Conditions in south Arlington at 9:30 PM:
Tuesday, February 2, 2010
Snow Continues!
Moderate to, at times, heavy snow continues across the DC Metro region. About 2 inches have fallen in parts of Arlington with probably another 2 to come before the storm winds down after 2 AM.
Conditions in south Arlington at 9:30 PM:
Conditions in south Arlington at 9:30 PM:
First Flakes!
From our on-the-ground reporter, Bryna, we hear of first flakes flying at around 5 PM in Arlington. Steadier light snow now in progress at 5:50 - looks like it's here to stay for a while!
Enjoy!
Enjoy!
3:00 PM Update
The storm looks kind of disorganized to me on the radar, but we're officially under a Winter Storm Watch from the National Weather Service who is going generally for 3-6 inches overnight.
I think we might end up on the lower end of that range but based on some of the computer models, I don't think it's unreasonable.
Snow should start up here within a couple of hours, unfortunately. The later the better so that I don't have to deal with commuting issues!
I think we might end up on the lower end of that range but based on some of the computer models, I don't think it's unreasonable.
Snow should start up here within a couple of hours, unfortunately. The later the better so that I don't have to deal with commuting issues!
And stronger still...
The little storm that could! Storm even stronger and tracking slightly more north than previously.
3-4 inches seems probable now, 6 inches is just possible.
I love this Winter!
3-4 inches seems probable now, 6 inches is just possible.
I love this Winter!
Snow on the Way
The snow is coming. Storm looking a little stronger and better-organized. At least a couple of inches sounds like a good bet. 4 is not out of the question.
This morning's GFS (Global Forecast System) computer model run shows about 0.25 - 0.50 inches of liquid equivalent precipitation for the DC metro.
Remember that a good rule of thumb is 1 inch of liquid equivalent = 10 inches of snow.
So a forecast of 2-4 seems about right.
This morning's GFS (Global Forecast System) computer model run shows about 0.25 - 0.50 inches of liquid equivalent precipitation for the DC metro.
Remember that a good rule of thumb is 1 inch of liquid equivalent = 10 inches of snow.
So a forecast of 2-4 seems about right.
PV Storm #2: February 5-7 [OUTLOOK]
Just a quick note about the potential for a major winter storm to affect our area from Friday through late Saturday. Timing, intensity and track are all variables at this point - so no one should run out and get bread quite yet. But, to give you some idea of the hype and excitement that meteorologists sometimes have to contain, I want to show you a map from a weather forecast model called "DGEX".
If your eyes are good, you'll see that the DGEX is suggesting that by the time the storm is over and done with the East Coast, the DC area will have around 2 feet of snow on the ground with 30 inches possible just to our south.
Do I think this will come true? WAY too early to say. But it suggests the possibility of a serious storm coming this weekend.
Monday, February 1, 2010
PV Storm #1: February 2-3 [Expected Class: 2]
Quick Look: Well, this looked like a minor nuisance until this morning's model runs. Now it looks like we in the DC area could get around 1-2 inches of snow, with isolated 3-inch amounts, beginning tomorrow afternoon into tomorrow night.
If the storm was coming later, there would likely be more accumulation. But as a lot of the precipitation will fall during the day, and temperatures will be in the high 30's, much of it will melt until the sun goes down. I'd guess 3 inches isn't impossible, but an inch or two is more likely at this point.
Forecast Rationale: Here's a model that mets use for short-term forecasts. It's called the NAM (North American Mesoscale model). We use it because it has more detail than most models and it's pretty reliable in the short-term.
So what do we see here? This is a plot of precipitation, surface pressure and temperature in the atmosphere at 850 mb (around 5000 feet). Meteorologists look at the 850mb temperature to guess what type of precipitation will be falling (rain? snow? sleet?). We look at the precipitation plot to forecast the amount that will fall and the surface pressures to judge how strong the storm is.
First, find Virginia (or Maryland or DC) on the map. Notice the dark blue line that goes from just southeast of DC through south-central Virginia and into North Carolina. That's the 0-degree Celsius line. Everything north of that will be frozen precipitation of some type.
Note that much of Virginia is covered in green and, specifically in the DC area, we're covered in medium-green which, looking at the legend on the left, corresponds to between .10 and .25 This is in inches of liquid precipitation equivalent.
Note also that just to our south, in central Virginia, the NAM shows darker green which corresponds to .25-.50 liquid precipitation equivalent.
So, we take those numbers and use the rule of thumb that 1 inch of liquid water equals 10 inches of snow. Therefore, in the DC area, the NAM suggests 0.10 X 10 = 1 inch of snow at a minimum and up to 0.25X10 = 2.5 inches of snow as a maximum.
Based on atmospheric conditions and flow, this seems reasonable to me.
If the storm was coming later, there would likely be more accumulation. But as a lot of the precipitation will fall during the day, and temperatures will be in the high 30's, much of it will melt until the sun goes down. I'd guess 3 inches isn't impossible, but an inch or two is more likely at this point.
Forecast Rationale: Here's a model that mets use for short-term forecasts. It's called the NAM (North American Mesoscale model). We use it because it has more detail than most models and it's pretty reliable in the short-term.
So what do we see here? This is a plot of precipitation, surface pressure and temperature in the atmosphere at 850 mb (around 5000 feet). Meteorologists look at the 850mb temperature to guess what type of precipitation will be falling (rain? snow? sleet?). We look at the precipitation plot to forecast the amount that will fall and the surface pressures to judge how strong the storm is.
First, find Virginia (or Maryland or DC) on the map. Notice the dark blue line that goes from just southeast of DC through south-central Virginia and into North Carolina. That's the 0-degree Celsius line. Everything north of that will be frozen precipitation of some type.
Note that much of Virginia is covered in green and, specifically in the DC area, we're covered in medium-green which, looking at the legend on the left, corresponds to between .10 and .25 This is in inches of liquid precipitation equivalent.
Note also that just to our south, in central Virginia, the NAM shows darker green which corresponds to .25-.50 liquid precipitation equivalent.
So, we take those numbers and use the rule of thumb that 1 inch of liquid water equals 10 inches of snow. Therefore, in the DC area, the NAM suggests 0.10 X 10 = 1 inch of snow at a minimum and up to 0.25X10 = 2.5 inches of snow as a maximum.
Based on atmospheric conditions and flow, this seems reasonable to me.
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