Saturday, December 1st, 2012
It was still snowing lightly when I headed out to Stowe for some turns in the early afternoon, but it was done by the time I got back around dinner time. It looks like the next chances for snow are Wednesday and then Friday per the BTV forecast discussion:
WEDNESDAY AS TEMPS FALL THRU THE 30S TUESDAY NIGHT. TRAILING UPR TROUGH AND NWLY FLOW WEDNESDAY SHOULD BRING GENERALLY A CLOUDY DAY WITH POTENTIAL FOR OROGRAPHIC SNOW SHOWERS AND VALLEY RAIN/SNOW SHOWERS. WITH STRONG DPVA DURING THE AFTN...RAISED POPS TO LIKELY IN THE ACROSS THE NRN ADIRONDACKS AND NRN GREENS FOR SNOW SHOWERS. SNOW ACCUM 2-4" POSSIBLE IN THE MTNS. COOLDOWN WEDNESDAY WITH HIGHS IN THE UPR 30S/LWR 40S IN THE VALLEYS...LOW/MID 30S IN THE MTNS. SHOULD SEE TRANSIENT ANTICYCLONE BRING CLEARING SKIES AND GOOD RADIATIONAL COOLING CONDITIONS FOR WEDNESDAY NIGHT WITH NEAR CALM CONDITIONS. COLD TEMPS EXPECTED...OVERNIGHT LOWS IN THE TEENS TO LOWER 20S (WARMEST CHAMPLAIN VALLEY). SFC HIGH PRESSURE BRINGS LIGHT WINDS AND MOSTLY SUNNY SKIES FOR THURSDAY WITH TEMPS NEAR NORMAL (UPR 30S). PROGRESSIVE FLOW PATTERN MEANS INCREASED UNCERTAINTY FOR THE END OF THE PERIOD...NEXT FRONTAL BNDRY POSSIBLE LATE FRIDAY INTO SATURDAY WITH A CHANCE OF RAIN OR SNOW SHOWERS.
Monday, December 3rd, 2012
Roger Hill didn’t have much to say about Wednesday’s possible snow in his broadcast this morning, but the BTV NWS is certainly following the potential with a paragraph in the latest discussion with mention of several inches of snow and travel difficulties:
COOLER/MORE SEASONABLE AIR MASS DURING THE DAY WEDNESDAY WITH NWLY LOW-LEVEL FLOW REGIME SETTING UP. 2-M TEMPS AROUND 40F AT 12Z WEDNESDAY ACROSS VT REMAIN STEADY OR SLOWLY FALL THRU THE DAY AS 850MB TEMPS DROP FROM -2C AT 12Z TO -13C AT 00Z THURSDAY. ANY RAIN/SNOW SHOWERS IN THE VALLEYS WILL TRANSITION TO SNOW SHOWERS. MAIN FOCUS WILL BE IN THE HIGHER TERRAIN AS TRAILING UPR VORT MOVES ACROSS THE REGION 15-00Z. SETUP LOOKS FAVORABLE FOR OROGRAPHIC SNOW SHOWERS IN THE ADIRONDACKS AND NRN GREENS...AND INDICATED LIKELY POPS IN THE FAVORED LOCATIONS. SEVERAL INCHES OF SNOW EXPECTED FROM THE WRN SLOPES OF THE GREENS INTO THE HIGHER SUMMITS...AS WELL AS ACROSS THE NRN ADIRONDACKS. MAY SEE TRAVEL IMPACTS ALONG I-89 FROM BOLTON TO BROOKFIELD AND HIGHER ELEVATIONS ROADWAYS THRU THE GREENS WITH SOME ACCUMULATION ON ROADS.
really did not think it was supposed to be this cold... not even close to our
At noon we are forecast to be:
It keeps dropping too... temp has fallen about 5-8F across the board since 5am.
We'll be 10-12F lower than guidance today.
That’s pretty cool from a snow preservation standpoint – I checked the Bolton Valley Weather Station at 2,100’ and it’s similar on the west side as well; sub freezing at that elevation:
CONDITIONS CONTINUE TO FAVOR
UPSLOPE SNOW SHOWERS ACROSS THE
ADIRONDACKS AND NORTHERN GREENS... WITH SEVERAL INCHES OF SNOW
EXPECTED. FORECAST FROUDE NUMBERS INDICATE FLOW WILL BE UNBLOCKED
SO EXPECT MUCH OF THE PRECIPITATION WILL FALL CLOSE TO THE
MOUNTAIN SUMMITS AND ON THE LEE SIDE...FAVORING LOCATIONS SUCH AS
JAY PEAK...NEWPORT AND THE REST OF THE NORTHEAST KINGDOM.
Glad to see this getting some discussion, as I was going to ask about it – seems like they are knocking it up a notch in terms of the technicalities of upslope forecasting. This is the first time I’ve seen the discussion allude to the unblocked flow and Froude Numbers (which are velocity ratios as far as I can see – but hopefully one of the meteorologists on the board can fill us in on how they are used in this meteorological context).
The Froude Number is a measure of whether the flow can make it over the mountains or not. It is basically a test of stability versus the wind perpendicular to the mountain trying to push it over. If the Froude Number is low, the air will not make it over the mountain and the precip backs up. If it is high, the air will flow freely over the mountains and deposit the heaviest precip on the east side.
Nice – PF, you should find out how to calculate/use the appropriate Froude Numbers in your snowfall forecasting, then we could compare to all the snowfall obs and see how well they work in determining east side/west side snowfall numbers in upslope events.
Tuesday, December 4th, 2012
As for Wednesday into Thursday...yes, upslope pattern looks good. I'd say a good 3-4 of upslope is possible. I esp. like that the -10c isotherm is progged to move through the region. As PF and I have talked about, that's the isotherm that makes fluffy snow. And we like fluffy snow. Esp. on top of the snow brick currently draped over the mountains.
It was interesting to hear Roger Hill’s early broadcast this morning – he seemed to write off (or certainly strongly deemphasized) any snow potential with these next 2-3 systems (his discussion focused on the positive tilt of these troughs and time spent in the warm sector). For tomorrow’s system, the only mention of snow was, “tailing off with a few wet snowflakes”, and that was similar for the potential weekend/early next week system(s). He could have been focusing on a general low-elevation population forecast, but usually he’ll mention when there’s the potential for the mountains to get accumulations. The BTV NWS still seems to have the same/similar discussion that they’ve been posting over the past couple of days, with a good chunk of a paragraph allotted to the snowfall. A quick look through the models (GFS/ECMWF/NAM) does show some variation with respect to the coincidence of the cold air/moisture, but a blend of those certainly suggests some snow to me. Roger did seem intrigued by potential changes that take place after the 12th of the month however.
Wednesday, December 5th, 2012
As of roughly noontime we’ve got snow falling here in Burlington.
Thursday, December 6th, 2012
Event totals: 0.5” Snow/0.03” L.E.
It was snowing on and off in Burlington with no accumulation when I left around 5:30 P.M., and although it was difficult to see in the dark outside the bus, on I-89 through the mountains I could tell that the driver was taking his time and I was able to make out that the road was white. At the Waterbury Park and Ride I found ~¼” of snow on my car, and then at the house I found 0.5” on the snowboard comprised of 0.02” liquid. There was a touch of refrozen material on the board, and 0.03” worth of material in the rain gauge, so there was presumably a touch of non-frozen precipitation or snow that melted on contact at the start of this event. The very light snow continues with another tenth or two on the board as of 8:00 P.M., and there’s similar stuff upstream based on the radar, so there may be a bit more to report in the morning.
It is nice to have everything white again. We’re actually right at the average date of the start to the winter snowpack here based my data, but I’m not sure this snow will hold unless the forecast cools a bit.
Some details from the 6:00 P.M. Waterbury observations are below:
New Snow: 0.5 inches
New Liquid: 0.02 inches
Snow/Water Ratio: 25.0
Snow Density: 4.0% H2O
Temperature: 28.6 F
Sky: Light Snow
Snow at the stake: 0.5 inches
Event totals: 0.7” Snow/0.03” L.E.
A couple of additional tenths of an inch is as much as I saw for snow accumulation beyond last night’s 6:00 P.M. observations; the snow was so light that it was difficult for it to collect on some surfaces as PF indicated yesterday evening, and that was the case even in our location with just a little wind. I didn’t see much for accumulations reported at the local ski resorts, but presumably snowmaking can be fired up with the current temperatures. The next chances for snow appear to be tomorrow night into Saturday, and then again on Monday, but neither of those is very clean in terms of snow vs. mixed precipitation.
With this event complete, I did a quick assessment on where things stand around here at this point in the snow season. We’re on the early side, so variability will of course be high, but the 8.0” of snow we’ve had at the house thus far is well within one S.D. of the mean (16.0 ± 12.8”). One could say snowfall is at half the average level, or 8 inches behind; probably the latter is more appropriate at this early stage. The average snowpack on Mt. Mansfield for this date looks like it’s ~16”, so the 5” there is again below average, but only one good storm away from catching up since the numbers are relatively small. We’ve had 1.11” of liquid equivalent at the house through just the first six days of the month, so availability of precipitation doesn’t appear to be an issue. That’s typically the biggest concern I have around here, so as long as the moisture keeps coming (and it seems like precipitation is in the pipeline), the mountains will start building snowpack. Actually, even with these upcoming mixed events, anything frozen can beef up the liquid equivalent in terms of snowpack, it’s just that sleet and freezing rain (or even liquid rain that gets into the snow) makes for poor ski surfaces.
Some details from the 6:00 A.M. Waterbury observations are below:
New Snow: 0.2 inches
New Liquid: Trace
Temperature: 25.4 F
Sky: Mostly Clear
Snow at the stake: 0.5 inches
Saturday, December 8th, 2012
through December 8th last season at Burlington, VT- 7.7"
Snow this season through today this season at Burlington, VT- 4.3"
Hard to imagine we're doing worse (or better depending on your point of view) than last year...
I made an assessment relative to average a few days ago, but I hadn’t thought of looking at how snowfall compared to last season:
Snow through December 8th last season at VT-WS-19 - 15.4"
Snow this season through today at VT-WS-19 – 8.0"
So we’re at 51.9% of last season’s snowfall through this date, very similar to Burlington’s progress (55.8%). I generated the usual plot showing this season (red) relative to the mean (green with 1 S.D. error bars) and previous seasons from my data set.
It’s interesting to note that we’ve been at 30 to 40 inches of snowfall by this point in some seasons, which helps to make the current snowfall progress feel rather slow. We’re still just inside the 1 S.D. mark though, so this is nothing too aberrant yet. The snowfall hasn’t been as low as 2009-2010 was at this point (4.4”), but it is similar to the slow-starting 2006-2007 (10.0”). It certainly seems like there’s more potential for NNE snowfall as we move forward in the next couple of weeks, but there will need to be a lot done in the second half of the month if it is going to get near average – mean December snowfall is over 40 inches here based on my data.
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