Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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000
FXUS64 KOUN 192127
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
427 PM CDT Sun May 19 2019

.DISCUSSION...
...Significant Severe Weather and Flooding Expected Monday into
Early Tuesday Morning...

For tonight, a warm front is forecast to lift northward in
response to the approaching shortwave trough. As the warm front
lifts northward, elevated thunderstorms may develop late tonight
into tomorrow morning with a threat for hail. The warm front may
stall somewhere in vicinity or north of I-40 with continued
showers/storms north of the boundary throughout the day.

By early afternoon, the parameter space south of the warm front
will be on the high-end of severe weather climatology with the
potential for significant, widespread severe weather. This
includes the risk for very large hail, damaging wind gusts, and
tornadoes. Low-level shear is forecast to increase markedly into
the evening hours (>30 knots) with large, looping hodographs as
the low-level jet strengthens. There will be the potential for
significant tornadoes with any discrete supercells with this
parameter space. Currently, it appears the greatest risk for
tornadoes will be from western north Texas, into southwest
Oklahoma, and into central Oklahoma (south of the warm front).

The greatest forecast uncertainties are 1) the extent of warm
sector convection and 2) the storm mode/evolution. These two
factors will augment the magnitude of the severe weather. With
regards to the warm sector, forecast soundings indicate a
uncapped/nearly uncapped environment. Most convective-allowing
models have at least small cells in the warm sector, which
suggests some convective initation is probable in the warm sector.

The other uncertainty is if the storms may remain discrete. More
discrete cells would result in a higher-end tornado threat while
storm mergers/training cells would result in a more significant
flooding threat. The evolution into the evening hours is not
completely clear, but to some degree both situations may occur
(i.e., both a flooding and tornado risk).

By Monday night into Tuesday morning, thunderstorms across the
eastern Texas panhandle/western Oklahoma are forecast to grow
upscale into a quasi-linear convective system (QLCS) as the
strong, linear forcing spreads eastward as the attendant shortwave
trough lifts northeastward. Increasing low-level wind shear
(45-50 knots), augmented by a strengthening low-level jet, will
result in a continued threat for damaging wind gusts and embedded
mesovortices with a risk for tornadoes.

In addition to severe weather, there is the potential for
significant, life-threatening flooding (as noted earlier). For
some locations, there could be several rounds of training
thunderstorms. If these training thunderstorms happen to be in an
urban area (i.e., the OKC metro), the flooding could be quite
substantial. In addition, periods of thunderstorms north and/or
along the warm front may also result in substantial flooding in
these areas. This is a risk that shouldn`t be taken lightly. A
Flood Watch was issued to account for this risk.

Beyond Tuesday, an unsettled weather pattern is forecast to
persist through the end of the period. Severe weather and flooding
will continue to be a risk, especially across northwest/western
Oklahoma.

Mahale

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  58  76  63  75 /  10  50  80  50
Hobart OK         59  77  60  75 /  10  60  80  10
Wichita Falls TX  62  83  64  78 /  10  40  80  30
Gage OK           54  65  56  74 /  30  80  80  10
Ponca City OK     56  67  64  74 /   0  90  90  60
Durant OK         61  82  65  77 /  10  30  40  80

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Flood Watch from Monday morning through Tuesday afternoon for
     OKZ004>048-050>052.

TX...Flood Watch from Monday morning through Tuesday afternoon for
     TXZ083>090.

&&

$$

11/10


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