175  
FXUS61 KBOX 122255  
AFDBOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BOSTON/NORTON MA  
655 PM EDT THU JUL 12 2018  
   
SYNOPSIS
 
 
HIGH PRESSURE BRINGS DRY WEATHER WITH SEASONABLE TEMPERATURES  
AND COMFORTABLE HUMIDITY THROUGH SATURDAY MORNING. HIT OR MISS  
HEAVY RAINERS AND THUNDERSTORMS ARE POSSIBLE AT TIMES OVER THE  
WEEKEND INTO NEXT WEEK. NEAR OR ABOVE SEASONABLE CONDITIONS  
THROUGHOUT.  
 

 
   
NEAR TERM /THROUGH FRIDAY/
 
 
7 PM UPDATE...  
 
WHILE NO MAJOR CHANGES WITH THE FORECAST UPDATE, MAIN CONCERN  
REVOLVES AROUND PRESENT ONSHORE SEA-BREEZES. DEWPOINTS HAVE  
JUMPED UP AS HIGH AS 10 DEGREES INTO THE UPPER 50S, ESPECIALLY  
AROUND NARRAGANSETT BAY. WITH RADIATIONAL COOLING ON TAP AND  
FORECAST LOWS DOWN INTO THE LOW TO MID 50S FOR TYPICALLY PRONE  
SPOTS, THERE IS THE THREAT OF SHALLOW GROUND FOG FOR SOME  
LOCATIONS. PER THE RAPID REFRESH SHORT-TERM ENSEMBLE, OR NARRE,  
THE RISK APPEARS GREATEST FOR SE-COASTAL NEW ENGLAND WHERE  
PRESENTLY DEWPOINTS HAVE RISEN. VISIBILITY LESS THAN 4 MILES IS  
ENTIRELY POSSIBLE. CAN'T RULE OUT ISSUES FOR SOME OF THE ISLANDS  
ESPECIALLY MARTHAS VINEYARD.  
 
PREVIOUS DISCUSSION...  
 
HIGH PRESSURE AT THE SURFACE REMAINS OVER NEW ENGLAND TONIGHT  
WHILE UPPER TROUGH SLOWLY MOVES EAST. THIS SHOULD BE A DRY  
PATTERN, BUT PRESENCE OF THE TROUGH SUGGESTS A FEW CLOUDS FROM  
NORTHERN NEW ENGLAND MAY HANG AROUND LONG ENOUGH TO SWEEP ACROSS  
SOUTHERN NEW ENGLAND.  
 
OTHERWISE A QUIET NIGHT WITH CLEAR SKIES AND LIGHT WIND. DEW  
POINTS REMAIN IN THE 50S, SO RADIATIONAL COOLING WILL ALLOW  
TEMPS TO COOL INTO THE 50S MOST PLACES, WITH LOW 60S IN SOME  
URBAN CENTERS. PATCHY LATE NIGHT RADIATION FOG IS POSSIBLE IN  
THE TYPICAL PRONE LOCATIONS.  
 

 
   
SHORT TERM /FRIDAY NIGHT/
 
 
TROUGH MOVES OFF TO THE EAST OF OUR AREA WHILE UPPER RIDGE MOVES  
IN. EXPECT SUNNY SKIES AND DRY WEATHER WITH ANOTHER ROUND OF  
DIURNAL CUMULUS FOR THE MIDDAY AND AFTERNOON. THE MIXED LAYER  
ONCE AGAIN GOES DEEP, UP TO 800 MB, TAPPING SIMILAR TEMPERATURES  
TO TODAY...THUS SUPPORTING MAX SFC TEMPS IN THE UPPER 70S TO MID  
80S INLAND. LIGHT FLOW AT THE SURFACE WILL AGAIN ALLOW SEA  
BREEZES ALONG THE COAST WITH SFC TEMPS IN THE 70S.  
 
STILL UNDER THE INFLUENCE OF THE RIDGE, WE EXPECT QUIET WEATHER  
FOR FRIDAY NIGHT WITH LIGHT SURFACE FLOW. TEMPS WILL COOL TO  
BETWEEN 55 AND 65 DEGREES.  
 

 
   
LONG TERM /SATURDAY THROUGH THURSDAY/
 
 
*/ HIGHLIGHTS...  
 
- WEEKEND HIT OR MISS HEAVY RAINERS, THUNDERSTORMS  
- TUESDAY SWEEPING LINE OF HEAVY RAINERS, THUNDERSTORMS  
- LATE WEEK SHOT OF WET WEATHER  
- NEAR OR ABOVE SEASONABLE CONDITIONS THROUGHOUT  
 
*/ OVERVIEW...  
 
WEEKEND INTO FOLLOWING WEEK SCATTERED SHOWERS AND THUNDERSTORMS AT  
TIMES. INTERROGATING THE ATMOSPHERE, INTERESTINGLY A PHASE 5/6 MJO  
HOWEVER LATELY WE'VE SEEN STRONG H85 AND H2 WESTERLY ANOMALIES FOR  
EARLY JULY OVER THE N PACIFIC AND CONUS, NEGLIGIBLE ANOMALIES ALONG  
THE EQUATOR. SIGNALS THAT SUGGEST EXCESSIVE HEAT, HUMIDITY REMAIN  
OUT OF OUR REGION. MORE NOTABLE IS A +2 AO. DOMINANT POLAR LOW WITH  
A NEGATIVE ANOMALY EXTENDING ON UP THROUGH THE STRATOSPHERE. TAKE-  
AWAY ARE LESS PRONOUNCED TROF-DIPS ACROSS THE N HEMISPHERE. SO ITS  
NO SURPRISE ENSEMBLE MEANS SIGNAL NEAR-ZONAL FLOW FROM THE N PACIFIC  
THROUGH THE CONUS WITH A SUBTLE H5 TROF PATTERN AND WEAK WAVE ACTION  
OVER THE E-HALF OF N AMERICA INTO LATE JULY.  
 
THAT BEING SAID, FORECASTING A SERIES OF SWEEPING WEAK DISTURBANCES  
FOR THE FORESEEABLE FUTURE. TRAILING COLD FRONTS ALONG WHICH WE'LL  
SEE HIT OR MISS HEAVY RAINERS, THUNDERSTORMS FOLLOWED BY REFRESHING  
AIRMASSES.  
 
*/ DETAILS...  
 
THE WEEKEND LOOKS BUSY WITH HIT OR MISS ELEMENTS, PERHAPS SATURDAY  
ASSOCIATED WITH REMNANT MCS ACTIVITY THAT RE-FLARES OVER-NIGHT INTO  
SUNDAY ROUND A DOMINANT SE-CONUS H5 RIDGE. BETTER CHANCES OF W WET-  
WEATHER OUTCOMES. WHILE ON SUNDAY A STOUT H5 TROF AXIS DIGS IN FROM  
THE N RENEWING FOCUS. MARGINAL SHEAR, WEAK STEERING FLOW THROUGHOUT.  
PRECIPITABLE WATERS UP TO 2-INCHES. WATCHING K-INDICES, HIGH VALUES  
OF THETA-E. HIT OR MISS, HEAVY RAINERS AND THUNDERSTORMS, PERHAPS  
GUSTY WINDS.  
 
OVER THE WEEK, ANOTHER SWEEPING COLD FRONT TUESDAY, MORE PRONOUNCED,  
PERHAPS LATE. SW INFLOW OF DECENT MOISTURE, INSTABILITY. MARGINAL  
SHEAR, HOWEVER GOOD LIFT AND FORCING, SEEMINGLY BETTER CHANCES OF  
WIDESPREAD OUTCOMES RATHER THAN HIT OR MISS. LOOKING LIKE A LINE OF  
CONVECTIVE OUTCOMES.  
 
ANOTHER ROUND OF WET-WEATHER BY THE END OF THE WEEK. FURTHER OUT IN  
TIME, A LOW CONFIDENCE FORECAST HOWEVER LOOKING LIKE FRIDAY IMPACTS.  
 

 
   
AVIATION /00Z FRIDAY 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/...HIGH CONFIDENCE.  
 
0Z UPDATE...NO MAJOR CHANGES TO THE FORECAST.  
 
MAINLY VFR WITH SCT-BKN 6-10 KFT CIGS. SOME SCT-BKN IFR-LIFR  
POSSIBLE ASSOCIATED WITH LOW GROUND FOG AT TYPICALLY PRONE  
INTERIOR TERMINALS (I.E., BAF, MVY). LIGHT WINDS THROUGHOUT  
WHICH WILL ALLOW ONSHORE SEA- BREEZES TO DEVELOP ALONG  
COASTLINES MID TO LATE MORNING CONTINUING THROUGH AFTERNOON.  
 
KBOS TERMINAL...SEA BREEZE CONTINUES THROUGH 0Z-2Z (8P-11P). A  
NEW SEA BREEZE DEVELOPS 10 AM-NOON FRIDAY.  
 
KBDL TERMINAL...LOW RISK IFR-LIFR VSBYS ASSOCIATED WITH SHALLOW  
GROUND FOG AROUND 9Z-11Z (5A-7A).  
 
OUTLOOK /SATURDAY THROUGH TUESDAY/...  
 
SATURDAY: VFR. SLIGHT CHANCE SHRA.  
 
SATURDAY NIGHT: VFR. SLIGHT CHANCE SHRA, SLIGHT CHANCE TSRA.  
 
SUNDAY: VFR. CHANCE SHRA, CHANCE TSRA.  
 
SUNDAY NIGHT: VFR. SLIGHT CHANCE SHRA, SLIGHT CHANCE TSRA.  
 
MONDAY THROUGH MONDAY NIGHT: VFR.  
 
TUESDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. BREEZY. CHANCE  
SHRA, CHANCE TSRA.  
 

 
   
MARINE
 
 
FORECASTER CONFIDENCE LEVELS...  
 
LOW - LESS THAN 30 PERCENT.  
MODERATE - 30 TO 60 PERCENT.  
HIGH - GREATER THAN 60 PERCENT.  
 
SHORT TERM /THROUGH FRIDAY NIGHT/...HIGH CONFIDENCE.  
 
HIGH PRESSURE MOVES OVER THE WATERS. LIGHT WINDS TREND OUT OF  
THE SOUTHEAST OR SOUTH FRIDAY, WITH SEA BREEZES REDEVELOPING  
NEARSHORE DURING FRIDAY. WINDS LESS THAN 25 KNOTS AND SEAS LESS  
THAN 5 FEET THROUGH FRIDAY NIGHT.  
 
OUTLOOK /SATURDAY THROUGH TUESDAY/...  
 
SATURDAY: WINDS LESS THAN 25 KT.  
 
SATURDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING  
5 FT. SLIGHT CHANCE OF RAIN SHOWERS, SLIGHT CHANCE OF  
THUNDERSTORMS.  
 
SUNDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING 5 FT.  
CHANCE OF RAIN SHOWERS, CHANCE OF THUNDERSTORMS.  
 
SUNDAY NIGHT: WINDS LESS THAN 25 KT. SLIGHT CHANCE OF RAIN  
SHOWERS, SLIGHT CHANCE OF THUNDERSTORMS.  
 
MONDAY THROUGH MONDAY NIGHT: WINDS LESS THAN 25 KT.  
 
TUESDAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS UP  
TO 25 KT. AREAS OF SEAS APPROACHING 5 FT. CHANCE OF RAIN  
SHOWERS, CHANCE OF THUNDERSTORMS.  
 

 
   
TIDES/COASTAL FLOODING
 
 
ASTRONOMICAL TIDES WILL BE RATHER HIGH DURING THE NIGHT TIME  
HIGH TIDE CYCLES TONIGHT THROUGH SAT NIGHT. FORTUNATELY WAVE  
ACTION WILL NOT BE MUCH OF A FACTOR AND SURGE IS LIMITED.  
HOWEVER, LEFTOVER SE SWELL MAY RESULT IN MINOR SPLASHOVER FOR  
VULNERABLE AREAS ALONG EAST COASTAL MA TONIGHT.  
 
TIDES ARE SLIGHTLY HIGHER FRI NIGHT AND SAT NIGHT SO ADDITIONAL  
ROUNDS OF SPLASHOVER ARE POSSIBLE DURING THESE HIGH TIDE  
CYCLES.  
 
INTERESTING TO NOTE...ASTRONOMICAL HIGH TIDES WILL AGAIN BE  
HIGH IN MID-AUGUST BUT A LITTLE LOWER THAN THE CURRENT SET OF  
ASTRO TIDES. THE NEXT SET OF HIGH ASTRONOMICAL TIDES IN JAN-  
FEB WILL BE LOWER THAN THE AUGUST TIDES. THIS TREND TO LOWER  
VALUES FOR THE HIGH ASTRONOMICAL TIDES CONTINUES THROUGH THE  
END OF 2019.  
 
BOSTON ASTRO HIGH TIDE...  
 
12.06 FEET THURSDAY 11:22 PM  
12.25 FEET SATURDAY 12:16 AM  
12.23 FEET SUNDAY 1:11 AM  
 
NANTUCKET ASTRO HIGH TIDE...  
 
4.33 FEET FRIDAY 12:21 AM  
4.38 FEET SATURDAY 1:18 AM  
4.34 FEET SUNDAY 2:15 AM  
 

 
   
BOX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
MA...NONE.  
RI...NONE.  
MARINE...NONE.  
 

 
 

 
 
SYNOPSIS...WTB/SIPPRELL  
NEAR TERM...WTB/SIPPRELL  
SHORT TERM...WTB  
LONG TERM...SIPPRELL  
AVIATION...WTB/SIPPRELL  
MARINE...WTB/SIPPRELL  
TIDES/COASTAL FLOODING...WFO BOX STAFF  
 
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