** Winter weather warning from 3 to 9 pm on Monday **
BWI (1 °) and Dulles (-1 °) broke their record low temperatures today that could be the coldest morning of 2018. Many other places also fell below zero or in single digits in what the National Meteorological Service described as the "coldest morning for our region since February 2015." We have a cool and calm climate to spend tonight before a mixture of rainfall generates some headaches on the trip on Monday night.
Ice conditions are likely for the afternoon trip on Monday
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Through tonight: Clouds will generally increase overnight. Otherwise, it's another cold afternoon, though not as cold as in the past. The low temperatures will range between 13 and 18 degrees, and the highest readings will be limited to urban places. Staying dry with dew points to zero or in a single digit. The winds will be light from the south at 5 mph.
See current weather conditions in The Washington Post.
Tomorrow (Monday): A complex forecast is emerging for the last part of El dia. Mostly cloudy and dry during the first part of the day, with a slight south wind that tries to force the smoothest air on the surface. In most places, afternoon temperatures will reach a peak between 31 and 35 degrees. Light precipitation (in the form of rain or sleet) will begin to emerge from west to east sometime after 3 p.m. There is a possibility that some freezing rain may occur at dusk, especially north and west of the city. Even in places where precipitation is maintained as rain or sleet, there is a high probability that it will freeze at the contact given by the cold pavement. The icy spots are possible for the afternoon trip. All precipitation must end at 10 p.m. and we are left with mostly cloudy skies and low temperatures ranging from 27 to 32 degrees.
A Winter Weather Warning (blue shading) has been issued for Monday afternoon and afternoon. Danger: Ice glaze from sleet and freezing rain that will cause slippery conditions for Monday afternoon. You expect some inches of snow in the mountains. #DCwx #MDwx #VAwx #WVwx pic.twitter.com/DJKuhGsxs2
– NWS DC / Baltimore (@NWS_BaltWash) January 7, 2018  See Greg Porter's forecast throughout the week. And if you have not already done so, join us on Facebook and follow us on Twitter and Instagram. For news related to traffic, consult Dr. Gridlock.
Tomorrow is a complicated forecast: A forecast configuration like tomorrow is what keeps meteorologists awake at night. As people of the time, we have become quite used to leaning heavily on models or guides when creating forecasts. But in a scenario like tomorrow, the models will not be very helpful. The brief answer to why a combination of small-scale physical processes together with the surrounding environment is reduced. Follow me on the path of the nerd climate for a moment.
- It has been cold. Really cold. And cold air is denser than hot air. That means that cold air entrenches itself on the surface much more easily than hot air. And when you have a series of very cold days and nights followed as we have had, that stubbornness to move around becomes even more robust.
- The air temperature may not matter much and arrive tomorrow night. We may see some places with temperature readings at or above the freezing mark, but still experience rain that freezes immediately upon contact. That's because the ground is frozen and our roads lose "heat" much more easily than the air around them. Then, the air temperature could be 35, but the path below it could be more like 30 degrees, leading to instant black ice.
- The effect of wet bulb. You can find more about this term here. But essentially, when precipitation falls, it cools the air around you. This process improves when the precipitation falls in very dry air, which accelerates the evaporation process and cools the air even more. Then, when the rain, sleet or whatever begins to fall tomorrow night, you can drag the air temperature below the freezing temperature.
All this amounts to a complex forecast that contains minute details in which even our best forecast models have difficult time simulating What is worse, this has the potential to be a high-impact event, so the lack of Certainty looms even more. Therefore, be sure to monitor the forecast as much as possible between today and tomorrow night, as things could change in a hurry.
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