Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 151950 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 350 PM EDT TUE APR 15 2014 .SYNOPSIS...
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A STRONG COLD FRONT WILL BRING GUSTY WINDS...SOAKING RAIN...AND POSSIBLY EVEN A BRIEF CHANGE TO A WINTRY MIX BEFORE ENDING DURING THE EARLY MORNING HOURS WED. HIGH PRESSURE BUILDING IN WILL BRING DRY BUT UNSEASONABLE CHILLY AIR TO THE REGION WED/WED NIGHT. DRY WEATHER CONTINUES THU INTO THE FIRST PART OF FRI WITH MODERATING AFTERNOON TEMPS INLAND...BUT REMAINING CHILLY ALONG THE COAST. LOW PRESSURE MAY BRING A ROUND OR TWO OF RAIN SHOWERS SOMETIME FRI NIGHT INTO SAT...THEN DRY AND COOLER SUNDAY/MONDAY.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... 200 PM UPDATE... COLD FRONT PUSHING INTO THE HUDSON RIVER VALLEY. SUB-TROPICAL MOISTURE CONVERGENCE COUPLED WITH STRONG LIFT AND DYNAMICS COMING TOGETHER ACROSS SOUTHERN NEW ENGLAND. BEGINNING TO SEE AN AREAL INCREASE IN RAIN COVERAGE WITH EMBEDDED HEAVIER SHOWERS AND AN ISOLATED THUNDERSTORM. H925 WINDS FROM VERTICAL WIND PROFILERS VIA WSR-88D SHOWING ENHANCING S-WINDS OF 60-70 KTS. WILL LIKELY SEE AN INCREASE IN IMPACTS DUE TO THE ATTRIBUTABLE THREATS OUTLINED BELOW: HEAVY RAIN/FLOODING... FLOOD WARNINGS HAVE BEEN ISSUED FOR MULTIPLE POINTS ALONG THE CONNECTICUT RIVER BASIN WITH THE EXPECTATION OF MINOR RIVER FLOODING...PERHAPS MODERATE FLOODING AT MIDDLE HADDAM. AN AREAL FLOOD ADVISORY HAS BEEN ISSUED FOR ALL OF RI AND THE SURROUNDING AREA. EARLIER...THE SATELLITE ANALYSIS BRANCH NOTED ANOMALOUS DEEP MOISTURE SURGING NORTH FROM THE GULF ON THE ORDER OF 3-4 STANDARD DEVIATIONS ABOVE NORMAL WHILE WPC PUT OUT A SLIGHT RISK TO THE WEST OF THE REGION OF EXCESSIVE RAINFALL AND FLASH FLOODING. LATEST SPC MESOANALYSIS HIGHLIGHTS A SURGE OF 1.5 INCH PWATS INTO SOUTHERN NEW ENGLAND COLLOCATED WITH STRONG CONVERGENT H85 MOISTURE TRANSPORT. COUPLING WITH AN AMPLIFYING LLJ ALREADY OBSERVED BY THE EARLIER MENTIONED VERTICAL WIND PROFILERS THE CONVERGENT NOSE OF WHICH LIES OVER SOUTHERN NEW ENGLAND BENEATH THE RRQ OF AN UPPER-LEVEL JET...AND CONSIDERING THE APPROACH OF A SHARP COLD FRONT AND DEEP FRONTOGENETICAL LIFT...AND YOU HAVE A PRETTY GOOD SETUP FOR HEAVY RAIN AND FLOODING. CONVECTIVE ELEMENTS AND MOIST ADIABATIC LAPSE RATES...AND THERE IS SOME CONDITIONAL INSTABILITY TO WARRANT THE THREAT OF ISOLATED THUNDERSTORMS. THUS THE FLOOD WATCH CONTINUES WITH THE EXPECTATIONS AS OUTLINED ABOVE. AVERAGE STORM-TOTAL RAINFALL AMOUNTS ARE FORECAST AROUND 2 INCHES AND EXPECT LOCALLY HIGHER AMOUNTS OF AROUND 3 INCHES IN A TIMEFRAME OF AROUND 6-HOURS. THE BASIS FOR THE FLOOD WATCH IS DUE TO ALREADY SWOLLEN RIVERS FROM UPSTREAM SNOWMELT TAKING ON ADDITIONAL WATER AND LIKELY GOING INTO MINOR FLOOD...POSSIBLY INTO MODERATE FLOOD. RIVER BASINS OF CONCERN INCLUDE CONNECTICUT/MERRIMACK/PAWCATUCK. ALSO ANTICIPATE IMPACTS TO LOCAL STREAMS/CREEKS/TRIBUTARIES...ESPECIALLY THOSE THAT ARE NARROWER AND FLASHIER. THOSE WITH INTERESTS ALONG AREA RIVERS SHOULD PAY ATTENTION TO THE LATEST FORECASTS AND CURRENT WATER LEVELS. THE FLOOD WATCH ALSO INCLUDES URBAN AND POOR DRAINAGE ISSUES THE HEIGHT OF WHICH WILL CENTER AROUND THE DRIVE-HOME COMMUTE FOR MOST ROADWAYS THROUGHOUT SOUTHERN NEW ENGLAND. CONCERNED FOR THE I-91 CORRIDOR SURROUNDING SPRINGFIELD MA AND HARTFORD CT...AS WELL AS THE I-95/I-195 CORRIDORS AROUND BOSTON AND PROVIDENCE...EVEN OUT I-90 INCORPORATING WORCESTER. PONDING OF WATER ALONG AREA ROADWAYS WILL LIKELY BE A BIG ISSUE TO AREA TRAFFIC. PLEASE SEE THE COASTAL FLOODING SECTION BELOW FOR COASTAL FLOOD THREATS. WINDS... SEVERAL LOCATIONS ACROSS CENTRAL/EASTERN NEW ENGLAND OBSERVING WIND GUSTS IN EXCESS OF 40 KTS /46 MPH/. WSR-88D VERTICAL WIND PROFILERS SHOWING WINDS AT H925 AMPLIFYING TO 70 KTS. INCREASING AREAL COVERAGE OF RAIN WITH EMBEDDED HEAVIER SHOWERS AIDING IN THE PRECIP-DRAG / MECHANICAL MIXING OF FASTER MOMENTUM ALOFT DOWN TO THE SURFACE. SHOULD SEE THESE WINDS CONTINUE INTO THE EVENING HOURS. WIND ADVISORIES CONTINUE ACCORDINGLY. ANY HIGH-WINDS TO WHICH WE CONTINUE TO MONITOR FOR WILL BE HANDLED WITH SHORT-FUSED WARNINGS. THOSE TRAVELING OVER BRIDGES /THINKING THE SAGAMORE AND BOURNE/ SHOULD BE AWARE OF FIERCE CROSSWINDS. GUSTS IN EXCESS OF 50 MPH WILL BE POSSIBLE. ALREADY RECEIVING NUMEROUS REPORTS OF TREES AND WIRES DOWN...BLOWN TRANSFORMERS AND POWER OUTAGES. THESE IMPACTS AND THREATS WILL CONTINUE OVER THE NEXT SEVERAL HOURS AHEAD OF THE COLD FRONT SWEEPING THROUGH THE REGION. WINTRY MIX/FLASH FREEZE POTENTIAL... TEMPERATURES QUICKLY FALLING IMMEDIATELY BEHIND THE COLD FRONT. CONSIDERING THE STRONG DYNAMICS AND LIFT ASSOCIATED WITH THE RRQ OF THE UPPER-LEVEL JET ACROSS AND TO THE REAR OF THE FRONT... THERE IS THE POTENTIAL FOR LINGERING PRECIPITATION WITHIN THE SHALLOW COLD-AIR MASS. THUS THERE REMAINS THE POSSIBILITY OF A BRIEF CHANGEOVER TO A SNOW/SLEET MIX...MAINLY ACROSS PORTIONS OF N MA AND S NH ALONG AND NORTH OF THE ROUTE 2 CORRIDOR. ANY ACCUMULATIONS WILL BE LIGHT AROUND A TRACE TO PERHAPS A TENTH OR TWO...ENOUGH TO MAKE FOR SLIPPERY CONDITIONS. DRIER AIR WILL WORK INTO THE REAR OF THE STORM RESULTING IN THE BACK EDGE OF PRECIP TO DISSIPATE. SHOULD ALSO SEE THIS DRY AIR AT THE SURFACE. THUS IT IS A QUESTION AS TO WHETHER WET SURFACES FROM THE RAIN WILL FREEZE AHEAD OF EVAPORATING. EITHER WHICH WAY...THERE IS THE POTENTIAL FOR BLACK-ICE AND SLIPPERY CONDITIONS THAT MAY EXIST FOR THE WEDNESDAY MORNING COMMUTE. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... WEDNESDAY... AN UNSEASONABLY CHILLY AIRMASS WILL CONTINUE TO WORK INTO THE REGION AS LARGE HIGH PRESSURE BUILDS IN FROM THE WEST. ANY LEFT OVER PRECIPITATION SHOULD HAVE EXITED THE CAPE/ISLANDS BY EARLY TO MID MORNING...AS THE COLD FRONT WILL BE WELL OFFSHORE. NORTHWEST WINDS CONTINUE TO GUST BETWEEN 30 AND 40 MPH DURING THE MORNING...BUT WILL DIMINISH DURING THE AFTERNOON. ANOMALOUS 850 MB TEMPS FOR THIS TIME OF YEAR BETWEEN -6C AND -10C ARE EXPECTED. HOWEVER...PLENTY OF STRONG APRIL SUNSHINE WILL OFFSET THIS TO SOME DEGREE. ALL IN ALL...MUCH OF THE REGION SHOULD SEE HIGHS RECOVER WELL INTO THE 40S DURING THE AFTERNOON. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
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HIGHLIGHTS... * DRY BUT UNSEASONABLY CHILLY WED NIGHT * DRY WEATHER CONTINUES INTO FRI AND BECOMING MILDER INLAND * A PERIOD OF SHOWERS POSSIBLE FRI NIGHT INTO SAT BUT LOW CONFIDENCE AN ACTIVE AND SURPRESSED NORTHERN STREAM JET THIS PERIOD WILL RESULT IN TEMPERATURES AT OR COOLER THAN NORMAL ALONG WITH A FEW CHANCES OF SHOWERS. VERY TYPICAL PATTERN FOR MID APRIL. DAILY DETAILS... WEDNESDAY NIGHT... CHILLY AIRMASS OVER THE REGION ALONG WITH MAINLY CLEAR SKIES AND DIMINISHING WINDS. THIS WILL RESULT IN COLD TEMPS OUTSIDE OF THE URBAN AREAS WITH MOST LOCATIONS IN THE 20S! THURSDAY AND FRIDAY... STRONG /1044 MB!/ HIGH PRESSURE ADVECTS INTO THE CANADIAN MARITIMES. THIS WILL EVOLVE INTO A COOL MARITIME AIRMASS FOR SOUTHERN NEW ENGLAND WITH LARGE TEMP DIFFERENCES FROM THE COAST TO INLAND. ACROSS EASTERN MA THE VERY CHILLY OCEAN WATERS WITH SSTS IN THE L40S WILL ACT LIKE A SNOWCOVER AND ENHANCE THIS COOL MARITIME AIRMASS. CHILLY ONSHORE WINDS WILL ADVECT THIS VERY COOL AND SHALLOW MARITIME AIRMASS INTO THE COASTAL PLAIN. THEREFORE ONLY EXPECTING HIGHS IN THE 40S OVER EASTERN MA...MEANWHILE STRONG APRIL SUN HEATS UP THE INTERIOR INTO THE 50S. AIRMASS CONTINUES TO MODIFY FRI WITH HIGHS 45- 50 EASTERN MA AND 55-60 WELL INLAND. FRIDAY NIGHT AND SATURDAY... MODELS CONTINUE TO STRUGGLE ON AMPLITUDE AND INTERACTION OF NORTHERN AND SOUTHERN STREAM WAVES. 12Z GFS REMAINS MORE ROBUST AND PHASING THAN THE 12Z ECMWF. THUS THE GFS IS THE WETTER SOLUTION OF THE TWO. ENSEMBLES INDICATE MORE STREAM SEPARATION AND ARE SLOWER PHASING THE STREAMS BUT THIS IS SOMEWHAT TYPICAL GIVEN THE LOWER RESOLUTION OF THE ENSEMBLES. TEMPS LIKELY REMAIN NEAR NORMAL...HIGHS IN THE 50S. SUNDAY/MONDAY/TUESDAY... AS EXPECTED LOTS OF TIMING ISSUES HERE GIVEN THE FAST FLOW ACROSS THE NORTHERN STATES. GIVEN THIS FLOW REGIME AND TIME RANGE HERE WILL FOLLOW A MODEL BLEND WHICH YIELDS TEMPS NEAR NORMAL AND A RISK OF SHOWERS IN THE MON NIGHT/TUE TIME FRAME.
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&& .AVIATION /20Z TUESDAY THROUGH SUNDAY/...
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LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH WEDNESDAY/...MODERATE CONFIDENCE. DETERIORATING CONDITIONS WITH CIGS/VSBYS FALLING IFR-VLIFR WITH +RA TOWARDS CONTINUING INTO THE EVENING PERIOD. POTENTIAL FOR ISOLATED TSRA BUT WITH UNCERTAINTY WILL NOT MENTION IN TAF. STRONG S-WINDS WITH GUSTS IN EXCESS OF 40 KTS FOR S/E TERMINALS. DESPITE THIS...WILL SEE LLWS IMPACTS OVER ALL TERMINALS AS LOW-LEVEL WINDS ARE AMPLIFYING TO 60-70 KT 2 KFT AGL. COLD FRONT PUSHES THROUGH THE TERMINALS AROUND MIDNIGHT. WILL SEE WINDS BACK WEST REMAINING GUSTY UP TO 40 KTS. CONDITIONS QUICKLY IMPROVING TO VFR. MAY SEE RAIN TRANSITION TO SNOW/SLEET BRIEFLY WITH MINOR ACCUMS. BEST CHANCES OVER NW MA INTO S NH. KBOS TERMINAL...MODERATE CONFIDENCE. KBDL TERMINAL...MODERATE CONFIDENCE. OUTLOOK...WEDNESDAY NIGHT THROUGH SUNDAY... WEDNESDAY NIGHT THRU FRIDAY...VFR VSBYS LIKELY WITH MVFR CIGS POSSIBLE...HIGHEST PROBABILITY ACROSS RI AND EASTERN MA. FRIDAY NIGHT INTO SATURDAY...MVFR IN SCATTERED SHOWERS POSSIBLE BUT CONFIDENCE IS VERY LOW. SUNDAY...IMPROVING TREND WITH VFR LIKELY ALONG WITH INCREASING NW WINDS.
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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 TUESDAY/...HIGH CONFIDENCE. S-SW WINDS CONTINUE TO INCREASE THROUGH THE DAY SUCH THAT GALE FORCE WINDS ARE LIKELY BY THIS AFTERNOON...CONTINUING INTO THE OVERNIGHT HOURS. GALE WARNINGS CONTINUE FOR THIS THREAT. THESE WINDS WILL SHIFT TO THE W-NW EARLY WED MORNING BUT CONTINUE WITH GALE FORCE GUSTS UNTIL THEY SUBSIDE BY MID MORNING WED. SOME HEAVY RAIN/FOG AND ISOLATED THUNDERSTORMS ARE POSSIBLE MAINLY THIS AFTERNOON AND EVENING AS WELL. SEAS INCREASE TO 10-12 FT. OUTLOOK...WEDNESDAY NIGHT THROUGH SUNDAY... WED NIGHT THRU FRI...TREND HERE WILL BE DECREASING SOUTHERLY SWELLS WITH INCREASING ENE WIND WAVES. MAINLY DRY WITH MARITIME AIRMASS OVER THE WATERS COURTSEY OF 1040 MB HIGH ACROSS NEWFOUNDLAND. FRI NIGHT AND SAT...LOW CONFIDENCE FORECAST WITH LOW PRES APPROACHING FROM THE SOUTH AND ANOTHER FROM THE GREAT LAKES. DILEMMA WILL BE HOW MUCH SEPARATION BETWEEN THESE SYSTEMS OR IF LOWS WILL MERGE INTO ONE STRONGER SYSTEM. STILL TOO EARLY TO SAY. SUNDAY...IMPROVING TRENDS WITH LOW PRES STRENGTHENING WELL EAST OF NEW ENGLAND FOLLOWED BY A MODEST NW WIND.
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&& .TIDES/COASTAL FLOODING... STRONG SOUTHERLY WINDS OVER THE WATERS GUSTING 30 TO 40 MPH WILL YIELD AN AVERAGE 1.5 FOOT SURGE ALONG THE SOUTH COAST. COMBINED WITH HIGH TIDE AROUND 9-10 PM /NOT ASTRONOMICALLY HIGH/...THERE IS THE POSSIBILITY OF SPLASHOVER ALONG LOW-LYING AREAS...BUT AT THIS PRESENT TIME WE ARE NOT CONSIDERING MINOR COASTAL FLOODING. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...FLOOD WATCH THROUGH WEDNESDAY MORNING FOR CTZ002>004. MA...FLOOD WATCH THROUGH WEDNESDAY MORNING FOR MAZ002>021-026. WIND ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR MAZ004>007- 012>024-026. NH...FLOOD WATCH THROUGH WEDNESDAY MORNING FOR NHZ011-012-015. RI...FLOOD WATCH THROUGH WEDNESDAY MORNING FOR RIZ001>007. WIND ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR RIZ001>008. MARINE...GALE WARNING UNTIL NOON EDT WEDNESDAY FOR ANZ230>234-236-250- 251. GALE WARNING UNTIL 10 AM EDT WEDNESDAY FOR ANZ235-237-256. GALE WARNING UNTIL 2 PM EDT WEDNESDAY FOR ANZ254-255.
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&& $$ SYNOPSIS...NOCERA/SIPPRELL NEAR TERM...SIPPRELL SHORT TERM...SIPPRELL LONG TERM...NOCERA AVIATION...SIPPRELL MARINE...NOCERA TIDES/COASTAL FLOODING...RMT

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