Sep 22, 2021 0600 UTC Day 1 Convective Outlook
Updated: Wed Sep 22 05:37:27 UTC 2021 (20210922 1200Z Day 1 shapefile | 20210922 1200Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20210922 1200 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 24,746 4,574,927 Pittsburgh, PA...Youngstown, OH...Warren, OH...Boardman, OH...Mount Lebanon, PA...
MARGINAL 108,940 17,191,459 Charlotte, NC...Cleveland, OH...Greensboro, NC...Akron, OH...Winston-Salem, NC...
Probabilistic Tornado Graphic
20210922 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 % 24,690 4,576,963 Pittsburgh, PA...Youngstown, OH...Warren, OH...Boardman, OH...Mount Lebanon, PA...
2 % 67,855 7,964,641 Akron, OH...Erie, PA...Roanoke, VA...Canton, OH...Lynchburg, VA...
Probabilistic Damaging Wind Graphic
20210922 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 % 24,711 4,580,477 Pittsburgh, PA...Youngstown, OH...Warren, OH...Boardman, OH...Mount Lebanon, PA...
5 % 109,281 17,287,577 Charlotte, NC...Cleveland, OH...Greensboro, NC...Akron, OH...Winston-Salem, NC...
Probabilistic Large Hail Graphic
20210922 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
No Risk Areas Forecast
   SPC AC 220537

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1237 AM CDT Wed Sep 22 2021

   Valid 221200Z - 231200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE UPPER
   OHIO VALLEY AND CENTRAL APPALACHIANS...

   ...SUMMARY...
   Scattered strong to severe storms will spread across portions of the
   Ohio Valley and central Appalachians.  Damaging winds are the
   primary threat, though a few tornadoes could be noted.

   ...OH Valley/Central Appalachians...

   Early-morning water-vapor imagery depicts a well-defined mid-level
   short-wave trough digging into the lower MO Valley. This feature is
   forecast to track across the lower OH Valley during the day as an
   80kt 500mb speed max translates across the TN Valley into northern
   KY by 18z. During the latter half of the period, this feature should
   deepen with a closed low advancing into northwest OH. Strong
   mid-level 12hr height falls will precede this upper trough with wind
   profiles/shear expected to increase markedly across eastern OH into
   western PA.

   Latest NAM guidance suggests partial clearing will allow strong
   boundary-layer heating along a corridor extending from western VA
   into eastern OH/western PA. This will result in steepening low-level
   lapse rates (7 C/km) immediately ahead of the front. Forecast
   soundings by early afternoon across eastern OH exhibit MLCAPE in
   excess of 1000 J/kg and lifted parcels should easily convect, both
   along the advancing front and ahead of the boundary. While
   supercells are expected, especially with more discrete updrafts
   ahead of the wind shift, strong lift should contribute to a forced
   squall line that will advance across the upper OH Valley in response
   to the strong short wave. While damaging winds will be the primary
   concern, low-level SRH and bulk shear favor some tornado potential.
   Greatest risk for tornadoes will be during the afternoon into early
   evening hours when the boundary layer will be most buoyant,
   primarily over eastern OH/western PA.

   ..Darrow/Moore.. 09/22/2021

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z