EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 830 AM EST TUE JAN 17 2017 VALID 12Z FRI JAN 20 2017 - 12Z TUE JAN 24 2017 ...MORE WET WEATHER SLATED FOR CA, FURTHER RELIEVING DROUGHT CONDITIONS... ...HEAVY PRECIPITATION EXPECTED FROM THE SOUTHEAST THROUGH THE MID-ATLANTIC STATES INTO SOUTHERN NEW ENGLAND... OVERVIEW & MODEL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ZONAL FLOW ACROSS THE PACIFIC INTO THE LOWER 48 ACTS TO ROLL UP CLOSED CYCLONES EAST OF THE ROCKIES DURING THE MEDIUM RANGE PERIOD UNDER THE BASE OF A BURGEONING 500 HPA HEIGHT ANOMALY OVER HUDSON BAY/QUEBEC. THE GUIDANCE SHOWS VERY GOOD AGREEMENT THROUGH THE PERIOD. AS SUCH, THE PRESSURES, 500 HPA HEIGHTS, WINDS WERE BASED ON A COMPROMISE OF THE 00Z CANADIAN, 00Z UKMET, 06Z GFS, 00Z ECMWF EARLY ON BEFORE USING INCREASING AMOUNTS OF THE 00Z NAEFS AND 00Z ECMWF ENSEMBLE MEAN FROM SUNDAY ONWARD. THE TEMPERATURES, DEW POINTS, CLOUDS, WEATHER, AND PRECIPITATION CHANCE GRIDS WILL BE BASED ON A MORE ENSEMBLE MEAN-HEAVY BLEND, AS USUAL. THE PLAN FOR THE DAY 4-7 QPF IS FOR A SOLUTION CLOSE TO A 06Z GFS/00Z ECMWF COMPROMISE. WEATHER HIGHLIGHTS/THREATS ~~~~~~~~~~~~~~~~~~~~~~~~~~ CONFIDENCE REMAINS ABOVE AVERAGE FOR AT LEAST A COUPLE EPISODES OF SIGNIFICANT RAIN/HIGH ELEVATION SNOW AND STRONG WINDS ALONG THE WEST COAST WITH THIS ENHANCED ACTIVITY EXTENDING INTO THE SIERRA NEVADA RANGE AND SOUTHWEST. CONTINUE TO EXPECT AREAL AVERAGE AMOUNTS TO LIE IN THE 5-8 INCH AMOUNTS ALONG SOME COASTAL LOCATIONS AND OVER THE SIERRA NEVADA WITH POTENTIALLY HIGHER TOTALS ALONG WINDWARD SLOPES. FOR SRN CA/AZ THE HEAVIEST PRECIP SHOULD OCCUR AROUND FRI-FRI NIGHT AND AGAIN AROUND SUN-MON. MUCH OF THE REMAINDER OF THE WEST SHOULD SEE LIGHTER PRECIPITATION. THE UNSETTLED WEATHER WILL TEND TO KEEP TEMPERATURE RANGES MORE NARROW THAN USUAL WITH BELOW NORMAL HIGHS... ON A LOCALIZED BASIS BY GREATER THAN 10F... AND NEAR TO ABOVE NORMAL LOWS. PORTIONS OF THE EAST/MIDWEST WILL SEE SOME RAIN ON FRI FOLLOWED BY A BRIEFLY DRIER PERIOD. LOCALLY MDT/HVY RNFL MAY DEVELOP NEAR THE GULF COAST AROUND FRI NIGHT-SAT ALONG A LINGERING FRONT. AS ENERGY FROM THE INITIAL WEST COAST STORM CROSSES THE PLAINS/SOUTHEAST... MORE HEAVY RAINS MAY DEVELOP AND SPC IS MONITORING THE POTENTIAL FOR SEVERE CONVECTION NEAR THE ERN HALF OF THE GULF COAST DURING THE WEEKEND. CONSULT LATEST SPC PRODUCTS FOR FURTHER INFORMATION. THE PLAINS TO OH VLY/MID ATLC SYSTEM WILL SPREAD A BROAD AREA OF PCPN MOSTLY IN THE FORM OF RAIN ACROSS THE ERN HALF OF THE COUNTRY. THERE IS STILL A FAIRLY GOOD SIGNAL FOR A PERIOD OF STRONG LOW LEVEL INFLOW FROM THE ATLANTIC THAT WOULD ENHANCE RAINS ALONG THE EAST COAST/ERN SLOPES OF THE APLCHNS. IT STILL APPEARS THAT ANY SNOW THAT DOES OCCUR WOULD BE LIMITED TO NEAR THE UPPER LOW MOVING ACROSS THE SOUTHERN TIER OF THE COUNTRY AND TERRAIN OF THE APPALACHIANS AND AT THE NRN FRINGE OF THE MSTR SHIELD IF IT REACHES CLOSE TO THE CANADIAN BORDER. WITHIN A PATTERN OF ABOVE TO MUCH ABOVE NORMAL TEMPS OVER MOST AREAS EAST OF THE ROCKIES... THE UPPER MS VALLEY CONTINUES TO BE THE EXPECTED FOCUS FOR HIGHEST ANOMALIES... AVERAGING PLUS 25-35F FOR MINS OVER THE 5-DAY PERIOD. THERE MAY BE MULTIPLE DAYS WITH MORNING LOWS NEAR OR ABOVE RECORD WARM VALUES. ROTH/RAUSCH