158  
FXUS61 KBOX 102334  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE TAUNTON MA  
634 PM EST WED JAN 10 2018  
   
SYNOPSIS
 
 
HIGH PRESSURE MOVES EAST OF THE REGION TODAY AND TONIGHT,  
BRINGING MILDER WEATHER THURSDAY. UNSEASONABLY MILD CONDITIONS  
ARE ANTICIPATED FRIDAY INTO FRIDAY NIGHT, ALONG WITH PERIODS OF  
HEAVY RAIN, BREEZY WINDS, AND THE POTENTIAL FOR FLOODING. THE  
RAIN MAY END AS FREEZING RAIN ACROSS THE INTERIOR SATURDAY IF  
THE MUCH COLDER AIR ARRIVES BEFORE THE PRECIPITATION ENDS. DRY  
AND VERY COLD WEATHER IS FAVORED SUNDAY INTO MONDAY. A WINTER  
WEATHER SYSTEM IS POSSIBLE BY MIDWEEK.  
 

 
   
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
 
 
630 PM UPDATE...  
 
MONITORING THE MID-LEVEL IMPULSE ACROSS N NEW ENGLAND AS WELL AS  
ATTENDANT ISENTROPIC UPSLOPE AHEAD OF THE FEATURE. MORE PROMISING  
OUTCOMES WITH OROGRAPHIC SUPPORT ALONG THE W-SLOPES OF HIGHER  
TERRAIN GIVEN THE LIMITED AMOUNT OF MOISTURE, LACK OF MOISTENING  
WITHIN THE DENDRITIC GROWTH ZONE. SWEEPING OVER A WEDGE OF COLD  
AIR DAMMING ALL THE WAY DOWN INTO VA/NC, LOOKING AT A WINTRY MIX  
OF FREEZING RAIN / SLEET.  
 
THE POTENTIAL INTO OUR NECK OF THE WOODS IS SOMEWHAT DOUBTFUL  
GIVEN THE LACK OF ASCENT WHICH LIES FURTHER N. CAN'T RULE OUT  
SOME IMPACT OVER THE N BERKSHIRES AND WILL ALLOW LATER FORECAST  
CREWS TO EVALUATE THE WARM AIR ADVECTION PROCESSES AND OUTCOMES  
COMING OUT OF WSR-88D TLX IN UPSTATE NY. SPOTTY FREEZING DRIZZLE  
AT MOST. WILL HANDLE WITH SHORT-FUSED HEADLINES SHOULD THE  
THREAT BECOME MORE APPARENT, OTHERWISE NOT EXPECTING TERRIBLY  
TOO MUCH IMPACT.  
 
SURFACE HIGH PRESSURE OFFSHORE, PUSHING E, WILL BEGIN TO SEE  
RETURN S FLOW. NON-DIURNAL TEMPERATURE TREND SO EXPECT THE  
LOWEST OF TEMPERATURES BETWEEN NOW AND ROUGHLY MIDNIGHT.  
 
HIGHER DEWPOINT AIR IN THE 40S STILL RESIDING OVER NC, LOWER  
30S OFF THE WATERS. WATCHING CLOSELY, BUT THINK WE'LL BE OKAY  
VISIBILITY-WISE TONIGHT. THE DENSE FOG COMING IN ALONG THE COAST  
DURING THE DAY THURSDAY AND THEN BUILDING INTO THE INTERIOR  
OVERNIGHT INTO FRIDAY WITH THE S ONSHORE PUSH OF MILD, MOIST AIR  
OVER THE COLD WATERS / SNOWPACK.  
 

 
   
SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/
 
 
VERY MILD WEATHER BY MID JANUARY STANDARDS EXPECTED THURSDAY  
AND THURSDAY NIGHT, WITH READINGS AT LEAST 15 DEGREES ABOVE  
NORMAL THROUGH THIS PERIOD. EXPECTING CONTINUAL SNOWMELT DURING  
THIS TIME, WHICH WILL BEGIN TO SET THE STAGE FOR A FLOODING  
THREAT LATER THIS WEEK. AREAS OF FOG ALSO EXPECTED, SOME OF  
WHICH MAY BE FAIRLY DENSE, ESPECIALLY THURSDAY NIGHT.  
 
EXPECTING MAINLY DRY WEATHER THURSDAY, WITH AN INCREASING RISK  
FOR RAIN FROM WEST TO EAST THURSDAY NIGHT, ESPECIALLY FROM  
WORCESTER COUNTY AND RI, WEST.  
 

 
   
LONG TERM /FRIDAY THROUGH WEDNESDAY/
 
 
*/ HIGHLIGHTS...  
 
- MODERATE TO HEAVY RAIN AND SNOWMELT CONTRIBUTING TO POSSIBLE  
FLOODING FRIDAY INTO SATURDAY  
 
- SURGING WARMER AIR BEGINNING THURSDAY THROUGH SATURDAY,  
POTENTIAL FOR ISOLATED ICE JAMS, RIVER FLOODING  
 
- COLDER AIR SURGING INTO THE REGION FOR EARLY NEXT WEEK, A POSSIBLE  
SNOW EVENT TOWARDS MIDWEEK  
 
*/ OVERVIEW...  
 
AN ACTIVE WEATHER PATTERN WITH IMPRESSIVE TEMPERATURE SWINGS. LESS  
AMPLIFIED PATTERN OVER THE N PACIFIC, THE ATTENDANT H3 JET BREAKING  
FURTHER E INTO THE W CONUS, USHERANCE OF MILDER AIR, POTENTIAL MJO  
IMPLICATIONS, DOWNSTREAM OPPORTUNITIES OF ONSHORE ENERGY TO TAP INTO  
BOTH N AND S STREAMS. AGAINST A STOUT H5 ATLANTIC RIDGE, MAINTAINED  
BY FORECAST TRAFFIC AROUND THE AZORES, A SLOWED H5 PATTERN, BOTH N  
AND S STREAM ENERGY HAS THE CAPABILITY OF STRENGTHENING THROUGH THE  
PREFERRED H5 TROF PATTERN OVER THE E CONUS CAPTURING TROPICAL AIR  
AND ENERGY N IN ADVANCE WHILE DRAGGING S ARCTIC AIR TO THE REAR. THE  
CLASH OF AIRMASSES, ESPECIALLY ACROSS THE NE CONUS, ATMOSPHERIC  
RESPONSE TO RESTORE BALANCE, LOOKING AT A STORMY PATTERN BY THE END  
OF THE WEEK AND THROUGH THE WEEKEND TO WHICH WILL BE ADDRESSED BELOW.  
 
*/ FRIDAY INTO SATURDAY...  
 
PREFERRED H5 TROF EVOLVING OVER E/NE CONUS, CAPTURING BOTH S AND N  
STREAM ENERGY, TRANSPORTING N HIGHLY ANOMALOUS TROPICAL AIR WHILE  
SWINGING REARWARD COLD, ARCTIC TEMPERATURES. LIFT AND QG-FORCING  
MECHANISMS APPARENT ALONG CONVEYOR BELT MOTIONS AS WAVES OF LOW  
PRESSURE EMERGE ALONG THE BAROCLINIC / COLD FRONTAL ZONE BENEATH  
INDIVIDUAL MID-LEVEL IMPULSES. ACTING UPON DEEP COLUMN MOISTURE WITH  
HIGH FREEZING LEVEL HEIGHTS (UPWARDS OF 12 KFT), EFFICIENT RAINFALL  
PROCESSES APPARENT. MODERATE TO HEAVY AT TIMES, ALONG WITH STRONG S  
WINDS ALOFT AND HIGH DEWPOINT AIR, ACROSS REMNANT DEEP SNOWPACK AND  
ICED UP RIVERS AND TRIBUTARIES, THE POTENTIAL FOR FLOODING EXISTS AS  
WELL AS DAMAGING WINDS WHICH WILL BE DISCUSSED IN SHORT BELOW ALONG  
WITH ANY HEADLINES.  
 
HEAVY RAIN / FLOODING...  
 
FROM A CONSENSUS OF ENSEMBLE AND PROBABILISTIC GUIDANCE, LOOKING AT  
A TROPICAL-SOURCE PLUME TO BE ADVECTED AND FORCED UPWARD THROUGH THE  
ATMOSPHERIC LAYER BY STRONGLY CONVERGENT LOW-LEVEL (H925-85) WINDS  
AND ATTENDANT MID-LEVEL IMPULSES BENEATH THE RIGHT REAR QUADRANT OF  
THE UPPER LEVEL JET. EFFICIENT WARM RAIN PROCESSES AND CONSIDERATION  
OF A S/SW PERSISTENT STREAM OF DEEP LAYER MOISTURE, NO SURPRISE TO  
SEE PROBABILISTIC GUIDANCE HIGHLIGHTING THE DECENT CHANCE OF STORM  
TOTAL RAINFALL AMOUNTS UP TO 4-INCHES ESPECIALLY OVER SE NEW ENGLAND  
WITH THE POTENTIAL OF 1 TO 2 INCHES IN A 12-HOUR PERIOD, POSSIBLY AS  
SHORT AT 6-HOURS.  
 
A REMNANT SNOWPACK AROUND 6 TO 12 INCHES OVER MUCH OF S NEW ENGLAND,  
ABSORBING MOISTURE OUT OF THE AIR AND IN SOME INSTANCES THE GROUND,  
HAVE QUICKLY GATHERED SNOW WATER EQUIVALENT MEASUREMENTS OF AROUND 2  
INCHES UPWARDS OF 3 INCHES. ALSO NEED TO CONSIDER THE FROZEN GROUND  
WHICH SIMPLY AIDS THE RUNOFF OF ANY LIQUID INSTEAD OF LEECHING INTO  
THE GROUND.  
 
CONSIDERING SNOW MELT THAT WILL PRECEDE HEAVY RAIN, INCREASING S  
WINDS AND RISING SURFACE DEWPOINTS THAT'LL DEFINITELY EAT THE SNOW,  
A LOT OF WATER GOING INTO THE SYSTEM FROM A VERY ANOMALOUS EVENT.  
YES, SNOW PACK WILL ABSORB SOME OF THE WATER, BUT THERE'S A LOT OF  
WATER GOING INTO THE SYSTEM. FEEL THE WRITING IS ON THE WALL. THAT  
AND POTENTIAL ISOLATED ICE JAMS ON THE RIVERS, HAVE GONE AHEAD AND  
ISSUED A FLOOD WATCH FOR THE ENTIRE AREA. NOT SPLITTING HAIRS GIVEN  
THREATS OF EITHER OR ARE AREA-WIDE. THE FLOOD THREAT EXACERBATED BY  
AFOREMENTIONED ISOLATED ICE JAMS ALONG ANY RIVERS, AND WITHIN URBAN  
LOCATIONS, ANY SNOW CLOGGED DRAINS.  
 
AS TO RIVERS AND STREAMS, WITH ENOUGH THAWING HOURS IN ADVANCE AND  
DURING THE STORM, BEGINNING THURSDAY AFTERNOON, A FOOT OF ICE OR  
MORE ON SOME OF THE RIVERS, THERE IS THE ISOLATED POSSIBILITY OF ICE  
JAMS ESPECIALLY IF THE RIVER HEIGHT CAN EXCEED 3-TIMES THE THICKNESS  
OF THE ICE PROMOTING MECHANICAL BREAK-UP. ALSO A DEPENDENCE ON WHAT  
HAPPENS N OF US IN THE RIVER / SMALL-STREAM SYSTEM. IN ALL, ENSEMBLE  
RIVER FORECAST GUIDANCE HIGHLIGHTING A NUMBER OF POINTS TO GO INTO  
MINOR TO MODERATE FLOODING STATUS INTO THE WEEKEND.  
 
STRONG / DAMAGING WINDS...  
 
A STOUT INVERSION IN PLACE WITH A PRONOUNCED WARM-NOSE LAYER AROUND  
H95-85. LOOKING AT TWO PERIODS AT THE TOP OF THE INVERSION WHERE S  
WINDS WILL BE SUSTAINED AT HURRICANE FORCE, DURING FRIDAY FOR ALL OF  
S NEW ENGLAND AND AROUND SATURDAY MORNING FOR SE NEW ENGLAND. BUT A  
QUESTION OF WHETHER MECHANICAL MIXING / PRECIPITATION DRAG FROM RAIN  
COULD BRING DOWN FASTER WINDS TO THE SURFACE, ENSEMBLE PROBABILITIES  
SIGNALING A STRONG CHANCE OF REACHING 45 TO 55 MPH GUSTS. HESITANT  
AS CIPS ANALOGS OFF THE 10.12Z GUIDANCE HAVE ONLY A MODERATE CHANCE  
OF 35 MPH GUSTS, A LOWER NEARLY NON-EXISTENT CHANCE OF GUSTS OVER 40  
MPH.  
 
CERTAINLY 2M TEMPERATURE / DEWPOINT DEPENDENT, MODELS AND ASSOCIATED  
SOUNDINGS COULD BE TOO COOL, INVERSION LESS STOUT, GREATER ABILITY  
FOR WINDS TO MIX DOWN TO THE SURFACE. HOWEVER LOW CONFIDENCE AT THIS  
TIME, FEEL ENSEMBLES CAN'T CAPTURE THE SMALL-SCALE INVERSION. WILL  
HOLD OFF ON ANY WIND HEADLINES WITH THIS FORECAST.  
 
AREAS OF DENSE FOG...  
 
HIGHER DEWPOINT AIR STREAMING OVER REMNANT SNOWPACK AS WELL AS THE  
COLDER OCEAN WATERS, LIKELY TO GET A COMBINATION OF LOW CLOUDS AND/OR  
DENSE FOG WITH VISIBILITY IN SPOTS DOWN TO A MILE OR LESS DESPITE  
THE MODERATE TO HEAVY RAIN THREAT AS WELL AS BREEZY S WINDS. MOISTURE  
TRAPPED BENEATH THE AFOREMENTIONED H95-85 WARM NOSE, THE STOUT INVERSION,  
EXPECTING SOUPY CONDITIONS AND HAZARDOUS TRAVEL CONDITIONS. HIGHEST  
CONFIDENCE ALONG THE S-COAST AND ACROSS THE HIGH TERRAIN.  
 
ICE THREAT...  
 
ON SATURDAY, THE SECOND WAVE OF LOW PRESSURE SWEEPING N/E ACROSS S  
NEW ENGLAND, COLDER AIR ON THE CUSP, WAITING IN THE WINGS ASSOCIATED  
WITH SURFACE HIGH PRESSURE BUILDING S OUT OF CANADA TO THE REAR OF  
THE PREFERRED H5 TROF, THERE'S THE POTENTIAL FOR ANABATIC COLD FRONT  
PROCESSES TO YIELD A PERIOD OF FREEZING RAIN / WINTRY MIX ACROSS THE  
INTERIOR NE CONUS.  
 
A FEW THINGS WORTH NOTING: 1.) DRY WITHIN THE DENDRITIC GROWTH ZONE,  
2.) ABSENT SURFACE HIGH PRESSURE N/E, PRONOUNCED NEARLY 1050 MB N/W,  
AND 3.) PER BOTH SURFACE WINDS AND AGEOSTROPHIC FLOW, INDICATIONS OF  
W UNDERCUTTING FLOW THAT LEND TO A DEEPENING COLD LAYER BELOW H9  
TOWARDS -10C, AND 4.) CYCLONIC FLOW, LOW-LEVEL MOISTURE, LIFT ALONG  
THE ANABATIC COLD FRONT WITH SOME MID TO UPPER LEVEL SUPPORT WITH  
ADDITIONAL ENERGY AHEAD OF A WEAK H5 TROF AXIS BENEATH A CONTINUED  
RIGHT-REAR QUADRANT OF THE UPPER LEVEL JET.  
 
EVERYTHING IN PERSPECTIVE, THERE IS THE THREAT ESPECIALLY OVER N/W  
MA OF A PERIOD OF FREEZING RAIN POTENTIALLY TRANSITIONING TO SLEET  
BEFORE ALL IS SAID DONE. WILL HIGHLIGHT IN THE HAZARDOUS WEATHER  
OUTLOOK THE POTENTIAL THREAT, SOMETHING WE'LL NEED TO WATCH.  
 
*/ SUNDAY ONWARD...  
 
A QUICK GLANCE AT THE FORECAST, A PERIOD OF COLD WEATHER AS USHERED  
BEHIND AND THROUGH THE PREFERRED H5 TROF PATTERN. ANOTHER PACIFIC  
DISTURBANCE ROTATING THROUGH THE FLOW, THE BAROCLINIC ZONE / COLD  
FRONT PUSHED OFFSHORE, CONSENSUS OF MODEL GUIDANCE PICKING UP ON A  
WAVE LOW POTENTIALLY OUTSIDE OF THE BENCH MARK. STILL A SPREAD WITH  
ENSEMBLE MEMBERS, WE LIKELY WILL NOT HAVE A BETTER IDEA TILL WE GET  
WITHIN 96 HOURS AT A MAXIMUM. BEHIND THE SYSTEM, KEEP THE COLD AIR  
IN PLACE BUT CAN'T RULE OUT A BUMP OF MILDER AIR IF THE PACIFIC  
PATTERN OUTLINED IN THE OVERVIEW CONTINUES, SHOTS OF MILDER AIR INTO  
THE CONUS, HIGHER HEIGHTS AND COLDER AIR SHUNTED N.  
 

 
   
AVIATION /23Z WEDNESDAY THROUGH MONDAY/
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH THURSDAY NIGHT/...HIGH CONFIDENCE.  
 
TONIGHT...  
VFR. LIGHT WINDS BECOMING S.  
 
THURSDAY...  
MAINLY VFR. LOWERING MVFR-IFR ALONG THE S COAST, CREEPING N  
ACROSS THE INTERIOR TOWARDS EVENING. INCREASING S WINDS.  
 
THURSDAY NIGHT...  
LOWERING IFR-LIFR. WIDESPREAD FOG. CONTINUED S WINDS. WIDESPREAD  
LLWS THREAT. INCREASING AREAL COVERAGE OF -RA TOWARDS FRIDAY  
MORNING.  
 
KBOS TERMINAL...HOLD OFF ANY IFR TILL THURSDAY EVENING LOWERING  
INTO THE OVERNIGHT HOURS. ATTENDANT LLWS IMPACTS AS WELL.  
 
KBDL TERMINAL...IFR WITH LOW CLOUDS / FG MAY CREEP N THROUGH THE  
CT RIVER VALLEY LATE IN THE DAY TOWARDS THE PM PUSH. HIGHER  
CONFIDENCE OF IMPACTS CLOSER TO EVENING.  
 
OUTLOOK /FRIDAY THROUGH MONDAY/...  
 
FRIDAY: MAINLY MVFR, WITH AREAS IFR POSSIBLE. WINDY WITH AREAS  
GUSTS TO 30 KT. RA, AREAS BR.  
 
FRIDAY NIGHT: MAINLY IFR, WITH LOCAL MVFR POSSIBLE. BREEZY. RA,  
AREAS BR.  
 
SATURDAY: MAINLY IFR, WITH AREAS MVFR POSSIBLE. WINDY WITH  
LOCAL GUSTS TO 30 KT. RA LIKELY, AREAS BR, CHANCE FZRA.  
 
SATURDAY NIGHT: MAINLY MVFR, WITH LOCAL VFR POSSIBLE. BREEZY.  
SLIGHT CHANCE FZRA.  
 
SUNDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE.  
 
SUNDAY NIGHT: VFR.  
 

 
   
MARINE
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH THURSDAY NIGHT/...  
 
INCREASING S TO SW WINDS LATER TONIGHT THROUGH THURSDAY NIGHT.  
EXPECTING WINDS TO REMAIN MAINLY BELOW 25 KT. SOME OF THE WATERS  
EAST OF MA MAY SEE GUSTS UP TO 25-30 KT. DECIDED TO HOIST SMALL  
CRAFT ADVISORIES WHERE CONFIDENCE IS HIGHEST. ADDITIONAL  
ADVISORIES MAY BE NEEDED WITH LATER FORECASTS.  
 
INCREASING RISK FOR RAIN FROM W TO E THURSDAY NIGHT.  
 
OUTLOOK /FRIDAY THROUGH MONDAY/...  
 
FRIDAY: STRONG WINDS WITH GUSTS UP TO 35 KT. ROUGH SEAS UP TO  
11 FT. RAIN, AREAS FOG.  
 
FRIDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH  
GUSTS UP TO 30 KT. ROUGH SEAS UP TO 12 FT. RAIN, AREAS FOG.  
VISIBILITY 1 TO 3 NM.  
 
SATURDAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH LOCAL  
GUSTS UP TO 30 KT. ROUGH SEAS UP TO 12 FT. RAIN, AREAS FOG,  
CHANCE OF FREEZING RAIN. AREAS OF VISIBILITY 1 TO 3 NM.  
 
SATURDAY NIGHT: WINDS LESS THAN 25 KT. ROUGH SEAS UP TO 10 FT.  
CHANCE OF RAIN, AREAS FOG, SLIGHT CHANCE OF FREEZING RAIN.  
 
SUNDAY: WINDS LESS THAN 25 KT. AREAS OF ROUGH SEAS.  
 
SUNDAY NIGHT THROUGH MARTIN LUTHER KING JR DAY: WINDS LESS THAN  
25 KT. SEAS UP TO 5 FT. SLIGHT CHANCE OF SNOW.  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...FLOOD WATCH FROM FRIDAY MORNING THROUGH SATURDAY AFTERNOON FOR  
CTZ002>004.  
MA...FLOOD WATCH FROM FRIDAY MORNING THROUGH SATURDAY AFTERNOON FOR  
MAZ002>024-026.  
RI...FLOOD WATCH FROM FRIDAY MORNING THROUGH SATURDAY AFTERNOON FOR  
RIZ001>008.  
MARINE...SMALL CRAFT ADVISORY FROM 11 PM THIS EVENING TO 6 AM EST  
FRIDAY FOR ANZ230-250-251-254.  
SMALL CRAFT ADVISORY FROM 6 AM TO 4 PM EST THURSDAY FOR ANZ231.  
 

 
 

 
 
SYNOPSIS...BELK/SIPPRELL  
NEAR TERM...BELK/SIPPRELL  
SHORT TERM...BELK  
LONG TERM...SIPPRELL  
AVIATION...BELK/SIPPRELL  
MARINE...BELK/SIPPRELL  
 
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