160  
FXUS02 KWBC 071909  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
308 PM EDT THU APR 07 2022  
 
VALID 12Z SUN APR 10 2022 - 12Z THU APR 14 2022  
 
...ACTIVE WEATHER IS LIKELY NEXT WEEK, WITH HEAVY SNOW SPREADING  
FROM HIGHER ELEVATIONS OF THE WEST INTO THE NORTH-CENTRAL U.S. AND  
HEAVY RAIN AND SEVERE THUNDERSTORM CHANCES IN THE SOUTH-CENTRAL  
CONUS...  
   
..OVERVIEW
 
 
LATEST GUIDANCE CONTINUES TO SHOW AN AMPLIFIED PATTERN IN WHICH  
ONE UPPER TROUGH DEPARTS FROM THE EAST AFTER SUNDAY WHILE ENERGY  
DIGGING IN FROM THE NORTHEASTERN PACIFIC REINFORCES WESTERN U.S.  
MEAN TROUGHING THAT SHOULD FINALLY EMERGE INTO THE PLAINS BY  
AROUND MIDWEEK. THERE IS A DECENT SIGNAL IN THE GUIDANCE THAT THIS  
PATTERN SHOULD PRODUCE ACTIVE WEATHER OVER A SIGNIFICANT PORTION  
OF THE LOWER 48 NEXT WEEK--INCLUDING RAIN/SNOW OVER THE WEST,  
EVENTUALLY A VIGOROUS LOW PRESSURE SYSTEM OVER THE PLAINS/UPPER  
MIDWEST WITH SOME SNOW TO THE NORTHWEST OF ITS TRACK, AND A THREAT  
FOR AREAS OF HEAVY RAINFALL PLUS STRONG TO SEVERE CONVECTION OVER  
SOME SOUTHERN AREAS OF THE CENTRAL U.S. HOWEVER WITHIN THIS BROAD  
THEME THERE ARE A NUMBER OF UNCERTAINTIES FOR DETAILS THAT TEMPER  
CONFIDENCE IN SPECIFICS OF THE FORECAST, NOT ONLY FOR THE MAIN  
AREA OF FOCUS OVER THE WESTERN-CENTRAL U.S. BUT ALSO FRONTAL  
POSITION OVER THE EAST DUE TO DIFFERENCES IN HOW LEADING SHORTWAVE  
ENERGY INITIALLY EJECTING ACROSS THE PLAINS ULTIMATELY EVOLVES.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
MODEL GUIDANCE REMAINS CONSISTENT WITH THE UPPER TROUGH DEPARTING  
FROM THE EAST EARLY IN THE PERIOD. AND FORTUNATELY, THE 00/06Z  
MODEL CYCLE (AND NEW 12Z???) IS SHOWING BETTER AGREEMENT COMPARED  
TO THE LAST FEW CYCLES WITH THE WESTERN TROUGH AS WELL, THOUGH  
WITH TYPICAL LINGERING DIFFERENCES IN THE DETAILS. ONE SUCH DETAIL  
IS LEADING SHORTWAVE ENERGY IN THE BASE OF THE TROUGH OVER THE  
NORTHERN ROCKIES/HIGH PLAINS EARLY SUNDAY THAT SHOWS DIFFERENCES  
IN ITS EJECTION ACROSS THE NORTHERN TIER AND ITS EFFECTS ON  
FRONTAL POSITION IN THE NORTH-CENTRAL AND NORTHEASTERN U.S. BY  
MONDAY-TUESDAY. THE 00Z UKMET AND GFS WERE AMONG THE STRONGER  
SOLUTIONS WITH THIS SHORTWAVE AND PUSHED THE FRONT FARTHER SOUTH  
COMPARED TO THE 06Z GFS/00Z ECMWF AND CMC THAT DEFLECTED THE  
SHORTWAVE ON THE NORTHERN SIDE OF THE RIDGE. THE WPC FORECAST  
LEANED TOWARD THE LATTER CLUSTER GIVEN CONTINUITY AND NOT MUCH  
SUPPORT FOR THE SOUTHWARD EXTENT OF THE UKMET ESPECIALLY FOR GREAT  
LAKES SHORTWAVE IN INDIVIDUAL ENSEMBLE MEMBERS.  
 
THE NEXT SHORTWAVE WITH NOTABLE DIFFERENCES STEMS FROM ENERGY IN  
THE GULF OF ALASKA IN THE SHORT TERM, AND IS FORECAST TO DROP  
SOUTH ACROSS THE NORTHEASTERN PACIFIC/WESTERN CANADA COAST TO FORM  
POSSIBLY A POTENT SHORTWAVE NEAR THE PACIFIC NORTHWEST ON MONDAY.  
THIS FEATURE VARIES SOMEWHAT WITH ITS POSITION BUT PARTICULARLY  
VARIES IN STRENGTH, WHICH AFFECTS A SURFACE LOW UNDERNEATH AS  
WELL. MOST GUIDANCE IS NOW INDICATING A SMALL CLOSED UPPER LOW BUT  
THE 00Z AND NEW 12Z ECMWF ARE PERSISTENT IN SHOWING AN OPEN  
SHORTWAVE FARTHER EAST IN THE NORTHWEST AND A WEAKER, DISPLACED  
SURFACE LOW. THE ENSEMBLE SPAGHETTI PLOTS ARE EXTREMELY MESSY OVER  
THE EASTERN PACIFIC AND WESTERN U.S. SO DETAIL CONFIDENCE REMAINS  
QUITE LOW. THE WPC FORECAST CONTINUED WITH A SOLUTION STRONGER  
THAN THE ECMWF BUT NOT AS STRONG AS THE OTHER GUIDANCE.  
 
BY TUESDAY-THURSDAY, MODEL AGREEMENT HAS IMPROVED REGARDING THE  
EVOLUTION OF THE TROUGH AND ITS MOVEMENT, WITH THE 00Z ECMWF A BIT  
WEAKER THAN ITS PREVIOUS RUNS BUT CLUSTERING BETTER WITH OTHER  
GUIDANCE. GFS RUNS SINCE 00Z HAVE BEEN CONSISTENT IN SHOWING A  
SOLUTION SIMILAR TO WHAT THE ECMWF HAS HAD, NAMELY A UPPER LOW  
THAT CLOSES OFF IN THE NORTHERN PLAINS WEDNESDAY AND MOVES INTO  
THE MIDWEST THURSDAY, AND THE CMC IS SIMILAR AS WELL. THE TRACK OF  
THE ASSOCIATED SURFACE LOW IS ALSO FAIRLY WELL CLUSTERED FOR THE  
LATE MEDIUM RANGE PERIOD. THUS MODELS ALL INDICATE AN IMPACTFUL  
STORM SYSTEM ACROSS THE CENTRAL U.S. DESPITE DIFFERENCES IN THE  
EXACT DETAILS.  
 
TRAILING FLOW COULD BRING ANOTHER SYSTEM TOWARD THE PACIFIC  
NORTHWEST BY WEDNESDAY-THURSDAY, WHICH IS NOW ADVERTISED BY THE  
BULK OF GUIDANCE AFTER PREVIOUS CYCLES OF THE GFS DID NOT SHOW  
THIS FEATURE. DESPITE BETTER AGREEMENT NOW FOR A SYSTEM, TIMING OF  
THE SHORTWAVE TRACK REMAINS QUESTIONABLE.  
 
BETTER AGREEMENT BETWEEN GFS/ECMWF/CMC DETERMINISTIC GUIDANCE LED  
TO THE WPC FORECAST UTILIZING A BLEND OF THESE EARLY IN THE  
PERIOD, AND EVEN MAINTAINED A MAJORITY OF OPERATIONAL MODELS  
THROUGH THE LATTER PART OF THE PERIOD THOUGH PHASED IN SOME EC AND  
GEFS ENSEMBLE MEANS TO TEMPER INDIVIDUAL MODEL DIFFERENCES.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
EARLY IN THE PERIOD EXPECT THE BEST RAIN/MOUNTAIN SNOW FOCUS TO BE  
OVER THE PACIFIC NORTHWEST AND CENTRAL WEST COAST. HOWEVER THE  
DETAILS OF LOCATION AND INTENSITY ARE UNUSUALLY UNCERTAIN FOR A  
FORECAST ONLY 3-4 DAYS OUT IN TIME AS GUIDANCE VARIES WIDELY FOR  
THE STRENGTH AND TRACK OF ARRIVING LOW PRESSURE. LIGHTER ACTIVITY  
SHOULD PREVAIL EASTWARD THROUGH THE NORTHERN ROCKIES. THEN SOME  
MOISTURE SHOULD EXTEND SOUTHWARD INTO THE SIERRA NEVADA, WITH RAIN  
AND MOUNTAIN SNOW EXTENDING ACROSS CENTRAL AND POSSIBLY SOME  
SOUTHERN PARTS OF THE WEST. BY TUESDAY THE SOUTHERN MONTANA INTO  
COLORADO ROCKIES AND NORTH-CENTRAL HIGH PLAINS SHOULD BEGIN TO SEE  
A FAVORABLE COMBINATION OF UPPER TROUGH DYNAMICS AND LOW LEVEL  
UPSLOPE FLOW THAT WOULD INCREASE PRECIPITATION OVER THOSE AREAS,  
WITH THE HIGH PLAINS POSSIBLY SEEING SOME SPRINGTIME SNOW IN  
ADDITION TO THE ROCKIES. POTENTIALLY STRONG LOW PRESSURE THAT MAY  
TRACK FROM THE PLAINS INTO THE UPPER MIDWEST WOULD EXTEND SNOW  
FARTHER NORTHEAST ACROSS THE NORTHERN TIER ALONG WITH STRONG  
WINDS. MEANWHILE IN THE WARM SECTOR, THERE WILL 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. PERSISTENCE OF THE GULF INFLOW  
COULD LEAD TO A COUPLE DAYS OR SO WITH A HEAVY RAIN THREAT OVER OR  
NEAR THE LOWER MISSISSIPPI VALLEY. ALSO THE STORM PREDICTION  
CENTER IS MONITORING THE POTENTIAL FOR SEVERE WEATHER OVER SOME  
SOUTHERN AREAS IN THE CENTRAL U.S. CHECK THEIR LATEST OUTLOOKS FOR  
MORE INFORMATION. FARTHER NORTH, A FRONT DRAPED OVER THE MIDWEST  
COULD ALSO PROVIDE A FOCUS FOR RAINFALL THOUGH LIKELY WITH LOWER  
TOTALS GIVEN LESS MOISTURE/INSTABILITY. LACK OF CONFIDENCE IN SOME  
SPECIFICS OF EASTERN PACIFIC/WESTERN U.S. FLOW MAINTAINS THE  
POTENTIAL FOR SOME CHANGES IN THE ABOVE MOST LIKELY SCENARIO.  
 
COLDER AIR MOVING INTO THE WEST WILL INITIALLY BRING HIGHS DOWN TO  
AS MUCH AS 10-20F BELOW NORMAL OVER THE NORTHWEST/NORTHERN ROCKIES  
AS OF SUNDAY. AN AREA OF MINUS 10-25F ANOMALIES FOR HIGHS SHOULD  
THEN REACH INTO THE INTERMOUNTAIN WEST, ROCKIES, AND  
NORTHERN-CENTRAL PLAINS BY NEXT TUESDAY-WEDNESDAY. THE NORTHERN  
HALF OF THE PLAINS SHOULD STILL SEE HIGHS AROUND 15-20F BELOW  
NORMAL ON THURSDAY. SUNDAY SHOULD PROVIDE THE BEST POTENTIAL FOR  
SOME LOCATIONS IN THE NORTHWEST TO SEE MAX TEMPERATURES NEAR OR  
BELOW CURRENT RECORD COLD HIGHS BUT MONDAY COULD STILL PRODUCE A  
FEW LINGERING RECORDS. MEANWHILE MOST OF THE EASTERN HALF OF THE  
COUNTRY SHOULD TREND FROM MOSTLY BELOW NORMAL TEMPERATURES (MINUS  
5-15F ANOMALIES) ON SUNDAY, AND POTENTIAL FOR A LATE FROST ACROSS  
PARTS OF THE SOUTHEASTERN QUADRANT OF THE COUNTRY, TO MOSTLY ABOVE  
NORMAL READINGS (PLUS 5-15F ANOMALIES FOR HIGHS AND PERHAPS  
SLIGHTLY WARMER FOR MORNING LOWS) SPREADING FROM WEST TO EAST  
AFTER THE WEEKEND. HOWEVER CONFIDENCE IS LOWER FOR EXACT  
TEMPERATURES OVER THE NORTHERN HALF OF THE EAST DUE TO UNCERTAIN  
POSITION OF A FRONT DURING THE FIRST HALF OF NEXT WEEK.  
 
TATE/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  
 

 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page