Interesting Morning Snow Plume Updates

UPDATE March 5th: We've expanded our snow map into New England, as it now looks like the GFS was right that a pocket of energy will rotate around the storm as it ends. The NCEP Plumes' snowfall means went UP in amounts overnight, but then came back down this morning for the stations that I looked at:

(SHD = Shenandoah, VA; FDK = Frederick, MD).

This storm is going to be a tough forecast. This animation of the SREF Ensembles snowfall (contours) and forecast confidence (colors) illustrates two things: 1.) The movement and morphing nature of the snowfall and 2.) The lack of confidence in this forecast for the eastern area.

UPDATE: The next round (09Z) of plumes has upped D.C. & Shenandoah from 10" to 12" mean, with a pretty even distribution. In Philipsburg however, it has dropped the mean from 5 to 2.5, with the distro on the low end. Maybe that previous run was a fluke for Central PA!

ORIGINAL POST: A major snow storm is coming to the mid-Atlantic; our latest snowfall projection is shown here, as of Monday morning. For updates, stay tuned to this news story.

I saw some interesting things on the overnight (03Z) "NCEP Snow Plume" data; points are discussed below (from bottom to to top). This data represents two sets of "ensemble" forecasts from the ARW & NMM high-res models.

Shenandoah, VA had the largest amounts I could find, with forecasts averaging at 11 inches with a range of 0 to 30 inches. (I usually say that AccuWeather goes too low for their highest snow range on the map, but this time I don't see that a breakdown inside the "12 inches +" area is warranted). Washington, D.C. wasn't too far behind, with 9.5" mean and 1-22" range. However, the area over a foot is going to be quite limited, if you believe these Ensembles. Note that, if you go too far SW from Shenandoah, amounts drop off quickly (Roanoke mean is 2" with 4" at Hot Springs) because the 850 mb low goes north of there (something that was reflected in our morning map update above).

Amounts in Pennsylvania are way over-performing compared to maps I've seen. York (THV) comes in at 9 inches with a rage of 0-20" on these plumes. Even In Philipsburg, PA (just NW of here), where AccuWeather has us in the 1-2" range, the mean plume forecast is over 6 inches, and as many members are above as below. This is much higher than most forecasts I have seen for this area, and may be due to some models dragging the storm too far north. We'll just have to wait and see.