Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 292006 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 406 PM EDT WED OCT 29 2014 .SYNOPSIS...
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SHOWERS CONCLUDE BEHIND A COLD FRONT PUSHING OFFSHORE TONIGHT. SEASONABLE AND DRIER WEATHER FOLLOWS INTO THE END OF THE WEEK UNDER HIGH PRESSURE. A COASTAL STORM WILL LIKELY DELIVER A GLANCING BLOW TO THE REGION LATE SATURDAY INTO SUNDAY...BUT THE OPPORTUNITY FOR A HIGHER IMPACT STILL EXISTS. MAINLY DRY WEATHER FOLLOWS WITH A SIGNIFICANT WARMING TREND BY NEXT TUESDAY AND WEDNESDAY.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... 230 PM UPDATE... COLD FRONT PUSHING ACROSS S NEW ENGLAND WITH SHOWERY WEATHER AND THICKER CLOUDS IN TOW. CONDITIONS CONTINUE TO WARM BENEATH THE THIN VEIL OF MID- TO HIGH-LEVEL CLOUDS. SW-FLOW CONTINUES TO GUST IN EXCESS OF 25 MPH ALONG THE S/SE SHORELINE. MAIN CONCERN FOR THE REMAINDER OF THE FORECAST PERIOD INTO THIS EVENING IS THE TIMING OF SHOWERS AHEAD OF THE MAIN DRIVING FORCE THAT BEING THE STRETCHED MID-LEVEL TROUGH AXIS. WITH CONDITIONS WARMING ACROSS SE NEW ENGLAND BENEATH A CONDITIONALLY UNSTABLE ENVIRONMENT...ECHO OVERNIGHT FORECASTERS THOUGHTS CONCERNING THE POSSIBILITY OF AN ISOLATED THUNDERSTORM OR TWO ACROSS SE NEW ENGLAND. NOTHING SEVERE. ASIDE...EXPECT A BAND OF SHOWERS WITH EMBEDDED HEAVIER DOWNPOURS TO MARCH ACROSS THE REGION INTO THIS EVENING BENEATH FAVORABLE DEEP-LAYER ASCENT. FEEL THE HIGH-RES WRF GUIDANCE AND HRRR HAVE A GOOD HANDLE ON THE PRESENT SITUATION...ALBEIT SLIGHT DIFFERENCES. COULD SEE THE LINE OF SHOWERS BECOME DIFFUSE WITH ITS TRACK TO THE S AND E. SPECULATE THIS TO BE CONSEQUENTIAL OF STRETCHED MID-LEVEL ENERGY AND PERHAPS THE COLD FRONT BECOMING TOO SEPARATED FROM ITS PARENT MID-LEVEL TROUGH. ALSO PERHAPS AS THE COLD FRONT PUSHES OFFSHORE TOWARDS A BETTER MOIST-INSTABILITY AXIS ACTIVITY ERUPTS THAT USURPS ACTIVITY TO THE W. ALL SORTS OF FACTORS...BUT ASIDE NOT A BIG DEAL BUT JUST A SWEEPING WET-WEATHER MAKER. ALREADY 72-DEGREES HERE AT THE TAUNTON WFO. EXPECT CONDITIONS TO CONTINUE WARMING INTO THE MID-70S FOR S/SE NEW ENGLAND. A BLEND OF THE RAP APPEARS GOOD ENOUGH WITH REGARDS TO 2M TEMPERATURES THOUGH NOT HANDLING THE WARM-FRONT ALL THAT WELL. TONIGHT... MAIN TROUGH AXIS PUSHING THROUGH THE REGION OVERNIGHT. COLD FRONT PUSHES OFFSHORE AS CLOUDS AND SHOWERS LINGER REARWARD ACROSS S- AND E-PORTIONS OF NEW ENGLAND TOWARDS THURSDAY MORNING. SURFACE HIGH PRESSURE BUILDS INTO THE AREA FROM THE OHIO RIVER VALLEY. LIKELY BLANKET OF MID- TO HIGH-LEVEL CLOUDS AND WET WEATHER WILL KEEP CONDITIONS MILD TOWARDS SHORES WITH LOWS AROUND THE MID-40S. ELSEWHERE...GRADUAL CLEARING EXPECTED W TO E AS W-WINDS DRIVE COOLER AND DRIER AIR ACROSS THE REGION. COOLEST CONDITIONS N AND W YET WINDS /MENTIONED BY THE PREVIOUS FORECASTER/ WILL LIKELY LIMIT EFFECTIVE RADIATIONAL COOLING. EXPECTING LOWS AROUND THE UPPER-30S. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... THURSDAY... HIGH PRESSURE CONTINUES TO BUILD E. SUBSIDENCE AND SINKING AIR IN CONTROL OF THE REGIONS WEATHER. WITH A COOLER AIRMASS CONTINUING TO BUILD WITHIN THE LOW-LEVELS /H85 JUST BELOW THE FREEZING MARK/ EXPECT A WELL-MIXED BOUNDARY-LAYER ALLOWING FOR DRIER AIR TO MIX- DOWN /DEWPOINTS INTO THE MID-30S/ AND DEVELOPMENT OF A SCATTERED CUMULUS DECK AROUND 5-6 KFT. HIGHS AROUND THE 50S EXPECTED WHICH IS JUST ABOUT NORMAL FOR THIS TIME OF YEAR ACROSS SOUTHERN NEW ENGLAND. LIGHT WESTERLY WINDS. THURSDAY NIGHT... HIGH PRESSURE ACROSS NEW ENGLAND. LIGHT AND VARIABLE WINDS. COLD AIRMASS BELOW FREEZING REMAINS ALOFT. A GOOD CASE FOR EFFECTIVE RADIATIONAL COOLING...THAT IS IF CLOUDS DO NOT BECOME AN ISSUE. CONSIDERING DEWPOINTS AROUND THE MID-30S ON THURSDAY...IT IS POSSIBLE LOCATIONS COULD COOL BELOW THE CROSSOVER THRESHOLD IF THE CONDITIONS ARE RIGHT AND WE ARE ALLOWED TO RADIATE OUT EFFECTIVELY. BUT BENEATH CYCLONIC FLOW THROUGH WHICH WEAK IMPULSES WILL GLIDE... THERE IS ALWAYS THAT POTENTIAL FOR ENHANCEMENT OF MID-LEVEL LIFT AND CONVERGENCE YIELDING A BLANKETING CLOUD BASE. IF CONDITIONS REMAIN CLEAR...THERE IS ENOUGH CONFIDENCE TO SPECULATE THAT SHALLOW GROUND FOG WILL DEVELOP WHEREVER SOILS ARE SATURATED /I.E. SWAMPY BOGS/. LOWS WOULD BOTTOM DOWN AROUND THE MID-30S...LOW- 30S FOR THOSE AREAS THAT RADIATE. WARMEST CONDITIONS ALONG THE SHORES. BUT WILL GO CONSERVATIVE WITH THIS FORECAST CONSIDERING THE POTENTIAL FOR MID-LEVEL CLOUD DECKS AND HOLD WITH LOWS AROUND THE UPPER-30S. WILL NEED TO MONITOR FOR FROST / FREEZE HEADLINES MAY BE NECESSARY FOR S/E COASTAL MA AND RI. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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HIGHLIGHTS... * COOL ON FRIDAY * GLANCING BLOW FAVORED SAT/EARLY SUN BUT HIGHER IMPACT POSSIBLE * BIGGEST CONCERN IS STRONG WINDS LATE SAT/SUN ESP CAPE COD * ACCUMULATING SNOW IS STILL POSSIBLE BUT A RATHER LOW PROBABILITY * MUCH MILDER WEATHER RETURNS BY NEXT TUE AND WED DETAILS... FRIDAY... AN ENLONGATED HIGH PRESSURE SYSTEM ACROSS EASTERN CANADA WILL RESULT IN A RATHER CLOUDY/COOL DAY WITH EASTERLY WINDS. A SPOT SHOWER AND PERHAPS EVEN SOME DRIZZLE WILL BE POSSIBLE ALONG THE COAST DURING THE AFTERNOON...BUT THE MAJORITY OF THE DAY WILL BE DRY. HIGHS WILL MAINLY BE IN THE UPPER 40S ACROSS THE HIGHER TERRAIN...TO THE LOWER TO MIDDLE 50S ELSEWHERE. SATURDAY AND SUNDAY... FORECAST CONFIDENCE REMAINS QUITE LOW OVER THIS TIME. ENSEMBLE SENSITIVITY PLOTS SHOW THE ENERGY RESPONSIBLE FOR DEVELOPING THE EVENTUAL STORM IS STILL NEAR THE ARCTIC CIRCLE. THIS LEAVES PLENTY OF UNCERTAINTY IN THE TRACK/STRENGTH AND IMPACTS ACROSS THE REGION. WITH THAT SAID...CURRENT MODEL CONSENSUS FAVORS A GLANCING BLOW AND NOT A DIRECT HIT FOR OUR REGION. THE BIGGEST CONCERN RIGHT NOW IS FOR STRONG TO PERHAPS DAMAGING WINDS...ESPECIALLY ACROSS THE CAPE AND NANTUCKET. THERE ARE TWO MAIN SHORTWAVES INVOLVED IN STORM FORMATION. INITIALLY...MOST MODELS FORM AN ENLONGATED LOW PRESSURE SYSTEM OR EVEN TWO CENTERS BEFORE CONSOLIDATING INTO ONE STORM. CURRENT INDICATIONS ARE THAT THIS HAPPENS TOO LATE FOR A SIGNIFICANT RAIN/SNOW EVENT IN SOUTHERN NEW ENGLAND. A BIG CAVEAT IS THAT THIS EVENT IS CURRENTLY PROGGED BETWEEN 72 AND 96 HOUR OUT...WHICH IS QUITE A BIT OF TIME IN THE MODEL WORLD. IF THE INITIAL SHORTWAVE IS WEAKER THAN CURRENTLY DEPICTED...THE STORM WILL INTENSIFY EARLIER AND CLOSER TO THE COAST. WHILE THIS IS A LOWER PROBABILITY AT THIS POINT...ITS CERTAINLY IN THE REALM OF POSSIBILITIES. WHAT EVER HAPPENS...WE CAN SAY THAT EASTERN NEW ENGLAND WILL HAVE MORE OF AN IMPACT THAN THE INTERIOR. PTYPE AND TIMING... A LOT OF THIS WILL DEPEND ON HOW FAR WEST THE MAIN PRECIPITATION SHIELD REACHES. INITIALLY...ALL PRECIPITATION WILL BE IN THE FORM OF RAIN OR JUST SCATTERED SHOWERS SATURDAY. IN FACT...MOST OF THE PRECIPITATION WILL BE IN EASTERN NEW ENGLAND...WITH JUST A FEW SHOWERS ACROSS WESTERN SECTIONS IF THE CURRENT TRACK VERIFIES. IF THE TRACK SHIFTS WEST AND WE END UP GETTING INTO HEAVIER PRECIPITATION SAT NIGHT AND EARLY SUN...DYNAMIC COOLING WOULD CHANGE PTYPE TO SNOW AT LEAST IN THE HIGHER TERRAIN. AGAIN...BASED ON EXPECTED TRACK ACCUMULATING SNOW IS A RATHER LOW PROBABILITY...BUT STILL CAN/T BE RULED OUT. WHAT EVER HAPPENS...MOST PRECIPITATION SHOULD HAVE EXITED THE REGION BY MID MORNING ON SUNDAY. STRONG WINDS... STRONG WINDS ARE THE ONE THING WE ARE FAIRLY CONFIDENT THAT WILL DEVELOP. EXCELLENT MIXING ON THE BACKSIDE OF THE STORM SHOULD RESULT IN NORTH TO NORTHWEST WIND GUSTS OF 40 TO 50 MPH DEVELOPING LATE SAT AND ESPECIALLY SUN AS MIXING INCREASES. ACROSS THE CAPE AND NANTUCKET...DEPENDING ON THE TRACK OF THE STORM MAY SEE A PERIOD OF 50 TO 60 MPH WIND GUSTS. WIND ADVISORIES MAY BE NEEDED FOR MUCH OF THE REGION AND PERHAPS HIGH WIND WATCHES/WARNINGS FOR THE CAPE AND NANTUCKET. GIVEN MANY TREES STILL HAVE AT LEAST SOME LEAVES ON THEM...THE RISK FOR TREE DAMAGE AND ISOLATED POWER OUTAGES WILL BE ENHANCED. MONDAY THROUGH WEDNESDAY... DEEP UPPER TROUGH LIFTS NORTHEAST OF THE REGION AND WE ENTER AN AREA OF UPPER LEVEL RIDGING. A SIGNIFICANT WARMING TREND EXPECTED WITH SOME OF THE COASTAL PLAIN POSSIBLY SEEING HIGHS BREAK 60 BY TUE OR WED. MAINLY DRY WEATHER OVER THIS TIME...BUT A SPOT SHOWER OR TWO IS POSSIBLE.
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&& .AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
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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. MAINLY VFR. LOW-END VFR/MVFR WITH LINE OF -RA EXPECTED TO SWEEP THE TERMINALS INTO THIS EVENING AHEAD OF WHICH SW-WINDS PREVAIL GUSTING AROUND 20-25 KTS ALONG THE S/SE SHORELINE. AN ISOLATED TSRA IS POSSIBLE OVER SE-TERMINALS...BUT NOT ENOUGH CONFIDENCE TO PREVAIL IN TAF. TONIGHT...WINDS BACK W BEHIND THE LINE...DIMINISHING. MAINLY VFR. LOW-END VFR/MVFR CIGS WITH -RA LINGER OVER S AND E TERMINALS INTO MIDNIGHT...IMPROVING AFTER AS ACTIVITY PUSHES OFFSHORE. THURSDAY...VFR. LIGHT W-WINDS. SCT CIGS 4-5 KFT ACROSS INTERIOR TERMINALS. THURSDAY NIGHT...VFR. LIGHT/VRB WINDS. SKC. SHALLOW PATCHY GROUND FOG POSSIBLE AT PRONE TERMINALS. KBOS...HIGH CONFIDENCE IN TAF. KBDL...HIGH CONFIDENCE IN TAF. OUTLOOK...FRIDAY THROUGH MONDAY... FRIDAY AND FRIDAY NIGHT...MODERATE CONFIDENCE. VFR TO START BUT ONSHORE FLOW MAY RESULT IN MVFR CIGS DEVELOPING FRI AFTERNOON AND ESPECIALLY FRI NIGHT. A SPOT SHOWER OR TWO IS POSSIBLE. SATURDAY AND SUNDAY...LOW CONFIDENCE BASED ON UNCERTAINTY OF TRACK/STRENGTH AND TIMING OF COASTAL LOW PRESSURE SYSTEM. MOST LIKELY SCENARIO IS VFR TO BE MIXED IN AT TIMES WITH MVFR SAT INTO SAT NIGHT. LOWER CONDITIONS MOST LIKELY AT THE COAST WITH RAIN OR SCATTERED SHOWERS. LOW PROBABILITY FOR A CHANGE TO SNOW AT THE END. CONDITIONS IMPROVE TO VFR BY SUNDAY...BUT NORTH TO NORTHWEST WIND GUSTS OF 30 TO 40 KNOTS EXPECTED. STRONGEST WINDS CAPE AND NANTUCKET WITH GUSTS OF 40 TO 50 KNOTS POSSIBLE. MONDAY...MODERATE TO HIGH CONFIDENCE IN VFR.
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&& .MARINE...
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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. WINDS STILL AN ISSUE ALONG THE S/SE COASTLINE WITH GUSTS UP TO 25 KTS AND WILL REMAIN SO AHEAD OF THE COLD FRONT WHICH WILL SWEEP ACROSS THE WATERS THIS EVENING. WINDS BACK W AND DIMINISH ALONG WITH THE CHANCE OF SHOWERS TOWARDS THURSDAY MORNING. SHOULD SEE SEAS GRADUALLY DIMINISH BELOW SMALL-CRAFT THRESHOLDS UNDER LIGHT W-WINDS AS HIGH PRESSURE BUILDS INTO THE REGION OVERNIGHT INTO THURSDAY. MUCH OF THE DAY THURSDAY...AND ONTO THURSDAY NIGHT... LOOKS LIKE GOOD BOATING WEATHER. OUTLOOK...FRIDAY THOUGH MONDAY... ***STORM FORCE WIND GUSTS AND 20 FOOT SEAS POSSIBLE LATE SAT INTO SUNDAY ACROSS THE EASTERN ATLANTIC WATERS*** FRIDAY...HIGH CONFIDENCE. HIGH PRESSURE TO OUR NORTH WILL RESULT IN EASTERLY WINDS OF 5 TO 15 KNOTS. GRADIENT WILL BE WEAK ENOUGH THOUGH TO KEEP WINDS SPEEDS/SEAS WELL BELOW SCA THRESHOLDS. SATURDAY AND SUNDAY...MODERATE CONFIDENCE. HIGH IMPACT MARINE EVENT EXPECTED. WHILE UNCERTAINTY REMAINS ON THE EXACT TRACK AND TIMING OF COASTAL LOW PRESSURE...GALE FORCE NORTHERLY WIND GUSTS ACROSS MOST WATERS ARE PRETTY MUCH A SLAM DUNK LATE SAT INTO SUN. IN FACT...DECENT CHANCE IN A PERIOD OF STORM FORCE WIND GUSTS WITH 20 FOOT SEAS ACROSS OUR EASTERN ATLANTIC WATERS. EXACT WIND SPEEDS AND WAVE HEIGHTS WILL DEPEND UPON THE EXACT TRACK/INTENSITY OF COASTAL LOW PRESSURE...BUT APPEARS THERE IS A GOOD CHANCE OF A HIGH IMPACT MARINE EVENT. MONDAY...MODERATE CONFIDENCE. NORTHWEST SCA WIND GUSTS AND SEAS WILL LIKELY CONTINUE MUCH OF THE DAY WITH GOOD MIXING IN THE COLD AIR ADVECTION PATTERN.
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&& .TIDES/COASTAL FLOODING...
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ASTRONOMICAL HIGH TIDES ARE NOT HIGH LATE SAT INTO SUN...BUT THERE IS EVEN A LOW PROBABILITY FOR MINOR COASTAL FLOODING. THE CONCERN IS FOR THE EARLY MORNING HIGH TIDE ON SUNDAY. IF WE END UP REALIZING 20 FOOT SEAS OVER THE OPEN OCEAN AND NORTHERLY WIND GUSTS OF 40 TO 50 KNOTS...THERE COULD BE SOME MINOR COASTAL FLOODING AND EROSION. SOME OF THE HOT SPOTS WOULD BE SALISBURY AND PLUM ISLAND...HULL...SCITUATE AND PERHAPS SANDWICH HARBOR AND NANTUCKET HARBOR. AGAIN...IT WILL DEPEND ON EXACT WIND SPEEDS/WAVE HEIGHTS OUT OVER THE OCEAN DURING THE EARLY MORNING SUNDAY HIGH TIDE CYCLE.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR ANZ231>234-250. SMALL CRAFT ADVISORY UNTIL 2 AM EDT THURSDAY FOR ANZ235-237. SMALL CRAFT ADVISORY UNTIL 8 AM EDT THURSDAY FOR ANZ254>256.
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&& $$ SYNOPSIS...FRANK/SIPPRELL NEAR TERM...SIPPRELL SHORT TERM...SIPPRELL LONG TERM...FRANK AVIATION...FRANK/SIPPRELL MARINE...FRANK/SIPPRELL TIDES/COASTAL FLOODING...FRANK

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