Morning Update

Surface Map 7 A.M. EST

Surface Map 7 A.M. EST

Well, for areas north & west of Hartford, down into New York City, it’s certainly not historic.  In fact it’s not even all that bad.  Further east, it’s a more significant event, but it’s historical significance is open to debate.  I’d prefer to wait until the dust (or in this case, the snow) clears before tackling that one.  So far, it looks like many parts of CT saw between 12″-26″ of snow, however amounts are much smaller north & west of Hartford.  At last check Bridgeport only had 5.0″.  The storm track was a bit further east than some of the modeling had indicated, so basically everything was pushed east by about 60 miles.  This was within the margin of error on the forecast map I posted yesterday, and is a good example of why I am uncomfortable when terms like “historic“, “epic“, and “crippling” start getting thrown around before an event has even begun (more on that later).

Temperatures today are in the low-mid 20′s and wind chills are in the single numbers.  There will be periods of lingering snow and flurries at times today.  Some places will get some additional accumulation – maybe even a couple inches.  Others, just another coating.   Areas of blowing & drifting snow will continue.

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The Plot Thickens!

HRRR Model Forecast Radar at 5 A.M. EST

HRRR Model Forecast Radar at 5 A.M. EST (Click To Enlarge)

The Plot Thickens!  I see The Weather Channel is downgrading the snow amounts for CT & southeastern NY based on short term guidance keeping the heaviest snow to the east.  There is a surprising amount of disagreement between models, considering that the event is already in progress!  I have been concerned about the same.  For now, I’ll keep the forecast unchanged, but am watching developments closely.  Notice how on the High Resolution Rapid Refresh model to the left, there is a sharp difference between precipitation amounts north & west of Hartford, CT vs. south & east at 5 A.M.  Can you imagine if this were to verify and the 9 million people in New York City wake up to just an ordinary snowfall?  What would the fallout be?  Should be an interesting night!

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Midday Blizzard Update

Snowfall Forecast

Snowfall Forecast

This is a very rough idea of what I’m thinking for storm totals.  The surface storm will get stacked up underneath the mid-level low (see black arrow on image below).  This will cause it to slow down and move erratically for a while.  This could cause further fluctuations in forecast snow amounts and how they line up.  Based on differences between models, the snowfall forecast image contour lines have a margin of error of +/- 75-100 miles.  These big storms always have mesocale bands that develop and produce the heaviest snow totals and sometimes contain thunder & lightning.  The location of these bands really can’t

NAM 500-mb (mid-level) and Surface Forecast for 1 PM Tuesday

NAM 500-mb (mid-level) and Surface Forecast for 1 PM Tuesday

be placed accurately until they show up on radar, but that is where the “locally highest” totals will occur.  The GFS is the least impressive model right now, but also a bit of an outlier, so I have underweighted it.

 

 

  • The heaviest snow will kick in toward and after midnight.  Many places in the 15″-30″ area will see over a foot fall in a 6-hour time frame.
  • Winds will gust over 40 mph inland by early Tuesday and over 50 mph closer to the coast and in parts of eastern CT.  Even higher gusts across southeastern New England.
  • Wind-Chills will be in the single numbers to around 0 late tonight & Tuesday.
  • Blowing & drifting of the snow will cause problems.  It will be a dry, powdery snow.
  • Visibility overnight into early Tuesday morning will be reduced to between 0 and 1/4 mile at times in the Blizzard warning areas.
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Models Trend Back West

1 AM NAM Total Precipitation Forecast (Liquid).  Compare difference to previous run below.

1 AM NAM Total Precipitation Forecast (Liquid). Compare difference to previous run below.

After trending eastward a bit during Sunday, the overnight night model runs have jogged back to the west. This means that the threat for big snow amounts (15″-30″) continues across all of southern New England and parts of southeastern NY, including New York City.  To give you an idea of the fluctuation in snow amounts being forecast in some places consider the past few runs of the NAM:

 

 

————————————————–1 PM Sunday       7 PM Sunday     1 AM Monday

Canaan, CT (Litchfield Cty.)                   10.9″                        5.5″                     25.1″

LaGuardia Airport (NYC)                        24.9″                       8.4″                     22.3″

Windsor Locks, CT                                    25.9″                       15.2″                   21.5″

Poughkeepsie, NY                                      8.8″                          5.0″                    18.7″

7 PM Sunday NAM Precipitation Forecast (liquid).  Compare to most recent run above.

7 PM Sunday NAM Precipitation Forecast (liquid). Compare to most recent run above.

You can see how much these amounts have varied in some places from run to run on the NAM, however there has been less variability in other locations like Boston, which has been up around 20″ or so on the last few runs (currently at 23.9″).  This illustrates why we shouldn’t put too much stock in a single model or single run, but have to give more weight to the trend and to a consensus of the models (after tossing outliers).  The ECMWF (Euro) model has probably been the most consistent all along, and continues to thump the entire region with big snow.  With the other models now trending back west, big snow looks like a good bet for all of southern New England, southeastern NY, and southern NH.

Expect some occasional light snow and flurries to get going during the day today.  There could be a couple inches on the ground by evening.  The real snow will come down between midnight and early Tuesday morning.  In a few hours, the morning guidance will be available and it will be time to make a final call on specifics.

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What Could Go Wrong?

NAM Precipitation Forecast (liquid)

NAM Precipitation Forecast (liquid). Notice the sharp cutoff near the NY/CT border.  Click to enlarge.

 

By now you’ve heard the mega numbers and menacing adjectives swirling around the coming storm.  Historic, crippling, 15-30″.  Is there any chance it won’t be that bad?  Well the ingredients are still there for big storm potential, but I have noticed that everything has trended a tad eastward during the past few model runs.  It would seem that unless things fluctuate back to the west again, the jackpot snows would most likely occur in eastern areas of New England.  There is the possibility that this storm won’t live up to the hype in westernmost areas.  I don’t want you to put too much stock in one model run, but consider this:  The 9 million people in New York City have been told to expect 18″-24″, with the potential for 30″ from the storm, with possibly “crippling” effects.

GFS Precipitation Forecast (liquid).  Click to enlarge.

GFS Precipitation Forecast (liquid). Click to enlarge.

The afternoon run of the NAM was putting out 24.9″ of snow for LaGuardia Airport.  Tonight’s run of the same model? 8.4″.  Why?  Because there is a fairly sharp cutoff between the mega snow amounts and much more pedestrian ones.  And New York City is very close to that cutoff.  And everything has nudged slightly to the east at last check.  For the same reason, you could argue that in the far northwest corner of Litchfield County, CT, 6″-12″ would be a reasonable forecast  based on the latest trend, and that parts of interior, eastern NY state  that are under winter storm and blizzard warnings could have trouble verifying.    Again, this is just one model, but the slight eastward trend can be seen in several models to varying extents.  With the potential high impact to our region from this storm, keep up-to-date with the latest changes.  But at this point, I think there is some question as to just how great that impact will be in westernmost areas.

1:26 A.M. update: BTW, tonight’s run of the ECMWF (the Euro) is in now and it still clobbers everybody, as it’s been doing all along.

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Blizzard Watch!

Blizzard Watch 1A Blizzard Watch has been issued for the counties in green from Monday afternoon through Wednesday morning.  All other counties (in blue) are under a Winter Storm Watch.  We don’t see blizzard watches issued that often, so now is a good time to review what that means and some general questions that always come up about big snowstorms.  Blizzard conditions are when the visibility is reduced by falling and/or blowing snow to 1/4 mile or less and winds are sustained at, or frequently gusting to at least 35 miles per hour.  Both of these conditions though, have to persist for at least 3 consecutive hours for it to be a blizzard.  Notice that according to the definition, you can have a blizzard with zero new snow accumulation (a “ground blizzard” due to blowing snow already on the ground).

Blizzard 2As the various model runs continue to indicate snow and wind for us from this storm, as we get closer to the start time (tomorrow), it is becoming increasingly likely that it will happen.  Here are some things to know:

There is the threat for a foot or more of snow in many parts of southern New England and the potential even exists for 2 feet or more somewhere in southern New England.  In addition to that there will likely be deeper drifts due to strong wind.

Could the storm go out to sea/miss us?  Yes, that is always possible, although a complete miss is becoming unlikely at this point.  These storms usually have one or more bands of especially heavy snow that develops (mesoscale bands). This is where the greatest snow amounts will fall, but it can be difficult/impossible to place these band(s) ahead of time.

Any forecast you hear becomes invalid within 6-12 hours.  Weather forecasts are not static.  They change constantly, as does the atmosphere.  Major model runs come in every 6-12 hours, and new short-term guidance is generated every hour. What you heard yesterday or even earlier today may no longer be valid.  Stay up-to-date.

Historic?  Dispelling weather rumors is more difficult than ever in the age of social media.  This storm is a good example why.  As you know, likes and shares on Facebook are similar to TV ratings.  The more you have, the more valuable your platform is.  I can understand why some would say that this storm has the potential to be historic or compare it to a past blizzard.  That will also generate a lot of likes & shares.  It looks like a lot of the ingredients are there.  But if this thing blows up a little further to the south & east, then you’ll end up with big storm over the ocean that brushes us, that most people won’t remember.  So, while you cannot dismiss this as being a memorable and potentially “historic” storm  if it lives up to its potential, it’s really too early to be throwing those kind of descriptors out.  I’d be more comfortable talking about its significance after it actually happens, if it does pan out.

The storm that will affect us has not even formed yet.  Some of the ingredients are moving east, but the main “storm” wouldn’t start developing until tomorrow.  At this point, expect some snow around by Monday afternoon, with the threat for heavy snow & wind Monday night into Tuesday.  Lighter snow may linger into Tuesday night and even part of Wednesday according to some of the models.

 

 

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Snow Storm Potential Monday Night/Tuesday

NAM Forecast 1 PM EST Tuesday

NAM Forecast 1 PM EST Tuesday (Click To Enlarge)

Models are now projecting snowstorm potential for Monday night & Tuesday!  Suggestion is jackpot amounts could be in eastern New England.  Although I’d like to see another model run or two (or three) to confirm this event, the NAM, GFS, ECMWF & GEM are all putting out snow & wind for this time frame now.

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Another Arctic Front!

2 PM Surface Plots (Click To Enlarge)

2 PM Surface Plots (Click To Enlarge)

Some flurries and snow showers (and maybe a squall here or there) around this afternoon in advance of the arctic front.  Lows overnight headed for the single numbers in many places with sub-zero wind chills.  Some cold spots well inland near or below zero by morning with some coastal areas staying in the teens.

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Work Week Starts On A Messy Note

Snowfall Forecast For Monday, January 12, 2015 (Click To Enlarge)

Snowfall Forecast For Monday, January 12, 2015 (Click To Enlarge)

A southwest flow aloft will carry moisture now over the mid-South and approaching the Mississippi Valley in our direction late tonight and Monday, as high pressure moves off the east coast.  Some light snow and mixed precipitation will develop during the predawn and early morning hours Monday.  There will not be a lot of snow with this system, as temperatures should warm sufficiently aloft to limit any snow accumulations to under an inch in many cases, with an inch or so possible in some of the northwest hills of CT and 2″-5″ in parts of the Berkshires.

Tomorrow morning is one of those times when you should get up a little earlier that normal to check on conditions. They probably won’t be the same everywhere during the morning commute.  Some place will be slick and it’s possible that if your day has you leave early enough in the morning (especially in eastern areas), the precipitation may not have started or barely started by the time you leave).  There will be mixed precipitation around the region in the morning and the National Weather Services has a Winter Weather Advisory beginning during the predawn hours, for potential slippery travel.  Any freezing rain or mixed precipitation should go over to plain rain by Monday afternoon (this will happen during the morning in a number of places not too far from the coast, except north & west of roughly Chester, MA, where most of the precipitation that falls will be light snow.   Temperatures however, will likely remain in the 30′s in most places.

Any lingering precipitation ends Monday night.  The rest of the week looks mostly dry & cold.

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Snow Update

Radar 9:15 A.M. EST

Radar 9:15 A.M. EST (Click to Enlarge)

9 AM totals range from a half inch in many places up to 4.75″ in North Canaan.  Final totals will likely be between 1.5″-5.0″ for most of the state, with most of us on the lower end of the scale.  Heaviest snow now is south & east of Hartford (dark blue & green on radar image to left).  Snow should taper off in central CT by 10:00-10:30 A.M. and in the southeast corner of CT by noon or shortly thereafter.

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