613  
FXUS02 KWBC 261601  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1201 PM EDT FRI APR 26 2019  
 
VALID 12Z MON APR 29 2019 - 12Z FRI MAY 03 2019  
 
...HEAVY RAIN AND THE POTENTIAL FOR FLOODING AND FLASH FLOODING  
ARE EXPECTED FOR PARTS OF THE SOUTHERN PLAINS AND LOWER/MIDDLE  
MISSISSIPPI VALLEY TO OHIO VALLEY...  
 
...OVERVIEW AND ASSESSMENT OF MODEL/ENSEMBLE GUIDANCE AND  
PREDICTABILITY...  
 
A FAIRLY PERSISTENT PATTERN WILL DEVELOP IN THE MEDIUM RANGE  
PERIOD, WITH A DEEP UPPER LOW IN NORTH CENTRAL CANADA GRADUALLY  
RETROGRADING A BIT WESTWARD LATER IN THE PERIOD, AND TROUGHING  
OVER THE NORTHWESTERN U.S. EXTENDING SOUTHWARD. A SUBTROPICAL  
RIDGE IS FORECAST TO BUILD OVER THE SOUTHEAST THROUGH MIDWEEK  
BEFORE PUSHING OUT BY FRIDAY. THE OVERALL PATTERN SEEMS TO BE  
GENERALLY WELL HANDLED BY THE MODELS, WITH SOME TYPICAL  
UNCERTAINTY IN TIMING AND PLACEMENT OF SHORTWAVES MOVING ACROSS  
THE GENERAL TROUGHING PATTERN IN THE WEST AND CENTRAL U.S. WPC  
USED A MULTI-MODEL DETERMINISTIC BLEND OF THE 00Z AND 06Z GFS, 00Z  
UKMET, AND 00Z ECMWF EARLY IN THE PERIOD, THEN LEANING TOWARD THE  
EC AND GEFS MEANS LATER IN THE WEEK AS UNCERTAINTY DEVELOPS IN THE  
DETERMINISTIC RUNS REGARDING THE UPPER LOW IN WESTERN CANADA AND  
POTENTIALLY SHEARING OUT ITS ENERGY, WHICH AFFECTS THE DOWNSTREAM  
FEATURES. RUN TO RUN INCONSISTENCY REMAINS HIGH, SO STAYED WITH  
THE MEANS FOR NOW.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
PASSAGE OF MULTIPLE SHORTWAVES/HEIGHT FALLS IN BOTH NORTHERN AND  
SOUTHERN STREAMS WILL GENERATE SOME ENHANCED RAINS AND MOUNTAIN  
SNOWS FOR PORTIONS OF THE GREAT BASIN AND CENTRAL/NORTHERN ROCKIES  
EARLY IN THE PERIOD. THESE SYSTEMS WILL PROGRESS DOWNSTREAM AND A  
MAIN WEATHER FOCUS WILL DEVELOP OVER THE CENTRAL U.S. MOISTURE  
INFLOW/POOLING INTO A PERSISTENT/SLOW MOVING/WAVY FRONT WILL FOCUS  
MULTIPLE ROUNDS OF SHOWERS AND THUNDERSTORMS, WITH THE POTENTIAL  
FOR SEVERE WEATHER AND AREAS OF HEAVY RAINFALL. THE STRONGEST  
SIGNAL FOR HEAVY RAINFALL OF MULTIPLE INCHES WILL BE FROM THE  
SOUTHERN/CENTRAL PLAINS TO THE LOWER/MID-MISSISSIPPI VALLEY, WITH  
SOME POTENTIAL FOR HEAVY RAIN IN THE OHIO VALLEY AND INTO THE  
NORTHERN MID-ATLANTIC TO LOWER GREAT LAKES REGION AS WELL.  
FLOODING WILL BE POSSIBLE AS PARTICULARLY THE MISSISSIPPI VALLEY  
HAS HAD FLOODING CONCERNS FOR WEEKS, AND WITH THE CONVECTIVE  
ELEMENT OF THE PRECIPITATION, FLASH FLOODING IS POSSIBLE AS WELL.  
ON THE NORTHERN FRINGE THE PRECIPITATION, SUFFICIENT COLD AIR MAY  
BE IN PLACE TO SUPPORT SNOWS FOR PORTIONS OF THE NORTHERN HIGH  
PLAINS WITH LOW GENESIS AND APPROACH.  
 
TATE/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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