768  
FXUS02 KWBC 051620  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1219 PM EDT TUE JUN 05 2018  
 
VALID 12Z FRI JUN 08 2018 - 12Z TUE JUN 12 2018  
   
..PATTERN OVERVIEW
 
 
GUIDANCE SHOWS A GENERAL TROUGH-RIDGE-TROUGH PATTERN ALOFT  
PERSISTING THROUGH A MAJORITY OF THE FORECAST PERIOD. PASSAGE OF  
A VIGOROUS SHORTWAVE TROUGH ACROSS THE NORTHWEST DURING THE  
WEEKEND FOLLOWED BY LOW AMPLITUDE NORTH PACIFIC FLOW WILL LIKELY  
SERVE TO FLATTEN/BROADEN THE OVERALL MEAN TROUGH OVER WESTERN  
NORTH AMERICA LATE IN THE PERIOD AND PUSH THE DOWNSTREAM RIDGE  
INTO THE EAST-CENTRAL PART OF THE CONTINENT. HOWEVER NORTHEASTERN  
U.S. MEAN TROUGHING MAY BE RELUCTANT TO DEPART IN SPITE OF THE  
BROADENING EVOLUTION TO THE WEST. MEAN RIDGING ALOFT ANCHORED  
OVER THE SOUTHERN PLAINS MAY WEAKEN A BIT DURING THE WEEKEND AND  
REBUILD OVER/NEAR THE SOUTHERN ROCKIES AROUND NEXT TUE. FARTHER  
EAST THERE WILL BE A WEAKNESS ALOFT OVER THE EASTERN GULF OF  
MEXICO/FLORIDA. THIS FEATURE WILL WEAKEN GRADUALLY THROUGH THE  
PERIOD.  
 
   
..MODEL GUIDANCE/PREDICTABILITY EVALUATION/PREFERENCES
 
 
FOR THE DAYS 3-5 FRI-SUN PART OF THE FORECAST A BLEND OF LATEST  
OPERATIONAL MODEL GUIDANCE REPRESENTED CONSENSUS WELL FOR FEATURES  
THAT HAVE A REASONABLE DEGREE OF SYNOPTIC PREDICTABILITY. THE  
WESTERN-CENTRAL PATTERN WILL SHARPEN AS THE STRONG UPPER TROUGH  
AND LEADING SURFACE COLD FRONT REACH THE WESTERN U.S. WHILE THE  
CENTRAL CANADA RIDGE BUILDS. THIS WILL START THE PROCESS OF  
RELOADING THE EASTERN TROUGH ALOFT WITH INITIAL WEAK NORTHERN U.S.  
ENERGY CONTRIBUTING TO FRONTAL WAVINESS THAT REACHES THE EAST BY  
SUN. WAVE DETAILS WILL HAVE LOW PREDICTABILITY AND LIKELY DISPLAY  
MEANINGFUL RUN TO RUN VARIABILITY.  
 
BY DAYS 6-7 MON-TUE THE FORECAST STARTS TO INCORPORATE GEFS/ECMWF  
MEANS ALONG WITH LATEST OPERATIONAL RUNS AS DETAIL UNCERTAINTIES  
INCREASE. TIMING SPREAD DEVELOPS FOR THE WESTERN TROUGH WITH  
ECMWF/CMC ENSEMBLE MEMBERS TENDING TO SHOW FASTER EJECTION THAN A  
MAJORITY OF GEFS MEMBERS, WHILE SOLUTIONS ARE ALL OVER THE PLACE  
FOR THE SHORTWAVE DETAILS OF LOW AMPLITUDE FLOW IMMEDIATELY  
UPSTREAM. ISSUES WITH THE WESTERN TROUGH ULTIMATELY AFFECT THE  
FRONT THAT REACHES THE PLAINS. THE AVERAGE OF GUIDANCE YIELDS A  
FASTER ADJUSTMENT VERSUS CONTINUITY BUT WOULD LIKE TO AWAIT  
CONFIRMATION FROM FURTHER RUNS BEFORE TRENDING AS FAST AS THE 06Z  
GFS/00Z ECMWF RUNS. MODELS/MEANS APPEAR SOMEWHAT MORE AGREEABLE  
FOR PERSISTENCE OF THE NORTHEASTERN U.S. TROUGH BUT SOME  
INDIVIDUAL ENSEMBLE MEMBERS SHOW POTENTIAL FOR HIGHER HEIGHTS  
ALOFT LATE IN THE PERIOD. AT THIS TIME PREFER THE MAJORITY  
SCENARIO THAT FAVORS PERSISTENCE OF THIS TROUGH.  
 
   
..WEATHER HIGHLIGHTS AND HAZARDS
 
 
RIDGING ALOFT WILL SUPPORT HOT TEMPERATURES FROM THE DESERT  
SOUTHWEST EASTWARD INTO THE PLAINS, THOUGH WITH ANOMALIES FOR  
DAYTIME HIGHS TENDING TO BE LESS THAN PLUS 10F. GREATER ANOMALIES  
FOR MAX/MIN READINGS ARE LIKELY TO EXTEND FROM THE INTERMOUNTAIN  
WEST INTO THE NORTHERN-CENTRAL PLAINS FROM FRI INTO MON AHEAD OF  
THE COLD FRONT THAT PUSHES INTO THE WEST. THIS COLD FRONT WILL  
BRING SOME CHILLY TEMPERATURES INTO THE WEST WITH THE WEEKEND  
LIKELY FEATURING SOME HIGHS UP TO 10F OR SO BELOW NORMAL FROM THE  
NORTHERN HALF OF THE WEST COAST NORTHEASTWARD. UPPER TROUGHING  
WILL PROMOTE NEAR TO BELOW NORMAL READINGS NEAR THE EAST COAST.  
 
MULTIPLE MESOSCALE COMPLEXES WILL LIKELY EXTEND FROM THE NORTHERN  
PLAINS INTO THE GREAT LAKES/OHIO VALLEY REGION. THE WAVY FRONT  
FROM THE PLAINS TO EAST COAST LATE THIS WEEK THROUGH THE WEEKEND  
WILL PROVIDE A SIGNIFICANT FOCUS FOR LOCALLY HEAVY/STRONG  
CONVECTION. AMPLIFYING UPPER TROUGHING WILL ALSO PROMOTE WET  
CONDITIONS OVER THE EAST DURING THE WEEKEND. FARTHER SOUTH,  
EXPECT SHOWERS/STORMS ACROSS FLORIDA AND PARTS OF THE SOUTHEAST,  
ESPECIALLY LATE THIS WEEK INTO THE WEEKEND IN ASSOCIATION WITH THE  
WEAKNESS ALOFT. THE STRONG UPPER TROUGH/SURFACE FRONT AFFECTING  
THE WEST WILL BRING ABUNDANT PRECIP TO THE PACIFIC  
NORTHWEST/NORTHERN ROCKIES AND EVENTUALLY MAY GENERATE SOME  
CONVECTION OVER THE NORTHERN PLAINS.  
 
RAUSCH  
 
WPC MEDIUM RANGE FORECASTS OF 500 MB HEIGHTS, SURFACE SYSTEMS,  
WEATHER GRIDS, QUANTITATIVE PRECIPITATION, AND WINTER WEATHER  
OUTLOOK PROBABILITIES CAN BE FOUND AT:  
 
HTTP://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF  
HTTP://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF  
HTTP://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML  
HTTP://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML  
HTTP://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
 

 
 
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