Storm Prediction Center Mesoscale Discussion 76

   Mesoscale Discussion 0076
   NWS Storm Prediction Center Norman OK
   0242 PM CST Sat Feb 08 2025

   Areas affected...northwest to south-central Pennsylvania into far
   northern West-Virginia/Maryland

   Concerning...Winter mixed precipitation 

   Valid 082042Z - 090045Z

   SUMMARY...Snow transitioning to a combination of sleet and freezing
   rain is expected to overspread northwest to south-central
   Pennsylvania and far northeast West Virginia/northwest Maryland
   through the late afternoon hours. Freezing rain rates up to 0.03
   in/hour are possible.

   DISCUSSION...Regional radar imagery depicts a swath of stratiform
   precipitation overspreading OH with an additional precipitation band
   associated with strengthening isentropic ascent developing across WV
   into northwest VA/western MD. Over the past hour, surface
   observations and mPING reports from north-central OH have reported a
   mixture of freezing rain (with one-hour accumulations up to 0.03
   inches) and sleet as surface temperatures wet-bulb down to the upper
   20s/low 30s. Slightly cooler conditions are noted downstream across
   PA where surface temperatures are largely below freezing with
   dewpoints in the teens to mid 20s. Initially sub-freezing
   temperatures throughout the column over PA should promote mainly
   snow as the initial p-type as precipitation begins overspreading the
   region. 

   With time, strengthening mid-level warm advection will result in a
   1-4 C warm nose within the 850-700 mb layer. Concurrently, wet-bulb
   cooling within the lowest kilometer will maintain sub-freezing
   temperatures near the surface. These thermodynamic trends will
   promote a transition from mainly snow to a mix of freezing rain and
   sleet, similar to recent upstream observations. The propensity for
   one precipitation type over the other will largely depend on the
   strength of the warm nose aloft, which varies across recent
   deterministic solutions leading to limited confidence in coverage of
   sleet/freezing rain and accumulation amounts. Regardless, moderate
   to heavy precipitation rates - especially under any embedded
   convective elements - may result in periods of moderate sleet and/or
   freezing rain.

   ..Moore.. 02/08/2025

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...PHI...BUF...CTP...LWX...PBZ...CLE...

   LAT...LON   39897939 40447889 40747894 40927924 40927988 41118051
               41578058 41908037 42017987 42047877 42037851 41987816
               41937785 41567717 41187668 40747624 40427611 40087610
               39897628 39777661 39547796 39487856 39467902 39547937
               39697946 39897939