Area Forecast Discussion
Issued by NWS Boston, MA

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183 FXUS61 KBOX 172250 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 650 PM EDT SUN MAY 17 2015 .SYNOPSIS... MARITIME HIGH PRESSURE BUILDS OVER NEW ENGLAND TONIGHT BRINGING A COOLER MARINE AIR TONIGHT AND MONDAY. ANOTHER COLD FRONT WILL BRING SCATTERED SHOWERS TO THE REGION MON NIGHT INTO TUE WITH A LOW POTENTIAL FOR AN ISOLATED THUNDERSTORM. DRY WEATHER WILL FOLLOW FOR MID WEEK LASTING INTO NEXT WEEKEND. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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700 PM UPDATE... OVERALL TREND IN THE FORECAST REMAINS ON TRACK. BACKDOOR COLD FRONT HAS BEEN SWINGING ITS WAY ACROSS THE AREA PER RADAR ECHOES. TEMPERATURES ARE ALREADY STARTING TO DROP BEHIND THE FRONT. ANTICIPATE THE FRONT TO MAKE ITS WAY TO THE WESTERN PORTION OF THE REGION. THIS FRONT WILL ALLOW FOR EASTERLY FLOW ACROSS THE REGION PULLING IN THE OCEAN MOISTURE. ADDED FOG AND DRIZZLE INTO THE FORECAST FOR OVERNIGHT AS VSBYS MAY DROP TO 3SM...PERHAPS PATCHY DENSE FOG ALONG THE MASS EAST COASTLINE. STILL A LOT OF UNCERTAINTY SO HELD OFF ON DENSE FOG ADV. PREVIOUS DISCUSSION... UPPER RIDGE BUILDS OVER THE EASTERN GREAT LAKES WITH A NORTHWEST FLOW ACROSS NEW ENGLAND. A SHORTWAVE OVER THE MARITIMES WILL MOVE OUT TO SEA TONIGHT. THIS WILL TWIST THE UPPER FLOW AND DRAW HIGH PRESSURE THROUGH THE MARITIMES AND DOWN THROUGH NORTHERN NEW ENGLAND. THE RESULT WILL BE AN EAST FLOW ACROSS SOUTHERN NEW ENGLAND THAT SHOULD DRAW LOW LEVEL MOISTURE ACROSS THE REGION. THE RESULT WILL BE LOW CLOUDS/FOG WITH THE MOST LIKELY TIME COMING AFTER MIDNIGHT THROUGH SUNRISE. SOME SIGNS IN THE MODEL DATA OF WEAK LIFT LATE NIGHT NEAR THE SURFACE...THE WARM PART OF THE LAYER...WHICH SUGGEST POTENTIAL FOR SOME DRIZZLE ALONG WITH THE FOG ESPECIALLY IN EASTERN MASS. THE FORECAST WILL GO WITH INCREASING CLOUDS/FOG/DRIZZLE OVERNIGHT. MIN TEMPS WILL BE NEAR THE DEW POINT...IN THE 50S.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... MONDAY...HIGH PRESSURE IN CONTROL SURFACE AND ALOFT WITH EAST SURFACE FLOW BECOMING VARIABLE DURING THE AFTERNOON. THE EAST FLOW WILL SLOW THE BURN-OFF OF LOW CLOUDS DURING THE MORNING...BUT THEN DECREASING CLOUDS IN THE AFTERNOON AS THE FLOW TURNS LIGHT. DAYTIME TEMPERATURES WILL BE COOLEST IN EASTERN MASS WHERE THE FLOW OFF THE COLD WATER IS MOST IMMEDIATE. THE WARMEST TEMPS WILL BE IN THE CT VALLEY WHERE MIXING TO 950 MB WOULD SUPPORT MAX TEMPS IN THE MID 70S. MONDAY NIGHT... HIGH PRESSURE SHIFTS SOUTHEAST. THE SURFACE FLOW OVER NEW ENGLAND SHOULD COME AROUND FROM THE SOUTHWEST AND BRING MILDER MORE HUMID AIR. THE INCREASE IN MOISTURE WILL BRING PRECIPITABLE WATER VALUES TO AROUND 1.75 INCHES...WHICH IS ABOUT 2 STD DEV ABOVE NORMAL. UPPER SHORTWAVE MOVES THROUGH THE GREAT LAKES OVERNIGHT WITH THE JET DYNAMICS SUPPORTING LIFT ACROSS THE GREAT LAKES AND NORTHERN NEW YORK. THIS IS WELL TO OUR WEST AND SUGGESTS A QUIET NIGHT. NOT MUCH LOW LEVEL JET INFLOW EITHER. BUT WE HAVE MAINTAINED CHANCE POPS IN THE FORECAST WITH HIGHEST VALUES IN THE WEST. IT IS REASONABLE THAT SHOWERS COULD MOVE INTO THE REGION AFTER FORMING IN NEW YORK/PENNSYLVANIA. THE INCREASING PRECIPITABLE WATER VALUES SUGGEST POTENTIAL FOR LOCAL HEAVY DOWNPOURS IN WESTERN MASS AND CT. && .LONG TERM /TUESDAY THROUGH SUNDAY/... HIGHLIGHTS... * SCATTERED SHOWERS WITH AN ISO THUNDERSTORM ON TUESDAY WITH A PASSING COLD FRONT * DRY WEATHER AND MODERATING TEMPS WELL INTO NEXT WEEKEND OVERVIEW... FORECAST GUIDANCE CONTINUES TO BE IN GOOD AGREEMENT FOR MUCH OF THE EXTENDED. NO SIGNIFICANT DIFFERENCES AMONGST THE GUIDANCE....MINUS A FEW MINOR MESOSCALE DIFFERENCES. OVERALL HAVE MODERATE TO HIGH CONFIDENCE IN THE FORECAST. UPPER LEVEL SHORTWAVE WILL PUSH TOWARDS THE REGION ON TUESDAY SWINGING A COLD FRONT THROUGH...WITH A SECONDARY COLD FRONT TUESDAY NIGHT. OTHERWISE NEW ENGLAND WILL BE IN A FLAT TO CYCLONIC FLOW ALOFT WITH THE CORE OF UPPER TROUGHING OVER ERN CANADA. A WEAK COLD FRONT MAY PASS THROUGH LATE FRIDAY NIGHT AS UPPER LEVEL LOW PIVOT OVER HUDSON BAY. DETAILS... * TUESDAY...HIGH CONFIDENCE. LOW PRESSURE SYSTEM WILL MOVE ACROSS SOUTHERN CANADA...DRAGGING A COLD FRONT ALONG PUSHING HIGH PRESSURE OUT TO SEA. ANTICIPATE SOME PRECIP ALONG THIS FRONT...BUT DEF NOT A DROUGHT BUSTER. PWAT VALUES ARE CLOSE TO 1.6 INCHES INDICATING A FAIRLY MOIST ATMOSPHERE... HOWEVER STILL MISSING A GOOD INFLOW JET. GUIDANCE STILL INDICATING SOME INSTABILITY WITH K INDEX ABOVE 30 AND A FEW HUNDREDS OF CAPE...SO AN ISOLATED THUNDERSTORM IS POSSIBLE WITH THE BETTER DYNAMICS NORTH AND WEST OF THE REGION. THEREFOR BELIEVE THAT PRECIP WILL BE SCATTERED IN NATURE AS THE FRONT PASSES THROUGH. ALSO WITH WEAK STEERING ALOFT...COULD SEE VERY HEAVY DOWNPOURS THANKS TO HIGH PWAT VALUES AND SLOW MOVING STORMS. A SECONDARY COLD FRONT WILL PASS THROUGH LATE TUESDAY/TUESDAY NIGHT WHICH WILL PUSH MORE COMFORTABLE AIR INTO THE REGION. * WEDNESDAY INTO NEXT WEEKEND...MODERATE CONFIDENCE. DRY WEATHER RETURNS BEGINNING ON WEDNESDAY LASTING INTO NEXT WEEKEND. ONLY CAVEAT IS PERHAPS A WEAK COLD FRONTAL PASSAGE ON FRIDAY/FRIDAY NIGHT. NOT A LOT OF MOISTURE TO WORK WITH...BUT CANT RULE OUT A POP-UP SHOWER OR TWO. WEDNESDAY WILL BE THE COOLER OF THE TWO DAYS AS CAA MOVES INTO THE AREA ALLOWING FOR DOWNSLOPING AND GUSTY WINDS CLOSE TO 30 MPH. OTHERWISE EXPECT TEMPS TO MODERATE NEAR TO ABOVE AVERAGE INTO THE WEEKEND. && .AVIATION /00Z MONDAY 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 SUNDAY NIGHT/... TONIGHT...HIGH CONFIDENCE. MVFR/IFR CONDITIONS LIKELY IN FOG...LOCAL LIFR CIGS/VSBYS IN FOG CAPE COD AND ISLANDS. MONDAY...HIGH CONFIDENCE. VFR WITH POSSIBLE SCT MVFR. SEABREEZES LIKELY. MONDAY NIGHT...MODERATE-HIGH CONFIDENCE. CIGS LOWERING TO AT LEAST LOW-END MVFR. SOME IFR POSSIBLE. MVFR VSBYS IN SHOWERS AFTER MIDNIGHT. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...TUESDAY THROUGH FRIDAY... TUE...MODERATE CONFIDENCE. AREAS OF MVFR/IFR DEVELOPING WITH SCT TO NUMEROUS SHOWERS AND POSSIBLY A TSTM. WED...HIGH CONFIDENCE. VFR. DRY WEATHER LIKELY. W/NW GUSTS TO 25 KT WED. THURS INTO FRI...HIGH CONFIDENCE. VFR...SEA BREEZE POTENTIAL ALONG THE COASTLINES.
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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 SUNDAY NIGHT/...HIGH CONFIDENCE. QUIET BOATING WEATHER EXPECTED WITH HIGH PRESSURE OVER THE WATERS. LIGHT/VARIABLE WINDS BECOME EAST-NORTHEAST TONIGHT AND MONDAY MORNING. WINDS SHIFT SOUTH MONDAY NIGHT. WINDS AT OR BELOW 15 KNOTS AND SEAS AT OR BELOW 4 FEET THROUGH THE PERIOD. OUTLOOK...TUESDAY THROUGH FRIDAY... TUE...HIGH CONFIDENCE. SOUTHERLY WINDS EARLY TUESDAY WILL SHIFT TO W/NW LATE IN THE EVENING BEHIND FROPA. SCT SHOWERS AND PATCHY FOG WILL REDUCE VSBYS. GUSTS MAY REACH 25 KTS THROUGHOUT THE DAY. WED...HIGH CONFIDENCE. W/NW WINDS WITH GUSTS TO 25 KT. MARGINAL SCA CONDITIONS POSSIBLE. THURSDAY INTO FRIDAY...HIGH CONFIDENCE. WINDS BECOMING WSW WITH GUSTS UP TO 20 KT. SEAS BELOW SCA. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...WTB/DUNTEN NEAR TERM...WTB/DUNTEN SHORT TERM...WTB LONG TERM...DUNTEN AVIATION...WTB/DUNTEN MARINE...WTB/DUNTEN

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