280  
FXUS02 KWBC 020654  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
254 AM EDT THU MAY 02 2019  
 
VALID 12Z SUN MAY 05 2019 - 12Z THU MAY 09 2019  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
A LEAD LOW WILL LIFT OFFSHORE SUNDAY INTO MONDAY TO PRODUCE AN  
AREA OF ENHANCED RAINS OVER THE NORTHERN MID-ATLANTIC AND SOUTHERN  
NEW ENGLAND. A TRAILING FRONT BACK ACROSS THE SOUTHEAST, THE GULF  
AND THE SOUTHERN PLAINS WILL MEANWHILE REMAIN A FOCUS FOR LOCAL  
HEAVY RAIN/THUNDERSTORMS.  
 
WELL UPSTREAM, UPPER RIDGING WILL REMAIN ANCHORED OVER THE  
NORTHEASTERN PACIFIC WHICH WILL KEEP DRIVE SPLIT FLOW OVER THE  
LOWER 48 NEXT WEEK. AN UNSETTLING AND INITIALLY CLOSED SOUTHERN  
STREAM LOW WILL WORK INTO CALIFORNIA AND THE SOUTHWEST AS A SERIES  
OF COOLING AND PRECIPITATION FOCUSING NORTHERN STREAM SYSTEMS  
SKIRT ALONG THE US/CANADIAN BORDER.  
 
EXPECT SCATTERED SHOWERS AND SOME CONVECTION INTO THE GREAT  
BASIN/ROCKIES. PRECIPITATION (GENERALLY RAIN WITH HIGH SNOW  
LEVELS) WILL MOSTLY FOCUS ON HIGHER ELEVATIONS, BUT SOME VALLEY  
RAIN. MOISTURE INFLUX INTO THE REGION APPEARS TO BE MODEST. THIS  
PATTERN WILL ALSO FAVOR PERIODS OF ORGANIZED STRONG CONVECTION  
WITH A CELL TRAINING/EXCESSIVE RAINFALL/RUNOFF THREAT AS A SERIES  
OF HARD TO TIME NORTHERN AND SOUTHERN STREAM IMPULSES EJECT OVER  
THE EAST-CENTRAL U.S. OVERTOP A BUILDING UPPER RIDGE OVER THE DEEP  
SOUTH. SYSTEMS MAY BE PRIMED TO PERIODICALLY TAP DEEPENING  
MOISTURE AND INSTABILITY POOLED BY RETURN GULF OF MEXICO INFLOW  
INTO TWO SURFACE FRONTAL SYSTEMS/ENHANCED BAROCLINIC ZONES.  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
THE WPC MEDIUM RANGE PRODUCT SUITE WAS COMPOSED FROM A BLEND OF  
COMPATABLE GFS/ECMWF/UKMET/CANADIAN MODEL GUIDANCE SUNDAY. OPTED  
TO TRANSITION TO AN ENSEMBLE MEAN BASED FORECAST STARTING MONDAY  
AMID GROWING FORECAST SPREAD AND UNCERTAINTY, PRIMARILY WITH  
SMALLER SCALE IMPULSE TIMING/INTERACTIONS AND CONVECTION GENESIS.  
THIS MAINTAINS GOOD WPC CONTINUITY.  
 
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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