Couple Things to Watch

Been a quiet few days after the New England Blizzard. I’m also in a transitional phase of life, moving from California to the East Coast starting next weekend. So apologies for that, though there hasn’t been much to talk about either. But let’s focus on a couple things. We have a couple main stories to discuss: A mixed precip event this week, followed by more cold, and then the potential for another major East Coast storm. Let’s look them over.

Messy Mix

The map to the left (click to enlarge) shows the precipitation type being forecast by the NAM model for Tuesday (credit Wxcaster.com: http://wxcaster.com/regional_snowfall.htm). The green is rain, purple/pink is sleet, red is freezing rain/ice, and blue is snow. Notice that as the precipitation moves in and through, especially across the higher terrain north and west of the Big Cities, it starts as an icy mix, before warmer air begins to gradually flood in, changing the mix to rain. The GFS shows a similar scenario, but with more precipitation. Total amounts range from about 1/3″ to 1/2″ liquid on average. So this won’t be a crippling storm, but there could be some localized nasty travel Tuesday and Tuesday night, especially in interior NW Connecticut, parts of NY State (especially south of Albany and north of the NJ border), and possible interior western Massachusetts. Some of the valleys further east in New England could also lock in the cold air at the ground a little longer and may see some localized issues. This looks more like an advisory level event rather than a warning level event. But keep it in mind if you’re traveling Tuesday or Tuesday night.

It will then stay rather cold heading through next weekend. The models seem to have backed off in the last couple days on how serious the cold will be, but it still looks relatively cold for the time being.

European model forecast for next weekend: Credit - http://raleighwx.americanwx.com

Then we have to watch the next area of concern. The map to your right is a forecast from this morning of the European model for next weekend. Yes, that’s a 976 mb low just east of Boston. The GFS model shows a lot of energy, but not quite the major storm scenario…for now. Both models have been showing some sort of storm possible in the Northeast around this timeframe for several runs now. What has to be watched is energy moving into the Western US later this week, likely bringing a quick bout of snow to the Intermountain Region and Rockies. As that progresses east, we’ll see if the pattern still looks ripe for storminess…but there’s a lot of energy around in the atmosphere starting late week or early weekend. This may be what is needed to generate the next round of excitement in the Northeast. Stay tuned.

————-

State of Occlusion is on Facebook! I’ll post some additional cool links, quick model status updates, and snow maps early on that page. “Like” the blog by clicking here!

Advertisements

Clipper Snowfall

Still looking at a volatile and challenging system for the Northeast tomorrow and Saturday. My first and final accumulation map is below:

Snowfall Forecast: Thursday Night-Saturday Evening (Click to enlarge)

There could still be some significant variability in the snow totals, especially in the area bounded by Syracuse-Albany-Worcester-Hartford-Newburgh, NY. Snow will move in tomorrow morning. From about Trenton, NJ south this looks to be a very low impact event. There may be a brief period of heavier snow to cause some havoc on roadways, but accumulation will be limited. The main area of impact for this storm should be the Catskills, Mohawk Valley, Adirondacks, Berkshires, Litchfield Hills, and perhaps parts of SW Connecticut and Long Island. The main event will wind down Friday evening, but lake enhancement will begin to deliver heavier snow to parts of Upstate NY through Saturday night, leading to the chance of higher amounts there. The Norlun trough effect could take over in Maine and southern New Hampshire Saturday night, leading to higher totals than advertised above (remember this map ends Saturday 7 PM). Max amounts could top off around 12″, with a few higher amounts, primarily in the mountains/upslope of Upstate NY courtesy of lake enhancement or pure lake effect.

Models continue to show a favorable pattern for a large storm for midweek next week. More on that after this system passes.

Select snow amounts through Saturday evening:

DC/Baltimore, MD: Trace
Philadelphia, PA: Coating-1″
Trenton, NJ: Coating-2″
New York City: 1-2″ average
Morristown, NJ: 1-3″
Bridgeport, CT: 2-5″
Syracuse, NY: 3-6″
Utica, NY: 4-8″
Albany, NY: 3-7″
Hartford, CT: 2-5″
Boston, MA: 1-3″

———–

Don’t forget, State of Occlusion is on Facebook! I’ll post some additional cool links and snow maps before they’re published here on that page. “Like” the blog by clicking here!

Norlun Troughs?

Going to get a little technical briefly. Going to put this pretty plainly: What’s coming Friday will more than likely not be forecasted very well. Why? We’re dealing with a phenomenon that’s pretty common in the Northeast in winter…it usually rears its ugly head at least once. We call this an inverted trough…Norlun trough…or instability trough. What is it? Well, typically, when you think of an atmospheric trough, you think of a “U” or “V” shaped pattern. In an inverted trough, this, well, inverts. It looks more like an upside down U. The lower pressure, or lower heights end up on the north side, rather than the south side. These sorts of setups can produce some nasty weather, heavy precipitation, and thunder.

Here’s more info on Norlun troughs (recognized in the 90s and named for the meteorologists who discovered it).
A technical paper on Norlun trough events.
And here’s more on inverted troughs.

So what’s it to you? Well, the models are beginning to hone in on how this storm on Friday and Saturday is going to behave. And they are indicating that an inverted/Norlun trough type setup may occur. The bottom line is that there will be snow. The question is twofold: Will the Norlun event occur, and if so, where will it setup? This morning’s models pegged it right over North Jersey and NYC. This evening it looks to be shifted a little further north. This is important, because outside of the Norlun trough there will be a generic sort of snowfall. But under the narrow Norlun trough, there should be significant snow, with the possibility of thundersnow and more.

Right now, the NAM model (a mesoscale, small scale, higher resolution model) is showing extremely heavy snow (and has on three straight runs today) for areas immediately north of NYC, Long Island, the Catskills, and the Western Mohawk Valley. The GFS model is suggesting this will be further north and east into New England and the Adirondacks.

Latest Snowfall Risk Assessment for Friday and Saturday

So my snow “assessment” has a broad area of potentially significant snow showing in red. I right now have this from about the Bronx, east-southeast into Long Island (yes, that places the division of snow vs. heavy snow within NYC). It stretches up into the western Hudson Valley, Catskills, western Mohawk Valley and southwestern Adirondacks. I also include much of southwest Connecticut as well, including Bridgeport and New Haven. The problem is that it’s next to impossible to pinpoint exactly where within this idealized zone the prolific snow will be. The yellow territory indicates the basic “cone of error” of sorts. I don’t foresee the risk of heavy snow shifting south of NYC much, if at all. The risk to me is clearly on the northern and eastern sides. This could shift further north, so the axis of the heavy snow stretches from Syracuse/Utica through Albany, the Berkshires, and Central Connecticut to the coast. And it could even shift further north too.

The heavy snow band will be awesome though, with extremely heavy rates of snow, likely some thunder, lightning, and whiteout conditions. I could see max amounts of 10-15″ in this band. You will only need to go a few miles from that core of heavy snow however to find amounts of 6″ or less…that’s the type of storm we’re looking at: Very narrow gradient, very sharp gradient, with extremely variable snowfall totals. Thus, this makes forecasting this system extremely difficult, if not impossible at this point. So if you live from NYC into Central New York and all of Southern New England, stay tuned. As I said, the forecasts for this will more than likely be challenging, vague, and possibly even wrong initially. But that’s the story.

Outside of the heavy snows, expect a brief period of maybe some heavy snow, with a coating or so, up to about 3″ in spots across much of NJ, PA and central New England. Closer to the heavy snow axis, there may be some 3-6″ amounts. But those will be isolated.

New model data indicating the possibility still of a major snowstorm Tuesday of next week. There are still a multitude of questions as to whether it will track in the sweet spot for a DC-Boston hit, as tonight’s GFS is showing, or if it will pass further south. More on that after this first event passes.

———–

Don’t forget, State of Occlusion is on Facebook! I’ll post some additional cool links and snow maps before they’re published here on that page. “Like” the blog by clicking here!

Quick Weekend Snow Risk Assessment

Not much to say beyond what was said yesterday. Just looking at the models today and going off past experience, I feel this first system Friday-Saturday is not going to be a backbreaker on a large scale. I think we’re dealing with a more localized storm in areas more suited to handle heavy/surprise snow…an Alberta Clipper system that starts to explosively develop off the New England coast, which may for some point carry one of my favorite descriptions: A ballistic clipper. These types of storms can really hammer areas north of I-80 if the situation is right.

Snowfall Risk Assessment for the Northeast Friday-Saturday (Click to enlarge)

So anywhere from about Rochester or Syracuse eastward is fair game for this possibly overachieving. Right now, I think the odds of the “clipper” overachieving are highest in the Catskills, but this could easily be extended north toward the Mohawk Valley or even the southern Adirondacks and Berkshires. The secondary area is where the intense coastal development will take place, which is off the Massachusetts coast, possibly putting Portsmouth, Boston, Providence, and Cape Cod under the gun for a period of heavy snow. I’m non-commital on that area though, and more enthused with the idea of parts of the interior being “surprised” by this. For now, you can see my highest risk areas. These may be expanded or contracted later. Additionally, the area of 3″ accumulating snow could end up pushing a little further south, but if I lived south of I-195 in Jersey, I wouldn’t be too concerned or enthused for snow at this point. I think this first event will be primarily a north of I-80/east of I-81 storm. I’ll keep you posted.

We still have this other system showing up on the models for midweek next week, and that one I’m still not writing off or committing to at this point…but I will say, given recent model trends and the overall pattern, it would make sense that someone will see a significant winter storm for the middle of next week. Stay tuned.

———–

Don’t forget, State of Occlusion is on Facebook! I’ll post some additional cool links and snow maps before they’re published here on that page. “Like” the blog by clicking here!

First Winter Storm of 2010-2011 in the East

I’ve always been a fan of out of season snow events. That’s not to say that mid-October is out of season in the mountains of New York and New England, but it still feels awfully early, especially when it was 102 degrees inland here in SoCal yesterday. Still it looks favorable that somewhere in the Southern Greens, Berkshires, or eastern Adirondacks above 2,000′ or so is going to end up with a pretty decent amount of early season snow. This is always an issue because with the nor’easter, you’re also going to have wind and with the water content of the snow high, this is a perfect recipe for power outages, downed tree limbs, etc.  Fortunately these are fairly sparsely populated areas being impacted. Additionally, this storm looks to dump a lot of rain. It looks like 1-3″ of rain on average from Eastern NY into New England. Should be a pretty dynamic storm to say the least.

There might be another brief  dose of wintry type weather, possibly some early season lake effect precipitation, as we go into next week. Either way, it looks cooler than it has been in the East.

What will be interesting is whether this is just another nor’easter or hinting at what could be a favored storm track heading into the cool season. Very often, these early storms prelude what ends up happening…not to say that this is, but it is at least worth noting. One major difference between this nor’easter and what was seen much of last year is that the heavy precip from this will fall in New England (last autumn and winter, this was displaced much further south). This is something we’ll have to keep an eye on going forward.

Winter Storm Watch for the mountains of NY, MA and VT (NWS Burlington has a policy to not issue watches just for their mountains, but the spine of the Greens could get spanked in this storm).

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE ALBANY NY
412 PM EDT THU OCT 14 2010

MAZ001-NYZ032-033-042-047-051-058-063-082-VTZ013-014-151000-
/O.NEW.KALY.WS.A.0008.101015T1200Z-101016T2200Z/
NORTHERN BERKSHIRE-NORTHERN HERKIMER-HAMILTON-NORTHERN WARREN-
SCHOHARIE-WESTERN ALBANY-WESTERN GREENE-WESTERN ULSTER-
NORTHERN FULTON-BENNINGTON-WESTERN WINDHAM-
INCLUDING THE CITIES OF...PITTSFIELD...NORTH ADAMS...ATWELL...
BIG MOOSE...EAGLE BAY...MCKEEVER...NOBLEBORO...NORTHWOOD...
OLD FORGE...SPECULATOR...WARRENSBURG...COBLESKILL...MIDDLEBURGH...
ALTAMONT...HUNTER...TANNERSVILLE...WINDHAM...SUNDOWN...
ELLENVILLE...WOODSTOCK...WEST HURLEY...KERHONKSON...NAPANOCH...
PHOENICIA...NORTHVILLE...MAYFIELD...BENNINGTON...JACKSONVILLE...
NEWFANE
412 PM EDT THU OCT 14 2010

...WINTER STORM WATCH IN EFFECT FROM FRIDAY MORNING THROUGH
SATURDAY AFTERNOON...

THE NATIONAL WEATHER SERVICE IN ALBANY HAS ISSUED A WINTER STORM
WATCH FOR ELEVATIONS ABOVE 2000 FEET...WHICH IS IN EFFECT FROM
FRIDAY MORNING THROUGH SATURDAY AFTERNOON ACROSS THE SOUTHERN
ADIRONDACKS...NORTHEAST CATSKILLS...AND HELDERBERGS...THE
SOUTHERN GREEN MOUNTAINS...AND NORTHERN BERKSHIRES.

RAIN IS EXPECTED TO MIX WITH...AND EVENTUALLY CHANGE TO WET SNOW
ACROSS HIGHER ELEVATIONS WITHIN THE WATCH AREA...BEGINNING FRIDAY
MORNING ACROSS THE SOUTHERN ADIRONDACKS AND NORTHEAST
CATSKILLS...AND ACROSS THE SOUTHERN GREEN MOUNTAINS AND NORTHERN
BERKSHIRES FRIDAY AFTERNOON. PERIODS OF SNOW...POSSIBLY HEAVY AT
TIMES...WILL CONTINUE INTO FRIDAY NIGHT...BEFORE GRADUALLY
TAPERING OFF SATURDAY.

THE POTENTIAL EXISTS FOR SNOWFALL ACCUMULATIONS OF 7 INCHES OR
GREATER WITHIN THE WATCH AREA. THE WEIGHT OF WET SNOW MAY BRING
DOWN TREE LIMBS...ESPECIALLY IN AREAS WHERE LEAVES REMAIN. THIS
MAY RESULT IN SOME POWER OUTAGES.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT
SNOW...SLEET...OR ICE ACCUMULATIONS THAT MAY IMPACT TRAVEL.
CONTINUE TO MONITOR THE LATEST FORECASTS.