EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1100 AM EST TUE JAN 03 2017 VALID 12Z FRI JAN 06 2017 - 12Z TUE JAN 10 2017 ...MULTI-DAY HEAVY PRECIPITATION EVENT EXPECTED ACROSS NORTHERN AND CENTRAL CALIFORNIA LATE THIS WEEKEND INTO EARLY NEXT WEEK... PATTERN OVERVIEW AND MODEL ASSESSMENT/PREFERENCES... DETERMINISTIC AND ENSEMBLE GUIDANCE ARE IN REASONABLE AGREEMENT WITH THE LARGE SCALE EVOLUTION OF FLOW OVER THE LOWER 48 THIS WEEKEND AND EVEN EXTENDING INTO EARLY NEXT WEEK. MAIN FEATURES OF THE FORECAST WILL BE A DEEP VORTEX SLOWLY DROPPING SOUTHWARD THROUGH THE NORTHEAST PACIFIC AND TOWARDS THE NORTHWESTERN U.S. THIS WEEKEND...WITH A DOWNSTREAM MEAN RIDGE BUILDING FROM THE SOUTHERN ROCKIES/PLAINS TO THE UPPER MIDWEST AND A BROAD TROUGH SETTING UP OVER THE EASTERN U.S....AND THE LATEST MODEL GUIDANCE IS IN AGREEMENT WITH PROGRESSING THESE FEATURES EASTWARD EARLY NEXT WEEK. GERHARDT WEATHER HIGHLIGHTS/THREATS... ON FRIDAY/SATURDAY...WELL BELOW NORMAL TEMPERATURES SHOULD INHABIT A VAST MAJORITY OF THE COUNTRY GIVEN DEEP CYCLONIC FLOW IN PLACE. FORECAST ANOMALIES ARE EXPECTED TO RANGE FROM 10 TO 20 DEGREES BELOW NORMAL BEFORE CONDITIONS REBOUND AS HEIGHTS BUILD ACROSS THE CENTRAL TO EASTERN U.S. IN FACT...BY MONDAY..HIGH TEMPERATURES MAY BE 10 TO 15 DEGREES ABOVE NORMAL FROM THE INTERMOUNTAIN WEST TO THE HIGH PLAINS WHILE CONTINUING TO EXPAND EASTWARD IN TIME. GIVEN THE COMBINATION OF DEEP UPPER TROUGHING AND A QUASI-ACTIVE SOUTHERN STREAM...THERE REMAINS A THREAT FOR WINTRY PRECIPITATION SOMEWHERE ACROSS THE EASTERN U.S. DEPENDING ON THE FATE OF THAT NEBULOUS SHORTWAVE MOVING OUT OF THE HIGH PLAINS. THERE ARE PLENTY OF POSSIBLE SOLUTIONS AT HAND WHICH WOULD LEAD TO AN ARRAY OF SENSIBLE WEATHER IMPACTS. AND AS MENTIONED EARLIER...EXTREMELY WET CONDITIONS WILL AFFECT THE WEST COAST...PARTICULARLY NORTHERN/CENTRAL CA. THE AMOUNT OF PRECIPITATION SUGGESTED IN THE GUIDANCE COULD EASILY LEAD TO NUMEROUS HYDROLOGIC IMPACTS WHICH WOULD INCLUDE MUDSLIDES...DEBRIS FLOWS...ETC. WHILE THE PATTERN IS RATHER MILD...EXPECT HEAVY SNOW TO AFFECT THE HIGHER ELEVATIONS...ESPECIALLY THE SIERRA. RUBIN-OSTER