074  
FXUS02 KWBC 151908  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
308 PM EDT FRI MAR 15 2019  
 
VALID 12Z MON MAR 18 2019 - 12Z FRI MAR 22 2019  
   
..OVERVIEW
 
 
A BLOCKING MID/UPPER-LEVEL RIDGE INITIALLY CENTERED FROM THE  
PACIFIC NORTHWEST TO WESTERN CANADA EARLY NEXT WEEK SHOULD VERY  
SLOWLY SHIFT EASTWARD THROUGH THE FORECAST PERIOD. AN UPSTREAM  
TROUGH REACHING THE NORTHEASTERN PACIFIC BY THE LATTER HALF OF THE  
WEEK MAY HELP TO REINFORCE/REBUILD THE WESTERN CANADA RIDGE BY  
FRI. THE WESTERN NORTH AMERICA RIDGE WILL PROMOTE A MEAN TROUGH  
OVER THE EASTERN PART OF THE CONTINENT. MULTIPLE SHORTWAVES  
EMBEDDED WITHIN THE OVERALL TROUGH--LESS PREDICTABLE DUE TO THEIR  
SMALLER SCALE--WILL MAKE IT DIFFICULT TO RESOLVE SOME FORECAST  
DETAILS. STRONG WESTERLY FLOW ACROSS THE NORTH CENTRAL PACIFIC  
WILL SPLIT AS IT ENCOUNTERS THE RIDGE, WITH SOME SHORTWAVE ENERGY  
DIRECTED NORTH INTO THE HIGHER LATITUDES OF CANADA AND THE REST  
SEPARATING INTO THE SOUTHERN STREAM. BY LATE NEXT WEEK THE  
PERSISTENCE OF RIDGING OVER WESTERN CANADA MAY BEGIN TO DIRECT  
STRONGER HEIGHT FALLS FROM THE NORTH PACIFIC CLOSER TO THE PACIFIC  
NORTHWEST.  
 
   
..GUIDANCE ASSESSMENT/PREFERENCES
 
 
CONFIDENCE IN SPECIFICS OF THE SYSTEM FORECAST TO APPROACH/REACH  
CALIFORNIA AROUND MIDWEEK HAS DECREASED OVER THE PAST DAY DUE TO A  
SIGNIFICANT DIVERGENCE OF SOLUTIONS FOR THE FEATURE ITSELF AND  
UPSTREAM FLOW THAT MAY INFLUENCE IT. GFS RUNS (THE 00Z VERSION IN  
PARTICULAR) HAVE TRENDED TOWARD MUCH STRONGER UPSTREAM ENERGY  
REACHING THE PACIFIC NORTHWEST--LEADING TO A FASTER AND MORE OPEN  
UPPER SYSTEM REACHING CALIFORNIA. ON THE OPPOSITE SIDE OF THE  
SPECTRUM, THE 00Z CMC BECOMES SLOWER THAN CONSENSUS WITH FLOW  
FARTHER UPSTREAM OVER THE PACIFIC--RESULTING IN AN UPPER LOW THAT  
BECOMES AN EXTREME TO OUTLIER SOUTHWESTWARD SOLUTION BY THU-FRI.  
OVERALL PREFER THE 00Z ECMWF/ECMWF MEAN/CMC MEAN AND 06Z FV3 GFS  
WHICH REPRESENT THE MOST CONSISTENT FORECAST RELATIVE TO PRIOR  
RUNS. MODESTLY SLOWER ADJUSTMENT IN THE 06Z GFS PROVIDES A LITTLE  
ADDED CONFIDENCE IN THE FAVORED SCENARIO. NOTE THAT BY LATE NEXT  
FRI THE 06Z FV3 GFS MAY BECOME A LITTLE TOO AGGRESSIVE WITH ITS  
SHORTWAVE NEARING CALIFORNIA.  
 
AT THE SAME TIME THE MODELS AND INDIVIDUAL ENSEMBLE MEMBERS  
CONTINUE TO BE QUITE DIVERSE FOR THE EVOLUTION FOR SHORTWAVE  
ENERGY REACHING THE NORTHERN PLAINS AND VICINITY BY TUE AND  
CONTINUING INTO THE EAST THEREAFTER. UKMET/CMC RUNS HAVE BEEN  
PERSISTENT IN DEPICTING A SLOW AND AMPLIFIED/CLOSED FEATURE WHILE  
LATEST GFS/ECMWF RUNS ARE QUITE OPEN AND PROGRESSIVE. SOME ECMWF  
RUNS FROM A COUPLE DAYS AGO WERE SLOWER THOUGH. TELECONNECTIONS  
RELATIVE TO THE POSITIVE HEIGHT ANOMALY CENTER SEEN IN MULTI-DAY  
MEANS OVER WESTERN CANADA LEAVE THE DOOR OPEN TO SOME TROUGH  
ELONGATION OVER THE MIDWEST/PLAINS BUT PERHAPS WITH GREATER  
PROGRESSION THAN THE UKMET/CMC SCENARIO. WOULD RECOMMEND A  
BLENDED APPROACH FOR THE PURPOSES OF A SINGLE DETERMINISTIC  
FORECAST.  
 
LATER IN THE WEEK THERE ARE TYPICAL DIFFERENCES IN CENTRAL/EASTERN  
CANADA FLOW THAT MAY AMPLIFY INTO THE NORTHEAST. A MODEL/ENSEMBLE  
MEAN BLEND LOOKS REASONABLE FOR THIS PART OF THE FORECAST, ASIDE  
FROM THE 06Z FV3 GFS THAT BECOMES SHARPER AND MORE AMPLIFIED THAN  
MOST OTHER GUIDANCE.  
 
BASED ON PREFERENCES OVER THE WEST IN PARTICULAR, THE FORECAST  
PLACES GREATEST EMPHASIS ON THE 00Z ECMWF DURING THE FIRST HALF OF  
THE PERIOD WITH MINORITY INPUT FROM THE 00Z UKMET/CMC AND 06Z FV3  
GFS. AFTER MIDWEEK THE FORECAST REDUCES CMC/FV3 INPUT WHILE  
INCREASING WEIGHT OF THE 00Z ECMWF MEAN AND NAEFS MEAN (WHICH  
INCLUDES THE CMC ENSEMBLES).  
 
   
..WEATHER HIGHLIGHTS AND HAZARDS
 
 
A LINGERING FRONTAL BOUNDARY SOUTH OF THE FLORIDA PENINSULA AND  
ONE OR MORE EMBEDDED WAVES WILL SUPPORT WIDESPREAD AND POTENTIALLY  
HEAVY RAINS OVER THE SOUTHERN HALF OF THE FLORIDA PENINSULA DURING  
THE FIRST HALF OF THE WEEK. FARTHER WEST, THE PREFERRED FORECAST  
FOR THE PACIFIC SYSTEM TRACKING INTO CALIFORNIA SHOULD SPREAD RAIN  
AND HIGH ELEVATION SNOW INTO THE SIERRA NEVADA, GREAT BASIN, AND  
CENTRAL/SOUTHERN ROCKIES BY NEXT WED-FRI. SOME LOCALIZED  
ENHANCEMENT OF PRECIPITATION OVER FAVORED TERRAIN WILL BE  
POSSIBLE. NOTE THAT A LESS LIKELY SCENARIO EXISTS THAT WOULD  
BRING MORE MOISTURE INTO NORTHERN CALIFORNIA. MOISTURE FROM  
UPSTREAM FLOW MAY REACH THE PACIFIC NORTHWEST BY NEXT FRI. ONE OR  
MORE AREAS OF MOSTLY LIGHT RAIN/SNOW MAY PROGRESS ACROSS THE GREAT  
LAKES/NORTHEAST WITHIN CYCLONIC FLOW ALOFT, WITH SOME ACTIVITY  
POSSIBLY EXTENDING FARTHER SOUTHWESTWARD ALONG A FRONT.  
 
THE MOST PROMINENT TEMPERATURE TREND NEXT WEEK WILL BE THE  
DEVELOPMENT OF ABOVE NORMAL READINGS (ESPECIALLY FOR MORNING LOWS)  
OVER THE WEST AND PROGRESSING/EXTENDING INTO THE NORTH-CENTRAL  
PLAINS. THERE SHOULD BE DECENT COVERAGE OF PLUS 10-20F ANOMALIES  
FOR MIN TEMPS OVER THE INTERIOR WEST BY WED-THU AND PARTS OF THE  
HIGH PLAINS BY FRI. WARMEST HIGHS (PLUS 10F OR SO ANOMALIES) OVER  
THE WEST WILL LIKELY BE NEAR THE WEST COAST EARLY IN THE WEEK  
WHILE HIGHS FROM CALIFORNIA INTO THE FOUR CORNERS STATES TREND  
GRADUALLY COOLER WITH THE ARRIVAL OF CLOUDS/PRECIPITATION. COOL  
TEMPERATURES OVER THE SOUTH/EAST (10-15F BELOW NORMAL OVER  
SOUTHWESTERN TEXAS EARLY IN THE WEEK, GENERALLY 5-10F BELOW NORMAL  
ELSEWHERE) EARLY IN THE WEEK SHOULD MODERATE CLOSER TO NORMAL BY  
THU-FRI.  
 
RAUSCH/RYAN  
 
ADDITIONAL 3-7 DAY HAZARDS INFORMATION CAN BE FOUND ON THE WPC  
MEDIUM RANGE HAZARDS CHART AT:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDICES ARE 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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