742  
FXUS02 KWBC 070700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
159 AM EST THU MAR 7 2019  
 
VALID 12Z SUN MAR 10 2019 - 12Z THU MAR 14 2019  
   
..WEATHER PATTERN OVERVIEW
 
 
AN ACTIVE WEATHER PATTERN IS EXPECTED DURING MUCH OF THE MEDIUM  
RANGE PERIOD AS TWO LARGE SCALE TROUGHS ORIGINATING FROM THE  
PACIFIC LEAD TO SURFACE LOW DEVELOPMENT ACROSS THE CENTRAL U.S.  
AND MIDWEST STATES. THE FIRST STORM SYSTEM OVER THE GREAT LAKES  
REGION AT THE BEGINNING OF THE FORECAST PERIOD SUNDAY WILL BRING  
WIDESPREAD RAIN AND THUNDERSTORMS TO THE EASTERN U.S. AND SNOW FOR  
THE UPPER MIDWEST AND GREAT LAKES. THE SECOND PACIFIC DISTURBANCE  
CROSSES THE DESERT SOUTHWEST ON MONDAY AND THEN UNDERGOES  
SECONDARY CYCLOGENESIS OVER THE WESTERN HIGH PLAINS BY THE MIDDLE  
OF NEXT WEEK WITH AN EVOLUTION THAT IS SIMILAR TO THE FIRST STORM  
SYSTEM.  
 
   
..GUIDANCE AND UNCERTAINTY ASSESSMENT
 
 
THE DETERMINISTIC MODELS ARE IN GOOD OVERALL AGREEMENT REGARDING  
THE PLACEMENT AND OVERALL STRENGTH OF THE SURFACE LOW CROSSING THE  
GREAT LAKES REGION ON SUNDAY, WITH THE GFS SLIGHTLY FASTER THAN  
THE MODEL CONSENSUS, AND QUICKER WITH COLD FRONT PASSAGE FOR THE  
EAST COAST. THE SPEED DIFFERENCES ARE MORE APPARENT WITH THE GFS  
AND ALSO THE GEFS MEAN WITH THE MID WEEK STORM SYSTEM ACROSS THE  
PLAINS. THERE IS GOOD MODEL CLUSTERING AMONG THE CMC/ECMWF/FV3  
SOLUTIONS, AND GIVEN THAT THESE ARE CLOSER TO WPC CONTINUITY  
COMPARED TO THE FASTER GFS/GEFS MEAN, THE FORECAST WAS MORE IN  
LINE WITH THE CMC/ECMWF/FV3.  
 
TAKING ALL OF THESE FACTORS INTO ACCOUNT, THE FORECAST WAS  
PRIMARILY DERIVED FROM THE 12Z ECMWF/18Z FV3/12Z UKMET FOR THE  
FIRST THREE DAYS, AND THEN A SLIGHTLY HIGHER PERCENTAGE OF THE EC  
MEAN WHILE STILL KEEPING A SIGNIFICANT PERCENTAGE OF THE  
DETERMINISTIC FV3, ECMWF, AND SOME OF THE CMC AS IT RELATES TO THE  
SECOND LOW PRESSURE SYSTEM. THE FV3 WAS SUBSTITUTED FOR THE  
OPERATIONAL GFS FOR THIS FORECAST PERIOD GIVEN THE TIMING  
DIFFERENCES NOTED. THE WPC FORECAST IS VERY SIMILAR TO THE  
PREVIOUS FORECAST IN TERMS OF TRACK AND EXPECTED LOW EVOLUTION.  
 
   
..WEATHER HIGHLIGHTS AND HAZARDS
 
 
WIDESPREAD RAIN AND THUNDERSTORMS ARE EXPECTED TO DEVELOP FROM THE  
GULF COAST TO THE SOUTHEAST U.S. ON SUNDAY AS A RICH SUPPLY OF  
GULF MOISTURE SURGES NORTHWARD AHEAD OF A STRONG COLD FRONT FROM  
THE MIDWEST SURFACE LOW.  
 
UPSTREAM, THE PATTERN AGAIN FAVORS AN AMPLIFIED MID-UPPER LEVEL  
TROUGH DEVELOPING OFF THE WEST COAST THIS WEEKEND. THIS WILL  
SUPPORT ANOTHER ROUND OF PRECIPITATION OVER THE SOUTHWESTERN U.S.  
AS THE TROUGH MOVES INLAND ON MONDAY. ADDITIONAL WIDESPREAD RAIN  
MAY THEN DEVELOP ACROSS THE CENTRAL AND SOUTHERN PLAINS THROUGH  
THE MISSISSIPPI VALLEY/MIDWEST IN ABOUT A WEEK AS THE TROUGH  
INDUCES ANOTHER DEEPENING SURFACE LOW/STORM EAST OF THE ROCKIES.  
THERE IS ALSO THE POTENTIAL FOR SEVERE WEATHER WITH THIS STORM  
SYSTEM, AND DETAILS ON THIS WILL BECOME MORE EVIDENT IN THE  
UPCOMING DAYS.  
 
D. HAMRICK  
 
ADDITIONAL 3-7 DAY HAZARDS INFORMATION CAN BE FOUND ON THE WPC  
MEDIUM RANGE HAZARDS CHART AT:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, 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/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 
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