D.C. Christmas weather timeline: heavy rain, falling temperatures, snow

A flash flood watch is in effect through 4 a.m. Friday for one to three inches of rain areawide. Gusty storms late Christmas Eve afternoon and again around midnight may be particularly heavy.

Meanwhile, a wind advisory runs from until 2 a.m. for our eastern counties along the Chesapeake Bay for wind gusts up to 50 mph.

Given the wind threat within storms passing through the region, it would be a good idea to secure or bring inside loose outdoor furniture or decorations.

After the blast of wind and rain in the middle of the night, temperatures will plummet about 30 degrees between Thursday night and Friday morning. Temperatures on Friday will hover near freezing with wind chills in the high teens and 20s with scattered snow showers and flurries.

While there has been some chatter and hype about a flash freeze in the Washington region early Christmas morning, we think the risk is low because precipitation will taper off before cold air arrives and strong winds should dry things out. While we can’t rule out some patchy slick spots, especially in our colder areas, we are not anticipating a widespread flash freeze.

During the day Friday and into the evening, however, scattered snow showers could drop a coating or so in some areas leading to slippery roads.

Because conditions will be changing so quickly over the next 24 hours, let’s break down the forecast into several intervals:

Through 7 p.m. Thursday: Occasional rain, with locally heavy downpours and gusty winds, mild.

Rain moves through the region from southwest to northeast and may be heavy at times. Thunderstorms with strong winds may develop inside the area of rain. With a bit of spin in the atmosphere, a short-lived tornado could spin up somewhere but seems unlikely. Temperatures hold steady around 60 degrees.

7 p.m. to 10 p.m. Thursday: A break for some but a few showers, breezy, mild.

We may see the rain break up a bit with more widely scattered showers. The rain may stop entirely in some areas for a period of time. Temperatures hover in the upper 50s as winds remain gusty, at times exceeding 30 mph (and 40 mph near the Bay).

10 p.m. Thursday to 1 a.m. Friday: Possible heavy storms with strong winds

Models show the possibility of a squall line with gusty winds and heavy rain jetting across the region. During this time, we can’t rule a severe thunderstorm warning or two. Once again, a brief tornado somewhere isn’t entirely out of the question. This squall line, if it develops, would move through quickly. Temperatures near 60 begin rapidly falling after midnight from west to east.

Winds could gust to 30 to 45 mph in the immediate area and perhaps to near 50 mph or so near the Bay. Locally higher gusts can’t be ruled out in the squall line.

1 a.m. to 5 a.m. Friday: Temperatures plunge, precipitation gradually tapers off

By 4 a.m., temperature are some 20 to 30 degrees colder than they were at midnight, falling into the 30s. Rain showers taper off and could change to some scattered snow showers, especially in our western areas. Winds gust over 25 mph at times.

5 a.m. to 10 p.m. Friday: Cold, windy, scattered flurries/snow showers.

Temperatures range from 30 to 35 degrees by sunrise and widely scattered snow showers and flurries are possible. Winds gust over 20 mph and wind chills dip into the 20s or even high teens in our colder areas.

10 a.m. to 6 p.m. Friday: Variably cloudy, breezy, cold, scattered flurries/snow showers.

Temperatures hold in the low 30s into the afternoon before dipping into the 20s during the evening. Scattered snow showers and flurries possible, and a coating or so can’t be ruled out, with a boom potential up to an inch or so. Some models show the most snow focusing southeast of Washington. Roads could turn slick during any heavier bursts. Winds chills hover in the highs teens and 20s.

4:30 p.m. — Narrow line of heavy storms moving through immediate D.C. area

Radar shows skinny squall line with heavy downpours and gusty winds moving inside the Beltway. It should pass through during the next 30 to 45 minutes. There is no longer a severe thunderstorm warning in effect, but some winds could gust over 40 mph or so as this passes. The squall line will be followed by a period of moderate rain before we may catch a bit of a break early to mid-evening.

3:45 p.m. — Severe thunderstorm warning for area south of the Beltway until 4:15 p.m.

A storm with very heavy downpours and pockets of strong winds (up to 60 mph) has developed to the northwest of Fredericksburg and is pushing north toward southern Fairfax County. It will sweep north along the Interstate 95 corridor passing through Aquia Harbor and Dale City over the next half-hour.

Embedded within a large area of rain, the storm warning is associated with a developing line of storms between Leesburg and Richmond sweeping northeast toward Washington. It should move inside the Beltway between 4:15 and 5 p.m. and may produce very heavy rain and…