Jun 29, 2021 0600 UTC Day 2 Convective Outlook
Updated: Tue Jun 29 05:44:38 UTC 2021 (20210629 0600Z Day 2 shapefile | 20210629 0600Z Day 2 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20210629 0600 UTC Day 2 Outlook Graphic
Day 2 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 103,987 19,377,265 Boston, MA...Worcester, MA...Springfield, MA...Syracuse, NY...New Haven, CT...
MARGINAL 207,971 51,388,266 New York, NY...Philadelphia, PA...Columbus, OH...Cleveland, OH...Pittsburgh, PA...
Probabilistic Tornado Graphic
20210629 0600 UTC Day 2 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 2 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
2 % 33,150 1,433,722 Concord, NH...Lewiston, ME...Bangor, ME...Auburn, ME...Augusta, ME...
Probabilistic Damaging Wind Graphic
20210629 0600 UTC Day 2 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 2 Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 104,129 19,348,453 Boston, MA...Worcester, MA...Springfield, MA...Syracuse, NY...New Haven, CT...
5 % 207,041 51,415,568 New York, NY...Philadelphia, PA...Columbus, OH...Cleveland, OH...Pittsburgh, PA...
Probabilistic Large Hail Graphic
20210629 0600 UTC Day 2 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 2 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
5 % 31,661 1,443,388 Concord, NH...Lewiston, ME...Bangor, ME...Auburn, ME...Augusta, ME...
   SPC AC 290544

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1244 AM CDT Tue Jun 29 2021

   Valid 301200Z - 011200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM CENTRAL PA
   THROUGH MUCH OF THE NORTHEAST...

   ...SUMMARY...
   Several severe thunderstorms are possible Wednesday afternoon and
   evening from the Upper Ohio Valley into Northeast States. Isolated
   severe thunderstorms may also occur across the Great Basin.

   ...Synopsis...
   Subtropical ridging is forecast to persist across the southern
   Plains and Southeast States on Wednesday, while a weak upper flow
   regime continues over the Southwest and Great Basin. Upper ridging
   centered of southern Alberta early Wednesday is expected to
   gradually shift eastward throughout the day as a compact shortwave
   trough traverses its western periphery over British Columbia.

   Farther east, a series of shortwave troughs will likely progress
   through the base of an upper trough extending from the Hudson Bay
   into the Upper Midwest early Wednesday. Evolution of these
   shortwaves coupled with the eastern moving upper ridge will likely
   result in an overall eastward progression of the upper trough, with
   some deepening also possible. 

   A largely nondescript surface pattern is expected east of the
   Rockies, with a tropical air mass covering all but the northern and
   central Plains. Some low-level convergence is possible from central
   KS northeastward into Lower MI, along the weak stationary front
   separating the tropical air mass to the south/east and more
   continental air mass to the north/west. 

   ...OH Valley into the Northeast...
   Upper 60s to low 70s dewpoints are expected to be in place across
   the OH Valley and much of the Northeast early Wednesday morning.
   This moist air mass will destabilize quickly amid daytime heating,
   with moderate buoyancy anticipated by early afternoon. Given the
   lack of convective inhibition, scattered to widespread thunderstorm
   development is possible across the region with both surface
   convergence and subtle large-scale forcing for ascent acting as
   forcing mechanisms. 

   Closer proximity to the shortwave troughs moving through the parent
   upper trough will result in both stronger large-scale forcing ascent
   and stronger vertical shear over the Northeast. A predominantly
   multicellular storm mode is anticipated, but stronger vertical shear
   in the region could result in a few more organized line segments,
   with an attendant threat for damaging wind gusts. Given the
   favorable overlap between buoyancy and shear, a greater severe
   potential appears to exist from central PA through central/eastern
   NY into much of New England. This includes much of VT and NH as well
   as central/eastern Maine, where stronger low-level flow could
   support a few supercells.

   ...Great Basin...
   Increasing mid-level moisture will help support isolated to
   scattered thunderstorms development Wednesday afternoon. Weak
   vertical shear should limit storm organization, but high cloud bases
   amid a deeply mixed boundary layer could still result in a few
   strong gusts with more robust storms.

   ...North-Central/Northwest MN into Northwest WI...
   Shortwave trough dropping south through western Ontario is forecast
   to reach northern MN during the afternoon, contributing to
   thunderstorm development amid modest buoyancy. Storm coverage
   remains uncertain, but moderate northwesterly flow aloft could
   result in a few strong storms. Coverage uncertainty precludes adding
   probabilities with this outlook.

   ..Mosier.. 06/29/2021

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   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z