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Area Forecast Discussion
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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...

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. 

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...

* 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. 

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...

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.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...

*/ 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.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...

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.

&&

.MARINE...

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.

&&

.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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