Issued by NWS Buffalo, NY
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-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --000 FXUS61 KBUF 211433 AFDBUF AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BUFFALO NY 933 AM EST SAT NOV 21 2009 .SYNOPSIS... HIGH PRESSURE WILL BUILD OVER THE REGION THIS WEEKEND BEFORE SHIFTING OFF THE NEW ENGLAND COAST BY EARLY NEXT WEEK. WHILE HIGH PRESSURE WILL BE IN PLACE TODAY...RESIDUAL CLOUD COVER WILL REMAIN BEFORE GIVING WAY TO SUNSHINE FOR SUNDAY AND MONDAY. A STORM SYSTEM WILL APPROACH FROM THE MIDWEST ON WEDNESDAY AND BRING THE NEXT CHANCE OF RAIN WITH UNSETTLED CONDITIONS LASTING THROUGH THE END OF THE WEEK. TEMPERATURES WILL CONTINUE TO REMAIN ABOVE AVERAGE THROUGH THE FIRST HALF OF NEXT WEEK BEFORE A COOLING TREND BY THE THANKSGIVING HOLIDAY. && .NEAR TERM /THROUGH TONIGHT/...-- Changed Discussion --930 AM UPDATE...LOCALLY DENSE FOG FORMED AROUND SUNRISE ACROSS MUCH OF THE AREA..BUT IT HAS JUST ABOUT DISSIPATED AS OF 1430Z. WE WILL THEN HAVE TO DEAL WITH PLENTY OF LOW LEVEL MOISTURE TODAY...WITH SOME BREAKS ON VIS SATELLITE ATTM..ESPECIALLY ACROSS WRN SRN TIER...SET TO FILL IN AS WE GET A BIT OF MIXING. WV LOOP SHOWS WEAK MID LEVEL TROF MOVING ACROSS NRN OHIO WITH SOME ENHANCED CLOUDINESS OVER LK ERIE AND EVEN A FEW LK EFF SHWRS NORTH OF CLEVE. THESE SHOULD TEND TO DISSIPATE BY NOON AS THEY DRIFT EAST BUT WILL INSERT SLGT CHC POPS CHAUT CO TILL ABOUT 17Z. OTHERWISE...OUR PROBLEM TODAY WILL BE THE "DIRTY" SFC HIGH SPRAWLED OVER THE LAKES. CANT RULE OUT A FEW SUNNY BREAKS...BUT JUST TOO MUCH LOW LEVEL MOISTURE TO ALLOW FOR MUCH...SO WILL CONTINUE WITH A MOSTLY CLOUDY FORECAST FOR THE AFTERNOON. TEMPS WONT BUDGE MUCH...HOLDING MOSTLY IN U40S WITH LGT WINDS. MODELS CONTINUING TO INSIST THAT IMPROVING CONDITIONS WILL TAKE PLACE TONIGHT. MID LEVEL RIDGING ADVANCING INTO THE REGION TONIGHT BEHIND THE UPPER WAVE WILL HELP PUSH OUT THE MID LEVEL MOISTURE AND SOME SHALLOW WARM AIR ADVECTION COULD WEAKEN THE SUBSIDENCE INVERSION AND ALLOW FOR SOME PARTIAL CLEARING. ANY CLEARING WILL RESULT IN THE DEVELOPMENT OF FOG LATE TONIGHT. TEMPERATURES OVERNIGHT WILL DEPEND GREATLY ON AMOUNT OF CLEARING WHICH CAN TAKE PLACE. WITH LITTLE CHANGE IN AIR MASS EXPECTED WILL LEAN OVERNIGHT TEMPERATURES TOWARD BIAS CORRECTION NUMBERS SUGGESTING UPPER 20S TO LOWER 30S ALONG THE SOUTHERN TIER AND EAST OF LAKE ONTARIO TO THE MID AND UPPER 30S ALONG THE LAKE PLAIN.-- End Changed Discussion --&& .SHORT TERM /SUNDAY THROUGH TUESDAY/... AT THE START OF THE PERIOD AN EXPANSIVE AREA OF HIGH PRESSURE WILL STRETCH FROM QUEBEC SOUTHWARD ACROSS THE LOWER LAKES AND DOWN THE APPALACHIANS. SOME STRATUS MAY STILL LINGER IN THE MORNING ACROSS THE HIGHER TERRAIN OF THE SOUTHERN TIER...BUT EXPECT CONTINUED SUBSIDENCE AND DRYING TO FINALLY ERODE THIS AND LEAVE PLENTY OF SUNSHINE EVERYWHERE DURING THE AFTERNOON. 850MB TEMPS OF AROUND +4C WILL CONTINUE TO SUPPORT ABOVE AVERAGE TEMPS WITH HIGHS IN THE LOWER 50S IN MOST LOCATIONS...WITH UPPER 40S ACROSS THE NORTH COUNTRY. THE SURFACE HIGH WILL SLOWLY DRIFT INTO THE CANADIAN MARITIMES BY MONDAY. SOUTHEAST RETURN FLOW MAY ALLOW SOME INCREASE IN MOISTURE DURING THE DAY ACROSS THE SOUTHERN TIER...BUT OTHERWISE EXPECT A FAIR AMOUNT OF SUNSHINE. SIMILAR 850MB TEMPS WILL SUPPORT HIGHS IN THE LOWER 50S AGAIN ACROSS THE LOWER ELEVATIONS...A FEW DEGREES COOLER ACROSS HIGHER TERRAIN. MONDAY NIGHT AND TUESDAY SIGNIFICANT MODEL DIFFERENCES BECOME APPARENT WITH THE HANDLING OF A WEAK COASTAL SYSTEM. MOISTURE CHANNEL IMAGERY SHOWS A WEAK SOUTHERN STREAM CUTOFF LOW MOVING THROUGH SOUTHEAST TEXAS EARLY THIS MORNING. THE GFS CONTINUES TO TAKE A PIECE OF THIS SYSTEM AND PLUME OF ASSOCIATED MOISTURE UP TO THE WEST OF THE APPALACHIANS...WITH ANOTHER PIECE OF ENERGY SPAWNING A WEAK COASTAL LOW OFF THE CAROLINAS. THIS ALLOWS A NOTABLE PERIOD OF RAIN TO LIFT NORTH ACROSS THE CWA MONDAY NIGHT AND TUESDAY IN THE GFS SOLUTION. THE NAM AND CANADIAN GEM EMPHASIZE THE COASTAL SYSTEM ONLY...KEEPING ALL OF THE PRECIP ALONG THE COASTAL PLAIN MONDAY NIGHT INTO TUESDAY. THE DIFFERENCE IN SENSIBLE WEATHER IS HUGE... WITH A RAINY GFS SOLUTION VERSUS A DRY AND EVEN PARTLY SUNNY NAM SOLUTION. THE NEW 00Z ECMWF JUST COMING IN ALSO SUPPORTS THE NAM SOLUTION WITH MOST IF NOT ALL OF THE PRECIP FOCUSING ALONG THE COAST. WILL CHOOSE TO FOLLOW THE MODEL CONSENSUS AND THROW OUT THE GFS SOLUTION. THIS ALLOWS US TO STAY CLOSE TO FORECAST CONTINUITY WITH A DRY FORECAST FOR MOST OF THE CWA MONDAY NIGHT AND TUESDAY. WILL KEEP SOME LOW CHANCE POPS EAST OF LAKE ONTARIO TO HANDLE THE POTENTIAL FOR COASTAL MOISTURE MAKING IT BACK THAT FAR WEST. && .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/... THE NOW WELL ADVERTISED PATTERN CHANGE STILL APPEARS ON TRACK TO ARRIVE FOR THE THANKSGIVING HOLIDAY. THE CURRENT PATTERN ACROSS THE NOAM SECTOR IS MORE OR LESS ZONAL...WITH TRANSIENT RELATIVELY LOW AMPLITUDE TROUGHS MOVING THROUGH THE WESTERLIES ALONG AND JUST NORTH OF THE US/CANADIAN BORDER. THE GEFS ENSEMBLE MEAN CONTINUES TO FORECAST THE NAO INDEX TO BECOME WEAKLY NEGATIVE BY THE END OF THE MONTH...WITH THE PNA INDEX TRENDING POSITIVE. IN THE MEAN...THIS SHOULD YIELD A COLDER PATTERN FOR THE GREAT LAKES AND NORTHEAST FOR THE LAST WEEK OF NOVEMBER INTO EARLY DECEMBER WITH A TROUGH FAVORED OVER THE EASTERN CONUS IN SUCH A PATTERN. THE INDICES ARE NOT FORECAST TO BE PARTICULARLY STRONG HOWEVER...SO NO DRAMATIC PATTERN CHANGE IS EXPECTED...RATHER A TREND TOWARDS COOLER AND MORE SEASONABLE TEMPERATURES. LOOKING AT THE DETAILS...THERE ARE STILL THE TYPICAL DIFFERENCES IN THE HANDLING OF SHORTWAVE FEATURES AND ASSOCIATED SURFACE SYSTEMS FOR THE SECOND HALF OF THE WEEK. THE GFS CONTINUES TO EJECT A LEAD SHORTWAVE AND ASSOCIATED SURFACE LOW INTO THE GREAT LAKES REGION ON WEDNESDAY WITH ANOTHER SYSTEM FOR THURSDAY AND FRIDAY AS THE MAIN MID LEVEL TROUGH CROSSES THE REGION. THE ECMWF DOES NOT SUPPORT THIS FIRST LOW ON WEDNESDAY...BUT DOES COME INTO AGREEMENT WITH THE SYSTEM FOR THURSDAY/FRIDAY. THE CANADIAN GEM IS IN GOOD AGREEMENT WITH THE GFS SOLUTION SHOWING BOTH SYSTEMS. FOR NOW...GIVEN THE MODEL UNCERTAINTY WILL SIMPLY STICK WITH FORECAST CONTINUITY AND KEEP CHANCE POPS FROM WEDNESDAY RIGHT THROUGH FRIDAY. TEMPERATURES BECOME COLD ENOUGH BY THURSDAY AND FRIDAY TO BRING PRECIP TYPE ISSUES INTO THE FORECAST. ON THANKSGIVING...THE GFS FORECASTS 850MB TEMPS OF AROUND -4C WHILE THE ECMWF...WITH ITS SLOWER SINGLE LOW EVOLUTION HAS 850MB TEMPS ABOVE FREEZING STILL. HAVE LEANED TOWARDS THE GFS/GEM IDEA... BUT EVEN THIS WOULD STILL SUPPORT MAINLY RAIN ACROSS THE LOWER ELEVATIONS WITH A RAIN/SNOW MIX ACROSS HIGHER TERRAIN. COLDER AIR FILTERS INTO THE REGION THURSDAY NIGHT AND FRIDAY WITH A CHANCE OF RAIN/SNOW EVERYWHERE. AT THIS TIME...PATTERN DOES NOT LOOK AT ALL FAVORABLE FOR ANY MEANINGFUL SNOW...WITH JUST WEAK WRAP AROUND PRECIP AND AN UNFAVORABLE NW FLOW PREVENTING ANY SIGNIFICANT LAKE EFFECT. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...-- Changed Discussion --EARLIER IFR/LIFR RESTRICTIONS DUE TO FOG WILL HAVE IMPROVED TO MVFR CIGS OVER ALL SITES BY 15Z. PLENTIFUL AMOUNTS OF LOW LEVEL MOISTURE WILL CONTINUE TO CIRCULATE ACROSS THE FORECAST AREA THIS MORNING...THEN BECOME TRAPPED UNDER A DEVELOPING SUBSIDENCE INVERSION AS HIGH PRESSURE BUILDS EASTWARD FROM THE CENTRAL LAKES AND WESTERN OHIO VALLEY. MVFR CEILING RESTRICTIONS ANTICIPATED FOR MOST OF THE DAY. LATE THIS AFTERNOON AND EARLY EVENING...CLEARING SKIES ANTICIPATED. OUTLOOK... TONIGHT...POSSIBLE IMPROVEMENT FROM MVFR TO VFR. SUNDAY THROUGH TUESDAY...MAINLY VFR. WEDNESDAY...VFR WITH CHC SHOWERS.-- End Changed Discussion --&& .MARINE... WINDS AND WAVES WILL SLOWLY DIMINISH TODAY...ALTHOUGH CHOPPY CONDITIONS WILL CONTINUE. HIGH PRESSURE BUILDS OVER THE REGION TONIGHT AND SUNDAY WITH LIGHT WINDS. AS THE HIGH DEPARTS...EAST WINDS WILL INCREASE SOME ON MONDAY AND TUESDAY WITH CHOPPY CONDITIONS DEVELOPING ON THE WEST HALF OF LAKE ONTARIO...BUT CONDITIONS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...NONE. MARINE...NONE. && $$ SYNOPSIS...HITCHCOCK NEAR TERM...SFM/TMA SHORT TERM...HITCHCOCK LONG TERM...HITCHCOCK AVIATION...SFM/TMA MARINE...HITCHCOCK
