EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1158 AM EDT MON MAR 12 2018 VALID 12Z THU MAR 15 2018 - 12Z MON MAR 19 2018 ...PATTERN OVERVIEW/MODEL ASSESSMENT/PREFERENCES... MODEL GUIDANCE HAS CONTINUED THE TREND TOWARD A LESS AMPLIFIED SOLUTION THROUGH THE END OF THE EXTENDED PERIOD; HOWEVER, NUMEROUS TEMPORAL AND SPATIAL DIFFERENCES REMAINED UNRESOLVED. FORECAST CONFIDENCE REMAINS FAIR AT BEST GIVEN DETAILS REMAIN UNCERTAIN. THE LATEST ECWMF ONCE AGAIN IS LARGELY UNUSABLE IN PART BECAUSE OF DIGGING FARTHER SOUTH ACROSS THE WEST AND BECOMING SIGNIFICANTLY OUT OF PHASE BY THE END OF THE FORECAST. BEYOND DAY 3, THE CMC RESEMBLES THE ECWMF IN PART, BUT ISN'T OVERLY EGREGIOUS ON THE TROUGH OVER THE WEST AND HOW IT EVOLVES. THE BEST DETERMINISTIC MODEL CONTINUES TO BE THE GFS. THE 06Z RUN SPLIT THE DIFFERENCE BETWEEN THE 00Z SOLUTIONS OF THE GFS AND ECWMF WITH SHORTWAVE ENERGY TRACKING ACROSS THE KENAI PENINSULA THURSDAY AND FRIDAY AND EMBEDDED ENERGY WITHIN THE NORTHERN STREAM ACROSS CANADA; WHICH AFFECTS DEPARTING LOW OVER COASTAL CANADA/MARITIMES. ALTHOUGH THE DETERMINISTIC ECWMF WAS UNDESIRABLE, ITS ENSEMBLE MEANS ACTUALLY WERE DECENT AND CLUSTERED WELL WITH THE GFS AND GEFS MEAN- THEREFORE WERE THE PREFERRED MODEL BLEND, WITH LESS WEIGHTING ON THE DETERMINISTIC GFS THROUGH DAYS 5-7. ...WEATHER HIGHLIGHTS/THREATS... THE BEST FOCUS FOR RAIN AND HIGHER ELEVATION SNOW INITIALLY ENCOMPASSES NORTHERN CA/SIERRA NEVADA RANGE ON THURSDAY AND WILL STEADILY EXPAND SOUTHWARD INTO SOUTHERN CALIFORNIA AND THE SOUTHWEST BY THE WEEKEND. THE EXPANSIVE MOISTURE SHIELD AHEAD OF THE OVERALL WEST COAST TROUGH WILL BRING PERIODS OF PRECIP INTO THE GREAT BASIN AND ROCKIES. UNRESOLVED DETAIL ISSUES ALOFT TEMPER CONFIDENCE IN DETERMINING THE TIMING AND INTENSITY OF ENHANCED PRECIPITATION OVER SOUTHERN AREAS. EXPECT ONE OR MORE EPISODES OF PRECIP FROM THE PLAINS EASTWARD BUT WITH BELOW AVERAGE CONFIDENCE IN SPECIFICS GIVEN POOR CONTINUITY/HIGH SPREAD AMONG THE FULL ARRAY OF GUIDANCE. THE MOST COMMON SIGNAL IN THE GUIDANCE FOR HIGHEST 5-DAY TOTALS IS CENTERED OVER THE TN VALLEY AND EXTENDING INTO PARTS OF THE LOWER MS VALLEY AS WELL AS LOWER OH VALLEY. POTENTIAL FOR SOME LOW LEVEL GULF INFLOW ALONG WITH THE LIKELY MULTI-DAY PRESENCE OF A PLAINS TO EAST COAST FRONT SUGGEST THE POSSIBILITY OF LOCALLY HEAVY RAINFALL AT TIMES. DEPENDING ON HOW UPPER ENERGY/LOW PRESSURE EJECT OUT OF THE WEST, THERE MAY BE AN AXIS OF ENHANCED PRECIP OVER THE NORTH-CENTRAL PLAINS. SOME OF THIS PRECIP MAY BE IN THE FORM OF SNOW. FARTHER EAST EXPECT SNOW TO REMAIN FAIRLY FAR NORTHWARD. SNOW TO THE LEE OF THE EASTERN GREAT LAKES SHOULD TAPER OFF LATE THIS WEEK. A FEW LOCATIONS ACROSS THE NORTHERN HIGH PLAINS MAY OBSERVE TEMPERATURES AT LEAST 10F BELOW NORMAL FOR SEVERAL DAYS AS COLD AIR SETTLES INTO THE REGION. MEANWHILE AREAS FROM THE CENTRAL PLAINS EASTWARD/SOUTHEASTWARD SHOULD SEE THE HIGHEST WARM ANOMALIES WERE LOCATIONS COULD AVERAGE 10-20F ABOVE NORMAL. CAMPBELL/RAUSCH