Saturday storm: A little snow, a little mix, a little rain – no big deal on balance

December 12, 2013

A little storm will pass through the region on Saturday, producing a mixed bag of precipitation. Right now, it does not have the look of a major winter storm, but more of a nuisance event for the immediate metro region. From western Montgomery County to Loudoun County and to the northwest, the storm may have a somewhat greater impact. Overall, I view it as a poor man’s version of last Sunday’s snow, ice and rain event with fewer disruptions.

“I’m sure not impressed with the potential for much winter weather in and around the Beltway,” says Wes Junker, our winter weather expert. “Our far western areas still could see and inch or two but even that is no sure thing.”

How the storm may play out

* Areas of light snow may develop early to mid- Saturday morning, gradually mixing with sleet and/or rain as the morning wears on in the metro region. Less than 1 inch of snow and sleet is most likely in the D.C. area, with perhaps a bit more in western Montgomery, Loudoun, and Frederick counties where the changeover to a wintry mix may be delayed (and colder temperatures would better allow accumulation).

GFS simulation of precipitation at 7 a.m. Saturday (WeatherBell.com)
GFS simulation of precipitation at 7 a.m. Saturday (WeatherBell.com)

* On Saturday afternoon, it’s mostly cold rain in the metro region, but a wintry mix may hang on in western Montgomery, Loudoun, and Frederick counties.


GFS simulation of precipitation at 1 p.m. Sunday (WeatherBell.com)

* A cold rain falls in most of the metro region Saturday evening, but pockets of freezing rain may linger in western Loudoun and Frederick counties, and especially west into the Shenandoah Valley and near the 1-81 corridor. Precipitation gradually winds down after midnight.


GFS model simulation of precipitation at 7 p.m. Saturday evening (WeatherBell.com)

An important note: Sometimes in these kinds of setups, cold air hangs around a little longer than models indicate. So there is some risk snow and/or ice lingers in the metro region longer than we’ve indicated. However, the cold air source for this storm is not as strong as last Sunday’s …so we expect the impact from frozen precipitation to be less. We will refine this forecast tomorrow.

Snow amounts

The National Weather Service forecast office in Sterling, Virginia – on its excellent winter weather page – developed this nifty table which I think does a good job describing the chances of different amounts of snow at various locations across the region.


Snowfall possibilities Saturday (National Weather Service)

The bottom line is that D.C. has just about a 10 percent chance of an inch or more, but if you head out to Frederick, there’s about a 60 percent chance of an inch or more.

For a regional glance at snowfall chances, see the maps below showing the odds of at least one inch and four inches of snow – also from the National Weather Service.


Chance of at least 1 inch of snow Saturday (National Weather Service)

Chance of at least 4 inches of snow Saturday (National Weather Service)

Note that while this storm isn’t likely to produce a sprawling area of heavy amounts (exceeding four inches), it does have a good chance to produce at least an inch of snow over a sizable region spanning Ohio through much of New England Saturday into Saturday night (with some hefty amounts in interior New York state). Keep that in mind if traveling.

Ice amounts

Unlike the storm last Sunday night, significant icing is not expected in the immediate D.C. area since temperatures will rise above freezing by mid-late Saturday morning or early afternoon. However, out towards the Shenandoah Valley, a glaze of ice is a legitimate possibility. The map below – from the National Weather Service – shows the chances of at least 0.1″ of ice.


Chance of at least one-tenth of an inch of ice Saturday and Saturday night (National Weather Service)

Other views

Computer models are in reasonably good agreement as to how this will evolve and most forecasters are more or less on the same page with respect to this storm’s impacts. Of course, the devil is always in the details with respect to the storm’s exact timing, precipitation types, and amounts.

The National Weather Service forecast office in Sterling offers these thoughts on the storm for the D.C. area and surrounding region:

MUCH OF THE PRECIPITATION AT THE ONSET LATE FRIDAY NIGHT INTO SATURDAY MORNING WILL LIKELY BE IN THE FORM OF SNOW. THEREAFTER...EXPECT SNOW TO TRANSITION TO RAIN BUT HOW FAR NORTHWEST THE RAIN/SNOW LINE MAKES IT /AND WHEN/ IS IN QUESTION. IN ADDITION...ITS POSSIBLE THAT WARMER AIR ALOFT MAKES IT PRETTY FAR NORTHWEST THROUGH THE CWA BUT WITH A COLD WEDGE SURFACE TEMPERATURES MAY HAVE TROUBLE RISING ABOVE FREEZING THROUGH THE SHENANDOAH VALLEY. THEREFORE IN ADDITION TO SNOW THERE COULD BE SOME ICING ISSUES.

See below forecast summary maps from WxRisk.com meteorologist Dave Tolleris and AccuWeather – both of which look good to me, more or less consistent with our thoughts.


Precipitation forecast from Dave Tolleris (WxRisk.com on Facebook)

AccuWeather forecast for snowfall this weekend (AccuWeather.com)

Bottom line

Around the D.C. area, if there is any slick travel Saturday, it’s most likely to be in the morning and probably concentrated in the colder suburbs. As the afternoon wears on and into the evening, this is probably more of a cold rain storm, except in western Loudoun and Frederick counties and out towards the Shenandoah Valley.

Jason is currently the Washington Post’s weather editor. A native Washingtonian, Jason has been a weather enthusiast since age 10.
Comments
Show Comments
Most Read Local
Next Story
Jason Samenow · December 12, 2013