-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBOX 180834
AFDBOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
434 AM EDT SAT MAY 18 2013

.SYNOPSIS...
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HIGH PRESSURE PROVIDES MAINLY DRY AND SEASONABLE WEATHER FOR THE
WEEKEND. AN APPROACHING WARM FRONT WILL INCREASE THE CHANCE OF
RAIN SUNDAY NIGHT INTO MONDAY. THE FRONT WILL LIFT NORTH OF THE
REGION EARLY NEXT WEEK AND THEN STALL OVER NEW YORK AND CENTRAL
NEW ENGLAND. WEAK WAVES OF LOW PRESSURE WILL MOVE ALONG THE FRONT
MIDDLE OF NEXT WEEK BRINGING WARMER...MORE HUMID CONDITIONS ALONG
WITH SCATTERED SHOWERS AS WELL AS POSSIBLE THUNDERSTORMS...MOST
LIKELY DURING THE AFTERNOON AND EVENING HOURS.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
340 AM UPDATE...

MID LEVEL CLOSED LOW MOVING ACROSS ATLANTIC CANADA TODAY WILL
PROVIDE MARITIME HIGH PRES OVER THE GULF OF MAINE. THIS SETUP WILL
PROVIDE MAINLY DRY AND SEASONABLE TEMPERATURES OVER THE AREA
TODAY. THE EDGE OF THE COLD POOL ALOFT WILL CLIP SOUTHEAST NH AND
NORTHEAST MA THIS AFTERNOON. THUS THERE COULD BE AN ISOLATED
SHOWER OR SPRINKLE ACROSS THIS REGION. OTHERWISE DRY WEATHER
PREVAILS. AS FOR POPS...SIDED WITH THE DRIER ECMWF SO MAINLY STUCK
WITH PREVIOUS FORECAST.

THERE WILL BE CLOUDS FROM TIME TO TIME AS MENTIONED ABOVE WITH
INSTABILITY ALOFT ACROSS NORTHEAST MA AND NEARBY SOUTHEAST NH. IN
ADDITION WARM ADVECTION CLOUDS WILL STREAM ACROSS WESTERN MA/CT
AND INTO RI FROM TIME TO TIME.

AS FOR TEMPERATURES...SIMILAR REGIME AIRMASS OVER THE REGION AS
YESTERDAY SO NOT EXPECTING MUCH TEMP CHANGE. HOWEVER COASTAL
COMMUNITIES WILL BE COOLER AS SEABREEZE WILL DEVELOP EARLIER TODAY
THAN FRI. TEMPS WERE DERIVED FROM IN HOUSE BIAS CORRECTED MAV/MET
AND ECMWF.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
TONIGHT...
AN ISOLD SHOWER/SPRINKLE COULD LINGER INTO THE EVENING ACROSS NE
MA AND SOUTHERN NH...OTHERWISE DRY CONDITIONS PREVAIL AS 1030 MB HIGH
SETTLES OVER GEORGES BANK. ANOTHER COOL NIGHT /40S/ GIVEN DRY DEW
PTS FROM GOOD BLYR MIXING SAT AFTN COMBINED WITH LIGHT WINDS.
ALTHOUGH NOT AS COOL AS FRI NIGHT/SAT AM GIVEN MORE CLOUDS ARE
EXPECTED TONIGHT.

AS FOR POPS...SIDED AGAIN WITH THE DRIER ECMWF AS COLUMN STRUGGLES
TO SATURATE ALONG WITH WEAK INSTABILITY AND FORCING FOR ASCENT.
THUS MAINLY A DRY NIGHT.

SUNDAY...
WARM FRONT ACROSS MID ATLC REGION BEGINS TO LIFT NORTHWARD AS MID
LEVEL CLOSED LOW OVER ATLC CANADA DEPARTS SEAWARD. THEREFORE ANY
SUN IN THE MORNING WILL FADE BEHIND INCREASING AFTERNOON
CLOUDINESS. WAA/UPGLIDE BEGINS TO DEVELOP LATE IN THE DAY FROM
WEST TO EAST. THEREFORE HAVE LEANED TOWARD THE DRIER ECMWF AND ITS
LATER ONSET TIME FOR SHOWERS. THUS HAVE FOCUSED CHANCE POPS
LATE IN THE DAY. AS A RESULT BULK OF THE DAY WILL BE DRY.

&&

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

*  WARM AND HUMID WITH SCATTERED SHOWERS THRU AT LEAST THU

ECMWF AND GFS MODELS AGREE UPON AN AMPLIFIED PATTERN MON THRU FRI
OF NEXT WEEK WITH SEEMINGLY ANOMALOUS BLOCKING THIS FAR INTO
SPRING. NEW ENGLAND LOOKS TO BE AT THE CONVERGING END OF A SPLIT
FLOW ACROSS NORTH AMERICA. WHAT SHOULD PASS THRU AS A WARM FRONT
ON MON WILL LIKELY STALL JUST NORTH OF THE FORECAST AREA. A
RELATIVELY MODEST SHIFT IN THE LARGE SCALE PATTERN COULD MAKE A
SIGNIFICANT DIFFERENCE ON WHETHER WE REMAIN WETTER OR DRIER.
ENSEMBLES AND LATEST OPERATIONAL MODELS SUGGEST THAT SOUTHERN NEW
ENGLAND WILL PROBABLY HAVE RELATIVELY UNSETTLED WEATHER OVER MUCH
OF THE WEEK. THERE IS A CHANCE OF SHOWERS FOR NEARLY EVERY DAY IN
THE LONG TERM FORECAST BUT IN REALITY IT SHOULD NOT BE RAINING ALL
WEEK LONG. THE SHOWERS WILL LIKELY BE MODULATED TO SOME DEGREE
DIURNALLY WITH AFTERNOONS/EVENINGS THE MOST FAVORED TIME. THE
PROBLEM IS THAT WE ARE UNABLE TO RESOLVE THE FORCING MECHANISMS
FOR THE SHOWERY PERIODS. IT IS UNLIKELY THAT ANY ONE DAY WILL BE A
COMPLETE WASHOUT...AND IF THE NORTHERN STREAM SHOULD PROVE A
LITTLE STRONGER...THE FRONT COULD SAG BACK SOUTH FAR ENOUGH TO DRY
REGION OUT.

MON... HAVE A CHANCE OF SHOWERS IN THE FORECAST WITH THE BEST
CHANCE IN THE EARLY MORNING HOURS WHEN THERE IS A WEAK INSTABILITY
BURST SIGNATURE WITH LOW LEVEL WARMING SEEN AT 850 MB AND AN
INCREASE IN THE K INDEX. IT MAY TURN DRY AND WARM WITH INCREASED
HUMIDITY BY MON AFTERNOON BUT CONFIDENCE IS LOW.

TUE... BOTH THE ECMWF AND GFS OPERATIONAL RUNS SUGGEST A SHORT
WAVE PASSAGE AND RELATIVELY UNSTABLE AIR MASS...ESPECIALLY WESTERN
ZONES. THUS...THUNDER MAY BE A GOOD POSSIBILITY TUE
AFTERNOON/EVENING. CONTINUED MILD AND HUMID...PERHAPS ESPECIALLY
NOTICABLE AT NIGHT AS CLOUDS PREVENT MUCH RADIATIONAL COOLING.

WED... NOT MUCH CHANGE WITH FRONTAL BOUNDARY EXPECTED TO REMAIN A
LITTLE NORTH OF AREA. BOTH GFS AND ECMWF POINT TOWARD BEST
AFTERNOON/EVENING INSTABILITY ACROSS THE SOUTHERN ZONES BUT JUST
TOO MUCH INHERENT UNCERTAINTY IN THIS TYPE OF PATTERN TO BE VERY
SPECIFIC AT THIS STAGE.

THU... STILL MORE OF THE SAME. BOTH ECMWF AND GFS OPERATIONAL
MODELS POINT TOWARD CONSIDERABLE INSTABILITY THU AFTERNOON AND A
SURFACE WAVE PASSING ALONG THE FRONT JUST TO THE NORTH. THIS MAY
RESULT IN A FAIRLY ACTIVE DAY FOR CONVECTION. ON THE OTHER
HAND...BOTH MODELS COULD JUST AS EASILY BE OFF ON TIMING OF SHORT
WAVE ENERGY THAT FAR OUT.

FRI... BY FRI WE SEE MORE SIGNIFICANT DIVERGENCE IN THE MEDIUM
RANGE MODEL SOLUTIONS. THE GFS DETACHES AN UPPER LEVEL TROF OVER
THE OH VALLEY THAT IN TURNS INSTIGATES WAVE DEVELOPMENT OVER THE
MID ATLC COASTAL PLAIN FRI NIGHT. THE ECMWF IN CONTRAST PLACES
MORE ENERGY IN THE NORTHERN STREAM WITH A SHORT WAVE TROF THAT IS
MORE LIKELY TO SWEEP COOLER AND DRIER AIR INTO THE REGION SOMETIME
FRI.

IN SUMMARY...A LARGE SCALE BLOCKING PATTERN IS EXPECTED TO SET UP
A FAIRLY UNSETTLED WEEK WITH A LOT OF UNCERTAINTY IN THE DETAILS.
-- End Changed Discussion --

&&

.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
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FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /THROUGH SUNDAY NIGHT/...MODERATE CONFIDENCE.

HIGH CONFIDENCE FOR VFR CONDITIONS INTO SUN MORNING BUT THEN LOWER
CONFIDENCE ON TIMING OF MVFR CONDITIONS AND SHOWERS LATER SUN.
ISOLATED AFTN SHOWER POSSIBLE TODAY OTHERWISE DRY INTO SUN AM.
THEN CHANCES INCREASE LATER SUN FROM WEST TO EAST AS WARM FRONT
APPROACHES FROM THE SOUTHWEST. SEA BREEZE DEVELOPS EARLIER TODAY
THAN FRIDAY. MODEL GUIDANCE....BASICALLY FOLLOWED AN EVEN BLEND OF
THE 00Z NAM AND GFS.

KBOS TERMINAL...HIGH CONFIDENCE IN TAF. SEABREEZE DEVELOPS EARLIER
TODAY THAN FRI. ISOLATED AFTN/EARLY EVENING SHOWER. OTHERWISE DRY
WEATHER PREVAILS INTO SUNDAY.

KBDL TERMINAL...HIGH CONFIDENCE IN TAF. LOW RISK OF AN ISOLATED
SHOWER THIS AFTERNOON/EARLY EVENING. THEN HIGHER CHANCES OF RAIN MID
TO LATE AFTN SUNDAY.

OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY...

MODERATE CONFIDENCE. FREQUENT PERIODS OF MVFR CIGS/VSBYS EXPECTED
IN SCT SHOWERS AND FOG WITH POCKET OF IFR CIGS/VSBYS LIKELY AT
NIGHT...ESPECIALLY ALONG THE SOUTH COAST.
-- End Changed Discussion --

&&

.MARINE...
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FORECASTER CONFIDENCE LEVELS...

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

SHORT TERM /THROUGH SUNDAY/...HIGH CONFIDENCE.

HIGH PRES SETTLES OVER THE GULF OF ME TODAY AND THEN GEORGES BANK
SUNDAY. THUS LIGHT WINDS EXPECTED TRANQUIL SEAS. VSBY WILL GOOD.
DRY WEATHER PREVAILS WITH JUST A LOW RISK OF SHOWERS LATE SUN
ACROSS THE RI WATERS.

OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY...

MODERATE CONFIDENCE. A PERSISTENT SW FLOW WILL LIKELY SET UP AN
EXTENDED PERIOD OF SEAS AT OR ABOVE 5 FT WITH PERIODS OF SCA SW
WINDS AS WAVES MOVING ALONG THE FRONT TO THE NORTH TIGHTEN THE
SURFACE PRES GRADIENT.
-- End Changed Discussion --

&&

.FIRE WEATHER...
DRY CONDITIONS WILL CONTINUE THIS WEEKEND. MINIMUM RELATIVE
HUMIDITIES SATURDAY WILL BE BELOW 30 PERCENT IN THE INTERIOR BUT
WINDS WILL BE RATHER LIGHT. ON SUNDAY...HIGHER RELATIVE
HUMIDITIES ARE EXPECTED...FROM 45 TO 60 PERCENT WITH S-SE WINDS
AROUND 10 MPH.

&&

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

&&

$$
SYNOPSIS...NOCERA/THOMPSON
NEAR TERM...NOCERA
SHORT TERM...NOCERA
LONG TERM...THOMPSON
AVIATION...NOCERA/THOMPSON
MARINE...NOCERA/THOMPSON
FIRE WEATHER...NOCERA