Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 232358 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 658 PM EST SUN NOV 23 2014 .SYNOPSIS... A WARM FRONT WILL BRING A BRIEF PERIOD OF HEAVY RAIN AND STRONG WINDS ALONG THE SOUTHEAST COAST MONDAY MORNING...FOLLOWED BY UNSEASONABLY MILD CONDITIONS MONDAY AFTERNOON. QUIET AND MILD TUESDAY WITH SOME GUSTY SW-WINDS. STORM SYSTEM ANTICIPATED WEDNESDAY INTO THURSDAY MORNING...YET SPECIFIC OUTCOMES REMAIN UNCERTAIN. GRADUALLY TURNING COLDER INTO THE WEEKEND. && .NEAR TERM /THROUGH MONDAY/...
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7 PM UPDATE...NO MAJOR CHANGES TO THE FORECAST. ***BRIEF PERIOD OF HEAVY RAIN MONDAY MORNING ALONG WITH STRONG WINDS ACROSS SOUTHEAST NEW ENGLAND*** TONIGHT AND MONDAY MORNING... 1) BRIEF PERIOD OF HEAVY RAIN DRY CONDITIONS WILL PREVAIL THIS EVENING...BUT THE WEATHER WILL RAPIDLY DETERIORATE FROM SOUTHWEST TO NORTHEAST BETWEEN 6Z AND 12Z MONDAY. LOW PRESSURE WORKING UP TOWARDS THE GREAT LAKES WILL INDUCE A STRONG SOUTHERLY LOW LEVEL JET. THIS WILL TRANSPORT DEEP MOISTURE NORTHWARD AS PWATS CLIMB TO BETWEEN 3 AND 4 STANDARD DEVIATIONS ABOVE NORMAL. THAT COMBINED WITH STRONG FORCING SHOULD YIELD A BRIEF PERIOD OF HEAVY RAIN. THUNDER INDICES ARE MARGINAL BUT ENOUGH FORCING COULD GENERATE AND ISOLATED THUNDERSTORM OR TWO ACROSS THE FAR SOUTHEAST NEW ENGLAND COAST. FORTUNATELY THE SYSTEM IS FAIRLY PROGRESSIVE...SO EXPECT THE STEADY/HEAVY RAIN TO BE OVER BY MONDAY AFTERNOON. RAINFALL AMOUNTS SHOULD BE ON THE ORDER OF 0.50 TO 1 INCHES IN MOST LOCALES...BUT CAN/T RULE OUT SOME LOCALLY HIGHER AMOUNTS...ESPECIALLY IF WE CAN GENERATE ANY ISOLATED CONVECTION IN OUR SOUTHEAST ZONES. SO NOT CONCERNED ABOUT ANY SIGNIFICANT FLOODING...OTHER THAN TYPICAL NUISANCE POOR DRAINAGE STREET FLOODING WHICH WILL UNFORTUNATELY COINCIDE WITH THE MONDAY AM RUSH HOUR. 2) STRONG WIND GUSTS POTENTIAL ACROSS THE SOUTHEAST COAST THE OTHER CONCERN WILL BE THE POTENTIAL FOR A PERIOD OF STRONG SOUTHERLY WIND GUSTS ACROSS SOUTHEAST NEW ENGLAND...ESPECIALLY MONDAY MORNING. GIVEN THE INVERSION...ITS ALWAYS TRICKY TO SEE HOW MUCH WIND WILL BE ABLE TO MAKE IT DOWN TO THE GROUND. LOW LEVEL JET AT 850 MB IS AROUND 80 KNOTS ALONG THE SOUTHEAST NEW ENGLAND COAST BETWEEN 12Z AND 16Z. TAKING HALF OF THAT OFTEN CAN GET YOU IN THE BALL PARK OF WHAT WILL BE REALIZED AT THE SURFACE. THIS WOULD RESULT IN WIND ADVISORY CRITERIA BEING MET ACROSS OUR SOUTHEAST ZONES. THEREFORE...HAVE HOISTED A WIND ADVISORY FOR SOUTHERN RHODE ISLAND AND FAR SOUTHEAST MA MONDAY MORNING. THIS IS FOR THE POTENTIAL FOR A PERIOD OF SOUTHERLY WIND GUSTS OF 40 TO 50 MPH. IF WE CAN GET A FINE LINE GOING...CONFIDENCE WOULD INCREASE MORE IN BEING ABLE TO BRING THE STRONG WINDS DOWN TO THE GROUND. NONETHELESS...STILL THOUGHT IT WAS WORTH THE ADVISORY. MONDAY AFTERNOON... THE STRONG MID LEVEL LIFT/MOISTURE WILL HAVE LIFTED TO OUR NORTHEAST BY MONDAY AFTERNOON. THEREFORE...THE STEADY AND HEAVY RAIN WILL HAVE COME TO AN END. WE WILL STILL HAVE A LOT OF LOW LEVEL LIFT/MOISTURE AROUND FOR A FEW PASSING SHOWERS SO MAINTAINED SOME POPS. OTHERWISE...IT LOOKS LIKE A VERY MILD DAY IN STORE FOR THE REGION WITH 850 MB TEMPS ON THE ORDER OF +10 TO +12C. DESPITE A LOT OF CLOUDS...STRONG SOUTHERLY FLOW SHOULD ALLOW HIGHS TO SURGE WELL INTO THE 60S. NOT SURE IF WE WILL SEE MUCH SUN GIVEN SO MUCH LOW LEVEL MOISTURE...BUT IF WE END UP WITH MORE THAN EXPECTED SOME LOCATIONS COULD REACH OR EXCEED 70. REGARDLESS...WILL ACTUALLY FEEL A BIT MUGGY FOR LATE NOVEMBER STANDARDS...WITH DEWPOINTS CLOSE TO 60! ALSO...THERE IS A LOT OF WIND JUST OFF THE DECK INTO MONDAY AFTERNOON. WE COULD SEE GUSTS OF 30 TO 40 MPH DEVELOP EVEN IN THE INTERIOR...DEPENDING ON IF WE CAN MUSTER ANY PEEKS OF SUNSHINE.
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&& .SHORT TERM /MONDAY NIGHT/...
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MONDAY NIGHT... STRONG SOUTHWESTERLY LOW LEVEL JET WILL NOT ALLOW WINDS TO DECOUPLE. THIS COMBINED WITH UNSEASONABLY WARM 850 MB TEMPERATURES WILL RESULT IN AN UNSEASONABLY MILD NIGHT. LOW TEMPERATURES WILL HOLD IN THE 50S IN MOST LOCATIONS! MUCH OF THE NIGHT WILL BE DRY...BUT A FEW SPOT SHOWERS WILL BE POSSIBLE DURING THE FIRST PART OF THE NIGHT.
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&& .LONG TERM /TUESDAY THROUGH SUNDAY/... */ HIGHLIGHTS... - DRY AND MILD TUESDAY - STORM WEDNESDAY INTO THURSDAY...TRAVEL IMPACTS - TURNING COLDER INTO THE WEEKEND */ OVERVIEW AND MODEL CONSENSUS... MAIN FOCUS IS ON THE WEDNESDAY - THURSDAY TIMEFRAME. IN AGREEMENT WITH WPC: CONTINUED SPREAD OF GUIDANCE UPSTREAM RESULTING IN THE POOR RESOLVING OF DOWNSTREAM IMPACTS. INDIVIDUAL MODEL SOLUTIONS / ENSEMBLES STILL UNDECIDED ON THE RELATIVE TRACK / STRENGTH OF DOWN- STREAM ENERGY ACROSS THE NE-CONUS. DIFFICULT TO RESOLVE DETAILS ACROSS THE REGION OF WHICH WE MAY NOT KNOW THE TRUE OUTCOMES TILL ABOUT 2-3 DAYS PRIOR. NEVERTHELESS...CONTINUE TO WEIGH PREFERENCE UPON THE W-ENVELOPE OF FORECAST SOLUTIONS. BELIEVE THE 23.6Z / 23.12Z GFS AND THE 23.12Z EC ENSEMBLE MEAN OFFER THE MOST REASONABLE NE-TRACK OF THE SYSTEM IN THE VICINITY OF THE 40N/70W BENCHMARK S OF NANTUCKET. AGREE WITH WPC NOTING THERE HAS BEEN A WIDE SPREAD OF EC DETERMINISTIC SOLUTIONS ON THE W-HALF OF THE GUIDANCE ALONG WITH THE UKMET...WHILE THE CANADIAN REMAINS TO THE RIGHT. EXPECT A MODERATE DEVELOPMENT OF THE SYSTEM WHICH WILL RESULT IN IMPACTS ACROSS THE REGION...THOUGH THERE REMAINS A SIGNIFICANT AMOUNT OF UNCERTAINTY ON BOTH THE STRENGTH AND THE EXACT TRACK OF THE SYSTEM. ASIDE...EXPECTING SOME SORT OF RAIN AND / OR SNOW BAND SOMEWHERE ACROSS S NEW ENGLAND...WITH A CLIMATOLOGICAL PREFERENCE OF RAIN OVER COASTAL COMMUNITIES AND SNOWS FOR THE INTERIOR. THE ONLY CERTAINTY TO THE FORECAST IS THE TIMING OF THE SYSTEM OF WHICH IMPACTS ARE ANTICIPATED TO BEGIN DURING THE DAY WEDNESDAY... INCREASING INTO THE EVENING WITH THE HEIGHT OF THE STORM AROUND MIDNIGHT THURSDAY. MODEL CONSENSUS HAS THE STORM CONCLUDING THURSDAY MORNING. DETAILS... TUESDAY INTO TUESDAY NIGHT... DRY AND MILD. HIGH PRESSURE IN CONTROL BENEATH THE DRY-SLOT REARWARD OF THE DEPARTING LOW OVER THE ST LAWRENCE RIVER VALLEY IN CANADA. AM EXPECTING BLUSTERY SW-FLOW WITH GUSTS 30-35 MPH ALONG THE S-COAST. WINDS RELAXING INTO THE EVENING. LIGHT FLOW OVERNIGHT COULD MAKE FOR A GOOD RADIATIVE COOLING SETUP. BUT ANTICIPATING MID- TO HIGH-LEVEL CLOUDS TO INCREASE FROM THE S INTO WEDNESDAY MORNING LIMITING THE POTENTIAL. WEDNESDAY INTO WEDNESDAY NIGHT... SYNOPTICALLY...SUCCESSIVE PACIFIC-IMPULSES MAINTAIN AN OPEN-WAVE H5 TROUGH INTO THE GULF. UNDERGOING A NEGATIVE-TILT ACROSS THE E-CONUS INITIATES AND INTENSIFIES AN AREA OF LOW PRESSURE FROM THE N-GULF NE OVER THE W-ATLANTIC ACROSS THE 40N/70W BENCHMARK S OF NANTUCKET BY MIDNIGHT THURSDAY. NO APPRECIABLE DOWNSTREAM BLOCKING SIGNIFIES A PROGRESSIVE-FLOW PATTERN /+NAO/ RESULTING IN THE ABSENCE OF A CLOSED- LOW PATTERN ABOVE H7 /LESS EMPHASIS OF A CYCLONIC BRANCH OF THE WARM CONVEYER BELT/...WHILE LOW PRESSURE TROUGHING OVER THE GREAT LAKES ASSOCIATED WITH A STRONG POLAR-LOW HOLDS ARCTIC AIR REARWARD ACROSS C-CANADA /+AO/ RESULTING IN THERMAL PROFILES AROUND THE FREEZING MARK OVER S NEW ENGLAND. TOWARDS EVENING...BAROCLINIC LEAF / OVER-RUNNING PATTERN OF BROAD- SCALE ASCENT YIELDS TOP-DOWN MOISTENING DYNAMICALLY COOLING WITH TIME. WITH SURFACE INTERIOR N-FLOW WITH COASTAL NE-FLOW...AND MODEST W-COMPONENT OF AGEOSTROPHIC FLOW...AND DRIER AIR N/W INITIALLY...AM EXPECTING WETBULBING TOWARDS THE DEWPOINT AROUND THE FREEZING MARK THE DIVISION OF WHICH MAY BE ALONG A POSSIBLE COASTAL FRONT SETUP. OVERNIGHT...INTENSIFYING LOW SWEEPS NE IN THE VICINITY OF THE 40N / 70W BENCHMARK S OF NANTUCKET. WITH A PROGRESSIVE FLOW-PATTERN AND LACK OF A CLOSED LOW ABOVE H7...MUCH OF THE EMPHASIS IS WITH THE ANTI-CYCLONIC BRANCH OF THE WCB. NEVERTHELESS A FRONT-END THUMP IS ANTICIPATED WITH SLANTWISE ASCENT / FORCING PER FRONTOGENESIS NW OF H85 LOW EXTENDED E...ALONG WITH INDICATIONS OF WEAK TROWALING TOWARD THE NW-QUADRANT OF THE LOW. BENEATH ENHANCED ASCENT PER MID-LEVEL IMPULSE AND RRQ OF THE UPPER-LEVEL-JET...STRONG DEEP-LAYER LIFT THROUGH MOIST DENDRITIC ZONES SHOULD YIELD A SW-NE BAND SIGNATURE ACROSS S NEW ENGLAND...THOUGH WHERE EXACTLY REMAINS UNCERTAIN AS IS THE EXACT TRACK AS WELL AS THE DEPTH / STRENGTH OF THE STORM. IF A COASTAL FRONT SETUP EMERGES BENEATH NEAR-ISOTHERMAL PROFILES JUST BELOW FREEZING UP TO H7 PER THE PREFERRED MODEL SOLUTIONS NOTED EARLIER...THEN WOULD EXPECT INTERIOR SNOWS /WITH A NEAR 1:10 RATIO/ AND COASTAL RAINS. KEY TO THIS ENTIRE FORECAST IS THE TRACK OF THE H85 LOW ALONG WITH H925 TEMPERATURES AT OR BELOW -2C. THE DIVIDING LINE IS VARIED AMONG PREFERRED MODEL SOLUTIONS. CIPS ANALOG GUIDANCE DOES WEIGH SOME INDICATION PER PROBABILITIES OF > 2 INCHES OF SNOW. LOW CONFIDENCE FORECAST. 23.12Z EC / UKMET CONTINUE TO BE ON THE WARMER-END OF SOLUTIONS. IF THE 23.12Z GFS / GEFS AND 23.15Z SREF ARE CORRECT WITH THE TRACK OF THE H85 / SURFACE LOW...WHICH IS IN THE MIDDLE OF THE GUIDANCE SPREAD /CANADIAN THE FAR E SOLUTION/ THEN WOULD EXPECT A PLOWABLE SNOW ACROSS THE INTERIOR N/W OF THE I-95/495 CORRIDOR...KEEPING IN MIND THERE IS LIKELY WIGGLE ROOM OF THE RAIN / SNOW BAND DUE TO THE UNCERTAINTY IN THERMAL PROFILES THIS FAR OUT IN THE FORECAST. SO WITH THAT BEING SAID...WILL NOT ISSUE OUT ANY SNOW- FALL GRAPHICS WITH THIS FORECAST. THERE IS ABSOLUTELY NO CERTAINTY AS TO SNOW-OUTCOMES. CIPS ANALOGS HAVE TONED DOWN ON THE WIND PROBABILITIES. BUT WITH THE AFOREMENTION MODEL PREFERENCE...WILL NEED TO WATCH THE NE-FLOW OVER E MA INCLUDING CAPE COD AND THE ISLANDS. GUSTS EXCEEDING 45 MPH ARE POSSIBLE BUT DEPENDENT ON HOW STRONG THE STORM ACTUALLY GETS...WHICH AGAIN IS UNCERTAIN. FORECAST TIDES OF 10 FEET EXPECTED AT BOSTON SHORTLY AFTER MIDNIGHT THURSDAY. ANTICIPATING A SHORT-RESIDENCY TIME OF THE STORM...PERHAPS A MINOR SURGE AND MAYBE SOME SPLASHOVER IF THE NE-WINDS DISCUSSED ABOVE VERIFY. ALL SORTS OF DEPENDENCIES AND INTANGIBLES. ITS A HARD KNOCK LIFE. THANKSGIVING AND BEYOND... CONTINUED PACIFIC ENERGY ROTATING THROUGH THE BROADER OPEN-WAVE H5 TROUGH WILL TO NEED TO BE MONITORED AS TO WHETHER MID-LEVEL IMPULSES INVOKE ANOTHER OFFSHORE LOW AROUND FRIDAY. ONCE THE H5 TROUGH PUSHES THROUGH THE REGION...EXPECT THE RETURN OF BELOW-AVERAGE TEMPERATURES USHERED BY NW-FLOW. && .AVIATION /00Z MONDAY THROUGH FRIDAY/...
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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 MONDAY NIGHT/... TONIGHT INTO MONDAY...MODERATE CONFIDENCE. VFR THIS EVENING. CONDITIONS DETERIORATE SW TO NE 6-12Z WITH RAIN AND A LOW RISK OF TSRA LINGERING THROUGH MONDAY MORNING. MIX OF MVFR-IFR...IFR-LIFR WITH +RA / TSRA. S-WINDS 35-40 KTS WITH LLWS 2 KFT OUT OF THE S AROUND 45 KTS. RAIN PUSHES E AROUND MIDDAY...THOUGH MVFR-IFR CONDITIONS CONTINUE WITH S-WINDS AROUND 35 KTS. SPOT SHOWERS AND THE THREAT OF LLWS OUT OF THE SW LINGERS. MONDAY NIGHT...MODERATE CONFIDENCE. MVFR-IFR CONDITIONS IMPROVE TO VFR OVER N/W TERMINALS OF S NEW ENGLAND. BLUSTERLY SW-WINDS CONTINUE. KBOS TERMINAL...MODERATE CONFIDENCE. POTENTIAL WIGGLE IN TIMING SPECIFICS. WILL KEEP IFR OUT OF THE FORECAST WITH EXPECT GUSTY S-WINDS. KBDL TERMINAL...MODERATE CONFIDENCE. LLWS WILL BE OF GREAT CONCERN WITH WEAK E-FLOW WINDS WITH MODERATE RAIN. POTENTIAL WIGGLE IN TIMING SPECIFICS. WITH ANY +RA ANTICIPATE IFR IMPACTS. OUTLOOK...TUESDAY THROUGH FRIDAY. TUESDAY THROUGH TUESDAY NIGHT...MODERATE CONFIDENCE. W/SW-FLOW DIMINISHING THROUGH TUESDAY WITH GUSTS OF AROUND 30 KTS OVER SE-COASTAL TERMINALS INITIALLY TUESDAY MORNING. VFR. WEDNESDAY INTO THURSDAY MORNING...LOW CONFIDENCE. SIGNIFICANT STORM ANTICIPATED. POSSIBLE THREATS OF A PLOWABLE SNOW OVER INTERIOR S NEW ENGLAND...WITH STRONG NE WINDS OVER E MA / CAPE COD / ISLANDS...MAYBE EVEN +RA. MIX OF IFR-VLIFR ANTICIPATED. STORM IMPACTS BEGINNING WEDNESDAY ENHANCING WEDNESDAY NIGHT. HEIGHT OF THE STORM AROUND MIDNIGHT THURSDAY...CONCLUDING INTO THURSDAY MORNING. LATER-THURSDAY INTO FRIDAY...LOW CONFIDENCE. IMPROVING VFR. BUT MUCH OF THIS DEPENDS ON STORM MORPHOLOGY.
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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 MONDAY NIGHT/...MODERATE CONFIDENCE. 7 PM UPDATE...NO MAJOR CHANGES TO THE FORECAST. DEEPENING LOW LIFTING TOWARDS THE GREAT LAKES WILL INDUCE STRONG WINDS ALOFT MONDAY MORNING. WHILE POTENTIAL MIXING TO THE SURFACE WILL BE LIMITED...STILL THINK THERE IS A DECENT SHOT OF SOUTHERLY 35-40 KT GUSTS. SUCH GALE-FORCE WIND GUSTS MAY CONTINUE INTO MONDAY EVENING OUT OF THE SW. GALE WARNINGS HOISTED FOR ALL WATERS EXCEPT BOSTON HARBOR. SEAS SHOULD BUILD TO BETWEEN 10 AND 15 FEET ACROSS THE SOUTHERN WATERS. OUTLOOK...TUESDAY THROUGH FRIDAY. TUESDAY INTO TUESDAY NIGHT...MODERATE CONFIDENCE. WINDS TURNING W/SW REMAINING BLUSTERY WITH GUSTS AROUND 30 KTS FOR TUESDAY MORNING...RELAXING THROUGH THE DAY. WAVES AROUND 10 FEET ON THE OUTER WATERS TUESDAY MORNING...DIMINISHING THEREAFTER. WEDNESDAY INTO THURSDAY...LOW CONFIDENCE. SIGNIFICANT STORM ANTICIPATED PASSING NEAR THE 40N/70W BENCHMARK S OF NANTUCKET. POSSIBLE THREATS OF STRONG NE GALES OVER E MA / CAPE COD / ISLANDS...INCLUDING ALL ADJACENT AND OUTER WATERS. HEAVY RAIN LENDING TO REDUCED VISIBILITIES AT TIMES. STORM IMPACTS BEGINNING WEDNESDAY ENHANCING WEDNESDAY NIGHT. HEIGHT OF THE STORM AROUND MIDNIGHT THURSDAY...CONCLUDING INTO THURSDAY MORNING.
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&& .TIDES/COASTAL FLOODING...
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ASTRONOMICAL TIDES ARE FAIRLY HIGH DURING THE MON MORNING HIGH TIDE CYCLE. WITH SOUTHERLY GALES EXPECTED...A STORM SURGE OF 1-2 FT IS LIKELY ALONG THE SOUTH COAST. THIS MAY BRING A FEW LOCATIONS TO MINOR FLOOD. THE MAIN THREAT FOR MINOR COASTAL FLOODING WILL BE ALONG NARRAGANSETT BAY AND WESTPORT HARBOR DUE TO SOUTHERLY FETCH. COASTAL FLOOD ADVISORIES HAVE BEEN ISSUED FOR THE SOUTH COAST. NO FLOODING IS EXPECTED ALONG THE EAST COAST.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...WIND ADVISORY FROM 5 AM TO 2 PM EST MONDAY FOR MAZ018>024. COASTAL FLOOD ADVISORY FROM 7 AM TO 11 AM EST MONDAY FOR MAZ020>022. NH...NONE. RI...WIND ADVISORY FROM 5 AM TO 2 PM EST MONDAY FOR RIZ003>008. COASTAL FLOOD ADVISORY FROM 7 AM TO 11 AM EST MONDAY FOR RIZ002-004>007. MARINE...GALE WARNING FROM 5 AM TO 10 PM EST MONDAY FOR ANZ231>235-237- 250-251-254>256. SMALL CRAFT ADVISORY FROM 5 AM TO 10 PM EST MONDAY FOR ANZ230. GALE WARNING FROM 5 AM TO 2 PM EST MONDAY FOR ANZ236. && $$ SYNOPSIS...FRANK/SIPPRELL NEAR TERM...FRANK/SIPPRELL SHORT TERM...FRANK LONG TERM...SIPPRELL AVIATION...FRANK/SIPPRELL MARINE...FRANK/SIPPRELL TIDES/COASTAL FLOODING...FRANK

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