February 23, 2012 Forecast Discussion

000
FXUS61 KALY 231743
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
1243 PM EST THU FEB 23 2012

.SYNOPSIS…
A WEAK AREA OF LOW PRESSURE WILL EXIT THE REGION THROUGH THIS
AFTERNOON. ANOTHER…STRONGER LOW PRESSURE SYSTEM…WILL AFFECT
THE REGION LATE TONIGHT INTO FRIDAY NIGHT WITH ADDITIONAL SNOW
AND RAIN. SOME LINGERING SNOW SHOWERS ALONG WITH WINDY CONDITIONS
WILL OCCUR IN THE WAKE OF THE STORM ON SATURDAY.

&&

.NEAR TERM /THROUGH TONIGHT/…
— Changed Discussion —
AS OF 1235 PM EST…COLD AIR ADVECTION CONTINUES ACROSS THE
REGION. HOWEVER…DEEP MIXING HAS ALLOWED TEMPS TO REACH THE LOWER
50S ACROSS PORTIONS OF THE MID HUDSON VALLEY REGION…WITH
WIDESPREAD LOWER/MID 40S ACROSS THE REMAINDER OF THE HUDSON RIVER
VALLEY AND MOHAWK RIVER VALLEY. SOMEWHAT STEEP LOW LEVEL LAPSE
RATES HAVE KEPT TEMPS IN THE UPPER 20S TO MID 30S ACROSS HIGHER
ELEVATIONS.

THE CONTINUED COLD ADVECTION…INSTABILITY…AND MOISTURE FROM THE
NEARBY LAKES HAS ALLOWED FOR SCATTERED SHOWERS OF RAIN AND SNOW TO
PERSIST ACROSS PORTIONS OF THE WESTERN ADIRONDACKS…UPPER HUDSON
VALLEY AND SOUTHERN VT. WE EXPECT THESE TO PERSIST THROUGH EARLY
AFTERNOON…AND HAVE BOOSTED POPS ACCORDINGLY IN THESE AREAS.
HIGHER ELEVATIONS ACROSS THE WESTERN ADIRONDACKS COULD RECEIVE UP
TO AN ADDITIONAL INCH OF SNOWFALL DURING THIS TIME WITHIN THE MOST
PERSISTENT SNOW SHOWERS.

HAVE ALSO BOOSTED WINDS AND WIND GUSTS THROUGH THIS
AFTERNOON…WITH OBSERVED WIND GUSTS REACHING 25-35 MPH IN SOME
AREAS…ESP CLOSE TO THE MOHAWK RIVER VALLEY…CAPITAL REGION AND
BERKSHIRES.

AS FOR TONIGHT…A LOOK AT ALL 00Z/06Z GUIDANCE AND ENSEMBLES AND
SOME OF THE NEW 12Z NAM AND GFS…SOME NOTICEABLE DISAGREEMENTS ON
THE PLACEMENT OF THE MAXIMUM PRECIPITATION ASSOCIATED WITH THE
WARM ADVECTION LATE TONIGHT AND TOMORROW MORNING. PROBABILITIES
FOR VARIOUS QPF IN THE SREF AND GEFS AND PROBABILITIES FOR >4
INCHES OF SNOW IN THE SREF SHOW JUST UNDER CONFIDENCE THRESHOLDS
TO ISSUE WATCHES OR WARNINGS BASED ON THE GUIDANCE.

SOME DETERMINISTIC GUIDANCE SUGGESTS ADVISORY OR LOW END WARNINGS
IN HIGHER ELEVATIONS OF THE CATSKILLS…SOUTHERN ADIRONDACKS AND
SOUTHERN GREEN MOUNTAINS…PERHAPS INTO THE NORTHERN BERKSHIRES.
HOWEVER…PICKING AND CHOOSING ONE DETERMNISTIC MODEL OVER
ANOTHER IS NOT WISE WHEN SUCH A SPREAD IS SEEN IN THE DERIVED
FIELDS OF THE DETERMINSTIC GUIDANCE AND LOOKING AT MULTIPLE
MEMBERS OF ENSEMBLES. FULL 12Z GUIDANCE WILL DETERMINE POTENTIAL
FOR HEADLINES TONIGHT INTO TOMORROW MORNING. MAY NEED TO GO
STRAIGHT TO LOW END WARNINGS IN SOME AREAS AND JUST TO ADVISORIES
IN OTHER AREAS DEPENDING ON EXPECTED EVOLUTION SUGGESTED IN 12Z
GUIDANCE.

LOWS TONIGHT WILL BE IN THE MID 20S TO MID 30S.
— End Changed Discussion —

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY/…
— Changed Discussion —
MAINLY CATEGORICAL POPS THROUGH EARLY FRIDAY AFTERNOON…THEN
POPS DECREASING DURING THE AFTERNOON AS A DRY SLOT SURGES INTO THE
REGION.

COLD ENOUGH FOR MAINLY SNOW OR SLEET THROUGH EARLY FRIDAY
MORNING…THEN A TRANSITION TO MAINLY RAIN IN ALL AREAS BY EARLY
FRIDAY AFTERNOON.

AS THE STORM MOVES BY LATE FRIDAY AFTERNOON AND FRIDAY EVENING…
COLDER AIR WILL BEGIN TO RETURN AT THE MID LEVELS AND PCPN WILL
TRANSITION BACK TO SNOW FRIDAY EVENING. BY THAT TIME STEADY PCPN
WILL HAVE ENDED WITH THE PCPN BECOMING SHOWERY IN NATURE AS A MOIST
NORTHWESTERLY FLOW PREVAILS FRIDAY NIGHT INTO SATURDAY.

HAVE FORECAST ADVISORY LEVEL SNOW FOR PARTS OF THE REGION FROM THE
EASTERN CATSKILLS TO THE ADIRONDACKS AND EASTWARD TO SOUTHERN
VERMONT. WITH THE PCPN NOT STARTING UNTIL LATE IN THE SECOND PERIOD
PREFFERED TO HOLD OFF ON ACTUALLY ISSUEING ANY ADVISORIES AT THIS
TIME.

HIGHS FRIDAY IN THE MID 30S TO UPPER 40S…LOWS FRIDAY NIGHT
GENERALLY BETWEEN 20 AND 30…AND HIGHS SATURDAY IN THE UPPER 20S
TO LOWER 40S.
— End Changed Discussion —

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/…
A PERIOD OF TRANQUIL WEATHER OPENS THE LONG TERM…AS AN UPPER
LEVEL TROUGH REMAINS OVER THE NORTHEAST…AND A BROAD CANADIAN
HIGH BUILDS IN FROM SOUTHERN ONTARIO TO CLOSE THE WEEKEND. A
SECONDARY COLD FRONT SLIPS THROUGH THE FCST AREA SATURDAY NIGHT
WITH ISOLD-SCT SNOW SHOWERS ENDING WEST OF THE HUDSON RIVER VALLEY
BEFORE MIDNIGHT…AS THE LOW AND MID LEVEL FLOW BECOMES
ANTICYCLONIC…AND THE SUBSIDENCE INVERSION LOWERS. H850 TEMPS
FALL INTO THE -10C TO -15C RANGE OVER THE FORECAST AREA WITH LOWS
IN SINGLE DIGITS OVER THE SRN DACKS…AND NRN LAKE GEORGE REGION.
TEENS WILL BE COMMON ELSEWHERE…EXCEPT IN THE CAPITAL
DISTRICT…MID HUDSON VALLEY…SRN TACONICS AND SRN LITCHFIELD
COUNTY WHERE SOME LOWER TO M20S WILL BE POSSIBLE. THE WINDS WILL
BE GRADUALLY SUBSIDING OVERNIGHT…AS THE LOW-LEVEL PRESSURE
GRADIENT WEAKENS.

SUNDAY-SUNDAY NIGHT…SFC HIGH PRESSURE CRESTS OVER NY AND NEW
ENGLAND TO CLOSE THE WEEKEND WITH SUNNY AND COLD CONDITIONS.
TEMPERATURES WILL BE NEAR NORMAL FOR LATE FEB. THE SFC HIGH
RETREATS EASTWARD OVER NRN NEW ENGLAND…AND THE CANADIAN MARITIMES.
THE WEAK MID LEVEL RIDGING FLATTENS…AS A CLIPPER LOW APPROACHES
FROM THE UPPER MIDWEST AND THE WRN GREAT LAKES REGION.

MONDAY-MONDAY NIGHT…THE BEST LOW-LEVEL BAROCLINIC ZONE WITH THE
CLIPPER STAYS WELL NORTH OF THE FCST AREA OVER SRN QUEBEC…AND
EXTREME NRN NY DURING THE DAY. A SLIGHT CHC OF RAIN OR SNOW SHOWERS
WAS KEPT OVER MOST OF THE FCST AREA MON PM. TEMPS WILL BE ABOUT 5
DEGREES ABOVE NORMAL. THE COLD FRONT TO THE SYSTEM SWINGS THROUGH
MON NIGHT INTO TUESDAY MORNING WITH SOME SCT SNOW SHOWERS. THE
MOISTURE CONVERGENCE ISN/T VERY IMPRESSIVE WITH THIS BOUNDARY BASED
ON THE LATEST GFS/ECMWF/CANADIAN GGEM.

TUESDAY…ANOTHER SECONDARY COLD FRONT MOVES THROUGH THE REGION
DURING THE DAY WITH A SURGE OF SEASONABLY COLD AIR. WE KEPT MOST OF
THE DAY DRY WITH HIGH PRESSURE RIDGING IN FROM THE NORTH AGAIN.
HIGH WILL GENERALLY BE IN THE MID AND U30S OVER THE MTNS…WITH
LOWER TO MID 40S COMMON IN THE VALLEYS.

TUESDAY NIGHT INTO WEDNESDAY…HIGH PRESSURE CRESTS OVER THE REGION
TUESDAY EVENING…AS A VIGOROUS LONGWAVE TROUGH IS CARVED OUT OVER
THE CNTRL PLAINS/UPPER MS RIVER VALLEY. THE GFS IS QUICK BRINGING
THE LOW PRESSURE SYSTEM INTO THE CNTRL GREAT LAKES REGION WITH
ISENTROPIC LIFT AHEAD OF THE WARM FRONT MOVING INTO THE REGION BY
DAYBREAK WEDNESDAY. THE ECMWF IS SLOWER WITH THE DEVELOPMENT OF THE
UPPER TROUGH BY 12-18 HOURS. WE LEANED CLOSER TO HPC HERE WITH THE
WARM ADVECTION PCPN AHEAD OF THE WARM FRONT GRADUALLY MOVING IN FROM
SOUTHWEST TO NORTHEAST DURING IN THE DAY. WE HAVE SLIGHT AND LOW
CHC POPS WED…AND CHC POPS THROUGH WED NIGHT. PREDOMINANT PTYPE
WILL BE SNOW AT THIS POINT WITH THE ONSET. THIS SYSTEM MAY UTILIZE
AN ABUNDANCE OF GULF MOISTURE…SO IT BEARS WATCHING LATE IN THE
WEEK. THERE ARE ALSO INDICATIONS OF A SECONDARY LOW FORMING
SOMETIME ON THU WITH THE PRIMARY WEAKENING OVER THE ERN GREAT LAKES
REGION. HIGHS ON WEDNESDAY WILL GENERALLY BE IN THE U20S TO M30S
OVER THE MTNS…AND M30S TO NEAR 40F IN THE VALLEYS.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/…
— Changed Discussion —
VFR CONDITIONS WILL PREVAIL MOST OF THE DAY WITH SCATTERED VARIABLE
BROKEN CEILINGS ABOVE 3000 FEET. A LOW PRESSURE SYSTEM WILL
APPROACH FROM THE OHIO VALLEY TONIGHT BRINGING A WINTRY MIX AND
MVFR/IFR CONDITIONS RETURNING TO THE E-CNTRL NY TERMINALS BETWEEN
08Z-15Z/FRI.

THERMAL ADVECTION PCPN WILL MOVE INTO THE REGION AFTER MIDNIGHT.
SNOW SHOULD BE THE PREDOMINANT PRECIPITATION TYPE DURING THE ONSET
AROUND 08Z-09Z. MODEL SOUNDINGS AND CRITICAL THICKNESS PROFILES
INDICATE MAINLY A SNOW AND SLEET PTYPE PRIOR TO 12Z AT KPOU BEFORE
TRANSITIONING TO RAIN SHORTLY THEREAFTER. BY 15Z…SNOW SHOULD
CONTINUE AT KGFL WHILE A RAIN SNOW MIX SHOULD PREVAIL AT KALB AND
JUST RAIN AT KPOU. ONCE PRECIPITATION CHANGES TO RAIN OR A MIX THE
INTENSITY COULD DIMINISH AND CONDITIONS COULD BE BETTER THAN
FORECASTED IF A DRY SLOT MOVES ACROSS THE REGION…STAY TUNED.

GUSTY WEST TO NORTHWEST WINDS AT AROUND 15 MPH WITH GUSTS TO 20 TO
25 MPH WILL DIMINISH TO LIGHT THIS EVENING AND OVERNIGHT. WINDS
WILL BECOME NORTH TO EAST TOMORROW MORNING AT 6 KT OR LESS.

OUTLOOK….
FRI…MVFR/IFR CIGS/VSBYS…TRANSITION TO RA FROM KPOU TO KGFL IN
THE MORNING. BECOMING WINDY.
FRI NGT…VFR/MVFR…CHC -SHSNS.
SAT…VFR…SLIGHT CHC -SHSN. WINDY.
SAT NIGHT-SUN…VFR…DECREASING WINDS.
MON…VFR SLIGHT CHC -SHRA/-SHSN.
TUE…VFR.
— End Changed Discussion —

&&

.HYDROLOGY…
HYDRO PROBLEMS APPEAR MINIMAL THE NEXT FIVE DAYS. LOW PRESSURE
EXITING THE REGION THIS MORNING WITH LIGHT PRECIPITATION AMOUNTS.
ANOTHER STRONGER SYSTEM LATE THURSDAY NIGHT INTO FRIDAY HAS THE
POTENTIAL TO BRING MODERATE PRECIPITATION AMOUNTS TO THE REGION WITH
AMOUNTS RANGING FROM LESS THAN HALF AN INCH…TO POSSIBLY AN INCH…
WHICH WOULD CAUSE MINOR RISES ON RIVERS AND STREAMS.

THE PROBABILITIES FOR FLOODING IS GENERALLY BELOW NORMAL DUE TO
BELOW NORMAL SNOWPACK AND LACK OF RIVER ICE. PLEASE REFER TO OUR
WINTER/SPRING FLOOD POTENTIAL OUTLOOK (ALBESFALY) ISSUED ON
FEBRUARY 16TH FOR DETAILS. NEXT ISSUANCE OF THIS PRODUCT IS
SCHEDULED FOR MARCH 1ST 2012.

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…NAS
NEAR TERM…KL/NAS/GJM
SHORT TERM…KL/GJM
LONG TERM…WASULA
AVIATION…NAS/WASULA
HYDROLOGY…GJM

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