144  
FXUS02 KWBC 292003  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
402 PM EDT FRI APR 29 2022  
 
VALID 12Z MON MAY 02 2022 - 12Z FRI MAY 06 2022  
   
..OVERVIEW
 
 
CONTINUING FROM THE SHORT RANGE TIME FRAME, 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  
MONDAY 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 ISSUED AN EXPERIMENTAL MEDIUM RANGE  
SLIGHT RISK FOR EXCESSIVE RAINFALL EARLY IN THE WEEK OVER/NEAR THE  
EASTERN SOUTHERN PLAINS. 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
 
 
THE MOST CONTENTIOUS ASPECT OF THE FORECAST IN RECENT DAYS HAS  
GENERALLY BEEN THE SYSTEM REACHING THE WEST ON MONDAY AND THEN  
CONTINUING THROUGH THE WESTERN-CENTRAL U.S. FOR THE REST OF THE  
WEEK. AFTER A SLOWER ADJUSTMENT IN THE ECMWF A COUPLE DAYS AGO,  
THERE WAS A CONSISTENT GUIDANCE SPREAD BETWEEN FASTER GFS RUNS AND  
SLOWER ECMWF WHILE THE CMC/UKMET TENDED TO BE IN THE MIDDLE TO  
SLOWER PART OF THE ENVELOPE. OVER THE PAST DAY THE GFS AND GEFS  
MEAN HAVE MADE A FAIRLY DRAMATIC SLOWER ADJUSTMENT, LEADING TO  
IMPROVED CLUSTERING WITHIN WHAT HAD BEEN THE SLOWER PART OF THE  
SPECTRUM. NEW 12Z MODELS MAINTAIN CONTINUITY WITH THIS DEVELOPING  
MAJORITY SCENARIO THROUGH EARLY DAY 6 THURSDAY SO CONFIDENCE IS  
IMPROVING AT LEAST THROUGH THAT TIME. SOME DIVERGENCE STILL ARISES  
THEREAFTER, WITH VARYING IDEAS FOR UPSTREAM FLOW ENTERING THE WEST  
AND FLOW IN THE SOUTHWEST PART OF THE EASTERN CANADA MEAN  
TROUGH--WITH POTENTIAL EFFECTS ON THE SYSTEM REACHING THE CENTRAL  
U.S. FOR BOTH OF THOSE AREAS THE 06Z/12Z GFS OFFER SOMEWHAT LESS  
CONFIDENT SOLUTIONS, BRINGING MORE AMPLIFIED TROUGHING INTO THE  
WEST AND SHOWING MORE SOUTHWESTWARD TROUGH ELONGATION INTO THE  
GREAT LAKES VERSUS PREVAILING CONSENSUS. NOTE THAT MODEL/ENSEMBLE  
SPREAD FOR THE TROUGH NEAR THE WEST COAST INCREASES SIGNIFICANTLY  
AFTER EARLY THURSDAY, AND THE ECMWF/ECMWF MEAN HAVE TRENDED TOWARD  
A LESS AMPLIFIED TROUGH OVER THE PAST DAY. FOR THE EARLY WEEK  
SYSTEM TRACKING FROM THE SOUTH-CENTRAL HIGH PLAINS THROUGH THE  
GREAT LAKES, THERE ARE STILL SOME DETAIL/STRENGTH DIFFERENCES WITH  
TRENDS GENERALLY FAVORING AN INTERMEDIATE SOLUTION. SOME  
DIFFERENCES ARE RELATED TO STILL-UNRESOLVED DETAILS OF INTERACTION  
WITH NORTHERN STREAM FLOW. CMC RUNS HAVE BEEN PERSISTENT WITH  
SLOWER TIMING THAN OTHER GUIDANCE TO THE EAST OF THE PLAINS.  
 
A 06Z/00Z OPERATIONAL MODEL BLEND EARLY FOLLOWED BY A  
MODEL/ENSEMBLE MEAN MIX REPRESENTED THE IMPROVING SLOWER CONSENSUS  
FOR THE WESTERN THROUGH CENTRAL U.S. SYSTEM WHILE YIELDING THE  
DESIRED INTERMEDIATE (AND CLOSER TO CONTINUITY) FORECAST OF THE  
LEADING SYSTEM EARLY IN THE WEEK. UPPER TROUGHING/LEADING SURFACE  
FRONT PUSHING INTO THE WEST LATE IN THE WEEK ARE FAIRLY STABLE  
RELATIVE TO PREVIOUS FORECAST.  
 
   
..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-FRIDAY SHOULD BRING A RENEWED  
PRECIPITATION FOCUS INTO THE PACIFIC NORTHWEST AND THEN FARTHER  
INLAND. THE SOUTHERN EXTENT OF PRECIPITATION WILL DEPEND ON THE  
UPPER TROUGH'S PRECISE AMPLITUDE WHICH BECOMES INCREASINGLY  
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.  
 
THE NORTHERN HALF OF THE PLAINS AND MIDWEST WILL BE ON THE CHILLY  
SIDE NEXT WEEK. THE MOST EXTREME ANOMALIES SHOULD BE OVER THE  
NORTH-CENTRAL PLAINS ON MONDAY (NORTH OF THE FIRST CENTRAL U.S.  
SYSTEM) WITH HIGHS 15-25F BELOW NORMAL. EXPECT A TREND CLOSER TO  
NORMAL TOWARD THE END OF THE WEEK. THE WEST WILL SEE TEMPERATURES  
VARY FROM WEST TO EAST WITH SYSTEM PROGRESSION, WITH SOME HIGHS  
5-15F BELOW NORMAL CROSSING THE REGION DURING THE FIRST HALF OF  
THE WEEK TO BE FOLLOWED BY ABOVE NORMAL HIGHS OF SIMILAR MAGNITUDE  
WEDNESDAY-THURSDAY. THE WEST COAST WILL TREND BACK TO  
NEAR/SLIGHTLY BELOW NORMAL LATE IN THE WEEK. MOST OF THE EAST WILL  
TEND TO SEE ABOVE NORMAL TEMPERATURES NEXT WEEK WITH  
TUESDAY-WEDNESDAY LIKELY PRODUCING THE GREATEST COVERAGE OF PLUS  
10F OR GREATER ANOMALIES.  
 
RAUSCH/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  
 
HAZARDS:  
- HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL/SOUTHERN PLAINS, AND  
THE MIDDLE/LOWER MISSISSIPPI  
VALLEY, MON, MAY 2 AND WED, MAY 4.  
- SEVERE WEATHER ACROSS PORTIONS OF THE CENTRAL/SOUTHERN PLAINS,  
AND THE MIDDLE/LOWER MISSISSIPPI  
VALLEY, MON, MAY 2.  
- SEVERE WEATHER ACROSS PORTIONS OF THE CENTRAL/SOUTHERN PLAINS,  
WED, MAY 4.  
- FLOODING POSSIBLE ACROSS PORTIONS OF THE UPPER MISSISSIPPI  
VALLEY AND THE NORTHERN PLAINS.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE UPPER  
MISSISSIPPI VALLEY AND THE NORTHERN  
PLAINS.  
- FLOODING LIKELY ACROSS PORTIONS OF THE UPPER MISSISSIPPI VALLEY  
AND THE NORTHERN PLAINS.  
- ENHANCED WILDFIRE RISK ACROSS PORTIONS OF THE CENTRAL/SOUTHERN  
PLAINS, THE CENTRAL/SOUTHERN  
ROCKIES, THE CENTRAL GREAT BASIN, AND THE SOUTHWEST, TUE, MAY 3.  
- ENHANCED WILDFIRE RISK ACROSS PORTIONS OF THE SOUTHERN ROCKIES,  
THE SOUTHERN PLAINS, AND THE  
SOUTHWEST, MON, MAY 2.  
- FLOODING POSSIBLE ACROSS PORTIONS OF MAINLAND ALASKA, MON-FRI,  
MAY 2-MAY 6.  
 
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  
 

 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page