176  
FXUS02 KWBC 290457  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1256 AM EDT FRI JUN 29 2018  
 
VALID 12Z MON JUL 02 2018 - 12Z FRI JUL 06 2018  
 
...LONG DURATION HEAT WAVE TO CONTINUE OVER THE NORTHEASTERN  
PORTION OF THE LOWER 48...  
   
..HEAVY RAIN THREAT FOR THE NORTHERN GULF COAST
 
 
   
..OVERVIEW
 
 
MODELS AND ENSEMBLES REMAIN IN GOOD AGREEMENT NEXT WEEK WITH THE  
UPPER PATTERN THAT WILL FEATURE AN EXPANDING UPPER HIGH THAT WILL  
LIKELY STRETCH FROM SOUTHERN CALIFORNIA NORTHEASTWARD TO THE  
APPALACHIANS. THIS WILL SUPPORT WELL ABOVE AVERAGE TEMPERATURES  
OVER THE EASTERN GREAT LAKES/NORTHEAST/MID-ATLANTIC WITH DAILY  
RECORD HIGHS LIKELY TO BE BROKEN. ONE UPPER LOW WILL LINGER OVER  
THE PACIFIC NORTHWEST AND ANOTHER OFF THE SOUTHEAST COAST WITH YET  
ANOTHER TO THE SOUTHWEST OF THE UPPER HIGH OVER THE GULF COAST. A  
SURFACE FRONTAL BOUNDARY WILL LIE ASTRIDE THE NORTH/NORTHWEST SIDE  
OF THE EXPANDING 594-597DM (MAYBE 600DM?) UPPER HIGH -- ROUGHLY  
FROM THE PACIFIC/INTERIOR WEST THROUGH THE NORTHERN PLAINS INTO  
THE GREAT LAKES.  
 
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
THE LATEST DETERMINISTIC MODELS FORMED A GOOD STARTING POINT FOR  
THE FORECAST (GFS/ECMWF/CANADIAN/UKMET) THOUGH THE 12Z/18Z GFS AND  
MOST GEFS MEMBERS WERE SLOWER THAN THE REST OF THE  
MODELS/ENSEMBLES TO BRING THE UPPER LOW SOUTHWARD TOWARD WESTERN  
WASHINGTON EARLY NEXT WEEK. AFTER THAT, GFS/ECMWF FALL WITHIN THE  
ENSEMBLE SPREAD AND A BLEND WITH THEIR ENSEMBLES TEMPERED THE  
DIFFERENCES OUT TO NEXT FRIDAY. BIGGEST TROUBLE SPOT MAY BE OFF  
THE EAST COAST WITH THE UPPER LOW -- BOTH IN ITS TRACK AND  
STRENGTH (AND EVENTUAL IMPACT VIA PRECIPITATION).  
 
   
..WEATHER THREATS/HIGHLIGHTS
 
 
ASCENDANT UPPER HIGH WILL FORCE PRECIPITATION AROUND ITS  
CIRCULATION, FIRSTLY IN THE NORTHWEST IN CONJUNCTION WITH  
SOUTHWEST FLOW AHEAD OF THE UPPER LOW ATOP THE SURFACE BOUNDARY.  
THIS WILL EXTEND EASTWARD ACROSS MONTANA INTO THE PLAINS AND GREAT  
LAKES AS THE SURFACE LOW WANDERS THROUGH SOUTHERN CANADA. A LEAD  
FRONT INTO THE NORTHEAST NEXT MON/TUE WILL DO LITTLE BUT KNOCK  
TEMPERATURES A FEW DEGREES AND PERHAPS TOUCH OFF A SHOWER/STORM AS  
IT DISSIPATES BY WEDNESDAY. THE SOUTHEAST INTO FLORIDA MAY SEE AN  
INCREASE IN PRECIPITATION SHOULD THE ATLANTIC UPPER LOW WOBBLE  
WESTWARD TOWARD THE CAROLINAS LATER IN THE WEEK. FINALLY, THE MOST  
SIGNIFICANT PRECIPITATION MAY LIE ALONG THE GULF COAST FROM LA/MS  
WESTWARD TO THE UPPER TEXAS COAST AS A WEAKNESS DRIFTS WESTWARD.  
ECMWF/UKMET/CANADIAN SEEMED A BIT AGGRESSIVE/WET BUT WITH PLENTY  
OF MOISTURE TO TAP (PW ANOMALIES ABOUT +2 TO +3 SIGMA) HEAVY  
RAINFALL IS CERTAINLY A POSSIBILITY.  
 
TEMPERATURES WILL BE NEAR/ABOVE RECORDS IN THE NORTHEAST EARLY IN  
THE WEEK WITH A SLOW DOWNWARD TREND (BUT STILL ABOVE AVERAGE) BY  
LATE IN THE WEEK AS THE CORE OF THE UPPER HIGH MOVES  
SOUTHWESTWARD. WIDESPREAD 90S ARE FORECAST FOR MOST OF THE LOWER  
48 STATES WHILE COOLER THAN AVERAGE TEMPERATURES ARE EXPECTED FOR  
THE NORTHWEST AND ALSO ALONG THE GULF COAST (ESPECIALLY MAX TEMPS)  
GIVEN EXTENSIVE CLOUD COVER AND RAIN.  
 
FRACASSO  
 
WPC MEDIUM RANGE FORECASTS OF 500 MB HEIGHTS, SURFACE SYSTEMS,  
WEATHER GRIDS, QUANTITATIVE PRECIPITATION, AND WINTER WEATHER  
OUTLOOK PROBABILITIES ARE 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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