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November 2014

Winter Storm Threat: November 26 (Final Call)

Well, the model trends over the last 24 hours were not in the direction I though they were going to go, so I had to cut back the forecast along I-95 and make some smaller adjustments on the western edges of the contours. Overall, things have shifted slightly warmer across much of northern VA, DC, MD, NJ and southeastern PA in areas near and west of I-95. With such marginal temperatures of 33-36F at the surface, snowfall rates will be the big thing to watch tomorrow to see who will cash in and who will get stuck with little or nothing. Sloppy, wet snow for the major population centers along and near I-95.

20141126_MAsnow_final

The difference between 4 inches and 8 inches within that contour range will be elevation. Lower elevations can expect totals closer to 4-6 inches, with the higher elevations getting more into the 6-8 inch range. Along the Blue Ridge and Central Appalachians, a few of the higher peaks could hit 8+ inches. I didn’t include it on the map, but I wouldn’t be that surprised if there was one or two reports of 8+ inches in the highest elevations of north-central MD.

Some of the models even show some sleet mixing in, mostly from far northeastern MD into southeastern PA and NJ. That may actually be a blessing in disguise, as sleet can accumulate more easily than snow in marginal temperature situations, and a base of sleet would make it easier for any snow afterward to stick.

Forecast confidence remains on the low side, mostly with the eastern edge of the contours where the rain/snow/mix is the most problematic. A one or two degree change to the surface temperature could mean a big difference for some areas, both to the high side and the low side. There’s also still the question of where the best banding will set up, which will produce the heavier rates and increase the chance for higher accumulations for a select few. My best guess for that is just inside the eastern edge of the 4-8 inch contour up into the 8-12 inch contour.

Perhaps if we can get some big, fat dendrites cascading down along I-95, then that area could actually get a decent accumulation. However, looking at the temperature profiles, that seems pretty unlikely.

Winter Storm Threat: November 26 (Initial Call)

A hectic day before Thanksgiving is in store for many in the Mid-Atlantic and Northeast. Toughest challenges are 1) finding that crucial rain/snow line, and 2) honing in on QPF totals, especially when considering the deformation band that’s expected. It will be a heavy, wet snow that will at least initially struggle to accumulate on the roads. Expecting it to start as rain around the greater D.C. region, changing over to snow in the mid-to-late morning hours.

20141126_MAsnow_initial

Best confidence is for places 20-30 miles north+west of I-95 and points west. Western edges could shift a decent amount still from the MD/WV Panhandles into PA, depending on the storm track. There’s high bust potential in both directions along the I-95 corridor, where heavy snow rates will battle against marginal surface temperatures of 33-35 degrees.

New Page: NWS Snow Maps

For years, the NWS snow forecast maps have been sometimes hard to find and inconsistent from WFO to WFO. I decided that it’s time for one web site that has links to ALL of the NWS snow forecast maps across the CONUS.

I also displayed many of the Mid-Atlantic maps directly on the page for one-stop browsing. They were chosen because I am currently D.C./Mid-Atlantic focused, and they suit my needs the most.

At the moment, I have the Northeast and Mid-Atlantic offices completed. I will hopefully have the rest done by the end of the week (at which point I will update this post).

http://madusweather.com/nws-snow-maps/

Enjoy!