Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KBOX 292301 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 701 PM EDT MON SEP 29 2014 .SYNOPSIS... A COLD FRONT DROPPING THROUGH THE REGION LATE TODAY AND TONIGHT WILL BRING COOL TEMPERATURES THROUGH MOST OF THIS WEEK AS PERSISTENT NORTHEAST WINDS REMAIN IN PLACE. ONE OR TWO WEAK WAVES OF LOW PRESSURE MAY BRING THE CHANCE OF SHOWERS FOR THE REGION. AN APPROACHING FRONT WITH ASSOCIATED LOW PRESSURE LOOKS TO AFFECT SOUTHERN NEW ENGLAND FRIDAY NIGHT AND SATURDAY. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... ADJUSTED THE FORECAST TO ACCOUNT FOR CURRENT CONDITIONS. BACK DOOR COLD FRONT HAS ALREADY MOVED THROUGH A GOOD PORTION OF THE REGION. AS THIS FRONT PASSES...TEMPERATURES DROP A FEW DEGREES. HOWEVER THE MOISTURE INCREASES AND WITH A LOW TEMP/DEWPOINT SPREAD...FOG AND LOW CLOUDS HAVE PUSHED ACROSS THE EAST COAST. IN FACT BVY IS DOWN TO LESS THAN 2 MILES AND BOSTON DOWN TO 5SM. PER WEBCAMS ANTICIPATE THIS FOG TO CONTINUE TO PUSH ACROSS THE SOUTH SHORE AND ACROSS CAPE AND ISLANDS. STILL SOME QUESTIONS ON HOW FAR WESTERWARD THE FOG WILL GET. HOWEVER LOW CLOUDS WILL PUSH WELL INTO SOUTHERN NEW ENGLAND THROUGHOUT THE EVENING. ANTICIPATE DRIZZLE TO DEVELOP AS WELL OVERNIGHT. OTHERWISE BULK OF THE FORECAST REMAINS ON TRACK. PREVIOUS DISCUSSION... CLOUD COVER HAS ONCE AGAIN REGAINED CONTROL ACROSS THE AREA AFTER A BRIEF BREAK WITH MORE SUN THAN CLOUDS EARLIER THIS AFTERNOON. THIS HAS OCCURRED AS THE TWO MOISTURE STREAMS...ONE TO THE N ASSOCIATED WITH A DIGGING UPPER LVL CUTOFF AND BACKDOOR- ESQUE COLD FRONT AND A DEVELOPING MID ATLANTIC COASTAL LOW PRES. USING A MIX OF CURRENT SFC OBS AND MSAS ISALLOBARIC FLOW...THE COLD FRONT LOOKS TO HAVE BEGUN SLIDING INTO THE REGION...AND IS CURRENTLY DRAPED NEAR THE CT VALLEY INTO SE MA. NE FLOW HAS ALREADY DEVELOPED AND BEGUN TO INCREASE ACROSS THE REGION BEHIND THE FRONT AS IT SLIDES THROUGH. AS THE FRONT CONTINUES TO MAKE SW MOVEMENT AND OUT OF THE BOX CWA DURING THE OVERNIGHT HOURS...COOLER MARINE FLOW OFF THE GULF OF MAINE WHERE SST/S ARE AROUND 60F WILL BE UNDERCUTTING WARMER MOIST AIR JUST ABOVE THE SFC. THE REMNANTS OF A MID LVL RIDGE IS ALSO PRESENT AS A MID LOW-MID LVL DRY LAYER. THEREFORE...LOOKS LIKE A GOOD SETUP FOR LOW CLOUDS AND DRIZZLE TO FORM ACROSS THE AREA DURING THE OVERNIGHT HOURS FROM NE TO SW. LIKED PREVIOUS FORECASTER/S THINKING ON THIS SO FOLLOWED THEIR LEAD FAIRLY CLOSELY. IT LOOKS LIKE...AT LEAST THANKS TO THE CONTINUED N-NE FLOW THAT THERE MAY BE JUST ENOUGH NEAR SFC MIXING TO PRECLUDE FOG IN FAVOR OF DRIZZLE CAUSING VSBY REDUCTIONS. HOWEVER...A FEW PATCHES OF DENSE FOG CAN/T BE RULED THANKS TO THE COOLER MOIST FLOW MOVING INLAND. BY EARLY MORNING...A WEAK INVERTED TROF LOOKS TO DEVELOP BETWEEN THE OFFSHORE SYSTEM MOVING S OF THE REGION AND THE UPPER LVL CUTOFF. THIS MAY LEAD TO AN INCREASING THREAT FOR -SHRA RATHER THAN DRIZZLE...PARTICULARLY FOR EASTERN PORTIONS OF THE FORECAST AREA...REFLECT THIS AS INCREASING POPS TO CHANCE OVERNIGHT. LOWS OVERNIGHT DIP BACK INTO INTO THE 50S...NOT AS COOL AS WOULD BE POSSIBLE GIVEN THE OVERNIGHT CLOUD COVER AND MOIST AIR. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... TOMORROW... INVERTED TROF AND N-NE FLOW REMAINS IN PLACE THROUGH THE MORNING SO IT MAY TAKE SOME TIME FOR DRIZZLE...FOG AND LOWER CLOUDS TO COMPLETELY COME TO AN END. IN FACT...-SHRA MAY LINGER INTO THE AFTERNOON IN THE E. HOWEVER...THANKS TO SOME DIURNAL BL MIXING...SUSPECT THAT THERE WILL BE A BREAK IN THE DRIZZLE ACROSS MUCH OF THE AREA...WITH ONLY THE WIDELY SCT -SHRA IN THE E. NOT EXPECTING A WASHOUT BY ANY MEANS AS THERE IS LITTLE BAROCLINICITY. OTHERWISE...HIGH TEMPS GENERALLY BELOW NORMAL. ALTHOUGH EVEN 2M TEMPS HAVE WARMED IN RECENT RUNS INTO THE LOW-MID 60S. TOMORROW NIGHT... FAIRLY SIMILAR SETUP TO TONIGHT ALTHOUGH SLIGHTLY BETTER CHANCE FOR PRECIP AS UPPER LVL CUTOFF BEGINS TO SHIFT WITH IT/S BASE MOVING INTO THE REGION BY MORNING. THEREFORE...GIVEN SIMILAR SETUP AND COLUMN ACROSS THE AREA...SUSPECT THERE WILL BE SOME DRIZZLE...FOG AND SHOWERS CONTINUING WITH MIN TEMPS ONCE AGAIN FALLING BACK INTO THE 50S. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... HIGHLIGHTS... * NORTHEAST WINDS AND CLOUDS THIS WEEK WILL KEEP TEMPS NEAR NORMAL * CHANCE FOR SHOWERS AND DRIZZLE ON WED AND THU * COLD FRONTAL PASSAGE ON SATURDAY WILL BRING PRECIP TO THE REGION OVERVIEW... FALL IS HERE TO STAY FOR SOUTHERN NEW ENGLAND AS 12Z GUIDANCE CONTINUES TO SHOW PERSISTENT NORTHEASTERLY WINDS. OVERALL THE 12Z GUIDANCE IS IN GENERALLY AGREEMENT WITH THE UPPER LEVEL PATTERN WITH ISSUES DOWN AT THE SURFACE. THE TREND FOR THE GLOBAL GUIDANCE IS THAT THE EC IS MORE AMPLIFIED WHERE THE GFS IS MORE PROGRESSIVE IN THE OVERALL PATTERN. THE CMC IS ALSO LESS AMPLIFIED THEN THE EC WHERE THE UKMET IS THE IN BETWEEN MODEL. BECAUSE OF THE DIFFERENCES IN GUIDANCE DID A MODEL BLEND AS WELL AS HPC FORECAST FOR THE EXTENDED. HAVE A HIGHER CONFIDENCE THAT AVERAGE TEMPS WILL OCCUR ACROSS THE REGION THIS WEEK. LOW CONFIDENCE ON THE PRECIP POTENTIAL FOR WED AND THURSDAY. HIGH CONFIDENCE THAT PRECIP WILL OCCUR ON SATURDAY BUT STILL TOO MUCH UNCERTAINTY ON TIMING AND WHO WILL SEE THE HIGHER QPF. DETAILS... WEDNESDAY THROUGH THURSDAY... UPPER LEVEL LOW WILL CUT OFF RIGHT OVER SOUTHERN NEW ENGLAND DURING THIS TIME FRAME...KEEPING A SURFACE TROUGH/NORTHEASTERLY FLOW OVER THE REGION. THIS LOW WILL BRING A FEW SHORTWAVES ACROSS THE REGION INCREASING THE POTENTIAL FOR SCT SHOWERS. EASTERN MA HAS THE BEST CHANCE TO SEE ACCUMULATING PRECIP ESPECIALLY ON WED INTO WED NIGHT. ANTICIPATE DRIZZLE AND FOG FOR THURSDAY ESP IN EASTERN AREAS AS UPPER LEVEL LOW BEGINS TO MOVE OFFSHORE AND UPPER LEVEL RIDGE INCHES EASTWARD INTO THE REGION. THUNDER IS NOT ANTICIPATED ON WED AS THE MARINE LAYER WILL KEEP THE ATMOSPHERE STABLE AND GUIDANCE IS NOT SHOWING ANY INSTABILITY AT THIS TIME. TEMPERATURES WILL BE AT OR BELOW NORMAL FOR THIS TIMEFRAME. FRIDAY... QUICK MOVING RIDGE WILL CREST OVER THE REGION ON FRIDAY. THIS WILL ALLOW FOR RETURN FLOW AND TEMPS INTO THE UPPER 60S TO LOW 70S. DRY WEATHER SHOULD PREVAIL AS WE WILL BE BETWEEN SYSTEMS. WEEKEND... STRONG UPPER LEVEL TROUGH WILL SWING THROUGH THE GREAT LAKES ON FRIDAY AND IMPACT SOUTHERN NEW ENGLAND ON SATURDAY. THIS WILL PUSH A COLD FRONT THROUGH THE REGION AND BRING SOME MUCH NEEDED RAINFALL. STILL A LOT OF UNCERTAINTY IN REGARDS TO THE DETAILS OF THIS SYSTEM AS THE EC SEEMS TO BE OUT OF PHASE WITH THE MAJORITY OF THE GUIDANCE. THEREFORE TRENDED MORE TOWARDS THE 12Z GFS AND ENSEMBLES FOR THIS PORTION. NOTE THAT IT APPEARS THAT THE ENERGY ASSOCIATED WITH THIS SYSTEM DOES GET STRETCHED AND IS NOT AS ROBUST AS IT IS ACROSS UPSTATE NEW YORK. THE OTHER POINT IS THAT THE RIDGE ON FRIDAY...HOW STRONG WILL IT GET AND HOW MUCH DRY AIR WILL LINGER AS THE FRONT APPROACHES THE REGION ON SATURDAY. RIGHT NOW PLAN ON KEEPING CHC POPS TO THE SOUTH AND LIKELY POPS TO THE NORTH...CLOSER TO THE UPPER LEVEL ENERGY. HOPEFULLY GUIDANCE WILL LINE UP WITHIN THE COMING DAYS. TRENDING WITH THE GFS/CMC...HIGH PRESSURE WILL BUILD IN ON SUNDAY BUT STILL COULD SEE SOME ISOLATED SHOWERS LINGER EARLY SUN MORNING ACROSS THE CAPE AND ISLANDS. CAA BEHIND THE FRONT WILL KEEP TEMPS BELOW AVERAGE WITH BREEZY CONDITIONS. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...HIGH CONFIDENCE ON TRENDS BUT LOWER CONFIDENCE IN TIMING OF LOWER CATEGORIES THIS EVENING. INTO TONIGHT... VFR WILL GRADUALLY DIP TO MVFR WITH POCKETS OF IFR THROUGH THE EVENING AND EARLY OVERNIGHT. LOW CIGS WITH SOME DRIZZLE AND FOG WILL START IN NE MA AND SE NH...THEN GRADUALLY MOVE TOWARD THE SW...REACHING THE CT VALLEY AND S COASTS THE LATEST. THEN...MVFR/IFR REMAINS IN CONTROL THE REST OF THE NIGHT UNDER PERSISTENT NELY WINDS. TOMORROW AND TOMORROW NIGHT... GENERALLY MORE OF THE SAME...ALTHOUGH CONDITIONS DURING THE DAY MAY IMPROVE TO VFR MID MORNING-MID DAY. SOME SHOWERS /HEAVIER THAN THE OVERNIGHT DRIZZLE...BUT NOT TOO HEAVY/ ARE POSSIBLE ESPECIALLY EARLY IN THE DAY ACROSS E MA AND RI. ANOTHER ROUND OF LOW CLOUDS AND FOG AND POSSIBLE DRIZZLE EXPECTED TOMORROW NIGHT. KBOS TERMINAL...HIGH CONFIDENCE IN TRENDS. MVFR/IFR CIGS OVERNIGHT. KBDL TERMINAL...HIGH CONFIDENCE IN TAF TRENDS BUT LOWER CONFIDENCE ON EXACT DETAILS. OUTLOOK...WEDNESDAY THROUGH SATURDAY... WEDNESDAY...MODERATE CONFIDENCE. WIDESPREAD MVFR CIGS AND VSBYS IN SHOWERS. PATCHY IFR CIGS/VSBYS POSSIBLE ACROSS EAST COASTAL SECTIONS WEDNESDAY NIGHT. THURSDAY AND FRIDAY...MODERATE CONFIDENCE. MAY SEE LEFTOVER MVFR CIG/VSBYS EARLY THU ALONG THE E COAST BUT CONDITIONS WILL IMPROVE FROM WEST TO EAST ON THURSDAY TO VFR. FRIDAY WILL BE VFR. SATURDAY...HIGH CONFIDENCE. CONDITIONS WILL LOWER TO MVFR TO LOCAL IFR IN A LINE OF SHOWERS MOVING FROM WEST TO EAST THROUGHOUT THE DAY. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...HIGH CONFIDENCE THROUGH TUE NIGHT. TONIGHT... WINDS SHIFT NE ACROSS ALL WATERS THROUGH THE OVERNIGHT HOURS WITH A FEW GUSTS NEAR 25 KT AND SEAS 4-5 FT MAINLY OVER THE WATERS SURROUNDING CAPE ANN. ELSEWHERE...LESS OF A RISK FOR SMALL CRAFT ADVISORY CONDITIONS ALTHOUGH INCREASING RISK FOR DRIZZLE AND FOG AND LOWER VSBYS. TOMORROW AND TOMORROW NIGHT... NE FLOW CONTINUES. THIS PROLONGED NE FETCH WILL YIELD A GRADUALLY BUILDING SWELL WHICH COULD APPROACH 5 FT BY LATE TOMORROW NIGHT. SMALL CRAFT ADVISORIES MAY ONCE AGAIN BE NEEDED FOR THIS RISK. OTHERWISE...NE WIND GUSTS GENERALLY REMAIN BELOW 20 KT. ANOTHER ROUND OF FOG AND DRIZZLE POSSIBLE ESPECIALLY DURING THE OVERNIGHT HOURS TOMORROW NIGHT. OUTLOOK...WEDNESDAY THROUGH SATURDAY... PERSISTENT NORTHEAST WINDS WILL BE IN PLACE ACROSS THE WATERS THROUGH THURSDAY NIGHT. COMBINED WITH EASTERLY SWELL WILL HELP BUILD SEAS UP TO 5-7 FEET. SCA WILL BE NEEDED. WEAK HIGH PRESSURE WILL MOVE OVER THE WATERS ON FRIDAY ALLOWING FOR BOTH SEAS AND WINDS TO RELAX. LINGERING SEAS OF 5 OR 6 FEET WILL KEEP THE SCA IN PLACE FOR THE OUTER WATERS. APPROACHING COLD FRONT ON SATURDAY WILL ALLOW FOR RETURN FLOW AND INCREASE IN GUSTS...CLOSE TO 30 KTS. SEAS WILL ALSO BUILD AHEAD OF AND BEHIND THE FRONT...NEAR 7 FEET. SCA WILL BE NEEDED. MAY EXPERIENCE A STORM SURGE OF 1 TO 1.5 FEET DURING MIDWEEK BUT THE ASTRONOMICAL TIDES ARE NOT ALL THAT HIGH. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 11 AM EDT TUESDAY FOR ANZ250-251. && $$ SYNOPSIS...DOODY/DUNTEN NEAR TERM...DOODY/DUNTEN SHORT TERM...DOODY LONG TERM...DUNTEN AVIATION...DOODY/DUNTEN MARINE...DOODY/DUNTEN

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.