November 26, 2012 Forecast Discussion

000
FXUS61 KALY 270025
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
715 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 700 PM EST…THE NUISANCE LAKE EFFECT SNOW SHOWERS…MOSTLY
LIGHT…WERE SLOWLY LIFTING BACK NORTH OF THE CAPITAL REGION. LOOKS
AS IF THEY SHOULD BE DONE FROM ALBANY SOUTHWARD…BUT WILL PERSIST
AWHILE LONGER TO THE NORTH. REMOVED ANY MENTION OF SNOW SHOWERS FROM
ALBANY NORTH UNTIL LATE TONIGHT.

CLOUDS ARE THE TRICKIEST PART OF THE FORECAST. THE PREVIOUS FORECAST
UNDERSTANDABLY WENT HIGHER THAN MACHINE GUIDANCE BASED ON THE FACT
THAT THE PAST TWO NIGHTS…CLOUDS PERSIST DESPITE GUIDANCE
SUGGESTING OTHERWISE. SATELLITE PICTURES DO INDICATE THAT THE LAKE
EFFECT CLOUDS (ONE BAND OFF ERIE AND THE OTHER LAKE ONTARIO) WERE
ERODING AT THE ENDS…NEAR THE CAPITAL DISTRICT…BUT IT IS NOT
CONVINCING ENOUGH TO GO AHEAD AND ADJUST ANY LOW READINGS YET. THE
CLOUDS COULD JUST AS EASILY FILL BACK IN UNDERNEATH THE LOWERING
SUBSIDENCE INVERSION SO WILL LEAVE GOOD ENOUGH ALONE FOR NOW.

MEANWHILE…THE SOUTHERN STREAM ENERGY CONTINUES TO RACE EAST INTO
THE OHIO VALLEY…TOWARD THE MID ATLANTIC. THE LATEST NAM (18Z) CAME
IN WITH A LOT HIGHER QPF POUNDING THE MID ATLANTIC INTO OUR EXTREME
SOUTHERN AREAS. NOT BUYING IT YET AS MOST OTHER MODEL GUIDANCE IS A
LOT LIGHTER WITH THE QPF AND IFR SATELLITE PICTURES INDICATED VERY
LITTLE COOLING CLOUDS TOP. THIS SUGGESTED THAT THE BAROCLINIC LEAF
IS NOT RAMPING UP THE WAY THE 18Z NAM WOULD SUGGEST.

SO FOR NOW…LEAVE IT VARIABLY CLOUDY AND MAINLY DRY THROUGH THE
EARLY OVERNIGHT (STILL THOSE PESKY LIGHT SNOW SHOWERS NORTH).
THEN…FOLLOW THE PREVIOUS PACKAGE AND BRING LIGHT SNOW INTO THE
REGION SOUTH OF ALBANY TOWARD DAYBREAK. THE STEADIEST SNOW SHOULD
REMAIN SOUTH OF ALBANY WHERE A COUPLE OF INCHES COULD
ACCUMULATE…VERY LITTLE OR NO ACCUMULATION FROM THE CAPITAL
DISTRICT NORTHWARD. THERE WILL BE ADDITIONAL LAKE EFFECT SNOW OFF
ONTARIO PRODUCING MAYBE AN INCH OR TWO OF ITS OWN DOWNWIND INTO THE
ADIRONDACKS.

OVERNIGHT TEMPS LOOK TO FALL BETWEEN 25-30 MOST PLACES (AGAIN
ASSUMING THE CLOUDS HOLD).

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/…
THE STORM WILL TRACK WELL SOUTH OF THE REGION AND BE TO OUR EAST
LATER ON TUESDAY. LIGHT SNOW OR SNOW SHOWERS WILL PERSIST INTO THE
AFTERNOON HOURS WELL SOUTH OF ALBANY…WHILE LIGHT SNOW SHOWERS OR
FLURRIES WILL TAKE PLACE FURTHER NORTH.

DRIER AIR WILL OVERSPREAD THE REGION NORTHWEST TO SOUTHEAST HEADING
INTO THE AFTERNOON HOURS. THERE MIGHT EVEN BE A FEW BREAKS OF
SUNSHINE FROM ALBANY NORTHWARD DURING THE AFTERNOON.

HIGH TEMPERATURES WILL ONCE AGAIN FALL SHORT OF NORMAL…GENERALLY
IN THE MID TO UPPER 30S IN THE VALLEYS…BUT ONLY UPPER 20S TO MID
30S.

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 /00Z TUESDAY THROUGH SATURDAY/…
NO WEATHER RELATED PROBLEMS THROUGH MIDNIGHT AS ANY SNOW SHOWER
ACTIVITY SHOULD STAY TO THE WEST AND NORTH OF THE TAFS. THE ONLY
EXCEPTION MIGHT BE A FEW SNOW SHOWERS AT KGFL…BUT EVEN HERE…NOT
EXPECTING ANYTHING OTHER THAN VFR.

LATER OVERNIGHT…LIGHT SNOW IS EXPECTED TO BREAK OUT ACROSS AREAS
TO THE SOUTH OF ALBANY. EVEN BEING LIGHT…WE FEEL THIS SNOW SHOULD
FAIRLY QUICKLY DROP CONDITIONS TO IFR AT KPOU AND KPSF BY THE
MORNING PEAK. FURTHER NORTH…THE SNOW LOOKS VERY LIGHT…PROBABLY
DROPPING CONDITIONS TO MVFR AT WORST AT KALB.

IFR CONDITIONS COULD LAST INTO THE AFTERNOON HOURS AT KPOU AND KPSF
BUT WILL IMPROVE WITH TIME DURING THE AFTERNOON. ANY MVFR WILL
QUICKLY GO BACK TO VFR BY AFTERNOON AT KALB.

AT KGFL…ONLY ISOLATED SNOW SHOWERS AT WORST WITH VFR EXPECTED TO
PREVAIL ALL OF TUESDAY.

THE WIND WILL BE NOT BE A PROBLEM AT THE TAF SITES…GENERALLY
STAYING BELOW 10KTS…VARIABLE TO WESTERLY.

OUTLOOK…
TUE NIGHT…VFR. NO SIG WX.
WED…VFR WITH SLIGHT SUB-VFR CHC -SHSN AT KALB/KGFL.
WED NIGHT-SAT…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…HWJIV/BGM
SHORT TERM…BGM/HWJIV
LONG TERM…IRL
AVIATION…HWJIV
HYDROLOGY…BGM/WASULA

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