-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBTV 152003
AFDBTV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
403 PM EDT WED MAY 15 2013

.SYNOPSIS...
A WARM FRONT WILL SHIFT EASTWARD ACROSS THE NORTH COUNTRY THIS
EVENING BRINGING CLOUDY SKIES AND SCATTERED RAIN SHOWERS. GUSTY
SOUTH WINDS THROUGH THIS EVENING WILL SHIFT INTO THE WEST TONIGHT
WITH THE FRONTAL PASSAGE. THE LINGERING UPPER LEVEL LOW AND A WEAK
SURFACE TROUGH WILL BRING ISOLATED TO SCATTERED RAIN SHOWERS
ACROSS THE NORTHERN HALF OF THE FORECAST AREA DURING THURSDAY
AFTERNOON. OTHERWISE...GENERALLY DRY WEATHER CONDITIONS ARE
EXPECTED OVER THE NEXT SEVERAL DAYS. TEMPERATURES WILL BE NEAR
TO SLIGHTLY ABOVE SEASONAL AVERAGES FOR MID-MAY THROUGH THE
UPCOMING WEEKEND.

&&

.NEAR TERM /UNTIL 7 AM THURSDAY MORNING/...
AS OF 328 PM EDT WEDNESDAY...LEADING EDGE OF RESIDUAL ELEVATED MIXED
LAYER PLUME IS SHIFTING RAPIDLY EWD ACROSS CENTRAL/N-CENTRAL NY
THIS AFTN...AND IS ASSOCIATED WITH A REGION OF STEEPENING MID-
LEVEL (700-500 MB) LAPSE RATES AND MUCAPE OF 250-500 J/KG. THIS -
IN ADDITION TO - ASSOCIATED WAA IS GENERATED BANDS OF SHOWERS AND
A FEW EMBEDDED TSTMS ACROSS NERN NY INTO WRN VT AS OF 1830Z. HAD
ONE REPORT OF PEA-SIZE HAIL IN POTSDAM NY AROUND 1245 PM.
ANTICIPATE SHOWER AND EMBEDDED CONVECTIVE ELEMENTS WILL CONTINUE
TO PUSH ESEWD AND GENERALLY MOVE EAST OF THE CT RIVER VALLEY BY
00-01Z. LESSER THREAT OF LIGHTNING EAST OF THE CHAMPLAIN
VALLEY/RUTLAND COUNTY...BUT HAVE INCLUDED SLIGHT CHANCE MENTION AS
IT IS DIFFICULT TO DETERMINE EXACT EWD CUTOFF OF ELEVATED
INSTABILITY THRU EARLY THIS EVENING. AXIS OF SHOWERS/TSTM
RELATIVELY NARROW AND GENERALLY EXPECTING ONLY 0.10-0.20"
PRECIPITATION FOR MOST LOCATIONS. PARTIAL CLEARING IS ANTICIPATED
OVERNIGHT...GIVEN UPSTREAM SATELLITE TRENDS WEST OF SFC TROUGH
AXIS ACROSS WRN NY AND SERN ONTARIO. AN OUTSIDE CHANCE FOR
PATCHY/BRIEF FOG FORMATION IN AREAS THAT SEE RAIN LATE THIS
AFTN/EVE. HOWEVER...IT ALSO APPEARS THAT AS WINDS SHIFT FROM THE
SOUTH TO WSW OVERNIGHT WITH TROUGH PASSAGE THAT GRADIENT REMAINS
STRONG ENOUGH TO MAINTAIN WIND SPEEDS OF 5-10 MPH OVERNIGHT. THIS
SHOULD LIMIT ANY WIDESPREAD FOG DEVELOPMENT. PBL WINDS WILL
LIKEWISE PROMOTE MIXING AND HAVE RAISED MIN TEMPS A FEW DEGREES
ABOVE THE MOS CONSENSUS. GENERALLY LOOKING AT LOWS TONIGHT IN THE
MID 40S.

&&

.SHORT TERM /7 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
AS OF 328 PM EDT WEDNESDAY...
ON THURSDAY...CLOSED MID-LEVEL LOW ROTATES EWD FROM SRN QUEBEC INTO
NORTHERN MAINE...WITH MODERATELY STRONG P-GRADIENT IN PLACE ACROSS
THE NORTH COUNTRY. WITH DAYTIME HEATING/MIXING...ANTICIPATE STEEP
LAPSE RATES AND BREEZY/GUSTY CONDITIONS FROM THE LATE MORNING THRU
AFTN HOURS. LOOKING AT W-WNW WINDS OF 15-25 MPH WITH GUSTS UP TO 35
MPH. SHALLOW INSTABILITY COMBINED WITH WEAK TROUGH/COLD FRONTAL
PASSAGE FROM NW-SE WILL BE SUFFICIENT TO GENERATE ISOLD TO SCATTERED
SHOWER ACTIVITY...MAINLY DURING THURSDAY AFTN. BASED ON LOCAL WRF
RUNS...SHOWER ACTIVITY SHOULD BE MOST CONCENTRATED ACROSS NRN HALF
OF THE FORECAST AREA...AND NRN GREEN MTNS IN PARTICULAR...AND THEN
DISSIPATE WHILE MOVING SWD THRU CENTRAL VT TOWARD EARLY EVENING.
HAVE INCLUDED POPS 40-50 PERCENT FROM THE NRN ADIRONDACKS NEWD
ACROSS THE CHAMPLAIN VALLEY INTO N-CENTRAL VERMONT...WITH LESSER
POPS TO THE WEST AND SOUTH. RELATIVELY WARM AIR MASS IN PLACE SOUTH
OF THE TROUGH/COLD FRONT...AND WITH PARTIAL SUNSHINE WILL SEE HIGH
TEMPS IN THE LOW 70S FOR THE SRN CHAMPLAIN VALLEY AND IN THE CT
RIVER VALLEY. MID-UPR 60S EXPECTED ACROSS NRN NY AND NRN VT.

SHOWER ACTIVITY SHOULD DISSIPATE DURING THURSDAY EVENING WITH
GENERALLY DRY CONDITIONS FOR THE BALANCE OF THURSDAY NIGHT. LOWS IN
THE LOW-MID 40S WITH A FEW MID 30S VCNTY KSLK.

COULD BE A STRAY SHOWER OVER THE NRN MTNS FRIDAY AFTN WITH MINIMAL
INSTABILITY WITH DAYTIME HEATING. WILL MENTION ISOLD -SHRA OVER
THE NRN MTNS. GENERALLY TRANQUIL FRIDAY NIGHT WITH PARTLY CLOUDY
CONDITIONS AND LIGHT WINDS. LOW TEMPERATURES GENERALLY IN THE LOWER
40S WITH GOOD RADIATIONAL COOLING. MAY SEE SOME MID-UPR 30S IN THE
NORMALLY COLDER SPOTS IN THE NORTHEAST KINGDOM OF VERMONT AND
ACROSS THE NRN ADIRONDACKS.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
AS OF 400 PM EDT WEDNESDAY...BOTH GFS/ECMWF SHOW A BUSY MID/UPPER
LVL PATTERN ACRS THE EASTERN CONUS FOR DAYS 4 THRU 7...BUT DEEP
LAYER MOISTURE IS LIMITED UNTIL NEXT WEEK. THIS WL RESULT IN A
MAINLY DRY FCST THRU MONDAY...WITH INCREASING CHCS FOR PRECIP LATE
MONDAY THRU WEDS OF NEXT WEEK...ALONG WITH TEMPS TRENDING ABOVE
NORMAL. HAVE MENTIONED LOW CHC POPS ACRS NORTHERN VT ON SAT AFTN
ASSOCIATED WITH WEAK 5H VORT AND LOBE OF MID LVL RH ROTATING
AROUND CLOSED 5H/7H CIRCULATION ACRS EASTERN CANADA. BEST CHC WL
BE DURING PEAK DAYTIME HEATING AND OVERALL COVERAGE/INTENSITY OF
ANY SHOWERS WL BE LIMITED. OTHERWISE...MID/UPPER LVL RIDGE BUILDS
ACRS THE NE CONUS FOR SUNDAY THRU MONDAY...RESULTING IN DRY
CONDITIONS AND WARMING TREND. PROGGED 85H TEMPS CLIMB FROM 6C TO
10C BY 18Z MONDAY. THIS WL SUPPORT TEMPS IN THE M60S MTNS TO L70S
ON SATURDAY...WARMING INTO THE U60S MTNS/NEK TO M/U 70S WARMER
VALLEYS. HAVE USED A BLEND OF GMOS/ECE BC GRIDS TO POPULATE
TEMPS...TO BETTER SHOW TRRN AND COOLER LAKE CHAMPLAIN TEMPS. BY
LATE MONDAY INTO TUES...A SFC BOUNDARY WL SLOWLY DROP SOUTH TWD
OUR NORTHERN FA. THIS WL TIGHT THE NORTH/SOUTH THERMAL GRADIENT
ACRS OUR FA...ALONG WITH INCREASE THE DEEP LAYER 850 TO 500MB RH.
THIS INCREASE IN RH...COMBINED WITH SEVERAL 5H VORTS AND WEAK AREAS
OF SFC LOW PRES SLIDING ALONG SFC BOUNDARY WL ENHANCE OUR CHCS FOR
PRECIP...ESPECIALLY TUES INTO WEDS. FURTHERMORE...WITH MORE
CLOUDS/PRECIP AND DEVELOPING THERMAL GRADIENT TEMP FCST WL BECM
MORE COMPLEX TWD THE MID OF NEXT WK. TRIED TO SHOW A NORTH TO
SOUTH GRADIENT WITH HIGHS TRENDING BACK TWD NORMAL. ANTICIPATING
AT OR ABOVE NORMAL TEMPS FOR OVERNIGHT LOWS THRU THE PERIOD.
-- End Changed Discussion --

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
THROUGH 18Z THURSDAY...AVIATION CHALLENGE THRU THIS AFTN WL BE
-SHRA AND POTENTIAL IMPACTS ON TAF SITES/GUSTY WINDS...FOLLOWED BY
POTENT MVFR CIGS AT SLK/MPV THIS EVENING. CRNT RADAR SHOWS A
BROKEN LINE OF -SHRA MOVING INTO THE CPV ATTM...WITH SOME
LIGHTNING ACTIVITY NOTED ACRS THE SLV. THESE SHOWERS ARE
ASSOCIATED WITH A WARM FRONT AND SOME WEAK ELEVATED INSTABILITY.
DUE TO VERY DRY CONDITIONS NEAR THE SFC...EXPECT LEADING EDGE OF
PRECIP TO FALL AS VIRGA WITH CIGS BTWN 5000 AND 8000 FEET.
HOWEVER...LLVLS WL SATURATE ENOUGH TO PRODUCE A BRIEF 1 TO 2 HOUR
WINDOW OF -SHRA AT OUR TAF SITES THIS AFTN...WITH MAINLY VFR
CONDITIONS...WITH POTENTIAL OF A BRIEF 15 TO 30 MINUTES OF MVFR AT
SLK/MPV. SHOWERS WL QUICKLY SHIFT EAST OF TAF SITES BY 22Z THIS
EVENING...WITH SOME GUIDANCE SHOWING THE POTENTIAL FOR MVFR
CIGS...ESPECIALLY AT MPV/SLK. WL MENTION INTO TEMPO GROUP BTWN
00Z-04Z TONIGHT FOR MVFR CIGS. FINALLY...GUSTY SOUTH WINDS AT 15
TO 30 KNTS WL PREVAIL BEFORE THE SHOWERS ARRIVE THIS AFTN...BECOME
LIGHTER WHEN THE RAIN IS FALLING...THEN SHIFT TO THE SOUTHWEST AND
INCREASE AGAIN AT 10 TO 20 KNOTS THIS EVENING...BEFORE DECREASING
UNDER 10 KNTS BY 05Z.

OUTLOOK 18Z THURSDAY THROUGH MONDAY...
A WEAK S/W WL PRODUCE ISOLATED/SCATTERED SHOWERS ACRS OUR
CENTRAL/NORTHERN TAF SITES BTWN 18Z-22Z THURS...WITH A BRIEF
PERIOD OF MVFR POSSIBLE AT MPV/SLK. OTHERWISE...SFC HIGH PRES AND
VFR CONDITIONS WL PREVAIL THRU THE WEEKEND. HOWEVER...AS INSTABILITY
INCREASES ON SUNDAY...A FEW AFTN/EVENING SHOWERS WL BE
POSSIBLE...ALONG WITH A BRIEF PERIOD OF MVFR.

&&

.MARINE...
A LAKE THUNDERSTORM ADVISORY IS IN EFFECT INTO THIS EVENING.
SCATTERED SHOWERS AND A FEW THUNDERSTORMS WILL MOVE ACROSS THE
LAKE...ESPECIALLY THROUGH 6 PM. A LAKE WIND ADVISORY ALSO REMAINS
IN EFFECT THROUGH THE EVENING HOURS WITH SOUTH WINDS FROM 20 TO 30
KNOTS CONTINUING. WAVES OF 2 TO 4 FEET ARE LIKELY. THESE WINDS
WILL DECREASE TO 10 TO 20 KNOTS OVERNIGHT WITH WAVES SUBSIDING TO
1 TO 2 FEET.

&&

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

&&

$$
SYNOPSIS...BANACOS
NEAR TERM...BANACOS
SHORT TERM...BANACOS
LONG TERM...TABER
AVIATION...TABER
MARINE...