The current Baltimore/Washington watch & warning map shows the counties shown in purple-blue are under Winter Weather advisories from 4AM to 11AM Friday 12-11-08 (in addition to Flood Watches overnight). As you know, the counties shown in green have only flood watches at present. Based on past trends, and road conditions, I expect this Friday morning:
NO DELAY: Howard County. They have no days/hours built into the calendar, surface air cold is marginal, temps will remain above freezing, most of their paved surfaces are in suburban environments than more rural Carroll County. However Ho Co is under a Winter Weather advisory. If you are a teacher or student there, I suggest setting the alarm and just let go of any idea you're in for a delay. The same applies to Baltimore City, Anne Arundel County.
2 HOUR DELAY: Counties of Baltimore, Harford, Cecil, Carroll, Frederick. Rationale: Higher terrain and more than 1/2 of their geographical area will be affected by winter weather conditions in the crucial time from 4AM to 7AM. While accumulation on roads is unlikely, a quick burst of snow could easily produce many slippery spots. Sun angle has no bearing on this event, nor does surface temperatures. The deciding factor will be a short period of heavy wet snow that hinders visibility. I suspect these counties may have to wait until they see "ground truth" that the NWS forecast is verifying and what road conditions present at 5:30 A.M. So you had better SET THE ALARM regardless and tomorrow morning, closely monitor your news station (or radio if in the car). Last winter a 2-hour delay decision was changed to closed after I left the house, and though I have very little distance to travel, that was not the case for untold hundreds of teachers and parents who learned of the closing upon their arrival at schools.
CLOSED: Highly unlikely any of these counties will see the conditions that prevent school for the entire day, with temperatures remaining above freezing across Maryland except for far western areas.
New Orleans Snow Note: My overview of the Surprise Dixie Storm was moved back to draft status so I can add more pictures and clean up the formatting. Will re-post this Friday with my winter analysis writuep.