Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 310859 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 459 AM EDT SUN AUG 31 2014 .SYNOPSIS... WARM HUMID FLOW OVER THE NORTHEAST U.S. A UPPER LEVEL SHORTWAVE FROM THE GREAT LAKES DIVES EAST THROUGH NEW ENGLAND LATE AFTERNOON/EVENING BRINGING POTENTIAL THUNDERSTORMS WITH HEAVY DOWNPOURS AND STRONG WINDS. SHOWERS AND THUNDERSTORMS WILL LINGER INTO MONDAY EVENING...WITH THE BEST CHANCE ACROSS CT/RI AND SOUTH OF THE MASS PIKE. ANOTHER COLD FRONT APPROACHES LATER TUESDAY INTO TUESDAY NIGHT. WARM BUT LESS HUMID WEATHER WILL THEN FOLLOW FOR WEDNESDAY THROUGH FRIDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THROUGH 8 AM... WARMER MORE HUMID AIR CONTINUES TO FLOW INTO SOUTHERN NEW ENGLAND. AS OF 2 AM DEWPOINTS HAD CLIMBED INTO THE LOW TO MID 60S. EXPECT THESE VALUES TO SLOWLY INCREASE THROUGH MORNING. CLOUDS ARE FILLING IN OVER THE NORTHEAST...SO WE EXPECT MOSTLY CLOUDY SKIES THROUGH SUNRISE. TODAY... BACK EDGE OF THE CLOUD AREA IS SOUTHWEST OF PHILADELPHIA. THIS IS ABOUT WHERE DEWPOINTS ARE AROUND 70. THIS MEANS A CLOUDY START TO THE DAY...BUT POTENTIAL FOR THE SUN TO BREAK THROUGH LATER IN THE MORNING OR EARLY AFTERNOON. A SOUTHWEST UPPER FLOW AND SURFACE COLD FRONT IN THE GREAT LAKES SUGGESTS NO FROPA TODAY. THE UPPER SHORTWAVE PASSES ACROSS NORTHERN NEW ENGLAND...BUT CLOSE ENOUGH TO AFFECT SOUTHERN NEW ENGLAND. A PRE-FRONTAL TROUGH SUPPORTED BY AN UPPER SHORTWAVE IS A REASONABLE SCENARIO...WITH BEST CHANCE CLOSEST TO THE SHORTWAVE IN WESTERN/NORTHERN MASS AND IN SOUTHERN NH. AT THE LEAST THIS SHOULD BE A WARM VERY HUMID DAY. THE AIRMASS WILL CONTAIN DEEP TROPICAL MOISTURE WITH PRECIPITABLE WATER VALUES FORECAST AT 2.0 TO 2.30 INCHES...ABOVE 2 STD DEVIATIONS AND SO QUITE SIGNIFICANT. QUESTIONS OF THE DAY ARE POTENTIAL FOR CONVECTION AND POTENTIAL FOR DAMAGING CONVECTION. STABILITY PARAMETERS ARE FAVORABLE FOR TSTMS...LI AROUND -2 TO -4/TOTALS INTO THE MID 40S. UPPER WIND FIELDS SUGGEST SEVERE WIND POTENTIAL WITH 30 KNOTS AT 850 MB AND 40-50 KNOTS AT 500 MB. AFTERNOON/EVENING SHEAR VALUES LOOK SUFFICIENT TO PROVIDE ORGANIZATION TO SOME TSTMS. PUTTING IT ALL TOGETHER: POTENTIAL FOR AFTERNOON/EVENING STRONG THUNDERSTORMS WITH WIND AND HEAVY DOWNPOURS...AND A LOWER BUT REAL POTENTIAL FOR DAMAGING WIND GUSTS. FLASH FLOOD INDICES ARE ABOVE 3.5 INCHES... SO FLOODING PROBLEMS WILL BE ALONG THE LINES OF URBAN AND POOR DRAINAGE FLOODING. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... TONIGHT... CONVECTION LINGERS INTO AT LEAST THE START OF THE NIGHT. SIGNS IN THE MODEL DATA THAT THE SURFACE BOUNDARY MAY LINGER OVER SOUTHEAST MASS/RI/CT LATER AT NIGHT. THIS MAY PROVIDE A FOCUS FOR AT LEAST SCATTERED CONVECTION CONTINUING OVERNIGHT IN THIS AREA. NO AIRMASS CHANGE SO IT SHOULD BE A WARM AND HUMID NIGHT WITH DEWPOINTS AROUND 70...AND SO MIN TEMPS SHOULD BE AROUND 70 OR IN THE LOWER 70S. MONDAY... WARM HUMID AIRMASS LINGERS OVER THE REGION. PRECIP WATER VALUES CONTINUE ABOVE 2 INCHES SOUTH OF THE MASS PIKE AND 1.5 TO 2.0 INCHES NORTH. DYNAMICS WILL BE DIMINISHING...BUT SOUTHERN NEW ENGLAND WILL CONTINUE UNDER THE RIGHT ENTRANCE REGION OF THE DEPARTING UPPER JET FOR AT LEAST PART OF THE DAY. WE WILL CONTINUE WITH CHANCE POPS FOR SHOWERS/TSTMS...AND WITH LOCALLY HEAVY DOWNPOURS. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... OVERVIEW AND MODEL PREFERENCES... BROAD RIDGING IS THE DOMINATE FEATURE ACROSS THE EASTERN U.S. THROUGH MOST OF THIS FORECAST PERIOD...MORE TYPICAL FOR THE MIDDLE OF SUMMER RATHER THAN EARLY SEPTEMBER. HOWEVER...EARLY IN THIS PERIOD...THERE WILL BE A COUPLE OF FAST MOVING SYSTEMS IN THE BROAD NORTHERN STREAM FLOW THAT WILL AFFECT THE REGION. THE RIDGE FINALLY BECOMES ESTABLISHED AROUND MID WEEK...WITH WARM BUT DRY CONDITIONS THROUGH THE END OF THE WEEK. SOME QUESTIONS AS TO WHEN THE RIDGING MAY BREAK DOWN...AS MODEL SOLUTIONS LATE IN THE RUN TRY TO BREAK DOWN THE RIDGE WHILE BRINGING DOWN A H5 CUTOFF LOW ACROSS NORTH CENTRAL CANADA INTO NORTHERN QUEBEC. A LOT OF SOLUTION DIVERGENCE DURING THAT PORTION OF THE FORECAST...HOWEVER. OVERALL...HAVE FAIRLY GOOD CONFIDENCE WITH MOST OF THE FORECAST... THOUGH SOME QUESTION AS TO TIMING THE FRONT OFF THE COAST EARLY MONDAY NIGHT AS THE H5 PATTERN MAY BRIEFLY HANG UP...THEN MORE QUESTIONS WITH THE POSSIBLE CHANGES IN THE STEERING PATTERN OVER THE NORTHERN TIER LATE IN THE CYCLE. HAVE LEANED TOWARD A BLEND OF AVAILABLE GUIDANCE INTO FRIDAY...THEN PUSHED TOWARD A BLEND OF THE ECENS AND GEFS MEANS WHICH SHOWED A SLOWER BREAKDOWN OF THE RIDGING ACROSS THE REGION...WITH LOWER CONFIDENCE IN THE FRIDAY-SATURDAY TIMEFRAME. DAILIES... MONDAY NIGHT... H5 SHORT WAVE HANGS UP A BIT ALONG THE S COAST EARLY MON NIGHT WHICH WILL KEEP CHANCE FOR SCT SHOWERS/TSTMS THROUGH ABOUT MIDNIGHT. FAIR AMOUNTS OF INSTABILITY MOVE ALONG WITH THIS FRONT...WITH K INDICES IN THE LOWER-MID 30S AND TOTAL TOTALS APPROACHING 50. WILL REMAIN RATHER HUMID AND...WITH ANY LOW LEVEL MOISTURE FROM RAINFALL...WILL SEE SOME PATCHY FOG REDEVELOP AFTER MIDNIGHT. WILL REMAIN STICKY OVERNIGHT WITH LOWS IN THE 65 TO 70 DEGREE RANGE. TUESDAY... ANOTHER FRONTAL SYSTEM STEADILY WORKS ITS WAY ACROSS OUT OF NY STATE DURING TUESDAY...THOUGH SOME TIMING ISSUES IN PLACE AMONGST THE OPERATIONAL MODEL SUITE. FOR NOW...DID INTRODUCE CHANCE POPS ACROSS SW NH/W MA AROUND MIDDAY /THOUGH THIS MAY BE A BIT TOO FAST/...THEN PUSHES ACROSS THE REMAINDER OF THE INTERIOR DURING THE AFTERNOON. MAY HOLD OFF UNTIL EVENING /IF THEN/ FOR COASTAL AREAS. LOOKS LIKE MOST ENERGY WILL REMAIN ACROSS THE INTERIOR AS THE H5 HEIGHTS LIFT BACK INTO NORTHERN NEW ENGLAND AND SOUTHERN QUEBEC TUE NIGHT. EXPECT THE FRONT TO CLEAR THE COAST LATE TUE NIGHT WITH ANY LEFTOVER PRECIP ENDING. WEDNESDAY... EXPECT DRIER AIR TO SLOWLY WORK ACROSS THE REGION DURING THE DAY ON LIGHT W WINDS. HIGH PRES RIDGE WILL BUILD OUT OF THE APPALACHIANS. TEMPS WILL REMAIN WARM WITH A GENERAL W WIND FLOW THROUGHOUT THE LAYER. HIGHS WILL BE IN THE LOWER-MID 80S. THURSDAY AND FRIDAY... EXPECT DRY AND MILD CONDITIONS CONTINUING WITH DEWPTS DOWN TO THE 50S...THOUGH AROUND 60 ALONG THE IMMEDIATE COAST. HIGHS WILL BE IN THE UPPER 70S TO MID 80S BOTH DAYS. A DRY FRONT MAY PUSH THROUGH EARLY FRI WITH LITTLE MORE THAN A WIND SHIFT. SATURDAY... LOTS OF QUESTIONS DURING THIS TIMEFRAME AS A COLD FRONT TRIES TO WORK ACROSS THE NORTHERN TIER...MAINLY DUE TO UPPER LEVEL PATTERN THAT MAY TRY TO CHANGE ACROSS NORTH CENTRAL CANADA. TIMING IS VERY MUCH IN QUESTION...THOUGH FOR NOW HAVE MENTIONED CHANCE POPS AS THE FRONT MAY TRY TO WORK IN. LOW CONFIDENCE WITH THIS FEATURE. && .AVIATION /09Z SUNDAY THROUGH THURSDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THRU SUNDAY NIGHT/...HIGH CONFIDENCE IN TRENDS BUT LOWER CONFIDENCE IN PRECISE DETAILS AND TIMING. TODAY...VFR SKY COVER WITH AREAS OF MVFR CIGS AROUND 2000 FEET. THE LOWER CIGS SHOULD IMPROVE TO VFR LATE MORNING AND AFTERNOON. DEVELOPING TSTMS AFTER NOON WITH BEST CHANCE AFTER 3 PM. BEST CHANCE WILL BE WESTERN/NORTHERN MASS AND SOUTHERN NH. MVFR/IFR CONDITIONS IN ANY STORMS WITH POTENTIAL FOR HEAVY DOWNPOURS AND STRONG WIND GUSTS...POSSIBLY A FEW DAMAGING WIND GUSTS. TONIGHT...CONVECTION CONTINUES INTO THE EARLY NIGHT BUT SHOULD DIMINISH AFTER SUNSET. MVFR/IFR CIGS AND VSBYS IN ANY THUNDERSTORMS. MVFR/IFR CIGS AND VSBYS IN FOG OVERNIGHT. MONDAY...MVFR CIGS/VSBYS IN SHOWERS AND SCATTERED TSTMS. IFR CIGS/VSBYS IN MORNING FOG. LOCALLY HEAVY DOWNPOURS STILL POSSIBLE. KBOS TERMINAL...HIGH CONFIDENCE IN TAF REGARDING TRENDS BUT LOWER CONFIDENCE ON PRECISE DETAILS AND TIMING. KBDL TERMINAL...HIGH CONFIDENCE IN TAF REGARDING TRENDS BUT LOWER CONFIDENCE ON PRECISE DETAILS AND TIMING. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY... MONDAY NIGHT...MODERATE CONFIDENCE. MVFR-IFR CIGS/VSBYS IN AREAS OF SHOWERS. POSSIBLE TSRA ESPECIALLY INLAND THROUGH MIDNIGHT. WILL SEE SOME IMPROVING CONDITIONS AS PRECIP MOVES OFFSHORE OVERNIGHT...BUT MAY CAUSE MVFR-IFR VSBYS IN AREAS OF FOG AFTER MIDNIGHT. TUESDAY...MODERATE CONFIDENCE. MVFR-IFR VSBYS THROUGH AROUND 14Z IN PATCHY FOG...THEN BRIEF PERIOD OF VFR. MAY SEE PERIODS OF MVFR IN SCT SHOWERS/TSTMS ESPECIALLY INLAND DURING THE AFTERNOON/EVENING. PRECIP SHOULD TAPER OFF AFTER MIDNIGHT. PATCHY FOG RETURNS AFTER 05Z-06Z WITH MVFR-IFR VSBYS IN NORMALLY PRONE INLAND LOCATIONS. WEDNESDAY AND THURSDAY...MODERATE CONFIDENCE. EXPECT MAINLY VFR CONDITIONS AS HIGH PRESSURE BUILDS IN. LOCAL MVFR- IFR VSBYS IN PATCHY FOG THROUGH 14Z WED. MAY AGAIN SEE LOCAL MVFR- IFR VSBYS IN PATCHY FOG AROUND DAYBREAK THU OVER THE FAR INTERIOR /SW NH AND N CENTRAL-W MA/. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. MODERATE CONFIDENCE TODAY THROUGH MONDAY. TODAY... DRY WEATHER FOR MUCH OF THE DAY. POTENTIAL FOR SHOWERS/TSTMS AFTER 4 PM...EXCEPT AFTER 2 PM NORTH OF CAPE ANN. ANY STORMS WILL HAVE STRONG WIND GUSTS AS WELL AS POOR VISIBILITY IN HEAVY DOWNPOURS. SOUTHWEST WIND WILL GUST TO 20-22 KNOTS WHICH IS CLOSE TO SMALL CRAFT LEVELS. THE PERSISTENCE OF THE WIND WILL BUILD SEAS A TAD WITH 5 FOOT HEIGHTS MOVING INTO THE OUTER WATERS LATE IN THE DAY. A SMALL CRAFT ADVISORY HAS BEEN PUT IN EFFECT ON THE OUTER WATERS STARTING THIS EVENING. IT IS MAINLY FOR THE 5 FOOT SEAS...BUT WINDS WILL BE CLOSE TO THRESHOLD AND SO WE WILL KEEP THE HEADLINE NON-SPECIFIC. TONIGHT... THE POTENTIAL FOR 5 FOOT SEAS WILL EXTEND INTO RI SOUND ON THE SOUTHWEST WIND. GAVE SOME THOUGHT ABOUT SIMILAR POTENTIALS FOR BLOCK ISLAND SOUND AND BUZZARDS BAY...BUT PREFERRED THE BETTER FETCH INTO RI SOUND WHERE A SMALL CRAFT ADVISORY WILL BE IN EFFECT. SHOWERS AND THUNDERSTORMS MAY MOVE ACROSS THE WATERS. BEST CHANCE ON TIMING OF THE STORMS WOULD BE THE FIRST PART OF TONIGHT...BUT CONDITIONS WILL REMAIN FAVORABLE THROUGH THE NIGHT. ANY STORMS WOULD HAVE STRONG WIND GUSTS EARLY TONIGHT AND POOR VISIBILITY IN HEAVY DOWNPOURS AT ANY TIME. MONDAY... WINDS AND SEAS DIMINISH BELOW SMALL CRAFT LEVELS. SMALL CRAFTS WILL LINGER OVER THE OUTER WATERS DURING THE MORNING. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY... MONDAY NIGHT...MODERATE CONFIDENCE. SW WINDS DIMINISH DURING THE NIGHT. LEFTOVER 5 FT SEAS MAY LINGER ACROSS THE FAR OUTER WATERS S AND E OF NANTUCKET EARLY MON NIGHT...THEN SHOULD SUBSIDE. TUESDAY THROUGH THURSDAY...MODERATE CONFIDENCE. EXPECT WINDS AND SEAS BELOW SMALL CRAFT CRITERIA. MAY SEE SOME SW WIND GUSTS UP TO 20 KT TUE NIGHT BEFORE SHIFTING TO W-NW AND DIMINISHING BY WED MORNING. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 5 AM EDT MONDAY FOR ANZ250. SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 11 AM EDT MONDAY FOR ANZ254>256. SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 6 AM EDT MONDAY FOR ANZ235. && $$ SYNOPSIS...WTB/EVT NEAR TERM...WTB SHORT TERM...WTB LONG TERM...EVT AVIATION...WTB/EVT MARINE...WTB/EVT

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