Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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 241756 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 156 PM EDT TUE MAR 24 2015 .SYNOPSIS...
-- Changed Discussion --
HIGH PRESSURE BRINGS DRY BUT COLD CONDITIONS TONIGHT...THEN MOVES OFFSHORE WEDNESDAY ALLOWING MORE SEASONABLE TEMPERATURES TO RETURN. A WARM FRONT BRINGS A PERIOD OF RAIN LATE WEDNESDAY AFTERNOON AND EVENING FOLLOWED BY MILD BUT SHOWERY WEATHER THU. A COLD FRONT THEN SWEEPS ACROSS THE REGION THURSDAY NIGHT BRINGING HEAVY SHOWERS TO THE AREA. COLDER WEATHER FOLLOWS LATE FRIDAY INTO THE WEEKEND WITH SNOW SHOWERS POSSIBLE FRI NIGHT INTO SAT NIGHT.
-- End Changed Discussion --
&& .NEAR TERM /UNTIL 7 PM THIS EVENING/...
-- Changed Discussion --
2 PM UPDATE... DESPITE FULL LATE MARCH SUN ANOMALOUS COLD/DRY AIRMASS ONLY WARMING INTO THE LOW AND MID 30S ACROSS THE AREA AT 130 PM. ALTHOUGH LIGHT WINDS AND FULL SUNSHINE TAKING A BIT OF THE EDGE OFF THE COOL TEMPS. OCEAN EFFECT CLOUDS OVER CAPE COD CONTINUE TO SLIDE SOUTH AND SHOULD PUSH OFFSHORE IN A FEW HOURS. WEAK PRES GRADIENT HAS RESULTED IN LIGHT AFTERNOON SEABREEZES. OTHERWISE PREVIOUS FORECAST LOOKS TO BE IN GOOD SHAPE.
-- End Changed Discussion --
&& .SHORT TERM /7 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
-- Changed Discussion --
2 PM UPDATE... TONIGHT... ANOTHER CHILLY NIGHT AHEAD AS DRY AIRMASS IN PLACE /DEW PTS IN THE SINGLE DIGITS AND TEENS/ COMBINES WITH MAINLY CLEAR SKIES AND LIGHT WINDS IN RESPONSE TO 1030 MB HIGH DRIFTING OVER THE REGION. COLDEST TEMPS WILL BE REALIZED WHERE RADIATIONAL COOLING IS MAXIMIZED... VALLEYS AND LOW LYING AREAS. THUS MIN TEMPS WILL BE DERIVED FROM THE COLDEST MOS DATASET ALONG WITH UNDERCUTTING GUIDANCE IN THE TYPICALLY COLDER LOCATIONS. WEDNESDAY... CHILLY START TO THE DAY BUT SUNSHINE AND LIGHT SOUTHERLY FLOW WILL HELP BOOST TEMPS INTO THE 40S DURING THE AFTERNOON. HOWEVER STRONG WARM AIR ADVECTION /WARM FRONT ALOFT/ ON THE NOSE OF THE 850-700 MB JET WILL RESULT IN A PERIOD OF OVERRUNNING RAIN FROM LATE AFTERNOON INTO THE EVENING. COLUMN WARM ENOUGH TO SUPPORT RAIN ESPECIALLY WITH VERY WARM NOSE OF +4C TO +5C AROUND 850-800 MB LAYER. HOWEVER PREFRONTAL AIRMASS IS STILL COOL AND VERY DRY IN THE LOW LEVELS PROVIDING COLD WET BULB TEMPS OF AROUND -6C AT 925 MB. THIS MAY BE SUFFICIENT FOR A LOW RISK OF SOME SLEET TO MIX IN WITH THE RAIN AT TIMES ACROSS THE INTERIOR LATE AFTERNOON/EARLY EVENING. IN ADDITION SURFACE WET BULB TEMPS INLAND ARE CLOSE TO FREEZING...SO NOT COMPLETELY OUT OF THE QUESTION THAT A FEW LOCATIONS COULD HAVE BRIEF SPOTTY FREEZING RAIN. HOWEVER SHOULD NOT BE MUCH OF A PROBLEM GIVEN SUNSHINE IN THE MORNING INTO EARLY AFTERNOON WILL WARM PAVEMENT SUFFICIENTLY FOR ICING NOT TO BE AN ISSUE. NEVERTHELESS...ONCE RAIN DEVELOPS LATE IN THE AFTERNOON AND EVENING EXPECT A NOTICEABLE TEMP DROP GIVEN COLD WET BULB TEMPS. WED NIGHT... ANY EVENING RAIN SHOULD TAPER OFF BY MIDNIGHT OR THEREAFTER AS INITIAL BURST OF WARM AIR ADVECTION LIFTS OFF TO THE NORTHEAST. STRONG LOW LEVEL WARM ADVECTION THEN DEVELOPS SECOND HALF OF THE NIGHT PROVIDING TEMPS RISING TOWARD MORNING ESPECIALLY ACROSS RI AND SOUTHEAST MA. THUS WILL FOLLOW A NON DIURNAL TEMP TREND WED NIGHT WITH MODEL 2 METER TEMPS PROBABLY MORE REALISTIC THAN MOS. THIS LOW LEVEL WARM ADVECTION ACROSS EXISTING SNOW COVER MAY RESULT IN AT LEAST SOME PATCHY FOG OVERNIGHT INTO THU AM.
-- End Changed Discussion --
&& .LONG TERM /THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
HIGHLIGHTS... * WARM BUT HEAVY RAIN ON THURSDAY AHEAD OF COLD FRONT * BLUSTERY AND BELOW AVERAGE TEMPS FOR THE WEEKEND * WEAK DISTURBANCE POSSIBLE ON MONDAY MODEL GUIDANCE... LATEST GUIDANCE IS SUGGESTING THAT THE AMPLIFIED WRN RIDGE/ERN TROUGH PATTERN FCST TO BE IN PLACE FOR MOST OF THE PERIOD MAY BEGIN TO EVOLVE TOWARD FLATTER MEAN FLOW BY NEXT WEEK. WHILE SOME EMBEDDED DETAILS WITHIN THE RIDGE/TROUGH CONFIGURATION HAVE BEEN AND CONTINUE TO BE PROBLEMATIC... ENSEMBLE GUIDANCE AND THE LIKELY TREND TOWARD FLATTER FLOW SUGGEST THAT OVERALL PREDICTABILITY OF SIGNIFICANT FEATURES MAY DECLINE RAPIDLY AFTER EARLY NEXT WEEK. OVERALL AMPLIFIED PATTERN WILL CONTINUE WITH 00Z GUIDANCE IN GOOD AGREEMENT. STILL SOME TIMING/INTENSITY ISSUES FOR UPCOMING WED PM INTO FRIDAY SYSTEM. SEVERAL SHORTWAVES WILL MOVE THROUGH THE FLOW DEVELOPING WAVES ALONG STALLED FRONTAL SYSTEM. DEPENDING ON INTENSITY AND STRENGTH...COULD HAVE FLOODING ISSUES FROM LEFTOVER SNOWPACK AND HIGH DEWPOINTS. OTHERWISE GUIDANCE IS IN GOOD AGREEMENT WITH POLAR JET DROPPING SOUTH...BRINGING BELOW AVG TEMPS FOR THE WEEK. GUIDANCE IS THEN SPLIT ON WEAK WAVE PASSING ON MONDAY. DETAILS... * THURSDAY INTO FRIDAY...MODERATE CONFIDENCE. HIGH CONFIDENCE PRECIP WILL OCCUR LOWER CONFIDENCE ON EXACT TIMING. JUST ONE OF MANY SHORTWAVES WILL PASS THROUGH THE FLOW ON WEDNESDAY NIGHT. AS WARM FRONT APPROACHES...TEMPS AND DEWPOINTS WILL REMAINS STEADY/SLOWLY INCREASE THROUGH THE NIGHT. THIS WILL INCREASE THE FOG POTENTIAL AND WE COULD SEE WIDESPREAD DENSE FOG. LOW CONFIDENCE ON WHERE EXACTLY THIS FAR OUT. PRECIP WILL BEGIN TO INCREASE IN THE MORNING HOURS AS THE FIRST WAVE WILL MOVE OFFSHORE BY EARLY WED NIGHT. THIS PRECIP WILL BE ALONG THE EAST TO WEST WARM FRONT AS IT MOVES INTO SOUTHERN NEW ENGLAND. BIGGEST QUESTION IS HOW FAR NORTH WILL THE FRONT REACH. GUIDANCE SEEMS TO ALWAYS STRUGGLE WITH THAT ASPECT...THEREFORE TRENDED A MODEL BLEND TO GET A DOWN THE MIDDLE APPROACH. TEMPS SOUTH OF THE FRONT WILL REACH INTO THE MID TO PERHAPS THE UPPER 50S WHILE NORTHWARDS WILL STAY IN THE 40S. REGARDLESS RAIN WILL BE OVERSPREADING FROM SOUTH TO NORTH ON THURSDAY WITHIN A VERY MOIST ENVIRONMENT AS DEWPOINTS CONTINUE TO RISE. THURSDAY AFTERNOON INTO THE OVERNIGHT HOURS SEEMS TO BE WHEN THE HEAVIEST PRECIP WILL OCCUR. NEXT SHORTWAVE WILL PUSH THROUGH ALLOWING FOR SURFACE LOW DEVELOPMENT ALONG THE EXTENDED COLD FRONT APPROACHING SOUTHERN NEW ENGLAND. THIS FRONT WILL BE THE FOCUS ON THE HEAVY PRECIP DURING THE AFTERNOON/EVENING HOURS. SW LLJ WILL BE ON THE INCREASE REACHING 50-65 KTS ACROSS THE REGION POOLING IN MORE MOISTURE INTO THE AREA. PWAT VALUES ARE ABOVE 1 INCH WHICH IS 2 TO 3 STANDARD DEVIATIONS AWAY WHILE THE MOISTURE FLUX IS 4 TO 5 STANDARD DEVIATIONS AWAY. DUE TO THE AMOUNT OF MOISTURE IN THE ATMOSPHERE AND THE APPROACHING FRONTAL SYSTEM...EXPECT HEAVY DOWNPOURS AND PERHAPS ISOLATED THUNDER. IN FACT MODELS HAVE INCREASED THEIR QPF FROM JUST 12 HOURS AGO. WITHIN THESE HEAVY DOWNPOURS...WE COULD MIX DOWN THE GUSTY WINDS ALOFT DOWN TO THE SURFACE. THIS HIGHLY ANOMALOUS SYSTEM COMBINED WITH THE SNOW PACK...COULD SEE SIGNIFICANT INCREASE IN RUNOFF AND RISES IN AREA STREAMS FROM WHAT WILL LIKELY BE MAJOR SNOWMELT. MORE DETAILS IN HYDRO SECTION. AS FRONT PASSES THROUGH PRECIP WILL END FROM WEST TO EAST OVERNIGHT THURSDAY INTO FRIDAY MORNING. FRIDAY WE WILL BEGIN TO DRY OUT AS TEMPS WARM INTO THE MID TO LOWER 40S. A SECONDARY COLD FRONT WILL PASS THROUGH LATE FRIDAY BRINGING IN STRONG CAA AND BLUSTERY CONDITIONS. * THE WEEKEND...HIGH CONFIDENCE IN TEMPS. DEEP UPPER LEVEL TROUGH WILL MOVE FROM THE GREAT LAKES TO OVER SOUTHERN NEW ENGLAND. THIS TROUGH AXIS WILL SETTLE OVER THE REGION LATE FRIDAY INTO SATURDAY. WELL BELOW AVG TEMPS ARE EXPECTED AT 850MB TEMPS DROP DOWN TO -12C. HOWEVER...WEAK RIDGE WILL PASS THROUGH ON SUNDAY INCREASE TEMPS AND ALLOWING FOR A MOSTLY PLEASANT DAY WITH HIGH TEMPS REACHING THE MID TO UPPER 40S. MONDAY...LOW CONFIDENCE. NEXT UPPER LEVEL DISTURBANCE WILL IMPACT SOUTHERN NEW ENGLAND LATE SUNDAY INTO MONDAY. THIS SYSTEM WILL BRING PRECIP AND COOLER TEMPS TO THE REGION. THIS MAY CAUSE FOR P-TYPE ISSUES BUT IT WILL NEED TO BE WATCHED OVER THE NEXT SEVERAL DAYS.
-- End Changed Discussion --
&& .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
-- Changed Discussion --
FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. 2 PM UPDATE... HIGH CONFIDENCE THROUGH WEDNESDAY THEN SOME UNCERTAINTY ON EXACT TIMING OF LOWER CIGS/VSBYS WITH RAIN LATE WED INTO WED EVENING. VFR THROUGH EARLY WED AFTERNOON THEN MVFR CIGS IN A PERIOD OF RAIN LATE WED AFTERNOON AND EVENING. RAIN ENDS OVERNIGHT WED NIGHT BUT CIGS AND VSBYS LOWER TO IFR IN AREAS OF FOG. KBOS TAF...HIGH CONFIDENCE THRU 21Z WED THEN SOME UNCERTAINTY ON EXACT TIMING OF LOWERING CONDITIONS. KBDL TAF...HIGH CONFIDENCE THRU 18Z WED THEN SOME UNCERTAINTY ON EXACT TIMING OF LOWERING CONDITIONS. OUTLOOK...THU THROUGH SATURDAY...MODERATE TO HIGH CONFIDENCE THURSDAY MORNING...GENERALLY VFR CONDITIONS EXCEPT POSSIBLY MVFR CIGS ALONG SOUTH COAST WEDNESDAY NIGHT INTO THE THURSDAY MORNING. IFR IS POSSIBLE IN FOG OVERSPREADING THE REGION. THURSDAY AFTERNOON AND NIGHT...WIDESPREAD MVFR CIGS AND VSBYS IN SHOWERS. MAY SEE AREAS OF IFR CIGS/VSBY IN HEAVY DOWNPOURS. LOW RISK OF THUNDER. FRIDAY THROUGH SATURDAY...HIGH UNCERTAINTY. COULD SEE A PERIOD OF MVFR OR EVEN IFR IN SNOW SHOWERS FRI NIGHT INTO SAT NIGHT ESPECIALLY RI AND SOUTHEAST MA.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. 2 PM UPDATE... HIGH CONFIDENCE THROUGH WEDNESDAY THEN SOME UNCERTAINTY HOW STRONG WINDS GET WED NIGHT AND BEYOND. TONIGHT...LIGHT WINDS AND TRANQUIL SEAS WITH HIGH PRES BUILDING OVERHEAD. GOOD VSBY AND DRY WEATHER TOO. WED...LIGHT/VARIABLE WINDS BECOME SOUTH DURING THE AFTERNOON AS HIGH PRES MOVES OFFSHORE. CHANCE OF RAIN LATE IN THE DAY. WED NIGHT...SSW WINDS INCREASE TO POSSIBLY 20-25 KT LATE. VSBY LOWERS IN AREAS OF FOG. OUTLOOK...THU THROUGH SATURDAY... MODERATE TO HIGH CONFIDENCE THROUGH FRIDAY. MODERATE CONFIDENCE FRIDAY NIGHT INTO SATURDAY. CONDITIONS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY CONDITIONS WEDNESDAY NIGHT THROUGH THURSDAY MORNING. STRONG SW WINDS DEVELOP ALOFT THURSDAY AFTERNOON AND EVENING BUT ANTICIPATE ONLY SOME OF THE WINDS MIXING TO THE SURFACE. MAY NEED A GALE WATCH BUT DEF SMALL CRAFT ADVISORY. AREAS OF DENSE FOG MAY BE A SIGNIFICANT HAZARD WED NIGHT INTO THURSDAY...ESPECIALLY ALONG THE SOUTH COASTAL WATERS. THERE IS A LOW RISK THAT JUST ENOUGH COLD AIR ADVECTION WITH NORTHERLY WINDS FRIDAY NIGHT AND SATURDAY COULD CAUSE A PERIOD NEARING SMALL CRAFT ADVISORY WIND GUSTS...BUT CURRENTLY LOOKS MORE LIKELY THAT GUSTS WILL NOT EXCEED 20 KT.
-- End Changed Discussion --
&& .HYDROLOGY... SEVERAL FACTORS ARE OCCURRING ON THURSDAY WHICH WILL INCREASE THE POTENTIAL FOR RUNOFF AND RISES IN AREA STREAMS. FIRST IS THE ANOMALOUS DEWPOINTS WHICH WILL BE STREAMING INTO THE REGION. 40+F DEWPOINTS WILL HELP EAT AWAY AT THE SNOW PACK ON TOP OF 50+ DEGREE TEMPERATURES. THIS MOISTURE LADEN AIR WILL ALLOW FOR CONDENSATION AND THUS HEAT UPON THE SNOW PACK INCREASING THE RATE OF MELTING. GUIDANCE SNOWS THAT THERE IS STILL ABOUT 2-5 INCHES OF WATER WITHIN THE SNOW PACK OR SWE...ACROSS THE REGION SO THESE HIGH DEWPOINTS WILL HELP RELEASE A GOOD PORTION OF THIS WATER. SECOND ASPECT IS THE UPCOMING RAIN POTENTIAL. EXPECT AROUND AN INCH OF QPF TO OCCUR ACROSS SOUTHERN NEW ENGLAND WITH HIGHER AMOUNTS LIKELY WITHIN HEAVIER DOWNPOURS BY THURSDAY NIGHT INTO FRIDAY MORNING. THEREFORE COMBINING THE RAPID SNOW MELT WITH THE UPCOMING QPF...WE COULD SEE ON THE ORDER OF 1.5-3 INCHES OF WATER HEADING INTO AREA RIVERS AND STREAMS. CURRENTLY THINK THAT SOME RIVERS WILL GET CLOSE TO OR ABOVE MINOR FLOODING...BUT MOST WILL FALL SHORT OF FLOOD LEVELS. HOWEVER IF DEWPOINTS ARE HIGHER OR QPF INCREASES THEN SEVERAL STREAMS WILL GO INTO FLOOD. LASTLY...MINOR URBAN FLOODING ALSO LOOKS LIKE A POSSIBILITY ESP IF DRAINAGE SYSTEMS ARE STILL BLOCKED FROM SNOW. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...NOCERA NEAR TERM...NOCERA SHORT TERM...NOCERA LONG TERM...DUNTEN AVIATION...NOCERA/DUNTEN MARINE...NOCERA/DUNTEN HYDROLOGY...

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