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Area Forecast Discussion (AFD)

Issued by Norman, OK (OUN)

                            
000
FXUS64 KOUN 200003
AFDOUN

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

.DISCUSSION...
00Z TAFs.

&&

.AVIATION...
MVFR ceilings will likely spread into the area Monday morning.
There will be some storm potential between sunrise and noon with
storms developing and moving northeast, with potentially higher
chances in the late afternoon. Showers will be very widespread
across northern Oklahoma (KWWR and KPNC) with storms more
scattered but potentially significant farther south. Severe storms
will be very possible and have added gusts of 45 knots and GR
(hail) in many of the TAFs, but there definitely is the potential
for locally stronger winds. 

&&

.PREV DISCUSSION... /issued 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.

&&

$$