U.S. Severe Weather Forecast (Previsión convectiva)

día tres

acus01 kwns 262001 
Storm Prediction Center ac 262000 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0300 PM CDT sun Mar 26 2017 

Valid 262000z - 271200z 

..there is a moderate risk of severe thunderstorms across central 
OK and far north-central Texas... 

..there is an enhanced risk of severe thunderstorms across 
central/eastern OK and North Texas... 

..there is a slight risk of severe thunderstorms across portions of 
the Southern Plains... 

..there is a marginal risk of severe thunderstorms from central Texas 
to the Ozarks... 

..there is a marginal risk of severe thunderstorms across the upper 
Ohio Valley... 

Numerous severe storms with very large hail, tornadoes, and damaging 
winds are expected after 4 PM CDT especially across central and 
eastern Oklahoma and North Texas through evening. 

The overall forecast philosophy remains relatively unchanged, with 
an expectation for severe thunderstorms to rapidly develop late this 
afternoon along a dryline across central Oklahoma southward into 
North Texas. Initial elevated convection that developed over central 
Oklahoma early this afternoon continues to advance east/northeast in 
tandem with a low-level jet. These cells may continue to briefly 
pose a marginally severe hail threat, but are expected to weaken 
with northeastward extent. 

Farther southwest, despite pockets of stronger mixing, dew points in 
the mid/upper 50s to lower 60s have streamed north ahead of the 
dryline, resulting in MLCAPE values around 1000-1500 j/kg across far 
southern Oklahoma and North Texas. As stronger large-scale ascent 
continues to overspread this corridor, storms should expand in 
coverage, with supercell modes capable of all very large hail, 
damaging winds, and a few tornadoes. The most notable change with 
this outlook is the expansion of higher hail and tornado 
probabilities southward across North Texas. Recent visible satellite 
imagery and hi-res guidance suggest a relative maximum in severe 
potential near and perhaps just south of the Red River. Cells 
developing to the west/southwest should mature as they enter this 
corridor of relatively greater low-level moisture. For more 
information on the threat, reference mesoscale discussion 335. 

.Picca.. 03/26/2017 

Previous discussion... /issued 1130 am CDT sun Mar 26 2017/ 

..Southern Plains... 
Embedded within a moderately strong belt of southern-stream 
westerlies, a relatively compact shortwave trough over the 
south-Central High plains at late morning will continue eastward and 
reach the Ozarks by late tonight. Within the base of this trough, 
12z upper-air analysis featured a 50 kt belt of mid/high-level (500 
mb and above) southwesterly winds that extend from southern/eastern 
nm into the Texas Panhandle/far western OK/southwest Kansas. Given that 
less that 48 hours has passed since the prior system (now over the 
midwest) at this general latitude/longitude, moisture 
return/availability across the Southern Plains remains a Point of 
uncertainty, especially regarding the magnitude of the tornado risk 
in an otherwise very favorable early-Spring Southern Plains setup. 

Beneath an eastward-advecting elevated mixed plume (sampled across 
the south-Central High plains at 12z), surface observations feature 
around 60f dewpoints into southern parts of dfw metroplex as of 16z. 
These near-60f dewpoints should reach parts of south-central OK by 
21z-00z. Visible satellite imagery shows a band of higher-level 
cloud cover that will overspread the increasingly moist warm sector 
this afternoon. While not typically a severe-favorable factor, this 
cloud cover should at least partially shield the boundary layer and 
somewhat deter mixing while otherwise supporting a gradual increase 
in near-surface moisture through the afternoon/early evening. 
Current trends/short-term guidance suggest this cirrus should 
overspread/progress east of the dryline toward/after roughly 21z. 

Ahead of the slow-eastward-mixing dryline, near-60f surface 
dewpoints should generally result in around 1500-2000 j/kg of MLCAPE 
by peak heating from south-central OK into western parts of North 
Texas. Weaker near-surface destabilization is expected farther north 
into northwest/north-central OK and extreme southern Kansas. 

As forcing for ascent and deep-layer shear (effectively 40+ kt) 
increase, late-morning thinking is that semi-discrete supercells 
will begin to develop by mid-afternoon (around 21z/4pm cdt) across 
west-central OK into western north TX, initiating just west of the 
I-35 corridor. Potentially very large hail is likely along with at 
least some tornado risk, which should at least somewhat increase 
through 23z-01z toward/east of the I-35 corridor, especially across 
south-central OK and far North Texas as low-level moisture continually 
increases and low-level hodographs enlarge. 

Sustained warm advection should contribute to an eventual clustering 
and bowing of storms by late evening as storms persist generally 
eastward especially across southeast OK and extreme northeast Texas. 
Accordingly, damaging wind potential may increase for a time late 
this evening before updraft/downdraft intensities wane overnight as 
storms progress into Arkansas/arklatex vicinity. 

..upper Ohio River valley... 
A shortwave trough centered over northern/central Illinois late this 
morning per water vapor satellite imagery will continue 
east/northeastward today, with a weakening/opening trend expected 
tonight. Moderately strong winds aloft (12z upper-air data and more 
contemporary WSR-88D vwp data) just ahead of this trough will 
overspread the upper Ohio River valley vicinity through the 
afternoon/evening. Modest moisture (lower to middle 50s f surface 
dewpoints aside), prevalent cloud cover and multiple ongoing bands 
of showers suggest that overall destabilization should remain 
limited. Even so, locally damaging winds, marginally severe hail and 
possibly a brief tornado could occur presuming at least modest 
diurnal destabilization. Parts of southern OH, northeast Kentucky into 
western/northern WV currently appear most susceptible to a 
severe-storm risk this afternoon/early evening. 


Mesoscale Discussion

acus11 kwns 262214 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 262213 

Mesoscale discussion 0336 
National Weather Service Storm Prediction Center Norman OK 
0513 PM CDT sun Mar 26 2017 

Areas affected...parts of central/eastern Oklahoma and north central 

Concerning...Tornado Watch 86... 

Valid 262213z - 262345z 

The severe weather threat for Tornado Watch 86 continues. 

Summary...severe thunderstorm potential will continue to increase 
across parts of north central Texas into south central Oklahoma 
through the 7-9 PM CDT time frame. 

Discussion...discrete storm development is now underway across parts 
of south central Oklahoma into north central Texas, where low-level 
convergence has become locally enhanced near a pre-cold frontal 
confluence zone in the vicinity of the dryline. Further 
intensification is likely during the next few hours within a 
strongly sheared environment characterized by at least modest 

Even within a narrow corridor of relatively higher moisture content 
ahead of the dry line, moisture remains somewhat marginal for 
intense convective development. However, thermal profiles are 
relatively cool at mid-levels with generally steep lapse rates that 
appear quite favorable for severe hail in strongest storms. 

A zone of enhanced mid-level forcing for associated associated with 
a short wave impulse pivoting east of the south Central High plains 
may augment storm development and perhaps support 
consolidation/upscale growth of initially discrete storms into an 
evolving line as early as the 00-02z time frame. As this occurs 
potentially damaging wind gusts may become a more prominent threat. 

Until then, large hail appears the primary severe threat. The 
extent of the tornadic potential remains a bit more unclear, but the 
leading edge of a corridor of better low-level moisture return that 
now appears to be spreading across the Dallas/Fort Worth metroplex 
may contribute to more favorable boundary layer conditions as it 
gradually continues to advect northward into the Red River vicinity 
through early evening. 

.Kerr.. 03/26/2017 

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


Latitude...Lon 35509662 35619569 35019512 32999633 32299727 32569842 
34719750 35509662