Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 231808 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 208 PM EST SUN NOV 23 2014 .SYNOPSIS... DRY AND MILD TODAY. A WARM FRONT WILL BRING A BRIEF PERIOD OF HEAVY RAIN AND GUSTY SOUTH WINDS ALONG THE COAST LATE TONIGHT AND MONDAY MORNING FOLLOWED BY UNSEASONABLY MILD CONDITIONS MONDAY AFTERNOON. GUSTY WINDS BUT DRIER WEATHER FOLLOWS FOR TUESDAY. A COASTAL STORM MAY BRING SOME MIXED PRECIPITATION TO THE REGION WEDNESDAY INTO THANKSGIVING DAY...BUT THERE IS A LOT OF UNCERTAINTY. COLDER WEATHER FOLLOWS LATE IN THE WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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2 PM UPDATE... BEAUTIFUL DAY IN PROGRESS WITH PARTLY TO MOSTLY SUNNY SKIES AND MILD TEMPERATURES. HIGHS WILL TOP OUT WELL UP INTO THE 50S...TO AROUND 60 ACROSS THE LOWER ELEVATIONS. GUIDANCE UNDERDONE ON TEMPS WHICH MAKES SENSE SINCE 850 MB TEMPS ARE AROUND +5C WITH AT LEAST SOME WESTERLY COMPONENT TO THE FLOW.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... ***BRIEF PERIOD OF HEAVY RAIN VERY LATE SUN NIGHT/MON MORNING IMPACTING THE AM RUSH HOUR*** DRY WEATHER EXPECTED THROUGH MIDNIGHT. LOW PRES MOVES INTO THE GT LAKES LATE TONIGHT WITH A WARM FRONT APPROACHING FROM THE S. GOOD ISENTROPIC LIFT ENHANCED BY A STRONG LOW LEVEL JET WILL BRING A PERIOD OF HEAVY RAINFALL LATE TONIGHT INTO MON MORNING. GEFS SHOWING PWAT ANOMALY INCREASING TO +3SD AND LOW LEVEL JET REACHES +4SD IN SNE AROUND 12Z MON SO THIS IS A GOOD SIGNAL FOR HEAVY RAIN. HOWEVER...THE SYSTEM IS QUITE PROGRESSIVE AND WE ARE ONLY LOOKING AT ABOUT A 6 HOUR PERIOD OF HEAVY RAIN BEFORE TAPERING OFF BY MIDDAY MONDAY. THIS WILL LIMIT RAINFALL AMOUNTS TO 0.50-1.00" WITH LOCALLY HIGHER AMOUNTS. MAIN THREAT IS TYPICAL MINOR POOR DRAINAGE FLOODING BUT THIS WILL BE OCCURRING DURING THE MORNING COMMUTE. ELEVATED INSTABILITY PARAMETERS ARE NOT THAT IMPRESSIVE BUT CANT RULE OUT AN ISOLD TSTM IN THE COASTAL PLAIN MON MORNING AT THE NOSE OF THE LOW LEVEL JET. THE OTHER CONCERN IS POTENTIAL FOR STRONG WINDS MONDAY MORNING ALONG THE SOUTH COAST. NAM IS MOST ROBUST WITH THE LOW LEVEL NEARING 75 KT AT 925 MB WHILE GFS/ECMWF SHOWING 65-70 KT. SOUNDINGS SHOW A GOOD INVERSION WHICH WILL LIMIT THESE WINDS FROM MIXING DOWN. A FINE LINE OF CONVECTION WHICH COULD HELP TO BRING DOWN THESE WINDS TO THE SFC IS NOT LIKELY AS INSTABILITY IS MARGINAL AND THERE IS NOT A COLD FRONT WHICH TYPICALLY PROVIDES A FOCUS FOR THESE FINE LINES. TAKING ABOUT 50 PERCENT OF THE JET SUGGESTS WIND GUSTS COULD PEAK AT 40-45 MPH WHICH IS NEAR WIND ADVISORY CRITERIA. BEST CHANCE OF REACHING ADVISORY CRITERIA WILL BE ACROSS CAPE/ISLANDS. BULK OF THE RAIN IS OVER BY MON AFTERNOON...EARLIER IN WESTERN NEW ENG...BUT CANT RULE OUT A FEW AFTERNOON SHOWERS AND LOW CLOUDS WILL LIKELY PERSIST THROUGH THE DAY. IT WILL BE UNSEASONABLY MILD WITH HIGHS WELL INTO THE 60S IN MANY LOCATIONS AND DEWPOINTS WILL APPROACH 60 WITH GUSTY S/SW WINDS TO 30-35 MPH IN THE COASTAL PLAIN. 925 MB TEMPS ARE QUITE MILD NEAR +15C WHICH WOULD NORMALLY SUPPORT HIGHS IN THE LOWER 70S BUT THINK LOW CLOUDS WILL LIMIT HEATING. IF WE CAN GET ANY SUN...70+ WOULD BE POSSIBLE. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... HIGHLIGHTS... * MILD BUT WINDY ON TUESDAY * COASTAL STORM WITH TRAVEL IMPACTS POSSIBLE WED-THU WITH UNCERTAINTY * COLDER WEATHER BY THE END OF THE WEEK OVERVIEW AND MODEL PREFERENCES... 23.00Z MODEL GUIDANCE SUITE CONTINUES TO SHOW MODERATE AGREEMENT THROUGH THE MID TERM PERIOD...INCLUDING THE REDEVELOPMENT OF DEEP LONGWAVE TROF BY MID- LATE WEEK ACROSS THE ERN THIRD OF THE CONUS. THE PRIMARY MODEL ISSUES AND DISAGREEMENTS ARE STILL REGARDING THE POTENTIAL COASTAL STORM FOR LATE WED-THU. THIS DISAGREEMENT IS LIKELY DUE TO THE FACT THAT THE EJECTING SHORTWAVE ASSOCIATED WITH THE FRONTAL WAVE DEVELOPMENT IS STILL WRAPPED IN THE NEAR ALEUTIAN ISLANDS LOW...AND MAY NOT BE BETTER SAMPLED FOR ANOTHER 24+ HOURS. AGREE WITH WPC...THE KEY WILL BE WHERE THE LOW PASSES IN REGARD TO THE 40/70 BENCHMARK...WITH THE GFS LEANING ABOUT 50-100 NM E AND THE ECMWF CLOSER TO BUT W OF IT. ECENS MEAN SEEMS TO SPLIT THIS DIFFERENCE WELL...AND GIVEN WPC/S PREFERENCE FOR IT AS WELL...WILL LEAN THERMAL PROFILES WITH THIS UPDATE CLOSER TO IT/S THINKING...ALTHOUGH ESSENTIALLY THIS IS CLOSE TO A GFS/ECMWF BLEND IN SPITE OF THE FACT THE ECMWF IS WELL W OF THE BENCHMARK. GIVEN THE UNCERTAINTY WITH THE STORM ITSELF...HOW EFFICIENTLY IT IS ABLE TO DRAW IN THE COLDER AIR FROM THE LONGWAVE TROF TO THE W REMAINS STILL A BIT OF A QUESTION MARK TOWARD THE END OF THE WEEK...BUT A TREND TOWARD COLDER CONDITIONS LOOKS LIKELY. DETAILS... MON NIGHT INTO TUE NIGHT... MAINLY DRY FORECAST HERE ALTHOUGH A FEW LINGERING SHOWERS ARE POSSIBLE MAINLY MON NIGHT AS UPPER LVL SHORTWAVE PIVOTS THROUGH ALONG WITH WEAKENING COLD FRONT. COLD AIR REMAINS TO THE W AND SO IN SPITE OF COLD ADVECTION W-FLOW...EXPECT TEMPS TO REMAIN NEAR TO EVEN SLIGHTLY ABOVE NORMAL. WED INTO THU... AS MENTIONED ABOVE...THERE IS STILL TOO MUCH UNCERTAINTY HERE FOR A HIGH CONFIDENCE FORECAST EVEN WITH THE POTENTIAL IMPACTS AT PLAY. IN ANY CASE...DO HAVE CONFIDENCE IN A MORE RAPIDLY DEEPENING COASTAL LOW PRES MOVING OUT OF THE MID ATLANTIC TO THE SE MA COASTLINE...MAKING IT/S CLOSEST PASS ESPECIALLY WED NIGHT...DIPPING BELOW 1000MB. THE EXACT TRACK IS THE MAIN QUESTION AND AS SUCH...WHAT THE THERMAL PROFILE IS MOST LIKELY TO LOOK LIKE. AT THIS TIME...0C H92 LINE VARIES BETWEEN JUST W OF THE BOS- PVD CORRIDOR TO OFFSHORE...SO EXACTLY WHERE ANY RAIN/SNOW LINE DEVELOPS REMAIN IN FLUX. GIVEN THE DYNAMICS AS POINTED OUT BY THE PREVIOUS FORECASTER...WETBULB/DYNAMIC COOLING ARE LIKELY TO LEAD TO COOLER TEMPS THAN THE STRAIGHT 2M MODEL TEMPS WOULD INDICATE...SO EVEN WITH THE FURTHER E TRACK...SNOW IS POSSIBLE. HOW MUCH IS JUST TOO UNCERTAIN TO CALL GIVEN NOT JUST THE THERMAL PROFILE ISSUES... THERE IS A BANDING SIGNAL AND TROWAL SIGNATURE TOWARD THE NE QUADRANT. WHICH COULD PROVIDE DYNAMIC COOLING. WHAT THIS ALL MEANS IS THAT THERE IS THE CHANCE FOR A COASTAL STORM...WITH WINTERY PRECIP AND POSSIBLY EVEN PLOWABLE SNOW DEPENDING ON THE FINAL TRACK FOR THE WED AFTERNOON INTO EARLY THANKSGIVING MORNING TIMEFRAME. EXACTLY HOW MUCH SNOW AND WHERE RAIN/SNOW LINE SETS UP REMAINS IN QUESTION. BUT PRECIP IS LIKELY TO LEAN E GIVEN SIGNALS FOR HEAVY RAIN ON THE RAIN SIDE AS WELL AS GUSTY WINDS IF THE TRACK IS CLOSER. COULD ALSO BE SIGNIFICANT GRADIENT BETWEEN WRN MA/CT/NH AND EARN MA/RI IN SNOW/RAINFALL. ALSO...AS MENTIONED BY PREVIOUS FORECASTER...COASTAL FLOODING THREAT APPEARS RELATIVELY LOW GIVEN THE RAPID MOVEMENT /LACK OF DOWNSTREAM BLOCKING/ AND LOW ASTRONOMICAL TIDES. ALL THESE FEATURES WILL HAVE TO BE WATCHED GIVEN THEY WILL BEGIN DURING A VERY BUSY TRAVEL PERIOD ON WED. FRI... COLDER AIR BEGINS TO BUILD IN BEHIND THE EXITING LOW PRES...EXPECT A TREND TOWARD DRIER BUT COLDER WEATHER BY LATE IN THE WEEK. NEXT WEEKEND... AS CORE OF COLD AIR TROF BEGINS TO MOVE OVER...EXPECT TEMPS BELOW NORMAL...AND POSSIBLY EVEN A WEAK WAVE OF LOW PRES/CLIPPER. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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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 MONDAY NIGHT/... THIS AFTERNOON...HIGH CONFIDENCE IN VFR CONDITIONS CONTINUING. TONIGHT INTO MONDAY...MODERATE CONFIDENCE. VFR CONDITIONS PERSIST THIS EVENING. CONDITIONS RAPIDLY DETERIORATE FROM SOUTHWEST TO NORTHEAST BETWEEN 6Z AND 12Z AS RAIN MOVES INTO SOUTHERN NEW ENGLAND. THIS WILL RESULT IN LOW END MVFR TO TIMES OF IFR CONDITIONS. THESE CONDITIONS WILL CONTINUE THROUGH MONDAY MORNING...WITH EVEN A LOW RISK OF AN ISOLATED THUNDERSTORM OR TWO ACROSS SOUTHEAST NEW ENGLAND. BULK OF THE RAIN IS OVER BY MONDAY AFTERNOON...BUT A FEW SPOT SHOWERS WILL REMAIN POSSIBLE WITH DEEP MOISTURE IN PLACE AND SOUTHWEST FLOW ALOFT. GIVEN A LOT OF LOW LEVEL MOISTURE IN PLACE...FEEL THAT MVFR TO EVEN IFR CONDITIONS WILL PERSIST THROUGH MUCH OF MON AFTERNOON. AS FOR WINDS...A PERIOD OF SOUTHERLY WIND GUSTS OF 35 TO 40 KNOTS ARE EXPECTED ACROSS THE SOUTHEAST NEW ENGLAND COAST. FURTHER INLAND...STILL MAY SEE 30 KNOT GUSTS BUT LLWS AT 1500 FEET WILL BE A CONCERN. MONDAY NIGHT...LOW TO MODERATE CONFIDENCE. MVFR TO IFR CONDITIONS WILL PROBABLY IMPROVE TO VFR AT LEAST ACROSS NORTHWEST SECTIONS. KBOS TERMINAL...HIGH CONFIDENCE THROUGH THIS EVENING. MODERATE CONFIDENCE LATE TONIGHT INTO MONDAY. LLWS EXPECTED TO DEVELOP BY DAYBREAK MONDAY KBDL TERMINAL...HIGH CONFIDENCE. MODERATE CONFIDENCE LATE TONIGHT INTO MONDAY. LLWS EXPECTED TO DEVELOP BY DAYBREAK MONDAY OUTLOOK...TUESDAY THROUGH THURSDAY. TUE INTO TUE NIGHT...MODERATE CONFIDENCE. MAINLY VFR. BUT A FEW LEFTOVER SHOWERS POSSIBLE MON NIGHT ESPECIALLY MAY YIELD MVFR CONDITIONS. W-SW WIND GUSTS ABOUT 20-25 KT AT TIMES EACH DAY. WED INTO THU...LOW CONFIDENCE. A COASTAL LOW PRES WILL MOVE SOMEWHERE BETWEEN JUST ONSHORE OF SE MA OR OFFSHORE. GIVEN THIS UNCERTAINTY IN TRACK...THERE IS UNCERTAINTY IN SNOW/RAIN POTENTIAL...BUT THERE IS THE POSSIBILITY OF EACH WITH ACCUMULATIONS OF SNOW. NE WINDS COULD ALSO GUST 25+ OR MORE EITHER DAY.
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&& .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH MONDAY/... TODAY...HIGH CONFIDENCE. SW GUSTS 25-30 KT SE WATERS EARLY...OTHERWISE DIMINISHING WIND THROUGH THE MORNING WITH GUSTS DROPPING BELOW SCA THRESHOLDS THIS AFTERNOON. TONIGHT AND MONDAY...MODERATE CONFIDENCE. DEVELOPING LOW LEVEL JET WILL RESULT IN GUSTY S WINDS LATE TONIGHT INTO MONDAY. THERE IS AN INVERSION OVER THE WATERS WHICH WILL LIKELY LIMIT GUSTS AND PREVENT STRONG WINDS FROM MIXING DOWN. HOWEVER GIVEN STRENGTH OF THE JET...GALE FORCE GUSTS TO 35-40 KT SEEM PLAUSIBLE AND GALE WARNINGS MAY BE NEEDED. SEAS WILL LIKELY BUILD TO BETWEEN 10 AND 15 FEET ACROSS THE SOUTHERN WATERS WITH VERY LONG FETCH. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY. MONDAY NIGHT THROUGH TUESDAY NIGHT...HIGH CONFIDENCE. AT LEAST SMALL CRAFT ADVISORY CONDITIONS WITH WINDS MAINLY SW-W AND GUSTS 25-30 KT INTO EARLY TUE. SEAS ALSO AROUND 8-10 FT. BOTH WINDS AND SEAS DROP OFF LATE TUE TONIGHT WITH A BRIEF LULL EXPECTED INTO EARLY WED. LOW PROBABILITY OF SOME GALE FORCE GUSTS ON TUE. WED AND THU...LOW CONFIDENCE. A COASTAL STORM WILL PASS SOMEWHERE NEAR 40N/70W...THIS WILL YIELD BUILDING SWELL AND WINDS SHIFTING FROM NE LATE WED TO WNW BY LATE THU. DEPENDING ON HOW CLOSE THE STORM COMES...HEAVY RAIN AND AT LEAST SMALL CRAFT ADVISORY CONDITIONS ARE POSSIBLE. GALES ALSO A POSSIBILITY. VISIBILITIES DROP IN RAIN/FOG. && .TIDES/COASTAL FLOODING... ASTRONOMICAL TIDES ARE FAIRLY HIGH DURING THE MON MORNING HIGH TIDE CYCLE. WITH SOUTHERLY GALES EXPECTED...A STORM SURGE OF 1-2 FT IS POSSIBLE ALONG THE SOUTH COAST WHICH MAY BRING SOME LOCATIONS TO MINOR FLOOD. THE MAIN THREAT FOR MINOR COASTAL FLOODING WILL BE ALONG NARRAGANSETT BAY AND WESTPORT HARBOR DUE TO SOUTHERLY FETCH. COASTAL FLOOD ADVISORIES MAY EVENTUALLY BE NEEDED. NO FLOODING IS EXPECTED ALONG THE EAST COAST. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR ANZ231>235-237. SMALL CRAFT ADVISORY UNTIL 3 PM EST THIS AFTERNOON FOR ANZ250- 254>256. && $$ SYNOPSIS...KJC/DOODY NEAR TERM...FRANK SHORT TERM...KJC LONG TERM...DOODY AVIATION...FRANK/DOODY MARINE...KJC/DOODY TIDES/COASTAL FLOODING...KJC

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