352
FXUS61 KBOX 201814
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
114 PM EST THU FEB 20 2025
SYNOPSIS
A DISTANT OCEAN STORM WILL BRUSH THE CAPE/ISLANDS WITH SOME
ACCUMULATING SNOW LATER TODAY INTO TONIGHT. BREEZY AND COLD
FOR FRIDAY WITH THE DEPARTURE OF A COASTAL LOW AND THE BUILDING
HIGH PRESSURE SYSTEM TO THE WEST. DRIER CONDITIONS AS WELL
CONTINUES INTO THIS WEEKEND WITH NEAR NORMAL TEMPERATURES. EARLY
NEXT WEEK SIGNS OF SOME UNSETTLED CONDITIONS AND SLIGHTLY ABOVE
NORMAL TEMPERATURES.
NEAR TERM /THROUGH TONIGHT/
1 PM UPDATE...
CHANGES FROM PREVIOUS FORECAST...
REGARDING OFFSHORE STORM AND ITS SNOW SHIELD THIS AFTERNOON AND
EVENING, NEW 12Z GUIDANCE HAVE ALL TRENDED SOUTH WITH QPF. THIS
SEEMS REASONABLE GIVEN WEST TO EAST FLOW ALOFT, PRECLUDING DEEP
LAYER MOISTURE OFFSHORE FROM ADVECTING NORTHWARD. XSECTIONS AND
TSECTIONS SHOW THIS NICELY AT ACK AND CHH, WITH COLUMN
STRUGGLING TO COMPLETE SATURATE. HENCE, LIMITING QPF/SNOWFALL. MOST
OF THE GUIDANCE ONLY OFFERING UP TO A TENTH OF AN INCH OF QPF
ACROSS THE CAPE AND ACK. THEREFORE, A COATING TO TWO INCHES IS
LIKELY THE NEW SNOW FORECAST. WE MAY HAVE TO DROP THE ADVISORY
FOR NANTUCKET, BUT MORE ON THAT IN A BIT. EARLIER DISCUSSION
BELOW.
KEY MESSAGES...
* SUN GIVES WAY TO TODAY WITH HIGHS NEAR 30/LOWER 30S
* PERIODS OF LIGHT SNOW LATER TODAY-TONIGHT TOWARDS THE CAPE/ISLANDS
DETAILS...
TODAY AND TONIGHT...
LOW PRESSURE EAST OF THE CAROLINAS VERY EARLY THIS MORNING WILL PASS
WELL SOUTHEAST OF THE BENCHMARK TODAY AND TONIGHT. AT THE SAME
TIME...UPPER LEVEL SHORTWAVE ENERGY WILL BE APPROACHING FROM THE
WEST. THE RESULT WILL THE FORMATION OF A SUBTLE INVERTED TROUGH AND
WEAK ONSHORE FLOW IN THE 850/925 MB LAYER. GIVEN 850T NEAR
-10C...THIS ONSHORE FLOW WILL ALLOW CLOUDS TO BACK IN OFF THE OCEAN
AS THE DAY WEARS ALONG. HIGH TEMPS WILL BE GENERALLY AROUND 30/LOWER
30S.
GIVEN THE TRACK OF THE SURFACE LOW PRESSURE SYSTEM...ITS ASSOCIATED
MAIN SNOW SHIELD PROBABLY DOES NOT MAKE IT MUCH FURTHER NORTHWEST
THAN NANTUCKET AND PERHAPS BRIEFLY MVY AND PORTIONS OF CAPE COD.
HOWEVER...SHORTWAVE ENERGY WILL COMBINED WITH COLD NORTHERLY FLOW
AND A SST DIFFERENTIAL OF AROUND 15C FROM THE TOP OF THE MIXED
LAYER. THIS WILL ALLOW OCEAN EFFECT/OCEAN ENHANCED SNOW SHOWERS TO
DEVELOP ACROSS PARTS OF PLYMOUTH COUNTY AND ESPECIALLY THE
CAPE/MARTHAS VINEYARD LATER TODAY AND PARTICULARLY TONIGHT. SNOW
ACCUMULATIONS OF A DUSTING TO 1" FOR COASTAL PLYMOUTH COUNTY AND 1-
2" FOR THE CAPE/MARTHAS VINEYARD. NANTUCKET WHICH MAY BE CLIPPED BY
THE SNOW SHIELD FROM THE SYNOPTIC STORM ALONG WITH SOME OCEAN
ENHANCEMENT...WE ARE THINKING 2-3" OF SNOW IS REASONABLE WITH A LOW
RISK FOR UP TO 4". THEREFORE...WE WILL CONTINUE THE WINTER WEATHER
ADVISORY FOR NANTUCKET BUT NOT EXPAND IT ANY FURTHER NORTHWEST.
ACROSS THE REST OF THE REGION...NOTHING MORE THAN A BRIEF SPOT
SNOW SHOWER/FLURRY IF EVEN THAT FROM THE SHORTWAVE ENERGY.
OTHERWISE...THE SNOW SHOWERS SHOULD DEPART THE CAPE AND ISLANDS
TOWARD DAYBREAK AS DRIER AIR WORKS IN FROM THE NORTHWEST AND IT
BECOMES A BIT BREEZY. LOWS OVERNIGHT SHOULD DROP MAINLY INTO
THE MIDDLE TEENS TO THE LOWER 20S.
SHORT TERM /FRIDAY/
KEY MESSAGES...
* DRY, COLD, AND BREEZY FRIDAY
FRIDAY...
LOW PRESSURE SYSTEM EXITS EAST OF NEW ENGLAND WITH
STRONG HIGH PRESSURE BUILDING OVER THE CENTRAL CONUS, AROUND
1035+ MB, RESULTING IN A GUSTY CONDITIONS DUE TO THE INCREASED
PRESSURE GRADIENT. GUSTS REMAIN BELOW ADVISORY CRITERIA, GUSTS
25 TO 35 MPH SEEM MOST LIKELY. STILL A FAIRLY COLD DAY,
CONSIDERING AVERAGE HIGHS ARE BETWEEN THE MID-30S AND 40F. WITH
925MB TEMPERATURES BETWEEN -8C AND -10C, YIELDS HIGHS FROM THE
UPPER 20S TO MID-30S. DRY CONDITIONS CONTINUE INTO THE OVERNIGHT
AS THE COLUMN DRIES OUT WITH SURFACE HIGH MOVING EAST. ANOTHER
CHILLY NIGHT AHEAD WITH LOWS IN THE SINGLE DIGITS AND TEENS,
COMPARED TO THE AVERAGE LOW OF THE LOW AND MIDDLE 20S. IF THE
WINDS WERE TO SUBSIDE QUICKER, THE FORECAST TEMPERATURES COULD
BE TOO "WARM", RESULTING IN BETTER RADIATIONAL COOLING, THUS
WOULD NEED TO TREND TEMPERATURES COLDER.
LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/
KEY MESSAGES...
* FAIRLY QUIET WEATHER THIS WEEKEND AND EARLY NEXT WEEK. WILL WATCH
A WEAKER SHORTWAVE SLIDES THROUGH LATE SATURDAY NIGHT INTO EARLY
SUNDAY, AND THEN A POTENTIAL CLIPPER SYSTEM FOR EARLY NEXT WEEK.
* TEMPERATURES MODERATE THIS WEEKEND INTO EARLY NEXT WEEK.
FRIDAY THROUGH MONDAY
SATURDAY AND SUNDAY: HIGH PRESSURE BREAKDOWN OVER THE COURSE OF
THE WEEKEND, THOUGH SHOULD HAVE FAIRLY QUIET WEATHER DURING
THIS PERIOD. A SUBTLE MID-LEVEL TROUGH AND ASSOCIATED WEAK
SHORTWAVE CROSSES THE REGION SOMETIME OVERNIGHT SATURDAY INTO
SUNDAY MORNING. FEEL THIS RESULTS IN ADDED CLOUD COVER WITH A
LOW CHANCE FOR AN ISOLATED SNOW SHOWER. TEMPERATURES TREND
SLIGHTLY "WARMER" WITH HIGHS BETWEEN THE MIDDLE AND UPPER 30S,
AND OVERNIGHT LOWS FROM THE MID TEENS TO THE MID-20S.
LOOK AHEAD TO NEXT WEEK: MID-LEVEL FEATURES A FEW SUBTLE TROUGHS AND
PROGRESSIVE SHORTWAVES FOR THE FIRST-HALF OF NEXT WEEK. WHILE IT
ISN'T AN OVERLY ACTIVE WEEK, THERE COULD BE A FEW NUISANCE FEATURES
TO KEEP US ON OUR TOES. LOOKING AT ENSEMBLE GUIDANCE, THERE IS SOME
AGREEMENT THAT A CLIPPER SYSTEM MAY SWEEP ACROSS NEW ENGLAND LATE ON
MONDAY NIGHT, PERHAPS EARLY TUESDAY, TIMING WILL BE IMPORTANT IF YOU
WERE TO WANT ONE PTYPE. ADDITIONALLY, THERE IS SOME HINTS A WAVE OF
LOW PRESSURE COMES UP THE COAST AROUND THE SAME TIME. AS PREVIOUS
FORECASTER MENTIONED, THIS PART OF THE FORECAST CARRIES LOW
CONFIDENCE. WHERE THERE IS A BIT MORE CONFIDENCE REVOLVE AROUND THE
INCREASING TEMPERATURES NEXT WEEK, WHICH IS HIGHLIGHTED BY CPC WHO'S
TEMPERATURE OUTLOOK FOR FEB 25 TO MAR 1, IS LEANING ABOVE NORMAL FOR
TEMPERATURES. DAYTIME HIGHS MONDAY, TUESDAY, AND WEDNESDAY ARE IN THE
LOWER TO MIDDLE 40S. NIGHTLY LOWS ARE NEAR NORMAL IN THE UPPER-20S
TO LOW-30S.
AVIATION /18Z THURSDAY THROUGH MONDAY/
FORECAST CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
18Z TAF UPDATE...
THRU 12Z FRIDAY...HIGH CONFIDENCE.
MVFR CIGS ACROSS EASTERN AND CENTRAL MA, RI AND INTO EASTERN CT.
VFR CLOUD BASES LIKELY ACROSS WESTERN/CENTRAL CT INTO WESTERN
MA. OTHER THAN SCATTERED FLURRIES, MAINLY DRY WEATHER PREVAILS.
THE EXCEPTION WILL BE OVER CAPE COD AND THE ISLANDS, WHERE MVFR
TO VFR VSBYS 21Z-03Z IN LIGHT SNOW, WITH A COATING TO PERHAPS UP
TO 2 INCHES AT ACK. LIGHT N-NE WINDS THIS AFTERNOON, BECOMES NW
TONIGHT AND INCREASES WITH GUSTS UP TO 25 KT, HIGHEST OVER CAPE
AND ISLANDS.
FRIDAY AND FRIDAY NIGHT... HIGH CONFIDENCE.
VFR AND DRY. GUSTY NW WINDS 10-20 KNOTS WITH GUSTS 25-30 KNOTS,
HIGHEST OVER CAPE COD AND ISLANDS.
KBOS TAF...HIGH CONFIDENCE IN TAF.
KBDL TAF...HIGH CONFIDENCE IN TAF.
OUTLOOK /SATURDAY THROUGH MONDAY/...
SATURDAY: VFR. BREEZY.
SATURDAY NIGHT THROUGH SUNDAY NIGHT: VFR.
MONDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE.
MARINE
FORECASTER CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENT.
MEDIUM - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
TODAY AND TONIGHT...HIGH CONFIDENCE.
LOW PRESSURE EAST OF THE CAROLINAS EARLY THIS MORNING PASSES WELL
SOUTHEAST OF THE BENCHMARK INTO THIS EVENING. WHILE WINDS/SEAS
REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS TODAY...EXPECT NW WIND
GUSTS OF 20-30 KNOTS TO DEVELOP BEHIND THE DEPARTING SYSTEM TONIGHT.
SMALL CRAFT ADVISORIES ARE POSTED FOR MOST OF OUR OPEN WATERS.
OUTLOOK /FRIDAY NIGHT THROUGH MONDAY/...
FRIDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 25 KT. SEAS UP TO 5 FT. CHANCE OF FREEZING SPRAY.
SATURDAY THROUGH SUNDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY
APPROACHING 5 FT.
SUNDAY NIGHT THROUGH MONDAY: WINDS LESS THAN 25 KT.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...WINTER WEATHER ADVISORY UNTIL 7 AM EST FRIDAY FOR MAZ024.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 1 AM EST
SATURDAY FOR ANZ231-250-254>256.
SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 7 PM EST
FRIDAY FOR ANZ232>235-237-251.
SYNOPSIS...FRANK/DOOLEY
NEAR TERM...FRANK/NOCERA
SHORT TERM...DOOLEY
LONG TERM...DOOLEY
AVIATION...FRANK/NOCERA
MARINE...FRANK/DOOLEY
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