654  
FXUS02 KWBC 010535  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
135 AM EDT THU NOV 01 2018  
 
VALID 12Z SUN NOV 04 2018 - 12Z THU NOV 08 2018  
   
..PATTERN OVERVIEW
 
 
A MEAN UPPER-LEVEL TROUGH IS EXPECTED TO PERSIST ACROSS THE  
CENTRAL U.S. THROUGH THE EXTENDED PERIOD. THE TROUGH WILL BE  
REINFORCED BY A SERIES OF SHORTWAVES ORIGINATING IN THE NORTH  
PACIFIC (NORTH OF A PERSISTENT UPPER-LEVEL RIDGE), POTENTIALLY  
INTERACTING WITH ADDITIONAL SHORTWAVE ENERGY OF POLAR/ARCTIC  
ORIGIN AS THEY CROSS THE CANADIAN ROCKIES BEFORE AMPLIFYING AS  
THEY ENCOUNTER THE AREA OF BROAD AND PERSISTENT CYCLONIC FLOW  
ACROSS THE CENTRAL U.S. A SERIES OF FRONTAL/LOW PRESSURE SYSTEMS  
WILL ACCOMPANY THESE SHORTWAVES ACROSS THE CONUS, GENERALLY 1-2  
DAYS APART, RESULTING IN A PERIOD OF RELATIVELY ACTIVE WEATHER.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
A SOLUTION CLOSE TO THE CONSENSUS OF THE ECENS AND GEFS MEANS WAS  
PREFERRED WITH THE LOW PRESSURE SYSTEM CROSSING THE  
MID-MISSISSIPPI VALLEY/UPPER MIDWEST DURING DAYS 3-4 (SUN-MON).  
THE ECMWF WAS THE CLOSEST DETERMINISTIC SOLUTION TO THE ENSEMBLE  
CONSENSUS WITH THE TRACK/TIMING OF THE SURFACE LOW, FOLLOWED BY  
THE GFS. THUS, A ECMWF/GFS (MORE WEIGHT TOWARD THE ECMWF) BLEND  
SERVED AS A STARTING POINT FOR THE WPC FORECAST DURING THAT TIME  
FRAME. BY MON THE NEXT SHORTWAVE SHOULD BE EXITING THE ROCKIES  
INTO THE PLAINS, WITH DEVELOPMENT OF YET ANOTHER SURFACE LOW  
PRESSURE SYSTEM EXPECTED. SPREAD AMONG THE DETERMINISTIC GUIDANCE  
SEEMS TO HAVE INCREASED RATHER SUBSTANTIALLY WITH THIS SECOND  
SYSTEM BY DAY 5 (TUE) AND ONWARD. THE LAST FEW RUNS OF THE GFS  
HAVE DEVIATED FROM THE ENSEMBLE CONSENSUS AND QUICKLY MOVE THE  
SURFACE LOW NORTHWARD INTO CANADA, WITH ANOTHER FRONTAL WAVE  
DEVELOPING FARTHER SOUTH ALONG THE FRONT. THE ECENS MEAN AND EVEN  
THE GEFS/NAEFS MEANS CONTINUE TO LOOK MUCH MORE LIKE THE ECMWF,  
WHICH REMAINS REASONABLY WELL CENTERED WITHIN THE ENSEMBLE SPREAD.  
THUS, SOMETHING ALONG THE LINES OF THE MEANS AND THE ECMWF REMAINS  
THE PREFERRED SOLUTION, WHICH ALSO KEEPS REASONABLY GOOD  
CONTINUITY WITH THE PREVIOUS FORECAST. THIS SCENARIO SHOWS A  
STRENGTHENING SURFACE LOW MOVING NORTH-NORTHEASTWARD ACROSS THE  
GREAT LAKES ON TUE AND CONTINUING TO DEEPEN (PERHAPS QUITE  
SUBSTANTIALLY) AS THE LOW MOVES INTO EASTERN ONTARIO TOWARD JAMES  
BAY ON DAY 6 (WED). THROUGH LATE IN THE FORECAST PERIOD, THE SAME  
GENERAL PATTERN LOOKS TO HOLD STRONG, WITH ADDITIONAL SHORTWAVES  
CONTINUING TO REINFORCE THE MEAN TROUGH (ALTHOUGH THE DETAILS OF  
THESE SYSTEMS ARE QUITE MURKY). GIVEN THE INCREASED SPREAD  
ESPECIALLY AFTER DAY 5, WEIGHTING WAS SHIFTED TOWARD THE ENSEMBLE  
MEANS DURING THE DAY 6-7 TIME PERIOD, WITH A BIT OF CONTINUED  
EMPHASIS ON THE ECMWF THROUGH DAY 6.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
THE MISSISSIPPI AND OHIO VALLEYS WILL SEE THE POTENTIAL FOR RAIN  
TO BECOME MORE WIDESPREAD LATE IN THE WEEKEND INTO NEXT WEEK AS A  
COUPLE FRONTAL SYSTEMS TRAVERSE THE REGION AND TAP INTO GULF OF  
MEXICO MOISTURE. AN EXPANDING AREAS OF RAIN WILL SPREAD  
NORTHEASTWARD AHEAD OF THE MIDWEEK SYSTEM (TUE-WED) WITH AN INCH  
OR MORE OF RAIN POSSIBLE OVER A LARGE AREA, PARTICULARLY OVER THE  
OHIO/TENNESSEE VALLEYS NORTHWARD TO THE LOWER GREAT LAKES. OFF THE  
COAST, THE LINGERING STATIONARY FRONT MAY PUSH BACK TOWARD THE  
COAST AND BRING THE POTENTIAL FOR PRECIPITATION BACK TO THE  
NORTHEAST. HEAVY RAIN AND HIGHER ELEVATION SNOW WILL BE POSSIBLE  
ACROSS THE PACIFIC NORTHWEST INTO EARLY NEXT WEEK AS UPPER  
SHORTWAVES/SURFACE FRONTS TRAVERSE THE NORTHERN PERIPHERY OF THE  
UPPER RIDGE. THESE FEATURES WILL ALSO BRING ROUNDS OF SNOW TO THE  
HIGHER ELEVATIONS OF THE NORTHERN AND THEN CENTRAL ROCKIES EARLY  
NEXT WEEK. CHILLY CONDITIONS WILL BE PREVALENT ACROSS PORTIONS OF  
THE CENTRAL U.S. BENEATH THE PERSISTENT UPPER TROUGH, WHERE HIGHS  
WILL GENERALLY BE 5 TO 10 DEG F BELOW AVERAGE. CHILLY AIR MAY MAKE  
ITS WAY INTO THE EASTERN U.S. BY LATER NEXT WEEK BEHIND A STRONG  
COLD FRONT. MEANWHILE, ABOVE AVERAGE TEMPERATURES WILL PERSIST  
ACROSS PORTIONS OF THE WEST, FROM CALIFORNIA INTO THE GREAT BASIN  
(ESPECIALLY SUN-TUE), WHERE HIGH TEMPERATURES MAY REACH 5 TO 15  
DEG F ABOVE AVERAGE DOWNSTREAM OF PERSISTENT UPPER-LEVEL RIDGING.  
 
RYAN  
 
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