Saturday, December 19, 2009



6:45 PM UPDATE 12-19  Blizzard warnings, which were in effect across the entire Baltimore-Washington metro area have been discontinued by the Sterling, VA NWS. The Winter Storm Warning remains in effect until 6 AM Sunday. Regarding final snow totals, for my long time friends and colleagues in Dundalk, MD where this site began-- I ran the final numbers for our town as a sampling of the outcome. At 7AM I observed 4" at my house. The period 7AM Saturday to 12AM Sunday may produce a total of 1.50 liquid x 16.7 ratio (provided by Terpguy) = 25.05 + 4 = 29.05" for Dundalk, MD. Stay on top of the shoveling tonight if you can!

The forecast team believes a third and final shortwave will cross central Maryland  later this evening, extending the duration of accumulating snowfall into the early morning hours. This may add an additional 2-5" depending on your location. Higher totals near the Bay, lesser near the Blue Ridge.

Bursts of heavy, thunder-laden snow, falling at 2-3" per hour across much of Maryland today resulted in part from several upper level shortwaves. Mr. Snowlover in western Baltimore County has tracked this upper level system since Wednesday night on NOAA charts. The original shortwave energy engaged a nearby upper level low in the Midwest. Upon the low's arrival in this area, it enhanced pre-existing conditions further, and contributed to the heavy snow and the thunder today. Note that the forecast team on Friday morning 12-18 predicted thundersnow and rates of 2-3" per hour for this afternoon, 30 hours in advance. Photo: Dundalk, MD at arrival time of 850 mb shortwave.

STORM GRADE TOTALS by 12 PM Sunday 12-20
For new readers, the "StormGrade" refers to a percent accuracy grade assigned to these counts based on deviation of actual from predicted at end of storm. We use NWS data and/or NWS spotter reports only. Since this effort is also a student research project, we do not adjust the numbers once they are confirmed. Then we use a simple accountability system to determine accuracy. Key: total liquid x predicted ratio = final accumulation.
Source of liquid equivalent data for our calculations.

PENNSYLVANIA locations added 1:00 PM 12-19
Philadelphia 1.77 x 12 = 21" | Allentown 1.25 x 14 = 17.5" 
Lancaster = 18" | Harrisburg 1.2 x 15 = 11" | State College = 6.5" | Altoona  = 7"

DELAWARE: Wilmington (pending) | Dover 2.62 x 10 = 26"

MARYLAND locations added 1:00 PM 12-19
Hagerstown 1.75 x 15 = 26" | Frederick (tbd) | Reisterstown (tbd)
Parkville (tbd) | Baltimore 2.37 x 12 = 28" | Dundalk 1.50 x 16 = 29"
Belair (tbd) | Salisbury 1.7 x 8 = 14"

VIRGINIA: Washington 2.08 x 14 = 29" | Richmond 2.22 x 10 = 22"

STUDENT SNOWFALL REPORT: 9:30 AM UPDATE 12-19 The snowcast kudos go to 9th grade science students at the Baltimore County Public School's Crossroads Center. (Baltimore Sun article) On Thursday 12-17, Mr. Foot's students conducted similar calculations as noted above, and reached a preliminary estimate that storm totals could exceed 12 inches. On Friday 12-18 their analysis was refined to  24.72" by Sunday 12 PM for BWI airport as a representative location for the Mid-Atlantic. Below: a photo of 9th grader J.E.'s TI-84 calculator and his liquid equiv. calculations.

However, these forecasts would not be possible without the extensive research on climate data conducted by our intrepid band of student climate collaborators. The climate team consists of Ms. Gerst's inquisitive 5th grade students at Perry Hall Elementary AND the multi-tasking 9th grade science students of Ms. Abrahm's at Mount Saint Joseph's High School in southwest Baltimore. Since early November, those two teams closely tracked  atmospheric and oceanic data to pinpoint a trigger event which led our collaborative effort to conclude a major storm would develop.

5:30 AM 12-19 UPDATE: Northeast base reflectivity radar from the National Weather Service shows heavy bands of snow continue to move north across Virginia, Maryland and well into Pennsylvania. The National perspective shows why there may be occasional lulls in the snow this morning. Heavier snowfall rates are likely as the second set of shortwaves and upper level lows in the midwest move through the Mid-Atlantic. Our intrepid team of winter storm forecasters will iron out those details this morning, and post our report by 11AM if possible. The totals reflect our projection of the storm potential as of 11:00 PM Friday 12-18-09.   

Regional coverage of our snowfall totals will be expanded to include other key locations where many loyal readers reside. Spotter reports from the Sterling, VA NWS Office continue to show accumulations climbing throughout the night, although we were stunned just by how much had fallen in places like Charlottesville, VA (11") by midnight Saturday. Spotter reports from the surrounding NWS offices will be added once the links can be located. Check back often, additional media and content will be made available including Facebook, Twitter and photo sharing space for use  during non-instructional time. The objective is to provide meaningful scientific analysis and enrich your experience on this site as we all collectively share in this historic moment.

Link to this morning's Baltimore Sun article on our student climate and weather project. And, as you can see, we in the Foot household are getting out to enjoy the storm.

No comments: