584  
FXUS02 KWBC 171551  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1150 AM EDT WED OCT 17 2018  
 
VALID 12Z SAT OCT 20 2018 - 12Z WED OCT 24 2018  
   
..PATTERN OVERVIEW
 
 
A RELATIVELY BENIGN PATTERN SHAPES UP THE MEDIUM-RANGE PERIOD  
THROUGH NEXT WEDNESDAY, WITH TROUGHING PERSISTING IN THE NORTHEAST  
WHILE A REX BLOCK PATTERN DEVELOPS AND LINGERS IN THE WEST. THE  
WETTEST PART OF THE COUNTRY SHOULD BE ALONG THE GULF COAST WHERE  
MOISTURE CONTINUES TO CIRCULATE AROUND A SUBTROPICAL HIGH CENTERED  
OVER CUBA. THE PACIFIC NORTHWEST WILL SEE THE NEXT BATCH OF  
PRECIPITATION ARRIVING TOWARD THE MIDDLE OF NEXT WEEK WITH LITTLE  
WINTRY WEATHER EXPECTED IN THE HIGHER ELEVATIONS.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
MODELS AND ENSEMBLES CONTINUE TO OFFER GOOD CLUSTERING THROUGH THE  
NEXT 5-6 DAYS WITH EXPECTED TIMING/AMPLITUDE DIFFERENCES BY NEXT  
TUE/WED. A DETERMINISTIC BLEND OF THE GFS/ECMWF OFFERED A GOOD  
STARTING POINT CLOSE TO CONTINUITY FOR SAT-MON AS A LEAD AND  
SECONDARY COLD FRONT PUSH OFF THE EAST COAST AND ANOTHER CANADIAN  
FRONT DIPS INTO THE WESTERN GREAT LAKES. BY NEXT TUE/WED AN  
APPROACHING PACIFIC SYSTEM (OR COUPLE OF SYSTEMS) WILL EVENTUALLY  
BREAK THE RIDGE OVER THE WEST, BUT THE ECMWF ENSEMBLES REMAIN  
QUICKEST TO LOWER HEIGHTS INTO THE PACIFIC NW WHICH IS RATHER  
UNCHARACTERISTIC IN THE LONGER TERM, BUT HAS BEEN NOTED RECENTLY.  
 
SOME SPREADS IN THE MODEL SOLUTIONS BEGIN TO SHOW UP ON DAYS 6 AND  
7 NEAR THE CANADIAN BORDER REGARDING THE COLD HIGH PRESSURE SYSTEM  
DIPPING INTO THE GREAT LAKES AND THE NE U.S. THE 00Z ECMWF NOW  
SHOWS A PRESSURE PATTERN IN CLOSER AGREEMENT WITH THE GFS, WHICH  
HAS BEEN SHOWING BETTER CONSISTENCY IN THAT REGION. THEREFORE,  
THE WPC MORNING GRID FILE PACKAGE IS A CONSENSUS BETWEEN THE 00Z  
ECMWF/EC MEAN, 00Z AND 06Z GFS, 00Z GEFS WITH MORE OF THE ENSEMBLE  
MEANS INCORPORATED FOR DAYS 6 AND 7.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
THE PACIFIC NORTHWEST WILL SEE SEVERAL DAYS OF ABOVE AVERAGE  
TEMPERATURES AND DRY CONDITIONS THROUGH THE WEEKEND. RAIN CHANCES  
WILL INCREASE NEXT WEEK STARTING LATE MONDAY AS THE FIRST COLD  
FRONT APPROACHES THE COAST. WARM ANTECEDENT TEMPERATURES WILL  
PRECLUDE SNOW FROM ALL BUT THE HIGHEST ELEVATIONS, BUT THAT WILL  
CHANGE AS COOLER AIR WORKS ITS WAY EASTWARD. RAIN WILL BECOME  
WIDESPREAD AND MODERATE TO LOCALLY HEAVY BY MIDWEEK NEXT WEEK. THE  
REST OF THE CONUS WILL SEE NEAR TO BELOW AVERAGE TEMPERATURES WITH  
THE CORE OF THE COOLEST AIR FROM TEXAS NORTHEASTWARD TO THE  
NORTHEAST/NEW ENGLAND. EVEN FLORIDA WILL SLOWLY TREND BACK TOWARD  
MORE TYPICAL LATE OCTOBER TEMPERATURES IN THE UPPER 70S (NORTH) TO  
MID 80S (SOUTH).  
 
COASTAL TEXAS HAS THE HIGHEST PROBABILITY OF THE GREATEST AMOUNT  
OF PRECIPITATION EAST OF THE ROCKIES DUE TO AN INITIAL AND THEN  
SUBSEQUENT STATIONARY BOUNDARY THROUGH THE GULF NEXT TO AN  
INVERTED TROUGH. THOUGH MOST OF THIS MAY STAY OFFSHORE, AREAS  
NEAR BROWNSVILLE MAY SEE SEVERAL INCHES OF RAIN OVER THE PERIOD.  
MUCH LESS PRECIPITATION IS EXPECTED ELSEWHERE WITH EACH FRONTAL  
PASSAGE EXCEPT FOR PERHAPS FLORIDA WITH STRONG EASTERLY FLOW.  
COASTAL WA/OR WILL SEE LIGHT-MODERATE RAIN DEVELOP AND EXPAND  
INLAND EARLY NEXT WEEK AS UPPER TROUGHING APPROACHES WITH SEVERAL  
INCHES POSSIBLE ALONG THE IMMEDIATE COAST BY NEXT WEDNESDAY.  
 
KONG/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  
 

 
 
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