Mesoscale Discussion 59

Issued

Jan 23, 2016, 8:51 AM EST (13:51 UTC)

Expired

Jan 23, 2016, 12:45 PM EST

In force

4 hr

Issued by

the Storm Prediction Center

The Philadelphia radar (KDIX), 87 km from the middle of the area, began a volume at 13:51 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.

912 
ACUS11 KWNS 231352
SWOMCD
SPC MCD 231351 
CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-DCZ000-VAZ000-WVZ000-231745-

MESOSCALE DISCUSSION 0059
NWS STORM PREDICTION CENTER NORMAN OK
0751 AM CST SAT JAN 23 2016

AREAS AFFECTED...NORTHERN VA/DC METRO AND MD/DE/WV TO NJ/PA AND
SOUTHERN NY/CT

CONCERNING...HEAVY SNOW 

VALID 231351Z - 231745Z

SUMMARY...HEAVY SNOW WILL PERSIST THROUGH MIDDAY FROM NORTHERN VA/DE
AND DC METRO/WV EASTERN PANHANDLE/INTERIOR MD TO NJ AND
SOUTHERN/EASTERN PA TO FAR SOUTHERN NY INCLUDING THE NYC METRO/LONG
ISLAND...WHILE INCREASING INTO SOUTHERN CT. PEAK SNOW RATES WITHIN
THIS CORRIDOR WILL LOCALLY EXCEED 2 IN/HR...WITH BLIZZARD OR
NEAR-BLIZZARD CONDITIONS CONTINUING PARTICULARLY IN AREAS NEAR/JUST
WEST OF THE I-95 CORRIDOR.

DISCUSSION...WATER VAPOR IMAGERY/UPPER-AIR DATA FEATURE THE SLOW
EASTWARD ADVANCEMENT OF A CLOSED MID-LEVEL CYCLONE OVER/JUST EAST OF
THE CENTRAL APPALACHIANS WITH A STRONG/COUPLED UPPER-LEVEL JET
FOCUSED OVER THE COASTAL NORTHEAST STATES. 13Z/8AM EST OBSERVATIONS
DEPICT AN OFFSHORE SURFACE LOW /APPROX 988 MB/ OFF THE COAST OF
SOUTHEAST VA/DELMARVA WITH A PERSISTENT NORTH/NORTHWESTWARD-
EXTENDING NEAR-COASTAL CORRIDOR OF EARLY-MORNING PRESSURE FALLS OF
AS MUCH AS 2-3 MB/2-HR OFF NJ INTO NEAR-COASTAL SOUTHERN NEW
ENGLAND.

SIMILAR TO 06Z...RECENT 12Z OBSERVED SOUNDINGS FROM
WASHINGTON-DULLES AND NEW YORK CITY SAMPLED A SATURATED
THERMODYNAMIC ENVIRONMENT CONDUCIVE FOR HEAVY SNOW WITH A DENDRITIC
LAYER AROUND 500-600 MB AND AN AGGREGATION-CONDUCIVE NEARLY
ISOTHERMAL LAYER BETWEEN 700-900 MB. RELATED TO THE
NORTHEASTWARD-ADVANCING DRY SLOT PER WATER VAPOR IMAGERY...THE 12Z
OBSERVED SOUNDING FROM WALLOPS ISLAND VA SAMPLED A RELATIVELY STEEP
LAPSE RATE/WEAK ELEVATED CAPE BETWEEN 850-500 MB...WHICH RELATES TO
THE NEAR-COASTAL WEAK UPRIGHT INSTABILITY AND WEAK STATIC STABILITY
THAT EXISTS ACROSS A BROADER PART OF THE REGION. SINCE AROUND
09Z...OCCASIONAL CLOUD-TO-GROUND/IN-CLOUD LIGHTNING HAS BEEN NOTED
FROM AROUND THE DC METRO/BALTIMORE VICINITY INTO SOUTHEAST PA...AND
BRIEF/LOCALIZED BOUTS OF THUNDERSNOW WILL REMAIN A POSSIBILITY.

BASED ON RECENT MANUALLY AUGMENTED SNINCR OBSERVATIONS...2 IN/HR
SNOW RATES CONTINUE TO BE NOTED AT NEW YORK JFK...MIDDLETOWN/
HARRISBURG PA...NEWARK NJ AND NEW YORK LA GUARDIA AS OF 13Z/8AM
EST...WITH A 3 IN/HR RATE NOTED AT ISLIP/MACARTHUR NY.
BLIZZARD-CALIBER WIND GUSTS ARE ALSO NOTED AT THE NEW YORK CITY/LONG
ISLAND VICINITY OBSERVATIONS...HIGHLIGHTED BY A 41 KT GUST AS 1235Z
AT NEW YORK LA GUARDIA. REGIONAL WSR-88D VWPS CONTINUE TO SAMPLE A
NORTHWARD-SHIFTING CORRIDOR OF VERY STRONG EAST-NORTHEASTERLY WINDS
WITHIN THE LOWEST 1-2 KM AGL...ACCENTUATED BY 50-65 KT WINDS AROUND
1 KM PER STERLING VA-KLWX...DOVER AIR FORCE BASE-KDOX...
PHILADELPHIA/MT HOLLY-KDIX...AND UPTON NY WSR-88D VWP DATA. 

PER THE AFOREMENTIONED OBSERVATIONS AND SHORT-TERM RAP
GUIDANCE...THE COLLOCATION OF AMPLE MID-LEVEL FRONTOGENETICAL
FORCING AND WEAK STATIC STABILITY WILL CONTINUE TO SUPPORT MULTIPLE
WSW/ENE-ORIENTED INTENSE BANDS OF HEAVY SNOW. EMBEDDED RATES ARE
LIKELY TO CONTINUE TO EXCEED 2 IN/HR FOR A MULTI-HOUR DURATION
THROUGH MIDDAY/EARLY AFTERNOON. BLIZZARD OR NEAR-BLIZZARD CONDITIONS
WILL ALSO CONTINUE PARTICULARLY FOR AREAS NEAR AND JUST WEST /WITHIN
50 MILES OR SO/ OF INTERSTATE 95 INCLUDING THE NEW YORK CITY
VICINITY.

..GUYER.. 01/23/2016

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

ATTN...WFO...OKX...PHI...BGM...CTP...LWX...

LAT...LON   39777439 39677547 38547766 38647837 39167877 40197787
            41397425 41347237 40877254 40557369 39777439

Mesoscale Discussions in New Jersey, 2016Mesoscale Discussions in Pennsylvania, 2016Mesoscale Discussions in Virginia, 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.