Small-Moderate Snowfall tomorrow

Temperatures have varied in 2013 so far for Southern New England.  We opened with a cold stretch that dropped temperatures close to 0 for many of us.  We rebounded with temperatures in the 60's yesterday.  Yesterday was a tease as snow is in the immediate forecast with cold to follow.  There is high confidence in a flip to below normal temperatures beginning tomorrow.

2013 Year to date Temp Anomalies (image wxbell)

So far we are approx 0.05 C above normal in North America.  The eastern warmth has been nearly offset by stubborn western cold.  The first step to changing this will be to breakdown the southeast ridge.  A nearly stationary cold front is working through the South.

Surface Map 4 AM EST

I've circled two areas of high pressure and a wave on the stationary front.  Today that wave will begin to deepen and work its way towards the northeast.

2 m Temps 5 am EST (image wxbell)

One can see the likely track of the system.  The ultimate track is important for where the rain snow line develops.  Right now I'm thinking it will set up in a similar location as the late December quick hitter.  This is not a storm with great upper level support but none the less a weak surface low should develop.  The Jet Stream tomorrow looks like

06/15 NAM 250 stream valid 1 am Wed

Notice the jet really digging into Texas before ejecting over the ridge in the SW Atlantic.  At 500 mb the flow remains strong but without any vort maxes.  Vort maxes are found with a shortwave at the 850 mb level

06z/15 NAM 850 vort valid 1 am EST Wed

A good area of low level upper motion should result in good snow zones tomorrow.  Here is the 850 temp for the same time

06z/15 NAM 850 mslp, T valid 1 AM Wed

The zero line is forecast to stay close to the coast by the NAM.  The EURO brings it further inland but the cold air will remain dense and in place with the high to the north in southern Ontario.  Here is the EURO ensemble temp forecast for tomorrow, usually one of the most reliable temperature models

00z/15 EPS 2 M T max valid 1 PM Wed (image wxbell)

So I buy the NAM totals.  Here is the model output for snowfall according to the NAM

06/15 NAM accumulated snowfall valid Wednesday night

The NAM has done pretty well in the short term with snowfall this season.  Sometimes the regional models can get a better handle on unique synoptic setups because they are not as complicated physically speaking as global models.  None the less agreement is good for at least 3 inches south of the Pike to parts of NW RI and NE CT.   I have to say I don't usually disagree with the HPC but I am today.  I think the 4 inch band is further south just to the west of the rain/snow line.

HPC Day 2 snowfall probs > 4 inches

Finally here are some city grams from the GFS around SNE

06z/15 Boston

1-2 inches in Boston

06z/15 Worcester

2-4 Worcester

06z/15 Chicopee

1-2 Chicopee

06z/15 Hartford

1-2 Hartford

06z/15 Providence

2-4 Providence

Those commuting south should stay mostly snow until mid day tomorrow at least.  Update tomorrow morning have a good day, thanks for reading.

City grams image credits- Dr. Ryan Maue and Wxbell.  

Pats Forecast and Weekly Take

Update- 1236 PM 1/14
It will snow Wednesday. Overlooked on Sunday will update later. Football was on my mind

For the first time in my life I found myself standing and clapping for the Ravens last night.  My friends and I were jumping up and down like the Pats had just won the game when Flacco connected with Jones late in the fourth quarter.  While I think beating Denver would have been easier than beating Baltimore  I love when Peyton Manning pukes on his feet in the playoffs.  If you still think Peyton Manning belongs in the conversation with Tom Brady as best of the generation you are out of your mind.  Peyton Manning and Brett Favre belong together; Super Bowl Champion, record setting QBs who threw as many game costing INTs in the playoffs as they did game sealing TDs.    Btw Joe Flacco is 7-4 in the playoffs and if the Ravens hire Norv Turner as OC watch out, that offense has talent.

1997 Divisional Playoffs Pats Steelers (image via Bostino.com and Brokencigar.com)

I had to lead with that, it was one of the best games I've ever seen.  The weather for the Patriots game today is similar to the first game in December.  It will be mild for January with no precipitation.  The air mass is just kind of sitting around

Surface Map HPC 7 AM

A low pressure system is marching across the South but the boundary draped across NY, PA, WV, VA, and NC is not moving much.  There is low level moisture across the area as shown by this map.  Our value is around 0.5/0.6 inches which is soupy without any rainfall.

0.5 precipitable water from SPC

combine this with a snowpack and ice we will have patchy dense fog across the region, including Foxboro.  The radar returns are blank so that leaves us with a mild but murky afternoon.

 Here are the forecast high temperatures

06z GFS 2 m Temps this afternoon (image Wxbell)

The Pats O should be fine.  Pats (-9.5) and over/under is 48.5.  Of course check with your friends for changes in the lines.  The over is enticing as the offenses will not be slowed.  Texans left a lot of points on the field last game.

A Look Ahead

There will be a chance of showers tomorrow as the cold front will get moving and kick the system out.  This is looking like the only precipitation threat for the week.  Here is the 7-day precip totals from the HPC

7 day precip

Temperatures are going to remain above average this week, but will only be topping out around 40 for most.  By the end of the week we will return to a winter pattern.  For the 0-7 day period 

GFS 0-7 day 2 m temp anomaly (image wxbell)

Here is the 8-14 day forecast from the Climate Prediction Center

classic flip from cool west/warm east to warm west/cool east

This is supported by the various "teleconnections" used in meteorology as the NAO/AO are both forecast to dip negative which is a cold mode for the US.  The PNA is forecast to go positive and we are in a neutral ENSO phase.  What does that look like?

8-14 top 10 analog upper air pattern

There are several major snowstorms on this list.  This is an ideal blockbuster snowfall pattern.  The flip beings Thursday evening so enjoy the 40's this week!  What will happen is the mild Pacific air will ride up into Alaska and down the west coast.  The cold Arctic air will be forced south into the eastern half of the US.   Meanwhile there will also be a block up by Greenland.  As long as the NAO is not too negative New England stands a good chance of big snows.

Big snows that show up in 8-14 day analog

February 1994

1993-1994 is an analog year

Presidents Day 2003 Blizzard

Boston set its all time record snowfall with this storm.  2002-03 is an analog year

Valentine's Day 2007 storm

2007 is another analog year.  I'd expect something more like 1994 or 2003 and not an inland runner like 2007 and not a Mid Atlantic masher like 2010.  Again this looks like a February threat but I will be watching for weaker systems cutting through the Great Lakes.  Go Pats!

Mid Week Weather Thoughts

There has been a special weather statement issued by the National Weather Service valid until mid morning for black ice.  Fog has developed in a lot of places overnight and has created pockets of black ice on untreated roads.  Temperatures will rise into the mid 40's today and clouds will be increasing.  Lows tonight around 30. There will be a dip in the jet stream that will send some cooler air into SNE tomorrow.  Temperatures Thursday will be around 40 and overnight lows will drop to the lower 20's.  Friday will see increasing clouds and a likely some rain (brief snow?) Friday evening and overnight.  Some evidence for the predictions...

Current Temps

2 M Temps valid 5 AM 1/9/13 (image weatherbell)

Current Surface

Surface Chart 535 AM 

Afternoon high temps, via 00z EPS (click to enlarge)

1/9/13 00z EURO 2 M temp (image credit weatherbell)

Skipping ahead to Thursday Night here are the lows, again via 00z EPS

valid 1 am-7 am Friday. Image credit Weatherbell

Most get into the 20's, but people west of 495 drop close to the teens.  Finally here is the next rain event

00z EURO, valid Saturday 1 AM (image credit Weatherbell)

Here is the national precipitation outlook for the next 5 days

HPC 5 day

This will help dent the drought in Texas; alrready several inches have fallen in the Lone Star State

Latest US drought monitor

The folks in the Great Plains could use a storm track up through Chicago but this is good for Texas who has seen drought in 2011 and 2012.  This is common when the Pacific goes into its cold mode as La Nina's tend to dominate.  Have a good day, thanks for reading.

Calm Weather to Begin Week

There has been some chatter about 50 degree warmth this week.  While that will be possible in coastal cities such as Boston and Providence, the majority of the region will be in the upper 30's and lower 40's.  Overnight lows will be in the lower 20's for most of the region with lows in the upper teens in the usual colder  spots.  Very little precipitation is expected in the next 5 days.  There will be isolated snow flurries this afternoon and early evening in addition to the light snow some received overnight.  The next storm chance is the end of the week/weekend and it looks to be wet, not white.

Here are the regional temperatures from 5 AM

5 AM 2 m temperatures (1)

Temperatures have rebounded nicely, here is 9 AM

9 AM 2 m temperatures (2)

In general here is what to expect this afternoon

1/6/13 00z Euro Ensemble 2 m Temp forecast valid 1- 7 PM

This model, the Euro Ensemble (EPS) likes temperatures into the 30's for most and 40's along the coast.  Here is what we look like at the surface

Surface Analysis 840 AM

High pressure is dominating over Canada and this will move through the northeast later today.  Northern New England and upstate New York have the best chance to see some snowfall from this system.  At the mid and upper levels of the atmosphere the Northeast is near boundary from cool/mild today, but we will re-enforce some of the cold tonight

1/6/13 06z GFS 500 mb heights valid Monday 1 am

Where the green starts can be thought of as the warm/cool boundary (generally speaking).  Where this dips heights are falling which lowers temperatures.  Where this pumps up (like the Southern Plains) heights rise and so do temperatures.

1/6/13 06 gfs 250 mb Jet valid 1 am Monday

At the same time here is the jet stream at the 250 mb level.  I am using 250 rather than 300 because there is more of a west to east type of flow across the Northern Hemisphere which is a bit more mild.  Notice the band of red and pink off the east coast.  Known as a "jet streak" this helps confirm the above average temperatures for next week.  This strong jet streak will help deepen a trough over the Atlantic while lifting a ridge northward across the Eastern US.

1/6/13 EPS 500 mb forecast Friday Night

For the 5 day period 

GFS 5 day temperature anomaly 

One thing to remember is that there is a snowpack and its January.  The sun is not strong and average temperatures are in the low 30's upper 20's.  A few degrees above average will feel nice but we will not be approaching any record highs.  The 8-16 day period begins to restore winter to the lower 48

January 14-22

This is also just one of several computer models.  They all pretty much support winter returning after Jan 18 or so to New England.  Here are some city by city forecasts around New England.  

Providence

GFS Providence

Boston

GFS Boston

Worcester

GFS Worcester

Hartford

GFS Hartford

Just as a bonus I want to show what the GFS is predicting for Las Vegas on Friday

GFS Las Vegas

There isn't much support among the other models but a deep trough is going to dig into the west and an upper level system may cut off.  Measurable snow occurs once every 10 years or so in Vegas.  Have a good Sunday!

Images are credited to Dr. Ryan Maue and Weatherbell

Cold Again Tonight, January Thaw Next Week?

After a cold start to 2013 temperatures look to rebound later this weekend and next week.  That said the cold Wednesday, Thursday, and Friday morning will be bitter.  Overnight low temperatures fell into the single digits for much of Central and Northern New England.  Some places in Maine fell as much as 10-15 degrees below zero

Northeast Temps, 1/2/13 7 am EST (1)

The EURO overdid the cold just a bit and the GFS and NAM were too warm.  Temperatures this afternoon should moderate to the mid 20's under mostly sunny skies.  There will be light winds so temperatures will feel like the upper teens/lower 20's.  By tonight the mainly clear skies will allow for rapid heat loss to space.  The NAM and GFS are warmer than the EURO and the EPS, so I'll balance them.  Tonight temperatures should drop close to zero for much of Central and Western MA.  Some locations in Metrowest and Merrimack Valley will also approach zero.  Here is the EPS for the 1 AM to 7 AM period tomorrow morning

EURO ensemble 1/2/13 00z run (2)

The GFS citygram for Worcester shows

1/2/13 06z GFS citygram Worcester (3)

This likes temperatures to fall to about 4 degrees overnight but then one can see the warm up.  So how does one get cold temperatures like this?  As always we will start at the surface and work up in the atmosphere.  Remember that we measure height in the atmosphere with units of pressure.  For example the surface is usually 1010-1015 mb but we will use 1000 mb.  850 mb is approximately 5000 feet up, 700 mb is 10,000 ft, 500 mb is about 18,000 feet and 300 mb is 30,000 feet (jet stream).

Surface analysis 7 am EST 1/2/13 (4)

High pressure in Ontario is helping to push cold Arctic air into the Northeast.  A weak Arctic front is going to push through the region today which will re-enforce the cold tonight.  Here is the 850 for 7 PM tonight

temperatures at 850 are forecast to be below -10 C (5)

At 500 mb

ridge is pumping in the west, trough digging in the east (6)

And at 300 mb

jet streak with winds in excess of 150 MPH (7)

I use 300mb in winter and 200 mb in summer due to the atmosphere being more dense in the winter time in the Northern Hemisphere but either one would work for a forecaster.  Analyzing these trends I expect the coldest temperatures to be Indianapolis to Cincinnati Harrisburg then diagonal to NYC.  This is because the jet seperates the warm air from the cold air.  When it has a 150 mph streak (purple) the gradient is strong.

The data supports temperatures near zero.

The jet will play a role in our pattern going forward.  Since the winds are strong to the right of the Midwest trough and strong to the left of a trough over the Atlantic the Midwest trough will weaken and lift north while the trough over the Atlantic will strengthen and move south.  During this process a ridge is likely to develop over the east US in time.

By Friday Night here is the EURO 500 mb

1/2/13 00z EURO valid Friday 7 PM EST (8)

At 850 mb

1/2/13 EURO 850 valid Friday 7 PM EST (9)

This is a fast pattern with lots of smaller scale features moving across the United States.  A couple of days in the 30's look good early next week.  However predictably is low

Relative Measure of Predictability (10) Day 5

Temperatures in the 6-10 range look like this, according to the CPC

CPC 6-10 (11)

Certainly the 6-15 day range will be above normal with temperatures.  There is still quite a snowpack so its possible the warmth is overdone a bit.

UPDATE

Rather than re-write the blog I should mention that the latest American GFS is coming in and has let up on the warmth this weekend.  So while temperature will not be approaching zero it will still feel like January

Pictures 1, 2, 3, 8, 9 courtesy of Dr. Ryan Maue and Weatherbell a premium weather site

Pictures 4,5,6,7,10,11 all available through US government agencies free for all