Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 220938 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 437 AM EST MON DEC 22 2014 .SYNOPSIS... A WAVE OF LOW PRESSURE WILL BRING PERIODS OF WET WEATHER MAINLY LATE TONIGHT INTO TUESDAY NIGHT...WHICH MAY BEGIN AS A BRIEF PERIOD OF FROZEN PRECIPITATION 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 WITH ABOVE NORMAL TEMPERATURES EXPECTED CHRISTMAS AFTERNOON INTO SATURDAY. LOW PRESSURE MAY BRING A RETURN TO UNSETTLED WEATHER BY NEXT SUNDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... UPPER LEVEL RIDGE BUILDS AHEAD OF DIGGING MIDWEST TROUGH WITH HIGH PRESSURE REMAINING ANCHORED OVER THE CANADIAN MARITIMES THROUGH TONIGHT. EASTERLY FLOW WILL CONTINUE ONSHORE ALLOWING FOR THE PROFILE TO CONTINUE TO MOISTEN IN THE LOW LEVELS. IF THIS MOISTURE DEEPENS ENOUGH THEN WE COULD SEE LIGHT SHOWERS DEVELOP ESP ACROSS THE MASS EAST COASTLINE. OTHERWISE DRIZZLE MAY BE THE MAIN FACTOR AS THE UPPER LEVELS ARE FAIRLY DRY. OVERALL TODAY WILL BE A COOL AND CLOUDY DAY WITH HIGHS ONLY REACHING IN THE UPPER 30S TO LOW 40S AS CROSS SECTIONS ARE VERY MOIST IN THE LOW LEVELS. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... TONIGHT INTO TOMORROW... *LIGHT FREEZING RAIN IS POSSIBLE ACROSS THE INTERIOR NORTHWEST AND NORTHERN WORCESTER HILLS* A WEAK AREA OF LOW PRESSURE DEVELOPS ALONG A WARM FRONT OFF THE MID ATLANTIC...DRIFTING NORTHWARD TOWARD THE AREA. THIS LOW REMAINS WEAK AS THE WARM FRONT MOVES SLOWLY NORTHWARD TONIGHT INTO TOMORROW. DECENT WARM ADVECTION AHEAD OF THIS WAVE WITH SEVERAL HI-RES GUIDANCE MODELS SHOWS A POTENTIAL FOR COLD AIR DAMMING ACROSS THE INTERIOR INTO TUESDAY MORNING. BIGGEST QUESTION WILL BE THE MOISTURE POTENTIAL...IS THERE ENOUGH TO DEVELOP PRECIP ESP TONIGHT? GUIDANCE DOES SHOW ENOUGH LIFT AHEAD OF APPROACHING SURFACE LOW PER THE GFS/EC SO ANTICIPATE PRECIP TO DEVELOP AND OVERSPREAD ACROSS SOUTHERN NEW ENGLAND. IF THIS PLAYS OUT WITH COLD AIR DAMMING AND WARM AIR ADVECTION...THEN WE COULD SEE FREEZING RAIN/DRIZZLE ACROSS THE INTERIOR NORTHWEST AND NORTHERN WORCESTER HILLS VERY LATE TONIGHT INTO TUESDAY MORNING. A WINTER WEATHER ADVISORY MAY BE NEEDED. AS SURFACE LOW CONTINUES TO MOVE NORTHWARD...AND HIGH PRESSURE OVER EASTERN CANADA...ANTICIPATE AN INCREASING LLJ. THIS SOUTHEASTERLY JET WILL CONTINUE TO FEED MOISTURE INTO THE REGION AND WITH SOUNDINGS SHOW A VERY SATURATED PROFILE COULD SEE NUMEROUS SHOWERS WITH PERHAPS A FEW HEAVY DOWNPOURS. NOTICED GUIDANCE HAS INCREASED THE QPF OVER THE PAST FEW DAYS. AS THE WEAK SURFACE LOW MOVES NORTH OF SOUTHERN NEW ENGLAND...WARM FRONT WILL LIFT NORTHWARD SO ALL PRECIP BY THE LATE MORNING WILL BE IN THE LIQUID FORM. WE COULD ALSO SEE SOME MINOR COASTAL FLOODING CONCERNS ON TUESDAY WITH DUE EASTERLY FLOW INCREASING TO ABOUT 20 TO 25 MPH. SEE BELOW FOR MORE DETAILS. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... HIGHLIGHTS... * PERIODS OF RAIN TUE NIGHT 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... TUESDAY NIGHT 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 /09Z MONDAY THROUGH FRIDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH TUESDAY/... TODAY...HIGH CONFIDENCE. DRIZZLE OR A FEW FLURRIES POSSIBLE ACROSS EAST MASS TERMINALS. OTHERWISE ANY VFR CIGS WILL DROP TO MVFR CONDITIONS THROUGHOUT THE DAY. TONIGHT...MODERATE CONFIDENCE. MAINLY MVFR CONDITIONS CONTINUE IN SCATTERED LIGHT SNOW SHOWERS. LIGHT FZRA POSSIBLE LATE MONDAY NIGHT ACROSS NW MASSACHUSETTS. TUESDAY...MODERATE CONFIDENCE. MVFR CONDITIONS MAY DROP TO IFR WITHIN AND HEAVY RAIN FALL. VSBYS WILL BE REDUCED TO 5SM OR LESS AS WELL. KBOS TERMINAL...MODERATE CONFIDENCE. COULD SEE DRIZZLE LATER TODAY. KBDL TERMINAL...MODERATE CONFIDENCE. OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY... TUESDAY NIGHT 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/...MODERATE TO HIGH CONFIDENCE. HIGH PRESSURE ACROSS QUEBEC AND THE MARITIMES WILL RESULT IN PERSISTENT NORTHEASTERLY TO EASTERLY WINDS ACROSS THE WATERS THROUGH TODAY. THIS WILL BUILD SEAS TO 5FT ON THE EASTERN WATERS DESPITE WIND GUSTS UP TO 20 KNOTS. HAVE CONTINUED SCA. APPROACHING SURFACE LOW PRESSURE FROM THE MID-ATLANTIC TONIGHT WILL HELP INCREASE AN EASTERLY LLJ OVER THE WATER TOMORROW. THIS WILL BUILD THE SEAS BETWEEN 5-8 FT. COULD SEE WIND GUSTS BETWEEN 20-30 KTS AS THE FRONT PASSES. SCA HAS BEEN EXPANDED ACCORDINGLY. OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY...MODERATE CONFIDENCE TUESDAY NIGHT...LONG FETCH EASTERLY FLOW WILL CONTINUE TO RESULT IN SCA SEAS ACROSS THE OUTER-WATERS WITH HIGH PRESSURE MOVING EAST OF THE CANADIAN MARITIMES. WINDS SHOULD GENERALLY BE BELOW SMALL CRAFT THRESHOLDS. 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 FT AT MIDDAY. 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 EXPECT SOME SPLASH OVER/MINOR COASTAL FLOODING. CERTAINLY DO NOT EXPECT TO SEE ANY SIGNIFICANT ISSUES. WEDNESDAY...HIGH TIDE AT BOSTON WILL BE 11.7 FT AT MIDDAY. 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 FT THAT 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... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM 1 AM TO 7 PM EST TUESDAY FOR ANZ231- 232-251-256. SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 7 PM EST TUESDAY FOR ANZ250-254. SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 7 PM EST TUESDAY FOR ANZ255. && $$ SYNOPSIS...DUNTEN/FRANK NEAR TERM...DUNTEN SHORT TERM...DUNTEN LONG TERM...FRANK AVIATION...DUNTEN/FRANK MARINE...DUNTEN/FRANK TIDES/COASTAL FLOODING...FRANK

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