Tag Archives: Secondary Low


The models have been advertising another coastal snow storm development for Tuesday night into Wednesday.  Not all of the major models are totally on-board with this scenario, but it still appears more than likely.   The wind intensity of this storm will NOT be anything like this past Friday, although snowfall rates may look impressive during the day.

NAM Forecast Wednesday 1 PM

Incredibly, the current range is anywhere from 6-10 inches of snow for Philadelphia , based on the GFS (6″) and the NAM (10″).

Current timing- light snow develops during the evening Tuesday and increases in intensity after daybreak Wednesday, as the secondary coastal low develops and intensifies.

There’s still some thought that warm air might mix in, but right now the NAM and GFS critical temperatures all support snow.

I’ve given much thought about this past storm  I’m not going to get into the March sun angle, solar insolation and ground temperature effects, since it made giving an accurate accumulation forecast impossible.   I guess in March, it’s really about snowfall rate, not accumulation since accumulations mean much less in March— the snow can start melting as soon as it falls.

I’ll keep an eye on this one and will update tomorrow!

[su_note note_color=”#ebf2d9″]Sunday 10pm: The latest NAM data shows a significant snowstorm for Philadelphia on Wednesday.  QPF values are almost two inches water.  Critical temperatures show it falling as heavy wet snow.  Still too early to be sure, but this could be a major snowfall.

11pm:  Tonight’s GFS confirms a major snowstorm likely for PHL.  We’ll be waking up to heavy snow falling on Wednesday, snowfall increases for the rest of the day.  Current models suggest as much as 15 inches!  Too soon to hang our hat on this.



Winter Weather Update- Monday

How things change! A frontal passage with limited moisture and little development now appears to be somewhat more substantial.  QPF values for the NAM and GFS have increased closer to 0.20 inches water for PHL with greater amounts far NW of Philadelphia.

The latest models are beginning to suggest that a low pressure system might form off the coast, close enough to enhance the snowfall amounts Tuesday afternoon thru Tuesday night.  There’s been a wide range of model solutions with this frontal passage — most have either not had any development, or they had development far off the coast.  The Navy NAVGEM and the Canadian model were showing more precipitation yesterday, but I discounted both models, since the GFS and NAM were showing no development.

The experimental statistical models have consistently shown a low chance of snow through the Tuesday-Wednesday time period.

So the minor snow for Tuesday into Wednesday is beginning to appear that it might be more substantial.  Looking like 2-3 inches now, but too early to be that precise.   Stay tuned!

7 PM Monday-Further Complications to the forecast. This afternoon’s models show surface temperatures at or above freezing during the evening hours of Tuesday, not going below freezing until after midnight.  Some initial snow will melt and not add to accumulations in the immediate PHL area.