Wednesday, January 16, 2008

WILL POWDERHOUNDS BE PLEASANTLY SURPRISED?

WED 1/16 - 10:00 PM UPDATE: I am now expecting an earlier start time, based on rising dewpoints and faster than anticipated movement of the southern system. I believe you'll see snow and sleet mixed outside your window at 5 AM in the Baltimore/DC area. If I'm right and you see precip before daybreak, this will be the field goal that nets you that day off you've been hoping for so long (if you're in Baltimore County or City, Harford, Carroll, Frederick and yes even lil' ole' stodgy Howard County too, believe it or not.) The map below is the 10:30 PM Radar, and you can see precipitation is already intruding southwest Virginia. Even though much of that may not be reaching the ground, the speed of arrival tells me that it should overspread the area between 4:00 and 5:00 AM. Late-breaking addition...NWS Sterling, VA has upped the amounts on your Winter Weather Advisory, and upgraded large swaths of Virginia to Winter Storm Warnings. If that all comes to pass, the school forecast is, as George Tenet might say, a SLAM DUNK.

Thursday Surprise 3

Now compare how hugely different this map has become from just one hour previously. Didn't your grandfather always used to say "the biggest storms always came from the south." Here's a another weather rule that never fails: If it's snowing in Atlanta, it'll be snowing in Baltimore.

Thursday Surprise 2

WED 1/16 - 7:00 PM UPDATE: This projection from the GFS model indicates snow and/or frozen precip may still be falling even at 1 PM Thursday across most of central and western Maryland.

Thursday Surprise 1


WED 1/16 - 6:00 PM: I figured you'd be back here before long. Perhaps you were wondering if I would ever be back, but since the weather has provided us a new topic, as Captain Kirk might say: "Well, now you have something new to talk about." As many of you already know, the Baltimore/DC NWS issued a Winter Weather Advisory for the most of Maryland west of the Chesapeake Bay, including the DC and Baltimore Metro areas. I've been watching their discussions, the observations, satellite, and of course our old friend, the computer models, for several days now in anticipation this storm was going to deliver some sort of winter precipitation on Thursday. Those in this region whom follow winter weather are beginning to suspect that this system is not turning out as expected, and I anticipate a diversity of surprise closings and delays throughout the DC-Baltimore Metro areas are on tap Thursday morning. Low level cold air appears entrenched into the deep South, as evidenced by the extent of NWS winter weather advisories from here to Georgia.

This fast-moving system will display unique impacts across the Mid-Atlantic area (specifically in Maryland west of I-95, south central Pennsylvania, Northern Virginia, the West Virginia Panhandle, and of course the Shenandoah region):

1. Persisent high pressure "centers" in the Mid-Atlantic will allow temperatures overnight to drop below freezing. By daybreak, whatever precip that begins to fall will freeze on contact, allowing slippery travel conditions to develop quickly, and catch unsuspecting motorists/walkers off guard.
2. A rapid onset of precipitation from southwest to northeast in the pre-dawn hours.
3. The timing of snow and sleet is such that it will disrupt and delay traffic in the critical hours from 5 to 9 AM, and a changeover to "liquid precip" may not occur until afternoon.
4. Changing and unresolved precipitation timing concerns that may disrupt school schedules.
5. A fast moving system that WOULD become a major snowstorm were it not for lack of access to an Arctic high in Southeast Canada. (actually there is one there, but the timing and orientation are not right this round)

The biggest concern which prompted NWS to hoist advisories for the Maryland region is that computer models do not see to be handling the presence of low level cold air across the region. Secondly, the eventual intrusion of warm air aloft may be delayed such that frozen precip is now more likely over a wider area than originally thought, and for a longer period of time. Accuweather, on the other hand has been downplaying the potential for ice or mixed precip. As I remind my students in situations like this, the amounts sometimes does not matter if we have a mixture of frozen precip, because even one tenth of an inch of ice as you all know can wreak far greater havoc than just one inch of snow. The movement of this storm can be seen in a computer model animation from a site I've recently discovered: coolwx.com


For those who have wanted to know what's been going on: The lack of activity on this site is due mainly to the challenge of managing young children, on going winter illness and teaching high school. Those of you with children, or who teach children, or even just know how to spell children understand how rewardingly drained one feels at the end of the day sometimes. Hence there has been little energy left over to post on our recent weather events. I am grateful for the ongoing support of the many loyal readers out there, and feel bad I could not deliver more frequent updates the past month. Especially for my Pennsylvania, New Jersey and New England colleagues who must think we're no longer on speaking terms, as I stopped forecasting altogether even for Boston's recent snows, sorry guys! I will make it up to you. There are big things in the offing for next week and I have a special post in preparation for the announcement that "something is brewing out there...and it's not just the coffee."


Overnight and tomorrow morning: Please post your observations and location in the comments if you are able and willing.

10 comments:

Mr. Foot said...

Welcome back everyone and I hope you will be pleasantly surprised (that is, if you enjoy a little mid winter bonus)

Please post your observations and location, I will be interested to see how precip changes throughout the day.

If you have any suggestions for changes to the site links or format, the best time to make those updates happen is during a high profile weather event. Your input is always a valuable resource that helps refine the site.

I will post a roundup of morning school predictions, because I know some of you will be asking soon.

Ms. T. said...

Dear Mr. Foot,
Welcome back - glad you and your family are doing ok.

As a long time fan, first time poster, I am longing for some wintry weather! I teach at the elementary school down the road and our students are going CRAZY!!!!!

I hope the forecast cooperates with my needs - I'll be wearing my snow pjs inside out! :)

Russ L said...

mr. foot,
this storm is starting to remind me of the december storm--the little storm that could!

Russ L said...

just saw the radar--pretty large storm!

Mr. Foot said...

Welcome ms. t

I agree we all could use a day to "blow off the stink" and get some paperwork done!

Let me go out on a limb and say the following before I turn in:

1. It appears the cold air is locking into place stronger and more widespread than expected.

2. Dewpoints and %RH are up across the area. Clouds are moving in quickly.

3. I am thinking we're going to see an earlier start time to this, and it'll be snowing/sleeting by 5AM or even sooner in Balto Metro. If that happens, you'll see a near clean sweep of area schools.

I know this may seem like wishcasting, but I am starting to think it's going to be a rout tomorrow. Widespread snow and ice problems all day long. Districts will see it coming and not take the chance..especially with an earlier start time.

Foot Forecasts the following...

CLOSED:
-Baltimore County & City
-Howard, Harford, Carroll, Frederick, most NOVA schools and WV panhandle schools

2 HOUR DELAY:
-Anne Arundel, Cecil

We'll see how this looks at 5 AM tomorrow.

Remember it'll all going to changeover by mid afternoon, but not before the timing does the damage in the morning. That's what this storm all comes down to... precip timing. The very same precip type occuring in a different 6 hour time frame would not produce the same problems.

Mr. Foot said...

You'll notice NWS has been upping the amounts...now 2-4" and occuring throughout the day. That is sure to spook districts into pulling the plug, don't you think?
Besides, I sure could use a day to
get paperwork done, and get you prepared for the Big Kahuna next week.

(From the updated Winter Weather Advisory)

PRECIPITATION IS EXPECTED TO REMAIN SNOW INTO THE AFTERNOON
HOURS...BEFORE CHANGING OVER THE LIGHT RAIN AND AREAS OF FREEZING
DRIZZLE. TOTAL SNOWFALL OF 1 TO 3 INCHES IS EXPECTED FROM THE
DISTRICT SOUTH ALONG INTERSTATE 95. SNOWFALL OF 2 TO 4 INCHES MAY
OCCUR ACROSS THE BALTIMORE METRO AREA DURING THE DAY. TEMPERATURES
ARE EXPECTED TO HOVER NEAR FREEZING THURSDAY NIGHT SO HAZARDOUS DRIVING CONDITIONS COULD PERSIST AFTER THE PRECIPITATION ENDS.

Grant said...

Woohoo ! Finally, i have been waiting for a post for a long time, and we finally have a small little winter storm to settle our weekend out :) ! I'm also looking forward towards some wintery events sometime next week. Keep up the great work Mr.Foot See ya in class tomorrow !

Mr. B said...

And I sit up here with no adv/warnings yet. haha. I expect 5-6".

Prospero said...

5:15 and nothing yet.

Balto County will probably be in on time.

Mr. Foot said...

My earlier start time did not occur as I predicted, hence schools are going in on time. But alas, just watch and see what starts to happen from 9AM on.

This makes an early dismissal quite likely and problematic. The precip will be starting as high school students arrive, and will be picking up in intensity as elementary students arrive.

Headaches and hazardous travel will abound.