Clear skies for the moment this Sunday afternoon belies a warm front to be dragged through our area by a low pressure system passing through southern Canada tonight. The warm front will squeeze some moisture out of the cold air ahead of the front, which will fall as snow Monday morning.
It won’t amount to much – perhaps an intense-looking snow fall amounting to very little if any accumulation – followed by the warm front changing snow to rain, and could push afternoon temperatures to the 50s – near normal for this time of year.
Next, temperatures will dip on Tuesday, with some snow showers late Tuesday and overnight, ending by Wednesday morning.
The end of Holy Week will have rain showers and warmer temperatures as low pressure lingers over the eastern US – perhaps clearing out for Easter Sunday.
For Fri, Mar 20….
This is a classic storm forming off the Carolina coast and moving up off the northeast seaboard.
Here’s the factors at play….
- The computer forecast models like to make a storm of this situation, but differ on the results
- The major question is how long the cold-enough for snow air stays over our area.
- For the NYC area, the NWS’ best forecast is for snow, beginning in earnest after the Friday morning commute, changing to rain. The forecast is for staying all snow to the north and west, but less precip because they will be further from the storm there, so the snowfall amounts to about the same everywhere, with inland locations getting 2 to 5 inches, a bit less by the coast.
See http://www.weather.gov/okx/winter for the latest details and links to other areas in the northeast.
As the NWS says in the forecast discussion…where they like a point my brother Dan makes about heavier precip rates mean precip falling from colder air further up and more likely to be snow.
CONFIDENCE NOT AS HIGH AS WE WOULD LIKE FOR FRI INTO SAT. TYPICALLY THESE LATE SEASON EVENTS CAN THROW A LOT OF COMPLICATING FACTORS INTO MIX AND THIS IS NO EXCEPTION...INCLUDING HIGHER SUN ANGLE AND AMOUNT OF LOW LEVEL WARMING AND POTENTIAL FOR AN ISOTHERMAL ENVIRONMENT IN WHICH PRECIPITATION TYPE BECOMES VERY DEPENDENT ON INTENSITY
The forecast challenge is how fast the warm air will come up the east coast and change the snow to rain. If the cold air holds on at the surface, some of the rain will freeze on already-frigid surfaces.
From the Saturday morning NYC NWS office forecast discussion:
The NWS was expecting the highest amount of snow and freezing rain from NE NJ though the Hudson Valley into SW CT, but that axis is forecast further east now…..
GENERAL EXPECTATION IS A 1 TO 4 INCH SNOWFALL ACROSS NYC/LONG ISLAND WITH A GLAZE TO A FEW HUNDREDTHS OF AN INCH OF ICE...AND A 3-7 INCH SNOWFALL ELSEWHERE...HEAVIEST ACROSS INTERIOR PORTIONS OF S CT. ALSO OUTSIDE OF NYC AND LONG ISLAND...THERE WILL BE A BAND OF UP TO A TENTH OF AN INCH OF ICE IN A CORRIDOR RUNNING FROM NE NJ INTO SW CT...AND UP TO A GLAZE TO A FEW HUNDREDTHS OF AN INCH ICE ELSEWHERE...EXCEPT FOR ORANGE COUNTY...WHICH LOOKS TO REMAIN ONLY SNOW AT THIS TIME.
The storm ends rapidly with the passage of a cold front whipped around the storm, midday Sunday.
ANOTHER THEME IN THE 00Z [7pm Friday computer model forecasts ] SOLUTIONS...ONE THAT BUILDS IN THE TRENDS FROM LAST NIGHT...IS THAT THE PRECIPITATION SHOULD COME TO AN END FAIRLY RAPIDLY ON SUNDAY FROM NW TO SE...BASED ON A FASTER TIMING OF THE COLD FRONT MOVING THROUGH.
Then more deep freeze for the northeast, followed by a storm passing off the eastern seaboard Tuesday night/Wednesday.
The computer models are moving the storm further away from the east coast with each run, but recently….
TUESDAY NIGHT INTO WEDNESDAY...LARGE DIFFERENCES REMAIN AMONGST THE GLOBAL MODELS. THE GFS REMAINS WELL OFFSHORE BUT THE 12Z/20 EC PASSES JUST OUTSIDE THE BENCHMARK WITH AN INVERTED TROUGH AFFECTING THE REGION. 00Z/21 EC HAS TRENDED TOWARDS THE GFS...BUT AT THIS POINT DO NOT WANT TO MAKE HUGE CHANGES TO THE FORECAST SINCE THIS SCENARIO HAS BEEN OCCURRING ALL WINTER WHERE A COASTAL LOW SHIFTS OFFSHORE AND THEN COMES BACK A FEW RUNS LATER DUE TO THE DIFFICULTY THE MODELS HAVE WITH PHASING NORTHERN AND SOUTHERN STREAM ENERGY. THEREFORE...HAVE NOT MADE WHOLESALE CHANGES TO THE FORECAST AT THIS POINT. CHANCE SNOW REMAINS TUE NIGHT THROUGH WED AS AN ALBERTA CLIPPER PASSES NORTH OF THE AREA AND A SHORT WAVE PASSES SOUTH OF THE AREA. STAY TUNED.
Friday evening….. Freezing cold! Hands hurt so much I only lasted 35 minutes outside, and it’s hard to work a camera in gloves at 13 degrees and a wind, but not using the gloves was out of the question.
But the very thin moon was close to brilliant Venus and much dimmer Mars. And when we look closer at the photos, there are more surprises.
The earthshine on the moon was wonderful, but click on the photo to see it full size and look for details – near the bright limb of the moon is a star that the moon eclipsed just a few minutes before this photo was taken. Look at the south pole (lower left) of the moon and the white dot – a lunar mountain top standing up into the rising sun on the moon. Up in the sunlight, it might be a good location for solar collectors for a lunar colony some day.
Here’s a slightly longer exposure showing the sunlit lunar mountain and the star near the moon.
Here’s a view showing how the gathering of the planets looked in the western sky…. at this exposure, the color difference between bluer Venus and reddish Mars is easier to see.
Not until at least after next Wednesday.
From the National Weather Service, NYC office’s forecast discussion
THE BIGGEST ISSUE TO DEAL WITH OVER THIS TIME-FRAME WILL BE THE VERY COLD TEMPERATURES...WITH TEMPERATURES EXPECTED TO RANGE FROM 15 TO 25 DEGREES BELOW NORMAL FROM FRIDAY THROUGH MONDAY. DURING THIS TIME...EVEN THE WARMER AREAS IN AND AROUND NEW YORK CITY WILL STRUGGLE TO REACH 20 DEGREES AND OVERNIGHT LOWS WILL LIKELY DIP INTO THE SINGLE DIGITS EACH NIGHT OVER THE WEEKEND IN THE CITY...AND LIKELY DROP TO AT OR BELOW ZERO OUTSIDE OF THE CITY. THIS... COMBINED WITH PREDOMINANTLY WINDY CONDITIONS WILL RESULT IN DANGEROUSLY COLD WIND CHILLS BOTH SATURDAY AND SUNDAY NIGHTS...WITH WIND CHILLS OF 10 TO 20 BELOW ZERO.
THERE WILL BE THREE CHANCES FOR SNOW DURING THIS TIME. THE FIRST WILL BE THURSDAY AND THURSDAY NIGHT WITH A CLIPPER TYPE SYSTEM. THE LOW QUICKLY INTENSIFIES OFF THE COAST THURSDAY NIGHT... BUT....KEEPS THE HEAVIER PRECIPITATION OFF TO OUR EAST. EXPECT 1-2 INCHES ACROSS WESTERN SECTIONS AND 2-4 EAST WHERE THEY COULD REMAIN ON THE EDGE OF THE PRECIPITATION SHIELD A BIT LONGER. THE SECOND OPPORTUNITY WILL BE OVER THE WEEKEND...WITH ANOTHER CLIPPER TYPE SYSTEM THAT INTENSIFIES AS IT REACHES THE MID- ATLANTIC COAST...THIS SYSTEM WILL HAVE THE POTENTIAL TO BE A LITTLE MORE SUBSTANTIAL. THIS HAS THE POTENTIAL TO BE A MORE SIGNIFICANT SYSTEM FOR OUR AREA THAN THE ONE THURSDAY AND THURSDAY NIGHT. THE FINAL OPPORTUNITY WILL BE AT THE TAIL END OF THE FORECAST PERIOD NEXT TUESDAY. [warm air comes] UP ALONG THE EASTERN SEABOARD AHEAD OF A DEVELOPING LOW PRESSURE SYSTEM ALONG THE GULF STATES. THIS WILL RESULT IN A WARMING TREND...BUT WE START OUT SO COLD THIS WEEKEND THAT IT WILL STILL BE COLD ENOUGH FOR SNOW AT THE ONSET.
Don’t ask….from the Boston NWS office….
.LONG TERM /THURSDAY THROUGH TUESDAY/... */ HIGHLIGHTS... - TEMPERATURES AVERAGING BELOW-NORMAL FOR MUCH OF THE FORECAST - WINTER STORM NUMBER 1: THURSDAY INTO FRIDAY - WINTER STORM NUMBER 2: SATURDAY INTO SUNDAY
What more could you ask for? (At least there’s a high amount of uncertainty about how bad these storms will be….so far.)
cue dramatic music
fade to white.
For the NYC area, Monday’s storm will be more subtle than its other Monday cousins. Unless you are in Boston. Or you don’t have ice in your Monday morning commute.
There is less water in this storm for NYC and south, a snow equivalent of 5 to 8 inches and some of that will be in the form of ice pellets and freezing rain. We can get each of these forms of water during the Monday morning rush hour.
The masters of the weather forecasting models have noted the models agree on bringing cold air into the NYC metro area at ground level. That means whatever falls freezes as it falls through the surface layer. The variables in this storm are how much cold air comes in aloft and how fast the freezing rain turns to snow. (Although I’d rather have snow than freezing rain.)
This discussion is based on the 5pm National Weather Service forecast discussion and forecasts. Check the NWS or private forecaster for updates!
Good luck and be safe!
Thursday’s morning rush hour will be a bit slick as an inch or so of snow settles over the NYC metro area. Perhaps eastern Long Island will get more as a new storm develops well off shore. Inland, the highest amounts, such as they are, may be over the Hudson Valley, but the NWS is not guessing where the highest accumulations will occur – but no more than 2 to 3 inches.
The weekend features a stationary front that will drape itself from east to west to our south. The front will boost warm air up over us, and we’ll be cold enough for snow, on and off, during the weekend. Eventually one of the waves will strengthen offshore and move along the coast, perhaps continuing snow into Monday.
The amount of snow this weekend depends on how strong the high pressure system to our north is and how much it lets the front toward us or pushes it away from us. There’s enough moisture hanging around with this front to give an inch or so of rain, which would put out about 10 inches of snow, but over several days. If the high is weaker, the front could come further north and we could get more rain or ice pellets.
Watch the forecast for developments.