Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 261751 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 151 PM EDT SAT JUL 26 2014 .SYNOPSIS... HIGH PRESSURE SOUTH OF NEW ENGLAND WILL PROVIDE DRY AND WARM WEATHER TODAY. LOW PRESSURE DEVELOPING OVER SOUTHEAST CANADA WILL RESULT IN SCATTERED SHOWERS AND THUNDERSTORMS AT TIMES LATE TONIGHT INTO SUNDAY AS ITS ATTENDING WARM FRONT APPROACHES. A COLD FRONT THEN SWINGS ACROSS THE REGION MONDAY BRINGING MORE SHOWERS AND THUNDERSTORMS. THE FRONT THEN LINGERS EAST OF THE MASSACHUSETTS COAST THROUGH FRIDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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150 PM UPDATE... FORECAST ON TRACK FOR THIS AFTERNOON. A FEW SPRINKLES FROM MID CLOUDS WERE OCCURRING ACROSS CT. THESE WILL SLIDE EASTWARD INTO RI AND SOUTHEAST MA THIS AFTERNOON. OTHERWISE MOST AREAS WILL REMAIN PARTLY SUNNY WITH HIGH TEMPERATURES IN THE LOWER TO MID 80S AND SOUTH TO SOUTHWEST WINDS GUSTING TO 10 TO 20 MPH AT TIMES.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... TONIGHT... QUIET/DRY WEATHER PREVAILS MUCH OF THE NIGHT. HOWEVER LOW PRES EXITS THE GREAT LAKES AND REORGANIZES OVER SOUTHEAST CANADA. ITS ATTENDING WARM FRONT APPROACHES THE REGION FROM THE SOUTHWEST TOWARD MORNING. PATCHY FOG AND LOW CLOUDS WILL LIKELY DEVELOP BEFORE SUNRISE SUNDAY AHEAD OF THE FRONT ACROSS PORTIONS OF SOUTHERN NEW ENGLAND. GREATEST RISK OF SHOWERS AND T-STORMS WILL BE OVER WESTERN PORTIONS OF CT/MA AND TOWARD DAYBREAK SUNDAY. IT WILL BE A MILD NIGHT GIVEN SSW WINDS ADVECTING HIGHER DEW PT AIR INTO THE AREA. SUNDAY... MODELS STRUGGLING WITH LOCATION AND TIMING OF WARM SECTOR SUNDAY. 00Z ECMWF AND 00Z GEFS INDICATING BETTER INSTABILITY/WARM SECTOR AIRMASS ACROSS EASTERN NY AND WESTERN NEW ENGLAND WITH LESS INSTABILITY OVER RI AND EASTERN MA. THIS IS LIKELY DUE TO WARM FRONTAL CLOUDS AND PRECIP LINGERING ACROSS THIS REGION. AT THIS TIME RANGE LOOKS LIKE A PERIOD OF WARM FRONTAL CONVECTION DURING THE MORNING FOLLOWED BY A RISK OF STRONG TSTMS LATER IN THE DAY ACROSS WESTERN NEW ENGLAND GIVEN MAGNITUDE OF INSTABILITY AND DEEP LAYER SHEAR. OF COURSE THIS IS PENDING PARTIAL CLEARING ACROSS WESTERN NEW ENGLAND. AS FOR THE MORNING AND EARLY AFTERNOON COULD BE AN ACTIVE WARM FRONTAL PASSAGE AS MODELS SUGGEST MODEST SYNOPTIC SCALE LIFT /MID AND UPPER LEVEL Q-VECTOR CONVERGENCE/ COMBINED WITH DEEP LAYER MOISTURE AND INSTABILITY. QG FORCING WILL BE ENHANCED AS LFQ OF UPPER LEVEL JET STREAK MOVES ACROSS SOUTHERN NEW ENGLAND. TOO EARLY FOR MORE DETAILS GIVEN MODEL SPREAD HERE ON HANDLING WARM FRONTAL PASSAGE. NEVERTHELESS NOTICEABLY MORE HUMID AS DEW PTS CLIMB INTO THE 60S. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... BIG PICTURE... ONE THING CAN BE SAID ABOUT THE UPCOMING WEEK: ANY PACIFIC WEATHER WILL BE REACHING THE ATLANTIC VIA THE SCENIC ROUTE. DEEP TROUGHS OVER THE GULF OF ALASKA AND EASTERN NORTH AMERICA. MEANWHILE UPPER RIDGES REBUILD OVER WESTERN NORTH AMERICA AND THE WEST ATLANTIC. A SHORTWAVE MOVING THROUGH THIS FLOW MERGES WITH THE EASTERN NO-AM TROUGH SUNDAY AND SWINGS ITS ENERGY ACROSS NEW ENGLAND MONDAY. ANOTHER SHORTWAVE OVER THE CANADIAN ARCTIC DROPS SOUTH INTO THE TROUGH AND MAINTAINS ITS POSITION TO OUR WEST THROUGH MIDWEEK. THE TROUGH EJECTS NORTH THROUGH QUEBEC LATE IN THE WEEK...BUT LESS WELL DEFINED LOW PRESSURE REMAINS OVER EASTERN NORTH AMERICA AT WEEK/S END. THIS MEANS THAT THE UPPER FLOW ALONG THE EAST COAST WILL REMAIN S-SW TO N-NE THROUGH THE WEEK. THE MASS FIELDS AND THERMAL FIELDS OF THE GFS AND ECMWF LOOK SIMILAR IN OVERVIEW. SOME DIFFERENCES IN DETAILS EMERGE THURSDAY-FRIDAY. THE SIMILARITY BUILDS CONFIDENCE IN THE OVERALL FLOW OF THE FORECAST. THE LONGER RANGE DIFFERENCES IN DETAIL SUPPORT USING A BLEND OF THE FORECAST DATA. THE DAILIES... SUNDAY NIGHT-MONDAY... SHORTWAVE MOVES THROUGH THE GREAT LAKES SUNDAY NIGHT WITH SUPPORTING 100-KNOT JET. THIS APPROACHES THE COAST OVERNIGHT SUPPORTING INCREASED UPPER VENTING/LIFT. MEANWHILE 30-40 KNOT SOUTHWEST LOW LEVEL JET FEEDS MOISTURE UP THE COAST ALONG WITH LOW LEVEL ISENTROPIC LIFT. WILL BUILD POPS OVERNIGHT ACROSS ALL OF THE FORECAST AREA WITH PEAK VALUES IN THE LIKELY RANGE. ON MONDAY WITH UPPER JET NOSE OVER THE REGION AND COOLING TEMPS ALOFT AS THE TROUGH MOVES INTO NEW ENGLAND...EXPECT SUFFICIENT DESTABILIZATION FOR A SECOND ROUND OF PRECIP/CONVECTION ESPECIALLY IN THE AFTERNOON N AND W OF I-95. PRECIPITABLE WATER VALUES REACH 1.75-2 INCHES SUNDAY NIGHT...AND SHOULD LINGER NEAR 1.5 INCHES MONDAY. POTENTIAL FOR LOCALLY HEAVY DOWNPOURS/POOR DRAINAGE FLOODING. SHORTWAVE LIFTS NORTH MONDAY NIGHT. SURFACE REFLECTION OF THIS FEATURE ALSO PULLS NORTH/NORTHEAST. MODELS SHOW THIS SURFACE LOW PULLING THE COLD FRONT THROUGH OUR AREA MONDAY AFTERNOON/EARLY NIGHT. SO PCPN SHOULD DIMINISH MONDAY NIGHT. TUESDAY... SECOND SHORTWAVE DEEPENS THE MAIN UPPER TROUGH TO OUR WEST. THIS WILL ALSO HOLD THE UPPER JET IN PLACE WITH ENTRANCE REGION OVER NEW ENGLAND. CONTINUED COOLING ALOFT. LOW CONFIDENCE...BUT ENOUGH FACTORS IN FAVOR OF SHOWERS/TSTMS TO MAINTAIN CHANCE POPS IN SRN NH/EASTERN MASS WHERE THE UPPER DYNAMICS ARE BEST. WEDNESDAY THROUGH FRIDAY... WITH THE TROUGH AND ATLANTIC RIDGE REMAINING IN POSITION...EXPECT THE COLD FRONT TO LINGER EAST OF OUR AREA WITH SHOWERS OVER THE OCEAN. ON FRIDAY AS THE BULK OF THE TROUGH LIFTS NORTH THROUGH CANADA LEAVING A MUCH WEAKER UPPER FLOW OVER EASTERN NORTH AMERICA...EXPECT THE OCEAN RIDGE TO NUDGE WESTWARD AND SHIFT THE UPPER FLOW WEST. THIS WILL BRING THE STALLED FRONT CLOSER TO THE COAST AND BRING AN INCREASED CHANCE OF SHOWERS TO THE CAPE AND ISLANDS...POSSIBLY TO THE COASTAL PLAIN. WILL SHOW CHANCE POPS IN THESE AREAS ON FRIDAY. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. CIGS AND VSBYS MAINLY A BLEND OF GFS AND ITS MAVMOS OUTPUT. SHORT TERM /THIS AFTERNOON THROUGH SUNDAY/...HIGH CONFIDENCE THROUGH THIS EVENING THEN LOWERING CONFIDENCE LATE TONIGHT INTO SUNDAY ON SPECIFIC TIMING OF LOWER CIGS/VSBYS ASSOCIATED WITH SHOWERS/T-STORMS. THIS AFTERNOON...VFR CONDITIONS. COULD SEE A FEW SPRINKLES IN CT...RI...AND SOUTHEAST MA. SW WINDS 15-20 KT WITH A FEW GUSTS UP TO 25 KT POSSIBLE OVER SOUTHEAST MA. TONIGHT...DRY WITH VFR TO START THEN LOWERING TO MARGINAL VFR/MVFR TOWARD MORNING ALONG WITH A LOW PROB OF IFR CIGS WELL INLAND. SCATTERED SHOWERS AND T-STORMS ENTER WESTERN NEW ENGLAND LATE. SUNDAY...MARGINAL MVFR/VFR IN SCATTERED SHOWERS AND T-STORMS... MOST NUMEROUS IN THE MORNING. KBOS TAF...HIGH CONFIDENCE THROUGH THIS EVENING THEN LOWER CONFIDENCE ON EXACT TIMING OF SHOWERS/T-STORMS LATE TONIGHT INTO SUNDAY. MODEST SW WIND TODAY WITH SPEEDS OF 15-20 KT. KBDL TAF...HIGH CONFIDENCE THRU THIS EVENING THEN LOWER CONFIDENCE ON EXACT TIMING OF SHOWERS/T-STORMS LATE TONIGHT INTO SUNDAY. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY...MODERATE CONFIDENCE. SUNDAY NIGHT-MONDAY... VFR BUT WITH AREAS OF MVFR IN SHOWERS/TSTMS. AREAS OF IFR/LIFR IN LATE NIGHT/EARLY MORNING FOG ESPECIALLY ALONG THE SOUTH COAST. TUESDAY...VFR BUT WITH SCATTERED MVFR IN SHOWERS/TSTMS MAINLY SRN NEW HAMPSHIRE AND EASTERN MASS. WEDNESDAY...VFR. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THIS AFTERNOON THROUGH SUNDAY...HIGH CONFIDENCE INTO THIS EVENING AND THEN LOWERING CONFIDENCE LATER TONIGHT INTO SUNDAY REGARDING TIMING AND AREAL COVERAGE OF SHOWERS/T-STORMS. THIS AFTERNOON...ANOTHER NICE BOATING DAY WITH DRY WEATHER AND GOOD VSBY. ONLY WRINKLE WILL BE MODEST SW WINDS 15-20 KT WITH A FEW GUSTS NEAR SHORE POSSIBLY APPROACHING 25 KT. HELD OFF ON A SMALL CRAFT ADVISORY AS MOST LOCATIONS WILL HAVE WINDS LESS THAN 25 KT. TONIGHT...QUIET TO START BUT AN APPROACHING WARM FRONT WILL LEAD TO PATCHY FOG/LOW CLOUDS REDUCING VSBY TOWARD DAYBREAK SUNDAY. LOW RISK OF SHOWERS/T-STORMS TOWARD SUNRISE SUNDAY. SUNDAY...SW WINDS 15-20 KT WITH A LOW RISK OF GUSTS TO 25 KT. SCT SHOWERS/T-STORMS POSSIBLE AS WELL. TODAY DEFINITELY THE BETTER OF THE TWO WEEKEND DAYS. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY...MODERATE CONFIDENCE. SUNDAY NIGHT-MONDAY...INCREASING SOUTHWEST WINDS ESPECIALLY ON MONDAY AS A COLD FRONT APPROACHES. WINDS MAY REACH 25 KNOTS AT TIMES. THE STEADY SOUTHWEST FLOW SHOULD BUILD SEAS WITH 5-8 FEET ON THE EXPOSED WATERS. WARM HUMID AIR OVER THE WATERS WILL LEAD TO LOW VSBYS IN AREAS OF FOG. SHOWERS AND THUNDERSTORMS POSSIBLE WITH GUSTY WINDS AND LOCALLY HEAVY RAIN. A SMALL CRAFT ADVISORY MAY BE NEEDED DURING THIS PERIOD. TUESDAY...THE COLD FRONT MOVES ACROSS THE EASTERN WATERS WITH A CONTINUED CHANCE OF A SHOWER/THUNDERSTORM. WINDS WILL BE LIGHTER THAN MONDAY...STARING SOUTHWEST AND EVENTUALLY SHIFTING TO NORTHWEST. CONTINUED 5-6 FOOT SEAS ON THE OUTER WATERS. A SMALL CRAFT ADVISORY MAY BE NEEDED ON SOME OF THE WATERS. WEDNESDAY...LIGHTER WINDS AND SEAS AS HIGH PRESSURE BUILDS OVER THE WATERS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...WTB/NOCERA NEAR TERM...FIELD SHORT TERM...NOCERA LONG TERM...WTB AVIATION...WTB/NOCERA/FIELD MARINE...WTB/NOCERA/FIELD

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