Thursday, February 22, 2007

HERE WE GO AGAIN
slight revisions Thursday evening 2/22

STICKY, SLEETY SITUATION THIS WEEKEND

Since the title of this site is "Basic Weather For Busy People" I'll get right to it. Please note to those in school systems receiving this message that your servers will likely block the computer model image I have above. You can instead go to the European computer model link to see it yourself.

Any talk of a big warmup in the news media has been swept away by a big cold front and accompanying Alberta Clipper which chargec into the Northeast and Mid-Atlantic Thursday, 2/22. As you probably already noticed, your Saturday-Sunday local forecasts have been flopping all over the place and are now trending colder. A few days ago, my Weather Channel Local Forecast for Saturday in Dundalk, MD was Rain, 65*F. Now it is "Wintry Mix" with temperatures in the 30's. Well what happened? Quite simply, US-based computer models were trying to send the Ohio Valley Low right into a sprawling High in the Hudson Bay. That would have allowed tremendous warm air to surge northward ahead of the storm. Thanks to the Laws of Physics, computer models have finally caught on to the fact that the primary low will have to stay farther south, introducing the wintry mix scenario you now see in your forecasts. My concern is the colder trend could continue, to the point that Sunday night we might be looking at a sleet/freezing rain situation along north and west of I-95 from DC to Philly into interior Maryland, southern/central Pennsylvania. Plain rain south and east of I-95.

I see two distinct possibilities with this weekend system:

1. The NWS forecast holds up. Here's an example forecast from suburban Philly. What prevents this from becoming a big surprise ice/snowstorm is location of the High. The cold air is not in the right place, as indicated by the bright pinks surrounding the High way up in Hudson Bay. The low moving into Ohio Valley develops a secondary along Del-Mar-Va, but enough cold air is left over, and ample moisture is fed into the Mid-Atlantic/Northeast from onshore flow in advance of either low, the precip starts as snow/ice Saturday into Sunday. However the secondary tracks too close to the coast (as with the Valentine's Day Storm) and by Sunday evening the metro areas end up as rain, with some snow in interior sections (Appalachians, southern/central/southeastern PA). This will no doubt prompt "Winter Weather Advisories" from DC up to Philly along with the regions associated with those cities.

2. Surprise, Surprise. The secondary low develops farther south off the Mid-Atlantic coast than we expect, and tracks a few more miles out than what is currently believed. This allows the secondary to pull in just enough additional cold air from the "improperly placed High" that would the changeover is delayed or barely occurs. What starts as sleet/freezing rain/snow mixed stays that throughout Sunday and into the night. I am leaning away from this scenario due to location of the High.

If you can see the map above, the Euro is projecting the "zero line at 850 mb" to be in the I-95 corridor. (This is essentially a lower-level indicator of whether or not precip would be frozen at the surface based on where this line is located geographically). Look for the light-bluish/whitish band of color in the Mid-Atlantic. You can see that by 8PM Saturday night, most metro and interior sections are well within the 0*C line. Question is how long does that line remain, does onshore flow push that line back (north) allowing the changeover to rain? You can also see how there is a bit of a battle being setup between three pressure systems. The Canadian High seeming to want to nose it's way down, the Maritime surface Low in the right corner helping to funnel cold air down the Eastern seaboard, and the approaching Ohio Valley low seeming to send warm air into the mix from the south. What an interesting setup this is going to be.

The saving grace for everyone is Monday air behind the storm should be milder so despite either scenario, that might prevent schools in the metro areas from being closed or delayed. Interior schools could face delay issues Monday morning. I really doubt this can turn out as an unexpected big snowstorm in case you were wondering, but it will make for travel and scheduling headaches Saturday and Sunday.

Is winter over? Not exactly. There is potential for 1-2 more storms over the next 10-15 days. I am skeptical either storm will become a major snow event for the Mid-Atlantic, due in part to higher sun angle as we move into March. There could be some snow and ice from either storm, but sun angle could eat away at most of it. The exception of course would be storms like March 13-15, 1993 and March 20, 1958, but don't get your hopes up that this winter goes out in a white blast.

The comments feature will return this weekend after I make a few modifications. Thank you to the 275+ of you whom have made the switch to the Feedblitz program. This greatly streamlines the updating process directly to your e-mailbox. I sincerely appreciate your continued support and readership of this site.

9 comments:

Mr. Foot said...

The PhantonKahuna has returned... as will the comments for now.

Whether or not you are in a public or private school system...if you post a comment on this website, please keep in mind the following:

1. Your supervisor (or mine) may be reading this, and doing so fairly regularly during a winter weather event.

2. The word "supervisor" should be interpreted to include the following leadership positions, all of which have been or are current readers of this site throughout the Baltimore DC Philadelphia Metro regions to Central and Eastern Pennsylvania, Virginia and West Virginia. These people are:
- Department Chairs, Assistant Principals, Directors, School Superintendents, CEO's and business leaders, state and federal workers, military officers, members of the medical profession, including Doctors at Johns Hopkins and other regional hospitals.

3. While the comment feature is a "public forum" it is conducted by the honor system. Statements that are overtly and unnecessarily critical of school systems for inclement weather decisions will not be tolerated. It is expected that each member posting here would do so using the highest standards of professionalism, proper English and respect for others as if the person reading were your spouse, friend or ::::drum roll::::

SUPERVISOR.

Thank you all for your continued support and readership. Our next storm looks to be very interesting... so off to the races we go!

Newton said...

Mr. F.
As one of the aforementioned "supervisors" I have never found any comment here to be overtly critical. (Nothing more than could be heard in any teacher's lounge across the state) I commend you for your caution and constant striving to not offend. Some should just relax.
Now how about this surprise storm? I, like some others, had tuned out with the warmer conditions this week, and then tonight I hear Winter Storm Watch! Wow!
Any thoughts about the icy build-up?
1/4" ? Similar to last week?

kristine said...

I have a friend coming in from out of town this weekend..should we worry about the drive home to Philly on Sunday?

Newton said...

I saw the forecast for Philly, and it was all about sleet and snow from Sunday afternoon until Sunday night.

Mr. Foot said...

About Philly..let's just say the Foot family was thinking about subcontracting a grammy to visit, but if we can't get her here by Saturday evening, it's not going to happen. Mom isn't about to drive south into snow, sleet and freezing rain.

There's something fishy about this storm, I'm surprised at how quickly many of the models jumped to the colder solution. NWS offices were trending their forecasts toward a snow/rain mix and in the past 24 hours we've moved (obviously) to within projected warning criteria for the DC-Baltimore Metro area, southern and central PA and it looks as though Philly is going to raise headlines as well.

It is time for an update so that will be the focus this evening. Wording from the Philly NWS office Special Weather Statement is strong and the surrounding offices (DC-Balto, State College) all seem to be leaning toward an increasingly significant event in the realm of .25" ice. There's uncertainty about the amount of liquid available for this storm, and that could really torpedo these NWS headlines if amounts come in much lighter than anticipated now that expectations have been raised fairly high for icing, to the angst of the public.

I'll investigate "bust potential" and report back after baby's bath and bedtime!

Julee said...

Will someone please unearth Andy?

Mr. Foot said...

Ms. Julee:

You mean Dr. E.H. yes? I believe he's carousing (sp?)about in Europe, probably trying to tweak the ECMWF so it can turn this storm into a New England Kahuna.

I recall he would be back the 24th. Everyone quick email or fax 4" of snow to him and then he'll get the blizzard he's been waiting for in his emailbox.

Putting the children to bed, be back when all is quiet on the upper front.

Mr. Foot said...

How stupid am I? I'm having pre-storm late stage junior moments, getting my forecast postees misidentified.

Julee, you meant southern york county andy. He's probably in babybedtimeland also!

Justin said...

This storm needs to wait a little....Terps play on Sunday

Interesting though how the reports moved all over for it