December 15, 2012 Forecast Advisory

Freezing Rain Advisory

000
FXUS61 KALY 151805
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
105 PM EST SAT DEC 15 2012

.SYNOPSIS…
HIGH PRESSURE WILL BRIEFLY BUILD ACROSS THE REGION THIS AFTERNOON
RESULTING IN FAIR WEATHER. A WARM FRONT WILL MOVE TOWARDS OUR AREA
LATE TONIGHT INTO SUNDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE
GREAT LAKES REGION. THIS WILL BRING A WINTRY MIX OF PRECIPITATION
TO THE REGION SUNDAY INTO MONDAY. ADDITIONAL WEATHER SYSTEMS WILL
IMPACT THE REGION NEXT WEEK…WITH UNSETTLED WEATHER POSSIBLE FOR
SEVERAL DAYS.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/…
MINOR ADJUSTMENTS BASED ON OBSERVATIONAL DATA. HIGH CLOUDS
CONTINUE TO APPROACH FROM THE WEST WHERE SOME WEAK WARM ADVECTION
IS BEGINNING. HIGH PRESSURE BUILDING INTO THE REGION FROM CANADA
CONTROLLING OUR WEATHER NOW…SHOULD BUILD EAST THIS AFTERNOON
ALLOWING FOR WEAK WARM ADVECTION TO BEGIN IN OUR REGION AS WELL.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/…
MODELS CONTINUE TO BE IN FAIRLY GOOD AGREEMENT WITH FIRST SURFACE
LOW TRACKING INTO WESTERN GREAT LAKES TONIGHT AND UPPER GREAT
LAKES SUNDAY AND SUNDAY NIGHT. MUCH MORE UNCERTAINTY EXISTS WITH
THE SECOND LOW PRESSURE SYSTEM WHICH IS EXPECTED TO FORM ALONG
THE WARM FRONTAL BOUNDARY DRAPED TO OUR SOUTH OVER THE MIDDLE
ATLANTIC REGION LATE SUNDAY NIGHT AND SLOWLY LIFT EAST OR
NORTHEAST PERHAPS AS A DOUBLE BARREL LOW PRESSURE SYSTEM LATE
MONDAY. THE PRECISE LOCATION OF THESE SYSTEMS AS WELL AS THE
LOCATION OF THE WARM FRONT AND ROLE OF THE DEPARTING HIGH PRESSURE
CENTER TO THE NORTHEAST…HOLD THE KEY TO THE FORECAST ESPECIALLY
WITH REGARDS TO PTYPE.

TONIGHT AND SUNDAY…AS THE FIRST LOW PRESSURE SYSTEM MOVES INTO
THE UPPER GREAT LAKES REGION AND THE FRONTAL BOUNDARY WHICH PASSED
THROUGH OUR REGION EARLY THIS MORNING STARTS MOVING BACK TOWARDS
OUR REGION TONIGHT…ISENTROPIC LIFT AND OVERRUNNING PCPN WILL
START TO ADVANCE ACRS THE FA FROM SOUTHWEST TO NORTHEAST STARTING
LATE TONIGHT AND CONTINUING DURING THE DAY ON SUNDAY. PARTIAL
THICKNESS VALUES AND MODEL SOUNDINGS INDICATE THAT MOST OF THE FA
WILL BE COLD ENOUGH FOR SNOW AT THE ONSET THROUGH MID MORNING WITH
A TRANSITION TO SLEET AND FREEZING RAIN IN MANY AREAS FROM MID
MORNING INTO THE AFTERNOON. THE WINTRY MIX ACROSS VALLEY
LOCATIONS ACRS THE SOUTHERN THIRD OF THE FA WILL BE RATHER
BRIEF…A FEW HOURS AT MOST AND THEN TRANSITION TO RAIN SUNDAY
AFTERNOON. THE MAIN AREA OF CONCERN AT THIS TIME WILL BE AREAS TO
THE NORTH FROM THE SOUTHERN ADIRONDACKS ACROSS THE LAKE GEORGE
SARATOGA REGION AND INTO SOUTHERN VERMONT AND PERHAPS THE NORTHERN
BERKSHIRES WHERE TEMPS WILL STRUGGLE TO REACH FREEZING ON SUNDAY
AND WHERE SNOW WILL TRANSITION TO FREEZING RAIN AND SLEET. QPF
AMOUNTS ARE QUITE LOW HOWEVER THROUGH SUNDAY WITH GENERALLY A
TENTH TO TWO TENTHS OF AN INCH. SNOW AMOUNTS AT THIS POINT ARE
EXPECTED TO BE A FEW TENTHS OF AN INCH TO SLIGHTLY OVER AN INCH
WITH ICE ACCRETION LESS THAN A TENTH OF AN INCH. EXPECT LOWS
TONIGHT TO RANGE FROM THE MID TEENS NORTHWEST TO THE UPPER 20S TO
AROUND 30 SOUTHEAST WITH HIGHS ON SUNDAY FROM THE UPPER 20S TO
LOWER 30S NORTH TO UPPER 30S SOUTH.

SUNDAY NIGHT INTO MONDAY…WARMER AIR IS EXPECTED TO CONTINUE TO STREAM
IN ALOFT AS FIRST LOW PRESSURE SYSTEM HEADS TOWARDS GEORGIAN BAY.
HOWEVER NOSE OF DEPARTING HIGH ACROSS CANADIAN MARITIMES WILL
RESULT IN COLD AIR DAMMING. MODEL SOUNDINGS FAVOR A PROLONGED
PERIOD OF SLEET AND FREEZING RAIN ACROSS NORTHEAST THIRD OF FA
WITH INDICATIONS THAT TEMPS WILL FALL A FEW DEGREES SUNDAY NIGHT
ACROSS THESE AREAS AND NOT WARM ABOVE FREEZING UNTIL MID TO LATE
MONDAY MORNING. THERE IS LESS CONCERN FARTHER SOUTH AND WEST AS
MODEL SOUNDINGS KEEP TEMPS ABOVE FREEZING WITH TEMPS PERHAPS EVEN
RISING LATE SUNDAY NIGHT AND CONTINUING ON MONDAY. ADDITIONAL QPF
AMOUNTS ARE EXPECTED TO BE TWO TO FOUR TENTHS OF AN INCH AND WHILE
LITTLE SLEET ACCUMULATION IS EXPECTED…ICE ACCRETION OF ONE TO
TWO TENTHS OF AN INCH IS POSSIBLE ESPECIALLY FROM THE SOUTHERN
ADIRONDACKS…ACROSS THE LAKE GEORGE SARATOGA REGION INTO SOUTHERN
VERMONT AND PERHAPS THE NORTHERN BERKSHIRES. EXPECT LOWS SUNDAY
NIGHT TO RANGE FROM THE MID TO UPPER 20S NORTH TO MID 30S SOUTH
AND HIGHS ON MONDAY TO RANGE FROM THE MID AND UPPER 30S NORTH TO
MID 40S SOUTH.

FOR NOW WILL CONTINUE TO HIGHLIGHT IN THE HWO SINCE ANY MIXED
PRECIPITATION IS NOT EXPECTED UNTIL SUNDAY MORNING.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/…
ACTIVE PATTERN TO CONTINUE THROUGH THIS PORTION OF THE
FORECAST…WITH ONE SYSTEM TO IMPACT REGION MON NT THROUGH
TUE…THEN POTENTIALLY ANOTHER SYSTEM FOR THU NT-FRI. HAVE GENERALLY
POPULATED THIS PORTION OF THE GRIDDED DATABASE WITH 00Z/15 HPC
GUIDANCE…WHILE INCORPORATING 00Z/15 ECMWF.

MON NT-TUE NT…BOTH DETERMINISTIC MODELS…AND GEFS INDICATE
ANOTHER SHORTWAVE APPROACHING FROM THE SOUTHWEST DURING THIS TIME
PERIOD…WITH A DEVELOPING SFC LOW TRACKING FROM THE OHIO VALLEY
TOWARD THE NORTHERN MID ATLANTIC STATES. SOME UNCERTAINTY STILL
EXISTS IN EXACTLY HOW THIS SFC LOW TRACKS…AND IF ONE CENTER
REDEVELOPS SLIGHTLY FURTHER EAST CLOSER TO THE COASTLINE. THERE
REMAINS SUFFICIENT CONFIDENCE THAT ANOTHER PERIOD OF MODERATE
PRECIPITATION SHOULD OCCUR DURING THIS TIME FRAME ACROSS THE REGION.
WHAT REMAINS SOMEWHAT UNCERTAIN IS P-TYPE…WHICH WILL BE HIGHLY
DEPENDENT ON AFOREMENTIONED SFC LOW TRACK/REDEVELOPMENT…AS WELL AS
DYNAMIC COOLING POTENTIAL AS UPPER LEVEL SYSTEM APPROACHES. AT THIS
TIME…IT APPEARS THAT PRECIP MON NT THROUGH MUCH OF TUE SHOULD BE
MAINLY RAIN IN VALLEY LOCALES. HOWEVER…ACROSS THE SOUTHWEST
ADIRONDACKS…AS WELL AS ACROSS HIGHER ELEVATIONS OF THE
CATSKILLS/SCHOHARIE VALLEY REGION…AND FROM THE SOUTHERN GREEN
MOUNTAINS INTO THE BERKSHIRES…ENOUGH COLD AIR MAY PERSIST TO ALLOW
FOR FREEZING RAIN AND/OR SLEET…WHICH COULD LEAD TO SOME ADDITIONAL
ICE ACCUMULATIONS. PRECIP SHOULD BECOME MAINLY RAIN FOR A PERIOD
DURING TUE IN ALL AREAS…BEFORE COLDER AIR ALOFT SEEPS BACK INTO
THE REGION…POSSIBLY CHANGING RAIN TO SNOW ACROSS HIGHER ELEVATIONS
BY LATE IN THE DAY…AND ACROSS MOST AREAS TUE NT. EXPECT TEMPS TO
FALL INTO THE LOWER/MID 30S IN MOST AREAS MON NT…ALTHOUGH SHOULD
RISE IN VALLEY AREAS LATER AT NIGHT…WITH TUE MAX TEMPS MAINLY
REACHING 35-40…WITH SOME LOWER/MID 40S POSSIBLE IN SOUTHERN VALLEY
LOCATIONS. TEMPS FOR TUE NT SHOULD FALL BACK INTO THE 20S TO LOWER
30S.

WED-THU…LINGERING SNOW SHOWERS WILL REMAIN POSSIBLE WED…ESP
ACROSS NORTHERN AREAS. A BRIEF BREAK IN THE PRECIPITATION WILL BE
POSSIBLE LATER WED INTO AT LEAST EARLY THU…ALTHOUGH CLOUDS MAY
HANG TOUGH. EXPECT MAX TEMPS TO REACH 35-40 IN VALLEYS…AND 30-35
ACROSS HIGHER ELEVATIONS…WITH OVERNIGHT MINS FALLING INTO THE 20S
TO LOWER 30S.

THU NT-FRI…NEXT SYSTEM APPROACHES FROM THE WEST DURING THIS TIME
FRAME…ALTHOUGH DETAILS REMAIN UNCERTAIN ON EXACT TRACK AND
EVOLUTION. SEVERAL 00Z/15 GEFS MEMBERS…AS WELL AS THE 00Z/15 ECMWF
SUGGEST THE POTENTIAL FOR A RATHER DEEP SFC LOW TO APPROACH THE
SOUTHERN GREAT LAKES BEFORE POSSIBLY REDEVELOPING CLOSER TO THE
NORTHERN MID ATLANTIC COASTLINE. THIS COULD LEAD TO A PERIOD OF
MODERATE TO HEAVY PRECIPITATION…WHICH COULD BE IN THE FORM OF SNOW
OR A WINTRY MIX FOR AT LEAST SOME NORTHERN AREAS.
AGAIN…UNCERTAINTY REMAINS RATHER HIGH IN EXACT DETAILS…BUT THERE
IS AT LEAST SOME POSSIBILITY FOR A FAIRLY STRONG STORM SYSTEM TO
AFFECT THE REGION DURING THIS TIME FRAME.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/…
HIGH PRESSURE BUILDS IN FROM SOUTHEAST CANADA INTO THIS EVENING. ONE
PATCH OF CLOUDS JUST OVER THE KGFL AREA SHOULD ERODE EARLY THIS
AFTERNOON. HIGH AND MID LEVEL CLOUDS WILL THEN INCREASE THIS
AFTERNOON INTO TONIGHT AS A STORM SYSTEM MOVES INTO THE GREAT
LAKES…AND ITS ASSOCIATED WARM FRONT APPROACHES FROM THE SOUTHWEST.
SOME LIGHT SNOW AT KGFL AND KPSF OR A MIX OF LIGHT SNOW AND LIGHT
RAIN AT KALB AND KPOU MAY DEVELOP BETWEEN 13Z-15Z/SUNDAY…POSSIBLY
PRODUCING MVFR VSBYS/CIGS.

WINDS WILL CONTINUE FROM THE NORTH TO NORTHEAST AT 5-10 KT THIS
AFTERNOON…BEFORE BECOMING LIGHT/VARIABLE BY AND AFTER SUNSET.
WINDS SHOULD BE LIGHT NORTHEAST TO SOUTHEAST AT 6 KT OR LESS
TOMORROW.

OUTLOOK…
SUN…SUB VFR. PRECIPITATION LIKELY. SNOW CHANGING TO RAIN AT
KPOU…KALB AND KPSF. AT KGFL MIXING WITH OR CHANGING TO
RAIN AND/OR SLEET.
SUN NT…SUB VFR. RAIN LIKELY AT KPOU AND KALB. MIXED PCPN LIKELY
AT KPSF AND KGFL.
MON-WED…SUB-VFR. CHC RAIN/SNOW…EXCEPT FOR MAINLY RAIN AT KPOU.

&&

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

CONDITIONS ARE EXPECTED TO BE MAINLY DRY UNTIL LATE TONIGHT.
A WINTRY MIX OF PRECIPITATION IS THEN EXPECTED TO START LATE
TONIGHT AND CONTINUE INTO MONDAY ACROSS NORTHERN AREAS WITH THE
PRECIPITATION TRANSITIONING TO RAIN ACROSS SOUTHERN AREAS AS
WARMER AIR WORKS INTO THE REGION. TOTAL LIQUID EQUIVALENT AMOUNTS
THROUGH MONDAY ARE EXPECTED TO RANGE FROM AROUND A THIRD OF AN
INCH TO A LITTLE OVER HALF AN INCH WITH SOME OF THE PRECIPITATION
FALLING IN THE FORM OF SNOW AND ICE ESPECIALLY FROM THE SOUTHERN
ADIRONDACKS ACROSS THE LAKE GEORGE SARATOGA REGION AND INTO
SOUTHERN VERMONT.

ADDITIONAL WEATHER SYSTEMS WILL IMPACT THE REGION NEXT
WEEK…WITH UNSETTLED WEATHER POSSIBLE FOR SEVERAL DAYS. THE
TIMING AND TRACK OF INDIVIDUALS SYSTEMS IS UNCERTAIN…PLEASE
REFER TO THE LONG TERM SECTION OF THIS DISCUSSION.

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

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