Monthly Archives: January 2019

Winter Weather

WINTER WEATHER UPDATE

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 Updates

WEATHER UPDATE- SUNDAY

[su_box title=”Weather Update Sun 9:00 PM” box_color=”#defcdc” title_color=”#000000″]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.   [/su_box]

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.

Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

High pressure that moved in on Friday will linger into Saturday morning.  Milder air aloft will approach  during the day on Saturday as winds become southeasterly. In effect, a weak warm front.  Disturbances (vorticities) in the upper flow may give us additional clouds on Sunday.

Saturday will start mostly sunny, but mid-level cloudiness will increase during the day.  The GFS is showing a significant layer of altocumulus and altostratus cloudiness by afternoon.  High will be near 35.  Low about 25.

Sunday will be milder, with some sunshine, but it appears that these weak disturbances in the upper flow may also result in some cloudiness.  High 42-44.

A potentially interesting situation for Tuesday into Wednesday-  The European ECMWF has been consistently showing a coastal low developing along an arctic front as it moves through our area.  This would mean snow for us..  This has been supported by the Canadian CMC model.  However the GFS and FV3-GFS do NOT show this low pressure development.  Something to watch.  Stay tuned.