December 17, 2013 Forecast Discussion

000
FXUS61 KALY 172200
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
500 PM EST TUE DEC 17 2013

.SYNOPSIS…
LOW PRESSURE WILL MOVE INTO THE GULF OF MAINE TONIGHT
…AS PERIODS OF SNOW WILL TRANSITION TO SCATTERED SNOW SHOWERS AND
FLURRIES. AN UPPER LEVEL DISTURBANCE WILL PRODUCE SOME SCATTERED
SNOW SHOWERS NORTH AND WEST OF THE CAPITAL DISTRICT…AND NEAR THE
SOUTHERN GREENE MOUNTAINS TOMORROW. SOME LAKE EFFECT SNOWFALL WILL
OCCUR FOR THE WESTERN ADIRONDACKS INTO WEDNESDAY NIGHT…AND HIGH
PRESSURE WILL RIDGE IN FROM THE SOUTH FOR THURSDAY WITH A
MODERATING TREND WITH TEMPERATURES AND MAINLY DRY WEATHER.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/…
AS OF 400 PM EST…THE BACK EDGE OF THE SNOW SHIELD IS QUICKLY
ADVANCING EASTWARD ACROSS THE FCST AREA WITH THE COASTAL LOW
PRESSURE SYSTEM MOVING N/NE TOWARDS ERN LONG ISLAND AND SE NEW
ENGLAND. THE LATEST MSAS MSLP PRESSURE FALLS WITH THE ISALLOBARIC
COUPLET ARE ON THE ORDER OF 3-5 HPA/3 HRS. A FAIRLY IMPRESSIVE
BAND MOVED ACROSS THE CAPITAL REGION IN THE PAST 1-2 HRS. THE LATEST
KENX RADAR HAS A BANDLET SIGNATURE AT 3-4 PM FROM THE HUDSON
RIVER VALLEY EASTWARD. THE WINTER WX ADVISORY WILL CONTINUE FOR
THE PM AND EARLY EVENING COMMUTE /CURRENT HEADLINE IS FOR 7 PM TO
END/. IT IS BEING DROPPED FOR SRN HERKIMER CTY WITH THE SNOW EAST
OF THE WRN MOHAWK VALLEY. SNOWFALL TOTALS…SO FAR HAVE BEEN
BETWEEN A HALF AN INCH AND TWO AND A HALF INCHES. AN ADDITIONAL 1
TO 3 INCHES IS LIKELY FROM THE HUDSON RIVER VALLEY EASTWARD.

THE BEST 850-700 HPA 2D FGEN SHIFTS EASTWARD EARLY THIS EVENING.
TEMPS ARE REALLY TRICKY…AS THEY WILL LIKELY RISE AND BE STEADY
OVERNIGHT INTO THE TEENS. CURRENT TEMPS ARE STILL IN THE UPPER
SINGLE DIGITS/LOWER TEENS FROM THE CAPITAL DISTRICT NORTH AND WEST.
THE UPPER LEVEL TROUGH TURNS NEGATIVELY TILTED OVER SE ONTARIO/SRN
QUEBEC EARLY THIS EVENING. THE ASSOCIATED COLD POOL WITH THE UPPER
TROUGH…AND AN IMPULSE ROTATING AROUND IT ACROSS THE UPPER MID
ATLANTIC REGION MAY FOCUS SOME SNOW SHOWERS AND FLURRIES INTO THE
OVERNIGHT PERIOD. THE BEST CYCLONIC VORTICITY ADVECTION TAPPING
INTO THIS COLD POOL /H500 TEMPS -35C TO -38C/ AND THE RESIDUAL
LOW-LEVEL MOISTURE WILL BE OVER LOCATIONS NORTH AND WEST OF THE
HUDSON RIVER VALLEY…AND THE FAVORED WESTERLY OROGRAPHIC REGIONS
OF THE SRN GREENS AND NRN BERKS. SLIGHT AND LOW CHC POPS WERE
MAINTAINED THERE WITH LIGHT SNOW ACCUMS OF A HALF AN INCH OR
LESS…THOUGH A FEW HEAVIER SNOW SHOWERS MAY BE POSSIBLE WITH THE
COLD POOL AND STEEP MID LEVEL LAPSE RATES.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/…
TOMORROW…THE UPPER LEVEL TROUGH AXIS MOVES DOWNSTREAM ACROSS NRN
NEW ENGLAND IN THE MORNING WITH W/NW FLOW ALOFT. THE LOW-LEVEL
FLOW IN THE BOUNDARY LAYER WILL BE WESTERLY…AND SOME LAKE EFFECT
SNOWFALL WILL BEGIN DOWNSTREAM OF LAKE ONTARIO FOR THE WESTERN
ADIRONDACKS.

THE NAM INDICATES THE LAKE EFFECT SNOW BAND WILL LIKELY KICK IN
DURING THE PM…AROUND 20Z. A LAKE EFFECT SNOW ADVISORY HAS BEEN
ISSUED BASED ON THE LOCAL CSTAR LAKE BAND INLAND EXTENT PROGRAM. A
INSPECTION OF BUFKIT PROFILES NEAR NRN HERKIMER AND HAMILTON
COUNTIES HAS THE CAPPING INVERSION AT 2.5 KM /8-10 KFT AGL/ WITH A
MEAN LAKE TEMP OF 7C COUPLED WITH FAVORABLE DELTA T/S BETWEEN THE
LAKE TEMP AND H850/H700. A QUICK GEORGIAN BAY MULTI-LAKE
CONNECTION LOOKS POSSIBLE WITH THE EXTENSION ABOUT 75-80 MILES
INTO THE ALY FCST AREA. THE SNOW IS LIKELY TO IMPACT THE RT 28
CORRIDOR NORTHWARD…INCLUDING OLD FORGE…EAGLE BAY AND INLET.
THE SNOW IS EXPECTED TO CONTINUE INTO WED NIGHT…WITH SHEAR…AND
LIKELY HIGH PRESSURE BUILDING IN FROM THE SOUTH PUSHING THE BAND
OR BANDS NORTHWARD…AND DISRUPTING IT WELL AFTER MIDNIGHT. THE LOW LEVEL
WARM ADVECTION INCREASING WED NIGHT. THE LAKE EFFECT SNOW ADVISORY
WILL BE FOR 3 TO 6 INCHES OF SNOWFALL /CLOSE TO A 20:1 SNOW TO
LIQUID RATIO/ FOR NRN HERKIMER AND ESPEC NW HAMILTON COUNTY FROM 3
PM EST WED TO 6 AM EST THU.

OTHER SNOW SHOWERS AND FLURRIES WILL BE POSSIBLE WEST OF THE
HUDSON RIVER VALLEY…AND ALONG THE SPINE OF THE SRN GREEN MTNS.
SNOW ACCUMULATIONS THERE WILL GENERALLY BE A COATING TO A HALF AN
INCH. TEMPS WILL BE MILDER THAN TODAY…WITH H850 TEMPS OF -10C OR
SO. EXPECT HIGHS TO BE IN THE U20S TO L30S OVER THE HILLS AND IN
THE VALLEYS /A FEW MID 30S IN THE MID HUDSON VALLEY/…AND SOME
LOWER TO M20S OVER THE HIGH PEAKS.

WED NIGHT…THE LAKE EFFECT SNOW IS EXPECTED TO DISSIPATE BASED ON
THE NAM AND MESOSCALE MODELS TOWARDS 09Z/THU. LOW AND MID LEVEL
WARM ADVECTION OCCURS…AS THE UPPER LEVEL FLOW BECOMES ZONAL.
HIGH PRESSURE BUILDS IN FROM THE SOUTH….AND THE INVERSION LOWERS
QUICKLY. TOTAL ACCUMS ARE EXPECTED TO BE 3 TO 6 INCHES. OUTSIDE
THE LAKE EFFECT SNOWFALL…A FAIRLY QUIET NIGHT IS EXPECTED WITH
PARTLY TO MOSTLY CLOUDY CONDITIONS. MIN TEMPS CLOSE TO THE WARMER
METMOS VALUES WERE FAVORED WITH LOWS GENERALLY IN THE MID TEENS TO
NEAR 20F.

THU-THU NIGHT…THE BOUNDARY LAYER FLOW BECOMES SOUTHWEST TO WEST
WITH MILDER AIR WORKING INTO THE REGION. SOME RESIDUAL SNOW
SHOWERS OR FLURRIES MAY GRAZE THE NRN TIER OF THE SRN DACKS DURING
THE DAY…AS ZONAL FLOW ALOFT WILL PREVAIL. H850 TEMPS RISE TO -3C
TO -7C FROM THE CAPITAL REGION NORTH AND WEST…AND 0C TO -3C TO
THE SOUTH AND EAST BY LATE IN THE DAY. SOME SUN MAY MIX WITH
CLOUDS FROM THE CAPITAL DISTRICT SOUTH AND EAST. MAX TEMPS WILL
GENERALLY BE IN THE M30S TO 40F OVER MOST OF THE FCST AREA…WITH
SOME L30S OVER THE HIGHER TERRAIN. SOME WARM ADVECTION PCPN
ASSOCIATED WITH A WARM FRONT…AND A SFC CYCLONE APPROACHING FROM
THE CNTRL AND ERN GREAT LAKES REGION WITH BRING SOME LIGHT PCPN TO
PARTS OF THE REGION OVERNIGHT…ESPECIALLY NORTH OF THE MOHAWK
RIVER VALLEY AND CAPITAL REGION. A QUICK SHOT OF SNOW
SHOWERS…BEFORE POSSIBLY TURNING TO RAIN SHOWERS LATE FRI
MORNING. THERE IS A SMALL CHC FOR A LIGHT WINTRY MIXTURE TOO…IF THE
LOW LEVEL COLD AIR DOES NOT ERODE QUICKLY. LOWS MAY OCCUR EARLY ON
IN THE M20S TO L30S…AND MAY RISE AFTER MIDNIGHT.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/…
THE LONG TERM PERIOD WILL BE CHARACTERIZED BY AN UNSETTLED AND
POTENTIALLY QUITE WET WEATHER PATTERN…AS A FRONTAL BOUNDARY STALLS
NEAR THE REGION AND WAVES OF LOW PRESSURE MOVE ALONG IT.

AT THE START OF THE LONG TERM PERIOD…LONG RANGE GUIDANCE CONTINUES
TO SLOWLY COME INTO BETTER AGREEMENT HANDLING THE SYNOPTIC PATTERN
AND EVOLUTION HEADING INTO THE WEEKEND.

ALOFT…A BROAD AND DEEP LONGWAVE TROUGH WILL BE ANCHORED ACROSS
MUCH OF THE CENTRAL CONUS…WITH LITTLE IN THE WAY OF SUBSTANTIAL
PACIFIC ENERGY TO KICK THIS TROUGH DOWNSTREAM. THIS STAGNANT PATTERN
WILL RESULT IN OUR REGION BEING UNDER A CONFLUENT SOUTHWEST FLOW
REGIME WITH EMBEDDED PIECES OF ENERGY EJECTING OUT OF THE SOUTHERN
STREAM SUBTROPICAL JET. THESE EJECTING PIECES OF ENERGY WILL RESULT
IN WAVES OF LOW PRESSURE DEVELOPING ALONG A FRONTAL BOUNDARY THAT
WILL BE ORIENTED SOUTHWEST TO NORTHEAST ACROSS THE FORECAST AREA.
WHILE THERE WILL BE CHANCES FOR PRECIPITATION TO END THE WORK WEEK
AND CONTINUING INTO THE WEEKEND…THERE STILL REMAINS SIGNIFICANT
TIMING DIFFERENCES AMONGST THE LONG RANGE GUIDANCE.

THESE TIMING DIFFERENCES WILL HAVE LARGE IMPLICATIONS REGARDING THE
SENSIBLE WEATHER EXPERIENCED ACROSS THE FORECAST AREA. AT THIS TIME
THERE LOOKS TO BE TWO MAJOR IMPULSES THAT WILL AFFECT THE
REGION…THE FIRST AFFECTING THE REGION FRIDAY INTO FRIDAY NIGHT AND
A SECOND…AND MORE SIGNIFICANT…IMPULSE AFFECTING THE REGION
SATURDAY NIGHT INTO SUNDAY.

THE FIRST IMPULSE AND ASSOCIATED WAVE OF LOW PRESSURE AFFECTING THE
REGION FRIDAY INTO FRIDAY NIGHT WILL BE LIMITED SOMEWHAT BY
DISPLACED UPPER-LEVEL JET DYNAMICS…AND WEAK CYCLOGENESIS ALONG THE
FRONTAL BOUNDARY. AT THIS TIME…MOST AREAS LOOK TO TRANSITION FROM
A RAIN/SNOW MIX EARLY FRIDAY MORNING TO ALL RAIN BY THE AFTERNOON
HOURS…EXCEPT FOR THE HIGHER TERRAIN OF THE ADIRONDACKS WHERE
COLDER AIR MAY ALLOW FOR SOME WET SNOWFLAKES TO MIX IN WITH RAIN.
HIGHS FRIDAY WILL RANGE FROM THE UPPER 30S TO MID 40S. PRECIPITATION
SHOULD TRANSITION BACK TO RAIN/SNOW FRIDAY NIGHT…WITH EVEN A BRIEF
PERIOD OF SLEET POSSIBLE MAINLY NORTH OF THE CAPITAL DISTRICT…AS
TEMPERATURES FALL TO NEAR OR SLIGHTLY BELOW FREEZING.

MUCH OF THE DAY SATURDAY MAY END UP BEING DRY BETWEEN UPPER-LEVEL
IMPULSES…HOWEVER HAVE KEPT CHANCE POPS IN THE FORECAST TO ACCOUNT
FOR POTENTIAL TIMING ISSUES WITH THE LONG RANGE GUIDANCE HANDLING
THE CONFLUENT FLOW PATTERN ALOFT. TEMPERATURES SATURDAY WILL RANGE
FROM THE MID 30S TO MID 40S.

A STRONGER AND MORE DYNAMICALLY-FORCED IMPULSE WILL APPROACH THE
REGION BY SATURDAY NIGHT…BRINGING A POTENTIALLY SIGNIFICANT
PRECIPITATION EVENT TO THE REGION AS PLENTY OF GULF MOISTURE IS
ENTRENCED IN THE SYSTEM…WITH ENSEMBLE GUIDANCE INDICATING PWAT
VALUES 2-3 STANDARD DEVIATIONS ABOVE NORMAL. FURTHER AIDING THIS
SYSTEM WILL BE AN IMPRESSIVE ANTICYCLONICALLY-ORIENTED UPPER-LEVEL
JET…WITH SOME MODEL GUIDANCE INDICATING THE WIND FIELD BEING OVER
200 KNOTS. THE REGION WILL BE UNDER THE FAVORABLE EQUATORWARD
ENTRANCE REGION OF THIS JET STREAK…COINCIDING WITH A STRONG
LOW-LEVEL JET 2-3 STANDARD DEVIATIONS ABOVE NORMAL.

THE QUESTION STILL REMAINS EXACTLY WHERE THE PRECIPITATION
TRANSITION ZONE WILL SET UP GIVEN STRONG LOW-LEVEL WARM AIR
ADVECTION. HOWEVER…GIVEN THE IMPRESSIVE JET DYNAMICS…A STRONG
AGEOSTROPHIC CIRCULATION MAY SET UP ACROSS NORTHERN PORTIONS OF THE
FORECAST AREA…RESULTING IN A NORTHERLY WIND TRAPPING COLD AIR NEAR
THE SURFACE. WHILE IT LOOKS LIKE THE STRONG WARM AIR ADVECTION WILL
RESULT IN A POTENTIALLY SIGNIFICANT RAIN EVENT FOR SOUTHERN PORTIONS
OF THE FORECAST AREA…A PROLONGED MIXED PRECIPITATION EVENT IS
BECOMING INCREASINGLY LIKELY FOR NORTHERN AREAS…WITH THE POTENTIAL
FOR SIGNIFICANT ACCUMULATIONS OF SNOW/SLEET/FREEZING RAIN POSSIBLE
BEFORE TRANSITIONING TO ALL RAIN BY LATE SUNDAY MORNING AS BOUNDARY
LAYER TEMPERATURES WARM ABOVE FREEZING. TO THE SOUTH…THE
COMBINATION OF SNOWMELT AND POTENTIALLY SIGNIFICANT RAIN
ACCUMULATIONS MAY LEAD TO HYDRO ISSUES. TEMPERATURES LOOK TO REACH
INTO THE 50S ACROSS SOUTHERN LOCATIONS…AND INTO THE 40S FOR
NORTHERN LOCATIONS.

A NORTHWEST FLOW REGIME WILL SET UP ACROSS THE REGION TO START NEXT
WEEK…WITH CHANCES FOR LAKE EFFECT SNOW AND MOSTLY CLOUDY WEATHER.
TEMPERATURES WILL BE COLDER WITH HIGHS IN THE 20S AND 30S AND LOWS
DIPPING TO NEAR ZERO TO THE MID TEENS.

&&

.AVIATION /22Z TUESDAY THROUGH SUNDAY/…
COASTAL WAVE WAS TAKING SHAPE AS ANY BRIEF LULL IN THE SNOW IS
EXPECTED TO FULL BACK IN THIS AFTERNOON. THIS WILL KEEP FLIGHT
CONDITIONS WITHIN MVFR AND TEMPORARILY IFR CONDITIONS AS THESE BANDS
OF MODERATE SNOWFALL DEVELOP AND IMPACT THE TAF SITES. PER THE
LATEST GUIDANCE AND UPSTREAM INFORMATION…SEEMS THIS SNOW WILL EXIT
THE REGION BY EARLY THIS EVENING WITH IMPROVEMENTS.
HOWEVER…FLIGHT CONDITIONS WILL REMAIN WITHIN MVFR THRESHOLDS WITH
SOME IFR EXPECTED AT KPOU OVERNIGHT.

WINDS ARE EXPECTED TO REMAIN RATHER LIGHT WITH A GENERALLY NORTH
DIRECTION. THE MAGNITUDES ARE EXPECTED TO DIMINISH FURTHER THIS
EVENING WITH A WEST-NORTHWEST DIRECTION DEVELOPING THROUGH
WEDNESDAY.

OUTLOOK…

WED-WEDNESDAY NIGHT: NO OPERATIONAL IMPACT. NO SIG WX.
THURSDAY: LOW OPERATIONAL IMPACT.BREEZY NO SIG WX.
THURSDAY NIGHT: LOW OPERATIONAL IMPACT. SLIGHT CHANCE OF SHSN.
FRIDAY: MODERATE OPERATIONAL IMPACT. CHANCE OF RA…SN.
FRIDAY NIGHT: MODERATE OPERATIONAL IMPACT. CHANCE OF SHRA…SHSN.
SATURDAY: MODERATE OPERATIONAL IMPACT. CHANCE OF SHRA…SHSN.
SATURDAY NIGHT: HIGH OPERATIONAL IMPACT. LIKELY SHRA…SHSN.
SUNDAY: HIGH OPERATIONAL IMPACT. LIKELY SHRA…SHSN.

&&

.HYDROLOGY…
TOTAL LIQUID EQUIVALENT WITH THE CURRENT SYSTEM IS EXPECTED TO RANGE FROM
ONE TO THREE TENTHS OF AN INCH WITH THE HIGHEST AMOUNTS OVER THE
ERN CATSKILLS…W-CNTRL MOHAWK VALLEY…AND WRN NEW ENGLAND. THIS
SYSTEM WILL QUICKLY MOVE NORTHEAST INTO THE GULF OF MAINE TONIGHT.

SOME LAKE EFFECT SNOW IS POSSIBLE WED-THU WITH LIGHT SNOW
AMOUNTS…AND LIQUID EQUIVALENTS GENERALLY LESS THAN TWO TENTHS OF AN
INCH FOR THE WRN DACKS REGION…AND NRN TIER OF THE HSA.

FOR THE MID WEEK…TEMPS WILL CONTINUE TO BE BELOW NORMAL AND ICE
WILL CONTINUE TO FORM AND THICKEN ON AREA RIVERS…STREAMS AND
PARTICULARLY LAKES.

A MODERATING TREND IN TEMPS IS LIKELY THU INTO FRI…WITH A
FRONTAL BOUNDARY BRINGING SOME SHOWERS TO CLOSE THE WORK WEEK.
SOME SNOW MELT IS LIKELY THIS WEEKEND. ALSO…A STORM SYSTEM
MOVING ALONG A FRONTAL BOUNDARY NEAR THE HSA MAY BRING SIGNIFICANT
PCPN TO THE FORECAST AREA SAT NIGHT INTO SUNDAY WITH EVEN MILDER
TEMPS. THIS WILL CONTINUE TO BE MONITORED FOR THE UPCOMING
WEEKEND FOR THE POSSIBILITY OF SOME HYDRO ISSUES.

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 UNTIL 7 PM EST THIS EVENING FOR CTZ001-
013.
NY…WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR NYZ039-
040-047>054-058>061-063>066-082.
LAKE EFFECT SNOW ADVISORY FROM 3 PM WEDNESDAY TO 6 AM EST
THURSDAY FOR NYZ032-033.
MA…WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR MAZ001-
025.
VT…WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR
VTZ013>015.

&&

$$
SYNOPSIS…WASULA
NEAR TERM…WASULA
SHORT TERM…WASULA
LONG TERM…IRL
AVIATION…BGM
HYDROLOGY…KL/WASULA

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