SPC AC 011940

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0240 PM CDT Fri Jul 01 2022

   Valid 012000Z - 021200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHEAST
   WY...SOUTHWEST SD...AND NORTHWEST NE...AND ACROSS PARTS OF NORTHERN
   VA AND MD...

   ...SUMMARY...
   Scattered severe wind and hail will be possible from about 4 to 10
   PM MDT in northeast Wyoming across the Black Hills to the Nebraska
   Sandhills. Additional strong to locally damaging wind gusts are
   possible across northern Virginia into the northern Chesapeake Bay
   vicinity through 7 PM EDT.

   ...20z Update...

   A Slight risk has been included across parts of northern VA into the
   northern Chesapeake Bay vicinity where WW 417 is in effect. Loosely
   organized, pulse-like convection across this area has occasionally
   produced tree damage from sub-60 mph gusts, and small hail. This
   activity will continue to develop eastward the next 2-3 hours and
   may continue to sporadically produce strong/locally damaging gusts. 

   Otherwise, the previous outlook remains on track and no other
   adjustments to severe probabilities have been made with this update.
   See discussion below for more details.

   ..Leitman.. 07/01/2022

   .PREV DISCUSSION... /ISSUED 1102 AM CDT Fri Jul 01 2022/

   ...High Plains...
   Scattered thunderstorms are expected to develop off the Big Horns to
   the Sangre de Cristos and spread east across the adjacent High
   Plains later this afternoon within a plume of upper 40s to mid 50s
   surface dew points. The greatest potential for organized severe
   storms will exist across the northern portion of this region from
   eastern WY into western SD and northwest NE. Here, moderate to
   strong deep-layer speed shear with height will yield effective bulk
   values of 40-50 kt and an elongated straight-line hodograph. A few
   high-based outflow-dominated supercells with mid-level rotation
   should develop and congeal into a cluster this evening. Initial mix
   of severe hail and wind transitioning to predominately wind will be
   the primary threats. A lack of appreciable low-level forcing for
   ascent this evening in conjunction with a nocturnally stabilizing
   boundary layer should result in these threats diminishing towards
   late evening. Farther south to the Raton Mesa, slow-moving
   thunderstorms may pose a threat for very isolated severe wind gusts
   and marginally severe wind hail during the late afternoon and
   evening.

   ...Lower Great Lakes to the Lower MO Valley...
   A low-amplitude shortwave impulse near the NE/IA border will shift
   east along the southern periphery of seasonably moderate to strong
   mid-level westerlies across the Great Lakes to northern IL/IN/OH.
   Isolated to scattered thunderstorms will be possible along and just
   ahead of a cold front sagging southeast across southeast Lower MI
   through eastern KS later this afternoon. Abundant cloud coverage and
   weak mid-level lapse rates should temper updraft intensity in the
   more strongly sheared regime near the Lower Great Lakes.
   Nevertheless, a few multicell clusters and transient supercell
   structures may develop with a threat for isolated damaging winds and
   severe hail through about dusk.

   ...Mid-Atlantic States...
   Localized damaging winds and marginally severe hail will be possible
   through this afternoon as low-level warm theta-e advection-driven
   convection over the central Appalachians spreads east towards the
   Mid-Atlantic coast. Poor mid-level lapse rates evident in available
   12Z observed soundings and modest deep-layer flow will be limiting
   factors to a more robust/organized severe threat. See MCD 1314 for
   further short-term discussion. Additional thunderstorms may spread
   towards the region tonight from the Lower Great Lakes/Upper OH
   Valley, but should largely be in a decaying state.

   ...Northern ME...
   Pronounced differential diabatic heating and weak low-level
   convergence may aid in isolated thunderstorms near the Saint
   Lawrence Valley into southeast QC later this afternoon. Morning
   guidance suggests a nadir in low-level moisture will be present
   across parts of western New England, but adequate moisture may still
   hold across northern ME. This may yield a corridor of weak buoyancy
   amid poor mid-level lapse rates. The most favorable factor will be
   effective bulk shear of 40-50 kts, which would conditionally support
   a supercell or two, but confidence is low.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z