December 18-20, 2008 Storm: Quick Thoughts

[donsutherland1]

At this time, I am increasingly confident that a complex storm system where a strong low tracks across Michigan and another reforms along the Mid-Atlantic Coast will bring parts of southern Ontario, New York State, and New England their biggest snowfall of the winter so far. Farther south, the Mid-Atlantic region's old nemesis (which shows up quite well on the 500 mb GFS ensemble mean anomalies) will likely ruin things.



Given the overrunning signature and the expected evolution of the systems, my guess is that the boundary from little or now snow to a significant accumulation will be quite narrow. Hence, a small difference in the track--50 miles or so--could make the difference for some cities between little snow to a sizable accumulation. My guess is that while NYC could see several inches of snow before a changeover to sleet and rain, the proverbial equal chances of much less or much more applies there.

For now, my early thinking is as follows:

High Risk: 6" or More (10" or more is possible in many of those cities):
Albany, Boston, Concord, Hartford, Portland, Providence, Poughkeepsie, Toronto, Westfield (MA), Worcester

High Risk: 4" or More; Moderate Risk: 6" or More:
Binghamton, Burlington, Ottawa, White Plains

Some Chance: 4" or More:
Montreal, New York City

[tropicana]

yay! im glad you posted , i really love your predictions. Environment Canada has latched on to this storm system and it certainly appears Southern Ontario is in for a duzzy of a snowstorm for Friday, they used the term "snow-mageddon" in their special weather statement. It wasn't meant to alarm anyone, but taken into account we just had a significant snowfall last night that dropped up to 11cm of snow ( near 6 inches) in spots, and with this major new storm on the way that could produce up to 20cm of snow ( 10 inches) , along with severe blowing and drifting snow, creating whiteouts and low visibility, and even another snowstorm of similar consequences on Sunday into Monday.

Additionally, they are taking into account how heavily populated this area of Ontario is, particularly areas like Toronto, and the time of the year. This is one of the busiest shopping weekends of the year coming up, and this Friday is supposedly one of the busiest "visa" shopping days of the year when the most transactions are recorded. Furthermore, the week before christmas is one of biggest travel times of the year, whether by plane, train or automobile. All of these methods of transportation will be severely hampered on Friday, and long delays or cancellations are likely at Pearson Airport in Toronto.

-justin-

[Stephanie]

It's great to see your forecast, Don.

[donsutherland1]

Thanks Stephanie and Tropicana.

[donsutherland1]

After considering some of the trends in the GFS guidance, I suspect that locations that could see just a little snowfall or a lot of snowfall will include Greenwich, Newark, New York, and White Plains. A small shift in the track and/or the timing of the changeover will make a significant difference as to how much snow falls at those locations. Considering the latest information, along with a degree of winter storm climatology for December, my initial snowfall estimates are as follows:

Albany: 5"-10"
Allentown: 2"-4"
Boston: 6"-12"
Concord: 5"-10"
Danbury: 6"-12"
Detroit: 5"-10"
Hartford: 6"-12"
New York City: 2"-4"
Newark: 2"-4"
Providence: 6"-12"
Scranton: 5"-10"
Toronto: 4"-8" (10.2 cm-20.3 cm)
Westfield: 6"-12"
White Plains: 4"-8"
Worcester: 6"-12"

Whether the 12z Euro agrees with the 12z NAM or 12z GFS could add further insight into whether the colder NAM or warmer GFS solution is more likely to verify. There remain some sizable differences between the two models.

Given the model differences and the large difference a small shift in the track can make, I will likely offer a revised estimate at some point tonight.

[Category 5]

Great work as always Don.

[Stephanie]

Looking forward to the update.

[srainhoutx]

Looking forward to your 00Z's update. I have always have enjoyed your analysis Don. NE friends with travel plans are getting concerned.

[donsutherland1]

With the latest NAM trending ever so slightly cooler and the northward trend seeming to have stopped on the 18z GFS, I have greater confidence in the storm's track. I believe that New York City could see quite a spread in accumulations from around 2" in Queens to near 6" in the north Bronx.

My final estimates are as follows:

Albany: 6"-12"
Allentown: 3"-6"
Binghamton: 7"-14"
Boston: 6"-12"
Concord: 5"-10"
Danbury: 6"-12"
Detroit: 5"-10"
Hamilton, Ontario: 5"-10" (12.7 cm-25.4 cm)
Hartford: 6"-12"
New York City: 3"-6"
Newark: 2"-4"
Portland: 3"-6"
Providence: 7"-14"
Scranton: 5"-10"
Toronto: 4"-8" (10.2 cm-20.3 cm)
Westfield, MA: 6"-12"
White Plains: 6"-12"
Worcester: 6"-12"

[donsutherland1]

Thanks Srainhoutx.

[Ed Mahmoud]

If the 0Z NAM is right, I think BOS is closer to 10 to 15 inches. About an inch of liquid equivalent, and 850 mb temps around -10ºC High relative humidities. I think better than the normal 10:1 fluff ratio.

Not sure about the immediate coast with an onshore wind for a time, but the general NYC area looks like it may have some sleet, as there is a spread between the 1000-500 mb, 1000-700 mb thicknesses and the 850 mb freezing line between about lunch and dinner.

East Coast NAM loop from PSU e-Wall.

[Stephanie]

Quite an active pattern for the northern tier of the US through next week. Those poor people in New England can't catch a break. All of that ice and now all of the snow that you've forecasted.

The ski resorts are loving it, I'll bet!

We're still on the warm side and will probably be for tomorrow night's and maybe Christmas Eve. I hope we get a little snow for Christmas (no ice, thank you).

[Nimbus]

00 GFS 24 hour precipitation charts look interesting heaviest NE accumulation looks to be near the coast.

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 4_066m.gif

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 4_072m.gif

[jinftl]

Boston may see some melting of the snowpack by mid-week but with even more snow possible sunday night, a white christmas looks likely.

[Nimbus]

The models continue trending colder so areas like Portland and Augusta Maine should see a foot or more of snow. Don't know where the rain snow line will occur in Boston but areas like Needham west of 128 could see over a foot as well.

[Stephanie]

Freezing rain right now in Southwestern New Jersey. We're under a Winter Weather advisory until 11:00 am. We've been stuck between 31 or 32 degrees. It's supposed to go over freezing today, but I'm afraid of the re-freeze we'll have overnight. The highs tomorrow are only going to be in the upper 20's with 20 - 30 mph winds.

[donsutherland1]

Verification:

From 12/18/2008 12:58 pm:
Albany: 5"-10"; Actual: 11.3"; Error: 1.3"
Allentown: 2"-4"; Actual: 2.8"; Within range
Boston: 6"-12"; Actual: 12.5"; Error: 0.5"
Concord: 5"-10"; Actual: 8.3"; Within range
Danbury: 6"-12"; Actual: 8.5"; Within range
Detroit: 5"-10"; Actual: 7.9"; Within range
Hartford: 6"-12"; Actual: 9.4"; Within range
New York City: 2"-4"; Actual: 4.5"; Error: 0.5"
Newark: 2"-4"; Actual: 5.4"; Error: 1.4"
Providence: 6"-12"; Actual: 9.8"; Within range
Scranton: 5"-10"; Actual: 7.4"; Within range
Toronto: 4"-8" (10.2 cm-20.3 cm); Actual: 6.1" (15.4 cm); Within range
Westfield, MA: 6"-12"; Actual: 12.0"; Within range
White Plains: 4"-8"; Actual: 6.0"; Within range
Worcester: 6"-12"; Actual: 14.1"; Error: 2.1"

From 12/18/2008 10:34 pm:
Albany: 6"-12"; Actual: 11.3"; Within range
Allentown: 3"-6"; Actual: 2.8"; Error: 0.2"
Binghamton: 7"-14"; Actual: 6.4"; Error: 0.6"
Boston: 6"-12"; Actual: 12.5"; Error: 0.5"
Concord: 5"-10"; Actual: 8.3"; Within range
Danbury: 6"-12"; Actual: 8.5"; Within range
Detroit: 5"-10"; Actual: 7.9"; Within range
Hamilton, Ontario: 5"-10" (12.7 cm-25.4 cm); Actual: 6.2" (15.8 cm)
Hartford: 6"-12"; Actual: 9.4"; Within range
New York City: 3"-6"; Actual: 4.5"; Within range
Newark: 2"-4"; Actual: 5.4"; Error: 1.4"
Portland: 3"-6"; Actual: 6.5"; Error: 0.5"
Providence: 7"-14"; Actual: 9.8"; Within range
Scranton: 5"-10"; Actual: 7.4"; Within range
Toronto: 4"-8" (10.2 cm-20.3 cm); Actual: 6.1" (15.4 cm)
Westfield, MA: 6"-12"; Actual: 12.0"; Within range
White Plains: 6"-12"; Actual: 6.0"; Within range
Worcester: 6"-12"; Actual: 14.1"; Error: 2.1"

[vbhoutex]

Good job as usual Don!! Wish you had to do those for our area!!! Well, I probably really don't, but one fantasy snowfall would be good. I am already surprised at our winter here in Texas. We have now had two december winter precip events in SE TX, which I don't remember happening in the 37 years I've been in Houston. If the -NAO comes to fruition we may see more.

[Stephanie]

You just want the snow David, NOT the ice!

Don's estimates for snow depth are usually spot on.

[vbhoutex]

You just want the snow David, NOT the ice!

Don's estimates for snow depth are usually spot on.

Exactly!!!We hate ice down here as much as anyone else does. Texans or for tha tmatter Southerners have enough trouble driving well on dry roads, much less ice covered roads!!