Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 022036 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 436 PM EDT THU JUL 2 2015 .SYNOPSIS... A COLD FRONT SHIFTS SOUTH OF NEW ENGLAND TONIGHT. HIGH PRESSURE BUILDS OVER THE REGION LATER TONIGHT AND FRIDAY. A MAINLY QUIET AND DRY 4TH OF JULY HOLIDAY WEEKEND BENEATH HIGH PRESSURE IS MAINTAINED INTO EARLY NEXT WEEK. THEREAFTER THE WEATHER TAKES A TURN TOWARDS A WARM...MUGGY...WET-WEATHER PATTERN WITH CHANCES OF SHOWERS AND THUNDERSTORMS BY MIDWEEK POSSIBLY CONTINUING INTO THE FOLLOWING WEEKEND. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... COLD FRONT LIES ALONG OUR SOUTH COAST. ONE AREA OF SHOWERS/TSTMS IS PASSING SOUTH OF THE REGION. THE TRACK OF THIS WEATHER KEEPS MOST OF IT OFFSHORE...BUT COULD CLIP THE ISLANDS DURING THIS EVENING. OUTSIDE CHANCE OF SHOWERS REACHING THE SOUTH COAST ESPECIALLY AROUND THE ELBOW OF CAPE COD. PER WATER VAPOR IMAGERY...A SHORTWAVE MOVING THROUGH THE GREAT LAKES IS INDUCING A WAVE ALONG THE COLD FRONT THAT IS MOVING ACROSS THE APPALACHIANS. THE RIGHT ENTRANCE REGION OF THE SUPPORTING UPPER JET WILL SWEEP ACROSS NEW ENGLAND DURING THE FIRST PART OF TONIGHT. THIS SHOULD SUPPORT CLOUDS AND SHOWERS THROUGH MIDNIGHT...BUT MOSTLY OFFSHORE. AGAIN...THE BEST CHANCE WILL BE ACROSS THE ISLANDS WITH DIMINISHING CHANCE FARTHER NORTH. AS THE WAVE MOVES PAST THE SURFACE FLOW SHOULD TURN NORTHWEST AND DRAW DRIER AIR FARTHER SOUTH. EXPECT DRY WEATHER FOR MOST AREAS WITH DIMINISHING SKY COVER AFTER MIDNIGHT. DEW POINTS IN THE 50S INLAND AND LOWER 60S ALONG THE COAST...WHICH PROVIDES A GOOD ESTIMATE FOR OVERNIGHT LOW TEMPS. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... FRIDAY... HIGH PRESSURE BUILDS OVER THE REGION WITH PLENTY OF SUBSIDENCE. EXPECT CLEAR OR MOSTLY CLEAR SKIES. PRESSURE GRADIENT WILL BE LIGHT...SO LIGHT WINDS THROUGH THE DAY. THIS SHOULD ALLOW SEA BREEZES TO FORM ALONG THE COASTS LATE MORNING/EARLY AFTERNOON. THE MIXED LAYER IS FORECAST TO REACH 850 MB WITH AFTERNOON TEMPS AT THAT LEVEL AROUND 10C. MIXING THIS TO THE SURFACE SHOULD SUPPORT MAX TEMPS IN THE UPPER 70S...CALL IT 75 TO 80. COOLER VALUES WHERE THE SEA BREEZE TAKES HOLD. FRIDAY NIGHT... HIGH PRESSURE SHIFTS EAST BUT REMAINS IN CONTROL OVER NEW ENGLAND. ANOTHER SHORTWAVE MOVES OVER THE GREAT LAKES AND FORMS ANOTHER WAVE ALONG THE FRONT TO OUR SOUTH. THIS SHOULD GENERATE ANOTHER AREA OF CLOUDS AND SHOWERS THAT APPROACH FROM OUR SOUTH OVERNIGHT. WE WILL BRING SOME INCREASE IN SKY COVER DURING THE NIGHT WITH THE MOST COVER ALONG THE SOUTH COAST. BUT THE DRY AIR IN PLACE AND THE FOCUS OF SUPPORTING LIFT TO OUR SOUTH SHOULD KEEP THE WEATHER DRY. WITH DEW POINTS IN THE 50S...MIN TEMPS SHOULD BE IN THE 50S AND AROUND 60. && .LONG TERM /SATURDAY THROUGH THURSDAY/... */ HIGHLIGHTS... - POSSIBLE SHOWER ACTIVITY FOR THE 4TH OF JULY? - DRY INTO EARLY NEXT WEEK...PERHAPS WARMER - RETURN OF WARM...MUGGY...AND WET-WEATHER BY MIDWEEK - CHANCES FOR THUNDERSTORMS AND HEAVY RAIN */ DISCUSSION... AN EBB AND FLOW PATTERN. SHOULD A H5 LOW ANOMALY MAINTAIN ACROSS THE N ATLANTIC WITH H5 RIDGING IN AND AROUND THE VICINITY OF THE W CONUS THEN H5 TROUGHING WOULD BE PREFERRED THROUGH THE C-CONUS ALONG THE E- PERIPHERY OF WHICH THE NE-CONUS WOULD EXPERIENCE AN ACTIVE WEATHER PATTERN WHILE WOBBLING BETWEEN AIRMASSES. NOTHING IS CERTAIN AS THE ATMOSPHERIC IS CHAOTIC...BUT INTERPRETING ANOMALIES AS OF LATE WHILE INTERROGATING ENSEMBLE DATA LEADS TO CONFIDENCE THAT WE WILL NOT BE SEEING HEAT-WAVES NOR 100-DEGREE TEMPERATURES ANYTIME SOON. A SWAY OF TEMPERATURES NOT OUT OF THE QUESTION WITH EXCHANGING AIRMASSES... GOING FROM COOL AND DRY TO WARM AND MUGGY...A PATTERN AS OF LATE THAT IS LIKELY TO CONTINUE. IT WILL BE INTERESTING TO SEE IF WE DRAW PARALLELS TO THE WEAK EL-NINO SUMMER OF 2004 WITH THE C-CONUS HAVING WELL BELOW-NORMAL SUMMER TEMPERATURES WITH THE NE-CONUS HOLDING NEAR- NORMAL. LETS KEEP IT SIMPLE AND STRAIGHT-FORWARD WITH THE ABOVE DISCUSSION IN MIND. A CONSENSUS OF FORECAST GUIDANCE IS WARRANTED AS THERE IS OVERALL GOOD AGREEMENT INTO EARLY NEXT WEEK. BY MIDWEEK THERE ARE SIGNALS OF DISCREPANCY AS FORECAST GUIDANCE HANDLES THE RETURN OF WARM AND MUGGY CONDITIONS ALONG WITH THE CHANCE OF SHOWERS AND THUNDERSTORMS. BEST TO LOOK AT CIPS ANALOGS TO SEE IF THERE IS ANY- THING WE SHOULD BE CONCERNED ABOUT ON THE HORIZON. */ DAILIES... JULY 4TH WEEKEND: WEAK HIGH PRESSURE AND DRY-CAPPING MECHANISM KEEPS US PERHAPS QUIET AND DRY THROUGHOUT THE PERIOD? YET THERE HAS BEEN AN INDICATION OF A STOUT STRETCHED MID-LEVEL VORTEX THROUGH THE OVERALL TROUGH-PATTERN FOR QUITE SOME TIME. WILL NEED TO MONITOR THE RELATIVE STRENGTH OF THE HIGH UP AGAINST THE FORCING MECHANISMS ASSOCIATED WITH MID-LEVEL ENERGY ALOFT...WHETHER WE CAN GET SOME SHOWER ACTIVITY MAINLY PER MID-LEVEL FORCING IN WHAT APPEARS TO BE A RATHER DRY ENVIRONMENT WITH A MEASURE OF STABILITY. WILL KEEP WITH A MOSTLY-DRY FORECAST FOR NOW BUT HOLDING SLIGHT CHANCE POPS OVER S AND W PORTIONS OF S NEW ENGLAND...WITH CHANCE POPS S OFFSHORE. OTHERWISE LOW- TO MID-LEVEL CLOUD DECKS ENCROACH FROM THE WEST. FLOW LOOKS TO BE RATHER LIGHT...AND BENEATH HIGH PRESSURE MAY MAKE FOR SOME SMOKEY FIREWORKS DISPLAYS. PERHAPS SOME FASTER FLOW MOVES IN BY 3Z AS THE 02.12Z NAM SUGGESTS BUT THINK ITS TOO ROBUST. WIND SPEEDS THROUGH MIDNIGHT LOOK TO BE AROUND 5 MPH AND NOT ENTIRELY CLEAR AS FROM WHAT DIRECTION. SEASONABLE TEMPERATURES THROUGHOUT. EARLY NEXT WEEK: KEEPING IT DRY. HIGH PRESSURE SWEEPS ACROSS THE REGION. CHILLY INTO MONDAY MORNING BUT BEGIN TO SEE RETURN S-FLOW BY THE END OF THE DAY GOING ON INTO TUESDAY. COULD SEE A WARMER-THAN-AVERAGE PATTERN AT LEAST BY TUESDAY WITH H85 +14C AIR MOVING IN ALOFT. HIGHS AROUND THE MID-80S WITH LOW-LYING INTERIOR RIVER VALLEYS INTO THE UPPER-80S. MIDWEEK: A RETURN OF WARM-MUGGY CONDITIONS AHEAD OF A SWEEPING SYNOPTIC LOW DISTURBANCE FROM THE N. INCREASING INSTABILITY AND MOISTURE ALONG AND AHEAD. CONFIDENCE TOWARDS CHANCES OF SHOWERS AND THUNDERSTORMS. FROM THE CIPS ANALOG GUIDANCE...ANALOGS DERIVED FROM THE 0Z GEFS HAVE A 60% CHANCE OF ABOVE-AVERAGE PRECIPITATION FOR PORTIONS OF THE NE-CONUS...AND NATURALLY WITH THE AFOREMENTIONED ENVIRONMENT...THE THREAT OF HEAVY RAIN IS NOT OUT OF THE QUESTION. SHOULD THE TROUGHING PATTERN PERSIST AS A CONSENSUS OF DETERMINISTIC SOLUTIONS SUGGEST THEN WE COULD BE LOOKING AT ROUNDS OF WET-WEATHER ALL THE WAY THROUGH THE WEEK INTO NEXT WEEKEND. LOW CONFIDENCE. NO CERTAINTY ON OUTCOMES. WILL MAINTAIN SEASONABLE CONDITIONS THROUGH- OUT THE FORECAST. && .AVIATION /21Z THURSDAY THROUGH TUESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /THROUGH FRIDAY NIGHT/... TONIGHT...HIGH CONFIDENCE. MAINLY VFR. SHOWERS LIKELY FOR KACK...POSSIBLY REACHING THE VINEYARD. LOW PROBABILITY OF SHOWERS FOR CAPE COD. AREAS OF MVFR/IFR POSSIBLE IN ANY SHOWERS/FOG. FRIDAY...HIGH CONFIDENCE. VFR. SEA BREEZES DEVELOPING. FRIDAY NIGHT...HIGH CONFIDENCE. VFR. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK /SATURDAY THROUGH TUESDAY/...MODERATE CONFIDENCE. VFR. VRB WINDS WITH SEA-BREEZES ALONG THE COASTS. MORE PROMINENT S- WINDS BY TUESDAY. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /THROUGH FRIDAY NIGHT/... TONIGHT... BUOY REPORTS CONTINUE TO SHOW 5 FOOT SEAS ON THE SOUTHERN OUTER WATERS...BUT MARGINAL. WE WILL KEEP SMALL CRAFTS UP THROUGH THE EVENING FOR THOSE WATERS. SEAS BELOW 5 FEET FOR MOST OF OUR WATERS. WEST TO SOUTHWEST WINDS BECOME NORTHWEST TO NORTH...BUT REMAIN WELL BELOW 20 KNOTS. FRIDAY AND FRIDAY NIGHT... HIGH PRESSURE MOVES OVER NEW ENGLAND. WINDS AND SEAS SHOULD REMAIN BELOW SMALL CRAFT THRESHOLDS. OUTLOOK /SATURDAY THROUGH TUESDAY/... VARIABLE WINDS THROUGHOUT WITH SEA-BREEZES ALONG THE COASTS WILL MAKE FOR GOOD BOATING WEATHER THROUGH MONDAY. MORE PROMINENT S-WINDS ARE ANTICIPATED BY TUESDAY WITH GUSTS UP TO 15 KTS. WILL HOLD SEAS BELOW 5-FEET DESPITE ANTICIPATED SWELL FROM W-E S-OFFSHORE STORM SYSTEMS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EDT THIS EVENING FOR ANZ255- 256. && $$ SYNOPSIS...WTB/SIPPRELL NEAR TERM...WTB/SIPPRELL SHORT TERM...WTB LONG TERM...SIPPRELL AVIATION...WTB/SIPPRELL MARINE...WTB/SIPPRELL

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