January 23-24, 2006 Event: Snowfall Estimates

[donsutherland1]

While this storm will likely see elevated areas and interior sections of northeastern Pennsylvania to interior New England do best in terms of snowfall, this system does not look anywhere near as impressive as the January 2-3 storm that brought 6" or more snowfall to a large portion of these same areas.

Based on model runs over the past few days and current soundings, I expect:

∙ the air mass at the onset of the system will be warmer than that for the January 2-3 system
∙ warmer air will make inroads even into interior sections of Pennsylvania and parts of New England resulting in at least some sleet, freezing rain, and even plain rain
∙ any area of backlash snows will be limited

Initial estimates:

Albany: 2"-4"
Allentown: 1"-3"
Binghamton: 2"-5"
Boston: 1" or less
Burlington: 1"-3"
Concord: 2"-5"
Harrisburg: 2" or less
Hartford: 1"-3"
Providence: 1" or less
Worcester: 3"-6"

[donsutherland1]

After looking at the 18z data (including soundings) and current conditions, I believe that my initial assumptions remain on track:

∙ the air mass at the onset of the system will be warmer than that for the January 2-3 system
∙ warmer air will make inroads even into interior sections of Pennsylvania and parts of New England resulting in at least some sleet, freezing rain, and even plain rain
∙ any area of backlash snows will be limited

It should be noted that for a few locations e.g., NYC, the actual lower-level temperatures (e.g., 950 mb) have been running somewhat warmer than forecast by the soundings. As a result, I would not be surprised if at least mixed precipitation punches into the Albany and Worcester areas even if just for a short period of time.

Finally, there is a possibility that I might have to tweak a few numbers. However, major changes do not appear to be in order at this point in time.

Initial estimates:

Albany: 2"-4"
Allentown: 1"-3"
Binghamton: 2"-5"
Boston: 1" or less
Burlington: 1"-3"
Concord: 2"-5"
Harrisburg: 2" or less
Hartford: 1"-3"
Providence: 1" or less
Worcester: 3"-6"

[donsutherland1]

Per a review of the current data, the 1/23 0z NAM and its soundings, and a brief look at the 0z GFS qpf, I have tweaked a few amounts.

Things look worse at Allentown than they did earlier. Instead of 1"-3" at Allentown, I believe 2" or less (with a heavy emphasis on the lower part of the range) is likely there. I still do not expect much if any accumulations at Harrisburg. In fact, it is plausible that neither city picks up any accumulations of snow.

Amounts for Albany, Boston, and Worcester were also refined. Nevertheless, no big changes were made anywhere

Final estimates:

Albany: 2"-5"
Allentown: 2" or less
Binghamton: 2"-5"
Boston: 2" or less
Burlington: 1"-3"
Concord: 2"-5"
Harrisburg: 2" or less
Hartford: 1"-3"
Providence: 1" or less
Worcester: 3"-7"

[terstorm1012]

the 2" or less is good for Harrisburg. We had sleet for two hours last night between 8 and 10, then it turned over to mostly rain, then turned back to sleet for about a half hour this morning around 6am (woke me up).

[donsutherland1]

There were busts in New England and at Albany. Once I have final totals, I'll post the verification.

[donsutherland1]

Verification:

Across New England, I generally called for too little snow. Key reasons for that were:

∙ I considered the modeled soundings generally reliable
∙ I had expectations concerning the qpf (which actually worked out well)
∙ The 1/23 0z guidance shifted fairly dramatically to a colder solution. I made final estimates just after having reviewed the 0z NAM’s soundings but also employed a degree of continuity with the earlier idea.

This approach proved overly conservative and especially big busts were recorded at Hartford (3.0” outside range), Boston (2.4” outside range), Providence (1.8” outside range) and Worcester (1.7” outside range).

Was the situation foreseeable? Could the forecast have been markedly better? Upon review, the answer to both questions is “yes.”

In reviewing outcomes against the performance, I try to pay particular attention to forecasts that performed in a superior fashion. My objective is to search for possible insights that might have value. If such insights can be applied in the future, an invaluable lesson that would enhance future forecasts can be learned. I, certainly, have benefited from this approach.

John (Typhoon Tip) had some remarkable insight early on of possible scenarios whereby a colder solution than what was modeled was potentially viable for the most recent snowstorm. Two of his posts stand out: January 18 and January 21.

On January 18, John observed:

What I find interesting is that the heights over the Caribbean are tending to decay prior to the passage of the impulse along 35/90 - 40/80, so that by the time it arrives at the latter destination (132hrs) the heights over MIA have come beneath H582... This suggests compressibility, indicating lowering shear values to S aspects of trough amplification - potential for meridional expression begins.

So...the two possibilities are:
a) Greater phasing with a few ensemble members hinting arctic impulse insertion and a real bomb potential..
b) The lesser phased...which would still (I believe) bring a wet system with a pretty good wallop of snow on the N side of the mean polar boundary, and yes...again with this convection for areas S of wf.. Just not sure how pervasive the snow area would be…

He outlined a possible correction to the south and east for the short wave relative to the modeled position.

On January 21, he noted that the second scenario had been working out quite well and added:

The ESE/SE instantiating inflow off deep latitudes appears to have been correct and as this N/A-scale motivating moisture flux migrates quickly toward the NE, there will be increasingly favored isentropic lifting do to marginally cold environ that is about to encapsulate the area in the near term. ...There is our necessitated leading CAA even if not as pretty as that outlined in KU science.... (In fact, ALB and BOX now have wind advisory/warning event (2 times now in 60 hours!), only this time for CAA sake... We had the NAM FOUS profile the other day, progging BOS with 44kt mid bl flow when substantial mixing to the sfc was given, do to huge omega components through the mixing depth...). The reason I called that "...N/A scaled motivating moisture flux", is because I believe that a WAA pattern would take place in the absence of a residual s/w tug; the s/w translation is what augments here…

...As far as the details go... this is what I often refer to as a "fat thickness snow event", or in this case, that potential therein. We have a comparatively isothermal layer that pretty much qualifies the bl for W areas of NJ, areas of PA, eastern/SE NY (save NYC) and interior SNE...

On January 22, he issued the following forecast:

More snow in NYC first of all... 1-3" there, and up along the immediate S/Coast, as far up the E Coast of Ma as perhaps TAN. 3-5" in 10-20 mile wide stripe either side of an axis from the NW 'burbs of NYC to just S of HFD, to just SE of PVD, to between BOS and TAN. In a wider birth, from N of there to S VT, S NH to about 10 miles S of the Ma Pike, 6+" inches, should fall short of a major event.

That forecast worked out very well and significantly outperformed the modeling from the time it was issued. Even in NYC, where most forecasts—including mine had no accumulations of snow—a trace fell. Just to the north (just north of White Plains), amounts of 1” or more fell. So, in the end the more meaningful accumulating snow came dangerously close to NYC. In the more distant suburbs, Putnam County saw amounts approaching 3” and Orange County saw some 4” amounts.

In short, I believe a valuable lesson can be learned from the insights provided above. Subtle factors that could lead to a change in the modeled solutions could lead to some fairly big changes in the sensible weather. That’s what happened in New England and Bostonians were able to enjoy a greater than 4” snowfall in the midst of an exceptionally warm January.

My verifications follow:

From January 22, 2006: 2:30 pm:
Albany: 2"-4"; Actual: 5.2”; Error: 1.2”
Allentown: 1"-3"; Actual: 0.8”; Error: 0.2”
Binghamton: 2"-5"; Actual: 2.3”; Within range
Boston: 1" or less; Actual: 4.4”; Error: 3.4”
Burlington: 1"-3"; Actual: 3.0”; Within range
Concord: 2"-5"; Actual: 5.8”; Error: 0.8”
Harrisburg: 2" or less; Actual: None; Within range
Hartford: 1"-3"; Actual: 6.0”; Error: 3.0”
Providence: 1" or less; Actual: 2.8”; Error: 1.8”
Worcester: 3"-6"; Actual: 8.7”; Error: 2.7”

January 22, 2006: 10:45 pm:
Albany: 2"-5"; Actual: 5.2”; Error: 0.2”
Allentown: 2” or less; Actual: 0.8”; Within range
Binghamton: 2"-5"; Actual: 2.3”; Within range
Boston: 2" or less; Actual: 4.4”; Error: 2.4”
Burlington: 1"-3"; Actual: 3.0”; Within range
Concord: 2"-5"; Actual: 5.8”; Error: 0.8”
Harrisburg: 2" or less; Actual: None; Within range
Hartford: 1"-3"; Actual: 6.0”; Error: 3.0”
Providence: 1" or less; Actual: 2.8”; Error: 1.8”
Worcester: 3"-7"; Actual: 8.7”; Error: 1.7”

[Tri-State_1925]

For what it's worth Don, I highly doubt Worcester got 8.7 inches of snow.

I'm heading back there this evening, and I'll take into consideration around 2-3 inches of melting since yesterday, and I bet I won't see more than 3 or 4 inches left on the ground.