Tuesday, January 13, 2009

UPDATE: MON JAN 12 - 8:45 AM. A more thorough analysis of the weather systems to affect the Mid-Atlantic this week reveals the following. 1/13 Revisions of 1/12 post are noted in red.

1. It will be quite cold, but for Maryland and most of the Mid-Atlantic, this is a short-lived outbreak totaling 3-4 days, with the core of cold from Thursday night to Saturday. Most of northern Maryland with snowpack will approach zero by Saturday morning, and single digit temperatures will be widespread across the western half of the state. For Friday morning, The GFS projects a 5000 foot temp of 24 degrees C below normal (about 11 degrees F lower than it should be). Update: surface temps are projected to be 20-25 degrees colder than climate norms, so YES, we are looking at the coldest air in the region since 1996. I am surmising that NWS forecasters and computer models alike are now taking into account a wider coverage of snowpack than expected.

2. (Note: This section was designed to focus on the Tuesday non-clipper only). For snow this week, add the word "scattered" in front of "chance" and what most of us will see is cloudy skies with occasional scattered flurries on Tuesday. The factors here are track of the surface low (well north of MD), source region of the moisture (central Canada.. not a real wet place right now), and the rainshadow/downsloping effect of the Blue Ridge to wring out any moisture that does make it over the top. I know the "fluff factor" is enhanced greatly in an Arctic air mass, but moisture is marginal to start with, and there's no help from an upper level shortwave to swing through and stir things up... then we're left with flurries at best. The ONE chance we have is the Thursday clipper, as HPC shows a possible track very close to Maryland. However, to get a good shot at accumulating snow that track HAS to travel south of DC, otherwise warm air intrudes. Update: No warm air this time, what was I thinking?

3. What about the Inaugural Storm? The GFS has generally "lost" the storm again, which it is prone to do in the long range anyway, but the European still points towards a semi-coastal low and a deep (albeit positively tilted) trough over the East. Obviously, many many people are watching this potential as well, so if someone else makes a unique predictive discovery, I will be sure to post that info here and credit them well. Update: NWS and others are returning to the idea of 'something' on Tuesday, will revisit this after Thursday's clipper is through.

4. Any chance school is delayed or closed this week? Whether you are in Philadelphia, it's western suburbs, or south-central PA, or the MD counties of Carroll, Baltimore, Cecil, your only shot at a snow-related delay is Thursday morning 1/15. That's if the clipper pulls a December 5, 2007 manuver - comes in faster than expected with more moisture, tracks a few miles more south, and the fluff factor brings a quick hit of snow overnight into the mid-morning. Friday 1/16 brings the possibility of cold-related delays, as windy conditions behind the low and arrival of the Arctic front create wind chills low enough Friday morning to also launch a round of delays. Update 1/13: NWS will likely post wind chill advisories for Thu PM through Friday. With a high in Towson not above 17 F (and that's not factoring in snowcover), this looks to be a real test of will. As in, WILL the issue of frostbite and small children who walk to school be factored into any decision-making? WILL the fact that it is a 3-day weekend anyway influence a Friday decision? WILL this week's HSA blitz ending on Thursday affect the outcome? How many teachers cars WILL NOT start Friday morning? How long WILL it take for the buses to warm up if there's no delay to allow extra time. WILL your classroom air supply device be providing you with COLD air, HOT air or NO air? Might we see high school students who wear only t-shirts (and no coats.. of their own free WILL mind you) finally learn their lesson when arriving to school shivering? Uh, probably not.
And finally... how much time WILL district and area office secretaries have to spend answering the phone on Friday if..... well, you know.

INTRODUCTION: SAT JAN 10 - 3:45 PM. This will be part of the new post in development to cover our upcoming Arctic outbreak. So you understand the depth and intensity of this event, it may equal or surpass that which occured in January 1994. Many of you across the Mid-Atlantic no doubt remember the on-going disaster that followed: the month of ice storms. Who can forget the school calender alterations...extending the school day by 45 minutes, and in some cases, time added at end of the year. I specifically remember my younger brother's school in Berwyn, PA had the last day of moved forward to June 30! Each year I relate the story, and tell my students that we should put some real meaning into July 4 and make it a REAL Independence Day.

While I am not suggesting a repeat, this period of historic cold will cause a lot of problems for a lot of people, even if no ice storms follow. If a snow-pack is present by next Saturday, parts of northern Maryland should see morning lows of 0 to -5 F. I learned on the Eastern US Weather Discussion site today that the GFS is indicating New York City may experience overnight lows of -5 F or colder. Starting this Tuesday the 13th, there are several opportunities for the southern I-95 corridor (metro areas of Richmond, DC, Baltimore) to receive accumulating snow. Snow is possible on 1/13, 1/15, 1/18 and yes, even during the Inauguration. A FAST but useful animation of precipitation type as projected by the GFS over the next week gives you a general what is coming and when.

A very unusual situation may set up for Tuesday 1/20 (as shown above and already noted by a participant on this site). The GFS has been advertising a coastal storm, and IF it evolved the way this image depicts, would probably force the swearing-in ceremony indoors! Please note I do not take credit for this graphic, but it was posted by a fellow weather watcher on the Eastern US Wx site. Wouldn't it be so ironic if record cold along with heavy snow and blustery winds (say, a blizzard) caused widespread school closings on that day? Regardless of your political tendencies, what a wild statistical anomaly it would be if the atmosphere made the final decision for those districts not currently planning to close for the Inauguration!

Scroll down to earlier posts for specifics on the Arctic outbreak. For those in the education community, I will post a closer examination of which dates present the greatest risk to the school schedule, because I strongly suspect we will not escape January without at least one day of the "clean sweep" (that's all the schools in your particular metro area calling out). Check back later for more details, and in this round of comments I will be responding to those of you who wrote in the previous post.

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