Winter Storm Watch posted: 12 to 20 inches
Here we go again. The National Weather Service forecast office in Sterling, Va., has just posted a Winter Storm Watch for nearly all of Maryland west of the Chesapeake. It warns of the possibility of more than a foot of snow, and "a good chance" for more than 20 inches in some places, by Saturday.
Here's more from the National Hydrometeorological Prediction Center, which uses the word "crippling." Here's AccuWeather.com (snow map at left). And here's Mr. Foot, who has been all over this one..
The Winter Storm Watch says the snow would begin by late morning on Friday, and continue through Saturday evening. Temperatures late Friday and Saturday should be in the upper 20s to 30 degrees. Says Sterling:
"THIS STORM HAS THE POTENTIAL TO BE SIMILAR TO THE DECEMBER 19TH STORM.
PLAN FOR SUBSTANTIAL DISRUPTIONS TO TRAVEL FRIDAY AFTERNOON THROUGH THE
That Dec. 19 storm dropped 21.1 inches at BWI over two days. If we get another 20-inch-plus snowstorm out of this at BWI, it will be the first time since snow records began in 1883 that's occurred. Hoo boy.
But there will be differences, according to the forecast discussion from Sterling:
"COMPARISONS HAVE BEEN DRAWN TO THE LATE DEC SNOW STORM
/MAINLY IN THE UPPER DYNAMICS...PROGRESSION AND EVEN TIMING - LATE
FRI THRU EARLY SUN/. IT MUST BE NOTED THO THAT THE INCOMING SYSTEM
WILL BE A BIT WARMER OVERALL...W/ A DEFINITE RAIN-SNOW LINE
FURTHER NORTH THAN THE DEC STORM AND STORM-TOTAL ACCUMULATIONS
"ENOUGH COLD AIR WILL BE IN PLACE /E
OF I-95/ FOR AN ALL-SNOW PRECIPITATION-TYPE /POSSIBLY A BRIEF PERIOD OF A RAIN-
SNOW-SLEET MIX AT ONSET/. ALONG AND EAST OF I-95 WILL CERTAINLY BE THE
MIX LINE FOR MUCH OF THE DAY...W/ A CHANCE OF A SNOW CHANGEOVER
LATER IN THE EVENING-OVERNIGHT AS A SFC LOW STRENGTHENS OFF THE
COAST OF CAPE HATTERAS AND PULLS SOME OF THE COLDER AIR BACK SWD.
"AS THIS LOW STRENGTHENS...MUCH LIKE THE DEC STORM...WINDS WILL
STRENGTHEN OVER THE BAY AND COASTAL REGIONS /NEARING GALE WARNING
FROM SAT AFTN-EARLY SUN/. BACK TO THE WEST...SNOW WILL CONTINUE OVER
THE REGION AND BE ESPECIALLY HEAVY AND CONTINUOUS LATE FRI INTO
EARLY SAT. EVEN AS THE SURFACE LOW TAKES A BULK OF THE SYSTEM OFF THE
MID ATLANTIC COAST SAT MORNING...SNOW WILL CONTINUE ALL THE WAY BACK
INTO THE OHIO VALLEY /HEAVIEST EAST OF THE APPALACHIANS/. ANOTHER ROUND OF
LIGHT-MODERATE SNOW WILL CONTINUE THRU MUCH OF THE DAY FOR THIS
REGION ASSOCIATED W/ THE PASSING UPPER TROF AXIS."
Enough warning for you?
Just to jazz up the hype machine a little... Just received this via Candy Thomson, The Sun's outdoors writer, who got it from a DNR guy who got it from a guy who works at the NOAA forecast center. (How's that for attribution?)
"Subject: Early Friday Scoop
"Have a few minutes before I delve into a report that is due this
Friday... so let's cut to the chase.
First... there is no question a storm is coming. There is also no
question that it will be a very large storm, with 2-3 days worth of Gulf
moisture inflow to work with. So it won't be lacking in the pcp
department. The westward-moving blocking high over the Davis Straight
should virtually ensure the system does not track to our west and
north... but rather suppresses it to our south. This would also ensure
that it is mostly a cold event for the entire region, and support snow
or sleet or snow grains (mostly snow).
"Timing.. The first batch of pcp will be overrunning pcp... pcp that
forms when warm, moist air from the Gulf runs into and over cold air
already in place. Overrunning pcp is not an easy animal to pinpoint wrt
timing cos it's not really an entity that moves from point A to point
B... but tends to kinda just develop. Models handle this differently...
with the latest NAM/WRF having the snow arrive ~ 8 pm on Friday, while
the GFS has snow falling in the metro area between 7-11 am on Friday
morning, with crippling snowfall rates by mid afternoon. Needless to
say, this is a huge discrepancy, and would directly impact most
everyone's planning (work, kids, shopping, etc). I think the safe bet
is to go with the earlier timing.
"Amounts: The GFS is "lighter"... with "only" 1.25 to perhaps as much
as 1.75". Assuming a conservative 10::1, that'll get you 10-18" of
snow. The WRF is the closest thing to Armageddon in a non-hurricane
fcst scenario that I've ever seen. It has a whopping 3" max over
Baltimore (literally centered on Mt Washington). with over 2.5"
everywhere else. Again, assuming all snow, that would be 25-30"+.
Ouch. Let's put it this way: Rulers may be useless for measuring snow
by late eve on Friday.
"Duration: OK... so we have some differences inre to the onset, but the
general idea is during the day on Friday. When does it all end?
Well... after the overrunning part of the storm starts to wind down, the
models all show a second, stronger coastal low developing which gives us
a second prolonged burst of wind-driven snow.... some of which would be
quite heavy. This is the part of the storm that will be occurring on
Saturday. No Hyperbole here: If the GFS and WRF are correct, the
region will be shut down on Saturday (and likely beyond). The coastal
low will be pulling colder air into the region from the north, causing
that snow to be fluffier and more apt to blow around into large drifts.
The snow would finally end as the remnant western low drifts over head
late Saturday eve or early Sunday.
"Analog: The NWS is using the Feb 10-11, 1983 storm as an analog. That
storm featured almost 23" of snow at BWI, with lightning and thunder.
Sounds good to me.
"Summary: Yes, it's still 2 days away... and while I tend to geek out
on y'all a bit, this storm should be taken seriously. My biggest worry
would be anyone who "has" to be at work on Friday... and they make it in
without any problem cos the pcp is slow to arrive, and then spend the
next 8 hours trying to get home. The NWS is buying into it at every
level (local and national offices), the models have it, and the storm
already exists. Safe to say, she's a comin'.
"I'll keep you posted if there are any changes. - E"