296  
FXUS02 KWBC 161600  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1200 PM EDT SAT MAR 16 2019  
 
VALID 12Z TUE MAR 19 2019 - 12Z SAT MAR 23 2019  
   
..OVERVIEW
 
 
MODELS AND ENSEMBLES SHOW A BLOCKING MID/UPPER-LEVEL RIDGE  
INITIALLY CENTERED FROM THE PACIFIC NORTHWEST TO WESTERN CANADA  
EARLY NEXT WEEK DRIFTING SLOWLY EASTWARD THROUGH THE FORECAST  
PERIOD. DOWNSTREAM FROM THIS RIDGE EXPECT A MEAN UPPER-LEVEL  
TROUGH INITIALLY ACROSS THE GREAT LAKES/NORTHEAST TO LIFT OUT  
BEFORE DEEPER TROUGHING MAY AMPLIFY INTO NEW ENGLAND AROUND NEXT  
FRI-SAT. MEANWHILE A SHORTWAVE OVER THE NORTHERN PLAINS SHOULD  
PROGRESS SOUTHEASTWARD THROUGH THE EASTERN U.S. EARLY-MID PERIOD.  
GUIDANCE CONTINUES TO DEPICT STRONG NORTH CENTRAL PACIFIC WESTERLY  
FLOW SPLITTING AS IT APPROACHES THE WESTERN COAST OF NORTH  
AMERICA. SOME OF THIS ENERGY WILL FORM A SYSTEM CROSSING THE  
SOUTHWESTERN U.S. WHILE THE REST FLOWS INTO THE HIGHER LATITUDES  
OF CANADA. STRONGER HEIGHT FALLS MAY APPROACH THE  
CENTRAL/NORTHERN WEST COAST BY NEXT FRI-SAT AS THE CONUS PORTION  
OF THE MEAN RIDGE SHIFTS FAR ENOUGH EASTWARD.  
 
   
..GUIDANCE ASSESSMENT/PREFERENCES
 
 
THE UPDATED FORECAST EMPHASIZES THE 00Z ECMWF/UKMET/CMC (WITH A  
SMALL 00Z NAEFS MEAN COMPONENT) FROM DAY 3 TUE INTO DAY 5 THU AND  
THEN ADJUSTS TO AN EVEN MODEL/MEAN BLEND CONSISTING OF THE  
ECMWF/CMC AND ECMWF/NAEFS MEANS.  
 
THIS CLUSTER REPRESENTS THE CURRENT MAJORITY FOR THE TROUGH/UPPER  
LOW EXPECTED TO TRACK INTO THE SOUTHWESTERN U.S. AND THE ROCKIES  
MID-LATE WEEK WHILE DEPICTING AN INTERMEDIATE TIMING FOR THE  
SHORTWAVE DROPPING SOUTHEASTWARD FROM THE NORTHERN PLAINS. FOR  
THE SYSTEM COMING INTO THE WEST, LATEST GFS/GEFS MEAN RUNS HAVE  
BACKED OFF SOMEWHAT FROM YESTERDAY'S FAST TIMING BUT NOT YET TO  
THE POINT OF JOINING CONSENSUS. THAT SAID, THE ECMWF HAS TRENDED  
A TAD FASTER OVER THE PAST DAY SO THE SLOWEST SOLUTIONS (THE 00Z  
CMC MEAN IN TODAY'S CASE) MAY NOT BE IDEAL EITHER. THE 06Z FV3  
GFS COMPARES MUCH BETTER TO THE FAVORED BLEND THAN THE OPERATIONAL  
GFS RUNS.  
 
FORECASTS TO THE SOUTHEAST OF CLOSED HIGHS--SUCH AS THE ONE OVER  
SOUTHWESTERN CANADA AS OF EARLY TUE--ARE NOTORIOUSLY DIFFICULT SO  
IT IS NOT EXACTLY SURPRISING TO SEE THE GREAT SPREAD AND RUN TO  
RUN VARIABILITY SEEN THUS FAR FOR THE SHORTWAVE ENERGY PROGRESSING  
FROM THE NORTHERN PLAINS THROUGH THE EAST. GUIDANCE TRENDS HAVE  
GENERALLY BEEN IN THE DIRECTION OF UKMET/CMC IDEAS FROM THE PAST  
COUPLE DAYS SO IT SEEMS REASONABLE TO ACCOUNT FOR THOSE RUNS AND  
SIMILAR ECMWF. THIS CLUSTER IS A GOOD MIDPOINT BETWEEN THE FAST  
00Z GFS AND SLOW 06Z GFS.  
 
DURING THE LATTER HALF OF THE PERIOD THE MODELS/MEANS ARE MORE  
AGREEABLE THAN AVERAGE WITH HEIGHT FALLS REACHING THE WEST COAST,  
FAVORING A MODEL/MEAN BLEND. THE 06Z FV3 GFS IS QUITE DEEP/SHARP  
VERSUS OTHER GUIDANCE FOR UPPER TROUGHING THAT AMPLIFIES INTO THE  
NORTHEASTERN U.S. THE 06Z GFS MAY BE A LITTLE TOO AMPLIFIED WITH  
THE SOUTHWESTERN PART OF THE TROUGH BUT OTHER MODELS/MEANS AGREE  
FAIRLY WELL.  
 
   
..WEATHER HIGHLIGHTS AND HAZARDS
 
 
THE PACIFIC SYSTEM TRACKING INTO CALIFORNIA SHOULD SPREAD RAIN AND  
HIGH ELEVATION SNOW INTO THE SIERRA NEVADA, GREAT BASIN, AND  
CENTRAL/SOUTHERN ROCKIES BY NEXT WED-FRI. SOME LOCALIZED  
ENHANCEMENT OF PRECIPITATION OVER FAVORED TERRAIN WILL BE  
POSSIBLE. BY FRI-SAT EXPECT MOISTURE TO INCREASE AHEAD OF THE  
SYSTEM, SUPPORTING GREATER COVERAGE/INTENSITY OF SHOWERS AND  
THUNDERSTORMS OVER PORTIONS OF THE SOUTHERN PLAINS WITH LOCALLY  
HEAVY RAIN POSSIBLE. ALSO IN THAT TIME FRAME THE STRONGER HEIGHT  
FALLS ALOFT AND A COLD FRONT APPROACHING THE PACIFIC NORTHWEST AND  
NORTHERN CALIFORNIA MAY BRING A RETURN OF RAIN/MOUNTAIN SNOW TO  
THAT AREA.  
 
EXPECT WIDESPREAD AND POTENTIALLY HEAVY RAIN OVER THE SOUTHERN  
HALF OF THE FLORIDA PENINSULA ON TUE AND PERHAPS INTO TUE  
NIGHT-WED AS A WAVE OF LOW PRESSURE MOVES ALONG A SURFACE FRONT  
STALLED SOUTH OF THE STATE. SOME RAINFALL OF MOSTLY  
LIGHT-MODERATE INTENSITY WILL BE POSSIBLE FROM THE CENTRAL PLAINS  
EASTWARD TUE-THU IN ASSOCIATION WITH AN UPPER SHORTWAVE AND WEAK  
SURFACE WAVE/FRONTAL SYSTEM. BY LATE IN THE WEEK LOCATIONS NEAR  
THE COAST OF THE CAROLINAS MAY SEE A BRIEF PERIOD OF RAINFALL AS  
LOW PRESSURE DEVELOPS OFF THE SOUTHEASTERN COAST BUT THEN TRACKS  
RAPIDLY FARTHER OFFSHORE. NORTHERN PARTS OF THE EAST SHOULD BE  
FAIRLY DRY EXCEPT FOR LIGHT LATE WEEK/EARLY WEEKEND SNOW OVER  
FAVORED TERRAIN OF NEW ENGLAND BEHIND A COLD FRONT THAT DROPS  
SOUTHEASTWARD FROM CANADA.  
 
A MAJORITY OF THE WEST SHOULD SEE ABOVE NORMAL MORNING LOWS DURING  
THE PERIOD (PLUS 10-15F ANOMALIES AT SOME LOCATIONS) WHILE THE  
SYSTEM CROSSING THE SOUTHERN HALF OF THE WEST WILL KEEP HIGHS NEAR  
TO BELOW NORMAL OVER AFFECTED AREAS AFTER TUE. THE SOUTHERN HIGH  
PLAINS WILL TEND TO BE ON THE COOL SIDE VERSUS NORMAL DURING THE  
PERIOD BUT THE NORTHERN-CENTRAL PLAINS WILL LIKELY SEE NEAR TO  
ABOVE NORMAL TEMPERATURES AS WARMTH SPREADS FROM THE WEST. THE  
EASTERN U.S. WILL BE 5-10F BELOW NORMAL TUE-WED BUT MODERATE  
TOWARD NORMAL THEREAFTER. A FRONTAL PASSAGE COULD BRING COOL AND  
BREEZY CONDITIONS TO THE NORTHEAST BY NEXT SAT THOUGH.  
 
RAUSCH/RYAN  
 
ADDITIONAL 3-7 DAY HAZARDS INFORMATION CAN BE FOUND ON THE WPC  
MEDIUM RANGE HAZARDS CHART AT:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDICES ARE 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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