Issued by NWS Albany, NY
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-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --000 FXUS61 KALY 240845 AFDALY AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBANY NY 345 AM EST TUE NOV 24 2009 .SYNOPSIS...-- Changed Discussion --WEAK HIGH PRESSURE WILL BUILD IN FROM EASTERN CANADA TODAY...POSSIBLY BRINGING SOME BREAKS OF SUNSHINE FOR THE AFTERNOON. THIS HIGH PRESSURE WILL HOLD INTO WEDNESDAY BEFORE DRIFTING OFFSHORE BY THANKSGIVING. A FEW DISTURBANCES WILL SPREAD SOME CLOUDS OUR WAY WITH ONLY MINIMAL CHANCES OF RAIN SHOWERS.-- End Changed Discussion --&& .NEAR TERM /THROUGH TODAY/...-- Changed Discussion --AS OF 330 AM...RADARS STILL INDICATED SCATTERED LIGHT SHOWERS...MAINLY EAST OF THE HUDSON VALLEY. MORE THAN LIKELY...PATCHY DRIZZLE OUT THERE WHICH IS HARD TO DETECT ON RADAR. THE MAIN DISTURBANCE STAYED WELL TO OUR SOUTH AND EAST BUT A PRETTY GOOD ONSHORE FLOW SATURATED THE LOWER LEVELS OF THE COLUMN. NOW...THE CHALLENGE IS TO FORECAST WHEN ANY AND ALL PRECIPITATION ENDS AND IF THE CLOUDS WILL BREAK UP. THE LATTER IS NO EASY TASK SINCE ONCE AGAIN...ANY MIXING WILL BE MITIGATED BY THE MERE FACT THAT WE ARE DEALING WITH NO MORE THAN A 23 DEGREE SUN ANGLE. ALSO...MODEL SOUNDINGS INDICATE A PRETTY IMPRESSIVE SHALLOW INVERSION THAT WOULD HAVE BE WORKED OUT BEFORE MIXING WOULD SCOUR THE CLOUDS. WE FELL ANY SHOWER/DRIZZLE ACTIVITY SHOULD BE OVER BY AFTERNOON IN ALL AREAS. WE WILL FOLLOW THE CANADIAN ASTRONOMICAL FORECAST AND FORECAST SOME "BREAKS" BY AFTERNOON (CLOUD COVER INTO THE HIGH END OF THE SCATTERED RANGE). THE CANADIAN ASTRONOMICAL FORECAST ACTUALLY LOOKS SLIGHTLY OPTIMISTIC TO US BUT IT HAS HAD A PRETTY GOOD TRACK RECORD IN OUR OPINION. BREAKS OR NOT...MODEL SOUNDINGS FROM BOTH THE NAM AND GFS INDICATE THAT OUR HIGH TEMPERATURES WILL LIKELY FALL A LITTLE SHORT OF BOTH THE NAM AND MAV MOS NUMBERS...DESPITE STARTING OUT ON THE MILD SIDE. WE FIGURE HIGH TEMPERATURES WILL TOP OUT WITHIN A FEW DEGREES OF 50S REGION WIDE...PERHAPS MID 50S IN THE MID HUDSON VALLEY.-- End Changed Discussion --&& .SHORT TERM /TONIGHT THROUGH THURSDAY/...-- Changed Discussion --OUR CLOUD CHALLENGE HARDLY ENDS AFTER TODAY. TONIGHT...THE BIG QUESTION WILL BE WHETHER CLOUDS REFORM UNDERNEATH MOISTURE TRAPPED UNDERNEATH THE INVERSION OR NOT. AT THE SURFACE...WEAK HIGH PRESSURE WILL BUILD DOWN FROM CANADA. THE KEY IS THAT THE HIGH IS INDEED WEAK...AND DEVELOPS UNDERNEATH A RIDGE ALOFT. THIS SETUP FAVORS A PRETTY GOOD INVERSION WHICH WOULD FAVOR THE REFORMATION OF STRATUS CLOUDS...AT LEAST IN VALLEY AREAS. IF THE SKY WERE TO REMAIN CLEAR...FOG WOULD LIKELY FORM. SIGNALS ARE CROSSED WHETHER THE FOG OR STRATUS CLOUDS WOULD DOMINATE. SINCE THE JURY IS STILL OUT...WE WILL PLAY IT IN THE MIDDLE...GOING WITH PARTLY CLOUD CONDITIONS...EXCEPT MORE CLOUDS IN THE ESPECIALLY THE HUDSON VALLEY. WILL MENTION PATCHY DENSE FOG FOR NOW. DEWPOINTS UPSTREAM ARE NOT ALL THAT LOW (IN THE 30S) SO WE DO NOT LOOK FOR TEMPERATURES TO FALL BELOW NORMAL...BUT CERTAINLY COOLER THAN THIS OVERNIGHT WAS. LOOK FOR LOW TEMPS GENERALLY IN THE 30S...EXCEPT UPPER 20S IN SOME SHELTERED MOUNTAIN VALLEYS IN THE DACKS. WEDNESDAY...THE BIG TRAVEL DAY BEFORE THANKSGIVING...STILL LOOKS MAINLY DRY ACROSS OUR REGION. AFTER STARTING OUT WITH SOME PATCHY DENSE FOG AND/OR LOW CLOUDS...SOME FILTERED SUNSHINE IS POSSIBLE BEFORE MORE HIGH CLOUDS MOVE IN FROM THE WEST. THERE IS A SHORT WAVE FORECAST TO LIFT SOUTHWEST TO NORTHEAST ACROSS OUR REGION. HOWEVER...INTEGRATED MOISTURE IN THE COLUMN WILL BE LIMITED (ONCE YOU GET MUCH OFF THE DECK) WITH VERY LITTLE IF ANY ISENTROPIC LIFT. WE WILL CONTINUE THE SLIGHT CHANCE OF SHOWERS WEST OF THE HUDSON VALLEY OVER THE ELEVATED TERRAIN...BUT ANY ISOLATED SHOWERS IN THESE AREAS WOULD BE LIGHT AND SHOULD HAVE ALMOST NO IMPACT ON TRAVEL. MIXING LOOKS SLIGHTLY BETTER ON WEDNESDAY...BUT STILL LIMITED...AND NO WHERE NEAR THE TYPICAL H850...OR EVEN H925MB FOR THAT MATTER. THIS WOULD TRANSLATE TO SURFACE TEMPERATURES A COUPLE POINTS HIGHER THAN TODAY...GENERALLY IN THE 50-55 RANGE...EXCEPT 45-50 RANGE ACROSS THE HIGHER TERRAINS. NEVERTHELESS...THESE VALUES ARE A GOOD 5-7 DEGREES OVER NORMAL HIGHS. "QUITE" WEATHER WILL CONTINUE WEDNESDAY NIGHT ALTHOUGH BY THIS TIME...A SURFACE RIDGE OVER THE NORTHEAST WILL BEGIN TO BREAK DOWN. CLOUDS...FROM AN EVOLVING UPPER AIR LOW WELL UPSTREAM...WILL TEND TO INCREASE. TEMPERATURES OVERNIGHT WILL LIKELY BE ABOUT 5 DEGS MILDER THAN TUESDAY NIGHT...GENERALLY IN THE 35-40 RANGE...WITH SOME COLDER READINGS IN OUTLYING REGIONS. THANKSGIVING WILL SEE THE AFOREMENTIONED UPPER AIR LOW/TROUGH BEGINNING TO MOVE TOWARDS US FROM THE OHIO VALLEY...BUT AT A SNAILS PACE. ALL THE GUIDANCE WE HAVE PERUSED WOULD INDICATE NOTHING MORE THAN A FEW SCATTERED LIGHT SHOWERS OR POCKETS OF DRIZZLE WITH AN OTHERWISE DRY DAY. THERE COULD EVEN BE A FEW BREAKS OF MIDDAY SUNSHINE BUT CLOUDS LOOK TO INCREASE DURING THE AFTERNOON. EVEN SO...HIGH TEMPERATURES LOOKS VERY SIMILAR TO WEDNESDAY. MORE ABOUT THE EVOLVING UPPER AIR LOW WILL FOLLOW IN THE EXTENDED.-- End Changed Discussion --&& .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...-- Changed Discussion --...CONSIDERABLE UNCERTAINTY REMAINS WITH DEVELOPING NOR-EASTER... UNLIKE THIS TIME YESTERDAY...THE GFS AND ASSOCIATED INTERNATIONAL GLOBAL MODELS HAVE DIVERGED ONCE AGAIN. THE GFS AND RELATED ENSEMBLE DATA ARE IN A CLOSE CLUSTER WITH LOW STANDARD DEVIATIONS ALOFT AND AT THE SURFACE WHICH FAVORS AN IMPRESSIVE NOR-EASTER FOR THE REGION. HOWEVER...THE GGEM/ECMWF AND EVEN THE 18Z/23 DGEX POINT TOWARD A FURTHER OFFSHORE SURFACE CYCLONE WITH THE MAIN IMPACT FOR THE REGION FROM THE UPPER LOW. BASED ON CLOSE COLLABORATION WITH NEIGHBORING OFFICES AND HPC...WE WILL FAVOR THE 00Z ECMWF AT THE SURFACE AND BLEND THE 500MB FIELDS WHICH POINTS US TOWARD ANOTHER SCENARIO. BASED ON CSTAR RESEARCH OF COOL SEASON CUTOFF UPPER LOWS...WE WILL HAVE TO MONITOR THE HIGHER TERRAIN AS THESE SYSTEMS CAN PRODUCE A BIT MORE QPF WHICH SEEMS TO MAXIMIZE DURING THIS MONTH. WITH THE FURTHER OFFSHORE SURFACE WAVE...UPPER LOW SHOULD BECOME THE MORE DOMINANT PLAYER HEADING INTO FRIDAY AND HAVE ADJUST POPS DOWNWARD INTO THE LIKELY RANGE TO AVOID A LARGE SWING FROM THE PREVIOUS FORECAST. BASED ON THE AFOREMENTIONED CSTAR RESEARCH...WILL GO TOWARD THE HIGHER END OF LIKELY WITH REGARD TO POPS AND RAISE THE QPF ROUGHLY A TENTH OF AN INCH PER 1K FEET. THE QUESTION NEXT BECOMES THE THERMAL PROFILE AS COLD ADVECTION IS EXPECTED TO PURSUE THROUGH THE DAY. THIS IS EXPECTED TO BE AN ELEVATION DEPENDENT RAIN/SNOW LINE AS WE HAVE ATTEMPTED TO REFLECT THIS NOTION IN THE GRIDS/FORECAST THROUGH FRIDAY. EVENTUALLY...THE COLDER AIR WILL PENETRATE THE ENTIRE COLUMN FRIDAY NIGHT WITH MOST PRECIP IN THE FROZEN VARIETY. WE WILL CONTINUE TO MONITOR THE POTENTIAL FOR A DEFORMATION AXIS AS THE UPPER LOW SLOWLY LIFTS NORTHEAST OVERNIGHT. THE NEXT CONCERN WILL BE WINDS FRIDAY NIGHT INTO SATURDAY AS 30-50KT WINDS AT 925MB AND 850MB RESPECTFULLY ARE EXPECTED WITH TIGHT SURFACE PRESSURE GRADIENT AS DEEP SURFACE LOW OVER THE CANADIAN MARITIMES. COINCIDING WITH THE COLD ADVECTION THIS MAY JUSTIFY THE POTENTIAL FOR ADDITIONAL HEADLINES WITH RESPECT TO THE WIND. THESE HAZARDS WILL BE ADDRESSED IN THE HWO THIS MORNING. QUIETER WEATHER EXPECTED FOR THE SECOND HALF OF THE WEEKEND AS SUBSIDENCE UNFOLDS WITH ASSOCIATED HEIGHT AND SURFACE PRESSURE RISES. A LIGHT OVERRUNNING EVENT...PER THE ECMWF...MAY BRING A LIGHT WINTRY MIX TO THE REGION OVERNIGHT SUNDAY INTO MONDAY. CONFIDENCE IN THIS SCENARIO IS QUITE LOW AND WILL ONLY PLACE 20 POPS AT THIS TIME. TEMPERATURES THROUGH THE PERIOD WERE A BLEND OF HPC AND ECMWF.-- End Changed Discussion --&& .AVIATION /08Z TUESDAY THROUGH SATURDAY/... UPPER LEVEL TROUGH AXIS CONTINUES TO SLOWLY ADVANCE NORTHEAST. THIS FEATURE IS ASSOCIATED WITH MVFR CIG AND BORDERING IFR WITH LIGHT RAIN SHOWERS AND/OR DRIZZLE. EXPECT THESE CIGS TO OVERSPREAD THE TAF SITES THROUGH THE REMAINDER OF THIS MORNING. AS THIS TROUGH LIFTS NORTHEAST AND WEAKENS...SOME IMPROVEMENTS ARE EXPECTED WITH A DECREASE IN PRECIPITATION COVERAGE AND SLOWLY RISING CIGS. COULD SEE VFR CONDITIONS LATE TODAY WHICH MAY RESULT IN ISSUES AFTER SUNSET. SURFACE RIDGE AXIS IS EXPECTED TO BE OVER THE REGION RESULTING IN LIGHT WINDS AND PARTIALLY CLEAR CONDITIONS. WITH EXPECTED AMPLE LOW LEVEL MOISTURE...WE COULD BE SETTING THE STAGE FOR FOG. WE WILL TREND TAFS INTO THIS DIRECTION AND MONITOR TRENDS/FORECAST SOUNDINGS. OUTLOOK... TUE OVNGT...VFR...CHANCE FOR IFR WITH FOG. 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. && .HYDROLOGY...-- Changed Discussion --NO HYDRO PROBLEMS THROUGH THANKSGIVING DAY. VERY LITTLE RAIN FELL WITH THE LAST SYSTEM AND HAD NO AFFECT ON RIVERS AND STREAMS. MAINLY DRY WEATHER EXPECTED THROUGH THANKSGIVING...WITH ANY LIGHT SHOWERS BRINGING WELL UNDER A TENTH OF AN INCH AND HAVING NO BEARING ON WATERSHEDS THROUGH THE HYDROLOGICAL SERVICE AREA. THE NEXT CHANCE OF WIDESPREAD PRECIPITATION WILL BE FROM LATE THURSDAY NIGHT INTO THE WEEKEND...AS A POTENTIALLY STRONG STORM MAY IMPACT THE REGION. SIGNIFICANT PRECIPITATION IS POSSIBLE BUT PRECIP AMOUNTS AND TYPE CONTINUE TO BE HIGHLY UNCERTAIN AT THIS TIME. 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.-- End Changed Discussion --&& .ALY WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. MA...NONE. VT...NONE. && $$ SYNOPSIS...HWJIV NEAR TERM...HWJIV SHORT TERM...HWJIV LONG TERM...BGM AVIATION...BGM HYDROLOGY...HWJIV
