There is going to be a storm. That mystery has been solved and the season that has eluded much of Maryland and the Mid Atlantic will go out with a bang. This storm still has many on edge and a little confused what to expect. So please read my notes here in my attempt to break it down for you so you get what you expect. I have been sharing my thoughts already on my Facebook Page, for a few days, here is where I can put them all together. Don’t be fooled by the sunny mild day today, heavy snow arriving overnight will erase that away for many.
Before I go any further, all due respect to the Capital Weather Gang for their hard work in DC and credit for naming this storm Snowquester. Sorry Weather Channel, this one is fits better.
Two issues that may be lost here and something I hope you consider when grading me on my forecast:
1) Regardless of how much snow sticks and piles up by you, even if roads are wet, the heavy snow falling will make it tough to see.
2) Winds will gust 30-40 + mph. This will be a very wet and sloppy snow that can stick on trees and power lines. There will be power outages.
See a history of notable March Snowstorms to get you in the mood.
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Quick Highlights:
· This storm will be impressive and generate its own cold air. So mild temps in the mid 30s will be beaten down by heavy snow rates of 1"-2"/hour. Thundersnow is possible as the forcing air with cyclogenesis (a new storm forming). That could really dump on some areas.
· Rain then turning to snow will arrive west of the Bay between 2-6 am Wed. Places near the Bay may stay wet.
· Stickage: This is the most opportune time to get the snow to lay and stay. There may be a coating to a few inches of snow on the ground by 7 am. During the day roads will be wet unless you get in the 1"/Hr snow rates.
· Getting a layer of snow to lay and stay before sunrise WILL MAKE A HUGE DIFFERENCE for the rest of the storm after sunrise. It will allow more to stick on grass AND Hold temps down.
· There will be a battle all day between snow intensity and temps near or just above freezing. Heavier snowfall at times will briefly drop the temps. Lighter intensity could mix with rain. But there will be snow falling and melting at the same time closer to the Chesapeake Bay.
· I mentioned 10"+ yesterday and I still think that will well within reach for some that stay all snow.
· Regardless of how much accumulates, the heavy snowfall in the afternoon will make it difficult to see at times. Travel will be impacted.
· Winds will gust 30-40 mph in the afternoon and evening. The heavy wet snow may stick on trees and powerlines and lead to outages. BGE brought in 500 out of state crews to support their crews. They expect power loss for over 100,000 people during this event.
The Canadian Model supports the theory that after the intense snow passes, warmer air will have this end as snow. See that compared to the NAM Model in the video clip below.
More forecast images and my final call for snowfall map can be found in the slide show. Details behind my thoughts can be found below. This is to cater to fellow meteorologists and enthusiasts.
The main point will be a marine layer near the Bay. Much higher snow amounts will fall away from the water. But watch the wind direction. Turning more to the north will bring in the colder air sooner, and could result in higher totals. My snow map is at the end of the slide show.
Weather Geek Stuff:
Rather than get too elaborate about blocking patterns and the wide view, here is just the basics from the extracted data centered on BWI that support snow. Note that the low ratios will be close to 8:1 vs. the normal 10:1. That means a better chance that 1 inch of liquid would equal 8 inches of snow instead of the normal 10 inches.
That said, check this out:
Storm Total Precip for BWI:
NAM Model = 1.96”
GFS Model = 0.90”
The NAM tends to have a high bias, but a blend between the two still brings in a lot of moisture. Then accounting for low ratios and some melting, the 10 inch mark is still within reach. Especially away from the warmer Bay. A difference of 2 degrees can result in another 6 inches or more of accumulation.
Other support from the extracted data:
Thickness parameters between 1000 mb to 500 mb all stay below the critical 540 dm mark. Breaking that down further
1000 mb- 850 mb stays below 1300 m for the entire storm
850 mb – 700 mb stays below 1540 m for the entire storm.
These both support snow.
Temperatures:
The surface temperatures are projected to be
NAM: 32F-35F
GFS: 35F-36F
The mild air will be just at the surface.
1000 ft above the ground and higher it stays below freezing. That is why higher elevations will be cold enough for much higher snow totals.
Surface Wind:
They start out from the northeast and turn to the due north or northwest during the storm. This limits the influence of the marine layer.
Lifting or rising air:
The NAM shows shows a 700mb vertical velocity of 13.1 ub/s. That is SCREAMING and supports convection late morning. So between 10 am and 1 pm, there could be thunder heard if you are lucky.
Note that fast rising air increases precipitation, which in turn would drag down colder air from the clouds. That is Dynamic Cooling.
Basically this all spells out a heavy snow storm, but the surface air could melt and waste many flakes. That is why elevation and proximity to the water will be critical. The final totals could very well be an additional 6 inches or more just 20-30 miles. Either way, this will be as much fun as a challenge to track.
Please read My Winter Forecasting Manifesto for my forecasting philosophy. For reference and other Baltimore snow history, see these weather pages on my web site justinweather.com.
• Winter Weather Precipitation
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