756  
FXUS02 KWBC 060701  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
259 AM EDT WED APR 06 2022  
 
VALID 12Z SAT APR 09 2022 - 12Z WED APR 13 2022  
   
..OVERVIEW
 
 
GUIDANCE CONTINUES TO SHOW AN AMPLIFIED BUT REASONABLY PROGRESSIVE  
UPPER PATTERN FROM THE WEEKEND INTO THE MIDDLE OF NEXT WEEK. A  
DEEPENING TROUGH OVER THE WEST WILL SPREAD RAIN/HIGHER ELEVATION  
SNOW AND WELL BELOW NORMAL TEMPERATURES ACROSS THE REGION, WITH  
THE COLDER AIR AND RAIN/SNOW REACHING INTO PARTS OF THE NORTHERN  
AND CENTRAL PLAINS BY EARLY-MID WEEK. AHEAD OF THE UPPER TROUGH  
AND ASSOCIATED WAVY SURFACE FRONT, MOISTURE FLOWING NORTHWARD FROM  
THE GULF OF MEXICO SHOULD PROMOTE RAINFALL OF VARYING INTENSITY  
OVER THE EASTERN PLAINS/MISSISSIPPI VALLEY NEXT WEEK. MEANWHILE A  
DEEP UPPER TROUGH CROSSING THE EAST DURING THE WEEKEND WILL  
PRODUCE COOL WEATHER WITH SHOWERS OVER SOME AREAS. AN UPPER RIDGE  
MOVING INTO THE REGION FROM THE CENTRAL U.S. WILL BRING WARMER  
TEMPERATURES TO THE EASTERN HALF OF THE COUNTRY AFTER THE WEEKEND.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
CONFIDENCE REMAINS FAIRLY GOOD FOR THE OVERALL PATTERN EVOLUTION  
AND MOST ASPECTS OF THE DEPARTING EASTERN TROUGH. HOWEVER IN SOME  
RESPECTS THE FORECAST FOR DETAILS OF THE WESTERN TROUGH MAY BE  
GETTING MORE COMPLICATED. TIMING/EVOLUTION DIFFERENCES FOR ENERGY  
INITIALLY OVER THE ALASKA PANHANDLE/GULF OF ALASKA AND FORECAST TO  
CONTRIBUTE TO A POSSIBLE UPPER LOW WITHIN THE WESTERN TROUGH HAVE  
PERSISTED OVER MULTIPLE RUNS, WITH SOME INFLUENCE ON LEADING  
SHORTWAVE ENERGY CROSSING THE NORTHERN TIER U.S. AND SOUTHERN  
CANADA. NOW MODELS/ENSEMBLES ARE ALSO DIVERGING WITH SPECIFICS OF  
FLOW OVER THE NORTHEASTERN PACIFIC/NORTHWESTERN NORTH AMERICA BY  
AROUND MONDAY AND THIS ISSUE HAS DOWNSTREAM EFFECTS ON THE WESTERN  
TROUGH BY LATE IN THE PERIOD.  
 
LOOKING AT THE 12Z/18Z GUIDANCE CONTRIBUTING TO THE UPDATED  
FORECAST, THE 18Z GFS GENERALLY TRENDED CLOSER TO THE  
MODEL/ENSEMBLE MEAN AVERAGE VERSUS THE 12Z RUN FOR LEADING FLOW  
ACROSS THE NORTHERN TIER U.S./SOUTHERN CANADA AND THE UPPER TROUGH  
DIGGING INTO THE WEST. GUIDANCE HAS BECOME SPLIT FOR TIMING THE  
ARRIVAL OF GULF OF ALASKA ENERGY THAT COULD FORM A CLOSED LOW AS  
THE 12Z UKMET SIDED WITH THE SLOWER GFS WHILE THE ECMWF/CMC WERE  
FASTER. TOWARD THE END OF THE PERIOD NEXT WEDNESDAY THE ENSEMBLE  
MEANS SUPPORTED AN UPPER TROUGH PROGRESSION (ITS AXIS REACHING THE  
ROCKIES/PLAINS) NEAR AN AVERAGE OF THE 18Z GFS AND SOMEWHAT FASTER  
12Z ECMWF. THE 12Z CMC HAD SIMILAR TIMING BUT WITH AN UPPER LOW  
TRACK WELL SOUTH OF OTHER GUIDANCE. PLUS ITS BROAD UPPER LOW  
CENTERED OVER THE ALASKA PANHANDLE DID NOT HAVE MUCH SUPPORT. A  
BLEND OF THE 18Z GFS AND 12Z ECMWF/CMC/UKMET EARLY FOLLOWED BY  
TRENDING TO THE 18Z GFS/12Z ECMWF WITH THEIR RESPECTIVE ENSEMBLE  
MEANS PROVIDED THE MOST REASONABLE DEPICTION AND CONTINUITY FOR  
THE WESTERN-CENTRAL U.S. EVOLUTION AS WELL AS FOR THE DEPARTING  
EASTERN U.S. UPPER TROUGH.  
 
THE MOST DRAMATIC CHANGE FROM THE NEW 00Z GUIDANCE IS IN THE CMC.  
FIRST IT HAS TRENDED SLOWER WITH THE GULF OF ALASKA  
ENERGY--JOINING THE GFS/UKMET. THIS CLUSTER WOULD HAVE A MUCH  
STRONGER SURFACE SYSTEM REACHING SOMEWHERE ALONG THE NORTHERN HALF  
OF THE WEST COAST THAN PREVIOUSLY FORECAST. THEN UPSTREAM CHANGES  
IN THE CMC LEAD TO A MUCH FASTER AND NORTHWARD PATH FOR THE CORE  
OF THE WESTERN UPPER TROUGH, STRAYING EASTWARD BEYOND OTHER  
SOLUTIONS OVER THE PLAINS. IN CONTRAST THE 00Z ECMWF HAS  
MAINTAINED REMARKABLE CONTINUITY GIVEN THE DIFFERENCES AND/OR  
CHANGES IN THE OTHER MODELS. IT DID TREND JUST A BIT SLOWER,  
LEADING TO A DAY 7 WEDNESDAY TROUGH PROGRESSION THAT NOW MATCHES  
THE MEANS.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
THE UPPER TROUGH CURRENTLY EXPECTED TO AMPLIFY INTO THE WEST AND  
APPROACH OR REACH THE PLAINS BY NEXT WEDNESDAY WILL FIRST BRING  
RAIN AND HIGHER ELEVATION SNOW INTO THE PACIFIC NORTHWEST AND  
NORTHERN ROCKIES DURING THE WEEKEND. MOST TOTALS SHOULD BE IN THE  
LIGHT TO MODERATE RANGE THOUGH SOME LOCALIZED ENHANCEMENT IS  
POSSIBLE OVER FAVORED TERRAIN. A MORE FAVORABLE COMBINATION OF  
UPPER TROUGH DYNAMICS AND LOW LEVEL UPSLOPE FLOW SHOULD INCREASE  
PRECIPITATION OVER THE NORTHERN-CENTRAL ROCKIES AND HIGH PLAINS  
DURING THE FIRST PART OF NEXT WEEK, WITH THE HIGH PLAINS POSSIBLY  
SEEING SOME SNOW IN ADDITION TO THE ROCKIES. THERE ARE STILL  
IMPORTANT UNCERTAINTIES OVER THE DETAILS OF THE UPPER TROUGH SO  
CONFIDENCE IS NOT GREAT IN SOUTHWARD EXTENT AND AMOUNTS OF  
PRECIPITATION ACROSS CENTRAL/SOUTHERN PARTS OF THE WEST--AND TO  
SOME DEGREE OVER THE ROCKIES/PLAINS--AT THIS TIME. THERE WILL ALSO  
BE INCREASING COVERAGE AND INTENSITY OF RAINFALL OVER THE EASTERN  
PLAINS/MISSISSIPPI VALLEY WITH THE ESTABLISHMENT OF MOIST LOW  
LEVEL FLOW FROM THE GULF OF MEXICO. FARTHER EAST, COLD AIR ALOFT  
ASSOCIATED WITH THE UPPER TROUGH CROSSING THE EAST DURING THE  
WEEKEND WILL PROMOTE AREAS OF DIURNALLY ENHANCED SHOWERS FROM THE  
OHIO VALLEY/APPALACHIANS INTO THE NORTHEAST ESPECIALLY ON  
SATURDAY. SOME PRECIPITATION COULD BE IN THE FORM OF SNOW, WITH  
THE BEST CHANCES ACROSS THE PEAKS OF THE CENTRAL APPALACHIANS IN  
WEST VIRGINIA.  
 
COLDER AIR MOVING INTO THE WEST WILL INITIALLY BRING HIGHS DOWN TO  
AS MUCH AS 10-15F BELOW NORMAL OVER THE NORTHWEST/NORTHERN ROCKIES  
DURING THE WEEKEND. AN AREA OF MINUS 10-20F ANOMALIES FOR HIGHS  
SHOULD THEN REACH INTO THE INTERMOUNTAIN WEST, ROCKIES, AND  
NORTHERN-CENTRAL PLAINS BY NEXT TUESDAY-WEDNESDAY. SUNDAY MAY  
PROVIDE THE BEST POTENTIAL FOR SOME LOCATIONS IN THE NORTHWEST TO  
SEE MAX TEMPERATURES NEAR OR BELOW CURRENT RECORD COLD HIGHS.  
MEANWHILE THE EASTERN HALF OF THE COUNTRY WILL TREND FROM MOSTLY  
BELOW NORMAL TEMPERATURES (UP TO MINUS 10-20F ANOMALIES SATURDAY),  
AND POTENTIAL FOR A LATE FROST ACROSS PARTS OF THE SOUTHEASTERN  
QUADRANT OF THE COUNTRY, TO MOSTLY ABOVE NORMAL READINGS (PLUS  
5-15F ANOMALIES) SPREADING FROM WEST TO EAST AFTER THE WEEKEND.  
 
RAUSCH  
 
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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