553  
FXUS02 KWBC 300701  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM EDT SAT APR 30 2022  
 
VALID 12Z TUE MAY 03 2022 - 12Z SAT MAY 07 2022  
   
..OVERVIEW
 
 
A SERIES OF PACIFIC SYSTEMS (EACH SUPPORTED BY AN UPPER TROUGH  
THAT MAY CONTAIN A CLOSED LOW FOR A PERIOD OF TIME) PROGRESSING  
ACROSS THE LOWER 48 WILL PRODUCE ACTIVE WEATHER DURING THE PERIOD.  
THESE SYSTEMS WILL SPREAD RAIN AND HIGH ELEVATION SNOW ACROSS THE  
PACIFIC NORTHWEST AND NORTH-CENTRAL ROCKIES/HIGH PLAINS, AND THEN  
MOSTLY RAIN OVER A LARGE PART OF THE CENTRAL/EASTERN U.S. THERE  
WILL BE TWO PRIMARY SYSTEMS OF INTEREST, ONE TRACKING FROM THE  
SOUTH-CENTRAL HIGH PLAINS THROUGH THE GREAT LAKES EARLY IN THE  
WEEK AND THE SECOND ENTERING THE WEST BY MONDAY AND REACHING NEAR  
THE MIDWEST BY FRIDAY. SOME THUNDERSTORMS COULD BE STRONG WITH SPC  
INDICATING A THREAT OF SEVERE WEATHER OVER THE SOUTHERN PLAINS AND  
VICINITY INTO TUESDAY WITH THE FIRST SYSTEM AND THEN AGAIN A  
COUPLE DAYS LATER AHEAD OF THE NEXT ONE. HEAVY RAIN WILL ALSO BE A  
THREAT WITH EACH SYSTEM. WPC HAS NOW ISSUED AN EXPERIMENTAL MEDIUM  
RANGE "SLIGHT RISK" FOR EXCESSIVE RAINFALL NEXT MIDWEEK OVER/NEAR  
THE EASTERN SOUTHERN PLAINS, WITH RUNOFF ISSUES AFFECTED BY  
ADDITIONAL SHORT RANGE RAINFALL. THE MIDWEEK THREAT SIGNAL IS  
STRONGER THAN NORMAL AS A CLOSED UPPER SYSTEM/LEAD UPPER  
DIFFLUENCE COMBINE WITH INCREASING INFLOW INTO A WAVY FRONT. LATE  
IN THE PERIOD THE GUIDANCE SUGGESTS AN EVOLUTION TOWARD LARGER  
SCALE FEATURES WITH MEAN TROUGHING ALOFT REACHING THE EASTERN  
PACIFIC/WEST COAST WHILE RIDGING BUILDS OVER CENTRAL CANADA AND A  
TROUGH REACHES EASTERN CANADA/NORTHEAST U.S. THE PATTERN DURING  
THE PERIOD WILL LIKELY LEAVE THE SOUTHERN HALF OR THIRD OF THE  
WEST, THE NORTHERN PLAINS NEAR THE CANADIAN BORDER, AND THE GULF  
COAST AS THE RELATIVELY DRIER AREAS DURING NEXT WEEK.  
 
   
..MODEL GUIDANCE EVALUATION
 
 
LATEST 18/00 UTC GFS AND 12/00 UTC ECMWF/UKMET MASS FIELD AND QPF  
SOLUTIONS SEEM BEST CLUSTERED DAYS 3-5 (TUE-THU) AND HAVE GOOD  
ENSEMBLE AND CONTINUITY SUPPORT IN A PERIOD WITH SEEMINGLY ABOVE  
NORMAL PREDICTABILITY. WPC PRODUCT CONTINUITY IS WELL MAINTAINED,  
BOLSTERING FORECAST CONFIDENCE.  
 
FORECAST SPREAD INCREASES DRAMATICALLY INTO DAYS 6/7 AS GUIDANCE  
STRUGGLES BOTH WITH PACIFIC SYSTEM TRACK ISSUES INLAND INTO THE  
WEST AND WITH CLOSED SYSTEM PROGRESSION OUT FROM THE PLAINS.  
RECENT GFS RUNS CURIOUSLY SHOW MUCH MORE ROBUST HEIGHT  
FALLS/SYSTEM DIGGING ACROSS THE WEST COAST TO THE SOUTHWEST WHILE  
IN CONTRAST THE CANADIAN AND ESPECIALLY THE ECMWF INSTEAD FOCUS  
INTO THE NORTHWEST. A FAVORED GEFS MEAN AND DOUBLE WEIGHTED ECMWF  
ENSEMBLE MEAN BLEND SHOWS ONLY MODERATE SYSTEM DIGGING INTO THE  
WEST ALONG WITH DOWNSTREAM SYSTEM PROGRESSIONS OUT FROM THE  
CENTRAL U.S. ON THE SLOWER SIDE OF THE FULL ENVELOPE OF GUIDANCE  
SOLUTIONS. THIS BEST TAKES INTO ACCOUNT THE NATURE OF PATTERNS  
WITH CLOSED LOWS/TROUGHS IN A SPLIT SOUTHERN STREAM.  
 
   
..SENSIBLE WEATHER/THREATS
 
 
OVER THE WEST, ANOTHER SYSTEM WILL SPREAD MOISTURE FROM THE  
PACIFIC NORTHWEST THROUGH THE ROCKIES INTO EARLY AND MIDDLE PART  
OF NEXT WEEK. DEPENDING ON EXACT SYSTEM DETAILS, THIS COULD  
PRODUCE SOME ENHANCED TOTALS, INCLUDING ACCUMULATING SNOWS INTO  
THE NORTH-CENTRAL ROCKIES AND ADJACENT HIGH PLAINS. SUBSEQUENTLY,  
AN AMPLIFIED UPPER TROUGH AND SURFACE FRONTAL SYSTEM FORECAST TO  
REACH THE WEST COAST NEXT THURSDAY-SATURDAY SHOULD BRING A RENEWED  
PRECIPITATION FOCUS INTO THE PACIFIC NORTHWEST AND THEN FARTHER  
INLAND. HOWEVER, THE SOUTHERN EXTENT OF PRECIPITATION WILL DEPEND  
ON THE UPPER TROUGH'S PRECISE AMPLITUDE BECOMES INCREASINGLY AND  
WILDLY UNCERTAIN BY NEXT FRIDAY.  
 
OVER THE CENTRAL/EASTERN U.S., THE NORTHEAST MAY SEE LINGERING  
LIGHT PRECIPITATION ON MONDAY WITH A WEAKENING FRONT. THE TRAILING  
COLD FRONT WILL LIKELY STALL OVER THE SOUTHERN PLAINS WHILE THE  
NEXT SYSTEM EMERGES FROM THE WEST, WITH THIS SYSTEM CURRENTLY  
EXPECTED TO TRACK THROUGH THE PLAINS/MIDWEST EARLY NEXT WEEK.  
THERE IS DECENT POTENTIAL FOR AREAS OF MODERATE TO HEAVY RAINFALL  
FROM PORTIONS OF THE CENTRAL/SOUTHERN PLAINS NORTHEASTWARD,  
INCLUDING A SLIGHT RISK AREA OF EXCESSIVE RAINFALL DURING MONDAY  
INTO EARLY TUESDAY OVER THE SOUTH-CENTRAL U.S. SOME SEVERE WEATHER  
IS ALSO POSSIBLE, WITH THE STORM PREDICTION CENTER CURRENTLY  
INDICATING THE BEST POTENTIAL FOR SEVERE THUNDERSTORMS ACROSS THE  
SOUTHERN PLAINS IN THAT SAME TIME FRAME. A LOCALIZED AREA OF SNOW  
MAY BE POSSIBLE OVER THE NORTH-CENTRAL HIGH PLAINS. THE GUIDANCE  
SIGNAL IS ALSO GROWING THAT THE NEXT SYSTEM IN THE SERIES TRACKING  
OUT OF THE WEST MAY PRODUCE YET ANOTHER AREA OF SIGNIFICANT  
RAINFALL OVER AND EAST FROM THE CENTRAL U.S. MID-LATE NEXT WEEK.  
CONFIDENCE IS SLOWLY IMPROVING FOR THIS SYSTEM'S DETAILS AT LEAST  
THROUGH THURSDAY, WITH PROGRESSION IN THE SLOWER PORTION OF PRIOR  
SPREAD ADDING SOMEWHAT TO THE HEAVY RAINFALL POTENTIAL OVER SOME  
LOCATIONS. PRIOR RAINFALL COULD MAKE SOME AREAS SENSITIVE TO  
ADDITIONAL RAINFALL FROM THIS LATTER SYSTEM. FORTUNATELY THE  
GUIDANCE CONTINUES TO PRODUCE MOST IF NOT ALL PRECIPITATION TO THE  
SOUTH OF THE FAR NORTHERN PLAINS WHERE SOIL CONDITIONS ARE THE  
WETTEST.  
 
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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