516  
FXUS02 KWBC 061605  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1104 AM EST TUE NOV 06 2018  
 
VALID 12Z FRI NOV 09 2018 - 12Z TUE NOV 13 2018  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
AN AMPLIFIED PATTERN IS EXHIBITED IN THE MEDIUM RANGE  
PERIOD--PRIMARILY WITH A TROUGH IN THE EASTERN U.S. AND A STRONG  
RIDGE CENTERED OVER THE WESTERN U.S. ON FRIDAY AND INTO SATURDAY,  
A MID-UPPER LEVEL TROUGH WILL DIG ACROSS THE UPPER MIDWEST TO  
GREAT LAKES--WITH TROUGHING EXTENDING INTO THE DESERT SOUTHWEST.  
THE 06Z GFS/00Z ECMWF ALSO SHOW A MID-LEVEL DISTURBANCE SLIDING  
DOWN INTO THE INTERMOUNTAIN WEST AND NORTHERN HIGH PLAINS DURING  
THIS TIME PERIOD AS AN UPPER LEVEL RIDGE BEGINS BUILDING OVER THE  
WEST COAST. AS THIS DIGGING TROUGH OVER THE GREAT LAKES SWINGS  
NORTHEAST OVER THE CANADIAN MARITIMES, THE DISTURBANCE THAT  
TRACKED OVER THE INTERMOUNTAIN WEST WILL DEVELOP A MID-UPPER LEVEL  
TROUGH OVER THE CENTRAL U.S., WITH THE UPPER LEVEL RIDGE  
MAINTAINING ITS POSITION IN THE WEST. THIS TROUGH WILL CONTINUE TO  
DIG AS IT SLIDES EASTWARD OVER THE EAST COAST. THE RIDGE FINALLY  
BEGINS TO SHIFT INLAND, WITH HEIGHT FALLS EXPECTED OVER THE  
PACIFIC NORTHWEST BY THE END OF THE MEDIUM RANGE PERIOD. OVERALL,  
BOTH THE 06Z GFS/00Z ECMWF WERE AGREEABLE EVEN THROUGH DAY 7, AS  
WERE THEIR ENSEMBLE MEANS. ONE OF THE BIGGEST OUTLIERS WAS THE 00Z  
CMC, SHOWING A CLOSED MID-UPPER LEVEL LOW DIGGING OVER THE CENTRAL  
GREAT BASIN, BUT EVEN THE 00Z CMC ENSEMBLE MEAN DID NOT SHOW THIS.  
THUS, WPC USED A 06Z GFS/00Z UKMET/00Z ECMWF BLEND WITH THE  
ENSEMBLE MEANS AND INCREASING THE MEANS MORE BY DAYS 6/7. HOWEVER,  
BECAUSE THE GFS/ECMWF WERE LINING UP WELL EVEN THROUGH DAY 7,  
THESE OPERATIONAL MODELS WERE USED THROUGH THE END OF THE MEDIUM  
RANGE PERIOD.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
AS THE MID-UPPER LEVEL TROUGH MOVES ACROSS THE CENTRAL TO  
NORTHEASTERN U.S. ON FRIDAY AND SATURDAY, A COLD FRONT WILL PUSH  
THROUGH THE OHIO VALLEY/LOWER MISSISSIPPI VALLEY EASTWARD TOWARD  
THE EAST COAST. ALONG AND AHEAD OF THIS FRONT, SOUTHERLY FLOW WILL  
TRANSPORT MOISTURE FROM THE GULF OF MEXICO--PROMOTING SHOWERS AND  
THUNDERSTORMS STRETCHING FROM THE SOUTHEAST TO NEW ENGLAND. A  
STATIONARY FRONT WILL ALSO LINGER OFF THE CAROLINA COAST AND MAY  
CONTRIBUTE TO RAIN NEAR THEIR COASTLINES. BY SATURDAY, MOST OF THE  
RAIN WILL PUSH OFF THE MID-ATLANTIC AND SOUTHEAST BUT THE MAIN LOW  
OF THIS FRONT WILL MOVE INTO THE NORTHEAST AND COULD ENHANCE  
PRECIPITATION ALONG THIS REGION. CYCLONIC FLOW ACROSS THE GREAT  
LAKES COMBINED WITH TEMPERATURES COOLING BEHIND THE FRONT MAY  
PROMOTE LAKE EFFECT SNOWS--AND COULD SPREAD INTO THE INTERIOR  
NORTHEAST. HIGHER ELEVATION SNOW CAN BE EXPECTED THROUGH THE  
WEEKEND AS THE DISTURBANCE MOVES INTO THE INTERMOUNTAIN WEST.  
 
AS THE NEXT TROUGH DEVELOPS BY SUNDAY AND INTO MONDAY, SNOW COULD  
MOVE ACROSS THE NORTHERN PLAINS AND INTO THE UPPER MIDWEST.  
ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS WILL OCCUR IN THE  
BEGINNING OF THE WORKWEEK AS THAT TROUGH DIGS EASTWARD AND THE  
SURFACE FRONT PUSHES ACROSS THE SOUTHEAST. THIS COULD BRING HEAVY  
RAIN TO THE CENTRAL GULF COAST--WITH PRECIPITATION SPREADING INTO  
THE MID-ATLANTIC. BY TUESDAY, RAIN WITH SNOW ACROSS THE INTERIOR  
OF NEW ENGLAND CAN BE EXPECTED AS THE OCCLUDED FRONT PUSHES  
NORTHWARD THROUGH THE AREA ALONG WITH LAKE EFFECT SNOW. BECAUSE OF  
THE PATTERN, TEMPERATURES WILL STAY BELOW NORMAL FOR THE CENTRAL  
AND EASTERN U.S. THROUGH THE MEDIUM RANGE PERIOD WHILE THE WEST  
COAST AND PARTS OF THE CENTRAL GREAT BASIN WILL EXPERIENCE ABOVE  
AVERAGE TEMPERATURES.  
 
REINHART  
 
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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