374  
FXUS02 KWBC 070823  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
323 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
 
 
ALTHOUGH THE MAJORITY OF THE HEAVY RAIN AND SNOW WILL HAVE LIKELY  
ABATED SOME BY THE BEGINNING OF THE FORECAST PERIOD ON SUNDAY,  
AREAS OF RAIN AND THUNDERSTORM ACTIVITY WILL CONTINUE ACROSS MUCH  
OF THE GULF COAST REGION AND ALONG THE IMMEDIATE EAST COAST.  
HEAVY SNOW IS STILL EXPECTED ACROSS INTERIOR PORTIONS OF NEW  
ENGLAND AS THE SURFACE LOW LIFTS NORTHEASTWARD ACROSS EASTERN  
CANADA, AND SOME LAKE ENHANCED SNOW WILL BE POSSIBLE. SOME SEVERE  
THUNDERSTORMS WILL ALSO BE POSSIBLE ACROSS PARTS OF THE SOUTHEAST  
ON SUNDAY AHEAD OF THE COLD FRONT, AND THIS IS SOMETHING THAT THE  
STORM PREDICTION CENTER IS CONTINUING TO MONITOR.  
 
LOOKING AHEAD FOR EARLY-MID WEEK, 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 IS EXPECTED TO DEVELOP ACROSS THE  
CENTRAL AND SOUTHERN PLAINS TO THE MISSISSIPPI VALLEY/MIDWEST  
DURING THE TUESDAY AND WEDNESDAY TIME PERIOD AS THE TROUGH INDUCES  
ANOTHER DEEPENING SURFACE LOW 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.  
ANOTHER ROUND OF HEAVY SNOW AND POTENTIAL BLIZZARD CONDITIONS IS  
BECOMING MORE PROBABLE ACROSS PARTS OF THE CENTRAL PLAINS AND THE  
UPPER MIDWEST AS THE SURFACE LOW INTENSIFIES AND COLDER AIR IN  
DRAWN IN BEHIND THE LOW.  
 
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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