Friday, February 20, 2015

Snow, Ice, Rain and a Brief Warm Up

A weak low pressure system will approach from the SW on Saturday and bring with it a variety of precipitation.  Though we are all sick of it snow is the preferred outcome.  However with a storm track to our west warmer air will work into New England changing the initial snow burst to ice and rain.  The details...
NWS Boston Advisories 
Region wide (sans CC) a winter weather advisory is effect from 1 pm tomorrow through 1 pm Sunday.  Everyone starts as snow early tomorrow afternoon.

Here is the current surface chart.  Notice the front in the southern plains pushing towards high pressure in the east
WPC surface analysis 4 PM
For visual learners here are the 5 PM US temperatures
US 2 m temperatures 5 pm (image Weatherbell)
Here is the water vapor satellite loop
GOES WATER VAPOR LOOP (IMAGE NOAA)
Before we get to any storm there is a very cold night ahead. Here is one high resolution weather models take for minimum temperature through 8 am
22z HRRR min 2 m temp (Image Weatherbell)
The storm will want to warm Southern New England.  But since cold air is more dense than warm air the warmer air will be forced up over the cold and so everyone starts as snow
Overrunning event diagram via Boston.com
Here is the surface around 1 pm
WPC surface forecast 1 pm Sat
Light snow breaks out around 3 pm. Here is a simulated radar image for 4 pm
18z NAM hires Sim radar 4 pm Sat (Image Weatherbell)
Boston to Providence to Hardfort South and East flip to ice than rain quickly.  3-5 inches of snow falls in Southern Worcester County, NE CT, and N RI before a period of freezing rain and then plain rain.  The snow will thump before the changeover.  Further N and W stay colder and thus more snow. I am currently expecting a changeover around 10-11 pm in S WOR, NE CT, N RI.  Looks to be around midnight around 495 (north of pike). Early Sun AM for N Worcester county. Mainly snow out west.

Snow totals
NWS Boston snow totals. 
Again I feel slightly higher amounts are likely north of Providence.  Hi res radars suggest quite a thump before the changeover. Plus every storm has over performed in E Mass during the blitz.

Ice totals
NWS Boston Ice Forecast 
This is just a pain in the ass. There shouldn't be power outages but it will lead to poor road conditions.  Overall over a half inch of liquid will be added to the snowpack
WPC 2 day precip outlook
If you are interested keep an eye out for a general blog analyzing what effect this snow pack will have on spring.  I am looking for her. We will have to settle for low 40s...maybe Sunday.  I think mid to upper 30s is more likely but it will feel great. Arctic air returns Monday.

Have a great night/weekend,

-Zack Green








Monday, February 16, 2015

Snow Map for Tuesday

After all we've been through the last 3 weeks tomorrow's snow will seem like a flurry to many.  SE MA will see a bit more which is why they are under a Winter Weather Advisory
NWS Boston Advisories
Light snow will break out S to N after 6 am.  It should reach The MA/CT/RI border by 7 am.  The heaviest snow falls around lunch. It tapers late afternoon with the exception of S coastal MA.  Totals....
NWS Boston snowfall forecast
I think more falls in Plymouth County and a bit more in the middle Cape.  Another blast of Arctic air late week, another storm possible this weekend.  

Talk to you again in a few days.

-Zack Green


Sunday, February 15, 2015

This Is Not a Recording- More Snow

I imagine most of you do not like me at the moment.  That's OK.  Before you know it I'll be forecasting heat waves and thunderstorms.  Before we get to that we have a date with history.  Boston and Worcester have climbed to 3rd place in seasonal snowfall totals.  February is Boston's snowiest month in recorded history by a foot. Both January and February are in the top 5 in Worcester for snowiest months. Hi.

I've buried the lead.  We are going to add to those totals Tuesday.  Before we get to that dangerous cold will invade the region.
WPC surface analysis 11 am
A cold Arctic high is dropping into the Central US.  Our storm is on its way to Canada.  The large pressure gradient is contributing to strong winds.  Temperatures as of 2 pm
2 Pm 2 m temps (image Weather bell)


Short range guidance suggests wind chill temperatures of -25 to -30 regionwide tonight! The Berkshires are looking at -35 to -40
18z HRRR wind chill temps 1 am (image Weather bell)

For this reason the National Weather Service in Taunton has issued a Wind Chill Warning almost everywhere Until 10 am tomorrow
NWS Boston hazards
Actual air temperatures will be -5 to -10.  February is on track to be one of the coldest months on record in Southern New England
Feb temperature anomaly (Image Weather bell)
If you want warmth head west.  Speaking of the west that is where the next storm will come from.  The upper air pattern is this
18z NAM 500 mb vort 1 pm Sun (image NCEP)
Notice the X diving through Utah.  Here it is on satellite
GOES_Composite water vapor satellite
Today's storm took a Northern track.  This will create a mess across Missouri, Kentucky, Tennessee, the Carolina's, and Virginia before trying to turn the corner up the coast.  

WPC surface forecast 7 am Tuesday
Looks like a decent set up for 3-6 inches, more in SE MA, S RI.  This should start around day break.  It is a quick mover thankfully.  There is also potential for snow Wednesday.  I'll address that tomorrow.  

Finally there was some great video of Jim Cantore on the Weather Channel today.  100% chance I would react the same way.  

PS-someone made a great point today.  We might as well smash all the seasonal snow records.  We didn't come this far for 2nd place.

-Zack Green

 


Friday, February 13, 2015

Latest on Weekend Snow

Good news first... I think we are on the lower end of accumulating snow this time around, at least west of 495.  Coastal MA up thru NH and Downeast Maine will bear the brunt of this storm.  This is where Blizzard Warnings are posted.
NWS Boston hazards
Eastern CT, Cmass, and RI are under a winter storm warning.  A winter weather advisory exists east of the Berkshires and in central CT.  The Berkshires can expect 4-6, mainly tomorrow PM/overnight.  

Snow breaks out early afternoon region wide.  2-4 is likely by evening.  A lull is possible overnight which is why I am not expecting snow totals as high as the last few storms.  Using the National Weather Service as a guide
NWS Boston forecast snow
These may be slightly high.  High resolutio resolution guidance suggests less in Worcester County.  The snow is a story because there is nowhere to put it.  The biggest story with this storm is the wind Sunday.  Here are some forecast gusts Sunday pm
NWS wind gust forecast
These are in its.  Basically 35 kts is 40 mph, 60 kts is 70 mph.  Winds will gust to hurricane force (75 mph) on the Cape.  What causes winds this strong?  A strong jet stream aloft
18 z NAM 300 mb jet 1 pm Sun (ncep)
and a tight pressure gradient at the surface.  The low will deepen to ~974 mb.  Meanwhile a ~1040 mb high drops into the plains.
WPC Sunday 7 am Surface forecast Sunday
Snow wraps up Sunday from SW to NE in Southern New England.  Bitter cold follows Monday.   Lows are well below 0. Highs won't reach 10.  Sounds fun eh?

Enjoy your weekend, I will post if something changes.  

-Zack Green





Thursday, February 12, 2015

Snowstorm this Weekend to Pack a Punch

Another weekend, another storm to track. Nearly everyone has had enough snow but mother nature does not care.  The record setting snow blitz is set to continue. Two lanes streets have been reduced to one, rooves are collapsing, cities and towns have blown through snow removal budgets and there is no where to put the snow.   I poke fun at people who remember the Blizzard of 78 and all in all that was a worse singular storm than any of the 3 we've endured these past few weeks.  January 2011 brought storm after storm and similarly high snow banks/roof collapses. That was over a 6 week stretch however, not 3.
Jan 9-13, 2011 storm (NESIS)
The Jan 11 storm highlighted that stretch.  The blizzard 3 weeks ago remains the foundation for our problems today.
Jan 25-28, 2015 storm (NESIS)
I said at the time it was the most fun I've had covering a storm. Well one week later, after cold temperatures allowed minimal melting, we got this.
Feb 2, 2015 storm (NESIS)
This storm actually ranked higher on the Northeast Snowfall Impact Scale (NESIScheck it out) due to a greater population affected.  This storm delayed the Patriots parade and generally crippled the MBTA. Still cold, a 3rd storm struck Sunday/Monday.  This provided a KO to the T and started to compromise the structure of buildings.

As I write this we are missing a major storm that will blow up in the Atlantic.  We probably won't get so lucky a second time
North America surface analysis 4 pm (WPC)

Our next storm is still in the Arctic Circle.  From the NAM 500 mb (~halfway up atmosphere)
18z NAM 500 MB VORT (NCEP)

The energy is north of Manitoba.  On the surface chart above you can see a weak surface low in NW Manitoba.  These means the storm source is truly polar in origin. Our air mass tomorrow will be bitter enough.  Highs will be in the teens while lows flirt with 0.

wind chill advisory is in effect tonight thru tomorrow AM.  It will feel -15 to -20 below. There is also enough confidence for winter storm and blizzard watches!
NWS hazards
Blizzard in lime green, winter storm in blue. Worcester county and N RI are also under this but the active Wind Chill Advisory supersedes it on the colored map.  A blizzard watch also is up for the Cape. See here.


So by Saturday AM the storm is in the Great Lakes
WPC surface forecast Sat 7 am

At the upper levels we are here
18Z NAM 500 mb fort 7 am Sat (NCEP)
The storm really deepens overnight Sat into Sunday. Sat 7 pm
WPC surface forecast 7 PM Sat 
To Sun AM
WPC surface forecast Sun 7 am
For is in Central MA this is a better solution, but still not great. This is a lashing for Maine and coastal MA, NH. Snow begins Saturday around noon. It may let up for a time Saturday evening after an initial 3-6 in Worcester County. It rages at the coast as winds by Sun AM are approaching 70 mph (likely higher at times).  

My guess is Boston sees 12-16, Worcester 8-12, Providence 5-9.  The wind will cause blowing and drifting snow.  No map yet, but I'll show you the NWS when they release it.  

Check for an update tomorrow PM.

-Zack Green





Saturday, February 7, 2015

Long Duration Snow Event Set to Begin

Here we go again! Another snow storm is on tap for Southern New England.  Winter 2014-15 started slow, but it has more than made up for its modest beginning and we are starting to enter legendary territory.  More snow threats are on my radar besides this storm and perhaps more impressive is an arctic blast not seen in these parts in years.  But first lets take a look at this storm.

NWS Boston watches/warnings/advisories 
A winter storm warning (pink) is in effect until Monday night.  It is snowing lightly right now as a disturbance moves through the region.
NWS Northeast Regional Radar
At the surface the pattern is active 
WPC Surface Analysis 4 PM EST
By tomorrow AM that boundary across Northern New England will sag south and set up around Long Island as Arctic High Pressure builds southeast.
WPC Surface Forecast 7 am Sunday
At the upper levels we see energy streaming across the Upper Plains
18z NAM 500 mb vort, heights 7 am Sun (image NCEP)
The initial snow that develops overnight and tomorrow AM is a result of warm moist air overrunning the arctic front .  Expect 2-4 inches by 7-8 AM before a bit of a lull sets in.  I wouldn't rule out 4-8 in Northeast MA/Southern NH by the morning.  
18z NAM 7 am temps (image Weatherbell)
The snow will be fluffy and it will add up quickly.  This is part 1 of the snow (or part 2 if you want to count today).  The next part will produce snow Sunday PM into Tuesday AM.  A coastal front will set up around I-95.  Check out the temperature differences between Central MA/RI and SE MA tomorrow at 8 PM
18z NAM hi-res 2 m temps 8 PM Sun (image Weatherbell)
33 in Brockton, 17 in Worcester.  Heavy fluffy snow should set up on both sides of this front.  Sunday overnight into Monday will feature periods of snow, at times heavy.  So how much total snow are we talking?

Again I will defer to the National Weather Service.  These guys have been spot on so far, if not underdone at times.
NWS Boston forecast snow accumulations thru Tuesday AM 
A general 14-24 is expected.  I believe the North Shore/NE MA will approach 30 in spots, especially Gloucester/Peabody.  The Cape may be underdone a bit as I think Barnstable/Sandwich/Bourne will do better than 4-6. Eastern Worcester county is looking closer to 18 than 14.  In fact 20 wouldn't be surprising.

Use good judgement.  We should all be able to handle driving in snow by now.  However the snow banks are going to be ridiculous after this.  Thursday PM-Friday is another storm threat.  If it hits we probably avoid record cold Friday.  If it doesn't temperatures could plummet to -10 to -20 Friday AM.  As it stands now that is what we see Saturday AM.  

Uncle.

-Zack Green







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