Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 242331 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 731 PM EDT TUE MAR 24 2015 .SYNOPSIS... 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. LOW PRESSURE WILL MOVE NORTH OF THE REGION LATE THURSDAY...FOLLOWED BY A COLD FRONT THAT SWEEPS ACROSS THE REGION THURSDAY NIGHT INTO FRIDAY. A SECOND FRONT WILL BRING COLDER TEMPERATURES LATER FRIDAY INTO THIS WEEKEND. ANOTHER FAST MOVING FRONT WILL PUSH ACROSS THE REGION SUNDAY NIGHT INTO MONDAY. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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725 PM UPDATE... LAST OF THE DIURNAL CUMULUS AND PATCHY HIGH CIRRUS CLOUDS MOVING OFF THE CAPE AND ISLANDS AT 23Z. OTHERWISE CLEAR SKIES NOTED ON IR SATELLITE IMAGERY. AFTERNOON SEA BREEZES HAVE PRETTY MUCH KICKED OUT WITH SUNSET...NOTING MAINLY LIGHT/VRBL OR CALM WINDS. MAY SEE LIGHT NW WINDS KICK IN AS COOLER AIR DRAINS IN AS HIGH PRES BUILDS E OUT OF NY STATE THIS EVENING. TONIGHT... ANOTHER CHILLY NIGHT AHEAD AS DRY AIRMASS IN PLACE /DEWPTS 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.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
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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.
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&& .LONG TERM /THURSDAY THROUGH TUESDAY/... HIGHLIGHTS... * PERIODS OF HEAVY RAINFALL LATE THURSDAY INTO EARLY FRI AS LOW PRESSURE MOVES NORTH OF THE REGION * BELOW AVERAGE TEMPS FOR THE WEEKEND * WEAK DISTURBANCE POSSIBLE ON MONDAY OVERVIEW AND MODEL PREFERENCES... 12Z MODEL GUIDANCE KEEPS THE OVERALL UPPER LEVEL PATTERN THAT HAS BEEN IN PLACE FOR THE LAST COUPLE OF MONTHS /AT LEAST/ WITH LONG WAVE RIDGING CONTINUING ACROSS THE WESTERN U.S. AND DEEP LONG WAVE TROUGH ACROSS THE EAST DURING A GOOD PORTION OF THE LONG TERM PERIOD. STILL TIMING AND TRACK QUESTIONS WITH INDIVIDUAL SHORT WAVES MOVING ALONG IN THIS OVERALL UPPER FLOW...THOUGH MODELS AND ENSEMBLES STARTING TO SHOW POSSIBLE BREAKDOWN OF THE UPPER STEERING FLOW TOWARD THE END OF THE PERIOD. WITH THE AMPLIFIED PATTERN IN PLACE...RATHER GOOD AGREEMENT CONTINUES WITH THE TIMING OF LOW PRES MOVING IN THE SW FLOW ON THU...THEN PUSHING ITS ASSOCIATED FRONTAL SYSTEMS THROUGH LATE THU AND FRI AS H5 SHORT WAVE MOVES AROUND THE BASE OF THE LONG WAVE TROUGH WHILE SHIFTING SLOWLY E. ONCE THIS OCCURS...EXPECT ANOTHER SHOT OF SOMEWHAT MODIFIED ARCTIC AIR MOVING IN ONCE AGAIN INTO THIS WEEKEND. SOME QUESTION AS TO ANOTHER PERIOD OF LIGHT PRECIP FOR S COASTAL AREAS AS SHORT WAVE MOVES S OF NEW ENGLAND SATURDAY. NW FLOW ALOFT TAKES OVER LATE THIS WEEKEND AS LONG WAVE TROUGH MOVES OFFSHORE. FAST MOVING H5 SHORT WAVE AND ASSOCIATED COLD FRONT CROSSES THE REGION AROUND SUN NIGHT/MON TIMEFRAME. DETAILS... THURSDAY AND FRIDAY...MODERATE TO HIGH CONFIDENCE. STRONG LOW LEVEL WARM AIR ADVECTION WILL BE WELL ESTABLISHED BY THIS TIMEFRAME AS H925 TEMPS RISE TO +8C TO +11C. S-SW WINDS WILL BE IN PLACE...WITH A GOOD H925 JET MOVING ACROSS /ON ORDER OF 50-70 KT/. MIXING IS NOT GOOD HOWEVER...SO ONLY A PART OF THIS WILL MIX DOWN WITH GUSTS UP TO AROUND 25 KT OR SO...HIGHEST ALONG THE S COAST. FIRST AREA OF PRECIP MOVES E EARLY THU MORNING...THEN WILL SEE SOME LIGHT SHOWERS LINGERING. NEXT LOW PRES APPROACHING OUT OF THE OHIO VALLEY BRINGING ANOTHER SLUG OF PRECIP TOWARD W MA/CT BY MIDDAY. TEMPS WILL TOP OFF IN THE UPPER 40S AND 50S. SOME QUESTION AS TO RISE IN DEWPTS...BUT SHOULD GET INTO THE 40S AT LEAST. PWAT VALUES WILL RISE BY LATE THU TO AROUND 1.1 TO 1.3 INCHES /ABOUT 2SD ABOVE CLIMO FOR LATE MARCH/. THIS...ALONG WITH SW FLOW IN PLACE BRINGING LOW LEVEL MOISTURE AND LOW PRES PASSING ACROSS OR JUST N OF THE REGION THU EVENING...WILL SEE POCKETS OF HEAVY RAINFALL ESPECIALLY ACROSS CENTRAL AND WESTERN AREAS. CURRENT PRECIP FORECAST FOR THE THU NIGHT/FRI MORNING TIMEFRAME RANGES FROM 0.5 TO 0.6 INCHES UP TO AROUND 1 INCH JUST W OF THE CT VALLEY. WITH THE RAINFALL ALONG WITH EXCELLENT CONDITIONS FOR CONTINUED SIGNIFICANT SNOW MELT...WILL BE MONITORING CONDITIONS ALONG SOME AREA RIVERS. DETAILS WILL BE IN THE HYDRO SECTION BELOW. ANOTHER QUESTION WILL BE INSTABILITY IN PLACE WITH TOTAL TOTALS IN THE LOWER 50S AND TQ VALUES AROUND 17 TO 19 /ELEVATED CONVECTION/. UNCERTAIN AS TO WHETHER ANY THUNDER WILL BE REALIZED AT THIS POINT...BUT SOMETHING TO MONITOR. EXPECT THE LOW TO MOVE ACROSS NORTHERN NEW ENGLAND OVERNIGHT THU...WITH COLD FRONT TRAILING ACROSS BY FRI MORNING. A SECOND COLD FRONT HOLDS ACROSS UPSTATE NEW YORK UNTIL LATER IN THE DAY AS ANOTHER SHORT WAVE ROTATES AROUND BASE OF LONG WAVE TROUGH. SO... TEMPS LOOK TO REBOUND TO THE MID 40S TO AROUND 50...RUNNING CLOSE TO OR A FEW DEGREES BELOW SEASONAL NORMS. LEFTOVER PRECIP WILL PUSH OFFSHORE BY MIDDAY THOUGH CLOUDS WILL LINGER INTO THE AFTERNOON. THE SECOND FRONT PUSHES ACROSS AROUND THAT TIME...SO WILL SEE TEMPS DROP WITH NW WINDS AROUND 10 KT OR SO. LATE FRIDAY THROUGH SUNDAY...MODERATE CONFIDENCE. DEEP LONG WAVE TROUGH IN PLACE JUST W OF THE REGION. MOST OF THE 12Z SHORT RANGE MODELS DID DEPICT ANOTHER SHORT WAVE ROTATING OUT OF THE EASTERN GREAT LAKES FRI NIGHT INTO SATURDAY...PASSING JUST S OF NEW ENGLAND. GOOD FORCING AND DECENT MOISTURE ASSOCIATED WITH THIS FEATURE...WITH THE GFS BEING MOST BULLISH AND THE NAM NOT TOO FAR BEHIND. STILL SOME UNCERTAINTY AS TO HOW CLOSE THIS SHORT WAVE WILL BE AS IT PASSES SAT MORNING. PUT MENTION IN FOR SLIGHT CHANCE POPS ACROSS NE CT/RI/SE MA...WHICH COULD START AS A PERIOD OF SNOW SHOWERS BEFORE TEMPS RISE ENOUGH TO CHANGE TO RAIN. WILL NEED TO MONITOR THIS FEATURE FOR POSSIBLE DEVELOPMENT. AT THIS POINT...EXPECT THIS WAVE TO PUSH OFFSHORE SAT AFTERNOON... SO SHOULD SEE DRY BUT CHILLY CONDITIONS. LOWS SAT NIGHT WILL BE IN THE 20S WELL INLAND TO THE LOWER 30S AT THE COAST. WILL BE A DRY BUT CHILLY DAY ON SUNDAY SUNDAY NIGHT AND MONDAY...LOW TO MODERATE CONFIDENCE. H5 SHORT WAVE IN THE UPPER LEVEL NW FLOW WILL WORK SE OUT OF THE GREAT LAKES. ONCE AGAIN...GFS IS RATHER BULLISH IN BRINGING DECENT QPF TO THE REGION AS SURFACE REFLECTION WORKS OFFSHORE. THIS MODEL EVEN TRIES TO REDEVELOP THE LOW OFFSHORE...THOUGH GGEM AND ECMWF HOLD OFF ON THIS AND KEEP THE LOW FURTHER N. EXPECT LIGHT PRECIP AT THIS POINT AS THE LOW AND COLD FRONT PASS DURING MONDAY. CARRIED CHANCE POPS LATE SUN NIGHT THROUGH MOST OF MONDAY...THEN SHOULD CLEAR OFFSHORE. TUESDAY...LOW TO MODERATE CONFIDENCE. DEPENDING UPON THE SUN NIGHT/MON SYSTEM...AT THIS POINT LOOKS LIKE CONDITIONS SHOULD BE MAINLY DRY AS HIGH PRES PASSES S OF THE REGION. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. HIGH CONFIDENCE THROUGH WEDNESDAY...THEN SOME UNCERTAINTY ON EXACT TIMING OF LOWER CIGS/VSBYS WITH RAIN LATE WED INTO WED EVENING. TONIGHT...HIGH CONFIDENCE. VFR CLR. LIGHT/VRBL OR CALM WINDS. WEDNESDAY AND WEDNESDAY NIGHT...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...THURSDAY THROUGH SUNDAY...MODERATE TO HIGH CONFIDENCE. THURSDAY...MAINLY MVFR CIGS/VSBYS WITH SHOWERS AND PATCHY FOG. THURSDAY NIGHT-FRIDAY...MVFR-IFR CIGS/VSBYS IN SHOWERS AND PATCHY FOG. LOCALLY HEAVY DOWNPOURS AND LOW RISK OF ISOLD THUNDER THU NIGHT INTO FRI MORNING. MAY SEE LOCAL -SHSN ACROSS N AND W MA AFTER 06Z FRI THROUGH 13Z-14Z FRI. PRECIP TAPERS OFF FROM NW-SE DURING FRIDAY. FRIDAY NIGHT AND SATURDAY...MAINLY VFR CONDITIONS. MAY SEE LOCAL MVFR CIGS/VSBYS ACROSS NE CT/RI/SE MA LATE FRI NIGHT AND SAT IN RAIN AND/OR SNOW SHOWERS. SATURDAY NIGHT AND SUNDAY...VFR CONDITIONS LIKELY.
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&& .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. 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...THURSDAY THROUGH SUNDAY... MODERATE TO HIGH CONFIDENCE THROUGH FRIDAY. MODERATE CONFIDENCE FRIDAY NIGHT INTO SUNDAY. THURSDAY-FRIDAY...SW WINDS WILL INCREASE...GUSTING TO 25-30 KT ACROSS MOST OF THE OPEN WATERS ESPECIALLY ALONG S COAST AS WELL AS THE S BAYS/SOUNDS. SEAS UP TO 5-7 FT THU WILL BUILD UP TO 11 TO 13 FT WELL OFFSHORE ON FRI. WINDS WILL SHIFT TO NW DURING FRI. FRI NIGHT-SUNDAY...N-NW WINDS MAY GUST CLOSE TO 25 KT...MAINLY LATE SAT INTO SUNDAY. SEA REMAIN AOA 5 FT MAINLY OVER THE OUTER WATERS. && .HYDROLOGY... CONTINUE TO NOTE GOOD AMOUNT OF RAINFALL WILL MOVE ACROSS THE REGION...AS WELL AS TEMPERATURES RISING TO THE UPPER 40S TO MID 50S ALONG WITH INCREASING DEWPTS /AT LEAST TO THE 40S/ THURSDAY INTO FRIDAY. THIS WILL COMBINE TO CAUSE SIGNIFICANT SNOW MELT ACROSS THE REGION. EXPECT RAINFALL AMOUNTS TO RANGE FROM 0.5 TO 1 INCH ACROSS THE REGION...HIGHEST ACROSS W MA/CT. HOWEVER...WITH MILDER TEMPS...WILL SEE A BIG WATER RELEASE WITH THE SNOW TO WATER EQUIVALENT /SWE/ ON ORDER OF 2-5 INCHES. MAY ALSO SEE SOME HEAVIER DOWNPOURS OVERNIGHT THU INTO FRI MORNING ESPECIALLY IF ANY CONVECTION DEVELOPS. COMBINING THE RAPID SNOW MELT WITH THE UPCOMING QPF...MAY SEE 1.5 TO 3 INCHES OF WATER FLOWING INTO AREA RIVERS AND STREAMS. SEVERAL OF THE MAIN STEM RIVER LEVELS MAY APPROACH ACTION STAGE DURING FRIDAY...WITH A COUPLE POSSIBLY APPROACHING MINOR FLOOD STAGE. CURRENT FORECASTS ISSUED BY THE NORTHEAST RIVER FORECAST CENTER HAVE THE DETAILS. CONTINUE TO MONITOR FORECAST UPDATES FOR MORE DETAILS ON THIS EVENT. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...NOCERA/EVT NEAR TERM...NOCERA/EVT SHORT TERM...NOCERA LONG TERM...EVT AVIATION...NOCERA/EVT MARINE...NOCERA/EVT HYDROLOGY...EVT

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