Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 121300 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 900 AM EDT SAT JUL 12 2014 .SYNOPSIS... DRY AND BEAUTIFUL SUMMER WEATHER CONTINUES TODAY. BREEZY AND TURNING MORE HUMID SUNDAY ALONG WITH A CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS WESTERN NEW ENGLAND LATE IN THE DAY. BECOMING UNSETTLED EARLY NEXT WEEK WITH PERIODS OF SHOWERS AND THUNDERSTORMS. SOME OF THE STORMS MAY BE STRONG ALONG WITH LOCALIZED FLASH FLOODING. A TREND TOWARD DRIER AND LESS HUMID WEATHER FOLLOWS MID TO LATE NEXT WEEK. && .NEAR TERM /UNTIL 7 PM THIS EVENING/... 9 AM UPDATE... A BEAUTIFUL DAY IN PROGRESS WITH SUNNY SKIES AT MID MORNING. SOME SCATTERED DIURNAL CUMULUS WILL DEVELOP THIS AFTERNOON PARTICULARLY ACROSS THE INTERIOR...BUT STILL PLENTY OF SUNSHINE EXPECTED. NOT ENOUGH MOISTURE/FORCING FOR ANY PRECIPITATION THIS AFTERNOON...SO WILL CONTINUE WITH A DRY FORECAST. HIGH PRESSURE WILL SLOWLY MOVE OFF THE COAST...ALLOWING FOR READINGS A FEW DEGREES WARMER THAN YESTERDAY. AFTERNOON HIGH TEMPS WILL MAINLY BE IN THE MIDDLE TO UPPER 80S...EXCEPT A FEW DEGREES COOLER ACROSS SOME LOCALES ON THE IMMEDIATE COAST WITH SEA BREEZES DEVELOPING. HUMIDITY LEVELS WILL REMAIN COMFORTABLE FOR JULY STANDARDS. && .SHORT TERM /7 PM THIS EVENING THROUGH 6 PM SUNDAY/... TONIGHT... A FEW SPOTTY SHOWERS MAY SPARK BY THE EVENING HOURS ESP ACROSS THE BERKS WHERE A THIN LINE OF INSTABILITY MAY DEVELOP. HOWEVER BECAUSE OF THE LOW PROBABILITY REMAINED A DRY FORECAST. HIGH PRESSURE WILL CONTINUE TO MOVE EASTWARD OUT TOWARDS GEORGES BANK LATE TONIGHT ALLOWING FOR RETURN FLOW. LOW LEVEL MOISTURE WILL INCREASE ALLOWING FOR THE POTENTIAL FOR FOG TO DEVELOP OVERNIGHT. OTHERWISE ANTICIPATE A DRY NIGHT AS THE BETTER FORCING AND LIFT FOR ANY SHOWERS IS TO FAR WEST. ASTRONOMICAL HIGH TIDE WILL OCCUR TONIGHT ALLOWING FOR THE POSSIBILITY OF MINOR SPLASHOVER ACROSS EAST FACING BEACHES ON THE MASS COASTLINE. TOMORROW... UPPER LEVEL TROUGH WILL BEGIN TO SWING ITS WAY TOWARDS THE EASTERN HALF OF THE REGION. A WEAK WAVE WILL MOVE THROUGH THE FLOW SPARKING OF SOME SHOWERS AND THUNDERSTORMS...ESPECIALLY ACROSS UPSTATE NEW YORK. STILL PLENTY OF DRY AIR ALOFT OVER SOUTHERN NEW ENGLAND ON SUNDAY SO BELIEVE THAT MUCH OF THE REGION SHOULD REMAIN DRY MINUS THE WESTERN ZONES. PWATS ARE INCREASING CLOSE TO 2 INCHES AND WITH 850MB LLJ INCREASING...COULD SEE SOME HEAVY RAINFALL OUT OF ANY THUNDERSTORMS THAT DEVELOP. ESP WEST OF THE CENTRAL HILLS...CAPE VALUES ARE INCREASING TO 1000 J/KG AND 0-6 KM SHEAR VALUES AROUND 325-30 KTS MAY ALLOW FOR SOME GUSTY WINDS AS WELL AS THE HEAVY RAINFALL POTENTIAL. BELIEVE AREAL COVERAGE WILL BE ISOLATED BY THE LATE MORNING/EARLY AFTERNOON...BUT INCREASE INTO THE EVENING HOURS AND SHORTWAVE APPROACHES SOUTHERN NEW ENGLAND. SOUNDINGS SUGGEST THAT MIXING UP TO 850 MB WILL OCCUR WHICH WOULD ALLOW FOR TEMPS TO WARM UP TO THE MIT TO UPPER 80S. WITH THE INCREASE IN 850 MB WINDS...EXPECT GUSTY WINDS BETWEEN 20-30 MPH ON SUNDAY. DEWPOINTS WILL ALSO BE ON THE INCREASE WHICH WILL ALLOW FOR THE RETURN OF THAT SUMMERTIME MUGGINESS. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... HIGHLIGHTS... * SHOWERS AND THUNDERSTORMS LIKELY SUN NIGHT THROUGH TUESDAY WITH STRONG STORMS POSSIBLE ALONG WITH A THREAT FOR FLASH FLOODING * DRIER AND LESS HUMID WEATHER RETURNS THURSDAY AND FRIDAY. SYNOPTIC OVERVIEW AND GUIDANCE EVALUATION... ENSEMBLES AND DETERMINISTIC GUIDANCE CONTINUE TO SHOW GOOD CONTINUITY ON AN EVOLVING HIGHLY AMPLIFIED PATTERN ACROSS NORTH AMERICA BEGINNING THIS WEEKEND AND CONTINUING INTO NEXT WEEK. THE LONG WAVE PATTERN WILL FEATURE TWO HIGH AMPLITUDE RIDGES...ONE ACROSS WESTERN CANADA ATTAINING HEIGHTS + 3 SD. THE OTHER RIDGE WILL BE LOCATED OVER THE NORTHWEST ATLC. BETWEEN THESE TWO RIDGES AN ANOMALOUS CLOSED LOW DIVES SOUTHWARD INTO THE GREAT LAKES WITH HEIGHTS REACHING -3 SD TUE OVER THE OH VLY. THIS HIGH AMPLITUDE MERIDIONAL FLOW WILL BE ACCOMPANIED BY A STRONG FRONTAL ZONE WITH TROPICAL MOISTURE TO THE EAST AND A SPRING-LIKE COOL AIRMASS TO THE WEST. THIS FRONTAL ZONE WILL ALSO BE ACCOMPANIED BY STRONG JET DYNAMICS...YIELDING A RISK FOR STRONG TO SEVERE TSTMS MON AND TUE ALONG WITH A THREAT FOR FLASH FLOODING. 00Z GEFS ENSEMBLES AND ITS OPERATIONAL 00Z GFS ARE MORE PROGRESSIVE WITH THE UPPER TROUGH AND FRONTAL PASSAGE THAN THE 12Z ECENS ENSEMBLES AND NEW 00Z ECMWF. THESE ARE TYPICAL MODEL BIASES WE SEE WITH FRONTAL PASSAGES... ECMWF/ECENS SLOWER THAN GFS/GEFS. GIVEN THE TIME RANGE HERE BEST COURSE OF ACTION IS TO FOLLOW A MODEL BLEND TO MINIMIZE MODEL BIASES. ALTHOUGH WOULD NOT BE SURPRISED TO SEE THE SLOWER ECMWF/ECENS SOLUTIONS VERIFY GIVEN THE HIGH AMPLITUDE MERIDIONAL FLOW. DAILY DETAILS... SUNDAY NIGHT...A MILD NIGHT AS WARM SECTOR OVERSPREADS SOUTHERN NEW ENGLAND. RISK OF SCATTERED SHOWERS/TSTMS AS WELL. MONDAY...LEAD SHORT WAVE TROUGH AND ATTENDING PREFRONTAL TROUGH SHOULD BE SUFFICIENT TO TRIGGER SCATTERED SHOWERS/T-STORMS ACROSS THE REGION WITH A MORE OF A FOCUS OVER WESTERN NEW ENGLAND GIVEN PROXIMITY TO TROUGH. PWATS + 2 SD COMBINED WITH AT LEAST MODEST INSTABILITY OF 1000-1500 ML CAPES SUPPORT T-STORMS WITH POTENTIAL HEAVY RAIN AND WIND. WARM AND MUGGY CONDITIONS AS WELL. TUESDAY...TIMING DIFFERENCES HERE REGARDING ARRIVAL OF TRAILING SHORT WAVE TROUGH AND ATTENDING SURFACE COLD FRONT. GFS AND ITS ENSEMBLES FASTER THAN THE ECMWF AND ECENS. NEVERTHELESS STRONGER JET DYNAMICS WITH THIS TRAILING SHORT WAVE TROUGH AS GEFS ANOMALIES SUGGEST 250 MB JET REACHING + 3 SD OVER NY STATE WITH RRQ ACROSS SOUTHERN NEW ENGLAND. THIS WILL PROVIDE STRONG QG FORCING. THESE SYNOPTIC SCALE FEATURES COMBINED WITH MODEL QPF SIGNAL HEAVY RAINFALL POTENTIAL WITH NEW 00Z ECMWF STORM TOTAL OF 1-3" ACROSS THE REGION...HEAVIEST AMOUNTS WESTERN CT/MA. 00Z GFS NOT FAR BEHIND WITH UP TO 2.5" ACROSS THE BERKSHIRES. THE MORE PROGRESSIVE 00Z GEFS INDICATE AREAS OF LOW PROBABILITY OF 2-3" RAINS FROM NJ NORTHEAST TO DOWNEAST ME. THUS A MODERATE RISK OF HEAVY RAIN AND LOCALIZED FLOODING HERE MON AND TUE. WARM AND MUGGY CONDITIONS CONTINUE AS WELL. WEDNESDAY...LOTS OF UNCERTAINTY HERE GIVEN MODEL SPREAD ON TIMING OF FRONTAL PASSAGE. A MODEL BLEND SUGGEST THIS WILL BE OUR TRANSITION DAY WITH A RISK OF SHOWERS/T-STORMS ACROSS EASTERN MA AND RI EARLY IN THE DAY...FOLLOWED BY A TREND TOWARD DRIER/LESS HUMID CONDITIONS FROM WEST TO EAST AS FRONTAL PASSAGE WORKS ACROSS THE REGION. THURSDAY AND FRIDAY...MID/UPPER LEVEL TROUGH REMAINS WEST OF NEW ENGLAND THU HOWEVER THE UPPER AIR PATTERN BEGINS TO DEAMPLIFY AS SHORT WAVE TROUGH LIFTS NORTHEAST INTO SOUTHEAST CANADA FRI. OVERALL THIS SUPPORTS A TREND TOWARD DRIER AND LESS HUMID WEATHER FOR SOUTHERN NEW ENGLAND. && .AVIATION /12Z 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/...HIGH CONFIDENCE. 7 AM UPDATE...NO CHANGE FROM 06Z TAFS. EARLIER DISCUSSION BELOW. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TODAY AND TONIGHT...VFR OTHER THAN PERHAPS A TOUCH OF LATE NIGHT/EARLY MORNING PATCHY GROUND FOG IN THE TYPICALLY PRONE LOCATIONS. SEA BREEZES ON BOTH COASTLINES. SUNDAY...VFR TO START. MVFR CIGS POSSIBLE IN SHOWER AND THUNDERSTORM DEVELOP BY LATE SUNDAY AFTERNOON ESP ACROSS WESTERN SITES. KBOS TAF...HIGH CONFIDENCE IN TAF. EASTERLY SEA BREEZE DEVELOPS AROUND 14-15Z. KBDL TAF...HIGH CONFIDENCE IN TAF. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY... MODERATE TO HIGH CONFIDENCE ON MVFR/IFR AT NIGHT IN AREAS OF FOG ALONG WITH SCATTERED SHOWERS/TSTMS. CONDITIONS MAY IMPROVE TO LOW END VFR DURING THE AFTERNOON HOURS. HOWEVER RISK OF SHOWERS/TSTMS INCREASE DURING THIS TIME. LOW PROBABILITY OF SOME IMPROVEMENT WED FROM WEST TO EAST. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TODAY THROUGH SUNDAY/...HIGH CONFIDENCE. NICE BOATING WEATHER THROUGH TONIGHT. WEAK PRESSURE GRADIENT WILL KEEP WINDS/SEAS BELOW SCA THRESHOLDS. VARIABLE WINDS THIS MORNING WILL BECOME SOUTHERLY AT 5 TO 15 KNOTS AS HIGH PRESSURE MOVES OFF THE COAST. WINDS WILL THEN BECOME SOUTH SOUTHWEST AT THE SAME SPEEDS BY TONIGHT. PRESSURE GRADIENT INCREASES ON SUNDAY ALLOWING FOR WINDS ACROSS THE WATERS TO INCREASE TO 20 KTS. EXPECT NEAR SHORE WATERS TO GUST CLOSER TO 30 KTS. SCA MAY BE NEEDED. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY... MODERATE TO HIGH CONFIDENCE ON MODEST SSW WINDS 15-20 KT WITH GUSTS UP TO 25 POSSIBLE. VSBY LOWERING AT TIMES IN AREAS OF FOG ALONG WITH TROPICAL DOWNPOURS SUN NGT THRU TUE. SOME IMPROVEMENT POSSIBLE WED AS FRONTAL PASSAGE MAY SWEEP ACROSS THE WATERS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...NOCERA/DUNTEN NEAR TERM...DUNTEN/NOCERA SHORT TERM...DUNTEN LONG TERM...NOCERA AVIATION...NOCERA/DUNTEN MARINE...NOCERA/DUNTEN

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