784  
FXUS61 KBOX 231730  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BOSTON/NORTON MA  
1230 PM EST SAT JAN 23 2021  
   
SYNOPSIS
 
 
A COLD AND BLUSTERY WEEKEND WITH POSSIBLE SUB-ZERO WIND CHILLS  
BY SUNDAY MORNING. WINDS SLACKEN ON SUNDAY NIGHT AS HIGH  
PRESSURE BUILDS INTO SOUTHERN NEW ENGLAND THROUGH MONDAY NIGHT.  
A SYSTEM PASSING TO OUR SOUTH MAY BRING A MINOR ACCUMULATION OF  
SNOW SOUTH OF THE MASSACHUSETTS TURNPIKE ON TUESDAY. HIGH  
PRESSURE THEN BECOMES RE-ESTABLISHED FOR MOST OF THE WORKWEEK,  
WITH TEMPERATURES AROUND SEASONABLE LEVELS. A COASTAL LOW NEAR  
THE MID-ATLANTIC WATERS ON THURSDAY MAY BRUSH OUR FAR SOUTHERN  
AREAS OR PASS FAR ENOUGH SOUTH TO BE A MISS.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
1 PM UPDATE...  
 
ARCTIC FRONT CONTINUES TO DROP THROUGH SOUTHERN NEW ENGLAND  
AFTER BRINGING A DUSTING TO HALF INCH OF SNOW FROM WORCESTER  
EAST TO THE OUTER CAPE. SHOWERS HAVE LARGELY MOVED OFFSHORE AND  
THINGS SHOULD BE DRY THE REST OF THE DAY. WINDS ARE GUSTING 25  
TO 30 MPH AND WILL REMAIN ELEVATED.  
 
PREVIOUS DISCUSSION...  
 
RADAR SHOWING SOME SOUTHEASTWARD-MOVING SNOW SHOWERS INTO THE  
ROUTE 2 CORRIDOR AND THE MERRIMACK VALLEY. THESE WILL CONTINUE  
TO PASS SOUTHEAST TOWARD THE NORTH SHORE/METRO BOSTON AND  
OFFSHORE. AS THEY DO SO HOWEVER, THEY WILL BRIEFLY REDUCE  
VISIBILITY AND PERHAPS PRODUCE A COATING OF NEW SNOW. EXPECT BY  
MID- MORNING THAT THESE PASSING SNOW SHOWERS WILL HAVE MOVED  
INTO THE COASTAL WATERS.  
 
OTHERWISE, CONSIDERABLE CLOUDINESS AND NORTHERLY WINDS HAVE KEPT  
CURRENT TEMPERATURES RUNNING MILDER THAN FORECAST EXPECTATIONS.  
WE'RE ALSO STILL AWAITING THE ARRIVAL OF THE COLDER/DRIER AIR  
WHICH STILL IS BACK ACROSS CENTRAL NY. EXPECT ONSET OF COLD  
ADVECTION AROUND MID MORNING, WITH INCREASING NORTHWEST WIND  
GUSTS. DIDN'T MAKE ANY CHANGES TO TEMPS, WHICH APPEAR ON TRACK.  
 
4 AM UPDATE:  
 
THE CORE OF A HIGH PRESSURE REMAINS TO OUR WEST TODAY. WHILE  
THIS HIGH SHOULD BE CLOSE ENOUGH TO KEEP OUR WEATHER MAINLY DRY,  
IT WILL NOT BE QUITE CLOSE ENOUGH TO FORCE WINDS TO DIMINISH. IN  
FACT, EXPECTING THE OPPOSITE EFFECT WHERE THE MODEST COLD AIR  
ADVECTION WILL INCREASE THE GRADIENT WIND ACROSS SOUTHERN NEW  
ENGLAND, ESPECIALLY THIS AFTERNOON.  
 
TEMPERATURES WILL BE BELOW NORMAL TODAY, WITH MOST AREAS NOT  
GETTING OUT OF THE 20S.  
 
CANNOT RULE OUT A FEW SNOW SHOWERS OR FLURRIES THIS MORNING,  
ESPECIALLY TOWARDS THE EAST COAST.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/
 
 
NOT MUCH CHANGE IN CONDITIONS TONIGHT INTO SUNDAY. STILL GUSTY  
WINDS AND TURNING SHARPLY COLDER COMPARED TO WHAT WE HAVE BEEN  
MOST OF THIS MONTH. MINIMUM WIND CHILL TEMPERATURES TONIGHT BELOW  
ZERO ACROSS MOST OF SOUTHERN NEW ENGLAND. NOT LOW ENOUGH WHERE  
AM THINKING WE WOULD NEED A WIND CHILL ADVISORY. THINKING WE  
COULD SEE SOME ISOLATED GUSTS UP TO WIND ADVISORY STRENGTH  
ACROSS THE OUTER CAPE TONIGHT. WILL LET THE NEXT SHIFT  
REEVALUATE.  
 

 
   
LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/
 
 
HIGHLIGHTS...  
 
* DRY WEATHER PREVAILS THROUGH MONDAY NIGHT UNDER HIGH PRESSURE.  
 
* LIGHT-ACCUMULATING SNOW MAINLY ACROSS WESTERN MA, CT INTO SOUTHERN  
RI TUES AS SYSTEM PASSES TO OUR SOUTH.  
 
* HIGH PRESSURE RETURNS FOR MID TO LATE WEEK WITH MAINLY DRY  
WEATHER; DO HAVE TO MONITOR COASTAL STORMINESS NEAR THE MID-  
ATLANTIC REGION THURS THAT MAY BRUSH OUR SOUTHERN AREAS BUT NOT A  
SURE BET.  
 
DETAILS:  
 
SUNDAY NIGHT INTO MONDAY:  
 
HIGH PRESSURE OVER THE APPALACHIANS CONTINUES TO BUILD EAST INTO OUR  
AREA SUNDAY NIGHT, AND REMAINS ESTABLISHED ACROSS SOUTHERN NEW  
ENGLAND THROUGH MON NIGHT.  
 
FOR SUNDAY NIGHT, WE SHOULD SEE SLACKENING NW WIND SPEEDS EARLY,  
TAKING LONGER TO OCCUR ACROSS EASTERN COASTAL MA. GOOD RADIATIONAL  
COOLING SEEMS LIKELY, ESPECIALLY OUR INTERIOR AREAS WHERE WINDS  
WILL EASE SOONER THAN AREAS FURTHER EAST. MOS ORDINARILY WOULD  
DO FAIRLY WELL IN SUCH A PATTERN FOR TEMPERATURES, BUT MAY BE  
TOO COLD GIVEN ITS ASSUMPTIONS THAT THERE IS A SNOWPACK; SO FOR  
LOWS I UTILIZED AN NBM/MOS BLEND TO NOT GO QUITE AS LOW AS MOS  
WOULD REFLECT. BRINGS LOWS MAINLY INTO THE LOW-MID TEENS, WITH  
SINGLE DIGITS ACROSS PARTS OF THE PIONEER VALLEY AND INTO THE  
BERKSHIRES.  
 
HIGH PRESSURE CONTINUES TO GOVERN ON MON, WITH FULL SUN TURNING  
FILTERED LATE IN THE DAY. BY EVENING, MOST AREAS SHOULD TREND OVC IN  
TERMS OF SKY COVER. UNDER MODEST NORTHERLY WINDS WHICH SHOULD TURN  
MORE NNE/NE BY MON NIGHT, SHOWED UPPER 20S TO UPPER 30S HIGHS WITH  
LOWS MID TEENS TO LOWER 20S.  
 
TUESDAY INTO TUESDAY NIGHT:  
 
PRIMARY LOW PRESSURE AT 12Z TUES OVER IL/IN, ASSOCIATED WITH A 500  
MB SHORTWAVE TROUGH WHICH ROUNDS THE NORTHWEST PERIPHERY OF A RIDGE  
AXIS OVER THE COASTAL SOUTHEAST CONUS. SHORTWAVE ALOFT MORE OR LESS  
SHEARS OUT AS IT NEARS THE MID-ATLANTIC/LOWER HUDSON VALLEY REGION  
ON TUES, WITH SECONDARY COASTAL DEVELOPMENT TAKING SHAPE LATER TUES  
INTO TUES NIGHT.  
 
00Z GUIDANCE SUITE SEEMS TO BE COMING INTO BETTER AGREEMENT ON WHAT  
IS APPEARING TO BE A LIGHT-ACCUMULATING SNOW FOR TUES INTO TUES  
EVENING. OF THE DETERMINISTIC GUIDANCE, THE GFS IS THE FURTHEST  
NORTH AND ALSO PACKS A LITTLE MORE QPF THAN THE ECMWF AND THE  
CANADIAN GEM. SHEARING VORT ENERGY, LIMITED QPF, A PROGRESSIVE  
SYSTEM AND HIGH PRESSURE TO OUR NORTHEAST SUPPLYING DRY AIR ARE ALSO  
LIMITING FACTORS FOR MORE APPRECIABLE ACCUMULATING SNOWS. OPTED FOR  
CHANCE-LEVEL POPS ACROSS CT INTO WESTERN MA WHERE THE BEST CHANCE  
FOR LIMITED/MINOR ACCUMULATION MAY BE ON TUES WITH UP TO A COUPLE  
INCHES OF SNOW HERE, TAPERING TO SLIGHT CHANCE FURTHER TO THE NORTH  
AND EAST. NBM-BASED SNOW PROBS ALSO SUPPORT A LIGHT/MINOR  
ACCUMULATION OF SNOW MAINLY INTO CT, WESTERN MA AND CENTRAL/SOUTHERN  
RI. DRIER AIR EVENTUALLY WINS OUT AND SHIFTS PRECIP AXIS INTO OUR  
FAR SOUTHERN WATERS TUES NIGHT.  
 
HIGHS MID 20S TO THE LOWER-MID 30S ON TUES, WITH LOWS MID TEENS TO  
MID 20S.  
 
WEDNESDAY INTO WEDNESDAY NIGHT:  
 
HIGH PRESSURE TO RE-BUILD BACK INTO SNE FOR MIDWEEK. DESPITE DRY  
WEATHER, STILL SOME RH LEFT BEHIND SUPPORTING PARTLY TO MOSTLY  
CLOUDY CONDITIONS AND ONSHORE NE FLOW. HIGHS UPPER 20S TO THE MID  
UPPER 30S WITH LOWS UPPER TEENS TO MID 20S.  
 
THURSDAY INTO FRIDAY:  
 
MODELS SHOWING A DEEPENING CYCLONE NEAR THE COASTAL MID-ATLANTIC AND  
CAROLINAS ON THURS, MOVING EASTWARD MAINLY SOUTH OF 40N LATITUDE. IT  
REMAINS TO BE SEEN IF SNE WILL SEE ANY (FRINGE) IMPACTS FROM THIS  
PROGGED CYCLONE, AS THERE'S SIGNIFICANT LATITUDINAL SPREAD IN LOW  
CENTERS. IN TERMS OF THE OPERATIONAL MODELS, THE ECMWF IS FURTHEST  
SOUTH AND WOULD OFFER A CONTINUATION OF DRY NORTHERLY FLOW. THE GEM  
AND MORE SO THE GFS (FURTHEST NORTH/SOMEWHAT CLOSER TO SNE) WOULD  
BRING PRECIP TO OUR SOUTHERN ROUGHLY THIRD OF THE FORECAST AREA.  
WILL NEED TO KEEP TABS ON THIS SYSTEM AND ITS DEVELOPMENTS, BUT  
AT THE MOMENT ENSEMBLES PRESENTLY SUPPORT A MISS OR AT WORST A  
GLANCING BLOW TO OUR SOUTHERN AREAS.  
 
SYSTEM PULLS AWAY THURS NIGHT WITH HIGH PRESSURE BUILDING BACK IN  
FOR FRIDAY SUPPORTING DRY WEATHER.  
 
TEMPERATURES PROJECT AROUND SEASONABLE LEVELS FOR LATE-WEEK.  
 

 
   
AVIATION /18Z SATURDAY THROUGH THURSDAY/
 
 
FORECASTER CONFIDENCE LEVELS.  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
18Z TAF UPDATE:  
 
TODAY THROUGH SUNDAY NIGHT: HIGH CONFIDENCE.  
 
VFR. STRONG GUSTY NW WINDS DEVELOPING TODAY, AND LINGERING  
THROUGH SUNDAY. WINDS DIMINISH SUNDAY NIGHT.  
 
KBOS TAF...HIGH CONFIDENCE IN TAF.  
 
KBDL TAF...HIGH CONFIDENCE IN TAF.  
 
OUTLOOK /MONDAY THROUGH WEDNESDAY/...  
 
SUNDAY NIGHT: VFR. WINDY WITH GUSTS UP TO 35 KT.  
 
MONDAY: VFR. BREEZY.  
 
MONDAY NIGHT: MAINLY VFR, WITH LOCAL IFR POSSIBLE. SLIGHT  
CHANCE SN.  
 
TUESDAY: MAINLY VFR, WITH AREAS IFR POSSIBLE. BREEZY. CHANCE  
SN.  
 
TUESDAY NIGHT: MAINLY VFR, WITH LOCAL IFR POSSIBLE. BREEZY.  
SLIGHT CHANCE SN.  
 
WEDNESDAY: VFR.  
 

 
   
MARINE
 
 
GUSTY WEST TO NORTHWEST WINDS CONTINUE ACROSS THE WATERS AND  
LINGER THROUGH SUNDAY. GALE WARNINGS REMAIN IN EFFECT THROUGH  
SUNDAY EVENING. THE AIR WILL BE COLD ENOUGH WHERE THERE IS A  
CONCERN FOR FREEZING SPRAY ACROSS MOST OF THE COASTAL WATERS  
INTO SUNDAY. DECIDED TO ISSUE FREEZING SPRAY ADVISORIES FOR  
PORTIONS OF THE EASTERN COASTAL WATERS TONIGHT DUE TO THE  
POSSIBILITY OF MODERATE FREEZING SPRAY. THREAT OF FREEZING SPRAY  
DIMINISHES SOME DURING THE DAY SUNDAY.  
 
OUTLOOK /SUNDAY NIGHT THROUGH WEDNESDAY/...  
 
SUNDAY NIGHT: LOW RISK FOR GALE FORCE WINDS WITH GUSTS UP TO  
35 KT. AREAS OF ROUGH SEAS. FREEZING SPRAY.  
 
MONDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING 5 FT.  
 
MONDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING  
5 FT. LOCAL VISIBILITY 1 TO 3 NM.  
 
TUESDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.  
CHANCE OF RAIN, SLIGHT CHANCE OF SNOW. VISIBILITY 1 TO 3 NM.  
 
TUESDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING  
5 FT. LOCAL VISIBILITY 1 TO 3 NM.  
 
WEDNESDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT.  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
MA...NONE.  
RI...NONE.  
MARINE...FREEZING SPRAY ADVISORY FROM 9 PM THIS EVENING TO 7 AM EST  
SUNDAY FOR ANZ231>234.  
GALE WARNING UNTIL 6 PM EST SUNDAY FOR ANZ230>237-250-251-  
254>256.  
FREEZING SPRAY ADVISORY FROM 9 PM THIS EVENING TO 10 AM EST  
SUNDAY FOR ANZ251.  
 

 
 

 
SYNOPSIS...BELK/LOCONTO  
NEAR TERM...BELK/LOCONTO/BW  
SHORT TERM...BELK  
LONG TERM...LOCONTO  
AVIATION...BELK/LOCONTO/BW  
MARINE...BELK/LOCONTO  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab MA Page
The Nexlab RI Page
The Nexlab NH Page
The Nexlab CT Page Main Text Page