322  
FXUS02 KWBC 262018  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
418 PM EDT THU MAY 26 2022  
 
VALID 12Z SUN MAY 29 2022 - 12Z THU JUN 02 2022  
 
...POTENTIAL FOR HEAVY PRECIPITATION NEXT WEEK FROM THE NORTHERN  
ROCKIES TO UPPER MIDWEST AND THEN SOUTHWARD TO THE CENTRAL  
PLAINS...  
   
..WEATHER PATTERN OVERVIEW
 
 
LATEST GUIDANCE CONTINUES TO SHOW AN EVOLUTION TOWARD AN AMPLIFIED  
WESTERN TROUGH/EASTERN RIDGE ALOFT SUNDAY-TUESDAY, WITH THE  
WESTERN TROUGH LIKELY MOST AMPLIFIED AROUND MONDAY AND THE EASTERN  
RIDGE STRONGEST AROUND TUESDAY. CONSENSUS THEN SHOWS A RAPID  
FLATTENING OF THE MEAN PATTERN AS THE WESTERN ENERGY EJECTS AND  
SOUTHERN TIER RIDGING RETROGRADES TO SOME DEGREE. BY THURSDAY AN  
APPROACHING EASTERN PACIFIC TROUGH MAY EVEN SUPPORT A WEAK UPPER  
RIDGE OVER THE INTERIOR WEST. THE INITIAL AMPLIFIED  
PATTERN/WESTERN UPPER DYNAMICS WILL SUPPORT POTENTIAL FOR SOME  
AREAS OF HEAVY PRECIPITATION FROM THE NORTHERN ROCKIES INTO THE  
PLAINS/UPPER MIDWEST, FOLLOWED BY A TRANSITION TO MORE EMPHASIS  
FOR HEAVY RAINFALL OVER THE CENTRAL PLAINS AS A WAVY FRONT BEGINS  
TO PUSH SOUTHEASTWARD. AN AREA OF VERY COOL TEMPERATURES WILL  
PROGRESS THROUGH THE WEST INTO THE NORTHERN PLAINS EARLY IN THE  
WEEK AND THEN MODIFY AS IT REACHES THE REST OF THE PLAINS.  
MEANWHILE VERY WARM TO HOT WEATHER INITIALLY OVER THE  
PLAINS/MIDWEST WILL SHIFT INTO THE NORTHERN HALF TO TWO-THIRDS OF  
THE EASTERN U.S. DURATION OF WARM TEMPERATURES OVER THE NORTHEAST  
IS A QUESTION MARK HOWEVER, AS FLOW AROUND A BROAD UPPER LOW OVER  
EASTERN CANADA MAY PUSH A FRONT INTO/THROUGH THE REGION.  
   
..MODEL GUIDANCE AND PREFERENCES
 
 
THE UPDATED FORECAST ACCOUNTING FOR 00Z/06Z GUIDANCE STARTED WITH  
AN OPERATIONAL MODEL COMPOSITE (MORE GFS COMPONENT FROM THE 00Z  
VERSUS 06Z RUN) EARLY IN THE PERIOD AND THEN TRENDED TOWARD 50-60  
PERCENT TOTAL 06Z GEFS/00Z ECMWF MEAN INPUT AS SPECIFICS BECAME  
INCREASINGLY UNCERTAIN. THERE ARE VARIOUS ASPECTS OF THE FORECAST  
THAT HAVE BEEN EXHIBITING SPREAD/TRENDS OVER RECENT RUNS. ISSUES  
WITH THE WESTERN TROUGH INVOLVE HOW SUNDAY-MONDAY ENERGY WILL  
ULTIMATELY EJECT FROM THE TROUGH, WITH PERIPHERAL INFLUENCE FROM  
PACIFIC FLOW (JUST OFFSHORE THE PACIFIC NORTHWEST AS WELL AS  
UPSTREAM) PLUS CENTRAL CANADA TROUGHING/POSSIBLE EMBEDDED LOW THAT  
HAVE BECOME MORE PRONOUNCED IN LATEST RUNS AND MAY INTERACT WITH  
THE EJECTING ENERGY. IN GENERAL THE PRIMARY TREND OVER THE PAST  
COUPLE DAYS HAS BEEN FOR THE WESTERN ENERGY TO EJECT A BIT FASTER,  
BUT WITH NO REAL CONSENSUS YET FOR THE DETAILS. THE PAST COUPLE  
UKMET RUNS HAVE BEEN RATHER EXTREME WITH THE SPEED OF UPSTREAM  
PACIFIC FLOW AND SOUTHEASTWARD AMPLITUDE OF TROUGHING THAT  
EVENTUALLY REACHES THE PLAINS (THE LATTER BEING AN ERROR IN SOME  
UKMET RUNS WITH A PRIOR EJECTING FEATURE AROUND A COUPLE WEEKS  
AGO). AT THE SAME TIME MOST GUIDANCE HAS GENERALLY TRENDED MORE  
PRONOUNCED WITH FLOW AROUND AN UPPER LOW CROSSING FAR EASTERN  
CANADA, BRINGING A BETTER DEFINED COLD FRONT THROUGH PARTS OF THE  
NORTHEAST AND PERHAPS STALLING THIS FRONT FOR A TIME SOMEWHERE  
BETWEEN THE NORTHERN MID-ATLANTIC AND NEW ENGLAND (WITH A LOT OF  
SPREAD IN THE GUIDANCE AT THIS TIME). THE 06Z GFS COMPARED MORE  
POORLY TO CONSENSUS FOR THE UPPER LOW TRACK/CYCLONIC FLOW  
AMPLITUDE VERSUS THE 00Z RUN OR MOST OTHER GUIDANCE. THE 12Z GFS  
RETURNED SOMEWHAT CLOSER TO THE MAJORITY. BY NEXT THURSDAY THERE  
IS DECENT AGREEMENT ON A MORE PROGRESSIVE/LOW AMPLITUDE SHORTWAVE  
OVER THE UPPER MIDWEST PUSHING ALONG THE CENTRAL U.S. FRONT FROM  
EARLIER IN THE WEEK, WHILE A WEAK UPPER RIDGE REACHES THE WEST.  
   
..SENSIBLE WEATHER/THREAT HIGHLIGHTS
 
 
FROM SUNDAY INTO THE EARLY PART OF THE NEXT WORK WEEK, THE UPPER  
LOW MOVING OVER THE PARTS OF THE WEST ALONG WITH AREAS OF LOW  
LEVEL UPSLOPE FLOW SHOULD COMBINE TO GENERATE A PERIOD OF MODERATE  
TO HEAVY PRECIPITATION OVER THE NORTHERN ROCKIES AND HIGH PLAINS  
WHILE A SLOWLY MOVING WAVY FRONTAL SYSTEM OVER THE PLAINS COULD  
HELP TO FOCUS LOCALLY HEAVY RAINFALL AS FAR EAST AS THE UPPER  
MIDWEST. CURRENTLY EXPECT HEAVIEST TOTALS OVER PARTS OF MONTANA  
AND NORTHERN WYOMING WITH SIGNIFICANT SNOWFALL POSSIBLE IN HIGHER  
ELEVATIONS OF THE ROCKIES. THE STORM PREDICTION CENTER IS ALSO  
MONITORING THE POTENTIAL FOR SEVERE WEATHER OVER PARTS OF THE  
PLAINS/UPPER MIDWEST IN THE SUNDAY-MONDAY TIME FRAME. TOWARD  
MIDWEEK THE FLATTER TREND FOR THE UPPER PATTERN SHOULD BEGIN TO  
PUSH THE PLAINS FRONT SOUTHEASTWARD, LIKELY SHIFTING THE EMPHASIS  
FOR HEAVIEST RAINFALL INTO OR NEAR THE CENTRAL PLAINS. THE  
EXTREME SOUTHERN TIER INCLUDING FLORIDA MAY SEE SOME SCATTERED  
DIURNALLY FAVORED CONVECTION, AIDED BY ENERGY ALOFT TO THE SOUTH  
OF THE EASTERN U.S. UPPER RIDGE. PARTS OF THE NORTHEAST COULD SEE  
ONE OR MORE EPISODES OF RAINFALL WITH A COLD FRONT THAT MOVES  
INTO/THROUGH THE REGION AND POSSIBLY STALLS FOR A TIME OVER NEW  
ENGLAND OR THE NORTHERN MID-ATLANTIC. SOME RAINFALL COULD BE  
LOCALLY MODERATE TO HEAVY BUT WITH LOW CONFIDENCE IN DETAILS THUS  
FAR.  
 
WARMEST TEMPERATURE ANOMALIES ON SUNDAY WILL EXTEND FROM THE  
SOUTHERN HIGH PLAINS INTO THE MIDWEST, WITH SOME LOCATIONS UP TO  
10-20F ABOVE NORMAL. PARTS OF THE CENTRAL/SOUTHERN PLAINS MAY SEE  
THE VERY WARM TO HOT WEATHER PERSIST INTO EARLY NEXT WEEK BUT  
OTHERWISE THE EMPHASIS FOR HEAT WILL SHIFT MORE INTO THE NORTHERN  
HALF TO TWO-THIRDS OF THE EAST WITH A BROAD AREA OF PLUS 10-20F  
ANOMALIES AND PERHAPS SOME DAILY RECORDS, MORE FOR MORNING LOWS  
VERSUS DAYTIME HIGHS. THE FRONT OVER THE NORTHEAST MAY BRING A  
COOLING TREND TO PARTS OF THAT REGION THOUGH. ON THE OTHER HAND,  
WELL BELOW NORMAL TEMPERATURES WILL PUSH ACROSS THE WEST INTO THE  
NORTHERN PLAINS SUNDAY ONWARD, WITH A BROAD AREA OF HIGHS 10-20F  
BELOW NORMAL SUNDAY-TUESDAY. SOME LINGERING MINUS 10-15F  
ANOMALIES ARE POSSIBLE INTO WEDNESDAY OVER THE NORTHERN-CENTRAL  
PLAINS BUT FURTHER MODERATION IS LIKELY THEREAFTER. A WARMER  
TREND OVER THE WEST WILL BRING MODERATELY ABOVE NORMAL HIGHS INTO  
THE REGION BY WEDNESDAY-THURSDAY.  
 
RAUSCH  
 
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 PRECIPITATION ACROSS PORTIONS OF THE NORTHERN  
PLAINS/ROCKIES, AND THE NORTHERN GREAT BASIN,  
SUN-MON, MAY 29-MAY 30.  
- HEAVY RAIN ACROSS PORTIONS OF THE PACIFIC NORTHWEST, SUN, MAY 29.  
- HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL/NORTHERN PLAINS, AND  
THE NORTHERN ROCKIES, SUN-MON, MAY  
29-MAY 30.  
- HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL PLAINS, TUE-WED, MAY  
31-JUN 1.  
- SEVERE WEATHER ACROSS PORTIONS OF THE CENTRAL/NORTHERN PLAINS,  
AND THE MIDDLE/UPPER MISSISSIPPI  
VALLEY, SUN, MAY 29.  
- SEVERE WEATHER ACROSS PORTIONS OF THE CENTRAL/NORTHERN PLAINS,  
THE MIDDLE/UPPER MISSISSIPPI  
VALLEY, MON, MAY 30.  
- FLOODING POSSIBLE ACROSS PORTIONS OF THE CENTRAL PLAINS.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE UPPER  
MISSISSIPPI VALLEY AND THE NORTHERN  
PLAINS.  
- FLOODING LIKELY ACROSS PORTIONS OF THE SOUTHERN PLAINS.  
- EXCESSIVE HEAT ACROSS PORTIONS OF THE SOUTHERN PLAINS, SUN, MAY  
29.  
- HIGH WINDS ACROSS PORTIONS OF THE CENTRAL PLAINS/ROCKIES/GREAT  
BASIN, THE SOUTHERN  
ROCKIES/PLAINS, AND THE SOUTHWEST, SUN-MON, MAY 29-MAY 30.  
- ENHANCED WILDFIRE RISK ACROSS PORTIONS OF THE SOUTHERN ROCKIES,  
THE CENTRAL/SOUTHERN PLAINS, AND  
THE SOUTHWEST, SUN-MON, MAY 29-MAY 30.  
 
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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