078  
FXUS02 KWBC 121602  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1102 AM EST SAT JAN 12 2019  
 
VALID 12Z TUE JAN 15 2019 - 12Z SAT JAN 19 2019  
   
..HEAVY PRECIPITATION FOR CALIFORNIA NEXT WEEK
 
 
   
..TURNING MUCH COLDER FOR THE UPPER MIDWEST
 
 
   
..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. AS THE LAST IN THE SERIES OF WESTERN CONUS FRONTS MOVES  
OUT OF THE ROCKIES NEXT FRIDAY, THE PRECIPITATION FOCUS WILL SHIFT  
OUT OF THE WEST AND THROUGH THE EAST-CENTRAL STATES INTO NEXT  
WEEKEND AS ARCTIC COLD SPILLS INTO THE NORTHERN TIER.  
 
   
..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. A BLEND OF THE DETERMINISTIC GFS/ECMWF/UKMET  
WAS USED TO FORM THE STARTING POINT FOR THE TUE-THU FORECAST.  
PREFERRED A MORE SOUTHERLY POSITION OF THE SFC/UPPER LOW OFF THE  
WA/OR COAST NEXT THU COMPARED TO THE ENSEMBLE MEANS WHICH WERE  
LIKELY STRETCHED NW/SE DUE TO UPSTREAM DIFFERENCES IN INCOMING  
SHORTWAVES. THIS ALSO FIT THE TREND SEEN IN THE PAST FEW RUNS OF  
THE ECMWF ENSEMBLE MEAN. FOR FRI-SAT NEXT WEEK, THE WESTERN SYSTEM  
WILL PUSH OUT OF THE ROCKIES AND INTO THE PLAINS AS AN ARCTIC  
FRONT DROPS OUT OF SOUTHERN CANADA AND SINKS EASTWARD AND  
SOUTHWARD OVERTOP THE PACIFIC FRONT. THIS MAY SET UP A POTENTIALLY  
IMPACTFUL WINTER STORM (AND SIGNIFICANT RAINFALL TO THE SOUTH) FOR  
THE EASTERN STATES NEXT WEEKEND AS THE SYSTEM SLIDES EASTWARD.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
THE WEST COAST WILL REMAIN QUITE ACTIVE WITH NEARLY A FRONTAL  
SYSTEM A DAY TUE-THU. THE HEAVIEST PRECIPITATION (LOW ELEVATION  
RAIN AND MOUNTAIN SNOW) WILL FOCUS ACROSS COASTAL CALIFORNIA AND  
THE SIERRAS WITH STILL SIGNIFICANT INLAND/VALLEY RAINFALL ALONG  
I-5 BUT ALSO EAST OF THE MOUNTAINS INTO NEVADA. TOTAL  
PRECIPITATION AMOUNTS OVER THE PERIOD WILL LIKELY EXCEED 4 TO 8  
INCHES (LIQUID) IN THE SIERRA AND COASTAL RANGES WHICH WILL MEAN  
WELL OVER 100" OF SNOWFALL DURING THE PERIOD AT FAVORED JACKPOT  
AREAS. SIGNIFICANT PRECIPITATION WILL SPREAD THROUGH NEVADA AS  
WELL BUT ESPECIALLY WITH THE LAST SYSTEM ON THURSDAY, FOCUSED ON  
THE SOUTHERN HALF OF THE SILVER STATE.  
 
FRIDAY INTO NEXT WEEKEND, ARCTIC AIR WILL SINK SOUTHWARD AND  
SPREAD EASTWARD OUT OF SOUTHERN CANADA INTO THE NORTHERN TIER  
WHERE TEMPERATURES WILL STRUGGLE TO REACH ABOVE ZERO OVER PARTS OF  
NORTH DAKOTA AND MINNESOTA AND OVERNIGHT TEMPERATURES MAY REACH  
INTO THE -20S. THIS COLD AIRMASS WILL SUPPORT SNOWFALL EXPANDING  
EASTWARD OUT OF THE PLAINS TOWARD THE OHIO VALLEY NEXT WEEKEND AND  
INCREASED RAINFALL AHEAD OF THE COLD FRONT MOVING OUT OF TEXAS.  
THIS WILL HAVE TO BE MONITORED FOR FUTURE WEATHER HAZARDS INTO THE  
EASTS AS IT PROGRESSES EASTWARD NEXT SATURDAY/SUNDAY.  
 
FRACASSO/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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