825  
FXUS02 KWBC 010644  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
243 AM EDT WED MAY 01 2019  
 
VALID 12Z SAT MAY 04 2019 - 12Z WED MAY 08 2019  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
WPC MEDIUM RANGE SURFACE/FRONTS AND 500 MB PROGS WERE MAINLY  
COMPOSED FROM A COMPOSITE OF COMPATABLE GFS/ECMWF/UKMET/CANADIAN  
MID-LARGER SCALE MASS FIELD GUIDANCE THIS WEEKEND. TRANSITIONED TO  
AN ENSEMBLE MEAN BASED FORECAST EARLY-MID NEXT WEEK AMID GROWING  
FORECAST SPREAD AND UNCERTAINTY. THIS BLENDED SOLUTION ACTS TO  
MITIGATE EMBEDDED SMALLER SCALE IMPULSE TIMING AND CONVECTION  
GENESIS UNCERTAINTIES AND MAINTAINS GOOD OVERALL WPC CONTINUITY.  
THE WPC FORECAST DID FAVOR ECMWF/ECMWF ENSEMBLES PRECIPITATION  
THAT BETTER FIT THE FLOW IN SHOWING MORE SOUTHWARD CONVECTIVE  
TENDANCIES INTO DEEPENING MOISTURE.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
A SLOW MOVING AND WAVY TRAILING FRONT WILL POOL MOISTURE TO FUEL A  
RISK OF LOCALLY HEAVY RAINS/THUNDERSTORMS WITH CELL TRAINING AND A  
LOCAL RUNOFF ISSUE FOCUS FROM THE LOWER MISSISSIPPI VALLEY TO THE  
MID-ATLANTIC THIS WEEKEND.  
 
UPSTREAM, CLOSED LOW/TROUGH ENERGY AND HEIGHT FALLS ARE EXPECTED  
TO MOVE INLAND INTO CA/SOUTHWEST EARLY NEXT WEEK IN THE SPLIT  
SOUTHERN STREAM. THIS MAY SUPPORT SCATTERED CA TO GREAT  
BASIN/ROCKIES CONVECTION. FLOW PROGRESSION MAY THEN RENEW LEAD  
CONVECTIVE FOCUS DOWNSTREAM OVER THE SOUTH-CENTRAL U.S.  
 
MEANWHILE, NORTHERN STREAM SYSTEMS WILL MEANWHILE PROGRESS OVER  
SOUTHERN CANADA AND EFFECT THE U.S. NORTHERN TIER. THESE WOULD  
SUPPORT PRECIPITATION/CONVECTION AHEAD OF A COOLING MAIN CLOSED  
LOW/TROUGH AND LEAD WEATHER FOCUSING SURFACE FRONTAL SYSTEMS. THIS  
AMPLIFIED MAIN SYSTEM WILL TRACK FROM S-CENTRAL CANADA THIS  
WEEKEND TO EASTERN CANADA EARLY NEXT WEEK. A STALLING TRAILING  
FRONT UNDERNEATH INTO WILL PERIODICALLY FOCUS ACTIVITY OVER THE  
NORTHERN ROCKIES, CENTRAL PLAINS, AND FROM THE MIDWEST TO THE  
NORTHEAST. THIS MAY INCLUDE SOME MAY SNOWS FOR THE ROCKIES AND  
FROM NORTHERN MINNESOTA TO THE UPPER GREAT LAKES.  
 
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  
 
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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