Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KBOX 160213 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 913 PM EST MON DEC 15 2014 .SYNOPSIS... HIGH PRESSURE WILL SLIDE EAST ACROSS THE REGION TONIGHT...WITH INCREASING CLOUDS EXPECTED. LOW PRESSURE WILL EMERGE FROM THE GREAT LAKES REGION ON TUESDAY...WITH A SECONDARY LOW CROSSING OVER OUR AREA DURING TUESDAY NIGHT. THIS WILL BRING A PERIOD OF WET WEATHER. HIGH PRESSURE FROM THE PLAINS THEN BUILDS OVER NEW ENGLAND LATE IN THE WEEK. A STRENGTHENING LOW PRESSURE CENTER IS EXPECTED TO PASS SOUTHEAST OF NEW ENGLAND LATE IN THE WEEKEND. IT IS VERY UNCERTAIN AT THIS TIME IF THIS SYSTEM WILL PASS CLOSE ENOUGH TO PRODUCE PRECIPITATION ACROSS SOUTHERN NEW ENGLAND. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... 910 PM UPDATE... LOW CONFIDENCE FORECAST ON WHETHER OR NOT ANY FREEZING DRIZZLE IS ABLE TO DEVELOP OVERNIGHT. THE NAM SOUNDINGS CONTINUE TO SHOW POTENTIAL FOR SPOTTY FREEZING DRIZZLE WITH DEEP SATURATED LAYER DEVELOPING BELOW 2000 FEET...AS SOUTHEAST FLOW INCREASES JUST OFF THE DECK. SOMETIMES NAM MOISTURE FIELDS CAN BE A LITTLE OVERDONE THOUGH...SO NOT TOTALLY SOLD ON THAT HAPPENING BUT IT CERTAINLY CAN/T BE RULED OUT. EVEN IF FREEZING DRIZZLE DOES NOT DEVELOP...THERE STILL WILL BE THE RISK FOR SOME FREEZING FOG/BLACK ICE DEVELOPING. GIVEN LIGHT SURFACE WINDS...SOME OF THIS WILL BE POSSIBLE EVEN ALONG THE COAST...SO WILL GO AHEAD AND RE-ISSUE THE SPECIAL WEATHER STATEMENT TO COVER THE ENTIRE REGION. IN FACT...BEST CHANCE FOR SLIPPERY TRAVEL MAY END UP CLOSER TO THE COAST WHERE BETTER LOW LEVEL MOISTURE RESIDES FOR EITHER SOME BLACK ICE/SPOTTY FREEZING DRIZZLE. PREVIOUS DISCUSSION: HIGH PRESSURE CROSSING THROUGH THE EASTERN SEABOARD TONIGHT. HIGH PRESSURE CENTER MOVES OFFSHORE AS THE NIGHT WEARS ON...WITH SURFACE AND/OR 925 MB WINDS BECOMING LIGHT ONSHORE FOR SOUTHERN NEW ENGLAND. SUBSIDENCE INVERSION IN PLACE WITH LOW LEVEL MOISTURE TRAPPED UNDER THE INVERSION. THIS SHOULD AMOUNT TO A GRADUAL INCREASE IN CLOUDS OVER THE COURSE OF THIS EVENING. WITH THIS LOW LEVEL MOISTURE...THERE IS A SLIGHT CHANCE FOR TRACE PRECIP OVER THE AREA TONIGHT INTO MID MORNING TUESDAY. THE 12Z NAM AND GFS SHOW A VERY SPOTTY 0.01" QPF...BUT NAM BUFKIT SOUNDINGS SHOW THE POTENTIAL FOR SPOTTY LIGHT FREEZING DRIZZLE OR DRIZZLE DEPENDING ON SURFACE TEMP. MID SHIFT AFD ALSO DISCUSSED THIS POTENTIAL. SO HAVE GONE WITH A SLIGHT CHANCE OF LIGHT FREEZING DRIZZLE OVERNIGHT AWAY FROM THE IMMEDIATE COASTLINE...LIGHT DRIZZLE ALONG THE IMMEDIATE COAST. OVERNIGHT LOWS MOSTLY IN THE MID 20S TO AROUND 30 EXPECTED...LOW TO MID 30S CLOSER TO THE COAST INCLUDING THE CAPE AND ISLANDS. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... TUESDAY... EXPECT CLOUDY SKIES TO REMAIN OVER THE AREA FOR THE DAY. POTENTIAL FOR SPOTTY LIGHT FREEZING DRIZZLE OVER THE INTERIOR TO START. LOW LEVEL ONSHORE FLOW IN RESPONSE TO APPROACHING WARM FRONT. WILL SEE SHOWERS DEVELOP DURING THE AFTERNOON FROM THE WEST WITHIN INCREASING BROADSCALE ASCENT ALOFT. COOL OVER THE INTERIOR BUT MILD CLOSER TO THE COAST...SOME LOCALES ALONG SOUTHEAST COASTAL NEW ENGLAND COULD REACH THE 50 DEGREE MARK. TUESDAY NIGHT... AS THE SOUTHERN STREAM SHORTWAVE MOVES THROUGH IT WILL DRIVE A COLD FRONT OR OCCLUDED FRONT ACROSS OUR AREA...WITH SECONDARY LOW DEVELOPMENT...LIKELY CROSSING OVER SOUTHEAST MA/CAPE. SOUTHERLY LOW LEVEL JET...OF SORTS...LEADS THE FRONT WITH SPEEDS AROUND 30 KNOTS. FOR THE MAJORITY OF OUR AREA...ANTICIPATING LIGHT RAIN WITH THIS SYSTEM. THERE REMAINS SOME QUESTION ABOUT PRECIP TYPE IN NORTHWEST MASS ESPECIALLY IN AROUND THE HILLS OF WESTERN HAMPSHIRE AND WESTERN FRANKLIN COUNTIES. THERE COULD BE ENOUGH 31-32 DEGREE AIR TO CREATE PATCHY FREEZING RAIN AND/OR A LIGHT WINTRY MIX. COVERAGE WILL BE LIMITED AND NO HEADLINES PLANNED AT THIS TIME. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... * SHOWERS ENDING WED MORNING * COLDER BUT NOT UNSEASONABLY SO FOR LATE IN THE WEEK * A STORM PASSING SE OF NEW ENGLAND LATE IN THE WEEKEND MAY BE CLOSE ENOUGH FOR SOME IMPACTS TO THE AREA OVERVIEW... MEDIUM RANGE MODELS DEPICT AN INTERESTING SPLIT FLOW PATTERN ACROSS NORTH AMERICA THIS WEEK THROUGH NEXT WEEKEND. THE LONG WAVE PATTERN DOES NOT LOOK PARTICULARLY STABLE AND CONFIDENCE IN ANY DETAILS DIMINISHES CONSIDERABLY WITH TIME. THERE IS NO SIGNIFICANT SOURCE OF COLD AIR AVAILABLE TO AFFECT THE REGION FOR THE NEXT 7 DAYS...BUT THE AIR MASS WILL BE JUST COLD ENOUGH FOR PTYPE TO BE A FACTOR IN ANY PRECIPITATION EVENTS DURING THIS FORECAST PERIOD. DETAILS... WED...REASONABLY GOOD AGREEMENT IN OPERATIONAL MODELS OF SHORT WAVE TROF LIFTING OUT ON WED WITH A DEVELOPING BUT PROGRESSIVE SURFACE LOW CENTER OVER THE GULF OF MAINE. LOOKS LIKE SHOWERS SHOULD END WED MORNING SW TO NE. THERE IS JUST A SLIGHT CHANCE OF SOME WRAP AROUND MOISTURE ACROSS NE MA IF THE GULF OF MAINE SYSTEM SHOULD DEVELOP A LITTLE SOONER AND FURTHER S AS HINTED BY A FEW ENSEMBLE MEMBERS. FOR TEMPERATURES...HAVE GONE A CONSENSUS OF MODEL OUTPUT PLUS AN ADDITIONAL 2 TO 3 DEGREES ACROSS SOUTHERN ZONES BASED ON EXPECTED H85 TEMPERATURES AND SOME DOWNSLOPE COMPONENT. WED NIGHT...COLDER AIR MOVES INTO THE REGION BUT UPPER CYCLONIC FLOW AND MOISTURE EXPECTED TO KEEP CONSIDERABLE STRATOCUMULUS CLOUDS ACROSS MOST OF SOUTHERN NEW ENGLAND EXCEPT FOR PERHAPS SOUTHERN RI AND SE MA. THESE WILL IMPEDE THE DROP OF SURFACE TEMPERATURES TO SOME EXTENT. DUE TO THAT CYCLONIC FLOW ALOFT AND AVAILABLE MOISTURE...HAVE PUT SLIGHT CHANCE POPS INTO THE FORECAST GRIDS FOR THE NORTHERN HALF OF THE AREA. THU THROUGH SAT...ANTICIPATING DRY WEATHER AND TEMPERATURES NEAR OR JUST SLIGHTLY BELOW THE CLIMATOLOGICAL NORMS FOR THIS TIME OF YEAR. THERE MAY BE LINGERING CLOUDINESS DURING MUCH OF THE DAY THU BUT MOSTLY SUNNY SKIES ON FRI AND AT LEAST TO START ON SAT. BY SAT AFTERNOON...ANTICIPATING INCREASING HIGH CLOUDINESS. SUN AND SUN NIGHT...THIS LOOKS TO BE POTENTIALLY THE MOST INTERESTING TIME FRAME AS A STRENGTHENING LOW PRESSURE CENTER WILL LIKELY PASS SE OF NEW ENGLAND. HOW FAR SE IS STILL IN QUESTION. OPERATIONAL ECMWF AND GFS MODEL TRENDS HAVE BEEN TO TRACK THE SYSTEM FURTHER OFFSHORE WITH A GLANCING BLOW IF ANY TO SE NEW ENGLAND. HOWEVER...THERE ARE SOME ENSEMBLE MEMBERS DEPICTING A TRACK CLOSER TO NEW ENGLAND FOR A RISK OF WINTER PRECIPITATION. CONFIDENCE IS LOW AT THIS POINT GIVEN THE SENSITIVITY OF SPLIT FLOW REGIMES TO RELATIVE SHORT WAVE TIMING AND INTENSITY AS WELL AS THE FACT THAT THE CONTRIBUTING ENERGY IS STILL A COUPLE DAYS AWAY OF BEING SAMPLED BY THE DENSER NORTH AMERICAN RADIOSONDE NETWORK. PTYPE IS ALSO UNCERTAIN. IF THE NORTHERN STREAM SHOULD PROVE MORE DOMINANT...THEN THE SURFACE SYSTEM IS LIKELY TO BE DEPRESSED. IF THE SOUTHERN STREAM IS SUFFICIENTLY STRONG...THEN THE SURFACE SYSTEM COULD TRACK CLOSE ENOUGH TO PRODUCE RAIN OR SOME MIXTURE TO SOUTHERN NEW ENGLAND. A THIRD VARIATION WOULD A BALANCE IN THE STREAMS THAT KEEPS MARGINALLY COLD AIR FLOWING FROM THE NORTH AND A CLOSE ENOUGH TRACK TO PRODUCE SNOW. GIVEN THE EXISTING UNCERTAINTY...HAVE RETAINED LOW CHANCE POPS FOR RAIN/SNOW ON SUN. TIDES ARE HIGH ENOUGH...ESPECIALLY DURING THE DAY...THAT THERE IS A POTENTIAL FOR SOME COASTAL IMPACTS IF THE SURFACE LOW TRACKS CLOSE ENOUGH TO THE COAST IN THE FORM OF SOME COASTAL FLOODING AND/OR EROSION. THE EXTENT OF ANY COASTAL IMPACT RISK SHOULD BECOME CLEARER BY AROUND WED OR THU. MON...MODERATE TO HIGH CONFIDENCE OF A DRY NW FLOW AHEAD OF HIGH PRESSURE MOVING TOWARD NEW ENGLAND WITH SEASONABLE OR SLIGHTLY BELOW SEASONABLE TEMPERATURES. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH MONDAY NIGHT/... 00Z UPDATE...SATELLITE IMAGERY INDICATES MVFR CIGS APPROACHING FMH IMMINENTLY AND PROBABLY INTO BOS 02Z-03Z. ANTICIPATE MVFR CIGS TO INCREASE ACROSS AREA 03Z-06Z AS LOW LEVELS BECOME SATURATED PER MODEL OUTPUT AND AS DESCRIBED IN PRIOR FORECAST. 21Z UPDATE... EARLY THIS EVENING...MODERATE CONFIDENCE. AS OF 21Z...MVFR CIGS REMAINED OVER FAR WESTERN MA AS WELL AS THE MID TO OUTER CAPE AND JUST EAST OF ACK. COULD SEE ACK AND FMH ACQUIRE MVFR CIGS PRIOR TO 00Z. OTHER TERMINALS SHOULD REMAIN VFR THRU 00Z. TONIGHT...MODERATE CONFIDENCE. EXPECTING AN INCREASE IN MVFR CIGS ACROSS THE AREA BETWEEN 00Z AND 06Z. AFTER 06Z MVFR CIGS EXPECTED TO REMAIN IN PLACE OVERNIGHT...WITH A SLIGHT CHANCE OF LIGHT FREEZING DRIZZLE AWAY FROM THE COASTLINE...CHANCE LIGHT DRIZZLE ALONG THE SHORE. TUESDAY AND TUESDAY NIGHT...MODERATE CONFIDENCE. TUESDAY...MVFR...LOW CHANCE IFR. SLOWLY EXPANDING RAIN SHOWER ACTIVITY ACROSS THE TERMINALS DURING THE AFTERNOON. TUESDAY NIGHT...MVFR CIGS/VSBYS IN AREAS OF RAIN. POSSIBLE PATCHES OF IFR CIGS/VSBYS. LOW PROBABILITY OF FREEZING RAIN PATCHES IN EXTREME NORTHWEST MASS. SOUTH WINDS WITH SPEEDS REACHING 30 KNOTS AT 2000 FEET AGL. MAY NOT BE ENOUGH FOR SIGNIFICANT LOW LEVEL WIND SHEAR...BUT COULD CAUSE SOME BUMPINESS. KBOS TERMINAL...MODERATE CONFIDENCE. ANTICIPATING ARRIVAL OF MARINE STRATUS 02Z-03Z. MVFR CIGS WILL LIKELY PREVAIL TONIGHT. KBDL TERMINAL...MODERATE CONFIDENCE. VFR CONDITIONS FOR THE EARLY EVENING BUT THEN ANTICIPATE MVFR CIGS TO DEVELOP NEAR/OVER KBDL AROUND 03Z. MVFR CIGS THEN EXPECTED TO PREVAIL INTO TUESDAY. OUTLOOK... WEDNESDAY THROUGH SATURDAY...MODERATE TO HIGH CONFIDENCE. WED...BECOMING VFR MOST AREAS BY MID MORNING. THU THROUGH SAT...VFR CONDITIONS EXPECTED. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. NEAR TERM...LIGHT WINDS AND PERSISTENCE OF A 2 FOOT SWELL ACROSS THE OPEN WATERS ARE EXPECTED OVERNIGHT. SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...HIGH CONFIDENCE. LIGHT N-WINDS VEERING S/SE WITH TIME TONIGHT INTO TUE. WINDS AND SEAS BELOW SMALL CRAFT THRESHOLDS THRU TUE NIGHT. SHOWERS INCREASING ACROSS THE WATERS ON TUESDAY AND TUESDAY NIGHT. WINDS AND SEAS WILL REMAIN BELOW SMALL- CRAFT ADVISORY THRESHOLDS. NO VISIBILITY IMPACTS ANTICIPATED AT THIS TIME. OUTLOOK...WEDNESDAY THROUGH SATURDAY...MODERATE TO HIGH CONFIDENCE. ANTICIPATE SMALL CRAFT ADVISORY WINDS IN NW FLOW BEHIND THE DEPARTING SYSTEM WED INTO THU. SEAS WILL LIKELY BE NEAR OR ABOVE 5 FEET ACROSS THE OPEN WATERS WED INTO THU. WINDS DIMINISHING AND SEAS SUBSIDING THU NIGHT AND LIKELY BELOW SMALL CRAFT ADVISORY LEVELS FRI THROUGH SAT. ALTHOUGH JUST BEYOND THE OUTLOOK PERIOD...WE CONTINUE TO MONITOR A POTENTIAL COASTAL STORM FOR LATE SATURDAY NIGHT AND SUNDAY. THERE IS A LARGE UNCERTAINTY IN THE TRACK AND INTENSITY OF THIS SYSTEM AND ANY CORRESPONDING IMPACT ON WINDS AND SEAS IN THE COASTAL WATERS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...WTB/NMB NEAR TERM...FRANK/NMB SHORT TERM...NMB LONG TERM...WTB/THOMPSON AVIATION...NMB/THOMPSON MARINE...NMB/THOMPSON

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.