976  
FXUS02 KWBC 161955  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
355 PM EDT MON MAY 16 2022  
 
VALID 12Z THU MAY 19 2022 - 12Z MON MAY 23 2022  
 
...PERSISTENT RECORD-BREAKING HEAT IS LIKELY IN THE SOUTH-CENTRAL  
U.S. THROUGH THIS WEEK WITH ANOMALOUS HEAT EXPANDING INTO THE EAST  
THIS WEEKEND...  
 
...HEAVY RAINFALL AND FLASH FLOODING POSSIBLE NEAR A STRONG  
NORTHERN TIER SYSTEM ON THURSDAY...  
 
   
..OVERVIEW
 
 
A DIGGING TROUGH OVER THE WEST AND RISING HEIGHTS ACROSS THE EAST  
LATE THIS WEEK WILL RESULT IN A MORE AMPLIFIED PATTERN ACROSS THE  
LOWER 48, YIELDING COOLER TEMPERATURES AND LOWERING SNOW LEVELS IN  
THE WEST AND A CONTINUED HOT REGIME FOR THE SOUTH AND EAST. A  
CLOSED LOW INITIALLY ALONG THE U.S.-CANADIAN BORDER ON THURSDAY  
COULD OPEN UP SOON THEREAFTER BUT EITHER WAY A DEEPENING LOW  
PRESSURE SYSTEM TRACKING FROM THE NORTHERN TIER/UPPER GREAT LAKES  
INTO CANADA WILL PUSH A STRONG COLD FRONT EASTWARD, BRINGING  
CHANCES FOR HEAVY RAINFALL AND SEVERE WEATHER TO SOME AREAS FROM  
THE EASTERN PLAINS/MISSISSIPPI VALLEY INTO THE EAST. THE UPPER  
TROUGH WILL REACH INTO THE CENTRAL AND EASTERN U.S. DURING THE  
WEEKEND INTO THE FIRST PART OF NEXT WEEK (POSSIBLY BECOMING A  
LITTLE MORE SHALLOW WITH TIME) WHILE GUIDANCE HAS BECOME  
INDECISIVE WITH DETAILS UPSTREAM. A NORTHWARD SURGE OF TROPICAL  
MOISTURE WILL ALSO INCREASE RAIN/THUNDERSTORM CHANCES ACROSS  
FLORIDA LATE THIS WEEK AND INTO THE WEEKEND.  
 
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
EVEN IN THE FIRST HALF OF THE PERIOD, GUIDANCE EXHIBITS SOME  
NOTICEABLE SPREAD AND CONTINUITY CHANGES FOR THE INITIAL UPPER LOW  
ALONG THE CANADIAN BORDER AND UPPER TROUGH EXTENDING THROUGH THE  
WEST. IN GENERAL THE 00Z/06Z MODEL RUNS HAVE TRENDED TOWARD AN  
EARLIER OPENING OF THE UPPER LOW AND THUS FAR THE 12Z RUNS HAVE  
FOLLOWED THROUGH ON THIS CHANGE. MEANWHILE RECENT GFS RUNS HAVE  
BEEN ON THE AMPLIFIED SIDE OF THE SPREAD FOR THE OVERALL TROUGH.  
THE 06Z GFS WAS PARTICULARLY STRONG WITH SOME OF ITS TRAILING  
ENERGY, ULTIMATELY LEADING TO A SLOWER TROUGH THAN THE MAJORITY OF  
GUIDANCE AND EVEN A CLOSED LOW OVER THE UPPER MISSISSIPPI VALLEY  
BY EARLY DAY 6 SUNDAY. THE 00Z GFS WAS CLOSER TO CONSENSUS AND THE  
NEW 12Z RUN HAS RETURNED TO A MORE MODERATE FEATURE.  
 
FROM THE WEEKEND INTO EARLY NEXT WEEK THE MOST PROMINENT SOURCE OF  
UNCERTAINTY BECOMES HOW QUICKLY UPPER LOW ENERGY AND SURROUNDING  
FLOW ESCAPE FROM THE NORTH PACIFIC (PART OF A LONGER TERM BLOCKY  
REGIME OVER THE PACIFIC AND BERING SEA/ALASKA). THE 00Z ECMWF  
DEVIATED SIGNIFICANT FROM ITS PRIOR RUN AND MOST OTHER GUIDANCE IN  
BEING RATHER FAST TO BRING THE NORTH PACIFIC ENERGY INTO WESTERN  
NORTH AMERICA. ON THE OPPOSITE SIDE OF THE SPECTRUM, GFS RUNS HAVE  
TENDED TO BUILD THE STRONGEST UPPER RIDGE JUST OFF THE WEST COAST  
BY SUNDAY-MONDAY TO YIELD MORE ROCKIES/HIGH PLAINS TROUGHING BY  
NEXT MONDAY. THE 12Z GFS HAS TEMPERED ITS LATE-PERIOD RIDGE-TROUGH  
PATTERN A LITTLE BIT. DIVERSE ENSEMBLE MEMBERS AVERAGE OUT TO A  
MODEST RIDGE-TROUGH PATTERN IN THE GEFS/CMCENS WHILE THE ECENS  
MEAN IS NEARLY ZONAL. HOW THE DETAILS FROM THE PACIFIC INTO THE  
WEST WORK OUT WILL EVENTUALLY AFFECT THE FORECAST OF THE TROUGH  
MOVING INTO THE EAST, WITH THE MAJORITY OF GUIDANCE AT LEAST  
SUGGESTING THE EASTERN TROUGH WILL BECOME LESS AMPLIFIED THAN SEEN  
IN THE 00Z ECMWF (WITH CORRESPONDING EFFECTS ON SURFACE FRONTAL  
POSITION). THE NEW 12Z ECMWF HAS TRENDED CLOSER TO WHAT CONSENSUS  
EXITS FOR MOST ASPECTS OF THE LATE-PERIOD PATTERN.  
 
BASED ON THE REVIEW OF 00Z/06Z GUIDANCE, THE UPDATED FORECAST  
STARTED WITH THE 00Z GFS/ECMWF/UKMET/CMC EARLY IN THE PERIOD TO  
REPRESENT LATEST TRENDS FOR THE NORTHERN TIER SYSTEM AND TO AVOID  
THE LESS CONFIDENT ASPECTS OF THE 06Z GFS. QUESTION MARKS IN BOTH  
THE GFS AND ECMWF DURING THE LATTER HALF OF THE PERIOD LED TO A  
RAPID TRANSITION TO 50-70 PERCENT TOTAL WEIGHT OF THE 06Z GEFS/00Z  
ECMWF MEANS, YIELDING A SOLUTION AS CLOSE TO CONTINUITY AS COULD  
BE HOPED IN LIGHT OF THE SPREAD AND VARIABILITY OF MODELS/ENSEMBLE  
MEMBERS.  
 
   
..WEATHER/THREAT HIGHLIGHTS
 
 
INITIAL UPPER RIDGING ACROSS THE SOUTHERN PLAINS AND RISING  
HEIGHTS FARTHER EAST OVER THE DEEP SOUTH WILL CONTINUE TO PROMOTE  
A BROAD AREA OF HEAT INTO SATURDAY. THE GREATEST AND MOST LASTING  
ANOMALIES 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. THE HEAT  
ACROSS TEXAS SHOULD FINALLY BEGIN TO MODERATE FROM NORTH TO SOUTH  
BY NEXT WEEKEND AN UPPER TROUGH PRESSING THROUGH THE WEST SUPPORTS  
AN ARRIVING COLD FRONT. HOWEVER, WARM TO HOT TEMPERATURES WILL  
EXTEND INTO THE SOUTHEASTERN QUADRANT OF THE U.S. WITH POTENTIAL  
FOR DAILY RECORD HIGHS, AND WARMER THAN AVERAGE TEMPERATURES BY  
10-20F OR SO SHOULD EXPAND IN COVERAGE ACROSS THE OHIO VALLEY TO  
EASTERN SEABOARD BY LATER IN THE WEEK.  
 
A WARM FRONT LIFTING THROUGH THE OHIO VALLEY/APPALACHIANS ON  
THURSDAY WILL CONTINUE TO PROVIDE A FOCUS FOR SHOWERS AND STORMS  
ON THURSDAY, WITH A VERY LOCALIZED FLOOD THREAT PARTICULARLY IF  
HEAVY RAINFALL FALLS IN AREAS THAT ARE ALREADY SENSITIVE.  
MEANWHILE, MODERATE TO LOCALLY HEAVY RAINFALL IS LIKELY ON  
THURSDAY IN ASSOCIATION WITH A DEEPENING NORTHERN TIER STORM  
SYSTEM THAT SHOULD LIFT AWAY FROM THE UPPER GREAT LAKES ON FRIDAY.  
THE SYSTEM'S EVOLUTION IS SOMEWHAT COMPLEX AND GUIDANCE IS STILL  
ADJUSTING WITH SOME SPECIFICS. CURRENTLY THE BEST POTENTIAL FOR  
FLOODING/FLASH FLOODING EXISTS OVER PARTS OF NORTH DAKOTA AND  
NORTHERN MINNESOTA WHERE ANTECEDENT CONDITIONS ARE THE WETTEST. A  
SEPARATE BAND OF ENHANCED RAINFALL MAY EXIST FARTHER  
SOUTH/SOUTHEAST WHERE GREATER INSTABILITY EXISTS. BY  
FRIDAY-SATURDAY, ABOVE AVERAGE MOISTURE AND INSTABILITY WILL ALLOW  
FOR RAIN AND THUNDERSTORMS TO SPREAD ALONG THE FRONTAL BOUNDARY AS  
IT PUSHES THROUGH THE GREAT LAKES/OHIO VALLEY/MISSISSIPPI VALLEY  
AND THEN INTO THE EAST. LOCALLY HEAVY RAINFALL IS POSSIBLE BUT  
ADDITIONAL TIME IS NEEDED TO RESOLVE AREAS OF GREATEST POTENTIAL.  
THE STORM PREDICTION CENTER HIGHLIGHTS A THREAT FOR SEVERE WEATHER  
OVER SOME OF THE SAME AREAS WITH HEAVY RAINFALL POTENTIAL ALONG  
AND AHEAD OF THE COLD FRONT THURSDAY AND FRIDAY. BEHIND THIS  
FRONT, UNSEASONABLY COOL TEMPERATURES WILL SLIDE ACROSS THE  
NORTHWEST/NORTHERN ROCKIES ON THURSDAY INTO THE NORTH-CENTRAL U.S.  
FRIDAY AND SATURDAY, WITH HIGHS GENERALLY 10-20F BELOW NORMAL.  
PARTS OF THE NORTHERN-CENTRAL HIGH PLAINS COULD BE COLDER THAN  
THAT ON FRIDAY. THIS COLD SPELL SHOULD LOWER SNOW LEVELS AND  
POSSIBLY ALLOW FOR SOME LIGHT SNOW TO FALL EVEN IN NORTHERN PARTS  
OF THE HIGH PLAINS. THE NORTHWEST WILL BE FAIRLY DRY LATE THIS  
WEEK BUT MAY SEE SOME MOISTURE RETURN DURING THE WEEKEND OR EARLY  
NEXT WEEK, WITH UNCERTAIN FLOW DETAILS KEEPING CONFIDENCE LOW FOR  
SPECIFICS OF TIMING/COVERAGE/AMOUNTS OF ANY PRECIPITATION. THE  
SOUTHERN HALF OF THE WEST SHOULD SEE A WARMING TREND EXPAND FROM  
WEST TO EAST SATURDAY-MONDAY WITH CALIFORNIA SEEING THE WARMEST  
HIGH TEMPERATURE ANOMALIES OF PLUS 10-15F. ELSEWHERE, GUIDANCE  
AGREES THAT TROPICAL MOISTURE SHOULD SURGE NORTHWARD ACROSS THE  
FLORIDA PENINSULA LATE THIS WEEK INTO THE WEEKEND, BRINGING A  
ROUND OF HEAVY RAINFALL TO PORTIONS OF THE SUNSHINE STATE.  
 
RAUSCH/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  
 
HAZARDS:  
 
- HEAVY RAIN ACROSS PORTIONS OF THE WESTERN GREAT LAKES, THE UPPER  
MISSISSIPPI VALLEY, AND THE NORTHERN PLAINS, THU-FRI, MAY 19-MAY  
20.  
- SEVERE WEATHER ACROSS PORTIONS OF THE CORN BELT AND UPPER  
MIDWEST, THU, MAY 19.  
- SEVERE WEATHER ACROSS PORTIONS OF THE CENTRAL/SOUTHERN PLAINS,  
MISSISSIPPI VALLEY, INTO THE GREAT LAKES, FRI, MAY 20.  
- SEVERE WEATHER ACROSS PORTIONS OF THE NORTHERN NEW YORK,  
INTERIOR MID-ATLANTIC, UPPER OHIO VALLEY, AND THE SOUTHERN  
APPALACHIANS, SAT, MAY 21.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE LOWER  
MISSISSIPPI VALLEY, THE UPPER MISSISSIPPI VALLEY, AND THE NORTHERN  
PLAINS.  
- FLOODING LIKELY ACROSS PORTIONS OF THE UPPER MISSISSIPPI VALLEY  
AND THE NORTHERN PLAINS.  
- FLOODING POSSIBLE ACROSS PORTIONS OF INTERIOR ALASKA.  
- EXCESSIVE HEAT ACROSS PORTIONS OF CENTRAL AND SOUTHERN TEXAS AND  
THE LOWER MISSISSIPPI VALLEY, FRI-SAT, MAY 20-MAY 21.  
- HIGH WINDS ACROSS PORTIONS OF THE NORTHERN AND CENTRAL ROCKIES,  
THU, MAY 19.  
- MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE NORTHERN  
AND CENTRAL ROCKIES INTO THE CENTRAL AND NORTHERN PLAINS, FRI-SAT,  
MAY 20-MAY 21.  
- ENHANCED WILDFIRE RISK ACROSS PORTIONS OF THE SOUTHERN ROCKIES,  
THE CENTRAL ROCKIES, THE SOUTHERN PLAINS, THE CENTRAL PLAINS, AND  
THE SOUTHWEST, THU, MAY 19.  
 
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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