Mesoscale Discussion 91

Issued

Feb 5, 2016, 7:44 AM EST (12:44 UTC)

Expired

Feb 5, 2016, 1:45 PM EST

In force

6 hr

Issued by

the Storm Prediction Center

The Brookhaven radar (KOKX), 84 km from the middle of the area, began a volume at 12:47 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

939 
ACUS11 KWNS 051245
SWOMCD
SPC MCD 051244 
MAZ000-NHZ000-RIZ000-CTZ000-NYZ000-VTZ000-NJZ000-051845-

MESOSCALE DISCUSSION 0091
NWS STORM PREDICTION CENTER NORMAN OK
0644 AM CST FRI FEB 05 2016

AREAS AFFECTED...LONG ISLAND INCLUDING NEW YORK CITY/CT/RI/MA

CONCERNING...HEAVY SNOW 

VALID 051244Z - 051845Z

SUMMARY...SNOWFALL RATES TO AROUND 1 INCH PER HOUR ARE FORECAST TO
OCCUR...AT TIMES...ACROSS LONG ISLAND THROUGH SOUTHERN NEW ENGLAND
THIS MORNING INTO THE EARLY AFTERNOON.

DISCUSSION...TRENDS IN EARLY MORNING SURFACE OBSERVATIONS SHOWED
MOST LOCATIONS ACROSS SOUTHERN NEW ENGLAND TO LONG ISLAND HAVE
TRANSITIONED TO SNOW AS THE PRIMARY PRECIPITATION TYPE...WITH THE
EXCEPTION BEING ACROSS SOUTHEAST MA WHERE THE PTYPE REMAINS RAIN.
COOLING WET-BULB TEMPERATURES TO LESS THAN 32 F WILL CONTINUE TO
OCCUR THIS MORNING FROM NORTHWEST TO SOUTHEAST.  MEANWHILE...THE
VERTICAL THERMAL PROFILE WILL UNDERGO FURTHER COOLING AS LOW-LEVEL
COLD AIR ADVECTION INCREASES WITHIN STRENGTHENING NORTHERLY
LOW-LEVEL WINDS LOCATED TO THE NORTHWEST TO NORTH OF THE DEEPENING
OFFSHORE SURFACE LOW.  THE SURFACE LOW...NOW LOCATED OFF THE
SOUTHEAST VA COAST...IS FORECAST TO TRACK NORTHEAST...REACHING
40N/70W BY 18Z...WHILE DEEPENING 4-5-MB PER 6 HOURS DURING THIS
PERIOD.  THESE PROCESSES WILL OCCUR AS INCREASING UPWARD VERTICAL
MOTION SPREADS ACROSS THE DISCUSSION AREA WITH THE APPROACH OF A
NEGATIVELY TILTED MIDLEVEL SHORTWAVE TROUGH...CURRENTLY LOCATED OVER
VA/NC.  JET COUPLING ALOFT WILL BECOME MORE PRONOUNCED TODAY AS
WELL...ENHANCING UPWARD VERTICAL MOTION.  

FORECAST SOUNDINGS SUGGEST VERTICAL MOTION WITHIN A MOIST DENDRITIC
GROWTH ZONE WILL SUPPORT THE POTENTIAL FOR HEAVIER SNOWFALL RATES
/AROUND 1 INCH PER HOUR/...ESPECIALLY AS AFOREMENTIONED VERTICAL
MOTION INCREASES THIS MORNING TO EARLY AFTERNOON ACROSS THE
DISCUSSION AREA.  LIGHTNING HAS BEEN DETECTED NEAR AN OFFSHORE
BAROCLINIC ZONE...SOUTHEAST OF LONG ISLAND...WHILE SOME INTRACLOUD
LIGHTNING WAS OBSERVED AT 1130Z IN VICINITY OF NYC.  LOW COVERAGE OF
LIGHTNING WILL REMAIN POSSIBLE WITHIN THE DEVELOPING HEAVIER
SNOWFALL...AS THE 12Z WALLOPS ISLAND SOUNDING SHOWED VERY WEAK
INSTABILITY ROOTED AROUND 700-MB AND FORECAST SOUNDINGS ALSO SHOW
SIMILARLY VERY WEAK INSTABILITY ROOTED BETWEEN 600-700 MB INTO
SOUTHERN NEW ENGLAND TODAY.

..PETERS.. 02/05/2016

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...GYX...BOX...OKX...ALY...PHI...

LAT...LON   40577428 42097380 42707281 43047144 42687081 41897081
            41537092 40977179 40697277 40467344 40577428

Mesoscale Discussions in New York, 2016Mesoscale Discussions in Massachusetts, 2016Mesoscale Discussions in Connecticut, 2016Every mesoscale discussion in 2016

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.