Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 232347 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 747 PM EDT WED JUL 23 2014 .SYNOPSIS...
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LINE OF THUNDERSTORMS ALONG AND AHEAD OF A COLD FRONT WILL SWEEP ACROSS THE REGION TONIGHT. THUNDERSTORMS WILL BE STRONG TO SEVERE MAINLY NORTH AND WEST OF THE WORCESTER HILLS TRANSITIONING TO SHOWERS SOUTHEASTWARD INTO THURSDAY WITH EMBEDDED RUMBLES OF THUNDER. HIGH PRESSURE BUILDS BACK IN WITH DRIER WEATHER FRIDAY INTO SATURDAY. UNSETTLED WEATHER RETURNS FOR SUNDAY INTO EARLY NEXT WEEK.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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* SEVERE THUNDERSTORM WATCH #432 CONTINUES UNTIL 10 PM EDT THIS EVENING FOR WESTERN MASSACHUSETTS AND SOUTHERN NEW HAMPSHIRE * * LINE OF STRONG TO SEVERE STORMS CONTINUES ACROSS NORTH AND WEST NEW ENGLAND INTO THIS EVENING. * * SEVERE THREATS ARE EXPECTED TO DIMINISH WITH TIME AS THE LINE SWEEPS SOUTHEAST * 730 PM UPDATE... LINE OF STRONG TO SEVERE THUNDERSTORMS CONTINUES TO MARCH E/SE WITH THE MAIN THREATS OF STRONG TO DAMAGING WINDS...ALONG WITH HEAVY RAIN / DOWNPOURS RESULTING IN THE RISK OF URBAN AND POOR DRAINAGE FLASH FLOODING. PER SPC MESOANALYSIS...INSTABILITY ON THE ORDER OF 2K J/KG W/N A REGION OF NEARLY 2+ INCH PWATS PREVAILS. YET THE LINE ENCROACHES ON A REGION OF VERY WEAK / NEGLIGBLE SHEAR. EXPECTING THE LINE TO WEAKEN AS IT CONTINUES TO SLIDE E/SE INTO THE EVENING...BECOMING DIFFUSE WITH JUST WIDESPREAD RAIN AND EMBEDDED THUNDERSTORMS. THIS A CONSEQUENCE OF WEAKER SHEAR AND CONCLUSION OF DAYTIME HEATING. HAVE MODIFIED THE FORECAST WITH THE LATEST TRENDS. KEPT CLOSE TO THE NEAR-TERM GUIDANCE BY INCORPORATING THE RAP/HRRR INTO THE PREVIOUS FORECAST WHICH GAVE A GOOD BLEND OF EXPECTED WEATHER. SEVERE THREATS OF DAMAGING WIND GUSTS AND HEAVY RAIN REMAIN OVER AREAS INCORPORATED IN THE WATCH. UPON CONCLUSION OF THE WATCH... HAVE CONTINUED WITH HEAVY RAIN / GUSTY WIND WORDING INTO THE EARLY MORNING HOURS WITH THE EXPECTATION THAT THERE WILL BE SOME EMBEDDED THUNDER IN A VERY SATURATED ENVIRONMENT. LINE WILL MARCH INTO CENTRAL-SOUTHERN NEW ENGLAND W/N THE NEXT COUPLE OF HOURS...REACHING THE BOSTON-PROVIDENCE CORRIDOR PRIOR TO MIDNIGHT. WILL SEE THE LINE SLOW WITH ITS APPROACH TO THE S/SE... SO IMPACTS FROM PROVIDENCE TO THE SE WILL LINGER INTO THE EARLY MORNING HOURS AND THEN ON INTO MORNING BEFORE CONCLUDING ROUGHLY PRIOR TO MIDDAY.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
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THURSDAY... COLD FRONT WILL SLOW DOWN DURING ITS PASSAGE ACROSS SOUTHERN NEW ENGLAND THURSDAY MORNING. BOTH THE EC AND NAM SHOW A WAVE DEVELOPING ALONG THE FRONT ALLOWING FOR THE SLOW DOWN WHILE THE GFS SEEMS TO BE THE OUTLIER ON PUSHING THE FRONT THOUGH BY 12Z. IN FACT THE UPPER LEVEL TROUGH AXIS IS STILL ACROSS UPSTATE NY BY 12/15Z RESULTING IN CLOUDS AND THE CONFIDENCE THAT PRECIP WILL LINGER ESP FOR AREAS SOUTH AND EAST OF THE BOS-PVD CORRIDOR. BELIEVE THAT BY 00Z THE FRONT AND THE BULK OF THE PRECIP WILL BE OFFSHORE BUT CANNOT RULE OUT A FEW LINGERING SHOWERS ESP FOR THE CAPE AND THE ISLANDS. BECAUSE OF THE SLOW DOWN AND THE POTENTIAL WAVE DEVELOPMENT... CANT RULE OUT THE POTENTIAL FOR EMBEDDED THUNDERSTORMS DURING THE DAY. DRIER AIR WILL WORK ITS WAY IN BEHIND THE FRONT RESULTING IN A COOLER DAY WITH HIGHS WELL BELOW AVERAGE AND CLOSE TO 15 DEGREES COOLER THEN TODAY. ASIDE FROM THE CLOUDS AND LINGERING PRECIP CHANCES...SHOULD BE A PLEASANT DAY.
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&& .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
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*/ HIGHLIGHTS... - DRY AND SEASONABLE INTO FRIDAY - RETURN OF WARM AND MUGGIER CONDITIONS FOR SATURDAY - SIGNIFICANT WEATHER SATURDAY NIGHT INTO EARLY NEXT WEEK - A RETURN OF DRY AND SEASONABLE WEATHER BY MIDWEEK */ OVERVIEW AND MODEL PREFERENCE... SURPRISING PATTERN AS WE CLOSE OUT THE MONTH OF JULY! AS PRESENT NW PACIFIC IMPULSE EJECTS E IT COUPLES WITH AN UPPER-LEVEL LOW PARKED OVER NE CANADA RESULTING IN TROUGH ENHANCEMENT THROUGH THE GREAT LAKES REGION. SUBSEQUENT DOWNSTREAM RIDGING OVER THE N-ATLANTIC AND RIDGE STRENGTHENING OVER THE W-CONUS AHEAD OF A PACIFIC IMPULSE BOTTLED IN THE GULF OF ALASKA...THE ATMOSPHERIC PATTERN BUCKLES. WITH THE STAGNANT PATTERN IN PLACE...ANOMALOUS CONDITIONS PREVAIL AS DECENT AGREEMENT AMONG ENSEMBLE MEMBERS SIGNAL A -3 TO -4 SD IN HEIGHTS/TEMPERATURE/HUMIDITY. BUT A NOTE OF CAUTION: SIMILAR ENSEMBLE MEMBERS OUT TO D8 AND INTO EARLY AUGUST ARE EXHIBITING CONSIDERABLE SPREAD WITHIN NAO/PNA TRENDS. IT IS WITH NO CERTAINTY AS TO HOW THIS PATTERN WILL EVOLVE. THIS MAKES THE FORECAST OVER THE NE-CONUS DIFFICULT FURTHER OUT IN TIME AS NEW ENGLAND ESPECIALLY FINDS ITSELF WITHIN THE E-PERIPHERY OF THE AFOREMENTIONED TROUGH. JUST A SLIGHT WOBBLE OF THE OVERALL BUCKLED PATTERN E OR W CAN RESULT IN CONSIDERABLE CHANGES IN THE FORECAST. FEEL THE DECENT AGREEMENT BETWEEN DETERMINISTIC AND ENSEMBLE MEMBERS WARRANTS A BLEND OF MODEL GUIDANCE TOWARDS THE FORECAST. WILL HIT ON THE MAIN POINTS ALONG WITH ANY PREFERRED GUIDANCE IN THE DAILIES BELOW. */ DAY-TO-DAY DETAILS... THURSDAY NIGHT THROUGH SATURDAY... THINKING A DRY FORECAST PERIOD WITH THE RRQ OF THE UPPER-LEVEL JET SHIFTING SE. FEEL THE COLD FRONT AND ATTENDANT WAVE LOW WILL REMAIN OVER THE WATERS. SHOWERS DISSIPATING /IF ANY/ TOWARDS MIDNIGHT AS DYNAMICS ARE SHUNTED OUT OF THE REGION. OTHERWISE...HIGH PRESSURE AND LIGHT NW-FLOW SWEEPS ACROSS NEW ENGLAND FRIDAY /SEA-BREEZES ALONG THE SHORES/ FOLLOWED BY RETURN BREEZY S/SW-FLOW FOR THE REMAINDER OF THE PERIOD AS THE HIGH SLIDES E/SE AND LOW PRESSURE BEGINS TO BUILD IN FROM THE W. SEASONABLE WX INITIALLY...BUT EXPECT THE RETURN OF WARMER/MUGGIER CONDITIONS BY SATURDAY. LOOKING CLEAR FOR FRIDAY...DIURNAL CUMULUS FOR SATURDAY. SATURDAY NIGHT INTO EARLY NEXT WEEK... THE EVOLUTION OF THE TROUGH AND THE PROXIMITY OF ITS E-PERIPHERY ARE KEYS TO THE FORECAST /AS IS THE OFFSHORE ENHACING RIDGE ACROSS THE N- ATLANTIC/. THE TRACK TIMING AND MORPHOLOGY OF INDIVIDUAL IMPULSES THROUGH THE CYCLONIC FLOW WILL ULTIMATELY DETERMINE THE POTENTIAL OUTCOMES FOR THE REGION. FOR SATURDAY NIGHT INTO SUNDAY...SEEMINGLY AN INITIAL IMPULSE IS A FOCUS FOR CONVECTIVE ACTIVITY /PERHAPS A MCS/ WHERE THERMAL/MOIST AXES AND SUBSEQUENT INSTABILITY CONVERGE AT THE SURFACE AND ALONG THE NOSE OF A LLJ REAR OF AN ATTENDANT WARM-FRONT. THE MORE ZONAL REGIME ADVECTS THIS ACTIVITY W-TO-E. NEARLY UNI-DIRECTIONAL SHEAR PRESENTS A THREAT OF DAMAGING WIND. BUT EARLY IN TIME AND LIKELY ABUNDANCE OF CLOUD COVER...THREAT MAY BE LIMITED. HINTS OF MID-LEVEL DRYING AND WAKE SUBSIDENCE? JUST A HUGE MESS. MAY BE LOOKING AT MORE WIDESPREAD STRATIFORM WITH EMBEDDED THUNDERSTORMS. WHO KNOWS...JUST A FIRST GUESS. BIGGEST CONCERN IS THE PLUME OF PWATS EXCEEDING 1.5 INCHES AND A POSSIBLE RISK OF FLASH FLOODING. SOME CONFIDENCE OF THAT AT LEAST. INTO MONDAY...THE LOW DEEPENS AS IT OCCLUDES OVER THE GREAT LAKES. ALONG AND AHEAD OF THE COLD FRONT WITHIN WARM/MUGGY/UNSTABLE CONDITIONS...CONVECTION IS LIKELY WITHIN AN ENVIRONMENT OF DEEP- LAYER FORCING...BUT IT IS JUST TOO EARLY TO GO INTO DETAIL. MANY QUESTIONS AS TO WHETHER THE ENVIRONMENT WILL DESTABILIZE BENEATH STRONG SW-NE UNI-DIRECTIONAL SHEAR. APPEARS ACTIVITY MAY OCCUR IN THE MORNING ONCE AGAIN FOLLOWED BY MID-LEVEL DRYING AND SUBSIDENCE. YEESH. AGAIN...LOTS OF UNCERTAINTY. ONLY CONFIDENCE IS WITH SURGING PWATS IN EXCESS OF 2-INCHES CONTINUING THE POSSIBLE RISK OF FLASH FLOODING. A FINAL NOTE...EVALUATING THE 23.0Z AND 23.12Z CIPS ANALOGS...BOTH PING UPON POTENTIAL CONVECTIVE THREATS SUNDAY AND MONDAY. THE PROBABILITIES OF SEVERE WEATHER IMPACTS HAVE SLIGHTLY INCREASED WITH THE 23.12Z ANALOGS /UP TO 70-PERCENT/. SO WHILE THE ABOVE DISCUSSION CONTAINS A FAIR AMOUNT OF UNCERTAINTY...THE FORECAST STILL WARRANTS CLOSE MONITORING. AT SOME POINT THE COLD FRONT SHOULD PUSH E BEHIND WHICH DRIER AND COOLER AIR WRAPPING INTO THE OCCLUSION SHOULD PREVAIL RESULTING IN SEASONABLE CONDITIONS FOR THE REGION. WHETHER THIS OCCURS ON TUESDAY OR WEDNESDAY...JUST TOO UNCERTAIN.
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&& .AVIATION /00Z THURSDAY THROUGH MONDAY/...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH THURSDAY/...MODERATE CONFIDENCE. LINE OF TSRA/+RA SWEEPING S/SE. STRONGEST MAINLY W OF LWM-BED-IJD. MIX OF MVFR-IFR IMPACTS WITH PASSAGE ALONG WITH NW GUSTS OF AROUND 20 KTS. STRONGER TO DAMAGING GUSTS POSSIBLE FOR W AND CENTRAL NEW ENGLAND TERMINALS. LINE WILL WEAKEN FURTHER S/SE WITH TIME. TAFS TRENDED ACCORDINGLY. FOR THOSE TAFS E OF MHT-ORH-IJD...WILL HOLD OFF ON TSRA MENTION TILL ACTIVITY GETS REASONABLY CLOSER. TOWARDS MORNING...WIDESPREAD RA W/ EMBEDDED TSRA LINGERS FOR THE S/SE TERMINALS EXITING OUT TO SEA BY ABOUT MIDDAY. COASTAL FOG ALONG WITH VLIFR-IFR CIGS ALONG THE IMMEDIATE S-COAST /ESPECIALLY ACK/ IS ANTICIPATED. CONDITIONS IMPROVING TOWARDS VFR NW-SE WITH TIME DURING THE DAY THURSDAY. KBOS TAF...MODERATE CONFIDENCE. WILL HOLD W/ VCTS AT 2Z. HOLD OFF ON TSRA MENTION UNTIL ACTIVITY CLOSES IN. TREND IS FOR TSRA TO WEAKEN BELOW THE POINT OF CONSIDERATION PRIOR TO THE TERMINAL. KBDL TAF...MODERATE CONFIDENCE. TSRA ON THE DOOR STEP SHOULD GET IN SHORTLY AFTER 0Z. PREVAILED ACCORDINGLY. W/N 0-1Z...STRONG LINE OF STORMS WITH FREQUENT LIGHTNING AND STRONG TO DAMAGING WINDS ANTICIPATED. OUTLOOK...THURSDAY NIGHT THROUGH MONDAY... THURSDAY NIGHT THROUGH SATURDAY...HIGH CONFIDENCE. VFR. -RA MOVES OUT THURSDAY NIGHT UNDER NW FLOW. LIGHT WINDS AND MOSTLY CLEAR ON FRIDAY /SEA-BREEZES ALONG THE SHORES/. SCT-BKN 5 KFT CIGS SATURDAY WITH BREEZY S/SW WINDS. SATURDAY NIGHT THROUGH MONDAY...LOW CONFIDENCE. PERIODS OF RA/TSRA. MIX OF MVFR-IFR CONDITIONS...WORST OF WHICH ANTICIPATED DURING OVERNIGHT PERIODS AND +RA. CONTINUED BLUSTERY S/SW WINDS.
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&& .MARINE...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH THURSDAY/...MODERATE CONFIDENCE. THE SW FLOW WILL STRENGTHEN AHEAD OF A COLD FRONT TO PRODUCE GUSTS APPROACHING 25 KT ACROSS MANY OF THE NEAR SHORE WATERS...THEREFORE SCA IS STILL IN EFFECT. SEAS MAY APPROACH 5 FEET EAST OF CAPE ANN THIS EVENING. OTHERWISE WILL NEED TO MONITOR FOR AREAS OF FOG THAT MAY DEVELOP ALONG THE SOUTH COASTAL WATERS TONIGHT. OUTLOOK...THURSDAY NIGHT THROUGH MONDAY... THURSDAY NIGHT THROUGH SATURDAY...HIGH CONFIDENCE. TRANQUIL BOATING WEATHER. SOME SHOWERS MAY LINGER ALONG THE SE OUTER- WATERS THURSDAY NIGHT...BUT SHOULD BE GOOD AFTER MIDNIGHT. HIGH PRESSURE AND LIGHT NW-FLOW FRIDAY /SEA-BREEZES ALONG THE SHORES/. WINDS VEER S/SW OVERNIGHT AND BECOME BREEZY DURING THE DAY SATURDAY. SATURDAY NIGHT THROUGH MONDAY...LOW CONFIDENCE. WEATHER TURNING SOUR. INCREASE S/SW WINDS AHEAD OF A STRONG LOW OVER THE GREAT LAKES REGION WILL RESULT IN SIGNIFICANT WAVE HEIGHTS OVER THE S-WATERS ESPECIALLY. SHOWERS/THUNDERSTORMS ANTICIPATED SOME OF WHICH COULD BE STRONG.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ230>237-251. SMALL CRAFT ADVISORY UNTIL 8 AM EDT THURSDAY FOR ANZ250-254. && $$ SYNOPSIS...DUNTEN/SIPPRELL NEAR TERM...DUNTEN/SIPPRELL SHORT TERM...DUNTEN LONG TERM...SIPPRELL AVIATION...DUNTEN/SIPPRELL MARINE...DUNTEN/SIPPRELL

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