May 10, 2018 2000 UTC Day 1 Convective Outlook
Updated: Thu May 10 19:59:51 UTC 2018 (20180510 2000Z Day 1 shapefile | 20180510 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20180510 2000 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 11,728 54,700 North Platte, NE...
SLIGHT 126,041 33,856,686 Philadelphia, PA...Baltimore, MD...Washington, DC...Virginia Beach, VA...Raleigh, NC...
MARGINAL 232,130 32,900,789 New York, NY...Charlotte, NC...Omaha, NE...Lincoln, NE...Yonkers, NY...
Probabilistic Tornado Graphic
20180510 2000 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
2 % 76,090 35,819,365 New York, NY...Philadelphia, PA...Baltimore, MD...Washington, DC...Newark, NJ...
Probabilistic Damaging Wind Graphic
20180510 2000 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
30 % 11,873 55,353 North Platte, NE...
15 % 122,204 33,462,811 Philadelphia, PA...Baltimore, MD...Washington, DC...Raleigh, NC...Newark, NJ...
5 % 221,799 33,063,054 New York, NY...Charlotte, NC...Virginia Beach, VA...Omaha, NE...Lincoln, NE...
Probabilistic Large Hail Graphic
20180510 2000 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
30 % 11,608 54,568 North Platte, NE...
15 % 53,157 605,355 Cheyenne, WY...Grand Island, NE...Kearney, NE...Norfolk, NE...Hastings, NE...
5 % 269,380 53,126,432 New York, NY...Philadelphia, PA...Baltimore, MD...Charlotte, NC...Washington, DC...
   SPC AC 101959

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0259 PM CDT Thu May 10 2018

   Valid 102000Z - 111200Z



   Afternoon severe thunderstorms will produce large hail and damaging
   winds over parts of the central Plains states.  A few severe storms
   capable of damaging winds are also expected to affect portions of
   the Mid-Atlantic to southern Appalachians.

   Given the presence of stronger westerly midlevel winds having spread
   into northern NC, while strong surface heating is resulting in very
   steep surface to 3-km lapse rates, the potential for damaging winds
   and hail should affect more of northern and perhaps central NC this
   afternoon to early evening.  These factors combined with a corridor
   of moderate instability extending south-southwest ahead of the wind
   shift support an expansion of the Slight risk area to include more
   of NC.

   Marginal instability along and east of the broken band of storms
   advancing east through WV this afternoon will continue to pose a
   risk for severe weather.  The Marginal severe risk has been expanded
   westward to this ongoing band of storms, as marginal instability
   should limit the coverage of strong-severe storms.

   ...Northern NJ into NY and western/northern PA...
   Cooler surface temperatures and weaker low-level lapse rates and
   buoyancy per objective analyses may limit the severe-weather threat
   across the northern extent of the Slight risk area.  Meanwhile,
   western portions of the Marginal risk area in central to part of
   northern NY and western to north-central PA will be removed from the
   severe threat, as the environment stabilizes with the passage of the
   cold front and convective band.  Similarly, the general thunderstorm
   area will be shifted east out of the upper Ohio Valley and Lower
   Great Lakes region.

   ...Central and southern Plains...
   No changes needed for these areas.

   ..Peters.. 05/10/2018

   .PREV DISCUSSION... /ISSUED 1120 AM CDT Thu May 10 2018/

   ...Central Plains...
   Water vapor loop shows a upper ridge centered over the central
   Rockies, with an low-amplitude upper trough over the western states.
    This trough will spread eastward today, with large-scale forcing
   affecting parts of the central High Plains.  Easterly post-frontal
   surface winds are present across much of NE and eastern WY, where
   40s and 50s dewpoints are being slowly transported westward.  This
   combined with strong daytime heating will yield afternoon MLCAPE
   values around 1000 J/kg in southeast WY, and approaching 2000 J/kg
   farther east in western NE.

   Present indications are that thunderstorms will intensify this
   afternoon to the east of the Laramie range and track eastward into
   the adjacent plains of western NE.  Initial storms will likely have
   supercellular characteristics due to favorable low level
   shear/hodographs.  An isolated tornado or two is possible, but
   greater threat appears to be large hail and damaging wind gusts
   today.  Storms are expected to grow upscale though the evening with
   numerous CAM solutions suggesting bowing storm structures and an
   increasing risk of damaging wind gusts.

   ...Mid Atlantic...
   Morning clouds/precipitation are slowly decreasing, allowing pockets
   of strong afternoon heating over portions of VA/MD.  This area will
   see re-development of thunderstorms by mid afternoon along/ahead the
   cold front currently over WV.  Local VAD and forecast soundings
   suggest sufficiently steep low-level lapse rates and wind fields to
   pose a risk of damaging wind gusts in the stronger cells.  Isolated
   severe hail is also possible.  

   Farther north, clouds are holding firm over eastern PA, NJ, and
   southeast NY.  Wind fields are stronger in this area than farther
   south, but weaker thermodynamics are a mitigating factor.  Have
   trimmed the SLGT risk in NY, but will maintain  across eastern PA/NJ
   where some heating may occur later today.