Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 300615
AFDBTV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
215 AM EDT MON MAR 30 2015

.SYNOPSIS...
A COLD FRONT MOVING EAST FROM THE WESTERN GREAT LAKES WILL BRING
A CHANCE OF RAIN AND SNOW SHOWERS TO THE NORTH COUNTRY ON MONDAY.
AFTER A BRIEF COOL DOWN TUESDAY AND WEDNESDAY...A WARMING TREND
WILL LEAD TO TEMPERATURES IN THE MID 40S TO LOW 50S BY THE END OF
THE WEEK.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
AS OF 159 AM EDT MONDAY...THIS WAS A PARTICULARLY CHALLENGING
UPDATE TO THE FORECAST AS RADAR TRENDS ARE SHOWING THE FRONT TO BE
ABOUT 1-2 HOURS QUICKER THAN THE SHORT TERM GUIDANCE SO I BOOSTED
POPS AND SHARPENED THE GRADIENT FOR SKY GRIDS AS WELL. THE
SOUTHERLY WINDS ARE KEEPING TEMPS UP EVEN AS THE FIRST PART OF THE
SNOW SHOWERS REACH THE AREA. ITS TOUGH TO GAUGE HOW MUCH OF THE
RADAR ECHOS ARE REACHING THE GROUND AS THE DRY AIR THAT WAS
PRESENT FOR MOST OF THE DAY IS STILL HOLDING ON AND DEW POINTS ARE
RUNNING IN THE TEENS TO SINGLE DIGITS IN NORTHERN NEW YORK.
HOWEVER WITH RADAR ECHOS IN THE 20-30DBZ RANGE THERE IS LIKELY
SOME PRECIP REACHING THE GROUND AND THAT WILL ONLY BE ENHANCED AS
THE LEADING EDGE BEGINS TO MORE INTO THE HIGHER TERRAIN. SO I
UPPED THE 12 HOUR RUNNING POPS TO REFLECT CATEGORICAL CHANCES OVER
ST LAWRENCE COUNTY BUT I REALLY WANTED TO USE OCCASIONALLY AS THE
DESCRIPTOR INSTEAD OF DEFINITE FOR HOW THE SHOWERS WILL PLAY OUT.
I EXPECT BRIEF BURSTS OF SNOW SHOWERS AND NOT A LONG DRAWN OUT
EVENT TO START HOWEVER WITH THE STEEP LAPSE RATES ALONG THE
FRONTAL BOUNDARY THE EVENT IS DEFINITELY MORE CONVECTIVE THAN
STRATIFORM. THOSE STEEP LAPSE RATES WILL ALSO CAUSE FAIRLY GUSTY
WINDS ESPECIALLY ALONG THE LEADING EDGE OF THE FRONTAL BOUNDARY
AND THAT`S ALREADY PLAYED OUT WITH GUSTS TO 35-40KTS REPORTED IN
BOTH BUFFALO AND NIAGARA FALLS. CONCERNING THE FORECAST TEMPS AND
HUMIDITY THE FORECAST WAS IN PRETTY GOOD TRACK SO THE ONLY REAL
CHANGES WERE TO INCREASE THE GRADIENT IN POPS AND SKY COVER TO
ACCOUNT FOR THE SPEED OF THE LEADING EDGE OF THE FRONT.

PREVIOUS DISCUSSION AS OF 1047 PM SUNDAY...SOUTHERLY WINDS
HELPING TO KEEP TEMPERATURES UP ACROSS THE REGION...SO BASED ON
THE LATEST GFS LAMP GUIDANCE HAVE RAISED MIN TEMPERATURES UP A FEW
DEGREES OVERNIGHT. COMPOSITE RADAR LOOP SHOWING PRECIPITATION
MOVING INTO WESTERN NEW YORK STATE AT THIS TIME. SURFACE WINDS IN
WESTERN NEW YORK HAVE SHIFTED TO THE SOUTHWEST WITH THE ARRIVAL OF
THIS PRECIPITATION. THIS PRECIPITATION HAS ALSO HELPED TO MIX DOWN
SOME STRONGER WIND GUSTS TO THE SURFACE...WITH SOME WIND GUSTS OF
30-40 KNOTS OBSERVED WITH THE ONSET OF THE PRECIPITATION IN
WESTERN NEW YORK STATE.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH TUESDAY NIGHT/...
AS OF 350 PM EDT SUNDAY...THE FIRST OF TWO FRONTAL SYSTEMS WILL
BE APPROACHING NRN NY IN THE MORNING BUT WITH THE S-SW FLOW EXPECT
THE TEMPS IN THE BOUNDARY LAYER TO SUPPORT ANY SHOW SHOWERS IN THE
HIGHER TERRAIN MIXING WITH RAIN IN VALLEYS BY 13-16Z. MODELS
SUGGEST A BRIEF DRY SLOT ALOFT POSSIBLE AROUND THAT TIME AS WELL
JUST AHEAD OF THE FIRST FRONT WHICH SHOULD BE REACHING THE
CHAMPLAIN VALLEY AROUND 18Z OR SO. STEEP LOW-LEVEL LAPSE RATES AND
EVEN SOME LOW VALUES OF CAPE, SO SOME GUSTY RAIN OR SNOW SHOWERS
MAY ACCOMPANY THE COLD FRONT AS IT MOVE THROUGH WITH WINDS
SHIFTING AROUND TO SW-W. TEMPS DURING THE DAY WILL WARM INTO THE
LOW TO MID 40S UNDER MODERATE AND GUSTY SOUTH WESTERLY FLOW OF 25
TO 30 KTS WITH OVERCAST SKIES. THE SOUTHERLY FLOW DURING THE DAY
ON MONDAY WILL SUPPORT CONTINUED WARMING TO NEAR NORMAL AS 850
TEMPS CLIMB TO -5C. HIGHS IN THE MID 40S IN THE VALLEYS AND UPPER
30S ELSEWHERE.

WINDS WILL GRADUALLY SHIFT FROM WEST TO NORTHWEST WITH UPSLOPE
FLOW DEVELOPING MONDAY NIGHT BEHIND A SECONDARY COLD FRONT. TEMPS
COOL ENOUGH SO THAT ANY RAIN SHOWERS WILL BE CHANGING TO SNOW
SHOWERS. FROUDE NUMBERS EXPECTED ABOVE 1 MOST OF THE PERSISTENT SNOW
SHOWER EXPECTED AT THE SUMMITS AND SLIGHTLY ON THE LEE SIDE OF THE
GREENS. A DUSTING TO AN AN INCH WILL BE POSSIBLE FOR MOST PLACES
WITH VERY LITTLE IN THE CHAMPLAIN VALLEY. OVER NORTHERN NEW YORK
AND THE NORTHERN GREENS INTO NORTHEASTERN VT SOME OF THE HIGHER
TERRAIN MAY GET 1-3" INCHES OF SNOW WITH HIGHER AMOUNTS AT THE
SUMMITS. EXPECT LOWS OVERNIGHT BEHIND THE COLD FRONT TO BE SIMILAR
TO SUNDAY NIGHT IN THE MID 20S.

TUESDAY BEHIND THE SURFACE FRONT AN UPPER LEVEL TROUGH WILL PASS
THROUGH THE REGION WITH NORTH WESTERLY FLOW. ANY LEFTOVER
OROGRAPHIC SNOW SHOWERS OR FLURRIES OVER THE ADIRONDACKS AND THE
GREENS WILL BE ENDING. 850 TEMPS WILL BE RUNNING ABOUT -9C ON ON
TUESDAY WHICH WILL WILL STAY ON THE COOLER SIDE RUNNING IN THE MID
30S TO NEAR 40 ACROSS THE AREA.

TUESDAY NIGHT LIGHT NORTHWEST FLOW CONTINUES AS A SURFACE HIGH
MOVES OVER THE GREAT LAKES. SHOULD BE JUST ENOUGH WIND AND MOISTURE
AROUND FOR PARTLY CLOUDY SKIES TO PREVENT THE BOTTOM DROPPING OUT
OF THE LOW TEMPERATURES BUT STILL CHILLY IN THE TEENS TO AROUND 20
FOR MOST OF US.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 350 PM EDT SUNDAY...EXTENDED PERIOD PICKS UP ON WEDNESDAY
WITH NORTHERLY LOW LEVEL FLOW AND 500 MB TROUGH EXITING THE
REGION. SURFACE RIDGE BUILDS THROUGH WEDNESDAY, THEN BY THURSDAY
MORNING LOW LEVEL FLOW RETURNS TO SOUTHERLY WITH HIGH SHIFTING TO
THE EAST. WILL GET SOME SUN UNDER THE HIGH PRESSURE, BUT COOL AIR
WILL LIMIT MAX TEMPS. 850 MB TEMPS AT 18Z WEDNESDAY ONLY -13C, AND
925 -7 BOTH SUPPORT MAX TEMPS IN THE LOW 30S. LOW LEVEL WIND
BEGINS TO SHIFT AROUND TO THE WEST TO SOUTHWEST BY THURSDAY
MORNING, BUT WARM AIR ADVECTION DOESN`T TAKE HOLD OVERNIGHT AND
LOWS STILL A CHILLY TEENS TO LOWER 20S.

FOR THURSDAY 500 MB TROUGH REACHES THE NORTHERN GREAT LAKES WITH THE
500 MB RIDGE EASTER OVER NEW ENGLAND AND QUEBEC. ECMWF SHOWING
HIGHER AMPLITUDE WITH ITS TROUGH/RIDGE COMBO. AT THE SURFACE LOW
PRESSURE IS PLACED A LITTLE AHEAD OF THE UPPER LOW. GFS HAS A
PREFRONTAL TROUGH RACING WELL AHEAD OF THE SYNOPTIC LOW, ACTUALLY
PLACING IT UNDER THE UPPER RIDGE. ECMWF IS A LITTLE SLOWER, LAGGING
PRECIP TIMING BY ABOUT 12 HOURS. GFS SEEMS A LITTLE SPEEDY GIVEN THE
UPPER PATTERN. EITHER WAY WITH SOUTHERLY FLOW ON THURSDAY
TEMPERATURES FORECAST TO WARM INTO THE 40S WITH CHANCE POPS FOR RAIN
IN THE WARM AIR. FOR THURSDAY NIGHT POPS INTO LIKELY CATEGORY WITH A
BLEND OF ECMWF AND GFS.

FOR FRIDAY PREVIOUS RUNS OF GFS AND ECMWF HAD DIFFERENCES WITH ECMWF
WITHOLDING COOLER AIR AND FORECASTING A HIGH OF 64 AT BTV ON FRIDAY.
AS APPEALING AS THIS SOUNDS IT IS TOO WARM, AND 12Z ECMWF IS MORE IN
LINE WITH OTHER GUIDANCE AND MAX TEMPS IN 40S TO LOW 50S FRIDAY.
SHOWERY POST FRONTAL AIR WITH NORTHWEST TO NORTH FLOW AND COLD AIR
ADVECTION WILL BRING FRIDAY NIGHT LOWS BACK DOWN TO THE 20S.

FOR SATURDAY BOTH MODELS IN OVERALL AGREEMENT OF A SECONDARY
SHORTWAVE TROUGH ROUNDING THE BASE OF THE UPPER LOW AND A
REINFORCING SHOT OF COLD AIR AT THE SURFACE WITH SOME LIGHT SNOW
SHOWERS LATE SATURDAY/EARLY SUNDAY. HIGHS BOTH SATURDAY AND SUNDAY
TO HOLD IN THE 30S, WITH SATURDAY NIGHT IN THE TEENS TO LOW 20S.
COLD AIR THIS TIME OF YEAR DOESN`T HAVE THE TEETH IT HAD A MONTH
AGO, BUT WE STILL CAN`T SEEM TO SHAKE LOOSE.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
THROUGH 06Z TUESDAY...A TROUGH OF LOW PRESSURE APPROACHING FROM
THE GREAT LAKES WILL BRING VFR CEILINGS AND PERIODS OF LIGHT RAIN
AND SNOW SHOWERS TO THE TAF SITES THROUGH THE PERIOD. INCREASING
P-GRADIENT WILL RESULT IN MODERATELY STRONG S-SW WINDS THIS
MORNING...WITH SUSTAINED WINDS GENERALLY 10-15 KTS AND GUSTS 25-28
KTS. CAN/T COMPLETELY RULE OUT LLWS...BUT IT APPEARS LOW-LEVEL
MIXING WILL BE SUFFICIENT TO REDUCE MAGNITUDE OF VERTICAL SHEAR
AND GET MODERATE/GUSTY WINDS TO THE SURFACE AS INDICATED IN TAFS.

WINDS WILL GRADUALLY SHIFT INTO THE SW AND W WITH SURFACE
TROUGH PASSAGE THIS AFTERNOON INTO THIS EVENING. PRECIPITATION IS
GENERALLY NOT EXPECTED TO BE SIGNIFICANT. BEST CHANCE FOR SNOW
SHOWER ACTIVITY WILL BE AT SLK/MPV THIS MORNING...AND AGAIN AFTER
22Z THIS AFTERNOON AS ORORGAPHIC ASCENT INCREASES. SHOULD SEE
PERIODS OF MVFR CONDITIONS AT SLK/MPV...WHILE CEILINGS AND VSBY
GENERALLY REMAIN VFR AT THE OTHER TAF LOCATIONS. GENERALLY
SPRINKLES/RAIN SHOWER ACTIVITY AT THE OTHER TAF SITES WITH WARMER
LOW-LEVEL CONDITIONS. WILL SEE A LOWERING OF CEILINGS FROM NEAR
10 KFT DURING THE PRE- DAWN HOURS...TO 4-5 KFT DURING THE DAYLIGHT
HOURS AND 3-4 KFT TONIGHT. HIR TRRN WILL BECOME OBSCD AT TIMES
DURING THE DAYLIGHT HRS MONDAY...AND THROUGH MONDAY NIGHT.

OUTLOOK 06Z TUESDAY THROUGH FRIDAY...IMPROVING TO VFR TUESDAY AND
THEN FAIR/VFR WITH LIGHT WINDS TUESDAY NIGHT THROUGH WEDNESDAY
NIGHT WITH SFC HIGH PRESSURE IN CONTROL. NEXT FRONTAL SYSTEM
BRINGS POTL S-SW WIND GUSTS 25-30 KTS DURING THURSDAY
NIGHT...FOLLOWED BY MVFR/INTERVALS OF IFR IN PERIODS OF RAIN LATE
THURSDAY NIGHT THROUGH FRIDAY.

&&

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

&&

$$
SYNOPSIS...SISSON
NEAR TERM...DEAL
SHORT TERM...SISSON
LONG TERM...HANSON
AVIATION...BANACOS



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