Area Forecast Discussion
Issued by NWS Boston, MA

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986 FXUS61 KBOX 182258 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 658 PM EDT MON MAY 18 2015 .SYNOPSIS... A CLUSTER OF SHOWERS WILL MOVE ACROSS THE REGION MAINLY TUESDAY MORNING INTO THE EARLY AFTERNOON BEFORE ENDING. OTHERWISE...A FEW STRONG THUNDERSTORMS POSSIBLE LATE TUESDAY AFTERNOON/EVENING ACROSS INTERIOR SOUTHERN NEW ENGLAND IN ASSOCIATION WITH A COLD FRONT. WIDELY SCATTERED SHOWERS ARE POSSIBLE WEDNESDAY...FRIDAY...AND MONDAY. BUT IN GENERAL DRY WEATHER AND SEASONABLE TEMPS ARE EXPECTED FROM MID WEEK THROUGH EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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730 PM UPDATE... STRATUS IS MOVING ASHORE IN THE EAST AND ACROSS THE CAPE AND ISLANDS. EXPECT THIS TREND TO CONTINUE THROUGH THE FIRST PART OF THE NIGHT. LESS CERTAIN AS TO WHETHER THIS WILL TIE IN WITH LOWERING VSBYS IN FOG. PROBABLY WILL BE SOME FOG ALONG THE EAST AND SOUTH COASTS AND AT LEAST SOME LIGHT FOG IN SOME INLAND LOCATIONS. RADAR TRENDS SHOW SHOWERS/TSTMS ACROSS EASTERN AND CENTRAL NEW YORK MOVING NORTHEAST. MUCH OF THIS SHOULD DIMINISH AS IT MOVES EAST EARLY TONIGHT AND INTO A LESS FAVORABLE ENVIRONMENT OVER SOUTHERN NEW ENGLAND. BUT SUFFICIENT INSTABILITY FOR CHANCE POPS OVER WESTERN AND CENTRAL SECTIONS OVERNIGHT. OTHERWISE...DRY WEATHER WITH LOW TEMPS IN THE 50S.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... ***A FEW STRONG TO PERHAPS A MARGINALLY SEVERE THUNDERSTORM OR TWO POSSIBLE ACROSS WESTERN MA/NORTHERN CT BETWEEN 4 AND 10 PM TUESDAY*** TUESDAY AND TUESDAY NIGHT... A CLUSTER OF SHOWERS AND PERHAPS AN EMBEDDED THUNDERSTORM OR TWO WILL MOVE ACROSS THE REGION FROM WEST TO EAST TUE MORNING INTO EARLY AFTERNOON WITH A BURST OF MARGINAL INSTABILITY. THE RAIN SHOULD NOT LAST TOO LONG IN A GIVEN LOCATION AND MOST AREAS SHOULD RECEIVE LESS THAN ONE QUARTER INCH OF RAIN...ALTHOUGH WE CAN/T RULE OUT SOME LOCALLY HIGHER AMOUNTS. OTHERWISE...THINGS DRY OUT FOR THE MOST PART BY MID AFTERNOON. WE SHOULD SEE A FEW HOURS OF PARTIAL CLEARING TAKE PLACE ACROSS THE INTERIOR AHEAD OF A PRE-FRONTAL TROUGH AND ITS ASSOCIATED COLD FRONT. THIS MAY BE ENOUGH TO RESULT IN SOME MARGINAL INSTABILITY OF 500 TO 1000 J/KG TO DEVELOP. THE MAIN CONCERN IS THAT THE 0 TO 6 KM SHEAR VALUES ARE BETWEEN 40 AND 45 KNOTS...WHICH IS QUITE IMPRESSIVE BUT WILL STILL NEED ENOUGH INSTABILITY. WITH ALL THAT SAID...IF WE CAN MUSTER 500+ J/KG OF CAPE IT PROBABLY WILL BE ENOUGH FOR A FEW DECENT STORMS ACROSS WESTERN MA/NORTHERN CT. THE RISK WOULD BE FOR A FEW STRONG TO PERHAPS EVEN A MARGINALLY SEVERE THUNDERSTORM OR TWO. THE MAIN CONCERN WOULD BE VERY LOCALIZED STRONG TO DAMAGING WIND GUSTS WITH HAIL A SECONDARY CONCERN. THE MAIN TIME RISK IS BETWEEN 4 AND 10 PM...BUT AGAIN ITS CONDITIONAL AND DEPENDS ON IF WE CAN MUSTER ENOUGH INSTABILITY. THE ACTIVITY SHOULD WEAKEN AS IT TRIES TO ENTER THE EASTERN HALF OF SOUTHERN NEW ENGLAND WITH A LESS FAVORABLE ENVIRONMENT. THE THREAT FOR ALL PRECIPITATION SHOULD COME TO AN END BY AROUND MIDNIGHT AS MUCH DRIER AIR SWEEPS IN BEHIND THE COLD FRONT. HIGH TEMPS ON TUE ARE TRICKY AND WILL DEPEND ON HOW MUCH PARTIAL CLEARING WE SEE ACROSS THE INTERIOR. CURRENTLY...THINKING A LATE DAY RALLY WITH HIGHS WELL INTO THE 70S IN OUR WESTERN ZONES WITH 60S ACROSS THE SOUTHEAST NEW ENGLAND COAST...WHERE THEY SHOULD REMAIN IN THE CLOUDS. LOWS TUE NIGHT WILL DROP INTO THE UPPER 40S TO MIDDLE 50S. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... BIG PICTURE... THE PATTERN EVOLVES THROUGH THE WEEKEND WITH FLAT FLOW IN THE EASTERN USA GIVING WAY TO A DIGGING TROUGH LATE WEEK. THE TROUGH RELAXS A LITTLE OVER THE WEEKEND. TWO SHORTWAVES MOVE THROUGH THE FLOW...ONE ON WEDNESDAY AND THE SECOND ON FRIDAY. CONTOUR HEIGHTS LOWER BELOW SEASONAL NORMS WEDNESDAY-THURSDAY...THEN RETURN TO NEAR SEASONABLE LEVELS OVER THE WEEKEND. JET PATTERN STARTS WITH NORTHERN AND SOUTHERN STREAMS...BUT THESE MERGE LATER IN THE WEEK IN THE EASTERN USA AS THE UPPER TROUGH DIGS. THE DAILIES... WEDNESDAY... COLD FRONT MOVES WELL OFFSHORE WEDNESDAY WITH COOLER DRIER AIR MOVING INTO NEW ENGLAND. UPPER SHORTWAVE AND COLDER TEMPS/MOISTURE ALOFT WILL GENERATE DIURNAL CU ESPECIALLY ALONG AND NORTH OF THE MASS PIKE. THE AIRMASS IS PROBABLY TOO DRY BELOW 5000 FEET FOR SCATTERED AFTERNOON SHOWERS. MIXING SHOULD REACH 850 MB WHICH WHERE TEMPS OF 1-4C SHOULD SUPPORT MAX SFC TEMPS IN THE 60S. TEMPS COULD REACH 70 IN THE SOUTH ESPECIALLY RI/SOUTHEAST MASS WHERE TEMPS ALOFT MAY BE A LITTLE MILDER OR MIXING A LITTLE DEEPER. WINDS IN THE MIXED LAYER WILL BE 20-25 KNOTS...SO WIND GUSTS SHOULD APPROACH THOSE SPEEDS. WINDS DIMINISH WEDNESDAY NIGHT AS HIGH PRESSURE BUILDS IN. WITH DEW POINTS IN THE 30S...TEMPS SHOULD FALL TO THE 30S IN THE COLDER SPOTS...WITH 40S SOUTH AND EAST. THURSDAY...AFTER THE CHILLY START HIGH PRESSURE SHOULD PROVIDE A FAIR DRY DAY. MIXING SHOULD REACH 800 MB WHERE TEMPS 0-2C SUPPORT MAX SFC TEMPS 65 TO 70. FRIDAY-SATURDAY-SUNDAY... UPPER SHORTWAVE AND CORRESPONDING SURFACE COLD FRONT SWEEP THROUGH ON FRIDAY. THIS MAY CAUSE WIDELY SCATTERED SHOWERS BUT PRECIP WATER VALUES AT OR BELOW 0.5 INCHES SUGGEST A DRY ENVIRONMENT TO OVERCOME. WE USED LOW-END SLIGHT CHANCE POPS FOR THIS PASSAGE. HIGH PRESSURE THEN BUILDS EAST SATURDAY AND PROVIDES DRY WEATHER MUCH OF THE WEEKEND. SUNDAY NIGHT-MONDAY...A COLD FRONT DROPS SOUTH INTO NEW ENGLAND. MODEL CONSENSUS SUGGESTS A FEW SHOWERS MOVING THROUGH THE REGION DURING THIS PERIOD...BUT QUESTIONS ABOUT HOW FAR SOUTH THE FRONT PROGRESSES BEFORE STALLING. WE WILL CONTINUE TO INDICATE A CHANCE OF SHOWERS. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THIS AFTERNOON THROUGH TUESDAY NIGHT/... TONIGHT...MODERATE CONFIDENCE. IFR/LIFR CIGS WITH MARINE STRATUS MOVING ASHORE IN EASTERN MASS. LAST VISIBLE LIGHT PICTURES OF THE DAY ARE SHOWING THE STRATUS ALSO COMING AROUND AND UP TOWARD THE SOUTH COAST. TREND FROM THE CENTRAL HILLS EASTWARD WILL BE FOR AN INCREASE IN 500-1000 FOOT CIGS THE FIRST HALF OF TONIGHT WITH 300-400 FOOT CIGS ON THE CAPE AND ISLANDS. POTENTIAL FOR VSBYS OF 3-5 MILES IN FOG...MAINLY AROUND AND AFTER MIDNIGHT. TREND IN WESTERN SECTIONS WILL BE FOR CLOUDS LOWERS TO MVFR CIGS AND POSSIBLY LOWER IN SPOTS. VSBYS OF 3-5 MILES IN SHOWERS AND AREAS OF FOG. TUESDAY AND TUESDAY NIGHT...MODERATE CONFIDENCE. A CLUSTER OF SHOWERS AND PERHAPS AN EMBEDDED THUNDERSTORM OR TWO ARE EXPECTED TO MOVE ACROSS THE REGION TUE MORNING INTO EARLY AFTERNOON...BEFORE EXITING THE REGION. LOW END MVFR TO IFR CONDITIONS EXPECTED FOR AT LEAST THE MORNING. TEMPORARY IMPROVEMENT TO VFR MAY OCCUR ESPECIALLY ACROSS THE INTERIOR TUE AFTERNOON. A FEW STRONG THUNDERSTORMS MAY WORK INTO WESTERN MA/NORTHERN CT LATE TUE AFTERNOON/EVENING. ISOLATED STRONG WIND GUSTS/HAIL WILL BE POSSIBLE WITH THIS ACTIVITY. EXPECT THE ACTIVITY TO WEAKEN AS IT MOVES INTO EASTERN MA/RI. CONDITIONS THEN IMPROVE TO VFR FROM WEST TO EAST. KBOS TERMINAL...MODERATE CONFIDENCE. LOW CIGS WERE MOVING ASHORE FROM THE EAST JUST BEFORE TAF ISSUANCE AND SHOULD REMAIN IN PLACE MOST OF THE NIGHT. KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. OUTLOOK...WEDNESDAY THROUGH SATURDAY...MODERATE CONFIDENCE. VFR THROUGH THE PERIOD. NORTHWEST WINDS WILL GUST TO 25 KNOTS WEDNESDAY.
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&& .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/... TONIGHT THROUGH TUESDAY NIGHT...HIGH CONFIDENCE. PRESSURE GRADIENT WILL REMAIN WEAK ENOUGH TO KEEP WINDS/SEAS BELOW SMALL CRAFT ADVISORY THRESHOLDS THROUGH TUESDAY NIGHT. THE MAIN CONCERN WILL BE FOR AREAS OF FOG TONIGHT INTO TUESDAY...WHICH MAY BE LOCALLY DENSE. ALSO...A CLUSTER OF SHOWERS AND PERHAPS AN EMBEDDED THUNDERSTORM OR TWO IS POSSIBLE TUE MORNING INTO THE AFTERNOON. OUTLOOK...WEDNESDAY THROUGH SATURDAY...MODERATE CONFIDENCE. WEDNESDAY... INCREASING NORTHWEST WINDS DURING THE DAY. THIS MAY BRING A PERIOD OF GUSTS TO 25 KNOTS DURING THE AFTERNOON. SEAS SHOULD REMAIN BELOW 5 FEET. WILL MONITOR FOR POTENTIAL SMALL CRAFT HEADLINES DUE TO AFTERNOON WIND GUSTS. THURSDAY-FRIDAY... HIGH PRESSURE MOVES OVERHEAD THURSDAY. A WEAK COLD FRONT PASSES THROUGH ON FRIDAY. WINDS AND SEAS SHOULD REMAIN BELOW SMALL CRAFT THRESHOLDS. FRIDAY NIGHT-SATURDAY... NORTHWEST WINDS BEHIND THE COLD FRONT WILL INCREASE AND BRING GUSTS TO 25 KNOTS ACROSS THE WATERS. THIS MAY BRIEFLY BRING SEAS UP TO 5 FEET. A SMALL CRAFT ADVISORY MAY BE NEEDED. && .FIRE WEATHER... WEDNESDAY...COOLER DRIER AIR MOVES IN. THE FORECAST HAS STAYED CLOSE TO MODEL CONSENSUS WHICH BRINGS DEW POINTS DOWN INTO THE 30S WITH RESULTING MINIMUM RELATIVE HUMIDITY PERCENTAGES IN THE 30S. THERE IS SOME CONCERN THAT THIS DATA IS MISSING THE PRESENCE OF DRIER AIR AT 5000 FEET/850 MB...WHERE DEW POINTS ARE FORECAST AT 26-30F DURING THE AFTERNOON. DAYTIME MIXING OF THIS AIRMASS MAY LOWER SURFACE DEW POINTS INTO THE UPPER 20S AND CREATE MIN RH VALUES OF 27-31 PERCENT. ALONG WITH THIS WILL BE EXPECTED WIND GUSTS NEAR 25 KNOTS. SO THE WEATHER PORTION OF THE FIRE WEATHER EQUATION IS INCHING TOWARD HIGHER CONCERN AND WILL NEED TO BE MONITORED. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...WTB/FRANK NEAR TERM...WTB/FRANK SHORT TERM...FRANK LONG TERM...WTB AVIATION...WTB/FRANK MARINE...WTB/FRANK FIRE WEATHER...

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