Warm front, cold front, snow
Temperatures in Baltimore have been rising steadily since sunset yesterday, nearing 60 degrees late this morning. You'd never guess we're expecting a big snowstorm this weekend.
But that seems to be increasingly likely. AccuWeather's extreme-weather blogger Henry Margusity is still hyping the storm, of course. But now, as the forecast range grows shorter, even the National Weather Service is becoming more confident.
The official forecast for the weekend still calls for "a chance of rain or snow" beginning Saturday afternoon, followed by "snow or rain likely" Saturday night, and "a chance of snow or rain" again Sunday.
But in their morning discussion, forecasters are sounding more convinced. There's still a lot of uncertainty about where the rain/snow line will fall, of course. But they acknowledge that the weekend storm "could be a high-impact event across the (forecast area)."
More on the storm in a minute. First, we need to pick our way through a lot of weather that's expected here between now and then.
First, as you no doubt noticed heading out this morning, there is a warm front pressing into the region from the south today. It's actually the same stalled front that's been giving us cool weather and periodic showers and fog all week. Only now it's on the march northward.
After temperatures flirt with the low 60s today, the front will move south again this evening as a cold front, dropping a few showers here and there and sinking temperatures tonight into the 30s. A storm system tracking along the front tomorrow will bring us some more precipitation. It could begin Thursday morning as freezing rain or sleet in western and northern counties, but mostly we should see rain. Welcome rain, I should add, a quarter- to a half-inch. They'll see ice and snow to our north.
Winter storm watches are already posted for tomorrow just north of the Mason-Dixon Line.
Whatever falls here, it should all be rain by late Thursday as the front moves north again as a warm front. And they're expecting it to end Thursday evening. Then high pressure and colder temperatures move in. Friday should actually be sunny. Remember sunny? But it's the sunny before the storm.
Forecasters say the real winter storm will approach us on Saturday. Morning lows will be in the upper 20s, rising to only 37 on Saturday at BWI. This morning's discussion says, "Confidence is reasonably high that such a storm will develop and affect the (forecast area) over the weekend. Yet there remain uncertainties about the details ...namely track, strength and timing."
And therein lies the rub. The storm center is expected to reach the central Appalachians, weaken there and spawn a secondary low off the Virginia coast. That would intensify the system, and gin up more snow and wind. And the storm track is critical to where there snow/rain line falls.
For now everybody - the NWS, AccuWeather and Madman Margusity - seems to be sketching that line in along the I-95 corridor. But a twitch either way could mean the difference between a few inches of slush and 6 or 10 inches of snow. Here's Capital Weather's take.
"Needless to say," the folks at Sterling said anyway, "specifics such as the rain/snow line will need to be resolved as we get closer to this potentially high impact storm."
For what it's worth, here's Henry's latest snow map:
Comments
I've only been watching this blog for a few weeks now, but you seem to suggest that readers should take Madman Margusity's forecasts with a large grain of salt. Care to share the background on that?
FDR - Sure. Anybody who puts out a snowfall map five days ahead of a storm is taking a scientific risk. There are simply too many variables in meteorology to be able to forecast - accurately and consistently - that far in advance. I think Henry himself would acknowledge that. But he does it anyway because that's his job; people who read weather blogs love it; it boosts Web traffic, and he's having a whale of a good time doing it. But he also makes lots of adjustments to his forecast as the time clicks by and the picture clears. Compare his first blush with his final forecast and I think you'll see what I mean. The NWS forecasters prefer to stick with what they can say with some confidence, and no more. That's simply better science - Frank
Posted by: Bill | December 12, 2007 1:00 PM