280
FXUS61 KBTV 171132
AFDBTV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
732 AM EDT WED OCT 17 2018
SYNOPSIS
THE COLDEST AIRMASS OF THIS FALL SEASON IS POISED TO MOVE ACROSS THE
NORTH COUNTRY TODAY WITH MAINLY VALLEY RAIN SHOWERS AND HIGH
ELEVATION SNOW SHOWERS. HOWEVER, AS THE ATMOSPHERE COOLS ALOFT THIS
AFTERNOON AND INSTABILITY INCREASES SOME CONVECTIVE SHOWERS WITH
EMBEDDED ICE PELLETS ARE POSSIBLE, EVEN IN THE VALLEYS, BUT LITTLE
ACCUMULATION IS EXPECTED. TONIGHT BRISK NORTHWEST UPSLOPE WINDS WILL
PRODUCE SCATTERED MOUNTAIN SNOW SHOWERS, ALONG WITH CHILLY OVERNIGHT
LOWS IN THE 20S TO LOWER 30S. WINDCHILL VALUES WILL FEEL MUCH
COLDER. A COLD AND BREEZY THURSDAY IS EXPECTED WITH INTERVALS OF
CLOUDS AND SUN.
NEAR TERM /THROUGH THURSDAY/
AS OF 723 AM EDT WEDNESDAY...CRNT RADAR SHOWS LIGHT RAIN ACROSS
PARTS OF NORTHERN NY AND HIGHER TRRN OF VT. I ASSUME SOME SNOW
IS FALLING NEAR THE SUMMITS AS WHITEFACE AND MT MANSFIELD TEMP
IS CURRENTLY 30 DEGREES. NO SIGNIFICANT CHANGES TO FORECAST WAS
MADE WITH THIS UPDATE, AS POPS/TEMPS AND WINDS LOOKED GOOD.
PREVIOUS DISCUSSION BELOW:
WATER VAPOR SHOWS DEEPENING MID/UPPER TROF ACROSS THE GREAT
LAKES WITH EMBEDDED 5H VORT OVER NORTHERN MI, WHILE FAST
CONFLUENT FLOW ALOFT PREVAILS ACROSS OUR FA. THIS POTENT 5H VORT
IS ALIGNED WITH A SFC COLD FRONT LOCATED OVER THE CENTRAL GREAT
LAKES AND WILL IMPACTS OUR CWA WITH A PERIOD OF SHOWERS TODAY.
IN ADDITION, ALIGNED SOUTHWEST SFC TO 850MB FLOW AHEAD OF
APPROACHING BOUNDARY IS HELPING TO ADVECT 925MB TO 775MB LAKE
ENHANCED MOISTURE INTO THE WESTERN DACKS/SOUTHERN SLV THIS
MORNING. HAVE CONTINUED TO MENTION LIKELY POPS FROM DACKS INTO
NORTHERN GREENS NEAR JAY PEAK TO COVER THIS PRECIP. RAP PROGGED
850MB TEMP ANALYSIS PLACES 0C CONTOUR ACROSS OUR CENTRAL CWA, SO
ANTICIPATE SNOW LEVELS NEAR SUMMITS THIS MORNING.
THIS AFTERNOON/EVENING PROFILES BECOME INTERESTING, AS RAPID COOLING
ALOFT OCCURS AND VERY STEEP LOW LEVEL LAPSE RATES DEVELOP WHEN
POTENT ENERGY ARRIVES. SOUNDINGS SHOW SFC TO 750MB LAPSE RATES
>9.0 C/KM, WITH UP TO 100 J/KG OF CAPE, INDICATING THE PRECIP
WILL BE CONVECTIVE IN NATURE. ALSO, SUPPORTING THIS THINKING IS
PROGGED HIGH COMPOSITE REFLECTIVITY FIELDS OFF THE RAP/HRRR/NAM
3KM. THINKING QUICK CONVECTIVE BURST OF SCATTERED SHOWERS THIS
AFTN/EVENING WILL HAVE THE POTENTIAL TO PRODUCE SOME POCKETS OF
ICE PELLETS AS COLD AIR FROM ALOFT IS TRANSFERED TO THE SURFACE
IN THE PRECIP DOWNDRAFTS, EVEN IN THE VALLEYS. ANY ACCUMULATIONS
WILL BE MINIMAL AND PRECIP WILL BE SCATTERED IN NATURE.
PROGGED 850MB TEMPS NEAR 0C SUPPORT HIGHS UPPER 30S TO LOWER 50S
DEPENDING UPON ELEVATION. BY 00Z TONIGHT 925MB TEMPS QUICKLY DROP
BELOW 0C, WHILE 850MB TEMPS ARE BTWN -3C AND -6C, SUPPORTING
LOWERING SNOW LEVELS AS STRONG LOW LEVEL COLD AIR ADVECTION
CONTINUES ON BRISK NORTHWEST WINDS. THINKING SNOW LEVELS WILL BE
AROUND 1500 FEET BY 00Z AND NEAR THE VALLEY FLOOR BY 06Z, BUT
DEEP LAYER MOISTURE IS QUICKLY ERODING AS DRIER AIR DEVELOPS ON
850MB WINDS OF 35 TO 45 KNOTS. SOUNDING SUPPORT GOOD MIXING
OVERNIGHT WITH SFC WIND GUSTS OF 30 TO 35 KNOTS LIKELY, GIVEN
THE MOMENTUM TRANSFER VALUES. THINKING AREAL COVERAGE OF PRECIP
BECOMES CONFINED TO THE TRRN AND DOWNWIND, GIVEN THE UNBLOCKED
FLOW.
EXPECT AS 850MB TEMPS COOL TO NEAR -11C BY 12Z THURSDAY INTERACTS
WITH VERY WARM LAKE CHAMPLAIN WATER TEMPS OF 13C, MODERATE TO
EXTREME INSTABILITY WILL DEVELOP TO HELP ENHANCE CLOUDS AND SOME
LIGHT PRECIP ALONG AND DOWNWIND OF THE GREEN MOUNTAINS LATE TONIGHT
INTO THURSDAY MORNING. HAVE INCREASED CLOUDS AND MENTIONED SCHC TO
CHC POPS IN THE MOUNTAINS OF VT OVERNIGHT WITH SOME LIGHT SNOW
ACCUMULATION POSSIBLE. THINKING TOTAL SNOW ACCUMULATION OF A DUSTING
TO 2 INCHES WITH HIGHEST VALUES TOWARD THE SUMMITS FROM MT MANSFIELD
TO JAY PEAK. LITTLE ACCUMULATION IS EXPECTED IN THE VALLEYS. LOWS
TONIGHT MID TEENS SUMMITS WITH WIND CHILL VALUES BELOW 0F TO LOW/MID
30S CHAMPLAIN VALLEY. A FREEZE WARNING MAYBE NEEDED IN THE CPV,
WHERE THE GROWING SEASON IS STILL ONGOING. DAYSHIFT CAN MAKE FINAL
DECISION.
THURSDAY WILL FEATURE MUCH BELOW NORMAL TEMPS AS DEEP MID/UPPER
LEVEL TROF PREVAILS ACROSS THE NORTHEAST CONUS. THE COMBINATION OF
BUILDING 1034MB HIGH PRES OVER THE OHIO VALLEY AND DEPARTING LOW
PRES OVER NORTHERN MAINE WILL CREATE A BRISK NORTHWEST WIND ACROSS
OUR CWA. THIS COMBINED WITH PROGGED 850MB TEMPS BTWN -9C AND -11C,
SUPPORT HIGHS ONLY IN THE UPPER 20S/LOWER 30S MOUNTAIN TOWNS TO
LOWER 40S NEAR LAKE CHAMPLAIN. SOME LEFTOVER FLURRIES/MOUNTAIN SNOW
SHOWERS ARE POSSIBLE DOWNWIND OF LAKE CHAMPLAIN.
SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY/
AS OF 400 AM EDT WEDNESDAY...THURSDAY NIGHT WILL REMAIN QUIET
WITH SURFACE HIGH PRESSURE RIDGE STILL RIDGING INTO OUR FORECAST
AREA. A WARM FRONT APPROACHES NORTH OF THE INTERNATIONAL BORDER
AND WILL RESULT IN SOME INCREASING CLOUDS ACROSS OUR AREA
DURING THE OVERNIGHT HOURS AND HEADED INTO FRIDAY MORNING. THEN
ON FRIDAY MORE INCREASING CLOUDS AND CHANCE FOR SHOWERS
ESPECIALLY HEADED INTO FRIDAY EVENING AS WARM FRONT MOVES ACROSS
OUR NORTHERN ZONES, ESPECIALLY ALONG THE INTERNATIONAL BORDER.
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
AS OF 410 AM EDT WEDNESDAY...NO BIG CHANGES FOR EXTENDED PORTION
OF THE FORECAST. PRETTY ACTIVE WEATHER WITH BELOW NORMAL
TEMPERATURES. OUR NEXT COLD FRONT AND UPPER TROUGH LOOKS TO
SWING INTO THE REGION FRIDAY NIGHT THROUGH SATURDAY WITH PERHAPS
A REPEAT PERFORMANCE FROM EARLIER IN THE WEEK...LAKE EFFECT AND
GUSTY SOUTHWEST WINDS ON THE FRONT-END FRIDAY NIGHT, FOLLOWED
BY SCATTERED RAIN SHOWERS SATURDAY AND PERHAPS SOME UPSLOPE ON
THE BACK-END SATURDAY NIGHT POST-FRONTAL PASSAGE. HIGH
PRESSURE RETURNS FOR SUNDAY NIGHT INTO MONDAY WITH LOWS BACK IN
THE 20S AND 30S AND HIGHS IN THE 40S, FOLLOWED BY A CHANCE FOR
SHOWERS MONDAY NIGHT INTO TUESDAY ASSOCIATED WITH A WEAK FRONTAL
PASSAGE.
AVIATION /12Z WEDNESDAY THROUGH SUNDAY/
THROUGH 12Z THURSDAY...VFR CONDITIONS AT ALL TAF SITES, EXCEPT
MVFR CIGS AT SLK. THINKING CLOUDS WILL CONTINUE TO LOWER
ACROSS OUR TAF SITES THIS MORNING WITH MAINLY VFR CONDITIONS.
EXPECT AREAL COVERAGE OF PRECIP TO EXPAND BTWN 12-16Z THIS
MORNING WITH POCKETS OF MVFR CIGS POSSIBLE AS A COLD FRONT
SWINGS THRU THE REGION. A BRIEF PERIOD OF IFR CIGS/VIS IS LIKELY
AT SLK BTWN 13-16Z THIS MORNING, AS SOME LAKE ENHANCED MOISTURE
DEVELOPS ON SOUTHWEST FLOW AHEAD OF BOUNDARY. BREEZY TO GUSTY
WINDS WILL DEVELOP FROM THE SOUTHWEST AT 15 TO 25 KNOTS, BEFORE
SHIFTING TO THE NORTHWEST THIS AFTN. A GRADUAL CLEARING TREND
WITH VFR CONDITIONS RETURNS BY 00Z WEDS, EXPECT SOME LINGERING
MVFR CIGS POSSIBLE AT SLK/MPV. ALSO, AS COLDER AIR MOVES OVER
THE RELATIVELY WARMER LAKE CHAMPLAIN WATERS, SOME LOCALIZED MVFR
CIGS ARE LIKELY OVERNIGHT AT BTV TAF SITE.
OUTLOOK...
THURSDAY: VFR. WINDY WITH GUSTS TO 30 KT. NO SIG WX.
THURSDAY NIGHT: VFR. NO SIG WX.
FRIDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. NO SIG WX.
FRIDAY NIGHT: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. CHANCE SHRA.
SATURDAY: MAINLY MVFR, WITH AREAS VFR POSSIBLE. LIKELY SHRA.
SATURDAY NIGHT: MVFR. CHANCE SHRA, CHANCE SHSN.
SUNDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. SLIGHT CHANCE SHRA,
SLIGHT CHANCE SHSN.
MARINE
LAKE WIND ADVISORY IS IN EFFECT FOR THIS AFTN INTO TONIGHT FOR
GUSTY WEST TO NORTHWEST WINDS OF 15 TO 25 KNOTS, INCREASING TO
20 TO 30 KNOTS TONIGHT. WAVE WILL BUILD 2 TO 4 FEET WITH SOME
HIGHER WAVES IN THE BOARD LAKE POSSIBLE.
CLIMATE
BELOW ARE THE RECORD LOW MAX TEMPERATURES FOR OCTOBER 18, 2018:
BURLINGTON, VT 38 (1976)
MONTPELIER, VT 36 (1976)
ST. JOHNSBURY, VT 38 (1939)
PLATTSBURGH, NY 35 (1989)
SARANAC LAKE, NY 33 (2015)
MASSENA, NY 36 (1989)
BTV WATCHES/WARNINGS/ADVISORIES
VT...NONE.
NY...NONE.
SYNOPSIS...TABER
NEAR TERM...TABER
SHORT TERM...NEILES
LONG TERM...NEILES
AVIATION...TABER
MARINE...
CLIMATE...LAHIFF
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