November 24, 2012 Forecast Discussion

000
FXUS61 KALY 241416
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
916 AM EST SAT NOV 24 2012

.SYNOPSIS…
A COLDER AIRMASS WILL BE USHERED INTO THE REGION OVER THE WEEKEND ON
BRISK AND GUSTY WEST TO NORTHWEST WINDS. THE COLDER AIR MOVING OVER
THE RELATIVELY WARM WATERS OF LAKE ONTARIO WILL RESULT IN LAKE
EFFECT SNOW SHOWERS OVER THE WEEKEND. ALSO…THERE MAY BE SOME
UPSLOPE SNOW SHOWERS ACROSS THE TACONICS…BERKSHIRES AND SOUTHERN
VERMONT TODAY.

&&

.NEAR TERM /THROUGH TONIGHT/…
AS OF 915 AM EST…MUCH COLDER AND A MORE SEASONABLE AIRMASS WILL
BE USHERED INTO THE REGION ON BRISK AND GUSTY WEST TO NORTHWEST
WINDS THROUGHOUT THE DAY TODAY.

THE 12Z KALY SOUNDING HAD A 850 MB TEMP OF -8 DEGREES C. 850 MB
TEMPERATURES ARE EXPECTED TO DROP TO AROUND -10 DEGREES CELSIUS
THIS AFTN BASED ON MODEL GUIDANCE. BASED ON GLERL THE LAKE- WIDE
AVERAGE SURFACE TEMPERATURE OF LAKE ONTARIO IS 49 DEGREES
FAHRENHEIT OR 9 DEGREES CELSIUS. DIFFERENTIAL IS GREAT ENOUGH FOR
LAKE EFFECT PRECIPITATION AND THERMAL PROFILES SUPPORT SNOW.

BANDS OF LAKE EFFECT SNOW HAVE BEEN ONGOING THROUGH THE MORNING
HOURS ACROSS THE WESTERN ADIRONDACKS AND IT HAS BEEN APPROACHING
NORTHERN PORTIONS OF THE MOHAWK VALLEY. RADAR REFLECTIVITY HAS
SHOWN SOME VALUES AROUND 30 DBZ WITHIN THE BANDS…SO MODERATE TO
HEAVY BURSTS WITH SNOW RATES AROUND ONE INCH PER HOUR ARE
CERTAINLY POSSIBLE.

SOME SNOW SHOWERS/FLURRIES ARE EVEN MAKING IT FAR ENOUGH EAST TO
REACH THE CAPITAL REGION/LAKE GEORGE/SARATOGA AREA…BUT SNOW
RATES WILL BE MUCH LOWER…AND NO MORE THAN JUST A BRIEF COATING
ON GRASSY/NON PAVED SURFACES IS EXPECTED AT MOST FOR THESE AREAS.

THE UPPER TROF AXIS WILL SWING THROUGH TODAY AS THE NEARLY STACKED
LOW MOVES ACROSS EASTERN CANADA ALONG WITH A SHORT WAVE ROTATING
THROUGH THE BASE. THIS WILL CAUSE A SHIFT IN THE LOW LEVEL FLOW FROM
WEST TO NORTHWEST SHIFTING THE FOCUS OF THE LAKE EFFECT FROM THE
WESTERN ADIRONDACKS SOUTHWARD ACROSS THE WESTERN MOHAWK VALLEY THEN
TO THE SCHOHARIE VALLEY AND EASTERN CATSKILLS. THIS MOVEMENT SHOULD
KEEP ACCUMULATIONS LIGHT AND BELOW ADVISORY CRITERIA.

IN ADDITION…WITH THE WESTERLY FLOW SOME UPSLOPE SNOW SHOWERS ARE
EXPECTED ACROSS THE TACONICS…BERKSHIRES AND SOUTHERN VERMONT.
COVERED THIS WILL CHANCES POPS.

AS FOR TEMPERATURES WENT ON THE COLD SIDE OF GUIDANCE AS
TEMPERATURES ALOFT DROP IN COLD AIR ADVECTION. EXPECTING HIGHS MOSTLY
30S WITH SOME LOWER 40S IN THE HUDSON RIVER VALLEY WITH SOME 20S
ACROSS THE HIGHER TERRAIN. FOR TONIGHT EXPECTING 20S AND TEENS WITH
SOME SINGLE DIGITS ACROSS THE SOUTHERN ADIRONDACKS.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/…
BY 12Z/SUNDAY THE UPPER FLOW ACROSS THE REGION WILL BECOME ZONAL AND
THIS IS EXPECTED TO PERSIST INTO MONDAY. A SHORT WAVE EXPECTED TO
MOVE THROUGH THIS QUICK FLOW AND ACROSS THE REGION. THE LOW LEVEL
FLOW WILL BECOME WESTERLY AND SHIFT THE FOCUS OF LAKE EFFECT BACK
NORTHWARD INTO THE WESTERN ADIRONDACKS. EXPECTING LIGHT TO
POSSIBLY MODERATE ACCUMULATIONS OCCURRING SUNDAY NIGHT. WILL
MENTION THIS IN THE HAZARDOUS WEATHER OUTLOOK FOR NORTHERN
HERKIMER AND HAMILTON COUNTIES.

A TROUGH IS EXPECTED TO APPROACH THE REGION FROM THE WEST MONDAY
AFTERNOON AND NIGHT RESULTING IN SOUTHWESTERLY FLOW DEVELOPING
ACROSS THE REGION. THIS CHANGE IN FLOW WILL DISRUPT THE LAKE EFFECT
BRINGING IT TO AN END.

SUNDAY WILL BE ANOTHER COLD AND BLUSTERY DAY WITH HIGHS MOSTLY IN
THE 30S. MONDAY IS EXPECTED TO BE A COUPLE/FEW DEGREES MILDER BUT
STILL FALLING SHORT OF NORMAL. WILL HAVE SOME SUNSHINE AND THE WINDS
WILL NOT BE A STRONG.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/…
THE MODEL SPREAD AND UNCERTAINTY CONTINUES FOR THE TUE TO WED TIME
FRAME FOR A POTENTIALLY QUICK MOVING WAVE OF LOW PRESSURE NEAR THE
MID ATLANTIC AND NEW ENGLAND COASTLINE.

THE NEW TWIST IS THAT THE 00Z GFS HAS TRENDED FURTHER NORTH…AND
HEAVIER WITH FAVORABLE THERMAL PROFILES FOR AN ALL SNOW EVENT…THAT
COULD BE ON THE MODERATE TO BORDERLINE HEAVY SIDE FOR PORTIONS OF
THE FCST AREA. HOWEVER…THE CANADIAN GGEM…AND LATEST ECMWF ARE
SHOWING MORE OF A LIGHT SNOW EVENT…WHERE ROUGHLY THE CAPITAL
REGION…ERN CATSKILLS…AND SRN VT SOUTH AND EAST GET CAUGHT IN THE
DEFORMATION ZONE OF THE COASTAL WAVE MOVING NORTHEAST FROM THE MID
ATLANTIC REGION TUE MORNING INTO TUESDAY NIGHT TO SOUTH OF LONG
ISLAND.

THE LATEST HPC GUIDANCE AND THE 00Z GLOBAL ENSEMBLE MEAN SEEM TO BE
A GOOD COMPROMISE FOR TUE INTO WED. THE 00Z GLOBAL ENSEMBLE MEAN
HAS A WEAK WAVE OF LOW PRESSURE E/SE OF LONG ISLAND BY 12Z WED WITH
SEVERAL MEMBERS /AROUND A HALF A DOZEN/ CLUSTERED NEAR THE 70W/40N
BENCHMARK AT 12Z WED. AT THIS POINT WE CONTINUED WITH HIGH CHC POPS
FROM THE CAPITAL REGION SOUTH AND EAST LATE TUE INTO TUE
NIGHT…WITH SNOW AS THE PREDOMINANT PTYPE…WITH PERHAPS A MIX WITH
RAIN BEFORE THE BOUNDARY LAYER COOLS QUICKLY. THE 850 HPA TEMPS
STAY BELOW FREEZING ON THE EC/GFS AS FAR SOUTH AS LONG ISLAND…WITH
THE 925 HPA TEMP NEAR 0C CLOSE TO THE LOWER HUDSON VALLEY. UNTIL
THEIR IS BETTER AGREEMENT WITH THE MEDIUM RANGE GUIDANCE WITH THE
TRACK…EVOLUTION…QPF AND TIMING OF THE SYSTEM…WE WILL NOT
MENTION IT IN THE HWO. OUR CONSENSUS RIGHT NOW IS FOR A LIGHT SNOW
EVENT WITH A FEW INCHES POSSIBLE /LESS THAN 4"/…BUT AGAIN THE GFS
IS HINTING AT GREATER ACCUMS WITH ITS TRACK…JUST EAST OF LONG
ISLAND…AND THEN CAPE COD BY NOON WED. A SOUTHERN STREAM AND NRN
STREAM SHORT-WAVE WILL HAVE TO PHASE ASSOCIATED WITH THE EVOLVING
LONG-WAVE TROUGH FOR THIS SCENARIO TO MATERIALIZE. BOTTOM LINE…LOW
CONFIDENCE FCST STILL…AND STAY TUNED.

WED PM-WED NIGHT…SFC LOW DEPARTS INTO THE CANADIAN MARITIMES WITH
CYCLONIC FLOW PERSISTING WITH PERHAPS A BRIEF PERIOD OF LAKE EFFECT
AND UPSLOPE SNOW SHOWERS AND FLURRIES. THE UPPER LEVEL TROUGH AXIS
ALSO MOVES DOWNSTREAM OF THE REGION BY THU MORNING.

THU…HIGH PRESSURE BRIEFLY BUILDS IN FROM THE SOUTHEAST AND MID
ATLANTIC REGION. MEANWHILE…ANOTHER WEAK UPPER AIR DISTURBANCE MAY
BRING ISOLATED OR SCATTER SNOW SHOWERS DURING THE NIGHT TIME PERIOD
NORTH AND WEST OF THE CAPITAL REGION. THE FLOW LOOKS TO VEER QUICKLY
TO THE N/NW ENDING ANY LAKE EFFECT.

FRI INTO NEXT WEEKEND…A LARGE DOME OF CANADIAN HIGH PRESSURE
BUILDS IN OVER THE NORTHEAST WITH COLD AND DRY WEATHER. TEMPS WILL
CONTINUE TO RUN BELOW NORMAL HERE.

OVERALL…TEMPS ARE EXPECTED TO RUN SLIGHTLY BELOW TO BELOW NORMAL
WITH PCPN HIGHLY DEPENDENT ON WHAT HAPPENS TUE-WED.

&&

.AVIATION /14Z SATURDAY THROUGH WEDNESDAY/…
A COLD FRONT CONTINUES TO MOVE EAST OF NEW ENGLAND THIS MORNING. A
SECONDARY COLD FRONT WILL MOVE THROUGH LATER TODAY. HIGH PRESSURE
WILL BUILD IN FROM THE SOUTH FOR THE SECOND HALF OF THE WEEKEND…
WITH LAKE EFFECT SNOWFALL ENDING BY SUNDAY NW OF THE CAPITAL REGION.

VFR CONDITIONS ARE EXPECTED IN THE WAKE OF THE COLD FRONT. THE CIGS
WILL REMAIN IN THE VFR RANGE THE NEXT 24-HRS AT 3.5-6 KFT AGL…WITH
POTENTIALLY SOME HIGH MVFR CIGS AT KPSF IN THE EARLY PM.

THE W/NW WINDS WILL STRENGTHEN TO 12-18 KTS BY THE LATE MORNING INTO
THE EARLY PM…WITH SOME GUSTS IN THE 25-30 KT RANGE DUE TO DEEPER
MIXING OF MOMENTUM FROM ALOFT. THE LOW LEVEL SFC PRESSURE GRADIENT
WILL ALSO BE STRENGTHENING BETWEEN DEPARTING LOW PRESSURE INTO THE
CANADIAN MARITIMES…AS HIGH PRESSURE OVER THE LOWER MS RIVER VALLEY.

THE WINDS WILL GRADUALLY SUBSIDE TONIGHT TO 5-12 KTS WITH RESIDUAL
CLOUDINESS DUE TO LAKE EFFECT SNOW SHOWERS UPSTREAM OF THE HUDSON
RIVER VALLEY PRIOR TO MIDNIGHT.

OUTLOOK…
SUN-MON…VFR. NO SIG WX.
TUE…VFR/MVFR/IFR. CHC SNOW.
WED…VFR/MVFR. CHC -SHSNS.

&&

.HYDROLOGY…
NO HYDROLOGIC PROBLEMS ARE EXPECTED THROUGH THE NEXT 5 DAYS. SOME

LAKE EFFECT SNOWS WILL AFFECT AREAS TO THE WEST OF THE HUDSON RIVER
OVER THE WEEKEND. ALSO…SOME UPSLOPE SNOWS WILL OCCUR ACROSS THE
TACONICS…BERKSHIRES AND SOUTHERN VERMONT.

WITH A COLDER MORE SEASONABLE AIRMASS BEING USHERED OVER THE
WEEKEND SOME ICE WILL START TO DEVELOP ON RIVERS AND PONDS ESPECIALLY
ACROSS NORTHERN COUNTRY AND THE HIGHER TERRAIN. SOME ICE EFFECTS
COULD BE SEEN ON GAGES BY LATE NEXT WEEK.

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
NEAR TERM…IAA/FRUGIS
SHORT TERM…IAA
LONG TERM…WASULA
AVIATION…WASULA
HYDROLOGY…IAA

Unless otherwise stated, the content of this page is licensed under Creative Commons Attribution-ShareAlike 3.0 License