077  
FXUS02 KWBC 131603  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1103 AM EST SUN JAN 13 2019  
 
VALID 12Z WED JAN 16 2019 - 12Z SUN JAN 20 2019  
   
..CALIFORNIA HEAVY PRECIPITATION WED-THU
 
 
...COLD AIR SURGES THROUGH THE NORTH-CENTRAL U.S. LATER THIS  
WEEK...   
..CENTRAL TO EASTERN U.S. HEAVY RAIN/SNOW THREAT NEXT WEEKEND
 
 
 
   
..OVERVIEW AND GUIDANCE EVALUATION/PREFERENCES
 
 
WHILE THE OVERALL LARGER SCALE FLOW PATTERN EVOLUTION REMAINS  
REASONABLY WELL-SUPPORTED BY THE GUIDANCE, AN UNCERTAIN SPLIT OF  
SMALLER SCALE FEATURES OVER THE EASTERN PACIFIC AND SUBSEQUENT  
PROGRESSION INLAND ACROSS NORTH AMERICA CONTINUES TO OFFER  
SIGNIFICANT RUN TO RUN DIFFERENCES IN DETERMINISTIC SOLUTIONS  
RIGHT FROM THE START OF THE MEDIUM RANGE TIME PERIOD. A BLEND OF  
THE DETERMINISTIC MODELS TO START (WED-THU) OFFERED A REASONABLE  
CONSENSUS-BASED FORECAST THAT HAS SERVED WELL THE PAST FEW DAYS AS  
A WEAKER LEAD SYSTEM APPROACHES NORTHERN CALIFORNIA WEDNESDAY AND  
A STRONGER SYSTEM PUSHES INLAND ON THURSDAY. FOR FRI-SUN, TRENDED  
TOWARD AN ENSEMBLE MEAN CONSENSUS THAT WAS SLOWER THAN THE 00Z/06Z  
GFS BUT NOT AS SLOW AS THE 00Z ECMWF/CANADIAN WITH THE UPPER  
TROUGH THROUGH THE PLAINS. THIS WILL SUPPORT SURFACE CYCLOGENESIS  
OUT OF TEXAS AND THROUGH THE LOWER MISSISSIPPI VALLEY LATE FRIDAY  
INTO SATURDAY AS ARCTIC HIGH PRESSURE SINKS THROUGH THE HIGH  
PLAINS/UPPER MIDWEST. BY NEXT SUNDAY, MODELS AND ENSEMBLE MEMBERS  
SHOW CONSIDERABLE SPREAD IN TRACK/SPEED/STRENGTH/EVOLUTION IN THE  
EASTERN THIRD OF THE CONUS. TREND HAS BEEN FOR A SLOWER/DEEPER  
SYSTEM LIKE THE 06Z FV3-GFS THAT MAY EXIT OFF THE SOUTHERN  
MID-ATLANTIC COAST PER THE PREFERRED CLUSTER OF SOLUTIONS. BACK TO  
THE WEST, ANOTHER SYSTEM MAY APPROACH/ENTER THE COAST OF WA/OR BY  
NEXT SUNDAY.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
IN THE WEST, AN INITIAL AND SUBSEQUENT SYSTEM WILL BRING  
INCREASINGLY MORE PRECIPITATION TO MOSTLY CALIFORNIA AND TO A  
LESSER EXTENT THE PACIFIC NORTHWEST WED/THU. 1-2" OF VALLEY RAIN  
AND SEVERAL FEET OF MOUNTAIN SNOWS ARE LIKELY THROUGH  
CENTRAL/NORTHERN CALIFORNIA AND THE SIERRAS, RESPECTIVELY, WITH  
LESS ACROSS SOUTHERN CALIFORNIA. WITH A HEALTHY INFLUX OF  
MOISTURE, PRECIPITATION WILL WORK INLAND THROUGH THE INTERMOUNTAIN  
WEST/GREAT BASIN/ROCKIES LATE THURSDAY AND FRIDAY WITH WINDY  
CONDITIONS AND VALLEY RAIN/MOUNTAIN SNOW. SNOW LEVELS WILL FALL AS  
HEIGHTS LOWER WHICH WILL TURN SOME LOWER ELEVATIONS OVER TO SNOW  
AS PRECIPITATION ENDS BY SATURDAY.  
 
DOWNSTREAM, GLANCING BLOWS OF COLD CANADIAN AIR WILL BECOME MORE  
SIGNIFICANT AND LONGER-LASTING AS IT SURGES SOUTHWARD THURSDAY  
INTO NEXT WEEKEND AS THE NORTHERN STREAM AMPLIFIES AROUND THE  
WOBBLING HUDSON BAY UPPER LOW. CONCURRENTLY, THE ROBUST WESTERN  
SYSTEM WILL ORGANIZE OVER THE SOUTHERN PLAINS WITH INCREASED GULF  
OF MEXICO MOISTURE AND LIFT THROUGH ARKANSAS ON SATURDAY AS THE  
ARCTIC FRONT TO THE NORTH PUSHES THROUGH THE NORTHEAST. AS  
PRECIPITATION OVERRUNS THE COLD AIRMASS TO THE NORTH, SNOW WILL  
SPREAD EASTWARD OUT OF THE CENTRAL PLAINS THROUGH THE MIDWEST/OHIO  
VALLEY AS POTENTIALLY HEAVY WARM-SECTOR RAINS/CONVECTION MOVE  
THROUGH THE SOUTHEAST. THOUGH CONFIDENCE DECREASES IN SPECIFICS IN  
THE EAST NEXT WEEKEND, THE ENSEMBLE SIGNAL FOR A SIGNIFICANT AND  
FAIRLY WIDESPREAD HEAVY SNOW/ICE EVENT EXISTS TO THE NORTH OF THE  
LOW TRACK. PLEASE CONSULT THE WPC DAY 4-7 WINTER WEATHER OUTLOOK  
FOR A PROBABILISTIC ASSESSMENT OF THE WINTER WEATHER THREAT FROM  
COAST TO COAST.  
 
 
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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