Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 280711 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 311 AM EDT MON JUL 28 2014 .SYNOPSIS... A RATHER STRONG LOW PRESSURE SYSTEM BY JULY STANDARDS WILL MOVE ACROSS UPSTATE NEW YORK TODAY BEFORE HEADING INTO NORTHERN NEW ENGLAND TONIGHT. IT WILL BRING SHOWERS AND STORMS THIS MORNING...FOLLOWED BY POSSIBLE STRONG STORMS THIS AFTERNOON. A COLD FRONT WILL CROSS THE REGION TONIGHT AND TUESDAY...BRINGING DRIER AND LESS HUMID WEATHER...AS THE FRONT REMAINS STALLED OVER THE MARITIMES AND NEW ENGLAND OFFSHORE WATERS THROUGH THE WEEKEND. && .NEAR TERM /THROUGH TODAY/... *** HEAVY RAINFALL/STORMS THIS MORNING *** *** FEW STRONG/SEVERE STORMS THIS AFTERNOON *** 310 AM UPDATE... BAND OF SHOWERS/STORMS FROM WESTERN AND CENTRAL NY INTO NYC AND NJ IS ASSOCIATED WITH STRONG MID LEVEL Q-VECTOR CONVERGENCE AS UPPER LOW CLOSES OFF OVER EASTERN GREAT LAKES. MODELS IN GOOD AGREEMENT THAT THIS ACTIVITY WILL LIFT THROUGH SOUTHERN NEW ENGLAND THROUGH THIS MORNING...BEFORE SHIFTING FARTHER N THIS AFTERNOON. MOST OF THIS MAY END UP AFFECTING LOCATIONS NEAR S COAST AS OPPOSED TO INTERIOR PER RADAR TRENDS. MAIN THREAT THIS MORNING IS LOCALIZED FLASH FLOODING FROM HEAVY RAINFALL...IN ADDITION TO FREQUENT LIGHTNING. ALSO CANNOT RULE OUT STRONG WIND GUSTS GIVEN ENVIRONMENT OF RATHER HIGH 0-6KM SHEAR AND DECENT MID LEVEL LAPSE RATES...THOUGH GIVEN TIME OF DAY CONFIDENCE IS LOW THAT STRONG WINDS WILL BE REALIZED. ONCE THIS INITIAL ROUND OF SHOWERS/STORMS LIFTS N BY EARLY AFTERNOON...ATTENTION THEN TURNS TO POSSIBLE REDEVELOPMENT OF SCATTERED SHOWERS/STORMS. MODELS INSISTENT THAT DRY SLOT WILL WORK ITS WAY UP COAST INTO SE NEW ENGLAND...AND DEEPER MOISTURE SHOULD RESIDE ACROSS INTERIOR AS SEEN IN K-INDEX FIELDS. INSTABILITY IS IN QUESTION AS WE ARE NOT CONFIDENT ON HOW MUCH CLEARING WILL OCCUR...IF AT ALL. BUT CONTINUED PRESENCE OF HIGH 0-6KM SHEAR /OVER 35KT/ AND GOOD LOW LEVEL TURNING IN FORECAST HODOGRAPHS SUGGESTS POTENTIAL FOR AT LEAST FEW STRONG OR SEVERE STORMS THIS AFTERNOON. DAMAGING WINDS AND HAIL ARE MAIN THREATS...BUT WE CANNOT RULE OUT AN ISOLATED WEAK TORNADO GIVEN HIGHLY SHEARED ENVIRONMENT...LOW LCL/S AND PRESENCE OF CLOSED UPPER LOW. SYSTEM ALSO HAS HISTORY OF PRODUCING A FEW WEAK TORNADOES THUS FAR AS WELL. GIVEN UNCERTAINTY IN AMOUNT OF HEATING...STAYED CLOSE TO MODEL BLEND FOR HIGHS TODAY /70S TO AROUND 80/ WHICH ALSO MATCHES MIXING TO 850 MB /10-11C/. && .SHORT TERM /TONIGHT THROUGH 6 PM TUESDAY/... COLD FRONT PUSHES THROUGH REGION TONIGHT BRINGING MUCH LESS HUMID AIR BY DAYBREAK AS SKIES CLEAR. LIGHT WINDS WITH LEFTOVER MOISTURE MAY LEAD TO PATCHY FOG ACROSS INTERIOR. RIDGE OF HIGH PRESSURE BUILDS OVER NEW ENGLAND TUE...RESULTING IN PLENTY OF SUNSHINE. NOT MUCH OF AIRMASS CHANGE SO HIGHS ONCE AGAIN SHOULD TOP OFF IN 70S TO AROUND 80 BUT WITH LOW HUMIDITY. WEAK GRADIENT SUPPORTS AFTERNOON SEA BREEZES ALONG BOTH COASTS. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... BIG PICTURE... MODELS CONTINUE TO ADVERTISE A MERIDIONAL TYPE FLOW THROUGH THE WEEK. THE FOUR LOBES OF THIS FLOW ARE THE GULF OF ALASKA TROUGH...WESTERN NORTH AMERICA RIDGE...EASTERN NORTH AMERICA TROUGH...AND WEST ATLANTIC RIDGE. MODELS CONTINUE TO SHOW A WEAK COLD POOL IN EASTERN NO-AM TROUGH...SUFFICIENT TO GENERATE DAILY INSTABILITY SHOWERS. ALSO SHOWERS ALONG THE STALLED FRONT OFFSHORE. THE CORE OF THE EASTERN NO-AM TROUGH EJECTS NORTH THROUGH QUEBEC FRIDAY AND SATURDAY. BUT A WEAKER TROUGH LINGERS OVER THE GREAT LAKES/MISS RIVER VALLEY OVER THE WEEKEND. THE SIMILARITY IN MODEL FIELDS FAVORS A BLEND OF AVAILABLE DATA. THE DAILIES... TUESDAY NIGHT THROUGH FRIDAY... WITH THE UPPER TROUGH TO OUR WEST AND UPPER RIDGE TO OUR EAST...EXPECT THE DEPARTED COLD FRONT TO ALIGN WITH THE UPPER FLOW AND STALL. UPPER FLOW OVER NEW ENGLAND WILL REMAIN FROM THE SOUTHWEST. MEANWHILE COLD POOL INSTABILITY UNDER THE UPPER TROUGH WILL BE OVER NY AND ONTARIO WHILE NEW ENGLAND IS UNDER THE LEFT ENTRANCE REGION OF THE UPPER JET...A SUBSIDENT ZONE. SURFACE HIGH PRESSURE WILL BUILD OVER SOUTHERN NEW ENGLAND. FOR THE MOST PART THIS LOOKS LIKE A DRY WEATHER PERIOD WITH DEWPOINTS IN THE 50S...TRENDING TO THE LOWER 60S FRIDAY. THIS WILL MEAN A CHANCE OF SHOWERS WELL OFFSHORE AND OVER NY/ONTARIO. MAIN CONCERN FOR PRECIPITATION IN SOUTHERN NEW ENGLAND WOULD BE IF SCATTERED DIURNAL SHOWERS/TSTMS FROM THE UPPER TROUGH WHICH COULD SLIDE ACROSS THE BERKSHIRES INTO THE CT VALLEY. SURFACE HIGH PRESSURE AND THE LEFT ENTRANCE REGION OF THE UPPER JET WILL FAVOR SUBSIDENCE AND DRY WEATHER. WE WILL HAVE SLIGHT CHANCE POPS IN THE BERKS WEDNESDAY AND WEST OF MHT-ORH-IJD THURSDAY-FRIDAY...AND CHANCE POPS ALONG/WEST OF THE CT VALLEY THURSDAY-FRIDAY. PATCHY FOG POSSIBLE EACH NIGHT. SATURDAY-SUNDAY... AS THE CORE OF THE UPPER TROUGH LIFTS NORTH...EXPECT THE ATLANTIC HIGH TO SHIFT A LITTLE TO THE WEST. THIS WOULD PUSH THE OFFSHORE FRONT WEST CLOSER TO THE COAST AND BRING AN INCREASE IN THE CHANCE OF SHOWERS...WITH THE BEST CHANCE ON THE CAPE AND ISLANDS. && .AVIATION /07Z MONDAY THROUGH FRIDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. LOW CONFIDENCE THROUGH 12Z...THEN MODERATE CONFIDENCE ON TRENDS BEYOND THAT. CONDITIONS LOWER TO IFR/LIFR THROUGH 12Z AS FOG/LOW CLOUDS BECOME MORE WIDESPREAD. AREA OF SHOWERS/STORMS LIFTING NE FROM NYC AREA WILL REACH CT VALLEY 06Z-08Z AND E MA COAST 08Z-10Z. POTENTIAL FOR GUSTY WINDS...HEAVY RAINFALL AND FREQUENT LIGHTNING. AS THIS ACTIVITY LIFTS INTO NORTHERN NEW ENGLAND BY EARLY AFTERNOON...MVFR CIGS PREVAIL BUT MANY AREAS SHOULD IMPROVE TO VFR BY 18Z. EXCEPTION IS ALONG S COAST WHERE IT WILL TAKE LONGER FOR LOWER CEILINGS TO LIFT. SCATTERED SHOWERS/STORMS SHOULD REDEVELOP ACROSS INTERIOR AFTER 18Z...MAINLY IN SW NH...WESTERN/CENTRAL MA AND N CT. IMPROVING CONDITIONS TO VFR AFTER 00Z TUE...ALTHOUGH PATCHY MVFR/IFR POSSIBLE IN FOG. VFR TUE WITH AFTERNOON SEA BREEZES. KBOS TAF...MODERATE CONFIDENCE. IFR CIGS/VSBYS DEVELOP AS SHOWERS/ISOLATED STORMS ARRIVE AFTER 08Z. FAIRLY CONFIDENT ON IMPROVING CONDITIONS AFTER 15Z. TS SHOULD REMAIN W OF AIRPORT 18Z-22Z. KBDL TAF...MODERATE CONFIDENCE. IFR CIGS/VSBYS DEVELOP AS SHOWERS/STORMS ARRIVE BY 08Z. FAIRLY CONFIDENT IN IMPROVING CONDITIONS AFTER 13Z. TS MOST LIKELY 18Z-22Z. OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY...MODERATE CONFIDENCE. VFR. AREAS OF IFR IN EARLY MORNING FOG EACH DAY. MVFR CIGS/VSBYS IN WIDELY SCATTERED AFTERNOON TSTMS MAINLY WEST OF MHT AND ORH. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. MODERATE CONFIDENCE THROUGH TUE. MAIN CONCERN IS FOR ROUGH SEAS ON S COASTAL WATERS WHERE SCA HAS BEEN EXTENDED INTO TUE. S/SW FLOW PREVAILS TODAY WHICH WILL LEAD TO BUILDING SEAS ON S COASTAL WATERS...REACHING AS HIGH AS 5 OR 6 FT OFFSHORE THIS AFTERNOON. THIS WILL ALSO MAINTAIN PATCHY DENSE FOG THIS MORNING ON S COASTAL WATERS. SHOWERS/STORMS WILL MOVE ACROSS WATERS THIS MORNING FROM LONG ISLAND. SO FAR THESE STORMS HAVE PRODUCED FREQUENT LIGHTNING AND MAY PRODUCE STRONG WIND GUSTS TO 35KT. POSSIBILITY OF A FEW MORE STORMS THIS AFTERNOON...ESPECIALLY ON E MA WATERS. COLD FRONT APPROACHES WATERS TONIGHT BUT EXPECT ANOTHER ROUND OF PATCHY DENSE FOG...AT LEAST EARLY TONIGHT BEFORE DRIER AIR ARRIVES OVERNIGHT. HIGH PRESSURE BUILDS OVERHEAD TUE WITH LIGHT WINDS AND AFTERNOON SEA BREEZES. SEAS SLOWLY SUBSIDE OFFSHORE. OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY...MODERATE CONFIDENCE. SEAS GENERALLY LESS THAN 5 FEET THROUGH THE PERIOD...BUT MAY APPROACH 5 FEET ON THE OUTER WATERS WEDNESDAY NIGHT AND THURSDAY. LIGHT WINDS THROUGH THE PERIOD...SOUTHWEST MIDWEEK SHIFTING TO SOUTHEAST FRIDAY. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 7 AM THIS MORNING TO 2 PM EDT TUESDAY FOR ANZ235-237-250-254>256. && $$ SYNOPSIS...WTB/JWD NEAR TERM...JWD SHORT TERM...JWD LONG TERM...WTB AVIATION...WTB/JWD MARINE...WTB/JWD

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