911  
FXUS02 KWBC 120628  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
228 AM EDT FRI APR 12 2019  
 
VALID 12Z MON APR 15 2019 - 12Z FRI APR 19 2019  
 
...ACTIVE PATTERN TO CONTINUE THROUGH NEXT WEEK FOR MUCH OF THE  
LOWER 48...  
 
   
..OVERVIEW
 
 
UPPER RIDGING PUSHED OUT OF THE NORTHEASTERN PACIFIC WILL SURGE  
BACK TOWARD THE WEST COAST OF NORTH AMERICA WHICH FAVORS RENEWED  
DOWNSTREAM TROUGHING IN THE CENTRAL/EASTERN STATES LATE NEXT WEEK.  
A LEAD SYSTEM OUT OF THE SHORT RANGE WILL EXIT THROUGH NEW ENGLAND  
MONDAY AS A COUPLE MORE PUSH THROUGH THE WEST. BY MIDWEEK, LOW  
PRESSURE WILL DEEPEN OUT OF THE SOUTHERN PLAINS AND LIFT TOWARD  
THE GREAT LAKES/SOUTHERN CANADA WITH ANOTHER ROUND OF RAIN,  
CONVECTION, AND SOME WINTRY WEATHER ON THE COLDER NORTHWEST SIDE.  
 
   
..GUIDANCE PREFERENCES AND PREDICTABILITY ASSESSMENT
 
 
MODELS/ENSEMBLES ALIGN WITH THE LONGWAVE PATTERN THROUGH NEXT  
WEEK, BUT DIFFER MOSTLY ON TIMING/DEPTH/TRACK OF ESPECIALLY THE  
LATE-WEEK SYSTEM. AT THE START OF THE PERIOD, MODELS HAVE STRUGGLE  
WITH THE QUICK FLOW SOUTH OF THE GULF OF ALASKA BETWEEN SOUTHERN  
RIDGING AND NORTHERN TROUGHING, SO A CONSENSUS POSITION IN BOTH  
DEPTH AND SPEED WAS PREFERRED AS RUN-TO-RUN CHANGES WILL CONTINUE.  
TREND HAS BEEN FOR A BIT WEAKER/FLATTER FLOW BUT NORTHERN FLOW  
ACROSS THE U.S./CANADIAN BORDER WAS UNCLEAR AS WELL. BY 12Z WED,  
SPLIT IN THE GUIDANCE WAS EVIDENT (AND MOSTLY MIMICKED IN THEIR  
PARENT ENSEMBLE SYSTEMS)--GFS/UKMET WERE SLOWER THAN THE  
ECMWF/CANADIAN/FV3-GFS AS THE TROUGH DIGS THROUGH THE GREAT  
BASIN/FOUR CORNERS REGION. ECMWF HAS TRENDED QUICKER WHILE THE GFS  
TRENDED SLOWER, AWAY FROM A COMMON SOLUTION 24 HRS AGO, BUT THE  
ENSEMBLES OVERLAPPING MOST JUST A BIT SLOWER THAN THE 12Z ECMWF.  
AS THE LOW LIFTS NORTHEASTWARD, 12Z GFS/ECMWF OFFERED REASONABLE  
CLUSTERING NEAR THE 12Z NAEFS MEAN WHICH WAS NOT AS QUICK AS THE  
ECMWF ENSEMBLE MEAN BUT NOT AS SLOW AS THE 18Z GEFS MEAN. THIS  
PAIRED WELL WITH CONTINUITY WHICH WAS PREFERRED UNTIL ANOTHER  
CYCLE OR TWO OF RUNS CAN BE REVIEWED FOR SHORT TERM CHANGES THAT  
MAY INFLUENCE THE LATE WEEK SYSTEM'S EXIT SPEED (I.E., UPSTREAM  
KICKER AND NORTHERN STREAM AFFECTS).  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
PRECIPITATION WILL AGAIN INCREASE BY WEDNESDAY INTO THURSDAY  
ACROSS THE MISSISSIPPI/MISSOURI VALLEYS INTO THE GREAT LAKES AS  
LOW PRESSURE STRENGTHENS OVER OKLAHOMA/KANSAS. MULTI-INCH RAINFALL  
TOTALS ARE PROBABLE (ENHANCED IN EMBEDDED CONVECTION) IN SOME  
LOCATIONS OF THE WARM SECTOR AND PERHAPS TO THE NORTH/NORTHEAST OF  
THE LOW WITH ADDITIONAL NORTHERN STREAM SUPPORT. TEMPERATURES TO  
THE NORTH/NORTHWEST OF THE LOW MAY ONLY BE MARGINALLY COLD ENOUGH  
FOR SNOW (AND PERHAPS ONLY AT NIGHT) DEPENDING ON THE AMOUNT OF  
COOLER AIR BEHIND A WEAKENING CANADIAN COLD FRONT WEDNESDAY.  
TEMPERATURES WILL LARGELY BE WITHIN 10 DEGREES OF AVERAGE VALUES  
FOR MID-APRIL BUT WITH A SLOWER MODERATION OVER PARTS OF THE  
DAKOTAS/MINNESOTA OWING TO THE NEAR-TERM SNOW COVER THAT WILL TAKE  
AT LEAST SEVERAL DAYS TO MELT.  
 
FRACASSO  
 
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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