Sunday, February 17, 2008

Let's talk Snow ! Good Prospects for later in the week for The Central & Northern M/A States.

6:00 AM Update
Tuesday: 2/19/08

Well Guys, it looks like we're on the way for Accumulating snow. I promised and update tues/wed and I'll have a more detailed first call tonight along with better snowfall estimates. It appears the global models are on board for an overrrunning southern slider with a possible good thump of moderate snow late Thursday night into Friday morning, then probably changing to a light mix from DCA/BWI to DE/SJ.

At this time I'm thinking a general 3" to 5" storm from BWI to PHL and SJ. Lesser amounts of 1" to 3" from parts of Northern VA into Southern DE and northern Delmarva.These are preliminary estimates, and I want to wait with a better writeup tonight.

So they are rough estimates and could go down or possibly up, with my final call Wednesday night or Thursday morning.Overall it's Looking very good for Parts of The interior central M/A and all of the Northern M/A states, for this snow threat Thursday Night into Friday.

Clipper Event for Wednesday Afternoon into the early evening hours will bring a period of snow and snow showers to the Delaware Valley. At this time I'm thinking a general Coating to 1" with a few spots possibly getting near 2". I'll have more on this tonight.
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Discussion:
Sunday 2/17/08
9:00 AM


That's right I said Snow, and this looks to be a classic Overrunning event, that brings Accumulating snow to much of the Central & Northern M/A States, for later this week. I've been watching this setup for a couple days now, and it's time to fire away with my thoughts on this event. There's 2 main setups that give our region good snowstorms: they are: Miller A or B Coastal Storms, and Overrunning Events. So what I'm saying is We're game for our biggest snow event of the winter season. This looks to be from Thursday Night into Friday Night, then another second wave could threaten with another shot of snow or Ice for Early next weekend. So let's look at this setup.

The Setup:

A Classic Arctic High moves southeast from Canada during the early and Middle part of this week, behind a big storm that cuts to the lakes on Monday. This High will move to a favorable position on Wednesday and Thursday, stretching from the Upper Midwest to the Great Lakes regions. This will pump in a North to Northwest flow of colder air into the area on Wednesday and Thursday. So this is our key ingredient for supplying the cold air, and the positioning of this Arctic high will lock it in for the later part of the week.

Now let's talk about the Upper Level Pattern and General flow. The Northern Branch/Arctic Jet, carves a trough over the Great Lakes and Northeast later this week, along with some upstream blocking in the Atlantic. This will prevent our High from moving out, or being ejected eastward. Confluence and a strong zonal flow developes underneith this High and trough, as a Split flow with the Pacific Jet, forms near the Rockies and Southern Plains. This flow will help feed in ample moisture and eject it eastward, towards the region. Another key factor to pump in this moisture, will be some ridging, and High Pressure off the SE US Coast. This will also feed moisture into this flow and precipitation, will begin to develop over the Southern Plains, and Tennessee Valley later Wednesday into Thursday.

With strong confluence and a zonal flow for the M/A states, this moisture will spread eastward, and Overrruning develops from WAA being thrown into our Cold air mass, thanks to our Arctic High over the Great Lake. This setup is classic for a Band of Light to Moderate snow, from the Lower Ohio Valley, into the Central and Northern M/A States, for Thursday into Friday Night.

A 150 to 200 Mile wide swath of Accumulating snow will setup in these areas. with some Snow, Ice, and Rain South of this Band, mainly for Southern VA and Parts of the Carolinas. So overall I'm looking for Accumulating snow for The Delaware Valley Thursday Night into Friday Night, and a mix of Snow, Ice, and Rain, further south as we head towards Central and Southern VA, into Interior sections of NC, for Thursday into Friday.

I'll have more on this early this week, with a more detailed forecast, and my thoughts on how much snow we can expect. It's to early for amount's, but accumulating snow looks to be a good bet for later this week.

Take Care,
Ruggie

2 comments:

Mr. Foot said...

Ruggie: Thanks for your nice response and I also meant to say you have a great site also, very detailed and your links provide many good idea on how to present info.

Did you see National Treasure 1? My favorite line from that movie I think applies perfectly in this case: "The secret lies with Charlotte"

I think the secret is the NAO. I wrote up some notes I'll try to organize and post on my site today. I see the 12Z GFS is apparently changing it's tune, but HPC does not appear to buy it. Something tells me there is a missing link out there and I'm trying to nail it down. I was reading your writeup and I wondered also about how the SE Ridge in cohort with the GL high would potentially sharpen the eastern trough, bringing the precip up your way.

Will be adding you to my "What Are Others Saying" List so we can keep tabs on each other.

Thanks for your hard work on behalf of all us weather types.

RUGGIE WEATHER said...

That Mr Foot ! No I didn't see National Treasure 1.

What I meant in saying the G/L High and Blocking or ridging off the se coast, is that this could cause the flow to become more SW to NE and precip could actualy come further north and or up the coast as it reaches the M/A region. a kink in the stream and flow could cause a weak storm to develope, since a sinking high into the midwest and High off the SE coast, could cause the overrunning band to shif it's axis.

Thanks for adding me to your site !

Take Care
Ruggie