691  
FXUS02 KWBC 272033  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
432 PM 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 WITH EMBEDDED LOW IN THE WEST AND RIDGING OVER MUCH OF  
THE EAST (THOUGH SUPPRESSED IN THE NORTHEAST BY AN EASTERN CANADA  
UPPER LOW). THIS CONFIGURATION 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 MEAN FLOW ALOFT SHOULD  
FLATTEN QUICKLY AS THE MAIN WESTERN UPPER LOW LIFTS INTO  
SOUTH-CENTRAL CANADA AND CONSOLIDATES WITH SEPARATE CENTRAL CANADA  
ENERGY TO YIELD A FAIRLY DEEP UPPER LOW. THE HIGHEST PRECIPITATION  
CHANCES SHOULD SHIFT INTO THE CENTRAL/SOUTHERN PLAINS AND ACROSS  
THE EAST ALONG AND AHEAD OF THE COLD FRONT THAT PUSHES EASTWARD  
FROM THE PLAINS. TOWARD THE END OF NEXT WEEK AN UPPER TROUGH MAY  
BRING A FRONT AND SOME ASSOCIATED MOISTURE INTO THE NORTHWEST.  
 
   
..MODEL GUIDANCE EVALUATION/PREFERENCES
 
 
LATEST GUIDANCE THROUGH THE 00Z/06Z CYCLES HAS GENERALLY FOLLOWED  
THROUGH ON RECENT TRENDS TOWARD FASTER EJECTION OF THE MAIN  
WESTERN U.S. UPPER LOW THROUGH THE NORTHERN TIER AND THEN STRONGER  
INTERACTION WITH CENTRAL CANADA ENERGY TO YIELD A RATHER DEEP  
UPPER LOW AND VIGOROUS SURFACE SYSTEM JUST SOUTHWEST OF HUDSON BAY  
BY MIDWEEK. THE DEEPER EVOLUTION ULTIMATELY LEADS TO SOMEWHAT  
FASTER PROGRESSION OF THE FRONT THAT BEGINS TO PUSH EASTWARD FROM  
THE PLAINS. EVEN WITH THE FASTER TREND, OTHER 12Z MODELS SUGGEST  
THE NEW GFS MAY BE TOO FAST WITH THE NORTHERN U.S./SOUTHERN CANADA  
SYSTEM BY EARLY TUESDAY. DETAILS OF A SEPARATE WEAKER NORTHWESTERN  
U.S. UPPER LOW SHEARING OUT AS THE MEAN PATTERN RAPIDLY FLATTENS  
CONTINUE TO BE SOMEWHAT AMBIGUOUS, AND WILL AFFECT FRONTAL  
WAVE/RAINFALL SPECIFICS TO THE EAST OF THE ROCKIES. OUTSIDE OF THE  
UKMET, NEW 12Z MODELS HAVE TRENDED STRONGER WITH THIS FEATURE  
THROUGH TUESDAY-WEDNESDAY. MEANWHILE THERE IS DECENT AGREEMENT IN  
PRINCIPLE THAT ENERGY UNDERNEATH THE EASTERN U.S. UPPER RIDGE MAY  
TRY TO CONSOLIDATE INTO A CLOSED LOW SOMEWHERE NEAR THE SOUTHEAST  
COAST/FLORIDA/NORTHERN BAHAMAS BY MIDWEEK. HOWEVER BY DAY 7 FRIDAY  
RECENT GFS/GEFS MEAN RUNS HAVE DEVELOPED A DEEPER AND MORE  
EXPANSIVE TROUGH COVERING THE SOUTHEAST U.S. AND EASTERN GULF  
RELATIVE TO MOST OTHER GUIDANCE. THE 12Z GEFS MEAN TRENDED A BIT  
WEAKER WITH ITS DAY 7 UPPER TROUGH THOUGH. ON THE NORTHERN SIDE  
OF THE EASTERN RIDGE, GUIDANCE IS GRADUALLY CONSOLIDATING TOWARD  
AN EPISODE OF FAIRLY STRONG CYCLONIC FLOW AROUND A FAR EASTERN  
CANADA UPPER LOW. THIS LEADS TO INCREASING POTENTIAL FOR THE  
ASSOCIATED COLD FRONT REACHING NEW ENGLAND EARLY IN THE WEEK TO  
PUSH AS FAR SOUTH AS THE NORTHERN MID-ATLANTIC AS A BACKDOOR FRONT  
BEFORE EVENTUALLY RETURNING NORTH AS A WARM FRONT. CONSENSUS IS  
REASONABLE FOR UPPER RIDGING TO RETROGRADE FROM THE  
EAST/MISSISSIPPI VALLEY AND THEN SETTLE OVER THE SOUTHERN  
PLAINS/NORTHERN MEXICO, CONNECTING WITH THE RIDGE THAT BUILDS OVER  
THE INTERIOR WEST/ROCKIES. FOR THE UPPER TROUGH APPROACHING THE  
WEST COAST LATE IN THE WEEK, GFS RUNS SHOW A LITTLE MORE  
SOUTHEASTWARD AMPLITUDE VERSUS THE MAJORITY AT TIMES BUT  
ULTIMATELY MODEL/MEAN DIFFERENCES ARE WITHIN TYPICAL ERROR RANGES  
FOR FORECASTS THAT FAR OUT IN TIME. GUIDANCE COMPARISONS LED TO  
USING A 00Z/06Z MODEL BLEND EARLY IN THE PERIOD FOLLOWED BY  
TRANSITIONING TO A MODEL/MEAN MIX, WITH SLIGHTLY MORE WEIGHT TO  
THE 00Z ECMWF/ECMWF MEAN VERSUS THE 06Z GFS/GEFS MEAN (WITH  
LINGERING 00Z CMC INPUT) DUE TO AFOREMENTIONED ISSUES OVER/NEAR  
THE SOUTHEAST.  
 
   
..SENSIBLE WEATHER/THREAT HIGHLIGHTS
 
 
EARLY NEXT WEEK, THE UPPER LOW EMERGING FROM 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 ANOMALOUSLY DEEP SYSTEM LEADS TO 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. ALONG THIS FRONT, A  
FAIRLY STRONG SURFACE SYSTEM DEVELOPING OVER THE NORTHERN TIER  
INTO SOUTHERN CANADA DURING THE FIRST HALF OF THE WEEK MAY HELP TO  
FOCUS RAINFALL AS WELL. SEVERE WEATHER AND HEAVY RAIN ARE BOTH  
POSSIBILITIES WITH THIS CONVECTION. AS THE UPPER PATTERN FLATTENS,  
LOWER AMPLITUDE TROUGHING WILL LIKELY 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 STILL WITH LOWER  
THAN AVERAGE CONFIDENCE FOR 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. THIS CONVECTION MAY BECOME MORE WIDESPREAD BY LATE  
WEEK. ALSO THE NORTHEAST MAY SEE MOSTLY LIGHT RAINFALL 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. A FRONT EXPECTED TO PUSH INTO THE NORTHWEST LATE IN  
THE WEEK MAY BRING AREAS OF LIGHT RAINFALL.  
 
THE EASTERN U.S./MISSISSIPPI VALLEY UPPER RIDGE WILL PROMOTE ABOVE  
AVERAGE TEMPERATURES BY 10-20F FROM THE PLAINS TO THE MIDWEST/OHIO  
VALLEY AND THE NORTHEAST/MID-ATLANTIC MONDAY-WEDNESDAY, WITH SOME  
DAILY RECORD HIGH MAXIMUM AND MINIMUM TEMPERATURES POSSIBLE. THE  
BACKDOOR FRONT REACHING NEW ENGLAND AND POSSIBLY AS FAR SOUTH AS  
THE NORTHERN MID-ATLANTIC WOULD BRING A COOLER TREND TO THESE  
AREAS THOUGH. MEANWHILE UPPER TROUGHING WILL BRING VERY COOL  
TEMPERATURES TO AREAS FROM THE INTERMOUNTAIN WEST THROUGH NORTHERN  
PLAINS EARLY IN THE WEEK WITH HIGHS FORECAST TO BE 10-20F OR BELOW  
NORMAL. THE FLATTENING PATTERN ALOFT WILL PUSH THE INITIAL PLAINS  
COLD FRONT EASTWARD WHILE LEADING TO A MODERATING TREND FOR BELOW  
NORMAL TEMPERATURES OVER THE CENTRAL U.S., WITH MOSTLY  
SINGLE-DIGIT NEGATIVE ANOMALIES BY THURSDAY-FRIDAY. THE EAST WILL  
SEE SHRINKING COVERAGE OF WARM TEMPERATURES AFTER WEDNESDAY. THE  
WEST COAST AND INTO THE GREAT BASIN COULD FLIP BACK TO WARMER THAN  
NORMAL TEMPERATURES BY AROUND 5-10F WEDNESDAY AND BEYOND, FOLLOWED  
BY MODEST COOLER TREND ON FRIDAY ALONG THE IMMEDIATE WEST COAST  
WITH THE ARRIVAL OF A PACIFIC FRONT.  
 
RAUSCH/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  
 
HAZARDS:  
- HEAVY PRECIPITATION ACROSS PORTIONS OF THE NORTHERN  
PLAINS/ROCKIES, MON, MAY 30.  
- HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL PLAINS, THE MIDDLE  
MISSISSIPPI VALLEY, AND THE SOUTHERN  
PLAINS, TUE-WED, MAY 31-JUN 1.  
- HEAVY RAIN ACROSS PORTIONS OF THE UPPER MISSISSIPPI VALLEY, AND  
THE NORTHERN PLAINS, MON, MAY 30.  
- SEVERE WEATHER ACROSS PORTIONS OF THE GREAT PLAINS, AND THE  
MIDDLE/UPPER MISSISSIPPI VALLEY, MON,  
MAY 30.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE  
CENTRAL/NORTHERN PLAINS, AND THE UPPER  
MISSISSIPPI VALLEY.  
- FLOODING LIKELY ACROSS PORTIONS OF THE CENTRAL PLAINS.  
- HIGH WINDS ACROSS PORTIONS OF THE CENTRAL PLAINS/ROCKIES/GREAT  
BASIN, THE SOUTHERN  
ROCKIES/PLAINS, AND THE SOUTHWEST, MON, MAY 30.  
- ENHANCED WILDFIRE RISK ACROSS PORTIONS OF THE SOUTHERN ROCKIES,  
THE CENTRAL/SOUTHERN PLAINS, AND  
THE SOUTHWEST, MON, MAY 30.  
 
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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