329  
FXUS61 KBOX 140844  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE TAUNTON MA  
344 AM EST SUN JAN 14 2018  
   
SYNOPSIS
 
 
CANADIAN HIGH PRESSURE WILL BRING VERY COLD WEATHER INTO MONDAY WITH  
SOME OCEAN EFFECT SNOW ACROSS PARTS OF EASTERN MA AND RI, MAINLY  
VERY LATE TONIGHT INTO MONDAY. LOW PRESSURE MAY BRING SNOW TO  
THE REGION FROM TUESDAY INTO WEDNESDAY NIGHT FOLLOWED BY  
MODERATING TEMPERATURES INTO THE WEEKEND.  
 

 
   
NEAR TERM /UNTIL 6 AM THIS MORNING/
 
 
A MOSTLY SUNNY BUT VERY COLD DAY IS IN STORE FOR MOST OF THE REGION  
TODAY. 1040+ MB HIGH PRESSURE SYSTEM OVER QUEBEC WILL ALLOW NORTH  
WINDS TO CONTINUE TO USHER IN SHALLOW COLD AIR INTO SOUTHERN NEW  
ENGLAND. DESPITE 850T NOT BEING TOO COLD, LIMITED MIXING AND LOW  
JANUARY SUN ANGLE WILL KEEP HIGH TEMPS IN THE 20S TODAY.  
 
WHILE THE VAST MAJORITY OF THE REGION WILL BE SUNNY, NORTHERLY WINDS  
WILL ALLOW FOR OCEAN EFFECT CLOUDS ON THE CAPE/ACK. 850T/SST  
DIFFERENTIALS ARE NOT EXTREME...BUT GIVEN NORTHERLY WINDS DO EXPECT  
SOME SCATTERED SNOW SHOWERS AND FLURRIES TO IMPACT THE CAPE. ACCUMS  
SHOULD BE LIMITED TO A DUSTING TO PERHAPS A HALF INCH IN A FEW  
SPOTS.  
 

 
   
SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/
 
 
***A FEW INCHES OF OCEAN ENHANCED SNOW POSSIBLE VERY LATE TONIGHT  
INTO MONDAY FROM THE SOUTH SHORE INTO PLYMOUTH COUNTY AND CAPE ANN***  
 
TONIGHT AND MONDAY...  
 
1045+ MB HIGH WILL CONTINUE TO SHIFT EAST INTO QUEBEC TONIGHT INTO  
MONDAY. THE RESULT WILL BE A VERY COLD NIGHT ACROSS MUCH OF THE  
REGION WITH LOTS OF SINGLE DIGITS AND EVEN A FEW BELOW ZERO READINGS  
UNDER MAINLY CLEAR SKIES. LOW TEMPS WILL BE A BIT MILDER ALONG  
PORTIONS OF THE EASTERN MA COAST, CAPE AND ISLANDS. SURFACE WINDS  
WILL TURN NNE OVERNIGHT ALLOWING OCEAN EFFECT CLOUDS AND SOME SNOW  
SHOWERS TO DEVELOP ESPECIALLY AFTER MIDNIGHT.  
 
THE MAIN FOCUS ON MONDAY WILL TURN TO THE MESOSCALE AND POTENTIAL  
FOR A FEW INCHES OF LOCALIZED SNOW ACCUMS. GIVEN THE STRONG HIGH  
SHIFTING INTO EASTERN CANADA AN EASTERLY 925 MB LLJ OF 20 TO 25  
KNOTS WILL DEVELOP. MEANWHILE...A MESOSCALE COASTAL FRONT WILL  
SETUP PROBABLY NEAR THE PLYMOUTH COUNTY COAST. SURFACE TEMPS MIGHT  
BE IN THE UPPER TEENS AND LOWER 20S TO THE NORTHWEST OF THE COASTAL  
FRONT...WHILE PORTIONS OF THE CAPE/ACK WILL LIKELY SEE TEMPS RISE  
ABOVE FREEZING. THIS SEEMS TO BE A VERY GOOD SETUP FOR OCEAN EFFECT  
SNOW SHOWERS WITH 925T BETWEEN -8C AND -12C ALONG WITH ADDED  
ENHANCEMENT ALONG THE COASTAL FRONT AND HELP FROM THE LAND/SEA  
INTERFACE. WHILE A COATING TO 1 INCH OF SNOW WILL BE POSSIBLE  
ACROSS EASTERN MA AND EVEN INTO PORTIONS OF RI...THE MAIN FOCUS WILL  
LIKELY RUN FROM BOSTON/S SOUTH SHORE AND INTO PLYMOUTH COUNTY ALONG  
THE COASTAL FRONT. CAPE ANN MAY ALSO BE IMPACTED BY THIS MESOSCALE  
SNOW AS WELL. SNOW ACCUMULATIONS OF 1 TO 3 INCHES ARE CERTAINLY  
POSSIBLE IN THIS REGION WITH THE LOW RISK OF VERY ISOLATED 4-5 INCH  
AMOUNTS. THIS COULD POTENTIALLY IMPACT BOTH THE MONDAY MORNING AND  
AFTERNOON COMMUTES...ESPECIALLY ON THE HIGHLY TRAVELED ROUTE 3  
CONNECTING BOSTON TO THE SOUTH SHORE. WHILE WE ARE NOT CONFIDENT  
ENOUGH IN AMOUNTS TO ISSUE A WINTER WEATHER ADVISORY AT THIS  
TIME...WILL GO AHEAD AND ISSUE A SPECIAL WEATHER STATEMENT TO  
HIGHLIGHT THIS POTENTIAL.  
 
MEANWHILE...NOT TOO FAR NORTHWEST OF THE BOS-PVD CORRIDOR PROBABLY  
WILL NOT SEE MUCH MORE THAN FLURRIES. HIGH TEMPS WILL MAINLY BE IN  
THE LOWER TO MIDDLE 20S...EXCEPT NEAR OR ABOVE FREEZING NEAR THE  
CAPE COD CANAL AND ISLANDS TO THE SOUTHEAST OF THE COASTAL  
FRONT.  
 

 
   
LONG TERM /MONDAY NIGHT THROUGH SATURDAY/
 
 
HIGHLIGHTS...  
 
- LIGHT SNOW ACROSS SE MA GRADUALLY ENDS MON NIGHT.  
- MODERATE SNOW EVENT POSSIBLE TUE INTO WED.  
- MODERATING TEMPERATURES LATE WEEK INTO THE WEEKEND.  
 
OVERVIEW AND MODEL PREFERENCES...  
STRONG REX BLOCK AND RESULTING HEIGHT ANOMALIES LOOK TO PHASE  
WITH THE HIGHER HEIGHT ANOMALIES ASSOCIATED WITH A CUTOFF HIGH  
PRES SETTLING ACROSS THE CENTRAL ATLANTIC. THE RESULT IS A BLOCK  
AN OVERALL BLOCKING PATTERN, THAT FORCES AN ARCTIC PV LOBE S  
INTO THE CONUS, WHICH GRADUALLY TRANSITIONS FROM A CUTOFF TO AN  
OPEN WAVE AS THE STRONGLY POSITIVE PNA/AO/NAO BREAKS DOWN. AS  
THIS PV ANOMALY SHIFTS E, IT LOOKS TO LEAD TO A SNOW EVENT MID  
WEEK. THE UNCERTAINTY PLAGUING THE FORECAST OF THIS EVENT STEMS  
FROM THE FACT THAT THIS PV ANOMALY REMAINS TRAPPED IN THE BAFFIN  
ISLAND VORTEX. THIS SHOULD BECOME BETTER SAMPLED LATER TOMORROW  
OR TOMORROW NIGHT. INTERESTING, THE OPERATIONAL GFS HAS TRENDED  
TOWARD THE OPERATIONAL ECMWF SOMEWHAT OF LATE, WHILE THE ECMWF  
IS LESS AMPLIFIED. IN ANY CASE, WILL CONTINUE TO ADD THE BULK OF  
THE WEIGHT TO ENSEMBLE MEANS AS THIS CONTINUES TO ACCOUNT FOR  
BOTH THE MOST ROBUST AND MODEST SNOWFALL SOLUTIONS, AND ACCOUNTS  
FOR UNCERTAINTY IN THERMAL PROFILES NEAR THE COAST. AFTER THIS,  
WITH A BREAKDOWN OF THE WAVE, THE REMNANTS OF THE REX BLOCK TO  
THE WEST WILL YIELD RISING HEIGHTS INTO THE WEEKEND, SUGGESTING  
ANOTHER MODERATION TO FOLLOW.  
 
DETAILS...  
 
MON NIGHT...  
THE LAST VESTIGES OF HIGH PRES YIELD A MAINLY DRY NIGHT MON  
NIGHT. INITIALLY SOUNDINGS ARE DRY ENOUGH FOR MODEST RADIATIONAL  
COOLING, BUT MID LVL WARM ADVECTION AND INCREASING CLOUDS WILL  
MITIGATE COOLING DURING THE EARLY MORNING. THIS WILL ONLY ALLOW  
TEMPS TO DROP INTO THE UPPER TEENS TO MID AND UPPER 20S, MILE  
COMPARED TO PREVIOUS NIGHTS.  
 
TUE INTO WED...  
A SLIGHT CONVERGENCE IN DETERMINISTIC GUIDANCE WILL ALSO BE  
NOTED WITH THIS UPDATE, BUT WILL CONTINUE WITH MEANS. THE  
INITIAL, MOISTURE STARVED CLIPPER WITH MSLP NEAR OR ABOVE  
1025HPA LOOKS TO LOSE EVEN MORE AS THE ATTENDANT WAVE, THE PV  
ANOMALY MENTIONED ABOVE OPENS AND GRADUALLY SHIFTS TOWARD NEAR  
NEUTRAL STATUS. THIS LOOKS TO YIELD OFFSHORE CYCLOGENESIS ALONG  
THE WEAK STALLED FRONTAL BOUNDARY. THIS SECONDARY LOW PRES TRACK  
WILL DETERMINE FINAL SNOWFALL TOTALS, AS PWATS INCREASE TO NEAR  
0.4 INCHES, WHICH, ALTHOUGH ABOVE NORMAL, IS GENERALLY LESS  
THAN 1 STD DEVIATION ABOVE NORMAL. LIFT IS WEAK, AND NOT ALWAYS  
FOCUSED WITHIN THE DGZ, EVEN AS THE PRECIP SHIELD IN ADVANCE OF  
THIS SECONDARY LOW OVERSPREAD S NEW ENGLAND. OPERATIONAL TOTAL  
QPF VALUES RANG FROM ABOUT 0.25 TO 0.5, AND ENSEMBLE MEANS  
SUPPORT THIS. SO MAY NEED TO WATCH FOR AN ADVISORY LVL SNOWFALL  
LATE TUE INTO EARLY WED ASSUMING THE SECONDARY LOW FALLS NEAR OR  
INSIDE THE 40/70 BENCHMARK (ENSEMBLE CLUSTERING IS CLOSE).  
HOWEVER, STILL ENOUGH UNCERTAINTY THAT THERMAL PROFILES COULD  
WARM ENOUGH ALONG PORTIONS OF THE SE COASTAL PLAIN TO LIMIT  
SNOWFALL, OR THAT THE TRACK COULD BE FAR ENOUGH SHORE TO ALSO  
LIMIT SNOWFALL. THESE WILL CONTINUE TO BE BETTER RESOLVED. TEMPS  
RUN CLOSER TO NORMAL, BUT GIVEN THE UNCERTAINTY IN WEAK LOW  
PRES PASSAGE, THERE IS ENOUGH UNCERTAINTY THAT TEMPS MAY CHANGE  
A BIT ESPECIALLY ACROSS THE SE, WHERE WARMER LOW LVL THERMAL  
PROFILES ARE MOST PRONOUNCED.  
 
THU...  
THE WAVE CONTINUES TO OPEN AND SHIFT E, ORIENTING THE TROF-BASE  
JET STREAK POLEWARD EXIT REGION OFFSHORE OF THE MID-ATLANTIC  
SUCH THAT YET ANOTHER, STRONGER COASTAL WAVE LOOKS TO DEVELOP.  
GIVEN THE SPREAD IN THE INITIAL WAVE, THERE IS EVEN MORE SO WITH  
THIS WAVE. ECMWF IS STILL THE MOST AMPLIFIED, WITH ENOUGH W  
DRAW TO INFLUENCE S NEW ENGLAND YET AGAIN ON THU, BUT SEVERAL  
ENSEMBLE MEMBERS FROM BOTH THE GEFS AND ECENS ARE OFFSHORE. WILL  
NEED TO WATCH THE HOW THE PV LOBE IS HANDLED AS IT IS BETTER  
SAMPLED, AS THIS COULD PROLONG THE PERIOD OF WINTRY PRECIP. THIS  
ALSO MARKS THE PEAK OF THE COLD DOME AS THE OPENING WAVE BEGINS  
TO LIFT TO THE ENE.  
 
FRI AND THE WEEKEND...  
THE PATTERN BREAKDOWN ALLOWS THE REMNANTS OF RIDGING TO YIELD  
RISING HEIGHTS AND MORE INFLUENCE FROM THE S STREAM THROUGH THE  
WEEKEND. A SHIFT TOWARD TEMPS ABOVE SEASONAL NORMALS ARE  
EXPECTED.  
 

 
   
AVIATION /09Z SUNDAY THROUGH THURSDAY/
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH MONDAY/...  
 
TODAY...HIGH CONFIDENCE. VFR EXCEPT MVFR CONDITIONS AT TIMES ACROSS  
THE CAPE/ACK IN OCEAN EFFECT CLOUDS AND PERHAPS SOME SCATTERED LIGHT  
SNOW SHOWERS AND FLURRIES.  
 
TONIGHT AND MONDAY...MODERATE TO HIGH CONFIDENCE. MVFR CIGS ACROSS  
THE FAR SOUTHEAST NEW ENGLAND COAST WILL PUSH NORTHWEST OVERNIGHT  
ACROSS EASTERN MA/RI AND PROBABLY FURTHER BACK INTO THE INTERIOR  
MONDAY. SCATTERED SNOW SHOWERS WILL LIKELY DEVELOP AFTER MIDNIGHT  
ACROSS EASTERN MA...ESPECIALLY FROM CAPE ANN AND INTO PLYMOUTH  
COUNTY WHERE LOCALIZED IFR TO EVEN LIFR CONDITIONS WILL BE POSSIBLE  
AT TIMES INTO MONDAY. SOME OF THESE SCATTERED SNOW SHOWERS MAY  
REACH INTO PORTIONS OF RI.  
 
KBOS TERMINAL...HIGH CONFIDENCE IN TAF INTO THIS EVENING...BUT THEN  
UNCERTAINTY AFTER MIDNIGHT AND MONDAY ON HOW OCEAN ENHANCED SNOW  
SHOWERS IMPACT THE TERMINAL. PROBABLY WILL SEE AT LEAST SOME SNOW  
SHOWERS, BUT DURATION AND INTENSITY IS UNCERTAIN.  
 
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.  
 
OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/...  
 
MONDAY NIGHT: MAINLY VFR, WITH LOCAL IFR POSSIBLE ALONG THE  
SOUTHEAST COAST. BREEZY.  
 
TUESDAY: MVFR/IFR CONDITIONS POSSIBLE. CHANCE SN.  
 
TUESDAY NIGHT: MAINLY IFR, WITH AREAS MVFR POSSIBLE. SN LIKELY.  
 
WEDNESDAY: MAINLY VFR, WITH AREAS IFR POSSIBLE. CHANCE SN.  
 
WEDNESDAY NIGHT: MAINLY VFR, WITH LOCAL IFR POSSIBLE. SLIGHT  
CHANCE SN.  
 
THURSDAY: VFR. BREEZY.  
 

 
   
MARINE
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH MONDAY/...  
 
TODAY THROUGH MONDAY...HIGH CONFIDENCE. NORTH WIND GUSTS OF 20  
KNOTS TODAY SHIFT TO THE NORTHEAST TONIGHT WITH GUSTS INCREASING TO  
25 KNOTS ON MONDAY. SMALL CRAFT HEADLINES PRETTY MUCH POSTED FOR  
ALL OPEN WATERS THOUGH MONDAY FOR SEAS AND WIND GUST. OCEAN EFFECT  
SNOW SHOWERS WILL LOWER VSBYS AT TIMES MAINLY LATE TONIGHT AND  
MONDAY.  
 
OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/...  
 
MONDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF ROUGH SEAS.  
SLIGHT CHANCE OF SNOW SHOWERS. LOCAL VISIBILITY 1 TO 3 NM.  
 
TUESDAY: WINDS LESS THAN 25 KT. AREAS OF ROUGH SEAS. SLIGHT  
CHANCE OF SNOW. AREAS OF VISIBILITY 1 TO 3 NM.  
 
TUESDAY NIGHT: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT. SNOW  
LIKELY, RAIN LIKELY. VISIBILITY 1 TO 3 NM.  
 
WEDNESDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT. CHANCE OF  
SNOW. VISIBILITY 1 TO 3 NM.  
 
WEDNESDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF ROUGH SEAS.  
CHANCE OF SNOW. VISIBILITY 1 TO 3 NM.  
 
THURSDAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS UP  
TO 25 KT. LOCAL ROUGH SEAS. LOCAL VISIBILITY 1 TO 3 NM.  
 

 
   
HYDROLOGY
 
 
HEAVY RAINFALL AND COMPLETE MELTING OF OUR SNOWPACK RESULTED IN  
SIGNIFICANT RISES ON RIVERS AND STREAMS. FLOOD WARNINGS REMAIN IN  
EFFECT FOR SEVERAL RIVERS (PLEASE REFER TO OUR FLOOD STATEMENTS AND  
WARNINGS). FOR DETAILS ON SPECIFIC AREA RIVERS,  
INCLUDING OBSERVED AND FORECAST RIVER STAGES, PLEASE VISIT THE  
ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR  
WEBSITE.  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
MA...NONE.  
RI...NONE.  
MARINE...SMALL CRAFT ADVISORY FROM 4 AM TO 7 PM EST MONDAY FOR  
ANZ231>234.  
SMALL CRAFT ADVISORY UNTIL 7 PM EST MONDAY FOR ANZ235-237-250-  
251-254>256.  
 

 
 

 
SYNOPSIS...FRANK/DOODY  
NEAR TERM...FRANK  
SHORT TERM...FRANK  
LONG TERM...DOODY  
AVIATION...FRANK/DOODY  
MARINE...FRANK/DOODY  
HYDROLOGY...  
 
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