Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 250206 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1006 PM EDT FRI JUL 24 2015 .SYNOPSIS...
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UNSETTLED WEATHER EXPECTED THROUGH EARLY NEXT WEEK...WITH MAINLY DIURNAL SHOWERS AND THUNDERSTORMS. STRONG TO SEVERE THUNDERSTORMS WILL BE POSSIBLE AGAIN SOMETIME SUNDAY INTO MONDAY. THE NEXT MAIN WEATHER HEADLINE WILL BE A POSSIBLE HEAT WAVE TUESDAY THROUGH THURSDAY.
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&& .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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SHOWERS DISSIPATING AS DIURNAL HEATING CONCLUDES AND THE BOUNDARY LAYER STABILIZES...AS WELL AS MUCH OF THE REGION FALLING BENEATH AN AREA OF SUBSIDENCE IN WAKE OF A MID-LEVEL VORTEX SWEEP SE OUT TO SEA ROUND THE BROADER CYCLONIC FLOW PARENT TO THE MID- TO UPPER-LEVEL LOW. THERE REMAINS THE POSSIBILITY OF ADDITIONAL ENERGY OVERNIGHT INTO THE MORNING PERIOD SWEEPING S/SE OVER E- PORTIONS OF NEW ENGLAND. CAN NOT RULE OUT A SPOT SHOWER FOR THESE AREAS. OTHERWISE QUIET WITH GRADUAL CLEARING UNDER LIGHT WINDS. THIS BRINGS UP A CONCERN ABOUT POTENTIAL FOG. ANTECEDENT RAINS HAVE LEFT DEWPOINTS HOVERING IN THE LOW-60S. SHOULD RADIATIONAL COOLING BE ALLOWED TO PROCEED AT ANY POINT THIS EVENING THERE IS THE POTENTIAL OF DENSE FOG DEVELOPMENT. DEWPOINT DEPRESSIONS ACROSS THE AREA PRESENTLY OF AROUND 2-4 DEGREES. NOT A LOT OF FORECAST GUIDANCE TO SUPPORT SUCH OUTCOMES. GOING WITH A GUT FEELING. WILL BE MONITORING CLOSELY INTO MORNING UPDATING THE FORECAST AS NECESSARY.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... SATURDAY... MID LEVEL MEAN TROUGH OVER GEORGES BANK MOVES SEAWARD ALLOWING HEIGHT RISES TO DEVELOP OVER NEW ENGLAND ALONG WITH FLOW BECOMING LESS CYCLONIC AND MORE ZONAL. TYPICALLY THIS SUBSIDENCE WOULD YIELD A DRY FORECAST. HOWEVER LEFTOVER BACKDOOR FRONT ACROSS THE REGION MAY ACT AS A FOCUS FOR SCATTERED LOW TOP AFTERNOON SHOWERS. MOST OF THE HI RES GUIDANCE HAS SHOWERS DEVELOPING IN THE AFTERNOON IN THE CT RIVER VALLEY AND THEN MOVING EASTWARD INTO RI AND CENTRAL MA LATER IN THE DAY. THIS SEEMS REASONABLE BUT WILL BE A BATTLE BETWEEN MID LEVEL SUBSIDENCE AND LOW LEVEL CONVERGENCE. NOT EXPECTING A WASHOUT OUT JUST A LOW RISK FOR A FEW SHOWERS. MARITIME AIRMASS FROM BACKDOOR FRONT WILL RESULT IN A LARGE TEMP GRADIENT ACROSS THE AREA WITH HIGHS ONLY IN THE U60S TO L70S ACROSS EASTERN MA TO L80S IN THE CT RIVER VALLEY. MORNING SUNSHINE WILL MIX WITH AFTERNOON CLOUDS. SATURDAY NIGHT... BACKDOOR FRONT LIFTS NORTH AS A WARM FRONT AND WARM ADVECTION PATTERN BEGINS TO UNFOLD YIELDING AN INCREASED RISK FOR SHOWERS AND T-STORMS ESPECIALLY SECOND HALF OF THE NIGHT. WARMER AND MORE HUMID THAN PREVIOUS NIGHTS. && .LONG TERM /SUNDAY THROUGH FRIDAY/... HIGHLIGHTS... * SCATTERED STRONG THUNDERSTORMS POSSIBLE SUNDAY * HEAT WAVE POSSIBLE TUESDAY THROUGH THURSDAY * SCATTERED STORMS POSSIBLE LATE THURSDAY SUNDAY...STILL LOOKS LIKE IT COULD BE AN ACTIVE WEATHER DAY. 0-1 KM HELICITY VALUES REMAIN RATHER ROBUST...ALTHOUGH INSTABILITY APPEARS TO BE LAGGING A FEW HOURS BEHIND. WITH MORNING SUNSHINE BREAKING OUT BEHIND THE DEPARTING UPPER DISTURBANCE...RAPID DESTABILIZATION IS EXPECTED DURING THE LATE MORNING HOURS WITH THE GFS CONTINUING TO INDICATE SURFACE-BASED CAPES APPROACHING 3000 J/KG ACROSS MOST OF THE REGION DURING THE AFTERNOON. A WARM FRONT WILL HAVE MOVED NORTHWARD INTO NORTH CENTRAL AND NORTHEASTERN MA BY THE AFTERNOON. WE ARE STILL VERY FAR AWAY AT THIS POINT...AND DO NOT WANT TO GET TOO CARRIED AWAY. THAT SAID...WE WILL NEED TO MONITOR THE POTENTIAL FOR MORNING CONVECTION INITIATION. EVEN IF THE WIND SHEAR AND INSTABILITY DO NOT PHASE IN TIME AND SPACE...THERE COULD BE ENOUGH INSTABILITY TO PRODUCE STRONG TO SEVERE THUNDERSTORMS SUNDAY AFTERNOON. THE MAIN RISK WOULD BE ACROSS INTERIOR SOUTHERN NEW ENGLAND. SUNDAY NIGHT AND MONDAY... A COLD FRONT STALLS ACROSS THE AREA. THIS IS SOMEWHAT TRICKY. THE MAJORITY OF THE LATEST GUIDANCE DEPICTS THIS FRONT BEING SQUEEZED BETWEEN TWO HIGH PRESSURES. AGAIN A LOT OF UNCERTAINTY AS THERE IS A GOOD AMOUNT OF CAPE AROUND...YET THERE IS HARDLY ANY SHEAR AS GUIDANCE SHOWS 10-20 KTS. HAVE COMPROMISED WITH SLIGHT CHANCE POPS FOR SHOWERS OR TSTMS. HIGH TEMPERATURES FORECAST TO BE A FEW DEGREES WARMER THAN SUNDAY...MAINLY 80 TO 85. TUESDAY THROUGH THURSDAY... THE COLD FRONT FINALLY GETS WASHED OUT SOMEWHERE OVER SOUTHERNMOST NEW ENGLAND BY TUESDAY. CANNOT RULE OUT AN ISOLATED SHOWER TUESDAY. OTHERWISE...AN UPPER LEVEL HIGH PRESSURE WILL SPREAD FROM THE MIDWEST TOWARD NEW ENGLAND. THIS WILL TRANSLATE TO MAINLY SUNNY CONDITIONS AND MUCH HOTTER WEATHER. IN FACT...925 MB TEMPERATURES REACH +28C WED AND THU AFTERNOONS. WE ARE FORECASTING NEAR 90 FOR HIGHS ON TUE AND LOWER TO MID 90S WEDNESDAY AND THURSDAY FOR MUCH OF THE INTERIOR...COOLER AT THE COAST. IT WOULD BE A HEAT WAVE IF WE COULD HIT 90 DEGREES FOR THREE CONSECUTIVE DAYS. THURSDAY EVENING INTO FRIDAY...MODELS ARE TRENDING TOWARD HAVING A COLD FRONT MOVE THROUGH THURSDAY NIGHT INTO FRIDAY. THERE SHOULD BE SOLID CAPPING DURING THE DAY ON THURSDAY WITH 700 MB TEMPERATURES FORECAST TO APPROACH +10C. THIS CAP COULD ERODE THURSDAY NIGHT INTO FRIDAY. THERE IS A CHANCE OF THUNDERSTORMS AS THIS COLD FRONT APPROACHES. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
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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 SATURDAY NIGHT/...HIGH CONFIDENCE. 2Z UPDATE... TONIGHT... SOME SCT -SHRA LINGERS. MAINLY VFR BUT FOR THOSE AREA WHICH RECEIVED A FAIR AMOUNT OF RAIN TODAY WILL NEED TO WATCH FOR POTENTIAL MVFR-IFR FOG DEVELOPMENT AS CONDITIONS CLEAR AND WINDS BECOME LIGHT. SATURDAY... LOW-END VFR CIGS WITH SCT -SHRA ALONG A BACKDOOR COLDFRONT SWEEPING W ACROSS INTERIOR NEW ENGLAND. SATURDAY NIGHT... VFR TO START BUT LOWERING TO MVFR AND LOW RISK OF IFR BY SUNDAY MORNING IN SCATTERED SHOWERS AND FOG. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. ONSHORE WINDS PERSIST THRU SATURDAY NIGHT. PERHAPS A SCT -SHRA OVERNIGHT INTO SATURDAY MORNING. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. -SHRA DEVELOPING TOWARDS THE LATER HALF OF SATURDAY. OUTLOOK...SUNDAY THROUGH WEDNESDAY... SUNDAY INTO MONDAY...MODERATE CONFIDENCE. MVFR IN SCATTERED SHOWERS AND THUNDERSTORMS. A FEW STRONG STORMS POSSIBLE LATE SUNDAY MORNING THROUGH SUNDAY EVENING WITH LOCAL IFR VSBYS. TUESDAY...MODERATE CONFIDENCE. VFR. POSSIBLE MVFR IN ISOLATED SHOWERS OVER THE INTERIOR. WEDNESDAY...HIGH CONFIDENCE VFR.
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&& .MARINE...
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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 SATURDAY NIGHT/...HIGH CONFIDENCE. TONIGHT... CONDITIONS IMPROVING. WILL BEING TO SEE THE PRESENCE OF A BACKDOOR COLD FRONT MOVING ONSHORE WITH LIGHT N/NE-WINDS TOWARDS SATURDAY MORNING. SATURDAY... LIGHT E/SE-WINDS. DRY WEATHER AND GOOD VISIBILITY. SATURDAY NIGHT... SE-WINDS. POSSIBLE LOW VISIBILITIES WITH FOG. SHOWERS AND THUNDERSTORMS POSSIBLE. OUTLOOK...SUNDAY THROUGH WEDNESDAY... HIGH CONFIDENCE. WINDS AND SEAS BELOW SMALL CRAFT ADVISORY LEVELS THROUGH THIS PERIOD AS WEAK PRESSURE GRADIENT PERSISTS ACROSS WATERS. WARM FRONT LIFTS N ACROSS THE WATERS EARLY SUNDAY. A SLOW-MOVING COLD FRONT APPROACHES THE WATERS MONDAY INTO TUESDAY...BUT MAY DISSIPATE BY TUESDAY. A FEW STRONG THUNDERSTORMS ARE POSSIBLE OVER THE WATERS SUNDAY INTO SUNDAY EVENING.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...BELK/NOCERA NEAR TERM...BELK/NOCERA/SIPPRELL SHORT TERM...NOCERA LONG TERM...BELK AVIATION...BELK/NOCERA/SIPPRELL MARINE...BELK/NOCERA/SIPPRELL

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