558 FXUS61 KALY 231750 AFDALY AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBANY NY 1248 PM EST MON NOV 23 2009 .SYNOPSIS... SURFACE HIGH PRESSURE OFF THE CANADIAN MARITIMES WILL CONTINUE TO DRIFT NORTHEAST TODAY...AS A LOW PRESSURE SYSTEM ALONG THE CAROLINA COAST CONTINUES TO MOVE NORTHEASTWARD. THIS LOW PRESSURE SYSTEM WILL PASS FAR EAST OF CAPE COD ON TUESDAY...RESULTING IN MAINLY LIGHT RAIN ACROSS THE NORTHEAST...ESPECIALLY AREAS SOUTH AND EAST OF ALBANY TONIGHT INTO EARLY TUESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF NOON...UPDATE TO BUMP UP MAX TEMPS ACROSS EASTERN HALF OF CWA. NOON TEMPS HAVE APPROACHED OR EXCEEDED FORECAST MAXS IN SOME LOCALES. GIVEN TIME OF YEAR AND CLOUD COVER...NOT EXPECTING TEMPS TO JUMP SIGNIFICANTLY HIGHER...BUT DID ALLOW FOR 2-3 DEGREES MORE ON NOON TEMPS. && .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... WHILE THE MAIN SURFACE LOW SHOULD TRACK WELL TO OUR EAST AND SOUTH...INFLOW OFF THE ATLANTIC OCEAN ...AND "HINTS" OF AN INVERTED TROUGH...INDUCING LOW LEVEL ISENTROPIC LIFT...WILL KEEP THE THREAT OF SOME RAIN TONIGHT INTO EARLY TUESDAY. WE HAVE SEEN THIS SETUP A FEW TIMES THIS PAST FALL...AND IN SOME CASES...WAS ENOUGH TO BRING A SIGNIFICANT RAINSTORM EVEN WHEN THE MAIN SYSTEM STAYED WELL SOUTH AND EAST. THE DIFFERENCE IN THIS CASE IS THAT PWAT VALUES DON'T GET ALL THAT HIGH...(1/2-3/4 INCHES). ALSO...AND PROBABLY MORE IMPORTANTLY...MODEL SOUNDINGS INDICATE THAT THE CLOUDS MIGHT REMAIN MAINLY ICE-FREE...WHICH WOULD LIMIT THE SIZE OF THE WATER DROPLETS AND CONSEQUENCE ACCUMULATION OF WATER (SINCE THIS IS OF COURSE A NON-TROPIC ENVIRONMENT). THEREFORE...WE EXPECT MAINLY LIGHT RAIN WITH THIS SYSTEM. ALSO...REMOVED ANY MENTION OF SNOW SINCE H850 HPA AND H925 HPA TEMPERATURES REMAIN WELL ABOVE FREEZING WITH THIS SYSTEM. WENT HIGHER THAN ALL GUIDANCE FOR OVERNIGHT LOWS...GENERALLY BOTTOMING OUT IN THE 35-40 DEGREE RANGE. THE ISENTROPIC LIFT WILL SHIFT EAST ON TUESDAY...BUT THEN THE PROBLEM IS HOW LONG DOES IT TAKE FOR THE CLOUDS TO GO AWAY? THE GFS WOULD DICTATE SUNSHINE MUCH OF THE DAY...BUT WE DO NOT BUY THIS SOLUTION. THE SLOWER CLEARING NAM HAS CLIMATOLOGY ON ITS SIDE. AFTER ALL...NOV IS ALBANY/S CLOUDIEST MONTH AND THUS FAR...THIS MONTH AS NOT BEEN ALL THAT CLOUDY. HOWEVER...THE PAST FEW DAYS HAVE SEEN CLOUDS STUBBORNLY HANGING ON UNDERNEATH AN INVERSION. WITH A VERY LOW SUN ANGLE...IT IS HARD TO BREAK UP CLOUDS THIS TIME OF YEAR...AND WITH NO GOOD DOWNWARD MOTION OR DRYING BEHIND THE SYSTEM...EXPECT IT WILL TAKE MUCH OF THE DAY FOR THE CLOUDS TO BECOME SCATTERED. FOR THAT REASON...WENT LOWER THAN EVEN THE NORMALLY COOLER MET NOS...UNDERCUTTING THEM BY A DEGREE OR SO. SINCE DRYING LOOKS TO BEGIN ACROSS OUR NW ZONES...TEMPERATURES OVER THE DACKS WILL PROBABLY GET AS HIGH (IF NOT A TOUCH HIGHER) THAN TEMPS SAY OVER THE MID HUDSON VALLEY...AND NORTHWEST CONNECTICUT. OVERALL LOOK FOR TEMPERATURES TO TOP OUT IN THE 45 TO 50 DEGREE RANGE. THEN TUESDAY NIGHT...THE DILEMMA IS WHETHER OR NOT CLOUDS WILL REFORM UNDERNEATH A LOWERING SUBSIDENCE INVERSION AS WEAK HIGH PRESSURE BUILDS OVER THE REGION. MODEL SOUNDINGS DON'T GIVE A CLEAR SIGNAL WHETHER OR NOT THIS WILL HAPPEN. FOR NOW...WILL LEAN SLIGHTLY WITH THE COLDER MAV NOS AND CALL IT PARTLY CLOUDY. DID HOWEVER...ADD SOME PATCHY FOG AS WELL. ON WEDNESDAY NIGHT EXPECT LOWS TO DROP IN THE 30-35 RANGE...EXCEPT 20S UP NORTH. WEDNESDAY IS OF COURSE THE BIG TRAVEL DAY BEFORE THANKSGIVING. RIGHT NOW...TRAVEL CONDITIONS ACROSS OUR CWA LOOK NEARLY OPTIMAL IN THAT WE EXPECT LITTLE OR NO PRECIPITATION. (WE DO HAVE A SLIGHT CHANCE IN THE AFTERNOON TO THE WEST OF THE HUDSON VALLEY). THE DAY COULD START OUT AT LEAST PARTLY SUNNY...WITH AN INCREASE OF CLOUDS LATER IN THE AFTERNOON. IF WE CAN "MIX" OUT AT ALL...TEMPERATURES SHOULD REACH 50-55 IN THE VALLEYS...45-50 OVER THE HIGHER TERRAIN. THESE VALUES ARE A LITTLE ABOVE NORMAL. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... MUCH OF THE LONG TERM PERIOD WILL BE DOMINATED BY A DEVELOPING TROUGH ACROSS THE EASTERN CONUS AND THE POSSIBILITY OF A PHASED STORM SYSTEM AFFECTING THE NORTHEAST. GLOBAL MODEL CONSENSUS IS BECOMING MORE CLEAR WITH DEVELOPING MID-WEST/GREAT LAKES TROUGH TOWARD THANKSGIVING HOLIDAY. POTENT PACIFIC WAVE SEEN IN THE H2O VAPOR IMAGERY THIS EARLY MONDAY MORNING WAS SITUATED BETWEEN LONGITUDE 130-150W AND NORTH OF LATITUDE 40N. MODELS APPEAR TO CAPTURE THIS FEATURE QUITE WELL WHICH RESULTS IN GOOD MODEL CONSENSUS. IN FACT...LATEST GFS ENSEMBLE DATA REVEALS TOO THE GUIDANCE ENVELOPE IS NARROWING WITH 500MB AND SFC STANDARD DEVIATIONS ARE CLOSING WITH VALUES LESS THAN 20MB. WITH THAT SAID...THANKSGIVING DAY SHOULD REMAIN DRY YET THE CLOUD COVER WILL BE INCREASING RATHER QUICKLY. AS THE AFOREMENTIONED TROUGH EVOLVES UPSTREAM...SURFACE WAVE IS EXPECTED TO DEVELOP OFF THE MID ATLANTIC COAST AND TRACK NORTHEAST THANKSGIVING EVENING INTO FRIDAY. AMPLE MOISTURE WILL BE ADVECTING NORTHWARD WITH PWATS FORECAST TO CLIMB ABOVE 1 INCH. WITH THESE VALUES AND IMPRESSIVE DYNAMICS...RAINFALL COULD BE LOCALLY HEAVY AS WE WILL CLOSELY MONITOR TRENDS. AT THIS TIME...THERMAL PROFILES FAVOR MORE LIQUID THAN SOLID AND WILL CONTINUE TO TREND WEATHER GRIDS/FORECAST IN THIS DIRECTION. ON FRIDAY...DEEP UPPER LOW AND EXPECTED NEGATIVE TILT TO THE UPPER FLOW WILL BE SURE TO ALLOW THE SURFACE LOW TO DEEPENING ACCORDINGLY INTO A NOR-EASTER. AS THIS WAVE TRACKS NORTHEAST LATE FRIDAY INTO FRIDAY NIGHT...PRESSURE GRADIENT INCREASES AS THICKNESSES FALL QUICKLY. THIS WILL RESULT IN ANY PRECIPITATION TO BECOME MIXED WITH AND CHANCE TO SNOW SHOWERS OVERNIGHT. WE WILL NEED TO WATCH FOR THE POTENTIAL OF A DEFORMATION AXIS WHICH COULD RESULT IN THE REGIONS FIRST ACCUMULATING SNOWFALL...BUT MUCH TOO EARLY TO GET PINNED DOWN ON SPECIFICS AT THIS TIME. THE CHANCE FOR RAIN/SNOW SHOWERS CONTINUE INTO THE FIRST HALF OF THE HOLIDAY WEEKEND AS AN EXPECTED VERTICALLY STACKED SYSTEM MOVES INTO THE CANADIAN MARITIMES. WITH SUB ZERO 850MB TEMPS...HIGH TEMPERATURES WILL AT BEST BE INTO THE LOWER 40S IN THE VALLEY...WITH MAINLY 30S EXPECTED. WEATHER IMPROVES SUNDAY AS THE NOR-EASTER LIFTS FURTHER AWAY AND SUBSIDENCE/RIDGING TAKES HOLD OVER THE REGION. PTSUNNY AND DRY CONDITIONS EXPECTED AT THIS TIME WITH A COUPLE DEGREE REBOUND EXPECTED IN THE AFTERNOON. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... VFR CONDITIONS AT KGFL AND KALB TO START THE PERIOD WILL DETERIORATE TO MVFR CIGS LATE THIS AFTERNOON. KPOU HAS FILLED IN WITH MVFR CIGS AS OF 1745Z. MVFR CLDS APPROACHING KGFL...HAVE INCLUDED TEMPO THROUGH 22Z. UPSTREAM SYSTEM ACROSS THE VIRGINIAS ARRIVES LATE TODAY INTO TONIGHT WITH AREAS OF DRIZZLE/LIGHT RAIN EXPECTED. THIS WILL RESULT IN PERSISTENT MVFR CIGS WITH MVFR VSBYS FOLLOWING THIS EVENING. THERE IS AN INCREASED POTENTIAL FOR IFR CONDITIONS OVERNIGHT...ESP AT KGFL WITH LIGHTER WINDS RESULTING IN IFR VSBYS. PRECIP EXPECTED TO ONLY BE VCSH AT KGFL WHILE MAIN SHIELD OF PRECIP WILL REACH KPOU THIS AFTERNOON AND KALB THIS EVENING. PRECIP WILL BE LIGHT BUT PERSIST THROUGH TUESDAY MORNING. CONDITIONS IMPROVING TO MVFR AT ALL TERMINALS BY LATE MORNING...FURTHER IMPROVING TO VFR IN THE AFTERNOON. WINDS WILL CONTINUE FROM THE N/NE AT 3-6KTS...DISSIPATING TO LGT AND VRB OVERNIGHT. LATE TUESDAY MORNING...WINDS WILL BE OUT OF THE N TO NE AROUND 5KTS. OUTLOOK... TUE PM-WED...VFR...NO SIG WX EXPECTED. WED NT-SAT...VFR TO MVFR/IFR...RAIN POSSIBLE THU THRU SAT. && .HYDROLOGY... THE NEXT THREAT OF PRECIPITATION WILL BE LATE TODAY INTO EARLY TUESDAY. EXPECT TOTAL QPF AMOUNTS TO BE FAIRLY LIGHT WITH LESS THAN A TENTH OF AN INCH OF QPF ACROSS NW ZONES TO A LITTLE OVER A THIRD OF AN INCH FAR SOUTHEAST ZONES. THIS EVENT SHOULD HAVE VERY LITTLE IMPACT ON RIVERS AND STREAMS. FURTHER OUT AN UNSETTLED PERIOD OF WEATHER LATE THURSDAY INTO THE WEEKEND COULD RESULT IN SIGNIFICANT PRECIPITATION AMOUNTS. 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...HWJIV/KGS NEAR TERM...OKEEFE/KGS SHORT TERM...HWJIV LONG TERM...BGM AVIATION...KGS HYDROLOGY...HWJIV/11