December 4, 2013 Forecast Discussion

000
FXUS61 KALY 041800
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
100 PM EST WED DEC 4 2013

.SYNOPSIS…
SOME LIGHT OF PRECIPITATION IS POSSIBLE LATE TONIGHT AS
A WARM FRONT APPROACHES. LOW PRESSURE WILL THEN TRACK NORTHEASTWARD
FROM THE UPPER GREAT LAKES INTO SOUTHEAST CANADA THROUGH
THURSDAY…WITH ITS ASSOCIATED FRONTAL BOUNDARIES EXPECTED TO CROSS
OUR AREA BRINGING SOME SHOWERS AND A SURGE OF MILD AIR. A STRONGER
COLD FRONT WILL GRADUALLY PUSH SOUTHWARD THROUGH THE REGION ON
FRIDAY…WHILE A WAVE OF LOW PRESSURE MOVES ALONG THE FRONTAL
BOUNDARY POTENTIALLY BRINGING WIDESPREAD RAINFALL OR A WINTRY MIX.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/…
AS OF 100 PM EST…RADAR RETURNS FROM KTYX AND KBGM ARE SHOWING
DISSIPATING PRECIPITATION AS THE SMALL AREA OF PRECIPITATION MOVES
INTO A DRIER AIRMASS THAT IS SITTING OVER OUR REGION. THE BEST
CHANCE WILL BE NORTH AND WEST OF THE CAPITAL REGION. THIS LIGHT
PRECIP IS ASSOCIATED WITH A QUICK SHOT OF ISENTROPIC LIFT THAT THE
MODELS HAVE HAD A DIFFICULT TIME DEPICTING. TEMPERATURES ARE NOW
ABOVE THE FREEZING MARK ACROSS THE ENTIRE REGION AS PARTLY CLOUDY
TO MOSTLY CLEAR SKIES ARE PRESENT IN VALLEY LOCATIONS ESPECIALLY
THE MID HUDSON VALLEY.

THIS PRECIPITATION WILL EXIT OR DISSIPATE BY EARLY AFTERNOON AS
ASCENT DECREASES. WE WILL BE LEFT WITH INCREASING CLOUDS…BUT
TEMPERATURES REACHING ABOVE FREEZING BY AFTERNOON…40 TO 45
ALBANY SOUTH…MID TO UPPER 30S FARTHER NORTH. WINDS WILL REMAIN
RATHER LIGHT.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/…
TONIGHT IT STILL LOOKS AS IF ISENTROPIC LIFT WILL BE FAIRLY WEAK
ACROSS THE REGION BUT THERE…PERHAPS JUST ENOUGH TO TRIGGER A FEW
LIGHT SHOWERS…MAINLY OVERNIGHT.

IT LOOKS AS IF THE CLOUDS WILL LIKELY PERSIST FROM THE DAYTIME WITH
PERHAPS A FEW BREAKS IN THE THEM. EVEN WITH THE CLOUDS…A LACK OF
WIND INITIALLY SHOULD ALLOW FOR TEMPERATURES TO DROP IN THE EVENING
HOURS. THEY MIGHT STALL…OR EVEN RISE A LITTLE AFTER MIDNIGHT BUT
CONFIDENT WAS NOT HIGH ENOUGH TO ACTUALLY HAVE THIS IN THE GRIDS
JUST YET.

LOOK FOR LOWS 25 TO 32 WELL NORTH OF THE GREATER CAPITAL
DISTRICT…WHERE ANY RAIN THAT FALL WOULD FALL AS FREEZING RAIN.
FURTHER SOUTH FROM THE CAPITAL REGION SOUTHWARD TEMPERATURES LOOK TO
REMAIN ABOVE FREEZING…IN THE MID TO UPPER 30S. SO ANYTHING THAT
FALL HERE WILL LIKELY BE JUST PLAIN RAIN.

ANY AND ALL PRECIPITATION WILL BE LIGHT…GENERALLY A TENTH OF AN
INCH OR LESS.

WITH INCREASED MOISTURE…PATCHY FOG FOG IS POSSIBLE…AND MIGHT
EVEN BECOME MORE EXTENSIVE. FOR NOW…JUST CALL IT PATCHY FOG.

THURSDAY…BRIEF RIDGING ALOFT AND HIGH PRESSURE TO OUR
EAST…WILL INDUCE A MORE SIGNIFICANT SOUTHERLY FLOW. WE WILL
ACTUALLY HAVE A BREEZE THAT DAY…A SOUTH WIND 10-15 MPH MOST PLACES
BY AFTERNOON. EVEN WITH LOTS OF CLOUDS…TEMPERATURES WILL GET A
BUMP UPWARD…REACHING 50-55 FROM ALBANY SOUTHWARD…45 TO 50
FURTHER NORTH.

REGARDING SHOWERS…THEY LOOK TO BE ISOLATED TO SCATTERED EARLY
WEDNESDAY…AS A WARM FRONT MOVES THROUGH. THERE MIGHT BE A MIDDAY
BREAK WITH ONLY ISOLATED COVERAGE. HOWEVER…BY LATE AFTERNOON AS A
STRONG COLD FRONT APPROACHES SHOWER CHANCES INCREASE AGAIN BY LATE
IN THE DAY.

THURSDAY NIGHT A PRETTY STRONG COLD FRONT LOOK TO WORK ACROSS THE
REGION WITH SCATTERED SHOWERS OF ITS OWN. THEN…MOST GUIDANCE
INDICATED A WAVE OF LOW PRESSURE WILL RIDE ALONG THE FRONT…SLOWING
DOWN TO OUR SOUTH. LOOKS LIKE A PRETTY GOOD SHOT OF
PRECIPITATION…MAINLY IN THE FORM OF LIQUID RAIN FROM THE CAPITAL
REGION SOUTHWARD. FURTHER NORTH…THE JURY IS STILL OUT AS TO WHAT
SPECIFIC PTYPE WILL ENSUE DUE TO HOW FAST LOW LEVEL COLD AIR WEDGES
INTO THE REGION AND HOW MUCH MOISTURE REMAINS IN PLACE.

OUR CURRENT THINKING HAS PRECIPITATION CHANGING TO FREEZING RAIN AND
SLEET BUT NOT SNOW RIGHT AWAY OUR THE ADIRONDACKS…LAKE GEORGE
AREA AND SOUTHERN VERMONT AS TEMPERATURES FALL TO FREEZING A LITTLE
LOWER. THERE COULD BE SOME ICING ISSUES IN ESPECIALLY THE
ADIRONDACKS WHICH FOR NOW…WE WILL ADDRESS IN THE HAZARDOUS WEATHER
OUTLOOK (HWO).

PRECIPITATION LOOKS TO LINGER INTO FRIDAY AS LOW LEVEL COLD AIR
BLEEDS FURTHER INTO THE REGION BUT AN INCREASING CONFLUENT REGION
TAKES PLACES JUST SOUTH OF OUR AREAS. WE UNDERCUT ALL GUIDANCE
REGARDING HIGH TEMPERATURES FOR FRIDAY DUE TO A PRETTY STRONG
AGEOSTROPHIC NORTH TO NORTHEAST WIND WHICH WILL LIKELY DRIVE LOW
LEVEL COLD AIR FASTER THAN ANY MODEL INDICATES. WE WENT WITH HIGHS
IN THE MID TO UPPER 40S MID HUDSON VALLEY AND LOWER LITCHFIELD
COUNTY…CLOSER TO 40 IN THE CAPITAL REGION…MID TO UPPER 30S
FURTHER NORTH AND WEST. TEMPERATURES MIGHT TEND TO FALL A LITTLE
DURING THE AFTERNOON BUT AGAIN THIS FAR OUT…DECIDED NOT TO PLACE
THIS THINKING IN THE GRIDS JUST YET.

WE ARE STILL LOOKING AT MAINLY LIQUID RAIN FROM THE CAPITAL REGION
SOUTHWARD (A COLD RAIN AT THAT) BUT A WINTRY MIX CHANGING TO SNOW
WELL NORTH. EVENTUALLY…THE COLD AIR WILL WIN OUT EVERYWHERE…AND
BY FRIDAY NIGHT IT SHOULD BE COLD ENOUGH FOR SNOW EVERYWHERE AS
TEMPERATURES DIP BACK DOWN MAINLY INTO THE 20S. THERE IS A CHANCE
THAT PRECIPITATION COULD END AS SNOW EVERYWHERE WITH MINOR
ACCUMULATIONS POSSIBLE. OVERNIGHT FRIDAY INTO EARLY SATURDAY.

W

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/…
THE PREVIOUS FORECAST DISCUSSION SUMMARIZES QUITE WELL THE SYNOPTIC
PATTERN FOR THE LONG TERM…

CONFLUENT UPPER SOUTHWESTERLY FLOW THROUGH THE PERIOD MEANS 2
THINGS…QUICK MOVING SYSTEMS THAT GUIDANCE HAS GREAT DIFFICULTY
ACCURATELY TIMING…AND FORCING IN THOSE SYSTEMS DOMINATED BY WARM
ADVECTION. AT LEAST FOR NOW…GUIDANCE AND ENSEMBLES ARE IN GENERAL
AGREEMENT ON THE TIMING OF SYSTEMS…AND THERMAL PROFILES…
AFFECTING PRECIPITATION TYPES AND TRANSITIONS IN THOSE SYSTEMS.

THE INITIAL SYSTEM DEPARTS TO OUR EAST SATURDAY MORNING WITH
BUILDING SURFACE PRESSURES ALONG WITH A CONTINUING TIGHT CONFLUENT
FLOW ALOFT. H850 TEMPS ARE PROGGED TO DROP BACK TO AROUND -12C
WHICH POINTS TO THE POTENTIAL FOR LAKE EFFECT SNOW. IT DOES SEEM
SOME LAKE ACTIVITY MAY IMPACT PORTIONS OF THE WESTERN DACKS AS WE
WILL CONTINUE WITH THE CHANCE POPS AT THIS TIME. THE INCREASING
ANTICYCLONIC FLOW REGIME SHOULD TAPER BACK ANY LAKE ACTIVITY BY LATE
SATURDAY AFTERNOON WITH SKIES IMPROVING. THOSE SKIES ARE EXPECTED
TO CLEAR OUT FURTHER SATURDAY NIGHT DROPPING THOSE TEMPS BACK INTO
THE TEENS AND LOWER HALF OF THE 20S.

THE HIGH RETREATS TO OUR NORTH AND EAST KEEPING OUR WEATHER MAINLY
DRY AS TEMPERATURES ATTEMPT TO REBOUND WITH LOWER 30S FOR VALLEY
LOCATIONS AND UPPER 20S ELSEWHERE. OUR ATTENTION SHIFTS FURTHER
UPSTREAM AS A POTENT PV ANOMALY COMES OUT OF THE FOUR CORNERS REGION
AND BEGINS TO INTERACT WITH A STRONG BAROCLINIC ZONE OVER THE MID
AND LOWER MISSISSIPPI RIVER AND OHIO RIVER VALLEYS SUNDAY NIGHT.
GULF OF MEXICO ENTRAINMENT AND STRENGTHENING ISENTROPIC LIFT WILL
ALLOW FOR CLOUDS TO QUICKLY ADVECT INTO THE REGION ALONG WITH
INCREASING POTENTIAL FOR PRECIPITATION DEVELOPMENT FROM SOUTH TO
NORTH. PER THE THICKNESS PROFILES…THE ONSET OF THIS PRECIPITATION
SHOULD BE IN THE FORM OF LIGHT TO MODERATE SNOW. SEVERAL INCHES OF
SNOW ARE EXPECTED BEFORE THE MID LEVEL WARM ADVECTION RESULTS IN A
WINTRY MIXTURE OF SNOW/SLEET/FZRA MONDAY MORNING. PER THE GLOBAL
MODEL TRENDS…THE WARMER AIR ADVECTING INTO THE REGION SHOULD ALLOW
FOR MANY LOCATIONS TO TRANSITION TOWARD MAINLY LIQUID BY MIDDAY
MONDAY. QPF/S THIS MORNING RANGE FROM ONE THIRD TO THREE QUARTERS
OF AN INCH.

THIS SYSTEM QUICKLY DEPARTS BY TUESDAY AS THE NEXT SURGE OF COLDER
AIR ARRIVES WITH H850 TEMPS DROPPING BACK THROUGH THE NEGATIVE
TEENS. THIS WILL LIKELY RESULT IN ADDITIONAL LAKE RESPONSE WITH LAKE
EFFECT SNOW SHOWERS AND SQUALLS WHICH COULD IMPACT PORTIONS OF THE
MOHAWK VALLEY…SCHOHARIE VALLEY AND WESTERN ADIRONDACKS.

&&

.AVIATION /18Z WEDNESDAY THROUGH SUNDAY/…
VFR CONDITIONS EXPECTED TOPREVAIL THROUGH THE REST OF THE
AFTERNOON INTO THE EARLY EVENING HOURS ACROSS THE TERMINALS…WITH
JUST SOME PASSING SCT- BKN MID LEVEL CLOUDS…ESPECIALLY FROM KALB
NORTHWARD.

LOWER LEVEL STRATUS CLOUDS ARE EXPECTED TO INCREASE LATER THIS
EVENING…AS THE FLOW TURNS MORE SOUTHERLY. WITH LINGERING LOW LEVEL
MOISTURE SOME LIGHT FOG MAY ALSO ACCOMPANY THE STRATUS. CONDITIONS
ARE EXPECTED TO DETERIORATE TO MVFR THEN IFR LATE TONIGHT AS CIGS
LOWER AND VSBY BECOMES MARGINAL AS WELL. WARMER AIR WILL BE MOVING
IN ALOFT WHICH WILL TRAP THE LOW LEVEL STRATUS AND FOG…SO
EXPECTING IFR CONDITIONS TO CONTINUE THROUGH 18Z THURSDAY. WINDS
WILL BE LIGHT AND VARIABLE…BECOMING SOUTHEAST AROUND 3 TO 7 KT
THURSDAY MORNING.

OUTLOOK…
THURSDAY: MODERATE OPERATIONAL IMPACT. LIKELY SHRA
THURSDAY NIGHT TO FRIDAY: HIGH OPERATIONAL IMPACT. LIKELY RA
FRIDAY NIGHT: MODERATE OPERATIONAL IMPACT. CHANCE OF RA…SN…SLEET.
SATURDAY TO SUNDAY: NO OPERATIONAL IMPACT. NO SIG WX.
SUNDAY NIGHT: HIGH OPERATIONAL IMPACT. LIKELY SN.
MONDAY: HIGH OPERATIONAL IMPACT. LIKELY RA…FZRA…SLEET.

&&

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

MAINLY DRY CONDITIONS TODAY WITH HIGH PRESSURE IN CONTROL. A FEW
WEAK FRONTAL BOUNDARIES WILL PASS THROUGH LATE WEDNESDAY ON
THURSDAY…BRINGING SOME LIGHT PRECIPITATION OF LESS THAN ONE
QUARTER INCH.

THURSDAY NIGHT INTO FRIDAY…AS A STRONG COLD FRONT GRADUALLY
PUSHES THROUGH OUR REGION…A WAVE OF LOW PRESSURE WILL LIKELY
PRODUCE A BIT MORE SIGNIFICANT RAINFALL ACROSS MAINLY OUR CENTRAL
AND SOUTHERN AREAS WHERE ONE QUARTER TO ONE INCH OF RAIN COULD FALL.
THESE RAINFALL AMOUNTS WOULD BE ENOUGH TO PRODUCE SOME WITHIN BANK
RISES ON MAIN STEM RIVERS…HOWEVER NO FLOODING IS EXPECTED.

IT WILL THEN TURN COLDER AFTER THIS SYSTEM FINALLY PUSHES THROUGH
FRIDAY NIGHT WITH ANY ADDITIONAL PRECIPITATION FALLING AS LIGHT SNOW.
IT LOOKS MAINLY DRY SATURDAY INTO SUNDAY BEFORE THE NEXT STRONG
STORM SYSTEM APPROACHES SUNDAY NIGHT INTO MONDAY. IT LOOKS COLD
ENOUGH FOR MAINLY SNOW AND/OR MIXED PRECIPITATION TO FALL WITH THIS
SYSTEM AT THIS TIME…POSSIBLY ENDING AS SOME RAIN.

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…HWJIV/JPV
NEAR TERM…HWJIV/LFM/JPV
SHORT TERM…HWJIV
LONG TERM…BGM
AVIATION…JPV
HYDROLOGY…HWJIV/JPV

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