011  
FXUS02 KWBC 200701  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
200 AM EST WED FEB 20 2019  
 
VALID 12Z SAT FEB 23 2019 - 12Z WED FEB 27 2019  
 
...EXCESSIVE RAINFALL/FLOODING THREAT FROM THE LOWER  
MISSISSIPPI/TENNESSEE/OHIO VALLEYS TO THE SOUTHERN/CENTRAL  
APPALACHIANS AND A SIGNIFICANT WINTER STORM FROM THE SOUTH-CENTRAL  
PLAINS TO THE UPPER MIDWEST/GREAT LAKES AND INTERIOR NEW ENGLAND  
THIS WEEKEND...  
 
   
..PATTERN OVERVIEW AND WEATHER HIGHLIGHTS/HAZARDS
 
 
POTENT UPPER LOW/TROUGH ENERGY LIFTS NORTHEASTWARD THIS WEEKEND  
FROM THE SOUTHERN PLAINS TO THE NORTHEAST OVERTOP AN AMPLIFIED AND  
SLOW TO ERODE BAHAMAS/SOUTHEAST U.S. UPPER RIDGE. THIS BRINGS A  
THREAT FOR SIGNIFICANT ACCUMULATING SNOW WITH SOME ICING POSSIBLE  
AROUND AN ASSOCIATED AND DEEPENING SURFACE LOW WITH A PRESSURE IN  
THE 980S BY SUNDAY OVER THE GREAT LAKES. THIS WOULD LIKELY RESULT  
IN GUSTY WINDS AND POTENTIAL BLIZZARD CONDITIONS ACROSS THE UPPER  
MIDWEST AND GREAT LAKES.  
 
UNDERNEATH, A MULTI-DAY HEAVY RAIN/TRAINING EPISODE REJUVINATES  
FROM THE LOWER MS/TN/OH VALLEYS TO THE SOUTHERN/CENTRAL  
APPALACHIANS SATURDAY, EXITING THE EAST COAST SUNDAY WITH FRONTAL  
PASSAGE. FLOODING/RUNOFF ISSUES WILL REMAIN FUELED BY ADVECTION OF  
HIGHLY ANOMALOUS MOISTURE/WARM AIR AND DEEP CYCLO/FRONTOGENESIS.  
SPC ALSO SHOWS A SEVERE WEATHER THREAT GIVEN SYSTEM ANOMALOUS  
NATURE/VIGOR.  
 
A LONG-STANDING AND WINTRY MEAN UPPER TROUGH OVER THE WEST WILL  
AGAIN BE REINFORCED SAT-MON AS ENERGY DIGS TO THE LEE OF A  
BLOCKING GULF OF ALASKA CENTERED UPPER RIDGE. THESE SYSTEMS WILL  
BE LESS AMPLIFIED THAN PRIOR SYSTEMS IN THIS RECENT PATTERN, BUT  
WILL BRING UNSETTLED WEATHER PATTERN THROUGH THE NORTHWEST AND  
NORTH-CENTRAL INTERMOUNTAIN WEST AND ROCKIES, WITH THE BEST CHANCE  
FOR ACCUMULATING SNOWFALL OVER THE CASCADES. GUIDANCE HAS NOT BEEN  
VERY CONSISTENT RECENTLY WITH THE EVOLUTION OF THE UPSTREAM FLOW  
NEXT WEEK, BUT NOW SHIFTS THE UPPER HIGH/RIDGE NORTHWARD OVER THE  
ALASKAN INTERIOR. THIS FLATTENS AND MODERATES FLOW INTO THE WEST  
BY TUE/WED WITH EMERGENCE OF UNDERCUTTING BUT LESS CERTAIN  
SOUTHERN STREAM PACIFIC FLOW AND PATTERN WITH NORTHERN STREAM  
ENERGY/HEIGHT FALLS EJECTING EASTWARD OVER THE N-CENTRAL TO  
NORTHEASTERN U.S. THIS SHOULD KEEP THE N-CENTRAL U.S COLD BUT ALSO  
SUPPORT SYSTEM DEVELOPMENT THAT COULD LEAD TO DEEPER DEVELOPMENT  
INTO THE EAST IN ABOUT A WEEK.  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT AND PREFERENCES
 
 
GUIDANCE IS REASONABLY WELL CLUSTERED AT MID-LARGER SCALES THROUGH  
MUCH OF THE MEDIUM RANGE PERIOD. WPC PROGS WERE PRIMARILY DERIVED  
FROM A COMPOSITE BLEND OF THE LATEST GFS/ECMWF AND GEFS/ECMWF  
ENSEMBLE MEANS. THIS MAINTAINS REASONABLE WPC CONTINUITY OVERALL.  
 
SCHICHTEL  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION AND WINTER WEATHER OUTLOOK  
PROBABILITIES ARE FOUND 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  
 

 
 
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