645  
FXUS02 KWBC 170600  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
200 AM EDT SUN MAR 17 2019  
 
VALID 12Z WED MAR 20 2019 - 12Z SUN MAR 24 2019  
   
..OVERVIEW AND GUIDANCE ASSESSMENT/PREFERENCES
 
 
MODELS/ENSEMBLES SHOW BROAD AGREEMENT THAT AN ANOMALOUS UPPER  
RIDGE AXIS INITIALLY EXTENDING FROM THE CANADIAN ROCKIES AND  
PRAIRIES SOUTH INTO THE NORTH CENTRAL U.S. BY THE MIDWEEK SHOULD  
SLOWLY SHIFT EASTWARD DURING THE FORECAST PERIOD, WHILE PERHAPS  
WEAKENING OF DISBURSING SOMEWHAT. SHORTWAVE ENERGY FROM THE  
PACIFIC WILL UNDERCUT THE RIDGE, SLOWLY PROGRESSING EAST FROM  
CALIFORNIA TO THE MISSISSIPPI VALLEY THU-SUN. A MEAN TROUGH WILL  
PERSIST DOWNSTREAM OF THE RIDGE, REINFORCED ACROSS THE LOWER GREAT  
LAKES AND THE NORTHEAST LATE IN THE WEEK BY A VIGOROUS SHORTWAVE  
TRAVERSING THE NORTHWESTERLY FLOW LATE IN THE WEEK. MEANWHILE, AS  
THE RIDGE SLIDES EAST, HEIGHT FALLS SHOULD REACH THE PACIFIC  
NORTHWEST BY THE WEEKEND, BRINGING A RETURN TO A MORE ACTIVE  
WEATHER PATTERN FOR THE WEST COAST.  
 
A BLEND OF THE ECMWF/GFS/CMC WAS USED A BASIS FOR THE FORECAST  
THROUGH MUCH OF THE PERIOD. MODELS HAVE CONTINUED TO TREND DEEPER  
WITH SHORTWAVE ENERGY CROSSING THE MIDWEST AND MISSISSIPPI VALLEY  
WED-THU, WITH SOME CONTINUED TIMING AND STRUCTURAL DIFFERENCES.  
CONSENSUS HAS IMPROVED OVER RECENT DAYS WITH RESPECT TO THE  
SOUTHERN STREAM SHORTWAVE AS WELL, WITH GUIDANCE IN GENERAL  
AGREEMENT THAT AN UPPER LOW SHOULD CLOSE OFF ACROSS THE SOUTHWEST  
BY THU THEN SLOWLY DRIFTING EAST INTO THE CENTRAL U.S. AGAIN, SOME  
TIMING DIFFERENCES ARE EVIDENT BUT SOLUTIONS ARE GENERALLY  
WELL-CLUSTERED AROUND THE ENSEMBLE MEANS, LENDING AT LEAST SOME  
DEGREE OF INCREASED CONFIDENCE TO SOLUTIONS WITHIN THE CENTER OF  
THE SPREAD. FINALLY, WHILE THERE IS BROAD AGREEMENT ON HEIGHT  
FALLS AND A COLD FRONT REACHING THE WEST COAST BY NEXT WEEKEND,  
MODELS CONTINUE TO SHOW VARIABILITY ON THE STRUCTURE OF THE TROUGH  
AND THE EMBEDDED SMALLER-SCALE SHORTWAVES. GIVEN THESE  
CONSIDERATIONS, WEIGHTING OF THE ECENS AND NAEFS ENSEMBLE MEANS IN  
THE FORECAST WAS INCREASED SIGNIFICANTLY BY DAYS 6-7 (SAT-SUN).  
 
   
..WEATHER HIGHLIGHTS AND HAZARDS
 
 
THE SOUTHERN STREAM SYSTEM WILL BRING RAIN AND MOUNTAIN SNOWS FROM  
CALIFORNIA TO MUCH OF THE FOUR CORNERS REGION WED-THU. AS MOISTURE  
INCREASES AHEAD OF THE SYSTEM ACROSS THE SOUTHERN PLAINS FRI-SAT,  
SHOWERS AND THUNDERSTORMS ARE EXPECTED TO BECOME MORE WIDESPREAD  
ACROSS THAT REGION, WITH THE POTENTIAL FOR SOME AREAS OF HEAVY  
RAIN. RAIN AND MOUNTAIN SNOW SHOULD SPREAD INTO THE PACIFIC  
NORTHWEST AND NORTHERN CALIFORNIA BY FRI-SAT AS THE UPPER TROUGH  
AND COLD FRONT APPROACHES, WITH HEAVY PRECIPITATION POSSIBLE IN  
FAVORED TERRAIN AREAS. GRADUALLY WARMING TEMPERATURES ARE EXPECTED  
ACROSS MUCH OF THE NORTHERN TIER. THE WARMEST TEMPERATURES WILL  
INITIALLY BE ACROSS THE PACIFIC NORTHWEST, WITH HIGHS 5-15 DEG F  
ABOVE AVERAGE WED-THU. THE WARM CONDITIONS WILL SPREAD EAST ALONG  
WITH THE UPPER-LEVEL RIDGE, WITH HIGH TEMPERATURES ANOMALIES OF  
SIMILAR MAGNITUDE REACHING THE MIDWEST BY FRI-SAT, AND PORTIONS OF  
THE MID-ATLANTIC AND NORTHEAST BY NEXT SUN.  
 
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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