Tuesday, November 27, 2012

Tuesday Snow Forecast

06/27 GFS accumulated snowfall- image credit Dr Ryan Maue and Weatherbell
There has been a subtle shift to the north with guidance overnight.  Its not unexpected, but will make tonight's commute a little slower.  Also watch for black ice if out tonight.  Highest snow totals for SNE look to be over the in Bristol and Plymouth counties.  Expecting about 1.5 inches in the Blackstone Valley.  Snow starts late morning/early afternoon and carries on until after midnight.  When the sun goes down road some snow may stick to the roads where it comes down the heaviest.

Pretty good slug of moisture to work with
HPC has upped snow probabilities into New England...now a wide swath has a 10% chance of 4 inches of snow

Day 1 snowfall probability forecast
All in all not a big deal, biggest issue will be with slick roads.  Moisture already streaming into SNE is evaporating before reaching the surface.  This will continue for awhile.  It will be cold tonight, bundle up.
Minimum temps between 1 PM and 7 PM today, EURO model- image Dr Ryan Maue and Weatherbell
Winds will remain light as this storm system is not very strong and there is not a tight pressure gradient.  The snow won't stick around too long although watching a clipper for Thursday night.  Warm up is expected next week.  More details on the extended range later...big playoff game tonight for the Beavers!

Sunday, November 25, 2012

Tuesday Snow Event...How Much?

Temperatures will moderate slightly for Monday, but winds will still gust to 25 mph so another cool and brisk day is on tap to kick off the final week of November.  Things change Tuesday as a generally light snowstorm moves into the region.  Most model guidance is keeping snowfall totals less than 2 inches but it will be falling Tuesday afternoon into the evening.  This will means the high school football playoff games will be played in snow.  Great for the players...and coaches who get to sit in a heated press box but for everyone watching the game dress warm.  

HPC snowfall probability 
The chart above shows less than a 10 percent chance of snowfall exceeding 4 inches in WV and PA and no chance anywhere in Southern New England.  The model support for a big event has gone away.  
EURO temperature forecast- from Dr. Ryan Maue and Weatherbell
This is Tuesday night at 7 PM.  Temperatures will be running in the upper 20's/lower 30's for most.
EURO precip forecast- from Dr. Ryan Maue and Weatherbell
A track slightly north of what is currently being forecast would bring those heavier precipitation bands into Southern New England.  As a meteorologist I find these type of snowstorms very difficult to forecast.  I've seen these little low pressure systems explode when the hit the gulf stream and the 1-3 inches of snow quickly becomes 8-12 (December 13, 2007 for example).  The jet stream will remain split so we don't need to worry about a major nor'easter.  
NAM wind forecast- From Dr Ryan Maue and Weatherbell
Not a heavy wind maker but will be a cold north wind.  So in summary we are looking at 1-3 inches of snow, but the potential for a 3-6 inch storm remains on the table.  Temperatures will be cold enough for snow and winds remain light.  More on the this tomorrow.

Saturday, November 24, 2012

Saturday Morning Weather Discussion

For the second time this November snow is in the forecast.  The 50 degree weather has went away for now.  For those of you who hate snow this isn't welcome, but the 50's may return in the long range.  We are going to have to deal with snow Tuesday evening into Wednesday morning.  Until then we are due for a stretch of below normal temperatures.

There could be a snow flurry today; other wise partly to mostly cloudy with temperatures in the low 40's.    Tonight is mostly clear allowing the heat to escape the surface; the result is lows in the lower 20's.  The coldest valleys where this cold air sinks will drop into the upper teens.  Sunday is more of the same although it will be harder to break 40 tomorrow.  If we could gamble on weather the line would be 38.5 degrees.  Clouds will be on the increase Sunday afternoon so Sunday night will not be as cold.  Temps in the mid to upper 20's.
Valid last night at 7 PM.  850 mb temperature anomaly from Dr. Ryan Maue and Weatherbell
The divide in temperatures clearly shows the cold front.  Here it is on the surface charts 
Valid 7 am this morning.  Cold front has pushed through
Current temperature observations in New England
9 am temperature observations
It will be hard for the temps to get much higher.  Winds will also be an issue today.  Very windy weather with the frontal passage.  Winds will be gusting over 30 mph this afternoon.  Its going to feel a lot colder than it actually is.  Here is the temperature anomaly (departure from average) for tonight at 7 PM (EURO thinking anyway)
7 PM EURO 11/24 00z 24 hr forecast. Notice wind arrows are longer, indicating stronger winds 
Some of you know, others may not that I coach HS football and we have a game Tuesday night.  For awhile I have seen support for some type of event on Tuesday.  After jumping the gun on a possible Thanksgiving week storm I held off for this one but there is agreement that at least several inches of snow will fall.  The event looks to start Tuesday night in time for the commute and the playoff games.  This is not set in stone; it could hold off until overnight Tuesday though I am leaning toward a Tuesday evening start.  

The EURO model is further offshore but it still produces 1-3 inches of snow for most of SNE.  The American GFS model is closer and has a heavier snow event.  Here is the predicted snowfall map from this mornings GFS run
This is valid Thursday morning.  System will be gone Wednesday  night
Too soon for specifics, but leaning towards accumulating snowfall for most.  For people of ski country do take the GFS with a grain of salt.  The EURO has very little precip for the mountains.  It will be interesting to see which solution ultimately verifies.  As usual its probably something in the middle.  

Extended Range
Analog forecast upper air pattern for 6-10 days
December is right around the corner.  What I find amazing is all of the analog dates occurred within a Cold PDO (2006 can be debated; even if we call 2006 a warm PDO its still 9/10 cold PDO).   I suggest searching the PDO and AMO if you want some information on naturally occurring climate patterns.  Anyway this set up screams blocking by Greenland and a trough in the east.  The 2010's and 1960's have shown consistency in producing big east coast snows.  White Christmas odds are high for 2012.

That said everything I have seen on the guidance is that in the 10-14 day range we see a warm up.  I think we see one last warm up in early December before winter kicks in.  Have a good weekend everyone, thanks for reading.

Tuesday, November 20, 2012

Calm Weather Through Thanksgiving then Winter?

A pleasant pattern has taken control over our weather and left us with cold mornings but seasonable afternoons.  This pattern continues until Saturday, gradually becoming warmer and warmer each afternoon.  High pressure is the dominant feature on the eastern US charts
00/20 EURO run, from Dr. Ryan Maue and Weatherbell
The storm I originally predicted for this week is on the charts, but will stay out to sea.  After Sandy and then the nor'easter I jumped the storm gun a little early but our coastal residents need a break.  The high pressure will continue to build south gradually changing the wind direction to the southwest by the end of the week.  This will allow temperatures to approach the upper 50's.  At the same time a low pressure system will move across the boundary between the arctic air and the air mass we currently are in.
EURO ensemble 850 hPa Temperature Anomaly- Dr Ryan Maue and Weatherbell 
The red/orange/brown colors indicate warmer than average temperatures while the blue/green/white/purple indicate colder than normal temperatures.  If this is correct (which it usually is) then we can expect some precipitation on Saturday.  Could be a snow event for the mountains; time will tell.  However we can the arctic air lurking for Sunday and Monday.  An area of low pressure is forecast to skirt south of New England on Tuesday morning.  Could lead to a few flakes for the morning commute.  This is 168 hours away so there is plenty of time to watch.

***CAUTION THIS MORNING reports of black ice caused by freezing fog.

Tuesday, November 13, 2012

Rain today, Quiet Pattern Follows

The highest temperatures of the day are being recorded right now.  A strong cold front is pushing east across New York and into New England.  There is a strong temperature gradient
From NCEP temperatures at 4 AM.  Widespread lower 60's (deep blue)
Along this gradient there are heavy showers and embedded thunderstorms
Northeast Radar image
First band will likely reach Central MA before 7 am while the bulk o the rain will fall between 9 AM and 3 PM.  Short range computer guidance has hinted at some moderate thunderstorms around 7-8 AM.  Temperatures will drop like a rock after the cold front passes.  Expect temperatures to fall from the mid 60's to the upper 40's.   After today the weather settles down for a 4-5 day stretch.  Temperatures will be in the mid to upper 40s Wednesday through Sunday.  Skies will be mostly sunny until Sunday, when clouds will begin to build back in.

There is a lot of chatter about a potential Nor'Easter next week.  It looks likely that something will form and try to move up the coast.  The American GFS from Dr Ryan Maue's Weatherbell model page
00z/13 run, hour 156.  
And the EURO
00z/13 run, hour 192
There are significant differences in both model runs.  However at this range it is important to note that each of the models is picking up on a coastal storm.  Each model also has high pressure to our North and East.  This needs to be watched because if the high ends up further over New England we could see snow from this event.  Thanksgiving week is always very busy so this storm may cause a lot of headaches and travel delays.  Will keep you posted.

Monday, November 5, 2012

Midweek Nor'easter to Impact Region

There will be a strong nor'easter developing along the east coast this week.  While the intensity of this nor'easter (May receive a name from the Weather Channel; would be Athena) will pale in comparison to Sandy, it will cause further problems for the areas hardest hit by the storm.  For coastal areas additional flooding is likely and for areas well away from the center a healthy dumping of snow will occur.  There is high agreement among model guidance on this event which is remarkable for this range.  When there is a block in the Atlantic computer guidance skill increases according to Dr. Ryan Maue of Weatherbell.

I'll show the evolution of this system and add some analysis on the weather preceding the Nor'Easter.  Please remember that in the atmosphere pressure decreases with height.  900 mb is around 5000 feet, 500 mb is around 18,000 feet and 300 mb is around 30,000 feet.

Surface Analysis valid Monday 230 AM

A strong low pressure system is about to impact the Pacific Northwest.  High pressure in control over Central Canada sending a cold Arctic air-mass into the Eastern Half of the United States.  Several low pressure systems are diving across the upper plains and a boundary exists along the gulf coast.  At upper levels the set up looks like this

500 mb
05/06 NAM run, initial conditions 
Polar vortex is over Canada allowing overnight lows to drop into the 20's for much of New England.  Energy diving through the Great Plains and more about to effect the Northwest.

300 mb
300 mb Jet, also 05/06 NAM (1 am this morning)
Strong Jet in the Pacific while the southern stream is over the Gulf Coast.

Now tonight, 7 PM
850 mb wind and Surface Pressure.  Image from Dr. Ryan Maue and Weatherbell EURO model
Tuesday will be nice across the northeast, albeit chilly.  Highs will only reach the low 40's in Southern New England.

500 mb
A well defined shortwave cutting through Arkansas
You can see the wave over Arkansas on both the surface and 500 mb chart.  This is the upper level support for the surface feature.
300 mb
Near record warmth likely out west with ridge, favors deepening trough over East
A classic Nor'Easter set up with a ridge out west, trough east, and subtropical jet stream running along Gulf Coast.

Now Tuesday night 7 PM
Low pressure to from along Gulf Coast, cross Florida and begin to strengthen over Gulf Stream
Again this is the EURO model which is the best of the medium range guidance.  Storm is taking shape off shore.  Blocking still dominating in the Atlantic so nowhere for this storm to go but up the coast.

500 mb
Upper level energy maximum right along the coast, favors a low pressure center just offshore
Ridge is really pumping out west allowing for the eastern trough to capture the developing nor'easter.

300 mb
Add caption
Energetic Jet to interact with storm while it makes its way up the coast.  This will allow the storm to deepen rapidly.  

That is how the upper air will allow this system to develop.  The end result for Wednesday night is this
EURO 72 hour forecast
The end result of all these images is a long duration slow moving Nor'easter will impact Southern New England and the Mid Atlantic.  Snow will occur on the far back side of the system.  The American GFS is showing this for snow totals
GFS valid Friday morning 7 am
This is probably a bit over done as I expect a track more over the outer cape, but if it is just over the benchmark (40 N. 70 W) somebody can look for close to 10 inches of snow especially in higher terrain.  For rainfall I defer to the HPC.  Here is their 5 day totals
5 day rainfall outlook
Thats a general 1-2 for most, isolated 3-4 inch amounts.  These heavier bands will be able to mix stronger winds to the surface.  Isolated tree damage and power outages are possible especially along the coast and Southeast MA, RI, CT, and Long Island.  Of course this is no Sandy but its still a strong storm and needs to be taken seriously.  I will post again tonight or tomorrow and will be more brief, just wanted to show the evolution of a Nor'Easter.


Friday, November 2, 2012

Upcoming Weather, Nor'Easter Next Week

One of the toughest things to do in meteorology is get back to the "regular" weather after a big storm.  Many meteorologists chose to study the science due to love of big storms, often from a very young age.  After Hurricane Sandy it was a little boring for a day.  Then the charts picked up something interesting for next week.  On Wednesday morning I buried a nugget about potential snow next week.  Its still on the table, but there are also signals that this storm will run along the coast and into New England, rather than just offshore which is the snow track.  First off the weekend forecast.

Mostly Cloudy, temperature around 50.  Chance of sprinkle today/flurry tonight.  Tonight low 33

Mix of sun and clouds.  High 48. Light wind from Northwest 6-10 mph. Saturday night low 32.

Mix of sun and clouds. High 48.  Steadier Northwest wind of 10-14 mph, gusts to 25. Sunday night low 26.

Mainly sunny, high 41.  Monday night low of 24.

Sunny, high 42.  Low of 29.

The next system will impact the region Wednesday into Thursday.  Right now I favor a rain with a light coating of snow to finish (60 percent) over an all snow solution (30) and a non event (10).  This is by reading the North Atlantic Oscillation (NAO index).  It is predicted to be trending positive, but not all the way.  So a storm crossing the Cape seems to be a good bet.  
NAO from Climate Prediction Center
The storm has been picked up by both the EURO and GFS models, always a good sign when looking for a storm.  Both model's ensemble members also have a storm clustering around the benchmark.  The Canadian (GEM) model shows a monster Gulf of Mexico-Atlantic Nor'Easter taking shape.  It would appear flooding and high winds will be an issue in Southern New England with snow in the higher elevations.  Here is the EURO ensemble package (Many models with the EURO's physics altered slightly when initializing).  Image from Weatherbell and Dr. Ryan Maue.
Would be a nice track for snowfall
And the GFS operational 
900 mb winds and MSLP. Valid Thursday 2 AM
More to follow on this event, enjoy the sunshine and bundle up.

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