December 24, 2012 Forecast Discussion

000
FXUS61 KALY 241809
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
1250 PM EST MON DEC 24 2012

.SYNOPSIS…
HIGH PRESSURE WILL BRIEFLY BUILD IN FOR TONIGHT AND MONDAY. A
LIGHT ACCUMULATION OF SNOW IS EXPECTED CHRISTMAS EVE NIGHT INTO
CHRISTMAS MORNING AS AN AREA OF LOW PRESSURE PASSES TO OUR SOUTH.
A POTENT STORM SYSTEM WILL IMPACT THE REGION LATE WEDNESDAY INTO
THURSDAY. INITIALLY SNOW WILL OVERSPREAD THE AREA FOLLOWED BY
MIXED PRECIPITATION AS WARMER AIR WORKS INTO THE REGION.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/…
AS OF 1230 PM…FINALLY…THE LOW CLOUDS HAVE BEGUN BREAKING UP…AT
LEAST THE CAPITAL REGION…STILL LINGERING ACROSS THE MOHAWK VALLEY
AND ADIRONDACKS. STILL THINK THEY WILL CONTINUE TO ERODE…BUT NOW
THE HIGH CLOUDS HAVE BEGUN STREAMING NORTH AND EASTWARD FROM THE
SYSTEM IN THE OHIO VALLEY THAT WILL BRING A LITTLE SNOW TONIGHT.

MEANWHILE…SOME SUNSHINE SEEN FROM THE HUDSON VALLEY EAST. DUE TO
THE SUNSHINE…AND HIGHER TEMPERATURES OVERNIGHT…CURRENT
TEMPERATURES HAVE IN SOME CASES…ECLIPSED THE CURRENT ADVERTISED
HIGHS…SO INCREASED TEMPERATURES FROM THE CAPITAL DISTRICT…BY A
COUPLE OF DEGREES.

IT WILL REMAIN DRY FOR THE REST OF TODAY…WITH A GRADUAL INCREASE
IN HIGH CLOUDINESS…BUT A REDUCTION THE LAKE ENHANCED CLOUDS TO THE
WEST OF THE CAPITAL REGION. EXPECT THE HIGH TEMPERATURES TO
GENERALLY RANGE FROM THE MID 20S NORTHWEST TO UPPER 30S SOUTHEAST.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/…
TONIGHT INTO CHRISTMAS MORNING…A WEAK AREA OF LOW PRESSURE IS
EXPECTED TO MOVE RAPIDLY EAST FROM THE OHIO VALLEY THIS EVENING
WITH A SECONDARY LOW DEVELOPING IN THE DELMARVA REGION LATE
TONIGHT AND THEN QUICKLY EXITING OFF THE NEW JERSEY COAST
CHRISTMAS MORNING. THE SPEED OF THE SYSTEM…LACK OF MOISTURE
ASSOCIATED WITH IT…AND INABILITY TO TAP MUCH IN THE WAY OF
ATLANTIC MOISTURE WILL ONLY PRODUCE LIGHT AMOUNTS OF QPF…BETWEEN
A TENTH AND TWO TENTHS OF AN INCH ACROSS THE FA. THE PTYPE IS
EXPECTED TO BE MAINLY SNOW…HOWEVER LATE TONIGHT ACROSS THE MID
HUDSON VALLEY AND LITCHFIELD HILLS IN CONNECTICUT PARTIAL
THICKNESS VALUES AND MODEL SOUNDINGS SUPPORT THE POSSIBILITY OF
SOME LIGHT FREEZING RAIN OR EVEN FREEZING DRIZZLE AS DRIER AIR
WORKS IN ABOVE THE -10C LEVEL. HAVE ADDED CHANCE OF FREEZING RAIN
TO THESE ZONES EARLY ON CHRISTMAS DAY. THE BULK OF THE
PRECIPITATION IS EXPECTED TO FALL FROM THIS EVENING THROUGH THE
OVERNIGHT WITH AREAS FROM THE SOUTHERN ADIRONDACKS THROUGH THE
LAKE GEORGE SARATOGA REGION INTO SOUTHERN VERMONT NOT LIKELY TO
SEE ANY SNOW UNTIL AROUND OR SHORTLY AFTER MIDNIGHT. THE SNOW IS
EXPECTED TO TAPER OFF FAIRLY EARLY CHRISTMAS MORNING WITH TOTAL
ACCUMULATIONS GENERALLY AROUND AN INCH IN THE VALLEYS AND 1 TO 3
INCHES ACROSS THE HIGHER TERRAIN…EXCEPT 2 TO 4 INCHES EXPECTED
ACROSS PASTS OF THE EASTERN CATSKILLS AND SOUTHERN ADIRONDACKS. LOWS
ARE EXPECTED TO BE IN THE MID TEENS TO MID 20S.

CHRISTMAS AFTERNOON THROUGH TUESDAY NIGHT…HIGH PRESSURE IS
EXPECTED TO NOSE INTO THE REGION FROM SOUTHERN CANADA RESULTING IN
SKIES BECOMING PARTLY SUNNY DURING THE AFTERNOON. THIS WILL BE
FOLLOWED BY A CHILLY NIGHT WITH MAINLY CLEAR SKIES AND GOOD
RADIATIONAL COOLING WITH A FRESH…ALBEIT THIN…SNOW COVER IN
MANY AREAS. EXPECT HIGHS ON CHRISTMAS DAY IN THE MID 20S TO UPPER
30S WITH LOWS TUESDAY NIGHT IN THE SINGLE DIGITS AND TEENS IN MOST
AREAS.

ON WEDNESDAY…EXPECT INCREASING CLOUDS DURING THE MORNING AND
PCPN DEVELOPING FROM SOUTHWEST TO NORTHEAST DURING THE AFTERNOON AS
A POTENT DOUBLE BARREL STORM SYSTEM LIFTS NORTHEAST THROUGH THE
TENNESSEE VALLEY AND VIRGINIA BY LATE WEDNESDAY. FAIRLY STRONG
FRONTOGENESIS IS ALREADY MOVING INTO SOUTHERN PORTIONS OF THE FA
BY DAYS END WITH THE LEADING EDGE OF SNOW EXPECTED TO BE ACROSS THE
SOUTHWEST 2/3RDS OF THE FA BY DAYS END. ANY ACCUMULATIONS ON
WEDNESDAY AFTERNOON WILL BE FAIRLY LIGHT GENERALLY A FEW TENTHS OF
AN INCH TO PERHAPS 2 INCHES ACROSS THE SOUTHEAST CATSKILLS. EXPECT
HIGHS ON WEDNESDAY TO RANGE FROM THE MID 20S NORTHWEST TO THE MID
30S SOUTHEAST.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/…
A VERY ACTIVE STRETCH OF WEATHER EXPECTED…WITH TWO POTENTIALLY
SIGNIFICANT WINTER STORMS…ONE WED NT-THU…THEN ANOTHER POSSIBLE
STORM FOR LATE SAT-SUN. IN BETWEEN…EXPECT BELOW NORMAL
TEMPS…ALONG WITH BLUSTERY CONDITIONS…AND POSSIBLE LAKE
EFFECT/ENHANCED SNOW SHOWERS. GENERALLY UTILIZED 00Z/24 HPC DATA FOR
POPULATING MOST PORTIONS OF THE GRIDDED DATABASE.

HERE ARE SOME SPECIFICS…

WED NT-THU…00Z/24 DETERMINISTIC MODELS AND GEFS CONTINUE TO NARROW
DOWN THE POTENTIAL PATH AND EVOLUTION OF THE STORM SYSTEM…WITH THE
INITIAL SFC LOW EXPECTED TO TRACK FROM THE WESTERN GULF COAST
REGION…INTO THE TENNESSEE VALLEY REGION WED AFTERNOON…BEFORE
REDEVELOPING EAST OF THE APPALACHIANS…SOMEWHERE NEAR OR JUST
NORTHEAST OF THE NATION/S CAPITAL. THIS NEW LOW CENTER IS THEN
EXPECTED TO TRACK NORTHEASTWARD…TO NEAR OR JUST EAST OF NYC THU
MORNING…TO NEAR CAPE COD BY LATE THURSDAY. THIS TRACK WOULD BE
QUITE FAVORABLE FOR A POTENTIALLY MODERATE TO HEAVY SNOWFALL FOR AT
LEAST AREAS NORTH AND WEST OF THE IMMEDIATE CAPITAL REGION. FORECAST
MODEL SOUNDINGS DO HINT AT A WARM NOSE OF ABOVE FREEZING TEMPS
BETWEEN 900-800 MB INTRUDING FOR AREAS NEAR…EAST AND SOUTH OF
ALBANY…BY DAYBREAK THURSDAY…BEFORE GRADUALLY ERODING THU
AFTERNOON AS DYNAMIC COOLING INTENSIFIES AS THE MID LEVEL LOW CENTER
PASSES JUST SOUTH AND EAST OF THE REGION. SO…FOR AREAS NORTH AND
WEST OF ALBANY…INCLUDING THE SOUTHERN ADIRONDACKS…MOHAWK
VALLEY…LAKE GEORGE/SARATOGA REGION…AND MUCH OF SOUTHERN VT…THE
POTENTIAL IS INCREASING FOR A MODERATE TO HEAVY SNOWFALL ALONG WITH
A PERIOD OF SLEET FROM LATE WED INTO THU. FROM THE SE
CATSKILLS…SCHOHARIE VALLEY REGION…THE GREATER CAPITAL
REGION…AND CENTRAL/NORTHERN BERKSHIRES…ALTHOUGH A BURST OF SNOW
IS LIKELY WITH THE WARM ADVECTION WED NT WHICH COULD LEAVE MODERATE
SNOWFALL AMOUNTS…ENOUGH WARMING ALOFT SHOULD ALLOW FOR SNOW TO MIX
WITH…AND EVENTUALLY CHANGE TO SLEET/FREEZING RAIN AND PLAIN RAIN
THU MORNING…BEFORE CHANGING BACK TO SNOW LATE THU. FURTHER SOUTH
AND EAST…ACROSS THE MID HUDSON VALLEY…SOUTHERN BERKSHIRES AND
LITCHFIELD HILLS…LESS SNOWFALL IS EXPECTED…BUT A PERIOD OF
SLEET/FREEZING RAIN WILL BE POSSIBLE BEFORE CHANGING TO PLAIN RAIN
BY THU MORNING. IN THIS AREA…LIGHT TO MODERATE ICE ACCRETION IS
POSSIBLE. THESE IDEAS ARE WELL SUPPORTED BY THE 00Z/24 ECMWF…WHICH
IS THE COLDER/FARTHEST SOUTHEAST OF THE SOLUTIONS…AND THE 00Z/24
GEFS. THE DETERMINISTIC 00Z/24 GFS ACTUALLY IS AMONG THE
WARMEST/FARTHEST NORTHWEST OF ITS MEMBERS…WITH THE GEFS MEAN
PLACEMENT OF THE SFC LOW CLOSER TO THE ECMWF SOLUTION. THE GEFS ALSO
INDICATE THE POTENTIAL FOR MODERATE TO HEAVY QPF…AS DENOTED BY THE
850 EASTERLY COMPONENT WINDS OF 5-6 STD OVER OUR REGION.

THU NT-FRI NT…WINDY AND COLD BEHIND THE FIRST SYSTEM. NUMEROUS
SNOW SHOWERS WILL BE LIKELY…WITH THE POSSIBILITY OF LAKE
ENHANCED/EFFECT SNOWBANDS IMPACTING NORTHWEST AREAS. EXPECT MAX
TEMPS TO REACH THE 20S TO LOWER 30S…EXCEPT TEENS ACROSS HIGHER
ELEVATIONS…WITH OVERNIGHT MINS MAINLY IN THE SINGLE DIGITS AND
TEENS.

SAT-SUN…ANOTHER STORM SYSTEM IS SUGGESTED BY 00Z/24 DETERMINISTIC
MODELS…WITH THE ECMWF FARTHEST NORTH AND WEST…AND MOST
AGGRESSIVE IN DEEPENING THE SFC LOW…WHILE THE GFS AND GEFS MEAN
ARE FURTHER SOUTH AND EAST. WILL INDICATE CHC POPS FOR SNOW FROM SAT
AFTN INTO SUNDAY…WITH THE HIGHEST POPS ACROSS SOUTHERN AND EASTERN
AREAS. SHOULD THE 00Z/24 ECMWF PROVE CORRECT…ANOTHER SIGNIFICANT
WINTER STORM COULD IMPACT AT LEAST PORTIONS OF THE REGION DURING
THIS TIME…FAVORING AREAS MAINLY SOUTH AND EAST OF ALBANY.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/…
NO AVIATION RELATED PROBLEMS THIS AFTERNOON THROUGH THE EVENING PEAK
WITH VFR CONDITIONS AND GENERALLY LIGHT WIND.

THERE OCCASIONALLY COULD BE A FEW GUSTS AT KPSF TO ABOUT 18KTS FROM
THE NORTHWEST…BUT THESE GUSTS LOOK TO DISSIPATE LATER ON THIS
AFTERNOON.

WEAK LOW PRESSURE WILL TRACK TO OUR SOUTH OVERNIGHT AND LOOKS TO
BRING LIGHT SNOW TO ALL THE TAF SITES. AHEAD OF THE LIGHT SNOW…THE
CLOUDS WILL LOWER AND THICKEN BY THIS EVENING. SINCE WE ARE TALKING
SNOW…WE EXPECT PREDOMINATELY IFR CONDITIONS LATER TONIGHT STARTING
OUT (05Z/KPOU…06Z/KPSF/07Z KALB/09Z KGFL). CALLING IT 2SM -SN
GENERALLY MVFR CIGS (EXCEPT IFR CIGS AT KPOU).

THERE WILL BE A TENDENCY FOR THE CLOUDS TO LOOSE THEIR ICE DOWN NEAR
KPOU…SO FOR NOW…INCLUDED A PROB30 FOR -FZDZ AFTER 13Z.
OTHERWISE…LOOK FOR LINGERING LIGHT SNOW…MAINLY AT KALB AND KGFL
THROUGH TUESDAY MORNING.

ANY SNOW OR LIGHT FREEZING DRIZZLE SHOULD END AFTER MIDDAY
TUESDAY…BUT MVFR CLOUDS COULD LINGER.

OUTLOOK…
TUE NT-WED AM…VFR. NO SIG WX.
WED PM…VFR/MVFR. SNOW LIKELY.
WED NT…SUB-VFR. SNOW OR MIXED PCPN.
THU…MVFR/IFR. SNOW OR MIXED PCPN BCMG MAINLY SNOW LATE.
THU NT-FRI…VFR/MVFR. CHC -SHSN. WINDY.
FRI…VFR. NO SIG WX.
SAT…VFR. CIG. CHC SUB-VFR IN -SN BY LATE IN THE DAY.
&&

.HYDROLOGY…
FAIRLY LIGHT PRECIPITATION IS EXPECTED TONIGHT INTO CHRISTMAS
MORNING WITH TOTAL QPF AMOUNTS OF A TENTH TO TWO TENTHS OF AN INCH
WITH MOST OF THE PCPN IN THE FORM OF SNOW.

A MORE POTENT STORM SYSTEM WILL IMPACT THE REGION LATE WEDNESDAY
INTO THURSDAY. INITIALLY SNOW WILL OVERSPREAD THE AREA WEDNESDAY
WITH MIXED PRECIPITATION EXPECTED AS WARMER AIR WORKS INTO THE
REGION WEDNESDAY NIGHT. THIS SYSTEM HAS THE POTENTIAL TO BRING
SIGNIFICANT QPF TO THE AREA. HOWEVER THE MODELS ARE STILL IN SOME
DISAGREEMENT ABOUT THE EXACT TRACK OF THE STORM…WHICH WILL HAVE
AN IMPACT ON P-TYPE. REFER TO THE LONG TERM DISCUSSION FOR MORE
DETAILS. WILL KEEP MENTION IN THE HAZARDOUS WEATHER OUTLOOK.

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/11
NEAR TERM…HWJIV
SHORT TERM…11
LONG TERM…KL
AVIATION…HWJIV
HYDROLOGY…IAA/11

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