EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1058 AM EST TUE MAR 04 2014 VALID 12Z FRI MAR 07 2014 - 12Z TUE MAR 11 2014 ...OVERVIEW... THE PREVAILING LONGWAVE PATTERN EXPECTED ACROSS NORTH AMERICA DAYS 3-7/FRI-TUE IS PROJECTED TO BE MOSTLY SPLIT...WITH SHORTWAVE TROUGHS EXITING THE EASTERN PERIPHERY OF A PACIFIC TROUGH AND SEPARATING INTO TWO OR MORE SEGMENTS WHILE CROSSING THE WEST... RESULTING IN PERIODIC DEVELOPMENT OF CLOSED LOWS OVER THE ROCKIES AND CROSSING THE DEEP SOUTH EVERY FEW DAYS. THIS PATTERN FAVORS PERIODIC AND OCCASIONALLY CONSTANT PRECIPITATION FOR THE PACIFIC NORTHWEST...WHILE HEAVY RAINFALL POSSIBLY ACCOMPANIED BY LESS SNOW AND ICE OCCUR ACROSS THE DEEP SOUTH. THE SOUTHERN STREAM SYSTEMS HAVE RELATIVELY GOOD MODEL AGREEMENT AND THUS ARE ASSOCIATED WITH NEAR TO AT TIMES ABOVE AVERAGE CONFIDENCE. HOWEVER...THE NORTHERN STREAMS HAVE ONLY AVERAGE AGREEMENT EARLY IN THE PERIOD BEFORE FALLING BELOW AVERAGE. DUE TO POSSIBLE INTERACTIONS OF THE VARIOUS STREAMS...PREDICTABILITY AS A WHOLE IS ABOUT AVERAGE WITH GREATER SEPARATION GENERALLY FAVORING HIGHER PREDICTABILITY WITH THE SOUTHERN STREAM DUE TO LESS COMPLEXITY. ...MODEL PREFERENCES AND SENSIBLE WEATHER HIGHLIGHTS... EXCEPT FOR THE 00Z UKMET/CANADIAN WHICH BEGIN TO STRAY FROM THE CONSENSUS...GUIDANCE IS IN REASONABLY GOOD AGREEMENT WITH A SHORTWAVE TROUGH REACHING THE PACIFIC NORTHWEST AROUND DAY 5/SUN...RESULTING IN MORE HEAVY PRECIPITATION FOR THE REGION. PREFERRED TO COMBINE THE GLOBAL ENSEMBLE MEANS WITH THE 06Z GFS/00Z ECMWF TO ADDRESS SOME OF THE GROWING SPREAD FOR THIS PARTICULAR SYSTEM. HOWEVER...FOR DAYS 6-7/MON-TUE...THE SOLUTION ENVELOPE BECOMES TOO LARGE AND UNCERTAIN TO USE MUCH DETERMINISTIC DETAIL WITH MUCH CONFIDENCE...AND THEREFORE PREFER TO RELY ENTIRELY ON ALL THE GLOBAL ENSEMBLE MEANS EQUALLY FOR ANY SUBSEQUENT SYSTEMS. OTHER THAN A COLD FRONTAL PASSAGE ACROSS PORTIONS OF THE NORTHERN PLAINS/UPPER MIDWEST EARLY DAY 3...MODEL AGREEMENT IS QUITE POOR CONCERNING THE SOMEWHAT FREQUENT COLD AND WARM FRONTAL PASSAGES EMBEDDED WITHIN THE FAST BUT UNCERTAIN FLOW ACROSS THE NORTH. WHILE IT WILL BE DIFFICULT TO DEPICT TEMPERATURES WITH A HIGH DEGREE OF CONFIDENCE FROM DAY 4/SAT ONWARD...TEMPERATURES AS A WHOLE SHOULD BE WARMER THAN RECENTLY OBSERVED DUE TO THE MORE ZONAL PATTERN AND INCREASING SUN ANGLE. LIGHT PRECIPITATION MAY ALSO ACCOMPANY THE FRONTAL PASSAGES. AS NOTED ABOVE...PREDICTABILITY IS SLIGHTLY HIGHER WITH THE SOUTHERN STREAM. THUS...EXCEPT FOR THE SOUTHEAST LOW ON DAY 3/FRI WHERE THE 00-06Z GFS ARE CONSIDERED TOO FAST AND OFFSHORE...GENERALLY RELIED UPON A DETERMINISTIC AND ENSEMBLE MEAN CONSENSUS FOR ALL SYSTEMS ACROSS THE SOUTH. MODELS HAVE TRENDED SLOWER WITH THE LOW ALONG THE GEORGIA COAST BY EARLY FRIDAY POSSIBLY RESULTING IN HEAVY RAIN OR MIXED WITH SNOW/ICE INLAND ACROSS THE CAROLINAS. HEAVY RAINFALL MAY BEGIN TO DEVELOP ACROSS THE CENTRAL TEXAS BY DAY 5/SUN BEFORE SPREADING EASTWARD ALONG THE GULF COAST EARLY NEXT WEEK IN ASSOCIATION WITH THE NEXT CLOSED LOW. THE CURRENT MODEL CONSENSUS SHOWS A WARMING TRENDS ACROSS THE SOUTH AS WELL...WITH IT BECOMING INCREASINGLY DIFFICULT TO PRODUCE SNOW/ICE AFTER THE FIRST CLOSED LOW EXITS THE SOUTHEAST EARLY IN THE PERIOD. JAMES