How much snow on Saturday/Sunday?
The models are coming together on the storm track for a coastal storm for the northeast United States this weekend.
They disagree on the temperatures, but the latest National Weather Service technical discussion says the differences will change the snow to rain too late in the storm to make an impact on snowfall amounts.
Look for light snow arriving early Saturday, with the stronger snowfall Saturday night, possibly changing to rain along the coast Sunday.
Stay tuned for updates – remember this is the type of storm where the storm doesn’t form until Saturday night. The early snow is warm air moving out ahead while the storm is being born from the remains of an earlier low pressure system.
From the early morning NWS Forecast Discussion…..
.LONG TERM /SATURDAY THROUGH WEDNESDAY/…
ALL EYES TURN TO LOW PRESSURE MOVING FROM THE SOUTHERN PLAINS TO
THE OH/TN VALLEYS FROM FRI NIGHT INTO SAT…THEN REDEVELOPING
ALONG THE NC COAST SAT NIGHT AND HEADING NE ACROSS THE 40N/70W
BENCHMARK SUNDAY MORNING. GFS/ECMWF ARE GOOD AGREEMENT ON THE LOW
TRACK AND INTENSITY…AND ON THE STRENGTH AND POSITION OF AN
ARCTIC HIGH TO THE NE THAT WILL PROVIDE A LOW LEVEL FEED OF COLD
AIR. LIGHT OVERRUNNING SNOWS SHOULD DEVELOP DURING THE DAY ON SAT
AS MOISTURE OVERRUNS THE NEARBY ARCTIC FRONT…THEN THE HEAVIEST
PRECIP SHOULD OCCUR SAT NIGHT VIA STRONGER ISENTROPIC LIFT AND
H7-8 FRONTOGENESIS AHEAD OF THE APPROACHING LOW. AS FAR AS THERMAL
PROFILES GO…BOTH MODELS ARE LIKELY TOO WARM IN THE BOUNDARY
LAYER…ESPECIALLY INLAND WHERE COLD AIR DAMMING SHOULD HANG IN
LONGER THAN MODEL FCST…AND EVEN AT THE COAST WHERE SNOWFALL
SHOULD COUNTERACT WARMING ON EASTERLY FLOW. THEY ALSO DISAGREE ON
THERMAL ALOFT PROFILES ESPECIALLY LATE SAT NIGHT…WITH THE ECMWF
COLD ENOUGH FOR AN ALL SNOW EVENT NW OF NYC…AND SNOW MIXING WITH
OR CHANGING TO RAIN FOR NYC AND LONG ISLAND…AND THE GFS SHOWING
A CHANGE TO FREEZING RAIN AND SLEET INLAND LATE SAT NIGHT. SINCE
THE BETTER PART OF THE PRECIP WILL HAVE FALLEN BY THE TIME P-TYPE
BEGINS TO CHANGE FROM SNOW…THESE DIFFERENCES SHOULD NOT HAVE A
MAJOR IMPACT ON SNOWFALL AMTS…SO THINK MOST INLAND SECTIONS AND
ALL OF SOUTHERN CT SHOULD SEE SNOWFALL AMTS OF 5-7 INCHES…WITH
NYC AND LONG ISLAND SEEING AMTS OF 2-4 OR 3-5 INCHES. CONFIDENCE
IS INCREASING ON THESE AMTS…AND A WINTER STORM WATCH MAY
EVENTUALLY BE ISSUED FOR MOST AREAS NW OF NYC AND SOUTHERN CT.
THE LOW WILL MOVE AWAY ON SUNDAY…WITH LEFTOVER LIGHT PRECIP
TAPERING OFF GRADUALLY DURING THE DAY.