Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 191423 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1023 AM EDT SAT JUL 19 2014 .SYNOPSIS... HIGH PRESSURE OVER THE NORTHEAST WILL SLOWLY MOVE OFFSHORE THROUGH SUNDAY. LOW PRESSURE DEVELOPING OFF THE CAROLINAS WILL PASS SOUTHEAST OF NANTUCKET DURING THE DAY ON SUNDAY. ANOTHER ROUND OF HIGH PRESSURE WILL BRING ABOUT DRY...BUT WARMER AND HUMID CONDITIONS THROUGH MID WEEK. A COLD FRONT FROM CANADA MOVES OVER NEW ENGLAND LATE IN THE WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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1030 AM UPDATE... WEAK OPEN-WAVE DISTURBANCE PRESENTLY TRANSLATING THROUGH THE EASTERN GREAT LAKES REGION ALONG WITH ACCOMPANYING ISENTROPIC LIFT AND WEAK ASCENT IS LENDING TO SHOWERS OVER THE OHIO RIVER VALLEY WITH BROKEN-OVERCAST CONDITIONS ELSEWHERE ENCOMPASSING A MAJORITY OF THE NORTHEASTERN CONUS. COMBINED WITH A SLIGHTLY COOLER AIRMASS IN PLACE ALOFT /H85 TEMPERATURES +10-12C WITH H925 AROUND +16C/ NETS HIGHS AROUND THE UPPER-70S...ROUGHLY 5-DEGREES BELOW NORMAL WITH RESPECT TO HIGHS FOR THIS TIME OF YEAR. ANY RADAR RETURNS OVER NEW ENGLAND ARE MAINLY WITHIN THE MID- TO UPPER-LEVELS. ABUNDANCE OF DRY AIR REMNANT TO THE DEPARTING HIGH PRESSURE WILL SQUASH ANY WET WEATHER FROM REACHING THE GROUND. SHOULD REMAIN A DRY DAY. OTHERWISE...AS NOTED BY THE PREVIOUS FORECASTER...CONTINUE TO MONITOR A WEAK MID-ATLANTIC IMPULSE LIFTING NORTHEAST ALONG A STALLED FRONTAL BOUNDARY WELL OFFSHORE OF NEW ENGLAND. INVOKING A WAVE LOW ALONG THE FRONT...THIS WILL BECOME AN AREA OF INTEREST TONIGHT INTO SUNDAY WITH SOME LIGHT SHOWERY WEATHER FOR S/SE COASTAL REGIONS. BUT ACTIVITY SOUTH OF THE FRONT WITHIN THE MORE TROPICAL AND SOUPY AIRMASS MAY LIMIT ACTIVITY NORTH. NO MAJOR CHANGES MADE TO THE FORECAST OTHER THAN MINOR TWEAKS TO ACCOUNT FORE PRESENT TRENDS.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... TONIGHT...AN OFFSHORE HIGH PRESSURE WILL KEEP THE WEATHER DRY MOST PLACES...AS A SURFACE RIDGE EXTENDS WEST ACROSS SOUTHERN NEW ENGLAND. WE CONTINUE TO WATCH A SOUTHERN STREAM SHORTWAVE THAT IS EXPECTED TO GENERATE A COASTAL LOW OFF THE CAROLINAS BY THIS EVENING. WITH SOUTHWEST FLOW ALOFT...WE EXPECT THIS WEAK LOW PRESSURE WILL MOVE TOWARD OUR REGION TONIGHT. THE QUESTION WHICH REMAINS IS HOW CLOSE THIS LOW PRESSURE WILL GET. JUST ABOUT ALL OF THE 19/00Z GUIDANCE BRINGS SOME PRECIPITATION INTO CAPE COD AND THE ISLANDS. SOME GUIDANCE SOURCES BRING SOME RAINFALL EVEN FARTHER NORTHWEST. THINKING THE SURFACE RIDGE WILL HOLD STRONG...SO HAVE KEPT THE BRUNT OF THE RAINFALL OFFSHORE. THIS IS SIMILAR TO PREVIOUS FORECAST THINKING. SUNDAY...BEST CHANCE OF SHOWERS WILL BE ACROSS THE CAPE/ISLANDS WITH A MOIST ONSHORE FLOW...WHILE A RIDGE OF HIGH PRESSURE SHOULD CURTAIL THE RAINFALL FROM MAKING FURTHER NORTH/WEST. HOWEVER... THIS WILL HAVE TO BE CLOSELY MONITORED. THERE WILL BE CONSIDERABLE CLOUDINESS...WITH A GRADUAL CLEARING TREND GETTING UNDERWAY... ESPECIALLY LATER IN THE DAY. AN ONSHORE FLOW WILL KEEP COASTAL AREAS IN PARTICULAR COOLER. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... HIGHLIGHTS... * INCREASING HUMIDITY MON. * WARMER AND MORE HUMID THROUGH MID WEEK. * BEST CHANCE OF SHOWERS AND THUNDERSTORMS IN THE WEDNESDAY AND THURSDAY TIMEFRAME WITH THE APPROACH OF A COLD FRONT. OVERVIEW AND MODEL PREFERENCES... WHILE THERE IS DECENT AGREEMENT THROUGH THE MID TERM BETWEEN BOTH OPERATIONAL AND ENSEMBLE MODELS...TYPICAL LATE LONG TERM ISSUES ARE EVIDENT IN THE FLOW. THE ISSUE AT HAND IS A DEEPENING AND DIGGING WAVE FROM CENTRAL CANADA AND INTO THE MIDWEST. IT IS ATTEMPTING TO SPLIT BUILDING MID AND UPPER LVL RIDGING BOTH ACROSS THE SW CONUS AND THE SUBTROPICAL RIDGE ASSOCIATED WITH THE BERMUDA HIGH. THESE FEATURES WILL DEFINE THE EARLY PART OF THE WEEK...BUT IT/S THIS LATE WEEK TROF...WHERE MOST OF THE UNCERTAINTY LIES...WHICH WILL DEFINE THE END OF THE WEEK. THE CAMPS ARE SPLIT BETWEEN THE MORE PROGRESSIVE GFS...WHICH PUSHES A COLD FRONT THROUGH BY THU WITH THIS TROF...WHILE THE DEEPER AND SLOWER ECMWF LEAVES THE FRONT TO LINGER ACROSS THE REGION INTO THE WEEKEND. FOR NOW...A CONSENSUS BLEND WILL BE USED UNTIL THE TROF/RIDGE BREAKDOWN IS BETTER RESOLVED. DETAILS... SUN NIGHT INTO MON... HIGH PRES SLOWLY REGAINS CONTROL ACROSS THE REGION AS A WEAK FRONTAL WAVE MOVES NE INTO THE MARITIMES...AND BOTH SW CONUS RIDGING AND THE BERMUDA HIGH BUILDS. THIS WILL BRING AN END TO ANY SHOWER THREAT FROM THE FRONTAL WAVE...HOWEVER LINGERING CLOUDS AND ONSHORE FLOW WILL KEEP MIN TEMPS MILD SUN NIGHT AND HIGHS ON THE COOL SIDE DURING THE DAY MON. WILL CARRY LOWS ABOVE NORMAL AND HIGHS BELOW. FRONTAL WAVE APPROACH WILL INCREASE THE THREAT FOR EVENING STRATUS/FOG. TUE INTO WED... WITH BUILDING SE RIDGE AND BERMUDA HIGH...INCREASING TEMPS AND HUMIDITY THROUGH THE COLUMN ARE EXPECTED. A WEAK WARM FRONT WILL MOVE NW OF THE AREA ON TUE...AND MAY YIELD AN ISOLATED THREAT FOR AFTERNOON CONVECTION BUT TO THE W...WHERE A WEAK SLACKENING IN THE PRES GRADIENT SUGGESTS A POTENTIAL WEAK TROF. FLOW IS WEAK SO WILL MAINLY HOLD POPS TO NIL EXCEPT FOR THE EXTREME W PERIPHERY OF MA/CT. BY WED WITH A COLD FRONT APPROACHING FROM CANADA/GREAT LAKES...SHOULD A TRUE PRE FRONTAL TROF DEVELOP MAY HAVE A BETTER SHOT AT AFTERNOON CONVECTION. AS PREVIOUS SHIFT NOTED...COLUMN IS CERTAINLY DESTABILIZED...BUT THE QUESTIONS ARE THE LACK OF SHEAR...A FOCUS FOR LIFT...OR CAP WITH H7 TEMPS NEAR +10C. SO ONLY LOW CHANCE OF SLIGHT CHANCE POPS WILL BE USED AT THIS TIME. H85 TEMPS APPROACH +18C EACH DAY...SO WITH ENOUGH SUNSHINE AND MIXING TEMPS ARE LIKELY TO REACH NEAR 90F IN SPOTS...WITH DWPTS IN THE 60S SUGGESTING HIGHER HUMIDITY. THU INTO FRI... A SLOWING COLD FRONT WILL CROSS THE REGION AT SOME POINT DURING THIS PERIOD. ALTHOUGH THE AMPLIFYING PATTERN FAVORS THE SLOWER SOLUTIONS. IN FACT...MODELS DO INDICATE A WAVE OF LOW PRES MAY DEVELOP ALONG THE FRONT AS IT SLOWS IN THE VICINITY OF SRN NEW ENGLAND. IN ANY CASE...THE PERIPHERY OF THE RIDGE STILL FEATURES MODESTLY UNSTABLE AIRMASS WITH MUCAPES APPROACHING 1000-1500J/KG AND A MORE SHEAR AS THE JET DEVELOPS TO THE W. THEREFORE...WILL CARRY CHANCE POPS HIGHEST DURING PEAK HEATING EACH DAY FOR SHOWERS AND THUNDERSTORMS. HEAVY RAIN IS POSSIBLE GIVEN PWATS 1.75-2.00 INCHES. NEXT WEEKEND... DEPENDENT ON FRONTAL TIMING. HOWEVER...THE PROJECTED AIRMASS SUGGESTS LOWER HUMIDITY AND SEASONABLE TEMPERATURES. HOWEVER...SHOULD THE FRONT STALL IN THE VICINITY...UNSETTLED WX MAY CONTINUE. && .AVIATION /14Z SATURDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH THURSDAY NIGHT/... TODAY...HIGH CONFIDENCE. VFR AFTER SOME PATCHY EARLY MORNING GROUND FOG BURNS OFF. SEA BREEZES LIKELY DEVELOP A BIT EARLIER THAN NORMAL...MAINLY BY MID MORNING THANKS TO WEAK EASTERLY COMPONENT TO THE WIND. TONIGHT...HIGH CONFIDENCE. VFR. SHOWERS MAY BRING BRIEF MVFR VSBYS TO THE ISLANDS LATE AT NIGHT. SUNDAY...MODERATE CONFIDENCE. MVFR/IFR POSSIBLE IN LOW CEILINGS AND SHRA MAINLY CONFINED TO CAPE COD AND THE ISLANDS. VFR EXPECTED ELSEWHERE. KBOS TAF...HIGH CONFIDENCE IN TAF. SEA BREEZE DEVELOPS AROUND 14-15Z TODAY. KBDL TAF...HIGH CONFIDENCE IN TAF. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY... MONDAY THROUGH WEDNESDAY...MODERATE CONFIDENCE. WHILE VFR WILL LIKELY DOMINATE MOST DAYS...SOME OVERNIGHT FOG/STRATUS MAY LEAD TO MVFR/IFR CONDITIONS ESPECIALLY ALONG S COASTAL LOCATIONS MON NIGHT AND TUE NIGHT. CHANCE FOR LOCALIZED MVFR/IFR CONDITIONS IN SHOWERS AND THUNDERSTORMS ESPECIALLY WED. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. THROUGH SUNDAY...HIGH CONFIDENCE. WAVE MODELS CONTINUE TO OVER-FORECAST WAVE HEIGHTS OFF OUR COAST BY ABOUT A FOOT. LOWERED THE WAVE HEIGHT GUIDANCE BY 20 PERCENT THROUGH THE FORECAST PERIOD. TRANQUIL BOATING WEATHER EXPECTED WITH HIGH PRESSURE OVERHEAD. LIGHT WINDS TREND TO SOUTHEAST TODAY AS THE HIGH MOVES OFFSHORE... THEN TO EAST TONIGHT. WINDS AND SEAS WILL REMAIN BELOW SMALL CRAFT THRESHOLDS THROUGH SUNDAY. COASTAL LOW PRESSURE DEVELOPING OFF THE CAROLINAS TODAY WILL MOVE UP THE COAST TONIGHT. CURRENT FORECAST TRACK WOULD KEEP MOST OF THIS STORM WELL OFFSHORE. BUT FORECAST MODELS AGREE ON LIGHT SHOWERS INTO OUR SOUTHERN WATERS AFTER MIDNIGHT TONIGHT... ESPECIALLY SOUTH AND EAST OF NANTUCKET. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY... AFTER LOW PRESSURE EXITS TO THE EAST LATE SUNDAY NIGHT...HIGH PRESSURE WILL ONCE AGAIN REGAIN CONTROL ACROSS THE WATERS. HAVE MODERATE CONFIDENCE THAT WINDS AND SEAS WILL REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS THROUGH THE PERIOD. BUT A FEW WIND GUSTS AND HIGHER SEAS ARE POSSIBLE ESPECIALLY BY WED AS THE SW WINDS INCREASE. SOME SHOWERS OR THUNDERSTORMS ARE POSSIBLE OVER THE SOUTHEAST WATERS SUN NIGHT WITH A THREAT FOR SHOWERS AND THUNDERSTORMS POSSIBLE ACROSS ALL WATERS ON WED. SOME FOG MAY LEAD TO VSBY RESTRICTIONS ON ESPECIALLY MON AND TUE NIGHTS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...BELK/DOODY NEAR TERM...SIPPRELL/DOODY SHORT TERM...BELK LONG TERM...DOODY AVIATION...BELK/DOODY MARINE...BELK/DOODY

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