Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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000
FXUS64 KOUN 192105
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
405 PM CDT Thu Oct 19 2017

.DISCUSSION...
Primary forecast issue is the risk for severe thunderstorms on
Saturday.

For late tonight into tomorrow, a shortwave that is currently
located across the Texas/New Mexico border is expected to lift
northeastward into western north Texas and Oklahoma. There will be
a low chance of showers/storms from wave, but severe weather is
not expected. Isentropic ascent/warm advection tomorrow night into
Saturday will result in a continued low chance of showers/storms.

By Saturday afternoon, a mid/upper-level trough will eject into
the Plains. Along the southern periphery of trough, a secondary
mid-level jet/vorticity maxima will rotate around the base of the
shortwave trough. In response to an embedded jet streak, a
surface low may develop across southwest Oklahoma and adjacent
parts of north Texas.

The attendant cold front will enter northwest Oklahoma Saturday
afternoon. Thunderstorms are expected to develop along the cold
front late afternoon through the evening. The environment will be
more than sufficient for severe thunderstorms with effective bulk
shear >50 knots and MLCAPE >2000 J/kg. Any discrete thunderstorms
could become superceullar with the given parameter space. If a
surface low develops, localized backing of surface winds would
increase the low-level shear and the attendant tornado threat.
Thunderstorms are expected to grow upscale into a quasi-linear
convective system due to strong forcing along the cold front.

The greatest uncertainty is the timing/speed of the cold front.
The 19/12Z NAM and 3 KM NAM are much faster with the cold front
than the 19/12Z GFS. Even the ECMWF is slightly faster than the
GFS. The faster solution would likely lead toward thunderstorms
becoming undercut by the cold front, which would mitigate the
spatiotemporal extent of any higher end severe/tornado risk;
however, damaging wind gusts will be still be a hazard along the
line of thunderstorms. For now, will trend the forecast toward the
faster solution based on the surface pressure bulge.

In the front`s wake, cooler and drier air will advect into the
region for Sunday. Sunday will be much cooler with highs in the
mid-60Fs to low 70Fs.

A brief warm-up is expected Monday afternoon before another cold
front passes by late Monday. A dry frontal passage is expected due
to limited moisture. Cooler weather with highs in the 60Fs are
expected Tuesday and Wednesday behind this front. Some locations
may have lows in the 30Fs by Wednesday morning.

Mahale

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  61  76  67  77 /   0  20  20  50
Hobart OK         62  76  65  81 /  10  20  20  40
Wichita Falls TX  62  78  68  83 /  10  20  10  50
Gage OK           61  73  63  75 /   0  20  20  20
Ponca City OK     58  77  68  77 /   0  20  20  50
Durant OK         58  78  67  80 /   0  20  20  30

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...None.
TX...None.
&&

$$

11/10


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