November 26, 2012 Forecast Dicsussion

000
FXUS61 KALY 262129
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
429 PM EST MON NOV 26 2012

.SYNOPSIS…
A WEAK LOW PRESSURE SYSTEM WILL MOVE FROM THE CAROLINAS TO WELL
SOUTH OF LONG ISLAND BY TUESDAY AFTERNOON. SOME LIGHT SNOW WILL
OCCUR FROM THE CAPITAL REGION SOUTH…BEFORE HIGH PRESSURE BRIEFLY
BUILDS IN TUESDAY NIGHT. ANOTHER COLD FRONT WILL MOVE THROUGH THE
REGION ON WEDNESDAY WITH AN ADDITIONAL CHANCE FOR MORE SNOW
SHOWERS AND FLURRIES.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/…
AS OF 4 PM EST…
A PROGRESSIVE SHORT WAVE TROUGH AXIS WAS APPROACHING FROM THE
CENTRAL CONUS. THERE IS A GREATER THAN 120KT 300MB JET ALOFT WHICH
HAS ASSISTED WITH ADDITIONAL DEVELOPMENT OF THE MID LEVEL
CLOUDS…ALONG WITH SOME LAKE CONTRIBUTION…CLOUD SEEDING SEEMS
TO BE OCCURRING ONCE AGAIN. THIS HAS RESULTED IN A REGION OF VERY
LIGHT RETURNS ON THE RADAR ACROSS THE MOHAWK VALLEY AND ALONG THE
THRUWAY. THIS TREND SHOULD CONTINUE THROUGH THE EVENING AND WE
WILL PLACE SCT-CHC POPS ACROSS THE CATSKILLS…MOHAWK
VALLEY…CAPITAL DISTRICT AND INTO THE DACKS.

REMAINDER OF THE OVERNIGHT…THE UPSTREAM SYSTEM WILL TAP INTO THE
PACIFIC MOISTURE ACROSS THE CENTER OF THE NATION WITH SURFACE LOW
DEVELOPING OVER THE OHIO VALLEY AND THEN REDEVELOP OFF THE MIDDLE
ATLANTIC COAST TOWARD MORNING. REGION OF WEAK QG FGEN AND SOME
AGEOSTROPHIC LIFT WITH THE DEPARTURE OF THE UPPER JET WILL BRING
SOME LIGHT SNOW SOUTH OF THE CAPITAL REGION TOWARD SUNRISE.

FURTHER NORTH…LAKE ENHANCEMENT WILL IMPACT PORTIONS OF THE
NORTHERN DACKS AS BOUNDARY LAYER WINDS WILL AVERAGE AROUND 250
DEGREES. INVERSION HEIGHTS ARE EXPECTED TO INITIALLY BE AROUND 8K
FEET BUT THEN FALL TOWARD MORNING WHICH SHOULD LIMIT INLAND
EXTENT. MINOR ACCUMULATIONS ARE EXPECTED…LESS THAN 2 INCHES.

WITH CLOUD COVER INCREASING…TEMPERATURES WILL REMAIN A BIT
ELEVATED /AS IT HAS THE PAST SEVERAL NIGHTS/ AND THIS WILL BE
REFLECTED IN THE GRIDS/FORECAST.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/…
AS OF 4 PM EST…

GUIDANCE HAS COME INTO EXCELLENT AGREEMENT WITH THE TRACK OF THE
WEAK SURFACE LOW WELL OFFSHORE. THE QG FORCING WILL BE MAXIMIZED
SOUTH OF I 90 WITH THE BEST BANDING POTENTIAL ALONG THE I84
CORRIDOR. HOWEVER…DUE TO THE FAST MOVEMENT AND WEAK NATURE OF
THE THIS WAVE…ITS IMPACTS WILL BE FELT MANY IN THE MORNING
HOURS. A PERIOD OF LIGHT SNOW WILL IMPACT THE MORNING COMMUTE WITH
ACCUMULATIONS OF 1 TO 2 INCHES EXPECTED. FURTHER NORTH…FLURRIES
OR LIGHT SNOW SHOWERS WITH LITTLE TO NO ACCUMULATION EXPECTED.
SURFACE RIDGE BUILDS IN FROM NORTH TO SOUTH THROUGH THE AFTERNOON
AS THE STORM SLIDES FURTHER OFFSHORE AND ITS ASSOCIATED MOISTURE
DECREASING. HOWEVER…AMPLE LOW LEVEL MOISTURE REMAINS IN PLACE SO
EXPECTATIONS ARE PLENTY OF CLOUD COVER TO REMAIN IN PLACE.
GUIDANCE TEMPS ARE FAIRLY CLOSE AND A BLENDED APPROACH WAS
UTILIZED.

TUESDAY NIGHT INTO WEDNESDAY…THE WEAK RIDGE OF HIGH PRESSURE WILL BE
BRIEF AS NEXT UPSTREAM SHORT WAVE APPROACHES. THIS SYSTEM DOES
HAVE RATHER STRONG FRONTOGENESIS FORCING BUT MOISTURE WILL BE
LACKING. THIS SYSTEM WILL HOWEVER TAP IN LAKE MOISTURE TO ASSIST
WITH LAKE ENHANCED SNOWFALL LATE TUESDAY NIGHT INTO WEDNESDAY. WE
WILL PLACE THE HIGHER POPS ACROSS THE DACKS AND LEAVE THE
REMAINDER OF THE CWA WITH EITHER SLIGHT CHANCE OR NO PRECIP.

HIGH PRESSURE WILL SETTLE INTO THE REGION WEDNESDAY NIGHT WITH
TRANQUIL CONDITIONS UNDER A VARIABLY CLOUDY SKY AS SOME LOW LEVEL
MOISTURE REMAINS AND AN INCREASE IN HIGHER LEVEL MOISTURE AS WARM
ADVECTION UNFOLDS UPSTREAM.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/…
AT THE START OF THE LONG TERM PERIOD…FAST ZONAL FLOW ALOFT
CONTINUES TO HINDER FORECAST CONFIDENCE AS MODEL GUIDANCE STRUGGLES
TO GRASP THE LONGWAVE PATTERN. BOTH THE GFS AND ECMWF ARE IN FAIRLY
GOOD AGREEMENT WITH AN UPPER-LEVEL LOW CENTERED IN THE VICINITY OF
HUDSONS BAY…WITH PIECES OF SHORTWAVE ENERGY ROTATING THROUGH IT.
MODEL GUIDANCE CONTINUES TO STRUGGLE WITH THE TIMING OF THESE
INDIVIDUAL DISTURBANCES MOVING THROUGH THE NORTHERN STREAM FLOW.
USED A BLEND OF HPC/GFS/ECMWF TO ACCOUNT FOR THESE DIFFERENCES.

WEAK HIGH PRESSURE WILL BUILD IN AT THE SURFACE FOR THURSDAY AND
FRIDAY…KEEPING THE AREA DRY. A FEW LAKE EFFECT SHOWERS MAY AFFECT
THE TUG HILL PLATEAU THURSDAY UNDER A NORTHWESTERLY ZONAL FLOW.

MODEL DIFFERENCES BEGIN TO INCREASE DURING THE WEEKEND AS PIECES OF
SHORTWAVE ENERGY WOBBLE THE NORTHERN STREAM FLOW SOUTH ACROSS THE
AREA SATURDAY. HAVE INTRODUCED SLIGHT POPS FOR THIS PERIOD
INCREASING THE POPS TO CHANCE AS A CLIPPER-TYPE LOW PRESSURE SYSTEM
APPROACHES THE REGION FROM THE NORTHWEST. HAVE KEPT FORECAST SIMPLE
WITH RAIN AND/OR SNOW…HOWEVER THERE COULD BE BRIEF PERIODS OF
MIXED PRECIPITATION AS WELL AS THE SYSTEM EXITS THE REGION DURING
THE MONDAY NIGHT-TUESDAY TIMEFRAME.

TEMPERATURES INITIALLY WILL BE BELOW NORMAL BEFORE MODERATING NEAR
THE END OF THE LONG TERM PERIOD AS THE SURFACE HIGH MOVES EAST
DURING THE WEEKEND AND SOUTHWESTERLY RETURN FLOW FILLS IN BEHIND.

&&

.AVIATION /21Z MONDAY THROUGH SATURDAY/…
MAINLY VFR CONDITIONS ARE EXPECTED TO PERSIST THROUGH THE REST OF
THE AFTERNOON/EVENING…AND MUCH OF THE OVERNIGHT HOURS. LAKE
EFFECT CLOUDS AND A FEW SNOW SHOWERS HAVE SHIFTED SOUTH OF A KALB-
KPSF LINE…WITH ONLY SCT CLOUDS TO THE NORTH. AS THE FLOW BACK TO
A MORE WESTERLY DIRECTION THROUGH THE AFTERNOON…CLOUDS AND ISOLD
TO SCT -SHSN WILL MAY POTENTIALLY MOVE BACK INTO THE KALB/KPSF
CORRIDOR. WILL MENTION VCSH AT THESE TWO SITES…WITH A LOW PROB
FOR BRIEF MVFR/IFR CONDITIONS ASSOCIATED WITH A PASSING SNOW
SHOWER OR TWO. CHANCES ARE TOO LOW TO MENTION RESTRICTIONS IN THE
TAFS THOUGH.

BY THIS EVENING…ANY LAKE EFFECT SNOW SHOWERS SHOULD BE NORTH OF
THE TERMINALS…WITH GENERALLY QUIET WEATHER AND VFR CONDITIONS. A
WEAK WAVE OF LOW PRESSURE APPROACHING THE MID ATLANTIC REGION WILL
BRING A LIKELY PERIOD OF -SN TO KPSF/KPOU TUESDAY MORNING INTO THE
AFTERNOON. THERE IS A SLIGHT CHANCE SOME LIGHT SNOW COULD MAKE IT
NORTH TO KALB…BUT WILL JUST MENTION VCSH FOR NOW. WILL INDICATE
IFR CONDITIONS WITH -SN FALLING AT KPOU/KPSF STARTING AROUND 11Z-
12Z TUESDAY. VFR CONDITIONS SHOULD PREVAIL AT KALB AND ESPECIALLY
AT KGFL.

WINDS WILL INITIALLY BE WESTERLY AROUND 10-12 KT WITH GUSTS TO 20
KT…BECOMING LIGHT AND VARIABLE AFTER DARK.

OUTLOOK…
TUE…LIKELY -SN SOUTH OF KALB WITH ASSOCIATED MVFR-IFR CONDITIONS.
TUE NIGHT…VFR. NO SIG WX.
WED…VFR-MVFR WITH SLIGHT CHC -SHSN AT KALB/KGFL.
WED NIGHT-FRI…VFR. NO SIG WX.

&&

.HYDROLOGY…
NO HYDROLOGIC PROBLEMS ARE EXPECTED THROUGH THE NEXT 5 DAYS.

THE PREDOMINANT PTYPE WILL BE SNOW DURING THIS WEEK. THE HEAVIER
SNOW TALLIES WILL BE IN THE FAVORED LAKE SNOW BELTS /WRN DACKS
AREA/ INTO TUESDAY.

THE BELOW NORMAL TEMPS MAY ALLOW SOME ICE TO START TO FORM NORTH
OF THE MOHAWK RIVER VALLEY INTO THE ADIRONDACKS. SOME ICE EFFECTS
COULD BE SEEN ON GAGES BY LATE IN THE 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…NONE.
NY…NONE.
MA…NONE.
VT…NONE.

&&

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

FOR THE LATEST UPDATES…PLEASE VISIT OUR WEBPAGE AT
WWW.WEATHER.GOV/ALBANY

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