867  
FXUS02 KWBC 170730  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
330 AM EDT WED APR 17 2024  
 
VALID 12Z SAT APR 20 2024 - 12Z WED APR 24 2024  
 
   
..OVERVIEW
 
 
THE PATTERN DURING THE MEDIUM RANGE PERIOD WILL CONTINUE TO  
TRANSITION TO MORE PROGRESSIVE FLOW BY THIS WEEKEND AS AN OMEGA  
BLOCK OVER THE NORTHEAST PACIFIC INTO WESTERN NORTH AMERICA AND  
THE NORTHERN U.S. TIER BEGINS TO BREAK DOWN. ENERGY FROM THE WEST  
SIDE OF A DEEP UPPER LOW INITIALLY OVER SOUTHEAST CANADA ON  
SATURDAY WILL INTERACT WITH ANOTHER SHORTWAVE INTO THE SOUTHERN  
PLAINS, INCREASING THE HEAVY RAIN THREAT ACROSS MUCH OF TEXAS ON  
SATURDAY, CONTINUING INTO SUNDAY ACROSS THE SOUTHEAST AS THE  
FRONTAL BOUNDARY IS SLOW TO MOVE THROUGH THE REGION. SECONDARY  
ENERGY EJECTING FROM AN UPPER LOW/TROUGH OVER THE NORTHEAST PACIFIC  
WILL SKIRT THE NORTHERN TIER AND MOVE THROUGH THE GREAT LAKES INTO  
THE NORTHEAST EARLY NEXT WEEK. TROUGHING GENERALLY WILL GET  
REESTABLISHED OVER THE WEST COAST BY NEXT TUESDAY-WEDNESDAY.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
THE LATEST GUIDANCE SHOWS VERY GOOD AGREEMENT ACROSS THE CONUS  
THROUGH MUCH OF THE PERIOD (SATURDAY-WEDNESDAY). THERE ARE SOME  
TIMING DIFFERENCES WITH SHORTWAVE TROUGHING THROUGH THE SOUTHEAST  
SUNDAY-MONDAY AND AGAIN WITH THE NEXT SHORTWAVE THROUGH THE GREAT  
LAKES/NORTHEAST TUESDAY-WEDNESDAY. THESE DETAILS CREATE SOME  
UNCERTAINTY IN THE EVENTUALLY (GENERALLY LIGHT) PRECIPITATION  
PATTERN ACROSS THE SOUTHEAST AND NORTHEAST EARLY NEXT WEEK. LOTS  
OF UNCERTAINTY LATE PERIOD AS WELL WITH THE EVOLUTION OF A DEEP  
CLOSED LOW OVER THE GULF OF ALASKA WHICH LOOKS TO SEND SOME  
ENERGY/TROUGHING TOWARDS THE WEST COAST.  
 
THE WPC FORECAST FOR TONIGHT USED AN EQUAL BLEND OF THE LATEST  
GFS, ECMWF, AND CMC FOR DAYS 3-5 (SATURDAY-MONDAY). FOR DAYS 6 AND  
7, REPLACED THE CMC WITH THE GEFS MEAN GIVEN GREATER CMC  
DIFFERENCES OFF THE WEST COAST. THE UKMET AND ECENS DATA CONTINUE  
TO BE UNAVAILABLE DUE TO ONGOING IT ISSUES AT WPC/COLLEGE PARK, MD.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
 
SHORTWAVE ENERGY INTO THE SOUTHERN PLAINS INTERACTING WITH A SLOW  
MOVING FRONTAL BOUNDARY AND ANOMALOUS MOISTURE AND INSTABILITY WILL  
INCREASE THE THREAT FOR HEAVY TO EXCESSIVE RAINFALL ACROSS MUCH OF  
THE SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI VALLEY ON SATURDAY.  
A SLIGHT RISK CONTINUES ON TONIGHTS DAY 4 EXCESSIVE RAINFALL  
OUTLOOK (SAT-SUN MORNING) ACROSS CENTRAL TO NORTHEAST TEXAS.  
RAINFALL WILL CONTINUE INTO THE SOUTHEAST/CAROLINAS ON SUNDAY AS  
THE FRONT SLOWLY SINKS THROUGH THAT REGION, AND THIS IS COVERED BY  
A MARGINAL RISK ON THE DAY 5 ERO. THE NEXT SHORTWAVE THROUGH THE  
NORTHERN PLAINS-GREAT LAKES-NORTHEAST WILL BE ACCOMPANIED BY SOME  
GENERALLY LIGHT PRECIPITATION AS WELL EARLY NEXT WEEK.  
 
THE UPPER TROUGH OVER THE NORTHERN TIER STATES AND EVENTUALLY INTO  
THE EAST WILL SUPPORT BELOW NORMAL TEMPERATURES (WITH GREATER  
ANOMALIES FOR HIGHS THAN LOWS) FOR MOST EAST OF THE ROCKIES BUT  
FLORIDA BY NEXT WEEKEND. ABOVE NORMAL TEMPERATURES ACROSS THE  
SOUTHWEST SHOULD GRADUALLY EXPAND NORTHWARD UNDERNEATH A BUILDING  
WESTERN U.S. RIDGE AND PROGRESS EASTWARD INTO THE ROCKIES EARLY  
NEXT WEEK. NORTHERN PARTS OF THE WEST MAY STAY NEAR NORMAL DUE TO  
THE UPPER SHORTWAVE/COLD FRONT CROSSING THE REGION NEXT WEEK.  
 
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  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION FORECAST (QPF), EXCESSIVE RAINFALL  
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT  
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:  
 
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  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW  
 

 
 
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