110  
FXUS02 KWBC 051937  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
337 PM EDT FRI APR 05 2019  
 
VALID 12Z MON APR 08 2019 - 12Z FRI APR 12 2019  
   
..OVERVIEW AND GUIDANCE ASSESSMENT/PREFERENCES
 
 
A MODERATELY PROGRESSIVE PATTERN IS EXPECTED ACROSS THE CONUS  
DURING THE MEDIUM RANGE WITH SPLITTING OF FLOW ACROSS THE WEST  
RESULTING A SERIES OF SOUTHERN STREAM SYSTEMS TRAVERSING THE  
NATION. THE FIRST OF THESE SHOULD CROSS THE LOWER MISSISSIPPI  
VALLEY/SOUTHEAST MON-TUE. THE SECOND AND MORE SIGNIFICANT OF THESE  
FEATURES SHOULD MOVE INTO THE WEST COAST MON-TUE BEFORE AMPLIFYING  
ACROSS THE ROCKIES ON WED AND PERHAPS DEVELOPING A CLOSED UPPER  
LOW ACROSS THE CENTRAL U.S. WED NIGHT-THU. FINALLY, A THIRD  
UPPER-LEVEL WAVE SHOULD AMPLIFY ALONG THE WEST COAST THU-FRI AS  
THE STRONG CENTRAL U.S. SYSTEM MOVES INTO THE LOWER GREAT LAKES.  
MEANWHILE, A NUMBER OF LOWER AMPLITUDE NORTHERN STREAM SHORTWAVES  
WILL TRAVERSE AREAS FROM THE NORTHERN PLAINS/MIDWEST TO THE  
NORTHEAST.  
 
IN GENERAL A BLEND OF THE 00Z ECMWF/UKMET/CMC WAS PREFERRED AS A  
FORECAST STARTING POINT DURING DAYS 3-5 (MON-WED). THESE SOLUTIONS  
HANDLED SIGNIFICANT FEATURES SIMILARLY DURING THIS TIME PERIOD.  
THE SHORTWAVE REACHING THE WEST COAST DURING THIS TIME FRAME  
SHOWED THE MOST SUBSTANTIAL DIFFERENCES AMONG THE GUIDANCE, WITH  
THE GFS CONTINUING TO SHOW A SLOWER PROGRESSION/LATER ARRIVAL TO  
THE COAST RELATIVE TO THE PREFERRED SOLUTIONS. THE GFS CONTINUED  
TO LAG THE PREFERRED CONSENSUS SOLUTION EVEN AS THE WESTERN SYSTEM  
REACHES THE CENTRAL ROCKIES TUE NIGHT-WED AND SIGNIFICANT  
CYCLOGENESIS COMMENCES ACROSS THE CENTRAL HIGH PLAINS. AS A STRONG  
LOW PRESSURE SYSTEM LIKELY CROSSES FROM THE CENTRAL PLAINS TO THE  
MIDWEST WED INTO THU, THERE WAS RELATIVELY GOOD CLUSTERING AMONG  
ECENS AND CMCE MEMBERS IN THE VICINITY OF THE DETERMINISTIC 00Z  
ECMWF. THE GFS BEGINS TO SUFFER FROM THE OPPOSITE ISSUE TO EARLIER  
IN THE PERIOD, SHOWING A MUCH WEAKER SYSTEM ALOFT AND RACING THE  
SURFACE LOW QUICKLY EASTWARD INTO THE OHIO VALLEY, WITH THE CMC  
SOMEWHERE BETWEEN THE ECMWF AND GFS. GIVEN THE GOOD CLUSTERING  
AROUND THE ECMWF, THE FORECAST DURING DAYS 6-7 (THU-FRI) WAS  
COMPRISED OF A THREE-PART BLEND INCLUDING THE ECMWF AND THE  
ECENS/NAEFS ENSEMBLE MEANS. THIS APPROACH ALSO WORKED WELL FOR THE  
NEXT ROUND OF ENERGY DROPPING SOUTHWARD/AMPLIFYING ACROSS THE  
WESTERN U.S. LATE NEXT WEEK. MODEL SOLUTIONS HAVE SHOWN A HIGH  
DEGREE OF RUN-TO-RUN VARIABILITY WITH THAT FEATURE, VARYING  
BETWEEN A MORE OPEN WAVE OR ONE THAT QUICKLY DEEPENS INTO A CLOSED  
UPPER LOW OVER SOUTHERN CALIFORNIA. WITH ENSEMBLE MEANS SIMILAR  
HERE, A MAJORITY ENSEMBLE-BASED APPROACH WAS FAVORED.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
SHOWERS AND THUNDERSTORMS WITH LOCALLY HEAVY RAINS ARE POSSIBLE  
FROM THE SOUTHEAST/TENNESSEE VALLEY TO THE MID-ATLANTIC MON-TUE AS  
THE FIRST SOUTHERN STREAM SHORTWAVE/LOW PRESSURE SYSTEM TRAVERSE  
THOSE AREAS. A NORTHERN STREAM SYSTEM MAY ALSO BRING A ROUND OF  
SNOW TO PORTIONS OF NORTHERN NEW ENGLAND MON/MON NIGHT. THE SECOND  
AND MOST SIGNIFICANT SOUTHERN STREAM SYSTEM DURING THE PERIOD  
SHOULD PRODUCE WIDESPREAD RAINS AND MOUNTAIN SNOWS (SOME  
POTENTIALLY HEAVY) FROM CALIFORNIA TO THE PACIFIC NORTHWEST AND  
THEN INLAND ACROSS THE CENTRAL/NORTHERN ROCKIES MON-TUE. AS THE  
SYSTEM REACHES THE CENTRAL U.S. BY THE MIDDLE OF NEXT WEEK, A BAND  
OF DYNAMICALLY FORCED PRECIPITATION IS EXPECTED TO DEVELOP FROM  
THE NORTHERN HIGH PLAINS TO THE MIDWEST AND GREAT LAKES. WHILE THE  
DELINEATION OF PRECIPITATION TYPES IS UNCLEAR AT THIS TIME, A BAND  
OF POTENTIALLY HEAVY SNOW APPEARS PROBABLE NORTH AND WEST OF THE  
SURFACE LOW TRACK, WITH A TRANSITION ZONE AND AREAS OF POTENTIALLY  
HEAVY RAIN AS WELL. RELATIVELY WEAK MOISTURE RETURN AND A STRONG  
CAPPING INVERSION IN THE WARM SECTOR OF THE SYSTEM SHOULD KEEP  
SHOWERS AND THUNDERSTORMS LESS EXTENSIVE IN COVERAGE THAN WOULD  
OTHERWISE BE EXPECTED, BUT ANY CONVECTIVE ACTIVITY THAT IS ABLE TO  
DEVELOP COULD BE POTENTIALLY STRONG GIVEN THE DYNAMIC NATURE OF  
THE LOW PRESSURE SYSTEM.  
 
WARM TEMPERATURES ARE EXPECTED ACROSS MUCH OF THE CENTRAL AND  
EASTERN U.S. DURING THE EARLY TO MIDDLE PORTION OF NEXT WEEK AHEAD  
OF THE SIGNIFICANT LOW PRESSURE SYSTEM. HIGH TEMPERATURES RANGING  
FROM 10 TO 20 DEG F ABOVE AVERAGE ARE POSSIBLE MON-WED OVER A  
LARGE AREA, WITH THE GREATER ANOMALIES ACROSS THE PLAINS. COLDER  
AIR AND FURTHER AMPLIFICATION OF UPPER TROUGHING ACROSS THE WEST  
IN THE WAKE OF THE MID-WEEK SYSTEM WILL SUPPORT BELOW AVERAGE  
TEMPERATURES, WITH HIGHS 5 TO 15 DEG BELOW AVERAGE ACROSS MUCH OF  
THE INTERIOR WEST BY WED AND INTO THE CENTRAL/NORTHERN PLAINS BY  
THU-FRI.  
 
RYAN  
 
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 PRECIPITATION ACROSS PORTIONS OF CALIFORNIA AND THE  
PACIFIC NORTHWEST, MON, APR 8.  
- HEAVY PRECIPITATION FROM PORTIONS OF THE CENTRAL GREAT BASIN AND  
ROCKIES TO THE UPPER MIDWEST, TUE-THU, APR 9-APR 11.  
- HEAVY PRECIPITATION ACROSS PORTIONS OF THE NORTHERN ROCKIES,  
MON-TUE, APR 8-APR 9.  
- HEAVY RAIN ACROSS PORTIONS OF CENTRAL PLAINS AND UPPER MIDWEST,  
WED-THU, APR 10-APR 11.  
- HEAVY RAIN ACROSS PORTIONS OF THE GULF COAST AND THE SOUTHERN  
APPALACHIANS, MON, APR 8.  
- HEAVY SNOW ACROSS PORTIONS OF THE NORTHEAST, MON, APR 8.  
- FLOODING POSSIBLE ACROSS PORTIONS OF THE NORTHERN GREAT BASIN.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE  
MISSISSIPPI AND MISSOURI RIVER BASINS.  
- FLOODING LIKELY ACROSS PORTIONS OF THE MISSOURI RIVER BASIN AND  
THE UPPER MISSISSIPPI VALLEY.  
- HIGH WINDS ACROSS PORTIONS OF THE SOUTHERN ROCKIES AND THE  
SOUTHERN AND CENTRAL HIGH PLAINS, TUE-THU, APR 9-APR 11.  
- ENHANCED WILDFIRE RISK ACROSS PORTIONS OF THE THE SOUTHERN  
ROCKIES, THE SOUTHERN PLAINS, AND THE SOUTHWEST, WED, APR 10.  
 
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  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page