005  
FXUS02 KWBC 271916  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
316 PM EDT WED APR 27 2022  
 
VALID 12Z SAT APR 30 2022 - 12Z WED MAY 04 2022  
   
..OVERVIEW
 
 
LATEST GUIDANCE CONTINUES AN ACTIVE PATTERN WITH A SERIES OF  
PACIFIC SYSTEMS ENTERING AND PROGRESSING ACROSS THE LOWER 48. THE  
FIRST SYSTEM WILL BE A CLOSED UPPER LOW AND ASSOCIATED SURFACE LOW  
PRESSURE THAT SHOULD LIFT SLOWLY NORTHEASTWARD FROM THE  
NORTH-CENTRAL PLAINS, PASSING THROUGH THE NORTHEAST IN WEAKENED  
FORM BY NEXT MONDAY-TUESDAY. THIS WILL SPREAD RAIN ACROSS MUCH OF  
THE CENTRAL U.S. WITH SOME CHANCE OF WINTRY WEATHER SPREADING INTO  
THE NORTHERN HIGH PLAINS ON THE BACKSIDE OF THE LOW. LIGHTER  
RAINFALL WILL EXTEND FARTHER EAST. THE NEXT SYSTEM SHOULD BE  
SOMEWHAT WEAKER, PROGRESSING FROM THE WEST COAST TO NEAR THE EAST  
COAST DURING THE PERIOD. THEN A STRONGER SYSTEM IS LIKELY TO TRACK  
FROM THE WEST COAST INTO THE ROCKIES/PLAINS DURING  
MONDAY-WEDNESDAY. THE LATTER TWO SYSTEMS WILL BRING RAIN AND HIGH  
ELEVATION SNOW TO THE NORTHWEST AND THEN AREAS OF ENHANCED  
PRECIPITATION TO PARTS OF THE CENTRAL AND EASTERN U.S. DEPENDING  
ON SYSTEM/FRONTAL DETAILS.  
 
   
..MODEL GUIDANCE EVALUATION
 
 
WITHIN WHAT HAS BEEN A FAIRLY AGREEABLE PATTERN FROM THE MULTI-DAY  
MEAN PERSPECTIVE, SOME CHALLENGES ARE ONGOING FOR SPECIFICS OF  
INDIVIDUAL SYSTEMS. SOLUTIONS HAVE CONVERGED FAIRLY WELL FOR THE  
LEADING SYSTEM TRACKING OUT OF THE PLAINS DURING THE WEEKEND BUT  
STILL DIVERGE A BIT BY DAY 5 MONDAY WITH THE 06Z GFS AND NOW THE  
12Z UKMET STRAYING SOMEWHAT TO THE FASTER/NORTHWARD SIDE OF THE  
SPREAD. MEANWHILE THERE ARE STILL MEANINGFUL DETAIL AND TRACK  
ISSUES WITH THE SHORTWAVE REACHING THE WEST DURING THE WEEKEND,  
WITH THE NEW 12Z ECMWF AT LEAST ADJUSTING SOMEWHAT NORTH OF ITS  
00Z RUN WHOSE UPPER LOW CENTER WAS ON THE SOUTHERN SIDE OF THE  
ENVELOPE. ONCE THIS FEATURE EJECTS FROM THE WEST, MODEL RUNS OVER  
RECENT DAYS HAVE DIFFERED GREATLY OVER SPECIFICS (INCLUDING THE  
SURFACE REFLECTION). HOWEVER IN A POSITIVE TREND TODAY'S 00Z  
THROUGH 12Z RUNS SEEM TO BE CLUSTERING A LITTLE BETTER TOWARD  
MAINTAINING ENOUGH DEFINITION OF THE SHORTWAVE TO SUPPORT A  
SURFACE WAVE OVER OR JUST EAST OF THE MID MISSISSIPPI VALLEY BY  
EARLY TUESDAY AND NEAR THE EAST COAST WEDNESDAY. THERE IS STILL A  
SIGNIFICANT QUESTION OF STREAM INTERACTION OVER EASTERN NORTH  
AMERICA THAT COMPLICATES THE FORECAST AFTER EARLY TUESDAY. THE  
FINAL SYSTEM IN THE SERIES CONTINUES TO PROVIDE A DIFFICULT  
FORECAST THOUGH. GFS RUNS REMAIN ON THE FASTER SIDE OF THE SPREAD,  
BRINGING IT WELL INTO THE PLAINS BY MIDWEEK. THE 00Z ECMWF JUMPED  
BACK CLOSE TO THE PERSISTENTLY SLOW CMC (WHICH ITSELF CHANGED TO  
AN INTERMEDIATE TIMING IN THE NEW 12Z RUN) WHILE THE NEW 12Z ECMWF  
IS CLOSE TO ITS 00Z RUN. THE 06Z GEFS MEAN HEDGED BACK TO A  
COMPROMISE, CLOSE TO THE 00Z CMC MEAN AND A BIT AHEAD OF THE ECMWF  
MEAN, BEFORE GRAVITATING CLOSER TO THE OPERATIONAL RUN AGAIN IN  
THE 12Z CYCLE. THE ARRAY AND VARIABILITY OF LATEST RUNS FAVORED A  
COMPROMISE APPROACH BETWEEN THE GFS AND 00Z ECMWF ALOFT, SLOWER  
THAN CONTINUITY BUT OFFERING SOME FLEXIBILITY PENDING FUTURE  
TRENDS.  
 
BASED ON THE GUIDANCE AVAILABLE THROUGH THE 06Z CYCLE, THE UPDATED  
FORECAST USED A COMPOSITE OF 00Z/06Z MODELS EARLY TO TONE DOWN THE  
MORE EXTREME ASPECTS OF ONE OR MORE SOLUTIONS, FOLLOWED BY ADDING  
SOME INPUT FROM THE 06Z GEFS/00Z ECMWF MEANS ALONG WITH THE MODELS  
TO YIELD THE DESIRED INTERMEDIATE SOLUTION LATE. ADMITTEDLY THE  
FAVORED MODEL/MEAN BLEND ENDED UP PRODUCING A SURFACE EVOLUTION A  
TAD SLOWER THAN ULTIMATELY DESIRED BY DAY 7 WEDNESDAY THOUGH.  
 
   
..SENSIBLE WEATHER/THREATS
 
 
THE FIRST SURFACE LOW PRESSURE SYSTEM AFFECTING THE LOWER 48 OVER  
THE WEEKEND WILL SPREAD PRECIPITATION ACROSS MUCH OF THE CENTRAL  
AND EASTERN U.S., WITH SOME WINTRY WEATHER POSSIBLE IN THE DAKOTAS  
AND THE BEST CHANCES IN THE HIGHER ELEVATIONS OF THE BLACK HILLS.  
IN PORTIONS OF THE DAKOTAS, PRECIPITATION MAY BEGIN AS RAIN AND  
TRANSITION TO MIXED PRECIPITATION OR SNOW, THOUGH DETAILS OF THESE  
THREATS REMAIN SOMEWHAT UNCERTAIN. ADDITIONALLY, RAIN COULD BECOME  
HEAVY TO LOCALLY EXCESSIVE FROM PARTS OF THE PLAINS INTO THE  
MISSISSIPPI/OHIO VALLEYS ON SATURDAY. THEN AS THE LOW PRESSURE  
SYSTEM SHIFTS EASTWARD EARLY NEXT WEEK, PRECIPITATION CHANCES  
SHOULD SPREAD EASTWARD WITH HEAVIER ACTIVITY TENDING TO BECOME  
MORE LOCALIZED. THE TRAILING FRONT WILL LIKELY STALL OVER THE  
SOUTHERN PLAINS AS ANOTHER SYSTEM APPROACHES FROM THE WEST AND  
CURRENT FORECASTS SHOW POTENTIAL FOR HEAVY RAINFALL ON SUNDAY  
ACROSS THIS REGION. THERE IS ENOUGH UNCERTAINTY WITH DETAILS OF  
THIS INCOMING SYSTEM TO SUGGEST POTENTIAL FOR FUTURE SHIFTS IN THE  
EXPECTED AXIS OF HEAVIEST RAINFALL. WITH ANOTHER POTENTIAL  
EARLY-MID WEEK WAVE PLUS A TRAILING ONE REACHING THE PLAINS BY  
AROUND WEDNESDAY, RAIN/SHOWERS AND THUNDERSTORMS WILL LIKELY  
PERSIST FROM THE PLAINS EASTWARD THROUGH MUCH OF NEXT WEEK. SOME  
AREAS OVER THE CENTRAL U.S. WILL NEED TO MONITOR FORECASTS OF THE  
MIDWEEK SYSTEM GIVEN ITS POTENTIAL TO PRODUCE SIGNIFICANT WEATHER  
AND SENSITIVITY TO ADDITIONAL RAINFALL. THE LATTER TWO UPPER  
SHORTWAVES/SURFACE SYSTEMS WILL BRING ROUNDS OF MOSTLY LIGHT TO  
MODERATE PRECIPITATION (SNOW IN THE HIGHER ELEVATIONS AND RAIN IN  
THE LOWER ELEVATIONS) ACROSS THE NORTHWEST, MAINLY IN THE  
SATURDAY-MONDAY PERIOD AND PERHAPS LINGERING OVER PARTS OF THE  
ROCKIES AFTER THEN.  
 
TEMPERATURE-WISE, THE GENERAL TREND OVER THE LOWER 48 WILL BE FOR  
COOLER THAN AVERAGE WEATHER IN THE NORTHERN TIER AND WARMER THAN  
AVERAGE IN THE SOUTHERN TIER. THE CORE OF THE COLDEST AIR SHOULD  
BE ACROSS THE NORTHERN HIGH PLAINS TO MIDWEST, WHERE HIGHS WILL BE  
AROUND 10-20F BELOW AVERAGE DUE TO BEING IN THE COLD SECTOR OF  
INITIAL LOW PRESSURE AFFECTING THE REGION FOLLOWED BY INFLUENCE  
FROM THE SOUTHERN PERIPHERY OF CANADIAN HIGH PRESSURE AND MOISTURE  
ARRIVING WITH ANOTHER SYSTEM TOWARD MIDWEEK. LOWS SHOULD STAY  
CLOSER TO NORMAL THOUGH. MEANWHILE, SLIGHTLY ABOVE NORMAL  
TEMPERATURES SHOULD STRETCH ACROSS MUCH OF THE SOUTHERN TIER, WITH  
MAINLY WARMER THAN AVERAGE LOWS ALSO SPREADING INTO THE  
OHIO/TENNESSEE VALLEYS DURING THE WEEKEND AND MORE OF THE EAST  
NEXT WEEK. BEST POTENTIAL FOR SOME PLUS 10-15F ANOMALIES FOR  
HIGHS WILL BE OVER THE SOUTHERN HIGH PLAINS EARLY NEXT WEEK WHILE  
SIMILAR ANOMALIES FOR MORNING LOWS MAY BE A LITTLE MORE COMMON ON  
SOME DAYS.  
 
RAUSCH/TATE  
 
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 LOWER MISSISSIPPI VALLEY AND  
THE SOUTHERN PLAINS, SUN-MON, MAY  
1-MAY 2.  
- HIGH WINDS ACROSS PORTIONS OF THE CENTRAL/NORTHERN PLAINS, SAT,  
APR 30.  
- FLOODING POSSIBLE ACROSS PORTIONS OF MAINLAND ALASKA, SAT-WED,  
APR 30-MAY 4.  
 
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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