January 20, 2012 Forecas Discussion

000
FXUS61 KALY 202204
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
500 PM EST FRI JAN 20 2012

.SYNOPSIS…
HIGH PRESSURE WILL CREST OVER NEW YORK AND NEW ENGLAND THIS EVENING.
WEAK LOW PRESSURE WILL TRACK FROM THE TENNESSEE VALLEY TONIGHT TO
OFF THE NEW JERSEY COAST SATURDAY. ANOTHER HIGH PRESSURE SYSTEM WILL
BUILD INTO THE NORTHEAST FOR THE REST OF THE WEEKEND… SLIDING
OFFSHORE SUNDAY NIGHT. THIS WILL RESULT IN A SOUTHERLY FLOW OF
MILDER AND MORE MOIST AIR INTO THE REGION ON MONDAY…AS A POWERFUL
STORM MOVES FROM THE UPPER GREAT LAKES INTO WESTERN QUEBEC.

&&

.NEAR TERM /UNTIL 6 PM SATURDAY EVENING/…
AS OF 430 PM…12Z MODEL RUNS ARE REMARKABLY CONSISTENT WITH EACH
OTHER…AND ALSO WHEN COMPARED TO PREVIOUS RUNS…IN TERMS OF
FORECASTING THE SYSTEM FOR LATE TONIGHT AND SATURDAY. MODEL QPF/S
AND SNOWFALL AMOUNTS ARE VERY SIMILAR TO THE AMOUNTS WE CURRENTLY
HAVE IN THE GRIDS…AND LITTLE HAS BEEN CHANGED SINCE THE 100 PM
UPDATE. SOUTHERN 3 COUNTIES (ULSTER…DUTCHESS AND LITCHFIELD)
REMAIN UNDER A WINTER WEATHER ADVISORY FOR SNOWFALL AMOUNTS OF 3 TO
6 INCHES. FOR THE NEXT ROW OF COUNTIES (GREENE…COLUMBIA AND
BERKSHIRE) SNOWFALL AMOUNTS WILL BE 2 TO 4 INCHES. MOST OF THE REST
OF THE REGION WILL HAVE 1 TO 3 INCHES…WITH ONLY AROUND AN INCH
ACROSS FAR NORTHERN AREAS.

IT WILL BE MAINLY CLEAR THIS EVENING WITH A RAPID INCREASE IN
CLOUDS LATE THIS EVENING AND AFTER MIDNIGHT. SNOW WILL ALSO RAPIDLY
OVERSPREAD THE REGION AFTER MIDNIGHT. LOWS WILL RANGE FROM AROUND 5
BELOW ZERO IN THE ADIRONDACKS…AND ZERO TO THE MID TEENS ELSEWHERE.

SNOW MAY BEGIN TO TAPER OFF DURING THE MORNING OVER THE NORTHWEST
PART OF THE FORECAST AREA…WITH SNOW ENDING IN ALL AREAS DURING THE
AFTERNOON. HIGHS SATURDAY WILL BE IN THE 20S.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/…
THE NEXT HIGH PRESSURE SYSTEM WILL BUILD OVER THE REGION VERY
RAPIDLY AND BE OVERHEAD SATURDAY NIGHT. THIS WILL INHIBIT ANY LAKE
EFFECT SNOW SHOWERSOR CLOUDS FROM DEVELOPING BEHIND THE LOW…WITH
MAINLY CLEAR SKIES EXPECTED AND LIGHT WINDS. WITH FRESH SNOW COVER
ON THE GROUND AS WELL…TEMPS WILL DIP TO BETWEEN 10 BELOW ZERO AND
10 ABOVE.

THE HIGH WILL MOVE OFF THE NEW ENGLAND COAST ON SUNDAY…BUT WILL
STILL BE CLOSE ENOUGH TO PRODUCE MOSTLY SUNNY SKIES ACROSS THE
REGION. HIGHS WILL BE IN THE MID 20S TO LOWER 30S…WITH A SOUTH TO
SOUTHEAST FLOW GRADUALLY PICKING UP BY AFTERNOON.

THE SOUTHERLY FLOW WILL CONTINUE INTO SUNDAY NIGHT WITH INCREASING
MOISTURE COMING IN OFF THE ATLANTIC. THIS MOISTURE WILL BE WELL
AHEAD OF THE NEXT STRONG LOW PRESSURE SYSTEM THAT WILL AFFECT THE
REGION ON MONDAY. AS A RESULT…MID/UPPER LEVEL FORCING WILL BE
MINIMAL AND MODELS ONLY SPIT OUT VERY LIGHT PCPN AMOUNTS SUNDAY
NIGHT…SO HAVE ONLY FORECAST CHANCE POPS FOR LATE SUNDAY NIGHT.
TEMPS AT MID LEVELS WILL HAVE ALREADY WARMED UP ENOUGH BY LATE
SUNDAY NIGHT FOR MIXED PCPN TO OCCUR…AND HAVE FORECAST A CHANCE OF
FREEZING RAIN OR SLEET. LOWS SUNDAY NIGHT IN THE UPPER TEENS TO
AROUND 30 WILL OCCUR BEFORE MIDNIGHT…WITH TEMPS STEADY OR SLOWLY
RISING THEREAFTER.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/…
THE PERIOD STARTS OUT WITH A DEEPENING CYCLONE MOVING NORTHWARD
THROUGH THE CENTRAL GREAT LAKES. STRENGTHENING SOUTHERLY FLOW AHEAD
OF THIS SYSTEM WILL DRAW WARMER AIR INTO THE AREA. INITIALLY…THE
WARMER AIR WILL MOVE IN ALOFT WITH COLDER AIR TRAPPED AT THE
SURFACE. SO A PERIOD OF SLEET AND/OR FREEZING RAIN WILL BE LIKELY
MONDAY MORNING BEFORE THE COLDER AIR GETS SCOURED OUT AT THE
SURFACE. LIGHT QPF OF ONE TENTH TO PERHAPS ONE QUARTER INCH IS
EXPECTED ASSOCIATED WITH ISENTROPIC LIFT MONDAY MORNING…WITH THE
HIGHER AMOUNTS ACROSS FAVORED SOUTH-FACING SLOPES OF ELEVATED
TERRAIN. SOUTHERLY WINDS WILL BE QUITE STRONG…BUT A LOW LEVEL
INVERSION SHOULD PRECLUDE A STRONG WIND EVENT. HOWEVER SOME HIGHER
ELEVATION LOCATIONS AND FAVORED AREAS COULD SEE SOME ADVISORY LEVEL
GUSTS. SURFACE TEMPS SHOULD WARM INTO THE 40S DURING THE AFTERNOON
AHEAD OF A SHARP COLD FRONT ADVANCING EASTWARD THROUGH CENTRAL NY.
VARIOUS SOURCES OF MODEL GUIDANCE INDICATING A FAIRLY SOLID PERIOD
OF RAIN AHEAD OF AND ALONG THE COLD FRONT SO WILL MENTION
CATEGORICAL POPS. ONE HALF TO ONE INCH OF RAIN COULD FALL IN A 6
HOUR PERIOD OR LESS…SO THERE COULD BE SOME DECENT RUNOFF BUT NO
RIVER FLOODING IS EXPECTED.

THERE ARE SOME TIMING DIFFERENCES IN THE MODELS FOR WHEN THE COLD
FRONT CROSSES THE AREA. THE GFS/NAM ARE FASTER THAN THE
ECMWF…WHICH LAGS AND BRINGS THE FRONT THROUGH LATER IN THE EVENING
ON MONDAY. REGARDLESS OF EXACT TIMING…THE COLD FRONT SHOULD CLEAR
THE AREA BY LATE EVENING. BEHIND THE FRONT COLDER…BUT NOT FRIGID
AIR WILL FILTER IN. THERE COULD BE A PERIOD OF LAKE ENHANCED/UPSLOPE
SNOW SHOWERS ACROSS THE ADIRONDACKS INTO TUESDAY…OTHERWISE MAINLY
DRY AND BREEZY CONDITIONS ARE EXPECTED THROUGH TUESDAY WITH TEMPS
COLDER THAN MONDAY BUT STILL ABOVE NORMAL.

HIGH PRESSURE WILL THEN BUILD IN FROM LATE TUESDAY NIGHT INTO
THURSDAY WITH TRANQUIL CONDITIONS AND GENERALLY SEASONABLE TEMPS.
THE NEXT SYSTEM THAT MAY IMPACT THE REGION APPEARS TO BE A SOUTHERN
STREAM SYSTEM THAT COULD TRACK OVER OR WEST OF THE REGION AGAIN.
THIS WOULD POSSIBLY IMPLY ANOTHER MIX TO RAIN SCENARIO BUT IT IS WAY
TOO EARLY FOR SPECIFICS. TIMING DIFFERENCES ARE ABUNDANT IN THE
MODEL GUIDANCE AS WELL SO WILL HAVE TO WAIT TO GET A CLEARER PICTURE
FOR HOW THIS STORM EVOLVES.

&&

.AVIATION /18Z FRIDAY THROUGH TUESDAY/…
VFR CONDITION WILL PREVAIL THROUGH THE EVENING HOURS.

THE SNOW SHOWERS AND FLURRIES THAT HAD VERY MINORILY IMPACTED THE
ALBANY TAF SITE HAVE DISSIPATED AS HIGH PRESSURE WAS BUILDING IN.

FOR THE REMAINDER OF THE AFTERNOON THROUGH EVENING ONLY SCATTERED
CLOUDS AT MOST EXPECTED AT ALL THE TAF SITES WHILE VISIBILITY
REMAINS UNRESTRICTED. THE WIND WILL STILL BE A BIT GUSTY FROM THE
NORTHWEST…ESPECIALLY AT KALB WITH GUSTS OCCASIONALLY EXCEEDING
20KTS.

THESE WINDS WILL DIMINISH TOWARD SUNSET.

A QUIET EVENING WITH HIGH CLOUDS ADVANCING BUT LITTLE OR NO WIND.

LOW PRESSURE OVER THE TENNESSEE VALLEY WILL TRACK NORTHEASTWARD
AND BRING A ROUND OF SNOW…FIRST AT KPOU BY 09Z/KALB BY 10Z AND
KGFL 11Z OR 12Z. CONFIDENCE IS HIGH (> 75 PERCENT) THAT IFR
CONDITIONS WILL PREVAIL AT KALB AND KPOU BY 12Z…MODERATE AT KGFL.
(ABOUT 60 PERCENT). IN FACT…WE ARE FORECASTING LIFR AT BOTH KALB
AND KPOU BY 12Z SATURDAY.

THE SNOW SHOULD PULL AWAY AROUND A LITTLE AFTER 18Z SATURDAY WITH
IMPROVING CONDITIONS THEREAFTER FOR THE REMAINDER OF SATURDAY.

OUTLOOK…
SAT NIGHT/SUN…VFR. NO SIG WX.
SUN NIGHT…SUB-VFR. CIG. CHC -RA/-SN/-PL/-FZRA.
MON SUB-VFR…CIG. CHC -RA.
TUE…VFR. SCHC MVFR CIG -RASN.

&&

.HYDROLOGY…
NO MAJOR PROBLEMS ARE EXPECTED ON THE MAIN STEM RIVERS THROUGH
NEXT THURSDAY. ANY PRECIPITATION WHICH FALLS THROUGH THE WEEKEND
WILL BE SNOW. MONDAY MAY BRING SOME LIGHT MIXED PRECIPITATION EARLY
AND 0.25 TO 0.50 OF RAIN DURING THE AFTERNOON.

ICE FORMATION ON BODIES OF WATER IS EXPECTED TO INCREASE AGAIN
THROUGH THE WEEKEND AS COLD AIR WILL BE IN PLACE ACROSS THE
REGION. TEMPS WILL BEGIN RISING LATE SUNDAY AND MONDAY…ONLY
COOLING TO NEAR OR SLIGHTLY ABOVE NORMAL 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…WINTER WEATHER ADVISORY FROM 1 AM TO 3 PM SATURDAY FOR
CTZ001-CTZ013.
NY…WINTER WEATHER ADVISORY FROM 1 AM TO 3 PM SATURDAY FOR
NYZ063>066.
MA…NONE.
VT…NONE.

&&

$$

SYNOPSIS…GJM
NEAR TERM…GJM
SHORT TERM…GJM
LONG TERM…JPV
AVIATION…HWJ
HYDROLOGY…GJM

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