Aug 16, 2018 1730 UTC Day 2 Convective Outlook
Updated: Thu Aug 16 17:30:47 UTC 2018 (20180816 1730Z Day 2 shapefile | 20180816 1730Z Day 2 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20180816 1730 UTC Day 2 Outlook Graphic
Day 2 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 26,920 7,240,717 Springfield, MA...Hartford, CT...Waterbury, CT...Albany, NY...Danbury, CT...
MARGINAL 650,889 100,790,254 New York, NY...Philadelphia, PA...Indianapolis, IN...Columbus, OH...Memphis, TN...
Probabilistic Graphic
20180816 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 % 26,920 7,240,717 Springfield, MA...Hartford, CT...Waterbury, CT...Albany, NY...Danbury, CT...
5 % 650,982 100,779,368 New York, NY...Philadelphia, PA...Indianapolis, IN...Columbus, OH...Memphis, TN...
   SPC AC 161730

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1230 PM CDT Thu Aug 16 2018

   Valid 171200Z - 181200Z


   Isolated severe thunderstorms with mainly a strong to damaging wind
   threat will be possible Friday afternoon and evening across parts of
   the Northeast and Mid-Atlantic.

   Within large-scale troughing over Ontario/Quebec and the Upper
   Midwest/Great Lakes region, several shortwave troughs will develop
   east-northeastward across the Northeast, Mid-Atlantic, and OH Valley
   through the period. A 30-40 kt south-southwesterly low-level jet is
   forecast to overspread parts of the Northeast by Friday afternoon.
   Farther west, a shortwave trough will move eastward across the
   Pacific Northwest and northern Rockies. At the surface, a weak
   surface low should develop northeastward into northern New England
   by Friday evening, with a trailing cold front extending
   southwestward from this low across the OH/TN Valleys into the
   Mid-South and southern Plains.

   ...Northeast and Mid-Atlantic...
   A warm front should lift northward over much of the Northeast
   through the day, and a very moist low-level airmass, with dewpoints
   in the upper 60s to lower 70s, will likely be in place to the south
   of this front. Even through mid-level lapse rates will remain poor,
   as diurnal heating occurs instability should increase into the
   1000-2000 J/kg range across southern VT/NH into eastern NY, western
   MA/CT and vicinity. Although relatively stronger mid-level flow may
   remain mostly displaced to the north of this region, forecast
   soundings from the NAM/RAP show sufficient veering/strengthening
   with height to support 25-35 kt of effective bulk shear. A mix of
   multicells and marginal supercell structures should occur, and most
   high-resolution guidance suggests convection will probably develop
   along a pre-frontal trough by Friday afternoon and subsequently
   spread eastward through the evening. Have introduced a Slight risk
   for part of the Northeast for the potential of isolated strong to
   damaging winds with one or more bowing clusters. A tornado or two
   may also occur along and south of the warm front given the forecast
   strength of the low-level jet.

   ...OH/TN Valley into the Southeast and Southern Plains...
   Thunderstorms will likely be ongoing across parts of the OH/TN
   Valleys Friday morning, and this will have a great influence on
   better convective potential in the afternoon. Have
   maintained/expanded Marginal risk across the OH Valley as some
   guidance is now suggesting additional thunderstorms could form along
   the cold front in the afternoon, and mid-level flow may be enough to
   support 25-30 kt of effective bulk shear and a few multicell
   clusters. Across the TN Valley into parts of the Southeast and
   southern Plains, mid-level flow and resultant shear should remain
   generally weak. Even so, ongoing convection Friday morning may
   re-strengthen along and ahead of the cold front and spread
   southeastward with time. Across this broad region, strong to locally
   damaging winds may occur on an isolated basis.

   ...Southern/Central High Plains...
   Isolated to scattered thunderstorms may develop across the higher
   terrain of the southern/central Rockies and then spread eastward
   into the southern/central High Plains through Friday afternoon and
   evening. This may be in response to a weak mid-level perturbation
   rounding the upper ridge over the western states. Forecast soundings
   from the NAM/RAP show sufficient shear in conjunction with weak to
   moderate instability to support a Marginal risk for hail and
   strong/gusty winds with any thunderstorms that occur.

   ...Northern Rockies/Great Basin...
   Steep mid-level lapse rates and large-scale ascent attendant to a
   shortwave trough will promote some destabilization by mid afternoon.
   However, instability should remain marginal (MLCAPE at or below 500
   J/kg) owing to limited low-level moisture. Storms are expected to
   develop over the higher terrain during the day and spread eastward
   through the evening. Inverted-V type forecast soundings showing a
   deeply mixed boundary layer will an isolated risk for strong/gusty
   downdraft winds from late afternoon through early evening.

   Tornado:   2%     - Marginal
   Wind:     15%     - Slight
   Hail:      5%     - Marginal

   ..Gleason.. 08/16/2018