An arctic front will bring another wave of bitterly cold air into the Washington Region Friday night as temperatures plummet into the teens overnight!
Rain showers are likely out ahead of this arctic front Friday morning in the DC Metro with an eventual change over to a period of snow showers before precipitation ends around noon. Northern Maryland could even see some snow accumulation as colder air bleeds south out of Pennsylvania into our region.
Then all eyes turn to an upper-level disturbance currently over the Pacific Ocean and its exact track during the Saturday night into Sunday time frame.
The disturbance riding the jet stream that will be the key player in how the weekend pattern evolves is still over the Pacific Ocean. This upper level feature won’t even arrive above the Pacific Northwest landmass until Thursday evening. Confidence and Consensus will begin to improve when the feature reaches land as there will be better information inputs into the forecast models (the equation will have more accurate data for a more accurate solution). Think of the term “garbage in garbage out” and it becomes clear why we have such low confidence during the Winter several days out ahead of a potential storm. The jet stream is after all a river of air that is very hard to predict and behaves very similarly to a river of water.What the model is trying to do is predict where a twig “the mid-level disturbance currently over the Pacific Ocean” dropped in the “river of water” (jet stream) will end up downstream (this weekend). The calculus that is involved in this equation is highly dependent upon good input data. We just don’t have enough coverage of buoys over the ocean to have excellent input data until the storm system reaches a landmass.
Image below shows the disturbance (circled in red) I am referring to at 1pm Thursday (still just off of the Pacific Northwest coast):