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: