212  
FXUS02 KWBC 130654  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
253 AM EDT FRI MAY 13 2022  
 
VALID 12Z MON MAY 16 2022 - 12Z FRI MAY 20 2022  
 
...HEAT THREAT FOR THE DESERT SOUTHWEST EARLY NEXT WEEK WHILE  
PERSISTENT SOUTHERN PLAINS HEAT INTENSIFIES AND EXPANDS EASTWARD  
INTO THE SOUTHEAST...  
 
   
..OVERVIEW
 
 
MEAN TROUGHS OVER THE EAST AND WEST COASTS, WITH RIDGING IN  
BETWEEN, SHOULD MAKE GRADUAL PROGRESS EASTWARD DURING THE FIRST  
HALF OF NEXT WEEK. UPPER RIDGING ACROSS THE SOUTHWEST AND  
SOUTH-CENTRAL U.S. SHOULD SPREAD INTO THE SOUTHEAST THE SECOND  
HALF OF THE WEEK IN RESPONSE TO AN AMPLIFYING TROUGH OVER THE  
WEST. THIS SHOULD CONTINUE TO LEAD TO A BROAD AREA OF UNSEASONABLY  
HOT WEATHER ACROSS THE SOUTHERN U.S., WITH THE MOST PERSISTENT AND  
RECORD-BREAKING HEAT CENTERED IN TEXAS AND LOUISIANA. MEANWHILE,  
EXPECTED SHOWERS AND THUNDERSTORMS TO ACCOMPANY AN INITIAL FRONT  
ACROSS THE EAST, WITH INCREASING SHOWERS ALSO EXPECTED ALONG  
STALLING FRONTS IN THE PLAINS. THE WEST SHOULD SEE COOLING  
TEMPERATURES IN RESPONSE TO UPPER TROUGHING AS THE WEEK  
PROGRESSES, ALONG WITH LOWERING SNOW LEVELS BY MIDWEEK WITHIN  
ROUNDS OF PRECIPITATION.  
 
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
RECENT GUIDANCE CONTINUES TO SHOW FAIRLY GOOD AGREEMENT WITH THE  
OVERALL PATTERN DURING THE EXTENDED RANGE, BUT STRUGGLE WITH  
LOW-PREDICTABILITY SHORTWAVE DETAILS WITH THE NORTHEASTERN TROUGH,  
AS WELL AS ENERGY MOVING THROUGH AND EJECTING FROM THE PACIFIC TO  
WESTERN U.S. TROUGH. FRONTAL POSITIONS AND THUS SPECIFICS OF  
CONVECTIVE FOCUS WILL BE SENSITIVE TO THESE UNCERTAIN ASPECTS  
WHICH COULD TAKE INTO THE SHORT RANGE TO RESOLVE. THE MOST NOTABLE  
DIFFERENCES SEEM TO ARRIVE AROUND WEDNESDAY WITH A LEADING  
SHORTWAVE EJECTING FROM TROUGHING OVER THE NORTHEAST PACIFIC INTO  
THE NORTHWEST AND EVENTUALLY NORTHERN PLAINS. UP UNTIL THE MOST  
RECENT 00Z RUN (AVAILABLE AFTER FORECAST GENERATION TIME), THE CMC  
HAD CONSISTENTLY BEEN FASTER AND MORE PRONOUNCED WITH THIS  
SHORTWAVE, WHILE THE GFS AND ECMWF ARE WEAKER. FARTHER UPSTREAM,  
UNCERTAINTY SURROUNDS THE DETAILS OF A CLOSED LOW OFF THE BRITISH  
COLUMBIA COAST WHICH MAY MOVE INTO THE NORTHWEST U.S. LATE NEXT  
WEEK. LIKELY IN RESPONSE TO A STRONGER DOWNSTREAM SHORTWAVE, THE  
12Z/MAY 12 CMC WAS SIGNIFICANTLY WEAKER AND LESS AMPLIFIED WITH  
THIS FEATURE AS IT MOVES THROUGH THE WEST BUT THE 00Z RUN IS MORE  
CONSISTENT WITH THE CONSENSUS. ENSEMBLES AND THE ENSEMBLE MEANS  
SUPPORT A MORE AMPLIFIED PATTERN ACROSS THE U.S. BY LATE NEXT WEEK  
AS SHOWN BY BOTH THE GFS AND ECMWF (WHICH BETWEEN THEMSELVES HAVE  
SOME PRETTY SIGNIFICANT TIMING AND TROUGH DETAIL DIFFERENCES BY  
DAY 6-7). THE WPC BLEND FOR TONIGHT USED THE DETERMINISTIC MODELS  
DAYS 3-5, WITH INCREASING ENSEMBLE MEANS LATE PERIOD TO DOWNPLAY  
THE MORE UNCERTAIN DETAILS. DID CONTINUE SOME MODEST ECMWF AND GFS  
JUST FOR SOME ADDED DEFINITION TO INDIVIDUAL SYSTEMS. THIS  
APPROACH FIT WELL WITH PREVIOUS WPC CONTINUITY AS WELL.  
 
   
..WEATHER/THREAT HIGHLIGHTS
 
 
INITIAL RIDGING ACROSS THE SOUTHWEST AND SOUTHERN PLAINS AND THEN  
EVENTUALLY RISING HEIGHTS FARTHER EAST OVER THE DEEP SOUTH WILL  
LIKELY PROMOTE A BROAD AREA OF HEAT ACROSS MUCH OF THE SOUTHERN  
U.S. DURING THE PERIOD. THE GREATEST AND MOST LASTING ANOMALIES  
THROUGH THE PERIOD SHOULD BE OVER TEXAS (PERSISTING FROM THE SHORT  
RANGE TIME FRAME) WHERE SOME LOCATIONS COULD SEE HIGHS UP TO  
15-25F ABOVE NORMAL, WITH NUMEROUS DAILY RECORD HIGHS LIKELY.  
PARTS OF THE SOUTHWEST U.S. SHOULD SEE EXCESSIVE HEAT EARLY IN THE  
WEEK, WITH A FEW RECORDS MONDAY-TUESDAY, BUT TEMPERATURES SHOULD  
MODERATE AS PACIFIC TROUGHING MOVES IN THEREAFTER. MEANWHILE BY  
TUESDAY OR WEDNESDAY THE COVERAGE OF HIGHS 10-15F ABOVE NORMAL  
SHOULD EXTEND EASTWARD THROUGH THE LOWER MISSISSIPPI VALLEY AND  
INTO THE SOUTHEAST WITH AGAIN, POTENTIAL FOR DAILY RECORD HIGHS.  
 
IN CONTRAST, THE SERIES OF SURFACE WAVES/FRONTS AHEAD OF THE  
APPROACHING/ARRIVING EASTERN PACIFIC UPPER TROUGH WILL KEEP THE  
PACIFIC NORTHWEST ON THE COOL SIDE WITH FREQUENT EPISODES OF  
PRECIPITATION. THE TROUGH SHOULD REACH FAR ENOUGH EASTWARD TO  
BRING HIGHS DOWN TO 10-15F BELOW NORMAL OVER THE  
NORTHWEST/NORTHERN ROCKIES BY NEXT WEDNESDAY-THURSDAY. SNOW LEVELS  
SHOULD BE QUITE HIGH INTO EARLY NEXT WEEK AND THEN BEGIN TO LOWER  
AS THE UPPER TROUGH ARRIVES. IT WILL LIKELY TAKE INTO THE SHORT  
RANGE TIME FRAME TO RESOLVE TIMING/INTENSITY ASPECTS OF EACH  
PRECIPITATION EPISODE DUE TO THE MEDIUM TO SMALLER SCALE OF THE  
SUPPORTING SHORTWAVES.  
 
AREAS TO THE EAST OF THE ROCKIES SHOULD GENERALLY SEE TWO RAINFALL  
REGIMES DURING THE PERIOD. ON MONDAY, THE BEST FOCUS FOR SHOWERS  
AND THUNDERSTORMS WILL BE ALONG A COLD FRONT PUSHING THROUGH THE  
EAST WITH THE BEST CHANCE FOR LOCALLY MODERATE TO HEAVY RAINFALL  
ACROSS NEW ENGLAND. LOCALIZED FLOODING IMPACTS OVER NEW ENGLAND  
ARE POSSIBLE GIVEN A SUITABLE ENVIRONMENT FOR HIGH RAINFALL RATES,  
BUT DRY SOILS AND THE FRONT BEING PROGRESSIVE TEMPERS CONFIDENCE.  
INTO THE MIDDLE PART OF THE WEEK, A STALLED BOUNDARY FROM THE  
PLAINS TO THE OHIO VALLEY WILL PROVIDE FOCUS FOR MULTIPLE AREAS OF  
SHOWERS AND THUNDERSTORMS/CONVECTIVE COMPLEXES ACROSS THE NORTHERN  
HALF OF THE PLAINS AND MISSISSIPPI VALLEY INTO THE OHIO VALLEY AND  
CENTRAL APPALACHIANS. INGREDIENTS ARE THERE FOR HEAVY RAINFALL,  
BUT PLENTY OF UNCERTAINTY REMAINS IN THE GUIDANCE WITH RESPECT TO  
COVERAGE AND AMOUNTS.  
 
SANTORELLI/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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