Friday, February 27, 2009

Two Coastal Storms, Deliver a 1-2 Punch Over The Weekend. Wintry Precip looks Very Likely, As We Turn Much Colder.

7:00 AM Update:

Good morning and get ready guys ! I continue to get more information in on Storm #2 that is pointing to a Major Snowstorm for The Delaware Valley and the I-95 Corridor from Richmond VA to Boston, MA. Once again areas East of PHL over DE and NJ could be looking at a real whopper here. I'll have my final Call and snowfall Map later today or this evening, with a full discussion. Stay Tuned.


NWS has Issued a Winter Storm Watch for Sunday Evening into Monday AM

Discussion: 5:00 PM
Friday 2/27/2009
For The Delaware Valley Region.

Have you all enjoyed the milder temps over the past couple of days ? It about to be pinched off quickly. We'll soon be reminded, It's still wintertime, and a late season event, will effect the entire region over the weekend. Let's start with tonight, as a cold front moves through with some shower activity during the evening hours. This cold front will clear the coast later tonight, and then stall out offshore tomorrow.

Colder air will begin filtering in during Saturday, as High Pressure builds in behind the cold front, and sets up to our North and West, from the Midwest into SE Canada. Temperatures will be in the upper 30's to mid 40's with partly to mostly cloudy skies.

Coastal Storm # 1
(Weaker and less dominate of the 2 storms, Mixed precip event)
Saturday Night into early Sunday AM.

During Saturday afternoon and evening, a wave of low pressure will develop over the SE States, and begin moving Northeastward to the NC Coast. This system will send a mixed bag of rain/sleet, and some snow to the Delaware Valley, from Saturday evening into Sunday morning. I'm forecasting areas N and W of PHL to see some rain and sleet during the evening hours which then quickly changes over to mainly sleet and snow from later in the evening, and into the overnight hours. Snow and Sleet accumulations of a Coating to 2" are possible. Temps will be in the low 30's during the evening hours, but drop to the mid and upper 20's overnight.

For PHL/Southern NJ, and DE, This will be mainly a mix of Rain and Sleet, changing to some Sleet and Snow, during later Saturday night and early Sunday morning before ending. Most of these areas will see a Coating to perhaps 1" of Sleet/Snow. Temps will be in the mid to upper 30's during the evening and drop to the upper 20's and lower 30's overnight.

Coastal Storm #2
(Stronger of the 2 storm systems, All Snow event, with possibly some mixing of sleet at times towards the coast)
Sunday afternoon into Monday morning

Now comes the fun part, with Coastal Storm #2 ! This system will have the most potential in producing some accumulating snow across the Delaware Valley. with areas South and East of PHL having the better chance for significant snow accumulations. This is going to be a very tricky storm to forecast, and I'm going to lay out some preliminary thoughts and estimates for now. I might have to make some adjustments during the weekend with this 2nd Storm.

This is a rather unusual setup for the beginning of March, as a potent closed H5 (500 mb) low digs into the Deep South and moves east into the SE States. This feature is cutoff from the main flow initially, but becomes phased with the Northern Branch Sunday into Monday. As phasing of the H5 low over the SE States and the northern stream occur towards the coast, another surface low develops near GA and SC during Sunday, and moves Northeast to the NC Coast, during Sunday night. So with the phasing of the Northern Stream occurring, the H5 and surface low over the SE States are pulled Northeast and up the east coast.

Precipitation will once again develop over much of the SE States and Lower M/A States during Sunday. With cold air in place and a Cold core H5 low, many areas from the Carolina's into VA will see accumulating snow for Sunday into Sunday night. This snow then spreads Northeast up the coast, during Sunday Night into Monday.

For the Delaware Valley Region:

Light Snow moves in for later Sunday afternoon and early evening. Snow will continue and become moderate at times Sunday night, especially over DE and Southern NJ. During Monday snow tapers off, from west to east during the morning hours. Some areas towards coastal DE and Southern NJ, could see some rain and sleet mixed in at times.

Total Snow accumulations: My Best estimate (These amounts could change with an updated and final call tomorrow) I'll likely do a Final snowfall Map, Saturday Afternoon or evening with storm #2.

PHL, SE PA, and Northern DE:
1" to 3" can be expected.

For Central/Southern DE, and Southern/Central NJ:
3" to 6" can be expected with possibly some sleet mixing in at times, over Coastal DE and NJ.

The I-95 Corridor from Raleigh NC to Boston MA, will also be threatened with accumulating snow from Sunday (South) into Monday Night (North). I'll have more for these areas later.

The exact track of this storm and how the H5 energy phases in, will determine the exact snowfall amounts. At this time I'm giving my preliminary thoughts and snowfall estimates. These are subject to change, and if needed I'll update later tomorrow.

Take care,

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