December 19-20, 2004 Event: Snow & Brief Shot of Bitter

[donsutherland1]

At 8 am EST, barometric pressures were beginning to fall across southeastern North Carolina and since then they have moved to northeastern North Carolina.

For watching such developments: .

Interestingly, this might be just a tad further south than had been modeled.

Overall, this system should ride northeastward and then develop at an increasing rate as it moves through the waters off the Mid-Atlantic region. However, its track will likely be too far offshore to bring the major Metropolitan areas from Washington, DC to New York City the chance of a significant snowfall. Strong cold air advection from the north should also help create a sharp boundary between areas that receive accumulating snow and those that do not.

One should also expect that the push of Arctic air will probably be stronger than modeled. For example, here are select comparisons of 12z temperatures and those forecast by the MAV:

Chicago: 5° vs. Forecast: 8°
Detroit: 6° vs. Forecast: 16°
Toledo: 10° vs. Forecast: 18°

Overall, in terms of temperatures, I expect the following for select cities tomorrow:

Boston: Falling into the teens during the latter part of the morning
New York City: 16° during the morning
Philadelphia: 17° during the morning
Washington, DC: 20° during the morning

New York City’s afternoon temperature may reach no higher than 22° and Boston may stay in the teens during most or all of the afternoon. Wind chills will be harsh.

My final ideas on the snowfall, which represent generally small adjustments that assume somewhat of a deformation zone to develop across eastern Connecticut, Rhode Island, eastern Massachusetts, and possibly easternmost Long Island:

Boston: 3” – 6”
Cape Cod: 4” – 8”
Greenwich: Coating to 1”
Montauk Point: 1” – 3”
New Haven: 1” – 2”
New York City: Coating to 1”
Newark: Coating to 1”
Philadelphia: Coating
Providence: 3” – 6”
White Plains: Near 1”

[PurdueWx80]

One should also expect that the push of Arctic air will probably be stronger than modeled. For example, here are select comparisons of 12z temperatures and those forecast by the MAV:

Chicago: 5° vs. Forecast: 8°
Detroit: 6° vs. Forecast: 16°
Toledo: 10° vs. Forecast: 18°

MOS values are from 6-9 degrees too warm here as well, w/ the Eta being the worst.

[Dave C]

This should be an interesting event for SE New England. We don't have many storms that have falling temps during storm period. With winds north or nw bringing in the colder air, temps should fall steadily except more slowly on the cape with a rain to snow scenerio there. Also, the potential ocean enhancement if winds have a little east of due north flow here in extreme east Mass. Too bad I have to work tom. am, would be fun to post updates on the board as the storm plays out.

[Terry]

Thanks for this heads-up on the colder than expected temps for Boston, Don.
I've warned my son to get ready....... Ouch. That will be a cold one for a Florida native.

[donsutherland1]

Terry,

The wind chills will be even worse. They could be subzero during the afternoon and early evening hours.

[donsutherland1]

Given later model guidance and trends, most notably a continuing south and westward shift of the modeled location for heaviest QPF, I’ve been compelled to adjust my figures for estimated snowfall an additional time.

Questions that remain include:
• Whether the continuing southwestward shift in the expected axis of heaviest snow will continue, leading to lesser amounts in Boston, Cape Cod, Providence, and possibly at Montauk Point
• Whether this continuing trend could put the heaviest axis of snowfall across northern New Jersey, southeastern New York, and southwestern Connecticut

Anticipated amounts are as follows:

Boston: 2” – 4”
Cape Cod: 2” – 4”
Greenwich: 1” – 3”
Montauk Point: 2” – 4”
New Haven: 2” – 4”
New York City: 1” – 2”
Newark: 1” – 2”
Philadelphia: Coating to 1”
Providence: 2” – 4”
White Plains: 1” – 3”

Just for perspective, the following are the lowest and highest estimates I had for each city:

Boston: Lowest: 2” – 4”; Highest: 3” – 6”
Cape Cod: Lowest: 2” – 4”; Highest: 4” – 8”
Greenwich: Lowest: Coating; Highest: 1” – 3”
Montauk Point: Lowest: 1” – 2”; Highest: 2” – 4”
New Haven: Lowest: Up to 1”; Highest: 2” – 4”
New York City: Lowest: No more than a coating; Highest: 1” – 2”
Newark: Lowest: No more than a coating; Highest: 1” – 2”
Philadelphia: Lowest: No more than a coating; Highest: Coating to 1”
Providence: Lowest: 2” – 4”; Highest: 3” – 6”
White Plains: Lowest: No more than a coating; Highest: 1” – 3”

The following idea on temperatures remains unchanged:

Overall, in terms of temperatures, I expect the following for select cities tomorrow:

Boston: Falling into the teens during the latter part of the morning
New York City: 16° during the morning
Philadelphia: 17° during the morning
Washington, DC: 20° during the morning

New York City’s afternoon temperature may reach no higher than 22° and Boston may stay in the teens during most or all of the afternoon. Wind chills will be harsh.

The 12z MAV numbers have trended downward:

Boston: Temperature down to 22° by early afternoon and holding nearly steady during the afternoon
New York City: 15° during the morning; 20° for the afternoon high
Philadelphia: 19° during the morning
Washington, DC: 20° during the morning

I still believe Boston and Philadelphia may be somewhat colder than the MAV guidance with Boston falling into the teens and likely remaining there most or all of the afternoon.

[donsutherland1]

Temperature Update: 10 pm Readings for Select Cities:

Boston: 39°
New York City: 26°
Philadelphia: 24°
Washington, DC: 22°

18z MAV Figures for Morning Lows:

Boston: 22°
New York City: 17°
Philadelphia: 19°
Washington, DC: 23°

With temperatures behind the front generally having fallen 25° to 30° from earlier highs across parts of central Pennsylvania and western New York, I expect the morning low temperature to fall below all of these figures in each of the above cities. Boston's readings should fall into the teens by the afternoon and then remain there for most or all of the afternoon. It should be noted that Washington, DC (DCA) has already fallen below the low progged by the MAV guidance.

[donsutherland1]

This morning's lows included:

Boston: 15° (had fallen as low as 14° early this afternoon)
New York City: 11°
Philadelphia: 10°
Washington, DC: 11°

Just as happened in parts of the Ohio Valley/Great Lakes region yesterday, the MAV guidance busted badly. Even this morning's 6z MAV understated this morning's cold by a few degrees in NYC, PHL, and DCA. It was off by more than 5° for Boston.