000 FXUS61 KALY 250213 AFDALY AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBANY NY 913 PM EST TUE NOV 24 2009 .SYNOPSIS... WEAK HIGH PRESSURE WILL HOLD OVER THE REGION THROUGH WEDNESDAY BEFORE DRIFTING OFFSHORE ON THANKSGIVING. RAIN SHOWERS...CHANGING TO SNOW SHOWERS ARE EXPECTED BY THE END OF THE WEEK AND EARLY IN THE WEEKEND AS LOW PRESSURE MOVES ACROSS THE REGION. && .NEAR TERM /THROUGH TONIGHT/... COMPLEX CLOUD LAYER EVOLUTION TONIGHT...AS LOW CLOUDS TRACK WEST AND SOUTHWEST ACROSS SOUTHERN NEW ENGLAND INTO THE MID HUDSON VALLEY. WEAK SURFACE HIGH IN SOUTHEASTERN CANADA CONTINUES TO NOSE INTO THE REGION...WITH LIGHT NORTHEAST TO EAST LOW LEVEL FLOW. MID AND HIGH CLOUDS WELL IN ADVANCE OF THE SYSTEM IN THE MIDWEST CONTINUE TO TRACK EAST AND THE EASTERN PERIPHERY IS DRYING UP OVER EASTERN NY. AREAS OF WESTERN NEW ENGLAND AND THE CATSKILLS HAVE SOME CLEARING. BASED ON SATELLITE TRENDS...LOW CLOUDS WILL CONTINUE TO MOVE INTO THE MID HUDSON VALLEY...AND MID AND HIGH CLOUDS WILL BUILD EAST IN INTERVALS THROUGH THE NIGHT. SO...MOST AREAS WILL SEE PERIODS OF CLOUDS...BUT DURING THE PERIODS OF CLEARING...THE TEMPERATURES WILL RAPIDLY DROP AND PATCHY DENSE FOG WILL FORM. SOME OF THE LOW CLOUDINESS IN THE MID HUDSON VALLEY COULD EXPAND ACROSS THE REGION OR JUST DEVELOP NORTHWARD AS TEMPERATURES FALL TO DEW POINTS. WITH THE LIGHT WINDS...AND AREAS OF CLEARING...SOME TEMPERATURES HAVE DROPPED RAPIDLY ALREADY... WHILE OTHER AREAS THAT HAVE BEEN IN THE CLOUDS HAVE NOT DROPPED MUCH AT ALL. CURRENT PREDICTED MINIMUM TEMPERATURES SEEM IN THE BALL PARK BASED ON EXPECTED INTERVALS OF CLOUDS AND CLEARING. ALSO KEEPING PATCHY DENSE FOG. ADJUSTED SKY COVER A BIT. OTHERWISE...NO OTHER CHANGES. PREV AFD BELOW... CLOUDS ARE LIKELY TO REFORM TONIGHT DUE TO MOISTURE TRAPPED UNDERNEATH THE INVERSION. AT THE SURFACE...WEAK HIGH PRESSURE WILL BUILD DOWN FROM CANADA AND THE WEAKENESS OF THE HIGH FAVORS A PRETTY GOOD INVERSION AND THE REFORMATION OF THE STRATUS CLOUDS... ESPECIALLY IN VALLEY AREAS. HOWEVER...IF THE SKY WERE TO REMAIN CLEAR...FOG WOULD LIKELY FORM ANYWAY. WITH THE HIGH DEWPOINTS AND FOG/STRATUS LIKELY TO FORM...PREFER THE WARMER MET MOS TEMPS AND HAVE FORECAST LOWS IN THE 30S. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY/... WEDNESDAY STILL LOOKS TO BE MAINLY DRY ACROSS OUR REGION. AFTER STARTING OUT WITH SOME PATCHY DENSE FOG AND/OR LOW CLOUDS...SOME FILTERED SUNSHINE IS LIKELY BEFORE HIGH CLOUDS BEGIN MOVING IN FROM THE WEST. A WEAK SHORT WAVE TROF COULD BRING A FEW SHOWERS...BUT HAVE ONLY FORECAST LOW OR SLIGHT CHANCE POPS DURING THE AFTERNOON. SOMEWHAT HIGHER POPS EARLY WEDNESDAY NIGHT AS THIS TROF MOVES THROUGH...THEN A DRY FORECAST FOR THANKSGIVING AS THE REGION REMAINS BETWEEN AN OFFSHORE SURFACE LOW AND AN UPPER LOW TO OUR WEST. MODELS OFFER DIFFERING VERSIONS AS TO WHAT MAY HAPPER THURSDAY NIGHT AND FRIDAY AS THESE TWO SYSTEMS INTERACT AND CLOSE IN ON THE REGION. RIGHT NOW THE FORECAST IS BASED PRIMARILY ON THE UPPER LEVEL SYSTEM AFFECTING THE REGION AS IT IS MOVES FROM WEST TO EAST ACROSS NEW YORK AND NEW ENGLAND. AS A RESULT...WILL KEEP THE PCPN SHOWERY FOR NOW...BUT WILL STILL FORECAST LIKELY POPS LATE THURSDAY NIGHT THROUGH FRIDAY. UPPER LEVEL TEMPS SUGGEST MAINLY RAIN SHOWERS THROUGH MOST OF THE DAY FRIDAY...BUT AS THE COLD POOL ASSOCIATED WITH THE UPPER LOW SLOWLY MOVES EAST...WESTERN HIGH TERRAIN AREAS COULD START TO GET SOME SNOW SHOWERS BY LATER IN THE DAY. TEMPS DURING THE PERIOD...HIGHS WILL BE IN THE UPPER 40S TO MID 50S ON WEDNESDAY AND THURSDAY...AND LOW OR MID 40S FRIDAY. LOWS WEDNESDAY NIGHT WILL BE IN THE 30S TO AROUND 40S...AND THE MID 30S TO AROUND 40 THURSDAY NIGHT. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... MODEL CONSISTENCY CONTINUES CONCERNING THE NOR`EASTER...BUT THEREAFTER MODELS DIVERGE...WITH HPC FAVORING A SOLUTION SOMETHING BETWEEN THE GFS AND THE ECMWF. HAVE THUS SELECTED HPC AS THE PRIMARY SOLUTION FOR THE PERIOD. THE DEEP COASTAL LOW IS HEADING UP OVER THE CANADIAN MARITIMES AT THE START OF THE PERIOD. A RELATIVELY STRONG NORTHWESTERLY FLOW WILL BEGIN TO SUBSIDE SATURDAY NIGHT AS THE PRESSURE GRADIENT BEGINS TO WEAKEN. THERE`S A GOOD CHANCE OF LAKE-ENHANCED SNOW SHOWERS UNTIL THEN...WITH MEASURABLE AMOUNTS INCREASINGLY LIKELY TOWARD LAKE ONTARIO...ALTHOUGH IT SHOULDN`T BE MUCH AS THINGS WIND DOWN QUICKLY. A SYSTEM OUT OF THE CENTRAL ROCKIES WILL BRING THE NEXT CHANCE OF PRECIP MONDAY THROUGH TUESDAY. THERE IS GREAT UNCERTAINTY CONCERNING THE PROGRESS OF THIS SYSTEM. IT COULD PRODUCE ANYTHING FROM ALL SNOW TO MOSTLY RAIN OR ANYTHING IN BETWEEN. GIVEN THE HPC TRACK OF THE LOW...A LIGHT SOUTHEASTERLY FLOW SHOULD ENSUE AHEAD OF IT...TENDING TO MOVE THE EVENT...OVERALL...TOWARD MORE OF A RAINY SOLUTION ON TUESDAY. HIGHS ON SATURDAY WILL RANGE MAINLY FROM THE MID 30S TO MID 40S. INCREASING SUNSHINE ON SUNDAY SHOULD HELP BALANCE THE EFFECTS OF COLD AIR INTRUSION BEHIND THE DEPARTING COASTAL LOW...RESULTING IN LITTLE CHANGE IN DAYTIME TEMPERATURES. SLIGHT MODERATION AHEAD OF THE NEXT SYSTEM WILL RAISE MONDAY`S HIGHS ABOUT 5 DEGREES...WHERE THEY`LL MORE OR LESS STAY PUT FOR TUESDAY. LOWS THROUGH THE PERIOD WILL BE MAINLY IN THE 20S AND LOWER 30S. NORMAL HIGHS IN ALBANY FOR THE END OF NOVEMBER ARE AROUND 40 DEGREES...WITH LOWS AROUND 25. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... WEAK HIGH PRESSURE IS BUILDING IN FROM CANADA...BUT SOME CLOUD COVER IS DRIFTING SOUTH AND SOUTHWEST OUT OF WESTERN NEW ENGLAND ON WEAK EAST TO NORTHEAST FLOW. MID CLOUDS ARE TRACKING NORTHEAST OUT OF THE OH VALLEY AND CENTRAL PA/NY IN ADVANCE OF THE NEXT SYSTEM. SO...THERE IS A HOLE IN THE CLOUDS OVER POU...WITH THE HOLE WORKING NORTH SLOWLY...BUT AT THE SAME TIME SLOWLY BEING PINCHED OFF BY THE CLOUDS IN WESTERN NEW ENGLAND. SO...KPOU SHOULD BE CLEAR FOR AT LEAST A FEW HOURS THIS EVENING...AND AS TEMPERATURES DROP...SOME FOG COULD FORM BEFORE 05Z. SOME CLEARING COULD BUILD NORTH INTO KALB BETWEEN 01Z- 03Z...AND AGAIN...SOME FOG COULD FORM BY 05Z. MID CLOUDS AROUND GFL COULD BREAK UP TOWARD 03Z-05Z...POSSIBLY CONTRIBUTING TO FOG FORMATION 05Z-06Z. ANY FOG THIS EVENING SHOULD BE MVFR AT WORST. LOW CLOUDINESS IN WESTERN NEW ENGLAND SHOULD SPREAD TO KPOU AFTER MIDNIGHT...AND BASED ON RELATIVELY HIGH DEW POINTS ACROSS THE REGION...ONCE TEMPERATURES FALL TO DEW POINTS AT KALB AND KGFL...LOW CEILING IN ADDITIONS TO FOG SHOULD DEVELOP THERE AFTER MIDNIGHT. SO...INDICATING CEILINGS AND VISIBILITIES JUST INTO IFR AT ALL SITES AFTER 06Z. THIS ALL DEPENDS ON HOW THE MID CLOUDS IN CENTRAL/WESTERN NY/PA EVOLVE. IF MID/HIGH CLOUDS SPREAD OVER THE ENTIRE REGION...WE MAY STAY AT MVFR OR VFR ALL NIGHT. CONDITIONS WILL IMPROVE TO MVFR BY 14Z-15Z TOMORROW...AND VFR BY 18Z- 19Z...CONTINUING THROUGH THE REST OF THE AFTERNOON. WINDS WILL BE LIGHT NORTH TO EAST TONIGHT AT 5 KT OR LESS...AND EAST TO SOUTHEAST AT 5 KT OR LESS TOMORROW. OUTLOOK... WED...VFR/MVFR...CIGS. NO SIGN WX EXPECTED AT THIS TIME. WED NT...MVFR...CHC IFR FOR FOG/DZ. THANKSGIVING DAY...VFR/MVFR...CIG...NO SIG WX EXPECTED AT THIS TIME. THU NGT-FRI...VFR TO MVFR/IFR...RAIN LIKELY. CHC LLWS. FRI NGT-SAT...MVFR/IFR...CHC -RA CHANGING TO -RASN. CHC LLWS. SUN...VFR. && .HYDROLOGY... NO HYDRO PROBLEMS THROUGH THANKSGIVING DAY. 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. HOWEVER...AT THIS POINT... ENOUGH RAINFALL TO SIGNIFICANTLY IMPACT AREA STREAMS AND RIVERS DOES NOT APPEAR LIKELY. 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...NAS NEAR TERM...NAS