D.C. area forecast: Spring to start the weekend, winter to end it; significant snow risk Sunday night into Monday

11:50 a.m. update: After going south in the late night run, this morning’s NAM ticked back north again, but still kept a sharp cutoff in precipitation across the area. That said, it supports a decent late-season snow, especially D.C. and south. Its track is also similar to snowier models. The GFS just rolled in, and it remains much more steady in its depiction of the event, with pretty much the whole area seeing a significant snowfall. It brings precipitation in by evening, and could be mainly snow throughout — perhaps a brief period of rain. The focus of the GFS’s heaviest activity is squarely in the overnight — good for accumulation potential — and it keeps at least light activity going through much of Monday.


This morning’s GFS, forecast showing precip that has fallen between 8 p.m. and 2 a.m. from late Sunday into Monday. (Weatherbell.com)

We’ll have a new post by 3 p.m. this afternoon, including timeline and a first call snow map.

9:00 a.m. update: Models continue to bounce around on their placement of the maximum precipitation area, and thus the story remains a little muddled. The overnight European run was south of the prior run, putting our area on the northern edge of the precipitation shield, and it would indicate lower snow totals locally, but still some with the maximum to the south. The most recent run of the NAM more or less supports this idea, but has an extreme cutoff right through the center of the area with little to no precipitation north of D.C. However, the overnight run of the GFS continued pushing the main body of snow right through the D.C. area, with more than a few inches of snow on the ground at the end.

I’ll update again as the morning models come in, and we’ll have a big in depth look at the event this afternoon.

Today’s Daily Digit

A somewhat subjective rating of the day’s weather, on a scale of 0 to 10.

8
Clouds may hang around early, but we see plenty of sun. Breezy, yet mild. Take it in with what’s to come.

Express Forecast

Today: Turning partly to mostly sunny. Highs: Near 60 to mid-60s.

Tonight: Partly to mostly cloudy. Lows: Near 30 to upper 30s.

Tomorrow: Mostly cloudy, evening showers turning to sleet and snow. Highs: Low-to-mid 40s.

FORECAST IN DETAIL

Temperature Map

Temperatures: Latest D.C. area temperature map. See interactive map on our Weather Wall.

Manic March. Today is fairly warm, tomorrow is colder, and then it’s back to our never-ending snowy winter. Snow this time of year isn’t necessarily uncommon, but getting any of consequence is not too typical either. This can be seen in snow norms ranging from about 0.3 inches at D.C. from today through the end of the snow season, and 1.4 inches at Dulles in the same frame. It seems like we could see a good bit more than that by the time we get through Monday. Another abnormally cold several days are on tap as well. But first, do get out and enjoy today if you can!

Today (Saturday): Skies may remain fairly cloudy as the sun rises, and as we’ve seen a few times recently the still strengthening sun can be slow to burn them off, though I’m hopeful they’re out early. For you Rock ‘n’ Roll Marathon goers, temperatures are near the mid-40s at start, rising past 50 by late morning. The day should end up partly to mostly sunny on the whole with highs ranging from around 60 to the mid-60s. Winds are from the west and northwest at 10-15 mph or so — those March breezes that never seem to end! Confidence: Medium-High

Tonight: We start off at least partly clear, but trend cloudier overnight. Winds also turn to the north, helping colder air trickle back in. Lows end up in the near 30 to upper 30s range (coldest suburbs to downtown). Still gusty evening breezes diminish overnight to around 5 mph. Confidence: Medium-High

For related traffic news, check out Dr. Gridlock. Keep reading for the forecast through the weekend…

Tomorrow (Sunday): It’s cloudier than not through the whole day, but perhaps some breaks are around in the morning through midday. As we get through the afternoon clouds thicken and lower. It looks like most of the daylight period remains dry. Highs head for the low-and-mid 40s, with winds from the north and northeast around 10 to 15 mph. Precipitation may begin pushing into the area as we get toward sunset, and that helps temperatures fall back into the 30s. If it’s in early, it probably starts as all rain. Confidence: Medium

Tomorrow night: Any rain on the front edge of the system (it’s possible there won’t be much depending on timing) should fairly rapidly change over to snow (80% chance). There may be a brief period of sleet as well. Once it starts and overspreads the area, snow continues through the night, potentially falling moderate to heavy at times, particularly in the hours around midnight and through dawn. There could be some lulls too, but mainly snowy.

Temperatures may initially be a bit too warm to support easy accumulation, though we should see them fall to and below freezing in the hours before midnight to the north and west and near or after midnight elsewhere. Freeze times could possibly be earlier or later depending on how quick cold air filters in, — we’ll narrow that down as we close. Lows eventually reach a range of about 25-30. Breezy too, but not super windy. Confidence: Low-Medium

A LOOK AHEAD

Snow Potential Index

A daily assessment of the potential for at least ~1″ of snow in the next week, on a 0-10 scale. More info

7 (↑) Sunday night into Monday snow threat increasingly real. Question becoming “how deep?” when it’s over.

We should be waking up to a white St. Patrick’s Day on Monday morning, and snow will want to continue through at least a few hours after sunrise, perhaps longer. Temps are slow to rise, which should allow for at least a little more accumulation during the day, but probably lighter than what we saw overnight. We could be talking several inches or more across the area when all is said and done, with the highest totals likely focused west in elevated areas. After the main snow dose, high temperatures could reach the low-to-mid 30s on the warm side. It should be breezy as well. We may also see an additional batch of light precipitation late or into the overnight. Confidence: Low-Medium

By Tuesday, surface high pressure noses in, but moisture may remain trapped below it, so we could still see a fair amount of cloudiness. Let’s call it mostly cloudy for now, but hope for partly cloudy? There’s also a slight chance a secondary low tries to throw some more precipitation our way, yet it’s not clear enough a risk to go there right now. With cold air still hanging around, as well as potential snow cover, look for highs mainly near 40 to the low 40s. Enough for some melting hopefully! Confidence: Low-Medium

(forecast prepared overnight)

Ian Livingston is a forecaster/photographer and information lead for the Capital Weather Gang. By day, Ian is a defense and national security researcher at a D.C. think tank.
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