FXUS61 KBGM 150614
AFDBGM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BINGHAMTON NY
114 AM EST TUE DEC 15 2009

.SYNOPSIS...
A WEAK AREA OF LOW PRESSURE WILL TRACK NORTHEAST ACROSS NORTHERN
NEW YORK STATE TONIGHT. SCATTERED LIGHT SHOWERS... DRIZZLE AND
AREAS OF FOG WILL ACCOMPANY THE LOW. A COLD FRONT WILL TRACK
SOUTHEAST ACROSS THE AREA ON TUESDAY... ACCOMPANIED BY SCATTERED
RAIN SHOWERS... WHICH COULD CHANGE TO SNOW SHOWERS DURING THE
AFTERNOON ACROSS NEW YORK. COLDER WEATHER WILL FOLLOW BEHIND THE
FRONT TUESDAY NIGHT AND WEDNESDAY WITH SOME SNOW SHOWERS...
ESPECIALLY SOUTHEAST OF LAKE ONTARIO.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
     UPDATED AS OF 730 PM...
RADAR/SURFACE OBS SHOW SCATTERED SHOWERS TRAVERSING
WESTERN/NORTHERN NY AS OF THIS WRITING. GIVEN THE APPROACH OF A
SURFACE FRONT FROM SOUTHERN ONTARIO OVERNIGHT INTO TUESDAY...AND
ALSO ADDITIONAL UPPER-LEVEL WAVES WITHIN A BROAD SOUTHWEST FLOW
ALOFT...WE FEEL THESE HIT AND MISS SHOWERS WILL PERSIST...AND IN
FACT EXPAND A BIT TOWARDS THE SOUTHEAST. OUR CURRENT GRIDS HAVE
THIS SCENARIO PRETTY WELL IN HAND...SO JUST TWEAKED THE NEAR-TERM
POP AND WEATHER GRIDS SLIGHTLY. 

SURFACE TEMPERATURES ARE SAFELY ABOVE FREEZING AREA-WIDE...AND
THESE READINGS SHOULD HOLD ABOUT STEADY THE REST OF THE NIGHT...AS
WE CONTINUE TO WARM ADVECT IN THE BOUNDARY LAYER...OUT AHEAD OF
THE AFOREMENTIONED COLD FRONT. ANY SHOWERS SHOULD STAY IN THE FORM
OF RAIN.

THE ONLY OTHER WEATHER CONCERN OVERNIGHT IS THE POTENTIAL FOR
DENSE FOG...ESPECIALLY AT THE HIGHER ELEVATIONS. AS OF EARLY
EVENING...MOST OF THE HIGHER SURFACE DEW POINTS (NEAR 40F) REMAIN
OVER WESTERN PA...THE OHIO VALLEY...AND LOWER MICHIGAN. AS THE
FRONT NEARS AFTER 06Z...THIS MORE ABUNDANT LOW-LEVEL MOISTURE
SHOULD MOVE INTO CENTRAL NY AND EASTERN PA...AND WE THINK THE
BETTER POTENTIAL FOR FOG WILL BE DURING THIS TIME FRAME (IN THE
PRE-DAWN HOURS). WE'LL CONTINUE TO WATCH FOR THIS DEVELOPMENT
LATER TONIGHT INTO EARLY TUESDAY.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH WEDNESDAY NIGHT/...
TUESDAY...COLD ADVECTION WILL BEGIN BY AFTERNOON BEHIND THE SFC
LOW AS IS TRACKS NORTHEAST TOWARD THE CANADIAN MARITIMES.
SCATTERED SHOWERS WILL INCREASE IN COVERAGE OVER WESTERN AND
CENTRAL NY AS A STRONG 500 MB SHORT WAVE MOVES EAST ACROSS THE
GREAT LAKES. TEMPERATURES WILL BE NEAR OR JUST ABOVE 40 IN MANY
PLACES DURING THE LATE MORNING... BUT TEMPERATURES WILL BE FALLING
BY MID AFTERNOON.

FORECASTING THE LOCATION AND INTENSITY OF LAKE EFFECT SNOW WILL BE
THE MAIN FORECAST CHALLENGE FROM TUESDAY NIGHT THROUGH THURSDAY.
BOTH THE NAM AND GFS INDICATE THAT A WEAK SFC TROUGH WILL PASS
SOUTH ACROSS CENTRAL NY AND NORTHERN PA TUESDAY EVENING...
ASSOCIATED WITH A BAND OF LAKE ENHANCED SNOW SHOWERS. THE FLOW
BEHIND THIS TROUGH WILL BE FROM 320 TO 330 DEGREES WHICH WILL
BRING ADDITIONAL SNOW SHOWERS SOUTHEAST FROM LAKE ONTARIO ACROSS
THE FINGER LAKES TO THE SOUTHERN TIER OF NY. THESE SNOW SHOWERS
COULD ACCUMULATE AN INCH OR 2 IN MANY PLACES AND COULD RESULT IN
SLICK ROADWAYS AS TEMPERATURES FALL FROM MILD AFTERNOON LEVELS. 

NAM SIMULATED REFLECTIVITY AND HISTORICAL ANALOGS BASED ON THE
EXPECTED FLOW PATTERN INDICATES THAT MULTI- BAND SNOW SHOWERS WILL
SHIFT SLIGHTLY NORTH ON WEDNESDAY... WITH THE BIGGEST
CONCENTRATION OF SNOW SHOWERS PROBABLY SETTING UP NEAR THE
SYRACUSE CORRIDOR FOR AWHILE WITH A FLOW FROM 290 TO 300 DEGREES.
THESE SHOWERS COULD PRODUCE LOCALIZED 1 TO 3 INCH AMOUNTS. ANOTHER
TROUGH IS THEN FORECAST TO DROP SOUTH ACROSS THE AREA WEDNESDAY
NIGHT... POSSIBLY PUSHING THE SNOW SHOWERS BACK TO THE SOUTH FOR
AWHILE. SNOW SHOWERS WILL BE DIMINISHING ON THURSDAY AS HIGH
PRESSURE BUILDS IN. 

TOTAL SNOW ACCUMULATIONS FROM THE MULTI-BAND LES TUESDAY NIGHT
INTO THURSDAY SHOULD REMAIN BELOW WARNING THRESHOLDS ACROSS THE
AREA AS NONE OF THE BANDS WILL BE AS INTENSE AS WHAT WAS SEEN LATE
LAST WEEK... PLUS THE FACT THAT THEY WILL BE SHIFTING. HOWEVER...
UP TO 5 OR 6 INCHES COULD ACCUMULATE TUESDAY NIGHT INTO THURSDAY
OVER THE HIGHER TERRAIN SOUTH OF SYRACUSE.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
THERE IS GOOD AGREEMENT IN THE MODEL WORLD THAT THIS PERIOD WILL
FEATURE COLD TEMPERATURES (SEASONABLE TO SOMEWHAT BELOW
AVERAGE...WITH HIGHS GENERALLY IN THE 20S TO LOWER 30S).

IT APPEARS THAT THE FIRST PORTION OF THIS TIME FRAME WILL BE
MAINLY DRY...AS HIGH PRESSURE BUILDS IN FROM THE UPPER
MIDWEST...BRINGING LAKE-EFFECT SNOW SHOWERS TO AN END BY THURSDAY
NIGHT.

OVER THE WEEKEND...MODEL CONSENSUS IS TO BRING A DEVELOPING
COASTAL LOW NORTHWARD...BUT FAR ENOUGH OFF SHORE...SO THAT CENTRAL
NY/NORTHEAST PA STAYS DRY.

BY MONDAY...AS THE FLOW IS PROGGED TO TURN NORTHWEST...LAKE-EFFECT
SNOW SHOWERS SHOULD RE-EMERGE ACROSS CENTRAL NY. 

MODELS BEGIN THE EXTENDED IN AGREEMENT. THEY INDICATE A STRONG
UPPER LOW WILL SIT CENTERED OVER CANADA...JUST TO THE NORTHEAST OF
MAINE. THIS WILL BRING COLD ARCTIC AIR DOWN INTO THE CWA.
HOWEVER...THEY MODELS ALSO SHOW THE LOW RETROGRADING THROUGH THE
WEEKEND. THIS IS WHERE THE MODELS DIFFER. THE ECMWF SHOWS THE LOW
SLOWLY MOVING WESTWARD AND ONLY MAKING IT AS A FAR AS QUEBEC IN
THE BEGINNING OF THE WEEK. IT ALSO SHOWS A SECONDARY LOW FORMING
OVER NORTHERN MICHIGAN ON SUNDAY. IT THEN SWINGS THIS LOW SOUTH
AROUND THE MAIN LOW.

NOW THE GFS HAS A DIFFERENT SOLUTION. IT RETROGRADES THE MAIN LOW
TO NORTHERN MICHIGAN AND KEEPS A BROAD AREA OF LOW PRESSURE
EXTENDING EASTWARDS TO THE GULF OF ST LAWRENCE. 

THERE IS QUITE A BIT OF UNCERTAINTY IN THE MODELS ENSEMBLES ALSO
WITH THE PROGRESSION OF THIS LOW. GIVEN THIS...JUST KEPT A SLIGHT
CHANCE OF PRECIP IN FOR THE WEEKEND AND USED A MODEL BLEND FOR
TEMPS.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
A FAIRLY CHALLENGING FORECAST EARLY THIS MORNING AS REGION
REMAINS UNDER THE INFLUENCE OF AN APPROACHING UPPER TROUGH NOW
LOCATED ACROSS WESTERN ONTARIO PROVINCE. THAT SAID...04Z SURFACE
ANALYSIS SHOWING TWO SFC TROUGHS LOCATED JUST TO THE WEST OF THE
FORECAST AREA...WITH THE FIRST RESIDING ACROSS THE WESTERN FINGER
LAKES AND THE OTHER FURTHER WEST ACROSS WESTERN NY. WINDS THROUGH
THE MORNING WILL BEGIN TO VEER MORE SOUTHWESTERLY WITH TIME AS
THESE FEATURES PASS THROUGH THE AREA. THE LOW-LEVEL ATMOSPHERE
REMAINS VERY MOIST AND WITH RELATIVELY WEAK WIND SPEEDS...AM
EXPECTED MOST LOCATIONS TO SEE VSBY RESTRICTIONS IN THE FORM OF
PATCHY FG. FOR MOST AREAS...MVFR VSBYS ARE EXPECTED...HOWEVER
TEMPORARY IFR VALUES WILL BE POSSIBLE BY SUNRISE. A STRONG COLD
FRONT IS THEN PROGGED TO MOVE THROUGH THE AREA BETWEEN 15 AND
18Z...WITH WINDS QUICKLY BECOMING NORTHWEST BEHIND ITS PASSAGE.
WINDS WILL GUST AT TIMES TOMORROW AFTERNOON AS HIGH AS 25KTS IN
RESPONSE TO A STRENGTHENING PRESSURE GRADIENT AS HIGH PRESSURE
APPROACHES THE REGION FROM THE MID/UPPER MISS RVR VLY. MVFR/IFR
CIGS WILL BRIEFLY IMPROVE BY LATE AFTERNOON FOLLOWING THE FRONTAL
PASSAGE...HOWEVER MVFR/IFR THRESHOLDS WILL AGAIN BE POSSIBLE
THROUGH THE EVENING/OVERNIGHT. MAIN CONCERN THROUGH THE END OF THE
FORECAST PERIOD CONTINUES TO BE LAKE EFFECT SNOW POTENTIAL AS COLD
AIR FILTERS OVER THE WARM WATERS OF LAKE ONTARIO. COOL
NORTHWESTERLY FLOW WILL LIKELY SET UP MULTIPLE BANDS OF LAKE
EFFECT SNOW...WITH KSYR AND KITH THE MOST LIKELY TERMINALS TO BE
INFLUENCED.

.OUTLOOK...

TUE THRU SAT...AREAS OF MVFR ACRS CNTRL NY IN LES. GNRLY VFR AT
AVP.

&&

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NY...NONE.

&&

$$
SYNOPSIS...MSE
NEAR TERM...MLJ/MSE
SHORT TERM...MSE
LONG TERM...MLJ
AVIATION...CMG