman OK
1137 AM CDT Sat Oct 21 2017

Please see the 18Z aviation discussion below.


Thunderstorms are still expected to impact most of the terminals
by early this evening. Initial development is expected around
22-23Z near CSM and HBR. The storms will then spread east and
merge as a squall line through the I35 and I44 corridors. Strong
wind gusts, and perhaps hail although not included for the moment,
will be possible. Low vsby will also accompany any of the storms.
Expect a northerly wind shift behind a cold front through the
overnight hours.


.PREV DISCUSSION... /issued 608 AM CDT Sat Oct 21 2017/

The 12Z aviation discussion follows....

A tight surface pressure gradient will maintain strong southerly
winds across Oklahoma and north Texas into the afternoon. A few
showers may occur in the moist airmass, but should not result in
any significant effects on aviation. However, widespread low
clouds (bases mostly 1,500 to 3,000 ft) will cover most of the
region early this morning, clearing/scattering slowly from the
west...although KPNC may not clear at all today.

During the early and mid afternoon, strong thunderstorms are
expected to form quickly ahead of a cold front that will be over
northwest Oklahoma. The initial storms will probably include
scattered supercell thunderstorms. Toward 00Z, the assembly of
strong/severe thunderstorms will begin to form into a solid line
of storms, on or slightly behind the advancing cold front (at 00Z,
the storms should extend approximately from KPNC/KEND to KSPS and
vicinity. The line of storms will move fairly quickly toward the
east, with rain ending at most sites about 3 hours after storms
begin. Brisk northwest winds will follow the front, but will
diminish during the early morning hours on Sunday.


PREV DISCUSSION... /issued 443 AM CDT Sat Oct 21 2017/

Windy conditions will persist this morning with the tight surface
pressure gradient. A few showers will be possible this morning
within the warm, moist airmass where weak isentropic lift can help
generate them.

Of much more significance is the cold front that is forecast to
move through Oklahoma and north Texas this afternoon and into the
night. Initial thunderstorm development should occur around mid-
afternoon, probably near a line from Alva to Elk City, then spread
east and increase in coverage. More discrete storm cells are
expected across southwest into central Oklahoma during the mid-
late afternoon and early evening. These storms will form in an
area of enhanced vertical wind shear (because of a weak surface
low that is forecast to form on the front), and are likely to
include a few supercell thunderstorms. The entire assembly is
expected to merge into a linear complex during the early evening,
reducing the threats of hail and tornadoes, but maintaining a
risk of strong winds well into the night. The last of the severe
storms should exit our southeastern counties during the early
morning hours on Sunday.

After the storms clear the region, relatively benign weather is
expected for several days. Temperatures will bob up and down
between fronts (one Monday, and another on Thursday). Model
differences become quite large toward the end of next week, so the
confidence level of the forecast is correspondingly low.


Oklahoma City OK  78  48  70  47 /  60 100   0   0
Hobart OK         80  46  72  47 /  60  80   0   0
Wichita Falls TX  83  51  72  48 /  50  80   0   0
Gage OK           75  40  71  44 /  30  20   0   0
Ponca City OK     75  48  70  45 /  80  90   0   0
Durant OK         82  56  72  47 /  20 100  10  10




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