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
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