We got about three inches of snow at my place before it changed over to sleet around 1am. It later changed over to a sleet and freezing rain mix. I’m not ultimately sure what type of ice accretions we got because I had to go to work early in the morning, but it was glazing badly as I left in the 6:00 hour. Seeing reports from around the area, this was a bust for most everyone in terms of snowfall and only out towards Fredneck did any real snow fall. My place seems to fall in line with those who are just northwest of I95 and those directly on it seemed to get 2.5 inches. The biggest bust in my forecast was northeastern MD, which seems to have only got about four inches. FAIL.

Totals:

Here’s the low as it fully formed:

As for the reason for the bust, the storm formed and tracked further west still from where both I and the models thought it would be and it tracked through eastern North Carolina and over the Norfolk area. In the morning it went just west of the mouth of the Chesapeake and on up over top of the Delmarva before exiting off the Delaware coast. Later in the afternoon it crossed Long Island. My understanding is that this was a bust for Philly to NYC to Boston too due to this track. I believe official forecasts were for snow to be measured in feet for those cities. FAIL.

Here’s what was the official forecast for New York City:

Here’s what it had changed to all of five hours later:


As for model performance, none of them got it right, but last night’s 0z NAM and Canadian forecasted the track correctly, but the storm had basically formed at that point so it shouldn’t have been that difficult. Not surprisingly, the 0z GFS still tracked the storm wrong and incredibly, so did the 06z GFS after the coastal had definitively fully formed. The fairly reliable (in the fist eight hours) HRRR indicated a colder solution in the middle of the night last night and that the mix would change back over to snow early in the morning and this was wrong too. The track on some model runs only a couple of days ago that took it well east were very wrong inside a time frame that is supposed to see improvement and further proof there’s still a long way to go to perfect the models. This after additional data from flights in the Atlantic were ingested into the models over the past couple of days to ensure forecast track and I’m sure additional weather balloon data too. FAIL.

The temperature did stay below freezing at my place for the duration of the precipitation heavy enough for accumulation, so I’ll give my forecast (and the models) that. It went below freezing at 9:05PM last night and went back above at 11:05am. Win.

Also to note: In one of the most perplexing things I’ve ever seen our local National Weather Service do, they dropped the Winter Storm Warning and put in a Winter Weather Advisory around 4:30am. I’ve never seen this in my ~32 years of watching the watches and warnings when there is ongoing heavy precipitation and the temperature is below freezing and not expected to go above, although they do it all the time when temps go above freezing. A winter storm warning is supposed to be 5 inches or more of snow or sleet within a 12 hour period, or enough ice accumulation to cause damage to trees or power lines, or a combination of both snow, ice and wind. We were certainly getting the combination of snow, ice and wind and were forecasted to through at least mid-day (the five inches of snow requirement has never counted when there’s mixing of icing). It was so odd, I had to go to the local NWS page to make sure they hadn’t changed the definition (they haven’t): http://www.weather.gov/lwx/WarningsDefined. I was completely baffled, but then I saw this article here and am thinking since they already had decided it was a fail before the storm started, they just went ahead and downgraded it regardless.

Later during the morning, tree limbs being down were reported everywhere. Here’s one in Canton that is on my drive to work:

Also to note: Only two weeks ago it was loudly declared by the CWG spring had arrived way early and that it could/would be an early record breaking cherry blossom year. A conveniently non-paywalled Washington Post article highlights this:

A couple of days later the NPS officially said the festival will kickoff tomorrow:

Now they’re saying they could be 90% dead:

LOL. Oops. FAIL.

The biggest threat of the season is almost here and already virtually all of the weather outlets have downsized their predictions pointing to a bust scenario being more likely. Currently the National Weather Service believes 5-7 inches will fall in Baltimore and 4-6 inches in DC:

This is because significant mixing with sleet is being portrayed by the models due to their belief the storm is going to directly hug the coast now as it passes by us. Here’s a loop from the High Resolution Rapid Refresh (HRRR) model showing an extended period of sleet for I95 in the Mid-Atlantic. This is one such possibility, but usually the sleet band is slightly thinner than what is being portrayed:

But there’s still room for both boom and bust – the first flurries started flying around 6pm in the Baltimore area, a solid three hours ahead of model forecasts, so already the storm is behaving a little different than expected. It may mean nothing, but no storm has ever gone exactly as a model predicted even at event time. And interestingly, the “expect at least this much” (10 percentile) and “potential for this much” (90 percentile) graphics have changed to both lower and raise totals across the area.

The 10 percentile graphic shows nothing for the I95 corridor now:

But the 90 percentile graphic shows an even larger area of 18+ inches intersecting with the Baltimore City line:

So while the National Weather Service has lowered expectations overall, there’s actually more uncertainty in their forecast than there was yesterday.

As for the models, the 12z euro gave 7 inches down the I95 line:

The 18z GFS gives 4-6 inches:

The 12z Canadian gives big amounts, but much of this is sleet being translated as snow on the map:

As for my forecast if I could change it, I would downsize too with a few inches of snow followed by significant sleet. Wednesday is going to be very cold behind this system with temperatures not getting above freezing, a rarity for mid-March. That’s all I’ve got.

I issue a final forecast 24 hours prior to the beginning of an anticipated snow storm. Beyond that is just nowcasting IMO.

  • Directly along I95 from DC to Baltimore: 4-8 inches with the lighter amounts the further south/east one lives
  • North and west of I95 from Owings Mills to Rockville to Centreville: 8-12 inches
  • Northeastern MD (Harford and Cecil counties): 9-13 inches
  • Southern Anne Arundel county, southern and eastern PG county, north, central and western Charles County: 2-4 inches
  • Southeastern Charles, Calvert, and St. Mary’s counties: 0-2 inches

There’s no real changes in amounts or my thought process from my previous forecast. It’s a certainty that schools will be closed everywhere Tuesday except southern MD given the hype. As for OPM, I’m not sure what their thinking will be. Timing of first snow flakes will be sometime between just after rush hour Monday and prior to 11pm. Heaviest precipitation rates will be between midnight¬†and 8am Tuesday and in those spots where it is snowing, rates could be two inches per hour or slightly higher for several hours.

A storm like this makes me happy I’m not a professional meteorologist. The issues noted in my previous post could lead to a very sharp gradient of snow totals and it’s within the realm of possibility that gradient could be quite large. It’s possible that someone somewhere along the I95 corridor ends up with a few inches of slush while someone 5 miles to the north and west as the crow flies receives 18 inches, although I don’t think the difference will ultimately be that dramatic over such a short distance. The 12z GFS showed no mixing of precipitation for the I95 corridor and the 18z was very similar:

But I find it unlikely to be entirely snow for everyone except southern MD like it shows. Our local National Weather Service agrees that mixing is a distinct possibility over the I95 corridor:

The 12z Canadian showed sleet for a time along the I95 corridor and I find that to be the most likely scenario and sleet would cut down on the accumulation totals:

The 12z euro gave 8-10 inches over the I95 corridor, because it was the strongest bomb of them all with its coastal front overtaking the I95 corridor as well:

Additional Notes:

  • Even if the moderate snow totals in my forecast were to verify, it still wouldn’t bring this winter up to normal snow fall. The map below shows the paltry snow for our area this winter down at the bottom.

  • As with any storm undergoing bombogenesis, thundersnow is possible. I wouldn’t be surprised if there are a couple of reports on social media of thunder being heard if the bombing occurs like the models say it will.
  • If an area of convective snow breaks out in our area, I wouldn’t be surprised if the National Weather Service upgraded to a blizzard warning. Right now most of the models keep the wind gusts just under blizzard criteria, but convection would bring stronger winds down to the surface. This scenario (where the NWS was originally not going to issue blizzard warnings, but then had to) happened in the third blizzard of the 2009-2010 season. The 12z euro’s wind gusts would meet blizzard criteria for portions of the area if snow were falling.
  • I finally bought a semi-professional weather station a few weeks ago when AcuRite had a good deal going. I figured today was as good as any day to set it up with the possible snow storm coming. It’s supposed to be able to connect to weather underground but the wunderground site is giving me no response when trying to create a site. I’ll try again tomorrow, but I’m not concerned whether it’s on wunderground or not.

For the record, the local NWS “most likely” scenario at the time of this writing (6:00pm, 03/12) is:

And the “expect at least this much” and “potential for this much” are: