EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 949 AM EDT SAT APR 23 2016 VALID 12Z TUE APR 26 2016 - 12Z SAT APR 30 2016 GENERAL FLOW PATTERN/MODEL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ THE GUIDANCE SHOWS GOOD AGREEMENT IN THE GENERAL FLOW PATTERN -- AND DETAILS -- FROM TUESDAY INTO THURSDAY AS ONE DEEP CYCLONE LEAVES THE WEST WHILE ANOTHER INVADES CA. LATE WEEK TIMING ISSUES FROM THE WEST TOWARDS THE PLAINS DEVELOP WITH THE ECMWF/ECMWF ENSEMBLE MEANS OUTPACING THE REST OF GUIDANCE. THERE HAS BEEN SOME SLOWING TREND IN THE ECMWF GUIDANCE, LEADING US TO TREND AWAY FROM THE DETERMINISTIC ECMWF OR PREFER A SOLUTION SLOWER THAN THE 00Z ECMWF ENSEMBLE MEAN WITH TIME. MEANWHILE...A STRONG GREENLAND RIDGE/EASTERN CANADIAN UPPER LOW BLOCKING COUPLET SHOULD CONTINUE TO DOMINATE EASTERN NORTH AMERICAN FLOW WELL INTO NEXT WEEK. THE MODEL PREFERENCE FOR THE SURFACE PRESSURES/500 HPA HEIGHTS WAS A COMPROMISE OF THE 00Z CANADIAN/00Z ECMWF/00Z UKMET/06Z GFS FROM TUESDAY INTO THURSDAY. THEREAFTER, THE CANADIAN AND ECMWF COMPONENTS WERE SWAPPED OUT FOR THE 00Z NAEFS MEAN AND 00Z ECMWF ENSEMBLE MEAN. THIS MAINTAINED REASONABLE CONTINUITY. THE TEMPERATURES/RAIN CHANCES/CLOUDS/WEATHER/DEW POINT GRIDS ARE USING A HEAVIER BLEND OF THE 00Z ECMWF/00Z NAEFS MEAN TO FURTHER ACCOUNT FOR UNCERTAINTY. WEATHER HIGHLIGHTS/THREATS ~~~~~~~~~~~~~~~~~~~~~~~~~~ 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 SPREAD OVER MUCH OF THE PLAINS AS WELL AS THE EASTERN/NORTHEAST UNITED STATES. SNOWS SHOULD FOCUS OVER FAVORED HIGHER TERRAIN. SOME ADDITIONAL 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 -- CONSULT LATEST SPC OUTLOOKS FOR UPDATED SEVERE WEATHER THREAT INFORMATION. ROTH/SCHICHTEL