Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 301856 AFDBTV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BURLINGTON VT 256 PM EDT SAT MAY 30 2015 .SYNOPSIS... A SLOW MOVING COLD FRONT WILL PRODUCE OCCASIONAL SHOWERS AND THUNDERSTORMS THIS AFTERNOON ACROSS THE NORTH COUNTRY. LOCALIZED HEAVY DOWN POURS...FREQUENT LIGHTNING...AND GUSTY WINDS WILL BE POSSIBLE WITH ANY THUNDERSTORMS. A WIDESPREAD RAINFALL IS EXPECTED TONIGHT INTO SUNDAY...WITH ADDITIONAL SHOWERS ON MONDAY. TEMPERATURES WILL WARM BACK INTO THE 70S AND 80S TODAY...WITH BREEZY SOUTH WINDS...BUT A COOLER AND WETTER PATTERN DEVELOPS FOR SUNDAY INTO EARLY THIS UPCOMING WEEK. && .NEAR TERM /UNTIL 7 PM THIS EVENING/... AS OF 1235 PM EDT SATURDAY...CONVECTIVE FORECAST FOR THIS AFTERNOON/EARLY THIS EVENING STILL ON TRACK. ISOLATED SHOWERS AND THUNDERSTORMS DEVELOPING ACROSS CENTRAL NEW YORK STATE AT 1630Z ARE EXPECTED TO GRADUALLY EXPAND IN COVERAGE AND INTENSITY AS THEY SPREAD NORTHEASTWARD INTO THE NORTHERN ADIRONDACKS AND INTO WESTERN VERMONT DURING THE MID TO LATE AFTERNOON HOURS. ISOLATED DAMAGING WINDS...HEAVY DOWNPOURS...AND DANGEROUS CLOUD TO GROUND LIGHTNING REMAIN THE PRIMARY THREATS. ONLY MINOR ADJUSTMENTS TO GRIDDED FORECASTS FOR THE AFTERNOON AND EVENING HOURS... PREVIOUS DISCUSSION...THE NORTH COUNTRY IS EMBEDDED WITHIN WARM/HUMID LOW-LEVEL AIR MASS WITH MODERATELY STRONG SOUTHERLY TO SOUTHWESTERLY GRADIENT FLOW IN PLACE (BETWEEN SURFACE ANTICYCLONE EAST OF NEW ENGLAND AND STRONG FRONTAL BNDRY ACROSS SWRN QUEBEC INTO SERN ONTARIO). SATELLITE IMAGERY SHOWS MID-LEVEL CLOUDS GRADUALLY ERODING AT 1330Z...AND AREAS WITH FULL SUN IN THE ST. LAWRENCE VALLEY ALREADY CLIMBING INTO THE LOWER 80S AT 14Z WITH SFC DEWPOINTS IN THE LOW TO MID 60S. EXPECTATION BASED ON BTV-4KM WRF AND NCAR 3KM WRF ENSEMBLE IS FOR MULTICELLULAR CONVECTION TO DEVELOP ACROSS CENTRAL NY AND SPREAD NEWD ACROSS NRN NY BY MID- AFTERNOON. GENERALLY LOOKING AT SBCAPE VALUES BETWEEN 1000-2000 J/KG AREAWIDE WITH LITTLE OR NO CIN ACROSS NRN NY INTO THE CHAMPLAIN VALLEY BY 18Z. FORCING IS NOT PARTICULARLY STRONG, WITH BETTER CONVERGENCE TO OUR NW ALONG THE FRONTAL ZONE. DEEP-LAYER SHEAR AND MID- LEVEL LAPSE RATES ARE MARGINAL FOR ORGANIZED SVR THREAT...BUT AMPLE LOW-LEVEL BULK SHEAR WITH 850MB LOW-LEVEL JET AND STEEP SFC BASED LAPSE RATES (FROM INSOLATIONAL HEATING) WILL RESULT IN SOME ROBUST UPDRAFTS THIS AFTERNOON. LOCALIZED DAMAGING WINDS REMAIN POSSIBLE WITH A FEW STRONGER CORES/DOWNDRAFTS. WITH PW VALUES 1.75-1.90" ALSO MAINTAINED MENTION OF LOCALLY HEAVY DOWNPOURS WITH T-STORMS. SOME BACKBULIDING POSSIBLE WITH CORFIDI VECTORS LESS THAN 5 KTS...SO WILL NEED TO MONITOR FOR TRAINING CELLS (THOUGH ANTECEDENT CONDITIONS ARE RELATIVELY DRY FOR ANY RIVER CONCERNS...MAIN ISSUE WOULD BE POOR DRAINAGE FLOODING OR RAPID RISES ON STREAMS IN STEEPER TERRAIN AREAS. LOCALIZED HEAVY RAINFALL IS POSSIBLE WITH ANY STORM. THINKING WIDESPREAD RAINFALL OF 0.50 TO 1.50 WITH LOCALIZED AMOUNTS NEAR 3.0" POSSIBLE. SOME MINOR POOR DRAINAGE/URBAN FLOODING IS POSSIBLE ASSOCIATED WITH THE HIGHER RAINFALL RATES. SOUTH TO SW WINDS WILL REMAIN 15-25 MPH WITH GUSTS 30-35 MPH (HIGHEST IN THE CHAMPLAIN VALLEY AND ST. LAWRENCE VALLEY) THROUGH MID AFTERNOON. FRONTAL BNDRY ARRIVES IN THE ST. LAWRENCE VALLEY BY 02-03Z...WITH NWLY WIND SHIFT AT THAT TIME. && .SHORT TERM /7 PM THIS EVENING THROUGH MONDAY NIGHT/... AS OF 330 AM EDT SATURDAY...SHOWERS AND ISOLATED THUNDERSTORMS WILL QUICKLY DECREASE IN AREAL COVERAGE AND INTENSITY AFT 04Z...WITH MAINLY LIGHT STRATO FORM RAIN LIKELY. SFC BOUNDARY IS EXPECTED TO BECOME STATIONARY ALONG THE MID ATLANTIC STATES/SOUTHERN NEW ENGLAND ON SUNDAY...WHILE ADDITIONAL ENERGY/MOISTURE NOW OVER THE MS RIVER VALLEY STREAMS INTO OUR REGION. THIS POTENT S/W ENERGY AND ASSOCIATED MID/UPPER LVL TROF WILL HELP TO DEVELOP SFC LOW PRES...WHICH WILL TRAVEL ALONG THE BOUNDARY AND ENHANCE RAINFALL ACRS OUR REGION ON SUNDAY AFTN INTO MONDAY. BOTH GFS/NAM SHOW IMPRESSIVE NOSE OF 85H JET OF 40 TO 50 KNOTS LIFTING ACRS CENTRAL NY ON SUNDAY EVENING...ALONG WITH GOOD DEEP LAYER THETA E ADVECTION...AND RRQ OF 25H JET. THIS MOISTURE AND STRONG LIFT WILL PRODUCE ANOTHER ROUND OF MODERATE TO HEAVY RAINFALL. GIVEN THE LACK OF INSTABILITY PER SOUNDINGS...AS WE ARE ON THE COLD SIDE OF FRONT...WITH JUST SOME WEAK ELEVATED INSTABILITY...NOT EXPECTING EXTREME RAINFALL RATES. HOWEVER...IF BOUNDARY LIFTS FURTHER NORTH THAN EXPECTED...SOME HIGHER PRECIP RATES WILL BE POSSIBLE. GIVEN THE AVAILABLE MOISTURE AND EXPECTED LIFT...ANOTHER WIDESPREAD 1 TO 2 INCHES OF RAINFALL IS POSSIBLE SUNDAY NIGHT INTO MONDAY. THIS WILL CAUSE SOME ADDITIONAL RISES ON LOCAL STREAMS AND RIVERS...BUT ONCE AGAIN NOT EXPECTING ANY LARGE STEM RIVER FLOODING. TEMPS WILL BE BELOW NORMAL ON SUNDAY AND MONDAY WITH HIGHS GENERALLY IN THE 50S/60S AND LOWS IN THE 40S TO MID 50S. GIVEN CLOUDS AND PRECIP...AND NORTH WINDS THE DIURNAL CHANGE WILL BE LIMITED. && .LONG TERM /TUESDAY THROUGH FRIDAY/... AS OF 256 PM EDT SATURDAY...WET AND COOL CONDITIONS CONTINUE TO BEGIN THE EXTENDED PERIOD BUT WE TREND DRIER AND BACK TOWARDS SUMMER-LIKE TEMPERATURES FOR MID-WEEK AND INTO NEXT WEEKEND. POTENT UPPER LOW TRACKING EASTWARD FROM GREAT LAKES MONDAY NIGHT INTO THE FORECAST AREA TUESDAY WILL CONTINUE CHANCES FOR RAINFALL ACROSS THE NORTH COUNTRY. ADDITIONAL AMOUNTS OF 0.25-0.5" IS POSSIBLE WITH TEMPERATURE REMAINING COOL WITH HIGHS GENERALLY IN THE MID 50S TO LOW 60S. BY TUESDAY NIGHT THE UPPER LOW SHIFTS EAST OF THE AREA INTO EASTERN CANADA WITH MID-LEVEL HEIGHTS ON THE RISE AS AN UPPER RIDGE BUILDS INTO THE GREAT LAKES. MEANWHILE AT THE SURFACE, HIGH PRESSURE BUILDS SOUTH FROM ONTARIO/QUEBEC AND WILL TAKE RESIDENCE OVER THE NORTHEAST THROUGH THE END OF THE WORK WEEK. THE RESULTING WEATHER WILL FEATURE DRY CONDITIONS, AND A RETURN TO MORE SUMMER-LIKE TEMPERATURES WITH HIGHS THROUGH THE PERIOD STARTING THE UPPER 60S TO LOW 70S FOR WEDNESDAY, WARMING INTO THE UPPER 70S TO LOWER 80S BY FRIDAY. LOWS WILL BE COMFORTABLE AND RIGHT AROUND SEASONAL NORMALS IN THE 40S AND 50S. AS WE LOOK OUT FURTHER TOWARDS NEXT WEEKEND, CHANCE FOR SHOWERS RETURN AS AN UPPER TROUGH OVER JAMES BAY LOOKS TO SLOWLY DRIFT SOUTHWARD TOWARDS THE INTL BORDER ALLOWING A FAST ZONAL FLOW TO SET UP ACROSS THE BTV CWA. NOT A WHOLE LOT OF CONFIDENCE TIMING SHORTWAVE ENERGY PASSING THROUGH THE FLOW THIS FAR OUT, SO WILL LEAN ON MODEL CONSENSUS LOW CHANCE POPS FOR NOW. && .AVIATION /19Z SATURDAY THROUGH THURSDAY/... THROUGH 12Z SUNDAY...GENERALLY VFR CONDITIONS ARE EXPECTED THROUGH 00Z WITH SHOWER/THUNDERSTORM COVERAGE INCREASING AFTER 18Z ACROSS NORTHERN NEW YORK AND AFTER 21Z ACROSS VERMONT. SOME STORMS COULD TURN STRONG WITH GUSTY OUTFLOW WINDS...LIGHTNING AND REDUCED VISIBILITY IN HEAVY DOWNPOURS. AFTER 00Z, THUNDERSTORMS ACTIVITY DISSIPATES TO MORE STRATIFORM SHOWERS WITH FLIGHT CATEGORIES TRENDING TO MVFR FOR THE OVERNIGHT HOURS WITH CIGS GENERALLY 020-030 AND VSBY 3-5SM. EARLY MORNING FROM ABOUT 08-10Z COLD FRONT SHIFTS INTO THE REGION WITH WINDS TURNING FROM SOUTHWEST TO NORTHWEST. WHILE I`VE INDICATED DRIER CONDITIONS IN THE TAFS, CHANCES FOR RAIN CONTINUES AS THE FRONT STALLS OUT OVER THE REGION. OUTLOOK 18Z SUNDAY THROUGH THURSDAY... 18Z SUNDAY THROUGH 00Z WEDNESDAY...PERIODS OF RAIN WITH MVFR CONDITIONS WITH STALLED FRONT OVER AND SOUTH OF THE AREA. 00Z WEDNESDAY THROUGH 00Z FRIDAY...TRENDING TO VFR UNDER BUILDING HIGH PRESSURE. && .MARINE... AS OF 700 AM EDT SATURDAY...A LAKE WIND ADVISORY IS IN EFFECT. SOUTH WINDS WILL BE INCREASING TO 15 TO 25 KTS THIS MORNING...AND MAY REACH 30 KTS ON THE BROAD LAKE THIS AFTERNOON INTO THE EVENING HOURS. THIS DUE TO TIGHTENING PRESSURE GRADIENT IN ADVANCE OF APPROACHING COLD FRONT. WITH PASSAGE OF THE FRONT TONIGHT...WINDS WILL SHIFT INTO THE WEST AND DIMINISH A BIT TO 15 TO 20 KTS. WAVE HEIGHTS WILL BUILD TO 2 TO 4 FEET THIS AFTERNOON. THE THREAT OF SHOWERS AND THUNDERSTORMS WILL BE INCREASING THIS AFTERNOON AND EVENING AS WELL...WITH SHIFTING WINDS...HEAVY DOWNPOURS AND DANGEROUS LIGHTNING POSSIBLE IN ANY THUNDERSTORMS. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...NONE. NY...NONE. && $$ SYNOPSIS...TABER NEAR TERM...BANACOS SHORT TERM...TABER LONG TERM...LAHIFF AVIATION...LAHIFF MARINE...NEILES

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