January 15, 2013 Forecast Discussion

000
FXUS61 KALY 152108
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
410 PM EST TUE JAN 15 2013

.SYNOPSIS…
A LIGHT TO MODERATE SNOWFALL WILL OCCUR ACROSS MUCH OF EAST CENTRAL
NEW YORK AND WESTERN NEW ENGLAND OVERNIGHT AND WEDNESDAY. AN AREA OF
LOW PRESSURE WILL MOVE OFF THE MID ATLANTIC COAST LATE TONIGHT AND
PASS SOUTH OF LONG ISLAND WEDNESDAY. THE SNOW WILL IMPACT THE
MORNING COMMUTE. AN ARCTIC FRONT WILL CROSS THE REGION THURSDAY
USHERING IN A COLDER AIRMASS.

&&

.NEAR TERM /THROUGH WEDNESDAY/…
AS OF 345 PM EST…WE HAVE LOST A LOT OF THE LAKE EFFECT CLOUDS AS
HIGH PRESSURE BUILDS IN…DISRUPTING THE FLOW OFF LAKE ONTARIO.
HOWEVER…NOW WE HAVE HIGH CLOUDS MOVING IN FROM THE SOUTH…WELL
AHEAD OF THE SYSTEM THAT WILL IMPACT MOST IF NOT ALL OF OUR REGION
LATE TONIGHT INTO MUCH OF WEDNESDAY WITH SNOW.

FOR THE REST OF THE AFTERNOON INTO EVENING HOURS IT WILL REMAIN DRY
WITH VARYING AMOUNTS OF HIGH CLOUDINESS. TEMPERATURES WILL START OUT
35-40 IN THE VALLEYS…COOLING TO AROUND 30 LATER THIS EVENING.
HIGHER TERRAIN WILL SEE READINGS STARTING OUT 30-35 DIPPING INTO THE
20S THROUGH THE EVENING.

THE WEST WIND 5 TO 15 MPH…WILL BECOME LIGHT AND VARIABLE.

LATER THIS EVENING…CLOUDS WILL THICKEN AND THE TEMPERATURE FALL
WILL HALT…BOTTOMING OUT IN THE LOWER TO MID 20S MOST
PLACES…TEENS ACROSS THE ADIRONDACKS.

AFTER MIDNIGHT…IT LOOKS AS IF SNOW WILL BEGIN TO OVERSPREAD THE
REGION FROM SOUTHWEST TO NORTHEAST. THE SYNOPTIC SETUP IS AN
IMPRESSIVE POSITIVELY TILTED TROUGH EXTENDED FROM THE SW CONUS
ACROSS THE EASTERN GREAT LAKES. THE GRADIENT BETWEEN THE TROUGH AND
RIDGE…STILL PARK OVER THE EXTREME SE CONUS…IS A CONDUIT FOR LOT
OF MOISTURE…ORIGINATING OVER THE PACIFIC (PINEAPPLE
EXPRESS)…THAT WILL WORK INTO OUR REGION VIA A WEAK SURFACE LOW AND
A STRONGER MID LEVEL SHORTWAVE…WORKING ALONG A STALL OUT FRONTAL
BOUNDARY…DRAPED WELL TO OUR SOUTH.

WHILE THE SURFACE FEATURE IS NOT IMPRESSIVE…OUR REGION WILL COME
UNDER THE ENTRANCE REGION OF 150KT+ H250 JET…COUPLED WITH AN
INCREASE SSW LOW LEVEL JET BY WEDNESDAY MORNING. THIS LOW LEVEL JET
WILL GENERATE ISENTROPIC LIFT…LIFTING MUCH MORE MOIST AIR TO OUR
SOUTH NORTH INTO THE SOMEWHAT COLDER AIR NOW ENTRENCHED OVER OUR
REGION. THERE MIGHT LIKELY BE FRONTOGENTIC FORCING HELPING THE CAUSE
OF PRECIPITATION…MAINLY SOUTH OF THE INTERSTATE 84. HOWEVER…THE
12Z NAM HINTED AT A SECONDARY AREA OF FGEN JUST NORTH OF THE CAPITAL
REGION. BELIEVE THIS FEATURE MIGHT BE A TAD OVERDONE BUT EITHER WAY
YOU SLICE IT…SNOW IS LOOKING LIKE A SURE BET…NOT ONLY IN THE
CAPITAL DISTRICT…BUT EVEN WELL NORTH AND WEST OF THE CAPITAL
REGION.

MAXIMUM SNOW GROWTH IS REALIZED NORTH AND WEST OF TOWN WHERE H700
TEMPS ARE CLOSER TO -12C …AND THIS IS WHERE SNOWFALL/LIQUID RATIOS
COULD APPROACH 20:1. HOWEVER MOST OF THE REGION WILL LIKELY SEE
SNOW/LIQUID RATIOS CLOSER TO A "CLIMO" AVERAGE OF 12:1…PERHAPS
CLOSER TO 10:1 TOWARD LOWER LITCHFIELD COUNTY. WELL SOUTH OF
ALBANY…THERE IS POTENTIAL FOR A LITTLE SLEET AND PERHAPS A TOUCH
OF FREEZING RAIN TO MIX IN WITH THE SNOW…BUT AT THIS POINT…THIS
TRANSITION SEEMS UNLIKELY ENOUGH TO KEEP OUT OF OUR FORECAST.

BY THE MORNING DRIVE…SNOW SHOULD FALLING AT CLIP AT RATES OF HALF
AN INCH PER HOUR FROM ALBANY SOUTHWARD…TO PERHAPS NEAR AN INCH PER
HOUR AT TIMES…ESPECIALLY OVER THE HIGHER TERRAIN TO THE SOUTH OF
ALBANY. SNOW WILL CONTINUE TO OVERSPREAD THE REMAINDER OF THE REGION
BY OR AFTER THE MORNING DRIVE.

BY MIDDAY… THE SNOW WILL BEGIN TO TAPER…AS THE CLOUDS APPEAR TO
LOOSE THEIR ICE BY AFTERNOON AND THE ISENTROPIC LIFT WEAKENS. SNOW
MIGHT END AS SOME PATCHY LIGHT DRIZZLE DURING THE AFTERNOON. THE
FLAT WAVE OF LOW PRESSURE WILL BE SLIDING OFF THE CAPE COD SHORELINE
BY DAY/ END.

AT THIS POINT…WE HOISTED WINTER WEATHER ADVISORIES FOR SNOWFALL OF
3-6 INCHES TO THE SOUTH AND EAST OF THE CAPITAL DISTRICT…2-4
INCHES FOR THE GREATER CAPITAL DISTRICT AND POINTS NORTH AND WEST
(WHERE AGAIN THE "FLUFF" FACTOR SHOULD BE HIGHER EVEN WITH LESS
QPF).

HIGH TEMPERATURES ON WEDNESDAY WILL RANGE FROM 30-35 REGION WIDE
(EVEN ACROSS THE HIGHER TERRAIN). WENT A POINT OR TWO LOWER THAN THE
AVERAGED MAV/MET VALUES.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/…
WEDNESDAY NIGHT…DRIER AIR IS EXPECTED TO PARTIALLY ERODE THE
CLOUDS AWAY…BUT THAT IS NOT ETCHED IN STONE. OFTEN TIMES…LOW
LEVEL MOISTURE CAN GET TRAPPED UNDERNEATH AN INVERSION…ALTHOUGH
THUS FAR…MODEL SOUNDINGS DO NOT SUPPORT THAT THINKING.

A WSW FLOW OFF ONTARIO MIGHT PRODUCE SOME BANDS OF SNOW SHOWERS
ACROSS THE ADIRONDACKS AHEAD OF A SECONDARY FRONT OVERNIGHT
WEDNESDAY. AT THIS POINT…ONLY LIGHT ADDITIONAL SNOW ACCUMULATIONS
ARE EXPECTED. OVERNIGHT LOWS WILL GENERALLY BE IN THE 20S (TEENS
NORTH).

THIS SECONDARY COLD FRONT WILL SINK DOWN ACROSS ALL OF OUR REGION ON
THURSDAY…NOT REACHING THE MID HUDSON VALLEY AND LOWER LITCHFIELD
COUNTY UNTIL VERY LATE IN THE DAY. MOISTURE WITH THIS FRONT SHOULD
BE LIMITED…BUT THIS FRONT WILL INTERACT WITH LAKE MOISTURE OFF
ONTARIO TO PRODUCE A CHANCE OF SNOW SHOWERS ACROSS MUCH OF THE
HIGHER TERRAIN…AND SLIGHT CHANCE OF SNOW SHOWERS SOUTH TO ABOUT
THE CAPITAL DISTRICT. THERE IS AN OUTSIDE CHANCE THAT THIS FRONT
COULD PRODUCE A BRIEF SNOW SQUALL OR TWO IN PLACES…MAINLY ACROSS
THE HIGHER TERRAIN…BRINGING A QUICK INCH OF SNOW…BUT RAPID
CHANGING DRIVING CONDITIONS. THIS POSSIBILITY WILL BE MONITORED AS
WE HEAD TOWARD THIS PERIOD.

TEMPERATURES ON THURSDAY LOOK TO REMAIN IN THE TEENS AND LOWER 20S
ACROSS THE ADIRONDACKS…MID 20S TO LOWER 30S THE REMAINDER OF THE
ELEVATED TERRAIN…35TO AROUND 40 FROM ALBANY SOUTHWARD IN THE
HUDSON VALLEY.

COLDER AIR BEHIND THE FRONT WILL SEND TEMPERATURES DOWN TO AROUND
ZERO ACROSS THE ADIRONDACKS THURSDAY NIGHT…SINGLE NUMBERS LAKE
GEORGE SARATOGA REGION…INTO VERMONT…TEENS FURTHER SOUTH.

ON FRIDAY…A SOUTHERLY FLOW AND SOME SUNSHINE WELL AHEAD OF A
STRONG CLIPPER MOVING WELL TO OUR NORTHWEST…WILL MODERATE
TEMPERATURES SOMEWHAT ACROSS OUR AREA. TEMPERATURES LOOK TO RECOVER
TO THE MID 30S MID HUDSON VALLEY AND LOWER LITCHFIELD
COUNTY…AROUND 30 IN THE CAPITAL DISTRICT…WELL INTO THE 20S MOST
NORTHERN PLACES. THE BEST FORCING WITH THIS SYSTEM LOOKS TO STAY
NORTH AND WEST OF ALBANY…SO WE CONTINUE WITH SNOW SHOWER CHANCES
MAINLY ACROSS THE ADIRONDACKS.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/…
THE LONG TERM PERIOD WILL BE DOMINATED BY COLDER TEMPERATURES AND
CHANCES FOR SNOW SHOWERS.

AT THE START OF THE LONG TERM PERIOD…HIGH PRESSURE WILL BE SLIDING
OFF THE EASTERN SEABOARD AS SOUTHWEST FLOW BUILDS IN ITS WAKE
ALLOWING FOR HIGH TEMPERATURES SATURDAY TO ACTUALLY BE ABOVE NORMAL.
MOST OF THE FORECAST AREA WILL REMAIN DRY THROUGH
SATURDAY…ALTHOUGH MODELS ARE HINTING AT A PIECE OF SHORTWAVE
ENERGY MOVING THROUGH THE BASE OF THE LONGWAVE TROUGH THAT COULD
BRING SOME MORE SCATTERED SNOW SHOWERS/FLURRIES MAINLY CONFINED TO
THE ADIRONDACKS.

AN ARCTIC BOUNDARY WILL CROSS THE REGION SATURDAY NIGHT INTO
SUNDAY…SIGNALING THE RETURN OF COLDER TEMPERATURES FOR THE
REMAINDER OF THE LONG TERM PERIOD. THERE WILL BE A CHANCE FOR SNOW
SHOWERS WITH THIS FRONTAL PASSAGE…WITH THE ECMWF STILL SHOWING A
BIT HEAVIER QPF ASSOCIATED WITH STRONGER UPPER LEVEL DYNAMICS.

SOME LAKE EFFECT SNOW SHOWERS WILL AFFECT WESTERN PORTIONS OF THE
ADIRONDACKS AND MOHAWK RIVER VALLEY…WITH FLURRIES EXPECTED
ELSEWHERE SUNDAY NIGHT INTO MONDAY. ANOTHER CLIPPER-TYPE SYSTEM MAY
SKIRT ACROSS THE FORECAST AREA MONDAY NIGHT INTO TUESDAY AS A POTENT
SHORTWAVE TROUGH DIPS SOUTH ACROSS THE GREAT LAKES REGION BRINGING
ANOTHER POTENTIAL ROUND OF SNOW SHOWERS.

COLD TEMPERATURES WILL DOMINATE THE BEGINNING OF THE WORK WEEK AS
850 HPA TEMPERATURES DIP BELOW -20C ACROSS THE REGION. IT IS STILL
UNCLEAR AMONGST THE LONG RANGE GUIDANCE IF THIS COLD AIR WILL REMAIN
IN PLACE OR SIMPLY PROGRESS THROUGH THE FLOW AFTER A COUPLE OF DAYS.
LOW TEMPERATURES SUNDAY WILL DIP BELOW ZERO ESPECIALLY IN THE HIGHER
TERRAIN OF THE ADIRONDACKS…WITH SINGLE DIGITS FROM THE CAPITAL
DISTRICT NORTHWARD AND LOW TEENS IN THE HUDSON RIVER VALLEY. HIGH
TEMPERATURES TO START THE WORK WEEK WILL STRUGGLE TO GET ABOVE 20 IN
VALLEY LOCATIONS…WITH MAINLY TEENS ACROSS MOST AREAS AND SOME
SINGLE DIGITS IN THE ADIRONDACKS. LOWS WILL CONTINUE TO BE FRIGID
THROUGH TUESDAY NIGHT…AS TEMPERATURES MAY FLIRT WITH ZERO NEAR AND
NORTH OF THE CAPITAL DISTRICT WHILE DIPPING BELOW -10F IN THE
ADIRONDACKS.

&&

.AVIATION /20Z TUESDAY THROUGH SUNDAY/…
VFR CONDITIONS WILL CONTINUE THROUGH THE ENTIRE DAY TODAY WITH LIGHT
WINDS. LOW LEVEL MOISTURE OFF THE GREAT LAKES IS TRAPPED BENEATH AN
INVERSION AND THIS HAS ALLOWED SOME BKN-OVC CIGS OF AROUND 4 KFT FOR
KALB/KGFL THIS MORNING. THESE CLOUDS MAY SCT OUT TOWARDS MIDDAY.
OTHERWISE…SCT-BKN MID AND HIGH LEVEL CLOUDS WILL STREAM OVER THE
REGION FROM THE SOUTH TODAY…ESP FOR AROUND KPOU.

MID LEVEL CLOUDS WILL INCREASE LATE THIS EVENING AS LOW PRESSURE
ORGANIZES NEAR THE MID ATLANTIC COAST. IT WILL STAY DRY ACROSS OUR
AREA FOR THE FIRST HALF OF THE NIGHT. LIGHT SNOW WILL MOVE FROM
SOUTH TO NORTH ACROSS THE REGION FOR THE SECOND HALF OF THE NIGHT
WITH VSBYS DROPPING INTO THE IFR RANGE…ALTHOUGH IT WILL TAKE UNTIL
NEARLY SUNRISE FOR LIGHT SNOW TO REACH KALB/KGFL.

OUTLOOK…
WED AM-WED PM…MVFR/IFR. -SN KALB SOUTH/CHC -SN KGFL.
WED NT-SAT…VFR…NO SIG WX.

&&

.HYDROLOGY…
WITH A COLDER AND MORE SEASONABLE AIRMASS IN PLACE ACROSS THE REGION
RUNOFF WILL NO LONGER BE AN ISSUE. RIVERS AND STREAMS ARE CRESTING
AND WILL LEVEL OFF AND BEGIN TO RECEDED. ICE WILL FORM.
PRECIPITATION WILL BE IN THE FORM OF SNOW THIS WEEK.

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 3 AM TO 7 PM EST WEDNESDAY FOR
CTZ001-013.
NY…WINTER WEATHER ADVISORY FROM 3 AM TO 7 PM EST WEDNESDAY FOR
NYZ054-058>061-063>066.
MA…WINTER WEATHER ADVISORY FROM 3 AM TO 7 PM EST WEDNESDAY FOR
MAZ001-025.
VT…WINTER WEATHER ADVISORY FROM 3 AM TO 7 PM EST WEDNESDAY FOR
VTZ013>015.

&&

$$
SYNOPSIS…HWJIV
NEAR TERM…HWJIV
SHORT TERM…HWJIV
LONG TERM…IRL
AVIATION…BGM
HYDROLOGY…HWJIV/IAA

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