December 7, 2013 Forecast Discussion

000
FXUS61 KALY 071653
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
1153 AM EST SAT DEC 7 2013

.SYNOPSIS…
HIGH PRESSURE WILL BUILD FROM THE GREAT LAKES INTO THE NORTHEAST
FOR THE REST OF THE WEEKEND. WEAK LOW PRESSURE WILL ORGANIZE OFF
THE MID ATLANTIC COAST AS THE HIGH RETREATS SUNDAY NIGHT.
INITIALLY SNOW IS EXPECTED TO OVERSPREAD THE AREA SUNDAY
NIGHT…BUT AS WARMER AIR MOVES IN THE SNOW WILL CHANGE TO A
WINTRY MIX…THEN TO RAIN MONDAY. HIGH PRESSURE WILL CREST OVER
THE REGION MIDWEEK.

&&

.NEAR TERM /THROUGH SUNDAY/…
AS OF 1130 AM EST…FCA UNDER SCT-MAINLY BKN STRATO-CU. WAVE
CLOUDS AS WELL AS 12UTC ALY RAOB SHOWS TWO INVERSIONS AND
TRAPPING. AWAY FM LK ONTARIO THESE CLOUDS WILL CONTINUE TO ERODE
AWAY THOUGH THE AFTERNOON AS THE UPPER INVERSION ERODES AND DRY
AIR FILTERS IN THE LLVLS.

LAKE EFFECT RESPONSE WILL BE MODEST REST OF TDY AND TNGT. AS
NIZIOL INSTAB CLASS ONLY COND…30-60 DEG OF SHEAR…SUB INVERSION
FLOW SHIFTING 270-290 TDY AND INVERSION BTWN 5-8KFT AND LLVL FLOW
ANTI CYCLONIC. MAINLY FLURRIES OVER HIR TRRN AND SCT -SHSN IN W
ADIRONDACKS.

OTRW ROARING SW-NE BAJA TO BANGOR 500 HPA FLO…AS SFC ARCTIC HIGH
BUILDS FM GRTLKS INTO NW TNGT AND SUN…BFE SLIDING OFF INTO THE
MARITIMES SUN NT. COASTAL FRONT BGNS ORGANIZING ALONG ATLC COAST
SUN AFT…AS WEAK RETURN FLOW AND OVERRUNNING BEGINS TO ORGANIZE
AHEAD OF NEXT SYSTEM. SOME MAINLY HIGH CLOUDS WITH THIS SYSTEM
WILL REACH THE RGN LATE SUN.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/…
SUNDAY NIGHT THROUGH MONDAY NIGHT LOOKS TO BE FAIRLY ACTIVE AS
THE SURFACE HIGH DEPARTS ACROSS NORTHERN NEW ENGLAND AND EASTERN
CANADA WHILE A WAVE OF LOW PRESSURE MOVES INTO THE GREAT LAKES
REGION AND A SECOND WAVE OF LOW PRESSURE STARTS TO LIFT NORTHEAST
FROM THE SOUTHEAST COAST. THE ORIENTATION OF THE SURFACE HIGH WILL
BE SUCH THAT COLD AIR DAMMING IN PLACE WHILE WARMER AIR ALOFT
ATTEMPTS TO RIDE OVER THE TOP OF THE DEPARTING RIDGE. PTYPE FROM
PARTIAL THICKNESS VALUES WAS USED FOR DETERMINING PTYPE SUNDAY
NIGHT THROUGH MONDAY NIGHT. INITIALLY ALL OF THE PTYPE WILL BE
SNOW SUNDAY NIGHT…HOWEVER LATER AT NIGHT THE PCPN IS LIKELY TO
CHANGE TO SLEET AND FREEZING RAIN ESPECIALLY SOUTH AND EAST OF THE
CAPITAL DISTRICT. GEFS PLUME DIAGRAM FOR KALB SHOWS A NUMBER OF
MEMBERS FAVORING THE CHANGE TO FREEZING RAIN LATE AT NIGHT AS DO
THE SREF PTYPE PROBABILITY FIELDS. WHILE IT IS TOO EARLY TO ISSUE
AN ADVISORY THIS WILL BE HIGHLIGHTED IN THE HWO. QPF AMOUNTS ARE
NOT EXPECTED TO BE GREAT HOWEVER A COUPLE OF INCHES OF SNOW
FOLLOWED BY LIGHT ICING MAY RESULT IN A DIFFICULT MORNING COMMUTE
ON MONDAY. DURING THE DAY ON MONDAY TEMPS ARE EXPECTED TO WARM
INTO THE MID 30S TO LOWER 40S WITH A CHANGEOVER TO RAIN EVERYWHERE
EXCEPT PERHAPS THE FAR NW PTN OF THE FA WHICH WILL REMAIN MAINLY
SNOW. THE WINTRY PCPN IS EXPECTED TO CONTINUE INTO AT LEAST MONDAY
EVENING WITH A CHANGE BACK FROM RAIN TO A WINTRY MIX ONCE AGAIN. A
FEW AREAS SUCH AS THE ERN CATSKILLS AND LITCHFIELD HILLS MAY PICK
UP A TENTH OF AN INCH OF ICING TOTAL WITH SNOWFALL AMOUNTS ACRS
THE AREA GENERALLY 1 TO 3 INCHES. LOWS MONDAY NIGHT ARE EXPECTED
TO BE IN THE UPPER TEEN TO MID 20S.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/…
HAVE POPULATED MUCH OF THIS PORTION OF THE DATABASE WITH 00Z/07
HPC…WITH SOME EXCEPTIONS AS NOTED BELOW.

IT APPEARS THAT THIS PERIOD WILL BE DOMINATED BY BROAD CYCLONIC MID
AND UPPER TROPOSPHERIC FLOW…WITH FAST MOVING…EMBEDDED
DISTURBANCES PASSING THROUGH WITHIN THIS FLOW. EACH DISTURBANCE THAT
PASSES WILL REINFORCE THE ARCTIC AIR ACROSS THE REGION…AND WILL
ALSO ACT TO SHIFT LAKE EFFECT SNOWBANDS ACROSS FAVORABLE PORTIONS OF
THE SOUTHWEST ADIRONDACKS…WESTERN MOHAWK VALLEY…AND SCHOHARIE
VALLEY…WITH SOME EXTENSIONS OF THESE BANDS POSSIBLY REACHING INTO
PORTIONS OF THE HUDSON RIVER VALLEY FROM ALBANY NORTH…AND ALSO
BECOMING LOCALLY ENHANCED WITHIN FAVORABLE UPSLOPE AREAS ACROSS
WESTERN NEW ENGLAND. HOWEVER…GIVEN SOMEWHAT LOW PREDICTABILITY OF
THE FAST MOVING DISTURBANCES…THE TIMING AND AREAL LOCATION OF
THESE SNOWBANDS AT THIS TIME RANGE REMAIN UNCERTAIN. MUCH BELOW
NORMAL TEMPS WILL CONTINUE THROUGH THIS PERIOD.

HERE ARE SOME MORE SPECIFICS…

TUESDAY…SEVERAL MEMBERS OF THE 00Z/07 GEFS INDICATE THAT ANOTHER
WAVE DEVELOPS ALONG A FRONTAL BOUNDARY TO OUR SOUTH ON
TUESDAY…POSSIBLY BRINGING SOME CLOUDS…AND PERHAPS LIGHT SNOW TO
SOUTHERN AREAS…ESP IN THE MORNING…WHERE SLIGHT CHC POPS ARE
INDICATED. OTHERWISE…EXPECT SOME LAKE EFFECT SNOW
SHOWERS/SNOWBANDS TO DEVELOP ACROSS THE WESTERN ADIRONDACKS BY LATE
IN THE DAY AS COLDER AIR INFILTRATES FROM THE WEST. EXPECT MAX TEMPS
TO REACH THE 20S ACROSS HIGHER ELEVATIONS…AND UPPER 20S TO LOWER
30S IN VALLEY AREAS.

TUE NT-FRI…AGAIN…SEVERAL FAST MOVING DISTURBANCES WILL PASS
THROUGH…WITH THE HIGHEST PROBABILITY APPEARING TO BE WED…AND
THEN POSSIBLY AGAIN LATE THU OR EARLY FRI. HAVE INDICATED MAINLY
LAKE EFFECT SNOW ACROSS THE WESTERN ADIRONDACKS/MOHAWK VALLEY AND
SCHOHARIE VALLEY…BUT AGAIN…BANDS WILL LIKELY BE SHIFTING NORTH
AND SOUTH WITH EACH PASSING DISTURBANCE…AND NOT REMAINING IN ONE
PARTICULAR AREA THROUGH THE WHOLE PERIOD. AT TIMES…THESE BANDS
COULD EXTEND INTO VALLEY AREAS…AND ALSO HIGHER ELEVATIONS ACROSS
WESTERN NEW ENGLAND…ESP WHEN LOW LEVEL INSTABILITY IS MAXIMIZED
WITH THE PASSING DISTURBANCES. TEMPS WILL REMAIN WELL BELOW
NORMAL…WITH MAX TEMPS ONLY REACHING THE 20S IN VALLEYS…AND TEENS
ACROSS HIGHER ELEVATIONS…AND OVERNIGHT LOWS FALLING INTO THE
SINGLE DIGITS ABOVE AND BELOW ZERO IN MOST AREAS.

IT SHOULD BE NOTED THAT SOME MODELS…PARTICULARLY THE 00Z/07 GEM
AND TO SOME DEGREE…THE 00Z/07 ECMWF…HINT AT A PARTICULARLY
BITTER COLD AIR MASS SEEPING SOUTHWARD INTO THE REGION BY
FRI…WHILE THE MAJORITY OF 00Z/07 GEFS MEMBERS AND THE 00Z/GFS KEEP
THE CORE OF THE COLDEST AIR ACROSS SOUTHEAST CANADA. SHOULD SOME OF
THIS BITTER COLD AIR REACH OUR REGION…MAX TEMPS MAY FAIL ONLY HOLD
IN THE SINGLE DIGITS AND TEENS DURING THE DAY…WITH WIDESPREAD
SUBZERO READINGS POSSIBLE AT NIGHT…ALONG WITH POTENTIALLY
DANGEROUS WIND CHILLS. TRENDS WILL NEED TO BE WATCHED ON HOW FAR
SOUTH THIS EXTREMELY COLD AIR WILL REACH.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/…
AREAS OF SCT-BKN030-050 CIGS THIS AFTN AND EVNG MAINLY IN W MHWK
VLY AND W ADRNDKS WITH SCT -SHSN. OTRW VFR CONDS WITH 10KT NW
WINDS RST OF TDY. VFR TNGT AND SUNDAY WITH LT AND VRBL WINDS.

OUTLOOK… SUNDAY NIGHT: HIGH OPERATIONAL IMPACT. LIKELY SN.
MONDAY: HIGH OPERATIONAL IMPACT. LIKELY RA…SN…SLEET. MONDAY
NIGHT: MODERATE OPERATIONAL IMPACT. SLIGHT CHANCE OF SN…FZRA.
TUESDAY: NO OPERATIONAL IMPACT. NO SIG WX. TUESDAY NIGHT: NO
OPERATIONAL IMPACT. NO SIG WX. WEDNESDAY: LOW OPERATIONAL
IMPACT.BREEZY SLIGHT CHANCE OF SHSN. WEDNESDAY NIGHT: LOW
OPERATIONAL IMPACT. SLIGHT CHANCE OF SHSN. THURSDAY: LOW
OPERATIONAL IMPACT. SLIGHT CHANCE OF SHSN.

&&

.HYDROLOGY…
NO HYDRO RELATED CONCERNS ARE EXPECTED OVER THE NEXT 5 DAYS.

HIGH PRESSURE IS EXPECTED TO BUILD IN TODAY…WITH THE NEXT ROUND
OF PRECIPITATION IS EXPECTED SUNDAY NIGHT AND MONDAY. INITIALLY
SNOW IS EXPECTED TO OVERSPREAD THE AREA SUNDAY NIGHT. HOWEVER AS
WARMER AIR MOVES IN THE SNOW WILL MIX WITH AND CHANGE TO SLEET AND
FREEZING RAIN WITH CHANGEOVER TO RAIN EXPECTED BY MONDAY AFTERNOON
ACROSS MOST OF THE AREA.

FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES…INCLUDING
OBSERVED AND FORECAST RIVER STAGES AND LAKE ELEVATIONS…PLEASE
VISIT THE ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON
OUR WEBSITE.

&&

.ALY WATCHES/WARNINGS/ADVISORIES…
CT…NONE.
NY…NONE.
MA…NONE.
VT…NONE.

&&

$$
SYNOPSIS…IAA/SND/SNYDER
NEAR TERM…SNYDER
SHORT TERM…11/SNYDER
LONG TERM…KL
AVIATION…KL
HYDROLOGY…11

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