441  
FXUS02 KWBC 160617  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
216 AM EDT TUE OCT 16 2018  
 
VALID 12Z FRI OCT 19 2018 - 12Z TUE OCT 23 2018  
   
..PATTERN OVERVIEW
 
 
REINFORCED UPPER TROUGHING WILL PERSIST IN THE EASTERN HALF OF THE  
CONUS WHILE RIDGING IS FORECAST TO LINGER OVER THE PACIFIC  
NORTHWEST. A SERIES OF FAIRLY WEAK CANADIAN FRONTS WILL SWING  
THROUGH THE GREAT LAKES TO MAINTAIN BELOW AVERAGE TEMPERATURES AND  
SPARK OFF SOME RAIN/SNOW SHOWERS ESPECIALLY IN FAVORED LAKE-EFFECT  
AREAS. THE STRONG UPPER RIDGE OVER FLORIDA WILL ONLY SLOWLY WEAKEN  
BY NEXT WEEK AND GET SQUASHED INTO CUBA. ON ITS WEST SIDE WILL BE  
A STALLED FRONT OFF THE TEXAS COAST WHICH WILL KEEP A DAILY CHANCE  
OF RAINFALL IN THE FORECAST, ESPECIALLY SOUTHERN TEXAS. FINALLY, A  
LOST UPPER LOW NEAR SOUTHERN CALIFORNIA WILL SEEK AN EXIT ROUTE  
THROUGH THE GREAT BASIN EARLY NEXT WEEK, HELPING TO WRING OUT SOME  
LIGHT SHOWERS.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
AN OPERATIONAL MODEL CONSENSUS CONTINUES TO REPRESENT INDIVIDUAL  
FEATURES WELL FOR FRI-SUN. AFTER THAT TIME MODEL RUNS BEGIN TO  
SHOW GREATER SHORTWAVE DIFFERENCES AMONG EACH OTHER AND/OR IN  
CONSECUTIVE RUNS, FAVORING A TREND TOWARD THE ECMWF ENSEMBLE MEAN  
AND GEFS MEAN. PACIFIC FRONT WILL ATTEMPT TO MOVE INTO  
WASHINGTON/OREGON LATE NEXT TUESDAY BUT THE ENSEMBLES DIFFER  
QUICKER/SLOWER (ECMWF/GEFS, RESPECTIVELY). ECMWF AND ITS ENSEMBLES  
HAVE HAD A TENDENCY TO BREAK DOWN THE WESTERN RIDGE TOO QUICKLY AT  
THAT TIME RANGE BUT A SHIFT NORTHWARD IN THE POSITIVE HEIGHT  
ANOMALY COULD ALLOW FOR AN OPENING INTO THE PAC NW AS QUICK AS THE  
ECMWF ENSEMBLE MEAN (PERHAPS NOT AS QUICK AS THE 12Z/15 ECMWF).  
FOR NOW, A MODEST MIDDLE GROUND SUFFICED.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
ABOVE AVERAGE TEMPERATURES ARE FAVORED IN THE WEST OUTSIDE THE  
INFLUENCE OF THE UPPER LOW, GENERALLY 5-10F ABOVE AVERAGE.  
TROUGHING IN THE EAST AND CLOUD COVER OVER TEXAS WILL KEEP  
TEMPERATURES BELOW AVERAGE THERE BUT WITH A LITTLE VARIATION  
AROUND FRONTAL PASSAGES. SOME AREAS WILL SEE NEAR RECORD WARMTH  
(WA/OR AND FL) WITH MORE WIDESPREAD COOL TEMPERATURES AND CHILLY  
AFTERNOON HIGHS AROUND THE LAKES INTO THE NORTHEAST (40S/50S).  
 
EXPECT HIGHEST 5-DAY RAINFALL TOTALS OVER PORTIONS OF TEXAS AND  
NEAR THE WESTERN GULF COAST, IN THE VICINITY OF AN INVERTED TROUGH  
AND TO THE NORTHWEST OF A STATIONARY BOUNDARY IN THE WESTERN GULF.  
SOME OF THIS SOUTHERN PLAINS MOISTURE MAY EXTEND NORTHEASTWARD  
ALONG A COLD FRONT CROSSING THE EAST DURING THE WEEKEND. THE  
LINGERING UPPER LOW IN THE SOUTHWEST WILL SUPPORT RAIN AND  
POSSIBLY HIGH ELEVATION SNOW SHOWERS MOSTLY FOCUSED ON/ALONG THE  
HIGHER TERRAIN WHILE A STATIONARY FRONT ACROSS FLORIDA WILL KEEP  
DAILY SHOWER/STORM CHANCES IN THE FORECAST. OVER THE GREAT  
LAKES/NORTHEAST LAKE-EFFECT PRECIPITATION WILL START ANEW THIS  
WEEKEND BEHIND A COLD FRONT AND THEN AGAIN LATE IN THE FORECAST.  
COASTAL WA/OR WILL SEE RAIN DEVELOP AND EXPAND INLAND STARTING ON  
MONDAY AND CONTINUING ON TUESDAY, DEPENDING ON THE SPEED OF THE  
FRONT.  
 
FRACASSO/RAUSCH  
 
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  
 

 
 
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