477  
FXUS02 KWBC 181916  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
315 PM EDT SAT JUN 18 2022  
 
VALID 12Z TUE JUN 21 2022 - 12Z SAT JUN 25 2022  
 
...EXPANSIVE AREA OF HEAT TO SHIFT FROM THE MIDWEST INTO THE SOUTH  
NEXT WEEK...  
 
   
..OVERVIEW
 
 
THE PREDOMINANT FEATURE IN THE MEDIUM RANGE PERIOD WILL BE A BROAD  
UPPER LEVEL RIDGE/HIGH CENTERED ACROSS THE LOWER MISSISSIPPI  
VALLEY EARLY NEXT WEEK SLOWLY DRIFTING WESTWARD INTO THE SOUTHERN  
HIGH PLAINS WHILE IT EXPANDS ACROSS MUCH OF THE SOUTH. MEANWHILE,  
WEAK AND PROGRESSIVE SYSTEMS SHOULD RIDE OVERTOP THE RIDGE ACROSS  
THE NORTHERN TIER, WHILE PARTS OF THE WEST AND EAST COASTS COULD  
SEE PERIODS OF TROUGHING ON EITHER SIDE OF THE HIGH AS WELL. THIS  
PATTERN WILL ALLOW FOR HOT TEMPERATURES ACROSS MUCH OF THE LOWER  
48 EAST OF THE ROCKIES, ALONG WITH SOME MONSOON TYPE RAINFALL IN  
THE FOUR CORNERS STATES AND ROUNDS OF RAIN IN THE CENTRAL U.S.  
WITH THE WEAK SHORTWAVES/FRONTAL SYSTEMS AND ALONG THE EAST COAST.  
 
   
..GUIDANCE/PREDICTABILITY EVALUATION
 
 
MODEL GUIDANCE REMAINS IN GOOD AGREEMENT WITH THE BROAD RIDGE  
FEATURE EXPANDING ACROSS MUCH OF THE SOUTHERN U.S. AS THE WEEK  
PROGRESSES. A SHORTWAVE ROUNDING THE RIDGE WHILE MOVING THROUGH  
THE NORTH-CENTRAL U.S./SOUTH-CENTRAL CANADA TO START THE PERIOD  
TUE-WED APPEARS WELL HANDLED, AND COMPACT SHORTWAVE ENERGY  
HOVERING NEAR CALIFORNIA SHOWS FAIR AGREEMENT, THOUGH THE GFS RUNS  
WEAKEN THAT FEATURE EARLIER THAN THE ECMWF/UKMET. ADDITIONAL  
ENERGY COMING IN UPSTREAM TOWARD THE NORTHWEST LATER IN THE WEEK  
SHOWS SOME DIFFERENCES IN THE DETAILS AND SOME RUN TO RUN  
INCONSISTENCIES BUT NOTHING TOO EGREGIOUS FOR THE LATE MEDIUM  
RANGE PERIOD.  
 
HOWEVER, THE MAIN CHALLENGE WITH THIS FORECAST CYCLE WAS THE  
POSSIBILITY FOR ENERGY TO SPLIT OFF FROM THE NARROW TROUGH EAST OF  
THE RIDGE IN THE ATLANTIC AND FORM AN UPPER LOW, AND WHERE THAT  
LOW MAY TRACK. DETAILS OF ENERGY WITHIN THE TROUGH ARE QUITE  
UNCERTAIN AS FEATURES EVEN ON THE SPATIAL SCALE OF MCSS/MCVS COULD  
PROVIDE SUFFICIENT ENERGY DIFFERENCES LEADING TO DIFFERING UPPER  
PATTERNS. RECENT MODELS MOSTLY SHOW AN UPPER LOW BREAKING OFF FROM  
THE TROUGH IN THE ATLANTIC, THEN TRACKING SOUTHWARD SOMEWHAT AND  
RETROGRADING TOWARD THE EAST COAST. THIS HAS BEEN A NEW TREND  
SINCE THE 12Z UKMET WAS BASICALLY THE ONLY MODEL TO SHOW THIS A  
DAY OR SO AGO. BUT NOW, NON-NCEP GUIDANCE SHOWS THIS TREND, THOUGH  
GFS RUNS ARE NOT SO MUCH. THE 00Z ECMWF, THE 00Z UKMET AND MANY OF  
THE EC ENSEMBLE MEMBERS INDICATE A CLOSED UPPER LOW RETROGRADING  
TOWARD THE MID-ATLANTIC FOR THE LATTER PART OF NEXT WEEK, AND THE  
12Z EC SHOWS A SIMILAR PATTERN. THE CMC RUNS ARE ALSO SIMILAR  
INITIALLY BUT END UP SOUTH BY FRI-SAT WITH THE UPPER LOW OFF THE  
SOUTHEAST COAST, FARTHER SOUTH THAN EVEN THE EC ENSEMBLE MEMBERS.  
HOWEVER, MOST GEFS MEMBERS AS WELL AS THE OPERATIONAL GFS RUNS  
(00Z AND THE NEW 12Z IN PARTICULAR) SHOW A CUTOFF LOW FORMING  
INITIALLY, MOVING TOWARD THE NORTHEAST, BUT THEN GETTING PICKED UP  
BY THE MAIN FLOW AND TRACKING EASTWARD. WHILE THE STAGNANT PATTERN  
OF RIDGING WITH A NARROW TROUGH TO THE EAST WOULD SUPPORT SOME  
POTENTIAL FOR A CUTOFF LOW TO FORM, THE DETAILS ARE QUITE  
UNCERTAIN AT THIS TIME. THUS THE WPC FORECAST WAS BASED ON A  
MULTI-MODEL BLEND EARLY ON BUT BLENDING IN CONSIDERABLE AMOUNTS OF  
THE ECMWF AND GEFS MEANS, PARTICULARLY THE EC MEAN THAT WAS A GOOD  
COMPROMISE, AS THE PERIOD PROGRESSED TO LESSEN THE DEPENDENCE ON  
ANY PARTICULAR DETERMINISTIC MODEL, CONSIDERING THEIR DIFFERENCES  
PARTICULARLY IN THE EAST. THIS WAS DONE TO INDICATE SOME POTENTIAL  
FOR TROUGHING AND POSSIBLY AN UPPER LOW COMING INTO THE EAST BUT  
NOT BUYING IN ON THE MORE AGGRESSIVE SOLUTIONS YET, PENDING  
FURTHER MODEL RUNS.  
 
   
..SENSIBLE WEATHER/THREAT HIGHLIGHTS
 
 
ANOMALOUSLY HIGH MONSOONAL MOISTURE FOR THIS TIME OF YEAR, LIKELY  
TIED AT LEAST IN PART TO EASTERN PACIFIC TROPICAL SYSTEMS LIKE  
BLAS, WILL CONTINUE STREAMING INTO THE FOUR CORNERS STATES AT  
LEAST THROUGH MIDWEEK AND POSSIBLY LATER INTO THE WEEK AS WELL.  
MODEL GUIDANCE AND FORECASTS SHOW THAT RAINFALL MAY FOCUS IN  
NORTH-CENTRAL NEW MEXICO ON TUESDAY IN PARTICULAR, WHICH COULD  
LEAD TO FLASH FLOODING CONCERNS CONSIDERING LARGE BURN SCARS IN  
THAT AREA AS WELL AS TERRAIN-DRIVEN ENHANCEMENTS, SO A SLIGHT RISK  
WAS ADDED TO THE EXPERIMENTAL EXCESSIVE RAINFALL OUTLOOK IN  
COORDINATION WITH WFO ALBUQUERQUE. A SHOWERY/STORMY PATTERN COULD  
ALSO SET UP AROUND TUESDAY TO FRIDAY ALONG CENTRAL PARTS OF THE  
PLAINS AND MISSISSIPPI VALLEY AS A FRONT BECOMES ALIGNED  
WEST-EAST, WITH SOME POTENTIAL FOR RAIN AND STORMS TO TRAIN IN  
SOME AREAS. FARTHER EAST, A ROUND OF RAIN IS FORECAST NEAR A WARM  
FRONT IN THE NORTHEAST TUESDAY-WEDNESDAY, AND RAIN IS FORECAST TO  
SPREAD INTO THE MID-ATLANTIC BY WEDNESDAY AND BEYOND. HOW MUCH  
RAIN LINGERS ACROSS THE EAST COAST WILL BE DEPENDENT ON THE  
AFOREMENTIONED UPPER LOW/TROUGH FEATURE'S EXISTENCE AND TRACK.  
 
THE BROAD RIDGE WILL ACT AS A HEAT DOME AND SPREAD ANOMALOUSLY  
WARM TEMPERATURES ACROSS THE PLAINS EASTWARD NEXT WEEK. THE  
GREATEST ANOMALIES (GENERALLY 10-15+ ABOVE NORMAL) WILL SHIFT FROM  
THE GREAT LAKES ON TUESDAY INTO THE SOUTH WEDNESDAY-FRIDAY, WITH  
HIGH TEMPERATURES IN THE MID-UPPER 90S AND LOW 100S AND LOWS WELL  
INTO THE 70S MEANING LITTLE RELIEF OVERNIGHT IN MANY AREAS. DAILY  
RECORD HIGH MAX AND MIN TEMPERATURES ARE LIKELY TO BE WIDESPREAD.  
RELATIVELY COOLER TEMPERATURES WITH WELL BELOW NORMAL HIGHS ARE  
FORECAST PARTICULARLY FOR NEW MEXICO GIVEN THE MONSOONAL CLOUDS  
AND RAIN COVERAGE, WHILE NEAR NORMAL TEMPERATURES STRETCH THROUGH  
THE ROCKIES.  
 
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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