December 10 2019

A Winter Weather Advisory has been issued for parts of central Maryland from NWS in Sterling VA. This will be effective between 2 AM and 8 AM for snow of 1 to 2 inches, with spots over 1000 Ft up to 3 inches. This area will drop below freezing, so slippery roads likely in the morning.

Note: This only covers that local National Weather Service Office. Southern PA should be added from the State College office next. There could be some impact closer to Baltimore at daybreak

My Initial Map

This looks a lot like my map I showed last night. There will be more affected as I will highlight below, so stand by for the counties to expand.

Notes and Questions

Why was my county not included?  

Advisories are based on National Weather Service Zones. See more on that here.

Can it snow when temps are above freezing?

Yes! Plus the colder the clouds and snowflakes, the longer the flakes can survive to the ground and even overcome the warmer ground to start stickage and accumulation.

Can snow stick on the roads after a rainy day in the 50s?

Yes! The colder rain and then snow this evening will help cool the pavement. Also, snow falling at night has a better chance to stick. Faster intensity can increase the likelihood for snow sticking to the roads even when above 32ºF. That is why I expect some slippery roads are possible for metro Baltimore and even the Eastern Shore during the morning.

Will there be school?

Most likely yes, but a delay is possible. School delay is most likely in the zone where the advisory has been issued:

Maryland: Washington, Frederick, Montgomery, Howard, Carroll, Baltimore, and Harford.

Pennsylvania: Adams, York, and Lancaster possible delay as well.

Weather Set Up

The rain and warms temps this afternoon will transition to snow tonight. This system is moving a little faster and it will have some impact on our region’s travel. The good news is that this will be happening a little sooner.  So the changeover for suburbs west of Baltimore will happen between 9 PM and midnight. Then gradually cross through central Maryland.

Water Vapor Satellite

The flow of moisture from east Texas through the Ohio Valley is strong.

Jet Streak = Energy Surge Tonight

The winds and energy at jet stream level will produce focused areas of faster winds called jet streaks. This is what should enhance the snow after midnight across central Maryland and southern PA.

Snow Timeline This Evening —> slider

The timing on the models continues to speed up. The snow may begin to show up between 8 PM and Midnight in western suburbs.

Temperatures at 7 AM

NEW SNOW MAP

I will post any update maps this evening.

FITF

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