The clipper will pass by our north today.

It's a 998mb low moving eastward across Lake Superior right now. This low tracks to our north across upsate NY today, but the track of this low and its upper level max is further south than in previous model runs, meaning that the band of snow expected for central New England has shifted south a bit into the far northern reaches of our viewing area, including Connecticut and some of NW New Jersey.

There is also a weak low over SE Viriginia which is responsible for some of the showers and t-storms currently showing up across SE Viriginia.

From the main clipper's low over Lake Superior, a cold front extends SWwrd from this low, the broad SW flow will warm temps at the surface across the Tri-State area today, so despite the fact that temps aloft and 1000-500mb thicknesses indicate snow for the city, much of the precip. will fall in the form of rain in the city thanks to the warm boundary layer.

By afternoon, the clipper is over western NY state, but the trough begins to go to a negative tilt and this will rapidly strengthen the weak surface low currently over SE Viriginia. Both the GFS and the NAM are now printing out over 1/4 of an inch of liquid this afternoon/evening for the city, most of it coming between Noon and 6pm or so. As the low at the coast rapidly develops, what is an empty radar should fill in fairly rapidly this midday across eastern PA and NJ and then that rain will track NEwrd as the coastal low moves NEwrd, and by this evening the main coastal low will have taken over as the main low, centered SE of the tip of LI by 7pm this evening. With cold air aloft and a negatively tilted trough, you can't rule out a rumble of thunder especially across central and south NJ where surface temps could be a bit milder, allowing for a little more surface instability. The precip. this afternoon will start as rain across western CT and the lower Hudson Valley and NW NJ as well, but the rain should come down hard enough to mix with and then changeover to wet snow in these areas before ending this evening as dry, cold NW flow wraps in on the low's backside.

I think we end with some wet snowflakes in the city from 6-8pm, but I also think the boundary layer will keep the accumulation from being a factor in the city. However, central and eastern Long Island will be a different story this evening as most of the computer models are consistent in showing heavier precip. across this area between 7pm and midnight and even though sfc temps in this area wil be jusut as warm (maybe even a bit warmer) than in the city itself, the heavier precip. will allow for more evaporational cooling, and I think a slushy coating to an inch of snow is possible for central and eastern Long Island. It may not get down to 32 the entire time it's snowing on LI this evening, but if the wet snow comes down hard enough and since it's after sunset, it'll manage to stick around somehat and leave a slushy accumulation anyway.

By late tonight the coastal low accelerates quickly NEwrd and we have a gusty, cold NW wind to contend with tonight and tomorrow. On Saturday, that cold NW wind continues as we still have a strong pressure gradient between high pressure over Hudson bay and the vortex over NE Canada.

The next storm system looks to arrive late Sunday and Sunday night, as the global models have trended a bit faster moving the precip. inot the city late Sunday. I feel that the strong jet ramming into the pacific NW this Sunday is causing the low (near Chicago by Sunday evening) to become more progressive as it comes NEwrd. A triple point low develops near the Delmarva on the occluded front Sunday PM. This low in tandem with high pressure over eastern Canada keeps our general flow easterly so we get cold air daming as the warm southerly flow aloft rides up and over the colder, denser surface cold air which is so tough to erode. This means problems N and NW of the city Sunday night with a wintry mix, and even in the city, sleet/freezing rain will be a concern. The storm moves offshore Monday, lingering flurries from the low's backside across LI are possible though we actually warm up a bit Monday though we dry slot and the flow becomes more SW at the surface eroding the cold air daming east of the mountains.

Bill Evans

thats why I dont understand the amounts the nws has for LI.1-3? 

Rgwp96, Walt Drag from NWS Taunton sent me an e-mail a few minutes ago -- here's his take for northwest NJ -- "midday event starts as rain but turns to heavy wet large flake snow and ideal dendritic growth. High terrain (1000') should see .05" rain then heavy snow for 1 to 3 hours somewhere in the noon to 5pm time frame. My guess is northwest NJ gets 2" to 3.5" of snow on grass/cars/trees/wires...possibly spot 5" if no rain and things line up right. Lower elevations more rain and much less snow".  Sounds like a highly localized and varied snowfall.

it sure sounds like an elevation snowstorm.  I may be far north here in dutchess county but i do not have elevation, so i wonder what i will get, temps are at about 23 degrees right now here in poughkeepsie, sounds like this will all be over by early evening? quick mover.

The possibility also exists that Long Island could get more snow as the storm intensefies to our southeast.

Vic, your location to the northeast of NYC, however, should line you up with more precip and snow. It looks like another tough/tough forecast as results may vary so much in the region, and that presumes the models are correct in the first place. Another nowcast event?

Dam, I'm only 784 ft. So I guess I'll have to drive to your house for dinner tonight if I want to see snow. LOL  ;D

Lab, the forecasts are splitting hairs it's so borderline and such a tough call, and this presumes the models are correct in the first place. It'll be a nowcast and I think changes will be made (up or down). As I posted earlier, Evans and the pros mets have a very good handle with their forecasts, but they're bound by the accuracy range of the models and available data given such marginal conditions. It will be interesting to see unfold.

LOL lab94 784 feet, try 164 feet here in poughkeepsie lol

yes a nowcast for sure.

I am already concentrating on sunday late into sunday nite, but it does not appear to be a big storm anymore, more of a over running thingy.

This Sun? I'm already for the event on 12/9/07 ;)

Vic, don't under-estimate the Sunday system. It could be a long duration event and could be pretty potent. Not saying that yet but definitely much potential.

cool robbbs!

i think the timing on this event today is very bad, seems like it will happen during the daytime hours and the sun angle being stronger might mean mainly wet conditions even if it is snowing

they have a snow advisory up for my area for 3 to 6 inches, i seriously doubt that.

To bad it did not happen at night. Im up to 37.5 already from 22.1 this morning  Dpt 23

Temps will begin to drop as the coastal starts to develop SE of Montauk Point and begins ushering down colder air from SE canada, not to mention areas under heavier precip (especially higher peaks) will be subject to dynamic cooling as heavier precip draws down colder air from aloft as well. Very interesting afternoon setting up. Certainly a nowcast situation.

John-- How much snow would you expect Eastern LI to get from this?

LIWEATHER -- It's way up in the air now. This is going to go into nowcast mode and still everyone will be clueless as I think radars are going to screw up royally tonight. I remember a similar situation to this one last year; radars were showing rain over the whole area when many areas were reporting snowfall, sometimes heavy (I believe it was in Feb as well). This was the same storm that robbbs told Snowshoe to "go to the HP mounment & find the snow" as the set-up was very strange. Highest peaks were getting heavy snow while some valley locales were getting rain/snow mix, but radar was showing rain and not a change in sight.

If anything, I would imagine eastern LI does decent compared to NYC and Central Jersey as Suffolk will be closer to the bombing low SE of Montauk Point; closer to the low means more precip available, which would mean cold air would be dragged down from SE Canada while precip would still be around and that precip (gets heavier as the storm bombs) would allow for dynamic cooling to set in.

No way to put out specific #'s as almost everybody is going to start off as rain during the onset.

Thanks for the explanation geek, if it starts as rain I would guess there is going to be some ice tonight with some snow on top of it making for a messy commute.

how much would u expect brooklyn to get?

Metsfan -- It's really up in the air. Where and when this coastal bombs out will dictate who gets what and when. Expect a nowcast.

ight,another nowcasting situation,we gonna be busy from this one to sunday event