Mar 1, 2018 1300 UTC Day 1 Convective Outlook
Updated: Thu Mar 1 12:56:58 UTC 2018 (20180301 1300Z Day 1 shapefile | 20180301 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20180301 1300 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Tornado Graphic
20180301 1300 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 1 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Damaging Wind Graphic
20180301 1300 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 1 Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Large Hail Graphic
20180301 1300 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 1 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
   SPC AC 011256

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0656 AM CST Thu Mar 01 2018

   Valid 011300Z - 021200Z


   Thunderstorms will be possible across the Gulf States into the
   Carolinas, along with portions of the Ohio Valley.

   In mid/upper levels, a progressive synoptic-scale to shortwave-scale
   pattern is in place.  A positively tilted, southern-stream
   perturbation -- now extending from MO across OK to southeastern NM
   -- is forecast to weaken and accelerate east-northeastward across
   the mid/lower Mississippi Valley.  The northern part should merge/
   phase with a northern-stream trough now over parts of MN/IA, as the
   latter dig southeastward across the upper Mississippi Valley and
   upper Great Lakes.  A closed 500-mb cyclone should evolve from this
   process over PA between 06-12Z and move to the southern NJ/DE area. 
   Meanwhile, a well-defined northeastern Pacific cyclone -- now
   evident in moisture-channel imagery west of Vancouver Island and WA
   -- will dig southeastward toward the coastal Pacific Northwest and
   northern CA, contributing to isolated lightning potential mainly
   near the coast.

   At the surface, 11Z analysis showed a surface low over the IL/IN
   border with two cold fronts -- a weaker boundary south-southwestward
   across northwestern MS and the TX coastal plain, and a stronger
   front over the Ozarks, southeastern OK, west-central TX, and
   southern NM.  The low should move eastward to PA and deepen through
   06Z, by which time a new low will develop just offshore from the
   Mid-Atlantic region.  By 12Z, the latter low will become dominant
   and deepen considerably south of RI or southeastern MA.  The cold
   fronts should merge through the period, moving offshore all but the
   northern/central FL Peninsula by 12Z.  A separate warm-frontal zone
   -- reinforced by precip to its north -- was drawn from a weak low
   over northeastern AL generally east-southeastward across northern
   GA.  This boundary may move slowly northward over SC and perhaps
   into southern NC today.

   ...Gulf States to Carolinas...
   Widely scattered to isolated thunderstorms are possible today into
   evening, embedded within a belt of convection now over the
   northern/western parts of the thunder-outlook area.  This activity
   should move eastward to northeastward, with a substantial component
   of mid/upper and mean flow parallel to the convection, indicating
   mainly quasi- linear mode.  Isolated convective gusts approaching
   severe limits are possible through afternoon into early evening from
   northeastern AL across portions of the Carolinas, as the primary
   convective band moves over the warm-frontal zone and into a moist,
   very weakly unstable boundary layer just to its south.  Small
   low/middle-level lapse rates -- including a sharply defined stable
   layer between 600-700 mb sampled by the 12Z FFC sounding (even after
   adjusting an unrealistic saturated MAUL below that), and to a lesser
   extent at BMX, indicate updrafts will struggle to maintain both
   depth and time continuity.

   Forecast soundings suggest strong deep-layer speed shear, despite
   the veered near-surface winds, with effective-shear magnitudes
   around 70 kt possible, and peak afternoon MLCAPE 200-500 J/kg from
   Piedmont eastward in the Carolinas, south of the boundary.  Lack of
   more robust lapse rates near that warm front, and concerns over
   messy storm mode, preclude re-introduction of unconditional severe
   probabilities for this region in this outlook cycle.  However, such
   a change may be warranted in a succeeding outlook given stronger
   low-level instability and/or deep-layer lift than currently

   ...Ohio Valley region...
   Isolated thunderstorms are possible within an arc of mostly
   low-topped, weak convection forecast to develop today in response to
   strengthening deep-layer forcing, cyclogenesis and frontogenesis
   over the region.  Strong gusts may occur in a few locales, but
   instability near the surface will be very limited at best.  As such,
   organized severe potential appears too low/conditional for a
   categorical outlook.

   ..Edwards/Dial.. 03/01/2018