SPC AC 221731

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1231 PM CDT Wed Jul 22 2020

   Valid 231200Z - 241200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN
   NEW ENGLAND...AND ACROSS PORTIONS THE NORTHERN PLAINS...AND ACROSS
   PORTIONS OF THE NORTHERN ROCKIES...

   ...SUMMARY...
   Strong to severe thunderstorms appear possible Thursday across parts
   of the northern Mid-Atlantic and southern New England, as well as
   over the northern Plains and northern Rockies/High Plains.

   ...Central Appalachians/Mid-Atlantic States into New England...
   A moist air mass will be in place across much of the eastern CONUS
   Thursday, with 70 deg F dewpoints possible as far north as northern
   NJ/NYC and 65 deg F dewpoints into ME. A low-amplitude shortwave
   trough is forecast to move eastward from the Upper Great
   Lakes/Ontario eastward through New England. Ascent associated with
   this shortwave trough and its attendant cold front are expected to
   result in widespread thunderstorms amid the moist and unstable air
   mass from the Mid-Atlantic States into New England. 

   Buoyancy is generally not expected to be overly strong, largely a
   result of poor mid-level lapse rates and more filtered diurnal
   heating. Instability is currently expected to be strongest from the
   VA Tidewater region south across central and eastern NC. This
   instability will be displaced south of the better vertical shear,
   which is expected to be farther north over New England, closer to
   the more amplified portion of the shortwave trough. More favorable
   shear in this region suggests a greater potential for more
   organized/stronger bowing line segments. Consequently, a 15% wind
   probability has be introduced with this outlook. The lack of
   stronger vertical shear farther south suggest a more disorganized
   storm mode and lower severe potential.

   ...Northern Rockies...Northern High Plains...
   A deep shortwave trough, extending throughout British Columbia and
   the Pacific Northwest early in the day, is expected to move into the
   northern Rockies Thursday afternoon. Increasing mid-level moisture
   associated with this shortwave and deep boundary-layer mixing will
   contribute to modest air mass destabilization across the northern
   Rockies and northern High Plains, particularly across central ID and
   into southwest MT. Strong forcing for ascent attendant to this
   shortwave will interact with this unstable air mass, resulting in
   afternoon thunderstorms. Deep-layer shear appears strong enough to
   support a few more organized storms, and perhaps even a convective
   line by late Thursday afternoon. As a result, the severe threat
   appears high enough from central ID  into southwest MT to merit a
   15% wind/Slight Risk.

   ...Northern Plains...
   A lead shortwave trough (moving ahead of the shortwave trough
   described in the previous paragraph) is expected to eject out into
   the northern Plains by Thursday afternoon. A sharpening lee trough
   will aid in strengthening the surface pressure gradient and
   increasing southeasterly surface winds ahead of the shortwave.
   Resulting low-level moisture advection will likely bring upper 60s
   dewpoints to the MT/ND border vicinity by the mid-afteroon. Remnant
   EML above this increasing low-level moisture will aid in the
   development of strong instability but also lead to capping
   throughout most of the day. This capping should limit storm
   initiation across much of the region, resulting in only isolated
   storm coverage. However, convective initiation is probable near the
   surface low, where both low-level convergence and large-scale
   forcing for ascent will be strongest. Vertical shear is only
   expected to be modest (i.e. around 20 kt of effective shear) but the
   strong instability suggests a relatively greater potential for hail
   in this area.

   ..Mosier.. 07/22/2020

   CLICK TO GET WUUS02 PTSDY2 PRODUCT

   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z