Friday, February 10, 2012

Updating Tonight's Rain To Snow

Precipitation is starting to move into Western Pennsylvania this afternoon as the storm system slowly begins to organize.   Looking at the latest modeling with this storm system, the trend seems to suggest this is not going to be an "all at once" event and that our projected pittance of snows will spit and fit through Saturday evening.  There will be breaks in the activity during Saturday but there are hints that we could see some additional enhanced snowfall as we work into Saturday evening with a disturbance tracking southeast in the cold flow of air on the backside of the cold front.

Winter weather advisories are out for Philly, Delco, New Castle County in Delaware, and suburban South Jersey starting at 10 PM this evening.  The burbs north and west are not in the advisory because advisory criteria snow is three inches...and most places should avoid that tonight.  Some spots will hit though...

We're still going to have to deal with light rain on the front end of this event, with precipitation starting after 10 PM in the city.  Light rain changes quickly to snow in the western suburbs, with rain changing to snow early Saturday morning (pre-dawn) in Philadelphia.  Computer modeling suggests the steadiest of light snows will fall in Philadelphia between 4 and 8 AM and we should pick up the bulk of our pittance of snows during this time frame.   Accumulation projections are below -- we've nudged the city into the one to three inch range but odds still favor the Airport on the one inch side of things.   The best chances of three inch totals would be on higher elevations across the Pennsylvania suburbs on into Central and North Jersey...some folks up there could pick up four inches of snow from this.

I mentioned the possibility of spits and fits of snow after this first wave of snow departs on Saturday morning. Snow showers are showing up on some of the higher resolution models for Saturday afternoon and evening as colder air draws down from the northwest.  A disturbance will travel in and a bit of a trough will set up with the departing coastal low (norlun trough possibility?), resulting in a couple of bands or streamers of snow showers.  The models are shifting around on where they set up but odds (as of late this afternoon) favor west of the city (Berks through Lancaster County?) with the steadiest band of snow showers.  We'll monitor trends on that as we get into tomorrow.

We'll have another full update in the morning on where we're at and how Saturday will fare.