711  
FXUS02 KWBC 281600  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1200 PM EDT THU JUN 28 2018  
 
VALID 12Z SUN JUL 01 2018 - 12Z THU JUL 05 2018  
   
..OVERVIEW AND GUIDANCE EVALUATION/PREFERENCES
 
 
MODEL GUIDANCE THIS MORNING CONTINUES TO INDICATE THE LIKELIHOOD  
OF A HEAT WAVE EXPANDING INTO THE EAST COAST THIS WEEKEND AND  
CONTINUE WELL INTO NEXT WEEK AS A STRONG SUBTROPICAL HIGH BECOMES  
A DOMINANT FEATURE. IN CONTRAST, AN UPPER-LEVEL VORTEX DROPPING  
DOWN FROM THE GULF OF ALASKA WILL KEEP A TROUGH IN PLACE ACROSS  
THE WESTERN U.S. INTO THE MIDDLE OF NEXT WEEK. THERE ARE  
DIFFERENCES IN THE WAY THE SMALLER SCALE SHORTWAVES ARE HANDLED IN  
THE MODELS BUT THE GENERAL CONSENSUS IS FOR A POSITIVELY TILTED  
TROUGH TO MAINTAIN ITSELF NEAR OR JUST OFF THE COAST OF THE  
PACIFIC NORTHWEST AS A CLOSED UPPER-LEVEL CENTER ATTEMPTS TO FORM.  
TOWARD THE MIDDLE OF NEXT WEEK, MODELS ARE UNANIMOUS ON BUILDING  
THE SUBTROPICAL HIGH WESTWARD ACROSS THE CENTRAL U.S. INTO THE  
ROCKIES, AND BEGINS TO PUSH THE TROUGH SLIGHTLY OFF THE WEST COAST.  
 
IT IS ALSO WORTH-MENTIONING THAT UNDERNEATH THE STRONG SUBTROPICAL  
HIGH OVER THE U.S., MODELS ARE INDICATING SOME SORT OF WEAK  
UPPER-LEVEL DISTURBANCE (NOTABLY THE ECMWF) MOVING GENERALLY  
WESTWARD ACROSS THE SOUTHEAST U.S. DURING THE WEEKEND AND THEN  
ALONG THE GULF COAST EARLY NEXT WEEK, REACHING THE TEXAS COAST BY  
NEXT THURSDAY. IT APPEARS THAT CONVECTION INTERACTING WITH A WEAK  
COASTAL BOUNDARY WILL KEEP A THREAT OF LOCALLY HEAVY RAIN ALONG  
THE GULF COAST INTO THE MIDDLE OF NEXT WEEK. IT REMAINS TO BE  
SEEN WHETHER A SURFACE CIRCULATION WILL BE SPAWNED NEAR THE  
BOUNDARY.  
 
IN ADDITION, MODELS ARE SHOWING THE POSSIBILITY OF A CYCLONIC  
CIRCULATION FORMING IN THE VICINITY OF BERMUDA DURING THE WEEKEND  
AS A RESULT OF WAVE-BREAKING UNDERNEATH THE STRONG SUBTROPICAL  
HIGH. THIS CIRCULATION IS THEN CARRIED GENERALLY WESTWARD TOWARD  
THE SOUTHEAST U.S. BY DAY 7 NEXT THURSDAY.  
 
WITH THE ABOVE CONSIDERATIONS, THE WPC MORNING GRID PACKAGE IS A  
CONSENSUS OF THE 00Z ECMWF/EC MEAN AND THE 06Z GFS/GEFS (WITH A  
SMALL PERCENTAGE FROM THE 00Z CANADIAN MODEL), TRENDING TOWARD 70  
PERCENT OF THEIR ENSEMBLE MEANS FOR DAYS 6 AND 7.  
 
KONG  
   
..WEATHER THREATS/HIGHLIGHTS
 
 
THE UPPER GREAT LAKES TO PLAINS FRONT AS OF EARLY SUN WILL BRING  
AREAS OF SHOWERS AND THUNDERSTORMS INTO THE EAST. MOST HEAVY  
ACTIVITY SHOULD BE FAIRLY LOCALIZED AS UPPER DYNAMICS LIFT INTO  
CANADA. THE TRAILING PART OF THE FRONT OVER THE PLAINS WILL LIFT  
BACK NORTH AS A WARM FRONT DURING THE PERIOD AND HELP TO FOCUS  
PERIODS OF CONVECTION, WITH BEST POTENTIAL FOR HEAVIER ACTIVITY  
OVER THE NORTHERN PLAINS/UPPER MIDWEST REGIONS. LOCATIONS ALONG  
AND/OR INLAND FROM THE GULF COAST MAY ALSO SEE ONE OR MORE DAYS OF  
SIGNIFICANT RAINFALL ENHANCED BY UPPER LEVEL ENERGY AND A WEAK  
SURFACE REFLECTION. CONFIDENCE IS LOW IN THE SPECIFICS OF THESE  
FEATURES BUT THE OVERALL PATTERN IS FAVORABLE FOR RAINFALL.  
BETWEEN THIS ACTIVITY AND THE EASTERN FRONT, EXPECT SOME PERIODIC  
CONVECTION OF VARYING INTENSITY IN RESPONSE TO DAYTIME HEATING.  
PORTIONS OF THE NORTHWEST MAY SEE SCATTERED AND MOSTLY  
LIGHT-MODERATE RAINFALL IN RESPONSE TO THE UPPER TROUGH DEVELOPING  
NEAR THE WEST COAST. PARTS OF THE SOUTHERN HALF OF THE ROCKIES  
AND VICINITY MAY SEE A LITTLE SCATTERED RAINFALL AS WELL.  
 
GUIDANCE CHANGES OVER THE PAST DAY SUGGEST POTENTIAL FOR GREATER  
PERSISTENCE OF HOT/HUMID WEATHER OVER THE NORTHEAST, THOUGH EXPECT  
THIS WEEKEND AND MON TO BE THE FOCUS FOR THE MOST EXTREME HEAT  
INDEX VALUES. RECORD WARM LOWS ARE POSSIBLE WITHIN A FAIRLY LARGE  
AREA OVER THE EAST. RECORD HIGHS ARE LIKELY TO BE LESS NUMEROUS  
AND TEND TO BE BETWEEN THE EASTERN GREAT LAKES AND NORTHERN MID  
ATLANTIC/NORTHEAST. IN THAT TIME FRAME SOME READINGS COULD  
LOCALLY REACH 15-20F ABOVE NORMAL. ANOMALIES MAY STILL REACH OR  
EXCEED PLUS 10F OVER SOME AREAS IN THE GREAT LAKES/NORTHEAST INTO  
MIDWEEK. MEANWHILE THE STRENGTHENING CENTRAL U.S. RIDGE ALOFT  
LATER IN THE PERIOD WILL BRING A RETURN OF WELL ABOVE NORMAL  
TEMPERATURES (UP TO PLUS 10-15F ANOMALIES) TO THE NORTHERN  
PLAINS/MIDWEST BY WED-THU. THE MOST PERSISTENTLY COOL  
TEMPERATURES IN ASSOCIATION WITH THE WEST COAST UPPER TROUGH WILL  
BE OVER THE PACIFIC NORTHWEST/NORTHERN ROCKIES WITH MON-TUE LIKELY  
TO HAVE THE COOLEST HIGHS, APPROACHING 10F BELOW NORMAL.  
CALIFORNIA SHOULD TREND COOLER AFTER THE WEEKEND AS THE UPPER  
TROUGH AMPLIFIES.  
 
RAUSCH  
 
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  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page