Wednesday, December 11, 2013

68 comments:
(Snow) Party in the U.S.A.
- Miley Cyrus

Current US snowcover from the NOAA National Ice Center
5:00 AM 12/11 (Winter Stormcast Team) If you're realllly ready to rock on some potentially serious snow in the Mid-Atlantic and Northeast, your wildest dreams may come true in the next phase of this beast of a pattern.

There's majorly disturbing language* in the latest Extended Forecast Discussion from the NOAA Weather Prediction Center. Even more so than the snippets we have below, taken from our Mid-Atlantic Winter Stormcast page in Facebook from Tuesday night. Read at your own peril. 

(3:30 PM 12/10) Look, it's not like we actually enjoy multiple storms in a row (ok, maybe we do a little), but for Powderhounds, the fun has just begun. Check out this little ditty from our colleagues at the NOAA Weather Prediction Center's Extended Forecast Discussion as of 10:58 AM Tue 12/10. 

"THE POTENTIAL EXISTS... PARTICULARLY IF THE SLOWER/STRONGER ECMWF [European Forecast Model] IS CORRECT...FOR ANOTHER SIGNIFICANT PRECIPITATION EVENT...INCLUDING SNOW/ICE...TO IMPACT AREAS FROM THE TENNESSEE VALLEY NORTHEASTWARD THIS WEEKEND...THE DETAILS OF WHICH REMAIN UNCLEAR AT THIS TIME." 
From the Sterling NWS Forecast Discussion as of 2:32 PM Tue 12/10:
"A COLORADO LOW IS EXPECTED TO FORM MID WEEK AND TRAVEL CLOSE TO THE GULF STATES BEFORE MAKING A TURN UP THE TN VALLEY AND TOWARDS THE MID ATLANTIC. BOTH THE GFS AND ECMWF ARE ON BOARD WITH THIS TREND AND A WINTRY MIX IS POSSIBLE AS IT APPROACHES THE MID ATLANTIC ON SATURDAY."
"HIGH PRESSURE SET UP OVER MAINE SHOULD ACT AS A BLOCKING HIGH AND ESTABLISH A COLD AIR DAMMING SCENARIO OVERNIGHT FRIDAY... HELPING KEEP SURFACE TEMPERATURES LOW FOR FOR THE ONSET OF PRECIP ON SATURDAY. OVERALL PTYPE AND TIMING SPECIFICS ARE STILL IN QUESTION."
*Seriously disturbing language in meteorology includes the words "Major Storm" and "Northeast Corridor" when all included in one sentence. Check back later today for more details on this invigorating development (Well, it is for Powderhounds, at least.)

Sunday, December 8, 2013

113 comments:

Will it be enough?

Current ice projections by the NOAA Weather Prediction Center in College Park, MD Lightest green is one-hundredth to one-tenth (0.01" to 0.10") light green is one tenth to one-quarter (0.10" to 0.25") and the real ice jackpot is the dark green and blue, with amounts greater than one-quarter inch of ice by Monday AM.

7:00 AM EST 12/8 (Forecaster Foot) Old-timers to this site who have traditionally hailed from the education and public safety communities break into three groups:
  1. Teachers and students, who just want a snow day no matter what it takes, any time of the year. (Heck, last season they had to wait until AFTER winter ended to get 1 measly day.)
  2. Parents and emergency managers, who just want the straight scoop on what is happening when, where, how long and how bad. When big decisions are pending, they don't have time for philosophical weather fluff
  3. Administrators and office workers, who only have 1 question: "Will it be ENOUGH??" This is a critical question that indicates the true potential severity of the storm -- will the intensity, duration and type of precipitation impact the region to the extent that offices are also closed for administrators? 

Saturday, December 7, 2013

6 comments:
A Freezing Rain Trick...That Is No Treat


Image source and article: The SkyBrary


6:00 AM EST 12/7 - Ever wonder what causes "freezing rain" ? By daybreak Monday morning, those in the Mid-Atlantic I-95 corridor and metro areas of DC/Baltimore will have a fast life lesson on the tricky science of a phenomena that has caught many a school system by surprise. If the significant icing that occurred in the Southern Plains and Tennessee Valley is an indication, portions of the Mid-Atlantic will face major travel disruption Sunday afternoon to Monday afternoon.


IS IT RAIN? The current NWS winter storm watches from West Virginia to Maryland and Virgina indicates several key ingredients will be in place to create a super-slippery surprise for those who think "it just looks like rain." The trick behind what turns a light rain into a disaster is called the "latent release of heat." With ground surfaces below freezing, anything that falls tomorrow morning will freeze on contact.



HOW TO GET TRICKED: If on Sunday night, snow and sleet are replaced by "rain" -- a weird thing will happen: The temperature will RISE even as a light glazing of ice is forming on surfaces. In the past, schools and businesses made their closing decisions on the change in temperature, as in "Look, the temp is going up! That means the ice will melt and we'll be in the clear!" Not so fast... A quick check of the latest Eastern Regional NWS advisory map shows they aren't falling for it.




KNOW THE SCIENCE: Freezing rain creates a different effect, for as the ice accretes on surfaces, the ground temperature often rises to near 32 F. Then, annoyingly, the temp can hovers near or at freezing for a few hours-- until enough warm air aloft can mix down to the surface. Why? Because accretion of ice is similar to condensation, a heating effect. While your thermometer reads air temps above 32, the ground UNDER the ice is may be less than 32! If any surface water on the ice "evaporates" - that causes a brief cooling effect, chilling the surface just enough to keep temps right around freezing.

A TRUE STORY: In Winter 2007-- one Maryland school system called for a 2-hour delay, only to have the bus drivers return to the lot reporting that the ice situation had actually gotten worse at 7:30 AM than it was at 5:30 AM! The delay was hastily changed to closed, and mayhem ensued with teachers having to turn around and go home, and parents having to call off work to pick up kids from schools that were open just 30 minutes before! What's your tale of winter woe from back in the day?

We chalk all this up to "Weather Politics" -- and this time, we hope that effective understanding of a scientific process will augment decision-making at those critical hours Tuesday morning.

(The Foot's Forecast Advisors)