970  
FXUS02 KWBC 251945  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
343 PM EDT MON MAR 25 2019  
 
VALID 12Z THU MAR 28 2019 - 12Z MON APR 01 2019  
   
..OVERVIEW
 
 
A POTENT/CLOSED EASTERN PACIFIC UPPER TROUGH WILL APPROACH THE  
WEST COAST MIDWEEK, WITH THESE SOUTHERN STREAM HEIGHT FALLS  
WORKING EASTWARD OVER THE NATION THU-SUN. SURFACE FRONTS IN THE  
WEST WILL SUPPORT SOME HEAVY PRECIPITATION INCLUDING HEAVY HIGHER  
ELEVATION SNOWS. LOW DEVELOPMENTS IN THE PLAINS AND SUBSEQUENT  
MOVEMENT THROUGH THE MS VALLEY/MIDWEST WILL COMBINE WITH A SURGE  
OF DEEPENING MOISTURE/WARMTH FROM THE GULF OF MEXICO, WHICH MAY  
FUEL ENHANCED RAIN/THUNDERSTORMS IN THOSE AREAS WITH ONGOING  
FLOODING LATE WEEK INTO THE WEEKEND. THIS PATTERN ALSO INCLUDES A  
RISK OF HEAVY SNOWS THU-SUN ON THE COOLED NORTHWEST TO NORTHERN  
PERIPHERY OF THE PRECIPITATION SHIELD FROM THE NORTHERN/CENTRAL  
ROCKIES/PLAINS TO THE MIDWEST/GREAT LAKES AND THEN INTO NORTHERN  
NEW ENGLAND.  
   
..GUIDANCE ASSESSMENT/PREFERENCES
 
 
A MULTI-MODEL BLEND SEEMS QUITE REASONABLE THU INTO SAT FOR THE  
LARGER-SCALE FEATURES (UPPER TROUGH/LOW TRAVERSING THE WEST  
UNDERNEATH A LARGE EAST-CENTRAL CANADIAN UPPER LOW) WHILE  
DE-EMPHASIZING THE SMALL-SCALE DIFFERENCES. THIS BLEND INCLUDES  
THE LATEST GFS, ECMWF, AND UKMET THAT CLUSTER WELL WITH THE LATEST  
GEFS/ECMWF ENSEMBLE MEAN DURING THIS TIME PERIOD. FORECAST SPREAD  
AND RUN TO RUN CONTINUITY ISSUES BECOME MORE PROBLEMATIC OVER THE  
WEEKEND AND NEXT MON. THIS BEGINS DAY 5/SAT WITH QUESTIONS ABOUT  
THE DEGREE OF SEPARATION IN THE NORTHERN AND SOUTHERN STREAMS,  
NAMELY THE MANNER IN WHICH A DEEP UPPER LOW IN CENTRAL CANADA  
PHASES WITH TROUGHING ACROSS THE CENTRAL CONUS. THE 00Z EC AND ITS  
MEAN EXHIBITS MORE PHASING OF THE FEATURES, WHILE THE GFS SUITE  
KEEPS MORE SEPARATION AT DAY 5 AND THEN VARIES SIGNIFICANTLY FROM  
RUN TO RUN AS TO WHEN THE PHASING OCCURS. PREFERRED A BLEND OF THE  
00Z GEFS/ECMWF ENSEMBLE MEANS AS A COMPROMISE FOR NOW, THOUGH BY  
DAY 7/NEXT MON THESE DO HAVE SOME DIFFERENCES IN PLACEMENT OF THE  
TROUGH AXIS IN THE EAST. UTILIZED THE 00Z GEFS MEAN RATHER THAN  
THE 06Z DUE TO BETTER HANDLING OF THE PATTERN ACROSS THE WEST BY  
EARLY NEXT WEEK.  
   
..WEATHER HIGHLIGHTS AND HAZARDS
 
 
WITH THE UPPER TROUGH/LOW APPROACHING THE WEST, A COUPLE OF FRONTS  
WILL MAKE THEIR WAY THROUGH THE WEST AND SOME HEAVY PRECIPITATION  
EXPECTED INTO THU. SOME HEAVIER VALLEY RAIN/MOUNTAIN SNOWS WILL  
THREATEN THE NORTHERN ROCKIES THU, WITH HEAVY SNOW FORECAST FOR  
THE CENTRAL ROCKIES BY THU/FRI. AS THE TROUGH ENERGY EJECTS OUT  
THROUGH THE WEST, IT IS EXPECTED TO INDUCE CYCLO/FRONTOGENESIS IN  
THE PLAINS THEN MISSISSIPPI VALLEY, MIDWEST AND NORTHEAST. THIS  
PLUS A NORTHERN STREAM COLD FRONT DROPPING SOUTHWARD OUT OF CANADA  
WILL WORK IN TANDEM WITH DEEPENING LEAD RETURN FLOW FROM THE GULF  
OF MEXICO TO FUEL A RISK OF ENHANCED RAINS/CONVECTION. IN THE COLD  
AIR BEHIND THE AFOREMENTIONED COLD FRONT COMING FROM CANADA,  
LATE-SEASON SNOW IS POSSIBLE IN THE NORTHERN/CENTRAL PLAINS TO  
MIDWEST/GREAT LAKES THEN NORTHERN NEW ENGLAND.  
 
TATE/SCHICHTEL  
 
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  
 
HAZARDS:  
- HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL PLAINS, THE MIDDLE  
MISSISSIPPI VALLEY, AND THE OHIO VALLEY, THU-SAT, MAR 28-MAR 30.  
- HEAVY SNOW ACROSS PORTIONS OF THE NORTHERN AND CENTRAL ROCKIES,  
AND THE CENTRAL PLAINS, THU-FRI, MAR 28-MAR 29.  
- FLOODING POSSIBLE ACROSS PORTIONS OF THE NORTHERN PLAINS.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE  
MISSISSIPPI AND MISSOURI RIVER BASINS.  
- FLOODING LIKELY ACROSS PORTIONS OF THE MISSISSIPPI AND MISSOURI  
RIVER BASINS.  
 
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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