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000 FXUS02 KWBC 221839 PMDEPD EXTENDED FORECAST DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 139 PM EST SUN NOV 22 2009 VALID 12Z WED NOV 25 2009 - 12Z SUN NOV 29 2009 THE ECMWF CONTINUES TO BE THE MOST CONSISTENT OF THE GLOBAL MODELS WITH THE HANDLING OF THE UPCOMING PATTERN ACROSS THE NATION...SO ONCE AGAIN RELIED HEAVILY ON ITS MASS FIELDS TO CONSTRUCT THE PRELIMINARY FRONTS AND PRESSURES FOR DAYS 3 THROUGH 7. THE 00Z/22 DETERMINISTIC ECMWF IS A MORE AMPLIFIED VERSION OF THE 12Z/21 EC ENSEMBLE MEAN...SO THE TWO BLENDED...PARTICULARLY AT THE LATER TIME RANGES...SHOULD AFFORD A MORE STABLE FORECAST. THE GFS...GEM GLOBAL...AND UKMET CANNOT AGREE ON THE DEGREE OF AMPLIFICATION OF THE CRITICAL WAVE OVER THE EAST BY DAYS 5 AND 6...SO ARE NOT ESPECIALLY USEFUL FOR THIS FORECAST. ...UPDATED PRELIMS AND AFTN FINALS ARE BASED ON 00Z ECMWF DAYS 3 AND 4 AND ECMWF/GFS ENS MEANS DAYS 5-7.THERE IS GOOD MODEL AGREEMENT DAYS 3 AND 4 WED/THU AS A CLOSED LOW MOVES NEWD IN THE GREAT LAKES REGION WHILE A STRONG DIGGING SHORTWAVE DIVES SEWD THRU THE DAKOTAS/CENTRAL PLAINS AND RESULTS IN FORMING ANOTHER STRONG CLOSED MID LEVEL LOW SYSTEM IN THE CENTRAL MS/LOWER OH VALLEY REGION BY EARLY THURSDAY. THIS RESULTS IN RAINY CONDITIONS ACROSS THE GREAT LAKES REGION WED WITH SNOW ACROSS THE ERN DAKOTAS IN MN AND WRN WI. SNOW CONDITIONS WILL SPREAD SEWD ACROSS IA/IL INTO IN/OH/KY AND NRN TN LATE THURSDAY AND INTO THE CENTRAL AND PORTIONS OF SRN APPLCHNS LATE THURSDAY INTO EARLY FRIDAY. THERE IS THE POTENTIAL FOR SOME POCKETS OF HEAVIER CONVECTIVE SNOWFALL AS THE MID LEVEL CLOSES OFF IN THIS REGION. DETAILS FOR DAYS 5-7 BECOME MORE DIFFICULT AND CONFIDENCE IS LESSENED AS TO THE LOCATION AND TRACK OF A CLOSED OFF MID LEVEL CENTER AS IT MOVES EAST AND NEWD THRU THE CENTRAL APPLCHNS AND NEWD. OP MODELS 00Z/06Z GFS/UKMET/GFSP/ECMWF ALL HAVE A MORE SRLY TRACK OF THE MID LEVEL CLOSED LOW THAN PRIOR RUNS WHILE CMC AND ENS MEANS OF GFS AND ECWMF TAKE A MID LEVEL CENTER 200-250 NM FARTHER NORTH. STRONG DYNAMICS/AND MID LEVEL COLD POOL WITH THE CENTER INDICATE A THREAT OF CONVECTIVE SNOWFALL NEAR ITS TRACK. THE SRN MOST SOLUTIONS ARE ACROSS VA AS FAR SOUTH AS THE NC BORDER AND CONSIST OF 06Z GFS AND 00Z/06Z GFSP RUNS. LAGGED AVERAGE FORECASTS OF THE PAST 4 RUNS OF GFS AND ECMWF ALONG WITH AN 8 MEMBER COMBINED LAGGED AVERAGE FORECAST OF THESE MODELS INDICATE A MID LEVEL LOW CENTER FARTHER NWD OVER NY TO LAKE ERIE. THIS IS A PREFERED HPC SOLUTION AT THIS TIME AND IS DEPICTED WELL BY GFS AND ECMWF ENS MEANS. THIS RESULTS IN A SNOW THREAT ACROSS FRIDAY ACROSS WRN PORTIONS OF PA/NY/ NWRN MTN PORTIONS OF WV/VA/MD AND INTO WRN NEW ENG LATE FRI WITH RAIN ACROSS THE MID ATLC AND NORTHEAST/NEW ENG COASTS. A MORE SWD TRACK OF THE MID LEVEL CENTER WOULD SHIFT THE COLDER PCPN TYPE FARTHER SWD. DEEPENING SFC LOW OFF THE NEW ENG COAST WILL BRING BREEZY CONDITIONS ACROSS MOST OF THE EAST FROM GA NWD FRI AND SAT. PARALLEL GFSP 00Z/06Z RUNS ARE VERY STRONG WITH THE MID LEVEL AND HAVE THE SRN MOST TRACK OF ALL MODELS. SFC LOW INDICATING PRESSURES AS LOW AS 975 MB OFF CAPE COD WITH INLAND HIGH WIND AND COASTAL STORM CONDITIONS. 12Z GFSP IS WEAKER THAN PRIOR RUNS BUT STILL THE FARTHEST SOUTH TRACK AND HAS RAISED ITS SFC PRESSURE 15MB OFF THE NEW COAST COMPARED TO ITS PRIOR RUN. THIS WILL BE A GOOD TEST FOR THIS MODEL AS IT IS CURRENTLY EXPECTED TO REPLACE THE CURRENT GFS MID DEC. NEXT COLD PAC TROF MOVES TO THE WEST COAST LATE THURSDAY AND FRIDAY AND EASTWARD TO THE ROCKIES SUNDAY. THERE ARE ENOUGH MODEL DIFFERENCES TO PREFER A BLEND OF THE ENS MEANS OF BOTH GFS/AND ECMWF TO RESOLVE THIS. COLD PAC HIGH PRESSURE SHOULD BUILD INTO THE INTERMTN REGION WITH A POTENTIAL OFFSHORE/SANTA ANA EVENT OVER THE WEST COAST MOST 12Z GUIDANCE MODELS INDICATE A GENERAL TREND OF TAKING THE MID LEVEL CLOSED LOW NWD OF THE 00Z/06Z TRACK RUNS WITH THE 12Z GFSP NOW HAVING A SFC CENTER OFF THE NEW ENG COAST 15 MB HIGHER THAN THE PRIOR RUNS. ECMWF REMANS SIMILR TO ITS FORMER 00Z RUN. THE ONLY ADJUSTMENT MADE WILL BE FOR DAY 5 H500 PROGS SPEEDING UP THE MID LEVEL CENTER TO THE ERN GREAT LAKES REGION. CISCO/ROSENSTEIN $$
