Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 261801
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
200 PM EDT THU MAR 26 2015

.SYNOPSIS...

LOW PRESSURE MOVING UP THE OHIO VALLEY WILL BRING RAIN TO OUR REGION
DURING THE AFTERNOON AND EVENING.  THE LOW WILL THEN SWING A COLD
FRONT THROUGH SOUTHERN NEW ENGLAND TONIGHT. A SECOND COLD FRONT WILL
BRING COLDER TEMPERATURES LATER FRIDAY INTO THIS WEEKEND. WEAK LOW
PRESSURE MAY BRING A PERIOD OF LIGHT SNOW FRIDAY NIGHT INTO SATURDAY
MORNING. HIGH PRESSURE WILL PUSH S OF NEW ENGLAND SUNDAY. ANOTHER
BATCH OF LIGHT SNOW IS POSSIBLE LATE SUNDAY NIGHT INTO MONDAY AHEAD
OF A COLD FRONT.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

2 PM UPDATE...

NUMEROUS SHOWERS WERE DEVELOPING ACROSS SOUTHERN NEW ENGLAND AT MID
AFTERNOON IN ASSOCIATION WITH A MID LEVEL SHORTWAVE.  PWATS OVER 1
INCH WERE ALLOWING FOR BRIEF LOCALIZED HEAVY RAINFALL.  THIS MAY
RESULT IN BRIEF TYPICAL NUISANCE POOR DRAINAGE STREET FLOODING...BUT
NO MAJOR ISSUES ARE EXPECTED.  IN ADDITION...SOME MARGINAL ELEVATED
INSTABILITY MAY RESULT IN AN EMBEDDED THUNDERSTORM OR TWO.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
TONIGHT...

LOW PRESSURE MOVES OVER NEW ENGLAND AND DRAWS A COLD FRONT
SOUTHEAST ACROSS THE REGION. THIS SYSTEM DEMONSTRATED IT HAD
PLENTY OF INSTABILITY AS IT MOVED PAST OKLAHOMA WEDNESDAY. MODEL
DATA SHOWS IT CONTAINING STRONG FGEN VALUES AS IT CROSSES NEW
ENGLAND. THIS ALONG WITH THE HIGH PRECIP WATER VALUES SHOULD
SUPPORT MORE RAIN...ALTHOUGH MORE OF A SHOWERY PRECIPITATION.
TEMPERATURE PROFILES SUGGEST RAIN...BUT POSSIBLY A RAIN/SNOW MIX
IN NORTHWEST MASS LATE AT NIGHT.

FRIDAY...
COLD FRONT DRIFTS FARTHER OFFSHORE WHILE UPPER TROUGH OVER THE
GREAT LAKES MOVES EAST. A 150 KNOT JET CORE WILL BE IN PLACE OVER
THE NORTHEAST CORRIDOR WITH SOUTHERN NEW ENGLAND UNDER THE RIGHT
ENTRANCE REGION. MEANWHILE...A SECOND COLD FRONT MOVES SOUTH FROM
THE ST LAWRENCE VALLEY. EXPECT AT LEAST SCATTERED PCPN WITH
TEMPERATURE PROFILES FAVORING RAIN. TEMPS ALOFT ALSO FAVOR MAX
TEMPS IN THE 40S.

&&

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

* SCT SNOW/RAIN SHOWERS ON SATURDAY
* A WEAK COLD FRONT WILL MOVE THROUGH ON MONDAY BRINGING SCT SHOWERS
* MODERATING SPRING-LIKE TEMPS INTO NEXT WEEK

MODEL GUIDANCE...

OVERALL AMPLIFIED TROUGH PATTERN WILL CONTINUE WITH 00Z GUIDANCE IN
GOOD AGREEMENT. STILL SUBTLE DETAIL DIFFERENCES AT THE MESO
LEVEL. BROAD UPPER TROUGH REMAINS OVER THE EAST COAST FRIDAY NIGHT
INTO SATURDAY WITH THE TROUGH MOVING EAST OF THE REGION LATE
SATURDAY NIGHT INTO SUNDAY. LOW PRESSURE SYSTEM WILL CROSS SRN
CANADA AND BRING A TRAILING FRONT THROUGH THE AREA ON MONDAY.
GUIDANCE STILL SHOWS PERSISTENT DIFFERENCES WITH SOUTHWARD EXTENT
OF THE TRAILING FRONT AS THE GFS IS FARTHER SOUTH. GUIDANCE WAS
SOMEWHAT CLOSER TO BEING EVENLY SPLIT 24 HRS AGO BUT THE PAST
COUPLE UKMET/CMC RUNS TRENDED TO THE NRN CLUSTER AND EVEN THE
18Z/00Z GEFS MEANS HAVE STARTED TO TREND NWD OF THE OPERATIONAL
GFS RUNS. SO TRENDED THIS PORTION TOWARDS THE EC/HPC. LASTLY THE
DOMINATE NORTHERN STREAM FLOW BECOMES MORE PROGRESSIVE AS STRONG
WESTERN RIDGE WEAKENS AS SEVERAL WAVES BEGIN TO MOVE THROUGH THE
FLOW MIDDLE OF NEXT WEEK. THESE WILL NEED TO BE WATCHED CLOSELY
FOR THE UPCOMING EASTER WEEKEND.


DETAILS...

* FRIDAY NIGHT INTO SATURDAY...MODERATE CONFIDENCE.

COLD AIR WILL USHER ACROSS THE REGION FRIDAY NIGHT INTO SATURDAY
BEHIND PASSING COLD FRONT. THE UPPER LEVEL TROUGH AXIS WILL BE
OVERHEAD...COULD SEE SOME SCT SNOW SHOWERS DURING THE DAY ON
SATURDAY. CONFIDENCE IS INCREASING COMPARED TO YESTERDAY AS MOST
OF THE GUIDANCE SPITS OUT SOME QPF. SURFACE LOW PRESSURE WILL MOVE
WELL SOUTH OF THE BENCHMARK FRIDAY NIGHT/SAT MORNING
HOWEVER...GUIDANCE IS HINTING AT A WEAK SURFACE/INVERTED TROUGH
OVER THE AREA ON SATURDAY. THIS COMBINED WITH LOW LEVEL MOISTURE
AND VERY STEEP LAPSE RATES WILL ALLOW FOR SCT SNOW/RAIN SHOWERS TO
DEVELOP. EXPECT MOSTLY CLOUDY SKIES SO TEMPS WILL STRUGGLE TO
REACH INTO THE UPPER 30S...SO THINKING P-TYPE IS MORE SNOW. MODELS
ARE ALSO HINTING AT POSSIBLE FRONTOGENESIS WHICH COULD INCREASE
SNOWFALL RATES. LOW CONFIDENCE ON WHERE THIS MAY SET UP BUT WILL
NEED TO WATCH FOR SOME AREA IN SOUTHERN NEW ENGLAND SEEING A
SURPRISED 1-2 INCHES POSSIBLY.

TEMPS OVERNIGHT WILL FALL WELL BELOW NORMALS WITH LOWS AROUND THE
TEENS TO LOW 20S. TEMPS MAY BE SLIGHTLY COLDER AT WE COULD RADIATE
OUT THANKS TO CLEARING SKIES AND LIGHT WINDS ACROSS THE INTERIOR.
LOW PROBABILITY OF LINGERING OCEAN EFFECT SNOW ACROSS THE CAPE.

* SUNDAY...HIGH CONFIDENCE.

SUNDAY IS A TRANSITION DAY AS DEEP TROUGH BEGINS TO PULL OFFSHORE
AND UPPER LEVEL RIDGE MOVES INTO THE REGION. TEMPS ON SUNDAY WILL
WARM INTO THE MID 40S TO LOW 50S AS WARM AIR ADVECTION ADVANCES.
EXPECT MOSTLY CLEAR SKIES IN THE MORNING BUT THEY WILL BEGIN TO
CLOUD UP DURING THE AFTERNOON AS THE NEXT SYSTEM APPROACHES FROM THE
WEST.

MONDAY INTO WEDNESDAY...LOW CONFIDENCE.

NEXT UPPER LEVEL DISTURBANCE WILL IMPACT SOUTHERN NEW ENGLAND LATE
SUNDAY INTO MONDAY. STILL A GOOD AMOUNT OF SPREAD AMONGST THE
GUIDANCE AS MENTIONED ABOVE...BUT TRENDED TOWARDS THE EC/HPC ON THIS
PORTION OF THE FORECAST. SURFACE LOW ACROSS THE GREAT LAKES WILL
PASS JUST NORTH OF SNE...DRAGGING ASSOCIATED COLD FRONT WITH IT.
TEMPS AT THE ONSET LOOK TO BE COOL THEN WARM UP DURING THE DAY ON
MONDAY PRIOR TO FRONTAL PASSAGE. TIMING OF THE FRONT WILL BE AN
ISSUE IMPACTING HIGH TEMPS. EC KEEPS THEM COOL WITH A FASTER PASSAGE
COMPARED TO THE GFS WHICH IS SLOWER BUT WARMS TEMPS UP INTO THE 50S.
AT THE ONSET OF PRECIP EXPECT A FEW SNOW SHOWERS...BUT THEN
TRANSITIONING TO RAIN FAIRLY QUICKLY AS TEMPS WARM.

A FEW QUICK MOVING SYSTEMS WILL MOVE THROUGH THE FLOW DURING THE
UPCOMING WEEK. FIRST ONE IS LATE TUESDAY INTO WED FOLLOWED BY
ANOTHER THUS/FRIDAY. AT THE SURFACE...HIGH PRESSURE WILL BUILD ON
TUESDAY FOLLOWED BY WEAK LOW ON WEDNESDAY AND A WARM FRONT ON
THURSDAY.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM...THIS AFTERNOON THROUGH FRIDAY...

THIS AFTERNOON AND TONIGHT...MODERATE CONFIDENCE.  PERIODS OF
SHOWERS ALONG WITH AN EMBEDDED THUNDERSTORM OR TWO EXPECTED THROUGH
TONIGHT.  MAINLY IFR CONDITIONS IN LOWER CLOUDS ALONG WITH AREAS OF
FOG...ESPECIALLY ALONG THE SOUTH COAST WHERE IT MAY BE LOCALLY
DENSE.  LLWS IS ALSO EXPECTED GIVEN LOW LEVEL JET AROUND 60 KNOTS.

FRIDAY...MODERATE TO HIGH CONFIDENCE.  RAIN SHOWERS SHOULD COME TO
AN END FOR MOST OF THE REGION DURING THE MORNING...ALTHOUGH MAY
LINGER A BIT LONGER ACROSS THE FAR SOUTHEAST MA COAST.  PTYPE MAY
ACTUALLY CHANGE TO A BIT OF WET SNOW BEFORE ENDING ACROSS THE HIGHER
TERRAIN...BUT ODDS OF ANY REAL ACCUMULATIONS ON RUNWAYS ARE RATHER
LOW.  OTHERWISE...CONDITIONS SHOULD IMPROVE TO MAINLY VFR BY
AFTERNOON ALTHOUGH SOME MARGINAL MVFR CIGS MAY PERSIST AT TIMES.

KBOS TAF...MODERATE CONFIDENCE IN TAF.

KBDL TAF...MODERATE CONFIDENCE IN TAF.

OUTLOOK...SATURDAY THROUGH MONDAY...MODERATE CONFIDENCE.

SATURDAY...CONDITIONS MAY DETERIORATE FROM EAST TO WEST ON SATURDAY
IN SCT SNOW SHOWERS. LOW CONFIDENCE ON ANY
ACCUMS ON RUNWAYS BUT FEEL BEST SHOT IS ORH.

SATURDAY NIGHT INTO SUNDAY...VFR CONDITIONS LIKELY. SCT MVFR ACROSS
THE CAPE IN OCEAN EFFECT SNOW SHOWERS.

MONDAY...VFR DROPPING TO POSSIBLE MVFR IN SCT RAIN SHOWERS.

&&

.MARINE...
FORECASTER CONFIDENCE LEVELS...

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

TODAY...INCREASING SOUTH TO SOUTHWEST WIND WITH GUSTS 25-33 KNOTS
THIS AFTERNOON. SEAS BUILDING TO 5-8 FEET ESPECIALLY ON THE
SOUTHERN WATERS. MOIST AIRMASS MOVING ACROSS THE 35-40 DEGREE
WATER MAY CREATE LOW VSBYS IN FOG...WITH LOCALLY DENSE FOG
POSSIBLE. RAIN MAINLY THIS AFTERNOON WITH AN ISOLATED TSTM ALSO
POSSIBLE. SMALL CRAFT ADVISORY IS IN PLACE FOR MOST OF OUR WATERS.

TONIGHT...A COLD FRONT CROSSES THE WATERS AFTER MIDNIGHT. SOUTH
TO SOUTHWEST WINDS 25-30 KNOTS EARLY...SHIFTING NORTHWEST AND
DIMINISHING AFTER MIDNIGHT. SEAS CONTINUE TO BUILD DURING THE
SOUTHWEST WINDS AND MAY REACH 8 TO 12 FEET ON THE OUTER WATERS AND
ON EXPOSED WATERS SUCH AS RI SOUND. LOCALLY DENSE FOG POSSIBLE
DURING THE EARLY NIGHT...THINNING AFTER THE WIND SHIFT.

FRIDAY...
NORTH WINDS 15 TO 20 KNOTS. SEAS LINGER 5 TO 8 FEET MAINLY ACROSS
THE OUTER WATERS. SMALL CRAFT HEADLINES WILL CONTINUE INTO THE DAY
MAINLY ON THE OUTER WATERS.

OUTLOOK...FRIDAY NIGHT THROUGH MONDAY...

MODERATE CONFIDENCE INTO MONDAY.

FRIDAY NIGHT....WINDS INCREASE UP TO 25-30KTS BEHIND FRONTAL
PASSAGE. SCA WILL BE NEEDED.

SATURDAY AND SATURDAY NIGHT...EXPECT NW WINDS TO CONTINUE TO GUST TO
SMALL CRAFT LEVELS WITH SEAS BUILDING UP TO 6-9 FT ON THE OUTER
WATERS THROUGH SAT NIGHT. LOW PROB OF SCT SNOW/RAIN SHOWERS DURING
THE DAY.

SUNDAY THROUGH MONDAY...WINDS AND SEAS BRIEFLY SUBSIDE AS WINDS BACK
TO SW SUN/SUN NIGHT...THOUGH SEAS MAY REMAIN AROUND 5 FT ON THE FAR
OUTER WATERS. WINDS AND SEAS INCREASE AGAIN MONDAY AHEAD OF NEXT
SYSTEM SO SMALL CRAFTS WILL LIKELY BE RENEWED.

&&

.HYDROLOGY...
BASIN AVERAGE RAINFALL AMOUNTS RANGE FROM 0.5 TO 1.25 INCHES ACROSS
THE REGION...POSSIBLY 1.50 IN SPOTS BUT NOT WIDESPREAD. NOHRSC
MODELING ADDS 1 TO 3 INCHES OF WATER FROM MELTING SNOW DUE TO
TEMPERATURES IN 40S/LOWER 50S COMBINED WITH DEWPOINTS RISING INTO
40S AND SW WINDS.

THIS WILL BRING RISES ON RIVERS AND STREAMS TODAY AND
TONIGHT...ESPECIALLY SMALLER ONES WHICH MAY APPROACH MINOR FLOOD
STAGE. HOWEVER GIVEN RAINFALL IS SPREAD OUT OVER A LONG DURATION
WITH MANY DRY PERIODS ALONG WITH DEW PTS ONLY BRIEFLY APPROACHING
50...RISK OF FLOODING IS TOO LOW FOR HEADLINES. IN FACT RFC ONLY
HAS A FEW POINTS ENTERING ACTION STAGE WITH NONE IN MINOR FLOOD.
THUS NO HEADLINES.

A MORE LIKELY CONCERN WILL BE URBAN/POOR DRAINAGE FLOODING. THE
CORE OF HIGHER RAINFALL IS EXPECTED ACROSS RI/SOUTHEAST MASS WITH
HEAVIEST AMOUNTS ALONG THE SOUTH COAST. LATER SHIFTS WILL NEED TO
MONITOR THIS FOR POTENTIAL SMALL STREAM/URBAN FLOOD ADVISORY.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...DENSE FOG ADVISORY UNTIL 6 PM EDT THIS EVENING FOR MAZ024.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 10 AM EDT FRIDAY FOR ANZ232>235-237.
     SMALL CRAFT ADVISORY UNTIL 2 AM EDT FRIDAY FOR ANZ231-236.
     SMALL CRAFT ADVISORY UNTIL 6 PM EDT FRIDAY FOR ANZ250-254>256.

&&

$$
SYNOPSIS...WTB/DUNTEN
NEAR TERM...FRANK
SHORT TERM...WTB
LONG TERM...DUNTEN
AVIATION...FRANK/DUNTEN
MARINE...WTB/DUNTEN
HYDROLOGY...STAFF



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