SPC AC 121943

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0243 PM CDT Fri Apr 12 2024

   Valid 122000Z - 131200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   EASTERN NEW YORK/WESTERN NEW ENGLAND AND FROM NORTHERN NEVADA TO
   WESTERN MONTANA...

   ...SUMMARY...
   Isolated severe wind gusts and hail may occur with thunderstorms
   over northern Nevada, eastern Oregon, Idaho, and far western Montana
   into early evening. A severe storm or two also remains possible
   across portions of western New England the next few hours.

   ...20z Update...

   The previous outlook remains on track and no changes have been made
   with the 20z update. For details regarding short term severe
   potential across portions of the Northwest states, refer to MCD 430.

   ..Leitman.. 04/12/2024

   .PREV DISCUSSION... /ISSUED 1143 AM CDT Fri Apr 12 2024/

   ...Champlain/Hudson Valleys of New York into western New England...
   Showers appear to be increasing at this time across the
   Hudson/Champlain Valleys, ahead of an occluded front moving eastward
   across eastern portions of Upstate New York early this afternoon.  A
   lobe of vorticity will continue rotating northeastward across the
   region this afternoon, on the eastern fringe of the upper low
   crossing the Great Lakes.  Cold air aloft combined with weak
   insolation through breaks in the cloud cover evident in visible
   satellite imagery will permit additional/modest destabilization.  As
   a result, low-topped thunderstorms are expected to develop across
   this area.

   With deep-layer flow somewhat unidirectional/meridional, but
   strengthening with height, shear will support organized storms and
   potentially a few rotating updrafts.  As a result, a brief/weak
   tornado or two will be possible, along with gusty winds that may
   approach severe levels locally, with a few stronger cells and/or
   line segments.  As such, a MRGL risk is being introduced across a
   portion of eastern New York and into parts of western New England. 
   For additional short-term information, please refer to SWOMCD #429.

   ...Parts of northern Nevada to western Montana...
   Ahead of the advancing upper low, daytime heating beneath steep
   mid-level lapse rates will result in modest destabilization, with
   degree of CAPE hindered due to scant moisture availability across
   this region.  Still, with a few hundred J/kg mixed-layer CAPE likely
   by late afternoon, widely scattered thunderstorms are expected to
   develop.

   With favorably strong flow aloft across this area, a few
   stronger/sustained updrafts appear likely.  With a very deep
   well-mixed boundary layer expected across the region, gusty
   downdraft winds -- enhanced due to evaporative cooling in the
   sub-cloud layer -- may reach severe levels in a few instances.  This
   warrants continuation of the MRGL risk across into early evening.

   ...Ohio Valley to the Mid-Atlantic region...
   Scattered showers should diurnally increase from parts of the OH
   Valley across the central Appalachians to the Virginia/North
   Carolina area, with eventual/embedded low-topped thunderstorms
   expected to develop within the broader area of precipitation this
   afternoon.

   The convection will be associated with cold mid-level temperatures
   accompanying a shortwave trough, that is embedded within the broader
   cyclonic circulation across the eastern CONUS. With generally
   west-northwesterly flow behind the cold front, instability should
   remain very weak.  Still, enhanced low-level winds may reach the
   surface given the anticipated well-mixed boundary layer, resulting
   in occasional strong/gusty winds with a few of the stronger
   convective elements.

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