Tonight’s model data just becoming available.  Some large model differences have emerged regarding Tuesday’s snow.

The NAM has rain starting in the afternoon, changing to snow in the evening and quickly ending by 10 pm Tuesday night.  Total snow less than an inch.  QPF values about 0.31 inches water.

Tonight’s GFS continues with the idea that there will be low pressure development along the front.  It has precipitation starting early, changing to snow earlier and lingering.  QPF values about 0.63 inches water and over 3 inches of snow possible.

The important takeaway from this divergence is that there’s more uncertainty with this snow than previously thought.  Stay tuned.


Weather Update Sun 9:00 PM
Today’s NAM shows about 1 inch of snow Tuesday evening.

Today’s GFS and FV3-GFS shows some low pressure development along the front with potentially higher snow totals, especially north and west of the city.  Current QPF for these models has increased to 0.60 inches water, and current snow algorithms show about 3 inches of snow. Stay tuned.  

A weak cold front will move through  about 6 PM and clouds will increase ahead of the front this afternoon.  A widely scattered shower is possible with the frontal passage.

Skipping over to Tuesday, another cold front, this time an arctic front,  will move through during late afternoon into  the evening. Rain is expected prior to the frontal passage, during the late afternoon.

As the strong front moves through, the rain is expected to change over to snow before ending a little after midnight Tuesday. Total QPF with this front is about 0.35 inches water.

Much of the precipitation will fall as rain, but about 0.10 inches water  will fall as snow, more to the north and west of Philadelphia.   Current snowfall totals is about 1, possibly 2 inches, with the higher totals north and west.