We have a little something heading our way tomorrow morning. After reaching 60 at Bridgeport this afternoon (a new record) parts of the state appear to be on track to pick up 1″-3″ tomorrow morning. Northern Connecticut will see the snow accumulation (little or nothing on the shore) but the concern with this event is the timing. It’s a quick-hitter and centered on the morning commute. Never good. The fact that this storm was virtually unforecasted 24 hours out also leads to potential traffic problems.

Here’s the 15z SREF probabilties for snow accumulation >1″ tomorrow. Nearly 100 percent along the Massachusetts border!

The NAM computer model, which is typically my comic relief during a shift forecasting weather, shows a much stronger thump of snow during the morning commute. Let’s throw the NAM out for now but seeing huge model changes like this 24-36 hours form the start of an event is very unusual these days. Everything seems to be trending colder and snowier.

Updates on Twitter and Facebook through the mini-storm!

Here’s the GFS 500mb height/vorticity forcast for 1 p.m. Saturday.

I circled a “vort max” or “shortwave” off the east coast. Think of this as a piece of energy in the mid levels of the atmosphere. To the west there is a large and relatively impressive trough digging through the Great Lakes. These 2 features will remain separate. They will not phase into one. That means we’re left with a relatively large but diffuse area of lift in the atmosphere offshore as opposed to a concentrated area of strong lift – which is how we get our biggest storms.

You can see the impact of that by looking at the sea level pressure prog for the same time.

Notice how diffuse the low is (i.e. not tightly packed/wound up)? This shows that this storm is going to have trouble getting organized until it reaches or passes our latitude. Not good for a big storm.

That said there will be enough lift and convergence to produce a widespread swath of snow across southern New England. Many locations will see 1″-3″ of snow. It’s possible that if the storm winds up organizing faster and closer to the coast we could see more impressive snow as a comma head develops.

There is one other thing to watch out for but at this point seems unlikely. The 00z and 06z NAM is developing an inverted trough from the low offshore back to New York City and southern Connecticut. This essentially maximizes low level convergence and

produces a narrow, but intense, band of heavy snow. At this point the NAM is the only model showing this so it’s hard to get too excited about it but it’s something to watch.  The 2 panels on the left show the 06z NAM at 1 p.m. Saturday with a relative QPF max over eastern Long Island and southern Connecticut with the lower panel showing why – a band of convergence stretching north from the Atlantic toward Connecticut.

For what it’s worth the 03Z SREF guidance shows relatively robust probabilities for >4″ of snow across parts of southern New England. The blue shading is >25% chance while the green is >50% chance. At this point I think these numbers are a bit high but there is a chance that this storm trends a bit more impressive for some of the reasons discussed above.

The storm that began before daybreak on February 6, 1978 started to rage by late morning. Though the snowfall totals weren’t record breaking the storms impact was likely overshadowed only by the March 1888 monster storm that dropped 40″+ of snow in part of the state.

I would argue that the October snowstorm of 2011 entered into the pantheon of snowstorms with historic impact – something that people will remember for a generation or two. It’s not the totals that separate the men from the boys it’s the impact.

The beast of a storm dropped 2 feet of snow in New Haven, about 20″ around Hartford, while eastern Connecticut had 20″-30″ of snow. What made the snow incredible was the wild drifts that developed thanks to winds gusting to nearly 60 mph during the height of the storm. It was the wind that turned what would have been a big snowstorm into a big paralyzing storm.

Besides the drifts that reached roofs (particularly eastern Connecticut) the coastal flooding was on par with hurricanes. The 1978 storm produced coastal flooding and storm surge worse than Irene and on par with the 1992 nor’easter. In fact my mom was rescued by the Fairfield fire department on Fairfield Beach Road when the water started coming up during the height of the storm!

The drifts coupled with stranded cars as far as the eye could see on some highways shut down the state. Here are the observations from Bridgeport (translated into METAR by Weather Underground) for 2/6/78.

METAR KBDR 060800Z 05013KT 5SM -SN OVC017 M06/M12 A3021 RMK SLP230 T10611117

METAR KBDR 060900Z 05012KT 4SM -SN BKN017 OVC030 M06/M12 A3019 RMK SLP224 T10611122

METAR KBDR 061000Z 05017KT 6SM -SN OVC025 M06/M12 A3015 RMK SLP210 T10561122

METAR KBDR 061100Z 05016KT 10SM BKN/// OVC/// M06/M12 A//// RMK SLP203 T10561117

METAR KBDR 061200Z 05015G23KT 5SM -SN FG OVC028 M05/M10 A3010 RMK SLP193 60000 T10501100

METAR KBDR 061300Z 05021KT 1SM -SN FG OVC/// M05/M08 A//// RMK SLP176 P0002 T10501078

METAR KBDR 061400Z 05020G28KT 1SM -SN FG OVC006 M05/M07 A3002 RMK SLP166 P0001 T10501067

METAR KBDR 061500Z 04021KT 3/8SM SN FG OVC/// M05/M06 A//// RMK SLP146 P0004 T10501061

METAR KBDR 061600Z 04022G30KT 1/2SM SN FG OVC003 M04/M06 A2991 RMK SLP129 P0003 T10441056

METAR KBDR 061700Z 03021G31KT 1/2SM SN -BLSN OVC002 M04/M06 A2982 RMK SLP098 P0005 T10441056

METAR KBDR 061800Z 04020G32KT 1/8SM +SN -BLSN OVC002 M04/M05 A2973 RMK SLP068 P0010 60020 T10391050

METAR KBDR 061900Z 04023G32KT 1/8SM +SN -BLSN OVC002 M04/M04 A2965 RMK SLP041 P0012 T10391044

METAR KBDR 062000Z 05026G37KT 1/8SM +SN -BLSN OVC002 M04/M04 A2961 RMK SLP027 P0009 T10391039

METAR KBDR 062100Z 05026G44KT 1/8SM +SN -BLSN OVC002 M04/M04 A2956 RMK SLP010 P0012 T10391039

METAR KBDR 062200Z 05036G48KT 1/8SM +SN -BLSN OVC002 M04/M04 A2951 RMK SLP993 P0007 T10391039

METAR KBDR 062300Z 03036G47KT 1/8SM +SN -BLSN OVC002 M04/M04 A2948 RMK SLP983 P0008 T10391039

METAR KBDR 070000Z 03032G48KT 3/8SM SN -BLSN OVC002 M04/M04 A2944 RMK SLP970 P0006 60051 T10441044

METAR KBDR 070100Z 02032G41KT 3/8SM SN -BLSN OVC001 M04/M04 A2936 RMK SLP942 P0005 T10441044

METAR KBDR 070200Z 03034G45KT 1/2SM SN -BLSN OVC001 M05/M05 A2932 RMK SLP929 P0007 T10501050

METAR KBDR 070300Z 03028G36KT 1/2SM SN -BLSN OVC002 M04/M04 A2930 RMK SLP922 P0004 T10441044

METAR KBDR 070400Z 04028KT 1SM -SN -BLSN OVC/// M03/M03 A//// RMK SLP919 P0002 T10331033

Some of the totals from coop stations:

22″ Storrs
12″ Bridgeport
24″ Thompson (30″ OTG)
16.9″ BDL (21″ OTG)
18.5″ Middletown (23″ OTG)
17.2″ Groton
20.1″ Haddam
24″ Norfolk
23.8″ Hamden

This January, however, was an absolute bore weatherwise. In fact while I sit here an type this blog post it’s over 60 degrees!!! Here’s a look back at January 2012 for greater Hartford:

• Average temperature – 31.6 (5.5 above normal)
• Precipitation – 2.96″ (0.27″ below normal)
• Snowfall – 6.8″ (5.5″ below normal)
• Snowfall Since 7/1 – 19.1″ (2.6″ below normal)

Contrast this with the epic January 2011:

• Average Temperature – 23.0 (2.7 below normal)
• Precipitation – 4.03″ (0.19″ above normal)
• Snowfall – 54.4″ (39.9″ above normal)
• Snowfall Since 7/1 – 68.5″ (43.1″ above normal)

Note: “average” temperatures and precipitation changed for this January with new 30-year means.

Going forward persistence seems to be the way to go. I don’t see any big shots of cold – maybe we can swing some snow but nothing jumps out at me right now. Enjoy spring!

Photo of Libby / Courtesy: Jeremy Keckler

An impressive mesoscale banding featured developed in southern Connecticut that sat and sat and sat over the same area. These things can produce some exceptional totals in a relatively short total and this was no exception. This produced the big totals thanks to a growing and relatively stagnant area of low/mid level frontogenesis that worked in tandem with synoptic scale lift from the right entrance region of a jet streak in central New England.

Here are the totals from my awesome weather watchers:

• East Haddam – 10.5″
• Salem – 10.5″
• North Guilford – 10.0″
• Woodbridge – 10.0″
• Montville – 10.0″
• Haddam – 9.8″
• Newtown 9.5″
• Higganum – 9.0″
• Branford – 8.3″
• Ansonia – 8.2″
• Wallingford – 8.0″
• Old Saybrook – 8.0″
• New Haven – 8.0″
• East Hampton – 8.0″
• Franklin – 7.0″
• Ledyard – 7.0″
• Naugatuck – 7.0″
• Oxford – 7.0″
• Groton – 6.5″
• Colchester – 6.5″
• Wolcott – 6.5″
• Bridgeport (BDR/Official) – 6.2″
• Southington – 5.5″
• Vernon – 5.0″
• Tolland – 3.9″
• West Hartford – 3.8″
• Litchfield – 3.0″
• Avon – 2.8″
• Stafford Springs – 2.6″
• Windsor Locks – 2.4″
• East Granby – 2.0″

Thanks for the reports! Enjoy the snow

There’s a big difference between dry and light snow that is easy to move and fluffy snow flakes that are able to accumulate fast! A meteorologist friend of mine in New Hampshire used this analogy:

Think of dendrites as a bunch of tree branches thrown into a pile. The pile gets stacked high the more you add as the branch structure traps air in between. Now throw them through a wood chipper and watch how much lower the pile gets. There’s your columns, needles, bullets, and small plates.

Dendrites (the beautiful and ornate crystals) are the flakes that can pile up quickly and result in high ratios of liquid precipitation to snow totals. Snow flakes grow through deposition. Deposition is the process where water vapor changes state to a solid on the ice crystal. This is the dominant process in producing snow.

The deposition process is maximized when temperatures are between -12c and -18c in the cloud. Besides a more efficient growth process dendrites also accumulate more rapidly due to their large suface area adding to extra space in between each individual flake.

Bottom line is that even though it’s in the teens that doesn’t guarantee good snow growth or a fluff factor!! Not even close!!! Having cold temperatures in addition to saturation and strong lift in the dendritic growth zone (-12ºc to -18ºc) is the key to getting a “fluff factor”.

When temperatures are too cold or too warm in the region of best lift you get other types of crystals that don’t form as efficiently and don’t accumulate as efficiently. The latter will reduce snow:liquid ratios. Snowflakes like plates or columns or needles accumulate slowly and produce a “fine” consistency to the snow.

Looking at a surface temperature and saying the snow will accumulate fast is bad meteorology. Use cloud microphysics folks – it’s the only way to forecast snow!

Finally some real snow in the forecast! Here’s the 12z NAM valid at 15z (10 a.m.) Saturday with 850mb temperatures (0c solid black) and 3-hour QPF shaded. As usual the NAM is the most robust of all our models in terms of precipitation.

A weak disturbance is ejecting east toward southern New England. Though the shortwave isn’t strong we’ll get a burst of QG forcing (lift) thanks to warm advection and a 60+ m/s jet streak to our north leaving us in the favorable right entrance region.

NAM dynamic tropopause forecast for 15z Saturday. Isotachs shown - note the 60m/s jet streak northeast of Connecticut on the DT.

12z NAM forecast of sea level pressure and 1000-500mb thickness valid 18z Saturday

In the NAM SLP/Thickness map you can see the relatively tight thickness gradient over NY and New England which will help maximize low level warm advection even with a relatively weak low level jet. In addition synoptic scale lift will be present through the column in right entrance region of jet streak to the north.

The bottom line is that snow will overspread the state shortly before daybreak Saturday with 4″-6″ of snow likely across all of Connecticut. I expect snow even down to the shoreline (including the Groton/Stonington snow hole). Snow to liquid ratios will be better than 10:1 with relatively cold soundings and some lift and saturation into the favorable dendritic growth zone. This isn’t a classic setup for good snow growth so I expect 15:1 snow:liquid ratios.

On a side note I couldn’t help but notice this National Weather Service map this morning. I generally don’t look at their forecasts or discussions but this really jumped out at me.

How the hell is this supposed to make any sense to anyone? A winter storm watch for Fairfield County and a winter weather advisory for the remainder of southern Connecticut. Nothing to the north? Why? Will Bridgeport get more snow than New Haven?  Snow should begin around the same time so why do we have watches, advisories, and nothing in effect when the storm appears ready to deliver similar impacts regionwide.

To be honest I don’t even know what the criteria is for each advisory or warning for each county because the definitions seems to change every couple years and they vary from county-to-county and state-to-state.

The NWS does a great job (most of the time) with severe thunderstorm and tornado warnings but maps like this do everyone a disservice. It makes no sense.

Still, well timed (or poorly timed, based on your perspective) disturbances will produce snow across Connecticut tonight and again on Saturday.

Tonight’s system is moisture starved and not terribly dynamic so I wouldn’t expect much. That said, 1″-2″ of snow is possible in some areas with a moist onshore flow keeping southern New England a bit more primed for snow than inland areas to our north and west. A touch of frontogenesis appears to be enough along with QG forcing/ascent to produce some locally heavy bands of snow this evening.

As for Saturday, most years this storm wouldn’t be much of a story, this year it is. A slightly more juicy and dynamic shortwave is ejecting from the Pacific northwest (the one that produced the snowstorm and ice storm near Seattle) will produce some strong lift and a more widespread batch of snow. A bit of mid level warmth gets introduced which may mean some sleet or freezing rain particularly for areas south of Hartford. Details to be determined but at this point I feel pretty good about 2″-4″ of snow on Saturday with the potential for 6″ somewhere though most of us will see less.

Here’s the 15z SREF snow probabilities which aren’t overly impressive though they should bump up in coming runs.

Don’t fret if you don’t like snow. It looks like the torch returns by Monday with a warm pattern setting up. Here’s the 12z GFS MOS for next week:

In the grand scheme of things this winter still is a bit of a downer but I do see some signs of larger storm threats beyond day 10. -NAO????? Stay tuned….

Up north the winter has been just brutal for many ski areas in northern New England. Last week’s synoptic and upslope snowstorm was an absolute blessing for struggling ski areas. Here’s a cool way to display snow depth at the famed Mount Mansfield snow stake (just off the Toll Road in the Stowe ski area).

The green is the average snow depth by date and I also plotted this year, last year, and the also ugly 2006-2007 winter. After a very slow start up north this winter has exceeded ’06-’07′s paltry snow depth but remains below average. While last year was an epic snow year in Connecticut it took until March for northern Vermont to really exceed average with a maximum depth around 100″!

Bottom line is hope is not lost for skiers. 2 snow chances and relatively cold this week should boost Vermont bases. Though the Day 8-20 period looks very mild it’s difficult for snow depths in the mountains to take big hits this time of year. Closer to home I don’t see much for winter lovers to get excited about through early February.

Speaking in terms of Oregon Trail this winter has thus far been plagued by dysentery, cholera, and a snakebite. Although the pattern change over the next 5-7 days is significant it appears the atmosphere will almost immediately revert back to a torch.

The growing consensus is for a large ridge of high pressure to deliver near record or record warmth across a large portion of the central and eastern U.S. in the next 7-15 days. An exceptionally hostile Pacific with a developing strong +EPO is ready to flood the lower 48 with warm air.

You can see the beginning of the torch in the 8-10 day 500mb height anomalies with a retrograding ridge moving from the Aleutians and Bering Strait toward Russia and a developing strong trough over the Pacific Northwest and eventually Alaska.

This is just a hideous, hideous pattern for people who want cold or snow. In fact the signals are growing for an exceptionally impressive burst of warmth across the southern plains and into portions of the midwest by day 10. Temperatures near 80 could reach places as far north as Kansas City, MO if some models like the operational Euro are to be believed.

The European weeklies that came out last night were also exceptionally mild during weeks 2 and 3 (days 12-25) across almost the entire continental United States and adjacent Canada.

It’s possible we revert back to cold by the second half of February but if the first half of winter was any indication I wouldn’t count on it. Things don’t look good now for winter lovers – but as with all long range predictions things can change quickly.