381
FXUS61 KBTV 201721
AFDBTV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
121 PM EDT SAT APR 20 2019
SYNOPSIS
THE POTENTIAL FOR FLOODING WILL EXIST TODAY THROUGH EARLY SUNDAY AS
RIVERS AND STREAMS CONTINUE TO RISE IN RESPONSE TO MODERATE TO HEAVY
RAINFALL AND SNOWMELT. WHILE THE RAINFALL GRADUALLY TAPERS OFF
TODAY...WARM TEMPERATURES IN THE HIGHER ELEVATIONS WILL ALLOW FOR
MORE SNOWMELT AND THUS THE POTENTIAL FOR ADDITIONAL FLOODING ACROSS
THE NORTH COUNTRY.
NEAR TERM /THROUGH SUNDAY/
AS OF 1149 AM EDT SATURDAY...MINOR UPDATE TO CHASE HOURLY TEMPS
BASED ON OBS, WHICH CONTINUE TO SHOW AN EXTREMELY SHARP BOUNDARY
ACROSS OUR CWA. HAVE TRIED TO INTEGRATE SOME HIGH RES DATA INTO
THE HOURLY GRIDS. OTHERWISE, BAND OF MODERATE TO LOCALLY HEAVY
RAINFALL IS QUICKLY MOVING INTO CENTRAL VT, WITH ADDITIONAL
RAINFALL OF 0.25 TO 0.50 ANTICIPATED. VSF REPORTED 0.24 IN THE
PAST 1.5 HOURS. QUICK MOVEMENT OF PRECIP BAND WILL MINIMIZE
FLASH FLOOD THREAT, BUT CONTINUE TO PRODUCE MORE QPF AND ENHANCE
RIVER FLOODING ISSUES.
HAVE UPDATED FORECAST TO INCREASE POPS/QPF ACROSS OUR EASTERN
DACKS INTO MOST OF CENTRAL/SOUTHERN AND EASTERN VT THRU EARLY
AFTERNOON. RADAR SHOWS AN AREA OF MODERATE TO LOCALLY HEAVY
RAINFALL QUICKLY MOVING TOWARD OUR SOUTHERN VT AND EASTERN DACK
ZONES THIS MORNING. THIS MOISTURE IS ASSOCIATED WITH DEEP
TROPICAL MOISTURE PLUME ADVECTING INTO OUR FA ON SOUTH TO
SOUTHEAST FLOW THRU 500MB, AS PW VALUE AT BROOKHAVEN, NY WAS
1.72. THIS MOISTURE PLUME CONTINUES TO ADVECT INTO OUR CWA,
WHILE MID/UPPER LVL DRY SLOT SLOWLY ADVANCES INTO
CENTRAL/NORTHERN NY. THE GOOD NEWS IS THE HEAVIEST ADDITIONAL
QPF WILL OCCUR MOSTLY OVER REGIONS THAT RECEIVED 0.25 TO 0.50 OR
LESS AND THE GENERAL MOVEMENT OF PRECIP IS FAST GIVEN THE
STRONG SOUTH FLOW OF 40 TO 60 KNOTS FROM 850 TO 700MB. HOWEVER,
THE BAD NEWS, IS SOME WEAK INSTABILITY IS PROGGED TO DEVELOP IN
THE WARM SECTOR AND WITH STRONG LOW LEVEL TRRN DRIVEN BOUNDARY
DRAPED ACROSS OUR CWA, THIS WILL ENHANCE RAINFALL AND POTENTIAL
RAINFALL RATES. THINKING ADDITIONAL RAINFALL AMOUNTS OF 0.25 TO
0.75 WILL BE POSSIBLE ACROSS CENTRAL/SOUTHERN AND EASTERN VT
SECTIONS, WITH 0.10 TO 0.30 ACROSS THE EASTERN DACKS INTO
NORTHERN VT. UPSTREAM OBS SHOW GENERALLY 1 HOUR RAINFALL RATES
OF 0.25 TO 0.40, WITH 3 HOUR TOTALS OF 0.50 TO 0.75 ACROSS
NORTHERN NJ AND EASTERN NY. THESE DEEP MOISTURE PLUMES AND
ASSOCIATED QPF AMOUNTS CAN BE EXTREMELY CHALLENGING, ESPECIALLY
GIVEN THE SHARP BOUNDARY ACROSS OUR CWA. THIS ADDITIONAL
RAINFALL SHOULD SLOWLY EXIT OUR NORTHERN AND EASTERN CWA BTWN
18-20Z THIS AFTN. HAVE TRIED TO SLOW THESE TRENDS IN OUR GRIDS.
NEXT DIFFICULT FORECAST IS THE CRNT TEMPS AND ASSOCIATED TRENDS
MOVING FORWARD. CRNTLY VERY SHALLOW LOW LEVEL COLD AIR MASS HAS
ADVECTED DOWN THE SLV/CPV AND INTO PARTS OF NORTHERN/CENTRAL VT,
WHILE SUMMITS AND SOUTHERN CWA REMAINS IN THE WARM SECTOR.
THINKING COLD AIR REMAINS PARKED IN THE SLV, BUT SHOULD MODIFY
SLIGHTLY WHEN THE HEAVIER PRECIP ARRIVES AND MIXES SOME
SLIGHTLY WARMER AIR TOWARD THE SFC, ESPECIALLY CPV. STILL NOT
EXPECTING VERY WARM HIGH TEMPS TODAY IN THE CPV OR SLV.
PREVIOUS DISCUSSION BELOW:
FLOOD WATCH REMAINS IN PLACE. FLOOD WARNINGS HAVE BEEN ISSUED
FOR SEVERAL RIVERS THIS MORNING AS WELL. FOR LATEST FLOOD
WARNINGS AND RIVER FORECASTS PLEASE SEE WEATHER.GOV/BTV. WE
CONTINUE TO EXPECT RISES ON AREA WATERWAYS TO CONTINUE THROUGH
THIS MORNING ACROSS THE ENTIRE AREA. OVER THE PAST 12 TO 18
HOURS GENERALLY A HALF INCH TO ONE INCH OF RAIN HAS FALLEN
ACROSS THE AREA WITH OVER AN INCH IN THE SAINT LAWRENCE VALLEY.
THIS COMBINED WITH SNOWMELT...MOUNT MANSFIELD LOST AT LEAST
EIGHT INCHES OF SNOW YESTERDAY. TEMPERATURES IN THE MOUNTAINS
WILL REMAIN ABOVE FREEZING AND THUS EXPECTING SNOWMELT TO
CONTINUE. THESE FACTORS PLUS SATURATED SOILS SHOULD LEAD TO
ADDITIONAL RISES ON AREA WATERWAYS...LIKELY AT A FASTER RATE
THAN YESTERDAY. RADAR TRENDS SUGGEST STEADIER PRECIPITATION
ACROSS NORTHERN NEW YORK AND THE NORTHERN THIRD OF VERMONT IS
LIFTING NORTH-NORTHEAST INTO CANADA. DEEPER PLUME OF MOISTURE
ACROSS NEW JERSEY AND POINTS SOUTH WILL MOVE NORTHWARD THROUGH
THE MORNING HOURS AND A GOOD PORTION OF VERMONT WILL SEE
ADDITIONAL RAINFALL...ANYWHERE FROM A QUARTER TO NEARLY AN INCH.
AGAIN THIS WILL SUPPORT THE IDEA OF A CONTINUED THREAT FOR
FLOODING. THE DEEPER PLUME OF MOISTURE DOES EVENTUALLY SHIFT
EAST THIS AFTERNOON AND TONIGHT AND THE AREAL COVERAGE OF
PRECIPITATION SHOULD DECREASE NOTICEABLY FROM WEST TO EAST. WITH
THE UPPER TROUGH AXIS STILL TO OUR WEST TONIGHT AND SUNDAY ONE
CANNOT RULE OUT THE POSSIBILITY OF SOME SHOWERS...BUT SHOULD NOT
BE A WIDESPREAD PRECIPITATION EVENT.
WHAT MIGHT ACTUALLY BE THE BIGGEST ISSUE TODAY IS THE
TEMPERATURES. COLDER AIR HAS WORKED DOWN ACROSS MUCH OF NORTHERN
NEW YORK AND INTO WESTERN VERMONT ON NORTH TO NORTHEAST WINDS.
THESE WINDS WILL HOLD IN THE A BETTER PART OF THE DAY TO HELP
KEEP THE COLDER AIR IN PLACE. HOWEVER...CAN SEE THE FLOW TURNING
AROUND LATE IN THE DAY AND SOME LOCATIONS WILL GET A SOUTHERLY
WIND DEVELOPING AND A SURGE OF WARMER AIR WORKS BACK INTO THE
REGION. HIGHS SHOULD REMAIN IN THE 50S ACROSS PARTS OF THE SAINT
LAWRENCE VALLEY...NORTHEAST NEW YORK...AND FAR NORTHWEST
VERMONT WITH HIGHS IN THE 60S ELSEWHERE. LINGERING MOISTURE WILL
KEEP LOW TEMPERATURES TONIGHT IN THE MID 40S TO MID 50S AND
SUNDAY WE SHOULD SEE WARMER TEMPERATURES OVER THE ENTIRE AREA
WITH HIGHS IN THE MID 60S TO LOWER 70S.
SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/
AS OF 404 AM EDT SATURDAY...SHOWERS CONTINUE TO TAPER OFF
SUNDAY NIGHT AS A CUT OFF UPPER LEVEL LOW PUSHES THROUGH THE MID
ATLANTIC AND A WEAK COASTAL LOW PRESSURE SYSTEM STARTS TO
DEVELOP. WITH AN UPPER LEVEL LOW TO OUR SOUTH I SUSPECT WE'LL
STILL SEE SOME SCATTERED SHOWERS BUT THEY WILL BE INCREASINGLY
RELIANT ON SOME OROGRAPHIC HELP. BY MONDAY AFTERNOON THE COASTAL
LOW WILL PUSH INTO THE GULF OF MAINE AND WE SHOULD SEE SOME
RESURGENT SHOWERS PUSH BACK INTO THE NORTH COUNTRY.
SUNDAY NIGHT REMAINS RELATIVELY WARM WITH LOWS IN THE MID TO
UPPER 40S. MONDAY AS SOME NORTHERLY FLOW DEVELOPS WE SHOULD SEE
TEMPS DROPPING FROM THE WEEKEND BUT WE'LL STILL WARM INTO THE
LOW TO MID 60S. MONDAY NIGHT LOWS SHOULD BE A FEW DEGREES COLDER
THAN SUNDAY WITH TEMPS IN THE LOW 40S.
LONG TERM /TUESDAY THROUGH FRIDAY/
AS OF 404 AM EDT SATURDAY...UNSETTLED WEATHER CONTINUES AS THE
THEME FOR THE WEEK. WE'LL HAVE AN UPPER LEVEL CUTOFF LOW THAT
LIFTS INTO MAINE WHILE ANOTHER SHORTWAVE TROUGH DIGS INTO THE
GREAT LAKES. THIS SHOULD BRING ADDITIONAL SHOWERS THROUGH THE
NORTH COUNTRY TUESDAY AFTERNOON THROUGH WEDNESDAY. WE MAY SEE A
BRIEF LULL WEDNESDAY EVENING BEFORE ANOTHER WEAK IMPULSE MOVES
THROUGH ON THURSDAY. THERE REALLY HASN'T BEEN MUCH RUN TO RUN
CONSISTENCY WITH THE MODELS FOR HOW LATE NEXT WEEK PANS OUT.
THERE'S NO BIG SYSTEM AND SO WHILE WE ARE CURRENTLY CARRYING THE
IDEA THAT THERE'S NEARLY A DAILY CHANCE FOR SCATTERED SHOWERS
WE COULD CERTAINLY SEE SOME AREAS THAT JUST STAY DRY THROUGH THE
PERIOD. TEMPERATURES THROUGH NEXT WEEK START ABOVE NORMAL DROP
TOWARDS NEAR NORMAL THROUGH THE MIDDLE OF THE WEEK AND THEN WILL
RETURN ABOVE NORMAL HEADING INTO NEXT WEEKEND.
AVIATION /17Z SATURDAY THROUGH THURSDAY/
THROUGH 18Z SUNDAY...A BAND OF MODERATE TO HEAVY RAIN SHOWERS IS
BEING OBSERVED ACROSS MUCH OF VERMONT THIS AFTERNOON. THIS WILL
BRING VISIBILITIES DOWN TO 2-4 MILES IN THE HEAVIEST OF SHOWERS.
CEILINGS CONTINUE TO REMAIN IN THE 400 TO 1500 FT RANGE AND WILL
LIKELY REMAIN IFR TO MFR THROUGH AT LEAST 00Z BEFORE BEGINNING
TO SLOWLY IMPROVE HEADING INTO THE EVENING AND OVERNIGHT HOURS.
PRECIPITATION WILL TAPER OFF FROM WEST TO EAST THROUGH THE
REMAINDER OF THE AFTERNOON WITH CONDITIONS IMPROVING FIRST AT
KSLK AND LASTLY KMPV. IT APPEARS THAT BY 06Z MOST LOCATIONS
WILL HAVE MIXED OUT THEIR IFR/MFR DECKS WITH A 3500 TO 5000 FT
DECK REMAINING THROUGH THE OVERNIGHT HOURS INTO EARLY SATURDAY
MORNING. WINDS HAVE GENERALLY BEEN LIGHT AND VARIABLE THROUGH
THE DAY SO FAR BUT ONCE THE PRECIPITATION EXITS TO THE EAST,
MOST LOCATIONS WILL PICK UP A DECENT SOUTHERLY WIND AROUND 10
KNOTS WITH A FEW LOCATIONS GUSTING TO 20 KT TOWARD SUNDAY
MORNING.
OUTLOOK...
SUNDAY NIGHT: VFR. NO SIG WX.
MONDAY: MAINLY VFR, WITH AREAS MVFR POSSIBLE. CHANCE SHRA.
MONDAY NIGHT: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. SLIGHT CHANCE
SHRA.
TUESDAY: VFR. CHANCE SHRA.
TUESDAY NIGHT: MAINLY VFR, WITH AREAS MVFR POSSIBLE. LIKELY SHRA.
WEDNESDAY: MAINLY MVFR, WITH AREAS VFR POSSIBLE. CHANCE SHRA.
WEDNESDAY NIGHT: MAINLY MVFR, WITH AREAS VFR POSSIBLE. SLIGHT
CHANCE SHRA, SLIGHT CHANCE SHSN.
THURSDAY: MAINLY VFR, WITH AREAS MVFR POSSIBLE. SLIGHT CHANCE
SHRA.
HYDROLOGY
AS OF 9300 AM EDT SATURDAY...A FLOOD WATCH REMAINS IN EFFECT
UNTIL NOON ON SUNDAY FOR THE ENTIRE NORTH COUNTRY.
RAINFALL YESTERDAY AND EARLY THIS MORNING HAS RANGED FROM 0.25
TO 1.75 INCHES WITH HIGHEST VALUES IN THE SAINT LAWRENCE
VALLEY/NORTHERN DACKS AND MUCH LESS OVER SOUTHERN VT. THIS
RAINFALL COMBINED WITH SNOW MELT HAVE RESULTED IN SHARP RISES ON
MANY STREAMS AND RIVERS, WITH SEVERAL BASINS REACHING FLOOD
STAGE. STILL EXPECTING MAINLY MINOR FLOOD WITH SOME POTENTIAL
FOR A FEW RIVERS TO REACH MODERATE STAGE BY LATER THIS MORNING
INTO EARLY THIS AFTN.
ADDITIONAL RAINFALL AMOUNTS TODAY WILL BE IN THE 0.25 TO 0.75 RANGE
WITH LOCALLY HIGHER AMOUNTS POSSIBLE...ESPECIALLY ACROSS THE
EASTERN DACKS INTO CENTRAL/SOUTHERN AND EASTERN VT MAINLY
THROUGH EARLY THIS AFTERNOON.
MAINSTEM RIVERS MOST AT RISK FOR FLOODING INCLUDE THE
PASSUMPSIC, THE WELLS, THE MISSISQUOI, THE LAMOILLE, THE
WINOOSKI, THE AUSABLE, AND THE SARANAC RIVERS. ADDITIONALLY,
LAKE CHAMPLAIN WILL CONTINUE TO BE NEAR FLOOD STAGE THROUGH THE
WEEKEND.
THOSE WITH INTERESTS IN LOW-LYING OR FLOOD PRONE AREAS SHOULD
ALSO CONTINUE TO MONITOR THE LATEST FORECASTS.
BTV WATCHES/WARNINGS/ADVISORIES
VT...FLOOD WATCH THROUGH SUNDAY MORNING FOR VTZ001>012-016>019.
NY...FLOOD WATCH THROUGH SUNDAY MORNING FOR NYZ026>031-034-035-087.
SYNOPSIS...EVENSON
NEAR TERM...DEAL/TABER
SHORT TERM...DEAL
LONG TERM...DEAL
AVIATION...CLAY
HYDROLOGY...WFO BTV
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