Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KBOX 222055 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 355 PM EST MON DEC 22 2014 .SYNOPSIS... LOW PRESSURE MOVING UP THE COAST WILL BRING PERIODS OF RAIN TO NEW ENGLAND LATER TONIGHT INTO TUESDAY. THE RAIN MAY BEGIN AS A BRIEF PERIOD OF SNOW OR FREEZING RAIN ACROSS NORTHWEST AND NORTH CENTRAL MASSACHUSETTS. A MUCH STRONGER STORM PASSING WELL TO OUR WEST WEDNESDAY INTO CHRISTMAS MORNING WILL BRING HEAVY RAIN...GUSTY WINDS AND PROBABLY MINOR COASTAL FLOODING. DRY WEATHER RETURNS CHRISTMAS AFTERNOON INTO SATURDAY. LOW PRESSURE MAY BRING A RETURN TO UNSETTLED WEATHER BY NEXT SUNDAY. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... HIGH PRESSURE OVER THE MARITIMES WITH RIDGING SOUTHWEST ACROSS INTERIOR SOUTHERN NEW ENGLAND. THIS WILL HOLD ONTO SOME LINGERING COLDER AIR AT THE SURFACE. BUT THE AXIS OF THIS DRAINAGE IS FOCUSSED MORE ON VT AND NY...AS PER LOW LEVEL AGEOSTROPIC FLOW...AND THIS IS ALLOWING MODERATION OF THE AIR OVER SOUTHERN NEW ENGLAND. EAST FLOW AT THE SURFACE CONTINUES INTO EASTERN MASSACHUSETTS AND RHODE ISLAND...KEEPING CLOUDS AND SCATTERED SHOWERS OVER THIS REGION EARLY TONIGHT. LOW PRESSURE OFF NORTH CAROLINA MOVES UP THE COAST TONIGHT. THIS WILL TIGHTEN THE PRESSURE GRADIENT AS THE LOW RUNS UP AGAINST HIGH PRESSURE OVER THE MARITIMES...INCREASING THE EAST TO SOUTHEAST FLOW LEADING THE LOW AND APPROACHING SOUTHERN NEW ENGLAND OVERNIGHT. AS THE EAST SOUTHEAST FLOW MOVES OVER OUR AREA IT WILL FLOW OVER THE REMAINS OF THE INTERIOR COLD AIR PROMOTING LOW LEVEL LIFT. THIS SHOULD BRING AN INCREASED CHANCE OF SHOWERS FROM SOUTH TO NORTH OVERNIGHT. THE AIR OVER NORTHERN CT/WESTERN AND CENTRAL MASS MAY BE COLD ENOUGH FOR LIGHT SNOW OR SNOW/RAIN MIX. A BRIEF PERIOD OF FREEZING RAIN MAY TAKE PLACE IN SPOTS IN NORTHWEST MASS. BUT THE TREND WILL BE TOWARD RAIN ALL AREAS BY MORNING. THE CLOUDS AND EAST FLOW WILL KEEP TEMPS FROM FALLING MUCH THIS EVENING...AND MAY HELP A STEADY OR SLOWLY RISING TREND OVERNIGHT. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... TUESDAY... THE SOUTHEAST LOW LEVEL JET WILL MOVE ACROSS SOUTHERN NEW ENGLAND DURING THE DAY. THIS WILL FEED MOISTURE TO MAINTAIN A SATURATED AIRMASS THROUGH MOST OF THE COLUMN...AND BRING OUR BEST CHANCE OF RAIN. THE JET MOVES NORTH OF OUR AREA DURING THE AFTERNOON WHICH WILL BRING DIMINISHING CHANCE OF PCPN. AS WARMER AIR FILLS IN...TEMPERATURES WILL MODERATE FURTHE WITH VALUES MOSTLY IN THE 40S. THE STEADY SOUTHEAST FLOW WILL BE 15-25 MPH WITH SOME HIGHER GUSTS POSSIBLE. THIS WINDS COMES AFTER A STEADY EAST FLOW TODAY WHICH HAS PUSHED THE OCEAN TOWARD THE EAST MASS COAST. THIS SUGGESTS BUILDING OCEAN LEVELS NEARSHORE...WITH SOME MINOR COASTAL FLOODING CONCERNS ALONG THE EAST MASSACHUSETTS COAST. THE BEST CHANCE WOULD BE AROUND BOSTON HARBOR AND NEAR SCITUATE. TUESDAY NIGHT... THE SOUTHEAST JET MOVES OFF TO THE NORTH. WE WILL CONTINUE TO HAVE A MOIST AIRMASS WITH WARM ADVECTION AND LOW LEVEL LIFT. THE RESULT WILL BE LINGERING SHOWERS AND DRIZZLE TUESDAY NIGHT. LOW LEVEL SOUTH JET WILL MOVE UP THE ATLANTIC COAST OVERNIGHT AND REACH SOUTHERN NEW ENGLAND AFTER MIDNIGHT. THIS WILL BRING INCREASED LIFT WHICH WILL MEAN INCREASED COVERAGE OF SHOWERS LATE AT NIGHT. THIS SOUTH JET IS ALSO DRAWING AN ANOMALOUSLY HUMID AIRMASS NORTH WITH PRECIPITABLE WATER VALUES OVER 1.5 INCHES. SHOWERS DEVELOPING LATE TUESDAY NIGHT WILL LIKELY HAVE SOME EMBEDDED DOWNPOURS. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... HIGHLIGHTS... * PERIODS OF RAIN WEDNESDAY INTO XMAS MORNING WILL BE HEAVY AT TIMES * DRY BY CHRISTMAS AFTERNOON BUT WINDY * TEMPS AROUND 60 FOR SOME LATE WED INTO CHRISTMAS MORNING * DRY BUT ABOVE NORMAL TEMPS CONTINUE FRI AND SAT * UNSETTLED WEATHER MAY RETURN BY SUN BUT LOW CONFIDENCE DETAILS... WEDNESDAY INTO CHRISTMAS... STRONG SHORTWAVE WILL DIG ACROSS THE CENTRAL U.S. AND ALLOW DEEP SOUTH TO SOUTHWEST FLOW ALOFT ACROSS SOUTHERN NEW ENGLAND. THIS WILL SEND AND ANOMALOUS MILD AIRMASS INTO SOUTHERN NEW ENGLAND FOR LATE DECEMBER. GEFS SHOWING PWATS 4 TO 5 STANDARD DEVIATIONS ABOVE NORMAL BY WED NIGHT ACROSS OUR REGION. WHILE HEAVY RAIN IS STILL EXPECTED...THE MODELS HAVE CUT DOWN ON THE QPF IN THE LAST FEW RUNS. THE MAIN LOW STILL PASSES WELL TO OUR WEST ACROSS GREAT LAKES...BUT THEIR SLOWER AND WEAKER WITH SECONDARY DEVELOPMENT ACROSS OUR REGION. THIS RESULTS IN A WEAKER LOW LEVEL JET...HENCE LESS QPF. GIVEN ANOMALOUS PWATS IN PLACE...DO NOT WANT TO COMPLETELY LET OUR GUARD DOWN WITH THE POTENTIAL FOR FLOODING...BUT DOES APPEAR SOMEWHAT LESS OF A RISK THAN YESTERDAY. NONETHELESS...STILL EXPECT TYPICAL NUISANCE POOR DRAINAGE STREET FLOODING. AS FOR TIMING...SOUTHERLY FLOW ALOFT WILL RESULT IN SCATTERED SHOWERS TUE NIGHT. BULK OF THE RAIN WILL OCCUR WED INTO EARLY CHRISTMAS DAY WHEN STRONGEST FORCING COINCIDES HIGH PWAT AIRMASS. SOME OF THIS RAIN WILL BE HEAVY AT TIMES MAY RESULT IN NUISANCE POOR DRAINAGE STREET FLOODING. STILL A LOW RISK FOR MORE SIGNIFICANT FLOODING GIVEN EXTREMELY HIGH PWATS...BUT SLOWER DEVELOPMENT OF SECONDARY LOW PRESSURE MAY BE A LIMITING FACTOR. REGARDLESS... EXPECT 1 TO 3 INCHES OF RAIN. WILL CONTINUE TO MENTION A SLIGHT CHANCE OF THUNDER WITH SHOWALTER INDICES NEAR ZERO. THE BULK OF THE RAIN SHOULD COME TO AN END CHRISTMAS MORNING WITH TEMPS PROBABLY AROUND 60 FOR MUCH OF THE REGION. WHILE GUSTY SOUTHERLY WINDS ARE EXPECTED WED NIGHT...INVERSION AND WEAKER LOW LEVEL JET WILL PROBABLY KEEP MOST AREAS BELOW ADVISORY CRITERIA. STILL HAVE TO WATCH FOR A SMALL WINDOW ON THE COASTAL PLAIN ESP IF TEMPS CAN EXCEED 60...BUT HIGHER CONFIDENCE IN WIND ON CHRISTMAS AFTERNOON AND EVENING BEHIND THE SYSTEM. INCREASING WESTERLY WIND ALOFT AND STEEPENING LAPSE RATES WILL BRING THE POTENTIAL FOR THESE WINDS. DECENT SHOT AT A PERIOD OF 35 TO 50 MPH GUSTS BEHIND THIS SYSTEM CHRISTMAS AFTERNOON AND EVENING. WHILE THE GFS IS AN OUTLIER...IT WOULD EVEN SUGGEST THE POTENTIAL FOR HIGH WIND CRITERIA TO BE MET WITH 70 KNOTS AT 850 MB. THAT MAY BE OVERDONE...BUT SOMETHING WILL HAVE TO KEEP AN EYE ON THE NEXT FEW DAYS. FRIDAY AND SATURDAY... UPPER LEVEL RIDGE OFF THE SOUTHEAST COAST WILL KEEP KEEP US IN MILD SOUTHWEST FLOW ALOFT. DRY WEATHER EXPECTED WITH FORCING FOR ANY PRECIPITATION WILL TO OUR NORTHWEST. HIGHS MAINLY IN THE 40S TO LOWER 50S. SUNDAY... CONFIDENCE IN THE FORECAST GOES DOWN CONSIDERABLY OVER THIS TIME. DEVELOPING UPPER LEVEL RIDGING INTO ALASKA WILL SEND THE POLAR JET SOUTHWARD INTO THE CENTRAL U.S. AT THE SAME TIME...UPPER LEVEL RIDGE OFF THE SOUTHEAST COAST WILL TRY TO HANG TOUGH. THE GFS INSISTS ON DRY AND COLDER WEATHER ARRIVING...BUT WERE NOT CONVINCED. GIVEN THE SOUTHEAST RIDGE...IT MAY HOLD THE COLD AIR UP AND ALLOW DEVELOPING LOW PRESSURE TO TRACK NEAR NEW ENGLAND SUN AND SUN NIGHT. THIS COULD BRING RAIN OR SNOW DEPENDING ON ITS TRACK...OBVIOUSLY A WEEK OUT SO PLENTY OF UNCERTAINTY BUT WOULD LEAN TOWARDS ANOTHER SYSTEM AND AWAY FROM THE DRY GFS. && .AVIATION /21Z MONDAY THROUGH SATURDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH TUESDAY/... THROUGH 00Z...MIXED AREAS OF VFR AND MVFR IN THE CONTINUED EAST FLOW ACROSS SOUTHERN NEW ENGLAND. TONIGHT...MODERATE CONFIDENCE. MAINLY MVFR CONDITIONS IN SCATTERED LIGHT RAIN AND SNOW SHOWERS. PATCHES OF LIGHT FREEZING RAIN POSSIBLE LATE TONIGHT ACROSS NW MASSACHUSETTS. TUESDAY...MODERATE CONFIDENCE. MVFR CONDITIONS MAY LOWER TO IFR IN SHOWERS. THE CORE OF THE SHOWERS WILL BE OVER OUR AREA DURING THE MORNING AND EARLY AFTERNOON...WITH VSBYS REDUCED TO 2-3SM IN THE HEAVIER SHOWERS. SHOWERS DIMINISH LATE IN THE DAY WITH VSBYS 5-6 MILES BUT CIGS LINGER AT 1000-1500 FEET. TUESDAY NIGHT...MODERATE CONFIDENCE. AFTER A SHORT PAUSE EARLY IN THE NIGHT...THE CHANCE OF SHOWERS WILL INCREASE AGAIN OVERNIGHT. CIGS WILL BE IFR OR LOW-END MVFR. VSBYS WILL BE 3-4 MILES WITH AREAS OF 2 MILE VSBYS. KBOS TERMINAL...MODERATE CONFIDENCE. KBDL TERMINAL...MODERATE CONFIDENCE. OUTLOOK...WEDNESDAY THROUGH FRIDAY... WEDNESDAY INTO THURSDAY MORNING...MODERATE CONFIDENCE. WIDESPREAD LOW END MVFR TO IFR CONDITIONS EXPECTED IN PERIODS OF HEAVY SHOWERS/LOW CLOUDS AND FOG PATCHES. A PERIOD OF SOUTHERLY WIND GUSTS OF 30 TO 40 KNOTS EXPECTED ON THE COASTAL PLAIN WED NIGHT. LLWS ALSO A CONCERN FOR THE ENTIRE REGION WED INTO EARLY THU. THURSDAY AFTERNOON INTO FRIDAY...MODERATE TO HIGH CONFIDENCE IN MAINLY VFR. HOWEVER...A PERIOD OF WESTERLY 30 TO 45 KNOT WIND GUSTS POSSIBLE THU AFTERNOON AND EVENING. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH TUESDAY NIGHT/...MODERATE TO HIGH CONFIDENCE. HIGH PRESSURE ACROSS QUEBEC AND THE MARITIMES WILL RESULT IN PERSISTENT NORTHEASTERLY TO EASTERLY WINDS ACROSS THE WATERS TONIGHT. LOW PRESSURE MOVING UP THE ATLANTIC COAST WILL TIGHTEN THE PRESSURE GRADIENT A LITTLE TONIGHT...AND MAY ALLOW WINDS TO GUST AROUND 20 KNOTS OR IN THE LOW 20S. THE PERSISTANT ESE FLOW WILL ALLOW SEAS TO BUILD TO 5 FEET ON THE EASTERN OUTER WATERS...WITH 2-4 FEET MOST OTHER WATERS. SMALL CRAFT ADVISORY CONTINUES. APPROACHING SURFACE LOW PRESSURE FROM THE MID-ATLANTIC TONIGHT WILL HELP INCREASE AN EASTERLY LLJ OVER THE WATER TUESDAY. THIS WILL BUILD THE SEAS BETWEEN 5-8 FT. COULD SEE WIND GUSTS BETWEEN 20-30 KTS AS THE FRONT PASSES. THE SMALL CRAFT ADVISORY HAS BEEN EXPANDED ACCORDINGLY. SOUTHEAST WINDS WILL DIMINISH BUT MAINTAIN TRANSPORT OF OCEAN WATER TOWARD THE NEW ENGLAND COASTLINE ESPECIALLY ALONG EASTERN MASSACHUSETTS. EXPECT SEAS AT OR ABOVE 5 FEET ON MANY OF THE SOUTHERN NEW ENGLAND WATERS THROUGH THE NIGHT. WINDS SHOULD GENERALLY BE BELOW SMALL CRAFT THRESHOLDS. OUTLOOK...WEDNESDAY THROUGH FRIDAY...MODERATE CONFIDENCE WEDNESDAY INTO EARLY THURSDAY...INTENSIFYING LOW PRESSURE PASSING WELL TO OUR WEST WILL CAUSE WINDS TO TURN SOUTHERLY AND BECOME GUSTY. SMALL CRAFT WIND GUSTS ARE A LOCK. THE MAIN UNCERTAINTY IS DO WE SEE SOUTHERLY GALES DEVELOP WED NIGHT. STRONG LOW LEVEL JET PRESENT...BUT WE WILL BE DEALING WITH AN INVERSION OVER THE RELATIVELY COOL OCEAN. REGARDLESS...STILL SHOULD SEE AT LEAST A PERIOD OF NEAR GALE FORCE SOUTHERLY WIND GUSTS. LATER THURSDAY INTO FRIDAY...A PERIOD OF WESTERLY GALE FORCE WIND GUSTS APPEARS LIKELY IN THE COLD ADVECTION PATTERN BEHIND THE STORM THU AFTERNOON AND NIGHT. WINDS SHOULD DIMINISH SOME ON FRIDAY. && .TIDES/COASTAL FLOODING... HIGH ASTRONOMICAL TIDES OCCUR TUE AND WED. EAST MASSACHUSETTS COAST: TUESDAY...HIGH TIDE AT BOSTON WILL BE 11.6 FEET AT MIDDAY WITH A SURGE OF 1 TO 1.5 FEET. WINDS WILL BE FROM THE EAST AT 10 TO 15 KNOTS...SO THERE WILL BE ONSHORE FLOW DURING THIS HIGH TIDE. WHILE THIS IS NOTHING TOO STRONG...GIVEN THE HIGH ASTRO TIDE AND PERSISTANCE OF EAST WINDS WE EXPECT SOME SPLASH OVER/MINOR COASTAL FLOODING. CERTAINLY DO NOT EXPECT TO SEE ANY SIGNIFICANT ISSUES. A COASTAL FLOOD ADVISORY HAS BEEN ISSUED FOR THE EAST MASS COASTLINE FOR THIS MIDDAY HIGH TIDE. WEDNESDAY...HIGH TIDE AT BOSTON WILL BE AT 11.7 FEET AT MIDDAY WITH A SURGE OF 1 TO 1.5 FEET. WINDS WILL BE FROM THE SOUTHEAST NEAR 10 KNOTS BUT THERE WILL BE SOME PRESSURE FALLS WITH INTENSIFYING LOW PRESSURE TO OUR WEST. THIS SHOULD BE ENOUGH FOR MORE SPLASH OVER/MINOR COASTAL FLOODING WITH THE HIGH ASTRO TIDES. HOWEVER...DO NOT EXPECT ANY SIGNIFICANT PROBLEMS GIVEN WINDS/SEAS SHOULD BE HELD IN CHECK DURING THE TIME OF HIGH TIDE. SOUTH COAST: WEDNESDAY EVENING...SOUTHERLY WINDS ARE EXPECTED AND ASTRONOMICAL TIDES INCREASE ALONG THE SOUTH COAST. HIGH TIDE IN PROVIDENCE WILL BE 5.2 FEET WEDNESDAY EVENING. 925 MB LLJ STRENGTHENS TO 55-65 KTS WHICH COULD PUSH A 1 TO 2 FOOT SURGE UP ALONG THE SOUTH COAST DURING THE TIME OF HIGH TIDE. THE LOW LEVEL INVERSION WILL PROBABLY HOLD THE STRONGEST WINDS JUST ABOVE THE GROUND...SO THINKING THE RISK IS FOR SPLASH OVER AND MINOR COASTAL FLOODING. THERE STILL IS A LOW RISK FOR MODERATE COASTAL FLOODING...BUT THAT IS OFTEN HARD TO GET IN A NON-TROPICAL SYSTEM ALONG THE SOUTH COAST. && .BOX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...NONE. MA...COASTAL FLOOD ADVISORY FROM 9 AM TO 3 PM EST TUESDAY FOR MAZ007-015-016-019-022. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM 1 AM TO 7 PM EST TUESDAY FOR ANZ231- 232. SMALL CRAFT ADVISORY FROM 1 AM TO 10 AM EST TUESDAY FOR ANZ233- 234. SMALL CRAFT ADVISORY FROM 1 AM TUESDAY TO 6 AM EST WEDNESDAY FOR ANZ235-237-251-256. SMALL CRAFT ADVISORY UNTIL 6 AM EST WEDNESDAY FOR ANZ250-254. SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 6 AM EST WEDNESDAY FOR ANZ255.
-- End Changed Discussion --
&& $$ SYNOPSIS...WTB/FRANK NEAR TERM...WTB SHORT TERM...WTB LONG TERM...FRANK AVIATION...WTB/FRANK MARINE...WTB/FRANK TIDES/COASTAL FLOODING...

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.