Latest NAM suggests the possibility of  some significant snow for Saturday afternoon before changing to sleet and freezing rain Saturday evening.  Ground temperatures have been very cold and snow covered for a long period.  The potential for prolonged icing exists.

As had happened in the “freak” ice storm in January, the models may be too quick in predicting  the ground to warmup .   So very difficult driving conditions possible late Saturday afternoon.   Stay tuned. 

If you’ve listened to any weather forecasts recently, you’ve likely heard that [several] oubreaks of cold air will be affecting us over the next week.

The models are in reasonable agreement that a deep upper air trough will develop over the eastern US, probably in three different stages. The first influx of cold air will enter Thursday afternoon.  Another will move in Saturday night.  A third will likely affect us next Tuesday into Wednesday.

What is less clear is the amount  snow (if any) that will accompany each of the clipper distubances that herald in the cold outbreaks.  Right now, the amount of snow expected in PHL for each of these disturbances looks to be less and less with each model run.  Thursday will likely just have some snow showers.  Saturday afternoon’s clipper also appears to be trending towards less snow here.   Additionally, the sharpness of the trough appears to be somewhat less, meaning less cold air in Florida.

The only real threat is next Tuesday, where a low pressure system from the southwest (not a clipper) may interact with the re-developing upper trough.  Of course, much can change in a week, but these are the current trends.

For Sunday evening– Low pressure will develop in the middle of the country and move eastward as it intensifies over PA and NJ Sunday evening through Monday morning. Snow will overspread our area Sunday evening and become heavy after midnight and during the predawn hours of Monday.

Warm air is expected to move in at about 5000 feet in and around PHL, so a changeover to sleet and possibly freezing rain will likely occur towards daybreak Monday morning. A change back to snow will likely occur before ending early Monday afternoon.

Uncertainty about the northward track of the low and the amount of warm air mixing in will make accumulation prediction very difficult around PHL, but areas to the far north and west may have snow amounts around 12+ inches.

Unlike the ‘blizzard’ that wasn’t, this storm will more likely be impactful with accumulations of 6 or more inches possible (but not definite) around PHL by Monday morning.

I suspect the NWS is being overly cautious about over-predicting this one.   I don’t think this one will fizzle out. Stay tuned.