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snow

Winter Storm Threat: April 2 (Only/Final Call)

Almost didn’t make a snow map for this event, but I like the novelty of an April snow. At least most of the snow will fall during the early AM hours on the 2nd, so there won’t be much of the Sun’s rays to kill the rates in the Mid-Atlantic. However, precipitation starts as rain south of the 40N line, and is all rain by the time you get to D.C. and points south. Surface wet-bulb temperatures will be above freezing within the southern edge of the 2″ or less zone, which along with warm ground temperatures will drastically cut into snow totals.

I would certainly think that risks run toward getting less snowfall than forecast rather than getting more. I could see a few spots on the southern edge getting more, especially in the higher elevations, if rates can be really heavy for a few hours.

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.

Winter Storm Threat: February 17-18 (Only/Final Call)

A nail-biter between warming low-to-mid level air and marginal temperatures/wet bulbs at the surface. At least the Sun won’t be fighting most people during most of this event from D.C. northeastward.

Biggest uncertainty lies with snowfall rates, especially in areas that have marginal wet bulb temperatures at or above freezing (i.e. anywhere south of the Frederick, MD to Philadelphia line, generally speaking). That wet bulb freezing line has also been creeping further north than what I had anticipated when looking at the setup over the past few days. We’ll see it the wet bulb temperature or the snow/sleet rates win.

Winter Storm Threat: January 3-4 (Only/Final Call)

Not too often we get a good coastal storm without a notable blocking pattern in the Atlantic, but here we are.

Emphasis on the “coastal” part. Without the blocking pattern in the Atlantic, there isn’t much to shove the coastal storm more inland, so what’s left is a mostly I-95-and-east event for the Mid-Atlantic. What’s not shown on the map is the wind, and boy is it going to get windy during the tail end of the storm and beyond. Some power outages are likely in the 4-8″+ zone. As the system departs the Mid-Atlantic, gusts behind it will kick up to the 30-40+ mph range, so look out for blowing snow and drifts across the roads!

There’s definitely going to be some mixing issues in far eastern North Carolina and perhaps briefly around Virginia Beach and the far southeastern Delmarva Peninsula, but other than that, we’re looking at full-on snow.

Winter Storm Threat: March 13-14 (Final Call)

The wintry mix of snow, sleet, and rain appears to be creeping closer to I-95 on the models, so I tightened up the gradient a bit to reflect lower totals from D.C. to Baltimore. The same is true for Long Island, and could be true for eastern New Jersey and New York City as well.

On the flip side, higher QPF across most of Pennsylvania into northern New Jersey and eastern Upstate New York increased the snow total forecast for these areas. Some small increases also occurred along the Appalachians.

Highest risk is still how far north and west the sleet/rain mixing line gets tonight, which could cut deeply into totals along I-95. Once you get far enough north and west and enter the “safe zone” where no mixing is expected, locally higher snow totals are possible.

Oh yeah, and don’t forget about those winds, especially along the coast. Gonna be fun.

Winter Storm Threat: March 13-14 (Initial Call)

As has been the pattern of recent Marches, we in the Mid-Atlantic find ourselves with a late-season snow storm that contains significant snowfall. While the storm evolution may not be classic, it seems that we will see a fairly common snowfall distribution, with the highest snow totals hitting mostly north and west of I-95 while areas south and east see more of a rain and a wintry mix.

The two main questions are where the rain/snow line ends up, and how warm will the surface temperatures be when the snow is falling. For the D.C. to Philadelphia corridor, this will mean a lot. The models differ on just how cold it is along the I-95 corridor as the precipitation is falling, which is where most of the uncertainty with this forecast lies.

The QPF is also a bit of an issue, but taking a model blend seems to be the best way to go at this point. I wouldn’t count hugely on anomalous pockets of minimal QPF, and I’m sure there will be some area that gets sweet deformation banding and ends up with more snow than expected.