Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 200541 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 141 AM EDT WED AUG 20 2014 .SYNOPSIS... MAINLY DRY WEATHER WITH TEMPERATURES NEAR OR SLIGHTLY BELOW NORMAL EXPECTED THROUGH THE WEEKEND. PATTERN STARTS TO BECOME A BIT MORE UNSETTLED EARLY NEXT WEEK WITH AN APPROACHING FRONT. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... 130 AM UPDATE... AS MENTIONED BEFORE...THE UPPER LVL CI HAS BECOME MAINLY BKN ACROSS THE REGION AND HAS SLOWED RADIATIONAL COOLING PROCESSES ACROSS THE AREA. HOWEVER...NOTE THAT CLEARING IS BEGINNING TO FILTER IN FROM THE W WITH DWPTS DROPPING INTO THE 40S. THEREFORE...STILL PLENTY OF TIME BETWEEN NOW AND SUNRISE FOR TEMPS TO FALL OFF THE TABLE. HAVE ADJUSTED HOURLY TEMPS AND MINS ACCORDINGLY WITH THIS UPDATE. PREVIOUS DISCUSSION... TONIGHT... GOOD MODEL AGREEMENT OF WEAK ENHANCEMENT OF THE MID-LEVEL RIDGE AS IT PUSHES E ACROSS THE NE-CONUS. WILL KEEP WITH A DRY FORECAST WITH PREVAILING SUBSIDENCE ACCOMPANIED BY HIGH PRESSURE UNDER LIGHT AND VARIABLE WINDS. WATCHING THE CLOUD DECK PRESENTLY OVER PA/NY. THIS SHOULD SLOWLY ADVECT E WITH THE W/SW-FLOW REARWARD OF THE MID-LEVEL RIDGE. HIGH CLOUDS ARE POSSIBLE OVERNIGHT...WITH THE POTENTIAL FOR LOWER AND THICKER CLOUDS INTO W NEW ENGLAND BY WEDNESDAY MORNING. THIS CAN RESULT IN COMPLICATIONS IN BOTH OVERNIGHT LOWS AND DENSE FOG POTENTIAL AND COULD TOTALLY RUIN THE FORECAST. YET ALTOGETHER...NOTING CLOUDS ALONG WITH LIGHT/VARIABLE WINDS HIGHEST CONFIDENCE ACROSS CENTRAL/EASTERN NEW ENGLAND OF ANOTHER NIGHT OF EFFECTIVE RADIATIONAL COOLING. CONSIDERING TUESDAY MORNING LOWS...WEDNESDAY MORNING LOWS SHOULD BE AROUND THE UPPER- 40S ESPECIALLY FOR THOSE AREAS WHICH RADIATE WELL. ELSEWHERE LOWS AROUND THE MID-50S WITH URBAN CENTERS SLIGHTLY WARMER. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/... WEDNESDAY... THREE BLIND MICE? SURE SEEMS LIKE IT. THE NEIGHBORING OF THE GREAT LAKES...NE-CANADA...AND NW-ATLANTIC LOWS LENDS TO A STRENGTHENING OF THE SURFACE LABRADOR HIGH AND MID-LEVEL RIDGE ALONG WITH PERSISTING SUBSIDENCE AND DRY AIR. SHOULD BE A QUIET DAY WEATHER-WISE. MAIN CONCERNS WILL BE THE CONTINUED ENCROACHMENT OF CLOUDS INTO NEW ENGLAND...THE THICKEST OF WHICH WILL BE INTO THE CT-RIVER VALLEY. SLIGHT CHANCE OF SHOWERS...BUT WILL KEEP W OF THE BERKSHIRES BASED ON GOOD MODEL AGREEMENT OF CONTINUED ABUNDANCE OF DRY AIR AS FAR W AS THE HUDSON-RIVER VALLEY. BEST ISENTROPIC MOTIONS / LIFT PARENT WITH MOISTURE AVAILABILITY REMAIN W ACROSS NY/PA COLLOCATED WITH THE SURFACE WARM FRONT. COMBINATION OF BOTH A THERMAL AND PRESSURE GRADIENT SHOULD RESULT IN AN ONSHORE SEA-BREEZE FLOW BY MID-MORNING. WARMER AIRMASS FILTERING INTO THE REGION ALOFT COUPLED WITH A WELL-MIXED BOUNDARY LAYER SHOULD ALLOW FOR MORE SEASONABLE CONDITIONS WITH HIGHS AROUND THE LOW-80S BENEATH A MIX OF SUN AND CLOUDS. WEDNESDAY NIGHT... TROUGHING PARENT TO THE GREAT LAKES LOW RENEWS LOW PRESSURE ALONG THE STALLED FRONTAL BOUNDARY ACROSS THE MID-ATLANTIC AND OUT TO SEA. SUBSEQUENT FALLING HEIGHTS AS THE NE-CANADA LOW LIFTING NE RESULTS IN THE GREAT LAKES CLOSED LOW AND ATTENDANT WARM-FRONT TO WOBBLE INTO THE NE-CONUS. WILL SEE CLOUDS INCREASE ACROSS THE REGION ALLOWING THE SLIGHT CHANCE OF SHOWERS INTO THE CT-RIVER VALLEY. EVALUATING MODEL FIELDS...THERE IS GOOD AGREEMENT OF SUBSIDENCE AND LOW- TO MID-LEVEL DRY AIR ACROSS MUCH OF NEW ENGLAND. EVALUATING ISENTROPIC FLOW AND FORCED ASCENT...ACTIVITY REMAINS ACROSS AND W OF THE HUDSON RIVER VALLEY. DECENT SURFACE CONVERGENCE AND ENHANCED ASCENT COUPLED WITH A S/SW COMPONENT OF ISENTROPIC FLOW KEEPS THE MAJORITY OF WET-WEATHER OUT OF OUR AREA. IN FACT...EVALUATING THETAE DURING THE OVERNIGHT PERIOD EXHIBITS EROSION AS IT ENCOUNTERS MOISTURE-DEPRIVED DRIER AIR TO THE E. ANOTHER EVENING OF LIGHT AND VARIABLE FLOW. WITH THE ENCROACHMENT OF THE GREAT LAKES SYSTEM AS A WHOLE...HAVE HIGH CONFIDENCE OF COOLEST NIGHTTIME LOWS ACROSS E/SE NEW ENGLAND...WHEREAS THICKENING CLOUDS OVER WESTERN AND CENTRAL NEW ENGLAND WILL KEEP THINGS MILD. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... HIGHLIGHTS... * QUIET WEATHER EXPECTED THROUGH MUCH OF THE LONG TERM * UNCERTAINTY INCREASES EARLY NEXT WEEK WITH AN APPROACHING FRONT. MODELS ARE IN GOOD AGREEMENT THROUGH MUCH OF THE LONG TERM. THE GFS HAS COME MORE IN LINE BOTH WITH TODAYS ECMWF AS WELL AS YESTERDAYS ECMWF RUN IN KEEPING LOW PRESSURE SYSTEMS COMING OFF THE MID- ATLANTIC COAST WELL EAST OF OUR SHORE LINE. A PERSISTENT UPPER LEVEL TROUGH OVER THE NORTHEAST WILL SLOWLY MAKE ITS WAY EAST... MOVING OFFSHORE THIS WEEKEND AS AN UPPER LEVEL RIDGE PUSHES NORTHWARD FROM THE SOUTHEASTERN U.S. THIS WILL RESULT IN COOLER... LESS SEASONABLE WEATHER WHILE HIGH PRESSURE IN QUEBEC WILL KEEP THINGS RELATIVELY DRY. THIS HIGH WILL SINK SOUTH THROUGH THE WEEKEND INTO EARLY NEXT WEEK...EVENTUALLY DROPPING SOUTH OF SOUTHERN NEW ENGLAND AND RETURNING US TO A MORE WESTERLY FLOW. LOW PRESSURE IN ONTARIO MAY EVENTUALLY MOVE EASTWARD INTO QUEBEC BRINGING A COLD FRONT THROUGH SOUTHERN NEW ENGLAND TUESDAY OR WEDNESDAY. DEPENDING ON AVAILABLE MOISTURE THIS MAY INITIATE A FEW SHOWERS AND THUNDERSTORMS AHEAD OF THE FRONT. BEYOND THIS WEEKEND...THE FORECAST HERE WILL LARGELY DEPEND ON THE EVOLUTION OF AN UPPER LEVEL TROUGH ACROSS THE NORTHWESTERN U.S. HOW QUICKLY THE TROUGH PUSHES EAST VARIES GREATLY BY MODEL SO EXPECT A GREATER THAN NORMAL POTENTIAL FOR AN EVER EVOLVING FORECAST FOR EARLY NEXT WEEK. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...THROUGH THURSDAY...HIGH CONFIDENCE. MAINLY VFR THROUGH THU. ONLY CAVEAT WILL BE SOME SPOTTY GROUND FOG AT TYPICALLY PRONE AIRPORTS BOTH THIS MORNING AND AGAIN LATE TONIGHT. A FEW SHOWERS POSSIBLY MAINLY W OF AN IJD-ORH-AFN LINE DURING THE DAY ON THU. FLOW SHIFTS FROM THE SW TO THE E THROUGH THE DAY TODAY...ASSISTED BY SEA BREEZES. LIGHT AND VRB FLOW RETURNS AGAIN TONIGHT...WITH E FLOW AGAIN ON THU. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...THURSDAY THROUGH SUNDAY... MODERATE CONFIDENCE. MAINLY VFR. LOW PROBABILITY OF PATCHY MVFR/IFR FOG EACH NIGHT. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM...THROUGH WEDNESDAY NIGHT...HIGH CONFIDENCE. QUIET BOATING WEATHER. PREVAILING E-WINDS. GUSTS OF 10-15 KTS POSSIBLE ACROSS THE SE-WATERS...AND PERHAPS ALONG THE IMMEDIATE NEAR-SHORE AS THE SEA-BREEZE DEVELOPS AROUND 10-11 AM WEDNESDAY. OUTLOOK...THURSDAY THROUGH SUNDAY... MODERATE TO HIGH CONFIDENCE. QUIET BOATING WEATHER IS EXPECTED THROUGH MUCH OF THE PERIOD WITH HIGH PRESSURE ACROSS THE REGION. LOW PROBABILITY OF PATCHY OVERNIGHT FOG LIMITING VISIBILITIES. SEAS MAY INCREASE ON THE OUTER WATERS THIS WEEKEND AS AN OCEAN STORM PASSES WELL EAST OF THE SOUTHERN NEW ENGLAND WATERS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...RLG/SIPPRELL NEAR TERM...DOODY/SIPPRELL SHORT TERM...SIPPRELL LONG TERM...RLG AVIATION...DOODY/RLG MARINE...RLG/SIPPRELL

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