Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 271411 CCA AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1010 AM EDT SAT JUN 27 2015 .SYNOPSIS... CLOUDS WILL CONTINUE TO INCREASE THIS AFTERNOON AS LOW PRESSURE APPROACHES FROM THE OHIO VALLEY. A WINDSWEPT SOAKING RAIN BEGINS THIS EVENING AND CONTINUES OVERNIGHT. THE RAIN TAPERS OFF SUNDAY WITH A DRYING TREND SUNDAY NIGHT. DRY WEATHER PREVAILS MONDAY BUT MORE UNSETTLED WEATHER AT TIMES IN THE FORM OF SCATTERED SHOWERS/THUNDERSTORMS TUESDAY AFTERNOON/NIGHT AND WED...THEN AGAIN FRI BUT MANY HOURS OF DRY WEATHER IN BETWEEN. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1010 AM UPDATE... DESPITE HIGH PRESSURE OVERHEAD AN ABUNDANCE OF MID/HIGH LEVEL CLOUDINESS HAS ALREADY OVERSPREAD MOST OF THE REGION...AHEAD OF AN APPROACHING LOW PRESSURE SYSTEM. GIVEN HIGH LATE JUNE SUN ANGLE...WILL PROBABLY SEE SOME DIM SUNSHINE FILTER THROUGH AT TIMES ESPECIALLY ACROSS THE SOUTHEAST NEW ENGLAND COAST. HIGHS SHOULD STILL TOP OUT MAINLY IN THE LOWER TO MIDDLE 70S FOR MOST OF THE REGION...EXCEPT UPPER 60S ON THE IMMEDIATE COAST WITH SEA BREEZES. DRY WEATHER WILL DOMINATE INTO THIS AFTERNOON. A FEW SPRINKLES/LIGHT RAIN SHOWERS MAY WORK INTO WESTERN MA/NORTHERN CT BY LATE LATE AFTERNOON. HOWEVER...THE BULK OF THE STEADIER/HEAVIER RAIN WILL HOLD OFF UNTIL THIS EVENING. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... TONIGHT INTO SUNDAY... *** ANOMALOUS LOW PRESSURE SYSTEM WILL BRING MULTIPLE HAZARDS TO SOUTHERN NEW ENGLAND BEGINNING LATE SATURDAY INTO SUNDAY AM *** OVERVIEW... VERY ATYPICAL PATTERN FOR LATE JUNE WITH ANOMALOUS LOW PRESSURE SYSTEM APPROACHING THE NORTHEAST. DEF NOT THE TYPE OF PATTERN EXPECTED FOR THE FIRST WEEKEND OF SUMMER. STACKED LOW OVER THE MID- WEST WILL PUSH OVER THE CATSKILLS...JUST LIKE AN INSIDE RUNNER WOULD IN THE WINTER. THIS LOW WILL DEVELOP A SECONDARY LOW OVER THE DELMARVA TONIGHT AND PUSH TOWARDS SOUTHERN NEW ENGLAND BY SUNDAY MORNING. MODELS INDICATE THAT THIS TRIPLE POINT LOW WILL PUSH A WARM FRONT CLOSE TO/OVER A PORTION OF SOUTHERN NEW ENGLAND...POTENTIALLY WARM SECTORING RI AND SE MASS. A TROPICAL CONNECTION...DEWPOINTS IN THE UPPER 60S. LEAVES US UNDER A VERY MOIST COLUMN WHERE PWATS APPROACH 2+ INCHES /AND NEARLY 3 STD DEVIATIONS ABOVE NORMAL/. THIS WILL BE ALONG WITH A STRONG 50-60 KT SE LLJ. ALL THE PLAYERS ARE THERE FOR A VERY DYNAMIC AND WET PERIOD DURING THE OVERNIGHT AND EARLY SUN TIMEFRAME. GUIDANCE ALSO SHOWS A DRY SLOT PUSHING ACROSS THE REGION...CONVECTION MAY DEVELOP AT THE NOSE OF THE DRY SLOT SUNDAY MORNING. HAZARDS BREAKDOWN BELOW. HAZARDS... * RAINFALL/FLOODING... A FLOOD WATCH HAS BEEN ISSUED FOR THE IMMEDIATE WESTERN ZONES...ALONG THE BERKSHIRES. FEEL THAT THIS AREA IS BEST DUE TO THE ANOMALOUS LLJ AND MOISTURE FLUX ALONG THE BERKSHIRES. IN FACT GUIDANCE IS SHOWING COULD BL CONVERGENCE AS WELL ALONG THE BERKS. HI-RES GUIDANCE CONTINUES TO SHOW A MAXIMUM ALONG THE BERKS IN WHICH 1-3 INCHES COULD FALL. MORE DETAILS BELOW IN REGARDS TO RIVERS AND URBAN SMALL STREAM FLOODING THREAT. A SECOND MAXIMUM OF HIGHER QPF WILL BE ACROSS THE CENTRAL HILLS UP INTO NORTHEAST MASS. IN FACT...BOTH HI-RES AND SYNOPTIC GUIDANCE IS PINPOINT THAT REGION. THIS IS DUE TO NOT ONLY THE SYNOPTIC RAINFALL BUT THE CONVECTION POTENTIAL AS WELL. THIS LOCATION IS RIGHT ALONG THE NOSE OF THE LLJ AND WITH PWAT VALUES NEARING 2+ INCHES COULD SEE SIGNIFICANT RAINFALL. NOT EXPECTING TRAINING CELLS AS THE SYSTEM IS VERY PROGRESSIVE BUT COULD SEE HEAVY DOWNPOURS LEADING TO POOR DRAINAGE FLOODING. ESP IN TOWNS THAT HAVE A HIGHER VULNERABILITY...IE PEABODY AND LYNN. * WIND THREAT...STRONG SOUTHEASTERLY LLJ WILL DEVELOP ACROSS THE REGION LATE SAT INTO SUNDAY. THE GFS/EC AND NAM ALL SHOW 925 MB WINDS INCREASING TO 50-60 KTS RIGHT OVER THE EASTERN WATERS. THIS IS CLOSE TO 4-5 STD AWAY. BIGGEST QUESTION IS IF THIS JET WILL MIX DOWN TO THE SURFACE. APPEARS THAT EAST COAST INCLUDING THE CAPE AND ISLANDS WILL GENERALLY BE INVERTED. HOWEVER ANY MOMENTUM TRANSFER WILL YIELD TO WIND ADV GUSTS. THIS COULD OCCUR DURING THE DAYTIME...WHEN MIXING INCREASES WITH SUNRISE. ALSO WITHIN ANY SHOWERS/CONVECTION WILL MIX THESE GUSTY WINDS DOWN AS WELL. THEREFOR HAVE HOISTED A WIND ADV ACROSS PORTIONS OF THE EAST MASS COASTLINE WHERE CONFIDENCE IS HIGHEST. THIS MAY NEED TO BE EXTENDED INTO SUFFOLK COUNTY. * SEVERE WEATHER THREAT...LOW CONFIDENCE ON SEVERE WEATHER POTENTIAL SUNDAY MORNING . THIS PATTERN IS SOMEWHAT SIMILAR TO OTHER TROPICAL-LIKE PATTERNS THAT HAVE YIELDED QUICK SPIN-UP OR LOCALIZED SVR WINDS WE HAVE SEEN IN THE PAST. THE BIGGEST QUESTION IS IF THE WARM SECTOR /TRIPLE POINT WILL GET FAR ENOUGH NORTH TO ALLOW FOR THE REGION TO DESTABILIZE. SHEAR WILL NOT BE A PROBLEM WITH EASTERLY WINDS AT THE SURFACE AND SW WINDS ALOFT...COULD YIELD 50-60 KTS OF SHEAR. ANTICIPATE LOW LCL DUE TO THE HIGH DEWPOINTS. SO THE MOISTURE..SHEAR AND WARM FRONTAL BOUNDARY WILL MOVE THROUGH...BIGGEST QUESTION IS THE INSTABILITY FACTOR. GFS IS THE ONLY PIECE OF GUIDANCE SHOWING DESCENT MUCAPE...WHICH IS A FLAG. HOWEVER IS DEWPOINTS INCREASE...OR IF CLDS BREAK OUT ENOUGH THIS WE COULD GET MORE INSTABILITY THEN GUIDANCE SUGGEST. THIS WILL NEED TO BE WATCH CLOSELY OVER THE NEXT 24 HOURS. * BEACH HAZARDS...STRONG LLJ WILL ALLOW FOR NEAR SHORE WATERS TO BUILD NEAR 8-10 FT CLOSE TO THE COASTLINE. THIS COMBINED WITH ONSHORE SWELL AND A PERIOD CLOSE TO 7-8 SEC...COULD SEE HIGH RISK OF RIP CURRENTS AND WELL AS HIGH SURF. THE BEST COASTLINE FOR THIS TO OCCUR IS ACROSS EAST FACING BEACHES OF MASSACHUSETTS. ANY BEACHGOERS OR OCEAN LOVERS ON SUNDAY SHOULD BE AWARE IF THESE RISKS AND STAY AWAY FROM JETTIES OR LOW LYING PIERS. REMEMBER WHEN IN DOUBT...DON`T GO OUT. * AVIATION/MARINE...SINCE THIS IS THE OFFICIAL FIRST WEEKEND OF SUMMER THIS SYSTEM WILL BE HAZARDOUS FOR MARINERS...ESP WITH HIGH SEAS NEAR 8FT AND A STRONG NE GALE. WHEN THE SYSTEM PASSES THROUGH ANTICIPATE LOW CLOUDS AND VSBYS IMPACTS. ALSO WITH STRENGTHEN LLJ EXPECT LLWS ESP FOR EASTERN TERMINALS. MORE DETAILS BELOW. AFTER THE BULK OF THE PRECIP MOVES THROUGH AND THE REGION IS DRY SLOTTED BUT COULD SEE A FEW SHOWERS DEVELOP WITH TRAPPED LL MOISTURE. HAVE INCLUDED THUNDER AS LAPSE RATES STEEPENED AND UPPER LEVEL LOW APPROACHES THE REGION. ONE LIMITING FACTOR IS THE INSTABILITY POTENTIAL. MODELS ARE NOT QUITE IMPRESSIVE...THEREFORE WILL KEEP MENTIONING ISOLATED/SCT. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... HIGHLIGHTS... * VERY PLEASANT WEATHER MON WITH DRY CONDITIONS AND MILD TEMPS * SCATTERED SHOWERS/T-STORMS POSSIBLE TUE/WED AND AGAIN FRIDAY * TEMPS NEAR NORMAL MUCH OF NEXT WEEK SYNOPTIC OVERVIEW...MAIN WEATHER FEATURE THIS PERIOD WILL BE A BUILDING LARGE AMPLITUDE RIDGE OVER THE WESTERN CONUS AND CANADA WITH HEIGHT ANOMALIES REACHING +2 STD DEVIATIONS ABOVE CLIMO. THIS INDUCES AN ANOMALOUS DOWNSTREAM TROUGH OVER THE MS AND OH VALLEYS. THIS PROVIDES AN ACTIVE NORTHERN STREAM JET WITH CYCLONIC FLOW ALOFT ACROSS SOUTHERN NEW ENGLAND MUCH OF NEXT WEEK. THUS MULTIPLE CHANCES FOR SHOWERS/T-STORMS...BUT BY NO MEANS A WASHOUT AS THERE WILL BE MANY HOURS OF DRY WEATHER TOO. AS FOR TEMPS...WITH MEAN TROUGH AXIS WEST OF NEW ENGLAND ACROSS THE GREAT LAKES/OH AND TN VALLEYS...CORE OF COOL AIR ASSOCIATED WITH THE TROUGH WILL BE WEST OF OUR REGION. THEREFORE EXPECT TEMPERATURES MUCH OF NEXT WEEK TO AVERAGE NEAR NORMAL. GUIDANCE EVALUATION...00Z GFS AND ECMWF IN VERY GOOD AGREEMENT THRU NEXT WED...THEN BEGIN TO DEVIATE NEXT THU AND FRI ON AMPLITUDE AND TIMING OF INDIVIDUAL NORTHERN STREAM SHORT WAVES. THEREFORE LEANED HEAVILY ON ENSEMBLES /GEFS/ LATE NEXT WEEK AND FOLLOWED A GFS/ECMWF BLEND OTHERWISE. DAILY DETAILS... SUNDAY NIGHT...MID LEVEL CLOSED LOW OVER NORTHERN NY STATE LIFTS NE INTO QUEBEC. AS IT DOES SO THERE COULD BE ENOUGH LIFT AND MOISTURE FOR A THREAT OF SHOWERS ACROSS NORTHWEST MA. OTHERWISE MOST OF THE REGION REMAINS DRY. COOL AIRMASS ADVECTS ACROSS THE AREA SUN NIGHT WITH 925 AND 850 TEMPS ABOUT -1 STD DEVIATION BELOW NORMAL. MONDAY...MID LEVEL CLOSED LOW OVER SOUTHERN QUEBEC CONTINUES TO LIFT NORTHEAST RESULTING IN HEIGHT AND TEMP RISES ALOFT OVER SOUTHERN NEW ENGLAND. THIS SUPPORTS DRY WEATHER ALONG WITH PARTLY TO MOSTLY SUNNY CONDITIONS. WEST SURFACE WINDS WILL PROMOTE DEEP BLYR MIXING AND TEMPS CLIMBING THRU THE 70S...INCLUDING THE BEACHES. DEW PTS IN THE 50S WILL PROVIDE A VERY COMFORTABLE DAY. FOR THOSE HEADING TO THE BEACH MON BE AWARE THAT LEFTOVER SE SWELLS WILL RESULT IN ROUGH SURF AND STRONG RIP CURRENTS ESPECIALLY AT OCEAN BEACHES ALONG THE SOUTH COAST OF MA AND RI INCLUDING CAPE COD. TUESDAY THROUGH FRIDAY...UNSETTLED AT TIMES AS NORTHERN STREAM REMAINS AMPLIFIED WITH A FEW SHORT WAVE TROUGHS AND ATTENDING COLD FRONTS TO ROTATE THROUGH THE MEAN TROUGH. TIMING THESE FEATURES IN THE EXTENDED IS ALWAYS A CHALLENGE AND THIS IS THE CASE WITH THE GFS AND ECMWF SHOWING TIMING AND AMPLITUDE DIFFERENCES ESPECIALLY BY NEXT THU AND FRI. AT THIS TIME RANGE PUTTING MORE WEIGHT TOWARD THE ENSEMBLES SUGGEST A RISK FOR SHOWERS/T-STORMS MAINLY TUE NIGHT AND WED. CAN/T RULE OUT ISOLATED CONVECTION TUE AFTN BUT SHOULD BE CONFINED TO WESTERN CT/MA GIVEN HOW FAR WEST TROUGH AXIS IS TO NEW ENGLAND. DRY WEATHER LIKELY THU BEHIND DEPARTING SHORT WAVE THROUGH. PATTERN REMAINS ACTIVE WITH NEXT NORTHERN STREAM TROUGH AND ASSOCIATED RISK OF SHOWERS/T-STORMS ARRIVE AROUND FRI. && .AVIATION /13Z SATURDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH SUNDAY/... TODAY...HIGH CONFIDENCE. VFR CONDITIONS CONTINUE THROUGH THE AFTERNOON DESPITE AN INCREASE IN MID LEVEL CLOUDINESS. MAY SEE SOME LIGHT RAIN SHOWERS/SPRINKLES WORK INTO WESTERN MA/NORTHERN CT BY LATE AFTERNOON...BUT VFR CONDITIONS WILL CONTINUE. TONIGHT INTO TOMORROW...HIGH CONFIDENCE IN TRENDS...LOWER CONFIDENCE IN TIMING. VFR TO START THE EVENING...THEN EXPECT GRADUALLY LOWERING CIGS TO MVFR THEN IFR BY EARLY MORNING. EXPECT REDUCED VSBYS IN FOG AND RAIN...PARTICULARLY AFTER MIDNIGHT LOCAL. SE WIND GUSTS MAY INCREASE TO AROUND 30 KT AT TIMES...ESPECIALLY IN EASTERN MA TOWARD DAYBREAK SUNDAY YIELDING TO LLWS. LOW PROB OF AN ISO -TSRA SUN MORNING ACROSS EASTERN TERMINALS. THEN AGAIN ACROSS THE INTERIOR. CONDITIONS WILL IMPROVE FROM SW TO NE AFTER 18/21Z. KBOS TERMINAL...HIGH CONFIDENCE. KBDL TERMINAL...HIGH CONFIDENCE. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY... SUNDAY NIGHT...ANY MVFR/IFR EARLY IMPROVES TO VFR AS WINDS BECOME WESTERLY. LOW RISK OF SCATTERED SHOWERS ACROSS WESTERN NEW ENGLAND. MODERATE CONFIDENCE. MONDAY...MODERATE CONFIDENCE. VFR. BREEZY W-WINDS WITH GUSTS 20-25 KTS. TUESDAY...MODERATE CONFIDENCE. MAINLY VFR...BUT MVFR IN SCATTERED SHOWERS/T-STORM IN WESTERN MA/CT TUE AFTERNOON SPREADING EASTWARD TUE NIGHT. WEDNESDAY...MODERATE CONFIDENCE. MAINLY VFR WITH LOW RISK OF SCATTERED SHOWERS/T-STORMS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH SUNDAY/... TODAY...HIGH CONFIDENCE. MAINLY QUIET BOATING WEATHER EXPECTED AS HIGH PRES SLIDES OVER THE WATERS. LIGHT E WINDS AND LOW SEAS WILL REMAIN IN PLACE. TONIGHT INTO TOMORROW...MODERATE CONFIDENCE. A STRONG LOW PRES CENTER WILL BE APPROACHING FROM THE W. THIS WILL YIELD A PERIOD OF RAIN AND FOG WITH LOW VSBYS. EXPECT SE WINDS TO INCREASE...REACHING GALE FORCE ON THE OCEAN WATERS BY ABOUT MIDNIGHT. A GALE WARNING HAS BEEN ISSUED FOR THE NE WATERS WHERE CONFIDENCE IS HIGHEST. THE WATCH CONTINUES FOR THE REMAINDER OF THE WATERS MINUS NARRAGANSETT BAY. SEAS WILL BE BUILDING TO 8-10 FT BY SUN MORNING LASTING INTO THE AFTERNOON HOURS. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY...MODERATE CONFIDENCE. SUNDAY NIGHT...SW 20 TO 30 KT STRONGEST WIND OVER THE SOUTHERN WATERS THEN TRENDING WESTERLY TOWARD SUNRISE AND DIMINISHING. MONDAY...WSW GUSTS TO 25 KT POSSIBLE. LEFTOVER LARGE ESE SWELLS LIKELY PERSIST ACROSS THE OCEAN WATERS. GOOD VSBY. TUESDAY....WINDS BECOMING S WITH GUSTS TO 20 KT AHEAD OF APPROACHING COLD FRONT. SEAS BELOW SCA. CHANCE OF SHOWERS/T-STORMS IN THE EVENING AND OVERNIGHT. WEDNESDAY...SW WINDS LESS THAN 20 KT TRENDING WEST LATE. LOW RISK OF SCATTERED SHOWERS/T-STORMS DURING THE DAY. && .HYDROLOGY... WITH PERIODIC HEAVY RAINFALL EXPECTED LATE THIS EVENING...AND INTO SUNDAY...WIDESPREAD RAINFALL OF 1-3 INCHES WITH LOCALLY HIGHER AMOUNTS IS EXPECTED. AT THIS TIME...MOST AREA RIVERS ARE AT THEIR NORMAL SEASONAL LOW POINTS AND GIVEN THIS RAIN WILL MOSTLY FALL OVER A 12+ HOUR PERIOD...THIS SHOULD BE HANDLED. HOWEVER...WITH THE VERY HIGH PWATS AND POTENTIAL FOR CONVECTIVE ELEMENTS...ITS POSSIBLE FFG MAY BE EXCEEDED IN SOME AREAS. WIDESPREAD FFGS ARE NEARLY 2.0 INCHES/1 HOUR...2.5 INCHES/3 HOUR...AND 3 INCHES/6 HOUR RATES. NORMALLY FLASHY BASINS/STREAMS MAY NEED TO BE MONITORED. ALSO...URBAN FLOODING WILL BE POSSIBLE AS WELL AS FFG RATES WILL BE LOWER IN THESE LOCATIONS. APPEARS THAT THERE WILL BE 2 MAXIMUM IN QPF. ONE OVER THE BERKS AND ONE OVER THE CENTRAL HILLS INTO NORTHEAST MASS. AGAIN GENERALLY 1-3 INCHES BUT HI-RES GUIDANCE DOES SHOW POSSIBLE 4 INCH AMOUNTS DUE TO THE CONVECTIVE POTENTIAL. THE FLOOD WATCH HAS BEEN ISSUED FOR THE WEST WHERE CONFIDENCE IS HIGHEST IN SEEING CLOSE TO 2 INCHES LEADING TO FLASHING STREAMS RISING OVER THEIR BANKS AND POOR DRAINAGE FLOODING. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...WIND ADVISORY FROM 2 AM TO 2 PM EDT SUNDAY FOR MAZ007-019- 022>024. FLOOD WATCH FROM LATE TONIGHT THROUGH LATE SUNDAY NIGHT FOR MAZ002-008-009. RI...NONE. MARINE...GALE WATCH FROM LATE TONIGHT THROUGH SUNDAY MORNING FOR ANZ231- 232. GALE WATCH FROM LATE TONIGHT THROUGH SUNDAY MORNING FOR ANZ233>235-237. GALE WATCH FROM LATE TONIGHT THROUGH SUNDAY AFTERNOON FOR ANZ230-254>256. SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 8 AM EDT SUNDAY FOR ANZ236. GALE WARNING FROM 2 AM TO 2 PM EDT SUNDAY FOR ANZ250-251. && $$ SYNOPSIS...NOCERA/DUNTEN NEAR TERM...FRANK SHORT TERM...DUNTEN LONG TERM...NOCERA AVIATION...FRANK/NOCERA/DUNTEN MARINE...NOCERA/DUNTEN HYDROLOGY...DUNTEN

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