Area Forecast Discussion
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000
FXUS61 KBOX 211407
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
1007 AM EDT THU AUG 21 2014

.SYNOPSIS...

SHOWERS ACROSS THE WESTERN HALF OF NEW ENGLAND THROUGH EARLY
FRIDAY. DRIER AND COOLER WEATHER FOLLOWS THIS WEEKEND. A WARM-UP
IS POSSIBLE NEXT WEEK PRIOR TO AN UNSETTLED PATTERN AHEAD OF A
FRONTAL BOUNDARY SWEEPING SOUTH OUT OF CANADA.

&&

.NEAR TERM /THROUGH TONIGHT/...

10 AM UPDATE...

ONE GIANT MESS. CLOSED LOW OUT OF THE GREAT LAKES TRANSITIONING AS
AN OPEN WAVE AS IT WEAKENS. NOTED WELL BY THE PRIOR FORECASTER...
LINGERING ENERGY PROVIDING MODEST LIFT THROUGH WEAK DIFFERENTIAL
VORTICITY ADVECTION UPON AVAILABLE MOISTURE IS LENDING TO SHOWER
ACTIVITY ACROSS THE AREA WITHIN A WEAK FLOW REGIME. THIS DESPITE
THE WARM-FRONT HELD UP TO THE W BY DRIER AIR ASSOCIATED WITH A
CUT-OFF HIGH PRESSURE CENTER SUSTAINED BY THE NEIGHBORING LOW SE
AND WELL OFFSHORE. AIR HAS TO SINK SOMEWHERE. THE WEAK ISENTROPIC
FLOW FROM THE SW IS ALLOWING FOR MOISTURE LOADING WITHIN THE MID-
LEVELS UP AGAINST THE DRIER AIR CLEARLY EVIDENT WITHIN MESORAP
H925-85 FIELDS AND 12Z CHATHAM/PORTLAND SOUNDINGS.

PRESENT ACTIVITY APPEARS FOCUSED ALONG THE CONVERGENT NOSE OF A
H85 PLUME PER MESORAP AND COLLOCATED WITH STRETCHED MID-LEVEL
ENERGY. FEEL THIS AREA OF ACTIVITY WILL LINGER INTO THE EVENING
HOURS TOWARDS THE NE ERODING INTO THE DRIER AIR AND GRADUALLY
DISSIPATING AS THE OPEN- WAVE LOW AND MAIN CRUX OF ENERGY SHIFTS
SE ALLOWING HIGH PRESSURE RIDGING TO BUILD SW. AS TO THE WEAKENING
LOW...DURING THE AFTERNOON INTO EVENING ANTICIPATING ATTENDANT
ENERGY THAT DEVELOPS OVER PA/NY THIS AFTERNOON TO SHIFT SE TOWARDS
BETTER THERMAL/INSTABILITY AXES.

HRRR- AND WRF-MODEL SOLUTIONS MAY HAVE THE RIGHT IDEA WITH REGARDS
TO TRENDS...BUT THE 21.06Z NAM DOES NOT LOOK TOO BAD WITH THE
ENERGY SHIFT TO THE SE. ECMWF/CANADIAN/GFS SHOW A SIMILAR TREND AS
TO THE NAM...KEEPING ACTIVITY NE LIGHT BENEATH BUILDING INFLUENCE
OF THE HIGH PRESSURE RIDGE. WILL KEEP THE FOCUS OF PRECIPITATION
ALONG A NE-SW LINE W OF THE WORCESTER HILLS WITH HIGHEST CHANCES
OVER THE CT-VALLEY TO THE W. CONDITIONALLY UNSTABLE ENVIRONMENT WITH
MOIST-ADIABATIC PROFILES AND DEEP-LAYER / OROGRAPHIC FORCING. HAVE
INSERTED ISOLATED THUNDER. FEEL ONGOING ACTIVITY WILL LIFT NE AND
LESSEN INTO THE REALM OF DRIER AIR. HAVE DONE THE BEST TO TIME OUT
POPS ACCORDINGLY ALONG WITH AVERAGE PRECIPITATION AMOUNTS AROUND
0.3 INCHES.

LOTS OF CLOUD COVER AND WET WEATHER. WILL HOLD TEMPERATURES AROUND
THE LOW-70S...QUITE UNSEASONABLE FOR THIS TIME OF YEAR.

&&

.SHORT TERM /TONIGHT INTO FRIDAY/...

TONIGHT...
SLIGHTLY INCREASED THREAT FOR OVERNIGHT SHOWERS...BUT STILL MAINLY
ACROSS THE W THANKS TO SOME LEFTOVER SUBSIDENCE CLOSER TO THE
GRADUALLY REBOUNDING INVERTED RIDGE. THE REMNANT VORT MAX FROM AN
UPPER LVL DISTURBANCE WILL BE MOVING ACROSS THE AREA THROUGH THE
OVERNIGHT HOURS. JET ENERGY THROUGHOUT THE COLUMN IS WEAK AND WHAT
IS LEFT OF A SFC WARM FRONT WILL LIKELY HAVE WASHED OUT FOR MOST
PART. THEREFORE...IT IS ONLY THE VORT MAX WHICH WILL BE PROVIDING
LIFT TO WORK ON THE 1.5 OR LESS PWAT AIRMASS IN PLACE ACROSS THE
REGION. DRIER AIR STILL REMAINS MAINLY ACROSS THE E...SO WILL
ONCE AGAIN FOCUS MAINLY FROM THE WORCESTER HILLS AND POINTS W FOR
THE SHOWERS. NO THUNDER WITH THIS UPDATE...AS THE AIRMASS REMAINS
QUITE STABLE THROUGHOUT. GUIDANCE HAS BACKED OFF ON THE QPF
BULLSEYES THAT IT WAS SHOWING IN PREVIOUS RUNS FOR THE MOST
PART...BUT THESE ARE LIKELY JUST A CONVECTIVE FEEDBACK ISSUE.
OTHERWISE...MILD OVERNIGHT MINS WITH A FAIR AMOUNT OF CLOUD COVER.
MAY NEED TO ALSO MONITOR ESPECIALLY THE E AND SE COASTLINES FOR
FOG AND STRATUS THANKS TO CONTINUED E FLOW AND SLIGHTLY HIGHER
DWPTS WITHIN THE MOISTENED COLUMN IN COMPARISON TO PREVIOUS DAYS.

FRIDAY...
UPPER LVL VORT MAX SLIDES TO THE SE DURING THE MORNING...COMBINING
WITH LEFTOVER CUTOFF ENERGY ACROSS ATLANTIC CANADA. WHILE THIS
WILL FORM A HANGING TROF WITH AXIS FROM THE MID ATLANTIC THROUGH
THE 40/70 BENCHMARK...MID LVL RIDGING WILL THEN BE ABLE TO REGAIN
CONTROL INTO WRN NEW ENGLAND. THIS WILL ALSO ALLOW THE INVERTED
RIDGE TO BUILD BACK IN ACROSS THE REGION. THIS SHOULD ALLOW
SHOWERS ACROSS THE AREA TO GRADUALLY DISSIPATE THROUGH THE DAY AS
THE COLUMN DRIES FROM INCREASING SUBSIDENCE. HAVE POPS DIMINISHING
THROUGH THE DAY ACROSS THE AREA. IT WILL LIKELY TAKE A BIT MORE
TIME FOR THE CLOUDS TO DISSIPATE GIVEN MOISTURE IS LIKELY TO BE
TRAPPED BENEATH THE SUBSIDENCE INVERSION AND E FLOW CONTINUES.
IN FACT...LOOKS LIKE AN UPPER LVL BACKDOOR COLD FRONT WILL LEAD
TO DECREASING H85 TEMPS. HAVE HELD HIGHS BACK...MAINLY IN THE 60S
TO AROUND 70. E COASTAL REGIONS ARE LIKELY TO TAKE THE LONGEST TO
SEE ANY CLEARING.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...

HIGHLIGHTS...

* QUIET WEATHER EXPECTED THROUGH MUCH OF THIS PERIOD
* UNCERTAINTY INCREASES MIDDLE OF NEXT WEEK WITH AN APPROACHING
  FRONT

21/00Z MODELS ARE IN GOOD AGREEMENT THROUGH ABOUT TUESDAY. THEN
SIGNIFICANT DIFFERENCES ARISE FOR THE LATTER HALF OF NEXT WEEK...
MAKING FOR A LOWER CONFIDENCE FORECAST FROM THE MIDDLE OF NEXT WEEK
ONWARD.

A PERSISTENT UPPER LEVEL TROUGH OVER THE NORTHEAST WILL SLOWLY MAKE
ITS WAY EAST...MOVING JUST OFFSHORE THIS WEEKEND AS AN UPPER LEVEL
RIDGE TRIES TO PUSH NORTHEASTWARD FROM THE SOUTHERN USA. THIS UPPER
TROUGH IS RATHER PERSISTENT THOUGH...WITH EACH SUCCESSIVE MODEL RUN
LINGERING THIS TROUGH OVER THE NORTH ATLANTIC LONGER AND LONGER.

COOLER...LESS SEASONABLE WEATHER IS EXPECTED WHILE HIGH PRESSURE IN
QUEBEC WILL KEEP THINGS RELATIVELY DRY. STILL AGREE WITH THE
PREVIOUS FORECASTER...THINKING 21/00Z GUIDANCE CONTINUES TO STRUGGLE
WITH CONVECTIVE FEEDBACK INTO EARLY NEXT WEEK. AS SUCH...KEPT A DRY
FORECAST ACROSS MOST OF SOUTHERN NEW ENGLAND.

A HIGH PRESSURE WILL SINK SOUTH INTO EARLY NEXT WEEK...EVENTUALLY
MOVING SOUTH AND EAST OF SOUTHERN NEW ENGLAND AND RETURNING US TO A
MORE WESTERLY FLOW. A LOW PRESSURE IN ONTARIO MAY EVENTUALLY MOVE
EAST INTO QUEBEC...SWINGING A COLD FRONT THROUGH SOUTHERN NEW
ENGLAND WEDNESDAY OR THURSDAY. THIS IS WHERE MODELS START TO DIVERGE
MORE SIGNIFICANTLY.

THE ECMWF LOOKS A BIT QUICKER THAN THE GFS WITH THE APPROACH OF THIS
FRONT...BUT NEITHER IS AS PROGRESSIVE AS THE CANADIAN. WILL TAKE A
BLENDED APPROACH WITH THE TIMING FOR NOW.  GIVEN THE STRENGTH OF THE
SURFACE RIDGE EXPECTED TO BE NEAR THE COAST...WOULD NOT BE OVERLY
SURPRISED IF THE ULTIMATE TIMING TURNS OUT TO BE SLOWER THAN THE
GFS. DEPENDING ON AVAILABLE MOISTURE...WE COULD SEE SOME SHOWERS AND
THUNDERSTORMS AHEAD OF THIS FRONT.

&&

.AVIATION /13Z THURSDAY THROUGH MONDAY/...

FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM...THROUGH FRIDAY...MODERATE CONFIDENCE.

TODAY AND TONIGHT...
MAINLY VFR. EXCEPT POSSIBLY FOR KACK...MOST OF THE RAIN REMAINS
TO THE W THROUGH THE DAY. THEN...BETTER CHANCE FOR SHOWERS ACROSS
WRN MA/CT/NH OVERNIGHT ESPECIALLY...WITH OCCASIONAL MVFR
CONDITIONS POSSIBLE. SOME LOW MVFR/IFR POSSIBLE MAINLY ACROSS THE
E COAST.

FRI...
CONDITIONS IMPROVE THROUGH THE DAY. SOME MVFR/IFR POSSIBLE IN THE
MORNING GIVES WAY TO VFR THROUGH THE DAY...BUT MAY TAKE MOST OF
THE DAY ALONG THE E COAST.

KBOS TERMINAL...MODERATE CONFIDENCE. MAIN CONCERN IS WHETHER A
BRIEF PERIOD OF IFR CONDITIONS MOVE IN EARLY THIS MORNING
BRIEFLY...AND THEN RETURNS LATE THU NIGHT. OTHERWISE VFR WITH E
FLOW ASSISTED BY SEABREEZES EXPECTED.

KBDL TERMINAL...HIGH CONFIDENCE IN TAF. -RA CHANCES BEGIN TOWARDS
THURSDAY MORNING ALONG WITH LOW-END VFR CIGS. MVFR CIGS POSSIBLE
THOUGH MAINLY TONIGHT...BUT REMAINS LOW-CONFIDENCE AT THIS TIME.

OUTLOOK...FRIDAY THROUGH MONDAY...

HIGH CONFIDENCE VFR. LOW PROBABILITY OF PATCHY MVFR/IFR FOG EACH
NIGHT.

&&

.MARINE...

FORECASTER CONFIDENCE LEVELS...

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

SHORT-TERM...THROUGH FRIDAY...MODERATE CONFIDENCE.

LOW PRES WILL GRADUALLY STRENGTHEN OFFSHORE THROUGH THE DAY...BUT
THEN MOVE E INTO FRI. A FEW SHOWERS ARE LIKELY TO IMPACT MAINLY
THE WATERS S OF THE VINEYARD AND ACK INTO MID DAY UNTIL THE LOW
MOVES FURTHER E. THE WEAK LOW PRES WILL ALSO GENERATE A MODEST
SWELL...BUT IT SHOULD GENERALLY REMAIN BELOW 4 FT INTO THE DAY ON
FRI. WINDS TOO MAY GUST TO ABOUT 15-20 KT AT TIMES OUT OF THE
E...BUT SHOULD REMAIN BELOW SMALL CRAFT ADVISORY LEVELS THROUGH
THE PERIOD.

OUTLOOK...FRIDAY NIGHT THROUGH MONDAY...

HIGH CONFIDENCE. QUIET BOATING WEATHER IS EXPECTED FOR MUCH OF THIS
PERIOD WITH HIGH PRESSURE ACROSS THE REGION. SEAS COULD APPROACH 5
FT ACROSS THE OUTERMOST SOUTHERN COASTAL WATERS THIS WEEKEND. NOT
ENOUGH CONFIDENCE TO ISSUE A SMALL CRAFT ADVISORY THOUGH. LOW
PROBABILITY OF PATCHY OVERNIGHT FOG LIMITING VISIBILITIES.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...

CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...NONE.

&&

$$

SYNOPSIS...BELK/DOODY
NEAR TERM...SIPPRELL
SHORT TERM...DOODY
LONG TERM...BELK
AVIATION...BELK/DOODY
MARINE...BELK/DOODY


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