Merry Christmas

Just like Bing sang about, many around KMDT will awaken to a beautiful snow covered landscaped around the Harrisburg area!  I was not at home to witness the onset of the snow, but it did come just prior to sunset and fell rather steadily as per the obs at KCXY for ~4 hrs.  Take a look at how the visibility was rapidly decreased once the snow began to fall.  The roads in the Lancaster area quickly became snow covered and slick as many cars slid off the roadway as I witnessed driving to Christmas Eve services!  Not good...I was wondering where PENN DOT was...this was not a secret...

Here is a quick map of where the snow accumulated across the Lower Susquehanna Valley as reported to the NWS in State College.  Not the highest amounts shaded right across the central part of York County with a bulls-eye right at my humble abode!  When I returned from Christmas Eve services, there was measured 2.5 inches on the ground...so I'm sure a reading of closer to 3" was accurate nearer to the ending of the heaviest accumulating snows!  Not too shabby for Christmas Eve in these parts...!

And there is more on the way...but the modeling, although increasing in its consistency, is still waffling back and forth on many issues from exact surface low placement to upper air flow downstream and upstream, to the amount of warm ocean air that intrudes ~1 mile above the surface.  All of these factors lead to a rather difficult and challenging forecast.  Over the years, I've seen these synoptics usually do the following in these parts:

1.  Begin as snow...and snow rather heavily at the start...
2.  Slowly mix with and then change to sleet and rain...
3.  End as a brief period of accumulating snow before getting blustery and very cold...

I believe this will once again be the scenario in these parts.  There will be an extremely tight gradient as well with the heaviest snow; places like Blaine, Perry Co may receive 12" while KMDT only 4-6", and Philly just 1".  If you are looking for the heaviest snows with this storm, I feel that State College, Dubois, Clearfield, Renovo, Lock Haven, etc are in the "sweet spot" as the upper levels will struggle to get above 0°C and copious amount of precip will fall as snow.  The latest GFS shows this rather narrow gradient in terms of accumulated snows...

This is a tricky forecast.  I just wished there was a stronger high pressure in southern Quebec!  Not that 1033 mb is a small high...just a few mb greater in terms of its air's density would make me feel a bit more confident in forecasting a major event for KMDT!

As I've been touting for the last several days now, we are looking at a plowable and possibly a high impact snow event later Wed into Thursday.  The other thing that makes me just a tad hesitant is that the 00Z Euro trended just a smidgen warmer overnight...but the GFS has been trending colder with each of its last several (6?) runs...so we will see what we will see.

And by the way there is potentially more fun and games waiting in the wings for this upcoming weekend!  We need to get closer to that event once the atmosphere exerts its energy potential the next few days...

So I wish y'all a very Merry Christmas...and I truly appreciate you taking the time to reads these posts, as I try to inform you of things the TV guys and the NWS State College may not be...I will leave you with this....Enjoy!

Merry Christmas y'all!

Smitty

AA:  Looking at a snow to rain back to brief snow event Wed-Thurs; then another potential storm over the weekend.  Getting MUCH colder next week!