Aug 18, 2017 1630 UTC Day 1 Convective Outlook
Updated: Fri Aug 18 16:30:43 UTC 2017 (20170818 1630Z Day 1 shapefile | 20170818 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170818 1630 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 68,531 40,704,888 New York, NY...Philadelphia, PA...Baltimore, MD...Washington, DC...Kansas City, MO...
MARGINAL 288,836 30,471,024 Virginia Beach, VA...Omaha, NE...Tulsa, OK...Wichita, KS...Raleigh, NC...
Probabilistic Tornado Graphic
20170818 1630 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 % 33,265 32,057,398 New York, NY...Philadelphia, PA...Baltimore, MD...Washington, DC...Newark, NJ...
Probabilistic Damaging Wind Graphic
20170818 1630 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 % 68,705 40,725,007 New York, NY...Philadelphia, PA...Baltimore, MD...Washington, DC...Kansas City, MO...
5 % 277,037 29,561,560 Virginia Beach, VA...Omaha, NE...Tulsa, OK...Wichita, KS...Raleigh, NC...
Probabilistic Large Hail Graphic
20170818 1630 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 % 26,815 1,812,216 Kansas City, MO...Independence, MO...Columbia, MO...Blue Springs, MO...Raytown, MO...
5 % 170,031 22,134,483 Baltimore, MD...Washington, DC...Omaha, NE...Tulsa, OK...Wichita, KS...
   SPC AC 181630

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1130 AM CDT Fri Aug 18 2017

   Valid 181630Z - 191200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
   MID-ATLANTIC REGION...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS A PORTION
   OF SOUTHWEST MINNESOTA...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   NORTHERN MISSOURI...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS COVERING
   PORTIONS OF THE NORTHEAST AND MID-ATLANTIC REGION...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
   THE CENTRAL U.S....

   ...SUMMARY...
   Scattered strong to localized severe gusts capable of wind damage
   are forecast from the Chesapeake Bay vicinity northward into
   southern New York.  Isolated severe thunderstorms are possible
   across portions southwestern Minnesota and northern Missouri.

   ...Mid-Atlantic region...
   Daytime heating of a very moist boundary layer in place east of the
   mountains is ongoing, within a relatively cloud-free zone from
   southeast Pennsylvania south-southwestward east of the Appalachian
   crest.  As moderate CAPE develops through early to mid afternoon, an
   increase in storms -- particularly within a weak zone of convergence
   observed in lee of the mountains -- is expected.  Strongest flow
   aloft will remain largely north of the area of greatest anticipated
   destabilization, but amply strong west-southwest flow extending
   southward across the mid-Atlantic region will likely support a few
   stronger storms/bands of storms.  As such, 15% wind probability/SLGT
   risk remains evident across this region.  Convection will move
   eastward with time, weakening into the early evening hours as storms
   approach/move off the coast.

   ...Southwest Minnesota...
   A compact center of circulation remains evident near the southeast
   North Dakota/northeast South Dakota border, moving slowly
   southeastward with time.  As clouds/lingering precipitation continue
   to move east across Minnesota, diurnal heating will permit ample
   destabilization -- supportive of convective redevelopment near/ahead
   of the center of circulation.  With amply strong deep-layer
   northwesterly flow aloft, an organized, southeastward-moving cluster
   of storms may evolve, with associated risk for locally damaging
   winds and hail.  Convection should weaken into the evening as it
   shifts south-southeast out of Minnesota and across Iowa with time.

   ...Parts of northern Missouri...
   As weak large-scale ascent spreads southeast in conjunction with
   mid-level short-wave troughing over the north-central states, a weak
   surface low and convergence zone now over the western IA vicinity
   will likewise drift southeast.  Agreement amongst some CAM members,
   and morning NAM and GFS output, suggest that storms will develop
   over the northern Missouri vicinity this afternoon/evening near the
   low, as destabilization peaks.  With amply strong northwest flow
   aloft, storms may organize locally, possibly growing upscale into an
   organized band with time.  Risk for hail and locally damaging winds
   may evolve with any stronger convection, warranting continuation of
   SLGT risk for this afternoon and evening.

   ..Goss/Broyles.. 08/18/2017

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z