Sat 04:50 PM Update — Looking over more advanced models than the NAM and NAM-NEST, the consensus is that it will be too warm for freezing rain in the immediate Philadelphia area tomorrow morning, nor is precipitation expected to change back to snow before ending Sunday evening. (Areas north of Allentown may see some snow.)   Rain will start 7-9 AM Sunday morning and will end in the evening.  (The new GFS v 16 still shows a chance of snow as the precip starts at 7 AM, then a quick change to rain.  See second graphic.  Possibly a ‘cold bias’.   We’ll find out.)

 

User Feedback Requested: 
Users, would you like  to see all  updates posted to Twitter or just the major new posts (as currently done)?   Thanks!

[yop_poll id=”1″]

Our area saw rain today, on schedule between 12- 3 PM, although some areas far to the west and north had a wintry mix, as temperatures remained below freezing. The mix did not occur as close to PHL as forecast.    Here’s the surface temperatures at 3 PM today—

For the weekend—

Saturday,  a strong flow of relatively mild air moves in.  Original forecasts showed significant sunshine for Saturday, but the latest GFS suggests considerable cloudiness, a period of sun mid to late morning, then  a mix of clouds and sun at times in the afternoon.  There’s high uncertainty about the cloud cover Saturday, as captured in this NBM graphic—

With more clouds forecast, the high temperature looks to be 51.4º (NBM) and 49º (GFS) (Seasonal average high is 40º)

For Sunday, a secondary low forms off of Virginia. Precipitation moves in between 7 and 9 AM, starting as light snow or a rain mix. Changes to rain for most of the immediate PHL area. A change back to light snow is possible Sunday evening, with a coating at most.

(It appears that the new GFS may have a cold bias and the snow totals posted yesterday are incorrect and over-done.)

Any other winter, we’d have snow, but a lack of cold air to our north will keep it mostly rain.

Thur 08:49 PM Update— Tonight’s models suggest any wintry precipitation on Sunday will be well north of the Philadephia area and suburbs.

An active weather pattern with a series of systems and fronts will affect the Philadelphia area from New Years Eve through Sunday.

Tonight (New Years Eve), a cold front will continue slip to our south. Additional showers broke out this afternoon, but no rain is expected this evening.

Thu 05:35 PM Update —Falling temperatures tonight may result in some black ice on roadways later tonight.

On Friday, the same front will slowly move back as a warm front, as low pressure moves up through the Great Lakes. Rain will return between 12 noon and 3 PM Friday and there may be some mixed sleet and freezing rain in the northern and suburbs. 

For Friday, freezing rain (red shading) is predicted by the NAM-NEST very far northwest, but it wouldn’t surprise me if it’s underestimating the wintry mix at the start and some sleet is falls closer to the city, north of the lavender line (upper level freezing) shown below—

Eventually, there will be a changeover to all rain even north of the city as the warm passes through.

Saturday features clearing and some sun. It will be unseasonably mild, with highs in the low to mid 50s.

Things get interesting Sunday, as the low pressure system near the Great Lakes spawns a coastal low off of Virginia—

Most models (and the model blend) have rain for our area on Sunday, but the latest “parallel GFS version 16” has greater low pressure intensification and more cold air on the northwest flank of the storm.

As a result, the new GFS version 16  is showing some snow and accumulation for Sunday afternoon north and west—

The latest NAM and NAM-NEST and GEFS also show some snow falling far northwest, although not as much as the GFS.

Based on comparing predicted temps with actual temps, the new GFS is running a little too cold today, which may explain the higher wintry precip forecast.

I guess we’ll see how good the new GFS model is. Stay tuned.