023  
FXUS02 KWBC 160701  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
259 AM EDT THU JUN 16 2022  
 
VALID 12Z SUN JUN 19 2022 - 12Z THU JUN 23 2022  
 
...HEAT OVER THE NORTHERN/CENTRAL PLAINS THROUGH THE WEEKEND  
LIKELY TO SHIFT INTO THE MIDWEST THROUGH SOUTHEAST NEXT WEEK...  
 
   
..OVERVIEW
 
 
THE LATEST GUIDANCE IS CONSISTENT IN SHOWING A TRANSITION FROM AN  
AMPLIFIED TROUGH-RIDGE-TROUGH CONFIGURATION ON SUNDAY TOWARD A  
MORE TYPICAL SUMMERTIME PATTERN BY NEXT WEDNESDAY-THURSDAY,  
FEATURING A BROAD UPPER RIDGE ACROSS MUCH OF THE SOUTHERN HALF OF  
THE COUNTRY AND PROGRESSIVE BAND OF WESTERLIES ACROSS THE NORTHERN  
TIER STATES. WIDESPREAD HOT TEMPERATURES WILL PREVAIL UNDERNEATH  
THE EVOLVING RIDGE, WITH HIGHS REACHING 100F AS FAR NORTH AS THE  
DAKOTAS INTO SUNDAY FOLLOWED BY THE MOST ANOMALOUS HIGH  
TEMPERATURES SHIFTING MORE INTO THE MIDWEST THROUGH SOUTHEAST FROM  
MONDAY ONWARD. THE AMPLIFIED FLOW REGIME IN PLACE THROUGH THE  
WEEKEND SHOULD PROMOTE AN EARLY MONSOON TYPE PATTERN OVER THE FOUR  
CORNERS STATES, WHILE THE STRONG DYNAMICS EJECTING THROUGH THE  
NORTHWESTERN STATES SUNDAY INTO MONDAY MAY HELP TO PRODUCE LOCALLY  
HEAVY PRECIPITATION OVER/NEAR THE FAR NORTHERN ROCKIES. CANADIAN  
LOW PRESSURE ASSOCIATED WITH THIS EJECTING ENERGY WILL PUSH A  
FRONT INTO THE PLAINS, PRODUCING SOME AREAS OF  
SHOWERS/THUNDERSTORMS. FARTHER EAST, THERE WILL BE POTENTIAL FOR  
RAIN AHEAD OF A WARM FRONT ADVANCING INTO THE GREAT  
LAKES/NORTHEAST AND SCATTERED DIURNAL SHOWERS/STORMS ACROSS  
FLORIDA.  
 
   
..GUIDANCE/PREDICTABILITY EVALUATION
 
 
AN INTERMEDIATE/CONSENSUS APPROACH, REPRESENTED BY A 12Z/18Z MODEL  
BLEND EARLY FOLLOWED BY A COMBINATION OF OPERATIONAL MODELS ALONG  
WITH THE 18Z GEFS/12Z ECMWF MEANS (MEANS COMPONENT TILTED SOMEWHAT  
TOWARD THE ECENS DUE TO BETTER DEFINITION WITH NORTHERN FEATURES),  
PROVIDED REASONABLE CONSISTENCY FOR MOST PARTS OF THE FORECAST.  
DURING THE FIRST HALF OF THE PERIOD THE GUIDANCE STILL SHOWS SOME  
WAFFLING WITH RESPECT TO THE MAINE/CANADIAN MARITIMES UPPER LOW  
THAT MAY BE EMBEDDED WITHIN THE INITIAL EAST COAST/WESTERN  
ATLANTIC TROUGH, WITH THE LATEST MAJORITY NUDGING IT A LITTLE  
SOUTHWARD VERSUS THE PREVIOUS CYCLE OR TWO. LATEST GFS RUNS ARE  
SOMEWHAT EXTREME IN THEIR PERSISTENCE/REDEVELOPMENT OF A MARITIMES  
UPPER LOW LATER IN THE PERIOD BUT THAT SCENARIO COULD STILL BE  
POSSIBLE GIVEN THE UPPER TROUGH AXIS IN THE ENSEMBLE MEANS. SUBTLE  
DETAILS OF THE GENERALLY WEAKENING MEAN TROUGH APPEAR TO HAVE A  
MEANINGFUL INFLUENCE ON THE WAVY FRONT REACHING THE NORTHEAST  
AFTER ARRIVING FROM THE WEST AS A WARM FRONT. MEANWHILE GUIDANCE  
HAS BEEN STEADILY CONVERGING FOR THE INITIAL TROUGH EJECTING FROM  
THE WEST EARLY IN THE PERIOD BUT THEN WITH DETAIL QUESTIONS AS IT  
MAY INTERACT WITH ANOTHER FEATURE OVER CENTRAL CANADA. THIS PART  
OF THE FORECAST LEADS TO SOME ONGOING VARIABILITY WITH CANADIAN  
LOW PRESSURE AND TIMING OF THE TRAILING FRONT MID-LATE PERIOD. THE  
BEST CLUSTERING OF GUIDANCE BRINGS A NORTHEASTERN PACIFIC UPPER  
LOW TO AROUND SOUTHERN BRITISH COLUMBIA BY NEXT THURSDAY. RECENT  
TRENDS OF GFS/GEFS MEAN RUNS HAVE GENERALLY BEEN FASTER TOWARD THE  
ECMWF/ECMWF MEAN AND THE PREVIOUSLY SLOW CMC HAS ADJUSTED TO THIS  
SCENARIO IN THE NEW 00Z RUN. THE 00Z GEFS MEAN ADJUSTED A LITTLE  
SLOWER BUT WITHIN TYPICAL RUN-TO-RUN VARIABILITY. ONE FINAL NOTE  
IS THAT IN SPITE OF THE SIMILARITY OF UPPER PATTERNS, MODEL  
GUIDANCE SHOWS SOME SURPRISINGLY LARGE DIFFERENCES IN 850MB  
TEMPERATURES OVER THE HOTTEST PARTS OF THE EAST BY THE LATTER HALF  
OF THE PERIOD. THE 12Z ECMWF WAS SIGNIFICANTLY WARMER THAN THE  
GFS/CMC, AND CAN RUN ON THE HOT SIDE AT TIMES, WHILE THE 00Z GFS  
HAS ADJUST A BIT WARMER FROM ITS PREVIOUS RUN.  
 
   
..SENSIBLE WEATHER/THREAT HIGHLIGHTS
 
 
THE STRONG UPPER TROUGH EJECTING THROUGH THE NORTHWESTERN U.S.  
DURING SUNDAY-MONDAY MAY FOCUS SOME AREAS OF LOCALLY MODERATE TO  
HEAVY PRECIPITATION OVER/NEAR THE FAR NORTHERN ROCKIES. THE  
VIGOROUS DYNAMICS, SUFFICIENT MOISTURE, AND RECENT SIGNIFICANT  
PRECIPITATION SUPPORTED THE INTRODUCTION OF A SLIGHT RISK AREA IN  
THE EXPERIMENTAL DAY 4 EXCESSIVE RAINFALL OUTLOOK (EARLY SUNDAY  
INTO EARLY MONDAY) OVER PARTS OF WESTERN MONTANA. HIGHEST  
ELEVATIONS MAY SEE SOME SNOW WITH THIS SYSTEM. THE UNUSUALLY EARLY  
MONSOON TYPE PATTERN FARTHER SOUTH WILL BRING MUCH ABOVE NORMAL  
MOISTURE FOR THE TIME OF YEAR NORTHWARD THROUGH THE FOUR CORNERS  
STATES AND VICINITY THROUGH THE WEEKEND, SUPPORTING AN INCREASE IN  
COVERAGE AND INTENSITY OF RAINFALL ACROSS THE REGION.  
RAIN/THUNDERSTORMS SHOULD CONTINUE INTO EARLY NEXT WEEK AS THE  
MOISTURE INTERACTS WITH THE FRONT SLOWLY ADVANCING THROUGH THE  
WEST, THOUGH WITH ACTIVITY TENDING TO DECREASE IN THE NORTHWESTERN  
PART OF THE FOUR CORNERS REGION. THERE ARE STILL MIXED SIGNALS  
OVER HOW MUCH RAINFALL THE INTERACTION OF THIS MOISTURE WITH THE  
WESTERN FRONT ADVANCING INTO THE PLAINS WILL PRODUCE. HOWEVER THE  
POTENTIAL FOR SOME TRAINING/REPEAT ACTIVITY MAY HAVE TO BE  
MONITORED AS CONSENSUS SHOWS THIS PLAINS FRONT BECOMING ALIGNED  
WEST-EAST ALONG THE SOUTHERN EDGE OF THE WESTERLIES BY  
WEDNESDAY-THURSDAY. FARTHER EAST, THE EAST COAST/WESTERN ATLANTIC  
UPPER TROUGH AND POSSIBLE EMBEDDED LOW MAY BRING SOME SHOWERS TO  
NEW ENGLAND THROUGH SUNDAY. THEN AN AREA OF SHOWERS AND  
THUNDERSTORMS MAY PUSH ACROSS THE GREAT LAKES AND POSSIBLY INTO  
THE NORTHEAST UNDER NORTHWESTERLY FLOW ALOFT AND AHEAD OF AN  
ADVANCING WARM FRONT, WITH SOME ACTIVITY POSSIBLY ON THE HEAVY  
SIDE. THIS FRONT MAY SLOW DOWN ONCE IT REACHES THE EASTERN GREAT  
LAKES AND MID-ATLANTIC/NORTHEAST. THE FLORIDA PENINSULA SHOULD SEE  
MULTIPLE DAYS OF DIURNAL SHOWERS/STORMS FROM THE WEEKEND INTO NEXT  
WEEK AS THE FRONT PUSHING INTO AREA DECELERATES AND EVENTUALLY  
DISSIPATES.  
 
THE MOST ANOMALOUS TEMPERATURES DURING THE PERIOD WILL BE WITH A  
HEAT WAVE ACROSS THE NORTHERN HALF OF THE PLAINS THROUGH SUNDAY  
AND PUSHING INTO THE UPPER MIDWEST AS WELL BY MONDAY, WITH HIGHS  
REACHING UP TO 20-25F ABOVE NORMAL. SOME DAILY RECORDS FOR HIGHS  
AND WARM LOWS WILL BE POSSIBLE, WITH EVEN SOME POTENTIAL FOR A FEW  
MONTHLY RECORDS FOR WARM LOWS, GIVEN THAT LOWS AT LEAST IN THE  
UPPER 70S ARE FORECAST IN PORTIONS OF THE NORTH-CENTRAL U.S. A  
FRONT MOVING INTO THE PLAINS SHOULD START A COOLING TREND/EASTWARD  
SHIFT OF THE HEAT, ESPECIALLY OVER THE NORTHERN PLAINS. AS THE  
HEAT EXTENDS INTO THE MIDWEST THROUGH SOUTHEAST FROM MONDAY  
ONWARD, PLUS 10-15F OR SO ANOMALIES FOR HIGHS SHOULD BECOME COMMON  
AND MAY CHALLENGE DAILY RECORD HIGHS/WARM LOWS. SOUTHERN PARTS OF  
THE PLAINS WILL STAY HOT THROUGH THE PERIOD BUT WITH ANOMALIES  
TENDING TO BE IN THE PLUS 5-10F RANGE. BEFORE NEXT WEEK'S WARMER  
TREND OVER THE EAST, THE NORTHERN HALF OF THE REGION WILL SEE  
HIGHS 5-10F (LOCALLY MORE) BELOW NORMAL ON SUNDAY, PERHAPS  
LINGERING INTO MONDAY OVER NORTHERN NEW ENGLAND. ALSO FROM SUNDAY  
INTO MONDAY THE UPPER TROUGH CROSSING THE WEST WILL BRING THE  
REGION A COUPLE COOL DAYS WITH HIGHS UP TO 10-15F BELOW NORMAL.  
AFTER MONDAY THE WEST WILL SEE VARIOUS AREAS OF SOMEWHAT ABOVE OR  
BELOW READINGS.  
 
RAUSCH/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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