030  
FXUS02 KWBC 100514  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
113 AM EDT WED APR 10 2019  
 
VALID 12Z SAT APR 13 2019 - 12Z WED APR 17 2019  
 
...HEAVY RAINFALL THREAT FROM EASTERN TEXAS/LOWER MISSISSIPPI  
VALLEY DURING THE WEEKEND...  
   
..OVERVIEW AND GUIDANCE ASSESSMENT/PREFERENCES
 
 
A SYSTEM WILL EXIT THE SOUTHWEST/SOUTHERN ROCKIES ON TO THE PLAINS  
AND MS VALLEY THIS WEEKEND, BRINGING WIDESPREAD RAIN TO MUCH OF  
EASTERN TEXAS, LOWER MISSISSIPPI AND WESTERN TENNESSEE VALLEY WITH  
THE POTENTIAL FOR EXCESSIVE RAINFALL AND FLASH FLOODING. A SURFACE  
LOW IS EXPECTED TO FORM ALONG THE BOUNDARY AND AID IN THE  
PROGRESSIVE TRACK TOWARD THE OHIO VALLEY. MODEL GUIDANCE SUGGESTS  
THAT THIS SYSTEM WILL OCCLUDE, WITH A NEW LOW FORMING NEAR THE MID  
ATLANTIC COAST AND PROCEEDING NORTHEAST NEAR OR OFF THE NEW  
ENGLAND COAST EARLY NEXT WEEK. THE GEFS AND ECMWF ENSEMBLE MEANS  
CLUSTER WELL WITH THE CYCLONE TRACK, WITH TIMING DIFFERENCES  
PERSISTENT AS THE OPERATIONAL ECMWF LAGS A FEW HOURS BEHIND THE  
ENSEMBLE TIMING, AND THE 18Z GFS A FEW HOURS AHEAD OF THE ENSEMBLE  
MEANS. CONSEQUENTLY, GREATER WEIGHTING CONTINUES TO BE PLACED ON  
THE RESPECTIVE 18Z GEFS/12Z ECMWF ENSEMBLE MEANS.  
 
THE MODELS/ENSEMBLES SHOW A COUPLE OF SHORTWAVES MOVING ONSHORE  
THE PACIFIC NORTHWEST AND INTO THE NORTHERN ROCKIES AND HIGH PAINS  
OVER THE WEEKEND INTO EARLY NEXT WEEK.  
GUIDANCE IS CLUSTERING BETTER THAN ON PRIOR DAYS SO A  
MODELS/ENSEMBLE MEAN BLEND SUFFICED FOR THIS REGION. THE WAVES  
WILL BRING PRECIPITATION TO THE PACIFIC NORTHWEST AND NORTHERN  
ROCKIES WITH VALLEY RAIN SHOWERS AND MOUNTAIN SNOWS. E NORTHERN  
HIGH PLAINS.  
 
THE MODELS SHOW THE SOUTHERN PORTION OF THE UPPER TROUGH MOVING  
ONSHORE CA SUNDAY NIGHT AND CROSSING INTO THE GREAT BASIN MONDAY  
AND THE ROCKIES TO THE PLAINS ON TUESDAY.  
THIS TROUGH IS EXPECTED TO INDUCE A FRONTAL WAVE ON THE PLAINS TUE  
INTO WED, WITH THE STRONGER 18Z GFS INDUCING THE WAVE FURTHER  
NORTH THAN THE ENSEMBLE MEANS/ECMWF.  
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
THE LOW PRESSURE DEVELOPING OVER SOUTHEAST TX AND MOVING INTO THE  
LOWER MS VALLEY WILL LEAD TO A HEAVY RAINFALL THREAT FROM EASTERN  
TEXAS AND THE LOWER MISSISSIPPI VALLEY REGION INTO THE  
APPALACHIANS, MID-ATLANTIC AND SOUTHERN NEW ENGLAND, AND POSSIBLY  
INCLUDING THE OHIO VALLEY. THE HIGHEST FORECAST RAINFALL AMOUNTS  
ARE CENTERED OVER THE LOWER MS VALLEY. THE NEXT SYSTEM DEVELOPING  
OVER THE PLAINS IN THE MIDDLE OF NEXT WEEK WILL LEAD TO AN  
INCREASE IN RAINFALL AMOUNTS AND COVERAGE, INCLUDING MORE RAIN  
EXPECTED IN THE LOWER MS VALLEY.  
 
THE PACIFIC NORTHWEST AND NORTHERN ROCKIES SHOULD SEE ADDITIONAL  
PRECIPITATION AFTER THE LATE WEEK SYSTEM IN ASSOCIATION WITH  
FRONTAL SYSTEMS MOVING ONSHORE AND INLAND.  
EARLY TO MID WEEK, SNOW FOCUSES ON THE RANGES OF THE GREAT BASIN  
TO THE CO/WY ROCKIES.  
 
THE COLD TEMPERATURE ANOMALIES WILL BE OVER THE ROCKIES/PLAINS  
SATURDAY, PEAKING 20-25 DEGREES BELOW NORMAL IN THE PLAINS STATES.  
ALSO DURING SATURDAY EXPECT ABOVE NORMAL TEMPERATURES OVER THE  
EAST, ESPECIALLY FOR MORNING LOWS WHICH MAY BE 10-20F ABOVE NORMAL  
IN THE MID ATLANTIC TO NEW YORK AND MUCH OF THE APPALACHIANS ON  
SATURDAY. EXPECT READINGS TO MODERATE OVER MUCH OF THE LOWER 48  
EARLY NEXT WEEK.  
 
AS THE TROUGH PROGRESSES ACROSS THE WEST MID WEEK, BELOW NORMAL  
TEMPS WILL REDEVELOP ACROSS THE GREAT BASIN TO THE ROCKIES TUE APR  
16 AND WED APR 17. IN THE RETURN SOUTHERLY FLOW AHEAD OF THE  
TROUGH ON THE PLAINS, A WARMUP IS EXPECTED TO RESULT IN ABOVE  
NORMAL MINIMUM TEMPERATURES MID WEEK.  
 
PETERSEN  
 
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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