607  
FXUS02 KWBC 101855  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
255 PM EDT SUN APR 10 2022  
 
VALID 12Z WED APR 13 2022 - 12Z SUN APR 17 2022  
 
...POTENT STORM SYSTEM TO BRING HEAVY SNOW/BLIZZARD CONDITIONS  
ACROSS THE NORTHERN PLAINS WITH HEAVY RAINFALL AND SEVERE WEATHER  
FROM THE GULF COAST TO THE MID/UPPER MISSISSIPPI VALLEY...  
   
..OVERVIEW
 
 
AN IMPRESSIVE SPRINGTIME LOW PRESSURE SYSTEM WILL SLOWLY MOVE  
THROUGH THE UPPER MIDWEST MID TO LATE WEEK, BRINGING HEAVY SNOW  
AND POSSIBLE BLIZZARD CONDITIONS ON ITS NORTHWEST SIDE ACROSS THE  
NORTHERN PLAINS INTO NORTHERN MINNESOTA. MEANWHILE IN THE WARM  
SECTOR, WIDESPREAD RAIN AND THUNDERSTORMS WILL TRACK AHEAD OF THE  
COLD FRONT, WITH SEVERE WEATHER AND HEAVY TO EXCESSIVE RAINFALL IN  
MUCH OF THE MISSISSIPPI VALLEY INTO THE TENNESSEE VALLEY. AFTER  
THAT, THE OVERALL PATTERN LOOKS TO DEAMPLIFY SOMEWHAT, BUT A ROUND  
OF WEAKER TROUGHING COULD COME INTO THE WEST FOR THE LATTER HALF  
OF THE WEEK.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
RECENT MODEL GUIDANCE STILL SHOWS A SIGNIFICANT SURFACE LOW IN THE  
MIDWEST AS THE PERIOD BEGINS WEDNESDAY THAT SHOULD SLOWLY LIFT  
NORTHEASTWARD THROUGH LATE WEEK. THIS IS IN CONJUNCTION WITH A  
DEVELOPING UPPER LOW THAT THE GFS/UKMET CONTINUE TO CLOSE OFF BY  
EARLY WEDNESDAY, EARLIER THAN THE ECMWF AND CMC. THE 00Z ECMWF  
APPEARS TO BE A SOUTH OUTLIER AT THIS POINT WITH THE SURFACE LOW  
POSITION AT 12Z WEDNESDAY, BUT THE 12Z ECMWF SEEMS TO SHOW BETTER  
CLUSTERING WITH OTHER GUIDANCE AND THE 00Z EC MEAN. DESPITE ALL  
THIS, MODEL GUIDANCE IS CERTAINLY IN BETTER AGREEMENT WITH THE  
TIMING OF THE SYSTEM COMPARED TO A COUPLE OF DAYS AGO--MODELS HAVE  
CONVERGED ON A SOLUTION IN BETWEEN THE SLOWEST AND FASTEST  
GUIDANCE, BUT PERHAPS MORE TOWARD THE FASTER GFS COMPARED TO THE  
SLOWEST RUNS OF THE ECMWF OVER THE PAST FEW DAYS. REGARDLESS, SOME  
DIFFERENCES IN THE LOW TRACK AND FRONTAL POSITION REMAIN, ALONG  
WITH SOME DIFFERENCES IN THE EVENTUAL EJECTION AND POSSIBLE  
SHEARING OF SOME ENERGY OF THE UPPER LOW TOWARD THE NORTHEAST INTO  
CANADA BY LATE WEEK, BUT GENERALLY WITHIN TYPICAL MODEL SPREAD FOR  
THE MEDIUM RANGE PERIOD. THE WPC FORECAST FAVORED AN OPERATIONAL  
MODEL BLEND FOR THESE FEATURES FOR AN INTERMEDIATE SOLUTION.  
 
FARTHER UPSTREAM, ADDITIONAL ENERGY LOOKS TO SPILL SOUTHWARD  
ACROSS THE NORTHEASTERN PACIFIC INTO THE PACIFIC NORTHWEST  
BEGINNING WEDNESDAY, WITH THE BULK OF RECENT GUIDANCE GENERALLY  
INDICATING AT LEAST A SMALL UPPER LOW PIVOTING THERE THURSDAY WITH  
A MINOR SHIFT EAST BY FRIDAY. THE DETAILS OF ENERGY EMBEDDED  
WITHIN THE UPPER LOW/TROUGH BECOME MURKIER FRIDAY AND BEYOND, WITH  
POTENTIAL FOR SOME ENERGY TO SHIFT EASTWARD WHILE SOME HELPS DIG  
TROUGHING IN THE WEST SATURDAY AND MOVING EASTWARD SUNDAY. THE  
TROUGH MAY PRODUCE LOW PRESSURE IN THE SOUTHERN PLAINS OVER THE  
WEEKEND. THIS SEEMS LIKE THE MOST LIKELY SOLUTION AT THIS POINT  
GIVEN DETERMINISTIC MODELS COMING INTO SLIGHTLY BETTER AGREEMENT,  
BUT ENSEMBLE SPREAD REMAINS HIGH SO THERE IS STILL CONSIDERABLE  
UNCERTAINTY. A BLEND OF THE 06Z GFS AND GEFS MEAN AND 00Z ECMWF,  
EC MEAN, AND CMC BY THE END OF THE PERIOD WORKED FOR THE MEDIUM  
RANGE FORECAST FOR NOW, BUT FURTHER ADJUSTMENTS ARE LIKELY IN  
UPCOMING DAYS WITH FRONTAL POSITION, PRECIPITATION, ETC. FORECASTS.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
BY WEDNESDAY A WELL DEVELOPED LOW PRESSURE SYSTEM SHOULD BE  
TRACKING ACROSS THE NORTHERN PLAINS/UPPER MIDWEST WITH A  
SIGNIFICANT SNOW STORM LIKELY TO THE NORTH AND WEST OF THE SURFACE  
LOW ACROSS THE DAKOTAS AND NORTHWEST MINNESOTA. HEAVY SNOWFALL,  
POSSIBLY EXCEEDING A FOOT IN SOME LOCATIONS, COMBINED WITH GUSTY  
WINDS COULD CREATE BLIZZARD CONDITIONS LEADING TO HAZARDOUS TRAVEL  
AND POWER OUTAGES IN MANY AREAS. MEANWHILE IN THE WARM SECTOR,  
THERE WILL BE INCREASING COVERAGE AND INTENSITY OF RAIN AND  
THUNDERSTORMS AHEAD OF THE ATTENDANT COLD FRONT GIVEN PERSISTENT  
GULF MOISTURE AND INSTABILITY. THE STORM PREDICTION CENTER'S  
EXTENDED OUTLOOK INDICATES SEVERE POTENTIAL ACROSS MUCH OF THE  
MISSISSIPPI VALLEY ON WEDNESDAY AND POSSIBLY SPREADING FARTHER  
EAST INTO THE OHIO/TENNESSEE VALLEYS AND SOUTHEAST LATE WEDNESDAY  
INTO THURSDAY. THE HEAVIEST RAINFALL THAT COULD CAUSE FLASH  
FLOODING MAY FOCUS ON THE SOUTHERN SIDE ACROSS THE LOWER  
MISSISSIPPI AND TENNESSEE VALLEY, BUT FARTHER NORTH, DYNAMICS  
WRAPPING AROUND THE LOW AND EVEN SOME INSTABILITY REACHING THAT  
FAR NORTH COULD SUPPORT AN ADDITIONAL AREA OF MODEST RAINFALL  
ACROSS THE UPPER MISSISSIPPI VALLEY. THIS MAY CAUSE LOCALIZED  
FLOODING AND FLASH FLOODING ISSUES THERE AS WELL PARTICULARLY IF  
RAIN FALLS OVER FROZEN OR SNOW COVERED GROUND. RAINFALL MAY LINGER  
ACROSS THE SOUTHEAST THROUGH FRIDAY INTO THE WEEKEND AS THE  
WESTERN PART OF THE BOUNDARY STALLS ACROSS THE REGION.  
 
OUT WEST, MODERATE TO HEAVY RAIN/MOUNTAIN SNOWS ARE POSSIBLE  
ACROSS PARTS OF CALIFORNIA/OREGON WITH THE NEXT LOW PRESSURE  
SYSTEM MOVING IN MID- TO LATE WEEK. MOISTURE LOOKS TO SPREAD EAST  
INTO THE INTERMOUNTAIN WEST AS WELL, BUT WITH MORE UNCERTAINTY BY  
NEXT SUNDAY REGARDING PRECIPITATION INTO THE PLAINS.  
 
BELOW NORMAL TEMPERATURES ARE FORECAST TO COVER THE WESTERN HALF  
OF THE U.S. AS THE PERIOD BEGINS WEDNESDAY. THE BIGGEST  
TEMPERATURE ANOMALIES ARE FORECAST FOR THE INTERIOR WEST INTO THE  
NORTHERN HIGH PLAINS, WITH LOWS 20+ DEGREES BELOW AVERAGE AND  
HIGHS 25-35 DEGREES BELOW AVERAGE, AND A FEW RECORD LOW MINIMUM  
AND MAXIMUM TEMPERATURES ARE POSSIBLE. SOME MODERATION IS LIKELY  
BY LATER IN THE WEEK ACROSS THE WEST, THOUGH STILL BELOW NORMAL  
WITH ADDITIONAL TROUGHING MOVING IN. BUT THE CHILLY TEMPERATURES  
WILL LAST IN THE NORTHERN PLAINS AND SPREAD INTO THE UPPER MIDWEST  
INTO NEXT WEEKEND. MEANWHILE, AHEAD OF THE COLD FRONT WITH THE BIG  
STORM, EXPECT TEMPERATURES FROM THE SOUTH-CENTRAL U.S. TO THE EAST  
TO BE ABOVE NORMAL, BUT TRENDING BACK TOWARDS NORMAL FOLLOWING  
PASSAGE OF THE COLD FRONT.  
 
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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