Winter Storm to Impact Hampton Roads on Monday

Monday will not be a fun day across Virginia. Travel will be difficult, if not dangerous at times. Businesses and schools are advised to plan ahead. This storm will be one where people will wake up at 7-8am and think, “Where is the storm?” Around 9 am, the sleet/snow will begin and everyone will freak out and leave, creating lots of traffic…

Another winter storm is going to impact the state on Monday, blanketing the state in snow and sleet. Winter Storm Watches and Warnings are out for many areas. WatchThe storm will begin as sleet in many areas, before transitioning to snow as the colder air works in. Total snowfall accumulations will vary from west to east, with the highest amounts typically being across north and western VA including the campuses of JMU, UVA, UMW and Washington DC. South and east of there, snow will mix more with sleet, and this will cut numbers down.

Rain vs Sleet vs Freezing Rain

Why does sleet form instead of snow? It’s due to warmer air aloft. When air above the ground is above 32°F, the snow that falls from the clouds melts on the way down. However, since the warm air is very shallow, and the air near the surface is cold, the water drops refreeze on the way down. They become ice pellets.

(Note: Sleet and hail are NOT the same things. Hail is a convective precip type that occurs when water drops are lifted up into a thunderstorm and then fall over and over in updrafts). 

How can you tell sleet from snow or rain? It’s simple! Sleet bounces and pings off your window. Rain and snow does not! If you see sleet, please let us know by reporting it on the mPing app. This app allows meteorologists to get ground proof of what precip type is falling, since radar actually scans a few thousand feet up into the air. The app is available for Android and Apple products.

Let’s break down the storm in terms of impacts:

Radar

TIMING: 

  • Hampton Roads- Sleet begins around 9am and lasts through about noon. Snow begins after.
  • Richmond- Sleet begins around 7am, transitions to snow around 10am.
  • William and Mary/Williamsburg-Sleet begins around 9am, now around 11.
  • JMU/Harrisburg- Storm begins around 2-4am.
  • UVA/Charlottesville- Storm begins around 2-4am.
  • VT/Blacksburg/Radford- Begins during late morning
  • Longwood/Farmville- Sleet begins around 8am, transitions to snow around 11am.
  • UMW/Fredericksburg- Sleet begins around 2-4am, transitions to snow around 8am.

Amounts:

  • Hampton Roads- 1-4″. Depends on how much sleet mixes in. If less, totals more
    towards higher range.
  • Richmond- 3-6″ with some sleet accumulations
  • William and Mary/Williamsburg- 3 to 6″ with some sleet accumulations
  • JMU/Harrisonburg- 6 to 12″
  • UVA/Charlottesville- 6 to 12″
  • VT/Blacksburg/Radford- 1 to 3″
  • Longwood/Farmville- 4 to 6″
  • UMW/Fredericksburg- 5 to 10″

The numbers above is my current thinking. The map below, is from the National Weather Service.

totalsnowNational Weather Service Forecast

Charlotte Forecasting Discussion

The discussion below is a little technical and more wordy than the normal discussions I issue. This was created for a forecasting class at UNC Charlotte. It is for the snowstorm 2/12-2/14 and was written the evening of 2/11. 

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A significant winter storm will impact the Charlotte area during the next few days. Monday evening, a surface front was situated off the coast of SC and NC. A 1036mb high was situated over the northern Great Plains. This high will move east, and help funnel cold air into the region aloft as cold air damming occurs.

 On Tuesday, models vary as to what amount of precipitation overruns the cold air and moves into our area. The NAM keeps most of the moisture south, while the GFS brings moisture into the whole region, with around a half of an inch of QPF. GFS appears to pick up on an area of upper level energy moving through, which helps enhance lift and cause the precipitation.  BUFKIT sounding profiles support snow across the region, even while surface temperatures are a degree or two above freezing. Ground temperatures are still rather warm, so if precip falls tomorrow some should originally melt. However, it should be noted than extended period of snow could add up, potentially up to a half inch or inch of snow through Midnight Wed if the GFS is right. 

On Wednesday, the big event takes shape with heavy precip amounts and an extended period of precipitation. Miller A storm track with surface low pressure forming in the Gulf of Mexico and moving up the coast. Precip should move into the area from the southwest as we go into early Wed morning.  There is surprisingly good consensus in midday runs in terms of QPF, however, evening runs vary with the NAM being nearly an inch higher in QPF than the GFS. We’ll need to watch future model runs to see how QPF varies and how models depict precip type events.

In terms of precip type, the 18z NAM shifted freezing rain and sleet further west, with almost a five hour period of freezing rain Wed evening due to a warm nose at 900 to 850mb. If this happens, power outages would become an issue when you combine the potential for heavy snow and ice. The 0z NAM-4 also supports this icing potential. The GFS on the other hand keeps the primary precip type as snow, with only a brief period of freezing rain very early Thu morning. The inversion on the GFS isn’t as significant, and leads me to think it could easily be overcome due to heavy snow rates. Obviously, models have been flip flopping run over run and as I mentioned above in terms of QPF though, shifts in the track of the low will need be watched over the next 24 hrs as these shifts could be critical in determining what type of precip we see and how much.

Heavy snowfall accumulations look to occur regardless of icing. Afternoon runs of the GFS and NAM both displayed snowfall amounts around 7 inches. SREF plumes mean average is around 7 to 8 inches as well. The question is, where does the deformation zone set up? Where this heavy band of snow forms may have a large impact on totals. If the heavy band sets up over Charlotte, a foot of snow may not be out of the question. Taking a blend of models, and factoring in the potential for icing, I feel as if a 6-10″ range for snowfall accumulations in Charlotte is not out of the question, with the low range being if we see more icing and the higher end being if we see more snow.

 Precip looks to continue into Thu, eventually tapering off late Thu morning as freezing rain or drizzle as the low pulls away to the northeast. High pressure builds back in for the weekend, with a few weak cold front moving through the area Friday night and Sunday. Precipitation at this time from those systems seems limited. 

Snow possible this week!

Eastern and Central VA will see the potential for some snow showers, and perhaps accumulating snow as we go into the week of New Years. The first chance of snow will come Monday night (12/30) into Tuesday morning (12/31). The second chance of snow will come later in the week, Thursday into Friday. The second chance of snow is still many days out though, and things could change. 

Image

Monday night, the precipitation could begin as snow across the area, and then transition over to sleet/snow. This is due to a developing wave of low pressure off the SE coast, that will provide the moisture for the snow. The best chances of snow will be over central VA, with the precipitation being more mixed towards the coast. I think there is a good probability though that all of us see at least a short period of all snow. At this time, accumulations look to be minor if any. The image to the right is a meteogram showing potential snowfall amounts for Newport News (KPHF).  This does not account for melting of snow on contact with the surface however. Due to this, I tend to believe accumulations will be small if any. 

Behind this system, temperatures remain cold through the week with highs generally in the mid 40s across eastern VA for Tuesday, New Year Day and Thursday. Thursday night into Friday, the next potential weather maker moves into our region. In my opinion, it is still too far out to determine if this event will be rain or snow. Having said that, it does appear that once again, a period of snow will be possible across the region. Your location may greatly determine your precipitation type. Stay tuned!

 

Ice Storm on Sunday

Welcome to Winter. It seems like just last week we were talking about the potential for some snow showers, and now Mother Nature is back with more! This time, it’s in the form of ice…

This weekend, Central/Western VA and portions of western NC will be “wedged in” with cold air. High pressure to our north and low pressure to our south will create a setup called cold air damming. When this happens, cold air gets trapped or wedged up against the Appalachian mountains and can’t escape, just like water in a dam. This is a fairly common thing for VA and NC.

Rain vs Sleet vs Freezing Rain

In cold air damming, the cold air is generally very shallow and close to the surface. This sets up the potential for freezing rain. To get freezing rain, you have to have cold air below 32°F at the surface and some warm air aloft. As the precipitation falls through the sky, it melts and falls as rain all the way down to the surface. Since the cold air is shallow, the water droplets don’t have time to re-freeze into sleet (ice pellets). As a result, they fall as rain and hit the ground as liquid precipitation. However, since the ground is below 32°F everything that falls freezes on contact, creating an icy glaze!

This type of setup is what is going to occur this weekend across central and western VA. The map below and to the right is from Matt DiNardo’s FB page. I’ve linked it because I feel like it is the best representation of the impacts I’ve seen thus far.

Let’s break it down region by region:1475871_614674358592831_1487743535_n

East of Richmond including Hampton Roads:

  • Most of the precip falls as rain, but some sleet and light freezing rain is possible
  • Generally no major travel issues

Richmond Metro along I-95 :

  • I believe that the dividing line between a major ice accumulations will be the Richmond metro area. Having said that, a glaze up to a half of an inch of ice is possible and this could certainly bring down some power lines in area.
  • Travel could become difficult at times, especially on untreated roads and sidewalks.

West of Richmond Metro including the University of VA, JMU, Longwood, VT and Radford: 

  • The potential exists in these areas for a major ice storm that causes significant travel disruptions and power outages.
  • Over a half of an inch of ice is possible in the Blue Ridge mountains, with slightly lesser amounts as you go down in elevation.
  • Some snow and sleet accumulation up to an inch is also possible across western VA, with higher amounts possible especially in the higher elevations N of Roanoke.

Ice storms are not fun… They cause power outages and can make travel impossible. I would strongly advise against any long distance travel on Sunday especially across western portions of VA.

As always, things can change. We, as weather forecasters are not as good as we think we are. We make mistakes and forecasting any type of weather, and especially winter weather is not easy…. There are many many factors that you have to take into account. Numbers and impacts are subject to change we get closer to Sunday.

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