May 20, 2017 1730 UTC Day 2 Convective Outlook
Updated: Sat May 20 17:28:59 UTC 2017 (20170520 1730Z Day 2 shapefile | 20170520 1730Z Day 2 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170520 1730 UTC Day 2 Outlook Graphic
Day 2 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 21,059 234,142 Del Rio, TX...Uvalde, TX...Hondo, TX...
MARGINAL 186,831 18,095,852 Houston, TX...San Antonio, TX...Austin, TX...New Orleans, LA...Corpus Christi, TX...
Probabilistic Graphic
20170520 1730 UTC Day Probabilitic Graphic
Probability of severe weather within 25 miles of a point.
Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.
Day 2 Prob. Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 20,693 222,402 Del Rio, TX...Uvalde, TX...Hondo, TX...
5 % 187,044 18,136,969 Houston, TX...San Antonio, TX...Austin, TX...New Orleans, LA...Corpus Christi, TX...
   SPC AC 201728

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1228 PM CDT Sat May 20 2017

   Valid 211200Z - 221200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   THE RIO GRANDE VALLEY IN TEXAS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM
   SOUTHWESTERN TEXAS TO THE CENTRAL GULF COAST...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE SOUTHERN HIGH PLAINS...

   ...SUMMARY...
   A few strong/severe storms will be possible from southwest Texas to
   the central Gulf Coast, with the highest likelihood near the Rio
   Grande Valley. Elsewhere, a few strong storms are possible across
   the southern high Plains and perhaps parts of the Ohio Valley and
   lower Great Lakes.

   ...Synopsis...
   Broad, mid-level cyclonic flow will encompass much of the central
   U.S. Sunday, as a closed low gradually weakens and lifts
   north/northeast into western Ontario. Meanwhile, along the
   southeastern periphery of the mid-level trough, a series of subtle
   impulses will translate east/northeast across the Ohio Valley,
   Appalachians, and Southeast. Farther west, a ribbon of higher
   vorticity within the southern stream will approach the Rio Grande
   Valley.

   ...Portions of southwest Texas to the central Gulf Coast...
   A stationary front, modulated by overnight convection and related
   cold pools, will stretch from near the Texas Big Bend eastward to
   the lower Mississippi Valley. Pockets of storms will likely be
   ongoing along/ahead of this front Sunday morning, and the location
   of later-day convection will be sensitive to outflow
   boundaries/convective overturning from these initial storms.
   Nonetheless, within pockets of heating, dew points in the upper
   60s/lower 70s will support moderate buoyancy within a modestly
   sheared environment. In turn, a few instances of marginally severe
   hail and/or strong wind gusts will be possible. 

   The highest likelihood of severe weather likely exists across parts
   of southern/western Texas near the Rio Grande Valley, where stronger
   mid/upper flow (associated with the sub-tropical jet) will be
   present. Here, effective shear upwards of 45-50 kt will be favorable
   for updraft organization/rotation in any semi-discrete cells. These
   storms would be capable of large hail and damaging winds, with the
   threat transitioning to primarily wind if cells grow upscale. One
   caveat with this severe potential is the possibility that early-day
   convective initiation across Mexico will reduce destabilization
   considerably over the region, resulting in more of a Marginal Risk
   of severe storms. However, the potential exists that sufficient
   buoyancy develops through the day to support a higher threat, and
   the Slight Risk is maintained to account for this scenario.

   ...Portions of the southern high Plains...
   Within a regime of broadly cyclonic flow aloft, modest forcing for
   ascent will support isolated/widely scattered convection across
   parts of eastern New Mexico, southeastern Colorado, the
   Texas/Oklahoma Panhandles, and far southwestern Kansas. Sufficient
   effective shear and modest low-level moisture may favor a few
   stronger storms capable of isolated large hail and strong wind gusts
   during the late afternoon and evening.

   ...Portions of the middle Ohio Valley...
   Along/ahead of a cold front pushing east, pockets of stronger
   heating may support weak surface-based buoyancy by afternoon. While
   stronger mid-level flow will exist farther northwest, modest deep
   shear may be adequate for a few stronger storms across eastern
   Indiana, Ohio, and parts of northern Kentucky during the day.
   However, the marginal nature of both the forecast instability and
   deep-layer wind fields suggest the potential for severe weather
   remains too low for probabilities at this time. A Marginal Risk
   could be introduced in later outlooks though.

   ..Picca.. 05/20/2017

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