Thursday, January 31, 2013

Heavy Winds/Rain Clearing This Morning

Power outages are rapidly increasing in number across Southern New England as a powerful low pressure system and associated cold front push through the region.  As of 610 AM the highest wind gust so far is 80 MPH atop Blue Hill Observatory in Milton.  There was a 60 MPH gust in Boston.  The winds will die down by 9 AM and rain should clear by 10.
610 AM radar
Here is the surface chart this morning
HPC surface Analysis
First we see a 974 mb low over Southeast Canada and the long cold front with it.  Notice the High Pressure dropping into the Montana/North Dakota region.  This high pressure is ushering cold dry Arctic air into the US.   In fact here are the US temperatures; New England and Florida are the warmest two locations
5 AM Temp Analysis (image wxbell)
That will change today.  Here is the forecast temperatures for 1 PM
10z RAP 2 m Temp (image wxbell)
The RAP is also hinting at a snow squall later this evening
10z RAP radar 7 PM EST (image wxbell)
Temperatures will return to the upper 20's tomorrow.  There are some snow chances for the weekend and next week.  I have interest in a Sunday evening system and a Tuesday evening event.  As of now I favor much of what we have seen so far in winter 2012-13; light snow from a storm that grazes SNE.

Wednesday, January 30, 2013

High Wind Watch Today/Tonight

Heavy rain and damaging winds will accompany a cold front through the region tonight.  After the passage temperatures will return to winter, albeit not as cold as last weeks snap.  Quick forecast...

First batch of rain moves through early afternoon
09z RAP simulated radar (image wxbell)
The winds will be gusty all day as the low level jet stream is helping to push temperatures into the 50's
RAP 2m T's 2 PM EST (image wxbell)
This will break records in the Northeast.  The winds at 5 PM
00z NAM Hires MSLP, 900 mb winds (image wxbell)
Finally the winds overnight, at the storms peak (5 AM)
00z NAM Hires 900 mb winds (image wxbell)
Total precip
HPC precip 48 hour total
That's all for now, on the road today.  Will tweet updates @zgreenwx

Tuesday, January 29, 2013

Temperatures to Rise Above 32 Today!

For the first time since the afternoon on January 20th temperatures will rise above freezing (albeit barely).  A very strong cold front is developing in the Midwest/Great Plains and pushing warmth into Southern New England.  A severe weather outbreak is expected today in these regions here

SPC Tuesday Thunderstorm Outlook
Temperatures today will be in the low 30's.  The coldest spots in the region may not break 32 but I am expecting a high of 37 for Boston, 34 for Worcester, 36 for Providence, and 36 for Hartford.  Winds will begin to increase overnight.  As I wrote yesterday I expect some rain tomorrow.  This is an interesting set up and it wouldn't surprise me to see Wind Advisories or High Wind Watches posted today.  

00z GFS 900 hpa Winds mslp (image wxbell)
This is valid 7 PM EST tonight. I've circled the subtropical Atlantic High pressure and a wave low pressure that will form and deepen along the baroclinic (thermal, or temperature gradient) zone.  Here is the forecast surface temperatures at the same time
00z GFS 2 m Temps (image wxbell)
You can see the contrast between warm and cold.  So the pressure gradient force and the baroclinicity are favorable for a strong storm.  That warmth will be pushed into New England via a 500 mb ridge

00z NAM 500 mb vort valid 7 am Tues
The big dip in the west is pushing east.  There are ridges on both the east and west coast.  Temperatures tomorrow will soar into the 50's.  Some light wintry precip will fall in the higher elevations tomorrow morning;  the warmth is moving in aloft but the cold will hold on strong at the surface.  Eventually the cold front will have to push through overnight Wednesday with 1-2 inches of rain and strong winds.  

I'm not sure how much of this will mix to the surface.  It depends on whether or not there is convection.  The cold air can inhibit mixing as well so we will also have to watch temperature trends.  
00z Hires NAM 900 mb windsm mslp 10 PM Wednesday
Here are the 3 day rainfall totals
HPC 1-3 day precip totals
That's all for now, have a good day!

Monday, January 28, 2013

Light Snow/Ice Moves in This Afternoon

Here are the probabilities for at least an inch of snowfall today
HPC day 1 snow probabilities
Here are the probabilities for 0.01 inches of ice or more

HPC day 1 Ice probabilities 
Snow will begin by 3 PM
08z RAP 1000-500 thickness, precip (image wxbell)
Here is the 4 PM simulated radar from one of our high resolution short range weather models
08z RAP simulated radar (image wxbell)
Generally I expect 1-3 inches South of Route 2 and 3-6 inches for Central and Northern New England.  Some ice is possible although it appears to be more of a threat for the Mid Atlantic states.  The majority of the snow ends before midnight although some will still be working off the Cape and Islands.  

2 m temps 3 AM
Finally it will be a chilly start but the warm up begins tomorrow.  It will be brief but it may approach 60 Wednesday.  You have to love New England

Sunday, January 27, 2013

Light Snow for Monday Afternoon Commute

The temperatures will continue to moderate today but before we can get into the upper 30's and 40's we will see a burst of light snow tomorrow night.  I expect light accumulation for most with the highest totals in New Hampshire and Maine.  Temperatures today will be in the upper 20's and lows tonight will be in the upper teens.  Its been 7 days for most people since we went above freezing and that streak will continue until tomorrow night.
9 AM 2 m Temps (image wxbell)
Here is the surface chart
US Surface Analysis 830 AM
The boundary between the warm and cold air will work towards the north and east today.  A snow/ice storm is impacting the Midwest and that will come our way.  The morning commute will be problem free from a weather perspective here are the temperatures for 7 AM
NAM Hires 2 m T minimums (image wxbell)
Northern New England stays cold but Southern New England is in the upper teens and low 20's.  The snow should move in around 3 or 4 PM.  A warm front lifting Northeast will be the cause of this storm.  Arctic air is in place and the warm air will want to push over the top of the cold (more dense).  This will create an icing situation after the initial snowfall.  The further west one lives in New England the more likely they will be to see ice.
Day 2 Snow Probability > 1 inch (HPC)
Northern New England should be more concerned about snow.  Here is the ice probabilities 
Day 2 ice Probability > 0.01 inches (HPC)
Here is the 1000-850 thickness of the storm for tomorrow at 10 PM
12z NAM 1000-850 thickness, mslp, 6 hr precip (image wxbell)
The actual 850 temps, according to the model
12z NAM 850 mb temps (wxbell)
And the surface temps
12z NAM 2 m T max (image wxbell)
Most areas will begin to flip from snow to sleet and freezing rain by midnight tomorrow.  Its a fast moving system so I don't expect any major damage from the ice in New England.  Snowfall amounts will be generally light.  Here are the probabilities for greater than 0.01 inches of precip for two periods

1 PM-7 PM tomorrow
Ensemble probabilities snow ice rain
7 PM-1 AM tomorrow
Ensemble probabilities snow ice rain
Notice that snow has the highest probability in the afternoon, while Ice is highest in the evening.  On Tuesday expect temperatures to rise to the upper 30's.  Some place will crack the low 40's.  On Wednesday another warm front will move into the Northeast and a burst ice is not out of the question.  Temperatures will once again warm into the upper 40's (50 for some people) before a strong cold front drops a half inch of rain.   That's all for now, have a good day.

Friday, January 25, 2013

Still Cold. Snow to Stay Offshore

Cold Arctic air remains in place across Southern New England and that will do two things.  1) It will be cold and 2) It will push the majority of a snowstorm out to sea.  I can't rule out a light dusting for some areas tonight and 1-3 on the Cape.  Regardless we are starting off cold again, albeit a bit "warmer" than yesterday.
5 AM 2 m Temps (image wxbell)
Here are the forecast wind chills from the RAP for 7 AM
10z RAP 2 m Windchill valid 7 am EST (image wxbell)
A windchill advisory is in effect until 10 AM for much of Massachusetts and parts of RI and CT.
NWS Taunton Windchill advisory til 10 AM
Here is the surface chart for this morning.  I've circled a pair of low pressure systems which is combine energy in the Ohio Valley and then reform a new center on the Coastal Plain.  I've drawn the wind direction around the high pressure in the Northeast, helping to suppress any waves from jumping up the coast.
HPC surface
So what to expect and how much?  Here is what last night's EURO run printed out in precipitation amounts
00z EURO 2 m T and precip (image wxbell)
It will be cold so can we saturate the atmosphere?  At 700 mb there is some lift and Relative Humidity is running over 90 percent
00z NAM 700 mb RH, VV valid Fri 10 PM (image wxbell)
At 850 mb however the ideal snow growth zone is too far to the south.  
00z NAM 850 Temps, heights valid 10 PM EST (image wxbell)
Here is the HPC probability for 1 inch of snow tonight
Day 1 Snow Probs 1 inch (HPC)
I won't make a map but I expect a dusting to 2 inches South of the Pike.  Saturday will be cold like the past few days.  Temperatures will begin to moderate during the overnights and during the day.  By that I mean expect highs in the mid 20's and lows in the upper single digits to low teens.  Temps will try to rise on Monday and there looks to be some precip.  Right now I think an icing event is likely.  A ridge isn't going to just push this cold dense Arctic air out, not without a fight.  Cold will linger in the lower levels.  

Here is last nights GFS with 850 temps shown
00z GFS 850 temps 1 am Tuesday
The 1000-850 average however looks like this
00z GFS 1000-850 thickness Tuesday 1 am (image wxbell)
Also notice the high pressure stuck up in Canada.  Looks like ice and I hope I am wrong.  There is nothing worse than ice.  Have a good day.

Thursday, January 24, 2013

Below Zero This Morning

The next several hours will be brutally cold and the wind chills will make it feel like Central Canada.  This cold air should keep the next storm system to our south.  I expect a light dusting for most people, much like the last storm.  I also expect the highest snow amounts to be in Southwest Connecticut and the Outer Cape, Martha's Vineyard, and Nantucket.  As has often been the case this winter, computer guidance has picked up on a storm days away and then loses it as the event comes closer.  Here are the current temps
5 AM 2 m temps (image wxbell)
Here are the projected wind chills for 7 am EST
09z RAP windchills (image wxbell)
Air temperatures should slowly moderate into the lower to mid teens.  Wind chills will briefly climb above zero this afternoon before increasing again when the sun goes down.  Tonight we again drop down close to zero with windchills again approaching -20 F.  Try not to stay outside in this too long today it will be nasty.  

Moving along to the potential snow Friday night into Saturday.  Guidance has is in good agreement of a track well south of the region and agree on phasing taking place too late for a major winter storm.  Now that we are within 48 hours of the event I do not expect any big changes from the models (but you never know).  Its still not a slam dunk forecast.  Here are some probabilities 
Probability of 1 inch in 6 hours snow blue rain green ice yellow
The relative measure of predictability  (RMOP)
Relative measure of predictability Friday 7 PM 
These two figures will update today but what the RMOP shows is uncertainty in the depth of the trough in the year and uncertainty in the ridge in the west.  It will be important to watch for jet streaks at 300 mb today to see if the ridge really wants to pump in the west or amplify the trough in the east.  As it stands the latest Short range ensembles are not big on precip but have good RH at 700 mb.  This should help the concerns over the air mass being too dry for snow.
03z SREF 700 mb RH
For what its worth there is a quite a system moving into the west
354 AM radar PST
Finally here is the North American surface chart.  Check out the high pressure on the US/Canada border
530 AM EST surface analysis
The US temps...very cold in New England and the Upper Midwest
4 am US Temps (wxbell)
Have a good day.

Wednesday, January 23, 2013

Bundle Up!

Its very cold this morning across all of  New England.  Luckily for Southern New England the winds didn't relax last night and there was some cloud cover.  That allowed temperatures to stay above zero but the winds are making temperatures feel well below zero.  Here are the air temperatures from 5 am
RTMA 2 m temp 5 am (image wxbell)
Here is the short term predicted wind chill (-7am EST)
10z Rap 2 hr Windchill (image wxbell)
For that reason a Windchill Advisory is in effect until 10 am for readings 15-18 degrees below zero
NWS Taunton Wind Chill Advisory
What is causing the Arctic Air?  In simple terms cold high pressure from Canada is sending true Arctic air into the Northeast and Great Lakes.
Surface Analysis 530 AM 
This will continue in fact tonight and tomorrow morning will be downright cold.
00z EURO 2 m T min 7 am Thursday  (image wxbell)
Still watching the potential for snow overnight Friday into Saturday.  It doesn't appear to the computer guidance to be a big deal at all.  However there are several things that make me question the model solution a bit; we have time to watch the system.  Here is the HPC 1 inch snowfall probability for Friday 7 AM- Saturday 7 AM.
HPC Day 3 1" snowfall prob
We could pick up another few inches on Saturday.  Also keep in mind it will be a fluffy snow that piles up quick.  If today's trends hold I'll have to admit the Arctic air wins and this system will move out to sea.  More later, have a good day!

Biggest Snow Storm Of The Season Heads To Impact Region Tonight

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