330  
FXUS02 KWBC 180700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM EDT MON JUL 18 2022  
 
VALID 12Z THU JUL 21 2022 - 12Z MON JUL 25 2022  
 
...DANGEROUS HEAT TO PERSIST OVER THE CENTRAL U.S. THROUGH THE  
START OF NEXT WEEK...  
   
..OVERVIEW
 
 
A STRONG UPPER RIDGE CENTERED OVER THE SOUTHWEST/FOUR CORNERS  
REGION AS OF EARLY THURSDAY MAY SHIFT ITS EMPHASIS SOMEWHAT  
EASTWARD BY THE WEEKEND, THOUGH WITH INCREASING UNCERTAINTY OVER  
EXACTLY WHERE RIDGING WILL BE LOCATED. THIS RIDGE WILL KEEP HOT  
AND HUMID WEATHER OVER THE CENTRAL/SOUTHERN PLAINS FOR A MAJORITY  
OF THE PERIOD. SOME SOUTHERN LOCATIONS COULD SEE READINGS APPROACH  
OR BREAK DAILY RECORDS FOR HIGHS AND VERY WARM NIGHTTIME LOWS.  
WITH SOMEWHAT LESS EXTREME ANOMALIES, AREAS FROM THE  
TENNESSEE/OHIO VALLEYS THROUGH MID-ATLANTIC/NEW ENGLAND WILL  
EXPERIENCE MULTIPLE HOT DAYS AS WELL. THE WEST SHOULD MODERATE  
AFTER MIDWEEK WITH THE APPROACH/EJECTION OF EASTERN PACIFIC UPPER  
TROUGH ENERGY. THIS ENERGY AND OTHER FEATURES ACROSS SOUTHERN  
CANADA AND THE NORTHERN TIER U.S. WILL FLOW AROUND THE RIDGE AND  
FEED INTO A BROAD NORTHEASTERN U.S. MEAN TROUGH, SUPPORTING ONE OR  
MORE WAVES/FRONTAL SYSTEMS AND EPISODES OF SHOWERS AND  
THUNDERSTORMS FROM THE NORTHERN TIER INTO THE EAST. MONSOONAL  
MOISTURE OVER THE SOUTHWEST/SOUTHERN ROCKIES WILL PROMOTE DAILY  
CHANCES OF SHOWERS AND STORMS, SOME OF WHICH COULD LEAD TO FLASH  
FLOODING. SOME INCREASE OF THIS ACTIVITY WILL BE POSSIBLE DURING  
THE WEEKEND IF THE FOUR CORNERS RIDGE DOES INDEED ADJUST EASTWARD  
FOR A TIME.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE MOST AGREEABLE AND CONSISTENT LARGE SCALE ASPECTS OF THE  
FORECAST CONTINUE TO BE WITH THE GENERAL THEME OF SOUTHERN TIER  
RIDGING AND THE BROAD MEAN TROUGHING OVER THE NORTHEASTERN  
QUADRANT OF THE LOWER 48. A LEADING EASTERN U.S. COLD FRONT  
ANCHORED BY EASTERN CANADA LOW PRESSURE LATE THIS WEEK ALSO HAS  
GOOD AGREEMENT AND CONTINUITY (THOUGH WITH SOME SPREAD/ADJUSTMENTS  
FOR THE LOW ITSELF).  
 
OTHER DETAILS HAVE LOWER PREDICTABILITY/CONFIDENCE. SOLUTIONS  
CONTINUE TO STRUGGLE WITH THE DAY-TO-DAY SPECIFICS OF LOW  
AMPLITUDE MEAN FLOW FROM THE NORTHEAST PACIFIC ACROSS SOUTHERN  
CANADA/NORTHERN U.S., AS WELL AS FOR AN UPPER LOW/TROUGH FORECAST  
TO EJECT FROM THE EASTERN PACIFIC. FOR THE LATTER, MULTI-DAY  
CONTINUITY SEEMS TO BE POINTING TOWARD AN INTERMEDIATE BUT  
SOMEWHAT SLOWER THAN MEDIAN TIMING WITHIN THE ESTABLISHED SPREAD  
FROM RECENT DAYS. THE 12Z MODEL RUNS SEEMED TO IMPROVE THEIR  
CLUSTERING WHILE THE 18Z GFS JUMPED AHEAD. PREFERENCE WAS WITH THE  
12Z CLUSTER. THE NEW 00Z GFS REVERTED TO A SLOWER SOLUTION WHILE  
THE NEW 00Z ECMWF JUMPED AHEAD TOWARD THE 18Z GFS. ANOTHER  
FORECAST PROBLEM INVOLVES THE DETAILS OF THE SOUTHERN TIER RIDGE  
BY MID-LATE PERIOD. IN GENERAL, MOST ECMWF RUNS AND GEFS/ECMWF  
MEANS HAVE BEEN CONSISTENTLY SHOWING AN EASTWARD ADJUSTMENT OF THE  
FOUR CORNERS RIDGE MORE INTO THE SOUTH-CENTRAL PLAINS/MISSISSIPPI  
VALLEY. GFS RUNS HAVE TENDED TO BE A BIT FARTHER EAST WHILE THE  
CMC HAS USUALLY KEPT ITS RIDGE MORE OVER THE FOUR CORNERS. THE 00Z  
UKMET ALSO MAINTAINS THE FOUR CORNERS RIDGE. THE CMC/UKMET DO  
SUPPORT A STRENGTHENING RIDGE OVER THE SOUTHEAST/MISSISSIPPI  
VALLEY AS WELL THOUGH. LATE IN THE PERIOD, THERE IS A GENERAL  
CONSENSUS THAT UPPER RIDGING SHOULD BUILD INTO THE NORTHWEST AFTER  
PASSAGE OF THE LATE WEEK/WEEKEND SHORTWAVE. THE 00Z GFS, WHICH IS  
MORE AGGRESSIVE THAN OTHER GUIDANCE WITH A GULF OF ALASKA INTO  
WESTERN CANADA UPPER LOW/TROUGH, SUPPRESSES NORTHWEST HEIGHTS  
RELATIVE TO OTHER GUIDANCE BY NEXT MONDAY.  
 
CONSENSUS AT THE START OF THE PERIOD AND THEN PREFERENCE FOR THE  
SHORTWAVE EJECTING FROM THE PACIFIC LED TO STARTING THE UPDATED  
FORECAST WITH VARYING COMPONENTS OF THE 12Z GFS/ECMWF/UKMET/CMC  
FOR DAYS 3-4 THURSDAY-FRIDAY. INCREASING DETAIL UNCERTAINTIES FOR  
VARIOUS ASPECTS OF THE FORECAST FAVORED A RAPID TRANSITION TOWARD  
50-60 PERCENT TOTAL WEIGHT OF THE 18Z GEFS/12Z ECMWF MEANS BY DAYS  
6-7 SUNDAY-MONDAY. GUIDANCE CHANGES OVER THE PAST COUPLE DAYS HAVE  
LED TO A GREATER SOUTHEASTWARD EXTENT OF A FRONT REACHING THE  
NORTHERN PLAINS/MIDWEST LATE THIS WEEK. ALSO A SLOWER TREND FOR  
THE SHORTWAVE EJECTING FROM THE PACIFIC AND FLOWING AROUND THE  
UPPER RIDGE HAS LED TO A CORRESPONDING DELAY WITH THE SURFACE WAVE  
NOW EXPECTED TO REACH THE CENTRAL U.S. DURING THE WEEKEND.  
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
THE MOST ANOMALOUS HEAT OVER THE CENTRAL U.S. WILL LIKELY FOCUS  
OVER THE CENTRAL PLAINS WHERE THE BEST POTENTIAL EXISTS FOR  
MULTIPLE DAYS OF HIGHS 10-15F ABOVE NORMAL. SOME OF THE HEAT MAY  
ALSO EVENTUALLY DRIFT INTO PARTS OF THE TENNESSEE VALLEY. TOWARD  
SUNDAY-MONDAY A COLD FRONT MAY SUPPRESS THE HEAT OVER THE  
NORTH-CENTRAL PLAINS. TYPICALLY HOTTER SOUTHERN PLAINS LOCATIONS  
WILL SEE LESS EXTREME ANOMALIES BUT OVERALL THERE WILL BE A BROAD  
AREA WITH HIGHS REACHING OR EXCEEDING 100F FOR HIGHS, WHILE VERY  
WARM LOWS IN THE UPPER 70S TO LOW 80S WILL PROVIDE LITTLE  
NIGHTTIME RELIEF. THIS HEAT WAVE WILL LIKELY BRING SCATTERED  
RECORDS, MOST LIKELY OVER THE SOUTHERN PLAINS TO LOWER/MID MS  
VALLEY.  
 
OVER THE WEST, MONSOONAL MOISTURE AND ASSOCIATED DIURNALLY FAVORED  
SHOWERS/STORMS WITH LOCALLY HEAVY RAINFALL MAY KEEP PARTS OF THE  
FOUR CORNERS/GREAT BASIN REGION WITHIN A FEW DEGREES ON EITHER  
SIDE OF NORMAL DURING THROUGH THE PERIOD. THE MOST LIKELY SCENARIO  
OF AN EASTWARD SHIFT OF UPPER RIDGING AFTER LATE THIS WEEK WOULD  
LEAD TO AN INCREASE OF MOISTURE/RAINFALL NEXT WEEKEND AND PERHAPS  
A BIT OF A WESTWARD SHIFT IN THE OVERALL MOISTURE AXIS. HOWEVER  
THERE IS A LOWER PROBABILITY POTENTIAL FOR THE FOUR CORNERS UPPER  
RIDGE TO BE MORE PERSISTENT, WHICH WOULD TEND TO MAINTAIN THE  
EXISTING LATE WEEK PATTERN. THE APPROACH/EJECTION OF PACIFIC  
TROUGH ENERGY SHOULD BRING HIGHS DOWN TO NEAR NORMAL LEVELS OVER  
AN INCREASING PORTION OF THE WEST BY FRIDAY-SATURDAY. A REBOUND OF  
UPPER RIDGING OVER THE NORTHWEST MAY BRING HIGHS TO 5-10F OR SO  
ABOVE NORMAL OVER THAT REGION BY SUNDAY-MONDAY.  
 
THE FAIRLY VIGOROUS LATE WEEK SYSTEM OVER EASTERN CANADA AND ITS  
TRAILING FRONT INTO THE EASTERN U.S. MAY PRODUCE SOME LOCALLY  
HEAVY RAINFALL. THERE WILL LIKELY BE OTHER AREAS OF ENHANCED  
RAINFALL FROM THE NORTHERN TIER INTO THE EAST DURING THE REST OF  
THE PERIOD, BUT WITH MUCH LESS CONFIDENCE IN SPECIFICS DUE TO  
GUIDANCE DIFFICULTY IN RESOLVING THE DETAILS WITHIN SOUTHERN  
CANADA/NORTHERN U.S. FLOW ALOFT, INCLUDING EJECTING PACIFIC ENERGY  
THAT JOINS THIS STREAM. THE MID-ATLANTIC AND NORTHEAST WILL BE ON  
THE VERY WARM TO HOT SIDE, WITH SOME LOCATIONS POSSIBLY SEEING  
MORE CONSECUTIVE DAYS OF PLUS 5-10F ANOMALIES FOR HIGHS THAN  
PREVIOUSLY EXPERIENCED SO FAR THIS SUMMER. THE FRONT REACHING THE  
EAST COAST BY FRIDAY COULD LEAD TO A BRIEF AND SLIGHT DIP IN  
TEMPERATURES BEFORE IT WEAKENS DURING THE WEEKEND. PERSISTENT  
MOISTURE WILL ALLOW FOR MULTIPLE EPISODES OF SHOWERS/THUNDERSTORMS  
OVER THE SOUTHEAST/FLORIDA AND CENTRAL GULF COAST REGION.  
CONTINUES TO EXPECT NEAR NORMAL TEMPERATURES OVER THOSE AREAS.  
 
RAUSCH/TAYLOR  
 
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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