111  
FXUS02 KWBC 120621  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
120 AM EST SAT JAN 12 2019  
 
VALID 12Z TUE JAN 15 2019 - 12Z SAT JAN 19 2019  
   
..CALIFORNIA HEAVY PRECIPITATION PATTERN NEXT WEEK
 
 
   
..OVERVIEW
 
 
IT REMAINS THE CASE THAT STEADILY PROGRESSIVE AND AMPLIFIED  
PACIFIC FLOW WILL BRING A SERIES OF SIGNIFICANT STORMS TO THE WEST  
COAST NEXT WEEK. AS THESE SYSTEMS MOVE EASTWARD, SPLIT FLOW WILL  
EMERGE AROUND AN AMPLIFIED DOWNSTREAM GREAT BASIN/ROCKIES UPPER  
RIDGE. NORTHERN STREAM ENERGY WILL AMPLIFY AS IT ENTERS BROAD  
CYCLONIC UPPER-LEVEL FLOW EAST OF THE RIDGE, WITH FREQUENT  
SHORTWAVES AND MEAN UPPER TROUGHING FROM THE UPPER MIDWEST TO THE  
NORTHEAST. MEANWHILE, AN ACTIVE WEST COAST WILL FEATURE AMPLIFIED  
TROUGH/UPPER LOWS TO ESPECIALLY THREATEN CALIFORNIA ALL NEXT WEEK.  
UNSETTLED FLOW/ORGANIZED PRECIPITATION SPREADS INCREASINGLY INLAND  
OVER THE WEST LATER NEXT WEEK AND EAST-CENTRAL U.S. NEXT WEEKEND.  
 
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
MODEL AGREEMENT DURING THE FORECAST PERIOD WAS FAIRLY GOOD IN THE  
LARGE SCALE, WITH SMALLER FEATURES SUCH AS SHORTWAVES MOVING  
THROUGH THE NORTHERN TIER OF THE U.S. AND THE WEST NOT HANDLED AS  
WELL FROM RUN TO RUN. THE DETERMINISTIC GFS AND EC AND THE GEFS  
AND ECENS WERE USED TO DERIVE THE WPC FORECAST INTO MIDWEEK, WITH  
MOST EMPHASIS APPLIED TO ENSEMBLE MEAN GUIDANCE IN THE DAYS 5-7  
TIMEFRAME AMID GROWING UNCERTAINTY. DESPITE MODEL UNCERTAINTIES IN  
THE DETAILS, FORECAST CONFIDENCE IS HIGH FOR THE THREAT OF HEAVY  
PRECIPITATION FOCUSED IN CALIFORNIA NEXT WEEK.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
THE WEST COAST WILL REMAIN QUITE ACTIVE GIVEN THE RAPID FREQUENCY  
OF SHORTWAVE ENERGIES AND FRONTAL SYSTEMS. THE HEAVIEST  
PRECIPITATION (LOW ELEVATION RAIN AND MOUNTAIN SNOW) WILL FOCUS  
ACROSS CALIFORNIA, WITH MULTIPLE ROUNDS OF PRECIPITATION POSSIBLE  
THROUGH THIS FORECAST PERIOD. TOTAL PRECIPITATION AMOUNTS OVER THE  
PERIOD WILL BE HEAVY, WITH UPSLOPE FLOW ENHANCING QPF TO 4 TO 8  
INCHES PLUS IN THE SIERRA AND COASTAL RANGES. LATER IN THE WEEK  
INTO NEXT WEEKEND, ORGANIZED HEAVIER PRECIPITATION/COOLING IS ALSO  
EXPECTED TO SPREAD OVER THE PACIFIC NORTHWEST AND THEN WORK INLAND  
ACROSS THE WEST IN A PATTERN AS HEIGHTS LOWER WITH MORE AMPLIFIED  
PACIFIC MID-UPPER LEVEL TROUGH PASSAGE. DOWNSTREAM, A TEMPERATURE  
PATTERN CHANGE IS ALSO EXPECTED FOR THE CENTRAL U.S. AND NORTHEAST  
TIER AS A LEADING SERIES OF COLD HIGH SURGES DIG SOUTHWARD FROM  
CANADA. THERE IS AN INCREASING GUIDANCE SIGNAL THAT EJECTING  
ENERGY INTERACTION WITH A LEAD BAROCLINIC ZONE MAY SPAWN  
EAST-CENTRAL U.S. CYCLOGENSIS AND INCREASINGLY FAVORABLE  
PRECIPITATION FUELING THETAE INFLUX FROM THE GULF OF MEXICO NEXT  
WEEKEND.  
 
SCHICHTEL  
 
WPC MEDIUM RANGE 500 MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDEXES ARE FOUND AT:  
 
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 
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