479  
FXUS02 KWBC 270656  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
256 AM EDT FRI MAY 27 2022  
 
VALID 12Z MON MAY 30 2022 - 12Z FRI JUN 03 2022  
 
...POTENTIAL FOR HEAVY PRECIPITATION NEXT WEEK FROM THE NORTHERN  
ROCKIES TO UPPER MIDWEST AND THEN SOUTHWARD THROUGH THE PLAINS...  
   
..WEATHER PATTERN OVERVIEW
 
 
THE MEDIUM RANGE PERIOD BEGINS MONDAY WITH A RATHER AMPLIFIED  
UPPER LEVEL PATTERN FOR LATE MAY, CONSISTING OF AN ANOMALOUSLY  
DEEP TROUGH AND EMBEDDED LOW IN THE WEST AND RIDGING OVER MUCH OF  
THE EAST (THOUGH SUPPRESSED IN THE NORTHEAST BY AN EASTERN CANADA  
UPPER LOW). THIS WILL ALLOW FOR POTENTIALLY HEAVY PRECIPITATION TO  
SPREAD FROM THE NORTHERN ROCKIES INTO THE NORTHERN PLAINS AND  
UPPER MIDWEST. HIGHER ELEVATION SNOW IS POSSIBLE IN THE ROCKIES  
WHILE HEAVY RAIN AND SEVERE WEATHER ARE THREATS IN THE PLAINS TO  
MIDWEST ALONG WITH WARMER THAN NORMAL TEMPERATURES. AS NEXT WEEK  
PROGRESSES, THE PATTERN IS FORECAST TO FLATTEN QUICKLY AS THE  
WESTERN TROUGH LIFTS INTO SOUTH-CENTRAL CANADA AND CONSOLIDATES  
WITH AN UPPER LOW. THE HIGHEST PRECIPITATION CHANCES SHOULD SHIFT  
INTO THE CENTRAL/SOUTHERN PLAINS AND ACROSS THE EAST ALONG AND  
AHEAD OF A COLD FRONT.  
 
   
..MODEL GUIDANCE EVALUATION/PREFERENCES
 
 
WHILE 12/18Z AND THE NEWER 00Z MODEL GUIDANCE CYCLES SHOW GENERAL  
AGREEMENT FOR THE INITIAL TROUGH/RIDGE PATTERN FLATTENING FOR THE  
LATTER HALF OF THE WEEK AS AN UPPER LOW CONSOLIDATES IN  
SOUTH-CENTRAL CANADA, UNCERTAINTIES IN THE DETAILS REMAIN. MODELS  
DISPLAY VARIOUS WAYS OF HANDLING ENERGY WITHIN THE UPPER  
TROUGH/LOW, AS WELL AS UPSTREAM ENERGY THAT COULD SPILL INTO THE  
WEST MONDAY-TUESDAY AND AFFECT THE TIMING OF THE TROUGH'S MOVEMENT  
EAST AND ITS LIFT NORTHWARD AND MERGING WITH ENERGY ACROSS CANADA.  
THERE HAS BEEN A GENERAL TREND FOR THE WESTERN ENERGY TO EJECT  
FASTER, LEADING TO A FASTER TREND FOR A COLD FRONT JUST AHEAD OF  
THE TROUGH AS WELL AS THE QPF, AND THIS TREND CONTINUED IN THE  
12/18Z MODELS AND AGAIN IN THE 00Z CYCLE. EVEN CONSIDERING THE  
FASTER TREND, THE 12Z UKMET REMAINED ON THE FAST SIDE OF GUIDANCE  
WITH THE TROUGH'S MOVEMENT EASTWARD AS IT LIFTS NORTH, BUT THE 00Z  
MAY BE MORE IN LINE WITH CONSENSUS. THOUGH THE AMPLITUDE OF THE  
TROUGH FLATTENS, THERE IS DECENT AGREEMENT FOR TROUGHING TO TREK  
ACROSS THE MIDWEST/GREAT LAKES THURSDAY INTO FRIDAY AND PUSH A  
COLD FRONT EASTWARD.  
 
ELSEWHERE, THERE IS GOOD AGREEMENT FOR RIDGING ACROSS MUCH OF THE  
EAST ON MONDAY AND FLATTENING THROUGH THE WEEK AS UPPER HIGHS  
(WITH LESS CERTAIN PLACEMENT) COULD BUILD ACROSS THE SOUTHERN  
TIER. AN EASTERN CANADA UPPER LOW PRODUCING LOW AMPLITUDE  
TROUGHING IN THE NORTHEAST FOR THE FIRST HALF OF THE WEEK COULD  
SEND A BACKDOOR FRONT ACROSS THE AREA, WHICH COULD POTENTIALLY  
STALL FOR A TIME BUT SHOWS UNCERTAIN PLACEMENT IN GENERAL.  
 
DESPITE SOME INDIVIDUAL MODEL INTRICACIES, A BLEND OF THE  
DETERMINISTIC GUIDANCE LED BY THE ECMWF AND GFS RUNS WORKED FOR  
THE EARLY PART OF THE WPC FORECAST, AND ADDED AND GRADUALLY  
INCREASED THE PROPORTION OF THE GEFS AND EC ENSEMBLE MEANS TO  
ALMOST HALF BY THE END OF THE PERIOD TO MINIMIZE THE SPECIFICS OF  
ANY PARTICULAR MODEL.  
 
   
..SENSIBLE WEATHER/THREAT HIGHLIGHTS
 
 
EARLY NEXT WEEK, THE UPPER LOW MOVING OVER PARTS OF THE WEST ALONG  
WITH AREAS OF LOW LEVEL UPSLOPE FLOW SHOULD COMBINE TO GENERATE  
MODERATE TO HEAVY PRECIPITATION OVER THE NORTHERN ROCKIES AND HIGH  
PLAINS. HIGHER ELEVATIONS OF THE NORTHERN ROCKIES PARTICULARLY IN  
SOUTHERN MONTANA TO NORTHERN WYOMING COULD SEE SIGNIFICANT LATE  
SEASON SNOW AS THE ANOMALOUS TROUGH/LOW CREATES COLDER THAN  
AVERAGE CONDITIONS. FARTHER EAST, RAIN AND THUNDERSTORMS ARE  
THREATS ACROSS THE NORTHERN PLAINS INTO THE MIDWEST ALONG A WAVY  
FRONT THAT SHOULD INITIALLY BE SLOW TO MOVE. SEVERE WEATHER AND  
HEAVY RAINFALL ARE BOTH POSSIBILITIES WITH THIS CONVECTION. AS THE  
UPPER PATTERN FLATTENS, LOWER AMPLITUDE TROUGHING IS FORECAST TO  
MOVE SLOWLY EASTWARD ACROSS NORTHERN PARTS OF THE CENTRAL AND  
EASTERN U.S. AND PUSH A COLD FRONT AHEAD OF IT INTO THE EAST BACK  
INTO THE CENTRAL/SOUTHERN PLAINS. THIS FRONT WILL SERVE AS A FOCUS  
FOR CONVECTION AS IT PRESSES EAST ACROSS THE OHIO VALLEY TO THE  
EASTERN SEABOARD AND SOUTH ACROSS THE PLAINS AND MISSISSIPPI  
VALLEY FOR THE LATTER HALF OF THE WORKWEEK. SOME MODERATE TO HEAVY  
RAINFALL IS POSSIBLE ESPECIALLY ACROSS PARTS OF THE CENTRAL U.S.  
BUT WITH LOW CONFIDENCE IN THE AREAL DETAILS AND AMOUNTS.  
ELSEWHERE, FLORIDA CAN EXPECT SOME SCATTERED DIURNALLY FAVORED  
CONVECTION, AIDED BY ENERGY ALOFT TO THE SOUTH OF THE EASTERN U.S.  
UPPER RIDGE, WHICH MAY BECOME MORE WIDESPREAD BY LATE WEEK. LIGHT  
RAINFALL IS ALSO POSSIBLE IN THE NORTHEAST ALONG A BACKDOOR FRONT  
FOR THE FIRST HALF OF THE WORKWEEK BEFORE THE BETTER FOCUS FOR  
RAINFALL AROUND THURSDAY JUST AHEAD OF THE MAIN COLD FRONT.  
 
THE CENTRAL TO EASTERN U.S. UPPER RIDGE WILL PROMOTE ABOVE AVERAGE  
TEMPERATURES BY 10-20F FROM THE PLAINS TO THE MIDWEST/OHIO VALLEY  
AND THE NORTHEAST/MID-ATLANTIC EARLY IN THE WORKWEEK, WITH SOME  
DAILY RECORD HIGH MAXIMUM AND MINIMUM TEMPERATURES POSSIBLE.  
MEANWHILE THE INTERMOUNTAIN WEST SHOULD BE QUITE COOL UNDERNEATH  
THE UPPER TROUGH AS HIGHS IN PARTICULAR ARE FORECAST TO BE 10-20F  
BELOW NORMAL. THE COLD FRONT PRESSING EASTWARD WHILE THE UPPER  
PATTERN FLATTENS WILL LEAD TO COOLING TEMPERATURES IN THE PLAINS  
BY MIDWEEK WHILE THE ANOMALOUS WARMTH GRADUALLY IS SHUNTED  
EASTWARD, THOUGH ANOMALIES WILL WEAKEN ALL AROUND. THE WEST COAST  
AND INTO THE GREAT BASIN COULD FLIP BACK TO WARMER THAN NORMAL  
TEMPERATURES BY AROUND 5-10F WEDNESDAY AND BEYOND.  
 
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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