Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 260004
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
804 PM EDT TUE AUG 25 2015

.SYNOPSIS...
A COLD FRONT WILL BRING SCATTERED SHOWERS AND THUNDERSTORMS AS IT
SLOWLY CROSSES SOUTHERN NEW ENGLAND TONIGHT. HIGH PRESSURE SLOWLY
BUILDS IN FOR MID AND LATE WEEK WITH MAINLY DRY AND SEASONABLE
WEATHER AND COMFORTABLE HUMIDITY LEVELS EXPECTED WEDNESDAY INTO
SATURDAY. WARMER TEMPERATURES AND HIGHER HUMIDITIES RETURN FOR THE
BEGINNING OF NEXT WEEK.

&&

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

735 PM UPDATE...

LINE OF SLOW MOVING SHOWERS AND THUNDERSTORMS CONTINUES FROM NW
WORCESTER AND EASTERN FRANKLIN COUNTIES SW THROUGH NEAR THE
HARTFORD-SPRINGFIELD AREA INTO NW HARTFORD COUNTY AT 2330Z.

AS THE SUN HAS SET...THREAT FOR SEVERE WEATHER HAS LOWERED.
HOWEVER...CONVECTION HAS BEEN TRAINING ACROSS PORTIONS OF THE CT
VALLEY AND MOVED VERY SLOWLY E OVER THE LAST FEW HOURS AHEAD OF
NEARLY STATIONARY FRONT NEAR THE NEW ENGLAND/NY STATE LINE. LOW
LEVEL CONVERGENCE AND HIGH DEWPTS /AROUND 70 DEGREES/ IN PLACE
HELPING WITH VERY HEAVY DOWNPOURS IN SHOWERS/TSTMS. HAVE ISSUED
FLOOD ADVISORIES AND WARNINGS IN THIS GENERAL AREA OVER THE LAST
FEW HOURS.

NOTING SOME LOW CLOUDS BEGINNING TO PUSH ONSHORE ACROSS THE MID
AND OUTER CAPE AND NANTUCKET WHICH LOOK TO SHIFT CLOSE TO THE
IMMEDIATE E COAST ON GENERAL S-SE WINDS. DEBRIS CLOUDS FROM THE
CONVECTION TO THE W WILL PUSH SLOWLY E THROUGH MIDNIGHT OR SO.
SOME QUESTION HOW FAR E THE CONVECTION WILL MOVE AS IT WEAKENS
OVERNIGHT AS THE FRONT SLOWLY CROSSES.

HAVE UPDATED NEAR TERM WEATHER TO SLOW THE PROGRESSION OF THE
SHOWERS/TSTMS A BIT OVERNIGHT...HAVING THEM ARRIVE INTO E MA/RI
UNTIL BETWEEN 06Z-08Z. BETTER ENERGY DOES EVENTUALLY LIFT NE WITH
WEAK WAVE ON THE FRONT AS IT SHIFTS E.

REMAINDER OF GRIDS IN DECENT SHAPE. HAVE UPDATED TO BRING CURRENT
AND INCORPORATED TIMING INTO OVERNIGHT FORECAST.

PREVIOUS DISCUSSION...
COLD FRONT CONTINUES TO SLOWLY MOVES ACROSS SOUTHERN NEW
ENGLAND...REACHING THE EAST MASS COAST TOWARD DAYBREAK. CHANCE OF
SHOWERS/FEW TSTMS WILL LINGER UNTIL IT MOVES THROUGH...BUT
INCOMING MID LEVEL DRY AIR WILL LIMIT THE ABILITY OF ANY SHOWER.
DEW POINTS WILL REMAIN HIGH MUCH OF THE NIGHT...BUT BEGIN TO LOWER
OVERNIGHT AFTER THE COLD FRONT MOVES THROUGH.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
UPPER LOW LINGERS OVER QUEBEC WITH CYCLONIC FLOW AND COLD
ADVECTION ALOFT OVER NEW ENGLAND. SURFACE HIGH PRESSURE SUPPLIES
SUBSIDENCE NEAR GROUND. PLENTY OF DRY AIR NEAR THE SURFACE AND A
MOIST LAYER ABOVE 850 MB. EXPECT THERE WILL BE SOME CLOUDS
WEDNESDAY...BUT OTHERWISE A FAIR DAY WITH MIXING REACHING UP TO
825 MB AND POSSIBLY A LITTLE HIGHER. TEMPS AT THAT LEVEL WILL
SUPPORT MAX SFC TEMPS IN THE LOW TO MID 80S. DEW POINTS WILL TREND
LOWER /MORE COMFORTABLE/ WITH AFTERNOON VALUES IN THE MID 50S TO
AROUND 60.

FAIR WEATHER CONTINUES WEDNESDAY NIGHT WITH A LIGHT NORTHWEST
WIND. MIN TEMPS WILL REACH NEAR DEW POINT MOST PLACES WITH VALUES
IN THE MID 50S TO LOW 60S...A LITTLE HIGHER IN BOSTON AND ALONG
THE CAPE AND ISLANDS.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...

OVERVIEW...

MEDIUM RANGE MODELS AND ENSEMBLES REMAIN IN VERY GOOD AGREEMENT
DURING THE THU-SAT TIMEFRAME...WEAKENING THE EASTERN LONG WAVE
TROUGHING AS CUTOFF LOW LIFTS NE OVER EASTERN CANADA. UPPER FLOW
BECOMES MORE ZONAL ACROSS THE EASTERN SEABOARD BY LATE THIS WEEK.
LARGE SURFACE HIGH PRESSURE WILL BE THE DOMINANT FEATURE ACROSS
THE EASTERN HALF OF THE U.S. INTO THIS WEEKEND.

DO NOTE DIVERGENCE IN SOME OF THE MODEL SOLUTIONS DURING THIS
WEEKEND...NAMELY THE 06Z/12Z GFS...IN HANDLING LINGERING H5 SHORT
WAVE WEAKNESS. MOST MODELS AND ENSEMBLES KEEP THIS HANGING AROUND
THE GREAT LAKES INTO OHIO VALLEY...BUT THE GFS SHIFTS IT E MUCH
FASTER AND OVERDOES THE PRECIP FIELD. ON SATURDAY...IT TRIES TO
WORK MOISTURE UP THE EASTERN SEABOARD AROUND THE SUBTROPICAL RIDGE
OFFSHORE...THEN SHIFTS SHORT WAVE ENERGY E AROUND THE
SUNDAY/SUNDAY NIGHT TIMEFRAME. THE 00Z ECMWF/GGEM KEEP THIS
WEAKNESS WELL W OF THE REGION AND NOT NEARLY AS MUCH CONVECTION
WITH IT AS THE HIGH PRES OFFSHORE REMAINS IN CONTROL. GEFS/ECENS
MEANS ALSO KEEP A MAINLY DRY FORECAST GOING...SO LEANED TOWARD THE
DRIER SOLUTION DURING THIS TIMEFRAME.

INTO EARLY NEXT WEEK...LOOKS LIKE HIGH PRES RETURNS AS W-NW FLOW
ALOFT TAKES OVER WITH HIGH AMPLITUDE UPPER RIDGE BUILDING INTO
HUDSON AND JAMES BAYS. SW SURFACE WINDS TAKE OVER...WHICH BRING
WARMER TEMPS AND HIGHER HUMIDITY.

LEANED TOWARD AVAILABLE GUIDANCE FOR THE EARLY PORTION OF THIS
FORECAST...THEN TRANSITIONED TOWARD THE ENSEMBLE MEANS FROM SUNDAY
ONWARD.

DETAILS...

THURSDAY THROUGH SATURDAY...HIGH CONFIDENCE.

LARGE HIGH PRES RIDGE BUILDS E OUT OF THE MIDWEST/GREAT LAKES.
EXPECT DRY CONDITIONS.

A GENERAL W-NW FLOW IN PLACE FOR THURSDAY-FRIDAY...THEN RIDGE AXIS
SHIFTS E ON SATURDAY BRINGING RETURN TO SW WINDS AND GRADUALLY
INCREASING HUMIDITY.

SUNDAY...LOW CONFIDENCE.

AS MENTIONED ABOVE...MODEL SOLUTION DIVERGENCE DUE TO TIMING OF
SYNOPTIC FEATURES ACROSS THE REGION. LEANED TOWARD THE HPC
GUIDANCE FOR THIS PERIOD. KEPT A DRY FORECAST GOING. WILL ALSO SEE
TEMPS RISE...WITH HIGHS POSSIBLY AS MUCH AS 5 TO 10 DEGREES ABOVE
NORMAL.

MONDAY AND TUESDAY...LOW TO MODERATE CONFIDENCE.

UPPER LEVEL RIDGE BUILDS ACROSS THE CENTRAL U.S. INTO CENTRAL
CANADA...KEEPING MAINLY DRY FLOW IN PLACE. SOME UNCERTAINTY DUE
TO DIVERGENCE WITH EARLIER SOLUTIONS...THOUGH LOOKING A BIT MORE
CONFIDENT.

TEMPERATURES WILL CONTINUE TO TREND ABOVE NORMAL DURING THIS
TIMEFRAME...WHICH IS BACK TO SCHOOL FOR SOME. BOTH MODELS AND
ENSEMBLES ARE HINTING AT UPPER 80S TO AROUND 90 AS UPPER LEVEL
RIDGE CONTINUES TO BUILD ACROSS THE CENTRAL U.S.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
FORECASTER CONFIDENCE LEVELS...

LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.

SHORT TERM /THROUGH WEDNESDAY NIGHT/...

THIS AFTERNOON...MODERATE CONFIDENCE. AREAS OF IFR FOG ALONG THE
MASS EAST COAST UNTIL WINDS BECOME SOUTH. OTHERWISE VFR WITH
PATCHES OF MVFR CIGS IN SCATTERED SHOWERS/TSTMS...MOSTLY IN
CENTRAL MASS AND NORTHEAST CT.

TONIGHT...MODERATE CONFIDENCE. LINE OF SHOWERS/TSTMS ACROSS CT
VALLEY REGION EARLY WITH LOCAL MVFR-IFR CONDITIONS POSSIBLE.
PATCHY FOR DEVELOPING OVERNIGHT WITH MVFR AND SOME IFR. WIND SHIFT
WITH COLD FRONT PASSAGE...WINDS BECOMING LIGHT WEST BY MORNING
MOST AREAS.

WEDNESDAY AND WEDNESDAY NIGHT...HIGH CONFIDENCE. VFR. PATCHY IFR
IN FOG LATE WEDNESDAY NIGHT.

KBOS TERMINAL...MODERATE CONFIDENCE IN TAF. EXPECT MAINLY VFR
THOUGH SOME MVFR CIGS AND SCT SHOWERS/TSTMS MAY APPROACH AHEAD OF
COLD FRONT AROUND OR AFTER 06Z THROUGH ABOUT 12Z. WIND SHIFT TO
WEST AS A COLD FRONT MOVES THROUGH...AROUND 12Z-14Z.

KBDL TERMINAL...MODERATE CONFIDENCE IN TAF.

OUTLOOK /THURSDAY THROUGH SUNDAY/...MODERATE TO HIGH CONFIDENCE.

THURSDAY THROUGH SUNDAY...MAINLY VFR CONDITIONS. COULD SEE WEAK
SEA BREEZES ALONG THE COASTLINES. MAY SEE BRIEF PATCHY FOG
OVERNIGHT THU NIGHT ACROSS NORMALLY PRONE INTERIOR VALLEYS.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.

SHORT TERM /THROUGH WEDNESDAY NIGHT/...HIGH CONFIDENCE.

WINDS AND SEAS WILL REMAIN BELOW 25 KNOTS AND 5 FEET THROUGH THE
PERIOD. A COLD FRONT MOVES ACROSS SOUTHERN NEW ENGLAND TONIGHT
AND MAY BRING A FEW SHOWERS TO THE WATERS...POSSIBLY A TSTM.

AREAS OF FOG ON THE EASTERN MASS WATERS WILL DIMINISH WITH THE
WIND SHIFT. ADDITIONAL FOG WILL AFFECT THE WATERS IN THE LIGHT
FLOW TONIGHT.

OUTLOOK /THURSDAY THROUGH SUNDAY/...HIGH CONFIDENCE.

EXPECT WINDS AND SEAS TO REMAIN BELOW SMALL CRAFT CRITERIA AS HIGH
PRESSURE TAKES CONTROL. EXPECT W-NW WINDS THU-FRI...SHIFTING TO
S-SW FRI NIGHT-SUNDAY.

&&

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

&&

$$
SYNOPSIS...WTB/EVT
NEAR TERM...WTB/EVT
SHORT TERM...WTB
LONG TERM...EVT
AVIATION...WTB/EVT
MARINE...WTB/EVT



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