... Dry and comparatively warmer weather will continue into Thursday and the first half of Friday before a low pressure system brings rain Friday night and Saturday.
NEAR TERM /THROUGH THURSDAY/... Snow showers continue to diminish in wake of a reinforcing weak cold front and passing shortwave. 920 PM radar imagery shows most shower activity has pushed southward to the Westmoreland county area, extending eastward into south-central PA. Given cold ground+air temperatures, even light activity such as this will easily stick to roads and any other surface. This activity will diminish nearly entirely for forecast area within the next couple hours as high pressure builds in behind the departing trough.
Previous discussion... Regional radars and observations show light snow showers have developed across the region in response to the passage of a shortwave trough. Limited moisture and displacement from strongest upper lift will keep snow amounts low in general, but did increase accumulation to a couple tenths from the previous forecast.
Precipitation will decrease later tonight as high pressure expands into the area and dry air infiltrates the mid-levels. Light wind and a mostly clear sky overnight will result in the temperature dropping into the teens by dawn Thursday.
Southerly flow / warm advection will return tomorrow as high pressure moves east and another trough digs across the Upper Midwest. Temperature should rebound to near climatological values (mid 30s to lower 40s for highs).
SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... After a clear start Thursday evening, the column slowly saturates ahead of the next weather system. An increased pressure gradient will result in a warmer night as minimum temperatures bottom out in the lower to mid 20s.
Temperatures will quickly recover Friday with warm advection in place. A trough will begin to traverse the area with a complicated atmospheric profile lending the ridges a chance for freezing rain until the surface temperature warms to above freezing. Some ice accumulation is possible in Garrett county. A substantial rain event is likely to accompany this trough with QPF values above 0.75 inches in most parts of the CWA. Rain will transition back to snow and a mix as temperature cools Saturday evening. This event may warrant headlines should this mixed precipitation trend continue.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... In wake of the baroclinic zone Saturday night, cold advection takes hold. This will change rain to snow showers as the thermal profile becomes favorable overnight. Given position of dendritic growth zone and westerly flow, do not expect much in the way of the snow accumulation. Best shot of a light accumulation would be in the higher terrain. Westerly flow not only will create an unfavorable upslope event on the back side of the system, but keep the temperature drop off minimal Sunday.
Long range camp of models continue to diverge on track and resultant impacts from potential winter system Tuesday. GFS by far is the warmest, which really limits ptype issues for a short window before rain overspreads the area. ECMWF and CMC are farther south and east with the track of the cyclone and thus places region in cold sector for a longer duration. This would yield a light snow accumulation across lower elevations and several inches in the mountains with ice at the onset /especially Garrett/. One can look as far as the statistical guidance from the GFS and ECMWF to the spread as daytime highs from operational runs vary by 15 degrees for daytime highs Tuesday. There is still a lot of time to hash out details with this being at the very end of the seven day forecast. If you have travel plans Monday and Tuesday, follow the forecast the coming days.