Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 211719 AFDBTV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BURLINGTON VT 119 PM EDT MON JUL 21 2014 .SYNOPSIS... SURFACE HIGH PRESSURE WILL CONTINUE TO BE LOCATED OVER EASTERN NEW ENGLAND TODAY...WITH WARM SOUTHERLY WINDS ACROSS OUR REGION. THIS WILL HELP PUSH TEMPERATURES INTO THE 80S WITH SOME INCREASE IN THE RELATIVE HUMIDITY LEVELS. A POP UP ISOLATED SHOWER WILL BE POSSIBLE DURING THE AFTERNOON HOURS ACROSS NORTHERN NEW YORK AND VERMONT...BUT COVERAGE WILL BE LIMITED. A BETTER CHANCE OF SHOWERS AND THUNDERSTORMS WILL ARRIVE WEDNESDAY AFTERNOON AND EVENING ASSOCIATED WITH A COLD FRONT. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... AS OF 1045 AM EDT MONDAY...BASED ON 06Z GFS MOS AND THE LATEST LAMP GUIDANCE HAVE LOWERED POPS ACROSS THE ADIRONDACKS TO SLIGHT CHANCE FOR THE REMAINDER OF TODAY. A WEAK SHORTWAVE MOVING EAST FROM THE GREAT LAKES WILL BRING A SLIGHT CHANCE FOR SOME SHOWERS AND ISOLATED THUNDERSTORMS ACROSS THE ADIRONDACKS AND A PORTION OF THE NORTHERN GREEN MOUNTAINS THIS AFTERNOON...AS WELL AS THE SAINT LAWRENCE VALLEY. VISIBLE SATELLITE LOOP SHOWING CUMULUS AND MID LEVEL CLOUDS ACROSS MOST OF THE ADIRONDACKS AT THIS TIME. BEST SURFACE CONVERGENCE IS ACROSS THE ADIRONDACKS TODAY. PREVIOUS DISCUSSION FROM 716 AM EDT MONDAY...UPDATED TO REMOVE FOG IN GRIDS AND ADJUSTED CLOUD COVER BASED ON CRNT SATL TRENDS. IR SHOWS MOSTLY CLR SKIES ACRS CENTRAL/EASTERN VT...WITH SOME MID/UPPER LVL CLOUDS ACRS THE DACKS. OTHERWISE...REST OF FCST IN GOOD SHAPE. FCST CHALLENGE TODAY WL BE SLIGHT CHCS FOR SHOWERS ACRS MAINLY THE HIGHER TRRN OF THE DACKS INTO EXTREME NORTHERN VT. WATER VAPOR SHOWS A VERY WEAK 5H VORT IN THE WESTERLY FLW ALOFT ACRS THE NORTHERN GREAT LAKES...WHICH IS PROGGED TO BE ACRS NORTHERN NY AROUND 18Z TODAY. THIS COMBINED WITH WEAK SFC CONVERGENCE FROM SOUTHWEST WINDS ACRS THE SLV AND MORE SOUTHERLY WIND COMPONENT ACRS THE EASTERN DACKS...WL INTERACT WITH JUST ENOUGH MID LVL MOISTURE TO PRODUCE A CHC OF SHOWERS. WL MENTION LOW CHC POPS ACRS THE DACKS WITH SCHC ACRS THE NORTHERN GREENS AND SLV. SFC INSTABILITY IS LIMITED WITH CAPE VALUES BTWN 200 AND 400 J/KG...SO THUNDER CHCS WL BE MINIMAL. THINKING CPV/CT RIVER VALLEYS WL STAY RAIN FREE TODAY. PROGGED 85H TEMPS WARM ANOTHER DEGREE OR SO TODAY WITH VALUES AROUND 12C...BUT CUMULUS CLOUD DEVELOP MAY LIMIT SFC HEATING ACRS THE HIGHER TRRN. WL MENTION HIGHS RANGING FROM THE M/U 70S MTNS/NEK TO L/M 80S WARMER VALLEYS...THINKING AROUND 84F FOR BTV. && .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/... AS OF 350 AM EDT MONDAY... AN ACTIVE WEATHER DAY IS EXPECTED ON WEDS...WITH STRONG TO POSSIBLE SVR STORMS. MID/UPPER LVL RIDGE BUILDS FROM THE OHIO VALLEY INTO THE NE CONUS ON TUESDAY...AHEAD OF POTENT S/W ENERGY AND ASSOCIATED TROF ACRS THE NORTHERN PLAINS. THE COMBINATION OF BUILDING HGHTS...WARMING MID LVL TEMPS/CAP...AND VERY DRY SOUNDING PROFILES WL LIMIT PRECIP CHCS ON TUESDAY. WL MENTION JUST SCHC (20%) ACRS THE MTNS...BUT THINKING CWA WL REMAIN DRY. PROGGED 85H TEMPS CLIMB BTWN 15-17C BY 00Z WEDS...SUPPORTING HIGHS IN THE L80S MTNS/NEK TO NEAR 90F CPV/SLV AND LWR CT RIVER VALLEY. THESE TEMPS WITH DWPTS READINGS IN THE 60S...WL RESULT IN HEAT INDEX VALUES IN THE L90S ACRS THE WARMER VALLEY LOCATIONS. A WARM AND MUGGY NIGHT IS EXPECTED ON TUES NIGHT/WEDS MORNING WITH SOUTHERLY FLW AND DWPT TEMPS IN THE 60S. LOWS WL RANGE FROM THE U50S DEEPER MTN VALLEYS TO NEAR 70F IN THE CPV/SLV. MANY INGREDIENTS COMING TOGETHER FOR SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS ON WEDS...WITH SOME STRONG TO POSSIBLY SEVERE. SYNOPTIC SCALE SHOWS DEVELOPING MID/UPPER LVL TROF ACRS THE CENTRAL GREAT LAKES WITH POTENT 5H VORT APPROACHING THE SLV BY 18Z WEDS. THIS TROF WL HELP INCREASE THE MID/UPPER LVL WIND FIELDS ACRS OUR REGION LATE ON WEDS AFTN...WITH 0 TO 6 KM SHEAR VALUES BTWN 30 AND 40 KNOTS. ALSO...HAVE NOTED 500MB WINDS INCREASE TO 40 KNOTS ACRS NNY BY 18Z WEDS. AT THE SFC A WELL DEFINED SFC COLD FRNT WITH CONVERGENCE WL BE LOCATED ACRS THE SLV/NNY AT 18Z...AND THRU MOST OF OUR CWA BY 00Z THURS. THIS TIMING ALONG WITH THE POTENT S/W ENERGY WL BE DURING PEAK HEATING/GREATEST INSTABILITY...HELPING WITH ROBUST UPDRAFTS AND STORM DEVELOPMENT. NAM PROGGED SFC BASED CAPE VALUES ARE BTWN 1500 AND 2000 J/KG WITH LIS VALUES AROUND -5C...WITH SOME HINTS AT A WEAK ELEVATED MIXED LAYER...WITH MODEST MID LVL LAPSE RATES. SOUNDINGS CONT TO SUPPORT A UNIDIRECTIONAL FLW FROM SFC THRU 500MB...RESULTING IN ORGANIZED LINE SEGMENTS OF STORMS/MULTI CELLS. THE PRIMARY SVR WX THREAT WL BE DAMAGING WINDS...WITHIN ANY BOWING LINE SEGMENT. WL UPDATED HWO AND MENTION THE POTENTIAL FOR SVR. STILL ENOUGH UNCERTAINTY IN TIMING OF SYSTEM AND MAGNITUDE OF INSTABILITY/SHEAR TO NOT MENTION SVR IN THE ZONES ATTM. ALSO...WITH PWS BTWN 1.75 AND 1.90" AND WARM CLOUD DEPTHS APPROACHING 12,000 FEET...LOCALIZED HEAVY DOWN POURS WL BE LIKELY. PROGGED 85H TEMPS REMAIN UNCHANGED AHEAD OF BOUNDARY FOR WEDS...AROUND 16C SUPPORTING HIGHS MAINLY IN THE 80S TO AROUND 90 IN THE WARMER VALLEYS. LATE MORNING/EARLY AFTN CUMULUS DEVELOPMENT MAY LIMIT FULL HEATING POTENTIAL. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... AS OF 340 AM EDT MONDAY...FRONTAL BOUNDARY THEN PROGRESSES SLOWLY BUT STEADILY SOUTHWARD WEDNESDAY NIGHT INTO THURSDAY WITH STEADIER SHOWERS/THUNDER EXITING CENTRAL AND SOUTHERN COUNTIES OVERNIGHT INTO THURSDAY MORNING. WILL CARRY HIGH CHANCE TO LIKELY POPS THROUGH THE EVENING HOURS CENTRAL/SOUTH ACCORDINGLY...THEN TAPER OFF THEREAFTER. BEHIND THE FRONT COOLER AND DRIER AIR WILL FILTER SOUTHWARD AS LONGWAVE UPPER TROUGH DIGS SOUTHWARD INTO THE NORTHEASTERN QUARTER OF THE NATION. BY FRIDAY INTO SATURDAY A SECONDARY SFC TROUGH ASSOCIATED WITH THE LARGER-SCALE UPPER TROUGH WILL SETTLE SOUTHWARD INTO THE NORTHERN HALF OF THE FORECAST AREA AND MAY SPARK A FEW SHOWERS...ESPECIALLY ACROSS THE HIGHER TERRAIN. GIVEN RELATIVELY DRY NATURE OF THE PBL WILL CARRY ONLY SLIGHT CHC POPS AT THIS POINT WITH MOST AREAS REMAINING DRY. THEREAFTER MEDIUM RANGE MODELS IN GENERAL AGREEMENT SHOWING THE PRIMARY LONGWAVE TROUGH TO RETROGRADE WESTWARD INTO THE GREAT LAKES AND DEEPEN/AMPLIFY OVER TIME AS MID TO UPPER FLOW TRENDS SOUTHWESTERLY AND GRADUALLY MOISTENS ACROSS NEW YORK/NEW ENGLAND. THUS A GRADUAL INCREASE IN POPS WILL BE OFFERED FROM SUNDAY ONWARD. TEMPERATURES WILL AVERAGE WITHIN +/- 5 DEG OF SEASONAL NORMS THROUGH THE PERIOD WITH COOLEST DAY ON THURSDAY (73-79)...FOLLOWED BY GRADUAL WARMING BY ABOUT 2 DEG PER DAY THEREAFTER. && .AVIATION /18Z MONDAY THROUGH SATURDAY/...
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THROUGH 18Z TUESDAY...VFR CONDITIONS WILL PERSIST THROUGH THE NEXT 24 HOURS. DIURNAL CUMULUS MOST ABUNDANT ACROSS THE HIGHER TERRAIN OF THE DACKS AND GREENS THIS AFTERNOON WILL DISSIPATE THIS EVENING/OVERNIGHT TO SKC...THEN BEGIN TO BUILD AGAIN AFTER 12-14Z TUESDAY. A WEAK DISTURBANCE IN THE FLOW ALOFT MAY SPARK AN ISOLATED SHOWER ACROSS THE DACKS THIS AFTERNOON...BUT COVERAGE NOT ENOUGH TO EVEN MENTION VCSH SO HAVE LEFT OUT OF FORECAST. LIGHT TERRAIN AND LAKE DRIVEN WINDS THIS AFTERNOON ABATE OVERNIGHT AND RETURN AFTER 12Z TUESDAY. OUTLOOK 18Z TUESDAY THROUGH SATURDAY... 18Z TUE - 12Z WED...MAINLY VFR WITH AN ISOLATED TERRAIN DRIVEN SHOWER POSSIBLE TUESDAY AFTERNOON. 12Z WED - 06Z THU...VFR TRENDING TO MVFR/IFR IN SHOWERS/STORMS AS A COLD FRONT TRACKS THROUGH THE REGION...MAINLY WEDS AFTERNOON/NIGHT. SOME STORMS MAY BE STRONG WITH TURBULENCE...GUSTY WINDS AND HAIL. 06Z THU - 00Z FRI...LINGERING MVFR SHOWERS POSSIBLE INTO THURSDAY MORNING...THEN TRENDING MAINLY DRY THEREAFTER AS FRONT SINKS SOUTHWARD AWAY FROM THE AREA. 00Z FRI - 00Z SUN...VFR UNDER SURFACE HIGH PRESSURE. AN ISOLATED AFTERNOON SHOWER ON THE HIGHER TERRAIN IS POSSIBLE.
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&& .BTV WATCHES/WARNINGS/ADVISORIES... VT...NONE. NY...NONE. && $$ SYNOPSIS...TABER NEAR TERM...WGH/TABER SHORT TERM...TABER LONG TERM...LAHIFF AVIATION...JMG

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