| The latest VIPIR Radar image shows severe storms dropping lots of hail moving now into areas north of Richmond to the greater Fredricksburg area.A somewhat weaker but still formidable scattering of storms is now trying to intensify as each cell moves NE at about 35 mph.There’s also a SECOND line of strong storms moving into the Alleghany Highlands at this hour with strong winds and hail possible there as well.Check out how well VIPIR’s Exclusive Hail Tracker did (in pink shading) against the actual hail reports in central Virginia. The diameter was around 0.5″ due to colder air moving in aloft while the sun warmed the ground below this afternoon.  For a potent severe weather day in our area, it helps when upper level winds are as westerly as they can get. That creates more wind shear as our surface winds are almost always from the SSW to SSE ahead of these systems.So when you can take today and learn from it. When there’s a dip in the jet stream in the Ohio Valley moving east, and if we’re on the bottom of the dip so that the winds aloft are out of the west, you’ve got a major ingredient for strong wind shear.You can see that on today’s water vapor satellite loop – clearly!  Wind shear produces spinning storms known as super cells and super cells can sometimes produce tornadoes. It’s interesting to note that only a tiny percent of super cells actually produce tornadoes. And researchers still don’t know what that final mechanism is yet.Wind shear also keeps a storm from dying a quick death. By definition storms are God’s way of balancing out the air. Warm air near the ground is lighter and more bouyant, while colder temps aloft are heavier due to the packed molecules bunched together. In a single cell storm with no wind shear, air rises – the updraft phase – bubbles into a cloud, and then the rain and or hail fall into the updraft, thus choking it off and balancing out the upside down density.Today, like many days with severe weather, we had the clouds break for sun right at the time when we see the more direct solar rays warm us up. Thats impressive considering we don’t get a lot of sunlight this time of the year.Look at what many models had for today. Expecting cloud cover and a faster moving system to limit any warming and thus not showing storms.Ummm yeah, that one busted.  I tell people all of the time, go by the meteorology, not the models. At least not all of the time. Today was looking at the here and now kinda day, and those are critical to each forecaster learnig and getting refreshed on the science behind WHY the models are right or wrong. And THAT’s how you learn. Imagine just reciting what you see on the models each day because they are so reliable. There would be no need for you!Not only did we warm up fast, colder air – the same cold air that will be building and building into the middle of January, is steadily moving in aloft. So we had things getting warmer and warmer below and colder and colder upstairs.But the wind shear is critical because once the air rises and rain and hail form, it’s the wind shear that keeps both fighters in their respective corners of the ring, so to speak. The rain and hail catch that SW wind aloft and fall AWAY from the updraft. When kept apart like that, wind shear keeps storms growing in intensity and in duration.  Here’s the rest of today from the 15 min HRRR model – lingering storms will be moving through into the evening hours then colder air will clear out areas east of the mountains while NW winds on the “wrap around” side of the system fuel robust snow enough for a Winter Storm for the Greenbrier Valley of West Virginia and a coating of snow in the Mountain Empire to a few inches on higher ridges, mainly the WEST sides of the higher mountains.  We can see some Significant Tornado Parameter values elevated across South Central Virginia on the 3kn NAM model and another area of elevated values that are quickly falling apart in the mountains with that second batch that’s going to weaken soon (one or two strong cells still possible, just to cover myself.)  The 19Z HRRR in motion shows that DARK blue for the Greenbrier Valley and Snowshoe, WV. It’s going to pour down there tonight through Wednesday.  Some snow squalls and areas of mainly light snow along and west of I-77 into the NW mountains of NC as well… here’s the National Blend of Models snow forecast… through Wednesday night or early Thursday morning, when the snow will taper off.  Here are some individual model forecasts for tonight through early Thursday morning. Some of those high peaks in pink is where the models show 10″. But the actual DEPTH of the snow may be lower.3km NAM usaully runs a little high.  The snow DEPTH CHANGE tries to figure out melting more than just the snow maps. But the snow maps are Kuchera equations, which takes into account more accurate temperatures rather than just using a 10 to 1 ratio.  HRRR Kuchera Snow  Tazewell County looks like a good spot for a possible coating to 2″ the higher up you go. Grayson Co will see some snow showers but you probably need to travel ALL THE WAY UP to Whitetop (I had some Grayson Co folks fuss one time bc they didn’t venture all the way to the peak, where roads get narrow and winding, but opens up to a flat parking lot. It’s a small dot on the map so it can appear as you’re moving up – actually with all of these mountain roads that lead to peaks – you’ll likely get to where you think it’s just flurries and then suddenly you’re in heavy, wind-blown drifting snow over 4-8″ near the top. I almost got stuck chasing some snow a few years ago in West Virginia.We looked at the Naitonal Blend of Models above but that was only through late Wednesday night or Thursday morning. Watch what happens on the Blend when we take it further out in time!BOOYAH!  Remember me saying to hang in there? Keep hanging, it can still change. But the jet stream to me looks good still. There’s still time for some shifting in Greenland of the NW US coast and that would take this potential snow away from us.But the trends aren’t moving around too much. The models just have a hard time with the smaller day to day details. What’s looking certain, is a deep dip with very cold air… it looked like it would be the coldest of the northern hemisphere Sunday but it’s backed off – only a little though.The EURO, GFS, Canadian, UKMET, ICON, ALL of the models are not consistent AT ALL on which day could bring wintry weather to our area. But the nearest chance is looking a little more certain. Monday morning. Snow or maybe a mix with ice. Too early to tell. Likely wintry though, not rain.Then beyond Monday, any day into the middle of the month COULD give us a good snow. What I like about the blend up there is while its showing 2″ or so – keep in mind it’s looking at a 15″ model, a few 0″ models some 2-4″ solutions and for different days of the week but clustered generally next week after Monday.So for the Blend to show ANYTHING this far out is VERY encouraging. the Blend also doesn’t simply take an average of all 151 models… it looks at each model’s recent track record and it weighs the most accurate models more than the least accurate. That’s a changing factor in and of itself. I do expect things to change back and forth for many days to come but I think we’re gonna have some wintry weather starting Monday morning, and that one could be mix as the cold-cold air will still be making progress south. But listen: it’s gonna steadily continue to build bit by bit south… so that a bigger snow follows by the middle of the month, and maybe another should the pattern hold.As always – stay tuned! |