Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 280800 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 400 AM EDT SUN JUN 28 2015 .SYNOPSIS... A WINDSWEPT RAIN...HEAVY AT TIMES CONTINUES EARLY THIS MORNING WITH LOCALIZED FLOODING POSSIBLE. RAIN TAPERS OFF TO SHOWERS AND/OR DRIZZLE LATE THIS MORNING AND EARLY AFTERNOON. STRONG EAST WINDS THIS MORNING MAY RESULT IN A FEW DOWN TREE LIMBS/BRANCHES AND ISOLATED POWER OUTAGES. DRY WEATHER RETURNS MONDAY WITH TEMPERATURES SLIGHTLY COOLER THAN NORMAL. WARMER WEATHER ARRIVES TUE AHEAD OF A COLD FRONT WHICH WILL RESULT IN SCATTERED SHOWERS/THUNDERSTORMS TUE NIGHT INTO WED. SOME STORMS MAY BE STRONG WED. BEHIND THE FRONT DRIER WEATHER RETURNS THU. SCATTERED SHOWERS/THUNDERSTORMS POSSIBLE AGAIN FRI AND/OR SATURDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 200 AM UPDATE... FIRST ROUND OF HEAVY RAIN IS MOVING THROUGH THE REGION THIS MORNING. LOOKING DOWNSTREAM APPEARS THAT PRECIP IS MORE SHOWERY IN NATURE. HOWEVER APPEARS THAT SURFACE LOW CONTINUES TO DEVELOP OVER THE DELMARVA REGION. AS IT DEVELOPS...SURFACE FRONTOGENESIS IS STRENGTHENING SOUTH OF LONG ISLAND AND WITH LLJ INCREASING AND VERY HIGH MOISTURE TRANSPORT...EXPECT PRECIP TO FILL IN SOUTH OF LI AND CONTINUE ITS NORTHWARD TREND. UPPER LEVEL WINDS OFF OF THE VWP CONTINUE TO SHOW THAT THE LLJ IS INCREASING. IN FACT SURFACE WINDS OVER LONG ISLAND AND WST ARE ALREADY GUSTING TO NEAR 30 KTS AND 35 KTS OVER THE WATER. WFO OKX IS ALREADY REPORTING SOME TREE DAMAGE ALONG LONG ISLAND WITH THE THE SATURATED GROUND EXPECT MORE REPORTS TO OCCUR. ONLY MAJOR CHANGE TO THE FORECAST WAS TO SPEED UP THE TIMING OF THE PRECIP SO EVERYONE IS OVER 100 POPS. ALSO CLEANED UP THE ENDING TIME AS CONDITIONS TREND TO BE MORE SCT IN NATURE. IN FACT ONCE DRY SLOT MOVES IN...WINDS GO CALM AND COULD SEE FOG/DRIZZLE THROUGH MUCH OF THE DAY TODAY. OTHERWISE FORECAST REMAINS ON TRACK FOR THIS MORNING. NO CHANGES TO THE HAZARDS AT THIS TIME. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... *** HEAVY RAIN/LOCALIZED FLOOD THREAT VERY LATE TONIGHT INTO SUNDAY MORNING WITH WINDY CONDITIONS ALONG THE COAST *** ANOMALOUS CLOSED LOW OVER THE GREAT LAKES WILL COMBINED WITH SURFACE LOW PRESSURE TRACKING ACROSS SOUTHEAST MA TO RESULT IN A HEAVY RAIN EVENT VERY LATE TONIGHT INTO SUNDAY MORNING. THE MAIN CONCERNS ARE FOR LOCALIZED FLOODING AND A PERIOD OF STRONG EASTERLY WINDS ALONG THE COAST. WILL BREAK DOWN THE POTENTIAL CONCERNS WITH THIS SYSTEM ONE BY ONE. 1) HEAVY RAIN AND LOCALIZED FLOOD POTENTIAL: AS WE MENTIONED QUITE THE ANOMALOUS SYSTEM FOR LATE JUNE STANDARDS. DEEP CLOSED LOW OVER THE GREAT LAKES AND ASSOCIATED LOW SURFACE TRACKING ACROSS FAR SOUTHEAST MA WILL SET THE STAGE FOR A HEAVY RAIN EVENT. THE ANOMALIES FOR THIS UPCOMING EVENT ARE QUITE REMARKABLE...ESPECIALLY WITH 925 MB EASTERLY WIND COMPONENT 5+ STANDARD DEVIATIONS FOR A TIME OVERNIGHT INTO SUNDAY MORNING. PWATS ARE ALSO 2 TO 3 STANDARD DEVIATIONS ABOVE NORMAL AND THERE IS SOME ELEVATED INSTABILITY. THIS WILL RESULT IN A PERIOD OF VERY STRONG FORCING AND HEAVY RAINFALL. SOME EMBEDDED THUNDERSTORMS ARE ALSO POSSIBLE WHICH MAY RESULT IN LOCALLY HIGHER RAINFALL AMOUNTS. FORTUNATELY...THIS SYSTEM IS FAIRLY PROGRESSIVE WHICH WILL LIMIT RAINFALL TOTALS TO SOME EXTENT. NONETHELESS...WE ARE STILL CONCERNED GIVEN HOW AN EXTREMELY ANOMALOUS EASTERLY JET COMBINED WITH PWATS OVER 2 INCHES AND ELEVATED INSTABILITY. GIVEN THE ABOVE PARAMETERS...HAVE OPTED TO EXPAND FLOOD WATCH INTO EASTERN MA AND RHODE ISLAND. BIGGEST CONCERN IN THIS REGION IS THE TYPICAL URBAN/STREET FLOODING WITH THE POTENTIAL OF 2+ INCH RAINFALL AMOUNTS OCCUR IN LESS THAN 1 HOUR....ESPECIALLY IN THE TYPICALLY PRONE LOCATIONS. FLOOD WATCH ALSO CONTINUES FOR EAST SLOPES OF BERKSHIRES WHERE EASTERLY FLOW SHOULD RESULT IN SOME ENHANCEMENT IN QPF. 2) WIND POTENTIAL: THERE IS SOME UNCERTAINTY ON HOW MUCH WIND WILL BE ABLE TO MIX DOWN FROM THE ANOMALOUS EASTERLY LLJ JET WITH INVERSION IN PLACE. HOWEVER...HEAVIER RAIN OR CONVECTIVE ELEMENTS MAY ALLOW SOME OF THIS TO MIX DOWN AT TIMES. THE NAM IS ALSO SHOWING A PERIOD OF 3 HOUR PRESSURE FALLS CLOSE TO 6 MB...WHICH SHOULD HELP IN GETTING A PERIOD OF 35 TO 45 MPH WINDS TO THE COASTAL PLAIN. WHILE MUCH OF THE REGION MAY REMAIN BELOW OFFICIAL WIND ADVISORY CRITERIA...FULL LEAFED TREES COMBINED WITH HEAVY RAIN MAY INCREASE THE RISK FOR SOME DOWNED TREES/ISOLATED POWER OUTAGES. THEREFORE...DECIDED TO ISSUE A WIND ADVISORY FOR EASTERN MA AND RHODE ISLAND. HIGHEST WINDS EXPECTED FOR VERY LATE TONIGHT INTO SUNDAY MORNING. 3) SEVERE WEATHER POTENTIAL: THE OVERALL SEVERE WEATHER POTENTIAL AND RISK FOR A TORNADO OR TWO APPEARS LOW...BUT ITS NOT ZERO EITHER. GIVEN THE TRACK OF THE SURFACE LOW PRESSURE SYSTEM...MUCH OF THE REGION WILL LIKELY REMAIN NORTH OF THE BOUNDARY ALL DAY. IN FACT...HIGH TEMPS MAY NOT MAKE IT PAST THE LOWER 60S TO THE NORTH OF THE MA PIKE. THE EXCEPTION WILL BE PORTIONS OF RHODE ISLAND AND SOUTHEAST MA...WHERE THEY SHOULD WARM SECTOR FOR A TIME. THE PROBLEM IS THAT THE BULK OF THE STRONG FORCING WILL HAVE LIFTED TO THE NORTH. ALSO...SHALLOW COOL AIR WILL BE SITTING JUST TO THE NORTH OF THE BOUNDARY WHICH IS NOT CONDUCIVE FOR A BRIEF TORNADO. SO ALL IN ALL...APPEARS THE RISK FOR A TORNADO ON SUNDAY IS RATHER LOW BUT GIVEN HIGH HELICITY ON THE BOUNDARY WE CAN NOT COMPLETELY RULE IT OUT. 4) HIGH SURF: GIVEN SEAS BUILDING TO BETWEEN 7 AND 13 FEET ACROSS OUR OUTER- WATERS...HAVE HOISTED A HIGH SURF ADVISORY FOR THE SOUTH AND EAST FACING OCEAN EXPOSED BEACHES OF MA/RI ON SUNDAY. DANGEROUS RIP CURRENTS ARE EXPECTED AS WELL...ALTHOUGH CERTAINLY FAR FROM AN IDEAL BEACH DAY. && .LONG TERM /MONDAY THROUGH SATURDAY/... HIGHLIGHTS... * DRY AND PLEASANT MONDAY * SCATTERED SHOWERS/T-STORMS POSSIBLE TUE NIGHT/WED AND AGAIN FRIDAY AND/OR SATURDAY WITH MANY HOURS OF DRY WEATHER IN BETWEEN * SOME STORMS MAY BE STRONG WEDNESDAY SYNOPTIC OVERVIEW AND MODEL PREFERENCES... ENSEMBLES AND DETERMINISTIC GUIDANCE IN VERY GOOD AGREEMENT ON THIS HIGH AMPLITUDE PATTERN CONTINUING THIS PERIOD WITH A PERSISTENT RIDGE/HEIGHT ANOMALY OVER WESTERN CONUS/SOUTHWEST CANADA. THIS MAINTAINS A DOWNSTREAM HIGH AMPLITUDE TROUGH WITH ITS MEAN POSITION CENTERED OVER THE GREAT LAKES. THIS RESULTS IN A VERY ACTIVE NORTHERN STREAM JET WITH CYCLONIC FLOW INTO NEW ENGLAND MUCH OF THIS PERIOD...YIELDING A CHANCE OF SHOWERS/T-STORMS ABOUT EVERY OTHER DAY. IN BETWEEN MANY HOURS OF DRY WEATHER ALONG WITH NEAR SEASONABLE TEMPERATURES. AS FOR THE MODEL GUIDANCE...THE OPERATIONAL GFS AND ECMWF ARE IN REMARKABLY GOOD AGREEMENT ON BOTH THE DEPTH AND TIMING OF INDIVIDUAL SHORT WAVES THRU WED. THUS WILL FOLLOW THIS GUIDANCE CLOSELY. HOWEVER BY LATE IN THE WEEK AND INTO NEXT WEEKEND THE DETERMINISTIC GUIDANCE BEGINS TO SHOW ITS TYPICAL SHORT COMINGS AT THIS TIME RANGE WITH LARGE DIFFERENCES IN TIMING AND AMPLITUDE OF INDIVIDUAL TROUGHS. THUS LEANED MORE ON THE ENSEMBLES HERE. DAILY SENSIBLE WEATHER... MONDAY...OPEN MID LEVEL WAVE IN ST LWRN RVR VLY EXITS INTO THE MARITIMES WITH HEIGHT RISES AND WARMING TEMPS ALOFT OCCURRING OVER NEW ENGLAND. DESPITE SOME MODELS GENERATING QPF THIS PATTERN WILL SUPPORT A DRY DAY WITH TEMPS SLIGHTLY COOLER THAN NORMAL. NEVERTHELESS A VERY NICE DAY. TUESDAY...NEXT SHORT WAVE TROUGH APPROACHES THE REGION FROM THE OH VLY. APPEARS WARM FRONTAL CONVECTION IS POSSIBLE TUE BUT LIKELY CONFINED TO THE CT RVR VLY AND WESTWARD INTO NY STATE. THUS MUCH OF SOUTHERN NEW ENGLAND WILL REMAIN DRY. S-SW SURFACE WINDS WILL SUPPORT WEAK LOW LEVEL WAA SO TEMPS CLIMBING INTO THE U70S AND L80S...JUST ABOUT NORMAL FOR LATE JUNE. COOLEST READINGS ALONG THE SOUTH COAST. WEDNESDAY...SHORT WAVE TROUGH CLOSER TO THE REGION YIELDING A HIGHER CHANCE FOR SHOWERS AND T-STORMS THAN TUE. GFS/ECMWF AND GEFS ALL SUGGEST MODEST INSTABILITY AND DEEP LAYER SHEAR FOR THE RISK OF A FEW STRONG T-STORMS. WARM AND HUMID WITH RELIEF ARRIVING WED NIGHT OR THU AS POST FRONTAL AIRMASS OVERSPREADS THE REGION. THU/FRI/SAT...AS MENTIONED ABOVE DETERMINISTIC GUIDANCE BEGINS TO DISPLAY LARGE SPREAD HERE SO LEANED HEAVILY ON THE ENSEMBLES FOR THIS TIME PERIOD...WHICH SUGGEST DRY AND SEASONABLE WEATHER THU BEHIND DEPARTING TROUGH WED. THEN A RISK FOR SHOWERS/T-STORMS FRI AND/OR SAT AS NEXT NORTHERN STREAM TROUGH APPROACHES NEW ENGLAND. TEMPS NEAR SEASONABLE FRI/SAT. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH SUNDAY/... BEFORE 12Z...MODERATE TO HIGH CONFIDENCE. CONDITIONS ARE DETERIORATING TO MVFR AS STEADY -RA CONTINUES TO MOVE ACROSS THE TERMINALS. SITES COULD DROP TO IFR WITHIN ANY +RA. EASTERLY WINDS WILL PICK UP WITH GUSTS NEAR 30 KTS ALONG THE COASTLINES OF RA/MA. AFTER 12Z...MVFR/IFR CONDITIONS AREA WIDE AS +SHRA CONTINUES TO MOVE ACROSS THE REGION. E-SE WIND GUSTS WILL INCREASE BETWEEN 30 TO 40 KNOTS DEVELOPING ALONG THE COAST. LLWS WILL AFFECT THE ENTIRE REGION WITH AN ANOMALOUS EAST TO SOUTHEAST LOW LEVEL JET. EMBEDDED ISOLD THUNDERSTORMS ARE ALSO POSSIBLE ESPECIALLY NEAR THE SOUTH COAST THIS MORNING. RAIN TAPERS OFF TO SCATTERED SHOWERS FROM WEST TO EAST THIS AFTERNOON. HOWEVER...IFR TO LOW END MVFR CONDITIONS LIKELY HANG TOUGH IN LOW CLOUDS AND FOG AND DRIZZLE PATCHES BUT SOME TEMPORARY IMPROVEMENT MAY OCCUR ACROSS RHODE ISLAND AND SOUTHEAST MA AS THE REGION WARM SECTORS. TONIGHT...CONDITIONS WILL STILL HANG TOUGH WITH LIGHT WINDS AND INVERSION OVER THE REGION. EXPECT PATCHY FOG ACROSS THE AREA WITH 2 SM FOG ALONG THE EAST MASS COASTLINE. IMPROVEMENTS AROUND DAYBREAK MONDAY. KBOS TERMINAL...MODERATE CONFIDENCE IN TAF TRENDS BUT LOW CONFIDENCE IN EXACT TIMING. KBDL TERMINAL...MODERATE CONFIDENCE IN TAF TRENDS BUT LOW CONFIDENCE IN EXACT TIMING. OUTLOOK...MONDAY THROUGH THURSDAY...MODERATE CONFIDENCE. MONDAY...VFR AND DRY WEATHER LIKELY. TUESDAY...VFR LIKELY FOR RI AND EASTERN MA WITH LOW RISK OF MVFR ACROSS CT INTO WESTERN-CENTRAL MA IN SCATTERED SHOWERS/T-STORMS. TUE NIGHT AND WED...HIGHEST RISK FOR SHOWERS AND T-STORMS. A FEW STRONG STORMS POSSIBLE. MVFR LIKELY. THU...TRENDING TOWARD VFR AND DRIER AS WELL. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TONIGHT AND SUNDAY/...MODERATE TO HIGH CONFIDENCE. ANOMALOUS LOW PRESSURE SYSTEM WILL RESULT IN WINDS AND SEAS INCREASING TONIGHT. STRONGEST WINDS EXPECTED VERY LATE TONIGHT INTO SUNDAY MORNING WITH EASTERLY GUSTS BETWEEN 30 AND 40 KNOTS. GALE WARNINGS IN EFFECT FOR ALL WATERS. SEAS ACROSS THE OUTER-WATERS WILL BUILD TO BETWEEN 7 TO 13 FEET BY SUNDAY MORNING. HEAVY RAIN AND A FEW EMBEDDED THUNDERSTORMS EXPECTED VERY LATE TONIGHT INTO SUNDAY MORNING. OVERALL...SEVERE WEATHER POTENTIAL IS LOW BUT CAN NOT COMPLETELY RULE OUT AN ISOLATED WATERSPOUT ACROSS OUR SOUTHERN WATERS. OUTLOOK...MONDAY THROUGH THURSDAY...MODERATE CONFIDENCE. MONDAY...ROUGH SEAS ON THE OCEAN WATERS FROM LEFTOVER LARGE SE SWELLS. DRY WEATHER AND GOOD VSBY. TUESDAY...WINDS BECOME SOUTH WITH MAINLY DRY WEATHER AND GOOD VSBY. TUE NIGHT AND WED...S-SW WINDS INCREASE AHEAD OF APPROACHING COLD FRONT. SHOWERS AND T-STORMS BECOME LIKELY AS WELL. THURSDAY...IMPROVING TRENDS WITH FRONT LIKELY WELL OFFSHORE. && .HYDROLOGY... 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 SHOULD REMAIN IN THEIR BANKS. HOWEVER...WITH THE VERY HIGH PWATS AND POTENTIAL FOR CONVECTIVE ELEMENTS...ITS POSSIBLE FFG MAY BE EXCEEDED IN SOME AREAS. WIDESPREAD FFG VALUES 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 EAST SLOPES OF THE BERKSHIRES WITH UPSLOPE FLOW. THE SECOND ONE WILL BE SOMEWHERE OVER EASTERN MA/RHODE ISLAND JUST TO THE NORTHWEST OF THE SURFACE LOW PRESSURE SYSTEM ESPECIALLY IF CONVECTIVE ELEMENTS CAN GET INVOLVED. THOSE ARE THE TWO AREAS WHERE A FLOOD WATCH HAS BEEN ISSUED. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...WIND ADVISORY UNTIL NOON EDT TODAY FOR MAZ005>007-013>024. HIGH SURF ADVISORY FROM 8 AM THIS MORNING TO 8 PM EDT THIS EVENING FOR MAZ007-015-016-019>024. FLOOD WATCH UNTIL 2 PM EDT THIS AFTERNOON FOR MAZ005>007- 013>021. FLOOD WATCH THROUGH LATE TONIGHT FOR MAZ002-008-009. RI...WIND ADVISORY UNTIL NOON EDT TODAY FOR RIZ001>008. HIGH SURF ADVISORY FROM 8 AM THIS MORNING TO 8 PM EDT THIS EVENING FOR RIZ006>008. FLOOD WATCH UNTIL 2 PM EDT THIS AFTERNOON FOR RIZ001>007. MARINE...GALE WARNING UNTIL 11 AM EDT THIS MORNING FOR ANZ231>237. GALE WARNING UNTIL 2 PM EDT THIS AFTERNOON FOR ANZ230-254>256. GALE WARNING UNTIL 5 PM EDT THIS AFTERNOON FOR ANZ250-251. && $$ SYNOPSIS...NOCERA NEAR TERM...DUNTEN SHORT TERM...FRANK LONG TERM...NOCERA AVIATION...NOCERA/DUNTEN MARINE...FRANK/NOCERA HYDROLOGY...STAFF

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