242  
FXUS02 KWBC 131859  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
258 PM EDT FRI MAY 13 2022  
 
VALID 12Z MON MAY 16 2022 - 12Z FRI MAY 20 2022  
 
...PERSISTENT RECORD-BREAKING HEAT IS LIKELY IN THE SOUTH-CENTRAL  
U.S. NEXT WEEK WITH PERIODS OF ANOMALOUS HEAT FOR THE REST OF THE  
SOUTHERN TIER AS WELL..  
 
   
..OVERVIEW
 
 
THE MEDIUM RANGE PERIOD WILL FEATURE UPPER TROUGHING IN THE  
EAST-CENTRAL U.S. MOVING EASTWARD AND LIFTING WITH TIME, WHILE A  
SERIES OF SHORTWAVES AND EVENTUALLY DEEPER TROUGHING LATE NEXT  
WEEK COME INTO THE NORTHWEST. BETWEEN AND SOUTH OF THESE TROUGH  
FEATURES, RIDGING WILL PROMOTE UNSEASONABLY HOT WEATHER ACROSS THE  
SOUTHERN U.S., WITH THE MOST PERSISTENT AND RECORD-BREAKING HEAT  
CENTERED IN TEXAS AND LOUISIANA. MEANWHILE, EXPECT 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 MODEL GUIDANCE REMAINS IN GOOD AGREEMENT WITH THE OVERALL  
PATTERN DESCRIBED ABOVE THROUGH MUCH OF THE MEDIUM RANGE PERIOD,  
BUT WITH CONTINUED DISCREPANCIES IN THE SMALLER SCALE DETAILS LIKE  
SHORTWAVES EMBEDDED IN THE NORTHEAST TROUGH AND THOSE MOVING  
THROUGH THE NORTHWEST. GUIDANCE HAS BEEN WAFFLING BUT HAS SHOWN A  
GENERAL TREND TOWARD A BIT MORE SEPARATION WITH THE HUDSON BAY  
UPPER LOW AND TROUGHING/A POTENTIALLY CLOSED LOW FARTHER SOUTHEAST  
CLOSER TO NEW ENGLAND AROUND TUESDAY, WITH SOME SEPARATION LASTING  
INTO WEDNESDAY. IN THE NORTHWEST, THE 00Z UKMET APPEARED TOO  
AGGRESSIVE/DISPLACED WITH A SHORTWAVE IN THE NORTHWESTERN TO  
NORTH-CENTRAL U.S. BY WEDNESDAY. ISSUES LIKE BOTH OF THESE CAN  
AFFECT FRONTAL POSITIONS AND THUS SPECIFICS OF CONVECTIVE FOCUS  
WILL BE SENSITIVE TO THESE UNCERTAIN ASPECTS WHICH COULD TAKE INTO  
THE SHORT RANGE TO RESOLVE. BUT THE OVERALL PATTERN WAS AGREEABLE  
ENOUGH THAT THE FIRST HALF OF THE WPC FORECAST USED A BLEND OF THE  
00Z/06Z DETERMINISTIC GUIDANCE, THOUGH ELIMINATING THE UKMET BY  
WEDNESDAY.  
 
BY THURSDAY-FRIDAY, THERE ARE SOME RELATIVELY LARGER DIFFERENCES  
WITH THE PATTERN, THOUGH STILL WITHIN REASON FOR A DAY 6-7  
FORECAST. MODELS VARY ON THE PROCESS OF DISLODGING THE UPPER LOW  
JUST WEST OF BRITISH COLUMBIA TO PRODUCE DEEPER TROUGHING ACROSS  
THE WESTERN U.S., WITH QUESTIONS OF MAINTAINING A CLOSED LOW OR  
OPENING UP A TROUGH AS THE ENERGY DIGS AND THE DEPTH TO WHICH IT  
DIGS, BUT AT LEAST THERE IS AGREEMENT THE TROUGH WILL AMPLIFY IN  
THE WEST. MEANWHILE, THE HUDSON BAY UPPER LOW SHOWS SOME  
SIGNIFICANT DIFFERENCES IN ITS TRACK/POSITION, WITH THE 00Z ECMWF  
AND NOW THE 12Z CMC INDICATING IT COULD RETROGRADE WEST WHILE  
OTHER MODELS MAINTAIN ITS POSITION OR SLOWLY MOVE IT EAST. WHILE  
THIS IS NORTH OF THE CONUS, IT AFFECTS THE NORTH-CENTRAL U.S. WITH  
POTENTIAL FOR TROUGHING OR RIDGING AND FRONTAL POSITION, AS WELL  
AS THE POSSIBILITY IT COULD INTERACT WITH THE WESTERN TROUGH/LOW.  
DID NOT FAVOR THE MODELS WITH THE MOST INTERACTION (LIKE THE 00Z  
ECMWF) AT THIS TIME, BUT THIS WILL CONTINUE TO BE MONITORED. THE  
LATTER PART OF THE WPC FORECAST PHASED IN SOME GEFS AND EC  
ENSEMBLE MEANS TO TEMPER INDIVIDUAL MODEL DIFFERENCES BUT STILL  
MAINTAINED ABOUT 60 PERCENT DETERMINISTIC MODELS TO KEEP  
SUFFICIENT STRENGTH OF SYSTEMS.  
 
   
..WEATHER/THREAT HIGHLIGHTS
 
 
INITIAL RIDGING ACROSS THE SOUTHWEST AND SOUTHERN PLAINS AND THEN  
EVENTUALLY RISING HEIGHTS FARTHER EAST OVER THE DEEP SOUTH WILL  
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 INTO THE CENTRAL GREAT BASIN AND SOUTHERN/CENTRAL  
ROCKIES CAN EXPECT HIGHS AROUND 10-15F ABOVE AVERAGE FOR THE FIRST  
HALF OF THE WEEK BEFORE A COOLING TREND AS THE DEEPER TROUGHING  
PRESSES INLAND. HOWEVER, WARM TO HOT TEMPERATURES COULD INCREASE  
FOR THE SOUTHEASTERN QUADRANT OF THE U.S. LATER NEXT WEEK, WITH  
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 10-20F BELOW NORMAL OVER THE  
NORTHWEST/NORTHERN ROCKIES BY NEXT THURSDAY-FRIDAY. SNOW LEVELS  
SHOULD BE QUITE HIGH EARLY NEXT WEEK AND THEN BEGIN TO LOWER AS  
THE MAIN UPPER TROUGH ARRIVES. IT COULD 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  
INITIAL AND 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 (SOME OF WHICH COULD BE STRONG TO SEVERE) WILL  
BE ALONG A COLD FRONT PUSHING THROUGH THE EAST WITH THE BEST  
CHANCES 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 COUPLE OF FRONTAL BOUNDARIES 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 WILL BE IN PLACE FOR HEAVY  
RAINFALL, BUT PLENTY OF UNCERTAINTY REMAINS IN THE GUIDANCE WITH  
RESPECT TO COVERAGE AND AMOUNTS.  
 
TATE/SANTORELLI  
 
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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