Snow and ice west, heavy rains east
A stalled cold front and a developing coastal storm tracking along the front have triggered winter weather advisories for the western counties of Maryland, and flood watches on the Eastern Shore as heavy rains approach.
Here in the middle of the state, we're looking at some heavy rain of our own, and the risk of a wintry mess Friday morning, if the forecast holds up. Here's how the folks in Sterling put it this afternoon:
"LOW PRESSURE WILL BRING COPIOUS AMOUNTS OF MOISTURE TO THE REGION. 1 TO 3 INCHES OF RAINFALL IS POSSIBLE THURSDAY AND THURSDAY NIGHT ACROSS THE OUTLOOK AREA. THIS
COULD PRODUCE MINOR FLOODING OF SMALL STREAMS AND CREEKS.
"IN ADDITION...LATE THURSDAY NIGHT INTO EARLY FRIDAY...RAIN MAY MIX
WITH FREEZING RAIN BEFORE CHANGING TO SNOW. SOME LIGHT ACCUMULATIONS
OF WINTRY PRECIPITATION ARE POSSIBLE. THE MOST LIKELY TIME FOR
WINTRY PRECIPITATION ACROSS THE BALTIMORE WASHINGTON METRO AREA
APPEARS TO BE WITHIN A FEW HOURS OF SUNRISE ON FRIDAY MORNING.
Look at it this way: If the cold front were colder and moved farther south faster, this storm could have dropped 10 to 30 inches of snow on our heads. There's something there for everyone - to celebrate, or to lament.
Here's the water vapor loop, shot from orbit, showing the Gulf moisture cranking up to our south and west.
Comments
"Look at it this way: If the cold front were colder and moved farther south faster, this storm could have dropped 10 to 30 inches of snow on our heads."
May I add some context?
While it/s true...1-3" liquid converts to 10-30" frozen @ 10:1...but it/s a virtual impossibility for that to happen and therefore it/s not a very good example.
In the general case...an air mass must be below freezing from the surface through the depth of the cloud to produce snow. When the air temperature is below freezing...the amount of water vapor is far less than the amount of water vapor in an air mass where temperatures are above freezing.
Just b/c the system may put down 1-3" of rain does not mean 10-30" of snow would have resulted if the temperature had been cold enough.
FR: Ah, science...
Posted by: TQ | December 10, 2008 9:08 PM