Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 300724 AFDBTV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BURLINGTON VT 324 AM EDT SAT MAY 30 2015 .SYNOPSIS...
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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.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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AS OF 330 AM EDT SATURDAY...FORECAST CHALLENGE WILL BE AREAL COVERAGE OF SHOWERS AND THUNDERSTORMS ALONG WITH POTENTIAL FOR STRONGER STORMS. WATER VAPOR SHOWS A BOARD SOUTHWEST FLW ALOFT WITH PLENTY OF DEEP LAYER MOISTURE ADVECTING INTO OUR REGION...AHEAD OF A SFC COLD FRNT. THIS MOISTURE WILL PRODUCE SOME MID LEVEL CLOUDS TODAY ACROSS OUR CWA...WHICH WILL LIMIT SFC HEATING/INSTABILITY AS LATEST GUIDANCE HAS BACK OFF ON CAPE/INSTABILITY PARAMETERS ACROSS OUR CWA. RAP13/NAM 12 AND GFS SHOW CAPE VALUES BTWN 1000 AND 1500 J/KG...WITH LI`S BTWN -2C AND -4C. SREF GUIDANCE SHOWS CALIBRATED SEVERE CHANCES OF 5 TO 10%...WHILE PROBABILITY OF THUNDERSTORMS FOR TODAY IS BTWN 50 AND 60%. MEANWHILE...LLVL GRADIENT WILL INCREASE THIS AFTN...WITH ENHANCED CHANNELING OF WINDS UP THE CHAMPLAIN AND SAINT LAWRENCE RIVER VALLEYS...HELPING TO PRODUCE 0 TO 3 KM SHEAR PARAMETERS BTWN 20 AND 30 KNOTS. THE BEST DEEP LAYER SHEAR ASSOCIATED WITH MID LEVEL WINDS OF 40 TO 50 KNOTS IS LOCATED WITH MID/UPPER LVL TROF ACRS THE NORTHERN GREAT LAKES/SOUTHERN CANADA THRU THIS AFTN. ITS EXTREMELY DIFFICULT TO DETERMINE STRENGTH OF STORMS THIS AFTN...GIVEN MODEST INSTABILITY AND SHEAR PARAMETERS...BUT THINKING MAINLY A FEW STRONG STORMS...WITH MAYBE AN ISOLATED SEVERE STORM OR TWO. THINKING WINDS IN WEAK BOW LIKE LINE SEGMENTS WOULD BE THE CONVECTIVE MODE. INGREDIENTS ARE NOT LINING UP FOR A MAJOR OR WIDESPREAD OUTBREAK...AS BEST DYNAMICS AND SFC CONVERGENCE WITH FRONT ARRIVES AFT 00Z TONIGHT...WHEN INSTABILITY IS LIMITED. HOWEVER...THIS SCENARIO DOES SUPPORT SEVERAL ROUNDS OF SHOWERS WITH EMBEDDED THUNDERSTORMS AND GIVEN PWS BTWN 1.50 AND 2.0...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...BUT GIVEN HOW DRY ITS BEEN ALL THE MAIN STEM RIVERS WILL BE ABLE TO HANDLE THE RAINFALL. PROGGED 85H TEMPS AROUND 15C SUPPORT HIGHS U70S MTNS TO MID 80S VALLEYS. BREEZY SOUTH TO SOUTHWEST WINDS OF 15 TO 25 MPH CAN BE EXPECTED WITH SOME LOCALIZED HIGHER GUSTS.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/...
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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 PREICP 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.
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&& .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... AS OF 400 PM EDT FRIDAY...RATHER TRANQUIL EXTENDED FORECAST PERIOD FORESEEN BASED ON CONSENSUS OF 00Z GFS/GFS ENSEMBLE MEAN AND 00Z ECMWF. DEEP-LAYER NWLY FLOW ON ERN PERIPHERY OF SFC ANTICYCLONE BUILDING EWD FROM THE GREAT LAKES REGION WILL PROVIDE DRIER CONDITIONS AND MORE SEASONABLE TEMPERATURES TO START THE PERIOD WEDNESDAY NIGHT. ANTICIPATE MOSTLY CLEAR SKIES...AND IF SURFACE WINDS DROP OFF SUFFICIENTLY...SHOULD SEE OVERNIGHT LOWS RANGING FROM NEAR FREEZING IN THE NORTHERN ADIRONDACKS AND FAR NORTHEASTERNVT...TO AROUND 40F IN THE CHAMPLAIN VALLEY REGION. AFOREMENTIONED SURFACE HIGH BUILDS SLOWLY EWD ACROSS THE NORTHEASTERN CONUS PROVIDING PLEASANT/MOSTLY CLEAR CONDITIONS THURSDAY THROUGH AT LEAST THE FIRST HALF OF FRIDAY. HIGHS WILL BE IN THE MID 60S THURSDAY...BEFORE MODERATING BACK INTO THE LOW 70S ON FRIDAY. SOME DIFFERENCES BETWEEN 00Z GFS AND 00Z ECMWF CONCERNING POTENTIAL SHORTWAVE TROUGH MOVING EWD FROM THE GREAT LAKES FRIDAY NIGHT INTO SATURDAY. THE GFS IS MORE ROBUST WITH THIS FEATURE...AND TRACKS STRONGEST UVV ACROSS OUR SRN ZONES LATE FRIDAY NIGHT INTO SATURDAY. THE 00Z ECMWF - ON THE OTHER HAND - KEEPS BEST PRECIPITATION CHANCES TO OUR SOUTH. THE OFFICIAL FORECAST INDICATES SOME INCREASING CLOUDS LATER FRIDAY...FOLLOWED BY 15-30 POPS FOR SHOWER ACTIVITY FRIDAY NIGHT THRU SATURDAY...WITH HIGHEST POP VALUES ACROSS SRN ZONES. CLOUDS COULD KEEP TEMPS IN THE UPR 60S TO AROUND 70F FOR SATURDAY...BEFORE TRENDING WARMING (LOW-MID 70S) WITH BETTER POTENTIAL FOR SUNSHINE ON SUNDAY. && .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... THROUGH 06Z SUNDAY...VFR (POSSIBLE MVFR MIST AT MPV) WITH INCREASING SOUTH WINDS TOWARDS MORNING. PRIMARY AVIATION FOCUS WILL BE IN THE LATTER HALF OF THE TAF PERIOD...DUE TO GUSTY SOUTH WINDS AND POTENTIAL FOR SHOWERS AND THUNDERSTORMS SATURDAY AFTERNOON/EVENING. MOSTLY CLEAR WITH SCT-BKN CIRRUS CLOUDS OVERNIGHT. CONTINUED MID- TO HIGH CLOUDS INTO SATURDAY. STRENGTHENING GRADIENT AHEAD OF SURFACE COLD FRONT SHOULD ALSO ALLOW FOR SOUTHERLY WINDS TO FURTHER INCREASE INTO THE 10-18 KT RANGE WITH GUSTS 25-28 KTS. SHOWER/THUNDERSTORM COVERAGE LIKELY TO BE MORE SCATTERED...BUT SOME COULD TURN STRONG WITH GUSTY OUTFLOW WINDS...LIGHTNING AND REDUCED VISIBILITY IN HEAVY DOWNPOURS. BEST SHOT AT SEEING THIS ACTIVITY AFTER 18Z WOULD BE AT MSS AND SLK...AND AFTER 22Z AT REST OF SITES. OUTLOOK 06Z SUNDAY THROUGH WEDNESDAY... PERIODS OF RAIN SATURDAY NIGHT WITH DEVELOPING N-NW WINDS BEHIND SURFACE COLD FRONT. TRENDING VFR ACROSS NORTHERN AREAS DURING THE DAYLIGHT HOURS SUNDAY...BUT STALLING FRONTAL ZONE MAY RESULT IN POSSIBLE MVFR SHOWERS AT TIMES SUNDAY NIGHT INTO MONDAY...MAINLY FOR RUT/MPV. AVIATION WX CONDITION PREDICTABILITY LOW AT THIS POINT FROM MONDAY NIGHT THRU WEDNESDAY. && .MARINE... AS OF 400 PM EDT FRIDAY...A COLD FRONT WILL MOVE ACROSS THE AREA SATURDAY AFTERNOON AND OVERNIGHT. SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED. A LAKE THUNDERSTORM ADVISORY MAY BE NEEDED FOR LAKE CHAMPLAIN SATURDAY AFTERNOON AND SATURDAY NIGHT. SOUTH WINDS WILL INCREASE TO 15 TO 25 KNOTS ON SATURDAY. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...NONE. NY...NONE. && $$ SYNOPSIS...TABER NEAR TERM...TABER SHORT TERM...TABER LONG TERM...BANACOS AVIATION...RJS/LOCONTO MARINE...NEILES

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