Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 291734 AFDBTV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BURLINGTON VT 134 PM EDT FRI AUG 29 2014 .SYNOPSIS... SURFACE HIGH PRESSURE TRANSLATING EASTWARD ACROSS NEW YORK AND NEW ENGLAND WILL BRING PLEASANT AND DRY WEATHER CONDITIONS TO THE NORTH COUNTRY TODAY AND TONIGHT. WARMER AND MORE HUMID WEATHER WILL RETURN FOR THE WEEKEND AS HIGH PRESSURE SHIFTS EAST OF THE REGION AND SOUTH TO SOUTHWEST FLOW DEVELOPS. SATURDAY SHOULD BE PRECIPITATION FREE... BUT SHOWERS AND THUNDERSTORMS ARE LIKELY SUNDAY AFTERNOON AS AN UPPER LEVEL DISTURBANCE MOVES INTO THE REGION FROM THE GREAT LAKES. SOME THUNDERSTORMS ON SUNDAY ARE EXPECTED TO PRODUCE BRIEF HEAVY DOWNPOURS. ABOVE NORMAL TEMPERATURES...WITH VALLEY HIGHS GENERALLY IN THE 80S...WILL CONTINUE THROUGH MOST OF NEXT WEEK. && .NEAR TERM /UNTIL 11 PM THIS EVENING/... AS OF 1240 PM EDT FRIDAY...THE EARLY OVERCAST STRATUS THAT WAS ONCE TRAPPED IN THE CHAMPLAIN VALLEY THIS MORNING HAS SINCE EVOLVED INTO FAIR WEATHER CUMULUS. EXPECTING PARTLY TO MOSTLY SUNNY SKIES FOR THE REMAINDER OF THE DAY UNDER THESE CUMULUS CLOUDS. NO CHANGE TO HIGH TEMPS OF 70-75F. PREVIOUS DISCUSSION FROM 954 AM FRIDAY... HIGH PRESSURE WILL CONTINUE TO CREST OVER THE REGION TODAY BRINGING A MOSTLY SUNNY DAY TO MUCH OF THE AREA. STILL HAVE A LOW STRATUS DECK TRAPPED UNDER THE SUBSIDENCE INVERSION AND NORTHERLY FLOW IN THE CHAMPLAIN VALLEY AND ALONG THE WESTERN SLOPES OF THE GREEN MOUNTAINS. THIS HAS BEEN BEGINNING TO SHRINK OVER THE PAST 1-2 HOURS. ALSO STARTING TO SEE OTHER AREAS MIX OUT AS INDICATED BY DAYTIME CUMULUS FORMING IN PARTS OF EASTERN VERMONT. THUS EXPECTING THE CHAMPLAIN VALLEY STRATUS TO CLEAR OUT AROUND 16Z (NOON). LATEST RAP/HRRR/4KM NAM SUPPORT THIS TIMING AS WELL. TEMPERATURES WARMING UP NICELY IN AREAS THAT ARE SEEING SUN...SO HIGHS FROM 70 TO 75 STILL LOOK GOOD. && .SHORT TERM /11 PM THIS EVENING THROUGH SUNDAY/... AS OF 329 AM EDT FRIDAY...SURFACE HIGH PRESSURE REMAINS IN CONTROL TONIGHT WILL DRIFTING EWD TOWARD THE GULF OF MAINE AFTER MIDNIGHT. AS A RESULT...SHOULD SEE SOME SOUTHERLY RETURN FLOW DEVELOP LATE...ESPECIALLY IN THE CHAMPLAIN VALLEY WITH CHANNELING EFFECTS. WINDS GENERALLY AROUND 10 MPH IN THE CHAMPLAIN VALLEY...BUT WITH STEEP LAPSE RATES OVER LAKE CHAMPLAIN DUE TO WARM LAKE WATERS...WILL SEE THE DEVELOPMENT OF 15-25 KT SOUTH WINDS BY 09Z OVER THE OPEN WATERS OF LAKE CHAMPLAIN. MODELS SUGGEST INCREASING RH IN 300-500MB LAYER...SO WILL LIKELY SEE AN INCREASE IN CIRRUS FROM WEST TO EAST OVERNIGHT. NO PRECIPITATION IS EXPECTED. FOG WILL BE MOST PREVALENT ACROSS THE VALLEYS OF CENTRAL AND ERN VT WHERE WINDS JUST ABOVE THE PBL WILL BE LIGHTEST AND CIRRUS CLOUDS WILL ARRIVE A BIT LATER. OVERNIGHT LOWS WILL GENERALLY BE IN THE LOW-MID 50S...WITH A FEW UPPER 40S IN THE NRN ADIRONDACKS AND FAR NERN VT. SOUTH TO SOUTHWESTERLY LOW-LEVEL FLOW WILL BE IN PLACE ACROSS THE NORTH COUNTRY ON SATURDAY...BETWEEN SFC HIGH PRESSURE DEPARTING TO THE EAST AND A WEAK SFC LOW AND MID- LEVEL TROUGH ACROSS THE GREAT LAKES. MODERATE LOW-TO-MID LEVEL WAA IS PROGGED BY 00Z NAM/GFS...WITH 850MB THERMAL RIDGE OF +15 TO +16C BUILDING INTO THE REGION BY 00Z SUNDAY. ISSUE ON TEMPERATURE WILL BE CLOUDS...AS HIGH 500-300MB RH SUGGESTS FILTERED SUNSHINE THROUGH CIRRUS/ALTOSTRATUS LAYER. ADJUSTED A BIT ABOVE MOS CONSENSUS...WITH HIGHS IN THE 80-83F FOR MOST VALLEY SECTIONS...BUT NOT QUITE AS WARM AS IT COULD BE UNDER FULL SUN. S-SW WINDS GENERALLY 10-15 MPH. WITH MID-LEVEL RIDGING STILL IN PLACE AND NOT MUCH EVIDENCE FOR LOW- LEVEL CONVERGENCE...IT APPEARS SATURDAY WILL REMAIN DRY AREAWIDE...AND WILL KEEP POPS BELOW 15 PERCENT. DEWPOINTS WILL SLOWLY CLIMB...LIKELY REACHING THE UPR 50S. WEAK MID-LEVEL HEIGHT FALLS COMMENCE SATURDAY NIGHT AS MID-LEVEL SHORTWAVE TROUGH PROGRESSES EWD ACROSS THE GREAT LAKES. SHOULD SEE MOSTLY CLOUDY SKIES...WITH A CHANCE FOR A FEW SHOWERS DEVELOPING ACROSS NRN NY...AND PERHAPS FAR NRN VT TOWARD DAYBREAK SUNDAY. CLOUDS AND CONTINUED LIGHT SOUTH WINDS SAT NIGHT...COMBINED WITH WARMER AIR MASS WILL RESULT IN VERY MILD OVERNIGHT LOWS...RANGING FROM THE UPR 50S ACROSS THE CT RIVER VALLEY...TO 65-68F IN THE CHAMPLAIN AND ST. LAWRENCE VALLEYS. SUNDAY LOOKS LIKE THE BEST CHANCE FOR PRECIPITATION OVER THE NEXT SEVERAL DAYS. SHORTWAVE TROUGH PROVIDES MID-LEVEL UVV WHILE WEAK SURFACE-BASED INSTABILITY DEVELOPS WITH DAYTIME HEATING (SBCAPE VALUES OF 500-1000 J/KG). DEEP LAYER SHEAR IS NOT PARTICULARLY IMPRESSIVE...WITH SFC-6KM BULK SHEAR OF ONLY 20-25 KTS. COMBINED WITH ONLY WEAK INSTABILITY WITH ABUNDANT CLOUD COVER IN PLACE...NOT ANTICIPATING ANY SEVERE WEATHER ACTIVITY. THAT SAID...SHOWER AND THUNDERSTORM ACTIVITY WILL GRADUALLY BECOME MORE WIDESPREAD TOWARD AFTERNOON WITH PEAK HEATING. WHILE NOT A "WASHOUT"...THESE SHOWERS COULD BE LOCALLY HEAVY...AS PW VALUES APPROACH 2.00" IN BOTH THE NAM AND GFS. HAVE INCLUDED HEAVY DOWNPOUR MENTION IN THE HAZARDOUS WEATHER OUTLOOK AND IN THE FORECAST GRIDS. DEFINITELY WOULD BE GOOD TO HAVE AN INDOOR BACKUP PLAN FOR ANY PLANNED OUTINGS ON SUNDAY GIVING POTENTIAL FOR BRIEF HEAVY RAINFALL. HIGH TEMPERATURES WILL RANGE FROM THE UPR 70S TO LOWER 80S. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... AS OF 329 AM EDT FRIDAY...FAIRLY ACTIVE WEATHER EXPECTED FOR THE FIRST PART OF THE EXTENDED FORECAST PERIOD...SUNDAY NIGHT THROUGH TUESDAY NIGHT...WITH DRYING TAKING PLACE WEDNESDAY AND THURSDAY. COLD FRONT MOVES ACROSS THE AREA SUNDAY NIGHT AND THUS GOING FORECAST OF LIKELY SHOWERS AND THUNDERSTORMS LOOKS REAL GOOD. NOT MUCH AIR MASS CHANGE BEHIND THE FRONT ON MONDAY AND THUS SUFFICIENT INSTABILITY SHOULD DEVELOP MONDAY AFTERNOON FOR SOME SHOWERS AND STORMS TO DEVELOP. A BRIEF BREAK IN THE CONVECTION TAKES PLACE LATER MONDAY NIGHT AND TUESDAY MORNING BEFORE ANOTHER COLD FRONT MOVES INTO THE REGION TUESDAY AFTERNOON. THUS LOOKING AT ANOTHER CHANCE OF SHOWERS AND THUNDERSTORMS THROUGH TUESDAY EVENING BEFORE DRIER WESTERLY FLOW ALOFT DEVELOPS OVER THE AREA WEDNESDAY AND THURSDAY. THERMAL PROFILE THROUGHOUT THE EXTENDED SUGGESTS DAYTIME HIGHS WILL BE AT OR A FEW DEGREES ABOVE SEASONAL NORMALS. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... THROUGH 18Z SATURDAY...THE EARLIER MVFR CEILINGS PRIMARILY IN THE CHAMPLAIN VALLEY HAVE LIFTED. HAVE SCT-BKN CEILING MADE UP OF SHALLOW DAYTIME CUMULUS, BUT VFR WITH CLOUD BASES GENERALLY 3500-4000FT. ANTICIPATE VFR FOR THE REST OF THE DAY WITH LIGHT/VARIABLE SURFACE WINDS. SHOULD BE VFR OVERNIGHT AS WELL. GUIDANCE INDICATES SLK AND MPV WILL BOTH FOG IN WITH LIFR CONDITIONS. THINK THE COMBINATION OF RELATIVELY DRY AIR NEAR THE SURFACE, INCREASING MID-LEVEL CLOUDS (ESPECIALLY FOR NORTHERN NY) AND STRENGTHENING WINDS A FEW HUNDRED FEET ABOVE THE SURFACE WILL PRECLUDE MUCH IN THE WAY OF FOG. CAN`T TOTALLY RULE IT OUT IN THE VALLEYS OF EASTERN VERMONT, SO THAT MEANS MPV COULD BE IMPACTED. AT THIS POINT THINK IT`S JUST AN MVFR SITUATION FROM ROUGHLY 06-12Z. ON SATURDAY, VFR AREA WIDE WITH INCREASINGLY GUSTY SOUTH/SOUTHWEST WINDS, ESPECIALLY IN THE CHAMPLAIN VALLEY. COULD SEE GUSTS OVER 20KT THERE, LESS ELSEWHERE. OUTLOOK 12Z SATURDAY THROUGH WEDNESDAY... 18Z SAT ONWARD...MAINLY VFR, THOUGH MVFR/BRIEF IFR IN SCATTERED SHOWERS AND THUNDERSTORMS THAT WILL BE MOST NUMEROUS SUNDAY AND PERHAPS AGAIN LATE TUESDAY. && .MARINE... SOUTH WINDS WILL INCREASE SHARPLY ON LAKE CHAMPLAIN TOWARD DAYBREAK SATURDAY...AS THE PRESSURE GRADIENT INCREASES BETWEEN HIGH PRESSURE DEPARTING EAST OF NEW ENGLAND...AND A DEVELOPING LOW PRESSURE SYSTEM ACROSS THE CENTRAL GREAT LAKES. LOOKING AT WINDS 15-20 KNOTS WITH GUSTS TO 25 KNOTS AFTER 5 AM...WITH SUSTAINED SOUTH WINDS 15-25 KNOTS THROUGH MUCH OF THE DAYLIGHT HOURS ON SATURDAY. WAVES OVER THE BROAD PORTION OF LAKE CHAMPLAIN WILL BUILD TO 2 TO 3 FEET SATURDAY MORNING. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...NONE. NY...NONE. && $$ SYNOPSIS...BANACOS NEAR TERM...MUCCILLI SHORT TERM...BANACOS LONG TERM...EVENSON AVIATION...NASH MARINE...TEAM BTV

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