763  
FXUS02 KWBC 230658  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
157 AM EST FRI NOV 23 2018  
 
VALID 12Z MON NOV 26 2018 - 12Z FRI NOV 30 2018  
 
 
SYNOPTIC SCALE OVERVIEW  
-----------------------  
ACTIVE PATTERN FOR THE WEST COAST AND THE NORTHEAST U.S. NEXT WEEK  
AS A LARGE SCALE TROUGH SETTLES OVER THE EASTERN GREAT LAKES AND  
MULTIPLE PACIFIC LOWS IMPACT THE PACIFIC NORTHWEST AND EVENTUALLY  
NORTHERN CALIFORNIA. COLDER THAN AVERAGE TEMPERATURES ARE LIKELY  
FOR THE CENTRAL STATES EASTWARD BUT CLOSER TO AVERAGE WEST OF THE  
ROCKIES.  
 
MODEL GUIDANCE AND UNCERTAINTY ASSESSMENT  
-----------------------------------------  
THE DETERMINISTIC MODELS ARE CONTINUING TO HAVE DIFFICULTY WITH  
THE EVOLUTION AND PROGRESSION OF AN ELONGATED UPPER LOW CENTERED  
OVER THE GREAT LAKES REGION EARLY NEXT WEEK. THERE IS SUPPORT FOR  
TWO SEPARATE LOW CENTERS, WITH GREATER DISAGREEMENT WITH THE  
WESTERN UPPER LOW ACROSS THE UPPER MIDWEST. BETTER MODEL  
AGREEMENT EXISTS FOR THE WEST COAST RIDGE ON MONDAY THAT  
EVENTUALLY GIVES WAY TO A BROAD UPPER LEVEL TROUGH MOVING IN FROM  
THE PACIFIC. AS THE UPPER RIDGE BECOMES LESS AMPLIFIED BY MID  
WEEK OVER THE ROCKIES, A QUASI-ZONAL FLOW DEVELOPS WITH SOME HINT  
OF A SOUTHERN STREAM TROUGH OVER MEXICO AND THE GULF, AND A CLOSED  
LOW REACHING THE WEST COAST BY THURSDAY. GIVEN LOWER THAN AVERAGE  
CONFIDENCE GIVEN THE MODEL SPREAD, THE FORECAST RELIED HEAVILY ON  
THE EC AND NAEFS MEANS FOR WEDNESDAY AND BEYOND AS A STARTING  
POINT, WITH SOME DETERMINISTIC GFS/ECMWF/UKMET USED THROUGH  
TUESDAY.  
 
SENSIBLE WEATHER  
----------------  
A STRONG LOW PRESSURE SYSTEM CROSSING THE OHIO VALLEY AND GREAT  
LAKES REGION ON MONDAY IS EXPECTED TO RESULT IN WIDESPREAD RAIN  
FROM THE MID-ATLANTIC TO SOUTHERN NEW ENGLAND. SNOW IS LIKELY TO  
THE NORTH AND WEST OF THE SURFACE LOW ACROSS WISCONSIN AND  
MICHIGAN, AND ALSO FOR THE HIGHER ELEVATIONS OF INTERIOR NEW  
ENGLAND AND UPSTATE NEW YORK. TRIPLE POINT LOW SHOULD WRAP ACROSS  
SOUTHEASTERN NEW ENGLAND AND INTO THE GULF OF MAINE BY TUESDAY  
BEFORE SLOWLY HEADING EASTWARD. THE TUESDAY THROUGH THURSDAY TIME  
PERIOD SHOULD BE ACTIVE FOR THE PACIFIC NORTHWEST WITH LOW  
ELEVATION RAIN AND HIGHER ELEVATION SNOW AS A LEAD AND SECONDARY  
SYSTEM COME ASHORE. PRECIPITATION WILL WORK ITS WAY SOUTHWARD  
THROUGH NORTHERN CALIFORNIA BY NEXT THURSDAY. TEMPERATURES WILL  
GENERALLY BE BELOW AVERAGE OVER MOST OF THE CONTINENTAL U.S. BY  
ABOUT 5-10 DEGREES, ESPECIALLY EAST OF THE ROCKY MOUNTAINS.  
 
HAMRICK  
 
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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