Foot's Forecast | Weather Intelligence

THE PROOF HAS ARRIVED, AND A LITTLE EARLY.

CHECK THE LATEST MID-ATLANTIC RADAR FOR PRECIP TRENDS

THU 9:30 PM. The Winter Storm Warning now in effect until 10 PM FRIDAY for Central and Western Maryland, Northern Virginia and the West Virginia panhandle probably comes as no surprise to those of you who have been following the development of this storm since last Friday. There are no changes to the forecast, because the truth has arrived : A high impact winter storm will affect the entire Northeast region Friday into Saturday, and not a soul on Earth can stop it. View the NWS spread of warnings and advisories to understand the extent of this storm already. As for the current radar, I'm sure you're noticing the "dry slot" of separation between the two storms, but that is simply an indication the two storms will not "phase" or merge together quickly. This allows the energy from both systems to slowly blend, which actually prolonges the event...and the pain for commuters. The alternative is a rapid phasing, a quick accumulation and then out to sea. That is not likely to happen.

STORM SUMMARY AND IMPACTS: An initial 1-3" of snow starting by midnight in the central Mid-Atlantic will be followed by nearly 24 hours of sleet and freezing rain to affect the entire I-95 corridor from Washington to New York City. Interior sections from Pennsylvania to England will see widespread snow possibly exceeding 6 inches. By Friday afternoon, areas affected by ice may come to a virtual standstill, even hampering the ability of emergency and utility workers to reach residents in need. If you have something important to do, get it done on Thursday, because travel on Friday for most of you will be limited to your living room, TV room and the nearest refrigerator (assuming there's power to keep it working!)

SCHOOLS, COLLEGES, OFFICES: Most schools throughout central and western Maryland, northern Virginia, West Virgina will be closed Friday, in addition to a number of colleges as well as many county, state and federal offices. Any activities, meetings or special events planned for Saturday will have to be rescheduled, so make necessary arrangements now. Those who attempt to open or hold an event will face a travel and logistical nightmare. However, conditions will improve behind the storm on Sunday, allowing roads to dry out in time for a regular school day on Monday.

BACKGROUND AND ANALYSIS: (Skip this part if you're not into the meteorology behind the forecast). The green-blue areas on the map below indicate moisture that will by 1AM Friday be running overtop an expansive dome of sub-freezing surface/lower level temperatures. The lines that bend southwest across Virginia indicate cold air damming, a classic setup for sleet and freezing rain, which may initially start as snow. Also note the 0 deg Celsius line at 5,000 feet is deep in southern Virginia, that indicates an extensive southward push of cold air. Warm air advection at or above the 5,000 foot level will intrude later Friday morning, this will be evidenced by snow changing to sleet and then eventually freezing rain by noon. This is well depicted in the NWS forecast for Baltimore as a representative location for the central Mid-Atlantic. Comparing this Wednesday night GFS projection for 1AM Friday to the current radar, it appears the precip is moving in faster than expected, but may result in just slightly higher snow totals if it starts earlier, despite your concern about the "dry slot."

THE MYSTERY OF FREEZING RAIN. Surface temperatures on Friday will start out in the 20's, and then you'll see a quick rise to 30-32 in many areas, followed by a whole day where the temp hovers just around freezing. This is a phenomenon that often occurs with freezing rain, because water turning into ice is actually a CONDENSATION process, which RELEASES heat into the atmosphere. This "latent release of heat" helps keep the temperature just around 32 or 33. But strangely enough, if slight melting begins to occur, EVAPORATION of that water from a solid back to liquid is a COOLING process, which in turn chills the surface layer just enough to stabilize the temperature. So in effect, once a freezing rain regime has setup, it just keeps on going until enough warm air aloft mixes down to the surface and provides enough warming to take the air temperature past 33. Given the depth and coverage of the cold High pressure dome that's now in charge, I doubt we'll see a change to all rain by Friday afternoon as projected by Baltimore's WJZ. It will be fun to see who is right in the end.

IF YOU WANT TO NOWCAST THE STORM, you don't have to wait for me...I recommend monitoring the following sites over the next 48 hours. For up-to-the-minute data on road conditions in MD, check Maryland Roadway Weather, and if you want the latest indications of precipitation type at BWI, this helpful graph from coolwx.com breaks down what may be falling when. A good sense of what's happening with precipitation and storm movement is best seen on AccuWeather's National Radar Loop and Regional Snow-Ice-Rain Radar, and this map of current observations. If you want more detail and like to decode secret messages written in acronyms, then follow the Baltimore/DC NWS Forecast Discussions, updated about 4-6 times per day. Those who seek serious hard core meteorological prognostication should review the HPC Short Range Discussions. (That's short for Hydrometeorological Prediction Center.) For weather analysis and long range entertainment, Henry Margusity's "Meteo Madness" provides a blend of both.

Justin Berk is a TV meteorologist with ABC2 News in Baltimore who operates a very worthy blog I suggest bookmarking, and since I've been a life-long fan of ABC, I can't recommend any other network anyway. For a long range glimpse of what US computer models are projecting for next week, take a peek at the GFS animation on wunderground.com. There's also the NOAA/NWS 5-day map series, and you can even see our future SuperKahuna indicated there starting Wednesday 2-27. Once we get the first Kahuna launched in full (translate: me home Friday for a day off to do the analysis), then I can start to show you data and maps for next weeks potentially major event that could make this upcoming storm look like a flurry!