594  
FXUS02 KWBC 110700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM 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 HEAT 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 CONTIGUOUS U.S. 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 TO THE EAST, 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
 
 
12Z/18Z MODELS AND ENSEMBLE MEANS (SERVING AS THE BASIS FOR THE  
UPDATED FORECAST) ALONG WITH THE NEW 00Z RUNS CONTINUE TO AGREE  
FOR THE OVERALL PATTERN EVOLUTION BUT EXHIBIT SOME  
SPREAD/VARIABILITY WITH DETAILS. AMONG THE 12Z/18Z SOLUTIONS THE  
MOST NOTABLE ISSUE INVOLVED THE GFS, ESPECIALLY THE 18Z RUN,  
STRAYING FASTER AND DEEPER THAN MOST OTHER GUIDANCE WITH THE  
SHORTWAVE REACHING THE NORTHWEST AROUND SUNDAY AND THE LARGER  
SCALE TROUGH PUSHING INTO THE WEST TUESDAY-WEDNESDAY. THIS IN TURN  
LED TO THE 18Z GFS BECOMING FASTER WITH THE EASTERN TROUGH. THE  
12Z GFS WAS CLOSER TO CONSENSUS DURING THE LATTER HALF OF THE  
PERIOD IN PARTICULAR. THE 12Z CMC BECAME SLOWER/MORE AMPLIFIED  
WITH THE PACIFIC TROUGH LATE IN THE PERIOD AND HAS ADJUSTED THAT  
FEATURE FAVORABLY IN THE 00Z RUN. HOWEVER THE NEW CMC HAS BECOME A  
LOT MORE AMPLIFIED WITH THE EASTERN TROUGH, WHICH HAS BEEN ITS  
TENDENCY IN A NUMBER OF EARLIER RUNS. MULTI-DAY TRENDS HAVE  
GENERALLY BEEN TOWARD SLIGHTLY LESS AMPLITUDE WITH THIS TROUGH BUT  
CONSECUTIVE MODEL RUNS ARE STILL OSCILLATING, CAUSING SHIFTS IN  
SOUTHWARD EXTENT OF THE SURFACE FRONT REACHING THE EAST. BASED ON  
THE GUIDANCE COMPARISONS THROUGH 18Z, THE UPDATED FORECAST STARTED  
WITH A BLEND OF OPERATIONAL MODELS EARLY (GFS SPLIT BETWEEN  
12Z/18Z RUNS) FOLLOWED BY SOME INCORPORATION OF THE 18Z GEFS/12Z  
ECMWF MEANS ALONG WITH THE 12Z GFS/ECMWF/CMC (BUT LOW ENOUGH CMC  
WEIGHT TO DOWNPLAY ITS PACIFIC TROUGH LATE IN THE PERIOD).  
   
..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 OF THE SOUTHERN PLAINS  
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 SHORTWAVE/SURFACE FRONT DETAILS  
ARE NOT SUFFICIENTLY AGREEABLE TO RESOLVE ANY DEFINED AREAS OF  
RELATIVELY GREATER POTENTIAL. 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.  
 
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  
 

 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page