May 10, 2018 0600 UTC Day 1 Convective Outlook
Updated: Thu May 10 06:00:37 UTC 2018 (20180510 1200Z Day 1 shapefile | 20180510 1200Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20180510 1200 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 121,292 28,234,872 Philadelphia, PA...Baltimore, MD...Washington, DC...Newark, NJ...Richmond, VA...
MARGINAL 276,523 41,029,127 New York, NY...Charlotte, NC...Virginia Beach, VA...Omaha, NE...Raleigh, NC...
Probabilistic Tornado Graphic
20180510 1200 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 % 257,267 66,154,840 New York, NY...Philadelphia, PA...Baltimore, MD...Charlotte, NC...Washington, DC...
Probabilistic Damaging Wind Graphic
20180510 1200 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
15 % 108,483 28,075,446 Philadelphia, PA...Baltimore, MD...Washington, DC...Newark, NJ...Richmond, VA...
5 % 271,812 40,847,806 New York, NY...Charlotte, NC...Virginia Beach, VA...Omaha, NE...Raleigh, NC...
Probabilistic Large Hail Graphic
20180510 1200 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
15 % 121,488 28,136,692 Philadelphia, PA...Baltimore, MD...Washington, DC...Newark, NJ...Richmond, VA...
5 % 275,896 41,031,198 New York, NY...Charlotte, NC...Virginia Beach, VA...Omaha, NE...Raleigh, NC...
   SPC AC 100600

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0100 AM CDT Thu May 10 2018

   Valid 101200Z - 111200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   THE NORTHEAST AND MID-ATLANTIC REGION...AS WELL AS OVER THE CENTRAL
   HIGH PLAINS AND INTO NEBRASKA...

   ...SUMMARY...
   Severe storms capable of producing large hail and damaging winds
   will be possible across the central high Plains this afternoon, with
   severe wind becoming the primary threat this evening and into the
   overnight hours across Nebraska.  Bands of strong to severe storms
   producing locally damaging wind gusts and hail are also expected
   this afternoon from parts of the lower Great Lakes into the central
   and southern Appalachians and eastward to the Mid-Atlantic.

   ...Synopsis...
   A weakening short-wave trough is forecast to advance across the
   eastern U.S. today, south of a stronger trough shifting across
   Ontario and Quebec.  Farther west, a low/trough is forecast to dig
   south-southeast from the British Columbia coastal area into the
   western states.  Downstream, a shorter-wavelength trough is expected
   to cross the Rockies through the day, and then Plains states through
   latter stages of the period.  

   At the surface, a cold front associated with the eastern upper
   trough will cross the Northeast and East Coast states.  The trailing
   portion of this boundary extending westward across the central
   Plains will sharpen near the KS/NE border as a lee low strengthens
   over eastern CO.

   ...The central and southern High Plains and eastward across
   Nebraska...
   As the aforementioned short-wave troughing crosses the west and
   approaches the High Plains, surface cyclogenesis is expected over
   eastern CO, along with sharpening of the west-to-east front
   near/just north of the NE border.  Afternoon heating will support
   moderate destabilization near and just north of the surface front,
   which will fuel initiation of storms by mid afternoon over the
   higher terrain of southeast Wyoming within an easterly/upslope flow
   regime.  

   With the low-level easterlies topped by west-southwesterly flow
   aloft, some risk for upscale growth into a fast-moving cluster of
   storms near the front appears possible through late afternoon/early
   evening.  However, with a cool/stable boundary layer expected to
   persist with northward extent into northern NE, hail will likely be
   the primary severe risk over roughly northern half of the outlook
   area.  Nearer the front however, damaging winds with eastward-moving
   surface-based storms can be expected -- particularly if the upscale
   linear growth indicated by a couple of the CAM members can
   materialize.  

   As a southerly low-level jet strengthens overnight and thus
   warm-advection-induced ascent increases, elevated convection will
   increase north of the front across northern NE and into SD, but
   expect storm coverage/intensity to gradually diminish south of the
   boundary.

   More isolated afternoon development is expected southward across the
   High Plains along the dryline.  However, the combination of sparse
   storm coverage and weaker flow aloft suggests a more limited severe
   risk, from late afternoon into early evening.

   ...New York and vicinity southward across the
   Mid-Atlantic/Appalachians...
   A band of decaying showers and thunderstorms should be moving across
   the PA/NY/WV vicinity at the start of the period, with lingering
   precipitation/cloud cover likely to hinder heating/destabilization
   to some degree.  However, ample CAPE development is forecast ahead
   of the advancing/weak surface front to support renewed convective
   development by early afternoon -- initially across the higher
   terrain from central NY southward to the eastern TN/western NC
   vicinity.  With enhanced /30 to 40 kt/ westerly flow through the
   lower and middle troposphere, upscale growth into small, quickly
   moving bands should occur with time, such that isolated risk for
   hail/wind may increase a bit as storms shift into eastern
   NY/northeast PA, and east of the mountains from southeast PA to VA. 
   Therefore, will upgrade to slight risk across this portion of the
   region.  Risk should begin to diminish by sunset, with storms
   shifting offshore during the evening.

   ..Goss/Leitman.. 05/10/2018

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