Sunday, March 30, 2014

Rainfall Enables River Rises

Heavy rain overnight enabled local rivers and streams to rise and the result is minor to moderate flooding across Southern New England.  Here is a map of the rainfall totals from this system

NWS Boston Rainfall Reports
5.22" have fallen in Hope Valley, RI which is the highest amount I have found so far. See reports here.  Not surprisingly several rivers are near or above flood stage.  Yellow is near flood stage, orange is minor flooding, and red is moderate flooding.
Northeast River Forecast Center Current River Conditions
You can view river forecasts here .  The Yantic River in SE CT is the only river in moderate flood stage at the moment
NERFC Yantic River forecast 
The forecasts call for only minor flooding from here on out.  I did notice the rivers rose faster and higher than most of the forecast.  For example the Blackstone was forecast to rise to 6.6 ft yesterday afternoon, yet it is already at 8.3 feet.
NERFC Blackstone River forecast
The question now becomes how much more rain?  First of all let's look at the local surface chart
WPC Surface Analysis 11 am
A stalled boundary over the Cape separates raw temperatures from more spring like weather.  Here are the 1 PM temperatures (click to enlarge)
1 PM 2 m temperatures (image Weatherbell)
The precipitation has split in two batches.  One is just offshore MA up through Eastern Maine.  Another is pouring on the Mid Atlantic states
NWS Northeast Regional Radar 148 PM
The precip in the Mid Atlantic is driven by an impressive upper level system
12z NAM 500 mb vort valid 2 PM (image NCEP)
This shows up nicely on the water vapor satellite loop
GOES_East Water Vapor Satellite Loop 115 (NOAA)
This is not in a hurry to move so expect dry conditions throughout the afternoon.  Rain looks to move back in tonight and it could be heavy.  Here is 10 PM simulated radar
16z HRRR simulated radar 10 PM (image Weatherbell)
Due to the nature of the system it may be cold enough North and West of Worcester for freezing rain tomorrow AM.  For that reason a Winter Weather Advisory has been issued
03/30/14 NWS Headlines
That includes Northern Worcester Co, but the Flood Warning for the Assabet River takes precedent.  Monday looks miserable with temperatures in the upper 30's/low 40's.  That's all for now, another update tonight or tomorrow AM.

-Zack Green

Saturday, March 29, 2014

Flood Watch For Interior Southern New England

Light rain fell across much of Southern New England (SNE) yesterday as a cold front moved into the Atlantic.  The result is pretty nice Saturday morning as heights have risen in the northeast.  This will be short lived as a coastal low will creep slowly past the South Shore resulting in inches of rain.  The National Weather Service in Taunton has issued a Flood Watch for interior SNE
03/29/14 NWS Boston Headlines
Current Conditions
A look at the regional visible satellite shows some breaks of sun in the clouds this AM
GOES_EAST visible satellite 1002 AM (NOAA)
This has allowed some temperatures to jump into the low 50's
NWS Boston 10 am Temperature OBS (Mesonet)
Here is the 500 mb for 11 am off the 12z NAM (8 am model run).  
12z NAM 500 mb vort 11 am Sat (image NCEP)
Notice the ridge over the NE?  That will push offshore into the Western Atlantic today.  The dip in the Mississippi River Valley is driving our rainstorm and that will slowly push east.  The rain is right on doorstep of SNE 
NWS Northeast Regional Radar 1008 am
The Water Vapor Loop shows how much moisture is available 
GOES_East Water Vapor Satellite Loop 915 am (NOAA)
That moisture is moving directly up the east coast
SPC 14z 850 mb Moisture Transport
Now let's move forward and talk about the impacts and timing for SNE

Short Range Forecast
The latest high res NAM is bringing temperatures into the mid 50's across many areas by 1-2 PM
12z NAM Hires 2 m temps 1 PM (image Weatherbell)
By 2 PM the rain line will be approaching the MA border
13z HRRR Simulated Radar 2 PM (image Weatherbell)
It will rain heavily overnight today.  Here are the projected rainfall totals through 8 am tomorrow 
WPC 1 day precip forecast 
If we move this through 8 am Monday we are looking at widespread 2" + of rain, and scattered 3" + amounts
WPC Day 1,2 precip forecast 
The storm will move very slowly because of blocking upstream in the Atlantic.  We couldn't get any blocking for our snowstorms this winter which meant they dropped their snow and continued on their merry way.  This low will slowly move past the Cape.  Here is the projected surface chart for 8 am tomorrow
WPC projected Surface Analysis 8 am Sunday
Here is the projected surface chart Monday AM
WPC projected Surface Analysis 8 am Monday
It may be cold enough for freezing rain Monday AM.  I will keep an eye on that.  

This is a very useful link for Southern New England River information .  You can track your local river right there.  My local river is the Blackstone River at Northbridge.  It is forecast to rise to 7.2 ft, which is below flood stage
NERF Blackstone River Hydrograph, forecast
2-3 inches of rain in the Blackstone Valley should keep the Blackstone in its banks,  However minor flooding is possible if some of the more aggressive short range models are correct and upwards of 4" fall.
09 SREF QPF Worcester (image Weatherbell)
There is a lot of information to digest but the bottom line is heavy rain is on the way for the next 2.5 days.  More as needed

-Zack Green

Thursday, March 27, 2014

Rounds of Rain This Weekend

Despite a snow pack that seemed to last forever this weekend, there are some pockets of the Northeast that could use a little rain.  The problem was worse after the dry fall and it has recovered nicely in the last 3 months.  This is where we were on New Years Eve
US Drought Monitor 12/31/2013
Here is where we are as of Monday (3/25)
US Drought Monitor 03/25/2014
Now we are looking at excessive rain over the next several days.  Two rounds of heavy are rain will move across Southern New England over the weekend, specifically Friday and Saturday night.  

Short Term Forecast
Temperatures are not going to drop much overnight so tomorrow morning will be warmer than the last few.  Temperatures will generally be in the mid 30's.  North and West of Worcester will see temps hovering at or below freezing.  So light rain will be falling in this region at the same time so the National Weather Service has issued a Winter Weather Advisory (in blue)
NWS Boston Headlines 
A warm front will get rid of the cold air and temperatures tomorrow will rise into the 50's.  Rain will break out again in the afternoon as a cold front approaches the coast
WPC Surface Forecast 2 PM Friday
Expecting rain in Western New England in early afternoon and moving in Southeastern New England mid to late afternoon. 0.25 to 0.5 inch of rain possible tomorrow.  It will end around midnight.  A 12-18 hour dry slot will occur on Saturday.  Some showers will develop mid to late morning but steady rain should hold off until Mid Afternoon on Saturday.  Here is one computer model (not a forecast, just a general idea) at 8 PM Saturday
18z NAM hires simulated radar 8 pm Sat (image weatherbell)
Temperatures are in the mid 30's at the same time.  Computer guidance suggests 3-4+" of rain is possible by Monday.  That means flooding is possible.  I'll keep you informed.  Here is the WPC 5 day rainfall totals
WPC 5 Day QPF forecast
Have a good evening.

-Zack Green

Tuesday, March 25, 2014

Powerful Storm to Clip SE New England

Thank you to everyone who prayed, cried, and sent positive thoughts to keep this storm largely out to sea.  Although some impacts will still be felt (especially on the Cape) the region by and large dodged a bullet.  A Winter Storm Watch is in effect for Bristol and Plymouth Counties while a Blizzard Watch is in effect for the Cape and Islands.  Other headlines include a High Wind Watch is also in effect for the Cape and Islands for wind gusts in excess of 60 MPH.  A Coastal Flood Watch is in effect for the North facing beaches on the Cape and Nantucket.
NWS Headlines 03/25/14
Its another cold start this morning.  Most of Southern New England is waking up to temperatures in the teens
4 am 2 m temps (image Weatherbell)
High pressure is in charge along the east coast, but this will retreat into the Atlantic Ocean during the day Tuesday.  You can see the two pieces of our storm on the chart already.  One low is diving through the Great Lakes while the other is organizing off the SE US coast
WPC Surface Analysis 2 am 
Here is the IR-rainbow satellite loop
GOES_Composite IR_rainbow satellite loop 445 am
Clouds will increase as the storm organizes and pulls north.  Expect temperatures in the Mid 30's today.  Winds will start from the SW but by this evening they will flip to the SE.

Temps drop into the mid to upper 20's.  Snow moves in after midnight.  Winds increase and flip to the NE.  Gust as high as 40 on outer cape, 20-30 further inland

Snow exits Cape early afternoon.  Winds gust as high as 60-70 on Cape/Islands.  Winds gust 35-45 further inland.

I am in agreement with the latest NWS snowfall forecast so I will present their map this morning
NWS Boston Storm Snow Total Forecast
This storm is expected to be the strongest storm in the NW Atlantic since Hurricane Sandy.  As a meteorologist its fun to track but I hope everyone stays safe in Atlantic Canada, Coastal Maine, and SE MA.

-Zack Green

Saturday, March 22, 2014

Mid Week Coastal Storm To Approach Southern New England

A strong ocean storm will develop off the East Coast and it looks like it track close enough to New England to produce some effects.  There are still plausible scenario's in which the storm slides out to sea and the impact is minimal.  However given the projected strength of the system let's take a look at it.

Short Term Forecast
Temperatures today warmed into the 50's in Southern New England (SNE) today
5 PM 2 m temps (image Weatherbell)
A surface low tracking through Northern New England and associated warm front allowed for these "warm" temperatures today.  This is short lived however as a strong Arctic high is descending into the Upper Plains
WPC 2 PM Surface Analysis
See the cold front north of Michigan?  That will bring potentially record breaking cold on Monday.  Sunday is not bitter cold, but temperatures in general will max out in the upper 30's outside of SE MA.  SE MA should reach the mid 40's
18z NAM hires 2 m temps 3 PM Sunday (image Weatherbell)
By Monday morning temperatures are in the single digits North and West of Worcester and in the teens for the rest.  Record low temps for Monday via NWS Boston are
  • Boston        6 (1874)
  • Worcester   6 (1906)
  • Springfield   7 (1906)
  • Providence  9 (1906)
Record Low Max temps (IE lowest high temp for date)
  • Boston       26 (1888)
  • Worcester  24 (1940)
  • Springfield  29 (1940)
  • Providence 28 (1940)
We will challenge these records, but probably fall just short.  The record Low Max temperatures are more likely to fall than the record low min temps.  Here is 5 am Monday
18z NAM hires 2 m temps 5 am Monday (image Weatherbell)
Here is the projected Surface Chart Monday 8 am. 
WPC projected surface analysis 8 am Monday
High temps are in the mid to upper 20's.  Monday night lows are in the teens.  By Tuesday our Arctic high will slide offshore as a coastal low begins to develop off the east coast.

Medium Range Outlook
Here is what I think I know
  • A powerful storm will develop Tuesday and track northeast
  • Highest impact is in SE MA
  • Strong Winds in SE MA
Why a powerful storm?  First of all the computer models are all developing a sub 980 mb storm.  Many are under 970, and a significant number are below 960.  Given this information let's examine the sea surface temperature gradient along the east coast.
NOAA/NESDIS SST Analysis 3.21.14 (OSPO)
The low will generally track long this gradient.  That puts the center south and east of the "benchmark" which is 40/70 (nearly all major New England snow storms track over the benchmark).  This is why I believe SE MA sees the greatest impact.  The rest of Southern New England is still vulnerable to snow.  Here is the 500 mb pattern according to the American GFS model
18z GFS 500 mb heights Wednesday 2 am (image NCEP)
This is actually a low impact event according the GFS as the low does not close off at 500 mb until it is past New England.  I have trust issues with the GFS and the EURO seems to handle these events better, but it foolish to discount a scenario that is still 84 hours away.  The Weather Prediction Center projected surface analysis for Wednesday at 8 am is more in line with my thinking
WPC Surface Forecast Wed 8 am 
This shows a 972 mb low which I actually think is underestimated.  I think a 955-960 low is more likely but we will see.  Here are the impacts I expect
Expected Impacts
Enjoy your Saturday, I'll keep evaluating data tomorrow.  

-Zack Green

Wednesday, March 12, 2014

PM Rain, Overnight Freeze for SNE

The National Weather Service in Taunton has issued a Winter Weather Advisory for all of Southern New England except for the immediate south coasts of CT, RI, and MA
NWS Boston Headlines 3.12.2014
This is for overnight tonight through early Thursday AM.  The main concern is a flash freeze tonight as a bitterly cold Arctic air mass is behind the storm.  1-3" of snow is also possible.

The temperature gradient is impressive across New England this AM. We stretch from the mid 20's in NH, VT, and ME to the low 40's in S CT, RI, MA.
4 am 2 m temps (image Weatherbell)
Here is the surface chart as of 2 am.  The storm is strengthening in the Mid Mississippi River Valley
WPC Surface Analysis 2 am EST
The system is large and is loaded with moisture.  Here is the IR satellite 
NOAA GOES_Composite IR Rainbow Satellite Loop 445 am
Timing, PM Forecast
Here is the radar as of 528 am.  Notice there is some snow breaking out in VT, but most of the precipitation has not moved into the NE yet
NWS Northeast Regional Radar 528 am
Although temperatures will be raw in parts of Middlesex, Essex, and Worcester Counties they will still be above freezing.  To those living south of the pike temps should spike into the 50's this PM
07z HRRR 2 m temps 3 PM (image Weatherbell)
The steady rain moves in between 3-4 PM
07z HRRR Simulated Radar 4 PM (Image Weatherbell)
Steady to heavy rain will fall until around midnight.  Then as temperatures fall winds will begin to howl setting the stage for a nasty Thursday.  Expect winds sustained 15-20 mph with gusts 30-40 on Thursday.  With a high temperature of 20 that means its going to feel like below 0.  Here is the NWS snow forecast for this storm
NWS Boston forecast snow total 3/12/14
Its likely Wind Advisories will go up for tomorrow.  I don't believe flooding will be a major issue, but track your local rivers here

Have a good one
-Zack Green

Biggest Snow Storm Of The Season Heads To Impact Region Tonight

The National Weather Service (NWS) in Norton, MA has issued a * Winter Storm Warning * from 7 PM tonight until 10 AM Wednesday.  A widesprea...