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A Change In the Air

Steve Scolnik @ 4:55 PM

One thing is certainly clear: Whatever changes February has in store, they will last for at least 3 days less than what we experienced in January. Yesterday's +10° temperature departure from the long-term average left the unofficial average for the month at 43.0, tying 1998 for 3rd place at Washington National and 7th place on the all-time Washington list for warmest Januaries.

The map of temperature departures for last week (click for a larger version) shows that we have been just on the edge of an even warmer area through much of the Midwest and Great Plains. This is quite different from our all-time warmest January of 1950, when it was actually very cold in the north-central U.S. It's becoming clearer that the models are itching for some pattern changes, though, so stay tuned for Josh's upcoming post for more details.

Under some broken high clouds, temperatures in the Washington DC metro area are starting off the new month above seasonal averages again, mainly in the mid 40s after an official low of 38. The next chance for rain (and it will be rain for essentially all of the East Coast) is tomorrow night into Friday. The more interesting situation is the following system coming along over the weekend. There is still major model disagreement on this, but the latest projection would favor rain east of the Appalachians.

Tonight and Tomorrow

For tonight, lows under partly to mostly cloudy skies will be near 36 in the city, a few degrees colder in the 'burbs. Tomorrow's highs will be near 57 with increasing clouds in the afternoon.

Extreme Snowfall Ratings

Here's a map which should warm the hearts of the snow lovers out there. It shows the snowfall from a NESIS Category 5 ("Extreme") storm, Jan 6-8, 1996. NOAA announced this week that it will be publicly releasing rankings of winter storm impacts on a 5-point scale analogous to the Saffir-Simpson hurricane categories and the Fujita F scale for tornadoes. The NESIS ("Northeast Snowfall Impact Scale") rating is based on a system developed by Paul Kocin of the Weather Channel and Louis Uccellini, director of NOAA's National Centers for Environmental Prediction.

The rating is calculated by combining the depth of snow, the area covered, and the population affected. The NESIS categories will be determined following a storm, so they will not be used in forecasts. No plans were announced for naming storms either, so we won't be hearing any time soon, "NESIS Category 5 storm Mike is headed for the Blue Ridge."

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