12/5/2007 Clipper: Initial Estimates

[donsutherland1]

At this time, there are some differences between the bone-dry NAM and more moist GFS concerning the upcoming clipper. Right now, I believe the system's dynamics will enable it to squeeze out a narrow band of 1"-3" snows with some widely scattered 4" figures. My initial snowfall estimates are based on a compromise between the NAM and GFS, both of which I believe go too far in one direction or another with respect to qpf.

My initial snowfall estimates are:

Baltimore: 1"-2"
Hagerstown: 1"-3"
Harrisburg: 1" or less
Newark: 0.5" or less
Philadelphia: 1" or less
Pittsburgh: 1"-3"
Richmond: 0.5" or less
Washington, DC: DCA: 1"-2"; IAD: 1"-3"
Wilmington (DE): 1" or less

[RL3AO]

It is snowing heavier here then it ever did during Saturday's "real" storm. So far I'd say 1.5-2.0 inches have fallen from the clipper at my house, and we should easily get to the 3-4" forecast. Areas about 20 miles NW could approach 5-6".

Quite impressive for the first clipper of the year.

[donsutherland1]

Thanks RL3AO for the report on the clipper. The modeling seems to have responded downstream by making the system a little wetter.

[donsutherland1]

Overnight, the modeling continued to trend a little wetter with the clipper. As a result, I have added a little to my snowfall estimates to the north of system's track. A few areas will likely see 4" of snow.

My final estimates are as follows:

Baltimore: 1"-3"
Hagerstown: 1"-3"
Harrisburg: 1" or less
Newark: 1" or less
New York City: 0.5" or less
Philadelphia: 1"-2"
Pittsburgh: 1"-3"
Richmond: 0.5" or less
Washington, DC: DCA: 1"-3"; IAD: 1"-3"
Wilmington (DE): 1"-2"

[Category 5]

I'm right outside of philly. It's been snowing since 11am and we've got I'd say about .25"

It's snowing lightly right now still.

[RL3AO]

The spotter in my town said 3.8" for us. I'll agree with that. Not too bad for a clipper.

[tomboudreau]

Picked up almost 4.5 inches of snow just outside of Pittsburgh. That definitely isn't bad for a clipper type of system.

[brunota2003]

I got a friend in Bel Air, MD and she said they have 5 inches and counting.

[Category 5]

I finally measured it.

1" and still snowing lightly.

[Squarethecircle]

At least three inches here; the local forecaster guesstimated no more than one inch.

[Stephanie]

Maybe an inch by me. The streets have been treated and are wet. The way it was coming down though as I made my way up the Atlantic City Expressway, I would've sworn that it was going to be more. The snow started to stick to the road, but there were trucks out treating it.

I almost spun out trying to pull into a gas station near my house! I didn't slam on my brakes but tapped them and moved to the right. I fish tailed one way and then the other before I got her under control.

[Category 5]

Close call Steph, glad you're alright.

It just started sticking to the roads here about 2 hours ago, but it's just dusted in spots.

[Category 5]

The snow has ended.

Final total: 1.5"

You nailed it Don.

[tomboudreau]

NWS Pittsburgh measured 3.3". I have 4.5 at my house that I measured tonight. Skies are completely clear tonight, so radiational cooling is going to drop the temps greatly tonight. We are already down to 16 degrees tonight. Probably going to fall around just a few degrees either side of 10 tonight.

[donsutherland1]

Verification:

I underforecast the clipper's snowfall amounts in a number of cities. The worst forecasts concerned a line running from Hagerstown to Baltimore to Wilimington. I had taken a compromise between the NAM and GFS, under the assumption that both models were extreme (one too dry, the other too moist). The GFS had a very good idea.

From 12/4/2007 1:00 pm:
Baltimore: 1"-2"; Actual: 4.7"; Error: 2.7"
Hagerstown: 1"-3"; Actual: 5.5" (Smithsburg, MD); Error: 2.5"
Harrisburg: 1" or less; Actual: 1.4"; Error: 0.4"
Newark: 0.5" or less; Actual: 0.1"; Within range
Philadelphia: 1" or less; Actual: 1.6"; Error: 0.6:
Pittsburgh: 1"-3"; Actual: 3.3"; Error: 0.3"
Richmond: 0.5" or less; Actual: Trace; Within range
Washington, DC:
... DCA: 1"-2"; Actual: 2.6"; Error: 0.6"
...IAD: 1"-3"; Actual: 2.5"; Within range
Wilmington (DE): 1" or less; Actual: 4.0"; Error: 3.0"

From 12/5/2007 7:00 am:
Baltimore: 1"-3"; Actual: 4.7"; Error: 1.7"
Hagerstown: 1"-3"; Actual: 5.5" (Smithsburg, MD); Error: 2.5"
Harrisburg: 1" or less; Actual: 1.4"; Error: 0.4"
Newark: 1" or less; Actual: 0.1"; Within range
New York City: 0.5" or less; Actual: 0.3"; Within range
Philadelphia: 1"-2"; Actual: 1.6"; Within range
Pittsburgh: 1"-3"; Actual: 3.3"; Error: 0.3"
Richmond: 0.5" or less; Actual: Trace; Within range
Washington, DC:
...DCA: 1"-3"; Actual: 2.6"; Within range
...IAD: 1"-3"; Actual: 2.5"; Within range
Wilmington (DE): 1"-2"; Actual: 4.0"; Error: 2.0"

[ohiostorm]

I live in Hopewell just north of Pittsburgh near the airport and we got around 4". At my house in Ohio, my mom said she measured close to 5". And my brother goes to West Liberty State College near Wheeling and he had more then that. Pretty good clipper if I say so myself.

[Stephanie]

Close call Steph, glad you're alright.

It just started sticking to the roads here about 2 hours ago, but it's just dusted in spots.

Thanks! Now I had a flat tire when I got to the parking garage at work tonight... I think she knows that I'm going car shopping this weekend.

Anyway, we had about 2 inches of snow. It was very pretty. Kind of the type of snow that you always want to have - sticks to the branches and everything else, but not on the roads.