798  
FXUS02 KWBC 111856  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
256 PM EDT WED MAY 11 2022  
 
VALID 12Z SAT MAY 14 2022 - 12Z WED MAY 18 2022  
 
...DEVELOPING HEAT THREAT FOR CALIFORNIA AND THE SOUTHWEST FROM  
THE WEEKEND INTO NEXT WEEK WHILE PERSISTENT SOUTHERN PLAINS HEAT  
INTENSIFIES AND EXPANDS EASTWARD...  
...RECORD WARMTH TO CONTINUE OVER PARTS OF NEW ENGLAND INTO  
SATURDAY...  
 
   
..OVERVIEW
 
 
A RAPIDLY OPENING UPPER LOW OVER THE EAST ON SATURDAY (SPREADING  
SOME RAIN ACROSS THE REGION) WILL PROVIDE THE LAST VESTIGE OF THE  
CURRENT BLOCKY PATTERN OVER AND NEAR THE LOWER 48. GUIDANCE IS  
CONSISTENT IN SHOWING THE UPSTREAM FLOW SETTLING INTO A  
TROUGH-RIDGE-TROUGH CONFIGURATION SOON THEREAFTER, WITH THE  
EASTERN PACIFIC TROUGH AXIS LIKELY PUSHING INTO THE WEST AROUND  
THE MIDDLE OF NEXT WEEK AS THE EASTERN TROUGH NEARS THE EAST  
COAST. THE COMBINATION OF UPPER RIDGING THAT CROSSES THE WEST,  
PERSISTENCE OF A MEAN RIDGE OVER THE SOUTHERN PLAINS, AND WITH  
TIME RISING HEIGHTS OVER THE SOUTHEAST, SHOULD LEAD TO AN  
EXPANDING AREA OF UNSEASONABLY HOT WEATHER ACROSS THE SOUTHERN  
U.S. THIS HEAT WILL CHALLENGE DAILY RECORD HIGHS FOR MULTIPLE DAYS  
AT SOME LOCATIONS. NEW ENGLAND MAY SEE RECORD HEAT EXTEND INTO  
SATURDAY AS WELL. A SERIES OF FRONTS PUSHED ALONG BY THE  
DEVELOPING CENTRAL-EASTERN U.S. CYCLONIC FLOW AND EXTENDING BACK  
INTO THE PLAINS WILL PRODUCE EPISODES OF SHOWERS AND THUNDERSTORMS  
THROUGH THE PERIOD. AT THE SAME TIME THE MEAN TROUGH EVENTUALLY  
REACHING THE WEST COAST SHOULD SEND MULTIPLE WAVES/FRONTS INTO  
WESTERN NORTH AMERICA, SUPPORTING PERIODS OF RAIN AND PERHAPS VERY  
HIGH ELEVATION SNOW OVER THE NORTHWEST.  
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
MODEL GUIDANCE REMAINS CONSISTENT WITH THE OVERALL PATTERN DURING  
THE MEDIUM RANGE PERIOD, WHICH BEGINS SATURDAY WITH A CLOSED UPPER  
LOW IN SOUTH-CENTRAL CANADA AND THE OPENING LOW/TROUGH CENTERED TO  
ITS SOUTHEAST, WHILE RIDGING BUILDS INTO THE INTERIOR WEST AND  
SOUTHERN PLAINS. THESE FEATURES ALL SHOW GOOD AGREEMENT IN THE  
00Z/06Z AND NEWER 12Z MODELS. SOMEWHAT MORE NOTABLE DIFFERENCES  
ARISE AS TROUGHING DEVELOPS ACROSS THE EAST-CENTRAL U.S. BY MONDAY  
FROM COMBINING FEATURES. GFS RUNS REMAIN FLATTEST/LESS DEEP WITH  
THE NORTHERN STREAM PART OF THE TROUGH WHILE CMC RUNS ARE DEEPER  
AND SLOWER THAN CONSENSUS AND ALMOST EVERY INDIVIDUAL ENSEMBLE  
MEMBER (THOUGH THE NEWER 12Z RUN PERHAPS IN BETTER ALIGNMENT THAN  
THE 00Z THROUGH MONDAY, BUT BEYOND MONDAY THE 12Z CMC CLOSES OFF  
AN UPPER LOW OVER THE NORTHEAST UNLIKE OTHER GUIDANCE). PREFERRED  
A MIDDLE GROUND SOLUTION LIKE THE 00Z ECMWF ALONG WITH THE UKMET  
FOR THE DEPTH/EXTENT OF THE EASTERN TROUGH ON MONDAY, AND THE  
ECMWF AND GEFS AND EC ENSEMBLE MEANS TUESDAY AND WEDNESDAY.  
 
THIS BLEND OF MODEL GUIDANCE (00Z/06Z DETERMINISTIC MODEL  
COMPOSITE LED BY THE EC EARLY ON, PHASING IN THE GEFS/EC MEANS AND  
PHASING OUT THE CMC BY DAY 5) ALSO WORKED WELL FOR RIDGING  
BUILDING WEST OF THE EASTERN TROUGH, AS WELL AS TROUGHING UPSTREAM  
OF THE RIDGING. AN UPPER LOW OFFSHORE OF BRITISH COLUMBIA COULD  
SEND SEVERAL SHORTWAVES THROUGH THE WEST WITH OVERALL LOW  
AMPLITUDE TROUGHING COMING IN, BUT WITH DIFFERENCES IN THE LOW  
PREDICTABILITY DETAILS. THE 00Z CMC ONCE AGAIN APPEARED TOO  
AMPLIFIED COMPARED TO CONSENSUS.  
   
..WEATHER/THREAT HIGHLIGHTS
 
 
THE COMBINATION OF INITIAL SOUTHERN PLAINS RIDGING PLUS THE UPPER  
RIDGE CROSSING THE WEST AND REACHING THE PLAINS, ALONG WITH  
EVENTUALLY RISING HEIGHTS OVER THE SOUTH WILL LIKELY PROMOTE AN  
EXPANDING AREA OF HEAT ACROSS MUCH OF THE SOUTHERN U.S. DURING THE  
PERIOD. THE PRIMARY FOCUS OF THIS HEAT DURING THE WEEKEND WILL BE  
OVER THE SOUTHERN PLAINS (PERSISTING FROM THE SHORT RANGE TIME  
FRAME) AND OVER THE SOUTHERN HALF OR SO OF THE WEST WITH HIGHS  
10-15F OR SO ABOVE NORMAL. BY MONDAY-WEDNESDAY THE GRADUAL  
PROGRESSION OF THE UPPER PATTERN SHOULD LEAD TO SLOW  
INTENSIFICATION OF THE HEAT OVER THE SOUTHERN PLAINS AS HIGHS  
COULD REACH UP TO 15-20F ABOVE NORMAL, WHILE PLUS 10-15F ANOMALIES  
SPREAD EASTWARD ACROSS THE SOUTH. THE UPPER TROUGH NEARING THE  
WEST COAST MAY OFFER SLIGHT COOLING OVER CALIFORNIA AFTER SUNDAY  
AND EVENTUALLY TRIM THE COVERAGE OF PLUS 10F ANOMALIES FARTHER  
INLAND. POTENTIAL FOR DAILY RECORD HIGHS WILL BE MOST PERSISTENT  
THROUGH THE PERIOD OVER PARTS OF THE SOUTHERN PLAINS. RECORD HIGHS  
ARE MOST LIKELY OVER SOUTHERN PARTS OF THE WEST SUNDAY INTO EARLY  
NEXT WEEK AND SHOULD STEADILY SPREAD EAST INTO THE LOWER  
MISSISSIPPI VALLEY AND SOUTHEAST DURING THE FIRST HALF OF NEXT  
WEEK.  
 
ON THE OTHER HAND, SURFACE WAVES/FRONTS AHEAD OF THE APPROACHING  
EASTERN PACIFIC UPPER TROUGH WILL TEND TO KEEP THE PACIFIC  
NORTHWEST ON THE COOL SIDE WITH PRECIPITATION OF VARYING  
INTENSITY. SNOW LEVELS SHOULD BE QUITE HIGH INTO EARLY NEXT WEEK  
AND THEN MAY DECLINE SOMEWHAT AS THE UPPER TROUGH BEGINS TO MOVE  
INLAND. INDIVIDUAL SUPPORTING SHORTWAVES HAVE LOW PREDICTABILITY  
SO IT WILL TAKE ADDITIONAL TIME TO RESOLVE DETAILS OF WHEN/WHERE  
PRECIPITATION COULD BE LOCALLY HEAVIER.  
 
MOISTURE AHEAD OF A COUPLE FRONTS COULD BRING LINGERING MODERATE  
TO HEAVY SHOWERS AND THUNDERSTORMS TO THE MISSISSIPPI VALLEY  
REGION EARLY IN THE WEEKEND, WITH A CONSOLIDATED FRONT BECOMING  
MORE PROGRESSIVE AS UPPER TROUGHING HEADS TOWARD AND INTO THE  
EAST. SOME RAINFALL ALONG THE FRONT COULD STILL BE FAIRLY INTENSE  
BUT THE GREATER PROGRESSION MAY TEMPER MAXIMUM TOTALS OVER THE  
EAST. ANOTHER TRAILING FRONT COULD ALSO SUPPORT SOME  
SHOWERS/THUNDERSTORMS, WHILE THE TRAILING PART OF EACH FRONT  
SHOULD STALL OVER THE PLAINS AND COULD FOCUS ADDITIONAL  
CONVECTION. CURRENTLY THERE ARE AT LEAST VAGUE SIGNALS FOR LOCALLY  
ENHANCED RAINFALL POTENTIAL WITHIN A BROAD AREA BETWEEN THE  
EASTERN PLAINS AND OHIO VALLEY/CENTRAL APPALACHIANS SOUTH TO THE  
LOWER MISSISSIPPI VALLEY. HOWEVER DISAGREEMENTS IN  
SHORTWAVE/SURFACE FRONT DETAILS MAKE IT DIFFICULT TO RESOLVE ANY  
DEFINED AREAS OF RELATIVELY GREATER POTENTIAL. AT THIS POINT  
SIGNALS POINT TO ENHANCEMENT ACROSS PARTS OF THE LOWER MISSISSIPPI  
VALLEY/MID-SOUTH ON SATURDAY, WHICH COULD CAUSE LOCALIZED FLOODING  
ESPECIALLY OVER AREAS OF TRAINING CONVECTION AND/OR WET SOILS.  
NEAR THE EAST COAST, RECORD HEAT SHOULD CONTINUE INTO SATURDAY  
OVER NEW ENGLAND. THE RAPIDLY OPENING UPPER LOW LIFTING THROUGH  
THE EAST WILL PRODUCE SOME AREAS OF RAINFALL FARTHER SOUTH OVER  
THE MID-ATLANTIC AND VICINITY.  
 
TATE/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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