Special Weather Discussion

Latest Weather Discussion by Kyle Elliott

* persistently cold pattern this month, but snow prospects uncertain *

11:45 a.m. Thursday, December 4, 2025:

As expected, there was a tight gradient in snowfall amounts along the I-78/81 corridors in PA during Tuesday's winter storm. The highest snowfall amounts occurred from the Poconos into New England with a "bullseye" in the Catskills of around one foot. In the Lower Susquehanna Valley, a general coating to 2" of snow fell south of the Turnpike and east of the South Mountain Range with 2-4" more common farther north and west (see below).

In the wake of the storm system, an area of high pressure settled into the central Appalachians on Wednesday and promoted mostly sunny and chilly conditions with high temperatures around 40°F. After a mainly clear and cold Wednesday night, an Arctic cold front will sweep through the Commonwealth this afternoon and usher a bitterly cold air mass into the Northeast late this week. Fortunately, only a few stray flurries will accompany its passage across south-central PA, and most areas should remain dry. Ahead of the front, high temperatures will reach the upper 30s to low 40s again under partly sunny skies, but northwesterly winds will be sustained at 12-25 mph with gusts up to 35 mph through 4 pm. As a result, wind chills will only be in the upper 20s to low 30s this afternoon. Winds will subside quickly after sunset, however, and be very light overnight. A Canadian high pressure system will settle into southern New England and northeastern PA later tonight, but a veil of mid- and upper-level clouds over southern PA should prevent temperatures from dropping below the mid-to-high teens. As a result, the December 5th record low of 11°F from 1926 at Millersville University appears to no longer be in jeopardy and should remain intact. Regardless, you will need to dress in layers and wear a winter coat and gloves before heading out the door to work or school on Friday, and temperatures will only rebound into the upper 20s to low 30s Friday afternoon. That's around 15°F below average by early-December standards.. yikes (see below)! In addition, skies will be mostly cloudy throughout the day, and a few flurries may graze areas south of the Turnpike as a weak storm system zips off the South Carolina coastline. I won't rule out a coating to 0.5" of snow between the Mason-Dixon Line and Interstate 70, but more substantial accumulations will be confined to areas farther south (see below). Thus, I will not be releasing a "Storm Outlook" Map for this event. 

Looking ahead into the upcoming weekend, a high pressure system will settle into the Commonwealth from Saturday into Saturday night and promote partly cloudy and somewhat more seasonable conditions. However, temperatures will still be several degrees below average with lows in the low 20s Friday night and highs around 40°F Saturday afternoon. The weather during the second half of the weekend will be virtually identical, but a clipper-type system may zip from the Ohio Valley or Great Lakes region through the northern mid-Atlantic States later Sunday into Sunday night and bring a period of light rain and/or snow to northern MD and southeastern PA. However, numerical computer models drastically disagree on the track and intensity of this potential system, and some do not even show the system at all. Thus, confidence in the forecast is currently very low from Sunday afternoon through Sunday night. Follow @MUweather on Twitter(X) for updates over the next 24-48 hours. 

The overall weather pattern should remain unseasonably cold across the Northeast and mid-Atlantic States, in aggregate, through most if not all of December. A weak Stratospheric Polar Vortex (SPV) and MJO activity in Phase 8 support a persistent trough, or dip in the Jet Stream, with multiple discharges of unseasonably cold air into the Central and Eastern U.S. over the next few weeks. However, the prospects for accumulating snow and/or a more significant snowstorm are far more uncertain. MJO activity in Phase 8 comes with the dreaded "cold and dry" risk due to persistent, northwesterly flow from Canada in the mid- and upper-levels of the atmosphere (see below). 

In this type of pattern, we'll deal with frequent, clipper-type systems diving southeastward out of Alberta and into the Upper Midwest. From there, their most likely track will be into the Upper Ohio Valley, eastern Great Lakes region and southern New England. This places northern MD, southeastern PA and the Lower Susquehanna Valley well south of their track. In terms of snow, that's less than ideal. Accumulating snow usually falls in a narrow swath along and just north/east of a clipper system's track, so I expect no more than a few rain/snow showers across the region at times next week. Honestly, many areas may receive no precipitation at all next week, and temperatures could actually climb a few degrees above average on Wednesday and/or Thursday (mid-to-upper 40s) depending on the exact track of that system. A reinforcing shot of Arctic air will likely arrive by the end of the week, but the odds of any snow accompanying it are not very high. There will certainly be rumors of storms and plenty of hype in the coming weeks, but you can never shovel potential! Details regarding the exact timing of any rain/snow showers next week are nebulous at this distance and won't be reliable until 2-3 days in advance of each system, so check back early next week for an update! The week will certainly start on a cold and dry note due to a reinforcing shot of Arctic air behind Sunday's potential clipper system. High temperatures on Monday and Tuesday may be similar to tomorrow, and lows will likely plummet into the teens again Monday night. Factor in a 15-30 mph northerly wind on Monday, and wind chills may be stuck in the single digits and teens all day. The winter coats and gloves won't be going anywhere in the foreseeable future.. -- Elliott