734  
FXUS02 KWBC 040701  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
301 AM EDT WED MAY 04 2022  
 
VALID 12Z SAT MAY 07 2022 - 12Z WED MAY 11 2022  
 
...NORTH-CENTRAL GREAT BASIN/ROCKIES COLD HEAVY SNOW THREAT TO  
CONTRAST EMERGING NORTH-CENTRAL U.S. CONVECTION AND RECORD  
SOUTH-CENTRAL U.S TO MIDWEST HEAT PATTERN WITH OMEGA-STYLE BLOCK  
DEVELOPMENT THIS WEEKEND INTO NEXT WEEK...  
...LEAD MID-ATLANTIC RAINFALL THREAT INTO SATURDAY WITH THE CLOSED  
LOW TO SETTLE OVER A BLOCKED WESTERN ATLANTIC NEXT WEEK...  
 
   
..PATTERN OVERVIEW AND GUIDANCE EVALUATION
 
 
MODEL AND ENSEMBLE SOLUTIONS STILL OFFER PESKY EMBEDDED SYSTEM  
TIMING AND EMPHASIS DIFFERENCES, BUT HAVE OVERALL CONVERGED UPON A  
BETTER CLUSTERED MID-LARGER SCALE PATTERN EVOLUTION HIGHLIGHTED BY  
OMEGA-STYLE BLOCK DEVELOPMENT OVER THE LOWER 48 AND VICINITY. 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 SATURDAY INTO MONDAY. THE  
GFS/ECMWF AND GEFS/ECMWF ENSEMBLE MEANS REMAIN BEST CLUSTERED AND  
IN LINE WITH WPC CONTINUITY AND THE NBM MONDAY-NEXT WEDNESDAY.  
DESPITE BETTER SIMILARITIES, RECENT RUN-RUN GUIDANCE CONTINUITY  
ISSUES OFFERS CAUTION WITH EMBEDDED FEATURE DETAILS. MOST OF THE  
NEWER 00 UTC GUIDANCE MAINTAIN SIMILAR TRENDS FROM EARLIER  
GUIDANCE, BUT THE CANADIAN IS NOT AS DIGGY OVER THE WESTERN  
ATLANTIC.  
   
..WEATHER/THREAT HIGHLIGHTS
 
 
A LEADING CLOSED UPPER TROUGH AND WELL ORGANIZED SURFACE  
LOW/FRONTAL SYSTEM WILL TRACK FROM THE OHIO VALLEY THROUGH THE  
APPALACHIANS/MID-ATLANTIC THIS WEEKEND. SOME STRONG STORMS AND  
LOCALLY HEAVY DOWNPOURS ARE POSSIBLE CONSIDERING SLOW SYSTEM TRACK  
AND POOLED MOISTURE/INSTABILITY. THE SYSTEM WILL THEN STALL AND  
RETROGRADE OVER THE WESTERN ATLANTIC NEXT WEEK AS PART OF A  
DEVELOPING OMEGA-STYLE BLOCK.  
 
ROBUST DIGGING OF A SERIES OF DYNAMIC UPPER SYSTEMS WILL LEAD TO A  
DRAMACTIC CHANGE OVER MUCH OF THE WEST LATER THIS WEEK 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.  
 
UNCERTAIN 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 WILL TRAP A  
SLOW MOVING AND WAVY FRONTAL ZONE OVER THE NORTH-CENTRAL U.S. TO  
SUPPORT AN EMERGING 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 TEMPERTURES 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  
 
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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