AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 655 PM EST FRI DEC 5 2014 .SYNOPSIS... LOW PRESSURE APPROACHING NEW ENGLAND WILL RESULT IN A BRIEF MIX OF SNOW AND SLEET THIS EVENING...THEN QUICKLY CHANGING TO ALL RAIN. THE EXCEPTION WILL BE ACROSS WESTERN MASSACHUSETTS WHERE FREEZING RAIN WILL LINGER A BIT LONGER. THE LOW TRACKS JUST SOUTH OF NEW ENGLAND SAT AND SAT NIGHT RESULTING IN PERIODS OF RAIN. THE LOW DEPARTS LATE SAT NIGHT YIELDING DRY BUT MUCH COLDER AND BLUSTERY WEATHER SUNDAY. DRY AND COLD WEATHER LINGERS INTO MON. BY TUESDAY A COASTAL STORM MAY DEVELOP AND IMPACT SOUTHERN NEW ENGLAND WITH RAIN AND WIND...POSSIBLY WET SNOW OVER WESTERN MASSACHUSETTS. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... 700 PM UPDATE... SCT SHOWERS ARE STARTING TO STREAM INTO CT AND WESTERN MASS WITHIN THE PAST HOUR. MANY LOCATIONS HAVE SEEN FLURRIES OR SNOW PELLETS PER PUBLIC REPORTS. KHFD DID REPORT UP FOR THE LAST HOUR SO WE WILL NEED TO WATCH HARTFORD CO IN POSSIBLE EXPANSION OF THE ADVISORY. OTHERWISE HI-RES GUIDANCE STILL SHOWS LARGE SWATH OF PRECIP MOVING INTO THE REGION BETWEEN 01-03Z SO HAVE ADJUSTED POP TIMING. ASIDE FROM A FEW MINOR EDITS THE BULK OF THE EVENING FORECAST REMAINS ON TRACK. PREVIOUS DISCUSSION... SOUTHERN STREAM SYSTEM EJECTING OUT OF THE MS/TN VLY EARLY THIS EVENING. WARM ADVECTION PRECIPITATION ALREADY INTO THE LOWER HUDSON VALLEY OF NY AT 330 PM. MODEL SOUNDINGS SUGGEST COLUMN TAKES UNTIL 00Z/7PM OR SO TO SATURATE ACROSS WESTERN MA/CT...AND 03Z-06Z FOR EASTERN MA AND RI. MODEL QPF IN AGREEMENT ON THIS TIMING AS WELL. MID LEVEL WARMING FROM 900-800 MB IS RAPID SO SNOW WILL QUICKLY CHANGE TO SLEET AND THEN RAIN ACROSS MUCH OF THE REGION. THE AREA OF CONCERN IS ACROSS THE CT RVR VLY OF MA WHERE SHALLOW COLD AIR WILL BE SLOWER TO ERODE/DISLODGE. LIGHT NORTHERLY FLOW AT BAF/BDL/HFD IS EVIDENCE OF THIS. 12Z NAM MODEL SOUNDINGS AND 2 METER TEMPS FROM THE 12Z NAM ALONG WITH SOME OF THE OTHER HIRES GUID SUGGEST TEMPS AROUND FREEZING MUCH OF THE NIGHT IN THE I-91 CORRIDOR OF WESTERN MA INCLUDING THE ROUTE 2 CORRIDOR OF NORTHERN MA. THUS WE ISSUED A WINTER WEATHER ADVISORY FOR THIS AREA FOR A PERIOD OF SNOW AND SLEET TRANSITIONING OVER TO SEVERAL HOURS OF FREEZING RAIN...POSSIBLY LINGERING INTO THE EARLY MORNING HOURS OF SAT. ELSEWHERE A CHILLY RAIN TONIGHT. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... SATURDAY... FRONTAL WAVE AND PERIODS OF RAIN MOVE ACROSS THE AREA. FAIRLY STRONG FRONTAL BOUNDARY DRAPED OVER THE REGION WITH HIGHS TOMORROW IN THE 50S ACROSS RI AND SOUTHEAST MA...WITH 40S TO THE NORTHWEST ACROSS NORTHERN CT...WEST-CENTRAL MA TO THE NORTH SHORE OF BOSTON. GIVEN THE WEAK PGRAD WINDS WILL BE FAIRLY LIGHT...ESPECIALLY IN THE COLD SECTOR. SSW WINDS MAY REACH 10-15G20 MPH ACROSS CAPE COD AND THE ISLANDS. SATURDAY NIGHT... BAROCLINIC WAVE INTENSIFIES WITH GOOD MID LEVEL FGEN. THIS FRONTAL SCALE FORCING COMBINING WITH PWATS UP TO +2 STD ABOVE CLIMO WILL RESULT IN PERIODS OF MODERATE TO HEAVY RAIN ACROSS CT/RI AND SOUTH OF THE MASS PIKE. GOOD MODEL AGREEMENT ON A SOAKING RAIN TONIGHT/SAT INTO SAT NIGHT WITH 12Z ECMWF/GFS/NAM AND GEFS FAIRLY HIGH PROBABILITY OF 1 INCH STORM TOTAL RAINFALL ACROSS CT/RI AND SOUTH OF THE MASS PIKE...WITH LESS NORTHWARD. IN ADDITION HIGHER RES DETERMINISTIC GUIDANCE SUGGEST ISOLATED AMOUNTS UP TO 2 INCHES OVER RI AND SOUTHEAST MA. BEHIND THE FRONT 06Z-12Z SUNDAY...SHARPLY COLDER AND WINDY ALONG THE COAST WITH GUSTS UP TO 40 MPH BY SUNRISE SUNDAY. RAIN MAY BRIEFLY TURN TO SNOW/SLEET BEFORE ENDING. && .LONG TERM /SUNDAY THROUGH FRIDAY/... HIGHLIGHTS... * MOSTLY DRY WEATHER EXPECTED SUNDAY W/ OCEAN EFFECT SNOW SHOWERS SUN PM * A COASTAL LOW MAY BRING ANOTHER ROUND OF WINTRY WEATHER OR HEAVY RAIN WITH WIND LATE MON INTO TUES * DRY WEATHER RETURNS WED AND THU OVERVIEW... HIGH PRESSURE BUILDS IN FOR SUNDAY. HOWEVER FOR THE MONDAY THROUGH WED TIMEFRAME THE 12Z SYNOPTIC PATTERNS ARE IN TWO DIFFERENT CAMPS THIS RUN. THE FIRST IS THE 12Z EC/UKMET/CHC WHILE THE OTHER IS THE 12Z GFS. THE INTERNATIONAL CAMP IS MORE AMPLIFIED IN THE FIRST PART OF NEXT WEEK REGARDING THE COASTAL SYSTEM ALLOWING FOR SOUTHERN STREAM INVOLVEMENT AND DEEPENING OF THE TROUGH. THE GFS APPEARS TO BE TO FLAT IN ITS DOWNSTREAM RIDGING AND THEREFORE NOT INCORPORATING THE SOUTHERN STREAM AND KEEPING THE SYSTEM AS A WEAK WAVE. BECAUSE OF THIS STEERED AWAY FROM THE GFS THIS RUN AND DID A BLEND OF THE EC AND UKMET. THE CANADIAN ALTHOUGH ROBUST STILL IS TOO FAST BY 24 HOURS. THE EC ALSO SEEMS HIGHLY AMPLIFIED SO THE UKMET SEEMS TO BE A GOOD COMPROMISE BETWEEN THE TWO. WPC AGREES AS WELL. REGARDLESS APPEARS THAT A SYSTEM WILL IMPACT SOUTHERN NEW ENGLAND...AND WITH MANY OF THE MODELS COMING IN WARM DO NOT SEE A BIG SNOW THREAT AT THIS TIME. AFTER THE SYSTEM MOVES OFF THE COAST...LOW CONFIDENCE ON THURS INTO FRIDAY AS GFS SHOWS HIGH PRESSURE WILL THE EC CONTINUES CYCLONIC FLOW. DETAILS... SUNDAY INTO SUNDAY NIGHT...HIGH CONFIDENCE. HIGH PRESSURE BUILDS IN FROM THE NORTH PUSHING THE FRONT OFFSHORE AND KEEPING AN UPCOMING THE WAVE SUPPRESSED. HOWEVER EXPECT STRONG CAA TO MOVE THROUGH ALLOWING FOR TEMPS TO BE WELL BELOW AVERAGE FOR THIS TIME OF YEAR. GUSTY WINDS WILL BE AN ISSUE OVER THE CAPE AS COLD AIR INTERACTS WITH THE WARM OCEAN WATERS. OVERNIGHT WITH STRONG CAA OVER THE RELATIVELY WARM WATER AND A NORTHEASTERLY FLOW...COULD SEE A FEW OCEAN EFFECT CLOUDS OF SHOWERS DEVELOP AND MOVE ON THE COAST. WINDS SWITCH TO A MORE EASTERLY DIRECTION OVERNIGHT PUSHING THE LOW LEVEL MOISTURE ONSHORE AS WELL AS ANY ISOLATED SNOW SHOWERS. SEA SURFACE TEMP UP TO THE BOUNDARY LATER HAS A TEMP DIFFERENCE TO 15F WHICH IS A GOOD SIGN THAT OCEAN EFFECT SNOW MAY DEVELOP. ALSO BUFKIT SOUNDINGS TO SHOW CAPE VALUES OVER 250 J/KG INDICATING FOR SOME INSTABILITY SO KEEP THE SHOWERS GOING THROUGH PERHAPS MONDAY MORNING. THEREFORE HAVE INSERTED IN A SLIGHT CHANCE OF SNOW SHOWERS FOR THIS TIME PERIOD ACROSS THE CAPE AND THE EAST MASS COASTLINE. MONDAY... HIGH CONFIDENCE. HIGH PRESSURE IN THE MID-LEVELS WILL BEGIN TO SCOOT OFFSHORE. THIS IS DO TO LACK OF BLOCKING IN THE UPSTREAM PATTERN PER +NAO AND THE APPROACHING COASTAL SYSTEM. ASIDE FOR A FEW OCEAN EFFECT SHOWERS IN THE MORNING DRY WEATHER IS ANTICIPATED AND COOLER TEMPS. MONDAY NIGHT INTO WEDNESDAY...LOW CONFIDENCE. INCREASING CONFIDENCE THAT A COASTAL SYSTEM WILL IMPACT SOUTHERN NEW ENGLAND SOMETIME BETWEEN MONDAY NIGHT AND WED...WITH THE HIGHEST CONFIDENCE ON TUESDAY. AGAIN THROWING OUT THE GFS...THE EC ENSEMBLES AS WELL AS THE GEFS STILL SHOW A DESCENT SPREAD IN THE SYSTEM...SO CONTINUE LOW CONFIDENCE THINKING. HOWEVER IT APPEARS THAT TIMING IS STARTING TO COME TOGETHER AROUND THE TUESDAY TIMEFRAME. SNOW...THE COASTAL SYSTEM CONTINUES TO TREND WARMER SO ANTICIPATE A MORE RAIN/WIND THREAT RATHER THEN SNOW AT THIS TIME. HOWEVER APPEARS THAT WHEN THIS SYSTEM DEEPENS AS IT APPROACHES SOUTHERN NEW ENGLAND. COLD AIR WILL BE WRAPPING AROUND AND LOCATIONS WEST OF I-91 MAY BE IMPACTED WITH A GOOD THUMP OF SNOWFALL THROUGH THE EVENT. RAIN...HEAVY RAIN WILL BE A FACTOR WITH THE COASTAL SYSTEM AS IT MOVES INTO THE REGION. COULD SEE RAINFALL TOTALS BETWEEN AN INCH TO 1.5 INCHES DEPENDING ON WHERE THE SURFACE LOW CROSSES. WIND...GUIDANCE SHOWS A 925 MB 50-60 KT JET MOVING OVER THE SOUTH COAST...CAPE...ISLANDS AND EVENTUALLY NORTHWARD ACROSS THE EASTERN MASS COASTLINE. IF THIS SIGNAL IS CONSISTENT THEN WIND HEADLINES WILL BE NEEDED. COASTAL FLOODING...LASTLY THE SPRING TIDE IS STARTING TO COME DOWN NEXT WEEK HOWEVER IF THE LLJ LINES UP WITH THE HIGH TIDE...A SURGE OF 2 FEET CANNOT BE RULED OUT...LEADING TO MINOR TO MODERATE FLOODING. RIGHT NOW APPEARS THAT THE STRONG JET OCCURS AT LOW TIDE SO MINOR SPLASHOVER IS POSSIBLE. IF THIS SYSTEM DOES CUT-OFF AS THE EC INDICATES THAT MULTIPLE HIGH TIDE CYCLES MAY BE IMPACTED AND BEACH EROSION COULD OCCUR AS WELL. THURSDAY INTO FRIDAY...LOW CONFIDENCE. THERE IS A BIT OF UNCERTAINTY IN THIS TIME PERIOD...SOME STEMMING FROM WHATEVER HAPPENS MONDAY AND TUESDAY. THE ECMWF HAS A SHORTWAVE/CUTOFF LOW MOVING THROUGH WHILE THE GFS HAS HIGH PRESSURE THROUGH THE ENTIRE PERIOD.
Posted on: Sat, 06 Dec 2014 02:06:38 +0000
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