Issued by NWS Burlington, VT
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-- Discussion containing changed information from previous version are highlighted. --000 FXUS61 KBTV 211917 AFDBTV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BURLINGTON VT 217 PM EST SAT NOV 21 2009 .SYNOPSIS...-- Changed Discussion --HIGH PRESSURE ACROSS THE GREAT LAKES AND OHIO VALLEY STATES WILL BUILD SLOWLY EAST TONIGHT AND SETTLE ACROSS THE NORTHEAST ON SUNDAY INTO MONDAY. THEREFORE...OUTSIDE ANY LINGERING CLOUDS ACROSS THE AREA THIS EVENING...EXPECT GENERALLY FAIR AND DRY WEATHER DURING THE PERIOD AS TEMPERATURES REMAIN ON THE MILD SIDE. THE NEXT CHANCE OF SIGNIFICANT PRECIPITATION WILL OCCUR BY THE MIDDLE TO LATER PORTIONS OF NEXT WEEK AS LOW PRESSURE TRACKS EAST FROM THE CENTRAL PLAINS.-- End Changed Discussion --&& .NEAR TERM /THROUGH TONIGHT/...-- Changed Discussion --AS OF 217 PM EST SATURDAY...QUIET CONDS ON TAP FOR TONIGHT AS BROAD HIGH PRESSURE BUILDS SLOWLY EASTWARD INTO THE AREA ALONG WITH DRY WX. ONLY PROBLEMATICAL QUESTION IN THE FCST FOR TONIGHT WILL BE HOW LONG PESKY LL STRATOCUMULUS DECK PERSISTS ACROSS PORTIONS OF THE AREA. CURRENT ACARS DATA OUT OF MONTREAL (CYUL) CONTINUES TO SHOW VERY SHARP SUBSIDENCE INVERSION NEAR 900 MB THIS AFTERNOON...AND ALONG WITH OROGRAPHICALLY FAVORABLE THOUGH WEAK NORTHWESTERLY FLOW CLOUDS HAVE HUNG TOUGH ACROSS MANY AREAS TODAY. GIVEN THESE FACTORS HAVE TRENDED TOWARD IDEA OF SOME BRIEF CLEARING EARLY THIS EVENING...THEN MORE CLOUDS LATER TONIGHT ALONG WITH SOME PATCHY BR/FG. WITH THE CLOUDS...LIGHT WINDS AND OVERALL LACK OF ADVECTIVE PROCESSES...MIN TEMPS WILL HOLD FAIRLY MILD OVERNIGHT BY LATE NOVEMBER STANDARDS ...BOTTOMING OUT GENERALLY IN THE UPPER 20S TO LOWER 30S MOST LOCALES.-- End Changed Discussion --&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...-- Changed Discussion --AS OF 217 PM EST SATURDAY...TRANQUIL AND MILD LATE FALL WEATHER THEN CONTINUES THROUGH THE REMAINDER OF THE SHORT TERM AS AFOREMENTIONED HIGH PRESSURE BUILDS ATOP THE NORTHEAST DURING SUNDAY/MONDAY TIME FRAME. THEREFORE EXPECT FAIR AND DRY CONDS THROUGH THE PERIOD ALONG WITH A FAIRLY WIDE DIURNAL RANGE IN TEMPS. WITH SHALLOW NATURE OF PBL THIS TIME OF YEAR DAYTIME TEMPS WILL BE RATHER UNIFORM... SLIGHTLY MILDER PERHAPS AT THE HIGHER ELEVATIONS WHERE SHALLOW PBL MIXING MAY BE ABLE TO TAP INTO WARMER 925 MB TEMPS ALOFT. NIGHTTIME LOWS WILL BE NEAR SEASONAL NORMS...THOUGH WITH AT LEAST SOME RADIATIVE EFFECTS EXPECTED...HAVE UNDERCUT MOS MINS TEMPS SLIGHTLY DURING OVERNIGHT PERIODS. BY MONDAY NIGHT...SOME DISAGREEMENT BEGINS TO CREEP INTO THE MODELS AS DEEPER MOISTURE ACROSS THE SOUTHEAST/WRN ATLANTIC ATTEMPTS TO CREEP NORTHWARD BENEATH WESTERN EXTENSION OF DEPARTING RIDGE AXIS. AT THIS TIME BELIEVE ANY DEEPER MOISTURE WILL HAVE A TOUGH TIME REACHING THIS FAR NORTH GIVEN PLACEMENT OF LL RIDGE AXIS...AND WITH BROAD SUPPORT FROM THIS MORNINGS OP ECMWF RUN AND GFS MEAN ENSEMBLES HAVE KEPT SENSIBLE CONDS ESSENTIALLY DRY THROUGH 12Z TUESDAY. MID TO UPPER LVL CLOUDS WILL LIKELY BE ON THE INCREASE HOWEVER IN UPPER ANTICYCLONIC FLOW...THUS HAVE KEPT OVERNIGHT MIN TEMPS SLIGHTLY MILDER THAN PRIOR COUNTERPARTS.-- End Changed Discussion --&& .LONG TERM /TUESDAY THROUGH FRIDAY/... AS OF 411 AM EST SATURDAY...AS THE ABOVE MENTIONED SYSTEM MOVES UP THE ATLANTIC COAST THE POTENTIAL FOR SHOWERS IN SOUTHERN ZONES INCREASES MON NIGHT...WITH SHOWERS POSSIBLE IN EASTERN VT AND EVEN CENTRAL/EASTERN DACKS TUESDAY. FOR MID WEEK THERE REMAINS CONSIDERABLE DISAGREEMENT OF GUIDANCE WITH HANDLING OF SHORTWAVE OVER THE HEARTLAND. MORE SPECIFICALLY...WITH THE FUJIWHARA EFFECT BETWEEN THE PRIMARY UPPER LOW AND PACIFIC ENERGY THAT ENTERS THE BROAD TROUGH. THE GFS OFFERS A MUCH MORE PROGRESSIVE SOLUTION...THOUGH HAS BEEN MUCH MORE INCONSISTENT FROM RUN TO RUN. THE ECMWF`S LESS PROGRESSIVE SOLUTION HAS BEEN MORE CONSISTENT AND IS THEREFORE FAVORED. UNDER THE ECMWF SOLUTION THE POTENTIAL FOR WIDESPREAD PRECIPITATION TUESDAY NIGHT AND WEDNESDAY IS MARKEDLY LESS THAN MOS GUIDANCE INDICATES...AS THE RIDGE OF HIGH PRESSURE TRIES TO REMAIN OVER THE REGION. THROUGH DIFFERING SOLUTIONS...BOTH GFS AND ECMWF EVENTUALLY BRING PRECIPITATION INTO THE NORTHEAST AROUND THE HOLIDAY...ESPECIALLY LATE THURSDAY INTO FRIDAY. BOTH ALSO BRING THE FIRST TRUE SEASONAL AIRMASS INTO THE NORTHEAST TOWARD THE END OF THE WORK WEEK. GIVEN THE UNCERTAINTY IN PLACEMENT OF SFC FEATURES AND THUS PLACEMENT OF THE COLD AIR...HAVE MAINTAINED THE RAIN/SNOW FORECAST...EXCEPT AT HIGHER ELEVATIONS WHICH SHOULD BE COLD ENOUGH FOR ALL SNOW. && .AVIATION /19Z SATURDAY THROUGH THURSDAY/...-- Changed Discussion --THROUGH 18Z SUNDAY...LOW CLOUDS HAVE BEEN HANGING IN ACROSS MOST OF THE REGION TODAY...ESPECIALLY OVER THE HIGHER TERRAIN...AS A LOW LEVEL INVERSION HAS TRAPPED THIS MOISTURE IN THE LOWER LEVELS. CONDITIONS RANGE FROM VFR CONDITIONS IN VALLEY LOCATIONS TO MVFR OVER THE HIGHER ELEVATION. EXPECTING SOME OF THIS CLOUD COVER TO BECOME SCATTERED AFTER 00Z SUNDAY...EXCEPT OVER THE ADIRONDACKS AND PORTIONS OF THE GREEN MOUNTAINS. EXPECTING SOME FOG AND MIST TO DEVELOP TONIGHT...MAINLY AFTER 05Z SUNDAY...WITH SOME MVFR CEILINGS AS A HIGH PRESSURE AREA BUILDS INTO THE REGION FROM THE OHIO VALLEY. ANY FOG OR MVFR CEILINGS WILL DISSIPATE BY 14Z SUNDAY...WITH SKIES BECOMING MAINLY CLEAR. OUTLOOK 18Z SUNDAY THROUGH THURSDAY...MAINLY VFR CONDITIONS EXPECTED FROM 18Z SUNDAY THROUGH 12Z TUESDAY AS A RIDGE OF HIGH PRESSURE WILL BE OVER THE REGION. MAINLY VFR CONDITIONS EXPECTED FROM 12Z TUESDAY THROUGH 18Z WEDNESDAY...AS A WEAK RIDGE OF HIGH PRESSURE WILL BE OVER THE REGION. 18Z WEDNESDAY THROUGH 12Z THURSDAY...AREAS OF MVFR IN SHOWERS. 12Z THURSDAY THROUGH 00Z FRIDAY...MAINLY VFR.-- End Changed Discussion --&& .BTV WATCHES/WARNINGS/ADVISORIES... VT...NONE. NY...NONE. && $$ SYNOPSIS...JMG NEAR TERM...JMG SHORT TERM...JMG LONG TERM...AMF AVIATION...WGH
