033  
FXUS02 KWBC 231550  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1050 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 AND ENSEMBLE MEANS HAVE STRUGGLED FOR DAYS WITH  
THE STRENGTH OF THE BLOCKING/RETROGRADING LOW OVER THE NORTH  
ATLANTIC AND THE SHORTWAVES WITHIN THE MEAN TROUGH OVER THE  
EASTERN THIRD OF THE U.S. ANOTHER RECENT CHALLENGE IS THE  
BREAKDOWN OF THE WESTERN RIDGE. CONFIDENCE WITH THE TIMING,  
INTENSITY AND EXACT TRACK OF SPECIFIC SYSTEMS REMAIN NEAR AVERAGE  
EARLY NEXT WEEK AND DROPS TO FAIR/BELOW AVERAGE AT BEST BY THE END  
OF THE EXTENDED FORECAST.  
 
ASIDE FROM THE AFOREMENTIONED CHALLENGES, THE NORTHERN  
MID-ATLANTIC/GREAT LAKES/NORTHEAST WILL HAVE A FAIRLY ROBUST  
WINTER STORM MOVE THROUGH. AS COLD CANADIAN AIR RUSHES IN BEHIND  
THE CENTRAL LOW PRESSURE, WINDS WILL INCREASE OVER THE LAKES AND  
MAY LEAD TO LOCAL ENHANCEMENT IN THE FAVORED LAKE EFFECT AREAS.  
NORTHERN NEW ENGLAND MAY SEE SEVERAL INCHES OF SNOW WHILE  
PRECIPITATION ACROSS SOUTHERN NEW ENGLAND AND COASTAL AREAS OF THE  
NORTHEAST/NORTHERN MID-ATLANTIC MAY REMAIN IN THE FORM OF RAIN.  
 
ONSHORE FLOW WITH MULTIPLE SYSTEMS APPROACHING THE WEST COAST WILL  
KEEP AT LEAST COASTAL AREAS IN AN ACTIVE WET PATTERN AS THE  
TROUGH, BUT PRECIPITATION EXTENDING BEYOND THE COASTAL RANGES MAY  
DEVELOP AS THE RIDGE GIVES WAY. GIVEN LOWER THAN AVERAGE  
CONFIDENCE OF THE MODEL GUIDANCE, THE FORECAST RELIED ON A FAIRLY  
EQUAL MIX OF THE MEANS AND 00Z/06Z GFS AND 00Z ECMWF/UKMET/CMC.  
 
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.  
 
CAMPBELL  
 
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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