May 1, 2017 0600 UTC Day 1 Convective Outlook
Updated: Mon May 1 05:33:56 UTC 2017 (20170501 1200Z Day 1 shapefile | 20170501 1200Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170501 1200 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 143,693 30,914,524 Baltimore, MD...Washington, DC...Pittsburgh, PA...Buffalo, NY...Greensboro, NC...
SLIGHT 172,185 49,328,280 New York, NY...Philadelphia, PA...Charlotte, NC...Virginia Beach, VA...Raleigh, NC...
MARGINAL 99,363 16,217,772 Cleveland, OH...Atlanta, GA...Columbus, GA...Worcester, MA...Knoxville, TN...
Probabilistic Tornado Graphic
20170501 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
5 % 133,475 31,762,806 Philadelphia, PA...Baltimore, MD...Washington, DC...Pittsburgh, PA...Buffalo, NY...
2 % 98,103 31,619,931 New York, NY...Charlotte, NC...Raleigh, NC...Newark, NJ...Jersey City, NJ...
Probabilistic Damaging Wind Graphic
20170501 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
30 % 143,883 31,072,156 Baltimore, MD...Washington, DC...Pittsburgh, PA...Buffalo, NY...Greensboro, NC...
15 % 171,845 49,201,894 New York, NY...Philadelphia, PA...Charlotte, NC...Virginia Beach, VA...Raleigh, NC...
5 % 100,104 16,338,856 Cleveland, OH...Atlanta, GA...Columbus, GA...Worcester, MA...Knoxville, TN...
Probabilistic Large Hail Graphic
20170501 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 % 70,296 7,498,398 Pittsburgh, PA...Roanoke, VA...Altoona, PA...West Seneca, NY...State College, PA...
5 % 107,569 25,165,450 Charlotte, NC...Washington, DC...Buffalo, NY...Greensboro, NC...Rochester, NY...
   SPC AC 010533

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1233 AM CDT Mon May 01 2017

   Valid 011200Z - 021200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
   INTO THE EVENING ACROSS MUCH OF THE LOWER GREAT LAKES REGION...THE
   UPPER OHIO VALLEY AND THE CENTRAL APPALACHIANS INTO MID ATLANTIC
   COAST....

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   ENHANCED RISK AREA...AS FAR SOUTH AT THE SOUTHERN MID ATLANTIC COAST
   REGION...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   SLIGHT RISK AREA...AS FAR SOUTH AS NORTHERN FLORIDA...

   ...SUMMARY...
   Thunderstorms are expected to develop and overspread much of the
   lower Great Lakes region, the upper Ohio Valley and central
   Appalachians into the Mid Atlantic region today, accompanied by
   potentially damaging wind gusts and the risk for a few tornadoes.

   ...Synopsis...
   Ridging within the mid-latitude westerlies, centered off both the
   Pacific and Atlantic coasts, may maintain amplitude during this
   period, but troughing in between may broaden across much of the
   interior U.S., as a significant embedded short wave trough continues
   lifting northeastward out of the Plains/Mississippi Valley region. 
   This latter feature will be accompanied by a deep lower/mid
   tropospheric cyclone which is forecast to track across and northeast
   of the Great Lakes region by 12Z Tuesday, with an associated cold
   front advancing into and across the Appalachians and much of the
   Atlantic Seaboard.

   As one smaller scale impulse continues pivoting around the eastern
   and northeastern periphery of the mid-level cyclone, and another
   digs to its west and south, models suggest that the short wave
   trough will gradually transition from a negative to positive tilt
   centered over the Great Lakes by the end of the period.  And the
   mid-level cold core will continue to considerably lag to the west of
   the warm sector of the occluding surface cyclone.  However,
   substantial strengthening of deep layer wind fields appears likely
   today within the warm sector, across much of the Atlantic Seaboard
   by late afternoon.  This is where forcing for ascent is expected to
   support considerable thunderstorm development, which will probably
   be accompanied by potentially damaging wind gusts, and perhaps a few
   tornadoes.

   ...Eastern states...
   Models indicate strengthening of warm sector 850-500 mb wind fields
   to 40-70+ kt during the day today, particularly across the lower
   Great Lakes region, the upper Ohio Valley and the central
   Appalachians into the northern Mid Atlantic Coast region.  This
   should prove more than favorable for organized severe thunderstorm
   development, given at least weak boundary layer destabilization, and
   surface dew points in the 60s probably will contribute to this with
   daytime heating, despite relatively warm and initially capping
   mid-level layers.

   Beneath increasingly difluent flow aloft, frontal and orographic
   forcing for ascent are expected to aid initiation of thunderstorms
   near/east of Lake Erie, southward along the western slopes of
   central into southern Appalachians by 18-21Z.  This activity seems
   likely to eventually consolidate and grow upscale into an organizing
   squall line as it crosses the Allegheny mountains and plateau, and
   to the lee of the Blue Ridge, by early evening.  As it does, it
   probably will be accompanied by increasing potential for damaging
   surface gusts, given the strength of the ambient wind fields, with
   damaging straight line winds becoming the predominant severe threat.
   However, supercell structures, within and perhaps ahead of the line
   as it evolves, may be accompanied by a risk for tornadoes, one or
   two of which could be strong.

   Strong/severe storms may reach the Champlain/Hudson Valleys and Mid
   Atlantic coastal areas by this evening, before weakening within a
   more stable environment.

   ..Kerr.. 05/01/2017

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