Monday, January 20, 2014

Snowstorm Forecast

Over the last few days models have brought the storm further north and west putting North Jersey in a winter storm warning. Some models still have the heaviest precip south of area with a 2"-5" event for the area, other models on the other extreme have as much as 12"+. My forecast will have a safe medium between the extremes and if any new model data in the 00z run shows a significant trend difference I'll revise my forecast.

Here are a look at the QPF on some models:

SHREF (Over 1.00" of liquid)

Generally taking the average of these models is the best bet for forecasting an accurate snowfall measurement, but first we need to figure out the snow ratios. Since it will be snowing in the teens and single digits we could see double what the normal ratio conversion is. Off the SHREF we see snow starting as 20:1 and toward the end of the event 35:1 this is opposed to the typical 10:1. 

For example if we have 0.5" of liquid equivalent typically we would call for 4"-6" but with 25:1 snow ratios we are now talking 10"-16" just because the air colder. 

Update tonight after the 00z runs if needed** (10:00pm or so)

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