596  
FXUS02 KWBC 010701  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM EDT SUN MAY 01 2022  
 
VALID 12Z WED MAY 04 2022 - 12Z SUN MAY 08 2022  
   
..MODEL GUIDANCE EVALUATION
 
 
GUIDANCE REMAINS VARIED WITH THE PROGRESION OF A CLOSED UPPER/LOW  
TRACKING OUT OF THE WEST INTO THE PLAINS AND EASTWARD, WITH THE  
GFS/GEFS MEAN STILL ON THE FAST SIDE COMPARED TO THE BEST  
CLUSTERED AND SLOWER 12/00 UTC SOLUTIONS OF THE  
ECMWF/UKMET/CANADIAN AND ECMWF ENSEMBLE MEAN. HAVE LEANED ON THE  
SLOWER SIDE OF THE FORECAST ENVELOPE GIVEN NATURE OF A SEPARATED  
SOUTHERN STREAM FLOW WITH EMBEDDED CLOSED SYSTEMS. THIS GUIDANCE  
COMBINATION ALSO SEEMS TO WORK WELL FOR MUCH OF THE REST OF THE  
LOWER 48 OVER MEDIUM RANGE TIME SCALES. WITH THE MEAN TROUGH  
SETTLING NEAR THE WEST COAST, THERE IS A GENERAL THEME OF A  
LEADING SHORTWAVE REACHING THE COAST THURSDAY AND THEN ANOTHER  
FEATURE ARRIVING AROUND SATURDAY. WHILE RECENT MODELS/ENSEMBLES  
HAVE VARIED WILDLY FOR LATER WEEK/WEEKEND AMPLITUDE, LATEST  
GUIDANCE IS CONVERGING ON A MORE COMMOM SCENARIO.  
   
..PATTERN OVERVIEW AND WEATHER/THREAT HIGHLIGHTS
 
 
AN ACTIVE SPRING PATTERN CONTINUES ACROSS MUCH OF THE LOWER 48  
STATES THIS WEEK. A LEAD MODERATE RAINFALL FOCUS WILL BE WITH A  
SYSTEM WORKING INTO THE NORTHEAST WEDNESDAY, WITH COOLING  
POST-FRONTAL CANADIAN HIGH PRESSURE SETTLING IN THE WAKE OF THE  
MAIN LOW. MEANWHILE, A CLOSED UPPER LOW/TROUGH LOW FORECAST TO  
TRACK THROUGH THE CENTRAL ROCKIES MIDWEEK AND ASSOCIATED SURFACE  
SYSTEM DEVELOPMENT WILL SPREAD RAIN AND HIGHER ELEVATION SNOW  
ACROSS THE NORTHERN-CENTRAL ROCKIES AND HIGH PLAINS. THIS SYSTEM  
COULD PRODUCE SOME LOCALLY TERRAIN ENHANCED TOTALS. THIS SYSTEM  
WILL THEN EMERGE OVER THE PLAINS AND PRESENT POTENTIALLY HEAVY  
RAINFALL, WITH THE WPC EXPERIMENTAL EXCESSIVE RAINFALL OUTLOOK  
STILL SHOWING A SLIGHT RISK OVER/NEAR PARTS OF THE SOUTH-CENTRAL  
PLAINS WEDNESDAY INTO THURSDAY. THE THREAT SIGNAL IS STRONGER THAN  
AVERAGE AS THE SOUTHERN STREAM CLOSED UPPER SYSTEM AND UPPER  
DIFFLUENCE/INSTABILITY COMBINE WITH INCREASING INFLOW OF GULF  
MOISTURE INTO A WAVY FRONT. THE STORM PREDICTION CENTER IS ALSO  
MONITORING SEVERE THREATS FOR THIS AREA WEDNESDAY-THURSDAY.  
ORGANIZED RAIN SHOULD TRANSLATE GENERALLY EASTWARD THROUGH THE  
REST OF THE WEEK WITH LOW/FRONTAL SYSTEM PROGRESSION THAT WILL  
FOCUS SOME WIDESPREAD MODERATE TO HEAVY AMOUNTS. THE MOST LIKELY  
AXIS OF HIGHEST RAINFALL TOTALS EXTENDS FROM THE MID-LOWER MS AND  
OH VALLEYS THROUGH THE CENTRAL APPALACHIANS AND MID-ATLANTIC GIVEN  
EXPECTED UPPER LOW/TROUGH AND SURFACE SYSTEM TRACK AND TRAILING  
COLD FRONT.  
 
UPSTREAM, A MODERATELY AMPLIFIED UPPER TROUGH AND SURFACE FRONTAL  
SYSTEM FORECAST TO REACH THE WEST COAST AND PROGRESS INLAND NEXT  
THURSDAY INTO NEXT WEEKEND SHOULD BRING A RENEWED PRECIPITATION  
FOCUS INTO THE PACIFIC NORTHWEST AND THEN FARTHER EASTWARD. THE  
SOUTHERN EXTENT OF PRECIPITATION WILL DEPEND ON THE UPPER TROUGH'S  
PRECISE AMPLITUDE WHICH HAS BEEN QUITE UNCERTAIN RECENTLY IN  
GUIDANCE, BUT LATEST TRENDS SUGGEST THAT MOST MOISTURE SHOULD BE  
CONFINED TO THE NORTHERN HALF OF THE WEST. THE UPPER  
DYNAMICS/SURFACE FRONT COULD REACH FAR ENOUGH EAST TO START  
PRODUCING AT LEAST SCATTERED RAINFALL OVER THE NORTHERN HIGH  
PLAINS BY NEXT WEEKEND. EXPECT RENEWED POTENTIAL AGAIN BY NEXT  
WEEKEND TO PROGRESS INTO AND ACROSS THE WEST WITH ANOTHER FRONTAL  
SURGE AS UNSETTLING UPPER TROUGH ENERGIES EARNESTLY DIG INTO THE  
REGION.  
 
SCHICHTEL  
 
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC  
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, EXPERIMENTAL EXCESSIVE RAINFALL  
OUTLOOK, 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/#PAGE=ERO  
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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