353  
FXUS61 KBOX 130640  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE TAUNTON MA  
140 AM EST SAT JAN 13 2018  
   
SYNOPSIS
 
 
MULTIPLE LOW PRESSURE AREAS ALONG AN APPROACHING COLD FRONT WILL  
BRING HEAVY RAINFALL, POTENTIAL FLOODING AND GUSTY WINDS  
THROUGH TONIGHT. A SHARP TURN TO MUCH COLDER WEATHER OCCURS  
RAPIDLY SATURDAY WHICH WILL ALLOW RAIN TO END AS A BIT OF LIGHT  
FREEZING RAIN AND SLEET, BUT MORE IMPORTANTLY A FLASH FREEZE IS  
EXPECTED ACROSS ALL OF SOUTHERN NEW ENGLAND. MAINLY DRY BUT  
COLD WEATHER IS EXPECTED SUNDAY AND MONDAY. LOW PRESSURE DIVING  
SOUTH FROM THE CANADIAN ARCTIC WILL BRING A CHANCE OF SNOW  
TUESDAY AND WEDNESDAY. DRY WEATHER MAY RETURN THURSDAY AND  
FRIDAY. WE WILL BE WATCHING A POTENTIAL COASTAL STORM THAT COULD  
CHANGE THAT THURSDAY FORECAST.  
 

 
   
NEAR TERM /UNTIL 6 AM THIS MORNING/
 
 
135 AM UPDATE...  
 
1) HEAVY RAIN/FLOODING AND COASTAL WIND...  
 
RAIN CONTINUES TO IMPACT MOST OF THE REGION VERY EARLY THIS MORNING.  
THE HEAVIEST RAIN WAS ACROSS SOUTHEAST NEW ENGLAND WHERE AN 80+  
KNOT LOW LEVEL JET WAS TAPPING INTO PWATS 4-5 SD ABOVE NORMAL.  
THIS HEAVY RAIN WILL CONTINUE TO IMPACT RI/SE MA OVER THE NEXT  
SEVERAL HOURS...BRINGING THE POTENTIAL FOR SIGNIFICANT URBAN  
STREET FLOODING. ENOUGH ELEVATED INSTABILITY IS AVAILABLE FOR A  
RUMBLE OR TWO OF THUNDER. IN ADDITION TO THE HEAVY RAIN...STRONG  
LOW LEVEL JET WILL ALLOW FOR 40-50 MPH SOUTHWEST WIND GUSTS  
ALONG AND SOUTHEAST OF THE BOS-PVD CORRIDOR SO THE WIND ADVISORY  
CONTINUES. ANOTHER BAND OF DECENT RAIN WAS ACROSS WESTERN  
MA/NORTHERN CT WHICH WAS BEING DRIVEN BY STRONG LOW LEVEL  
FRONTOGENETIC FORCING.  
 
OTHER THAN SIGNIFICANT URBAN STREET FLOODING...ISOLATED ICE JAM  
AND RIVER/STREAM FLOODING NEED TO BE WATCHED.  
 
2) DENSE FOG ALONG THE SOUTH COAST...  
 
HIGH DEWPOINT AIR BEING ADVECTED OVER THE COLD OCEAN CONTINUE TO  
RESULT IN VISIBILITY BETWEEN 1/4 AND 1/2 MILE ALONG THE SOUTH  
COAST, CAPE AND ISLANDS. THE DENSE FOG ADVISORY CONTINUES IN  
THIS REGION THROUGH DAYBREAK.  
 
3) STRONG COLD FRONT/ICE THREAT IN WESTERN MA TOWARD DAYBREAK...  
 
THE STRONG COLD FRONT IS NOW ENTERING EXTREME WESTERN MA AND  
NORTH ADAMS WAS DOWN TO 41 AS OF 1 AM...WHILE THE REST OF THE  
REGION WAS STILL BETWEEN 55 AND 60. TEMPERATURES ACROSS WESTERN  
MA WILL LIKELY DROP BELOW FREEZING BY 12Z. SINCE THE COLD SURGE  
INITIALLY COMES IN SHALLOW...THERE SHOULD BE A PERIOD OF  
FREEZING RAIN AND SLEET ACROSS WESTERN MA WITH SOUTHWEST FLOW  
ALOFT. THE BIGGER ISSUE WILL BE A FLASH FREEZE THAT WILL  
SWEEP ACROSS THE REST OF THE REGION SATURDAY WITH RAPIDLY  
FALLING TEMPS.  
 

 
   
SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/
 
 
***FLASH FREEZE ALL SNE ALONG WITH A BRIEF PERIOD OF FREEZING  
RAIN/SLEET, ESPECIALLY INTERIOR***  
 
COLD FRONT MOVES THROUGH REST OF SNE SAT MORNING FOLLOWED BY A  
RAPID TEMP DROP. BEST CHANCE FOR A PERIOD OF FREEZING RAIN AND  
POSSIBLY SOME SLEET BEFORE THE PRECIP ENDS WILL BE IN THE  
INTERIOR. LOWER CHANCES FOR FREEZING RAIN TOWARD THE COAST AS  
GUIDANCE SHOWS PRECIP MOVING OUT AS COLDER AIR RUSHES IN. IT  
WILL BE A RACE BETWEEN THE COLDER MOVING IN AND PRECIP MOVING  
OUT. HOWEVER, THE GREATER CONCERN IS THE FLASH FREEZE  
POTENTIAL AS TEMPS RAPIDLY DROP FROM THE 50S TO BELOW FREEZING  
IN ABOUT A 3 HOUR PERIOD. EXACT TIMING OF THE COLDER AIR IS A  
BIT UNCERTAIN DUE TO TIMING DIFFERENCES IN THE MODELS AND FLASH  
FREEZE TIMING MAY BE OFF BY A FEW HOURS. OUR FORECAST HAS THE  
FLASH FREEZE OCCURRING DURING THE MORNING IN THE INTERIOR AND  
LATE MORNING INTO EARLY AFTERNOON IN THE COASTAL PLAIN. EVEN  
WITH NW WINDS, THE RAPID TEMP DROP BELOW FREEZING AND LEFTOVER  
WET SURFACES WILL RESULT IN ICY SPOTS DEVELOPING.  
 
TEMPERATURES BY LATE AFTERNOON WILL BE FALLING INTO THE TEENS  
AND 20S.  
 

 
   
LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/
 
 
BIG PICTURE...  
 
LONGWAVE PATTERN THROUGH NEXT FRIDAY SHOWS TROUGH OVER THE EASTERN  
USA AND A RIDGE OVER THE WESTERN USA. SHORTWAVE PATTERN SHOWS A  
SHORTWAVE OVER THE CANADIAN ARCTIC SWEEPING SOUTH THIS WEEKEND AND  
THEN DIGGING OVER THE GREAT LAKES. THIS TROUGH MAINTAINS A  
PROGRESSIVE AXIS THROUGH TUESDAY. THE GFS AND ECMWF SHOW THE TROUGH  
THEN FORMING A CLOSED LOW ALONG THE NE USA COAST WEDNESDAY-THURSDAY.  
 
MODEL MASS FIELDS ARE SIMILAR THROUGH WEDNESDAY MORNING, THEN SHOW  
DIFFERENCES THROUGH FRIDAY. THERMAL FIELDS ALSO ARE SIMILAR THROUGH  
WEDNESDAY MORNING, THEN DIVERGE. CONFIDENCE IS HIGH THROUGH TUESDAY  
NIGHT, THEN LOW-MODERATE THE LATTER HALF OF THE WEEK.  
 
DETAILS...  
 
SATURDAY NIGHT THROUGH MONDAY...  
 
HIGH PRESSURE OVER THE MIDWEST/PLAINS WILL BE IN TRANSITION AS IT  
BUILDS INTO NEW ENGLAND. THE AXIS STARTS THE WEEKEND NNW-SSE, A COLD  
WEATHER SIGNATURE, AND MORPHS TO A NE-SW AXIS SUNDAY BEFORE LIFTING  
OUT THROUGH THE MARITIMES MONDAY. THE DEPARTING RIDGE LEAVES A COLD-  
AIR DAMMING SIGNATURE ACROSS NEW ENGLAND MONDAY NIGHT.  
 
EXPECT DRY WEATHER DURING THIS TIME WITH COLDER-THAN-NORMAL  
TEMPERATURES. TEMPERATURES ARE BORDERLINE FOR OCEAN-EFFECT  
CLOUDS/SNOW. BUT WIND DIRECTION TURNS FROM THE NORTH SUNDAY AND  
NORTHEAST MONDAY. MOISTURE/RH CROSS SECTIONS SHOW INCREASING VALUES  
BELOW 850 MB. NORTH WIND SUPPORTS CLOUDS AND SCATTERED SHOWERS ON  
THE CAPE AND ISLANDS SUNDAY. NORTHEAST WIND SUPPORTS THIS ACROSS  
EAST COASTAL MASS MONDAY. TEMPS IN THE MIXED LAYER SUPPORT MAX SFC  
TEMPS IN THE 20S TO AROUND 30. DRY AIR WILL SUPPORT MIN TEMPS IN THE  
SINGLE NUMBERS AND LOWER TEENS, EXCEPT A LITTLE HIGHER ON THE  
CAPE/ISLANDS.  
 
TUESDAY-WEDNESDAY...  
 
LOW PRESSURE FROM THE CANADIAN ARCTIC WILL SWEEP SOUTH TO THE GREAT  
LAKES MONDAY, THEN TURN EAST AND CROSS NEW ENGLAND ON  
TUESDAY/WEDNESDAY. TIMING OF FAST-MOVING SYSTEMS IS A CHALLENGE,  
ESPECIALLY 4-5 DAYS IN THE FUTURE. THE GFS FAVORS TUESDAY, THE 00Z  
ECMWF FAVORS WEDNESDAY. EXPECT A PERIOD OF LIGHT ACCUMULATING  
SNOW DURING THIS TIME.  
 
THURSDAY-FRIDAY...  
 
LOW-MODERATE CONFIDENCE, BUT THE GFS AND ECMWF SHOW POTENTIAL FOR AN  
UPPER LOW TO CLOSE OFF NEAR THE MID ATLANTIC COAST WITH UPPER SSW  
JET ALONG THE EASTERN USA COAST. THE JET AXIS PLACEMENT FAVORS  
DEVELOPMENT OF A COASTAL LOW OFF THE CAROLINAS. THE GFS AND GGEM  
MAINTAIN ENOUGH OF A PROGRESSIVE PATTERN TO MOVE THE LOW OUT TO SEA,  
WHILE THE ECMWF TURNS THE UPPER FLOW FROM THE SOUTH AND DIRECTS THE  
COASTAL LOW UP THE COAST TO OUTER CAPE COD. THIS LATTER SOLUTION  
SHOWS ENOUGH WARM AIR FOR RAIN IN EASTERN MASS/RI, AND POSSIBLY ALL  
THE WAY TO THE BERKSHIRES. AS IT IS THE MINORITY SOLUTION, WE OPTED  
FOR THE DRIER GFS FORECAST.  
 

 
   
AVIATION /06Z SATURDAY THROUGH WEDNESDAY/
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH TONIGHT/...  
 
THROUGH 10Z THIS MORNING...MODERATE TO HIGH CONFIDENCE. LOW END  
MVFR TO IFR CONDITIONS IN HEAVY RAIN THROUGH 10Z WITH LOCALLY  
DENSE FOG ALONG THE SOUTH COAST. LLWS ALONG WITH SOUTHERLY WIND  
GUSTS OF 35 TO 40 KNOTS EXPECTED ALONG AND SOUTHEAST OF THE BOS-  
PVD CORRIDOR. STRONG COLD FRONT SHOULD BE THROUGH WESTERN MA  
10Z ALLOWING PTYPE TO CHANGE TO -FZRA/IP.  
 
AFTER 10Z TODAY...MODERATE TO HIGH CONFIDENCE. IFR TO MVFR  
CONDITIONS SHOULD IMPROVE TO MAINLY VFR FROM WEST TO EAST THIS  
AFTERNOON. STRONG COLD FRONT REACHES THE BOS-PVD CORRIDOR BY  
15Z AND PROBABLY OFF THE SOUTHEAST NEW ENGLAND COAST BY 18Z.  
MOST OF THE LIGHT -FZRA/IP SHOULD BE CONFINED TO WESTERN AND  
NORTH CENTRAL MA...BUT A BRIEF PERIOD OF SPOTTY -FZDZ MAY OCCUR  
FOR AN HOUR OR TWO BEHIND THE FRONT ACROSS THE REST OF THE  
REGION. MAIN ISSUE WILL BE A FLASH FREEZE AS TEMPERATURES  
TUMBLE BELOW FREEZING AND INTO THE 20S IN MOST LOCATIONS BY MID  
AFTERNOON.  
 
KBOS TERMINAL...MODERATE TO HIGH CONFIDENCE IN TAF.  
 
KBDL TERMINAL...MODERATE TO HIGH CONFIDENCE IN TAF.  
 
OUTLOOK /SUNDAY THROUGH WEDNESDAY/...  
 
SUNDAY: VFR. BREEZY.  
 
SUNDAY NIGHT: VFR.  
 
MARTIN LUTHER KING JR DAY: MAINLY VFR, WITH LOCAL MVFR  
POSSIBLE ALONG THE EAST COAST OF MASSACHUSETTS. BREEZY.  
 
MONDAY NIGHT: MAINLY VFR, WITH LOCAL MVFR POSSIBLE.  
 
TUESDAY: MVFR/IFR CONDITIONS POSSIBLE. CHANCE SN.  
 
TUESDAY NIGHT: MAINLY IFR, WITH LOCAL MVFR POSSIBLE. CHANCE SN.  
 
WEDNESDAY: MAINLY VFR, WITH AREAS IFR POSSIBLE. BREEZY. CHANCE  
SN.  
 

 
   
MARINE
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH SUNDAY/...  
 
TONIGHT...MODERATE CONFIDENCE.  
GALE WARNINGS CONTINUE AND EXPANDED TO BOSTON HARBOR AND  
NARRAGANSETT BAY. 70-80 KT LOW LEVEL JET DEVELOPS THROUGH  
TONIGHT. STRONGEST GUSTS TO 40 KT WILL OCCUR OVER NEARSHORE  
WATERS WHERE MIXING IS BETTER. LESS WIND EXPECTED OVER THE OUTER  
WATERS DUE TO INVERSION BUT RISK OF GALES CONTINUE, ESPECIALLY  
IN ANY CONVECTIVE ELEMENTS. VSBYS BELOW 1 MIL E IN AREAS OF  
HEAVY RAIN AND FOG.  
 
SATURDAY...HIGH CONFIDENCE.  
SOUTHERLY GALES IN THE MORNING, THEN WINDS DIMINISHING AS LOW  
LEVEL JET MOVES OFFSHORE. WINDS SHIFTING TO NW LATE MORNING  
THROUGH AFTERNOON WITH GUSTS 20-25 KT.  
 
OUTLOOK /SUNDAY NIGHT THROUGH WEDNESDAY/...  
 
SATURDAY NIGHT: WINDS LESS THAN 25 KT. ROUGH SEAS UP TO 12 FT.  
SLIGHT CHANCE OF SNOW SHOWERS. LOCAL VISIBILITY 1 TO 3 NM.  
 
SUNDAY: WINDS LESS THAN 25 KT. AREAS OF ROUGH SEAS. LOCAL  
VISIBILITY 1 TO 3 NM.  
 
SUNDAY NIGHT: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT. SLIGHT  
CHANCE OF SNOW SHOWERS. LOCAL VISIBILITY 1 TO 3 NM.  
 
MARTIN LUTHER KING JR DAY: WINDS LESS THAN 25 KT. SEAS UP TO  
5 FT. SLIGHT CHANCE OF SNOW SHOWERS. AREAS OF VISIBILITY 1 TO  
3 NM.  
 
MONDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING  
5 FT.  
 
TUESDAY: WINDS LESS THAN 25 KT. LOCAL ROUGH SEAS. CHANCE OF  
SNOW, CHANCE OF RAIN. VISIBILITY 1 TO 3 NM.  
 
TUESDAY NIGHT: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT. CHANCE  
OF SNOW. VISIBILITY 1 TO 3 NM.  
 
WEDNESDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING  
5 FT. CHANCE OF SNOW. VISIBILITY 1 TO 3 NM.  
 

 
   
CLIMATE
 
 
RECORD HIGH TEMPS SET YESTERDAY:  
 
BOS 61 IN 2017,1975  
PVD 62 IN 2018  
BDL 60 IN 2018  
ORH 59 IN 2018  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...FLOOD WATCH UNTIL 1 PM EST THIS AFTERNOON FOR CTZ002>004.  
WINTER WEATHER ADVISORY FROM 9 AM THIS MORNING TO 4 PM EST  
THIS AFTERNOON FOR CTZ002>004.  
MA...FLOOD WATCH UNTIL 1 PM EST THIS AFTERNOON FOR MAZ002>024-026.  
DENSE FOG ADVISORY UNTIL 5 AM EST EARLY THIS MORNING FOR  
MAZ020-021.  
WINTER WEATHER ADVISORY FROM 11 AM THIS MORNING TO 4 PM EST  
THIS AFTERNOON FOR MAZ005>007-013>019.  
WIND ADVISORY UNTIL 9 AM EST THIS MORNING FOR MAZ018>024.  
WIND ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR MAZ013-  
015>017.  
WINTER WEATHER ADVISORY FROM 5 AM EARLY THIS MORNING TO 4 PM  
EST THIS AFTERNOON FOR MAZ002-003-008>011.  
WINTER WEATHER ADVISORY FROM 9 AM THIS MORNING TO 4 PM EST  
THIS AFTERNOON FOR MAZ004-012-026.  
DENSE FOG ADVISORY UNTIL 9 AM EST THIS MORNING FOR MAZ022>024.  
RI...FLOOD WATCH UNTIL 1 PM EST THIS AFTERNOON FOR RIZ001>008.  
DENSE FOG ADVISORY UNTIL 5 AM EST EARLY THIS MORNING FOR  
RIZ006>008.  
WINTER WEATHER ADVISORY FROM 11 AM THIS MORNING TO 4 PM EST  
THIS AFTERNOON FOR RIZ002>005.  
WIND ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR RIZ002-004-  
006-007.  
WINTER WEATHER ADVISORY FROM 9 AM THIS MORNING TO 4 PM EST  
THIS AFTERNOON FOR RIZ001.  
MARINE...GALE WARNING UNTIL 9 AM EST THIS MORNING FOR ANZ231>234-250-  
251-254>256.  
GALE WARNING UNTIL 7 AM EST THIS MORNING FOR ANZ230-235-236.  
SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR ANZ237.  
 

 
 

 
SYNOPSIS...WTB/KJC  
NEAR TERM...FRANK  
SHORT TERM...KJC  
LONG TERM...WTB  
AVIATION...FRANK/WTB  
MARINE...WTB/KJC  
CLIMATE...  
 
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