902  
FXUS02 KWBC 011841  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
240 PM EDT SUN MAY 01 2022  
 
VALID 12Z WED MAY 04 2022 - 12Z SUN MAY 08 2022  
   
..MODEL GUIDANCE EVALUATION
 
 
GUIDANCE REMAINS VARIED WITH THE PROGRESSION OF A CLOSED UPPER LOW  
TRACKING OUT OF THE WEST INTO THE PLAINS AND EASTWARD, WITH THE  
GFS/GEFS MEAN (INCLUDING THE NEW 12Z RUNS TODAY) STILL ON THE FAST  
SIDE COMPARED TO THE BETTER CLUSTERED AND SLOWER 00/12 UTC  
SOLUTIONS OF THE ECMWF/UKMET/CANADIAN AND ECMWF ENSEMBLE MEAN. THE  
WPC FORECAST CONTINUES TO LEAN TOWARDS THE SLOWER SIDE OF THE  
FORECAST ENVELOPE, GIVEN CONTINUITY, BUT ALSO THE GENERAL NATURE  
OF A SEPARATED SOUTHERN STREAM FLOW WITH THESE EMBEDDED CLOSED  
SYSTEMS. BY LATE PERIOD, SOME LARGER SCALE DIFFERENCES BEGIN TO  
EMERGE BETWEEN THE CMC AND ECMWF WITH THE EC WANTING TO MAINTAIN A  
STRONGER/CLOSED LOW WHILE THE CMC OPENS UP INTO GENERAL AMPLIFIED  
TROUGHING ALONG THE EAST COAST. FELT LEANING TOWARDS THE ENSEMBLE  
MEANS BY NEXT WEEKEND HELPED MITIGATE THESE VARIANCES. THIS  
GENERAL COMBINATION ALSO WORKED WELL FOR THE REST OF THE COUNTRY  
AND MAINTAINS GOOD WPC CONTINUITY. OUT WEST, THERE IS A GENERAL  
THEME OF A LEADING SHORTWAVE REACHING THE COAST THURSDAY AND THEN  
ANOTHER ARRIVING AROUND SATURDAY. MODELS/ENSEMBLES CONTINUE TO  
VARY ON AMPLITUDE AND TIMING FOR THE LATER TROUGHING, THOUGH THE  
MOST NOTABLE OUTLIER CONTINUES TO BE THE CMC WHICH FEATURES A  
FASTER AND MUCH WEAKER/LESS AMPLIFIED PROGRESSION OF THE SATURDAY  
WAVE INTO THE WEST, WITH A FASTER SYSTEM UPSTREAM DROPPING OUT OF  
THE GULF OF ALASKA BY SUNDAY COMPARED TO THE ECMWF AND GFS AND THE  
ENSEMBLES.  
   
..PATTERN OVERVIEW AND WEATHER/THREAT HIGHLIGHTS
 
 
AN ACTIVE SPRING PATTERN CONTINUES ACROSS MUCH OF THE LOWER 48  
STATES THIS WEEK. A LEADING SYSTEM INTO THE NORTHEAST SHOULD FOCUS  
SOME MODERATE RAINS ON WEDNESDAY, WITH COOLING POST-FRONTAL  
CANADIAN HIGH PRESSURE SETTLING IN THE WAKE OF THE MAIN LOW.  
MEANWHILE, A CLOSED UPPER 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, WITH SOME LOCALLY  
TERRAIN ENHANCED TOTALS. THIS SYSTEM WILL THEN EMERGE OVER THE  
PLAINS AND PRESENT A POTENTIALLY HEAVY RAINFALL THREAT, 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  
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.  
 
SANTORELLI/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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