404  
FXUS02 KWBC 211901  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
259 PM EDT THU APR 21 2022  
 
VALID 12Z SUN APR 24 2022 - 12Z THU APR 28 2022  
 
...SIGNIFICANT LATE SEASON WINTER STORM AFFECTING THE NORTHERN  
TIER INTO SUNDAY ALONG WITH POTENTIALLY HEAVY RAINFALL OVER  
PORTIONS OF THE SOUTHERN PLAINS AND MID MISSISSIPPI VALLEY...  
   
..WEATHER PATTERN OVERVIEW
 
 
AN AMPLIFIED FLOW PATTERN WILL EXIST EARLY IN THE PERIOD  
SUNDAY-MONDAY AS THE NORTHERN PLAINS/UPPER MIDWEST DEEP LOW LIFTS  
INTO CANADA WHILE A STRONG SOUTHEAST RIDGE EXTENDS NORTHWARD  
THROUGH MUCH OF THE EASTERN U.S. THE STORM SYSTEM'S ASSOCIATED  
TRAILING COLD FRONT COULD BRING A HEAVY RAINFALL THREAT OVER  
PORTIONS OF THE SOUTHERN PLAINS TO THE OZARKS AND MID MISSISSIPPI  
VALLEY. MOST GUIDANCE EXPECTS GRADUAL PROGRESSION OF THE MEAN  
PATTERN WITH TIME, ULTIMATELY LEADING TO TROUGHS NEAR EACH COAST  
AND A BROAD CENTRAL U.S. UPPER RIDGE. BOTH TROUGHS COULD CONTAIN  
AN EMBEDDED UPPER LOW. MUCH BELOW NORMAL TEMPERATURES MAY PERSIST  
FOR MULTIPLE DAYS OVER THE FAR NORTHERN PARTS OF THE PLAINS WHILE  
WELL ABOVE NORMAL READINGS ARE POSSIBLE OVER THE EAST DURING  
SUNDAY-MONDAY AND OVER THE GREAT BASIN/SOUTHWEST INTO PARTS OF THE  
PLAINS BY TUESDAY-THURSDAY.  
   
..MODEL GUIDANCE EVALUATION
 
 
OVERALL A CONSENSUS/AVERAGE OF 00Z AND 06Z MODELS EARLY IN THE  
PERIOD FOLLOWED BY A BLEND OF MODELS AND 06Z GEFS/00Z ECMWF MEANS  
PROVIDED A REASONABLE DEPICTION OF THE MOST LIKELY FORECAST  
SCENARIO THROUGH THE PERIOD. GUIDANCE STILL EXHIBITS SOME SPREAD  
FOR THE DEPARTING NORTHERN TIER STORM, AGAIN WITH THE GFS FASTEST  
AND CMC SLOWEST, WHILE THE ECMWF CONTINUES TO PROVIDE THE MOST  
CONSISTENT INTERMEDIATE SOLUTION. CLUSTERING IS GRADUALLY  
IMPROVING THOUGH. DIFFERENCES FOR THE TRAILING UPPER TROUGH  
CROSSING THE CENTRAL-EASTERN U.S. DURING THE FIRST HALF OF THE  
WEEK HAVE COME DOWN TO MAINLY LOW-PREDICTABILITY DETAIL ISSUES.  
MEANWHILE THERE IS GOOD AGREEMENT THAT ENERGY FROM THE INITIAL  
NORTHERN TIER UPPER LOW WILL CONTINUE NORTHEASTWARD THROUGH  
CANADA, WHILE TRAILING ENERGY CROSSING THE GREAT LAKES AND  
SOUTHEASTERN CANADA DEVELOPS AN UPPER LOW THAT REACHES NEW ENGLAND  
BY EARLY NEXT THURSDAY. LATEST MODELS AND MEANS SHOW BETTER THAN  
AVERAGE CLUSTERING FOR THIS POTENTIAL UPPER LOW RELATIVE TO  
TYPICAL DAY 7 FORECASTS, WITH ASSOCIATED LOW PRESSURE TRACKING  
CLOSE TO THE NEW ENGLAND COAST.  
 
ON THE OTHER HAND, MODELS AND INDIVIDUAL ENSEMBLE MEMBERS CONTINUE  
TO SHOW A LOT OF SPREAD FOR SPECIFICS OF INDIVIDUAL SHORTWAVES  
WITHIN THE MEAN TROUGH WHOSE AXIS SETTLES OVER THE EASTERN  
PACIFIC/WEST COAST FROM ABOUT TUESDAY ONWARD. THESE DIFFERENCES  
AFFECT THE FORECAST OF COVERAGE/AMOUNTS OF PRECIPITATION OVER THE  
WEST AND EVENTUALLY THE SURFACE PATTERN AS FAR EAST THE PLAINS BY  
DAY 7 THURSDAY. BY LATE IN THE PERIOD THE MAIN THEME OF  
MODELS/MEANS IS TO KEEP THE UPPER TROUGH AXIS CLOSER TO THE WEST  
COAST THAN THE PAST THREE ECMWF RUNS THROUGH 00Z. MOST NEW 12Z  
MODEL RUNS ARE STILL WITHIN THE MAJORITY CLUSTER WHILE THE ECMWF  
HAS ADJUSTED CLOSER TO CONSENSUS.  
   
..SENSIBLE WEATHER/THREATS
 
 
THE STRONG/SIGNIFICANT WINTER STORM AFFECTING THE NORTHERN PLAINS  
WILL BE ONGOING AT THE START OF THE MEDIUM RANGE PERIOD WITH THE  
SURFACE LOW LIKELY TRACKING ACROSS NORTHERN MINNESOTA ON SUNDAY.  
WRAPAROUND PRECIPITATION UNDERNEATH/AROUND THE CLOSED UPPER LOW  
WILL LIKELY CONTINUE SNOW SHOWERS, AND A STRONG/TIGHT PRESSURE  
GRADIENT SHOULD PRODUCE STRONG WINDS THAT WOULD CONTINUE BLOWING  
SNOW AND REDUCED VISIBILITY AT TIMES. CONDITIONS IMPROVE BY EARLY  
NEXT WEEK AS THE LOW WEAKENS AND TRACKS OVER SOUTHERN CANADA.  
MEANWHILE TO THE SOUTH, THE TRAILING COLD FRONT WILL INTERSECT  
WITH WARM/MOIST AIR FROM THE GULF AND A STRENGTHENING LOW LEVEL  
JET SUNDAY NIGHT INTO MONDAY MORNING SHOULD FOCUS A FEW MESOSCALE  
CONVECTIVE SYSTEMS THAT HAVE THE POTENTIAL TO TRAIN AND REPEAT  
OVER THE SAME AREAS. THE LATEST FORECAST GUIDANCE SUGGESTS  
POTENTIAL FOR MULTI-INCH TOTALS DURING THE DAY 4 PERIOD (ENDING  
12Z MONDAY APRIL 25) ACROSS AN AREA FROM NORTHEASTERN TEXAS  
THROUGH EASTERN OKLAHOMA, WESTERN/NORTHERN ARKANSAS, SOUTHERN  
MISSOURI, AND PERHAPS EXTENDING A LITTLE EAST FROM THERE. THE DAY  
4 EXCESSIVE RAINFALL OUTLOOK MAINTAINED A SLIGHT RISK AREA  
HIGHLIGHTING THIS REGION WITH ONLY SLIGHT REFINEMENTS FOR NEW  
GUIDANCE. STREAM FLOWS/SOIL MOISTURE/PRECIPITATION ANOMALIES ARE  
ABOVE NORMAL FOR MUCH OF THIS AREA DUE TO RECENT HEAVY RAINFALL.  
GUIDANCE IS STILL IN THE PROCESS OF RESOLVING THE TIMING AND WAVE  
DETAILS OF THE SURFACE FRONT SO ADDITIONAL REFINEMENTS IN THE MOST  
LIKELY COVERAGE AND MAGNITUDE OF RAINFALL TOTALS ARE CERTAINLY  
POSSIBLE. THE FRONT SHOULD ACCELERATE AS IT CONTINUES EASTWARD SO  
RAINFALL ACROSS THE EASTERN U.S. SHOULD BE LIGHTER DURING  
TUESDAY-WEDNESDAY. BY WEDNESDAY-THURSDAY THE UPPER LOW FORECAST TO  
APPROACH/REACH NEW ENGLAND AND ASSOCIATED LOW PRESSURE COULD FOCUS  
SOME PRECIPITATION OVER THE REGION, WITH COVERAGE AND AMOUNTS  
SENSITIVE TO THE EXACT TRACK OF THE SYSTEM. A PORTION OF THIS  
PRECIPITATION COULD BE SNOW IN THE HIGHER ELEVATIONS. UNSETTLED  
WEATHER WITH GENERALLY LIGHT TO MODERATE PRECIPITATION WILL SPREAD  
ACROSS AREAS FROM THE NORTHERN HALF OF THE WEST COAST INTO THE  
NORTHERN ROCKIES AS A SERIES OF SHORTWAVES MOVE THROUGH THE MEAN  
TROUGH SOUTH OF A CLOSED UPPER LOW POSITIONED OFF BRITISH  
COLUMBIA. TIMING AND COVERAGE WITH EACH EPISODE OF RAIN/HIGH  
ELEVATION SNOW WILL TAKE ADDITIONAL TIME TO RESOLVE GIVEN THE  
TYPICAL LOWER PREDICTABILITY OF MEDIUM TO SMALLER SCALE OF  
FEATURES CONTAINED WITHIN THE MEAN FLOW.  
 
THE WEEKEND STORM SYSTEM AND FLOW ON EITHER SIDE OF THE ASSOCIATED  
COLD FRONT WILL BRING CONTRASTING TEMPERATURE EXTREMES TO THE  
CENTRAL AND EASTERN STATES INTO EARLY NEXT WEEK. NORTHERN  
PLAINS/UPPER MIDWEST AREAS WILL SEE UNSEASONABLY CHILLY READINGS  
WITH HIGHS UP TO 20-30F BELOW NORMAL WHILE MORE MODERATE BELOW  
NORMAL ANOMALIES WILL SPREAD ACROSS THE REST OF THE CENTRAL U.S.  
AREAS NEAR THE CANADIAN BORDER MAY STAY BELOW NORMAL THROUGH  
THURSDAY. AHEAD OF THE COLD FRONT, EXPECT MANY AREAS TO SEE  
TEMPERATURES 5-20F ABOVE NORMAL AND POTENTIALLY EVEN WARMER  
ANOMALIES FOR MORNING LOWS OVER THE GREAT LAKES ON SUNDAY. THE  
EXCEPTION TO THE EASTERN WARMTH SHOULD BE FOR THE COASTAL  
NORTHEAST AREAS AND AT TIMES INTO THE MID-ATLANTIC WHERE SURFACE  
HIGH PRESSURE MAY KEEP TEMPERATURES ON THE COOLER SIDE. A FRONT  
MEANDERING TO THE SOUTH COULD LEAD TO 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.  
 
THROUGH THE PERIOD A WARMING TREND WILL SPREAD ACROSS THE SOUTHERN  
TWO-THIRDS OF THE WEST AND INTO THE CENTRAL/SOUTHERN PLAINS WITH  
PLUS 10-20F ANOMALIES FOR HIGHS BECOMING COMMON BY  
TUESDAY-THURSDAY. IN CONTRAST, THE UPPER TROUGH NEARING THE WEST  
COAST WILL SUPPORT SLIGHTLY BELOW NORMAL HIGHS FROM THE PACIFIC  
NORTHWEST/NORTHERN CALIFORNIA INTO THE NORTHERN ROCKIES TUESDAY  
ONWARD. THE UPPER TROUGH AND POSSIBLE EMBEDDED UPPER LOW REACHING  
THE EASTERN U.S. SHOULD LEAD TO BELOW NORMAL READINGS OVER THE  
REGION BY MIDWEEK WITH THE GREAT LAKES INTO CENTRAL APPALACHIANS  
BEING THE MOST LIKELY AREA TO SEE HIGHS 10-20F BELOW NORMAL FOR  
ONE OR MORE DAYS.  
 
RAUSCH/TAYLOR  
 
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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