It was only a matter of time with the expected chill on the way.  You may have noticed the chilly winds Friday afternoon, but the core of the cold air will arrive Saturday night. At that point, the winds will settle down which will allow for maximum loss of daytime heat.  By Sunday morning, temperatures will drop to 32F or lower, essentially cutting off the growing season. This is the first reminder to take in the plants you want to save and also disconnect your garden hose. Should water freeze in the line, it can burst.  Also note, below is the Freeze Watch, meaning likely potential. A warning will be issued over the weekend when it can be guaranteed. Also, Frost Advisories are likely fill in many areas not shown at this time.

UPDATE: Freeze Warning For Sunday, Watch Monday

Screen Shot2015-10-16 15_06_37One parameter we use to measure temperatures in winter events is the thickness of the layer of air between 1000 and 500 mb. The classic ‘540’ line is 5400 meters, which correlates to support for snow in storms and freezing air at the ground.  Considering this is going to be a clear sky and calm wind event, temperatures are likely to drop quite a bit, especially in inland valley locations. Near the Bay and urban areas, the surroundings act as enough heat to delay the coldest of air.

Related: Average First Frost in Maryland-Map and charts


Freeze Watch: Notes below

Screen Shot2015-10-16 15_00_54

This ‘Watch’ issued Friday afternoon includes much of southern and central Pennsylvania, as well as the Maryland suburbs north of Baltimore and western mountains.  This is a typical colder region that often gets more snow in the winter because it is more rural, elevated, and away from the bay. I expect at least frosty conditions and advisories will be included for the rest of the counties west of the Bay, perhaps even into southern Maryland. Stay tuned…

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