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| Light rain and snow likely late tonight into Monday morning; snowier wave possible late Monday | |
| (about 1 hour later) | |
| * Winter weather advisory late tonight and Monday except far south suburbs (see map) | Winter storm watch for Anne Arundel, Calvert, and St. Mary’s Counties | Winter storm warning from Winchester to Hagerstown (I-81) and west * | * Winter weather advisory late tonight and Monday except far south suburbs (see map) | Winter storm watch for Anne Arundel, Calvert, and St. Mary’s Counties | Winter storm warning from Winchester to Hagerstown (I-81) and west * |
| Update at 9:50 p.m.: Looking at the latest information coming in, there’s a decent chance that much of the metro area ends up with an inch or less from this storm by the time the last snow showers depart late Monday night or Tuesday morning. There still are a couple of windows for some disruptive accumulating snow: 1) Monday morning from around 7 a.m to noon, northern Loudoun and northern Montgomery counties and points north could see an inch or so of snow and slick roads. Further south into the immediate metro area, snow and/or mixed precipitation is possible and could reduce visibilities, but probably won’t impact main roads too much. 2) Monday night from around 6 p.m. to midnight presents a better chance of a coating to an inch of snow across the area with temperatures near or below freezing, assuming we see some steady snow showers set up over the area. Currently models suggest such snow showers would focus on the western suburbs. | |
| Update at 9 p.m.: What’s the story early Monday morning? The NAM model, which is pretty accurate within 12-24 hours, is updating now and suggests perhaps a dusting mainly on grass by 7 a.m. Monday for areas inside the Beltway and just south and east, while colder areas just north and west of the Beltway (e.g., in Montgomery and Fairfax counties) could be starting to see snow sticking to pavement at that time, although main roads would probably still be in decent shape. Further north and west, in Frederick and Loudoun counties, roads may already be on the slick side. This pretty much in line with we’ve been saying, but increases the confidence. Here’s a good timeline graphic, which is consistent with our forecast, from the National Weather Service office in Sterling: | Update at 9 p.m.: What’s the story early Monday morning? The NAM model, which is pretty accurate within 12-24 hours, is updating now and suggests perhaps a dusting mainly on grass by 7 a.m. Monday for areas inside the Beltway and just south and east, while colder areas just north and west of the Beltway (e.g., in Montgomery and Fairfax counties) could be starting to see snow sticking to pavement at that time, although main roads would probably still be in decent shape. Further north and west, in Frederick and Loudoun counties, roads may already be on the slick side. This pretty much in line with we’ve been saying, but increases the confidence. Here’s a good timeline graphic, which is consistent with our forecast, from the National Weather Service office in Sterling: |
| Update at 7:30 p.m.: Radar remains quiet across most of the area, other than the light rain (possibly mixed with a bit of sleet or snow) across Frederick, Carroll, and Baltimore counties and points north. Even there, temperatures are still up in the mid-to-upper 30s. Short-term modeling indicate the metro area won’t see much precipitation until after 10-11 p.m., primarily in the form of rain to start, but toward dawn mixing with or changing to snow from north to south. Again, we expect snow will have a hard time sticking to main roads in the immediate metro area and south leading up to and during the morning commute, with a better chance of slick roads from northern Loudoun County, northern Montgomery County, Howard County and points north. | Update at 7:30 p.m.: Radar remains quiet across most of the area, other than the light rain (possibly mixed with a bit of sleet or snow) across Frederick, Carroll, and Baltimore counties and points north. Even there, temperatures are still up in the mid-to-upper 30s. Short-term modeling indicate the metro area won’t see much precipitation until after 10-11 p.m., primarily in the form of rain to start, but toward dawn mixing with or changing to snow from north to south. Again, we expect snow will have a hard time sticking to main roads in the immediate metro area and south leading up to and during the morning commute, with a better chance of slick roads from northern Loudoun County, northern Montgomery County, Howard County and points north. |
| Update at 6:00 p.m.: Radar shows rain streaking into our northern suburbs, mostly north and northwest of Montgomery County. Temperatures there are in the upper 30s and low 40s, but should gradually fall in the coming hours and we’ll probably begin to see reports of rain transitioning to snow in this area. This rain should very slowly edge south and east into the metro area by between about 10 p.m. and midnight but it may take a number of hours – perhaps until just before dawn – for the rain to transition to snow, especially from D.C. south. | Update at 6:00 p.m.: Radar shows rain streaking into our northern suburbs, mostly north and northwest of Montgomery County. Temperatures there are in the upper 30s and low 40s, but should gradually fall in the coming hours and we’ll probably begin to see reports of rain transitioning to snow in this area. This rain should very slowly edge south and east into the metro area by between about 10 p.m. and midnight but it may take a number of hours – perhaps until just before dawn – for the rain to transition to snow, especially from D.C. south. |
| Update at 4:20 p.m.: We’ve added an accumulation map for the second half of the storm – Monday late afternoon to Tuesday morning (scroll down). A most likely storm total for both phases of the storm in the immediate D.C. area is in the neighborhood of 1-4 inches – but uncertainty is large. | Update at 4:20 p.m.: We’ve added an accumulation map for the second half of the storm – Monday late afternoon to Tuesday morning (scroll down). A most likely storm total for both phases of the storm in the immediate D.C. area is in the neighborhood of 1-4 inches – but uncertainty is large. |
| Original post from 2 p.m. | Original post from 2 p.m. |
| New information indicates temperatures overnight into Monday morning, when snow is expected to arrive, are probably going to be too warm for significant accumulation in the immediate D.C. area. However, a second wave of snow may develop Monday afternoon into Monday night, and create some slick travel conditions. | New information indicates temperatures overnight into Monday morning, when snow is expected to arrive, are probably going to be too warm for significant accumulation in the immediate D.C. area. However, a second wave of snow may develop Monday afternoon into Monday night, and create some slick travel conditions. |
| This is an extremely complicated forecast, which is best understood and consumed by thinking about it in three phases. | This is an extremely complicated forecast, which is best understood and consumed by thinking about it in three phases. |
| Phase 1: Tonight into Monday morning: | Phase 1: Tonight into Monday morning: |
| Phase 2: Monday morning through Monday mid-afternoon: | Phase 2: Monday morning through Monday mid-afternoon: |
| Snowfall map through Monday mid-afternoon. Important: This map does NOT include snow forecast late Monday afternoon through Tuesday morning. | Snowfall map through Monday mid-afternoon. Important: This map does NOT include snow forecast late Monday afternoon through Tuesday morning. |
| Phase 3: Monday late afternoon through Tuesday morning | Phase 3: Monday late afternoon through Tuesday morning |
| Monday morning SchoolCast: | Monday morning SchoolCast: |
| Monday morning FedCast: | Monday morning FedCast: |
| Some thoughts from winter weather expert, Wes Junker | Some thoughts from winter weather expert, Wes Junker |
| The models are now tracking a low pressure system eastward across Kentucky into West Virginia overnight, where it fizzles and its energy transfers to a strong storm off the coast during the day Monday. The band of heavier snow associated with this initial low pressure system is forecast to track across northern Maryland along the Mason Dixon line through Monday morning with the precipitation diminishing to the east and south. Mainly light snow should fall in the immediate metro area. | The models are now tracking a low pressure system eastward across Kentucky into West Virginia overnight, where it fizzles and its energy transfers to a strong storm off the coast during the day Monday. The band of heavier snow associated with this initial low pressure system is forecast to track across northern Maryland along the Mason Dixon line through Monday morning with the precipitation diminishing to the east and south. Mainly light snow should fall in the immediate metro area. |
| The initial track of the low so far north also helps to keep our surface temperatures above freezing until the storm off the coast takes over and starts really winding up. Under such a scenario, we sometimes end up in a relative “snow hole” and only tally a coating to an inch or two in and around the city. | The initial track of the low so far north also helps to keep our surface temperatures above freezing until the storm off the coast takes over and starts really winding up. Under such a scenario, we sometimes end up in a relative “snow hole” and only tally a coating to an inch or two in and around the city. |
| To get more snow, we need the coastal low to develop close enough to us to allow a second round of snow to develop on the west side of the developing ocean storm Monday evening. Today’s GFS and European models have such a scenario, which might offer a narrow stripe of 1-3 or even 2-4 inches or more somewhere along and east of the I-95 corridor. Unfortunately for snow lovers the models are sometimes more bullish about such scenarios than mother nature. | To get more snow, we need the coastal low to develop close enough to us to allow a second round of snow to develop on the west side of the developing ocean storm Monday evening. Today’s GFS and European models have such a scenario, which might offer a narrow stripe of 1-3 or even 2-4 inches or more somewhere along and east of the I-95 corridor. Unfortunately for snow lovers the models are sometimes more bullish about such scenarios than mother nature. |
| The Blizzard of 1978 (see above), which crushed Boston — much like this storm is expected to — produced a narrow swath of heavy snow in D.C.’s eastern suburbs. It not only impacted Baltimore with heavy snow (9 inches), but even produced up to 4-5 inches of snow in northern Calvert County. Reagan National Airport tallied about an inch. No two storms are exactly alike and a repeat of 1978 is unlikely, but Monday’s storm has the potential to produce wrap-around snows. The uncertainty in locations and amounts is large. | The Blizzard of 1978 (see above), which crushed Boston — much like this storm is expected to — produced a narrow swath of heavy snow in D.C.’s eastern suburbs. It not only impacted Baltimore with heavy snow (9 inches), but even produced up to 4-5 inches of snow in northern Calvert County. Reagan National Airport tallied about an inch. No two storms are exactly alike and a repeat of 1978 is unlikely, but Monday’s storm has the potential to produce wrap-around snows. The uncertainty in locations and amounts is large. |