U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 202004 
Storm Prediction Center ac 202002 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0302 PM CDT Mon may 20 2019 

Valid 202000z - 211200z 

..there is a high risk of severe thunderstorms across portions of 
Oklahoma and into parts of western North Texas and the Texas 

..there is a slight risk of severe thunderstorms across a large 
portion of the Southern Plains vicinity... 

An outbreak of tornadoes, some potentially long-track and violent, 
remains likely today into this evening over portions of northwest 
Texas into western and central Oklahoma. More isolated but still 
potentially dangerous severe weather, including tornadoes and 
destructive winds and hail, remains possible in surrounding parts of 
Texas, Oklahoma, Kansas, and Arkansas. 

Current expectations and reasoning laid out in prior outlooks 
remains valid, with a potentially dangerous severe weather/tornado 
outbreak in its initial stages at this time. Very few changes have 
been made to the outlook areas, with only minor tweaks to shift the 
northern fringe of the tornado risk a bit southward, due to current 
and anticipated outflow boundary location. Otherwise, the initial 
supercell storms have developed from the Texas South Plains region 
northeast into western Oklahoma, with a rapid increase in risk 
expected over the next couple of hours, and then lasting through the 
evening and into the overnight period. 

.Goss.. 05/20/2019 

Previous discussion... /issued 1126 am CDT Mon may 20 2019/ 

..Southern Plains... 
A tornado outbreak is forecast to unfold this afternoon and evening 
across parts of northwest Texas and western/central OK. Moisture 
continues to stream northward across the region, with dewpoints in 
the 70s yielding very high afternoon MLCAPE values of 3000-5000 
j/kg. Meanwhile, shear profiles are also rapidly increasing as a 
50-60 knot southerly low-level jet strenghens across the area. This 
is leading to a rare combination of extreme instability and large 
hodographs as depicted on forecast soundings throughout the region. 

Given the weak capping inversion, strong low-level Theta-E 
advection, and approaching large-scale forcing, all signs point to 
the development of numerous intense supercells this afternoon across 
the MDT and high risk areas. Any storm that persists in this 
environment will pose a risk of strong tornadoes, very large hail, 
and damaging winds. The corridor of greatest concern, including a 
threat of long-track and potentially violent tornadoes, will extend 
from the southeast Texas Panhandle into western and central Oklahoma. 

Multiple rounds of severe storms are expected to affect these areas, 
with new storms forming this evening over West Texas and spreading 
across North Texas and much of OK overnight. These storms will 
maintain a risk of large hail, damaging winds, and isolated 
tornadoes through the night in some areas. 

..northeast states... 
Relatively strong heating is occurring over New England and eastern 
NY, where a moist and moderately unstable air mass is present. 
Scattered afternoon thunderstorms are expected to form in this area, 
and spread eastward toward the New England coast during the late 
afternoon. Steepening low level lapse rates and westerly flow aloft 
will promote a risk of gusty/damaging winds and some hail in the 
stronger cells. 


Mesoscale Discussion

acus11 kwns 202047 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 202046 

Mesoscale discussion 0705 
National Weather Service Storm Prediction Center Norman OK 
0346 PM CDT Mon may 20 2019 

Areas affected...southwest and central OK 

Concerning...Tornado Watch 199... 

Valid 202046z - 202145z 

The severe weather threat for Tornado Watch 199 continues. 

Summary...tornado potential will likely increase across southwest OK 
during the next few hours. 

Discussion...radar mosaic shows several quasi-discrete supercells 
over the eastern Texas Panhandle into the Low Rolling Plains. 
Additional storm development is possible over southwest OK ahead of 
the supercells located to the west. It is less clear regarding 
convective initiation and supercell development farther east towards 
the I-44/I-35 corridors (besides the Logan County supercell). 

Surface analysis shows lower 70s surface dewpoints with temperatures 
ranging from the lower 80s over southwest OK to the middle 70s near 
okc. A composite front/outflow-reinforced boundary is located 
across the eastern Texas Panhandle arcing to the east-northeast to near 
Stillwater, OK. South of this boundary, a very unstable to 
extremely unstable airmass will support intense updraft development 
with existing storms. Ktlx VAD data shows a larger hodograph 
compared to kfdr's VAD (0-1km srh of 300 and 200 m2/s2, 

Short-term model guidance has trended away from a possible scenario 
of discrete storm development over south-central OK. The most 
probable scenario involves several tornadic supercells likely moving 
across southwest OK and approaching the I-40 corridor west of the 
okc Metro. 

.Smith.. 05/20/2019 

..please see www.Spc.NOAA.Gov for graphic product... 


Latitude...Lon 34820037 35489911 36019800 35849744 34419956 34820037