January 26, 2012 Forecast Discussion

000
FXUS61 KALY 262155
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
455 PM EST THU JAN 26 2012

.SYNOPSIS…
A POTENT STORM SYSTEM WILL TRACK NORTHEASTWARD THROUGH THE
TENNESSEE AND OHIO VALLEY REGIONS TONIGHT…AND ACROSS THE
INTERIOR NORTHEAST ON FRIDAY. THIS SYSTEM WILL BRING MAINLY RAIN
TO AREAS SOUTH OF ALBANY TONIGHT AND EARLY FRIDAY…WITH A WINTRY
MIX CHANGING TO FREEZING RAIN AND EVENTUALLY RAIN FOR HIGHER
TERRAIN AND AREAS NORTH OF THE CAPITAL REGION. THE STORM SYSTEM
WILL PASS TO OUR EAST LATE FRIDAY…WITH DRIER AND BREEZY
CONDITIONS DEVELOPING IN ITS WAKE. A FEW CLIPPER TYPE SYSTEMS WILL
MOVE ACROSS THE AREA FROM LATE SATURDAY THROUGH SUNDAY NIGHT.

&&

.NEAR TERM /THROUGH TONIGHT/…
AS OF 445 PM…PRECIPITATION ARRIVED VERY QUICKLY THIS AFTERNOON
WITH STRONG ISENTROPIC LIFT ON THE 295K SURFACE AT THE NOSE OF A
40-45 KT 850MB SOUTHWESTERLY JET. PRECIP HAS MAINLY BEEN IN THE
FORM OF SNOW FOR MUCH OF THE REGION DUE TO ISOTHERMAL TEMP PROFILE
AT 0C LINE…ALTHOUGH A CHANGE-OVER TO RAIN HAS OCCURRED ACROSS
PORTIONS OF THE MID HUDSON VALLEY. ANY AREAS THAT HAVE CHANGED TO
RAIN WILL LIKELY REMAIN AS PLAIN RAIN THROUGH THE DURATION OF THE
EVENT WITH SURFACE TEMPS REMAINING ABOVE FREEZING. ELSEWHERE…HAD
TO INCREASE SNOWFALL ACCUMULATIONS FOR MUCH OF THE AREA BASED ON
EARLIER ARRIVAL OF PRECIP AS SNOW. MAINLY AROUND AN INCH IS
EXPECTED IN THE HUDSON VALLEY REGION FROM THE CAPITAL REGION
SOUTHWARD BEFORE A CHANGE-OVER TO SLEET AND EVENTUALLY RAIN OCCURS
LATER THIS EVENING. ACROSS THE HIGHER TERRAIN FROM ALBANY
SOUTH…POCKETS OF FREEZING RAIN WILL DEVELOP AND BECOME MORE
WIDESPREAD THIS EVENING BEFORE CHANGING TO RAIN OVERNIGHT. NOT
MUCH CHANGE FRONT PREVIOUS FORECASTS IN TERMS OF ICING IN THESE
AREAS. NORTHERN LITCHFIELD COUNTY WAS ADDED TO THE WINTER WEATHER
ADVISORY FOR A FEW HOURS OF FREEZING RAIN THIS EVENING.

FOR AREAS NORTH OF THE CAPITAL REGION…THERE WILL BE A MORE
GRADUAL TRANSITION OF PTYPES AS COLDER AIR IS IN PLACE IN THE
LOWER LEVELS. SO…INCREASED SNOW AMOUNTS SLIGHTLY BEFORE THE
CHANGE-OVER TO SLEET AND FREEZING RAIN. QPF FORECASTS ARE SLIGHTLY
HIGHER INTO SOUTHERN VERMONT…SO THERE IS SOME CONCERN THAT ICING
COULD BE MORE SIGNIFICANT…ESPECIALLY FROM THE HIGHER TERRAIN IN
BENNINGTON COUNTY EASTWARD THROUGH ALL OF WINDHAM COUNTY. FOR NOW
HAVE INCREASED ICE ACCRETION AMOUNTS TO AROUND 0.4" AND WILL HAVE
TO MONITOR TRENDS FOR POSSIBLE UPGRADE TO ICE STORM WARNING IF
AMOUNTS LOOK THEY WILL EXCEED 0.5". WILL MENTION THIS POSSIBILITY
IN THE HWO. ELSEWHERE ACROSS NORTHERN AREAS IT LOOKS LIKE AROUND
1-3" OR 2-4" OF SNOW/SLEET FOLLOWED BY AROUND TWO TO THREE TENTHS
OF AN INCH OF ICE. AGAIN…THE GREATEST IMPACTS OF ICE ARE
EXPECTED TO BE ACROSS SOUTHERN VERMONT.

WARMER AIR ALOFT WILL RUSH IN THIS EVENING AND OVERNIGHT…HOWEVER
IT WILL TAKE TIME TO WARM SURFACE TEMPS. SO EXPECTING MIN TEMPS TO
OCCUR THIS EVENING…WITH A GRADUAL RISE LATE TONIGHT INTO EARLY
FRIDAY MORNING. MANY AREAS TO THE NORTH OF THE CAPITAL REGION MAY
STILL BE BELOW FREEZING BY SUNRISE FRIDAY. THE SURFACE LOW CENTER
IS EXPECTED TO BE OVER WESTERN NY STATE BY 7 AM…WITH WARMER AIR
BEING DRAWN NORTHWARD AHEAD OF THE SYSTEM.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/…
AS OF 445 PM…WARM NOSE OF AIR ALOFT WILL BE WELL PRONOUNCED
ACROSS THE AREA FRIDAY MORNING SO ONLY PTYPES SHOULD BE
RAIN/FREEZING RAIN. AFTER SUNRISE THERE WILL STILL BE ONGOING
FREEZING RAIN ACROSS PORTIONS OF THE MOHAWK VALLEY…SOUTHERN
ADIRONDACKS AND SOUTHERN VERMONT WITH SURFACE TEMPS HOVERING
AROUND FREEZING. OUTSIDE OF THE AREAS MENTIONED…PLAIN RAIN WILL
BE THE DOMINANT PTYPE. SURFACE LOW PRESSURE WILL TRAVERSE THE AREA
FROM WEST TO EAST THROUGH THE DAY…WITH RAIN CONTINUING. SOME
ADDITIONAL MINOR ICING WILL OCCUR ACROSS NORTHERN AREAS…WITH
RAIN AND RISING TEMPS EXPECTED ELSEWHERE. WINDS ARE NOT EXPECTED
TO BE A PROBLEM DUE TO A S-SW TRAJECTORY AS OPPOSED TO S-SE WHICH
USUALLY CAUSES ISSUES IN WESTERN NEW ENGLAND.

TEMPS WILL SPIKE DURING THE EARLY AFTERNOON AHEAD OF THE TRIPLE
POINT…WITH WIDE-RANGING VALUES ACROSS THE AREA. TEMPS SHOULD
WARM ENOUGH AT ALL LOCATIONS FOR PLAIN RAIN BY AFTERNOON…WITH
MAX TEMPS RANGING FROM THE UPPER 30S TO LOWER 40S NORTH AND WEST
OF ALBANY…AND UPPER 40S TO EVEN MID 50S FROM ALBANY SOUTHWARD.
THE WARMEST 50-55 READINGS WILL BE IN THE MID HUDSON VALLEY
EASTWARD TO LITCHFIELD CT. CANNOT RULE OUT SOME CONVECTIVE
DOWNPOURS EARLY MORNING THROUGH AROUND MID AFTERNOON SOUTH AND
EAST OF ALBANY AS MILD…MOIST AIR SURGES INTO THE AREA WITH SOME
ELEVATED INSTABILITY.

THE ENTIRE SYSTEM SHOULD MOVE EAST OF THE AREA BY FRIDAY EVENING.
SOME WRAP-AROUND/UPSLOPE RAIN/SNOW SHOWERS WILL BE POSSIBLE INTO
THE EVENING…BUT THE BULK OF THE PRECIP SHOULD BE OVER. BREEZY
CONDITIONS WILL DEVELOP AS W-NW WINDS INCREASE IN WAKE OF THE
SYSTEM.

EXPECTING TEMPS TO BE COOLER BUT STILL SOMEWHAT MILD FOR
SATURDAY…AHEAD OF A CLIPPER-TYPE LOW THAT WILL BE TRACKING
EASTWARD ACROSS SOUTHEAST CANADA. SOME RAIN/SNOW SHOWERS WILL BE
POSSIBLE MAINLY WEST OF ALBANY AHEAD OF THIS SYSTEM…WITH THE
POTENTIAL FOR SOME LAKE EFFECT SNOW ACROSS THE FAR REACHING
PORTIONS OF THE WESTERN ADIRONDACKS LATE SATURDAY NIGHT WITH A WSW
FLOW TRAJECTORY AND COLDER AIR ALOFT ADVECTING IN.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/…
MOS GUIDANCE. A PERIOD OF FAST-MOVING SYSTEMS BEGINNING WITH A WEAK
HIGH PRESSURE RIDGE OVER OUR REGION…REPLACED BY A FAST-MOVING
CLIPPER AND A WEAKENING FRONTAL BOUNDARY FOR THE START OF THE WEEK.
THEN…ANOTHER RIDGE BUILDS IN FROM THE WEST…AND MOVES OFF THE
EAST COAST AT MID-WEEK…REPLACED BY A WEAK WARM FRONT AHEAD OF LOW
PRESSURE TRACKING EAST ACROSS THE NORTHERN GREAT LAKES. THIS FRONT
WILL DRAG A COLD FRONT EAST THROUGH OUR AREA ON WEDNESDAY…WITH
ANOTHER COLD FRONT DIPPING SOUTH ON THURSDAY.

SUNDAY NIGHT AND WEDNESDAY WILL SEE THE GREATEST CHC POPS…WHILE
THURSDAY WILL BE THE DRIEST DAY. LOOKING AT SEVERAL PERIODS OF
MIXED PRECIP…MAINLY SHOWERY…WITH NO MAJOR QPF EVENTS.
TEMPERATURES WILL GO THROUGH MUCH DIURNAL SEE-SAWING…BUT WILL
AVERAGE SEVERAL DEGREES ABOVE NORMAL…WITH NO OUTSTANDINGLY COLD OR
MILD PERIODS.

&&

.AVIATION /21Z THURSDAY THROUGH TUESDAY/…
LATEST MOSAIC RADAR RETURNS SHOWS PRECIP CURRENTLY OVER THE
SOUTHERN TIER OF NY AND NE PA IS HEADING TOWARDS THE HUDSON
VALLEY TAF SITES. PRECIP WILL START TO DEVELOP FIRST AT KPOU OVER
THE NEXT HOUR OR TWO…BY MID AFTN FOR KALB…AND BY LATE
AFTN/EARLY EVENING FOR KGFL. AT KPOU…THERE MAY BE A BRIEF PERIOD
OF A FEW SNOWFLAKES…BUT PRECIP SHOULD GENERALLY BE RAIN.
MEANWHILE…KALB LOOKS TO HAVE A 1-3 HR PERIOD OF SNOW…WITH
SEVERAL HOURS OF SNOW EXPECTED AT KGFL. WITHIN THE
SNOWFALL…FLYING CONDITIONS MAY QUICKLY DROP TO IFR VSBYS.

BY THIS EVENING…KALB WILL CHANGE OVER TO JUST PLAIN RAIN AS
SURFACE TEMPS RISE ABOVE FREEZING. THIS WILL ALLOW FOR RAIN TO
OCCUR FOR MUCH OF THE NIGHT AT KALB/KPOU. FLYING CONDITIONS WILL
REMAIN POOR…WITH GENERALLY LOW END MVFR/IFR CONDITIONS DUE TO
CIGS WITHIN A STEADY RAINFALL. KGFL WILL BEGIN TO CHANGE OVER TO
FZRA/PL DURING THE LATE EVENING HOURS AND SHOULD REMAIN FZRA FOR
MUCH OF THE NIGHT AS LOW LEVEL COLD AIR WILL BE ENTRENCHED IN
PLACE. THIS WILL ALLOW FOR SOME ICE ACCRETION TO OCCUR. FLYING
CONDITIONS AT KGFL WILL ALSO BE IFR FOR MUCH OF THE NIGHT DUE TO
LOW CIGS AS WELL.

AFTER SUNRISE…THE PRECIP WILL START TO BECOME MORE SHOWERY IN
NATURE. IT SHOULD WARM UP ENOUGH AT THIS POINT FOR EVEN KGFL TO
JUST HAVE A COLD PLAIN RAIN. WITH THE LIGHTENING UP IN THE PRECIP
INTENSITY…THIS SHOULD ALLOW FOR SOMEWHAT OF AN IMPROVEMENT IN
CIGS/VSBYS…WITH FLYING CONDITIONS PROBABLY BACK UP TO LOW END
MVFR BY THE MID TO LATE MORNING.

SFC WINDS WILL BE LIGHT FROM A NORTHEAST DIRECTION THIS
AFTERNOON…AND BECOME NEARLY CALM FOR MUCH OF THE NIGHT. THEY WILL
SWITCH TO AN EAST TO SOUTHEAST DIRECTION BY MORNING AT LIGHT
SPEEDS…GENERALLY 7 KTS OR LESS.

OUTLOOK…
FRI NT-SAT…VFR. NO SIG WX.
SUN…VFR/MVFR. CHC -SHSN/-SHRA.
MON-TUE…VFR. NO SIG WX.

&&

.HYDROLOGY…
A COMPLEX STORM SYSTEM WILL MOVE ACROSS THE REGION TONIGHT INTO
FRIDAY. EXPECTED QPF STILL GENERALLY IN THE 0.75 TO 1.50 INCH
RANGE. THERE IS GOOD MODEL AGREEMENT WITH THESE AMOUNTS…HOWEVER
GREATER AMOUNTS OF 1.50 TO 2.00 INCHES WILL BE POSSIBLE ACROSS
SOME SOUTH FACING SLOPES OF HIGHER TERRAIN AS WELL AS IN WESTERN
NEW ENGLAND.

AFTER SOME MIXED PRECIPITATION EARLY THIS EVENING…A
DECENT AMOUNT OF THE QPF WILL FALL AS RAIN FROM ALBANY SOUTHWARD
SO THERE WILL BE RUNOFF. THERE WILL BE FREEZING RAIN WITH ICE
ACCRETION IN PORTIONS OF THE EASTERN CATSKILLS…BERKSHIRES AND
TACONICS. FARTHER NORTH THIS EVENT WILL PRIMARILY BE A WINTRY MIX
INCLUDING ICE WITH ONLY LIMITED RUNOFF.

AT THIS TIME…FLOODING ON MAIN STEM RIVERS DOES NOT APPEAR
LIKELY…ALTHOUGH THERE COULD BE SOME MINOR FLOODING OF SMALL
STREAMS AND POOR DRAINAGE LOCATION DUE TO FROZEN GROUND TO SEVERAL
INCHES BELOW THE SURFACE. THERE COULD ALSO BE PONDING OF WATER IN
LOW LYING…POOR DRAINAGE AND URBAN AREAS…AND ON ROADWAYS SHOULD
HEAVIER RAINFALL AMOUNTS OCCUR.

ONLY LIGHT PRECIPITATION IS EXPECTED FROM FRIDAY NIGHT THROUGH
EARLY NEXT WEEK WITH A FEW CLIPPER-TYPE SYSTEMS MOVING THROUGH.

&&

.ALY WATCHES/WARNINGS/ADVISORIES…
CT…WINTER WEATHER ADVISORY UNTIL 7 AM EST FRIDAY FOR CTZ001.
NY…WINTER WEATHER ADVISORY UNTIL 7 AM EST FRIDAY FOR NYZ038-040-
047-048-051-058-063.
WINTER WEATHER ADVISORY UNTIL 1 PM EST FRIDAY FOR NYZ032-033-
039-041>043-082>084.
MA…WINTER WEATHER ADVISORY UNTIL 7 AM EST FRIDAY FOR MAZ001-025.
VT…WINTER WEATHER ADVISORY UNTIL 1 PM EST FRIDAY FOR VTZ013>015.

&&

$$
SYNOPSIS…JPV
NEAR TERM…JPV
SHORT TERM…JPV
LONG TERM…ELH
AVIATION…FRUGIS
HYDROLOGY…JPV

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