Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Text Only | 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 030204 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1004 PM EDT WED SEP 2 2015 .SYNOPSIS... A COLD FRONT WILL SWEEP ACROSS NEW ENGLAND THURSDAY AHEAD OF WHICH THERE WILL BE THE CHANCE OF SHOWERS AND THUNDERSTORMS. HIGH PRESSURE FROM CANADA BUILDS OVER NEW ENGLAND FOR THE LABOR DAY WEEKEND. A COLD FRONT OVER CANADA STALLS OVER NORTHERN NEW ENGLAND EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
-- Changed Discussion --
10 PM UPDATE... ONLY SIGNIFICANT CHANGES WERE TO SPEED UP THE DIURNAL TEMP DROP THIS EVENING AS CLEAR SKIES/LIGHT FLOW HAS ALLOWED FOR MORE EFFICIENT RADIATIONAL COOLING. WITH DWPTS HOLDING NEAR THERE LATE AFTERNOON OBSERVED VALUES...SUSPECT AFTER ABOUT 1-2AM WILL SEE MORE WIDESPREAD FOG DEVELOP IN TYPICALLY PRONE VALLEYS/GRASSY SPOTS. PREVIOUS DISCUSSION...MOSTLY CLEAR CONDITIONS UNDER LIGHT WINDS AND HIGH PRESSURE MAKES FOR ANOTHER EVENING OF RADIATIONAL COOLING AND FOG DEVELOPMENT IN TYPICALLY PRONE LOW-LYING LOCATIONS. INCREASING DEWPOINTS WILL AID IN THIS DEVELOPMENT. LIKELY TO SEE A COMBINATION OF VISIBILITIES DOWN TO A HALF-MILE OR LESS AND LOW CLOUDS OF A FEW HUNDRED FEET.
-- End Changed Discussion --
&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... THURSDAY INTO THURSDAY EVENING... MID-LEVEL TROUGH AND ACCOMPANYING IMPULSE ENERGY SWEEP SE ACROSS THE NE CONUS DURING THE AFTERNOON INTO EVENING HOURS. A SURFACE COLD FRONT ALONG THE LEADING EDGE OF REFRESHING COOL-DRY AIRMASS BUILDING REARWARD WILL BECOME THE FOCUS OF SHOWERS AND THUNDERSTORMS ALONG AND AHEAD. EVALUATING THE ENVIRONMENT: DECENT LOW-MID LEVEL THETAE CONVERGENCE AHEAD OF THE COLD FRONT YIELDING A MOISTENING PROFILE OF PWATS 1.50- 1.75 INCHES. CONDITIONALLY UNSTABLE ALOFT...INSTABILITY VALUES BUILD WITH DAYTIME HEATING WITH VALUES OF AROUND 1-2K J/KG AS BOUNDARY- LAYER LAPSE RATES STEEPEN. PER BUFKIT...CAPE PROFILES DEEP AND NOT TOO THIN. INVERTED-V PROFILES AT THE SURFACE. YET SOME THINGS WORTH NOTING IS THE RATHER WEAK SHEAR. BETTER MID- TO UPPER-LEVEL VENTING RESIDES MORE TOWARDS THE NE. PREDOMINANT FLOW...EVEN AT H925-7...IS FORECAST OUT OF THE N AND THERE IS A LACK OF CONVERGENCE ALONG THE FRONT...WHILE ALSO BEING WEAK AROUND 10-15 MPH BETWEEN 0-6 KM. OVERALL IT LOOKS LIKE ALL THE INGREDIENTS NEEDED FOR SHOWERS AND THUNDERSTORMS APPEAR TO BE THERE BUT THIS DOES NOT APPEAR TO BE A STRONG TO SEVERE WEATHER EVENT /ECHOED BY CIPS ANALOGS/ AND NOR DOES IT APPEAR TO BE WIDESPREAD. CERTAINLY MORE FOCUS ALONG THE N-FACING SLOPES OF HIGH TERRAIN AND AS THE COLD FRONT COLLIDES WITH EXPECTED ONSHORE SEA-BREEZES DURING THE DAY. FOCUS ON THE HIGH TERRAIN AND ESPECIALLY ALONG THE E/SE-INTERIOR WITH THE COLD FRONT / SEA-BREEZE COLLISION. GOING BACK TO CIPS ANALOGS AND THE ENVIRONMENT EVALUATION...SHOULD ANY STORMS BECOME STRONG CAN NOT RULE OUT LARGE HAIL AND A DAMAGING WIND THREAT THOUGH THINK THIS WILL BE ISOLATED. THE MAIN THREAT APPEARS TO BE HEAVY RAIN WITH THE DECENT MOIST PROFILE AND FORECAST SLOW-MOVEMENT OF THE STORMS. COULD BE DEALING WITH POOR-DRAINAGE / URBAN FLOODING ISSUES. WILL HOLD OFF ON ANY ENHANCED WORDING IN THE FORECAST WITH THE ISOLATED TO SCATTERED WEATHER IMPACT EXPECTED. A HOT AND HUMID DAY. HIGHS NEAR 90. THURSDAY NIGHT... THE COLD FRONT PUSHES OUT OF OUR AREA TOWARDS THE S/W AS A CANADIAN HIGH AND COOL-DRY AIR BUILDS INTO THE REGION. COULD BE CONTENDING WITH CONTINUED SHOWER / THUNDERSTORM ACTIVITY TOWARDS MIDNIGHT BUT DIMINISHING AS THE MAIN MID-LEVEL ENERGY PUSHES OFFSHORE AWAY FROM BETTER DYNAMICS ALOFT AND WE FIND OURSELVES BENEATH A DRY-SUBSIDING AIRMASS. SURFACE DEWPOINTS CRASH. LOWS DROPPING DOWN AROUND THE LOW- 60S. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... BIG PICTURE... LONG WAVE PATTERN THIS WEEKEND WILL FEATURE A RIDGE OVER THE CENTRAL USA AND TROUGHS OVER THE MARITIMES AND PACIFIC COAST. THIS FLATTENS TO A ZONAL FLOW OVER CANADA AND THE NORTHERN USA BY MIDWEEK. CONTOUR HEIGHTS RUN NORMAL OR SLIGHTLY ABOVE NORMAL. THE SHORTER WAVELENGTHS SHOW A RIDGE BUILDING OVER THE NORTHEAST USA WITH ABOVE NORMAL HEIGHTS. THE RIDGE FLATTENS A LITTLE FOR THE FIRST HALF OF NEXT WEEK BUT SHORTWAVE HEIGHTS REMAIN ABOVE NORMAL. MODEL MASS AND THERMAL FIELDS ARE SIMILAR THROUGH AT LEAST TUESDAY... EVEN WEDNESDAY ISN/T TOO BAD. USING A BLEND OF THESE WOULD BE REASONABLE. THE DAILIES... FRIDAY... THE COLD FRONT MOVES OFF TO THE SOUTH WHILE HIGH PRESSURE BUILDS DOWN FROM CANADA. THIS PRODUCES AN APPRECIABLE N-S PRESSURE GRADIENT ACROSS SOUTHERN NEW ENGLAND WHICH BRING INCREASING NORTHEAST WINDS. THE GRADIENT DIMINISHES IN THE AFTERNOON...SO EXPECT A BREEZY MORNING FOLLOWED BY LIGHTER WINDS IN THE AFTERNOON. MOISTURE PROFILES SHOW LINGERING MOISTURE AT OR BELOW 800 MB SO THERE COULD BE SOME LINGERING CLOUDS IN THE MORNING ESPECIALLY SOUTH OF THE MASS PIKE. BUT THE TREND WILL BE TOWARD A DRYING AIRMASS...SO EXPECT ANY MORNING CLOUDS WILL DISSIPATE DURING THE DAY. MIXING REACHES TO 900 MB...AND TEMPS AT 900 MB WILL BE AT 13-15C. THIS IS SIMILAR TO 8-10C AT 850 MB...SO EXPECT MAX TEMPS IN THE 70S. COULD BE A FEW VALUES AT 80 IN WARM SPOTS SUCH AS THE CT VALLEY. THE ONSHORE FLOW SHOULD BUFFER VALUES IN EASTERN MASS. LABOR DAY WEEKEND... HIGH PRESSURE MOVES OVERHEAD SATURDAY AND SHIFT SOUTH OF OUR AREA FOR SUNDAY AND MONDAY. THE AIR WILL BE DRY AND SUBSIDENT THROUGH THE PERIOD. SO EXPECT CLEAR OR MOSTLY CLEAR SKIES THROUGH THE PERIOD. PERHAPS SOME INCREASING CIRRUS SUNDAY NIGHT AND MONDAY. MIXING CONTINUES TO 900 MB SATURDAY AND SUNDAY... AND TO 850 MB MONDAY. TEMPS AT THESE LEVELS...CONVERTED TO 850 MB VALUES...TREND FROM 10-12C SAT TO 13-15C SUNDAY TO 17-18C MONDAY. SO EXPECT VALUES U70-L80S SATURDAY...80S SUNDAY...AROUND 90 MONDAY. TUESDAY-WEDNESDAY... A COLD FRONT STALLS NORTH OF THE CANADIAN BORDER MONDAY. A SHORTWAVE MOVING TOWARD THE GREAT LAKES DRIVES THE COLD FRONT SOUTH INTO NEW ENGLAND TUESDAY NIGHT. THE FRONT STALLS OVER SOUTHERN NEW ENGLAND AND POSSIBLY DISSIPATES WEDNESDAY. LIMITED MOISTURE IS FORECAST WITH THE FRONT AND MOST OF THAT IS BELOW 750 MB. SO LOOK FOR A FEW CLOUDS AND MAYBE A STRAY SHOWER LATE TUESDAY OR WEDNESDAY. FOR NOW WE WILL MENTION SLIGHT CHANCE POPS IN NORTHERN AND WESTERN SECTIONS. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH THURSDAY NIGHT/...HIGH CONFIDENCE. TONIGHT...VFR. AREAS OF IFR FOG OR LOWER EXPECTED AFTER MIDNIGHT IN THE CT VALLEY...MOSTLY MASS...AND OTHER FOG PRONE LOCATIONS. THURSDAY... VFR. AFTERNOON INTO EVENING SHRA/TSRA. TEMPO MVFR IMPACTS. MAIN THREAT +RA. PERHAPS SOME BREEZY WINDS OUT OF THE N AND/OR HAIL SHOULD ANY TSRA BECOME STRONG. THINKING ISOLATED IMPACTS. LOW CONFIDENCE. SEA-BREEZES DEVELOPING ALONG THE COASTS DURING THE DAY. THURSDAY NIGHT... VFR. SHRA CONCLUDING. N-WINDS PREVAILING. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. SEA-BREEZE FOR THE MIDDAY PERIOD ON THURSDAY. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK /FRIDAY THROUGH MONDAY/...HIGH CONFIDENCE. VFR THROUGH THE PERIOD. AREAS OF EARLY MORNING IFR CIGS/VSBYS POSSIBLE IN FOG SATURDAY AND SUNDAY. STRONG NORTHEAST FLOW FRIDAY GIVES WAY TO LIGHT FLOW OVER THE WEEKEND WITH SEA BREEZES POSSIBLE SATURDAY. INCREASING WEST-SOUTHWEST FLOW SUNDAY-MONDAY. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH THURSDAY NIGHT/...HIGH CONFIDENCE. A COLD FRONT WILL SWEEP THE WATERS LATE THURSDAY INTO THURSDAY NIGHT BEHIND WHICH NE-WINDS WILL INCREASE WITH THE POTENTIAL FOR GUSTS UP TO 25 KTS TOWARDS FRIDAY MORNING. IT MAY BE WORTH CONSIDERING BY THIS TIME A SMALL CRAFT ADVISORY AS WAVES COULD REACH 5-FEET ESPECIALLY OVER THE E-WATERS. MORE IN THE OUTLOOK DISCUSSION. SCATTERED SHOWERS AND THUNDERSTORMS EXPECTED AHEAD OF THE COLD FRONT BUT ARE ANTICIPATED TO BE SUB-SEVERE. CAN NOT RULE OUT A STRONG STORM BUT THE BETTER CHANCE IS ACROSS THE E/SE-INTERIOR AWAY FROM THE COAST. OUTLOOK /FRIDAY THROUGH MONDAY/...HIGH CONFIDENCE. FRIDAY... INCREASING NORTHEAST WIND AS HIGH PRESSURE BUILDS SOUTH FROM CANADA. MODERATE POTENTIAL FOR 25 KNOT WINDS ESPECIALLY FRIDAY MORNING...WHICH MAY DRIVE SEA HEIGHTS OF 5-6 FEET. A SMALL CRAFT ADVISORY MAY BE NEEDED ESPECIALLY OVER THE EASTERN WATERS. SATURDAY THROUGH MONDAY... HIGH PRESSURE BUILDS OVER THE WATERS. WIND AND SEAS DIMINISH TO LIGHT SATURDAY AND SOUTHWEST SUNDAY- MONDAY. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...WTB/SIPPRELL NEAR TERM...DOODY/SIPPRELL SHORT TERM...SIPPRELL LONG TERM...WTB AVIATION...WTB/SIPPRELL MARINE...WTB/SIPPRELL

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