541  
FXUS02 KWBC 300552  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
151 AM EDT TUE APR 30 2019  
 
VALID 12Z FRI MAY 03 2019 - 12Z TUE MAY 07 2019  
 
...FLOODING/FLASH FLOODING THREAT LINGERS FOR THE SOUTHERN  
PLAINS/LOWER MISSISSIPPI VALLEY...  
 
...GUIDANCE/PREDICTABILITY ASSESSMENT AND WEATHER  
HIGHLIGHTS/THREATS...  
 
THE WPC MEDIUM RANGE PRODUCT SUITE WAS MAINLY DERIVED FROM A  
COMPOSITE OF REASONABLY WELL CLUSTERED GFS/ECMWF/UKMET/CANADIAN  
AND ENSEMBLE MEAN MID-LARGER SCALE GUIDANCE. THIS BLENDED SOLUTION  
ACTS TO MITIGATE EMBEDDED SMALLER SCALE IMPULSE TIMING AND  
CONVECTION GENESIS UNCERTAINTIES AND MAINTAINS GOOD OVERALL WPC  
CONTINUITY WITH RESPECT TO POTENTIAL WEATHER RELATED HAZARDS.  
 
A LEAD AND WAVY FRONTAL SYSTEM WITH MODERATE PRECIPITATION WILL  
PROGRESS FRI/SAT ACROSS THE EAST AS POWERED BY AN EJECTING  
SHORTWAVE TROUGH ALOFT. A WAVY TRAILING FRONT WILL STALL ACROSS  
THE U.S. SOUTHERN TIER AND POOLED MOISTURE AND CONVECTION OFFERS A  
DAILY THREAT OF HEAVY RAINS/THUNDERSTORMS AND CELL  
TRAINING/LOCALLY ENHANCED RUNOFF ISSUES WITH HARD TO TIME SOUTHERN  
STREAM IMPULSE PASSAGES. PACIFIC CLOSED LOW/TROUGH ENERGY AND  
HEIGHT FALLS ARE ALSO EXPECTED TO WORK INLAND INTO CA BY EARLY  
NEXT WEEK IN THIS SPLIT SOUTHERN STREAM. THIS MAY SUPPORT  
SCATTERED SOUTHWEST TO ROCKIES CONVECTION AND THEN RENEW LEAD  
CONVECTIVE FOCUS DOWNSTREAM OVER THE SOUTH-CENTRAL U.S. STRONG TO  
SEVERE THUNDERSTORMS WITH SOME HEAVY RAIN AND FLASH  
FLOODING/FLOODING POTENTIAL WILL PERIODICALLY THREATEN THE  
SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY IN THIS LINGERING  
PATTERN. FLOODING REMAINS POSSIBLE AS PARTICULARLY THE MISSISSIPPI  
VALLEY AND VICINITY HAS HAD FLOODING CONCERNS FOR WEEKS, AND WITH  
THE CONVECTIVE NATURE OF THE PRECIPITATION FLASH FLOODING IS  
POSSIBLE AS WELL.  
 
MEANWHILE, LEADING NORTHERN STREAM SHORTWAVES OVERTOP ARE EXPECTED  
TO PROGRESS FROM THE NORTHWEST EASTWARD ACROSS THE U.S. NORTHERN  
TIER. THIS WILL SUPPORT MODEST SYSTEM/PRECIPITATION DEVELOPMENT IN  
ADVANCE OF A COOLING/UNSETTLING MAIN CLOSED LOW/TROUGH AND LEAD  
WEATHER FOCUSING SURFACE FRONTAL SYSTEM. THIS AMPLIFIED SYSTEM MAY  
TRACK FROM WESTERN CANADA FRI TO S-CENTRAL CANADA/UPPER MIDWEST  
SUN TO EASTERN CANADA AND THE NORTHEAST IN ABOUT A WEEK. THE  
BAROCLINIC ZONE WITH THE STALLING TRAILING FRONT MAY PERIODICALLY  
FOCUS IMPULSE DRIVEN CONVECTION MAINLY OVER THE NORTHERN ROCKIES,  
CENTRAL PLAINS, AND OHIO VALLEY.  
 
SCHICHTEL  
 
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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