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Winter Storm Threat: March 20-21 (Only/Final Call)

Lots of uncertainty with this setup given that 1) surface temperatures are marginal, 2) mixed precipitation could greatly reduce snow/sleet totals depending on how far north+west the mixing line goes, 3) precipitation rates fighting daytime sun both Tuesday and Wednesday, 4) it’s actually two waves creating snow Tuesday night through Wednesday.

There’s going to be a lot of variability, but the corridor of 4-8″+ has the highest confidence based on the factors listed above. Anyone in the less than 4″ contours could see notable local variances based on elevation and where the best snow bands set up both Tuesday and Wednesday. Tuesday will be more elevation dependent than Wednesday, and banding will be the more significant factor Tuesday night into Wednesday.

Snowfall Verification for Jan 21

This was an interesting one to watch unfold…

 
Cold air damming allowed for more snow at the onset of the storm than what I was expecting, which resulted in broader 1-2 inch coverage east of the mountains in central VA, MD, DC and southern NJ. This also allowed the freezing rain and sleet to work a bit further south. The back end of the system also had a surprise up its sleeve, bringing up to seven inches of snow to the Pittsburgh area. The snow underperformed a bit along the southern edge in the mountains where warmer temperatures led to more mixing and plain old rain.

The higher snow totals were captured pretty well for the most part, especially along the southern edges of the 2-4 inch and 4-8 inch contours. The pink indicates areas that received 0.1-0.25+ inches of sleet and/or freezing rain (which was a bit trickier to contour due to the nature of the reports).

I knew the snow was a bit of a risk in the CAD region, but I didn’t pull the trigger on it and ended up paying for it. I’m going to give this forecast a grade of B-… the northern areas were quite good, but the southern areas suffered a bit.

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I have a new map design that I will roll out during the next snow event. On top of being a larger image, it also has county lines and interstates for easier interpretation.

Winter Storm Threat: Jan 21 (final call)

Following a southern trend of the models and recent temperature verifications compared to earlier forecasts, I have come up with this for my final forecast:

 
The pink contour indicates where 0.1-0.25+ inches of accumulating sleet and freezing rain is possible.

Some sleet will mix into the areas receiving over an inch of snow, and some freezing rain is also possible in the 1-2 inch snow contour.

Start time of the event was expanded earlier to better account for the precipitation in the western edge of the map.

Snow Threat: Jan 20-21 (final call)

Final map… probably 90% the same, with some tweaks to the snowfall gradient in West Virginia, extent of 4-8″ in the west, small adjustment north in northern Virginia and small adjustment south along the coast.

Added a HHMM timestamp (GMT/UTC time) on the issuance time because it seemed warranted. Hopefully this is the final version for awhile, but I might consider adding one more contour for the mixing/under an inch area.

 

Snow Threat: Jan 20-21 (first call)

Another fun storm is upon us as we head into the end of the work week. Mixing will be a huge issue in Northern Virginia, DC and areas south. Ultimately, I expect DC to stay in snow for most of the event. While the QPF for this storm isn’t terribly impressive, higher snowfall ratios will be available further north and west, which will make areas of 4-8″ possible. The risk is mainly to the lower side along the southern edges of the contours.

 
Expect a final call either this evening or early tomorrow.

The “So Close” Storm of December 2010 (18th-20th)

As this potential snow storm begins to materialize in the Southeast, it’s time to take a serious look at snowfall predictions. This storm appeared to be going out to sea at the start of this week, then for a couple of days it looked like the I-95 corridor would land a rare epic La NiƱa snowstorm along the East Coast. Unfortunately for the snow lovers of the East, the models are converging on a system that heads out to sea (OTS), with a quick snow dump over southern Virginia and a wintry mix in the Carolinas before sweeping northeastwards tantalizingly-close to the coast. The coastal areas of New England also have a shot at some snow.

Most of the precipitation will be off the coast, giving the fish a good time while the snow lovers despair over what could have been. At one point, 6-12 inches along the I-95 corridor seemed like a possibility. Now they’ll be lucky to get a dusting. Northern New England could get some backlash snow from this system after the 20th when the system tries to retrograde back to the west.

Here’s an estimate of what this system will put down on the 18th through the 20th (Sat-Mon):