-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBTV 210501
AFDBTV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
101 AM EDT TUE MAY 21 2013

.SYNOPSIS...
UNSETTLED WEATHER PATTERN IS EXPECTED...AS A FRONTAL BOUNDARY
AMBLES ABOUT THE NORTH EAST....RESULTING IN SEVERAL ROUNDS OF
RAIN SHOWERS AND THUNDERSTORMS INTO THE MIDDLE OF THIS WEEK. HIGH
PRESSURE AND DRIER CONDITIONS RETURN FRIDAY AND CONTINUE INTO THE
WEEKEND...WITH COOLER TEMPERATURES ABOUT 5 DEGREES BELOW NORMAL.

&&

.NEAR TERM /UNTIL 8 AM THIS MORNING/...
-- Changed Discussion --
AS OF 1251 AM EDT TUESDAY...ONGOING LINE OF CONVECTIVE SHOWERS AND
EMBEDDED THUNDERSTORMS VCNTY OF LAKE ONTARIO IS MOVING EWD INTO
A REGION OF SHORTWAVE RIDGING...BUT IS ALSO BEING FED BY MOIST
LOW-LEVEL SWLY FLOW OF 40-45 KTS PER KTYX VAD WIND PROFILE AT
0445Z. WHILE IT/S TOUGH TO PINPOINT EXACT LOCATION...ACTIVITY IS
PROGRESSING EWD ALONG STATIONARY BNDRY WITH 850-700MB WAA EXPECTED
TO INCREASE EWD ACROSS NRN NY INTO NWRN VT 06-12Z TIME FRAME. NAM
FORECAST SOUNDINGS SHOW ELEVATED INSTABILITY DEVELOPING EWD WITH
VALUES UP TO 600 J/KG INTO THE CHAMPLAIN VLY 09-12Z. LATEST RADAR
REFLECTIVITY ALSO INDICATES SCATTERED CELLULAR ACTIVITY DEVELOPING
NEAR WRN ST. LAWRENCE COUNTY...JUST IN ADVANCE OF THE PRE-
EXISTING CONVECTIVE LINE.

ABOVE FACTORS WARRANT RAISING POPS TO LIKELY ACROSS NRN NY INTO
WRN VT NEXT SEVERAL HRS...WITH CHANCE OF TSTMS MENTIONED ACROSS
NRN NY AND SLIGHT CHANCE INTO WRN VT. COULD SEE A QUICK QUARTER TO
HALF INCH OF RAINFALL WITH SOME OF THE HEAVIER ACTIVITY NEXT
COUPLE HOURS. AREAS OF PATCHY FOG MAY ACTUALLY DECREASE OVERNIGHT
AS RAIN MOVES EWD. TEMPERATURES WILL LIKELY HOVER IN THE MID-UPR
50S MOST SECTIONS THRU THE REMAINDER OF THE OVERNIGHT HOURS.
-- End Changed Discussion --

&&

.SHORT TERM /8 AM THIS MORNING THROUGH WEDNESDAY NIGHT/...
AS OF 355 PM EDT MONDAY...STALLED FRONTAL BOUNDARY REMAINS OVER
THE NORTH COUNTRY DURING THE SHORT TERM PERIOD AND WILL BE THE
FOCUS FOR PERIODS OF RAIN AND POSSIBLE THUNDERSTORMS THROUGH
WEDNESDAY.

RAIN SHOWERS SPREAD EWD TUESDAY MORNING WITH CLOUDY SKIES AND
SOUTHERLY WINDS. GFS BEING THE OUTLIER TAKES THE BOUNDARY TO OUR
SOUTH TUESDAY AFTN...WITH MOST GUIDANCE KEEPING IT OVER THE NORTH
COUNTRY. 925MB TEMPS DEPICT THE BOUNDARY OVER THE AREA
WELL...WITH COOLER TEMPS OVER THE NEK TUESDAY AND MOST OF THE
AREA SEEING 925MB TEMPS IN THE LOW TO MID TEENS. CLOUDS CONTINUE
OVER THE AREA WITH RAIN SHOWERS AND EVEN LIFTED INDICES OF -2 FOR
AT LEAST NRN NY AND SRN HALF OF VT. SOME CAPE AND TEMP LAPSE
RATES OF 6-7 C/KM COULD HELP TRIGGER A FEW TS TUESDAY AFTN.
MOISTURE CONTINUES TO STREAM IN TO THE NORTH COUNTRY WITH GEFS
SHOWING PWATS OF 1 TO 3 STANDARD DEVIATIONS ABOVE NORMAL
THROUGHOUT THE PERIOD.

TUESDAY NIGHT...WELL DEPICTED WARM FRONT LIFTING NORTH AS WE
CONTINUE TO BE IN THE WARM SECTOR AND 925MB TEMPS INCREASE TO
UPPER TEENS...POSSIBLY LOW 20S ON WEDNESDAY. SFC LOW MOVES INTO
SERN ONTARIO...RESULTING IN SW FLOW...BRINGING IN MORE
INSTABILITY ON WEDNESDAY. BEST CHANCES FOR TS WILL BE ON
WEDNESDAY AS LIFTED INDICES OF ZERO TO -4 SPREAD OVER THE ENTIRE
NORTH COUNTRY. TEMP LAPSE RATES GREATER THAN 7C/KM WILL ALSO MOVE
INTO THE AREA. SOME SHOWERS AND STORMS WILL LINGER INTO WEDNESDAY
NIGHT AS LOW LEVEL SW JET INCREASES IN STRENGTH AT 30-40 KTS.

TEMPS THROUGHOUT THE PERIOD WILL BE ABOVE NORMAL IN THE 70S
TUESDAY AND NEARING 80 ON WEDNESDAY. OVERNIGHT LOWS WILL BE MILD
DUE TO CLOUDS...IN THE 50S AND LOW 60S.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
AS OF 425 PM EDT MONDAY...

A COLD FRONT WITH SHOWERS AND THUNDERSTORMS ON THURSDAY WILL USHER
IN COOLER AND MAINLY DRY WEATHER FOR THE UPCOMING MEMORIAL DAY
WEEKEND.

CONFIDENCE FAIRLY HIGH IN THE LARGE-SCALE FEATURES AS UPPER TROF
PASSES SLOWLY ACROSS THE REGION. SOME UNCERTAINTY IN HOW THE TROF
EVOLVES AND HOW FAST IT MOVES OUT TOWARD THE END OF THE PERIOD.

ON THURSDAY THE COLD FRONT WILL MOVE SLOWLY SOUTHEAST THROUGH THE
AREA. INSTABILITY EXPECTED TO BE MARGINAL WITH CAPE VALUES AROUND
500 J/KG OR SO AND WILL DEPEND UPON CLOUD COVER. WITH LESS CLOUD
COVER VALUES COULD CLIMB NEAR 1000 J/KG ESPECIALLY SOUTH AND EAST
OF BTV. IF THE INSTABILITY MATERIALIZES AND 0-6KM BULK SHEAR
VALUES OF 30-40 KTS WILL HAVE TO WATCH FOR A FEW STRONGER STORMS.
HIGHS SHOULD BE IN THE 70S WITH 850 TEMPS AROUND +12C.

THURSDAY NIGHT WILL FEATURE A TRANSITION TO MUCH COOLER TEMPS WITH
850 TEMPS FALLING TO NEAR 0C BY 12Z FRIDAY. COULD BE SOME
LINGERING SHOWERS OVER NIGHT.

A COOL NW FLOW ON FRIDAY AND SATURDAY WITH 850 TEMPS AROUND 0 WILL
KEEP HIGH TEMPERATURES IN THE UPPER 50S TO MID 60S WITH PLENTY OF
CUMULUS CLOUDS AND EVEN A CHANCE OF A SHOWER DURING THE AFTERNOON
OR EVENING HOURS ESPECIALLY IN THE MOUNTAINS. LOW TEMPERATURES
WILL BE MAINLY 35 TO 45.

SUNDAY AND MONDAY SHOULD BE DRY AS HIGH PRESSURE MOVES INTO THE
NORTHEAST AND TEMPERATURE WILL BEGIN TO RETURN TO NORMAL WITH
HIGHS IN THE UPPER 60S TO LOW 70S AND LOWS IN THE 40S.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
THROUGH 00Z WEDNESDAY...LOW LEVEL MOISTURE REMAINS OVER THE AREA
AND THIS SHOULD LEAD TO A TREND FROM VFR CEILINGS AND VISIBILITIES
TO MVFR/IFR CEILINGS/VISIBILITIES BETWEEN 04Z AND 14Z. RAIN
SHOWERS WILL MOVE INTO SOUTHERN QUEBEC PROVINCE LATER TONIGHT AND
DROP INTO NORTHERN NEW YORK AND NORTHERN VERMONT AFTER 08Z. THE
THREAT FOR SHOWERS WILL CONTINUE THROUGHOUT THE MORNING AND
AFTERNOON HOURS ON TUESDAY. WINDS WILL BE VARIABLE UNDER 10 KNOTS.

OUTLOOK 00Z WEDNESDAY THROUGH SATURDAY...
TUE PM...WARM FRONT BRINGS MVFR SHOWERS WITH EMBEDDED TSTMS WITH
BRIEF IFR. WED- THU...SHOWERS/THUNDERSTORMS WITH PERIODS OF MVFR
CONDITIONS. THU NIGHT INTO FRI/SAT...MAINLY VFR AS DRY NWLY WINDS
DEVELOP.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...NONE.
NY...NONE.

&&

$$
SYNOPSIS...KGM
NEAR TERM...BANACOS
SHORT TERM...KGM
LONG TERM...SISSON
AVIATION...EVENSON/SISSON