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January 2012

Snowfall Verification for Jan 21

This was an interesting one to watch unfold…

Cold air damming allowed for more snow at the onset of the storm than what I was expecting, which resulted in broader 1-2 inch coverage east of the mountains in central VA, MD, DC and southern NJ. This also allowed the freezing rain and sleet to work a bit further south. The back end of the system also had a surprise up its sleeve, bringing up to seven inches of snow to the Pittsburgh area. The snow underperformed a bit along the southern edge in the mountains where warmer temperatures led to more mixing and plain old rain.

The higher snow totals were captured pretty well for the most part, especially along the southern edges of the 2-4 inch and 4-8 inch contours. The pink indicates areas that received 0.1-0.25+ inches of sleet and/or freezing rain (which was a bit trickier to contour due to the nature of the reports).

I knew the snow was a bit of a risk in the CAD region, but I didn’t pull the trigger on it and ended up paying for it. I’m going to give this forecast a grade of B-… the northern areas were quite good, but the southern areas suffered a bit.


I have a new map design that I will roll out during the next snow event. On top of being a larger image, it also has county lines and interstates for easier interpretation.

Winter Storm Threat: Jan 21 (final call)

Following a southern trend of the models and recent temperature verifications compared to earlier forecasts, I have come up with this for my final forecast:

The pink contour indicates where 0.1-0.25+ inches of accumulating sleet and freezing rain is possible.

Some sleet will mix into the areas receiving over an inch of snow, and some freezing rain is also possible in the 1-2 inch snow contour.

Start time of the event was expanded earlier to better account for the precipitation in the western edge of the map.

Winter Storm Threat: Jan 21 (first call)

A relatively weak area of upper-level energy will bring about some snow to the region on Saturday. The precipitation is expected to start out as snow for most, with some light sleet and/or freezing rain across the southern part of the pink contour. As the mid-levels warm, sleet and freezing rain will become dominant in the southern areas, allowing for accumulations 0.1-0.25+ inches. This will be more temporary along the southern edges as the mixed precipitation changes over to just rain mid-morning through the afternoon.

The pink contour indicates where 0.1-0.25+ inches of accumulating sleet and freezing rain is possible.

The southern areas of snow and mixed precipitation can thank cold air damming (CAD) for their accumulation as sub-freezing temperatures get wedged into the region east of the mountains at the surface. The CAD will eventually erode out of most of the region south of the Mason-Dixon, but when remains a key question, as it determines how much mixed precipitation accumulates and how long it sticks around. I think the models are doing a fairly good job handling the CAD for this event at this range, mostly due to the fact that the disturbance is fairly weak throughout the event and will not be advecting temperatures as much as a more energetic system would.

Coldest morning of the season in the Northeast

A lot of locales in the Northeast are experiencing their first sub-zero lows of the winter, with temperatures as cold as -24F in Watertown, NY! (Yes, it’s -24, not -23. The software rounds the Celsius conversions oddly in some cases)

A 1030mb high centered over southeastern Ontario is allowing for light to calm winds under mostly clear skies.

UPDATE: Grabbed the hour with the coldest temperatures and updated the map.

Storm chasing in 2012

Now that we have turned the corner into 2012, it is time to start getting plans ready for my 2012 Chasecation.

This year will be a lot different, as I have a more flexible looking calendar from mid May to mid June to spend two weeks out in the Great Plains. I really wish I could stay out longer, but I have not been able to save up that much time off. Next year I will have more time to play with, and I might consider skipping a year of chasing to stock up enough time off to do longer chases beyond that.

A lot of things culminated together last year to make it a pretty terrible chase, including dry, hot weather and a fairly tight chase schedule. On top of the improved schedule availability, over the last couple of months the southern Plains have gotten a fair amount of wet weather, which should help the overall weather pattern a little heading into the late spring. It would be ideal to see the wet weather continue in the southern Plains as the drought is still widespread despite the recent rain and snow taking a dent out of it.

For equipment, I have decided to invest in a DSLR camera for this trip. My old consumer-level digital camera has broken, and I do not want to use my cellphone as my primary camera. It will be a nice improvement that will bring all of my equipment up to the “prosumer” level. I do prefer shooting video, and I will use my Canon HG10 for that. While a prosumer-level camcorder, I plan on upgrading to a more professional digital camcorder a few years down the road. Other already-acquired equipment I will have available includes my HP laptop, tripod, Garmin nuvi 1450 (as a backup GPS) and a backup 400w power inverter.

For chase partners, I plan on teaming up with Jason Foster and Ian Livingston again this year (same as 2011). Jason has switched out the 2000 Subaru Legacy with a 2000 Jeep Cherokee, and that will be our chase vehicle if he can get it ready for the Plains in time. I will help him prep the vehicle if he requires assistance. If that fails, we will acquire another vehicle for the trip.

On top of being an excellent driver and navigator, Jason will also provide all of the chaser equipment for the trip, including a laptop stand, GPS and road map software, antennas and a signal booster, power inverter and extra plugs and a satellite internet card. He will also have a dashcam and has the capability to do live streaming.

This year is looking a lot better than last year (couldn’t get much worse, am I right?), and I can’t wait for May to get here!


Jason Foster

Web Site:
Twitter: @weatherwarrior1


Ian Livingston

Web Site:
Twitter: @islivingston

Radar watching – snow at two levels

Just wanted to post this as it is an interesting phenomena where you can see the low-level convective snow (the long and thin features oriented west-to-east) and the comma-head snow/clouds rotating around the Radar site:

The low-level convective snow is created as leftover moisture takes advantage of the steep low-level lapse rates behind the cold front, which forms low-topped convective clouds and precipitates. The comma-head snow in the mid-levels is pivoting around the 700mb low. It’s interesting to see both of these features together so distinctly on radar.

Quick thoughts on tonight’s/tomorrow’s snow

This rain-changing-over-to-snow event has been the main snow event to watch over the past few days, and now it looks like it will come to fruition… at least for those from DC and points north as the tail-end of precipitation rolls through the region between 2-5am.

The latest HRRR is putting down some light accumulation east of the mountains for those north of DC:

I would be a little weary for the total amount of accumulation east of the mountains, but it certainly is possible if the “thump” of snow is strong enough.

Some isolated flurries are also possible during the day tomorrow east of the mountains if enough moisture is available.