854  
FXUS02 KWBC 181601  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1200 PM EDT SAT MAY 18 2019  
 
VALID 12Z TUE MAY 21 2019 - 12Z SAT MAY 25 2019  
   
..OVERALL WEATHER PATTERN
 
 
THE UPPER LEVEL PATTERN ACROSS THE CONTINENTAL U.S. WILL REMAIN  
QUITE AMPLIFIED AND SLOW TO CHANGE NEXT WEEK. A HOT UPPER LEVEL  
RIDGE OVER THE SOUTHEAST U.S. BECOMES ANCHORED OVER THE REGION AND  
GRADUALLY BECOMES STRONGER FOR THE SECOND HALF OF THE UPCOMING  
WORK WEEK. ACROSS THE WESTERN U.S., A LARGE SCALE UPPER TROUGH  
WILL BE DOMINANT AS MULTIPLE SHORTWAVE PERTURBATIONS KEEP  
CONDITIONS COOL AND UNSETTLED. THIS WILL ALSO BE SLOW TO MOVE  
GIVEN THE EXPECTED DEVELOPMENT OF AN OMEGA BLOCK TYPE PATTERN  
UPSTREAM OVER THE EASTERN PACIFIC. LEAD MAIN WEATHER FEATURES  
INCLUDE A STRONG LOW PRESSURE SYSTEM FOR THE PLAINS AND UPPER  
MIDWEST TUE/WED, FOLLOWED BY WEAKER LOWS AND FRONTAL BOUNDARY  
MEANDERINGS FROM THE SOUTHWEST TO THE NORTHEAST U.S. LATER WEEK  
OVERTOP THE SOUTHEAST RIDGE. THE PATTERN OFFERS A PERIODIC LOCAL  
THREAT FOR STRONG TO SEVERE CONVECTION AND POTENTIAL FOR CELL  
TRAINING/EXCESSIVE RAINFALL.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
THE 06 UTC GFS AND 00 UTC ECMWF SEEM WELL CLUSTERED WITH  
GEFS/ECMWF ENSEMBLE SOLUTIONS TUE INTO THU AND A COMPOSITE SEEMS  
REASONABLE, BUT RUN TO RUN CONTINUITY ISSUES LIMIT FORECAST  
CONFIDENCE. OPTED TO QUICKLY TRANISTION TO A BLEND OF THE  
ENSEMBLES LATER THU INTO NEXT WEEKEND AMID GROWING FORECAST SPREAD  
AND UNCERTAINTY.  
 
   
..WEATHER HIGHLIGHTS AND HAZARDS
 
 
NUMEROUS SHOWERS AND THUNDERSTORMS CONTINUE TO BE IN THE FORECAST  
THROUGH THE MIDDLE OF NEXT WEEK FROM THE PLAINS TO THE UPPER  
MIDWEST THEN EASTWARD. MULTIPLE ROUNDS OF MCS ACTIVITY ARE LIKELY  
WITH BOTH OF THE LOW PRESSURE SYSTEMS THAT ARE PROGGED TO TRACK  
ACROSS THE PLAINS. THIS WILL HAVE THE POTENTIAL TO PRODUCE VERY  
HEAVY RAINFALL CAPABLE OF PRODUCING FLASH FLOODING, AND SEVERE  
WEATHER IS ALSO LIKELY ACROSS MUCH OF THE MIDWEST STATES BASED ON  
RECENT SPC FORECASTS. ADDITIONAL HEAVY RAIN IS ALSO POSSIBLE FROM  
THE NEXT STORM SYSTEM TRACKING EASTWARD FROM THE INTERMOUNTAIN  
WEST LATER IN THE WEEK, ALTHOUGH DETAILS ON TIMING AND PLACEMENT  
CONTINUE TO REMAIN LESS CLEAR AT THIS TIME.  
 
THERE WILL ALSO BE A DICHOTOMY OF TEMPERATURE ANOMALIES GIVEN THE  
AMPLIFIED FLOW PATTERN IN PLACE. TEMPERATURES ARE EXPECTED TO BE  
WELL ABOVE NORMAL TO NEAR RECORD WARMTH ACROSS MUCH OF THE  
SOUTHEASTERN U.S. OWING TO THE STRENGTH OF THE UPPER RIDGE, AND  
THIS WILL ALSO SERVE TO KEEP RAINFALL CHANCES MINIMAL. AFTERNOON  
HIGH TEMPERATURES MAY EXCEED 100 DEGREES FOR PARTS OF GEORGIA AND  
SOUTH CAROLINA BY LATER IN THE WEEK. THE OPPOSITE WILL BE THE CASE  
ACROSS MUCH OF THE WESTERN U.S. AND ALSO THE NORTHERN PLAINS WITH  
READINGS ON THE ORDER OF 10 TO 20 DEGREES BELOW CLIMATOLOGY, WHICH  
WILL BE UNDER THE INFLUENCE OF THE UPPER LEVEL TROUGH AND TO THE  
NORTH OF THE LOW TRACKS. HEAVIER LATE SEASON SNOWS ARE ALSO LIKELY  
FOR THE SIERRA NEVADA TO THE NORTHERN ROCKIES FOR THE MIDDLE OF  
THE WEEK.  
 
D. HAMRICK/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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