SPC AC 141723

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1223 PM CDT Mon May 14 2018

   Valid 151200Z - 161200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
   NORTHEAST PA/SOUTHEAST NY INTO WESTERN NEW ENGLAND...

   ...SUMMARY...
   Severe thunderstorms, primarily capable of damaging winds, are
   forecast across parts of the Mid-Atlantic and New England Tuesday
   afternoon and evening. Other strong storms will impact portions of
   northeast New Mexico into the southern Plains.

   ...Mid-Atlantic into New England...
   Zonal, slightly cyclonic mid-level flow will evolve across the
   region on Tuesday. Within this flow regime, a subtle but coherent
   impulse will advance east from the Midwest towards Pennsylvania/New
   York through the day. This progression should be favorably timed for
   boundary-layer heating to occur behind early morning precipitation
   (associated with a prior shortwave trough) and ahead of a cold front
   associated with the secondary impulse. Additionally, surface dew
   points should rise into the mid/upper 60s to near 70 from northeast
   PA / NJ into southern/central New England by the afternoon. Combined
   with 700-500mb lapse rates upwards of 7-7.5 C/km, these
   boundary-layer conditions should yield MLCAPE values around
   2000-2500 J/kg across parts of the Mid-Atlantic, and around
   1000-1500 J/kg into parts of New England.

   As the secondary wave approaches, low-level confluence (albeit not
   particularly strong) and mid-level ascent are expected to focus
   convective development/intensification from parts of western PA
   northeastward to the Hudson Valley and western New England. In
   conjunction with this wave, westerly 500mb flow will be robust --
   around 50-70 kt. Relatively straight hodographs suggest cells will
   organize into bowing segments that accelerate east across parts of
   PA, the Hudson Valley, and portions of western/southern New England.
   Some potential exists for enhanced/focused eastward propagation
   along a remnant outflow boundary from morning convection, and this
   would locally maximize the damaging wind threat (possibly from
   northeast PA/southeast NY into western CT/MA). Considering the
   mid-level wind fields, reasonable confidence in destabilization, and
   convective signal from several CAMs, the slight/marginal risks have
   been expanded northward, and an enhanced risk has been introduced
   from parts of northeast PA into far western New England.

   While background near-surface winds will generally be veered and not
   particularly strong, localized backing in area valleys and/or ahead
   of line-embedded vortices may favor a couple of tornadoes as well.

   ...Southern Plains...
   Convective potential continues to appear uncertain/unorganized.
   Complexities regarding outflow from the prior period, combined with
   subtle/convectively augmented impulses within the mid-level flow
   regime, will impact the focus of stronger convection across the
   region. Despite this, steep mid-level lapse rates and strong surface
   heating will encourage isolated pockets of strong/damaging winds and
   perhaps large hail with the most intense cores during the afternoon
   and evening.

   ...MAXIMUM RISK BY HAZARD...
   Tornado:   5%     - Slight
   Wind:     30%     - Enhanced
   Hail:      5%     - Marginal

   ..Picca.. 05/14/2018

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