PM Update: Cold tonight, mild Friday; snow melts faster under trees?

November 14, 2013

Temperature Map

Temperatures: Latest D.C. area temperature map. See interactive map on our Weather Wall.

After our coldest morning since last March, temperatures rebounded nicely into the mid-50s.  High pressure overhead promises a calm but cold night followed by sunshine and another warm-up Friday.  But by Friday afternoon, this high glides offshore and clouds streak back into the area.

Through Tonight: Much of the region logs its third straight sub-freezing night.  Mostly clear skies and calm winds let the atmosphere vent (let the heat out), and lows range from the mid-20s in the colder suburbs to right around freezing downtown.

Tomorrow (Friday): Mostly sunny skies to start the day quickly elevate temperatures through the 30s and 40s.  Afternoon highs should approach 60, even as mid-to-high level clouds make themselves known.  Winds come in from the south around 5-10 mph.

See David Streit’s forecast through early next week. And if you haven’t already, join us on Facebook and follow us on Twitter . For related traffic news, check out Dr. Gridlock.


The Korean War Veterans Memorial on Veterans Day. (Joe Newman via Flickr)

Snow melts faster under trees than in open fields in certain climates:  A new study out of the  University of Washington reports a surprising result: In certain circumstances, the sun doesn’t melt snow as efficiently as trees.  Here’s a snippet from the study news release:

Common sense says that the shade of a tree will help retain snow, and snow exposed to sunlight in open areas will melt. This typically is the case in regions where winter temperatures are below freezing, such as the Northeast, Midwest and most of central and eastern Canada. But in Mediterranean climates – where the average winter temperatures usually are above 30 degrees Fahrenheit – a different phenomenon occurs. Snow tends to melt under the tree canopy and stay more intact in open meadows or gaps in a forest.

This happens in part because trees in warmer, maritime forests radiate heat in the form of long-wave radiation to a greater degree than the sky does. Heat radiating from the trees contributes to snow melting under the canopy first.

Here’s a link to the study abstract: Lower forest density enhances snow retention in regions with warmer winters: A global framework developed from plot-scale observations and modeling

Some additional news items from today:

Panel Warns of ‘Catastrophic’ Gap in Weather Satellite Data (Climate Central)

Scientists nearing forecasts of long-lived wildfires (UCAR)

Image of the Day: Cloud Art (ImageGeo)

Jason is currently the Washington Post’s weather editor. A native Washingtonian, Jason has been a weather enthusiast since age 10.
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Jason Samenow · November 14, 2013