ZCZC SPCSWOMCD ALL ACUS11 KWNS 271158 SPC MCD 271158 PAZ000-NYZ000-MDZ000-WVZ000-271700- Mesoscale Discussion 2063 NWS Storm Prediction Center Norman OK 0558 AM CST Mon Dec 27 2021 Areas affected...Portions of far western MD...western/central PA...and far southwestern NY Concerning...Freezing rain Valid 271158Z - 271700Z SUMMARY...Freezing rain rates may exceed 0.05 inch per 3 hours through the morning, before precipitation gradually transitions to rain from west to east this afternoon. DISCUSSION...A fairly broad area of precipitation is moving eastward this morning from eastern OH into western PA and vicinity. This activity is being aided by strong warm/moist advection associated with a 45-50 kt southwesterly low-level jet over the OH Valley. This feature is expected to shift eastward across the central Appalachians over the next several hours in tandem with the ongoing precipitation shield. Dry air in the low/mid levels noted on the 00Z sounding from PIT still exists across parts of western/central PA and vicinity. But, gradual moistening of the low levels will occur this morning with light to moderate precipitation continuing to overspread this region. Surface temperatures are generally below freezing, and wet bulb cooling will likely aid in sub-freezing temperatures being maintained through much of the morning, especially across higher terrain. A warm nose aloft associated with the strong low-level warm advection will likely support partial to total melting of hydrometeors. An initial mix of snow/sleet should transition fairly quickly to mostly freezing rain this morning. Freezing rain rates around 0.05 inch per 3 hours may occur, with locally greater rates possible in higher terrain. The freezing rain should gradually transition to rain from west to east from late morning into the early afternoon. ..Gleason.. 12/27/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BUF...CTP...LWX...PBZ... LAT...LON 40407916 40967918 41027941 41197970 41377987 41587958 41777918 41947890 42147859 42157822 41757801 41257758 40607777 39787837 39577884 39397918 39487940 40407916 NNNN