EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 300 AM EDT SAT APR 23 2016 VALID 12Z TUE APR 26 2016 - 12Z SAT APR 30 2016 ...GUIDANCE/UNCERTAINTY ASSESSMENT... MODELS AND ENSEMBLES REASONABLY AGREE ALOFT WITH THE HIGH AMPLITUDE OF TWO MAJOR WRN U.S. TRAVERSING TROUGHS DOWNSTREAM FROM NERN PAC SPLIT FLOW. LATER WEEK TIMING ISSUES OUT FROM THE WEST TOWARD THE CENTRAL US DEVELOP WITH THE ECMWF/ECMWF ENSEMBLE MEANS OUTPACING THE REST OF GUIDANCE. WPC CONTINUITY IS BEST MAINTAINED WITH A SOMEWHAT SLOWER PROGRESSION THAN THE 12 UTC ECMWF/ECMWF ENSEMBLE MEAN AND THAT ALSO SEEMS SUPPORTED BY THE AMPLIFIED NATURE OF FLOW. MEANWHILE...A STRONG GREENLAND RIDGE/ERN CANADA UPPER LOW BLOCKING COUPLET SHOULD CONTINUE TO DOMINATE ERN NOAM FLOW WELL INTO NEXT WEEK. WPC MEDIUM RANGE PROGS/GRIDS HAVE BEEN ACCORDINGLY DERIVED FROM A COMPOSITE BLEND OF WPC CONTINUITY ALONG WITH REASONABLE WELL CLUSTERED AND COMPATABLE MID-LARGER SCALE GUIDANCE FROM THE 12 UTC GFS/ECMWF/CANADIAN MODELS AND GEFS/NAEFS/ECMWF ENSEMBLE MEANS. OVERALL...FORECAST CONFIDENCE REMAINS GENERALLY ABOVE NORMAL AND THE BLEND SMOOTHES LESS PREDICTABLE SMALLER SCALE VARIANCE. MANUAL ADJUSTMENTS FURTHER MAINTAIN WPC CONTINUITY. ...WEATHER HIGHLIGHTS/THREATS... A LARGE SCALE PATTERN OF MULTIPLE ENERGETIC/STEADILY PROGRESSIVE EMBEDDED SYSTEMS WILL BRING A SIGNIFICANT COVERAGE OF ACTIVE WEATHER ACROSS THE LOWER 48 DURING THE MEDIUM RANGE PERIOD. AN EMPHASIS FOR HIGHER PRECIPITATION TOTALS SHOULD EXTEND ACROSS THE WEST THEN EMERGE WITH SYSTEM TRANSLATIONS OVER MUCH OF THE PLAINS AND ERN/NERN US. SOME SNOWS SHOULD FOCUS OVER FAVORED HIGHER TERRAIN. SOME ADDITONAL SPRING SNOW IS ALSO POSSIBLE THE NRN FRINGE OF THE PRECIPITATION SHIELD NEAR THE CANADIAN BORDER. THERE IS ALSO POTENTIAL FOR STRONG TO SEVERE PLAINS/MS VALLEY THUNDERSTORMS SO PLEASE CONSULT LATEST SPC OUTLOOKS FOR UPDATED SEVERE WEATHER THREAT INFORMATION. SCHICHTEL