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D.C. area forecast: Wintry mix changes to substantial snow, record cold likely to follow (UPDATES)

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March 5, 2015 at 10:00 a.m. EST
Snow accumulations of 4-7 inches are likely in downtown D.C., and 5-10 inches to the north and west. Capital Weather Gang's Angela Fritz has your forecast. (Video: The Washington Post)

*Winter storm warning through 9 p.m. Thursday *

[School closings | Region braces for more snow | Metro warns of service changes for Thursday | Crews, schools prepare | When to expect plows]

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10:00 a.m. update: We have started a new post with our latest live updates. Please follow this link through the end of the storm: Winter storm warning: Snow, heavy at times, throughout the day (LIVE UPDATES)

Scroll way down for the forecast into early next week…

Storm summary

Timing: Mixed precipitation changes to snow from northwest to southeast through the region through the morning hours. From mid-morning to early afternoon, snowfall could be very heavy and will accumulate fast. Snow will continue through the late afternoon, but should begin to lighten up in the late afternoon and taper off in the early evening.

Accumulation: Anywhere from 4 to 7 inches within and south/southeast of the District, and 5 to 10 inches for points north. In general, the most snow will likely fall in the northwest suburbs, and the least in the southeast.

Impacts: Roads became slick in the early morning hours when wintry mix started, and they will continue to be hazardous through the afternoon as heavy snow falls and accumulates.

Follow below for our earlier updates and forecast through early next week…

9:30 a.m. update: Snow totals are on the rise! We’ve seen reports of 3 inches in Frostburg, Md., and 1.5 inches in Gaithersburg. Areas in Loudoun County have seen anywhere from 1 to 2 inches, and northern Beltway areas are at about 1 inch. Northeast D.C. is at 0.75 inches. Near western suburbs are close to an inch, as well.

9:05 a.m. update: A few snow reports from social media show that snow is sticking to some of the colder roads around the beltway, but others are still snow-free. Snowflakes are sometimes large and wet, and other times they are smaller and dry — but they are always steady!

8:25 a.m. update: The rain-snow line is pushing past the Beltway, and it is now mostly snow in the immediate metro area. Some near southern suburbs might still be seeing a mix of sleet and snow, and places farther to the southeast are still seeing a rainy mix. Snowfall rates are expected to become increasingly heavy through the morning hours, possibly exceeding one inch per hour, according to the Storm Prediction Center.

[D.C. loses the Capitol Hill sledding battle… for now.]

So far we’re seeing anything up to a dusting in the Beltway:

Temperatures are falling behind the rain-snow line. Our far northern suburbs are around 30 degrees now, while areas around the Beltway are running 32-34 degrees. Temperatures will continue to fall into the mid to upper 20s through the afternoon. This temp drop will make roads more slippery and prone to freezing.

Radar shows a sharp rain-snow line pushing southeast — blue is snow, pink is wintry mix and green is rain.

Important message (valid 6:30-8 a.m.): If you’re looking outside in immediate D.C. area and noticing conditions seems OK to commute to work, you’re right – through around 8 a.m. The issue is snow will be heavy from mid-morning to late afternoon. Getting home is likely to be very challenging if you live in neighborhoods where roads will become snow-covered, treacherous, and possibly difficult to pass through. We are expecting roughly to 4-8 inches in the immediate area. Keep that in mind.

7:45 a.m. update: The transition from rain to sleet to snow continues pressing southeast through the region.  North and west of the Beltway, it’s all snow falling and roads are deteriorating quickly.  The latest reports:

7:15 a.m. update: The changeover from rain to sleet and snow is happening VERY fast, moving inside the Beltway – into northwest D.C.  In our colder suburbs to the north and west of the Beltway, snow is already starting to stick on side roads. Some reports:

7:05 a.m. update: Here’s a great radar simulation (from the HRRR model) which does a nice job showing the rain to snow transition – occurring now from northwest to southeast – as well as the moderate to heavy snow through the afternoon:

6:50 a.m. update: The changeover from rain to sleet to snow is happening fast north and west of the city and will transpire in the city and nearby southeast suburbs over the next couple hours. Some reports:

6:20 a.m. update: We’re seeing increasing reports of rain mixing with and changing to sleet in our colder suburbs to the north and west – even inside the Beltway. In Frederick, precipitation is all snow and roads are covered.

For folks closer to town skeptical about the snow given the above freezing temperatures right now (temps 34-39 in the immediate metro region at 6 a.m.), just look at how cold it is to the northwest from where the air is streaming in today – north of Chicago it is below zero:

5:40 a.m. update: Temperatures are above freezing throughout the immediate metro area, ranging from around 35-40, with just light, scattered mixed precipitation. From the Beltway and to the south and east, the precipitation is mostly light rain. Some sleet starts to mix to the north and west. For the next one to two hours, getting around should be OK for most places within about a one county radius of D.C.

Well to the northwest, it is snowing around Frederick and Hagerstown, where temperatures have fallen to 30-34 and conditions are deteriorating.

What we’re seeing right now is entirely what we expected if you read our updates yesterday evening. Accumulating snow is likely to begin between about 8 and 11 a.m. from northwest to southeast across the area. The latest models continue to suggest the potential for the snow to be quite heavy in the mid-morning to late afternoon time frame, when travel will become increasingly difficult. Our accumulation forecast – below- is unchanged.

Original forecast from 5 a.m.

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

5/10: Snow lovers are delirious, this event is serious! Inches pile up through the day, as kids head out to play, spring is officially on delay.

EXPRESS FORECAST

Today: Wintry mix changing to all snow. Highs: 29-35 early, then falling
Tonight: Evening snow tapers off, clearing late. Lows: 8-15
Tomorrow: Mostly sunny, calm winds. Highs: 26-31

FORECAST IN DETAIL

Keep in mind: Cooling the air enough for rain and sleet to change to snow is work around here and may not be completed when you rise. But don’t be fooled, a  snow burst from about 10 a.m. to 4 p.m. looks likely to make travel challenging to extremely difficult. Today’s snowfall could challenge the daily record of 4.4 inches in Washington.

In the wake of today’s snow, record lows are possible the next two mornings at Dulles Airport and Friday’s afternoon highs may also be among the coldest recorded for the date. Spring slowly claws back this weekend with sunny and meekly milder offerings.

Today (Thursday): Though starting the day above freezing in many areas, temperatures should be on a downward glide path in the morning. A mix of rain, sleet, and snow should greet the clouded over sunrise. Our northern and western suburbs should  transition to all snow early on, followed by the rest of the region by mid-morning. There is a good chance the precipitation stays light until mid-morning when the main energy reaches the area and sets off about a 6 hour stint of moderate to occasionally heavy snow. Traveling is probably most hazardous from mid-morning to mid-to-late afternoon.

Much of the area could see 4-10 inch accumulations by late afternoon when the snow is expected to decrease. Heaviest amounts (5-10 inches) are favored north and west of downtown Washington, with somewhat less (4-7 inches) in the District and to the southeast. Amounts may fall on the low side of these totals if the changeover to snow is slowed and/or dry air works in and ends the snow prematurely. High-end totals are possible if locally heavy snow bands develop and remain stationary over the region

Temperatures should be in the low-mid 20s by late afternoon with wind chills in the teens courtesy a breeze from the north at 10-15 mph at times. Confidence: Medium-High

Tonight: Snow tapers off from northwest to southeast in the evening, with little additional accumulation. Skies clear overnight allowing a glimpse of the full “Sap” moon although I am not sure it lives up to  its name this year. Winds are still northerly at 5-10 mph.  Lows fall quickly over the fresh snow cover and end up in the extremely cold single digits north of town and low-mid teens in town and points south. Confidence: Medium-High

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

Tomorrow (Friday): The day is likely to dawn bright – in fact brighter than usual given the prospect of a significant snow cover. Winds quickly calm which is a blessing as highs struggle to reach the mid-20s to near 30 even with the sun shine unfettered. Given the cold conditions, motorists and pedestrians alike should be very cautious as any snow melt in the sun could quickly refreeze in untreated areas later in the day as the sun lowers. Confidence: High

Tomorrow night: The full moon should bring a sparkle to the landscape throughout the night. Calm winds facilitate the drop in temperatures and many areas have a shot at a  record low as readings bottom out in the single digits in nearly all areas, although may hold in the lower teens in the city.  Confidence: High

A LOOK AHEAD

Saturday starts the melt down as most areas reach the  upper 30s to lower 40s under mainly sunny skies to start the day. Occasional clouds dot the afternoon sky. Breezes pick up from the west and are helpful in slowing the drop of temperatures overnight. Lows still hit the upper teens to mid-20s in most areas thanks to our snow blanket. Confidence: High

Sunday starts out darker, that is if you remembered to move your clock ahead an hour. Payback is an extra hour of evening brightness with skies mainly clear through the day. Highs still struggle to do better than low-to-mid 40s so outdoor activities are likely to be short lived. Starry skies prevail through the night and calm winds allow lows to fall to the 20s in most areas and upper teens in coldest burbs. Confidence: Medium-High

Monday continues the fight to restore spring to the land and makes better headway with highs in the mid-upper 40s putting snow melt into full gear. Confidence: Medium-High

SNOW POTENTIAL INDEX
A daily assessment of the potential for at least 1 inch of snow in the next week, on a 0-10 scale.

9/10 (↑): Snow should crack the 1 inch mark across much of the area by midday, if not sooner.

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