EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 159 AM EST SUN NOV 01 2015 VALID 12Z WED NOV 04 2015 - 12Z SUN NOV 08 2015 ...ANOTHER EXCESSIVE RAINFALL THREAT FOR THE SOUTH-CENTRAL US... ...GUIDANCE/PREDICTABILITY ASSESSMENT... TODAYS WPC MEDIUM RANGE PRODUCT SUITE HAS BEEN PRIMARILY DERIVED FROM A COMPOSITE BLEND OF WELL CLUSTERED GUIDANCE FROM THE 18 UTC GFS/GEFS MEAN AND 12 UTC ECMWF/ECMWF ENSEMBLE MEAN. THIS COMBINATION OF DETERMINISTIC AND ENSEMBLE BASED INPUTS PROVIDES SOME ENHANCED DETAIL CONSISTENT WITH A PATTERN WITH BELOW NORMAL FORECAST SPREAD AND UNCERTAINTY. ...PATTERN OVERVIEW AND SENSIBLE WEATHER THREATS... IT REMAINS EVIDENT THAT SIGNIFICANT MID-LATITUDE FLOW AMPLIFICATION IS EXPECTED TO OCCUR NEXT WEEK FROM THE PACIFIC INTO THE LOWER 48 AS HIGHLIGHTED AT MID-UPPER LEVELS BY A COOLING/UNSETTLING TROUGH DIGGING INTO THE WRN/SWRN US AND A BUILDING/WARMING E-CENTRAL US/SERN US CENTERING RIDGE. THE TROUGH/LOW BECOMES QUITE AMPLIFIED AND SLOW MOVING AND OFFERS WIDESPREAD PCPN LINGERING INTO MEDIUM RANGE TIME SCALES...FROM THE SW US/S-CENTRAL GREAT BASIN NEWD TO THE ROCKIES. ENERGY/HEIGHT FALLS ARE KICKED INTO THE S-CENTRAL US THEN NEWD INTO THE E-CENTRAL STATES LATER WEEK INTO NEXT WEEKEND. THIS PROCESS ESPECIALLY SETS A THREAT FOR ANOTHER POTENTIAL ROUND OF EXCESSIVE RAINS OVER AN ALREADY DRENCHED S-CENTRAL US STATES AS GULF MOISTURE RETURN FEEDS INTO/OVERTOP A SLOW MOVING WAVY FRONTAL ZONE. GUIDANCE CONTINUES TO VARY MOST WITH THE SPECIFIC FRONTAL WAVE/PCPN FOCUS RESPONSE GIVEN UNCERTAIN ENERGY EJECTION TIMING/EMPHASIS. THE WPC BLEND OFFERS A COMPOSITE BLEND. THE MAIN WAVY FRONT MAY BE EVENTUALLY ABLE TO SPREAD MORE MODEST PCPN FOLLOWED BY GENERALLY A COOLER/DRIER POST-FRONTAL AIRMASS ACROSS MUCH OF THE NATION INTO NEXT WEEKEND...ALBEIT WITH ANOTHER PACIFIC SYSTEM PROGRESSION AGAIN BY THEN TOWARD/INTO THE NW US. SCHICHTEL