EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 941 AM EST SAT JAN 02 2016 VALID 12Z TUE JAN 05 2016 - 12Z SAT JAN 09 2016 ...OVERVIEW... THE FORECAST SPLIT-FLOW PATTERN OUT OF THE NORTHEAST PACIFIC CONTINUES WITH MULTIPLE SOUTHERN STREAM WAVES MOVING ONSHORE THE WEST COAST IN CA AND THEN PROGRESSING EAST ACROSS THE SOUTHWESTERN STATES AND THEN TURNING NORTHEAST INTO THE EASTERN US. THE LAST TROUGH MOVING ONSHORE ACROSS THE WESTERN US ALLOWS A TRANSITION TO A MID-UPPER RIDGE NEXT WEEKEND ALONG THE WEST COAST DOWNSTREAM FROM A DEEP LAYER TROUGH OVER THE CENTRAL PACIFIC. ...GUIDANCE EVALUATION/WPC PREFERENCES... THE ECMWF HAD SIGNIFICANT RUN TO RUN JUMPS IN SEA LEVEL PRESSURE/500 MB HEIGHT FORECASTS FOR EACH SYSTEM FROM YESTERDAYS 12Z RUN TO LAST NIGHTS 00Z RUN. THE GFS ALSO MADE SIGNIFICANT CHANGES...IN PARTICULAR MAKING THE 500 MB TROUGH HIGHER AMPLITUDE...THUS FORCING THE DAYS 6-7 LOW TRACKING FROM THE SOUTHERN PLAINS TO THE GREAT LAKES FURTHER NORTH/WEST FROM BOTH THE OLDER 00Z RUN AND ALSO FROM THE 00-06Z GEFS MEAN. THE 06Z GEFS/00Z ECENS MEANS WERE MORE PROGRESSIVE WITH THE 500 MB TROUGH AND THUS MOVED THE SFC LOW PRESSURE INTO THE OH VALLEY DAY 7...WITH A TRIPLE POINT LOW FORMING NEAR THE MID ATLANTIC COAST. A BLEND OF THE 06Z GFS/00Z ECMWF WITH THE GEFS/ECMWF ENSEMBLE MEANS WAS USED FOR THE DAYS 3-5 FORECAST...WITH MORE WEIGHTING ON THE ECMWF ENSEMBLE MEAN FORECAST DAYS 6-7. ...SENSIBLE WEATHER HIGHLIGHTS... RELATIVELY COLD TEMPERATURES ARE FORECAST IN THE EAST ON DAY 3 TUE WITH HIGHS 10-15 DEGREES BELOW NORMAL IN NEW ENGLAND. THE AIRMASS WILL MODERATE THROUGH THE END OF THE WEEK AS THE SFC HIGH SLIDES OFFSHORE WED-THU. TEMPERATURES BECOME ABOVE NORMAL DAY 4 WED ACROSS THE UPPER MS VALLEY AND SPREAD ACROSS THE GREAT LAKES TO THE NORTHEAST DAYS 5-6. TEMPERATURES IN THE WEST WILL GENERALLY BE NEAR/BELOW AVERAGE...PARTICULARLY IN THE SOUTHWEST WHERE MULTIPLE ROUNDS OF SHOWERS KEEP TEMPS DOWN DAYS 3-5 PLUS ON DAY 7 TEMPS ARE LOWER AS THE UPPER TROUGH AND CORE OF COLD AIR ALOFT PASSES OVER THE REGION...WITH AREAS AROUND 10 DEGREES BELOW AVERAGE. PRECIPITATION WILL FOCUS IN CALIFORNIA THROUGH THE DESERT SOUTHWEST ON DAYS 3-5 TUE-THU 07 JAN WITH WITH SUCCESSIVE SYSTEMS...WITH SNOW AT HIGHER ELEVATIONS. LATER IN THE WEEK ON FRI-SAT, THE TREND WILL BE TOWARDS LESS COVERAGE OF SHOWERS IN CA AND THE SOUTHWEST. WIDESPREAD PRECIPITATION IS EXPECTED DAYS 6-7 IN THE EAST IN TANDEM WITH THE AREAS OF LOW PRESSURE...WITH SNOW LIMITED TO THE NORTHERN FRINGE OF THE SHIELD OF PRECIPITATION FRI-SAT ACROSS THE GREAT LAKES INTO NORTHERN NEW YORK/NEW ENGLAND STATES AS HIGH PRESSURE OVER EASTERN CANADA REINFORCES COLD AIR IN PLACE. PETERSEN/FRACASSO