333  
FXUS02 KWBC 202031  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
429 PM EDT WED APR 20 2022  
 
VALID 12Z SAT APR 23 2022 - 12Z WED APR 27 2022  
 
...SIGNIFICANT LATE SEASON WINTER STORM INCREASINGLY LIKELY FOR  
THE NORTHERN PLAINS THIS WEEKEND AND POTENTIALLY HEAVY RAINFALL  
THREAT TO SOME AREAS FARTHER SOUTH...  
   
..WEATHER PATTERN OVERVIEW
 
 
A HIGHLY AMPLIFIED PATTERN WILL PREVAIL OVER THE WEEKEND INTO THE  
START OF NEXT WEEK AS A DEEP UPPER LOW TRACKS NORTHEASTWARD  
THROUGH THE NORTHERN PLAINS AND A STRONG SOUTHEAST RIDGE EXTENDS  
AN AXIS NORTHWARD. A STRONG SURFACE LOW FORECAST TO BE OVER THE  
DAKOTAS ON SATURDAY AND CONTINUE NORTHEAST THEREAFTER, ALONG WITH  
THE TRAILING FRONT, WILL BRING A WIDE VARIETY OF WEATHER HAZARDS -  
SIGNIFICANT SNOW AND WIND TO THE NORTHERN PLAINS AND EVENTUALLY A  
HEAVY RAIN THREAT EVOLVING LATE IN THE WEEKEND INTO EARLY NEXT  
WEEK OVER PORTIONS OF THE SOUTHERN PLAINS TO THE OZARKS AND MID  
MISSISSIPPI VALLEY. BY TUESDAY-WEDNESDAY, GRADUAL PROGRESSION OF  
THE MEAN PATTERN WILL BRING MODERATE UPPER TROUGHING TO THE EAST,  
A RIDGE TO THE ROCKIES/PLAINS, AND A TROUGH INTO THE EASTERN  
PACIFIC/WEST COAST. MUCH BELOW NORMAL TEMPERATURES MAY PERSIST FOR  
A WHILE OVER THE FAR NORTHERN PARTS OF THE PLAINS WHILE WELL ABOVE  
NORMAL READINGS ARE POSSIBLE OVER A MAJORITY OF THE EASTERN HALF  
OF THE COUNTRY THROUGH THE WEEKEND.  
   
..MODEL GUIDANCE EVALUATION
 
 
THE UPDATED FORECAST EMPHASIZED A BLEND OF THE 00Z ECMWF/00Z  
UKMET/06Z GFS DURING THE FIRST HALF OF THE PERIOD, FOLLOWED BY  
GRADUALLY INCREASING INPUT OF THE 06Z GEFS/00Z ECMWF MEANS SO THAT  
THE MEANS HAD HALF TOTAL WEIGHT BY DAY 7 WEDNESDAY. RECENT ECMWF  
RUNS HAVE GENERALLY PROVIDED THE BEST INTERMEDIATE TIMING FOR THE  
NORTHERN TIER STORM, WITH GFS RUNS CONSISTENTLY FASTER AND THE CMC  
SLOW. UKMET RUNS HAVE TENDED TO BE BETWEEN THE ECMWF AND CMC BUT  
THE NEW 12Z UKMET HAS ADJUSTED TO THE ECMWF, LEAVING THE CMC MORE  
IN THE SLOW MINORITY. MEANWHILE GUIDANCE HAS VARIED CONSIDERABLY  
OVER RECENT DAYS FOR THE AMPLITUDE AND TIMING OF THE TRAILING  
UPPER TROUGH THAT PROGRESSES THROUGH THE CENTRAL/EASTERN U.S.,  
AFFECTING THE TIMING AND WAVINESS OF THE COLD FRONT TRAILING FROM  
THE SURFACE LOW. OVER THE PAST DAY MOST GUIDANCE HAS BEEN  
CONSOLIDATING TOWARD GREATER PROGRESSION THAN RECENT CMC RUNS. IT  
IS POSSIBLE THAT LOW PRESSURE COULD EVOLVE NEAR NEW ENGLAND BY DAY  
7 WEDNESDAY DEPENDING ON SPECIFICS OF THE EASTERN NORTH AMERICA  
UPPER TROUGH. FOR THE EASTERN PACIFIC/WEST COAST UPPER TROUGH,  
FROM LATE SUNDAY ONWARD THERE IS STILL A LOT OF MODEL/ENSEMBLE  
SPREAD WITH RESPECT TO INDIVIDUAL SHORTWAVES FLOWING AROUND THE  
TROUGH AND THE EVENTUAL LOCATION OF THE EMBEDDED UPPER LOW. BY  
NEXT WEDNESDAY THE NEW 12Z ECMWF/CMC BRINGS THE UPPER LOW CLOSEST  
TO THE PACIFIC NORTHWEST WHILE THE 00Z ECMWF MEAN KEPT IT WELL TO  
THE NORTHWEST. PREFER A COMPROMISE APPROACH WITHIN THIS BROAD  
SPREAD UNTIL BETTER AGREEMENT EMERGES.  
   
..SENSIBLE WEATHER/THREATS
 
 
A STRONG TO POTENTIALLY SIGNIFICANT STORM SYSTEM WILL LIKELY TRACK  
OVER THE NORTHERN PLAINS AND UPPER MIDWEST DURING THE WEEKEND. THE  
BEST POTENTIAL FOR SIGNIFICANT TOTALS OF SNOW AND BLOWING SNOW  
EXTENDS FROM NORTHEAST WYOMING AND EASTERN MONTANA THROUGH MUCH OF  
WESTERN/CENTRAL NORTH DAKOTA AND FAR NORTHWEST SOUTH DAKOTA -  
IMMEDIATELY WEST TO NORTHWEST OF THE SURFACE LOW TRACK. THE STRONG  
WINDS AND HEAVY SNOW COMBINED COULD LEAD TO NEAR BLIZZARD  
CONDITIONS FOR SOME AREAS. THERE IS SOME LINGERING UNCERTAINTY IN  
THE SPEED AND TRACK BUT THE GRADUALLY IMPROVING GUIDANCE CLUSTER  
SUGGESTS GOOD CONFIDENCE IN A HIGH IMPACT LATE SEASON WINTER STORM  
FOR PORTIONS OF THE REGION WHERE THE LATEST WINTER WEATHER OUTLOOK  
SHOWS HIGH PROBABILITIES FOR AT LEAST SEVERAL INCHES OF SNOW.  
 
THE FRONTAL BOUNDARY ANCHORED BY THIS STORM WILL HELP TO FOCUS AN  
AREA OF HEAVY RAINFALL FROM PARTS OF THE SOUTHERN/CENTRAL PLAINS  
TOWARD THE OZARKS AND MID MISSISSIPPI VALLEY. SOUTHERLY FLOW OF  
WARM, MOIST AIR INTERSECTING THE BOUNDARY WILL LIKELY LEAD TO  
STRONG THUNDERSTORMS THAT MAY TRAIN OR REPEAT OVER THE SAME AREAS  
SUNDAY INTO MONDAY. MESOSCALE CONVECTIVE SYSTEMS REPEATING OVER  
THE AREA COULD LEAD TO AN AXIS OF MULTI-INCH TOTALS AND THE LATEST  
GUIDANCE SUGGESTS THE BEST POTENTIAL FOR FLASH FLOODING AND  
EXCESSIVE RAINFALL FROM FAR NORTHEASTERN TEXAS THROUGH EASTERN  
OKLAHOMA, NORTHWESTERN ARKANSAS, AND SOUTHERN MISSOURI ALONG WITH  
ADJACENT AREAS. THE DAY 5 EXPERIMENTAL EXCESSIVE RAINFALL OUTLOOK  
SHOWS A SLIGHT RISK OVER THIS REGION GIVEN THE POTENTIAL, AS  
STREAM FLOWS AND PRECIPITATION ANOMALIES ARE ALREADY ABOVE NORMAL  
DUE TO RECENT HEAVY RAINFALL AND WITH THE POTENTIAL FOR ADDITIONAL  
HEAVY RAINFALL LEADING UP TO DAY 5. GUIDANCE IS STILL IN THE  
PROCESS OF RESOLVING THE TIMING AND WAVE DETAILS OF THE SURFACE  
FRONT SO CHANGES IN THE MOST LIKELY COVERAGE AND MAGNITUDE OF  
RAINFALL TOTALS ARE CERTAINLY POSSIBLE. LIGHTER RAINFALL WILL  
SPREAD THROUGH THE EASTERN U.S. DURING TUESDAY-WEDNESDAY AS THE  
FRONT ACCELERATES.  
 
MOSTLY LIGHT PRECIPITATION OVER THE NORTHERN PART OF THE PACIFIC  
NORTHWEST TO START THE WEEK SHOULD EXPAND SOUTHWARD THROUGH OREGON  
AND EASTWARD INTO THE NORTHERN ROCKIES AFTER MONDAY AS AN UPPER  
TROUGH APPROACHES THE WEST COAST. SOME POCKETS OF MODERATE  
ACTIVITY ARE POSSIBLE. DAY-TO-DAY DETAILS ARE STILL UNCERTAIN DUE  
TO LOWER CONFIDENCE IN SPECIFICS OF SHORTWAVES WITHIN THE OVERALL  
UPPER TROUGH.  
 
EXPECT UNSEASONABLY COLD TEMPERATURES TO PERSIST OVER FAR NORTHERN  
PARTS OF THE PLAINS THROUGH THE PERIOD WITH NORTH DAKOTA IN  
PARTICULAR SEEING HIGHS 15-30F BELOW NORMAL FOR MULTIPLE DAYS.  
WHILE STILL BELOW NORMAL, ANOMALIES MAY FINALLY MODERATE SOME  
AROUND MIDWEEK. THE WEST WILL SEE MORE VARIABLE TEMPERATURES, WITH  
MINUS 5-15F ANOMALIES OVER THE INTERMOUNTAIN WEST/ROCKIES DURING  
THE WEEKEND FOLLOWED BY A WEST-TO-EAST WARMING TREND WITH  
INCREASING COVERAGE OF ABOVE NORMAL READINGS. WARMEST HIGHS OF  
10-15F ABOVE NORMAL ARE LIKELY TO EXTEND FROM THE GREAT  
BASIN/SOUTHWEST INTO THE CENTRAL HIGH PLAINS DURING  
TUESDAY-WEDNESDAY. AT THE SAME TIME CLOUDS/PRECIPITATION AHEAD OF  
THE UPPER TROUGH NEARING THE WEST COAST MAY BRING SLIGHTLY BELOW  
NORMAL HIGHS TO THE PACIFIC NORTHWEST. MUCH OF THE EASTERN HALF OF  
THE COUNTRY WILL SEE A SIGNIFICANT WARMING TREND DURING THE  
WEEKEND AND CONTINUING INTO EARLY NEXT WEEK OVER THE EAST. PLUS  
10-20F ANOMALIES SHOULD BE FAIRLY COMMON FOR ONE OR MORE DAYS AND  
PARTS OF THE MIDWEST/GREAT LAKES COULD SEE MORNING LOWS 20-25F  
ABOVE NORMAL. ONE EXCEPTION TO THE EASTERN WARMTH MAY BE OVER THE  
NORTHEAST/NORTHERN MID-ATLANTIC WHERE COOL SURFACE HIGH  
PRESSURE/RIDGING MAY PREVAIL FOR A WHILE. A FRONT MEANDERING OVER  
THE MID-ATLANTIC COULD PROVIDE A SHARP CONTRAST BETWEEN COOL AIR  
TO THE NORTH AND WARMTH TO THE SOUTH AND WEST, INCREASING THE  
CHALLENGE OF TEMPERATURE FORECASTING OVER THE REGION.  
 
RAUSCH/TAYLOR  
 
HAZARDS:  
- HEAVY PRECIPITATION ACROSS PORTIONS OF THE FAR NORTHERN PLAINS,  
SAT, APR 23.  
- HEAVY RAIN FROM ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN  
PLAINS INTO THE MIDWEST, SAT-SUN, APR 23-APR 24.  
- HEAVY SNOW ACROSS PORTIONS OF EASTERN MONTANA AND WESTERN NORTH  
DAKOTA, SAT, APR 23.  
- SEVERE WEATHER ACROSS PORTIONS OF THE CENTRAL PLAINS WEST OF THE  
MIDDLE TO UPPER MISSISSIPPI VALLEY, SAT, APR 23.  
- FLOODING POSSIBLE ACROSS PORTIONS OF GEORGIA AND THE NORTHERN  
PLAINS.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE SOUTHEAST  
AND CENTRAL MISSISSIPPI.  
- FLOODING LIKELY ACROSS PORTIONS OF THE SOUTHEAST.  
- HIGH WINDS ACROSS PORTIONS OF THE NORTHERN PLAINS, SAT-SUN, APR  
23-APR 24.  
- MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE NORTHERN  
PLAINS, SAT-TUE, APR 23-APR 26.  
- ENHANCED WILDFIRE RISK FROM THE FOOTHILLS OF THE SOUTHERN  
ROCKIES TO PORTIONS OF THE CENTRAL PLAINS, SAT, APR 23.  
 
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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