937  
FXUS02 KWBC 051959  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
359 PM EDT THU MAY 05 2022  
 
VALID 12Z SUN MAY 08 2022 - 12Z THU MAY 12 2022  
 
...HEAVY SNOW THREAT OVER A COLD NORTH-CENTRAL GREAT BASIN/ROCKIES  
TO CONTRAST NORTH-CENTRAL U.S. CONVECTION AND SOUTH-CENTRAL U.S TO  
MIDWEST RECORD HEAT AS PART OF OMEGA-STYLE BLOCK DEVELOPMENT OVER  
THE LOWER 48 AND ADJOINING OCEANS THIS WEEKEND INTO NEXT WEEK...  
 
18Z UPDATE: THE 12Z MODEL GUIDANCE SUITE IS IN VERY GOOD SYNOPTIC  
SCALE AGREEMENT FOR SUNDAY AND INTO EARLY TUESDAY AS AN OMEGA  
BLOCK PATTERN DEVELOPS OVER THE CENTRAL U.S., SO A  
MULTI-DETERMINISTIC BLEND SUFFICED AS A STARTING POINT IN THE  
FORECAST PROCESS FOR THAT TIME PERIOD. NOTICEABLE DIFFERENCES  
EMERGE WITH THE 12Z CMC ACROSS THE EASTERN PACIFIC AND  
SOUTHWESTERN U.S. BY WEDNESDAY, AND IT IS WEAKER WITH THE  
SHORTWAVE TROUGH EJECTING EASTWARD ACROSS THE ROCKIES COMPARED TO  
THE CONSENSUS. THE PAST TWO RUNS OF THE CMC HAVE TRENDED WITH THE  
GFS AND ECMWF REGARDING A RETROGRADING LOW OVER THE WESTERN  
ATLANTIC AND TOWARDS THE SOUTHEAST COAST BY THE END OF THE WEEK,  
WITH THE ECMWF TAKING THIS LOW FARTHEST WEST. MODEL PREFERENCES  
FOR THE LATTER HALF OF THE PERIOD MAINTAINED SOME OF THE GFS/ECMWF  
WHILST GRADUALLY INCREASING USE OF THE ENSEMBLE MEANS AND SOME  
PREVIOUS WPC CONTINUITY. IN TERMS OF SENSIBLE WEATHER, THE MAIN  
STORY WILL LIKELY BE THE EARLY SEASON HEAT WAVE THAT IS FORECAST  
TO ENCOMPASS MUCH OF THE SOUTH-CENTRAL U.S. AND INTO THE MIDWEST,  
WITH AFTERNOON HIGH TEMPERATURES RUNNING UP TO 20 DEGREES ABOVE  
NORMAL, AND THE POTENTIAL FOR MULTIPLE DAILY RECORD HIGHS TO BE  
SET. THE PREVIOUS FORECAST DISCUSSION FOLLOWS BELOW. /HAMRICK  
-------------------------  
   
..PATTERN OVERVIEW AND GUIDANCE EVALUATION
 
 
A COMPOSITE OF THE 18 UTC GFS/GEFS ALONG WITH THE 12 UTC  
ECMWF/UKMET/CANADIAN, ECMWF ENSEMBLE MEAN AND 01 UTC NATIONAL  
BLEND OF MODELS SEEMS TO PRESENT A REASONABLE FORECAST BASIS WHILE  
TENDING TO MITIGATE EMBEDDED SYSTEM VARIANCE CONSISTENT WITH A  
PATTERN WITH NEAR NORMAL PREDICTABILITY SUNDAY INTO MONDAY. THE  
GFS/ECMWF AND GEFS/ECMWF ENSEMBLE MEANS REMAIN BEST CLUSTERED AND  
IN LINE WITH WPC CONTINUITY AND THE NBM TUESDAY-NEXT THURSDAY.  
DESPITE BETTER SIMILARITIES, RECENT RUN-RUN GUIDANCE CONTINUITY  
ISSUES STILL SUGGESTS SOME CAUTION WITH EMBEDDED FEATURE DETAILS,  
ESPECIALLY DAYS 5-7. MOST OF THE NEWER 00 UTC GUIDANCE MAINTAIN  
SIMILAR TRENDS FROM EARLIER GUIDANCE, WITH THE CANADIAN REMAINING  
THE MOST OUT OF PHASE WITH OTHER GUIDANCE WITH THE TIMING/EMPHASIS  
ON SYSTEMS DIGGING INTO THE WESTERN U.S.UPPER TROUGH.  
   
..WEATHER/THREAT HIGHLIGHTS
 
 
A CLOSED UPPER TROUGH AND WELL ORGANIZED SURFACE LOW/FRONTAL  
SYSTEM WILL TRACK OFF THE MID-ATLANTIC SUNDAY. THE LOW STALLS AND  
RETROGRADES OVER THE WESTERN ATLANTIC BACK TOWARD THE SOUTHEAST  
COAST MID-LATER NEXT WEEK WITH WRAPPING RAINS WITHIN A DEVELOPING  
OMEGA-STYLE BLOCK.  
 
ROBUST DIGGING OF A SERIES OF DYNAMIC UPPER SYSTEMS WILL LEAD TO A  
DRAMATIC CHANGE OVER MUCH OF THE WEST LATER THIS WEEKEND INTO NEXT  
WEEK AS AN AMPLIFIED MEAN UPPER TROUGH AND WAVY FRONTAL SYSTEMS  
BECOME ESTABLISHED OVER THE REGION. THIS WILL SUPPORT SIGNIFICANT  
COOLING TO INCLUDE SPOTTY RECORD VALUES ALONG WITH A WIDESPREAD  
PRECIPITATION FOCUS FROM THE NORTHWEST/SIERRA THROUGH THE  
NORTH-CENTRAL GREAT BASIN/ROCKIES. THIS WILL INCLUDE A SUBSTANTIAL  
AND LINGERING THREAT FOR WIDESPREAD HEAVY SNOWS AS FURTHER  
ENHANCED IN FAVORED TERRAIN. EXPECT TEMPERATURES TO RANGE AS MUCH  
AS 10-20 DEGREES BELOW NORMAL.  
 
UPPER SYSTEM EJECTIONS CHANNELED BETWEEN AMPLIFIED EASTERN PACIFIC  
UPPER RIDGING/UPPER TROUGHING OVER THE WEST AND AMPLIFIED  
EAST-CENTRAL U.S. UPPER RIDGING AS PART OF THE AFOREMENTIONED  
OMEGA-STYLE BLOCK OVER THE LOWER 48 AND ADJOINING OCEANS WILL TRAP  
A SLOW MOVING AND WAVY FRONTAL ZONE OVER THE NORTH-CENTRAL U.S. TO  
SUPPORT AN EMERGING BUT UNCERTAIN CONVECTION/RAINFALL PATTERN.  
THIS OFFERS A RUNOFF THREAT GIVEN MOIST AMBIENT NORTHERN PLAINS  
SOIL CONDITIONS. THE STORM PREDICTION CENTER ALSO HIGHLIGHTS A  
CONCERN FOR SEVERE WEATHER INTO THE EASTERN CENTRAL PLAINS FOR AT  
LEAST SUNDAY AND MONDAY. THE PATTERN MEANWHILE FAVORS RECORD HIGH  
TEMPERATURES OVER THE SOUTH-CENTRAL U.S., WITH PRE-FRONTAL WARMTH  
GRADUALLY BUILDING NORTHEASTWARD NEXT WEEK THROUGH THE MS/TN  
VALLEYS/MIDWEST UNDER THE UPPER RIDGE, IN STARK CONTRAST TO THE  
WINTRY CONDITIONS OVER THE WEST AND MODERATED/COOLED HIGH PRESSURE  
DAMMED AIRMASS TO LINGER OVER THE EAST ON THE BACKSIDE OF A  
DIFFICULT TO DISLODGE WESTERN ATLANTIC CIRCULATION.  
 
SCHICHTEL/HAMRICK  
 
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 CALIFORNIA, THE CENTRAL  
GREAT BASIN, AND THE PACIFIC  
NORTHWEST, SUN-MON, MAY 8-MAY 9.  
- HEAVY SNOW ACROSS PORTIONS OF THE CENTRAL/NORTHERN ROCKIES, THE  
NORTHERN PLAINS, AND THE NORTHERN  
GREAT BASIN, SUN-MON, MAY 8-MAY 9.  
- SEVERE WEATHER ACROSS PORTIONS OF THE CENTRAL/NORTHERN PLAINS,  
THE MIDDLE/UPPER MISSISSIPPI  
VALLEY, MON, MAY 9.  
- FLOODING POSSIBLE ACROSS PORTIONS OF THE GREAT PLAINS, THE  
MISSISSIPPI VALLEY, THE GREAT LAKES,  
AND THE OHIO VALLEY.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE GREAT  
PLAINS, AND THE MISSISSIPPI VALLEY.  
- FLOODING LIKELY ACROSS PORTIONS OF THE GREAT PLAINS, AND THE  
MIDDLE/LOWER MISSISSIPPI VALLEY.  
- EXCESSIVE HEAT ACROSS PORTIONS OF THE CENTRAL/SOUTHERN PLAINS,  
AND THE LOWER MISSISSIPPI VALLEY,  
SUN-TUE, MAY 8-MAY 10.  
- HIGH WINDS ACROSS PORTIONS OF THE GREAT PLAINS, THE ROCKIES, THE  
CENTRAL GREAT BASIN, THE  
MID-ATLANTIC, CALIFORNIA, AND THE SOUTHWEST, SUN-MON, MAY 8-MAY 9.  
- ENHANCED WILDFIRE RISK ACROSS PORTIONS OF THE SOUTHERN ROCKIES,  
THE SOUTHERN PLAINS, AND THE  
SOUTHWEST, SUN, MAY 8.  
- FLOODING POSSIBLE ACROSS PORTIONS OF MAINLAND ALASKA, SUN-MON,  
MAY 8-MAY 9.  
- FLOODING POSSIBLE ACROSS PORTIONS OF MAINLAND ALASKA, SUN-THU,  
MAY 8-MAY 12.  
 
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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