211  
FXUS02 KWBC 090505  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
104 AM EDT THU AUG 09 2018  
 
VALID 12Z SUN AUG 12 2018 - 12Z THU AUG 16 2018  
   
..PATTERN OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
LATEST 12Z/18Z MODELS AND ENSEMBLES SHOW VERY GOOD CLUSTERING  
THROUGH THE PERIOD FOR THE CONUS, ESPECIALLY BETWEEN THE  
GFS/ECMWF. AN UPPER LOW WILL TEMPORARILY MEANDER NEAR THE OHIO  
VALLEY SUN-TUE BEFORE GETTING BUMPED NORTHEASTWARD BY CANADIAN  
TROUGHING. THE 12Z UKMET/CANADIAN WERE JUST A BIT DISPLACED  
(QUICKER/SLOWER, RESPECTIVELY) FROM THE GOOD GEFS/ECMWF ENSEMBLE  
CLUSTERING (WITH SUPPORTING DETERMINISTIC RUNS) SO OPTED TO KEEP  
IT SIMPLE AND USE THE GFS/ECMWF AND SOME OF THEIR ENSEMBLE MEANS  
ESPECIALLY BY NEXT WED/THU AS UNCERTAINTY INCREASES.  
 
   
..WEATHER HIGHLIGHTS AND HAZARDS
 
 
COOLER TEMPERATURES WILL PUSH THROUGH THE NORTHWEST AND HIGH  
PLAINS SUNDAY/MONDAY AS THE UPPER TROUGH AND SURFACE COLD FRONT  
PUSH THROUGH. A SEPARATED SOUTHWESTWARD EXTENSION FROM THE OHIO  
VALLEY UPPER LOW WILL HELP FUEL ORGANIZED RAIN/STORMS ACROSS TEXAS  
WESTWARD TO THE FOUR CORNERS REGION, ESPECIALLY NM/CO JUST TO THE  
EAST OF THE UPPER HIGH IN A REGION OF FAVORABLE UPPER DIFFLUENCE.  
GUIDANCE CONTINUES TO WAVER ON PLACEMENT BUT SEVERAL INCHES OF  
RAIN ARE LIKELY NEAR THE RED RIVER VALLEY (TX/OK) DURING THE  
SUN-THU TIME PERIOD.  
 
A WAVY FRONT WILL LINGER ACROSS THE U.S. SOUTHERN TIER DURING THE  
PERIOD WHICH WILL HELP SPARK AFTERNOON SHOWERS/STORMS AND LOCALLY  
HEAVY RAINFALL IN THE WARM/HUMID AIRMASS. AS THE UPPER LOW SLOWLY  
LIFTS TOWARD NEW ENGLAND, MORE WIDESPREAD PRECIPITATION MAY BE  
FAVORED TO ITS EAST SIDE ALONG THE APPALACHIANS TO THE I-95  
CORRIDOR WHERE THE GROUND REMAINS QUITE SATURATED IN PLACES  
(WESTERN VIRGINIA THROUGH MD/PA INTO THE SOUTHERN TIER OF NY AND  
POCONOS IN NJ. THIS COULD DEVELOP INTO A HEAVY RAINFALL THREAT  
CONSIDERING THE RELATIVELY SLOW SYSTEM TRANSLATION SOUTHERLY FETCH  
OF AMPLE MOISTURE OVER SEVERAL DAYS. CLOSED LOWS IN THE SUMMER CAN  
BE UNDERESTIMATED IN TERMS OF PRECIPITATION INTENSITY/AMOUNTS AND  
LONGEVITY (SEE CSTAR RESEARCH FROM UALBANY).  
 
ANOTHER FRONTAL BOUNDARY WILL DROP OUT OF CANADA TOWARD MONTANA  
NEXT THURSDAY OR SO WITH A RETURN OF 90+ DEGREE TEMPERATURES  
ACROSS THE HIGH PLAINS.  
 
FRACASSO  
 
WPC MEDIUM RANGE 500 MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDEXES ARE FOUND 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  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page