940  
FXUS02 KWBC 091901  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 PM EDT SAT APR 09 2022  
 
VALID 12Z TUE APR 12 2022 - 12Z SAT APR 16 2022  
 
...ACTIVE WEATHER IS LIKELY NEXT WEEK, WITH HEAVY SNOW SPREADING  
FROM HIGHER ELEVATIONS OF THE WEST INTO THE NORTHERN PLAINS AND  
HEAVY RAIN AND SEVERE THUNDERSTORM CHANCES ACROSS THE MISSISSIPPI  
VALLEY...  
   
..OVERVIEW
 
 
THE LATEST GUIDANCE CONTINUES TO SUPPORT AN AMPLIFIED AND ACTIVE  
WEATHER PATTERN ACROSS THE LOWER 48 NEXT WEEK. A REINFORCED  
WESTERN U.S. TROUGH LOOKS TO EMERGE INTO THE PLAINS BY AROUND  
MIDWEEK AS A VIGOROUS CLOSED LOW AND ASSOCIATED SURFACE LOW  
DEVELOP OVER THE PLAINS/UPPER MIDWEST. INITIALLY, THIS SHOULD  
BRING HEAVY MOUNTAIN SNOWS OUT WEST, WITH HEAVY SNOW AND POSSIBLE  
BLIZZARD CONDITIONS SPREADING NORTH AND WEST OF THE LOW TRACK INTO  
THE NORTHERN PLAINS. IN THE WARM SECTOR OF THE SYSTEM, SEVERE  
WEATHER AND HEAVY TO EXCESSIVE RAIN IS EXPECTED, WITH THE BIGGEST  
THREAT ACROSS THE MISSISSIPPI VALLEY BUT POTENTIALLY SPREADING  
EASTWARD AHEAD OF THE COLD FRONT. BY LATE WEEK, AT LEAST SOME  
ENERGY FROM THE CLOSED LOW SHOULD SHEAR OFF TO THE NORTHEAST DUE  
TO A BLOCKY RIDGE IN THE WESTERN ATLANTIC, WHILE THE FLOW UPSTREAM  
IS UNCERTAIN BUT CHANCES ARE ANOTHER WEAKER TROUGH WILL MOVE INTO  
THE WEST.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
RECENT MODEL GUIDANCE CONTINUES TO INDICATE A DEVELOPING WESTERN  
TROUGH BECOMING A DEEP CLOSED UPPER LOW AS IT TRACKS INTO THE  
CENTRAL U.S., THOUGH TIMING AND TRACK DIFFERENCES BETWEEN MODELS  
CONTINUE TO BE AN ISSUE. FOR A FEW DAYS NOW, THE GFS HAS BEEN A  
FAST AND NORTH OUTLIER, WITH THE ECMWF AND CMC THE FARTHEST  
WEST/SOUTH WITH THE SURFACE LOW WEDNESDAY INTO THURSDAY. WHILE  
THIS CONTINUES TO BE THE CASE, THE 00Z ECMWF AND THE NEWER 12Z RUN  
IS SLIGHTLY FASTER THAN IT WAS A DAY OR SO AGO, AND SHOWS A MORE  
WEST-EAST OBLONG THAN CIRCULAR HEIGHT PATTERN (SO NOT INDICATING  
TROUGHING AS FAR SOUTH THROUGH THE PLAINS/MISSISSIPPI VALLEY) THAT  
WOULD PUSH THE COLD FRONT FASTER THAN IN PREVIOUS RUNS. MEANWHILE,  
THE 06Z AND 12Z GFS RUNS WERE STILL FAST WITH THE CLOSED LOW TO  
DEVELOP AND NOT AS AMPLIFIED FARTHER SOUTH COMPARED TO OTHER  
GUIDANCE, BUT GENERALLY CLOSER TO CONSENSUS THAN THE 00Z AND  
PREVIOUS RUNS, AS UPSTREAM ENERGY SPILLING INTO THE PACIFIC  
NORTHWEST AROUND WEDNESDAY SHOWS A MORE FAVORABLE TRACK IN THE  
MORE RECENT GFS RUNS. SO OVERALL IT SEEMS THE GUIDANCE IS AT LEAST  
CONVERGING A BIT EVEN THOUGH THE DIFFERENCES REMAIN. INDIVIDUAL  
ENSEMBLE MEMBERS AND THUS THE ENSEMBLE MEANS CLUSTER WITH THEIR  
DETERMINISTIC COUNTERPARTS, WHICH DOES NOT INCREASE CONFIDENCE IN  
ONE SOLUTION OVER THE OTHER. THE WPC FORECASTS HAVE BEEN FAVORING  
A SLOWER TRACK OF THE UPPER/SURFACE LOWS COMPARED TO THE GFS. FOR  
THIS CYCLE, STUCK WITH THAT WITH A DETERMINISTIC MODEL BLEND  
FAVORING THE ECMWF FOR THE FIRST PART OF THE PERIOD, LEADING TO A  
FORECAST A BIT FASTER THAN CONTINUITY WITH THE SURFACE LOW AND  
ASSOCIATED FRONTS, PARTICULARLY GIVEN THE ECMWF ADJUSTMENT.  
 
BEYOND WEDNESDAY/THURSDAY, FLOW UPSTREAM OF THAT MAIN UPPER LOW  
FEATURE IS QUITE UNCERTAIN WITH SIGNIFICANT MODEL VARIABILITY. AS  
NOTED THE 06Z AND 12Z GFS RUNS DID LOOK CLOSER TO CONSENSUS WITH  
AN INITIAL BOUT OF ENERGY SPINNING NEAR THE PACIFIC NORTHWEST  
WEDNESDAY/THURSDAY, BUT THE TRACK OF THAT FEATURE VARIES FROM  
SERVING TO ENHANCE AND ELONGATE THE UPPER LOW (00Z ECMWF) OR  
MAINTAINING A TROUGHING IN THE WEST INTO LATE WEEK (06Z GFS AND  
NEWER 12Z GFS AND ECMWF AND THE EC ENSEMBLE MEAN). THE LATTER  
SEEMS MORE LIKELY NOW THAT MOST 12Z GUIDANCE IS IN. FOR THE WPC  
FORECAST CREATED WITH THE 00Z/06Z CYCLE, HEAVILY FAVORED THE ECMWF  
ENSEMBLE MEAN AMID RAPIDLY INCREASING MODEL DISCREPANCIES.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
BEGINNING TUESDAY, MOUNTAIN SNOW WILL BE ONGOING ACROSS  
PARTICULARLY THE OREGON CASCADES AS WELL AS FARTHER INLAND ACROSS  
THE INTERMOUNTAIN WEST. MEANWHILE, THE SURFACE LOW PRESSURE SYSTEM  
SHOULD BE CONSOLIDATING AND SO A FAVORABLE COMBINATION OF UPPER  
TROUGH DYNAMICS AND LOW LEVEL UPSLOPE FLOW SHOULD INCREASE  
PRECIPITATION, YIELDING A SPRINGTIME HEAVY SNOW THREAT INTO THE  
ROCKIES AND THE NORTHERN PLAINS. AS THE STRONG LOW PRESSURE LOOKS  
TO TRACK FROM THE PLAINS INTO THE UPPER MIDWEST WEDNESDAY INTO  
THURSDAY, HIGH WINDS ARE EXPECTED ALONG WITH THE SNOW, POSSIBLY  
CREATING BLIZZARD CONDITIONS. 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 FROM EASTERN PARTS OF  
THE SOUTHERN/CENTRAL PLAINS INTO THE MISSISSIPPI VALLEY EASTWARD.  
HEAVY TO EXCESSIVE RAINFALL CONCERNS MAY FOCUS ON THE SOUTHERN  
SIDE ACROSS THE LOWER MISSISSIPPI VALLEY, BUT FARTHER NORTH,  
DYNAMICS WRAPPING AROUND THE LOW MAY 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.  
WHILE THESE WINTRY WEATHER/HEAVY RAIN/SEVERE WEATHER THREATS ARE  
GENERALLY COMING INTO BETTER FOCUS, CONTINUE TO MONITOR FORECASTS  
FOR ADDITIONAL CHANGES IN TIMING AND LOCATION OF THESE IMPACTS.  
 
THE WESTERN U.S. SHOULD SEE SEVERAL DAYS OF BELOW NORMAL  
TEMPERATURES, WITH DAYTIME HIGHS 20+ DEGREES BELOW NORMAL SHIFTING  
EASTWARD WITH TIME INTO THE NORTH-CENTRAL CONUS. SOME MODERATION  
IS LIKELY BY LATER IN THE WEEK ACROSS THE WEST, THOUGH STILL BELOW  
NORMAL WITH ADDITIONAL TROUGHING MOVING IN. BY NEXT  
THURSDAY-SATURDAY, THE CORE OF THE COLD SHOULD BE OVER THE  
NORTHERN PLAINS WITH LOW TEMPERATURES 10-20F BELOW NORMAL AND  
HIGHS EVEN APPROACHING 30F BELOW AVERAGE. MEANWHILE, AHEAD OF 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/SANTORELLI  
 
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