991  
FXUS02 KWBC 041930  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
329 PM 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
 
 
UPPER TROUGH IN THE EAST WILL MOVE OFFSHORE, CLOSE OFF AND LINGER  
OFF THE SOUTHEAST COAST THROUGH THE MEDIUM RANGE. THERE WAS PLENTY  
OF SPREAD IN THE GUIDANCE, PARTICULARLY WITH THE 00Z  
CMC/CMCE/UKMET 06Z GEFS, WITH RESPECT TO THE INTENSITY OF THE  
CLOSED LOW IN THE ATLANTIC BEGINNING ON SUNDAY AND CONTINUING  
THROUGH WEDNESDAY. THE 00Z EC APPEARS TO BEST CAPTURE THE PATTERN  
ACROSS THE CONUS. THERE'S NOTABLE SPREAD IN THE 00Z EC ENSEMBLE  
MEMBERS WITH RESPECT TO THE UPPER-TROUGH IN THE WEST BY NEXT  
TUESDAY AND WEDNESDAY. THUS, A BLEND OF MAJORITY DETERMINISTIC 00Z  
EC AND 06Z GFS WAS UTILIZED THROUGH DAY 6. A MORE EVEN COMBINATION  
OF DETERMINISTIC AND ENSEMBLE GUIDANCE WAS BLENDED FOR DAY 7.  
   
..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  
DRAMATIC 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 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.  
 
KEBEDE/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  
 
HAZARDS:  
- HEAVY PRECIPITATION ACROSS PORTIONS OF THE PACIFIC NORTHWEST AND  
THE NORTHERN GREAT BASIN, SAT,  
MAY 7.  
- HEAVY PRECIPITATION ACROSS PORTIONS OF THE PACIFIC NORTHWEST,  
SAT-SUN, MAY 7-MAY 8.  
- HEAVY SNOW ACROSS PORTIONS OF THE CENTRAL ROCKIES, THE NORTHERN  
PLAINS, THE NORTHERN ROCKIES, AND  
THE NORTHERN GREAT BASIN, SAT-TUE, MAY 7-MAY 10.  
- SEVERE WEATHER ACROSS PORTIONS OF THE CENTRAL PLAINS, THE MIDDLE  
MISSISSIPPI VALLEY, THE UPPER  
MISSISSIPPI VALLEY, AND THE NORTHERN PLAINS, MON, MAY 9.  
- SEVERE WEATHER ACROSS PORTIONS OF THE CENTRAL PLAINS, SAT, MAY 7.  
- SEVERE WEATHER ACROSS PORTIONS OF THE CENTRAL PLAINS, THE MIDDLE  
MISSISSIPPI VALLEY, AND THE  
UPPER MISSISSIPPI VALLEY, SUN, MAY 8.  
- FLOODING POSSIBLE ACROSS PORTIONS OF THE CENTRAL PLAINS, THE  
LOWER MISSISSIPPI VALLEY, THE  
NORTHERN PLAINS, THE SOUTHERN PLAINS, THE MIDDLE MISSISSIPPI  
VALLEY, AND THE GREAT LAKES.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE UPPER  
MISSISSIPPI VALLEY AND THE NORTHERN  
PLAINS.  
- FLOODING LIKELY ACROSS PORTIONS OF THE MIDDLE MISSISSIPPI VALLEY  
AND THE NORTHERN PLAINS.  
- EXCESSIVE HEAT ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY  
AND THE SOUTHERN PLAINS, SAT-TUE,  
MAY 7-MAY 10.  
- HIGH WINDS ACROSS PORTIONS OF THE CENTRAL PLAINS, THE CENTRAL  
ROCKIES, THE CENTRAL GREAT BASIN,  
THE SOUTHERN ROCKIES, CALIFORNIA, THE SOUTHERN PLAINS, AND THE  
SOUTHWEST, SUN-MON, MAY 8-MAY 9.  
- HIGH WINDS ACROSS PORTIONS OF THE MID-ATLANTIC, SAT-TUE, MAY  
7-MAY 10.  
- ENHANCED WILDFIRE RISK ACROSS PORTIONS OF THE SOUTHERN ROCKIES,  
THE SOUTHERN PLAINS, AND THE  
SOUTHWEST, SUN, MAY 8.  
 
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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