
December 21, 2008: Seattle. Two Seattle residents enjoy impromptu sledding on Denny Way in Capitol Hill as the city kicks off winter with the most snow in over a decade. Photo credit: Mike Kane/Seattle Post-Intelligencer. Visit the storm gallery.



December 25, 2008: For Christmas Week, I have updated this post with a newer version of the music video I thought you might enjoy. This recently released single from Enya's new winter album is truly a heart-warming masterpiece of the simple things that make this time of year memorable and filled with anticipation. The lyrics and melody captured for me what it means to not only "honor the holidays" of all religions but to always observe the real reason behind the season.
" KEEP YOUR EYE ON LATE SAT NGT INTO SUN. SIG WINTER EVENT MAY BE UNFOLDING DRG THIS TIME. GFS IS GETTING CONSISTENT IN SHOWING A VERY CLASSIC PTN FOR WINTER WX IN THE METRO AREAS AND POINTS W. IAD FCST MAX TEMP OF 33 IS DOWN A DEG VERSUS YESTERDAYS MEX MAX GUIDANCE FOR SUN AND IT WILL START OFF BELOW FRZG TO START THE EVENT. 850 MB TEMPS START THE DAY AT MINUS 7 IN THE MTNS WITH SFC SYSTEM FCST OVR KY AT 12Z SUNDAY. 2NDRY LOW THEN BEGINS TO FORM ALG THE CAROLINA COAST. AGAIN...STAY TUNED. IF YOU DON'T LIKE WINTER WX...MIGHT BE A GOOD TIME TO CALL YOUR FAVORITE AIRLINE AND GET THAT TICKET TO MIAMI."
" I have reason yet to "just believe" in the potential for a major snow and ice event for the Mid-Atlantic and Northeast corridor before December ends. Although I originally targeted the first week of December as the likely period, a slowing of the pattern progression has delayed this possibility by 2-3 weeks. That places the next period conducive for measureable, significant snow (greater than 4") or ice (greater than 1/4") to December 17-25."
Based on my analysis of the "Nowcast" links, where I can perform a quick assessment of storm dynamics, it DOES NOT appear this will be a surprise ice storm for the Baltimore Metro region. Nor does it seem likely places like Southern Balto County, Howard, Anne Arundel or Montgomery will get any school delays out of this. Hereford Zone, Harford and Frederick might be the only ones this time. We have a classic "over-running" situation, (strong cold 1038mb high to the north, precip running over the cold air) but alas the surface/boundary layer cold air is too marginal this time. Sleet/freezing rain are "latent heat release" events, that tend to keep the temperature right at or just above 32. By contrast, snow is an evaporative cooling event, which pulls heat out of the atmosphere and thus chills it, thereby making the environment around the snow falling more conducive to producing additional snow. Despite your expectation of falling temps tonight, I think whatever they are right now will be exactly that by sunrise. That radar loop will look just about the same come morning I'll bet. A delay for all of BCPS could only occur if slightly more than half the county reporting areas observes slippery conditions by 5AM, which I doubt.
However, next week the drumbeats have already started on a major winter weather event taking shape for Saturday-Sunday. This looks to be the big kickoff I've been indicating for some time (just off on the timing!). More details about that Wednesday.
12/11 UPDATE: Forecast: New Orleans: Snow. Baltimore: Rain.
Are current anomalies indicators for the upcoming winter pattern?
I thought you might appreciate (or be jealous of) this unusual radar from the Southeast today, and powderhounds will no doubt wince at these hard facts: NWS reports accumulations of 2 to 8 inches throughout central and southern Louisiana. Here's "ground truth" proof. Scroll to end of the post for more details and links to news sites reporting on today's pre-season freak snow.
My analysis and forecast for the Northern Hemisphere seasonal pattern from December 1 to January 15. I realize the graphic below may be hard to read, so for those with unfiltered access to flickr, a copy of the image is available here. I will also post a written explanation of this graphic in the event you wish to use this as a teaching tool for your students. This approach enables climate teleconnection watchers to do exact comparison of the forecast versus the actual, as by the 15th it should become clear if this pattern I have laid out is developing or not.
The graphic above is why I have reason yet to "just believe" in the potential for a major snow and ice event for the Mid-Atlantic and Northeast corridor before December ends. Although I originally targeted the first week of December as the likely period, a slowing of the pattern progression has delayed this possibility by 2-3 weeks. That places the next period conducive for measureable, significant snow (greater than 4") or ice (greater than 1/4") to December 17-25. That does not automatically mean I am alluding to a white Christmas, so do not interpret this as a signal to activate false hopes. As you will read later, I am a lifelong skeptic of ever seeing the aforementioned highly-sought after winter weather event occur on a specific date so tied into our contemporary holiday lore. Not to dash you out of the snow, but my next essay in progress is titled: "Blame it on Dickens and Sunspots: The inconvenient truth about white Christmases." For now, you'll have to live vicariously through this video montage from the Polar Express, and ask yourself if you "believe."
"WHITE IS IN THE...DEEP SOUTH ?"
Certainly, the folks along the Gulf coast must still believe, because it seems that if you want real measureable snow these days..forget Baltimore, Washington or New York. The place to find that wintery white stuff is in the usual spots, like Houston, Jackson, Miss. or New Orleans. Just take a look at the current NWS US watch and warning map. notice where the Winter Storm Warnings are? Yeah, where you'd expect them this time of year: Southeast Louisiana, southern Mississippi, places that are so accustomed to snow, it probably did not even make headlines. (Oh wait, that's in the alternate universe Ice Age version).
Looks like the NOLA Times-Picayune is reliving their inner childhood, because when you see "white in the 'not-even-winter-yet' night in a place like "Southtown", there's no better way to describe it than simply with the headline of: "It's Snowing!" 9:30 AM update: The editors have since changed that to "Snow falling throughout the metro area"
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.
Looking for snow in the near future?
As of December 8, all I can say is there soon may be...
from Saturday, November 29:
SUNDAY STORM AND DECEMBER TRENDS
SAT AM UPDATE: I hope our tranquil Thanksgiving was enjoyable for you and your family, and gave you time to get "tanned, rested and ready" by Sunday, as we are heading full force into this season's first region-wide winter storm. However, coastal dwellers in the I-95 corridor will have to live vicariously through their interior Pennsylvania counterparts this time. This is yet another repeat of the storm dynamic the Northeast has had over the past 2 years: shallow fingers of cold surface air lodged in valleys over-ridden by warm moist air aloft. From Washington to Philadelphia and their metro regions, the cold layer is thin and will be scoured more quickly, turning a brief Sunday morning snowfall over to rain. The "kitchen sink" region will setup in the 219/220/99 corridor in western and central Pennsylvania from Johnstown to Altoona to State College. This area will see precip begin by dawn as light snow, and progress through the morning to sleet and possibly freezing rain depending on surface temperatures. North and west of this area should see mostly snow, but amounts will be limited to less than 4 inches until return flow in the storm's wake restarts the lake effect machine on Monday.
For the remainder of the Mid-Atlantic, east of I-81, morning snow mixed with sleet will prevent significant accumulation, but be enough to make roads challenging in the mid and late morning. Thus, if you are traveling Sunday, as I will be, my suggestion is to get on the road soon after sunrise when the precip will be light. I do not advise waiting to leave until you see a changeover to, as by then you'll have to negotiate a lot more slushy, slippery conditions and the bulk of holiday travelers returning home.
Passage of the primary low into western Pennsylvania, and the coastal low through Del-Mar-Va will change all precip over to rain by Sunday night - squashing any possibility of Maryland schools being closed on Monday, although some interior PA districts may have delays due to refreezing Sunday night.
This current European model projection for 7PM Sunday night supports my adage for these types of storms: "The primary low stays stronger longer." A 990mb low in Ohio will track across Pennsylvania, enhanced by upper level short-wave energy while a weaker secondary low moves through the southeast. Also to note is the lack of a surface high to resupply with cold air. In this scenario, no high and the separation between the two lows will prevent this system from cranking into a widespread coastal snowstorm.
I believe the setup of this storm finally reveals the true indications for December's weather patterns: the deep 850 mb trough in the midwest (pointing to a negative NAO), the Pacific/western ridge (leading to a positive PNA), and a new reserve of cold air, while not extreme, is beginning to reload in northern Canada. The next section focuses on my forecast and analysis for December into January, and over this weekend will be adding graphics and links to support the discussion.