476  
FXUS02 KWBC 111835  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
234 PM EDT SAT JUN 11 2022  
 
VALID 12Z TUE JUN 14 2022 - 12Z SAT JUN 18 2022  
 
...DANGEROUS/RECORD HEAT FROM THE MIDWEST INTO  
EAST-CENTRAL/SOUTHEASTERN U.S. ESPECIALLY DURING  
TUESDAY-WEDNESDAY...  
 
18Z UPDATE: THE MAJORITY OF THE DETERMINISTIC GUIDANCE CONTINUES  
TO INDICATE GOOD OVERALL AGREEMENT ON THE LARGE-SCALE PATTERN  
THROUGH THE END OF THE WEEK. THE ONE EXCEPTION WAS THE 00Z CMC  
THAT DIFFERS FROM THE UKMET/GFS/ECMWF CONSENSUS AS EARLY AS  
WEDNESDAY ACROSS THE PLAINS WITH A MORE POTENT TROUGH, AND IN THE  
WAKE OF IT LEAVES A MORE ZONAL FLOW ACROSS THE GREAT LAKES REGION  
AND UPPER MIDWEST FOR THE END OF THE WEEK, AND THIS SOLUTION HAS  
VERY LITTLE IN THE WAY OF ENSEMBLE SUPPORT. THE 12Z CMC IS BETTER  
AND MORE IN LINE WITH THE ENSEMBLE MEANS, ALTHOUGH IT IS A BIT  
MORE PROGRESSIVE ACROSS THE NORTHEAST BY THE END OF THE FORECAST  
PERIOD. IN TERMS OF QPF, AMOUNTS HAVE TRENDED HIGHER ACROSS THE  
FOUR CORNERS REGION FOR THE FRIDAY-SATURDAY TIME PERIOD WITH A  
STRONGER FEED OF MOISTURE AHEAD OF THE FRONT. ACROSS THE CENTRAL  
AND SOUTHERN APPALACHIANS, THERE HAS BEEN A SLIGHT DECREASE IN THE  
OVERALL QPF AHEAD OF THE FRONT FOR THE END OF THE WEEK. THE  
FORECAST WAS PRIMARILY DERIVED FROM A GFS/ECMWF/UKMET BLEND  
THROUGH THURSDAY, AND THEN SLIGHTLY MORE OF THE ENSEMBLE MEANS AND  
SOME PREVIOUS WPC CONTINUITY THROUGH NEXT SATURDAY. THE PREVIOUS  
DISCUSSION FOLLOWS BELOW. /HAMRICK  
----------------  
   
..OVERVIEW AND GUIDANCE/PREDICTABILITY EVALUATION
 
 
THE LATEST GUIDANCE CONTINUES TO SHOW A FAIRLY RAPID TRANSITION  
FROM ONE AMPLIFIED PATTERN TO ANOTHER, LEADING TO SIGNIFICANT  
WEATHER CHANGES OVER SOME AREAS DURING THE PERIOD. INTO MIDWEEK  
AN UPPER TROUGH WILL SUPPORT BELOW NORMAL TEMPERATURES OVER THE  
WEST (AIDED BY FLOW AROUND DEEP LOW PRESSURE OVER SOUTHERN CANADA)  
WHILE A STRONG EASTERN RIDGE WILL PROMOTE SUFFICIENTLY HOT  
CONDITIONS TO CHALLENGE DAILY RECORD HIGHS FROM THE MIDWEST INTO  
PARTS OF THE SOUTHEAST, WITH A CENTRAL U.S. COLD FRONT AND  
ACCOMPANYING SHOWERS/THUNDERSTORMS SEPARATING THE TWO EXTREMES.  
THEN DURING THE LATTER HALF OF THE WEEK EXPECT THE EASTERN RIDGE  
TO GIVE WAY TO THE TROUGH CONTINUING TO PROGRESS ACROSS THE  
NORTHERN HALF OF THE EAST, WITH RAINFALL OF VARYING INTENSITY  
CONTINUING ALONG THE LEADING COLD FRONT, WHILE A SHARPENING TROUGH  
REACHING THE WEST COAST BY SATURDAY ENCOURAGES UPPER RIDGE  
AMPLIFICATION OVER THE PLAINS. THIS NEW PATTERN SHOULD LEAD TO  
WELL ABOVE NORMAL TEMPERATURES OVER THE NORTHERN HALF OR SO OF THE  
ROCKIES/PLAINS TOWARD THE END OF THE WEEK.  
 
A CONSENSUS APPROACH AMONG THE MODELS EARLY IN THE PERIOD AND  
MODELS/ENSEMBLE MEANS LATER ON CONTINUED TO PROVIDE A FAIRLY  
STABLE FORECAST WITH TYPICAL RUN-TO-RUN REFINEMENTS AND  
ADJUSTMENTS. AMONG GUIDANCE AVAILABLE FROM THE 12Z/18Z RUNS, THE  
UKMET STRAYED TO THE SOUTHERN FRINGE OF THE SPREAD FOR THE UPPER  
LOW TRACKING ALONG AND NORTHEAST FROM THE NORTHERN MONTANA BORDER  
SO IT HAD THE LEAST WEIGHT IN THE UPDATED BLEND. THE NEW 00Z RUN  
COMPARES BETTER TO THE MAJORITY. MEANWHILE THE LATEST CMC RUNS  
TREND A LOT FLATTER WITH NORTHERN TIER FLOW THAT CONSENSUS SAYS  
SHOULD AMPLIFY TOWARD THE EAST COAST LATE IN THE WEEK. THUS THE  
CMC WAS PHASED OUT OF THE BLEND AFTER THURSDAY. GUIDANCE IS STILL  
REFINING DETAILS OF INDIVIDUAL IMPULSES WITHIN THE OVERALL TROUGH,  
AFFECTING FRONTAL SPECIFICS. LATEST CLUSTERING SUGGESTS THE  
LEADING FRONT REACHING THE GREAT LAKES BY THURSDAY MAY WEAKEN IN  
FAVOR OF AN UPSTREAM FRONT THAT BECOMES MORE PROMINENT BY FRIDAY.  
ADDITIONAL CHANGES ARE CERTAINLY POSSIBLE IN UPCOMING MODEL RUNS.  
FOR THE UPPER TROUGH NEARING THE WEST COAST, THE 00Z GFS SEEMS TO  
COMPLETE A CORRECTION (BEGUN IN THE 18Z RUN) FROM THE EARLIER 12Z  
RUN THAT HAD PULLED OFF A CLOSED LOW OFFSHORE CALIFORNIA. THE 12Z  
GFS EVOLUTION HAD VERY LITTLE SUPPORT FROM GEFS/ECMWF/CMC  
ENSEMBLES SO IT WAS NOT USED IN THE FORECAST. OTHER MODELS SHOW  
SOME VARIABILITY WITH THIS TROUGH AS WELL, SUPPORTING A  
BLENDED/ENSEMBLE MEAN DEPICTION.  
   
..SENSIBLE WEATHER/THREAT HIGHLIGHTS
 
 
STRONG LOW PRESSURE EVOLVING JUST NORTH OF THE CANADIAN BORDER AND  
THE SUPPORTING UPPER DYNAMICS MAY PRODUCE SOME ENHANCED RAIN AND  
EVEN HIGH ELEVATION SNOW OVER THE FAR NORTHERN ROCKIES AND  
VICINITY INTO TUESDAY. THE TRAILING FRONT PUSHING THROUGH THE  
PLAINS AND INTO THE GREAT LAKES MAY FOCUS AREAS OF LOCALLY  
MODERATE TO HEAVY RAINFALL, BUT WITH CONTINUING UNCERTAINTY  
REGARDING MAGNITUDE AND LOCATION OF HIGHEST TOTALS. THE  
COMBINATION OF IMPULSES IN NORTHWESTERLY FLOW ALOFT AND A FRONT  
ALIGNED FROM THE GREAT LAKES/OHIO VALLEY INTO THE  
MID-ATLANTIC/CAROLINAS TUESDAY-THURSDAY MAY GENERATE ONE OR MORE  
EPISODES OF CONVECTION. AGAIN THE GUIDANCE SIGNALS ARE VERY  
AMBIGUOUS WITH RESPECT TO THE DETAILS OF THIS ACTIVITY. MEANWHILE  
LOCATIONS ACROSS THE SOUTHEAST AND GULF COAST MAY SEE DIURNALLY  
FAVORED SHOWERS AND THUNDERSTORMS ON ONE OR MORE DAYS. THE UPPER  
TROUGH NEARING THE WEST COAST TOWARD THE END OF THE WEEK SHOULD  
BRING MAINLY LIGHT RAINFALL TO PARTS OF THE NORTHWEST. THE LARGE  
SCALE PATTERN AT THAT TIME COULD BRING ENOUGH MOISTURE NORTHWARD  
TO SUPPORT SOME RAINFALL OVER ARIZONA AND THE FOUR CORNERS REGION.  
 
EXPECT HIGHS TO BE 10-20F ABOVE NORMAL FROM THE MIDWEST AND PARTS  
OF THE GREAT LAKES INTO THE CAROLINAS DURING TUESDAY-WEDNESDAY,  
WITH NUMEROUS LOCATIONS CHALLENGING RECORD HIGHS. A BROAD AREA OF  
RECORD WARM LOWS WILL BE POSSIBLE AS WELL. SOME PLUS 10-12F  
ANOMALIES FOR HIGHS COULD PERSIST OVER THE OHIO VALLEY/GREAT LAKES  
INTO THURSDAY BUT WITH LESS POTENTIAL FOR DAILY RECORDS.  
NORTHERN/CENTRAL PARTS OF THE EAST SHOULD SEE A NOTICEABLE COOLING  
TREND BY FRIDAY-SATURDAY. AREAS FROM THE SOUTHERN PLAINS INTO THE  
SOUTHEAST WILL BE ON THE HOT SIDE THROUGH THE PERIOD WITH HIGHS  
TENDING TO BE 5-10F ABOVE NORMAL. THE CHILLY UPPER TROUGH  
CROSSING THE WEST WILL HOLD HIGHS TO 10-20F BELOW NORMAL OVER THE  
NORTHERN ROCKIES/GREAT BASIN ON TUESDAY WITH LESS EXTREME COOL  
READINGS ON WEDNESDAY. AS THE UPPER PATTERN TRANSITIONS,  
CALIFORNIA AND THE GREAT BASIN WILL SEE A COUPLE DAYS OF WARM  
READINGS MID-LATE WEEK FOLLOWED BY HIGHS OF 10-20F ABOVE NORMAL  
BECOMING ESTABLISHED OVER THE NORTHERN-CENTRAL PLAINS BY  
FRIDAY-SATURDAY. AREAS ALONG THE WEST COAST SHOULD SEE MODESTLY  
BELOW NORMAL HIGHS WHEN THE UPPER TROUGH REACHES THE AREA BY  
SATURDAY.  
 
RAUSCH  
 
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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