678  
FXUS02 KWBC 040646  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
245 AM EDT MON JUN 04 2018  
 
VALID 12Z THU JUN 07 2018 - 12Z MON JUN 11 2018  
   
..HEAT WAVE FROM THE DESERT SOUTHWEST TO THE SOUTH-CENTRAL U.S
 
 
   
..PATTERN OVERVIEW
 
 
TWO PRIMARY SYNOPTIC-SCALE FEATURES WILL BE FOCAL POINTS DURING  
THE PERIOD SPANNING JUNE 7-11, EACH OF WHICH WILL BE RATHER  
ANOMALOUS RELATIVE TO CLIMATOLOGY. A SPRAWLING UPPER RIDGE ACROSS  
THE SOUTH-CENTRAL U.S. AS WELL AS A DEEP-LAYERED CYCLONE OFF THE  
BRITISH COLUMBIA COAST ARE FORECAST TO FEATURE ANOMALIES ON THE  
ORDER OF 2 SIGMA. THIS PARTICULAR REGIME IS EXPECTED TO CHANGE  
VERY LITTLE DURING THE PERIOD OF INTEREST, GENERALLY SUSTAINING AN  
OMEGA BLOCK SETUP AS LOWER HEIGHTS ACROSS EASTERN NORTH AMERICA  
FILL OUT THIS SIGNATURE. THE LARGEST CHANGES ARE EXPECTED DURING  
THE DAY 5-7, JUNE 9-11, TIMEFRAME AS AN IMPRESSIVE LONGWAVE TROUGH  
ACCELERATES THROUGH THE PACIFIC NORTHWEST. ULTIMATELY, THIS SHOULD  
HELP ERODE THE NORTHERN EXTENT OF THE UPPER ANTICYCLONE OVER THE  
SOUTH-CENTRAL STATES. ACROSS THE SOUTHEASTERN U.S., A PERSISTENT  
MID/UPPER-LEVEL WEAKNESS WILL LINGER IN THE VICINITY OF FLORIDA  
FOR MUCH OF THE PERIOD. THIS AREA SHOULD BE JUXTAPOSED BY A RATHER  
HEALTHY MOISTURE PLUME AS EVIDENCED BY THE 1.50 INCH AND ABOVE  
PRECIPITABLE WATER VALUES.  
 
   
..MODEL GUIDANCE/PREDICTABILITY EVALUATION/PREFERENCES
 
 
STARTING ACROSS EASTERN NORTH AMERICA, A CONVEYOR BELT OF  
LOW-AMPLITUDE SHORTWAVES SHOULD MIGRATE ACROSS QUEBEC WHILE  
POTENTIALLY GRAZING NORTHERN NEW ENGLAND. A MORE AMPLIFIED SYSTEM  
WILL LIKELY TAKE SHAPE BY LATE IN THE WEEKEND INTO THE FOLLOWING  
WEEK WHICH ULTIMATELY SHIFTS A WAVY FRONTAL ZONE SOUTH/EAST TOWARD  
THE CAROLINAS BY 11/1200Z. OVERALL DIFFERENCES ARE NOT TERRIBLY  
SIGNIFICANT HERE WITH THE GLOBAL GUIDANCE SUITE ALL IN FAVOR OF  
THIS EVOLUTION. LIKEWISE, THERE IS SOLID AGREEMENT REGARDING THE  
POSITION OF THE WEAKNESS ACROSS THE SOUTHEASTERN U.S. INTO THE  
EASTERN GULF OF MEXICO. EVENTUALLY THE SIGNAL SHEARS OUT OVER THE  
WEEKEND ALTHOUGH MULTIPLE EMBEDDED VORTICITY CENTERS ARE LIKELY TO  
STILL SPIN ABOUT THE REGION IN ITS WAKE.  
 
MOVING TO THE CENTER OF THE NATION, A STOUT UPPER RIDGE WILL BE A  
FIXTURE FOR THE FORESEEABLE FUTURE WITH THE 588-DM HEIGHT CONTOUR  
OF THE MID-LEVEL HEIGHTS EXTENDING UP TOWARD THE NORTHERN PLAINS  
AT TIMES. LIKE YESTERDAY, THE 12Z CMC SEEMED TO BE MORE SUPPRESSED  
WITH THIS RIDGE WHICH IS DIRECTLY IN RESPONSE TO THE CREATION OF  
SIZABLE PERTURBATIONS ROUNDING THE RIDGE AXIS. OTHERWISE,  
SOLUTIONS APPEAR TO BE WITHIN TOLERANCE INTO THE WEEKEND AS  
EVENTUAL UPSTREAM PACIFIC HEIGHT FALLS BEGIN TO DENT THE NORTHERN  
EXTENT OF THE ANTICYCLONE CENTER. MUCH OF THIS OF COURSE IS BASED  
ON THE LEVEL OF PACIFIC AMPLIFICATION WHICH REMAINS SOMEWHAT  
NEBULOUS AT THIS TIME.  
 
OVER THE WEST COAST, A SEMI-PERMANENT UPPER LOW REMAINS FIXED OFF  
THE BRITISH COLUMBIA COAST. EVENTUALLY A NOTABLE SHORTWAVE ROUNDS  
THE BASE OF THIS TROUGH WITH POTENT HEIGHT FALLS ACCELERATING  
ACROSS THE PACIFIC NORTHWEST BY SATURDAY. ENSEMBLE SPAGHETTI PLOTS  
VARY WITH THE DEPTH OF THIS TROUGH AS WELL AS THE TEMPORAL  
EVOLUTION. IT APPEARS THE GFS/ECMWF HAVE TAKEN TURNS WITH BEING  
MORE ANOMALOUS THAN THE CONSENSUS SOLUTION AS THE TROUGH MOVES  
ACROSS THE PACIFIC NORTHWEST POTENTIALLY DOWN TO NORTHERN  
CALIFORNIA. MORE SPECIFICALLY, IT WAS THE 00Z GFS YESTERDAY AND  
THE 12Z ECMWF. SUCH SOLUTIONS HAVE GAINED SOME COMPANY WITH THE  
00Z CMC JOINING IT, ALBEIT IN A MUCH SLOWER FASHION.  
 
WHILE MANY UNCERTAINTIES EXIST IN THE PATTERN, MOST ARE ON THE  
MESOSCALE REVOLVING AROUND THE "RIDGE ROLLERS" WHICH CANNOT BE  
ADEQUATELY FORECASTED AT THIS TIME. AS SUCH, FELT A  
MULTI-OPERATIONAL MODEL BLEND WOULD SUFFICE THROUGH DAY 4/FRIDAY  
UTILIZING A COMBINATION OF THE 18Z/12Z GFS WITH THE 12Z  
ECMWF/UKMET SOLUTIONS. THEREAFTER, REMOVED THE 12Z UKMET IN FAVOR  
OF A CONSENSUS OF THE OPERATIONAL GFS/ECMWF MODELS IN CONJUNCTION  
WITH THEIR RESPECTIVE ENSEMBLE MEANS. THE BLEND BECAME FAIRLY  
HEAVY IN ENSEMBLE USE BY THE END OF THE FORECAST WITH SLIGHTLY  
MORE WEIGHTING TOWARD THE 18Z GEFS MEAN.  
 
   
..WEATHER HIGHLIGHTS AND HAZARDS
 
 
THE HEAT WAVE WILL BE THE MAIN STORY WITH READINGS 100 DEGREES  
PLUS ANYWHERE FROM THE DESERT SOUTHWEST EASTWARD ALONG THE MEXICAN  
BORDER INTO THE STATE OF TEXAS. DEPARTURES FROM CLIMATOLOGY SHOULD  
BE AROUND 10 DEGREES ALTHOUGH SLIGHTLY HIGHER NUMBERS CAN BE FOUND  
FARTHER NORTH INTO THE REMAINING GREAT PLAINS STATES AND INTO THE  
INTERMOUNTAIN WEST/ROCKY MOUNTAIN CHAIN. WIDESPREAD 80S AND 90S  
ARE LIKELY OVER THESE LOCATIONS ACCOMPANIED BY TEMPERATURE  
ANOMALIES IN THE 10 TO 15 DEGREE RANGE. REGARDING COOL SPOTS,  
THURSDAY SHOULD PROVE TO BE NEAR OR SLIGHTLY BELOW CLIMATOLOGY  
ACROSS THE EAST COAST WITH SUCH CONDITIONS PERSISTING INTO THE  
WEEKEND ACROSS FLORIDA GIVEN IMMENSE CLOUD COVER AND RAINFALL.  
ELSEWHERE, DEEP UPPER TROUGHING OVER THE PACIFIC NORTHWEST WILL  
HOLD TEMPERATURES AROUND 5 TO 10 DEGREES BELOW AVERAGE FROM  
SATURDAY ONWARD.  
 
IT SHOULD REMAIN INTERMITTENTLY WET OVER THE SOUTHEASTERN U.S.,  
PARTICULARLY FLORIDA, GIVEN A STAGNANT UPPER TROUGH/WEAKNESS IN  
CONJUNCTION WITH AN ANOMALOUS MOISTURE FEED. BACK TOWARD THE  
MIDDLE OF THE COUNTRY, MULTIPLE CONVECTIVE COMPLEXES ARE LIKELY TO  
ERUPT NORTH OF THE RIDGE WITH PROPAGATION DOWNSTREAM LIKELY TOWARD  
THE MIDDLE MISSISSIPPI VALLEY AND INTO THE GREAT LAKES/OHIO  
VALLEY. DETAILS WOULD BE FUZZY AT BEST THIS FAR INTO THE FORECAST  
BUT EXPECT BOUTS OF HEAVY RAINFALL ACCOMPANIED BY DISCERNIBLE  
SEVERE WEATHER THREATS. ELSEWHERE, IT SHOULD PROVE TO BE QUITE WET  
OVER THE PACIFIC NORTHWEST GIVEN THE DEEP CYCLONIC FLOW OVERHEAD.  
STRONG FORCING WITH THE TROUGH AND EVENTUAL FRONTAL PASSAGE COULD  
SPREAD CONSIDERABLE EARLY/MID JUNE PRECIPITATION TO THE REGION.  
 
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  
 
RUBIN-OSTER  
 

 
 
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