FXUS61 KBGM 252332
AFDBGM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BINGHAMTON NY
632 PM EST WED NOV 25 2009
.SYNOPSIS...
A WEAK FRONT WILL BRING SCATTERED LIGHT SHOWERS AND DRIZZLE TO THE
AREA TONIGHT. DRY WEATHER WILL FOLLOW BEHIND THE FRONT ON
THANKSGIVING DAY WITH UNSEASONABLY MILD TEMPERATURES. A STRONGER
SYSTEM WILL BRING SHOWERS TO THE AREA THURSDAY NIGHT. COLDER AIR
ARRIVING IN THE WAKE OF THIS SYSTEM MAY ALLOW FOR SOME OF THE
RAIN TO MIX WITH OR CHANGE TO SNOW LATE THURSDAY NIGHT OR FRIDAY.
&&
.NEAR TERM /UNTIL 10 PM THIS EVENING/...
MAIN UPPER-LEVEL WAVE IS PROGGED TO ROTATE THROUGH THE REGION AND
INTO EASTERN CANADA LATER THIS EVENING...WITH MOST OF THE SHOWER
ACTIVITY OCCURRING THROUGH ABOUT 10 PM.
LATER TONIGHT...LARGE-SCALE SUBSIDENCE SETS IN BEHIND THE ABOVE
MENTIONED WAVE. DESPITE THE SINKING MOTION ALOFT...MODEL SOUNDINGS
AND MOISTURE PROGS SHOW PLENTY OF LOW-LEVEL MOISTURE REMAINING.
THIS SHOULD TRANSLATE INTO RESIDUAL STRATUS CLOUDS AND SOME
ELEVATION FOG.
DUE TO ALL THE EXPECTED CLOUD COVER...TEMPERATURES ARE NOT LIKELY
TO FALL A GREAT DEAL OVERNIGHT...ONLY INTO THE UPPER 30S AND LOWER 40S.
&&
.SHORT TERM /10 PM THIS EVENING THROUGH SATURDAY/...
DRYING ALOFT WILL FOLLOW BEHIND THE SHORT WAVE THIS EVENING...
SETTING THE STAGE FOR A DRY THANKSGIVING ACROSS NORTHEAST PA AND
CENTRAL NY. HOWEVER... MODEL SOUNDINGS INDICATE THAT DRYING IN
THE 3 TO 5 KFT LEVEL WILL BE SLOW TOMORROW... WITH THE BEST CHC
FOR SOME CLEARING ACROSS NORTHEAST PA.
NEXT SYSTEM TO AFFECT THE AREA WILL ARRIVE LATER THURSDAY NIGHT.
A FAIRLY TYPICAL DEGREE OF MODEL DISAGREEMENT IS EVIDENT WITH THE
TRACK AND INTENSITY OF THIS SYSTEM AT THIS TIME RANGE. MODELS ARE
IN GENERAL AGREEMENT THAT A STRONG UPPER LEVEL SYSTEM WILL TRACK
EAST-SOUTHEAST ACROSS PA/SRN NY THURSDAY NIGHT AND FRIDAY
MORNING... THEN OFF THE COAST LATER FRIDAY. SFC LOW PRESSURE WILL
DEVELOP WELL OFF SHORE.
HOWEVER... MINOR DIFFERENCES IN THE TRACK AND DEEPENING RATE OF
THE UPPER SYSTEM WILL HAVE MAJOR EFFECTS ON THE DEVELOPMENT OF A
BAND OF MODERATE TO HEAVY PRECIPITATION NEAR AND NORTH-WEST OF THE
MID-UPPER LEVEL LOW. CURRENTLY... THE GFS IS FARTHEST NORTH
WITH THE TRACK OF THE UPPER SYSTEM... AND IS SLOWEST TO DEVELOP
THE DEFORMATION BAND ON THE NORTH-WEST SIDE OF THE LOW.
MEANWHILE... THE NAM IS FARTHEST SOUTH... DEVELOPING A DEFORMATION
BAND OF HEAVY PRECIPITATION OVER CENTRAL PA BY 12Z FRIDAY. THE
ECMWF APPEARS TO BE A COMPROMISE... TRACKING THE 500 MB LOW FROM
CENTRAL PA TO SOUTHERN NEW ENGLAND ON FRIDAY WITH MODERATELY
STRONG DEEPENING... FROM 531 DM TO 525 DM. THE 700 MB LOW IS
FORECAST TO CLOSE OFF OVER CENTRAL PA... THEN DEEPEN AS IT TRACKS
NORTHEAST. THE ECMWF DEVELOPS A DEFORMATION BAND OF MODERATE TO
HEAVY PRECIPITATION OVER CENTRAL NY AND NORTHERN PA BY 12Z FRIDAY.
THE EXACT LOCATION AND TIMING OF THE DEVLOPMENT OF THIS
DEFORMATION BAND OF HEAVIER PRECIPITATION WILL BE CRITICAL FOR OUR
AREA REGARDING BOTH PRECIPITATION AMOUNTS AND PRECIPITATION TYPE.
BOUNDARY TEMPERAUTRES ASSOCIATED WITH THIS SYTEM WILL BE GENERALLY
TOO WARM FOR SNOW THROUGH MOST OF FRIDAY... EXCEPT POTENTIALLY
UNDERNEATH ANY DEFORMATION BAND OF HEAVIER PRECIPITATION THAT CAN DEVELOP...
WHERE COOLING DUE TO MELTING AND LIFT COULD COOL TEMPERATURES
SUFFICIENTLY FOR WET SNOW... ESPECIALLY OVER HIGHER ELEVATIONS. AN
EXAMPLE OF THIS CAN BE SEEN BY LOOKING AT THE NAM FORECAST
SOUNDINGS AT IPT. IN THESE SOUNDINGS... AN ISOTHERMAL ZERO DEGREE
C LAYER FORMS DUE TO HEAVY PRECIPITATION... WHICH WOULD RESULT IN
A FEW HOURS OF HEAVY SNOW. SO... THE KEY QUESTION FOR FRIDAY IS
WHERE AND WHEN THE DEFORMATION BAND CAN SET UP.
WITH THIS HIGH LEVEL OF UNCERTAINTY... HAVE DECIDED TO PLAY THINGS
FAIRLY CONSERVATIVELY AT THIS TIME... AND AM GOING WITH SOME LIGHT
SNOW ACCUMULATIONS ACROSS MUCH OF THE AREA FROM LATE THURSDAY
NIGHT THROUGH FRIDAY NIGHT WITH MIXED RAIN AND SNOW SHOWERS. THIS
FORECAST IS FAIRLY CLOSE TO THE CURRENT HPC FORECAST... EXCEPT
THAT I PUT IN A LITTLE MORE DETAIL DUE TO ELEVATION DIFFERENCES. PRECIPITATION
SHOULD BE MAINLY LAKE ENHANCED SNOW SHOWERS DOWNWIND OF LAKE
ONTARIO BY LATE FRIDAY NIGHT WITH 850 MB TEMPERATURES EVENTUALLY
FORECAST TO FALL TO AROUND -5 OR -6 WITH A FLOW FROM AROUND 300 DEGREES.
ANY LIGHT LAKE ENHANCED RAIN OR SNOW SHOWERS SHOULD DISSIPATE ON
SATURDAY AS HIGH PRESSURE BUILDS IN.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
NW FLOW SAT NGT SHD RESULT IN A FEW MORE SHWRS OTRW HIPRES BLDS IN
SFC AND ALOFT CLRG WILL BE SHRT LIVED AS ANOTHER WV AND SFC FNT
APRCHS LATE MON AND EARLY TUE. CRNT MODEL SOLNS ARE BASICALLY A
COMPROMISE OF EARLIER RUNS WITH A PROGRESSIVE FNT BUT WITH A
DEEPENING LOW NORT OF NEW ENG. OPERATIONAL GFS IS STILL FCSTG A
DEEPER LOW AND THEN FLWS WITH MORE CAA BHD THE FNT. EITHER WAY
IT/S A QUICK SHOT OF COLD AIR BEFORE RDGG RETURNS LTR WED.
ONCE AGAIN FLWD THE LATEST HPC GUID WITH SOME MINOR TWEAKS OF THE
POPS AND TEMPS.
&&
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
VERY DIFFICULT FORECAST SITUATION SETTING UP. THE MAIN FACTORS
INCLUDE A SATURATED TERRAIN FROM EARLIER RAINS, AN OCCLUDED FRONT
APPROACHING FROM THE SOUTHWEST, ALONG WITH A LARGE AREA OF
CLEARING WHICH THREATENS TO OVERTAKE LARGELY MVFR CLOUD COVER
ACROSS NY/PA TERMINALS.
TWO WIDELY DIFFERENT SCENARIOS COULD PLAY OUT. FIRST SCENARIO IS
THAT DRY AIR DOES NOT MAKE IT MUCH PAST THE NY/PA BORDER, AND THE
NY TERMINALS REMAIN ENTRENCHED IN BORDERLINE VFR/MVFR CEILINGS.
SECOND SCENARIO IS THAT THE DRY AIR PUNCHES THROUGH NY, CAUSING RAPID
CLEARING ALOFT AND COOLING BELOW, AND FOG BEGINS TO FORM AFTER
MIDNIGHT.
THE MOST LIKELY AREA FOR DENSE FOG TO FORM IS OVER NORTHEASTERN
PA, INCLUDING THE AVP TERMINAL, WHERE WE HAVE FORECAST IFR
CONDITIONS DURING THE EARLY MORNING. SHOULD THE CLEARING EXPAND
NORTHWARD, THE ENTIRE SOUTHERN TIER OF NY WILL ALSO BE RIPE FOR
FOG FORMATION. AND THIS INCLUDES THE BGM, ELM, AND ITH TERMINALS.
WILL BE WATCHING CLOSELY, AND WILL AMMEND IF NECESSARY.
OUTLOOK...
LATE THUR NGT-FRI...MVFR/IFR RESTRICTIONS LIKELY...IN RAIN OR WET
SNOW.
FRI NGT-SAT...MVFR/IFR RESTRICTIONS AGAIN POSSIBLE...IN
RAIN/SNOW SHOWERS.
SUN...IMPROVEMENT TO VFR LIKELY.
MON...VFR.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NY...NONE.
&&
$$
SYNOPSIS...MSE
NEAR TERM...MSE
SHORT TERM...MSE
LONG TERM...DGM
AVIATION...DJP/MLJ
