550  
FXUS02 KWBC 110614  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
213 AM EDT THU APR 11 2019  
 
VALID 12Z SUN APR 14 2019 - 12Z THU APR 18 2019  
 
...HEAVY RAINFALL THREAT FOR THE MID-LOWER MISSISSIPPI/OHIO  
VALLEYS THIS WEEKEND AND AGAIN IN THE MIDDLE OF NEXT WEEK...  
 
...WEATHER HIGHLIGHTS/HAZARDS AND GUIDANCE/PREDICTABILITY  
ASSESSMENT...  
 
AN UPPER TROUGH CROSSES THE SOUTHERN PLAINS THROUGH THE MID-LOWER  
MS/OH VALLEYS THIS WEEKEND, BRINGING WIDESPREAD RAINS WITH  
POTENTIAL OF EXCESSIVE RAINFALL, FLASH FLOODING, AND STRONG TO  
SEVERE LEAD WARM SECTOR CONVECTION OVER THE SOUTH. THE POTENT LOW  
AND PRECIPITATION SHIELD WILL TRACK OVER THE NORTHEAST MONDAY,  
WITH THE TRAILING COLD FRONT MOVING ACROSS THE SOUTHEAST AND  
OFFSHORE INTO THE GULF OF MEXICO AND WESTERN ATLANTIC. A BLEND OF  
THE 18Z GFS/18Z GEFS MEAN/12Z ECMWF/12Z ECMWF ENSEMBLE MEAN WAS  
USED DUE TO GOOD CLUSTERING OF THESE SOLUTIONS.  
 
MEANWHILE UPSTREAM, MODELS/ENSEMBLES OVERALL AGREE TO BRING  
ANOTHER POTENT MID-UPPER LEVEL TROUGH/AMPLE HEIGHT FALLS/FRONTAL  
PRECIPITATION INTO THE WEST COAST SUNDAY.  
THE UPPER TROUGH AMPLIFIES WITH TIME AS IT CROSSES THE GREAT BASIN  
MONDAY  
AND INTO THE ROCKIES TUESDAY. HEIGHT FALLS ON THE HIGH PLAINS  
INDUCES CYCLOGENESIS WITH  
A RENEWED RETURN FLOW OF DEEPENING GULF MOISTURE AND ASCENT  
LEADING TO ENHANCED RAINFALL IN EASTERN OK/TX EXTENDING DOWNSTREAM  
INTO THE LOWER MS VALLEY.  
GIVEN A SIMILAR CYCLONE TRACK AND UPPER LEVEL TROUGH TRACK,  
SIMILAR AREAS HIT BY RAIN THIS WEEKEND ARE EXPECTED TO RECEIVED  
ADDITIONAL RAINS IN THE MIDDLE OF NEXT WEEK.  
 
THIS COULD RESULT IN A RENEWED FLOODING/FLASH FLOODING THREAT  
ACROSS EASTERN OK/TX INTO THE LOWER MS VALLEY. THE MODELS SPREAD  
GROWS FOR THIS SYSTEM AS THE ENSEMBLE MEANS HAVE MORE EMPHASIS ON  
LOW PRESSURE ALONG THE WAVY FRONT FURTHER NORTH IN THE MIDWEST  
WHILE THE OPERATIONAL GFS/ECMWF HEAVE MORE EMPHASIS ON LOW  
PRESSURE UNDER THE SOUTHERN STREAM PORTION OF THE UPPER TROUGH WED  
17 APR TO THU 18 APR. AN EQUAL BLEND OF THE 12Z GFS/12Z ECMWF  
MODELS/ 18Z GEFS/12Z ECMWF ENSEMBLE MEANS WAS USED TO MITIGATE THE  
DIFFERENCES UNTIL BETTER AGREEMENT DEVELOPS.  
 
THE DEVELOPING WESTERN TROUGH LEADS TO AN AREA OF BELOW NORMAL  
TEMPERATURES IN THE NORTHWEST AND NORTHERN ROCKIES MON 15 APR THAT  
EXPANDS SOUTHEAST ACROSS THE GREAT BASIN  
AND THEN CENTRAL ROCKIES TUE AND THEN THE PLAINS WED, WITH  
READINGS COMMONLY SEVERAL DEGREES BELOW AVERAGE. THE BUILDING  
WEST COAST RIDGE LEADS TO WARM TEMPERATURES IN CA/OR/WA NEXT THU.  
THE SOUTHERLY FLOW EAST OF THE CENTRAL US STORM LEADS TO AN AREA  
OF ABOVE NORMAL TEMPERATURES NEAR THE EAST COAST NEXT WED 17  
APR-THU 18 APR.  
 
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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