Sunday December 15 2019

A Winter Weather Advisory has been issued for the northern and western half of the region for Monday morning. This goes along classic lines father inland away form the big cities and warming from the Chesapeake Bay. We will all get snow, and it arrives early. But the places likely to have temperatures below freezing and impact on the roads are in the shaded counties below.

Winter Weather Advisory

Two Parts: Morning Snow, Late Day and Evening Ice

There are two model simulations sliders below. The show the early arrival of snow, then a lull. Northern areas are likely to remain near or below freezing while the second wave

School Impact?

I don’t make the school call, but if I was a betting man I would suggest this:  It will be snowing when the call is made.  It’s after a weekend and the last week before holiday break. If there is ever a time to be lenient on expecting icy roads and delaying school, this would be it in the counties with a Winter Weather Advisory.

A delay is what to aim for first, then maybe reevaluation. The northern Maryland and southern Pennsylvania advisory zones should get in on freezing rain later in the day. The impact on roads are likely as it gets dark after 4:30 PM. Evening activities might be canceled there.

However, this does not apply to all areas.  In Maryland the school decisions are county wide. The advisories below highlight the split in counties such as:

  • Western Montgomery and Howard, plus northern Baltimore and Harford Counties: It is possible you have wet roads by you, but other parts of your county are slick. This could be one of those days.
  • Southern PA: will be in the thick of the frozen zone with snow in the morning and ice later in the day.
  • Baltimore City, Anne Arundel, Cecil County and back to Prince Georges are on the edge of 50% chance of roads getting some stickage before daybreak. But likely staying wet closer to the water.

Compare To My Original Call

The NWS Advisory does allow for 1 to 3 inches of snow

I’ve fixed the icing to include ‘Through Evening‘.


Evening Set Up

Morning Snow

HRRR Model —> slider

This model brings in the snow even earlier. It could begin between 1 AM and 3 AM

The Freezing Line before sunrise will be about 5 to 10 miles inland from I-95. HRRR Model and NAM 3 Km are in agreement.
This is the best bet for road sitckage. It’s possible heavier burst could get some pavement coverage when above freezing, but it will be less likely closer to the Bay.
HRRR Model
NAM 3 Km Model
Freezing Rain Late Day and Evening
The NAM 3 Km Model here shows the morning snow, then the lull.
The freezing rain will develop after 3 or 4 PM and intensity in the evening. This will be a case with more icing in the dark of night after 5 PM. I would limit driving in northern counties of Maryland and southern PA where temps hold below freezing.
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I will be up in the morning to start updates after 4 AM

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Winter Outlook Series:

My Call For Snowfall Winter 2019-2020





Snowy Winters Following A Hot and Dry September


NOAA Winter Outlook Leaves Room For More Snow With Mild ‘Seasonal Average’ Temperatures

Other  Links:

See the maps for when we normally expect the first frost in this link.

Baltimore Weather At BWI May Not Be As Hot As Reported

Construction at the airport close to the weather station may be added artificial heat. Click here or the image for the details.



Was Your County Not Included?

Click this map for more on the regional forecast zones


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