Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 130537 AFDBTV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BURLINGTON VT 137 AM EDT SUN APR 13 2014 .SYNOPSIS... A WARM FRONT WILL LIFT NORTH THROUGH THE REGION LATER TONIGHT INTO SUNDAY WITH PERIODS OF SHOWERS AND A FEW THUNDERSTORMS...ESPECIALLY NORTH. AS THE FRONT CLEARS NORTH ON MONDAY...MUCH WARMER AIR WILL SURGE INTO THE REGION WITH WIDESPREAD HIGH TEMPERATURES INTO THE 70S. A COLD FRONT WILL CROSS THE REGION BY TUESDAY BRINGING MODERATE TO LOCALLY HEAVIER RAINFALL TO THE REGION FOLLOWED BY MUCH COOLER WEATHER BY NEXT WEDNESDAY. AS A RESULT OF THE RAINFALL AND EXPECTED SNOW MELT...MANY RIVERS WILL SEE SHARP RISES POSSIBLY INTO FLOOD DURING MONDAY NIGHT INTO EARLY WEDNESDAY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... AS OF 111 AM EDT SUNDAY...MAIN UPDATE ISSUE FOR THE FORECAST HAS BEEN TO INCREASE CLD COVER OVER THE AREA AS REGION MCLDY/CLDY. PRECIP STILL A BIT SLOW TO WORK INTO AREA BUT --RW IN N NY W/ MAIN BATCH STILL A FEW HRS AWAY...INCLUDING TRW. SO HAVE LEFT TIMING ALONE FOR NOW. OTHERWISE FORECAST ON TRACK. PREVIOUS DISCUSSION...HAVE LOWERED POPS A BIT TO DELAY THE ONSET OF THE SHOWERS INTO THE REGION...BUT STILL EXPECTING SHOWER ACTIVITY TO MOVE INTO THE REGION AFTER MIDNIGHT. UPDATED THE GRIDS WITH THE LATEST SURFACE OBSERVATIONS. && .SHORT TERM /6 AM THIS MORNING THROUGH MONDAY NIGHT/... AS OF 345 PM EDT SATURDAY...WARM FRONT THEN SLOWLY CLEARS NORTHWARD THROUGH THE DAYLIGHT HOURS ON SUNDAY. WIDESPREAD AND MOST PERSISTENT SHOWER/SCT T-STORM ACTIVITY SHOULD BE FOCUSED ACROSS THE NRN TIER DURING THE MORNING HOURS...LIFTING NORTH OF THE INTL BORDER BY MID-LATE AFTERNOON AS FORECAST AREA FIRMLY ENTERS THE WARM SECTOR. WITH ONGOING SNOWMELT AND THE THUNDER THREAT...WE`LL HAVE TO MONITOR SOME OF OUR NRN WATERSHEDS CLOSELY TOMORROW (SEE HYDRO SECTION BELOW). OTHERWISE TEMPERATURES BEGIN TO SURGE ON INCREASING SOUTHERLY FLOW. WITH 18-00Z BLENDED 925 MB TEMPS QUITE VARIABLE SW-NE ACROSS THE REGION...TEMPERATURES COULD GET A BIT TRICKY. AT THIS TIME FEEL LATE DAY HIGHS SHOULD CLIMB WELL INTO THE 60S TO LOWER 70S ACROSS THE SOUTHWESTERN HALF OF THE FORECAST AREA...THOUGH REMAIN IN THE UPPER 50S TO LOWER 60S FAR NRN/NERN VT DUE TO PROXIMITY OF DEPARTING WARM FRONT AND GREATER CLOUD COVER. BY MONDAY NIGHT THE ENTIRE FORECAST AREA SOLIDLY ENTERS THE WARM SECTOR OF PARENT SYSTEM WITH BROAD SOUTHERLY FLOW CONTINUING. OTHER THAN A FEW SHOWERS ALONG THE INTL BORDER COUNTIES...A MAINLY DRY NIGHT IS EXPECTED AS TEMPERATURES REMAIN MILD IN THE 50S TO LOCALLY NEAR 60 IN THE CASE OF THE CHAMPLAIN VALLEY. A FEW UPPER 40S POSSIBLE NERN VT. THEN QUITE THE WARM DAY ON TAP FOR MONDAY AS STRONG WRN ATLANTIC RIDGING KEEPS SFC COLD FRONT FAR TO OUR WEST AND STRONG SOUTHERLY FLOW CONTINUES. INDEED...WITH BLENDED 925 MB TEMPS RANGING FROM 14-16C...MOST AREAS SHOULD CLIMB INTO THE 70S...WITH SOME LOCATIONS IN THE CHAMPLAIN AND ST LAWRENCE VALLEYS NEARING THE 80F MARK. THERE COULD BE A FEW ROGUE SHOWERS OR AN ISOLD STORM OR TWO FAR WEST (MAINLY SLV) BY AFTERNOON...BUT DEEPER MOISTURE/BEST DYNAMICAL FORCING WILL HAVE EITHER 1)LIFTED NORTH WITH THE WARM FRONT, OR 2) WILL REMAIN FURTHER WEST WITH THE PRIMARY COLD FRONTAL ZONE. SFC COLD FRONT THEN SLOWLY CREEPS EAST MONDAY NIGHT...WITH WIDESPREAD SHOWER/ISOLD THUNDER ENTERING OUR NRN NY COUNTIES OVERNIGHT. FURTHER EAST...SCT SHOWERS LATER AT NIGHT/TOWARD MORNING INTO VT WITH FAR ERN COUNTIES LIKELY TO REMAIN MOSTLY DRY. LOW TEMP FORECAST TRICKY...BUT USING A BLENDED APPROACH WILL ADVERTISE MILDEST READINGS EAST (50S...LOCALLY NEAR 60F CHAMPLAIN VALLEY) AND UPPER 40S TO AROUND 50 DACKS WESTWARD. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 315 PM EDT SATURDAY...FLOOD WATCH REMAINS IN EFFECT THROUGH 00Z THURSDAY WITH POTENTIAL MINOR TO MODERATE MAIN-STEM RIVER FLOODING. VERY ACTIVE WX DAY ANTICIPATED ON TUESDAY ASSOCIATED WITH MID/UPPER LVL TROF AND SFC BOUNDARY CROSSING OUR CWA. ECMWF/GFS BLEND SHOWS SFC BOUNDARY APPROACHING THE SLV AT 12Z...INTO THE DACKS AT 15Z...CPV AROUND 18Z...AND THRU OUR CWA BY 00Z WEDS...WITH THE NAM SOLUTION 4 TO 8 HOURS SLOWER. FCST CHALLENGE WL BE AREAL COVERAGE/INTENSITY OF SHOWERS WITH EMBEDDED STORMS ASSOCIATED WITH BOUNDARY. MODELS SHOW PWS APPROACHING 1.0" WITH STRONG FGEN FORCING...AND GOOD LLVL CONVERGENCE WITH SOME INSTABILITY PRESENT. THE CONVECTIVE ENVIRONMENT SUPPORTS A HIGH SHEARED WEAK INSTABILITY TYPE PROFILE...SUPPORTING POSSIBLE LOW TOP CONVECTION ALONG THE BOUNDARY. THE TRICKY PART OF THE QPF FCST IS POSITION OF SFC LOW PRES DEVELOPING ALONG THE BOUNDARY...IF THIS OCCURS TO OUR NORTH AND WEST...MUCH LESS QPF ANTICIPATED...BUT IF SECONDARY SFC LOW PRES DEVELOPS ACRS CENTRAL PA AND MOVES DIRECTLY OVERHEAD...MUCH HIGHER QPF WOULD OCCUR. CRNT TRENDS SUPPORT A COMPROMISE BTWN THE TWO SOLUTIONS WITH CWA QPF VALUES RANGING BTWN 0.75 TO 1.25"...LOWEST ACRS THE CPV AND HIGHEST OVER THE DACKS/GREEN MTNS. ALSO...LOCALIZED HEAVIER AMOUNTS WL BE POSSIBLE IN STRONGER CONVECTIVE ELEMENTS ALONG THE BOUNDARY ON TUESDAY MORNING/AFTERNOON. THIS QPF COMBINED WITH ALREADY HIGH RIVER LVLS WL RESULT IN ADDITIONAL MINOR TO MODERATE RIVER FLOODING...ESPECIALLY BY TUES EVENING. GIVEN TIGHTENING THERMAL GRADIENT AND LLVL CAA QUICKLY DEVELOPING BEHIND THE FRNT...SOME OF THIS QPF WL FALL IN THE FORM OF SNOW. THINKING PRECIP WL CHANGE TO SNOW BY 21Z ACRS THE DACKS ABOVE 1500 FT ON TUESDAY AND BY 00Z WEDS ACRS THE CENTRAL/NORTHERN GREENS WITH SOME ACCUMULATION LIKELY ON TUESDAY NIGHT. A WINTER WX ADVISORY MAYBE NEEDED FOR THE MTN ZNS ON TUES NIGHT IF CRNT TRENDS CONTINUE. OTHERWISE...TEMPS WL BE TRICKY ON TUES AND HIGHLY DEPEND UPON POSITION OF BOUNDARY. WL MENTION U60S TO L70S EASTERN VT TO L50S AND FALLING FOR OUR WESTERN SLV/DACKS ON TUESDAY. THINKING EARLY MORNING HIGHS IN THE L/M 60S ON TUES IN THE CPV...QUICKLY FALLING BACK INTO THE U30S TO L40S BY SUNSET. TEMPS DROP BLW FREEZING MOST LOCATIONS BY WEDS MORNING WITH SOME CLRING. SFC HIGH PRES AND DRIER AIR RETURNS ON WEDS THRU FRIDAY...BEFORE NEXT WEAK SYSTEM ARRIVES ON SATURDAY. PROGGED 925MB TEMPS BTWN -5C AND -7C ON WEDS SUPPORT HIGHS ONLY IN THE U20S TO L30S MTNS TO U30S TO MID 40S VALLEYS. TEMPS WL QUICKLY WARM BACK TO NEAR NORMAL ON THURSDAY AND ABOVE NORMAL BY FRIDAY WITH SOUTHERLY WINDS. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/...
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THROUGH 12Z MONDAY...WARM FRONT LIFTING NWD ACROSS NY WILL ALLOW LIGHT RAIN TO DEVELOP AT THE TAF SITES DURING THE PRE-DAWN HOURS. PERIODS OF MVFR VSBY/CIGS ARE POSSIBLE 09-15Z BEFORE BULK OF ACTIVITY LIFTS NORTH OF THE REGION. MODEST ELEVATED INSTABILITY SUGGESTS A SLIGHT CHANCE OF A THUNDERSTORM EMBEDDED WITHIN BROADER AREAS OF PRECIPITATION...BUT PROBABILITY WASN/T SUFFICIENT TO WARRANT SPECIFIC MENTION IN THE TAFS. LIGHT AND VARIABLE WINDS WILL BECOME SOUTH 10-15KTS WITH GUSTS TO 25 KTS AFTER 14-15Z...AND GENERALLY PERSIST THRU SUNSET. CONTINUED MODERATE SOUTH TO SOUTHWEST WINDS FOR SUNDAY NIGHT...BUT WITH VFR CEILINGS (SCT- BKN050-080). OUTLOOK 12Z MONDAY THROUGH THURSDAY...MAINLY VFR MONDAY WITH GUSTY SOUTH WINDS 15-25 KTS. SLOW-MOVING COLD FRONT BRINGS WIDESPREAD RAIN WITH MVFR AND INTERVALS OF IFR CONDITIONS LATE MONDAY NIGHT ACROSS NRN NY...AND THRU MUCH OF TUESDAY ALL TAF SITES. PRECIPITATION MAY MIX WITH OR CHANGE TO WET SNOW BEFORE ENDING AT MPV/SLK LATE TUESDAY NIGHT AS FRONT MOVES EAST OF VT. HIGH PRESSURE BRINGS LIGHTER WINDS AND MOSTLY CLEAR CONDITIONS FOR WED-THU.
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&& .HYDROLOGY... AS OF 345 PM EDT SATURDAY...ENHANCED THREAT OF MAINSTEM RIVER FLOODING WILL EXIST DURING THE SUNDAY-EARLY WEDNESDAY TIME FRAME DUE TO RAINFALL AND SNOWMELT. HIGHEST THREAT OF FLOODING SHOULD INITIALLY OCCUR ACROSS FAR NORTHERN WATERSHEDS SUNDAY AFTERNOON/NIGHT DUE TO SHOWER/STORM ACTIVITY LATE TONIGHT INTO THE FIRST HALF OF SUNDAY. BASIN-AVG QPF DURING THE INITIAL TIME FRAME RANGES FROM 0.33-0.66 INCHES WITH MOST CONCERN ALONG THE CHAZY...MISSISQUOI AND LAMOILLE RIVERS. LESS OF A CONCERN INITIALLY ON BASINS FURTHER SOUTH...BUT LEVELS ARE RUNNING HIGH (CENV1 CASE IN POINT) SO WE`LL HAVE TO KEEP A CLOSE EYE ON THINGS. STILL LOTS OF RIPE SNOW IN THE HIGHER ELEVATIONS TO MELT OUT. SECOND ROUND OF MODERATE/HEAVIER PCPN TO OCCUR LATER MONDAY NIGHT INTO TUESDAY AS SFC COLD FRONT CROSSES REGION. DURING THIS SECOND WAVE...BASIN-AVG QPF RANGES FROM 0.75 TO 1.25 INCHES. THESE AMOUNTS ALONG WITH MORE RAPID SNOMELT GIVES RISE FOR FLOODING CONCERN ACROSS MANY BASINS...INCLUDING THE OTTER CREEK...WINOOSKI...MAD AND PASSUMPSIC TO NAME A FEW. NOT LOOKING AT MAJOR FLOODING AT THIS POINT...BUT MINOR TO LOCALLY MODERATE FLOOD LEVELS ARE CERTAINLY POSSIBLE BY LATER TUESDAY NITO TUESDAY NIGHT/WEDNESDAY MORNING AS WE LOSE MOST OF THE REMAINING SNOWPACK BELOW 2500 FEET. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...FLOOD WATCH THROUGH WEDNESDAY EVENING FOR VTZ001>012-016>019. NY...FLOOD WATCH THROUGH WEDNESDAY EVENING FOR NYZ026>031-034-035- 087. && $$ SYNOPSIS...JMG NEAR TERM...WGH/JN SHORT TERM...JMG LONG TERM...TABER AVIATION...BANACOS HYDROLOGY...JMG

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