February 5, 2013 Forecast Discussion

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000
FXUS61 KALY 052314
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
614 PM EST TUE MAR 5 2013

.SYNOPSIS…
A LOW PRESSURE SYSTEM WILL MOVE OFF THE MID ATLANTIC COAST
THROUGH MIDWEEK AND PASS WELL SOUTH OF LONG ISLAND WEDNESDAY INTO
THURSDAY. IT WILL BRING SOME ACCUMULATING SNOW TO EASTERN NEW YORK
AND ADJACENT WESTERN NEW ENGLAND WEDNESDAY AFTERNOON INTO FRIDAY.

&&

.NEAR TERM /THROUGH WEDNESDAY/…
MAINLY A CLEAR SKY CONTINUES OVER THE REGION…BUT SOME AREAS OF
CLOUDS OVER NEW ENGLAND COULD OFFER PERIODS OF CLOUDS IN WESTERN
NEW ENGLAND AND EASTERN NY THIS EVENING. STILL…WITH THE
WIDESPREAD CLOUDS OUTSIDE THE REGION…AND MOST OF THE NIGHT
MOSTLY CLEAR TO PARTLY CLOUDY. LOW TEMPERATURES SHOULD BE ABLE TO
FALL TO CURRENT FORECASTED LEVELS. ONCE ALL 00Z DATA
ARRIVES…SOME ADJUSTMENTS TO TEMPERATURES MAY BE NEEDED.
OTHERWISE…AT THIS TIME…JUST MINOR ADJUSTMENTS TO THE FORECAST
THROUGH TONIGHT.

PREV AFD BELOW…

LOWS TONIGHT WILL GENERALLY BE IN THE 20S IN MOST LOCATIONS…WITH
A FEW UPPER TEENS IN THE HIGHER ELEVATIONS OF THE ADIRONDACKS.
ALTHOUGH CLOUD COVER WILL BE INCREASING DURING THE DAY
WEDNESDAY…HIGH TEMPERATURES WILL STILL RISE INTO THE UPPER 30S
IN HIGHER ELEVATIONS AND LOW 40S IN VALLEY REGIONS AS SLIGHT WARM
ADVECTION AND A HIGHER SUN ANGLE HELP COMPENSATE FOR THE CLOUD COVER.

IT LOOKS LIKE WEDNESDAY MORNING WILL REMAIN DRY…BUT HAVE BUMPED
UP POPS TO SLIGHT CHANCE STARTING IN THE AFTERNOON TO ACCOUNT FOR
ANY RAIN/SNOW SHOWERS AHEAD OF THE AFOREMENTIONED STORM SYSTEM
THAT WILL BE DISCUSSED IN DETAIL IN THE SHORT TERM.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/…
A STORM SYSTEM MAY BRING ACCUMULATING SNOWFALL TO THE REGION
DURING THE SHORT TERM PERIOD.

THE SHORT TERM PERIOD WILL BE DOMINATED BY A POWERFUL STORM SYSTEM
CURRENTLY IMPACTING MUCH OF THE OHIO VALLEY AND MID ATLANTIC
REGION. MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT REGARDING
THE TRACK AND EVOLUTION OF THIS SYSTEM…FAVORING A LIGHT TO
MODERATE SNOWFALL EVENT ACROSS THE FORECAST AREA. A BLEND OF THE
12Z ECMWF/GFS/CANADIAN/UKMET WAS UTILIZED…AS THESE MODELS EACH
DEPICTED A SIMILAR TRACK AND EVOLUTION BETWEEN THE LAST COUPLE OF
MODEL RUNS. HAVE DISREGARDED THE NAM AS IT ONCE AGAIN CONTINUES TO
OVER DO PRECIPITATION AMOUNTS.

SYNOPTICALLY…THIS STORM SYSTEM WILL CONTINUE TO MATURE THROUGH
THE NEXT 12-18 HOURS AS IT INTERACTS WITH THE NORTHERN AND
SOUTHERN STREAM BRANCHES. LATEST PV SIGNATURES CONTINUE TO DEPICT
A CLASSIC TREBLE CLEF ORIENTATION…WHICH WOULD SUGGEST CONTINUED
INTENSIFICATION OF THE SYSTEM THROUGH THE OVERNIGHT.
MEANWHILE…HIGH PRESSURE ANCHORED OVER SOUTHERN CANADA AND THE
NORTHEASTERN CONUS WILL SLOWLY MOVE TO THE EAST…DEFLECTING THE
STORM SYSTEM EASTWARD AS IT EXITS OFF THE DELMARVA COAST.

IT IS AT THIS POINT WHERE THE MODEL GUIDANCE BEGINS TO DIFFER. THE
NAM/GFS CAMP HAS CONSISTENTLY FAVORED A MORE NORTHERN TRACK OF THE
COASTAL LOW WHILE THE ECMWF/UKMET/CANADIAN CAMP FAVOR A TRACK
FURTHER SOUTH OFF THE COAST OF LONG ISLAND. GIVEN THAT THE CURRENT
SOUTHERN STREAM JET STREAK POSITION APPEARS TO BE EAST OF THE
UPPER-LEVEL TROUGH AXIS ACCORDING TO THE LATEST SATELLITE
IMAGERY…HAVE SIDED WITH THE SOUTHERN CAMP OF MODEL GUIDANCE AS
THIS JET STREAK ORIENTATION SHOULD PROMOTE TROPOPAUSE FOLDING OF
THE PV LOBE…CUTTING THE UPPER-LEVEL SYSTEM OFF FROM THE FLOW
REGIME.

THIS SERIES OF EVENTS WILL THEN PROMOTE OCCLUSION OF THE OVERALL
STORM SYSTEM…AS IT BECOMES VERTICALLY-STACKED THROUGH THE COLUMN
OFF THE LONG ISLAND COAST. THE REMNANT PV LOBE AND ASSOCIATED JET
STRUCTURE WILL STILL SUPPORT A PERIOD OF ENHANCED ISENTROPIC LIFT
THROUGH THURSDAY…HOWEVER DUE TO THE SYSTEM ALREADY
OCCLUDING…THE BEST ISENTROPIC LIFT WILL LIKELY GET SHUNTED SOUTH
AND EAST OF THE FORECAST AREA…WHICH HAS BEEN SUPPORTED BY MOST
OF THE MODEL GUIDANCE. THERE WILL STILL BE A BRIEF PERIOD OF
FAVORABLE ASCENT ESPECIALLY ACROSS WESTERN AND CENTRAL NEW ENGLAND
THURSDAY THAT WILL PROMOTE AN INITIAL BURST OF SNOWFALL ACROSS
THESE AREAS WITH A COUPLE OF INCHES POSSIBLE.

ANOTHER ROUND OF SNOW WILL WILL AFFECT THE FORECAST
AREA THURSDAY NIGHT AS A SHORTWAVE TROUGH EMBEDDED IN THE NORTHERN
STREAM EJECTS SOUTHEASTWARD FROM SOUTHERN CANADA. QUESTIONS STILL
REMAIN AS TO HOW MUCH MOISTURE IS THROWN BACK WESTWARD TO INTERACT
WITH THE DEFORMATION ZONE BETWEEN THE TWO FEATURES…WHICH COULD
LIMIT QPF AND RESULTANT SNOWFALL AMOUNTS. ALTHOUGH THERE REMAINS
UNCERTAINTY IN THE EXACT DETAILS OF THE SYSTEM EVOLUTION AND HOW
THE NORTHERN STREAM SHORTWAVE WILL INTERACT WITH THE COASTAL
LOW…A LIGHT TO MODERATE SNOWFALL EVENT LOOKS TO OCCUR FOR MOST
OF THE FORECAST AREA WITH GENERALLY 2-4 INCHES EXPECTED MAINLY
NORTH AND WEST OF THE CAPITAL DISTRICT…WITH 4-6 AMOUNTS SOUTH
AND EAST. DUE TO CONTINUED MODEL UNCERTAINTY…HAVE ONLY
HIGHLIGHTED THE STORM IN THE HAZARDOUS WEATHER OUTLOOK…BUT
WINTER WEATHER ADVISORIES MAY BE NEEDED FOR PORTIONS OF THE
TACONICS AND WESTERN NEW ENGLAND AS WE GET CLOSER IN TIME.

HIGHS THURSDAY WILL GENERALLY BE IN THE UPPER 20S TO MID 30S WITH
LOWS THURSDAY NIGHT GENERALLY IN THE 20S. WINDS WILL GENERALLY BE
OUT OF THE NORTH/NORTHEAST AT 10-20 MPH WITH GUSTS UP TO 30 MPH
POSSIBLE ACROSS THE CATSKILLS.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/…
DURING THE DAY ON FRIDAY…THE LARGE CUTOFF COASTAL STORM OFF THE
COAST OF CAPE COD WILL CONTINUE TO SLOW MOVE AWAY FROM THE REGION.
AN ADDITIONAL UPPER LEVEL SHORTWAVE MOVING ACROSS THE NORTHEAST WILL
CONTINUE TO BECOME ABSORBED BY THIS LARGE SYSTEM OFF THE COAST. AS
THIS OCCURS…SOME ADDITIONAL LIGHT ACCUMULATION OF SNOW IS POSSIBLE
FOR FRIDAY MORNING INTO EARLY FRI AFTN…ESP FOR AREAS TO THE SOUTH
AND EAST OF THE CAPITAL REGION. AFTERWARD…THE STORM SHOULD BE
PULLING AWAY FROM THE REGION AND SKIES SHOULD BEGIN TO CLEAR OUT FOR
FRI AFTN. TEMPS ON FRI MORNING WILL BE IN THE LOWER TO MID 30S..BUT
SHOULD WARM TO THE MID TO UPPER 30S FOR MOST AREAS BY FRI AFTN FOR
HIGHS.

RIDGING WILL BUILD INTO THE REGION FOR FRIDAY NIGHT THROUGH SUNDAY
MORNING. THIS WILL ALLOW FOR DRY WEATHER ACROSS THE ENTIRE AREA AND
TEMPS TO WARM BACK UP TO NEAR TO EVEN SLIGHTLY ABOVE NORMAL FOR
SATURDAY/SUNDAY WITH 40S IN MOST AREAS. OVERNIGHT LOWS WILL DROP
BACK BELOW FREEZING…WITH 20S FOR MOST AREAS.

A FRONTAL SYSTEM WILL APPROACH FROM THE WEST FOR SUNDAY NIGHT INTO
EARLY NEXT WEEK. WITH THE MAIN STORM CENTER REMAINING TO OUR WEST
AND NORTH…THERE WILL BE A WARM SURGE OF AIR AHEAD OF THIS SYSTEM
WITH WARMING TEMPS ALOFT. SOME LIGHT SNOW WILL BE POSSIBLE ACROSS
HIGH TERRAIN AND NORTHERN AREAS AT THE ONSET SUNDAY
NIGHT…OTHERWISE…THE ENTIRE REGION LOOKS TO HAVE JUST RAIN FROM
THIS SYSTEM. THE STORM/S COLD FRONT LOOKS TO MOVE THROUGH LATE
MONDAY NIGHT OR TUESDAY MORNING…WITH COLDER TEMPS ALOFT RETURNING
BY TUESDAY…SOME HIGHER TERRAIN AREAS MAY CHANGE BACK TO SNOW
SHOWERS BEFORE ENDING. WILL GO WITH MAINLY CHC POPS FOR MOST OF THE
AREA FOR SUNDAY NIGHT THROUGH MONDAY NIGHT…WITH JUST SLIGHT CHC
POPS FOR TUESDAY.

&&

.AVIATION /23Z TUESDAY THROUGH SUNDAY/…
CLOUDS ABOVE 3000 FEET IN WESTERN NEW ENGLAND COULD SPILL INTO
EASTERNNY…ESPECIALLY KALB AND KGFL THIS EVENING. HOWEVER…MOST
OPF THE EVENING SHOULD BE HAVE JUST SCATTERED CLOUDS. SOME HINTS
IN GUIDANCE OF SOME FOG AND A LAYER OF LOW CLOUDS FORMING AROUND
OF AFTER MIDNIGHT…ESPECIALLY AT KGFL AND KPOU. ACKNOLEDGING SOME
POTENTIAL MVFR VISIBILITIES AT ALL SITES AFTER MIDNIGHT…BUT
KEEPING ANY LOW CLOUDS AS SCATTERED UNTIL DATA SHOWS A LOW CLOUD
DECK ACTUALLY DEVELOPING…WHICH IS NOT INDICATED BY DATA RIGHT
NOW. AN MVFR CLOUD DECK SHOULD SPREAD ACROSS ALL TAF SITES AFTER
12Z- 14Z AND CONTINUE THORUGH THE DAY. ANY POTENTIAL SNOW SHOWER
ACTIVITY SHOULD HOLD OFF UNTIL AFTERNOON…AND JUST PUTTING VCSH
IN TAFS AFTER 20Z.

NORTH TO NORTRHEAST WINDS AT LESS TAHN 10 KT SHOULD BECOME LIGHT
TONIGHT…THEN BECOME NORTHEAST AT NEAR 10 KT TOMORROW.

OUTLOOK…
WED NIGHT…VFR/MVFR. CHC SNOW WITH SNOW/RAIN IN THE EVENING.
THU…MVFR/IFR. SNOW LIKELY KPOU/KPSF/KALB AND CHC AT KGFL.
THU NIGHT…MVFR/IFR. SNOW LIKELY.
FRI…MVFR/IFR. SNOW LIKELY IN THE AM AT KPOU/KPSF…OTHERWISE CHC
SNOW.
FRI NIGHT-SUN…VFR. NO SIG WX.

&&

.HYDROLOGY…
NO HYDRO PROBLEMS ARE EXPECTED THE NEXT FEW DAYS. A STORM SYSTEM
EXPECTED TO MOVE OFF THE MID ATLANTIC COAST WEDNESDAY AND PASS SOUTH
OF LONG ISLAND WEDNESDAY NIGHT. THE LOW IS THEN EXPECTED TO BECOME
NEARLY STATIONARY FOR THURSDAY AND THURSDAY NIGHT BEFORE HEADING
EASTWARD ON FRIDAY. AT THIS TIME…STORM TOTAL QPF AMOUNTS THROUGH
FRIDAY MORNING ARE EXPECTED TO RANGE FROM ABOUT A QUARTER OF AN INCH
ACROSS THE NORTHWEST PORTIONS OF THE FORECAST AREA TO AROUND A HALF
AN INCH TO THE SOUTH AND EAST OF THE CAPITAL DISTRICT. LOOKING AT
MAINLY SNOW.

LOOKING OUT FURTHER IN TIME…HIGH PRESSURE IS EXPECTED TO BUILD
INTO THE REGION FOR THE WEEKEND. TEMPERATURES ARE EXPECTED TO
MODERATE TO ABOVE NORMAL WITH TEMPERATURES FALLING BELOW FREEZING AT
NIGHT…SO WILL HAVE DIURNAL SNOWMELT.

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…IRL/NAS
NEAR TERM…IRL/NAS
SHORT TERM…IRL
LONG TERM…FRUGIS
AVIATION…NAS
HYDROLOGY…IAA

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