May 22, 2018 2000 UTC Day 1 Convective Outlook
Updated: Tue May 22 19:55:26 UTC 2018 (20180522 2000Z Day 1 shapefile | 20180522 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20180522 2000 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 68,725 19,529,691 Columbus, OH...Washington, DC...Pittsburgh, PA...Cincinnati, OH...Akron, OH...
MARGINAL 519,210 24,436,962 Baltimore, MD...Denver, CO...Cleveland, OH...Virginia Beach, VA...Omaha, NE...
Probabilistic Tornado Graphic
20180522 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
No Risk Areas Forecast
Probabilistic Damaging Wind Graphic
20180522 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
15 % 67,148 19,029,381 Columbus, OH...Washington, DC...Pittsburgh, PA...Cincinnati, OH...Akron, OH...
5 % 326,127 21,357,657 Baltimore, MD...Denver, CO...Cleveland, OH...Virginia Beach, VA...Aurora, CO...
Probabilistic Large Hail Graphic
20180522 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
5 % 484,639 22,843,837 Columbus, OH...Denver, CO...Cleveland, OH...Omaha, NE...Pittsburgh, PA...
   SPC AC 221955

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0255 PM CDT Tue May 22 2018

   Valid 222000Z - 231200Z


   Isolated strong to severe thunderstorms remain possible this
   afternoon and evening across parts of the Mid-Atlantic States and
   Ohio Valley, as well as over portions of the High Plains and
   north-central Rockies.

   ...20Z Update...

   ...Upper OH Valley...
   Recent surface analysis places a surface low across north-central OH
   with a cold front extending southwestward into southern IL. This
   cold front also extends northward from the low to another low over
   Lake Ontario. A warm front extends southeastward from this second
   low across eastern PA and into the northern Delmarva. Thunderstorms
   have developed within the confluent warm sector ahead of the cold
   front across the OH Valley. Damaging wind gusts remain possible with
   the strongest storms in this region. More details are available in
   MCD 491.

   Another area of thunderstorms is moving from the higher terrain of
   VA into the more moist and unstable airmass across central VA.
   Damaging wind gusts are also the primary threat in this area with
   some isolated hail also possible.

   ...High Plains...
   Thunderstorms have developed across the higher terrain of the
   Rockies Mountains while much of the downstream High Plains is
   currently void of convection. Even so, strong heating will persist
   with eventual airmass destabilization and convective initiation.
   Vertical shear is relatively weak and supportive of predominately
   outflow-dominant multicells. The exception may be across portions of
   southeast WY/northeast CO where southeasterly upslope flow is
   contributing to more favorable low-level shear and vertical
   vorticity. In this area, an isolated supercell is possible.

   ..Mosier.. 05/22/2018

   .PREV DISCUSSION... /ISSUED 1128 AM CDT Tue May 22 2018/

   ...Upper Ohio Valley...
   Visible imagery indicates thinning cloud cover over Indiana and much
   of Ohio which will permit stronger diabatic heating and air mass
   destabilization to occur this afternoon, in advance of a
   southeastward moving cold front located from extreme northwest Ohio
   into southwest Indiana.  The decrease in cloud cover will spread
   into western Pennsylvania with time and contribute to a gradual
   increase in heating.  MLCAPE is expected to reach 1000-1500 J/kg,
   with greater instability expected with westward extent.  

   Short bands of mainly shallow convection are developing along/ahead
   of the front from northwest Ohio into east central Indiana. 
   Updrafts within this activity are expected to strengthen with
   several bands of northeast-southwest oriented thunderstorms forming
   by early-mid afternoon.  The storms will be located on the southern
   edge of stronger westerly winds aloft, including the right entrance
   region of an upper level jet, resulting in deep layer shear of 30-40
   kt that will enhance storm organization and intensity.  Stronger
   cells will be capable of producing damaging wind gusts with isolated
   hail also possible mainly with any storms that are able to develop
   transient updraft rotation.  The activity will spread eastward and
   southeastward through the evening hours before storms gradually
   weaken as boundary layer cooling and low-level stabilization occurs.

   ...Mid-Atlantic Region...
   More extensive cloud cover over Pennsylvania and northern West
   Virginia with fewer cloud to the south is creating a differential
   heating zone along the southern edge of the thicker clouds. 
   Stronger heating to the south will enhance destabilization in
   advance of storms beginning to develop over southern West Virginia
   at this time.  VAD winds at RLX and LWX exhibit westerly winds of
   30-40 kt above 4 km which will provide sufficient shear to support
   organized multi-cell storms and possibly an isolated supercell or
   two.  Storms are expected to develop eastward this afternoon with
   potential for localized damaging wind gusts although isolated hail
   will also be possible with stronger storms. 

   ...Eastern New Mexico and West Texas...
   Low-level moisture persists as far west as the upper Rio Grande
   Valley of New Mexico in the wake of widespread storms on Monday.  A
   few strong storms are expected to develop this afternoon and
   evening, initially over the mountains of central New Mexico, with
   the activity spreading eastward with time.  Other storms will
   develop over southwest Texas as well.  The region is on the edge of
   stronger southwest winds aloft associated with the upper low that is
   beginning to lift northeastward over the southern Great Basin.  A
   few stronger cells capable of producing hail and strong wind gusts
   will be possible.

   ......North-central Rockies to middle Missouri Valley...
   The Great Basin/southwest states-central upper low is beginning to
   move northeastward, with a lead shortwave trough currently lifting
   across northern Arizona expected to overspread the central
   Rockies/Wyoming through the afternoon into tonight. Orographic lift,
   increasing dynamic forcing for ascent coupled with adequate moisture
   will allow for the development and intensification of storms this
   afternoon initially across parts of Utah/western Colorado into
   interior Wyoming where locally severe storms will be possible. As
   forcing for ascent spreads northeastward by late afternoon, a
   somewhat more moist and unstable environment across central/eastern
   Wyoming could allow for more organized/sustained storm modes with
   hail/severe wind gusts possible as storms spread east-northeastward.

   Over the Plains, a nocturnally increasing low-level jet may help
   sustain storms into South Dakota and western/northern Nebraska this
   evening, in addition to an increase in storms farther east toward
   the Missouri River late in the evening/overnight with some hail