Area Forecast Discussion
Issued by NWS Boston, MA

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320 FXUS61 KBOX 091617 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1117 AM EST TUE FEB 9 2016 .SYNOPSIS... CLOUDY AND CHILLY WEATHER IS IN STORE FOR SOUTHERN NEW ENGLAND TODAY. FAST MOVING LOW PRESSURE MAY BRING SCATTERED LOCALLY HEAVY SNOW SHOWERS TO THE REGION WEDNESDAY WITH THE HIGHEST RISK ACROSS NORTHERN CONNECTICUT AND NEAR THE SOUTH COAST. SOME SCATTERED SNOW SHOWERS ARE LIKELY WEDNESDAY AND THURSDAY...WITH DRY WEATHER MAINLY ON FRIDAY. BITTERLY COLD WEATHER IS EXPECTED THIS WEEKEND. && .NEAR TERM /THROUGH TONIGHT/...
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1015 AM UPDATE... TWO AREAS OF INTEREST ON RADAR...FIRST IS AREA OF LIGHT SNOW/FLURRIES THAT DEVELOPED OVER WESTERN SECTION OF CT AND MA. THIS IS IN RESPONSE TO MID LEVEL SHORT WAVE/JET STREAK CIRCULATING IN THE MOIST CYCLONIC FLOW ALOFT. HOWEVER THIS FEATURE IS MOVING RAPIDLY NORTHWARD AND AS A RESULT FLURRIES/SNOW SHOWERS ARE PULLING OUT THIS REGION AND INTO VT AND NE NY STATE. OTHER AREA OF INTEREST ON RADAR IS SOME OCEAN EFFECT LIGHT SNOWS BEGINNING TO DEVELOP JUST EAST OF PLYMOUTH COUNTY. 12Z CHH SOUNDING SUPPORTS THIS ACTIVITY CONTINUING WITH MODEST LOW LEVEL LAPSE RATES OF -8C AT H9 WITH SST OF +6C YIELDING A DELTA-T OF 14C...WHICH SUPPORTS OES. HOWEVER NOT ENOUGH INSTABILITY FOR OTHER THAN NUISANCE TYPE MINOR ACCUMULATION AT MOST. THE LIGHT NNE FLOW SHOULD PERSIST GIVEN THE OCEAN LOW TRACK SOUTHEAST OF THE REGION. OTHERWISE ALL MODEL GUIDANCE HAS MID LEVEL SUBSIDENCE OVERSPREADING THE REGION ON THE BACKSIDE OF THE OCEAN LOW TRACKING SOUTHEAST OF THE BENCHMARK. THIS SHOULD BE SUFFICIENT IN KEEPING MOST OF THE AREA DRY WITH THE EXCEPTION OF CAPE COD/ISLANDS AND PLYMOUTH COUNTY WHERE OES MAY PERSIST. IN FACT SOME BREAKS ALREADY OCCURRING IN THE OVERCAST. PREVIOUS FORECAST CAPTURES THESE DETAILS NICELY SO NO MAJOR CHANGES WITH THIS FORECAST UPDATE. =================================================================== PREVIOUS DISCUSSION... BAND OF SCATTERED LIGHT SNOW SHOWERS/FLURRIES LINGERED ACROSS WESTERN MA/NORTHERN CT AND RI VERY EARLY THIS MORNING. EXPECT THIS ACTIVITY TO LIFT NORTHWARD THROUGH MID MORNING WITH MAINLY DRY WEATHER THEREAFTER...OTHER THAN A SPOT FLURRY/SNOW SHOWER. THE EXCEPTION MIGHT BE ALONG THE IMMEDIATE EASTERN MA COAST...PARTICULARLY CAPE AND EASTERN PLYMOUTH COUNTY WHERE SCATTERED LIGHT SNOW SHOWERS MAY PERSIST INTO EARLY AFTERNOON. THIS A RESULT OF COLD NNE LOW LEVEL FLOW RESULTING IN SOME LAND/SEA INTERFACE. OTHERWISE...A RATHER CLOUDY AND CHILLY DAY IS ON TAP FOR SOUTHERN NEW ENGLAND WITH LIGHT/MOIST LOW LEVEL NORTHERLY FLOW. THIS SHOULD HOLD HIGH TEMPS MAINLY IN THE UPPER 20S TO AROUND 30.
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&& .SHORT TERM /WEDNESDAY/... ***SCATTERED LOCALLY HEAVY SNOW SHOWERS POSSIBLE WEDNESDAY WITH THE HIGHEST RISK ACROSS NORTHERN CT/SOUTH COAST*** TONIGHT AND WEDNESDAY... MAINLY DRY WEATHER WILL PERSIST THROUGH AT LEAST MIDNIGHT WITH AN ABUNDANCE OF CLOUDS. A POTENT SHORTWAVE AND ITS ASSOCIATED SURFACE LOW PRESSURE SYSTEM WILL APPROACH FROM THE SOUTHWEST TOWARD DAYBREAK WEDNESDAY. THIS IS AN INVERTED TROUGH SITUATION AND THERE IS SOME MODEL DISAGREEMENT ON HOW FAR NORTH IT GETS. WHILE CURRENT GUIDANCE HAS THE HIGHEST RISK SOUTHWEST OF OUR REGION...THE 00Z MODEL SUITE HAS TRENDED FURTHER NORTH. WILL HAVE TO WATCH THIS CLOSELY...BECAUSE IF IT DOES IMPACT US THIS COULD BE ONE OF THOSE SHORT DURATION/LOCALIZED BUT HIGH IMPACT SNOW EVENT. ESPECIALLY IF IT MOVES IN BY THE WED MORNING RUSH HOUR. VERY STEEP MID LEVEL LAPSE RATES NEAR 8 C/KM ALONG WITH TOTAL TOTALS IN THE HIGH 50S TO NEAR 60 GIVE AN IDEA OF THE POTENTIAL INSTABILITY THIS SYSTEM HAS GOING FOR IT. FOR NOW WILL RUN WITH A PERIOD OF LIKELY POPS ON WEDNESDAY AS MOST AREAS SHOULD SEE AT LEAST BRIEF SNOW SHOWERS. AS FOR ACCUMULATIONS...WILL GO WITH A COATING TO 2 INCHES AS THE MOST LIKELY SCENARIO. HOWEVER...THERE IS A LOW RISK FOR LOCALIZED 3 TO 4 INCH AMOUNTS IF THIS TRENDS FURTHER NORTH. THESE INVERTED TROUGH SCENARIOS HAVE HIGH BUST POTENTIAL IN EITHER DIRECTION...BUT SOMETHING WILL HAVE TO WATCH CLOSELY OVER THE NEXT 12 TO 24 HOURS. HIGH TEMPS WILL MAINLY BE IN THE 30S ON WEDNESDAY. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... HIGHLIGHTS... * SHORTWAVES BRING SNOW SHOWERS AND CLOUDS WED NIGHT THRU THU * SNOW SHOWERS CONTINUE SAT * MUCH COLDER AIR MOVES INTO SOUTHERN NEW ENGLAND FOR THE WEEKEND OVERVIEW AND MODEL PREFERENCES... TRANSITIONING SYNOPTIC REGIME WITH THE NAO/AO BEGINNING THE WEEK STRONGLY POSITIVE BEFORE SHIFTING TOWARD THE NEGATIVE BY THE WEEKEND AND EARLY NEXT WEEK. POSITIVE PNA SUGGESTS THAT THE AMPLIFIED FLOW PATTERN ACROSS THE AREA REMAINS IN PLACE. SO THE ACTIVE PATTERN THAT ALLOWED FOR THIS MOST RECENT STORM DEVELOPMENT ISN/T GOING ANYWHERE TOO FAST. SEVERAL SHORTWAVES WILL BE SLIDING THROUGH THE LONGWAVE TROF...INCLUDING ONE DIRECTLY OUT OF THE ARCTIC LATE IN THE WEEK WHICH LOOKS TO DELIVER THE COLDEST AIR OF THE SEASON BY THE WEEKEND. THERE IS MODEST AGREEMENT THROUGH THE LONG TERM SUCH THAT A BLEND OF OPERATIONAL GUIDANCE SHOULD BE GOOD. HOWEVER...WILL LEAN MORE CLOSELY ON BLEND OF THE GEFS AND ECENS ENSEMBLES FOR FRI...WHEN THE AFOREMENTIONED STRONG/ARCTIC WAVE BEGINS IT/S INFLUENCE. SOME STREAM PHASING AT PLAY...WHICH WILL CULMINATE IN THE FORMATION OF A COASTAL STORM. HOW CLOSE REMAINS THE QUESTION...AND WILL ULTIMATELY DEFINE THE POTENTIAL IMPACTS FOR SRN NEW ENGLAND. DETAILS... WED NIGHT INTO THU...HIGH CONFIDENCE. FIRST IN A SERIES OF LONG TERM SHORTWAVES WILL BE MOVING THROUGH THE PERSISTENT LONGWAVE TROF. THIS MAY LEAD TO INVERTED TROF DEVELOPMENT BETWEEN THE UPPER SHORTWAVE AND LOW PRES IN THE GULF OF MAINE AND BAY OF FUNDY. MOISTURE IS LACKING AS THE OVERALL FLOW IS NW. SO...EXPECT ONLY ISOLATED TO SCT SHSN DEVELOPMENT. ANY ACCUMS WILL BE LIGHT. H92 TEMPS BETWEEN -12C AND -18C SUGGEST HIGHS/LOWS GENERALLY BELOW NORMAL...EXACERBATED BY PERSISTENT NW FLOW YIELDING LOW WIND CHILLS. EXPECT LOWS IN THE TEENS TO LOW 20S WITH HIGHS IN THE UPPER 20S TO LOW 30S. WIND CHILLS LIKELY REMAIN IN THE TEENS. FRI AND FRI NIGHT...HIGH CONFIDENCE. HIGH PRES BRIEFLY RIDGES OVER THE REGION SUGGESTING A MAINLY CLEAR AND DRY PERIOD. -10C TO -12C H92 TEMPS SUGGEST TEMPS NEAR TO SLIGHTLY BELOW NORMAL. SAT...MODERATE CONFIDENCE. LOW PRES ASSOCIATED WITH AN ARCTIC IMPULSE WILL BE SLIDING THROUGH THE REGION FROM ONTARIO. WHILE THE PARENT LOW IS EXPECTED TO PASS TO THE N...A TRANSFER OF ENERGY IS EXPECTED...LEADING TO A BOMBING LOW PRES DEVELOPMENT IN THE GULF OF MAINE TO NEAR NOVA SCOTIA. HOW CLOSE THIS RAPID CYCLOGENESIS OCCURS WILL BE THE ULTIMATE DETERMINING FACTOR IN SENSIBLE WX ACROSS THE REGION. A CLOSER PASS EQUALS MORE SIGNIFICANT IMPACT WITH SNOWS/WINDS THE PRIMARY ISSUE. THE CURRENT ENSEMBLE BLEND IS TOO FAR OFFSHORE FOR SIGNIFICANT IMPACT...BUT THIS WILL NEED TO BE MONITORED OVER THE NEXT FEW DAYS. ONE LIKELY IMPACT WILL BE THE POTENTIAL FOR OCEAN EFFECT SNOWS ACROSS CAPE COD AND IMMEDIATE COASTAL PLYMOUTH COUNTY IN MA. THE COLD ADVECTION ALOFT SUGGESTS DELTA-T VALUES BETWEEN 25 AND 30C AND FLOW 350-020. SOME HEADLINES MAY BE NEEDED FOR THIS ALONE. BITTERLY COLD AIRMASS BEGINS TO SETTLE IN...SO EXPECT TEMPS WELL BELOW NORMAL. SAT NIGHT THROUGH SUN...HIGH CONFIDENCE. EVER CONSIDERED VISITING ALERT...OR DO THE QUEEN ELIZABETH ISLANDS EXCITE YOU? IF SO YOU ARE IN LUCK...BECAUSE BACKWARD TRAJECTORIES SUGGEST THAT THE AIRMASS EXPECTED TO ARRIVE LATE SAT INTO EARLY NEXT WEEK ARE COMING FROM THAT EXACT REGION. H85 TEMPS DROP AS LOW AS -28C...NOT QUITE TO THE -30C DEVELOPING ACROSS NY. EXPECT BITTERLY COLD TEMPS...COMBINED WITH BRISK N-NW FLOW WHICH WILL YIELD WIND CHILLS WELL INTO THE NEGATIVE DOUBLE DIGITS FOR MANY. WILL LIKELY NEED AT LEAST WIND CHILL ADVISORIES IF NOT WARNINGS FOR A PORTION OF THIS PERIOD. SOME AREAS MAY ONLY SEE HIGHS IN THE SINGLE DIGITS IN SPITE OF AN INCREASE IN SUNSHINE. EARLY NEXT WEEK...LOW CONFIDENCE. IN SPITE OF THE COLD START...AN EASTWARD SHIFT IN THE TROF SUGGESTS THE PASSAGE OF AN INSIDE RUNNER WHICH MAY REMAIN COLD ENOUGH FOR SNOW OR EVEN A MIXED PRECIP EVENT. LOT/S OF UNCERTAINTY IN TIMING AND THERMAL PROFILES AT THIS POINT.TEMPERATURES DURING THIS TIME WILL ALREADY BE 5 TO 10 DEGREES BELOW NORMAL FOR MID FEBRUARY AND THE COLDER AIR IS YET TO COME. && .AVIATION /16Z TUESDAY THROUGH SATURDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. 15Z UPDATE ... NO MAJOR CHANGES FROM 12Z TAFS. ONLY NUISANCE SNOW SHOWERS TODAY WILL BE OVER CAPE COD/ISLANDS AND COASTAL PLYMOUTH COUNTY. ELSEWHERE CIGS LIFT TO MVFR-VFR. EARLIER DISCUSSION BELOW. =================================================================== TODAY...HIGH CONFIDENCE IN TRENDS...LOWER CONFIDENCE IN TIMING. MAINLY A MIX OF MVFR THROUGH THE MORNING HOURS...PRIMARILY DUE TO CIGS...ALTHOUGH VSBYS OCCASIONALLY MVFR IN LIGHT SN EARLY. OTHERWISE...A FEW BREAKS TO VFR THIS AFTERNOON AND EARLY EVENING POSSIBLE...BEFORE A GRADUAL TREND BACK DOWN OVERNIGHT. TONIGHT AND WEDNESDAY...MODERATE CONFIDENCE. MAINLY LOW END VFR TO MVFR CIGS TONIGHT. SCATTERED SNOW SHOWERS WHICH MAY WORK INTO OUR REGION TOWARDS 12Z WED. HIGHEST RISK WILL BE ACROSS NORTHERN CT AND THE SOUTH COAST AND THEY MAY PERSIST INTO THE AFTERNOON. MVFR CONDITIONS DOMINATE BUT BRIEF LOCALIZED IFR TO LIFR CIGS/VSBYS POSSIBLE LOCALLY HEAVY SNOW SHOWERS. KBOS TERMINAL...MODERATE CONFIDENCE IN TAF. KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. OUTLOOK /WEDNESDAY NIGHT THROUGH SATURDAY/... WED NIGHT INTO THU NIGHT...MODERATE CONFIDENCE. MAINLY VFR BUT PERIODS OF SHSN ARE POSSIBLE WITH LIGHT ACCUMS AND LOCALIZED IFR CONDITIONS. FRI...HIGH CONFIDENCE. MAINLY VFR. SAT...MODERATE CONFIDENCE. ONCE AGAIN A RISK FOR SNOW...PARTICULARLY CAPE/ISLANDS. OTHERWISE VFR OUTSIDE OF ANY SN. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH WEDNESDAY/...HIGH CONFIDENCE. 10 AM UPDATE ... NO MAJOR CHANGES WITH THIS FORECAST UPDATE. OCEAN LOW WILL TRACK SOUTHEAST OF THE 40N/70W BENCHMARK BUT NOT NEARLY AS INTENSE AS YESTERDAY/S CYCLONE. EARLIER FORECAST HANDLES THIS WELL. LIGHT NE WINDS WILL RESULT IN SCATTERED LIGHT SNOW SHOWERS OVER THE EASTERN MA WATERS NEAR SHORE OF CAPE COD/ISLANDS AND PLYMOUTH COUTY. EARLIER DISCUSSION BELOW. ================================================================== TODAY THROUGH WEDNESDAY...HIGH CONFIDENCE. WINDS WILL GENERALLY REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS THROUGH WEDNESDAY. HOWEVER...PERSISTENT EASTERLY SWELL FROM YESTERDAY/S OCEAN STORM COMBINED WITH ADDITIONAL WAVES OF LOW PRESSURE WILL KEEP SEAS ABOVE SMALL CRAFT ADVISORY THRESHOLDS THROUGH WED AFTERNOON ACROSS MOST OF OUR OUTER-WATERS AND WESTERN SOUNDS. OUTLOOK /WEDNESDAY NIGHT THROUGH SATURDAY/... WED NIGHT INTO THU NIGHT...HIGH CONFIDENCE. WINDS MAINLY W-NW WITH GUSTS 25-30 KT AT TIMES...BUT DISSIPATING BY THU NIGHT. THIS WILL YIELD SEAS AROUND 7-10 FT. SMALL CRAFT ADVISORIES ARE EXPECTED. FRI AND FRI NIGHT...HIGH CONFIDENCE. BRIEF HIGH PRES WILL YIELD W WINDS...WITH GUSTS MAINLY 20 KT OR LESS AND SEAS BELOW 5 FT. THEREFORE...A PERIOD OF RELATIVELY QUIET BOATING WEATHER IS EXPECTED. SAT...MODERATE CONFIDENCE. WINDS SHIFT TO THE N AND NW. GUSTS MAY REACH CLOSE TO GALE FORCE BUT AT LEAST SMALL CRAFT ADVISORY LEVELS ARE EXPECTED. SEAS ALSO INCREASE...ALONG WITH A LATE DAY RISK FOR FREEZING SPRAY. && .TIDES/COASTAL FLOODING...
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THE COMBINATION OF HIGH ASTRO TIDES AND LARGE EASTERLY SWELLS CONTINUING TO TRAVERSE INTO THE EASTERN MA WATERS WILL RESULT IN A ROUND OF MINOR COASTAL FLOODING LATE THIS MORNING AND EARLY AFTERNOON. WHILE WATER LEVELS MAY FALL JUST SHORT OF FLOOD STAGE LARGE WAVE ACTION ON TOP OF THE ELEVATED WATER LEVELS WILL RESULT IN MINOR COASTAL FLOODING. KEEP IN MIND IMPACTS TODAY WILL BE MUCH LESS THAN WHAT WAS EXPERIENCED YESTERDAY.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...COASTAL FLOOD ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR MAZ007-015-016-019-022-024. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EST WEDNESDAY FOR ANZ235-237- 250-254>256. SMALL CRAFT ADVISORY UNTIL 7 AM EST WEDNESDAY FOR ANZ251.
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&& $$ SYNOPSIS...FRANK/DOODY NEAR TERM...FRANK/NOCERA/DOODY SHORT TERM...FRANK LONG TERM...DOODY AVIATION...FRANK/NOCERA/DOODY MARINE...FRANK/NOCERA/DOODY TIDES/COASTAL FLOODING...NOCERA

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