476  
FXUS02 KWBC 140625  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
225 AM EDT SUN APR 14 2019  
 
VALID 12Z WED APR 17 2019 - 12Z SUN APR 21 2019  
 
...YET ANOTHER MAJOR SPRING STORM MID-LATE NEXT WEEK WILL PACK A  
HEAVY RAINFALL AND SEVERE WEATHER THREAT FOR THE CENTRAL TO  
EASTERN U.S...  
   
..OVERVIEW
 
 
POTENT UPPER LEVEL LOW WILL EXIT THE FOUR CORNERS REGION WEDNESDAY  
AND WORK ITS WAY EASTWARD/NORTHEASTWARD AS RIDGING BUILDS IN THE  
WESTERN ATLANTIC. THIS WILL LEAD TO A DYNAMIC SPRING STORM AGAIN  
FOR THE CENTRAL STATES WITH RAIN, SEVERE WEATHER, AND SOME  
NORTHERN FRINGE SNOW. RIDGING WILL ALSO PUSH INTO THE WEST COAST  
BUT BE REPLACED BY AN UPPER LOW LATE FRIDAY COMING INTO SOUTHERN  
CALIFORNIA WITH LITTLE FANFARE.  
 
   
..GUIDANCE PREFERENCES
 
 
ENSEMBLE SPREAD CONTINUED TO DECREASE MARKEDLY IN THE ROCKIES TO  
START THE PERIOD WITH THE ECMWF ENSEMBLES LARGELY SHIFTING SLOWER  
LIKE THE GEFS MEMBERS HAVE BEEN. BLEND OF THE GUIDANCE SUFFICED TO  
START, THOUGH THE CANADIAN WAS PERHAPS TOO STRONG WITH NORTHERN  
STREAM FLOW. FAVORED A MEAN POSITION BETWEEN THE ECMWF/GFS AND  
THEIR ENSEMBLE MEANS WHICH DIFFERED IN HOW THE SYSTEM EVOLVED EAST  
OF THE MISSISSIPPI. UNCLEAR HOW MUCH THE SOUTHERN PORTION OF THE  
UPPER TROUGH REMAINS SEPARATED FROM THE FLOW TO THE NORTH, PERHAPS  
SLOWING THE SYSTEM DOWN EVEN MORE BY THE WEEKEND. PACIFIC  
NORTHWEST WILL SEE A FRONT PUSH THROUGH THE REGION FRIDAY THROUGH  
THE WEEKEND, REACHING THE UPPER MIDWEST AND STRETCHED BACK TO  
CALIFORNIA. TIMING VIA A CONSENSUS HAS BEEN FAIRLY STEADY BUT  
DETERMINISTIC RUNS HAVE BEEN WAVERING.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
SIGNIFICANT PRECIPITATION WILL AGAIN INCREASE INTO WEDNESDAY AND  
SPREAD FROM THE MISSISSIPPI/MISSOURI VALLEYS THROUGH THE EAST AS  
LOW PRESSURE STRENGTHENS OVER THE PLAINS AND CORN BELT. MULTI-INCH  
RAINFALL TOTALS WITH LOCAL FLOODING ARE PROBABLE (ENHANCED IN  
EMBEDDED CONVECTION) BOTH ALONG/AHEAD OF THE FRONT AND TO THE  
NORTH/NORTHEAST OF THE SURFACE LOW. THE 12Z GEFS MEAN WAS  
FORECASTING 24H PRECIPITATION AMOUNTS MUCH HIGHER THAN TYPICAL FOR  
THIS LEAD TIME OVER PARTS OF MN/WI/MI. CONSULT SPC FOR THE LATEST  
ON THE SEVERE WEATHER RISK. MILD TEMPERATURES WILL PRECEDE THE  
FRONT (10-15F ABOVE AVERAGE) TO BE REPLACED BY COOLER THAN AVERAGE  
TEMPERATURES AFTER ITS PASSAGE.  
 
FRACASSO  
 
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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