Capital Weather Gang's first snowfall projection for Saturday.

* Winter weather advisory north and west of the District from 7 a.m. to 7 p.m. Saturday *

10:15 p.m — Forecast on track. Watch out for brief burst of snow early Saturday. Then mixed precipitation in the afternoon.

High-resolution models continue to support the idea of a very brief shot of snow early Saturday morning, moving through the region from southwest to northeast between about 6 and 10 a.m. The snow may briefly come down at a good clip and, with temperatures in the 20s, stick to untreated surfaces. However, it shouldn’t last more than an hour or two, which is only enough time to drop a dusting to an inch in most areas.


HRRR radar simulation between 5 a.m. and 11 a.m. Saturday.

Then, we should get a pause in the precipitation before a round of rain and, in colder areas, freezing rain between mid-afternoon and early evening as spelled out in detail below.

We’ll be back with updates starting at 5 a.m. Saturday.

2:00 p.m. — Winter weather advisory issued north and west of the District Saturday


The National Weather Service has issued a winter weather advisory mainly for locations just west of Interstate 95 on Saturday from 7 a.m. to 7 p.m. The advisory includes Fairfax and Montgomery counties but does not include the District (although a bit of snow and ice is still possible here).

In Washington’s immediate north and west suburbs, the advisory calls for up to an inch of snow and 0.1 inches of ice. For counties adjacent to the Mason Dixon line in northern Maryland, it’s calling for 1 to 3 inches of snow as well as 0.1 inches of ice.

Original article

A minor winter weather event will make for a messy Saturday around the Washington region, producing a mix of light snow and ice and, in milder parts of the region, rain.

Cold air streaming into the region ahead of this event means road surfaces will be cold enough for frozen precipitation to stick, especially on Saturday morning and even through the afternoon, in colder parts of the region north and west of downtown Washington.

However, precipitation will generally be light, and there is likely to be a midday pause when you can safely get around. Snow amounts should mostly range between a dusting and an inch while a light glaze of ice could fall on top of the snow in our colder areas.

“Despite the precipitation generally being light, untreated road surfaces and walkways could become slick especially in pockets of steadier precipitation,” said Wes Junker, Capital Weather Gang’s winter weather expert.

Precipitation timing and temperatures

Precipitation is likely to come in two waves, starting with snow early Saturday morning and then, following a pause, more of a mix of sleet, freezing rain, and rain in the afternoon and early evening.

Light snow could sweep through the region starting between 5 a.m. and 8 a.m. and ending between 8 a.m. and 11 a.m., from southwest to northeast, with temperatures in the 20s. The snow probably won’t last longer than a couple of hours in most locations.


HRRR model shows a fast-moving band of snow passing through the Washington region between the early and midmorning hours Saturday.

Then, most models suggest a pause in precipitation between mid- to late morning and midday or early afternoon, when temperatures rise to near freezing or a little above along and east of Interstate 95.

The second round of precipitation is most likely to start in the early afternoon and midafternoon Saturday and end in the early evening. In this round, sleet and freezing rain is most likely north and west of I-95, with more rain along and east of the interstate. Most precipitation should end between about 6 p.m. and 8 p.m. from west to east.


The NAM model shows mixed precipitation and rain passing through the Washington region between early afternoon and early evening Saturday.

During the second wave of precipitation, temperatures should range from around freezing or a little above along and east of I-95, and around freezing or a little below to the west.

After the precipitation ends, temperatures should remain steady or perhaps rise a bit, so we don’t expect a hard refreeze overnight, although freezing temperatures and slick conditions could linger in the colder parts of the region.


Forecast temperatures from the NAM model during the day and night Saturday.

Amounts

Snow/sleet

Because the first wave of snow will be so short-lived, just a dusting to an inch or so is most probable. Some models suggest the snow may miss our southern areas, south of Fairfax and Prince George’s County, where a dusting or less is most possible.

The band of snow may be a bit more pronounced and long-lived toward northern Maryland, where up to a couple of inches could fall.

Here are forecast amounts for the District, from different models:

  • High-resolution NAM: Dusting
  • Canadian: 0.1 inches
  • High-resolution Canadian: 0.3 inches
  • NAM: 0.5 inches
  • HRRR: 0.5 inches
  • European: 0.6 inches
  • American (GFS): 0.7 inches

Freezing rain

During the second wave of precipitation in the afternoon into the early evening, a light glaze of freezing rain is possible, mainly west and north of the Beltway. Generally 0.01 to 0.1 inches is possible, but we cannot rule out up to 0.2 inches or so in some of the colder pockets in upper Montgomery, western Loudoun and Frederick (Md.) counties.


Forecast ice accumulation Saturday, mostly between midday and early evening. (National Weather Service)

Inside the Beltway, a little freezing rain is possible (before changing to plain rain), especially on elevated surfaces and tree limbs, but we expect temperatures at the ground to rise enough that most ice should not accumulate.

Impacts

Untreated roads could briefly turn slick and snow-covered from the initial wave of snow passing by early to mid-Saturday morning over a large part of the region, except in our far southern areas, including Southern Maryland and Stafford County.

During the second wave of mixed precipitation (sleet, freezing rain and rain), temperatures may just be cold enough for untreated roads and sidewalks to be a concern in areas west of I-95. Temperatures should rise to freezing or a little above along and east of I-95.

If the warmer computer model forecasts are right, there’s even some chance that our colder areas west of I-95 warm above freezing and see little impact from the second wave, with more rain falling than freezing rain. However, we lean toward the colder model forecasts.

On Capital Weather Gang’s winter storm impact scale, this event rates as a Category 1 or “nuisance” event for areas west and north of downtown Washington. Elsewhere, it is unrated.