February 16, 2012 Forecast Discussion

000
FXUS61 KALY 161642
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
1142 AM EST THU FEB 16 2012

.SYNOPSIS…
LOW PRESSURE WILL APPROACH FROM THE GREAT LAKES TODAY AND MOVE NORTH
OF OUR REGION INTO QUEBEC TONIGHT…BRINGING A LIGHT MIXTURE OF RAIN
AND SNOW. THE LOW IN QUEBEC WILL DRAG A COLD FRONT THROUGH OUR
REGION LATE TONIGHT. AN UPPER LEVEL DISTURBANCE WILL CONTINUE THE
THREAT OF LAKE ENHANCED SNOW SHOWERS MAINLY NORTH AND WEST OF THE
CAPITAL REGION FRIDAY THROUGH FRIDAY NIGHT. TEMPERATURES WILL
CONTINUE TO BE ABOVE NORMAL FOR MID FEBRUARY.

&&

.NEAR TERM /THROUGH TONIGHT/…
— Changed Discussion —
AS OF 10 AM EST…HAVE MADE SOME CHANGES TO GRIDDED DATABASE
THROUGH EARLY TONIGHT. FIRST…BAND OF LIGHT PRECIP HAS DEVELOPED
ACROSS CENTRAL NYS…AND IS ALREADY APPROACHING OUR FAR WESTERN
COUNTIES. ALTHOUGH SOME OF THIS MAY NOT BE REACHING THE
GROUND…THERE WERE REPORTS OF LIGHT RAIN/SLEET FURTHER W WHEN IT
PASSED THROUGH. GIVEN SFC TEMPS REMAIN CLOSE TO…OR EVEN A BIT
BELOW FREEZING IN SOME OF THESE AREAS…HAVE INTRODUCED A CHC FOR
FREEZING RAIN/RAIN/SLEET THROUGH NOONTIME FOR THESE AREAS. SINCE
THE FREEZING RAIN IS EXPECTED TO BE VERY PATCHY IN AREAL
COVERAGE…HAVE ISSUED AN SPS TO ALERT FOR THE FREEZING RAIN
POTENTIAL…RATHER THAN AN ADVISORY. TEMPS SHOULD RISE ABOVE
FREEZING IN THESE AREAS BY OR BEFORE NOONTIME.

THE SECOND CHANGE WAS TO COOL TEMPS FOR THE AFTERNOON HOURS…ESP
ACROSS WESTERN AREAS ONCE PRECIP STARTS…AND ALSO ALLOW FOR MORE
MENTION OF SNOW…EVEN IN VALLEY AREAS. RECENT OBS ACROSS CENTRAL
PA INDICATE THAT…AFTER AN INITIAL PERIOD OF LIGHT RAIN/FREEZING
RAIN…WET BULB COOLING ALLOWED FOR THE PRECIP TO CHANGE TO MAINLY
SNOW…EVEN IN VALLEY AREAS. OUR REGION HAS EVEN DEEPER/DRIER AIR
TO OVERCOME…SO THE WET BULB COOLING POTENTIAL APPEARS EVEN
GREATER. SO…DESPITE SOME RAIN INITIALLY IN VALLEYS…EXPECT A
TRANSITION TO EITHER A SNOW/RAIN MIX…OR JUST SNOW BY MID TO LATE
AFTERNOON…WITH SNOW PREVALENT ACROSS THE UPPER HUDSON RIVER
VALLEY NORTH OF ALBANY…AND ACROSS THE MOHAWK VALLEY REGION. IN
SOME OF THESE AREAS…UP TO AN INCH OF SNOW COULD OCCUR BY THIS
EVENING ON COLDER…GRASSY SURFACES…WITH PERHAPS A COATING OF
SLUSH ON UNTREATED ROADWAYS. FURTHER S IN THE VALLEYS…ONLY A
COATING OF SNOW IS EXPECTED BY THIS EVENING ON COLDER SURFACES.
ACROSS HIGHER ELEVATIONS…ACCUMS OF AN INCH OR TWO COULD OCCUR IN
THE EASTERN CATSKILLS…THE SCHOHARIE VALLEY AND WESTERN
ADIRONDACKS…AS WELL AS ACROSS NORTHERN PORTIONS OF THE WESTERN
MOHAWK VALLEY.

PRECIP WILL BE LIMITED TO A THIRD OF AN INCH OR LESS AS THIS
SYSTEM WILL BE MOVING THROUGH FAIRLY QUICKLY. MOST AREAS WILL
RECEIVE AROUND 0.20-0.25" ALTHOUGH SOME UPSLOPE ENHANCEMENT OVER
THE EXTREME SOUTHERN ADIRONDACKS AND NORTHERN MOHAWK VALLEY SHOULD
YIELD CLOSE TO ONE THIRD OF AN INCH.

AS FOR OVERALL SNOWFALL TOTALS…GENERALLY EXPECTING SNOW
ACCUMULATIONS OF A COATING TO AN INCH FOR MOST VALLEY
REGIONS FROM ALBANY SOUTH…1-3" ACROSS THE EASTERN
CATSKILLS/TACONICS/BERKSHIRES/SOUTHERN GREENS AND PORTIONS OF THE
HUDSON RIVER VALLEY NORTH OF ALBANY WITH THE HIGHER AMOUNTS ABOVE
1500 FEET. AS MENTIONED BEFORE…WITH UPSLOPE ENHANCEMENT…2-4"
AMOUNTS ARE EXPECTED ACROSS THE SOUTHERN ADIRONDACKS AND NORTHERN
MOHAWK VALLEY AREA.
— End Changed Discussion —

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY/…
AS OF 345 AM…STEADY PRECIP WILL BE WELL EAST OF THE AREA BY
SUNRISE FRIDAY…WITH JUST ISOLATED TO SCATTERED SNOW SHOWERS MAINLY
OVER THE HIGHER TERRAIN FRIDAY MORNING. AS THE 500 MB LOW BARRELS
EASTWARD INTO QUEBEC FRIDAY AFTERNOON…A TRAILING UPPER LEVEL
DISTURBANCE IS FORECAST TO MOVE THROUGH OUT AREA. DRIER AIR WILL BE
IN PLACE IN THE LOW LEVELS WITH A WESTERLY FLOW. HOWEVER…SOME
UPSLOPE ENHANCEMENT COULD RESULT IN SNOW SHOWERS MAINLY ACROSS THE
WESTERN ADIRONDACKS.

IN WAKE OF THE DISTURBANCE…TEMPS ALOFT WILL BE JUST COLD ENOUGH
WITH WINDS WELL ALIGNED FOR A LAKE RESPONSE TO DEVELOP LATE FRIDAY
THROUGH FRIDAY NIGHT. LAKE ONTARIO SURFACE TEMP UP AROUND 4C TO 5C.
STILL UNCERTAIN WHETHER ORGANIZED BANDS WILL DEVELOP…BUT INVERSION
HEIGHTS WILL BE INCREASING TO AROUND 2.5 TO 3.0 KM WITH CONDITIONAL
INSTABILITY…SO THERE COULD BE SOME ACCUMULATING LAKE SNOWS.
DIFFICULT TO PINPOINT EXACT LOCATION THIS FAR OUT…BUT GENERALLY A
270-280 DEGREE TRAJECTORY WOULD FAVOR THE SOUTHWEST ADIRONDACKS AND
THE NORTHERN MOHAWK VALLEY.

ANY LAKE EFFECT SNOW SHOWERS WOULD TEND TO DIMINISH SATURDAY
MORNING…AS A WEAK AND SMALL SURFACE RIDGE OF HIGH PRESSURE BUILDS
IN AHEAD OF A WEAK CLIPPER-TYPE SYSTEM DIVING SOUTHEASTWARD THROUGH
THE GREAT LAKES. THIS SYSTEM WILL APPROACH LATE SATURDAY WITH
POSSIBLE ISOLATED RAIN/SNOW SHOWERS.

OVERALL TEMPS WILL REMAIN ABOVE NORMAL THROUGH SATURDAY…MORE
TYPICAL OF MID MARCH THAN MID FEBRUARY.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/…
HIGHLIGHT OF THE PERIOD IS AT THE START. LOW PRESSURE FORMS IN THE
NW GULF OF MEXICO FRIDAY NIGHT…THEN TRACKS EAST/NORTHEAST ACROSS
THE DEEP SOUTH DURING THE WEEKEND. MODELS VARY CONSIDERABLY AS TO
HOW FAR NORTH THIS SYSTEM WILL EVENTUALLY TRACK. GFS IS THE FURTHEST
NORTH. YESTERDAYS 18Z GFS RUN WOULD BURY THE FORECAST AREA IN HEAVY
PCPN IF IT WAS TO VERIFY…WHILE THE LATEST 00Z GFS RUN BACKED OFF
CONSIDERABLY AND IS NOW FORECASTING A LIGHT TO MODERATE PCPN EVENT
ACROSS MAINLY THE SOUTHERN PART OF THE FORECAST AREA. OTHER
MODELS…ECMWF/CANADIAN AND NAM ALL KEEP PCPN SOUTH OF THE REGION AS
THE SURFACE LOW TRACKS OFF THE MID ATLANTIC OR SOUTHEAST COAST. FOR
NOW WILL CONTINUE TO FORECAST A 30 TO 40 PERCENT POP FOR THIS EVENT
FROM LATE SATURDAY NIGHT THROUGH EARLY SUNDAY NIGHT…WITH THE
HIGHEST POPS OVER THE SOUTH. LOWS SATURDAY NIGHT WILL BE IN THE
UPPER TEENS AND 20S…HIGHS SUNDAY IN THE 30S…AND LOWS SUNDAY
NIGHT GENERALLY IN THE TEENS TO LOWER 20S.

BY MONDAY…A SURFACE HIGH AND RIDGING ALOFT WILL BUILD INTO THE
REGION AND PERSIST INTO THE MIDDLE OF THE WEEK WITH MAINLY CLEAR
SKIES. THE AIRMASS WILL INITIALLY BE COLD…WITH HIGHS MONDAY IN THE
UPPER 20S AND 30S AND LOWS MONDAY NIGHT IN THE UPPER SINGLE NUMBERS
AND TEENS. BY TUESDAY THE HIGH WILL BE TO THE EAST OF THE REGION AND
THE SOUTHERLY FLOW AROUND IT WILL BEGIN TO BRING MILDER AIR TO THE
REGION. HIGHS TUESDAY WILL BE IN THE MID OR UPPER 30S.

A WEAK TROF WILL MOVE ACROSS THE REGION TUESDAY NIGHT WITH SOME
SPOTTY LIGHT PCPN. LOWS TUESDAY NIGHT WILL BE IN THE 20S. ON
WEDNESDAY…A MUCH STRONGER SYSTEM WILL APPROACH FROM THE SOUTHWEST.
EVENTUALLY THIS SYSTEM WILL TRACK WELL TO OUR WEST WITH FAIRLY MILD
AIR DOMINATING AS THE LOW MOVES NORTHEAST THROUGH THE GREAT LAKES.
SO CONTINUING THE TREND OF MUCH OF THIS WINTER…THE EVENT DURING
THE MIDDLE AND END OF NEXT WEEK WILL PRIMARILY BE A RAIN EVENT.
HIGHS WEDNESDAY WILL SURGE INTO THE UPPER 30S AND MID 40S AND NOT
DROP VERY MUCH WEDNESDAY NIGHT.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/…
— Changed Discussion —
AS OF 1130 AM…PRECIP MOVING INTO THE AREA…WITH REPORTS OF
SNOW AND RAIN IN THE HIGHER ELEVATIONS WHERE PRECIP IS OCCURRING.
WITH TEMPERATURE-DEWPOINT SPREAD OF 5 TO 10 DEGREES THROUGHOUT
THE AREA…PRECIP THAT IS MOVING OVER THE AREA WILL TAKE SOME
TIME TO SATURATE THE LOWER LEVELS OVER THE ATMOSPHERE. SO WILL
SEE VIRGA AND VCSH THE NEXT FEW HOURS BEFORE ANY PRECIP MAKES IT
TO THE GROUND AROUND 18Z/19Z. EXPECT PRECIP TO START AS MAINLY
RAIN…WITH FEW FLAKES OF SNOW MIXING IN. WITH PRECIP
ONSET…WETBULB TEMPS EXPECTED TO BE NEAR FREEZING…THEREFORE
EXPECT -RA TO MIX WITH -SN SHORTLY AFTER ONSET OF PRECIP…AS
PRECIP BECOMES HEAVIER THIS AFTERNOON. WITH HEAVIER
PRECIP…CONDITIONS WILL DETERIORATE TO MVFR CIGS/VSBY BY AROUND
20/21Z…AND REMAINING MAINLY MVFR THROUGH THE END OF THE TAF
PERIOD (12Z FRIDAY).

IFR CONDITIONS ARE POSSIBLE OVERNIGHT…ESPECIALLY EARLY IN THE
NIGHT WHEN PCPN IS HEAVIEST. HOWEVER…PROBABILITY APPEARS LOW AT
THIS TIME SO DID NOT INCLUDE IN THE TAF FORECAST. IN ADDITION…
VSBYS WILL LIKELY BECOME VFR LATE TONIGHT…GENERALLY AFTER
10Z… AFTER A FRONTAL BOUNDARY MOVES THROUGH.

SURFACE WINDS WILL BE LIGHT AND SOUTHERLY AT LESS THAN 8 KTS FOR
THE REST OF THE TAF PERIOD. THE WINDS WILL SHIFT FROM LIGHT
SOUTHERLY TO LIGHT WESTERLY LATE TONIGHT AS A FRONTAL BOUNDARY
MOVES THROUGH.

OUTLOOK…
FRI-SAT…VFR…NO SIG WX.
SAT NGT-SUN…VFR/MVFR. CHC -SN POSS MIX WITH -RA.
MON…VFR…NO SIG WX.
— End Changed Discussion —

&&

.HYDROLOGY…
NO HYDRO PROBLEMS ARE EXPECTED OVER THE NEXT SEVERAL DAYS. SOME
GAGES WILL CONTINUE TO HAVE ICE EFFECTS NORTH OF THE MOHAWK RIVER
VALLEY IN THE ALBANY HYDRO SERVICE AREA.

A LOW PRESSURE SYSTEM AND ITS ASSOCIATED COLD FRONT WILL BRING SOME
RAIN AND/OR SNOW TO THE REGION FROM THIS AFTERNOON THROUGH TONIGHT.
QPF AMOUNTS GENERALLY EXPECTED TO BE AROUND TWO TENTHS OF AN INCH TO
ONE THIRD OF AN INCH ACROSS THE HSA.

SOME LAKE ENHANCED OR UPSLOPE SNOWFALL IS POSSIBLE FOR THE WESTERN
ADIRONDACKS FRIDAY INTO SATURDAY WITH LIGHT ACCUMULATIONS EXPECTED.

TEMPERATURES FOR THE WEEKEND STILL LOOK TO AVERAGE ABOVE NORMAL
FOR MID FEBRUARY.

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…KL/JPV
NEAR TERM…JPV
SHORT TERM…JPV
LONG TERM…GJM
AVIATION…GJM/KGM
HYDROLOGY…JPV

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