784  
FXUS02 KWBC 221901  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 PM EDT FRI APR 22 2022  
 
VALID 12Z MON APR 25 2022 - 12Z FRI APR 29 2022  
   
..OVERVIEW
 
 
AS UPPER/SURFACE LOWS TRACK INTO SOUTH-CENTRAL CANADA AS THE  
MEDIUM RANGE PERIOD BEGINS MONDAY, THE TRAILING COLD FRONT SHOULD  
SWEEP ACROSS THE SOUTH-CENTRAL TO EASTERN U.S. AND PROVIDE A FOCUS  
FOR RAIN AND THUNDERSTORMS. UPPER TROUGHING OVER THE MIDWEST/GREAT  
LAKES SHOULD SHIFT EASTWARD AS NEXT WEEK PROGRESSES AND LIKELY  
FORM AN UPPER LOW OVER/NEAR THE NORTHEAST LATER IN THE WEEK,  
PROMOTING A SHIFT FROM WARMER TO COOLER THAN AVERAGE TEMPERATURES  
AND KEEPING SOME PRECIPITATION OVER NEW ENGLAND. MEANWHILE MODEL  
GUIDANCE SUPPORTS MEAN TROUGHING FROM THE EASTERN PACIFIC INTO THE  
WESTERN U.S., LIKELY WITH AN EMBEDDED UPPER LOW, LEADING TO  
POTENTIAL FOR ROUNDS OF PRECIPITATION IN THE NORTHWEST.  
SUFFICIENTLY STRONG UPPER TROUGHING MAY MOVE INTO THE WEST BY NEXT  
FRIDAY TO ENHANCE PRECIPITATION OVER THE NORTHERN ROCKIES/PLAINS.  
EXPECT BROAD UPPER RIDGING BETWEEN THE TWO TROUGHS, LEADING TO  
WARM TEMPERATURES ACROSS THE SOUTHWEST TO SOUTHERN/CENTRAL HIGH  
PLAINS.  
 
   
..MODEL GUIDANCE EVALUATION
 
 
OVER RECENT DAYS THE GREATEST SPREAD AND RUN-TO-RUN VARIABILITY  
HAVE BEEN WITH THE OVERALL MEAN TROUGH OVER THE EASTERN PACIFIC  
AND WESTERN U.S. SOME IMPORTANT DETAILS REMAIN UNRESOLVED BUT AT  
LEAST THERE ARE COMMON THEMES EMERGING. ONE SHORTWAVE REACHING THE  
NORTHWEST AROUND TUESDAY SHOULD CONTINUE ONWARD INTO SOUTHERN  
CANADA, POSSIBLY FORMING A COMPACT UPPER LOW, AS IT TRACKS AROUND  
THE NORTHERN PERIPHERY OF THE CENTRAL U.S. MEAN RIDGE. THE 00Z CMC  
WAS FARTHEST SOUTH WITH THIS ENERGY (ADJUSTING TOWARD CONSENSUS IN  
THE 12Z RUN) WHILE OTHERWISE THERE IS STILL MEANINGFUL TIMING  
SPREAD WITH THE ENSEMBLE MEANS GENERALLY ON THE SLOW SIDE VERSUS  
THE OPERATIONAL MODELS. ANOTHER SHORTWAVE DROPPING INTO THE MEAN  
TROUGH SHOULD REACH NEAR THE WEST COAST BY THURSDAY, WITH THE FULL  
TROUGH INCLUDING THE UPPER LOW TO THE NORTH PROGRESSING INLAND  
THROUGH FRIDAY. THE MAJORITY CLUSTER THROUGH THE 06Z CYCLE  
CONSISTED OF THE 06Z GFS/00Z ECMWF AND CMC ALONG WITH THE ENSEMBLE  
MEANS. THE NEW 12Z GFS HAS STRAYED TO THE FASTER SIDE WHILE THE  
00Z GFS TRACKED ITS UPPER LOW ON THE SOUTH SIDE OF THE SPREAD LATE  
THURSDAY-EARLY FRIDAY WHILE THE 00Z ECMWF COULD BE A TAD ON THE  
AMPLIFIED WITH THE TROUGH. THERE IS ALSO SUGGESTION OF A WEAK  
SHORTWAVE REACHING THE SOUTHWEST AROUND WEDNESDAY BUT IT SHOULD  
HAVE AT MOST MODEST EFFECT AND SHEAR OUT AS IT HEADS DOWNSTREAM  
INTO THE MEAN RIDGE.  
 
MEANWHILE GUIDANCE MAINTAINS BETTER THAN AVERAGE AGREEMENT FOR THE  
IDEA THAT ENERGY JUST WEST OF LEADING LOW PRESSURE/UPPER LOW OVER  
ONTARIO WILL FORM AN UPPER LOW THAT SHOULD CROSS NEW ENGLAND  
AROUND LATE WEDNESDAY-THURSDAY AND MAY STILL LINGER CLOSE TO THE  
REGION THROUGH FRIDAY. THERE IS STILL SOME DEBATE OVER EXACTLY  
WHEN THE UPPER LOW WILL FORM (DEPENDING IN PART ON WHAT HEIGHT  
CONTOUR INTERVAL IS USED) AND THE TIMING/TRACK INTO FRIDAY. THE  
00Z ECMWF IS SLIGHTLY SLOW AROUND LATE WEDNESDAY WHILE THE 06Z/12Z  
GFS STRAY TO THE NORTHERN SIDE OF THE SPREAD BY FRIDAY.  
 
THE REVISED FORECAST INCORPORATED THE 00Z ECMWF, 06Z GFS, AND 00Z  
UKMET/CMC (IN ORDER OF MORE TO LESS WEIGHT) FOR ABOUT THE FIRST  
HALF OF THE PERIOD AND THEN ADDED SOME OF THE 06Z GEFS/00Z ECMWF  
MEANS BY DAYS 6-7 THURSDAY-FRIDAY. THE BLEND ALSO SPLIT GFS INPUT  
BETWEEN THE 06Z AND 00Z RUNS LATE IN THE PERIOD DUE TO DIFFERING  
PREFERENCES FOR THE NEW ENGLAND UPPER LOW AND WESTERN U.S. TROUGH.  
THIS APPROACH YIELDED MINIMAL CHANGES IN CONTINUITY.  
 
   
..SENSIBLE WEATHER/THREATS
 
 
THE COLD FRONT TRAILING FROM THE LOW MOVING ACROSS CANADA EARLY IN  
THE WORKWEEK WILL INTERSECT WITH WARM/MOIST AIR FROM THE GULF AND  
LEAD TO WIDESPREAD RAIN ALONG THE FRONT STRETCHING FROM THE GREAT  
LAKES TO OHIO/TENNESSEE VALLEYS AND INTO THE SOUTHERN PLAINS  
MONDAY, SHIFTING TO THE EASTERN SEABOARD TUESDAY. WHILE GREATER  
POTENTIAL FOR EXCESSIVE RAINFALL HAS PHASED INTO THE SHORT RANGE  
PERIOD, SOME HIGH RAIN RATES WITH UNSTABLE CONDITIONS COULD EXTEND  
INTO TEXAS AND THE LOWER MISSISSIPPI VALLEY ON MONDAY AND CAUSE  
LOCALIZED FLASH FLOODING. NEUTRAL TO WET SOILS MAY LOWER THE  
THRESHOLD FOR RUNOFF ISSUES OVER THE LOWER MISSISSIPPI VALLEY  
WHILE IT IS WORTH MONITORING THE POTENTIAL FOR THIS ACTIVITY TO  
OVERCOME THE DRIER GROUND CONDITIONS OVER TEXAS. ELSEWHERE, THE  
FRONT SHOULD ACCELERATE AND LEAD TO LIGHTER OVERALL RAINFALL  
AMOUNTS OVER THE EASTERN U.S. MONDAY-TUESDAY. THEN AS THE  
NORTHEAST UPPER LOW DEVELOPS MIDWEEK AND SURFACE LOW PRESSURE  
PIVOTS OVER THE REGION, PRECIPITATION IS FORECAST TO LINGER  
ESPECIALLY ACROSS NEW ENGLAND, WITH SOME POTENTIAL FOR HIGHER  
ELEVATIONS TO RECEIVE SNOW. HOW MUCH PRECIPITATION FALLS WILL BE  
SENSITIVE TO EXACT SYSTEM DETAILS. MEANWHILE IN THE WEST,  
UNSETTLED WEATHER IS LIKELY AS SHORTWAVE ENERGY MOVES THROUGH THE  
MEAN TROUGH SOUTH OF A CLOSED UPPER LOW POSITIONED OFF BRITISH  
COLUMBIA THROUGH THURSDAY. GUIDANCE IS STARTING TO RESOLVE A  
BETTER DEFINED EPISODE OF RAIN AND HIGH ELEVATION SNOW IN THE  
EARLY-MID PART OF THE WEEK WITH A LEADING SHORTWAVE (WITH LOWER  
CONFIDENCE FOR A SECOND FEATURE) FOLLOWED BY ANOTHER LATER IN THE  
WEEK WITH A SEPARATE SHORTWAVE AND THEN INLAND PROGRESSION OF THE  
OVERALL TROUGH/UPPER LOW BY FRIDAY. AT THAT TIME THE COMBINATION  
OF UPPER TROUGH DYNAMICS AND DEVELOPING NORTHERLY/EASTERLY LOW  
LEVEL UPSLOPE FLOW COULD LEAD TO AREAS OF HEAVIER PRECIPITATION  
OVER THE NORTHERN ROCKIES/PLAINS. SPECIFICS WILL TAKE TIME TO  
RESOLVE. CURRENTLY IT APPEARS THAT THE HIGHER ELEVATIONS OF THE  
NORTHERN ROCKIES WOULD SEE SOME SNOW WITH THIS EVENT WHILE PRECIP  
TYPE FARTHER EAST WILL BE SENSITIVE TO SYSTEM DETAILS. MEANWHILE A  
FRONTAL BOUNDARY DRAPED OVER THE CENTRAL PLAINS MAY HELP TO FOCUS  
SOME RAINFALL AS FAR SOUTHEAST AS THE MID MISSISSIPPI VALLEY LATE  
IN THE WEEK.  
 
WARMER THAN NORMAL CONDITIONS FOR THE EASTERN THIRD OF THE U.S.  
MONDAY-TUESDAY WILL SWITCH TO BELOW NORMAL BEHIND THE COLD FRONTAL  
PASSAGE. THE CORE OF THAT COLD AIR IS LIKELY TO KEEP TEMPERATURES  
15-30F BELOW NORMAL IN THE DAKOTAS AND UPPER MIDWEST EARLY IN THE  
WEEK (WITH A FEW RECORD LOWS POSSIBLE) AND EXTEND 10-20F BELOW  
NORMAL READINGS THROUGH THE GREAT LAKES/CENTRAL APPALACHIANS  
DURING TUESDAY-THURSDAY. THESE TEMPERATURES SHOULD MODERATE  
SOMEWHAT LATE NEXT WEEK. FARTHER WEST, UPPER RIDGING MIGRATING  
FROM THE SOUTHWEST INTO THE CENTRAL U.S. WILL SPREAD WARMER THAN  
AVERAGE TEMPERATURES FROM THE SOUTHWEST (WITH SOME RECORD HIGHS  
POSSIBLE IN SOUTHERN CALIFORNIA MONDAY) INTO THE FOUR CORNERS  
STATES AND INTO SOUTHERN/CENTRAL PARTS OF THE PLAINS. THE HIGH  
PLAINS MAY SEE TEMPERATURES AROUND 15-20F ABOVE NORMAL MID-LATE  
WEEK. THE NORTHWEST WILL SEE A GRADUAL COOLING TREND DURING THE  
PERIOD AND SLIGHTLY BELOW NORMAL HIGHS SHOULD EXTEND INTO  
CALIFORNIA AND THE GREAT BASIN BY LATE NEXT WEEK.  
 
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  
 
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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