Wednesday, March 21, 2018

What changed and what's next? 
SHORT TERM UPDATE FOR 8 am - 12 pm WED 3/21
7:30 AM 3/21 - WHAT CHANGED, WHY AND HOW MUCH TO GO? The attached image above is an 18-hour projection from the NOAA Short Range model depicting latest additional snowfall expected through 8 PM today. Current radar below, and below is our analysis.

Like you, we were expecting widespread snow cover from DC on north to Baltimore and east to Annapolis by now. So why not? Many areas north of I-70 and above the 695 beltway have the snow, but not what was expected. Despite the overnight timing, the reality of two back-to-back Lows obviously created a gap in precipitation that:
  • Lasted longer than forecast, and should close up by 8 AM;
  • Allowed for a warm pulse of air to embed in the lower levels overnight right where snow usually forms (around 5000 feet);
  • As seen on radar, the heavier snow pushed north of I-70 and stayed in place, whereas south of I-70 to DC, gaps opened up and allowed temps to drop, making for a glaze on most untreated surfaces. 
  • Oddly enough, snow cover would have been easier to manage, as slush can be handled better by tires and plows than a sudden glaze of ice. So where the snow cover *did not* occur as forecasted -- we are seeing the crashes and road closures more so than it seems areas with more snow cover.

WHEN WILL SNOW REALLY START TO CRANK? (For those in Frederick, Carroll, northern Baltimore, Harford and southern PA, it's more like .. when will this END??)

  1. The second system is approaching the southern Bay, and will bring bands of heavy snow north through late morning. 
  2. This next round of snow will pickup quickly and fill the radar in completely across the region. Though fighting sun angle and delayed onset, snowfall rates could reach 1/2" an hour by mid morning.
  3. The "No Bag Wearing" totals of 18-24" may not be realized, but between now and 6 PM tonight - 10" north of I-70 is very probable at 80% likelihood, south of I-70, up to 7" is possible in heavier bands with 4-5" very probable once snow resumes this morning.
Enclosed image is from the free sample graphics at if you sign up for a 7-day trial, go to Premium, then models, and then hunt for the HRRR 3 km page, you'll find it eventually,
like today's snow, that we hope will eventually find you. If not, I'll get that bag ready.

- Forecaster Foot and the FF Maryland Team


Westsidehideaway said...

Huge flakes and road sticking in West Bmore at 9:15am.

the married guy said...

Harford County snowing hard as heck. Looked at the radar, no end in sight.

Unknown said...

Not much snow to report in North East Bel Air Md. Mostly sleet/freezing rain thru the night & this morning. Transition to all snow started between 10:30 & 11:Am. Hope this keeps up & we get descent snow total before it's all over.

Butch Dynomite said...

Similar in Parkville but snowing harder now

Westsidehideaway said...

Snow hard at 1pm in West Bmore. Busses stopped running. Looks like 3-4 inches so far.

Rebecca said...

It was just beautiful...So glad we got 1 good snow. (And beyond thrilled to share it with Foot's team and all of you)