January 29-31, 2010 Mid-Atlantic Winter Storm...

Discussion...
Here is the final snow map for the storm. For the folks that saw our scenario map last night, we essentially made no deviations on it and went with the traditional 1-3, 3-6, and 6-12 ranges. Models remain in good agreement with respect to precipitation area placement and QPF. The GEFS and NAM place the heaviest QPF along the NC/VA border, with potential for between 1.25-1.50. It is here we decided to opt for placement of an isolated higher zone of 12-16 (for the potential of a few locations getting over a foot), but overall, still expecting most locations to fall within the range of 6-12.

Potential Issues:
First... Precipitation shield placement and track remains the main issue with respect to northern extent. Our map involves DC on the edge of 1-3 inches, while leaving Baltimore outside this range with the idea they stay under an inch. It continues to be a possibility that the precipitation shield penetrates further north bringing light accumulations north of a line from D.C. to Cape May County NJ, however given the amount of cold and dry air in place, we expect precipitation to have a very hard time reaching the ground with only light QPF forecasted to reach this area. Hence, we think amounts stay under an inch, however, will need to keep an eye today on the high-res models and radar trends.

Second... Another possible issue if the storm does come a bit further north would be dry slotting knocking storm totals down in the southern parts of the accumulation area, as the main deformation axis would set up further north. In addition, this would also increase the potential for some sleet to mix in across the far south, which would also slightly lower amounts. At the present time, think the only area that stands a chance at mixing is across immediate coastal areas near the vicinity of Virginia Beach.

Other than the slight possibility of either of these issues, this continues to be a high confidence forecast by us, with very little change implemented from 24 hours ago.

..GLUNT/EGAN.. 1/29/10