February 23, 2013 Forecast Discussion

000
FXUS61 KALY 231757
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
1257 PM EST SAT FEB 23 2013

.SYNOPSIS…
A WARM FRONT ASSOCIATED WITH LOW PRESSURE OVER THE GREAT LAKES
REGION WILL APPROACH FROM THE SOUTHWEST THIS AFTERNOON.
MEANWHILE…ANOTHER LOW PRESSURE SYSTEM WILL DEVELOP NEAR THE
DELMARVA REGION THIS AFTERNOON…AND WILL TRACK
NORTHEASTWARD…PASSING SOUTH OF LONG ISLAND AND SOUTHERN NEW
ENGLAND ON SUNDAY. THIS COMBINATION OF SYSTEMS LOOKS TO BRING A
LIGHT SNOWFALL FROM THE CAPITAL REGION AND BERKSHIRES NORTH…AND
A MIX OF RAIN…FREEZING RAIN AND SNOW TO THE SOUTH. THESE SYSTEMS
WILL PULL AWAY SUNDAY NIGHT…WITH HIGH PRESSURE BUILDING BACK IN
FOR MONDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/…
OVERALL FORECAST IS ON TRACK FOR THIS AFTERNOON. HAVE MADE SOME
ADJUSTMENTS TO TEMPERATURES AND FOR TRENDS IN LIGHT PRECIPITATION.
INCREASING WARM ADVECTION/ISENTROPIC LIFT ON THE 285-290K SURFACE
SHOULD ALLOW FOR AN EXPANSION OF PRECIPITATION THIS AFTERNOON.
TEMPERATURES PROFILES ARE INITIALLY COLD ENOUGH TO SUPPORT SOME
SNOW…ENOUGH BOUNDARY LAYER WARMING HAS OCCURRED FOR MAINLY LIGHT
RAIN/DRIZZLE TO OCCUR IN VALLEY WITH PERHAPS A MIX OF SNOW AND
RAIN ACROSS HIGHER ELEVATIONS. ANY SNOWFALL ACCUMS THAT OCCUR
THROUGH SUNSET SHOULD REMAIN VERY LIGHT…WITH PERHAPS A COATING
ON COLDER SURFACES IN VALLEY AREAS…AND LESS THAN ONE INCH ACROSS
HIGHER ELEVATIONS ACROSS THE SOUTHERN ADIRONDACKS AND VERMONT.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/…
WINTER WEATHER ADVISORIES ISSUED FOR TONIGHT FOR THE EASTERN
CATSKILLS/MID HUDSON VALLEY/SOUTHERN AND CENTRAL TACONICS AND
LITCHFIELD CO…AND TONIGHT THROUGH SUNDAY EVENING ACROSS THE
BERKSHIRES AND SOUTHERN VT…

AS THE NEW LOW FORMS NEAR THE DELMARVA PENINSULA AND TRACKS EAST
NORTHEAST…AND COMBINES WITH INCREASING QG FORCING FROM THE UPPER
LEVEL LOW TO OUR WEST…PRECIPITATION SHOULD INCREASE IN AREAL
COVERAGE ACROSS THE REGION THIS EVENING. HOWEVER…MODELS SEEM
RATHER INSISTENT THAT MID LEVEL DRYING WILL OCCUR…LIMITING ICE
CRYSTALS IN THE CLOUDS. THIS WILL ACT TO LIMIT OVERALL SNOWFALL
POTENTIAL IN THE REGION…ESP INITIALLY. WE EXPECT PRECIPITATION
TO BEGIN AS LIGHT RAIN THIS EVENING…BEFORE TRANSITIONING TO WET
SNOW BETWEEN 9-11 PM TONIGHT ACROSS CENTRAL AND WESTERN AREAS.
FURTHER SOUTH AND EAST…A BIT MORE SEEDER/FEEDER PROCESSES FROM A
HIGHER CLOUD DECK SHOULD ALLOW FOR SOME SNOW TO MIX IN WELL AFTER
MIDNIGHT. CLOUD DEPTH IS EXPECTED TO REMAIN SHALLOW PRIOR
TO MIDNIGHT…AND AS SFC TEMPS GRADUALLY COOL TO NEAR
FREEZING…A PERIOD OF FREEZING RAIN MAY OCCUR. THEREFORE…HAVE
ISSUED WINTER WX ADVISORIES TO THE EXPECTATION FOR SOME LIGHT
FREEZING RAIN LATER THIS EVENING…IN ADDITION TO SOME LIGHT SNOW
AFTER MIDNIGHT. FURTHER N AND W…EXPECT PERIODS OF MAINLY LIGHT
SNOW TO DEVELOP A FEW HOURS AFTER SUNSET…AND CONTINUE THROUGH
THE OVERNIGHT HOURS. HOWEVER…SHOULD CLOUD DEPTH REMAIN MORE
SHALLOW…LESS SNOW…AND MORE IN THE WAY OF RAIN/FREEZING RAIN
WOULD OCCUR…WHICH WOULD REQUIRE THE EXPANSION OF WINTER WEATHER
ADVISORIES FURTHER N AND W DUE TO POTENTIAL LIGHT ICING.

SO…AT THIS TIME…EXPECTING SNOWFALL AMTS BY SUNDAY MORNING TO
ONLY REACH 1-3 INCHES IN MOST AREAS…WITH THE LOWER AMTS EXPECTED
IN VALLEY LOCATIONS…AND MAY BE CONFINED TO COLDER SURFACES. IN
ADDITION…A COATING TO ONE TENTH OF AN INCH OF ICE WILL BE
POSSIBLE ACROSS THE EASTERN CATSKILLS/MID HUDSON VALLEY
REGION…CENTRAL AND SOUTHERN TACONICS…LITCHFIELD CO…AND
SOUTHERN BERKSHIRES.

FOR SUNDAY AND SUNDAY NIGHT…A BRIEF LULL IN OVERALL FORCING SHOULD
LEAD TO A PRECIP MINIMUM DURING THE MORNING HOURS…WITH GENERALLY
ONLY SPOTTY LIGHT SNOW EXPECTED. HOWEVER…AS THE AFTERNOON
PROGRESSES…THE REMNANT UPPER LEVEL LOW CURRENTLY ACROSS THE
GREAT LAKES IS EXPECTED TO TRANSLATE E/SE…PASSING ACROSS
NORTHERN OR CENTRAL PORTIONS OF THE FORECAST AREA. FOR AREAS NORTH
AND EAST OF THE PASSING MID LEVEL LOW CENTER…ENHANCED QG FORCING
WILL ALLOW FOR AN INCREASE IN THE AREAL COVERAGE OF SNOW ONCE
AGAIN…MOST LIKELY AFFECTING THE SOUTHERN ADIRONDACKS/LAKE GEORGE
SARATOGA REGION…SOUTHERN VT AND THE NORTHERN BERKSHIRES. THIS
SHOULD LEAD TO AN ADDITIONAL 1-2 INCHES OF SNOW IN VALLEY
AREAS…AND PERHAPS 2-4 INCHES ACROSS HIGHER ELEVATIONS OF
SOUTHERN VT AND THE NORTHERN BERKSHIRES. WE HAVE THEREFORE
INCLUDED WINTER WX ADVISORIES FOR SOUTHERN VT/NORTHERN BERKSHIRES
DUE TO THIS ADDED ACCUM…WHICH COULD BE EVEN GREATER SHOULD THE
AFOREMENTIONED MID/UPPER LEVEL LOW CENTER PASS MORE SLOWLY. THE
SNOW SHOULD GRADUALLY TAPER OFF AFTER MIDNIGHT. MEANWHILE…TO THE
SOUTH OF THIS MID/UPPER LEVEL LOW PASSAGE…PRECIP SHOULD BE MUCH
MORE INTERMITTENT AND SHOWERY…WITH EVEN SOME RAIN POSSIBLE
ACROSS PORTIONS OF THE MID HUDSON VALLEY SUN AFTERNOON. EXPECT
ADDITIONAL SNOWFALL ACCUMS OF LESS THAN ONE INCH FOR MOST OF THE
CAPITAL REGION…SCHOHARIE VALLEY…SOUTHEAST CATSKILLS AND
SOUTHERN BERKSHIRES…WITH LITTLE IF ANY ADDITIONAL ACCUM FURTHER
SOUTH AND IN VALLEY LOCALES. IT WILL BECOME BRISK…WITH
WEST/NORTHWEST WINDS INCREASING TO 15-25 MPH WITH HIGHER GUSTS BY
SUN AFTERNOON/EVENING. EXPECT MAX TEMPS TO REACH THE LOWER/MID 30S
ACROSS NORTHERN AREAS…AND MID 30S TO LOWER 30S FURTHER SOUTH.

MON-MON NT…HIGH PRESSURE SHOULD BUILD IN FROM THE WEST. SOME LOW
CLOUDS COULD LINGER MON MORNING…OTHERWISE EXPECT SOME SUNSHINE
FOR MON AFTERNOON…WITH CLEAR SKIES GRADUALLY GIVING WAY TO
INCREASING CLOUDS LATER MON NT. EXPECT MAX TEMPS TO REACH THE MID
30S TO LOWER 40S…AND OVERNIGHT MINS TO FALL INTO THE
20S…EXCEPT FOR SOME TEENS ACROSS HIGHER ELEVATIONS.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/…
THE EXTENDED FORECAST IS UNSETTLED WITH A STORM SYSTEM TO START
IT…THEN A SPRAWLING UPPER LEVEL LOW TO CLOSE THE WORK WEEK WITH
PERSISTENT CHANCES OF RAIN AND SNOW SHOWERS.

LOW PRESSURE WILL BE APPROACHING FROM THE LOWER MS RIVER VALLEY
EARLY TUESDAY MORNING…AS HIGH PRESSURE WILL BE RETREATING EASTWARD
FROM MAINE. THE LATEST ECMWF/GFS/CAN GGEM ARE IN PRETTY GOOD
AGREEMENT THE DAY WILL START OUT DRY…AS THE PRIMARY LOW AND ITS
ASSOCIATED POTENT H500 CLOSED COMPACT CIRCULATION MOVES OVER THE
MIDWEST. SOME OVER RUNNING PCPN AHEAD OF THE WARM FRONT TO THE
SYSTEM STARTS TO MOVE IN LATE IN THE DAY. A SHORT-WAVE ROUNDING THE
BASE OF THE TROUGH WILL ALLOW A POTENTIALLY A SECONDARY LOW TO MOVE
NEAR DELMARVA REGION TUE NIGHT. THIS LOOKS TO BE A MILLER TYPE B
SYSTEM WITH A PRIMARY AND SECONDARY LOW. THE QUESTION WILL BE HOW
MUCH COLD /SUBFREEZING/ AIR THROUGH A SUFFICIENT…DEEP ENOUGH LAYER
WILL BE IN PLACE FOR A SNOW PTYPE. OUR CONFIDENCE WAS NOT HIGH FOR
MIXED PCPN INCLUDING SLEET AND FREEZING RAIN AT THIS TIME. CRITICAL
PARTIAL THICKNESSES…AND BUFKIT MODEL SOUNDINGS FROM THE GFS
SUPPORT SOME SNOW TRANSITIONING TO RAIN AT NIGHT…AND THEN MAYBE
BACK TO SNOW. THE ECMWF THERMAL PROFILES LOOK COLDER. WILL
CONTINUE TO MENTION THIS STORM IN THE HWO…AND BOOSTED POPS TO
LIKELY VALUES TUES NIGHT INTO WEDNESDAY. HIGHS ON TUE WILL
GENERALLY BE IN THE 30S WITH SOME L40S IN THE MID HUDSON VALLEY.
LOWS WILL RANGE FROM THE 20S OVER THE MTNS TO LOWER TO MID 30S OVER
THE MTNS.

WEDNESDAY…THE ECMWF IS A LITTLE FURTHER WEST WITH THE PLACEMENT OF
THE PRIMARY LOW OVER THE ERN GREAT LAKES REGION COMPARED TO THE
GFS. THE HPC GUIDANCE IS A TAD CLOSER TO THE ECMWF. A SLUG OF
MOISTURE WITH THE SECONDARY LOW…AND THE OCCLUDED BOUNDARY BLASTS
THROUGH DURING THE LATE MORNING/AFTERNOON…BEFORE A DRY SLOT MOVES
IN. THE PCPN IS CHALLENGING WITH SNOW POTENTIALLY TURNING TO
RAIN…THEN BACK TO SNOW AS COLDER AIR MOVES BACK IN. LIKELY POPS
WERE CONTINUED HERE WITH HPC MAX TEMPS. THE DRY SLOT IN THE PM MAY
ALLOW MAX TEMPS TO BE 40-45F FROM THE CAPITAL REGION SOUTH AND EAST
/EXCLUDING THE NORTHERN BERKSHIRES/…AND 30S TO THE NORTH AND WEST.

WEDNESDAY NIGHT THROUGH FRIDAY…BROAD CYCLONIC FLOW WILL IMPACT NY
AND NEW ENGLAND WITH MULTIPLE EMBEDDED CIRCULATIONS ROTATING
AROUND…AND THROUGH THE LONGWAVE TROUGH. BASICALLY KEPT A CHANCE
OF RAIN OR SNOW SHOWERS TIED TO THE DIURNAL HEATING EACH PERIOD.
THE NIGHT TIME PERIODS WOULD SUPPORT MAINLY SCT SNOW SHOWERS. THE
LAST CLOSED H500 LOW FINALLY BEGINS TO EXIT BY LATE FRI. GENERALLY
USED THE SCT RAIN/SNOW SHOWER PHRASING IN THE LONG TERM FROM THE
PREVIOUS FORECASTS. TEMPS LOOK TO RUN CLOSE TO NORMAL TO CLOSE THE
WEEK WITH 30S TO L40S FOR HIGHS…AND 20S FOR LOWS.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/…
HIGH PRESSURE CONTINUES TO MOVE NORTHEAST OF MAINE THIS MORNING WITH
A WARM FRONT APPROACHING FROM THE SOUTH AND WEST. THIS BOUNDARY WILL
BRING SOME LIGHT SNOW AND RAIN LATER THIS AFTERNOON. A COASTAL LOW
WILL BRING BETTER MIXED PCPN TRANSITIONING TO SNOW TONIGHT…AS IT
PASSES WELL SOUTH OF SOUTHERN NEW ENGLAND. SOME FOG OCCURRING AT
KALB…KPOU AND KPSF SHOULD PERSIST AND CONTINUE ONCE PRECIPITATION
BEGINS.

THE LIGHT PCPN WILL LIKELY TRANSITION TO A MIXTURE OF SNOW AND RAIN
BTWN 18Z-23Z AT ALL THE TERMINALS…AS THE BOUNDARY LAYER WARMS.
THE MVFR CONDITIONS ARE EXPECTED TO PERSIST DURING THE DAY WITH
LAPSES TO IFR VSBYS/CIGS ESPECIALLY BTWN 22Z-01Z WHEN THE BETTER
LIFT AND PCPN IMPACTS THE REGION. EXPECT WIDESPREAD LOW MVFR/IFR
CONDITIONS AT ALL THE TAF SITES TONIGHT. KPOU WILL LIKELY HAVE
MOSTLY RAIN BEFORE SOME LIGHT FREEZING DRIZZLE TONIGHT. CONDITIONS
MAY BE IFR IN ALL THE TERMINALS WITH SATURATED AND MOIST BOUNDARY
LAYER CONDITIONS.

PRECIPITATION SHOULD CONTINUE THROUGH MUCH OF TOMORROW MORNING…BUT
CEILINGS AND VISIBILITIES SHOULD JUST BEGIN TO RISE LATER IN THE
MORNING AS THE LOW PRESSURE SYSTEM BEGINS TO EXIT.

WINDS WILL BE LIGHT TO CALM AT KPOU AND KGFL THROUGH MUCH OF THIS
AFTERNOON…BUT S/SE WINDS OF 5-12 KTS CAN BE EXPECTED AT KALB…AND
KPSF DURING THE AFTERNOON. EXPECT THE WINDS TO BECOME LIGHT TO CALM
OVERNIGHT. WINDS SHOULD BECOME LIGHT NORTHWEST LATER TOMORROW
MORNING AT LESS THAN 10 KT.

OUTLOOK…
SUN…MVFR/IFR. SNOW TAPERING OFF AT KALB/KGFL/KPOU WITH A CHC OF
RAIN/SNOW IN THE AFTN. KPSF…SNOW MAINLY IN THE AM.
MON-TUE MORNING…VFR. NO SIG WX.
TUE PM-WED…MVFR/IFR. CHC SNOW/RAIN.
&&

.HYDROLOGY…
NO HYDROLOGY PROBLEMS ARE EXPECTED THROUGH AT LEAST THE NEXT FIVE
DAYS.

A DEVELOPING COASTAL STORM LOOKS TO BRING LIGHT SNOW TO
MUCH OF THE REGION ON THE WEEKEND…ALTHOUGH SOME LIGHT RAIN MAY
MIX WITH MANY LOCATIONS SATURDAY BEFORE TRANSITIONING TO SNOW FROM
THE CAPITAL REGION NORTH BY THE EARLY EVENING…AND A WINTRY MIX
TO ALL SNOW TO THE SOUTH OVERNIGHT. TOTAL QPF OF LOOKS TO RANGE
FROM A QUARTER OF AN INCH TO ONE HALF OF AN INCH BY LATE IN
SUNDAY EVENING.

DRY WEATHER IS EXPECTED ON MONDAY BEFORE ANOTHER SYSTEM ARRIVES FOR
LATE TUESDAY INTO WEDNESDAY WITH POTENTIALLY MORE SNOW AND 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…WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 7 AM EST
SUNDAY FOR CTZ001-013.
NY…WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 7 AM EST
SUNDAY FOR NYZ058>061-063>066.
MA…WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO MIDNIGHT EST
SUNDAY NIGHT FOR MAZ001-025.
VT…WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO MIDNIGHT EST
SUNDAY NIGHT FOR VTZ013>015.

&&

$$
SYNOPSIS…KL/NAS
NEAR TERM…IAA/KL/NAS
SHORT TERM…KL
LONG TERM…WASULA
AVIATION…NAS
HYDROLOGY…KL/JPV/WASULA

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