Cmass495

https://forecast.weather.gov/product.php?site=BOX&issuedby=BOX&product=AFD&format=CI&version=1

Major bust in Worcester County

Have leaned toward the vast majority of the guidance, which results in confidence in snow totals being the highest north of the MA Pike. Less certain in totals along and south of the MA Pike. The reason for the uncertainty is with regards to nose of warmer air aloft punching into the region per the 925-700 Layer Max temps Friday morning. Have thrown out the NAM/NAMNest guidance at this point in time as it appears overly aggressive with its warm nose punching in. If correct then there would be Ptype issues for much of MA vs just along/south of the MA Pike. The aggressive northward push of the warmer air is likely due to the stronger 850/925 jet impinging a bit further northward than other pieces of guidance along with the secondary low tracking over the south coast vs south of the south coast. Need to keep a close eye on this because if other high resolution guidance follows the NAM/NAMNest then snowfall totals will need to be reduced as there will be more wintry mix/rain vs snow. Can see this clearly when looking at the SREF/WPC Superensemble plume guidance with snowfall amounts across interior MA vs our south coast. Regardless of the warm nose pushing in am anticipating everyone to start off as all snow Thursday night. Snowfall intensity will quickly pick up after midnight roughly from west to east. Will have the risk of 1" and perhaps some 2" per hour snowfall rates as we have strong speed convergence at 850 hPa and lift within the dendritic growth region. This also lines up with solid frontogenetical forcing in the 1000-850 hPa layer. Still quite difficult to pinpoint a fgen band this far out, but this will bring the greatest risk of those 1" or greater per hour snowfall rates. This will cause issues for the Friday morning commute. Think that there could still potentially be issues during the afternoon/evening, but snowfall should be lighter later in the day.

In Lancaster in the heart of the 495 band, waited all day for this, not disappointed.

FWIW, Bouchard just upped his map, went 18-24 from Holden east

Harvey: "This is a classic, this is a classic .... even in Worcester I can see 18-24."

HIGHLIGHTS... * WE NOW HAVE HIGH CONFIDENCE IN A HISTORIC MAJOR WINTER STORM FOR EASTERN NEW ENGLAND. WIDESPREAD 1 TO 2 FT SNOWFALL WITH LOCALIZED 3 FT IS LIKELY FOR EASTERN MA AND RI ALONG WITH BLIZZARD CONDITIONS. * SNOWFALL RATES COULD REACH 2 TO 4 INCHES PER HOUR AT TIMES DURING THE DAY ON SATURDAY WITH POSSIBILITY OF THUNDERSNOW ACROSS EASTERN MA AND RI. * IN ADDITION TO POTENTIAL HISTORICAL SNOWFALL, STRONG WINDS UP TO HURRICANE FORCE ESPECIALLY ALONG THE COAST WILL LEAD TO BITTERLY COLD WIND CHILLS ON SATURDAY ALONG WITH MINOR TO MODERATE COASTAL FLOODING. DETAILS... HEAVY SNOWFALL/EXTREME SNOWFALL RATES... MODELS HAVE NOW COME INTO CONSENSUS FOR A HISTORICAL BLIZZARD TO IMPACT EASTERN SOUTHERN NEW ENGLAND. EXPLOSIVE CYCLOGENESIS WILL OCCUR OFF THE MID ATLANTIC COAST TONIGHT, WITH AN IMPRESSIVE 40 MB PRESSURE DROP IN 24 HOURS AS A SURFACE LOW TRACKS FROM EAST OF THE CAROLINAS TO THE 70W/40N BENCHMARK. FOR REFERENCE, A BOMB CYCLONE'S CRITERIA IS A DROP OF 24 MB IN 24 HOURS. AT THIS POINT WITHIN 24 HOURS OF THE STORM, WE ARE NOW IN THE TIME FRAME WHERE THE NAM GENERALLY PERFORMS WELL DURING AN EAST COAST CYCLOGENESIS EVENT. WE NOW HAVE HIGH CONFIDENCE IN EXCEPTIONAL TO EXTREME SNOWFALL RATES WITH THE POSSIBILITY FOR THUNDERSNOW ACROSS EASTERN MA AND RI. SOMEWHAT LOWER CONFIDENCE IN THE EXACT PLACEMENT OF THE HEAVIEST BAND, HOWEVER. BOTH NAM AND GFS BUFKIT SOUNDINGS SHOW OVER 50 UNITS OF OMEGA COINCIDING WITH THE FAVORABLE SNOW GROWTH REGION. GIVEN THAT A DOUBLE BARREL LOW COULD DEVELOP WITH THE POTENTIAL FOR AN EYE- LIKE FEATURE AT SOME POINT, WHEREVER THE MESOSCALE SNOW BAND SETS UP COULD SEE 2 TO 4 INCHES PER HOUR SNOWFALL RATES WITH AN OUTSIDE CHANCE FOR 5 INCHES PER HOUR ESPECIALLY WHEN ON THE BACKSIDE OF THE SYSTEM. IF A DEFORMATION BAND CAN PERSIST WHEN THE ARCTIC AIR ARRIVES LATER IN THE DAY, SNOW TO LIQUID RATIOS (SLRS) COULD BE AS HIGH AS 20-25 TO 1. THEREFORE, WE FELT CONFIDENT ENOUGH IN THIS FORECAST PACKAGE TO INTRODUCE AN AREA OF 24 TO 30 INCHES STORM TOTAL SNOWFALL. IT IS POSSIBLE THAT THIS BAND COULD SET UP FURTHER WEST, OR THERE MAY BE TWO BANDS OF HEAVY SNOW WITH LESSER AMOUNTS IN BETWEEN. EITHER WAY, WE ARE CONFIDENT ENOUGH TO GO WITH A BLIZZARD WARNING FOR THE POTENTIAL OF BLOWING AND DRIFTING SNOW WITH NEAR ZERO VISIBILITY AT TIMES ACROSS MUCH OF EASTERN MA AND RI. STRONG WINDS/BLOWING SNOW... WITH 925MB WINDS AT 65-70 KTS OR 4 TO 5 STANDARD DEVIATIONS ABOVE NORMAL ACCORDING TO GEFS AND NAEFS SITUATIONAL AWARENESS TABLE AND COMBINED WITH EXCELLENT MIXING, THERE WILL BE HURRICANE FORCE WIND GUSTS AT TIMES ALONG THE IMMEDIATE COAST AND 50-60 MPH GUSTS FURTHER INLAND. THIS WILL TRANSLATE TO WIDESPREAD DRIFTING AND BLOWING OF SNOW WITH LOCALIZED SNOW DRIFTS OF UP TO 4 FT OR HIGHER. WITH TEMPERATURES IN THE TEENS TO LOW 20S, WE HAVE HIGH CONFIDENCE IN RATHER WIDESPREAD BLIZZARD CONDITIONS ACROSS EASTERN MA AND RI, INCLUDING THE PROVIDENCE TO BOSTON CORRIDOR. BASED ON THE LATEST GUIDANCE TRENDS, IT IS POSSIBLE THAT THE I-95 OR EVEN THE I-495 CORRIDOR ENDS UP WITH A SECONDARY LOCAL SNOWFALL MAXIMA. THE SILVER LINING IS THAT BECAUSE WE ARE DEALING WITH DRY POWDERY FLUFF, THERE IS LESS OF A CONCERN FOR SNOW LOADING ISSUES EXCEPT FOR PARTS OF THE OUTER CAPE AND NANTUCKET DUE TO THE COASTAL FRONT. POWER OUTAGE POTENTIAL LOOKS TO BE HIGHEST ACROSS CAPE/ISLANDS, WHERE THE WARMER TEMPS WOULD LEAD TO HEAVIER AND WETTER SNOW AND CONSEQUENTLY HIGHER SNOW LOADING. WITH 70 MPH WINDS, POWER OUTAGES WILL BE LIKELY. THERE IS SOMEWHAT LOWER CONFIDENCE HOW FAR WEST THE HEAVY SNOW OVERSPREADS AND THIS IS SOMETHING THAT WE CANNOT BE ENTIRELY SURE UNTIL THE MESOSCALE BAND SETS UP AS THE STORM GETS GOING TOMORROW MORNING. WHILE WE DO THINK THAT PLYMOUTH COUNTY IS STILL GOING TO END UP WITH ONE OF THE HIGHEST TOTALS FOR THIS STORM, HOWEVER, THE SLRS MAY BE AFFECTED BY THE DENDRITIC GROWTH ZONE'S LESS THAN IDEAL COINCIDENCE WITH THE BEST OMEGA RESULTING IN RIMING AND THE FACT THAT THE HURRICANE FORCE GUSTS COULD BREAK UP DENDRITES.

New.

HEAVY SNOW/BLIZZARD CONDITIONS... INTENSE CYCLONE DEVELOPING ALONG A HIGHLY BAROCLINIC ZONE, COUPLED WITH VERY STRONG JET DYNAMICS, DUAL UPPER LEVEL JET STREAK AND A FIRE HOSE OF ATLANTIC MOISTURE, WILL RESULT IN VERY HEAVY SNOWFALL ACROSS RI AND EASTERN MA. STILL SOME UNCERTAINTY ON THE WESTWARD EXTENT OF THE HEAVY SNOW. HOWEVER ENOUGH CONFIDENCE TO UPGRADE TO WARNINGS FOR THE ENTIRE REGION, EXCEPT WESTERN MA WHERE A WINTER STORM WATCH WAS ISSUED, GIVEN THIS WILL BE THE BACK EDGE OF THE HEAVY SNOW. FARTHER EAST ACROSS RI AND EASTERN MA, HEAVIEST SNOW WILL FALL DURING THE DAY SAT AND SAT EVENING, WHERE SNOWFALL RATES OF 2-4 INCHES PER HOUR ARE POSSIBLE AT TIMES ACROSS RI AND EASTERN MA, YIELDING STORM TOTALS OF 12-18" ACROSS THIS AREA. THE HIGHEST TOTALS WILL LIKELY BE REALIZED ACROSS EASTERN MA INCLUDING BOSTON,CAPE COD AND MARTHAS VINEYARD WHERE 18-24 INCHES IS LIKELY, AND A LOW PROB OF ISOLATED AMOUNTS OF UP TO 30" IS POSSIBLE. HOWEVER STILL TOO EARLY TO SAY EXACTLY WHERE THESE MESOSCALE BANDS SET UP, USUALLY JUST TO THE NW OF THE MID LEVEL LOW OR MID LEVEL BENT BACK WARM FRONT. IT'S POSSIBLE THIS HEAVY BAND OF SNOW MAY PIVOT AS FAR WEST AS EASTERN CT/RI INTO THE WORCESTER HILLS. SLR IN THIS BAND WILL LIKELY BE ON THE ORDER OF 15-20 TO 1, GIVEN STRONG FORCING IN THE SNOW GROWTH REGION. STILL TOO EARLY TO PINPOINT THESE MESOSCALE FEATURES AT THIS TIME RANGE. OTHER ISSUE WITH THESE MESOSCALE BANDS, IS THERE IS USUALLY CONSIDERABLY LESS SNOW ON EITHER SIDE OF THE BAND. THUS, SNOW TOTALS WILL VARY SOMEWHAT FROM LOCATION TO LOCATION. ISSUED A BLIZZARD WARNING FOR THE IMMEDIATE COAST, AS THIS IS THE AREA OF HIGHEST PROBABILITY OF HEAVY SNOW, STRONG WINDS AND VSBY NEAR ZERO AT TIMES. IT'S POSSIBLE THE BLIZZARD WARNING MAY NEED TO EXPANDED WESTWARD INTO RT-128 AND RI. WILL WAIT TO SEE TRENDS IN 12Z GUIDANCE. THUNDERSNOW IS POSSIBLE ON THE NOSE OF THE DRY SLOT, AS INTRUSION OF MID LEVEL DRY AIR STEEPENS LAPSE RATES. ALTHOUGH, IF THE DRY SLOT COMES TOO FAR ONSHORE, THIS WOULD CUT DOWN ON SNOW TOTALS, WHICH IS POSSIBLE ACROSS THE CAPE AND ISLANDS. SOMETHING WE WILL HAVE TO WATCH. CONSIDERABLE BLOWING AND DRIFTING SNOW WILL PERSIST INTO SAT NIGHT EVEN AFTER THE SNOW ENDS, IN RESPONSE TO VERY STRONG NNW WINDS. STRONG TO DAMAGING WINDS... IMPRESSIVE LOW LEVEL NNE JET OF 75-85 KT TRAVERSE THE REGION THIS AFTERNOON. MODEL SOUNDINGS INDICATE UP TO 65 KT GUSTS IS POSSIBLE FROM CAPE ANN TO CAPE COD INCLUDING THE ISLANDS. THUS, IT'S POSSIBLE A FEW LOCATIONS GUST TO HURRICANE FORCE 64 KT/74 MPH! THEREFORE, TREE DAMAGE AND POWER OUTAGES ARE POSSIBLE IN THIS REGION THIS AFTERNOON AND EARLY EVENING. DANGEROUS COLD... AS STORM INTENSIFIES, IT WILL DRAW UPON VERY COLD AIR OVER NY STATE AND NORTHERN NEW ENGLAND, ADVECTING THIS AIRMASS SOUTHWARD. THUS TEMPS WILL FALL THRU THE TEENS WITH HEAVY SNOW FALLING THIS AFTERNOON. GUSTY NNE WINDS WILL YIELD WIND CHILLS BETWEEN +5 TO -10F. SO NOT QUITE WIND CHILL ADVISORY CRITERIA, BUT GIVEN NEAR WHITE-OUT CONDITIONS AT TIMES, AGAIN, DON'T VENTURE OUT IF AT ALL POSSIBLE.

...WINTER STORM WATCH IN EFFECT FROM LATE SUNDAY NIGHT THROUGH MONDAY EVENING... * WINTER STORM WATCH, HEAVY SNOW POSSIBLE. TOTAL SNOW ACCUMULATIONS OF 3 TO 6 INCHES POSSIBLE. * WHERE...EASTERN FRANKLIN MA, NORTHERN WORCESTER MA AND NORTHERN MIDDLESEX MA COUNTIES.

3k man trend