FXUS61 KBTV 260516
AFDBTV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
1216 AM EST SAT DEC 26 2009
.SYNOPSIS...
SURFACE HIGH PRESSURE WILL SHIFT EASTWARD INTO THE GULF OF MAINE
TONIGHT AS AN OCCLUDED FRONTAL BOUNDARY MOVES SLOWLY NORTHEASTWARD
INTO THE NORTH COUNTY. THIS FRONT WILL BE ASSOCIATED WITH A BAND
OF SLEET AND FREEZING RAIN WHICH WILL MOVE ACROSS THE REGION
SATURDAY AND SATURDAY NIGHT. THE MOST SIGNIFICANT ICE ACCUMULATION
IS EXPECTED ACROSS FAR NORTHERN NEW YORK...INCLUDING THE ST.
LAWRENCE RIVER VALLEY. PRECIPITATION AMOUNTS WILL BE LIGHTER
ACROSS VERMONT...WITH RAIN EXPECTED AT TIMES ACROSS THE CHAMPLAIN
VALLEY AND SOUTH CENTRAL VERMONT. TRAVEL MAY BECOME DIFFICULT
ACROSS FAR NORTHERN NEW YORK AND PORTIONS OF VERMONT EAST OF THE
GREEN MOUNTAINS SATURDAY AND SATURDAY NIGHT.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
AS OF 1215 AM EST SATURDAY...UPDATED THE FORECAST TO PROGRESS TIMING
OF WINTRY MIXED PRECIPITATION MAINLY INTO THE SOUTHERN ST
LAWRENCE VALLEY TONIGHT. TRICKY FORECAST REGARDING ONSET. THE
OCCLUDED FRONT IS TO OUR SOUTHWEST WITH THE PRECIP BAND
APPROACHING THE SW BORDER OF OUR AREA. BUT...AS IT ADVANCES
NORTHEAST IT IS ENCOUNTERING A SLIGHTLY AMPLIFYING RIDGE. THE
RIDGE IS AMPLIFYING AS A COASTAL LOW IS DEVELOPING OFF THE
DELMARVA PENINSULA. AS THIS OCCURS...THE DYNAMICS ARE BEING
SHIFTED IN TWO DIRECTIONS...SOUTH TOWARD THE COASTAL LOW AND NORTH
WITH THE SOUTHERLY FETCH OF THE JET. WE ARE KIND OF LEFT IN THE
MIDDLE OVERNIGHT TONIGHT...WITH THE BAND OF PRECIP CLEARLY
STRETCHING APART OVER THE LAST HOUR OR SO. NONE THE LESS THE
PRECIPITATION IS APPROACHING A BIT FASTER THAN EARLIER INDICATIONS
SUGGESTED...THUS I HAVE BUMPED THE TIMING OF THE ADVISORY AND
WARNING UP TO PRESENT TIME...THOUGH PRECIPITATION WILL LIKELY NOT
BEGIN IN THE NORTHERN ST LAWRENCE VALLEY FOR ABOUT ANOTHER
HOUR...AND IN THE NORTHERN FRANKLIN AND WESTERN CLINTON COUNTIES
BY 3 AM.
FROM PREVIOUS DISCUSSION...
HAVE UPGRADED THE IMMEDIATE ST. LAWRENCE VALLEY AROUND KMSS AND
WRN CLINTON CO. TO A WINTER STORM WARNING...BEGINNING AT 5AM AND
CONTINUING THROUGH 5AM SUNDAY. A WINTER WX ADVISORY IS IN EFFECT
FOR SRN ST. LAWRENCE/SRN FRANKLIN/ESSEX NY.
NO SIGNIFICANT CHANGES IN NWP GUIDANCE...OTHER THAN A SLIGHTLY
SLOWER ARRIVAL TIME OF SLEET/FREEZING RAIN INTO ST. LAWRENCE
VALLEY AND WESTERN ADIRONDACKS TONIGHT. CURRENT MOSAIC RADAR
IMAGERY SHOWS THE SLOW NEWD MOVEMENT OF PRECIPITATION SHIELD
ASSOCIATED WITH OCCLUDED FRONT ACROSS WRN AND S-CENTRAL NY AT 20Z.
FOLLOWING 15Z SREF TIMING...EXPECT PRECIPITATION TO FINALLY BEGIN
IN ST. LAWRENCE CO AROUND 08-09Z...AND THEN ACROSS MOST OF THE ST.
LAWRENCE VALLEY AND WRN HALF OF THE ADIRONDACKS BY 09-12Z. DON/T
FORESEE ANYTHING IN VT...EXCEPT PERHAPS A FEW ADDITIONAL FLURRIES
FROM PREVAILING 2000 FOOT LOW CLOUD LAYER TRAPPED BENEATH THE
INVERSION.
THERMAL PROFILES CONTINUE TO SUPPORT FREEZING RAIN MIXED WITH
SLEET AT TIMES. MAX TEMPS ALOFT ARE IN THE +2 TO +3C RANGE PER 12Z
NAM AND GFS. TEMPERATURES WILL BE IN THE UPR 20S AT ONSET OF
PCPN...SO SOME LIGHT ICE ACCUMULATION BY DAYBREAK IS POSSIBLE IN
NRN NY. ELSEWHERE...EXPECTING MAINLY CLOUDY SKIES OVERNIGHT WITH
E/SE WINDS INCREASING TO 10-15 MPH. WINDS WILL BE ENE ACROSS THE
ST. LAWRENCE VALLEY AT 10-15 MPH.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY NIGHT/...
AS OF 317 PM EST FRIDAY...NO SIGNIFICANT CHANGE TO THE FORECAST
THROUGH THE PERIOD...HOWEVER TIMING/INTENSITY OF MIXED PCPN ACROSS
VT REMAINS PROBLEMATIC DURING THE DAY SATURDAY. MODELS CONTINUE TO
INDICATE DRY MID-LEVEL AIR AND SHADOWING EFFECTS WITH SELY FLOW
YIELDING LOW QPF AMTS ACROSS MOST OF VT. THIS IS TRUE EVEN IN THE
SREF ENSEMBLE MEAN GUIDANCE. THINK PRECIPITATION ACROSS VT WILL BE
INTERMITTENT AND LIGHT...WITH BEST CHANCES FOCUSED LATE IN THE
DAY. THE HIGHEST QPF REMAINS FOCUSED ACROSS THE ST. LAWRENCE
VALLEY...WHERE COLD NELY WINDS AROUND 15 MPH WILL MAINTAIN
TEMPERATURES AT OR SLIGHTLY BELOW FREEZING. SOME WARMING OCCURS
FURTHER SOUTH ACROSS THE ADIRONDACKS. HAVE SHOWN IP/ZR TO RAIN IN
THESE AREAS FURTHER SOUTH...AND THUS A WINTER WX ADVISORY FOR
LIGHTER ICE ACCUMULATIONS THERE. MEANWHILE...ICE ACCUMULATION IN THE
ST. LAWRENCE VALLEY COULD TOTAL 0.25 TO 0.50 IN...ESPECIALLY IN
ELEVATED SURFACES. ICY ROAD CONDITIONS WILL BE THE MAIN
THREAT...BUT ISOLATED TREE/POWERLINE DAMAGE IS ALSO POSSIBLE.
SFC TEMPERATURES WARM ABOVE FREEZING ACROSS WRN VT/CHAMPLAIN
VALLEY AND PORTIONS OF THE CT VALLEY DURING SATURDAY AFTN. AS PCPN
INCREASES LATE IN THE DAY...CHANCES BECOME BETTER FOR PLAIN RAIN
IN THESE AREAS. WE/LL NEED TO WATCH THE ERN SLOPES OF THE GREENS
UP THRU THE NE KINGDOM FOR A POSSIBLE ADVISORY...IF CONFIDENCE
INCREASES FOR MEASURABLE SLEET AND FREEZING RAIN. SELY WINDS TEND
TO FAVOR UPSLOPE ALONG THE ERN SLOPES OF THE GREENS...SO THAT
WOULD BE THE HIGHEST THREAT AREA. THESE CONDITIONS WILL PERSIST
INTO SATURDAY NIGHT BEFORE ENDING AS SNOW SHOWERS LATE AS
OCCLUSION LIFTS THRU.
STRONG SELY WINDS REMAIN A CONCERN ALONG THE WESTERN SLOPES OF THE
GREEN MTNS SATURDAY AFTN INTO SATURDAY NIGHT. GUSTS OF 35-45 MPH
ARE EXPECTED IN FAVORED DOWNSLOPE AREAS. THIS IS SLIGHTLY BELOW
WIND ADVISORY CRITERIA...SO HAVE ADDRESSED POTENTIAL IN THE
HAZARDOUS WEATHER OUTLOOK.
NO SIG WX SUNDAY. DEVELOPING SWLY FLOW SUNDAY NIGHT MAY BRING LAKE
EFFECT SNOW SHOWERS INTO SRN ST. LAWRENCE COUNTY AND HAVE INCLUDED
THIS POTENTIAL IN THE GRIDS. HIGHS SUNDAY WILL MAINLY BE IN THE
30S WITH LOWS SUNDAY NIGHT IN THE LOW TO MID 20S.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
AS OF 317 PM EST FRIDAY...WILL CONTINUE WITH CHCS FOR SHSN ON MONDAY
AS OLD PARENT OCCLUSION ACROSS THE MIDWEST FINALLY GETS KICKED
EASTWARD AND TRAVERSES THE NORTHEAST. STILL SOME UNCERTAINTY ON
EXACT TRACK OF THIS FEATURE THOUGH LATEST TRENDS ARE TO KEEP
BETTER LIFT/FORCING SOUTH OF THE REGION. STILL...PROXIMITY OF
FEATURE CLOSE ENOUGH TO WARRANT CHANCE POPS ACROSS THE AREA. OF
MORE IMPORTANCE WILL BE SHARPLY DIGGING UPPER TROUGH AND ATTENDANT
ARCTIC FRONTAL BNDRY SURGING SOUTHWARD FROM ONTARIO/WRN QUEBEC
LATER IN THE DAY AND INTO THE EVENING HOURS ON MONDAY. RAPID
SOUTHWARD MOVEMENT OF THESE FEATURES SHOULD ENSURE RATHER ROBUST
LL MOISTURE CONVERGENCE WITH DISTINCT POSSIBILITY OF HEAVIER
SHSN/SQUALLS ESP WITH SHARPLY CRASHING 925/850 MB POST-FRONTAL
TEMPERATURES. THIS MOST LIKELY TO OCCUR ACROSS NRN NY/NW VT WHERE
BACKING OF LL FLOW MAY ALLOW LK MODIFIED SNOW BANDS OFF LK ONTARIO
TO BECOME LOCALLY ENHANCED. GIVEN THIS REASONING WILL BUMP POPS UP
TO LIKELY HERE. SOME MARGINAL LL WIND CHILL CONCERNS LATER AT
NIGHT AS WELL ACROSS THE NRN MTNS AS TEMPS FALL INTO THE SINGLE
DIGITS TO NEAR ZERO IN MANY LOCALES. CLOUD COVER COULD KEEP TEMPS
JUST A TAD MILDER...NONETHELESS HAVE PLENTY OF TIME TO ASSESS AS
MONDAY NEARS.
THEREAFTER...A RETURN TO MID-WINTER COLD BY TUESDAY WITH HIGHS
STRUGGLING INTO THE 5-15 DEG RANGE..SOME 15-20 DEG BELOW NORMAL. ANY
LINGERING NRN MTNS FLURRIES/LIGHT SHSN SHOULD WANE BY LATER IN THE
DAY. HIGH PRESSURE THEN BUILDS EASTWARD TUE NIGHT INTO WED NT WITH
GENERALLY COLD AND DRY CONDS EXPECTED. BY LATER IN THE WEEK
TEMPERATURES MODERATE BACK TO NEAR SEASONAL NORMS WITH HIGHS IN THE
20S TO AROUND 30 AND LOWS IN THE TEENS. SOME UNCERTAINTY THIS FAR
OUT...BUT SOME HINTS AT UPPER TROUGHING SLIDING EAST MAY SPARK A
RENEWED THREAT OF LIGHT SNOWS AND/OR SHSN BY THIS TIME. BETTER
DETAILS AS WE PROGRESS INTO NEXT WEEK.
&&
.AVIATION /05Z SATURDAY THROUGH WEDNESDAY/...
THROUGH 00Z SUNDAY...CHALLENGING AVIATION FCST NEXT 24 HOURS. VERY
PESSIMISTIC FORECAST IS A DEPARTURE FROM PREVIOUS
PACKAGE...CONTINUING IFR TO LIFR CIGS THROUGH OVERNIGHT PERIOD.
AVAILABLE GUIDANCE INDICATING PRESENT IFR/LIFR CIGS TO
CONTINUE...AND EVEN KRUT WHICH IS CLEAR AT 00Z HAS IFR CIGS
UPSTREAM THAT WILL MOVE IN BY 03Z. HOWEVER NOT MUCH CHANGE IN
FREEZING RAIN FCST... KEPT TIMING FROM DAY SHIFT 12-14Z IN THE
ADIRONDACKS. FOR KBTV AND KPBG LEFT OUT OF TAF FCST...THINKING
PROBABILITY WAS TOO LOW TO MENTION. BY THE TIME ANYTHING MOVES IN
TO NRN CHAMPLAIN VALLEY TEMPS SHOULD WARM TO AT OR ABOVE FREEZING
AT KBTV/KPBG...AND SOUTHERLY DOWNSLOPE FLOW WILL ALSO WORK AGAINST
PRECIP. AT KRUT...DID ADD -RA AFT 21Z WITH WARMER TEMPS. KMPV GETS
FREEZING RAIN AFT 22Z BASED ON EXPECTED COLD TEMPS TO REMAIN AS
PRECIP MOVES IN. LOW CONFIDENCE IN ACCURACY OF PRECIP BEGIN AND
CHANGEOVER ACCURACY...SO STAY TUNED FOR FREQUENT UPDATES AS THE
SITUATION UNFOLDS.
OUTLOOK...00Z SUNDAY THROUGH WEDNESDAY...
00Z SUN THRU 00Z MON...MVFR W/OCNL IFR IN MIXED PCPN AS OCCLUDED
FRONT CROSSES AREA. GUSTY SOUTHEAST WINDS TO 35 KTS AT THE KRUT
TERMINAL.
00Z SUNDAY THRU 12Z MONDAY...CONDITIONS IMPROVING TO MAINLY VFR
EXCEPT OCNL MVFR IN MTN SHSN...ESPECIALLY AT KSLK/KMPV.
12Z MONDAY THRU 12Z TUE...VFR TRENDING MVFR/IFR IN SHSN/SQ AS UPPER
LOW AND STRONG COLD FRONT AFFECT THE REGION. GUSTY NORTHERLY WINDS
DEVELOPING AFTER 06Z TUE.
12Z TUE THRU 00Z WED...MAINLY VFR WITH SCT MVFR IN MTN SHSN...MAINLY
AT THE KSLK TERMINAL. GUSTY NORTHERLY WINDS.
00Z WED THRU 00Z THU...VFR WITH HIGH PRESSURE.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...NONE.
NY...WINTER WEATHER ADVISORY UNTIL 5 AM EST SUNDAY FOR NYZ029-030-
034-087.
WINTER STORM WARNING UNTIL 5 AM EST SUNDAY FOR NYZ026-027-031.
&&
$$
SYNOPSIS...BANACOS
NEAR TERM...BANACOS/AMF
SHORT TERM...BANACOS
LONG TERM...JMG
AVIATION...HANSON
