089  
FXUS02 KWBC 051601  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1100 AM EST MON NOV 05 2018  
 
VALID 12Z THU NOV 08 2018 - 12Z MON NOV 12 2018  
   
..PATTERN OVERVIEW AND GUIDANCE ASSESSMENT
 
 
THE MEDIUM RANGE PERIOD FEATURES SHORTWAVE ENERGY TRAVERSING THE  
NORTHERN TIER FROM THE NORTHERN PLAINS TO NORTHERN NEW ENGLAND  
WHILE A SECOND POSSIBLE SHORTWAVE DROPS DOWN INTO THE NORTHERN  
ROCKIES BY DAY 5 AND RIDING BUILDS OVER THE COASTAL EASTERN  
PACIFIC AND WEST COAST. THERE REMAINS GOOD AGREEMENT BETWEEN  
DETERMINISTIC MODELS AND ENSEMBLES IN THE DAYS 3-4 (THUR - FRI)  
PERIOD, WITH UNCERTAINTY INCREASING LATER IN THE PERIOD. THERE  
REMAINS SOME QUESTION WITH HOW MUCH, IF ANY, SHORTWAVE ENERGY  
DROPS DOWN INTO THE NORTHERN PLAINS ON DAY 5. THE ECMWF HAS GOOD  
CONSISTENCY WITH BOTH ITS PREVIOUS RUNS AND THE EC AND GEFS  
ENSEMBLE MEANS IN SHOWING SOME SEMBLANCE OF ENERGY AHEAD OF MORE  
AMPLIFIED RIDGING IN THE EAST PACIFIC WHILE THE GFS REMAINS ON THE  
SLIGHTLY FLATTER/WEAKER SIDE. THE BIGGEST OUTLIER REMAINS THE CMC  
AND ITS ENSEMBLE WHICH SHOWS A MUCH MORE DEFINED SHORTWAVE ACROSS  
THE WEST. THIS LIKELY IS A RESULT OF DIFFERENCES UPSTREAM OVER THE  
CENTRAL PACIFIC AND ALASKA.  
 
THE BLEND USED FOR THIS CYCLE OF THE MEDIUM RANGE PROGS FEATURES A  
MAJORITY DETERMINISTIC BLEND (BETWEEN THE LATEST ECMWF/GFS/UKMET  
RUNS) DAYS 3-4, WITH INCREASING WEIGHTING OF THE EC AND GEFS  
ENSEMBLE MEANS BY THE END OF THE PERIOD. DID MAINTAIN A LITTLE  
WEIGHTING OF THE DETERMINISTIC ECMWF THROUGH DAY 7 BECAUSE IT WAS  
THE CLOSEST TO THE SOLUTION PROVIDED BY THE ENSEMBLE MEANS, AND  
THIS OVERALL PATTERN FIT VERY CLOSE TO WPC CONTINUITY AS WELL.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
OCCASIONAL MODEST RAIN/SNOW IN THE WEST WILL PERIODICALLY BE TIED  
TO INCOMING SHORTWAVES AND SURFACE FRONTS. SYSTEM EJECTIONS FROM  
THE ROCKIES INTO THE PLAINS WHERE ENE FLOW AROUND A SURFACE HIGH  
MAY SUPPORT A SWATH OF SNOW FROM THE CENTRAL PLAINS NORTHEASTWARD.  
TO THE SOUTH, GULF MOISTURE WILL SUPPORT MODERATE RAINFALL  
(POTENTIALLY LOCALLY HEAVY VIA EMBEDDED CONVECTION) FROM THE  
WESTERN GULF COAST AND LOWER MISSISSIPPI VALLEY TO THE SOUTHEAST  
WITH FRONTAL PROGRESSION, WITH ADDITIONAL AMOUNTS UP THE  
APPALACHIANS/EASTERN SEABOARD AIDED BY ATLANTIC INFLOW. AS THE  
FRONT CLEARS THE EAST COAST, LAKE-EFFECT SNOW IS LIKELY WITH COLD  
TEMPERATURES ALOFT ATOP MILD LAKE TEMPERATURES IN GENERAL NW FLOW.  
TEMPERATURES WILL BE MOST ANOMALOUSLY COOL OVER THE UPPER  
MIDWEST/GREAT LAKES AS WELL AS TEXAS BEHIND THE COLD FRONT. SOME  
RECORD COLD MAXIMUM TEMPERATURES ARE POSSIBLE OVER THE MIDWEST. A  
CLIPPER LOW APPROACHING BY SUN/NEXT MONDAY MAY SUPPORT SOME SNOW  
FOR PARTS OF THE UPPER MIDWEST/GREAT LAKES AND THE NORTHEAST.  
 
SANTORELLI/SCHICHTEL  
 
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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