FXUS61 KALY 260530 AFDALY AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBANY NY 1230 AM EST THU NOV 26 2009 .SYNOPSIS... AN OCCLUDED FRONT WILL MOVE ACROSS THE REGION TONIGHT BRINGING A CHANCE OF SHOWERS. WEAK HIGH PRESSURE WILL BE OVER THE REGION ON THANKSGIVING WITH MILD...CLOUDY...AND DRY CONDITIONS. A COMPLEX STORM SYSTEM WILL IMPACT THE NORTHEAST THURSDAY NIGHT THROUGH FRIDAY NIGHT WITH UNSETTLED WEATHER INCLUDING RAIN...SOME SNOW...ESPECIALLY FOR THE HIGHER ELEVATIONS NORTH AND EAST OF THE MOHAWK RIVER VALLEY...AND BLUSTERY WINDS. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... CLOUDS AND SCATTERED SHOWERS CONTINUE IN THE REGION...AND BASED ON SATELLITE AND RADAR...SOME BREAKS POSSIBLE IN CENTRAL AND EASTERN AREAS FOR A BRIEF TIME DURING THE EARLY MORNING HOURS. HOWEVER...CURRENT LOW CEILINGS AND DEEP MOISTURE SEEN IN AREA 00Z SOUNDINGS SUGGESTS THAT ANY BREAKS IN THE CLOUDS WILL BE BRIEF...AND LOW CLOUDS AND PATCHY DENSE FOG WILL BE THE RULE THROUGH THE OVERNIGHT. ADJUSTED TEMPERATURES UPWARD A COUPLE OF DEGREES IN SOME AREAS...SO WORDING WILL BE NEAR STEADY TEMPERATURES FOR SOME AREAS. NO OTHER CHANGES. PREV AFD BELOW... AS OF 300 PM EST...SFC LOW PRESSURE CONTINUES TO DRIFT INTO THE NRN GREAT LAKES REGION WITH THE RUC13 SHOWING A SHORTWAVE TIED TO AN OCCLUDED FRONT FOCUSING MULTIPLE BANDS OF SHOWERS OVER NW PA...AND W-CNRL NY...VIA THE REGIONAL MOSAIC RADAR. SOME OF THESE SCT SHOWERS WITH THE OCCLUDED BOUNDARY WILL MOVE INTO THE REGION OVERNIGHT. WE BELIEVE THE BEST CHANCE OF SHOWERS WILL BE FROM THE CAPITAL REGION...AND ERN CATSKILLS NORTH AND WEST. WE PLACED SOME LIKELY POPS IN WEST OF THE HUDSON RIVER VALLEY. THE AIR MASS IS FAIRLY MOIST...AND MILD FOR LATE NOVEMBER. WE KEPT SOME PATCHY FOG IN EVERYWHERE AFTER MIDNIGHT WITH SOME LINGERING ISOLD-SCT SHOWERS. MIN TEMPS WILL BE MILD IN THE MID 30S TO L40S. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/... THANKSGIVING WILL BE THE QUIET BEFORE THE COMPLEX STORM TO FOLLOW THE NEXT FEW PERIODS. THE SOUNDINGS AND RH PROFILES ARE MOIST PRIOR TO NOONTIME. WE COULD SEE A FEW BREAKS OF SUN...IF ENOUGH SUBSIDENCE IS REALIZED BY THE WEAK BUBBLE SFC HIGH THAT NOSES IN FROM NORTHEAST NJ...AND PA...AS A COASTAL/OCEAN LOW WELL EAST OF THE MID ATLANTIC REGION SLOWLY LIFTS NORTHWARD. MEANWHILE...A STRONG UPPER LEVEL LOW ASSOCIATED WITH THE HIGH AMPLITUDE LONG WAVE NEUTRAL TILTED UPPER TROUGH MIGRATES CLOSER FROM THE LOWER GREAT LAKES REGION. THE FCST AREA WILL BE IN THE NULL ZONE BETWEEN SYSTEMS DURING THE DAY. TEMPS WILL BE VERY MILD FOR THE HOLIDAY WITH HIGHS IN THE U40S TO MID 50S. H850 TEMPS WILL BE ABOVE NORMAL IN THE 0-5C RANGE. MAX TEMPS WILL BE AROUND 10 DEGREES OR SO ABOVE NORMAL. THANKSGIVING NIGHT...THE DETERMINISTIC MODELS AND ENSEMBLES DIVERGE HERE ON HOW TO HANDLE THE COASTAL SYSTEM WITH THE UPSTREAM CLOSED/CUTOFF UPPER LOW. SOME PCPN GENERATED BY WEAK ISENTROPIC LIFT OF THE UPSTREAM LOW AND ITS OCCLUDED FRONT WILL BE APPROACHING FROM THE SOUTH AND WEST...WHILE LIFT GENERATED BY THE SFC WAVE SE OF CAPE COD WILL FOCUS MORE LIGHT RAIN MOVING N/NE. THE UPPER DYNAMICS INDICATE POTENTIAL PHASING WILL OCCUR BETWEEN THE TROUGHS...HOWEVER...THE 12Z GLOBAL ENSEMBLE MEAN INDICATES A STRONG CLUSTERING OF THE MEMBERS NEAR CAPE COD BY 12Z FRI. THE NAM/CAN REG DISAGREES WITH THE GFS/ECMWF/ENSEMBLES SCENARIO. THE MAIN PTYPE DURING THIS TIME LOOKS TO BE LIGHT RAIN WITH THE LOW LEVELS QUITE WARM...AND THE 0C ISOTHERM AT H850 JUST EAST OF KUCA. EXPECT LOWS TO BE IN THE MID30S TO L40S. THE EVOLUTION OF WHAT GOES ON FRI-FRI NIGHT IS WHERE THINGS BECOME VERY COMPLICATED. FRIDAY/FRIDAY NIGHT...CYCLOGENESIS CONTINUES IN THE VICINITY OF THE GULF OF MAINE WITH A 980-985 HPA LOW BY THE EARLY PM. THE PLACEMENT OF THE H500 CLOSED CIRCULATION IS CRITICAL FOR WHERE SNOW LEVELS FALL DURING THE DAY...AND WHERE THE LOW/MID LEVEL DEFORMATION OCCURS. WE ARE LEANING TOWARDS AN HPC/GFS/GEFS SCENARIO. THE GFS PLUME FOR KALB AT 06Z HAD MORE CONSISTENCY THAN THE 12Z...WHERE THE MAIN QPF IS AROUND AN INCH FOR THE EVENT. THE COLD CONVEYOR BELT KICKS IN WITH THE ECMWF/GFS SHOWING POTENTIALLY A HALF AN INCH TO AN INCH PLUS OF QPF THAT COULD BE TRANSITIONING TO SNOW ESPECIALLY FOR SRN VT....AND NORTH OF THE MOHAWK RIVER VALLEY. THERE IS QUITE A BIT OF UNCERTAINTY IN THE AMOUNT OF QPF AND TRACK OF THE SYSTEM. WHAT IS CERTAIN...IS THAT AN IMPRESSIVE LOW LEVEL PRESSURE GRADIENT SETS UP BETWEEN THE COASTAL LOW...AND SFC HIGH PRESSURE NEAR THE LOWER MS RIVER VALLEY. THE WINDS WILL INCREASE OUT OF THE W/NW LATE FRI PM...AND STRENGTHENS OVERNIGHT. WE COULD RECEIVE WIND GUSTS APPROACHING LOW END ADVISORY LEVEL...AS THE H850 WINDS INCREASE TO 45-60 KTS. WE WILL CONTINUE TO CONVEY THE POTENTIAL HAZARDS IN THE HWO PRODUCT. IN TERMS OF THE PCPN...WE HAVE FOLLOWED CLOSE TO HPC. THE BEST CHANCE FOR A LIGHT TO MODERATE SNOWFALL IN OUR PRESENT ASSESSMENT WOULD BE ACROSS THE SRN ADIRONDACKS...SRN GREENS...NRN BERKS...AND PERHAPS THE LAKE GEORGE REGION...ESPECIALLY IN THE OVERNIGHT PERIOD...AS A SUB SYNOPTIC UPSLOPE EVENT MAY MATERIALIZE DURING THE LATE PM THRU THE OVERNIGHT TIME FRAME. MOST LOCATIONS WILL LIKELY SEE SCT SNOW SHOWERS BY SATURDAY MORNING. SATURDAY...THE LOW BECOMES STACKED AND OCCLUDES NEAR NEW BRUNSWICK/GULF OF MAINE. IMPRESSIVE LOW LEVEL WIND FIELDS WILL STILL IMPACT THE REGION. ENOUGH SUBSIDENCE/DOWN SLOPING WILL ALLOW SOME AFTERNOON SUNSHINE. BLUSTERY AND COLD CONDITIONS WILL PREVAIL WITH LINGERING UPSLOPE SNOWS TIL NOONTIME OVER THE SRN DACKS/SRN GREENS. HIGHS WILL BE CLOSER TO NORMAL IN THE MID30S TO L40S. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... HIGH PRESSURE BUILDS IN ACROSS OUR REGION FROM THE SOUTHEAST AS LOW PRESSURE TRACKS FROM THE GREAT LAKES TO SOUTHERN QUEBEC THROUGH MONDAY. CHC POPS MOVE INTO THE PICTURE ON MONDAY. IT'S LOOKING LIKE MORE OF A VARIABLE MIXED EVENT THAN IT DID TWO 12-HOUR RUNS AGO...RAISING THE DEGREE OF UNCERTAINTY AS TO HOW THIS MIGHT PAN OUT DESPITE HOW THE GFS AND ECMWF HAVE NOW COME TOGETHER. IN A NUTSHELL...THIS IS LIKELY A BORDERLINE RAIN/SNOW EVENT WE'RE LOOKING AT. GFS ANALYZES THE 540 THICKNESS LEVEL ACROSS OUR SOUTHERN ZONES AT 00Z TUE...BEING SUPPRESSED ONLY FURTHER SOUTH OVERNIGHT WITH A PASSING COLD FRONT...BUT THE MAIN LOW IS TO THE NORTH WITH A LARGE BERMUDA HIGH PROVIDING A SOUTHERLY FLOW DURING THIS TIME. AT THIS TIME...IT'S JUST NOT SAFE TO CHOOSE A SIDE BETWEEN RAIN AND SNOW... BUT THE SHOWERY BACK END OF THIS SYSTEM ON TUE IS LIKELY TO BE MORE SNOW THAN RAIN...PARTICULARLY IN THE ADIRONDACKS. NO MATTER THE OUTCOME...NEITHER MODEL PRODUCES A GREAT DEAL OF QPF...SO WE'RE NOT TALKING ABOUT MUCH UNLESS ICE IS INVOLVED...WHICH THERE'S NOT MUCH TOO SUPPORT. HAVE CHC...THOUGH DECREASING...POPS CONTINUING THROUGH WED...AS GFS HAS LOW TRYING TO DEVELOP ALONG THE FRONT OVER THE SOUTHEASTERN PART OF THE COUNTRY. EXTENSIVE CLOUDINESS WILL PROBABLY BE HIGH CLOUDS SPRAWLING OUT AHEAD OF THIS LOW...AS HIGH PRESSURE IS PRESENT. HIGH TEMPERATURES WILL AVERAGE IN THE 40S AHEAD OF THE COLD FRONT WITH READINGS DROPPING BACK ABOUT 5 DEGREES ON TUESDAY. LOWS THROUGHOUT THE PERIOD WILL BE MAINLY IN THE 20S AND LOWER 30S. AVERAGE HIGHS AND LOWS FOR THE BEGINNING OF DECEMBER ARE AROUND 40 DEGREES AND THE MID 20S...RESPECTIVELY. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... ...IFR CONDITIONS TO PREVAIL THE NEXT SEVERAL HOURS FOR ALL TAF SITES... THE IFR CONDITIONS WILL BE MAINLY THE RESULT OF CIGS...ALTHOUGH...VISIBILITY COULD BECOME PROBLEMATIC TOWARD SUNRISE AND WILL PLACE A TEMPO GROUP AT THIS TIME AS WE CLOSELY MONITOR TRENDS. THIS LOW LEVEL MOISTURE IS EXPECTED TO REMAIN IN PLACE THROUGH THURSDAY BUT WITH DAYTIME HEATING...THIS SHOULD RAISE THE CIGS A BIT INTO THE MVFR CATEGORY /PERHAPS A PERIOD OF VFR BUT CONFIDENCE NOT THAT HIGH TO PLACE IN THE TAFS BEYOND 6 HOURS/. HEADING INTO TONIGHT...COMPLEX STORM EVOLVES WHICH WILL BECOME AN INCREASED AVIATION CONCERN WITH A COMBINATION OF PRECIP/CIGS-VIS AND POTENTIAL FOR LLWS. OUTLOOK... THU OVNGT-FRI...MVFR/IFR...-SHRA. CHC LLWS. FRI NGT-SAT NGT...MVFR/IFR...-SHRA CHG TO -SHSNRA. POSS LLWS. WINDY. SUN...VFR. NO SIG WX. MON...MVFR/IFR. -RA/-SN. && .HYDROLOGY... THE NEXT CHANCE OF WIDESPREAD PRECIPITATION WILL BE FROM LATE THURSDAY NIGHT INTO THE EARLY PART OF THE WEEKEND...AS A POTENTIALLY STRONG STORM MAY IMPACT THE REGION. THERE IS STILL A HIGH AMOUNT OF UNCERTAINTY WITH REGARDS TO THE EVOLUTION OF THE STORM AND ASSOCIATED QPF. SOME OF THE MODEL GUIDANCE DEPICTING SIGNIFICANT QPF ACROSS AREAS NORTH AND EAST OF ALBANY...HOWEVER OTHER SOURCES OF GUIDANCE TARGET AREAS TO THE SOUTH AND EAST. DEPENDING ON HOW THE STORM EVOLVES...SOME OF THE PRECIP MAY FALL AS SNOW AS WELL...ESPECIALLY ACROSS THE HIGHER ELEVATIONS. QPF AMOUNTS AND LOCATIONS ARE UNCERTAIN...BUT SOME AREAS MAY RECEIVE GREATER THAN ONE INCH. AT THIS TIME IT APPEARS SOME RISES WILL OCCUR ON RIVERS BUT SHOULD REMAIN WITHIN THEIR BANKS. DRY AND WINDY WEATHER IS EXPECTED FOR SATURDAY AS THE STORM PULLS AWAY INTO THE CANADIAN MARITIMES. WEAK HIGH PRESSURE WILL RESULT IN DRY CONDITIONS THROUGH SUNDAY. 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. && $$ AVIATION...BGM WWW.WEATHER.GOV/ALBANY