027  
FXUS02 KWBC 290718  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
316 AM EDT SUN MAY 29 2022  
 
VALID 12Z WED JUN 01 2022 - 12Z SUN JUN 05 2022  
 
...MULTIPLE ROUNDS OF HEAVY RAINFALL/CONVECTION WILL FOCUS ACROSS  
THE SOUTH-CENTRAL PLAINS NEAR A FRONT TUESDAY-THURSDAY...  
   
..OVERVIEW
 
 
THE MEDIUM RANGE PERIOD WILL BEGIN WEDNESDAY WITH A RELATIVELY  
DEEP UPPER LOW FOR EARLY JUNE ATOP SOUTH-CENTRAL CANADA, AND  
TROUGHING ASSOCIATED WITH THIS FEATURE WILL GRADUALLY PUSH A  
FRONTAL SYSTEM ACROSS THE NORTHEAST QUADRANT OF THE COUNTRY ALONG  
WITH SOME SHOWERS AND STORMS. THE BACK END OF THIS FRONTAL SYSTEM  
IS FORECAST TO SLOW, STALL, AND LIFT BACK NORTH THROUGH THE WEEK,  
AND WILL PROVIDE A FOCUS FOR ROUNDS OF RAIN AND THUNDERSTORMS THAT  
COULD CAUSE FLASH FLOODING ACROSS THE CENTRAL/SOUTHERN PLAINS.  
FARTHER SOUTH, TROPICAL MOISTURE CAN BE EXPECTED TO INCREASE  
ACROSS SOUTHERN FLORIDA THROUGH THE MEDIUM-RANGE PERIOD AS A  
SUBTROPICAL JET IS FORECAST TO INTERACT WITH MOISTURE COMING UP  
FROM TROPICAL CYCLONE AGATHA CURRENTLY LOCATED IN THE EASTERN  
PACIFIC. ELSEWHERE, UPPER-LEVEL RIDGING IS FORECAST TO BUILD  
ACROSS THE INTERIOR WEST WHILE AN EAST PACIFIC UPPER LOW PRODUCES  
TROUGHING ALONG THE WEST COAST.  
 
   
..MODEL GUIDANCE EVALUATION/PREFERENCES
 
 
RECENT MODEL GUIDANCE SHOWS SOMEWHAT REASONABLE AGREEMENT THAT AN  
UPPER LOW WILL BE CONSOLIDATING ACROSS SOUTH-CENTRAL CANADA THIS  
WEEK, THOUGH WITH SOME NOTABLE DIFFERENCES IN THE 12/18Z CYCLE  
EVEN AS THE PERIOD BEGINS DAY 3/WEDNESDAY. THE 12Z UKMET IN  
PARTICULAR SEEMED UNLIKE CONSENSUS WHERE IT SHOWED SEPARATE ENERGY  
TO THE EAST OF THE UPPER LOW OVER THE UPPER GREAT LAKES AND NOT  
YET CONSOLIDATED, WHICH DISPLACED THE SURFACE LOW TO THE  
SOUTHEAST. THE 12Z AND NEW 00Z ECMWF ARE PARTICULARLY STRONG WITH  
AN UPSTREAM SHORTWAVE LOCATED NEAR THE CENTRAL ROCKIES COMPARED TO  
OTHER GUIDANCE, BUT STILL SEEMED ACCEPTABLE TO USE IN A FORECAST  
BLEND. THEN BY THURSDAY-FRIDAY, THE 12Z CMC DRIFTS MORE  
SOUTHEASTWARD WITH ITS CENTROID OF THE UPPER LOW THAN OTHER  
MODELS, PRODUCING MORE TROUGHING IN THE GREAT LAKES/OHIO VALLEY  
COMPARED TO CONSENSUS AND BASICALLY EVERY ENSEMBLE MEMBER. THE 00Z  
CMC LOOKS TO BE IN BETTER ALIGNMENT. THE GFS RUNS AND THE ECMWF  
SEEMED TO BE ALIGNED THE BEST WITH EACH OTHER AND ENSEMBLE  
GUIDANCE, SO FAVORED THOSE ESPECIALLY DURING THE EARLY PART OF THE  
FORECAST. HOWEVER, BY THE WEEKEND, THERE ARE SOME CONSIDERABLE  
DIFFERENCES WITH THE UPPER LOW--THE 18Z GFS IN PARTICULAR STARTS  
TO DIVERGE AS IT MERGES THE AFOREMENTIONED UPPER LOW AND ANOTHER  
UPPER LOW THAT OTHER GFS RUNS AND OTHER MODELS SHOW OVER FAR  
NORTHEASTERN CANADA/THE WESTERN ATLANTIC. ENSEMBLE MEANS MAY ALSO  
BE MERGING TWO UPPER LOWS. BUT HAD TO FAVOR THE ENSEMBLE MEANS BY  
OVER HALF BY THE END OF THE PERIOD REGARDLESS GIVEN THE MODEL  
DIFFERENCES, BUT MAINTAINING A BIT OF 12Z GFS INFLUENCE AND MORE  
OF THE 12Z ECMWF, WHICH SEEMED TO BE THE BEST DETERMINISTIC MODEL  
PROXY TO CONSENSUS.  
 
MODELS STAY MORE AGREEABLE WITH TROUGHING OVER THE WEST COAST  
THROUGH THE WEEKEND DESPITE LINGERING LATITUDINAL DIFFERENCES WITH  
THE EAST PACIFIC UPPER LOW, WHILE RIDGING DEVELOPS IN THE INTERIOR  
WEST POSSIBLY INTO THE SOUTHERN HIGH PLAINS. GUIDANCE VARIES MUCH  
MORE CONSIDERABLY WITH THE PATTERN OVER THE GULF OF MEXICO AND  
FLORIDA THROUGH THE WEEK WITH AT LEAST TROPICAL MOISTURE EMERGING  
FROM AGATHA BUT ALSO POSSIBLY ENERGY FROM AGATHA, WHICH COULD  
COMBINE WITH WESTERN CARIBBEAN ENERGY. MANY MODELS AND ENSEMBLE  
MEMBERS PRODUCE POSSIBLY TROPICAL SURFACE LOWS CROSSING THE GULF  
AND THE FLORIDA PENINSULA, BUT WITH TIMING DIFFERENCES ON THE  
ORDER OF DAYS, AND SOME LINGER ENERGY AND LOW PRESSURE NEAR THE  
YUCATAN/BAY OF CAMPECHE/WESTERN CARIBBEAN. THE WPC FORECAST AT  
THIS POINT IS ON THE SLOW AND WEAK SIDE OF GUIDANCE, BUT WITH SOME  
EJECTION OF LOW PRESSURE NORTHEASTWARD INTO THE GULF BY THE  
WEEKEND. THIS IS MOST LIKE THE ECMWF IN TERMS OF THE DETERMINISTIC  
GUIDANCE.  
 
   
..SENSIBLE WEATHER/THREAT HIGHLIGHTS
 
 
A SURFACE LOW WELL INTO CENTRAL CANADA BY WEDNESDAY WILL SEND ITS  
TRAILING COLD FRONT ACROSS THE GREAT LAKES AND OHIO VALLEY  
WEDNESDAY AND THE NORTHEAST AND MID-ATLANTIC THURSDAY-FRIDAY. RAIN  
AND THUNDERSTORMS CAN BE EXPECTED ALONG THIS FRONT, AFTER SOME  
INITIAL SHOWERS IN PARTS OF THE NORTHEAST WEDNESDAY NEAR A  
BACKDOOR FRONT. HOWEVER, THE BACK END OF THE MAIN FRONT IS  
FORECAST TO MOVE MORE SLOWLY THROUGH CENTRAL AND SOUTHERN PARTS OF  
THE PLAINS AND MISSISSIPPI VALLEY, AND WILL PROVIDE A FOCUS FOR  
RAIN AND THUNDERSTORMS FOR MULTIPLE DAYS AROUND TUESDAY-THURSDAY.  
FLASH FLOODING IS POSSIBLE ESPECIALLY WHERE STORMS REPEAT OVER THE  
SAME AREA, WHICH AT THIS POINT APPEARS MOST LIKELY TO OCCUR AROUND  
KANSAS, OKLAHOMA, AND POSSIBLY MISSOURI. UNCERTAINTY REMAINS WITH  
THE AXIS OF THE CONVECTION EACH DAY/NIGHT, BUT A SLIGHT RISK OF  
EXCESSIVE RAINFALL IN WPC'S EXPERIMENTAL DAY 4 OUTLOOK SEEMED  
WARRANTED GIVEN MOISTURE AND INSTABILITY WILL BE ABUNDANT ALONG  
WITH A FOCUS FOR LIFT WITH THE FRONT IN PLACE, AND CONSIDERING  
ANTECEDENT CONDITIONS COULD BE QUITE WET WITH TUESDAY'S RAIN.  
 
THERE IS INCREASING FORECAST AGREEMENT FOR TROPICAL CYCLONE AGATHA  
OVER THE EASTERN PACIFIC TO TURN NORTHEASTWARD AND MOVE ACROSS  
MEXICO OVER THE NEXT FEW DAYS. SCATTERED SHOWERS AND THUNDERSTORMS  
ARE EXPECTED TO BECOME MORE FREQUENT AND WIDESPREAD ACROSS  
SOUTHERN FLORIDA LATER NEXT WEEK ALTHOUGH THE SPECIFICS ARE NOT  
CLEAR AT THIS TIME. FACTORS THAT INFLUENCE THE TIMING AND AMOUNTS  
OF RAINFALL WILL INCLUDE (A) THE INTERACTION OF A SUBTROPICAL JET  
WITH TROPICAL MOISTURE COMING FROM AGATHA, AND THE CYCLONE'S  
SUBSEQUENT TRACK AND INTENSITY AFTER CROSSING CENTRAL AMERICA, (B)  
THE PROXIMITY OF AN UPPER LOW FORECAST TO GRADUALLY GAIN TROPICAL  
CHARACTERISTICS NEAR AND NORTHEAST OF THE BAHAMAS MIDWEEK, AND (C)  
POSSIBLE INTERACTION WITH A TROPICAL WAVE MOVING INTO THE WESTERN  
CARIBBEAN SEA.  
 
ADDITIONALLY, RAIN CHANCES ARE EXPECTED TO INCREASE IN THE  
NORTHWEST DURING THE LATTER HALF OF THE WEEK GIVEN THE TROUGH AXIS  
NEAR THE WEST COAST AND A COUPLE OF FRONTAL SYSTEMS. THE SOUTHWEST  
SHOULD REMAIN DRY AND HOT THOUGH. ROUNDS OF RAIN ARE POSSIBLE IN  
THE CENTRAL U.S. NEXT WEEKEND, BUT WITH CONSIDERABLE UNCERTAINTY  
IN THE DETAILS AT THIS POINT.  
 
UPPER RIDGING AHEAD OF THE CENTRAL U.S./CANADA TROUGH/LOW WILL  
PROMOTE ABOVE AVERAGE TEMPERATURES BY 10-20F OVER THE MIDWEST/OHIO  
VALLEY AND PARTS OF THE NORTHEAST/MID-ATLANTIC WEDNESDAY, WITH THE  
EXCEPTION OF PARTS OF NEW ENGLAND DUE TO THE BACKDOOR FRONT.  
MEANWHILE UPPER TROUGHING WILL BRING CONTINUED COOL TEMPERATURES  
ACROSS THE ROCKIES AND CENTRAL HIGH PLAINS THROUGH MIDWEEK WITH  
HIGHS FORECAST TO BE 10-20F OR BELOW NORMAL. THE FLATTENING  
PATTERN ALOFT WILL PUSH THE COLD FRONT EASTWARD, LEADING TO A  
MODERATING TREND FOR BELOW NORMAL TEMPERATURES OVER THE CENTRAL  
U.S., WITH MOSTLY SINGLE-DIGIT NEGATIVE ANOMALIES BY  
THURSDAY-FRIDAY, THOUGH AROUND 10F BELOW NORMAL IN RAIN-COOLED  
KANSAS AND OKLAHOMA. THE EAST SHOULD SEE SHRINKING COVERAGE OF  
WARM TEMPERATURES ON THURSDAY AND ESPECIALLY FRIDAY INTO THE  
WEEKEND. THE WEST COAST AND INTO THE GREAT BASIN CAN EXPECT WARMER  
THAN NORMAL TEMPERATURES BY AROUND 5-15F WEDNESDAY AND BEYOND,  
FOLLOWED BY A MODEST COOLING TREND ON FRIDAY-SUNDAY ALONG THE  
IMMEDIATE WEST COAST WITH THE ARRIVAL OF A PACIFIC FRONT.  
 
TATE/KONG  
 
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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