Monday, December 12, 2005

AN ICE STORM COMETH?

Dec 3B

Forecasters and computer models are growing increasingly concerned over a complex winter weather situation developing in the Mid-Atlantic and Northeast for the Wednesday night-Friday night time period. The most recent indication of this is a Special Weather Statement issued by the Baltimore/DC NWS Office Monday afternoon. Emphasis is on the word COMPLEX. Let me break it down for those of you wrangling over what this may mean for schools, especially in Maryland. (Please note that for the time being I will refrain from specifically referring to certain larger K-12 educational institutions in the post by name for fear that doing so may result in this website being rendered unavailable to you at a public school)

1. WHAT IS LIKELY TO HAPPEN. A multiple Low pressure system will approach the Mid-Atlantic at same time that a fresh supply of cold air is becoming available from Quebec, Canada. Recent snow cover will serve to reinforce this process. The two air masses will clash starting Wednesday night and produce a wide range of precipitation types, including snow, sleet, freezing rain, sleet, fog and rain. However, the orientation of the Lows is such that the I-95 corridor is likely to see precip begin as snow, sleet and freezing rain, then in the mid-morning hours on Thursday, it may change to plain rain as the Low(s) will pass close to or over major cities. The timing of this is critical as it relates to the Thursday morning commute. At present it is expected the cold air will retreat slowly, allowing for a slower changeover of the precip from frozen to liquid. This scenario would result in Maryland, WV and Western/Interior Virginia schools being disrupted on Thursday morning with at least a delay.

2. WHAT IS NOT LIKELY TO HAPPEN. The Lows take a more inland/southerly track that would not scour out the cold air prior to arrival, and what was going to be an ice/rain storm becomes a surprise snowstorm with 6-12 inches on Thursday. The dynamics of this storm are much different than Dec 9, so do not expect this to happen. Interior sections of PA, western MD and NY will see a moderate snowfall as depicted by the graphic above, but not the major I-95 cities.

3. WHAT IS THE HANGUP OVER THIS? If the frozen precip Wed night takes longer to changeover Thu AM, Maryland schools may be looking at a "2 hour delay...reevaluate at 7AM" situation which happened in late January 2004. Continue checking back on this developing situation, as further posts will elaborate and analyze the storm in more detail.

5 comments:

Andy, Southern York County PA said...

Just have a gut feeling this will be much snowier than anticipated. Everytime I look at the forecasts they trend snowier and colder. Accuweather has 3.4 inches on their snow meter for york county and northern Balto. Co. I bet we get another 7 inches up here and some sleet maybe. Trend is colder and I bet it continues that way.

Andy, Southern York County PA said...

The below from the NWS seems to continue to indicate a colder trend. Far cry from yesterday. While they are still throwing in some ice and sleet mention, there seems to be less emphasis on it. This MIGHT be a nice storm. Keep trending colder and we may all have something to smile about!

HAZ. WEATHER OUTLOOK
DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

A STORM SYSTEM TRACKING INTO THE GREAT LAKES WILL LIKELY SPREAD
SNOW INTO CENTRAL PENNSYLVANIA EARLY THURSDAY. THE POTENTIAL
EXISTS FOR SEVERAL INCHES OF SNOW ACCUMULATION...AS WELL AS SOME
ICE.

ALSO...THURSDAY FORESCAST

Snow likely...a chance of freezing rain and sleet. Additional moderate accumulation possible. Not as cold with lows in the upper 20s. Chance of precipitation 60 percent.

Andy, Southern York County PA said...

Jim Cantore of the weather channel just indicated snow for the big cities then mix and back to snow, maybe in a hurry for Boston. If coastal low bombs out, an altogether dif. scenario for the cits. may occur.

Mr. Foot said...

Yeah Andy this forecast is definitely going to follow it's predecessors this winter... in flux right to the last moment.

I imagine Watches will be posted by Tuesday night, and Warnings by Wednesday noon. That should delight the schoolfolk.. a WSW usually is a good indicator of n school or a delay. Maybe the cold stays stronger and longer, thus changeover to rain in I-95 occurs later? Balt NWS says that onset appears to be slower now...early Thursday they said, wonder if that means just after midnight or early as in daybreak.

I am going to call for snow/sleet/freezing rain mix for a few hours starting after midnite. from MDL south, gradually changing over to rain by mid-morning, from MDL north the changeover is later and for a shorter time. Balto gets .5" then .25 ice then rain. School is closed Thursday 12/15. That's my early $.02

DerbsATerp said...

im just hoping for all rain, the powderhound in me wants the 6-12 not gonna happen scenario, but i just want to take my finals and head back to ellicott city for a few weeks of rest

as much as i love college park, i dont want to be taking a final on christmas eve.....